JP2000010418A - Intermediate transfer belt, its manufacture and image forming device provided with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of obtaining excellent image quality without scattering of toner at the time of transferring and also stably obtaining a transferred image having high quality. SOLUTION: The image forming device is equipped with an intermediate transfer belt B having a surface layer Ba which can come into contact with the surface of an image carrier 16 where a toner image is formed on a rotating and moving surface and whose the Young's modulus is >=30000 kg/cm2 and whose the surface resistivity is 1010-1014 Ω/(square) and an elastic layer Bb formed on the rear face side of the surface layer Ba and which is rotated and moved while successively passing through a primary transfer area Q3 where the toner image on the surface of the image carrier 16 is primarily transferred by coming into contact with the surface of the image carrier 16 and a secondary transfer area Q4 where the toner image primarily transferred at the primary transfer area Q3 is secondarily transferred to a transfer materials.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic copying machine,
The present invention relates to an image forming apparatus using an electrophotographic method, such as a laser printer, a facsimile, and a composite OA thereof.

[0002]

2. Description of the Related Art An image forming apparatus using an electrophotographic system is a laser in which a uniform charge is formed on an image carrier composed of a photoreceptor made of an inorganic or organic photoconductive material and an image signal is modulated. After forming an electrostatic latent image with light or the like, the electrostatic latent image is developed with 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.

Examples of belt materials used in an image forming apparatus employing the intermediate transfer member system include polyvinylidene fluoride (PVDF) (JP-A-5-200904 and JP-A-6-228335) and polycarbonate (PC). ) (JP-A-6-95521), polyalkylene terephthalate (PAT) (JP-A-6-1490)
No. 81), a blend material of PC and PAT (Japanese Unexamined Patent Publication No.
-149083), a blend material of ethylene tetrafluoroethylene copolymer (ETFE) and PC, ET
Blended material of FE and PAT, ETFE, PC and PA
A conductive endless belt in which a conductive agent such as carbon black is dispersed in a thermoplastic resin such as a blend material of T (Japanese Patent Application Laid-Open No. 6-149079) has been proposed. The above, PVD
Conductive materials composed of thermoplastic resins such as F and PC
Since the Young's modulus is 24000 kg / cm ² or less, which is inferior to the mechanical properties, the belt deforms greatly with respect to the stress during driving,
When applied to an intermediate transfer belt, there is a problem that a high quality transfer image cannot be stably obtained, and cracks are generated from a belt end portion at the time of driving, so that the durability of the belt is poor.

A material having excellent mechanical properties includes a polyimide resin material and the like. For example, Japanese Patent Application Laid-Open No. 63-11263 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 the film forming is to inject a polymer solution in which carbon black is dispersed into a cylindrical mold, for example,
The film is formed into a film by centrifugal molding while rotating the cylindrical mold while heating to 100 ° C to 200 ° C. The obtained film is released in a semi-cured state, covered with an iron core, and
At 0 ° C. to 450 ° C., the main curing is performed by advancing the polyimide conversion reaction (ring-closing reaction of the polyimide acid).

The surface resistivity of the intermediate transfer belt is from 10 ⁹ Ω / □ (= ⁹ log Ω / □) to 10 ¹⁴ Ω / □.
It is desirable that If less than 10 ⁹ Ω / □,
Since the electric field intensity in the pre-nip portion is increased and gap discharge is likely to occur in the pre-nip portion, there arises a problem that the granularity of image quality deteriorates. If it is higher than 10 ¹⁴ Ω / □, for example, 10 ^14.5 Ω / □, peeling discharge occurs at the post nip where the image bearing member and the transfer belt are separated from each other. turn into.

Since the polyimide resin is excellent in mechanical properties, when the transfer roller presses the intermediate transfer belt against the image carrier, the belt deforms little due to the pressing force. When the toner image is electrostatically transferred to the intermediate transfer member by applying an electric field in such a state, the load of the pressing force by the transfer roll is concentrated at the primary transfer portion. 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 of a hollow character in which a line image falls out occurs. This point has a similar problem also in the secondary transfer unit pressed against the intermediate transfer belt via the sheet by the transfer roll. As a measure for preventing the image quality defect, for example, a belt material whose surface is made of an elastic material is given.
When a rubber material such as silicon rubber is used as the surface material, there is a problem that the toner image is not transferred to the recording medium during the secondary transfer because the rubber material has adhesiveness.

Further, 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 has a problem in that the resin material of the surface layer has no elasticity, so that the adhesion to polyimide is poor, and the belt is peeled off from the belt due to deformation at the roll bending portion when the belt is driven.

[0008]

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. On the other hand, a belt material made of polyimide resin having excellent mechanical properties has 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 is generated. There's a problem. Further, in the case of a belt material whose surface layer is covered with a rubber material such as silicon rubber, there is a problem that the toner image is not transferred to a recording medium at the time of secondary transfer because the rubber material is sticky.

In view of the above problems, the present invention has the following technical contents (O01) and (O02) as technical subjects. (O01) To provide an image forming apparatus capable of obtaining a high quality image with no toner scattering at the time of transfer and stably obtaining a high quality transfer image. (O02) To provide an image forming apparatus free from image defects such as misregistration.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies and studies to solve the above-mentioned problems. As a result, by dispersing a conductive agent in a resin material having excellent mechanical properties, the present inventors have found that the present invention has been developed. It has been found that the technical problem can be solved by setting the resistivity in a specific range and using an elastic member as a lower layer. Next, the present invention devised to solve the problem will be described. Elements of the present invention are indicated by parentheses in the elements of the embodiment in order to facilitate correspondence with the elements of the embodiments described later. Add the items enclosed in. The reason why the present invention is described in correspondence with the reference numerals of the embodiments described below is to facilitate understanding of the present invention, and not to limit the scope of the present invention to the embodiments.

(First Invention) That is, the image forming apparatus of the first invention is characterized by having the following constituent elements (A01) to (A07). (A01) an image carrier (16) on which a toner image is formed on a rotating surface; (A02) a Young's modulus that can contact the surface of the image carrier (16) is 30000 kg / cm ² or more and a surface resistivity is 10 A surface layer (Ba) of ¹⁰ to 10 ¹⁴ Ω / □ and an elastic layer (Bb) formed on the back side of the surface layer (Ba)
And a primary transfer area (Q3) where the toner image on the surface of the image carrier (16) is primarily transferred in contact with the surface of the image carrier (16) and the primary transfer area (Q3). 1
Secondary transfer of the next-transferred toner image to the transfer material (S) 2
An intermediate transfer belt (B) rotating sequentially passing through the next transfer area (Q4); (A03) a belt supporting the back side of the intermediate transfer belt (B) and rotating the intermediate transfer belt (B); Support members (26 to 29), (A0
4) In the primary transfer area (Q3), the image carrier (1
6) A primary transfer device (T1) for transferring the toner image on the surface to the belt surface side, (A05) The toner image on the intermediate transfer belt (B) is transferred onto the transfer material (S) in the secondary transfer area (Q4). 2
A secondary transfer device (T2) for performing the next transfer, (A06) a fixing device (48) for fixing a secondary transfer toner image on the transfer material (S) in a fixing region (Q6), (A07) the secondary transfer region A transfer material transport device (42 to 47) for sequentially transporting the transfer material (S) to (Q4) and the fixing area (Q6).

In the image forming apparatus according to the first aspect of the invention, the surface layer (Ba) can be made of any one of polyimide, polyether sulfone, polyether ketone, and polyether ether ketone. In the image forming apparatus according to the first aspect, the elastic layer (Bb) can be made of a rubber material. The image forming apparatus of the first invention can be applied to the following image forming apparatuses. (1) The toner image formed on the image carrier (16) is primary-transferred to the intermediate transfer belt (B), and the primary-transferred toner image is secondary-transferred to the transfer material (S). Monochromatic image forming apparatus. (2) The toner images sequentially formed on the image carrier (16) are superimposed on the intermediate transfer belt (B) and primary-transferred, and the primary-transferred full-color toner image is collectively transferred onto the transfer material (S). A full-color image forming apparatus configured to perform secondary transfer. (3) A tandem-type color image forming apparatus in which a plurality of image carriers (16) on which toner images of different colors are formed are arranged in series on an intermediate transfer belt (B).

(Operation of the First Invention)
In the image forming apparatus of the present invention, a toner image is formed on the rotating surface of the image carrier (16). The image carrier (1)
6) The intermediate transfer belt (B) having a surface layer (Ba) capable of contacting the front surface and an elastic layer (Bb) formed on the back surface side of the surface layer (Ba) is a back surface of the intermediate transfer belt (B). The sides are supported by belt support members (26 to 29). The belt support members (26 to 29) rotate the intermediate transfer belt (B). The intermediate transfer belt (B) is in contact with the surface of the image carrier (16), and a primary transfer area (Q3) where the toner image on the surface of the image carrier (16) is primarily transferred, and the primary transfer area. In (Q3), the toner image that has been primary-transferred is sequentially rotated through a secondary transfer area (Q4) where the toner image is secondarily transferred to the transfer material (S). 1
The secondary transfer unit (T1) transfers the toner image on the surface of the image carrier (16) to the belt surface side in the primary transfer area (Q3). The transfer material transport devices (42 to 47) sequentially transport the transfer material (S) to the secondary transfer area (Q4) and the fixing area (Q6). The secondary transfer device (T2) secondary-transfers the toner image on the intermediate transfer belt (B) to the transfer material (S) in the secondary transfer area (Q4). The secondary transfer toner image on the transfer material (S) is fixed by a fixing device (48) in a fixing area (Q6).

In the image forming apparatus of the first invention, tension acts on the intermediate transfer belt (B) supported by the belt support members (26 to 29). By using a material having a Young's modulus of 30,000 kg / cm ² or more as the surface layer (Ba) of the intermediate transfer belt (B), the extension of the intermediate transfer belt (B) due to the tension can be reduced. Therefore, the belt length of the intermediate transfer belt (B) is stabilized for a long time. The intermediate transfer belt (B) has a surface resistivity of 10 ¹⁰ to ¹⁰
By setting it to 10 ¹⁴ Ω / □, primary transfer and secondary transfer can be performed well. The surface layer (Ba) having the above-mentioned properties includes polyimide, polyether sulfone,
It can be formed of either polyetherketone or polyetheretherketone resin. Also,
By forming the elastic layer (Bb) of the intermediate transfer belt (B) from a rubber material, the belt support member (2
6 to 29), the intermediate transfer belt (B) adheres closely.
Therefore, the widthwise movement of the belt support members (26 to 29) with respect to the belt support members (26 to 29) can be reduced, so that the positional deviation of the toner image transferred to the intermediate transfer belt (B) is reduced. can do.

(2nd invention) Further, the intermediate transfer belt of the 2nd invention has the following constituent features, (B)
01) A surface layer (Ba) having a Young's modulus of 30000 kg / cm ² or more and a surface resistivity of 10 ¹⁰ to 10 ¹⁴ Ω / □ and a surface layer capable of contacting the surface of the image carrier (16) on which a toner image is formed, and the surface layer An elastic layer (B) formed on the back side of (Ba) and rotatably supported by the belt support members (26 to 29).
b) and a primary transfer area (Q3) where the toner image on the surface of the image carrier (16) is primarily transferred by contacting the surface of the image carrier (16) and the primary transfer area (Q3) ), An intermediate transfer belt (B) that rotates and sequentially passes through a secondary transfer area (Q4) where the toner image primarily transferred is secondarily transferred to a transfer material (S).

The surface layer (Ba) of the intermediate transfer belt according to the second invention can be made of any one of polyimide, polyether sulfone, polyether ketone and polyether ether ketone.

(Operation of the Second Invention) The intermediate transfer belt according to the second invention having the above-mentioned constitutional requirements comes into contact with the surface of the image bearing member (16) on which a toner image is formed, and contacts the surface of the image bearing member (16). And a secondary transfer area (Q4) where the toner image primarily transferred in the primary transfer area (Q3) is secondarily transferred to the transfer material (S). ) And rotate. The intermediate transfer belt (B) has a Young's modulus capable of contacting the surface of the image carrier (16) of 30,000 kg / cm ² or more and a surface resistivity of 1
A surface layer (Ba) of 0 ¹⁰ to 10 ¹⁴ Ω / □ and a belt supporting member (26) formed on the back side of the surface layer (Ba).
To 29) have an elastic layer (Bb) rotatably supported. The intermediate transfer belt (B) has a surface layer (Ba) having a Young's modulus of 30,000 kg / cm ² or more, so that a change in belt length due to the extension of the intermediate transfer belt (B) when tension is applied is small. Become. Therefore, the belt length of the intermediate transfer belt (B) is stabilized for a long period of time. Further, the surface resistivity of the surface layer (Ba) is 10
By setting the resistance to ¹⁰ to 10 ¹⁴ Ω / □, the toner image can be transferred well. The elastic layer (Bb) of the intermediate transfer belt (B) is a belt support member (26 to 2).
9), the intermediate transfer belt (B) comes into close contact with the belt support members (26 to 29), and the movement of the intermediate transfer belt (B) in the width direction with respect to the belt support members (26 to 29) is small. Become. For this reason, it is possible to reduce the displacement during the transfer of the toner image. Further, by forming the elastic layer (Bb) of the intermediate transfer belt (B) from a rubber material, it is possible to prevent the widthwise movement of the intermediate transfer belt (B) with respect to the belt support members (26 to 29). it can.

(Third invention) A method of manufacturing an intermediate transfer belt according to the third invention has the following constitutional features: (C01) Seamless surface layer of polyimide resin by centrifugal molding (C01) Ba) a surface layer forming step of forming a forming belt; (C02) an elastic layer forming step of forming an elastic layer (Bb) of a rubber layer inside the surface layer forming belt.

(Operation of the Third Invention)
According to the method of manufacturing an intermediate transfer belt of the present invention, the intermediate transfer belt (B) of the second invention can be easily manufactured.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In the first and second inventions, the resin material constituting the surface layer (Ba) of the intermediate transfer belt (B) is polyimide, polyether sulfone, or the like.
Resins having excellent mechanical properties such as polyetherketone or polyetheretherketone are exemplified. Among them, polyimide is preferable from the viewpoint of availability. The polyimide resin has a feature that the deformation of the belt during driving is smaller than that of a conventionally used thermoplastic resin.

The polyimide resin is generally a polymer synthesized by condensation polymerization using tetracarboxylic dianhydride and diamine or diisocyanate as monomer components. Examples of the tetracarboxylic acid component of the dianhydride include pyromellitic acid, naphthalene-1,4,5,8-tetracarboxylic acid, naphthalene-2,3,6,7-tetracarboxylic acid, 2,3,5, 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'-benzophenonetetracarboxylic acid, 3,3 ', 4,4'-diphenylsulfonetetracarboxylic acid, 3,3' , 4,4'-azobenzenetetracarboxylic acid, bis (2,3-dicarboxyphenyl)
Methane, bis (3,4-dicaroxyphenyl) methane, β, β-bis (3,4-dicaroxyphenyl) propane, β, β-bis (3,4-dicaroxyphenyl) hexafluoropropane and the like can be mentioned. Can be

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, 3,4'-diaminodiphenyl ether, 4,
4'-diaminodiphenyl ether (oxy-p, p '
-Dianiline; ODA), 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 polyimide containing ODA as a diamine component (Kapton HA: manufactured by DuPont),
3 ', 4,4'-biphenyltetracarboxylic acid-based polyimide (UPILEX S: manufactured by Ube Industries, Ltd.) and the like.

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

Among these conductive agents, carbon black is preferred in view of cost and environmental stability. Furthermore, from the viewpoint of dispersibility, the average particle size manufactured by Mitsui Kinzoku Co., Ltd. is 0.1
μm tin oxide complex oxide (product name: UF), 0.3μ
m-based zinc oxide (Pastran Type-II), barium sulfate having an average particle diameter of 0.4 μm coated with a tin-based oxide (Pastran Type-IV), 0.2 μm ATO,
A metal oxide having an average particle size of 1 μm or less, such as ITO having a thickness of 0.2 μm, is also preferably used. The conductive metal oxide is preferably surface-treated with one or more of various silane coupling agents. Surface-treated metal oxides
Since the compatibility with the resin constituting the base material is improved, the dispersion becomes 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, PVDF, etc. Conventionally used thermoplastic resin materials have a Young's modulus of 2 when carbon black is dispersed.
It is 4000 kg / cm ² or less. On the other hand, in the present invention, since the Young's modulus of the resin material of the surface layer (Ba) is increased to 30,000 kg / cm ² or more, disturbance at the time of driving the belt (for example, when the cleaning blade contacts or separates from the belt surface). Load fluctuation that occurs when
Are the same, the elongation and shrinkage of the belt is 25
% Or more. Therefore, a high-quality transfer image can be stably obtained. In order to reduce the amount of displacement of the belt due to disturbance at the time of driving the belt and obtain a good quality transfer image, the thickness of the belt is preferably 50 μm or more. On the other hand, if the belt is too thick, the deformation of the belt surface at the portion of the tension roll becomes large, and when forming a color image, the position of the multiple toner image is shifted and color misregistration occurs. The thickness is 50-300μ
m, particularly preferably in the range of 70 to 200 μm.

As the lower elastic member, silicon rubber,
Fluorine rubber, urethane rubber, EPDM, NBR, CR,
A rubber material such as chlorinated polyisoprene, hydrogenated polybutadiene, butyl rubber or the like can be used alone or as a blend of two or more. If necessary to control the volume resistivity, a metal or alloy such as carbon black, graphite, aluminum, and copper alloy, tin oxide, zinc oxide, kalim titanate, tin oxide-indium oxide or tin oxide may be used as a conductive agent. -One or more fine powders of metal oxides such as antimony oxide composite oxides are used. Among them, carbon black is preferable as the conductive agent from the viewpoint of cost.

The surface resistivity of the surface layer resin material is 10 ¹⁰ to
In the range of 10 ¹⁴ Ωcm, preferably 10 ¹¹ to 10 ^12.5 Ωc
m. The surface resistivity can be easily adjusted to the above range by selecting the conductive agent, adjusting the amount of the conductive agent, and the like.

Next, specific examples (embodiments) of the embodiment of the image forming apparatus of the first invention and the intermediate transfer belt of the second invention will be described with reference to the drawings. It is not limited. FIG. 1 is an explanatory view of Embodiment 1 of the image forming apparatus of the present invention using the intermediate transfer belt B. In FIG. 1, an image forming apparatus F has a UI (user interface) and a transparent platen glass 2 on which a document (not shown) is placed.

The original placed on the platen glass 2 is illuminated by the light source 4 of the original illumination unit 3. The original reflected light is reflected by the first mirror 5 of the original illuminating unit 3 and the second mirror 7 and the third mirror 8 of the mirror unit 6, passes through the imaging lens 9, and is converted by the CCD into an analog signal of R, G, and B. Is read as The image signal read by the CCD is input to the IPS controlled by the controller C. The IPS image read data output unit 11 converts the input read image signal from analog to digital and outputs the read image signal.
Reference numeral 2 denotes an image memory 13 for converting the AD-converted data into Y, M, C, and K image data, performing data processing such as density correction and enlargement / reduction correction, and writing image data (laser Drive data).

The laser drive signal output device 14 is provided with the IP
A laser drive signal of an image corresponding to the image data output from S is output to a ROS (optical scanning device, that is, a latent image forming device) at a predetermined timing. The ROS outputs a laser beam L modulated by the laser drive signal. After the rotating image carrier 16 is charged by the charger 17, at the latent image writing position Q 1, K (black), Y (yellow), M (magenta), and C (cyan) are applied by the laser beam L. An electrostatic latent image corresponding to the image of each color component is written. A rotary developing unit 18 for developing the electrostatic latent image into a toner image includes developing devices 18k for each color of K (black), Y (yellow), M (magenta), and C (cyan) which rotate with a rotation shaft 18a. Each of the developing devices 18k to 18c rotates to a developing area Q2 facing the image carrier 16 to form an electrostatic latent image corresponding to the image of each color component into a toner of each color. Develop into an image.

The toner image formed on the surface of the image carrier 16 passes through a primary transfer area Q3 facing the intermediate transfer belt B. A primary transfer unit T1 disposed on the back side of the intermediate transfer belt B in the primary transfer area is provided with a primary transfer voltage (a voltage having a polarity opposite to the polarity of the toner charge, supplied from a power supply circuit D).
For example, the toner image on the image carrier 16 is primarily transferred to the intermediate transfer belt B by + (plus) about 1 to 4 kV). The residual toner on the surface of the image carrier 16 that has passed through the primary transfer area Q3 is removed by the image carrier cleaner 20.

The intermediate transfer belt B includes a driving roll 26,
It is rotatably supported by a plurality of belt support rolls (belt support members) 26 to 29 including a tension roll 27, an idler roll 28 and an inner secondary transfer roll (backup roll) 29. An inner secondary transfer roll (backup roll) 29, which is a support roll for the intermediate transfer belt B, is configured as a counter electrode of the outer secondary transfer roll 30, and an electrode roll 31 is in contact with the surface thereof. The outer secondary transfer roll 30 is disposed so as to be separated or approachable between a separated position separated from the inner secondary transfer roll 29 and a pressed close position, and is grounded (grounded). The inner secondary transfer roll 2
9, outer secondary transfer roll 30, and electrode roll 3
1 forms a secondary transfer unit T2.

A negative (-) secondary transfer voltage (a voltage having the same polarity as the charged polarity of the toner) is applied from the power supply circuit D to the electrode roll 31 of the secondary transfer unit T2. The secondary transfer unit T2 transfers a secondary transfer area Q4 formed by the nip (contact area) between the outer secondary transfer roll 30 and the intermediate transfer belt B to a recording sheet (that is, a transfer material) S.
Is passed, the toner image primarily transferred onto the intermediate transfer belt B is secondarily transferred onto the recording sheet S. The electrode roll 31 is not particularly limited as long as it is a conductive member having good 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 An electrode member such as a conductive resin plate can be used. A transfer voltage of -1 to -5 kV is applied from the electrode member through an inner secondary transfer roll (backup roll) 29. In addition,
The polarity of the voltage applied to the electrode member is + (plus) when the charging polarity of the toner is + (plus). The electrode member (including the electrode roll 31) is not necessarily a necessary member. For example, the secondary transfer voltage is applied to the conductive shaft of the secondary transfer roll (backup roll) 29 or the outer secondary transfer roll 30. It is possible.

The secondary transfer roll cleaner 33 is a member for removing the toner adhered to the outer secondary transfer roll 30 and, together with the outer secondary transfer roll 30, removes the toner from the inner secondary transfer roll 29. Move in the direction of separation or approach. A belt cleaner 35 is disposed along the surface of the intermediate transfer belt B and downstream of the secondary transfer area Q4. The belt cleaner 35 is disposed so as to be separated from or contact with the intermediate transfer belt B. When a color image is formed, the outermost unfixed toner image is primarily transferred onto the intermediate transfer belt B until the outermost unfixed toner image is transferred.
The next transfer roll 30, the secondary transfer roll cleaner 33, and the belt cleaner 35 are held at positions separated from the intermediate transfer belt B.

Further, a belt position sensor SN1 for detecting a position detection mark (not shown) formed at the outer end of the intermediate transfer belt B in the width direction is provided.
The timing of writing a latent image on the image carrier 16 is controlled by a very accurate position detection signal of the intermediate transfer belt B output from the belt position sensor SN1. The recording sheet S stored in the paper feed tray 41 is taken out by the pickup roll 42,
The sheets are separated one by one, temporarily stopped by the registration rollers 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 conveyed to the fixing area Q6 by the sheet guide 46 and the sheet conveying belt 47.
When passing through the fixing area Q6, the secondary transfer toner image on the recording sheet S is fixed by a pair of fixing rolls of a fixing device 48 and is discharged to a paper discharge tray 49. The elements indicated by the reference numerals 42 to 47 constitute recording sheet (ie, transfer material) transporting devices (42 to 47).

When forming a monochromatic image, the primary transfer area, Q3
The toner image primarily transferred to the intermediate transfer belt B is secondarily transferred to the recording sheet S immediately in the secondary transfer area Q4. At the time of full-color image formation, each time the intermediate transfer belt B passes through the primary transfer area Q3, the toner image of each color is sequentially superimposed on the intermediate transfer belt B and primary-transferred. After the primary transfer on B
The secondary transfer is collectively performed on the recording sheet S in the secondary transfer area.

(Embodiment 1 of Intermediate Transfer Belt B) FIG. 2 is an explanatory view of the cross-sectional structure of the intermediate transfer belt B used in the image forming apparatus of the first embodiment. In FIG. 2, the intermediate transfer belt B includes a surface layer Ba and an elastic layer Bb formed on the back surface of the surface layer Ba. Surface layer Ba = polyimide resin film, 50 μm Elastic layer Bb = NBR rubber, 50 μm

(Method of Manufacturing Intermediate Transfer Belt B in Example 1) In the following composition, "parts" indicating the ratio means "parts by weight". Polyimide varnish using N-methyl-2-pyrrolidone as a solvent (UPILEX S: Ube Industries, Ltd.)
Was added to 19 parts of carbon black with respect to 100 parts of the resin component, and mixed with a mixer. Next, the cylindrical film released from the semi-cured state is covered with an iron core, and the temperature is increased from 120 ° C. to 350 ° C. over 30 minutes to evaporate the solvent. The main curing of dehydrating and condensing the acid was performed. 50μ obtained
32 m thick carbon black dispersed polyimide film
Cut to 0mm width, seamless belt (surface layer) Ba
Was formed. Next, the seamless belt (surface layer)
As an NBR rubber material inside Ba, the unvulcanized hardness (J
ISA) 61mm N240S manufactured by Nippon Synthetic Rubber Co., Ltd.
(Product name) Paste the middle nitrile rubber sheet, 150
℃, the above seamless belt (surface layer) B
A rubber layer (elastic layer) Bb having a thickness of 50 μm was formed inside a.

The surface resistivity of the manufactured two-layer belt is 10 ^12.1 Ω / □, and the volume resistivity is 10 ^11.5 Ωc.
m (see Table 1). 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.

(Embodiment 2 of Intermediate Transfer Belt B) Surface Layer B
a and an elastic layer Bb. Surface layer Ba = polyimide resin film, thickness 50 μm Elastic layer Bb = EPDM rubber, thickness 50 μm (Method of manufacturing intermediate transfer belt B in Example 2) Surface layer Ba
Was formed in the same manner as in Example 1. Next, as an EPDM rubber material, EP33 (EPDM rubber sheet) manufactured by Japan Synthetic Rubber Co., Ltd. having an unvulcanized hardness (JISA) of 70 ° is attached to the inside of the seamless belt (surface layer) Ba. Heating to temperature produced a seamless intermediate transfer belt. The surface resistivity of the manufactured two-layer belt is 10 ^12.5 Ω / □, and the volume resistivity is 10 ^12.8 Ωc.
m (see Table 1).

(Comparative Example 1 of Intermediate Transfer Belt B) Comparative Example 1
Has a single-layer structure. Intermediate transfer belt B = Carbon black dispersed polyimide film, thickness 80 μm (Method of manufacturing comparative example 1 of intermediate transfer belt B) Polyimide varnish (Upilex S: Ube Industries, Ltd.) using N-methyl-2-pyrrolidone as a solvent , Its resin component 10
18 parts of carbon black was added to 0 parts 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 centrifuged 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, and the temperature is increased from 120 ° C. to 350 ° C. over 30 minutes to evaporate the solvent. The main curing of dehydrating and condensing the acid was performed. The obtained carbon black-dispersed polyimide film having a thickness of 80 μm was cut into a width of 320 mm to complete a seamless belt. The resulting belt has a surface resistivity of 10
^The volume resistivity was ^18.9 Ω / □ and the volume resistivity was 10 ^8.9 Ωcm.

Comparative Example 2 of Intermediate Transfer Belt B Comparative Example 2
Has a single-layer structure. Intermediate transfer belt B = Carbon black dispersed thermoplastic PC
(Polycarbonate) Resin Film, 150 μm Thickness (Production Method of Comparative Example 2 of Intermediate Transfer Belt B) A 150 μm-thick carbon black-dispersed thermoplastic PC (polycarbonate) resin seamless belt was produced by an extrusion molding method. The surface resistivity of this PC resin belt is 10
^{It is 11.9} Ω / □ and the volume resistivity is 10 ^12.5 Ωcm.

Comparative Example 3 of Intermediate Transfer Belt B Comparative Example 3
Has a single-layer structure. Intermediate transfer belt B = Carbon black dispersed thermoplastic ET
FE Resin, 150 μm Thickness (Method for Producing Comparative Example 3 of Intermediate Transfer Belt B) A 150 μm thick seamless belt made of carbon black-dispersed thermoplastic ETFE resin was produced by an extrusion molding method. This E
The surface resistivity of the TFE resin belt is 10 ^11.5 Ω / □, and the volume resistivity is 10 ^9.0 Ωcm.

(Comparative Example 4 of Intermediate Transfer Belt B) Comparative Example 4
Has a two-layer structure but no elastic layer. Surface coating layer = tetrafluoroethylene-hexafluoropropylene copolymer paint (FEP resin), thickness 5 μm Base layer of surface coating layer = polyimide resin film, thickness 50 μm (Comparative Example 4 of intermediate transfer belt B Production method) A carbon black-dispersed polyimide (base layer) obtained in the same manner as in Comparative Example 1 was a tetrafluoroethylene-hexafluoropropylene copolymer paint manufactured by Daikin Industries, Ltd. as a component for forming a surface layer. ND-4 (trade name) was coated at a thickness of 5 μm. The surface resistivity of the manufactured intermediate transfer belt is 10
^{It was 13.9} Ω / □ and the volume resistivity was 10 ^11.8 Ωcm.

(Mechanical Property Test of Intermediate Transfer Belt Material) Tensile strength and Young's modulus of the belt material forming the surface layer Ba manufactured in Examples 1 and 2 and the belt materials manufactured in Comparative Examples 1 to 4 ( Tensile modulus) according to JIS K7127
It measured according to. (See Table 1 for test results.) That is, the tensile strength was measured at a test speed of 200 mm / min using a 5 × 40 mm strip test piece. The Young's modulus was measured at a test speed of 20 mm / min using a strip test piece of 25 × 250 mm.

(Evaluation Results of Image Quality) Each of the intermediate transfer belts of the embodiment and the comparative example was mounted on the above-described image forming apparatus shown in FIG. 1, and the image quality obtained by performing a copy test was visually observed according to the following criteria. evaluated. (See Table 1 for evaluation results.) Hollow-character evaluation ○: No hollow character generated ×: Hollow character generated Primary transfer white point missing evaluation ○: No white point missing ×: White point missing Registration shift evaluation ○: No registration error x: Registration error occurred

Table 1 summarizes the measurement results of the surface resistivity and volume resistivity, tensile strength and Young's modulus of the belt material of the two-layered belt (Example) or the comparative example, and the evaluation results of the image quality.

[0048]

[Table 1]

As shown in Table 1, the two-layer belts of Examples 1 and 2 have a large Young's modulus of the surface layer so that the deformation of the belt due to the stress during driving is small, and the lower layer has an elastic layer. Since there was no stress concentration due to the transfer roll at the transfer portion, no hollow character was generated at the transfer portion. Further, since the surface resistivity of the belt material is in an appropriate range, gap discharge is likely to occur in the pre-nip portion, so that the granularity of image quality deteriorates. In addition, there was no problem such as peeling discharge occurring at the post nip portion and white spots at the discharge generating portion.

On the other hand, in the intermediate transfer belt of Comparative Example 1, since the Young's modulus is as large as 62000 kg / cm ² , the deformation of the belt due to the stress during driving is small, but the deformation due to the stress by the transfer roll at the transfer portion is small. , A hollow character occurred in the transfer portion.

In Comparative Example 2 in which the PC resin was used as the belt, the Young's modulus was 24000 kg / cm ² , and there was stress concentration due to the transfer roll at the transfer portion, so that a hollow character was generated at the transfer portion.

Comparative Example 3 using ETFE resin as a belt material
In this example, the occurrence of hollow characters was at a certain level, but since the Young's modulus was as small as 12000 kg / cm ² , the deformation of the belt due to the stress during driving was large, and color shift was observed in the obtained image.

As shown in Table 1, the belt material coated with the fluororesin of Comparative Example 4 had a large Young's modulus of the base material, so that the deformation of the belt due to the stress during driving was small, but the surface resistivity was 10 ^14. Since it is higher than Ω / □, peeling discharge occurs at the post nip where the image carrier and the transfer belt are separated from each other, resulting in discharge omission where a discharge occurs at a white spot. Peeling discharge occurs at the post nip,
There were problems such as white spots in the discharge generating part.

(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) In the secondary transfer area Q4, the electrode roll 3
Reference numeral 1 is not a necessary member. For example, a secondary transfer voltage may be applied to the conductive shaft of the inner secondary transfer roll 29 or the outer secondary transfer roll 30. (H02) The present invention can be applied to a monocolor image forming apparatus that forms an electrostatic latent image on an image carrier and develops only a toner image corresponding to the color. (H03) As the image carrier 16, a photosensitive drum or a photosensitive belt can be used. (H04) As the primary transfer device T1, a corona transfer device such as a corotron, a transfer roll, a transfer blade, or the like can be used. (H05) The present invention relates to a primary transfer area in which toner images formed on a plurality of image carriers arranged in parallel are primarily transferred to an intermediate transfer belt, and a toner image on the intermediate transfer belt to a transfer material. The present invention is applicable to a tandem-type image forming apparatus in which an intermediate transfer belt sequentially rotates and moves a secondary transfer area to be next transferred.

[0055]

The intermediate transfer belt according to the present invention has a large Young's modulus of the resin material of the surface layer of 3000 kg / cm ² or more. Since the stress concentration due to the transfer roll in the transfer unit is reduced, the deformation in the transfer unit is small, so no hollow characters are generated, and the lower layer is made of a viscoelastic member, so that the grip force on the drive roll is improved. Becomes larger, the belt slips on the roll surface, and the problem of minute displacement of the belt is eliminated.
High quality image quality can be stably obtained. In addition, since the surface resistivity is in the range of 10 ¹⁰ to 10 ¹⁴ Ωcm, gap discharge in the pre-nip portion is hardly generated, so that the granularity of image quality is not deteriorated. Further, since no peeling discharge occurs at the post nip portion, there was no problem such as white spots at the discharge generating portion.

[0056]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of Embodiment 1 of an image forming apparatus of the present invention using the intermediate transfer belt.

FIG. 2 is an explanatory diagram of a cross-sectional structure of an intermediate transfer belt B used in the image forming apparatus according to the first embodiment.

[Explanation of symbols]

F: image forming apparatus, B: intermediate transfer belt, Ba: surface layer, Bb: elastic layer, S: transfer material (recording sheet), Q3: 1
Next transfer area, Q4 ... Secondary transfer area, Q6 ... Fixing area, T1
... primary transfer unit, T2 ... secondary transfer unit, 16 ... image carrier, 2
6 to 29: belt support member, 42 to 47: transfer material (recording sheet) transport device, 48: fixing device.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Nagaoka Okegawa, 2274 Hongo, Fuji Xerox Co., Ltd., Ebina-shi, Kanagawa Prefecture Inventor Shinichi Ishigame 2274 Hongo, Ebina-shi, Kanagawa Prefecture F-Xerox Co., Ltd.F-term (reference) 2H032 AA05 BA09 4F213 AA28 AA32E AA34E AA40 AA45 AB18 AG03 AG16 AH81 WA97 WB01

Claims (5)

[Claims] An image forming apparatus having the following configuration requirements:
(A01) an image carrier on which a toner image is formed on a rotating surface; (A02) a Young's modulus capable of contacting the surface of the image carrier is 30000 kg / cm ² or more and a surface resistivity is 10 ¹⁰ to ¹⁰
It has a 10 ¹⁴ Ω / □ surface layer and the elastic layer formed on the back surface side of the surface layer of the primary to which the toner image of the contact with the image bearing member surface surface of the image bearing member is primarily transferred An intermediate transfer belt rotating and moving sequentially through a transfer area and a secondary transfer area for secondary transferring the toner image primarily transferred in the primary transfer area to a transfer material; (A03) a back side of the intermediate transfer belt (A04) a primary transfer device for transferring the toner image on the surface of the image carrier to the belt surface side in the primary transfer area; A secondary transfer device for secondary-transferring the toner image on the intermediate transfer belt to a transfer material in a next transfer area, (A06) a fixing device for fixing the secondary transfer toner image on the transfer material in a fixing region, (A07) Secondary transfer area and constant A transfer material transport device that sequentially transports the transfer material to the receiving area. 2. The image forming apparatus according to claim 1, wherein the surface layer is made of a resin selected from the group consisting of polyimide, polyether sulfone, polyether ketone, and polyether ether ketone. . 3. The method according to claim 1, wherein the following components are provided.
(A09) The elastic layer made of a rubber material. 4. An intermediate transfer belt having the following components:
(B01) A surface layer having a Young's modulus of 30000 kg / cm ² or more and a surface resistivity of ¹⁰ 10 Ω / □ to 10 ¹⁴ Ω / □ and a back surface side of the surface layer on which the toner image can be formed. A primary transfer area and a primary transfer area in which a toner image on the surface of the image carrier is primarily transferred in contact with the surface of the image carrier, and an elastic layer rotatably supported by a belt support member. An intermediate transfer belt that sequentially rotates and moves through a secondary transfer area where the toner image primarily transferred in the area is secondarily transferred to a transfer material. 5. A method of manufacturing an intermediate transfer belt comprising the following steps: (C01) a surface layer forming step of forming a seamless polyimide resin surface layer forming belt by centrifugal molding; and (C02) the surface layer forming belt. An elastic layer forming step of forming an elastic layer of a rubber layer inside the belt.