JP2007025096A - Transfer belt, transfer device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer belt which can be made longer in life by preventing peeling at the boundaries of an intermediate layer and a base layer constituting a three-layered structure when the three-layered structure is employed in order to suppress the occurrence of an abnormal image, such as a void in a character or a worm hole, and a transfer device, and an image forming apparatus using the transfer belt. <P>SOLUTION: The transfer belt 10 has the three-layered structure consisting of the surface 110, the intermediate layer 120 and the base layer 130 from an outer circumferential surface side in a thickness direction. The surface 110 has stretchability in a circumferential direction; the intermediate layer 120 has the stretchability in a circumferential direction and a thickness direction; and the base layer 130 has non-stretchability. A boundary section 140 between the base layer 130 and the intermediate layer 120 is formed so that the irregularities formed on the surfaces of the respective layers contactually facing each other may be formed as as to fit and bite each other other. When the thickness of the intermediate layer 120 of the transfer belt 10 is defined as t [μm], the maximum height Rz [μm] of the roughness of the surface on the intermediate layer side of the base layer 130 is preferably in a range of 3≤Rz<(t/2). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a FAX, and a transfer belt and a transfer apparatus used in the image forming apparatus.

Conventionally, as this type of transfer belt, a three-layer structure of a surface layer (release layer) having elasticity from the outer peripheral surface side in the thickness direction, an intermediate layer (elastic layer) having elasticity, and a base layer having non-elasticity A belt-shaped intermediate transfer member is known (for example, see Patent Document 1). This transfer belt (intermediate transfer member) is supported by a plurality of support rollers, and is rotationally driven by a driving force transmitted from a drive roller that is one of the support rollers in contact with the base layer. Since the base layer does not expand and contract, the driving force from the driving roller is transmitted smoothly, and the expansion and contraction of the image and the occurrence of positional deviation can be prevented. Further, the surface layer and the intermediate layer expand and contract, so that the toner image on the latent image carrier (photoreceptor) is transferred to the transfer belt (intermediate transfer member) and the toner image on the transfer belt. In the secondary transfer nip portion where the image is transferred to the recording medium, it is possible to prevent the occurrence of abnormal images such as missing characters in the following manner. For example, when the latent image carrier and the transfer belt are in contact with each other via the toner image on the latent image carrier in the primary transfer nip portion, the surface layer and the intermediate layer of the transfer belt expand and contract, thereby pressing the toner image. It becomes difficult for pressure to concentrate. Therefore, it is possible to suppress an increase in the adhesion force (cohesion force) between the toners and to prevent the occurrence of abnormal images such as missing characters. Similarly, in the secondary transfer nip portion, since the pressing force is less likely to concentrate on the toner image, an increase in the adhesion force (cohesion force) between the toners can be suppressed, and the occurrence of abnormal images such as missing characters can be prevented. .
JP 2003-215939 A

  However, when the conventional transfer belt having the three-layer structure is used, when the transfer belt is rotated and used, one of the intermediate layer and the base layer in contact with each other of the transfer belt expands and contracts, and the other does not expand and contract. There was a problem that peeling easily occurred at the interface of the layers. That is, when the transfer belt supported by the support roller is rotationally driven and used for image formation, the intermediate layer of the transfer belt expands and contracts and the base layer does not expand and contract. And is likely to peel at the interface between the two layers.

  The present invention has been made in view of the above problems. The purpose is to extend the life by preventing peeling at the interface between the intermediate layer and the base layer that constitutes the three-layer structure when the three-layer structure is used to suppress the occurrence of abnormal images such as missing characters and worm-eating. And a transfer device and an image forming apparatus using the transfer belt.

In order to achieve the above object, the invention of claim 1 has a three-layer structure of a surface layer, an intermediate layer and a base layer from the outer peripheral surface side in the thickness direction, and the surface layer has elasticity in the circumferential direction. A transfer belt on which the toner image on the image carrier is transferred, wherein the intermediate layer has elasticity in the circumferential direction and thickness direction, the base layer has non-stretchability, and the intermediate layer and the intermediate layer The interface with the layer is formed so that the unevenness formed on the surface of each layer in contact with and opposite to each other fits and bites into each other.
The invention of claim 2 has a three-layer structure of a surface layer, an intermediate layer and a base layer from the outer peripheral surface side in the thickness direction, the surface layer has elasticity in the circumferential direction, and the intermediate layer A transfer belt having a stretchability in a direction and a thickness direction, the base layer having a non-stretch property, and a toner image on an image bearing member being transferred, wherein the thickness of the intermediate layer is t [μm] The maximum height Rz [μm] of the surface roughness of the base layer on the intermediate layer side is in the range of 3 ≦ Rz <(t / 2).
Here, the above-mentioned “stretchability” is a property that is easy to stretch and shrink with a Young's modulus E showing a small value of 10 ⁷ Pa or less at room temperature. Further, the “non-stretchability” is a property that the Young's modulus E exhibits a large value of 10 ⁸ Pa or more at room temperature, and is difficult to stretch and shrink.
The volume resistivity ρv of the entire transfer belt is preferably in the range of 10 ⁷ Ω · cm to 10 ¹⁵ Ω · cm, particularly preferably in the range of 10 ¹⁰ Ω · cm to 10 ¹² Ω · cm. It is.
According to a third aspect of the present invention, in the transfer belt of the first or second aspect, at least one of the base layer and the intermediate layer is formed of a material having foamable voids.
According to a fourth aspect of the present invention, in the transfer belt of the first, second, or third aspect, the micro hardness H ₁ measured with respect to the outer peripheral surface of the surface layer is from 30 degrees to 70 degrees. It is characterized by.
The invention according to claim 5 is the transfer belt according to claim 1, wherein the maximum static friction coefficient by the Euler belt method measured on the outer peripheral surface of the surface layer is 0.5 or less. It is what.
The invention of claim 6 is a transfer apparatus comprising a transfer belt supported by a plurality of support rollers including a drive roller, and a transfer material transfer means for transferring a toner image on the transfer belt to a transfer material. The transfer belt according to claim 1, 2, 3, 4 or 5 is used as the transfer belt.
The transfer device according to claim 7 is the transfer device according to claim 6, further comprising a detent means for restricting movement of the transfer belt in the axial direction of the support roller, and the transfer belt being driven and rotated by the support roller. The tension per unit length in the width direction of the belt is 0.5 N / cm or more and 1.1 N / cm or less.
Further, the invention of claim 8 is the transfer device according to claim 6 or 7, wherein the tensile strength of the base layer of the transfer belt is X [MPa], the average thickness of the base layer is t _B [mm], and the support When the maximum tension per unit length in the width direction of the transfer belt that is supported by a roller and driven to rotate is defined as T _M [N / cm], X · t _B ≧ 2 × T _M is satisfied. To do.
According to a ninth aspect of the present invention, a latent image carrier, toner image forming means for forming a toner image on the latent image carrier, and a toner image on the latent image carrier are primarily transferred to an intermediate transfer member. 7. An image forming apparatus comprising: an intermediate transfer unit that secondarily transfers a toner image on the intermediate transfer member to a recording medium, wherein the intermediate transfer member is the transfer belt as the intermediate transfer unit. 7 or 8 transfer devices are used.
The invention according to claim 10 is the image forming apparatus according to claim 9, wherein a transfer facing member is brought into contact with and opposed to a portion of the intermediate transfer member supported by the support roller, and the primary transfer and the secondary transfer, respectively. The contact force per unit length in the width direction of the intermediate transfer body of each transfer facing member in the primary transfer nip portion and the secondary transfer nip portion where the transfer is performed is 0.05 N / cm or more and 1.0 N / cm or less. It is characterized by.

  In the image forming apparatus, the rotation direction dimension L1 of a portion of the outer peripheral surface of the surface layer of the intermediate transfer member passing through the primary transfer nip portion, and the portion of the portion passing through the secondary transfer nip portion. The difference from the rotation direction dimension L2 is preferably 3 times or less with respect to the 10-times length dimension of the minimum pixel diameter LD in the sub-scanning direction on the latent image carrier. In this case, the expansion and contraction of the base layer of the intermediate transfer member during primary transfer and secondary transfer is suppressed to almost zero, and the rotation of the intermediate transfer member surface integrated with the base layer via the intermediate layer occurs in the rotational direction. Difficult, the dimensional difference in the rotational direction becomes slight. For this reason, vibration due to expansion and contraction in the rotational direction of the surface of the intermediate transfer member is very small, speed stability is improved, and a transfer image with good dimensional stability can be formed.

According to the first aspect of the present invention, the interface portion between the base layer and the intermediate layer of the transfer belt is formed so that the irregularities formed on the surfaces of the respective layers that are in contact with each other are engaged with each other. As described above, the irregularities on the surface of the base layer and the surface of the intermediate layer are fitted into each other, so that the contact area between the base layer and the intermediate layer is increased and the maximum static friction coefficient of the intermediate layer with respect to the surface of the base layer is increased. As a result, when the intermediate layer expands and contracts in the circumferential direction without expanding or contracting during use of the transfer belt, the surface portion in contact with the base layer of the intermediate layer tends to shift in the direction along the interface with respect to the base layer. An anchoring effect that stops the squealing occurs, and the intermediate layer becomes difficult to peel from the base layer. Therefore, when a three-layer structure is used to suppress the occurrence of abnormal images such as missing characters and worm-eating, it is possible to extend the life by preventing peeling at the interface between the intermediate layer and the base layer constituting the three-layer structure. There is an effect that can be.
According to the invention of claim 2, when the thickness of the intermediate layer is t [μm], the maximum height Rz [μm] of the surface roughness of the intermediate layer side of the base layer is 3 ≦ Rz <(t / 2) By being in this range, the irregularities on the surface of the base layer and the surface of the intermediate layer that are in contact with each other are fitted into each other and bite into each other. As described above, the irregularities on the surface of the base layer and the surface of the intermediate layer are fitted into each other, so that the contact area between the base layer and the intermediate layer is increased and the maximum static friction coefficient of the intermediate layer with respect to the surface of the base layer is increased. As a result, when the intermediate layer expands and contracts in the circumferential direction without expanding or contracting during use of the transfer belt, the surface portion in contact with the base layer of the intermediate layer tends to shift in the direction along the interface with respect to the base layer. An anchoring effect that stops the squealing occurs, and the intermediate layer becomes difficult to peel from the base layer. Therefore, when a three-layer structure is used to suppress the occurrence of abnormal images such as missing characters and worm-eating, it is possible to extend the life by preventing peeling at the interface between the intermediate layer and the base layer constituting the three-layer structure. There is an effect that can be.

Hereinafter, an embodiment in which the present invention is applied to a color laser printer (hereinafter simply referred to as “printer”) as an image forming apparatus will be described.
First, the overall configuration of the printer according to the present embodiment will be described.
FIG. 1 is a schematic configuration diagram of a printer according to the present embodiment. In FIG. 1, around a drum-shaped photoconductor 1 as a latent image carrier rotating in the direction of an arrow, a photoconductor cleaning unit 2, a charger 4 as a charging means for uniformly charging the photoconductor, and image information. In accordance with the above, an exposure unit 5 as an exposure means for irradiating the photosensitive member 1 with light, developing means 6, 7, 8, 9 for developing the electrostatic latent image on the photosensitive member 1, and an intermediate transfer member (transfer belt) A transfer device having the intermediate transfer belt 10 is disposed. The toner image forming means for forming a toner image on the photosensitive member 1 includes the charger 4, the exposure unit 5, the developing means 6, 7, 8, 9 and the like.

  The developing means includes four developing units, a yellow developing unit 6, a magenta developing unit 7, a cyan developing unit 8, and a black developing unit 9. When forming a full-color image, a toner image (visible image) is formed in the order of the yellow developing device 6, the magenta developing device 7, the cyan developing device 8, and the black developing device 9, and the toner images of the respective colors are sequentially superimposed on the intermediate transfer belt 10. A full color image is formed by the transfer. The surface of the photoreceptor 1 after the toner image is transferred to the intermediate transfer belt 10 is cleaned by the blade 3 of the photoreceptor cleaning unit 2.

Next, the intermediate transfer belt 10 and a transfer apparatus including the intermediate transfer belt 10 will be described.
The intermediate transfer belt 10 is stretched by a plurality of support rollers (a driving roller 13, a primary transfer bias roller 11, and driven rollers 12a and 12b), and is driven by a driving motor (not shown). A pressure contact force of a primary transfer bias roller 11 as a primary transfer member that is in pressure contact with the photoreceptor 1 via the intermediate transfer belt 10 is adjusted by a pressure contact spring 30.

  The intermediate transfer belt 10 has a three-layer structure of a surface layer 110, an intermediate layer 120, and a base layer (back layer) 130 from the outer peripheral surface side (photoreceptor side) in the thickness direction. The surface layer 110 has elasticity in the circumferential direction (belt rotation direction). The intermediate layer 120 has elasticity in the circumferential direction and the thickness direction. The base layer 130 is non-stretchable in both the circumferential direction and the thickness direction.

The base layer 130 of the intermediate transfer belt 10 is preferably a film made of a resin that does not hinder smooth rotation as an intermediate transfer belt that is easy to bend and difficult to stretch. Examples of such a resin include known thermoplastic resins, thermoplastic elastomers, and thermosetting resins. Specific materials for this resin include PVDF (vinylidene fluoride), ETFE (ethylene-tetrafluoroethylene copolymer), PI (polyimide), PC (polycarbonate), polyester resin, polyamide resin, polyurethane resin, poly Examples include ether resins and polyvinyl resins. A layer having a volume resistivity in the range of 10 ⁷ to 10 ¹⁵ Ωcm is formed of a mixed / synthetic material in which an electrical resistance is adjusted by dispersing a conductive material (conductive filler) in a resin made of such a material. The base layer 130 is suitable. For example, the material of the base layer 130 is preferably PI (polyimide) in which carbon is dispersed as a conductive filler. A resin such as polyester in which a metal oxide such as titanium oxide or zinc oxide is dispersed can also be used as the conductive filler. Moreover, resin and elastomers, such as PVDF (vinylidene fluoride) which have ion conductivity by themselves without dispersing the conductive filler, can also be used.

  Further, the thickness of the base layer 130 is preferably 20 μm or more so as not to be easily damaged. In addition, the intermediate transfer belt 10 has a dielectric thickness (= thickness / dielectric constant) that is difficult to decrease, and the intermediate transfer belt 10 is wound around the driving roller 13 without slack without applying a large tension. Therefore, the thickness of the base layer 130 is preferably 150 μm or less. A more preferable range of the thickness of the base layer 130 is 40 to 80 μm.

  As the elastic material used for the surface layer 110 and the intermediate layer 120 of the intermediate transfer belt 10, rubber, elastomer, resin, or the like can be used. For example, as rubber and elastomer, natural rubber, epichlorohydrin rubber, acrylic rubber, silicone rubber, fluorine rubber, polysulfide rubber, polynorbornene rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, butyl rubber, ethylene-propylene rubber , Ethylene-propylene copolymer, chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, acrylonitrile butadiene rubber, urethane rubber, syndiotactic 1,2-polybutadiene, hydrogenated nitrile rubber, and thermoplastic elastomers (eg, polystyrene, polyolefin, One type or two or more types from polyvinyl chloride, polyurethane, polyamide, polyester, and fluororesin) can be used.

  Examples of resins that can be used for the surface layer 110 and the intermediate layer 120 include phenol resin, epoxy resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, polyvinylidene chloride, ionomer resin, polyurethane resin, silicone resin, Fluorine resin, ketone resin, polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene -Acrylate ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer and styrene-acrylic copolymer) Acid phenyl copolymers, etc.), styrene-methacrylate copolymers (styrene-methyl methacrylate copolymers, styrene-ethyl methacrylate copolymers, styrene-phenyl methacrylate copolymers, etc.), styrene-α- Styrenic resins (monopolymer or copolymer containing styrene or styrene-substituted product) such as methyl chloroacrylate copolymer and styrene acrylonitrile-acrylic acid ester copolymer, methyl methacrylate resin, butyl methacrylate resin, acrylic Ethyl acid resin, butyl acrylate resin, modified acrylic resin (silicone modified acrylic resin, vinyl chloride resin modified acrylic resin, acrylic / urethane resin, etc.), vinyl chloride resin, styrene-vinyl acetate copolymer, vinyl chloride-vinyl acetate Polymer, rosin modified maleic acid tree , Ethylene - ethyl acrylate copolymer, xylene resin, polyvinyl butyral resin, it is possible to use one kind or two or more kinds of polyamide resins and modified polyphenylene oxide resin.

Further, in order to adjust the electric resistance of the intermediate transfer belt 10, various conductive agents can be added to the rubber, elastomer and resin described above. Conductive agents include carbon, metal powders such as aluminum and nickel, metal oxides such as titanium oxide, quaternary ammonium salt-containing polymethyl methacrylate, polyvinylaniline, polyvinylpyrrole, polydiacetylene, polyethyleneimine, and boron-containing polymer compounds. In addition, one kind or two or more kinds of conductive polymer compounds such as polypyrrole can be used. Even when the conductive agent is added as described above, it is preferable to adjust the volume resistivity of the intermediate transfer belt 10 to be in the range of 10 ⁷ to 10 ¹⁵ Ωcm.

The elastic modulus of the intermediate layer 120 is preferably about 10 to 300 MPa when compressed at 20%. The mid layer 120 preferably has a JIS-A hardness of 10 degrees to 70 degrees.
The elastic modulus of the surface layer is preferably about 300 to 1000 MPa when compressed at 20%.

  Further, the surface of the intermediate transfer belt 10 may be coated with a release layer as necessary. Materials used for this coating include ETFE, PTFE (polytetrafluoroethylene), PVDF, PEA (perfluoroalkoxy fluororesin), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PVF (fluorine). Fluorine resin such as vinyl chloride) can be used, but is not limited thereto.

  FIG. 2 is a cross-sectional view illustrating a configuration example of the intermediate transfer belt 10 according to the present embodiment. In FIG. 2, the base layer 130 on the back side has the above-mentioned predetermined thickness (20 to 150 μm), so that it hardly expands and contracts under tension during actual use and is strong against bending deformation and is in close contact with the driving roller 13 for stable running. It has the characteristics to do. The intermediate layer 120 is a layer having a hardness that prevents concentration of pressure that exerts a change in toner characteristics and relaxes the pressure. The thickness of the intermediate layer 120 is preferably about 50 to 300 μm. The surface layer 110 is much thinner than the intermediate layer 120, and the thickness is preferably about 1 to 30 μm. The tensile strength of the surface layer 110 is preferably higher than that of the intermediate layer 120.

  FIG. 3 is an enlarged cross-sectional view of an interface portion between the intermediate layer 120 and the base layer 130 of the intermediate transfer belt 10 of FIG. The interface 140 between the base layer 130 and the intermediate layer 120 is formed so that the irregularities formed on the surfaces of the layers 120 and 130 that are in contact with each other are engaged with each other. As described above, the irregularities of the surface of the base layer 130 and the surface of the intermediate layer 120 are fitted into each other, so that the contact area between the base layer 130 and the intermediate layer 120 increases and the maximum of the intermediate layer 120 with respect to the surface of the base layer 130 is obtained. The coefficient of static friction increases. Accordingly, when the intermediate layer 120 does not expand and contract during the use of the intermediate transfer belt 10 and the intermediate layer 120 expands and contracts in the circumferential direction, the surface portion of the intermediate layer 120 in contact with the base layer 130 is at the interface with the base layer 130. An anchoring effect that stops the shifting in the direction along the direction is generated, and the intermediate layer 120 is difficult to peel off from the base layer 130.

  2 and 3, the surface of the base layer 130 on the intermediate layer side is a surface obtained by roughening the surface of the belt-shaped material. Further, the surface of the intermediate layer 120 on the base layer side is formed so as to bite into each of a large number of recesses formed on the surface of the base layer 130 so as to contact the base layer 130. Here, the surface roughness Rz (maximum height of JISB0601-2001) on the intermediate layer side of the base layer 130 is preferably 3 μm or more. In the case of Rz ≧ 3 μm, the intermediate layer 120 and the surface layer 110 are laminated on the base layer 130 to obtain a laminated type intermediate transfer belt having a highly durable elasticity that prevents the lamination interface from peeling off when used with the intermediate transfer belt 10. be able to. Further, when the thickness of the elastic intermediate layer 120 is t [μm], the surface roughness Rz (maximum height of JIS B 0601-2001) of the intermediate layer side of the base layer 130 is from (t / 2). Is preferably small. In the case of Rz ≧ (t / 2) that does not satisfy this range, the thickness unevenness of the intermediate layer 120 tends to be large, and the surface hardness is difficult to effectively decrease in a thin portion. Therefore, transfer pressurization (a general pressurization force mechanically applied by belt tension or pressing of a transfer bias applying means, 0.1 to 1.0 [N / cm] in terms of linear pressure in the driving roller axial direction. It is difficult to prevent “character dropout”, “worm-eaten”, and abnormal images called “transfer dust” that occur in voids around the toner image.

The surface roughness Rz (maximum height of JIS B 0601-2001) is measured with the following measuring device and conditions.
・ Measuring instrument: stylus type surface roughness measuring instrument (Tokyo Seimitsu Co., Ltd .: “Surfcom”)
・ Tip tip radius: 2μm
-Stylus pressure: 0.07gf
・ Measurement length 2.5mm
・ Measurement speed 0.3mm / s
・ Cutoff wavelength 0.8mm
・ Inclination correction, least square line

  Further, it is preferable that the value of the surface roughness Rsm of the base layer 130 (average length of contour curve elements of JIS B 0601-2001. Average interval of unevenness) is shorter than the shortest diameter of the minimum pixel of the image.

  The predetermined surface roughness of the surface of the base layer 130 can be obtained by making the mold surface of the molding a considerable roughness surface. In addition, if it is difficult to separate from the mold after molding and hardening, the surface of the base layer 130 is molded by a known sandblasting process, or a volume average particle size of 4 μm or more is added to the volume resistance of the same order as that of the base layer 130 to add resistance. Roughening treatment such as immobilization treatment may be performed on the surface of the resin fine particles adjusted with the adhesive together with the adhesive.

2 and 3, the intermediate layer (elastic layer) 120 is a layer laminated on the base layer 130 subjected to the surface roughening. The intermediate layer 120 is a layer that gives the surface of the intermediate transfer belt 10 stretchable elasticity that is easily adapted to the surface shape of the photoreceptor 1 that has become an irregular surface by carrying a toner image. In this way, by giving the surface of the intermediate transfer belt 10 a stretchable elasticity that is easily adapted to the surface shape of the photosensitive member 1, the pressure applied to the toner image is dispersed to prevent the character from being lost and to transfer with improved adhesion. Transfer dust at a so-called transfer nip where an electric field acts can be prevented. As the material of the intermediate layer 120, chloroplane rubber (CR) in which carbon is dispersed as a conductive filler is suitable. In addition, metal oxides such as titanium oxide and zinc oxide can be used as the conductive filler, and silicon and EPDM can be used as the rubber. Also, a rubber such as urethane that does not disperse the conductive filler and has ion conductivity by itself can be used.
The thickness of the intermediate layer 120 is sufficient to exhibit elasticity, and when it is wound around a support roller such as the drive roller 13 that supports the intermediate transfer belt 10, the outer periphery is little stretched and the surface layer is cracked. In order that the rubber itself does not easily approach the yield point and does not easily become brittle over time, 50 to 500 μm is preferable.

  2 and 3, it is desirable that the surface layer 110 has releasability so that the toner can be easily separated from the intermediate transfer member when subjected to the secondary transfer action and the cleaning action. The thickness of the surface layer 110 is preferably 1 to 20 μm so that the surface layer 110 will not be completely worn away by abrasion and the elastic effect of the intermediate layer 120 is sufficiently exerted on the surface of the intermediate transfer belt.

  FIG. 4 is a cross-sectional view showing still another configuration example of the intermediate transfer belt 10 of the present embodiment. FIG. 5 is an enlarged cross-sectional view of an interface portion of the intermediate transfer belt 10. In this example, the base layer 130 ′ is made of a foamable material having voids such as foamable polyurethane, or a porous material such as porous polyimide whose resistance is adjusted with carbon or the like. However, since the drive from the drive roller 13 needs to be smoothly transmitted to the intermediate transfer belt 10 without deviation from the peripheral speed of the drive roller 13 and the occurrence of image expansion and contraction must be eliminated, A foam or porous material that has very little expansion and contraction is used. In the case of the intermediate transfer belt 10, a part of the intermediate layer 120 enters into the hole of the surface of the foamable material or porous material of the base layer 130 ′, the adhesive strength at the interface between the two layers is increased, and peeling between the two layers is prevented. Further, it is less likely to occur, and the performance of the intermediate transfer belt 10 can be stabilized.

  As the foamable material constituting the base layer 130 and the intermediate layer, a foam having a flexible, non-porous, vapor-impermeable outer skin on the surface by combining the foam on the surface by heating on the surface (For example, refer to JP-A-5-085577). In the case of a foam having such an outer skin, the water vapor permeation preventing property is excellent, the electrical properties (resistance and dielectric constant) are stabilized, and the wear resistance, fracture resistance and flexibility are increased.

  FIG. 6 is a cross-sectional view showing another configuration example of the intermediate transfer belt 10 of the present embodiment. FIG. 7 is an enlarged cross-sectional view of an interface portion of the intermediate transfer belt 10. In this configuration example, the intermediate layer 120 ′ is made of a foamable material having voids such as foamable polyurethane. Since the voids become narrower when compressed and the volume of the entire layer is reduced, the compressive strain is difficult to propagate in the rotational direction, and the tangential shearing force that leads to peeling is less likely to act on the joint surface with the base layer 130. . Therefore, not only the effect of reducing the maximum load on the toner, but also a remarkable peeling prevention effect can be obtained for the intermediate transfer belt 10.

  Further, the surface of the intermediate layer of the intermediate transfer belt 10 on the intermediate layer side is configured to have a large number of dense projections, and the material of the dense projections has a characteristic that does not expand and contract in the rotational direction of the intermediate transfer belt 10. You may make it use. In this case, the heterogeneous material of the intermediate layer 120 having elasticity can be easily and stably disposed on the periphery of the dense protrusion, and the performance of the intermediate transfer belt 10 can be stabilized. Examples of a method for manufacturing a belt portion having dense projections on the base layer 130 of the intermediate transfer belt 10 include a casting method and a centrifugal molding method. The shape of the dense protrusion can be adjusted by adjusting the shape of the mold side corresponding to the surface of the belt portion having the dense protrusion. If necessary, the surface on the intermediate layer side of the base layer 130 having the dense protrusions may be adjusted by blasting.

  If the tension of the intermediate transfer belt 10 is as small as possible to ensure running stability, the effect of the present invention can be further enhanced. Specifically, the tension per unit length in the width direction (drive roller axial direction) of the intermediate transfer belt 10 supported by a plurality of support rollers and driven to rotate is 0.5 N / cm to 1.1 N / A range of cm or less is preferred.

The upper limit of the volume resistivity ρv of the intermediate transfer belt 10 (the average value of the volume resistivity ρv between the intermediate transfer belt surfaces) is 10 ¹⁵ Ωcm, but the volume resistivity ρv of the intermediate transfer belt 10 is 10 ¹³ Ωcm or less. Is more preferable. When the volume resistivity ρv exceeds 10 ¹³ Ωcm, the transfer bias necessary for transfer increases, which causes an increase in power supply cost. Further, since the charging potential of the intermediate transfer belt 10 becomes high, it is necessary to repeat the static elimination process a plurality of times, resulting in a problem that the time of the entire image forming operation is lengthened and the mechanical life is shortened.
On the other hand, the lower limit of the volume resistivity ρv of the intermediate transfer belt 10 is 10 ⁷ Ωcm, but the volume resistivity ρv of the intermediate transfer belt 10 is more preferably 10 ⁸ Ωcm or more. When the volume resistivity ρv is less than 10 ⁸ Ωcm, the charge potential decays quickly, which is advantageous for static elimination. However, the current during transfer flows in the direction of the surface upstream of the transfer nip, and there is a gap between the photoconductor 1 and the surface. Since the surface potential of the intermediate transfer belt 10 is greatly increased, toner scattering occurs.

The average value R _V of the volume resistivity between the primary transfer bias application electrode and the surface of the intermediate transfer belt is not less 10 ⁸ [Omega] cm or more and an average value R _S of the rear surface of the surface resistance of the intermediate transfer belt 10 greater than R _V It is preferable to do this. In this case, it is possible to suppress an increase in the electric field in a minute gap between the photosensitive member 1 upstream and downstream of the primary transfer nip in the belt moving direction and the intermediate transfer belt 10, and to achieve both high-efficiency transfer and transfer dust prevention. Can be improved.

  Further, in FIG. 1, it is preferable that the electrode shifted to the different polarity side from the primary transfer bias is in contact with or close to the back surface of the intermediate transfer belt 10 (not shown) upstream of the primary transfer nip in the belt moving direction. In this case, the surface potential of the intermediate transfer belt 10 can be shifted to a different polarity side from the primary transfer nip portion upstream of the primary transfer nip in the belt moving direction, and discharge in the gap upstream of the transfer nip can be prevented. Can be prevented.

  In FIG. 1, it is preferable that the electrode shifted to the different polarity side from the primary transfer bias is in contact with or close to the back surface of the intermediate transfer belt 10 (not shown) downstream of the primary transfer nip in the belt moving direction. In this case, the surface potential of the intermediate transfer belt 10 on the downstream side of the primary transfer nip in the belt moving direction can be shifted to a different polarity side from the primary transfer nip portion, and discharge in the gap on the downstream side of the transfer nip can be prevented. And reverse transcription can be prevented.

  The transfer pressure is preferably set as follows. The force applied to the primary transfer bias roller 11 when an intermediate transfer (primary transfer) bias is applied to the intermediate transfer belt 10 is preferably 1 to 10 N / image width (about 30 cm width). The force applied to the secondary transfer bias roller 14 when applying a secondary transfer bias for transferring (secondary transfer) from the intermediate transfer belt 10 to a transfer sheet as a recording medium is 10 to 40 N / image width (about 30 cm). Width) is preferred.

Here, the contact force between the photoreceptor 1 and the intermediate transfer belt 10 caused by the pressure contact by the primary transfer bias roller 11 is preferably in the range of 5 × 10 ⁻⁴ Mpa or more and 5 × 10 ⁻² Mpa or less. Within this range, transferability deterioration due to insufficient pressure contact force and toner aggregation due to overpressure contact can be prevented, transfer efficiency can be improved, and occurrence of void images can be more reliably prevented.

  Further, the surface of the intermediate transfer belt 10 has elasticity, and the surface microhardness is in the range of 30 to 70 degrees as measured by a micro rubber hardness meter (for example, MD-1 manufactured by Kobunshi Keiki Co., Ltd.). preferable. By having such a surface micro hardness, it is possible to prevent the transfer pressure from being concentrated on the toner image portion at the primary transfer nip portion, and to prevent a non-electrostatic adhesion increase between the toner image and the photoreceptor 1 during the primary transfer. , Primary transfer transcription can be prevented. Furthermore, irrespective of the surface properties of the transfer paper as a recording medium, transfer can be performed without occurrence of white spots, voids, crushed characters, color shifts, and the like.

Further, it is preferable that the static friction coefficient μ ₁ measured by the Euler belt method of the intermediate transfer belt 10 is relatively larger than the static friction coefficient μ ₂ of the photoreceptor 1 (μ ₁ ≧ μ ₂ ). In this case, the non-electrostatic adhesion between the toner image and the image carrier during primary transfer can be further suppressed, and primary transfer transfer can be prevented. In order to obtain the relationship of the predetermined static friction coefficient (μ ₁ ≧ μ ₂ ), for example, a little silicone oil SH200 (manufactured by Toray Dow Corning Silicone) is used for the protective layer on the surface of the photoreceptor 1 (0.1 by 0.1). Or a known technique such as applying a lubricant such as zinc stearate to the surface of the photoreceptor 1 can be used.

In the developing means 6, 7, 8, and 9, it is preferable to use a toner having an average circularity of 0.90 to 0.99, which is a nearly spherical toner such as a polymerized toner. In this case, an increase in non-electrostatic adhesion between the toner image and the photoreceptor 1 can be suppressed, the primary transfer electric field strength can be suppressed, and primary transfer transfer leakage can be prevented.
In addition, a toner in which a release agent such as wax is included in the base toner constituting the toner so that oil application is not required in the fixing portion, and the release agent is present on the toner surface slightly. Is preferable. In this case, the increase in non-electrostatic adhesion between the toner image and the photoreceptor 1 can be suppressed, the primary transfer electric field strength can be further suppressed, and primary transfer transfer can be prevented.
In addition, hydrophobic inorganic fine particles are externally added to the base toner, and silica (SiO ₂ ) is more preferably externally added. By this external addition, the fluidity of the toner is improved, the increase in non-electrostatic adhesion between the toner image and the photosensitive member 1 can be suppressed, and the primary transfer electric field strength can be suppressed. Here, as said silica, what hydrophobized the surface by the silane coupling agent, silicone oil, etc. is still more preferable.

Next, a method for measuring the electrical resistance (volume resistivity, surface resistivity) of the intermediate transfer belt 10 will be described.
The surface resistivity and volume resistivity are measured based on JIS K6911 5.13.1. That is, for the surface resistivity, an insulation resistance measuring device defined in JIS K6911 5.12 is connected between the outer annular surface electrode and the inner disk-shaped surface electrode of the test piece according to the conditions of JIS K69115.13. Measured. Further, the volume resistivity was measured by connecting the surface electrode and the back electrode of the test piece according to the conditions of JIS K6911 5.13 to the above insulation resistance measuring apparatus. Moreover, as another measuring method of electric resistance (volume resistivity, surface resistivity), it can also carry out by the method prescribed | regulated to JIS3256.

The measuring method of "JIS K6911 5.13.1" is shown below.
FIG. 8 shows the electrode arrangement of the resistivity test of “JIS K6911 5.13.1”. FIG. 8A shows a front electrode, and FIG. 8B shows a back electrode. In addition, the dimension unit in FIG. 8 is [mm]. FIG. 9 shows an electrode connection method of “JIS K69115.13.1”. FIG. 9A shows the case of the volume resistivity test, and FIG. 9B shows the case of the surface resistivity test.
(1) Apparatus (1.1) Conductive rubber or moisture-permeable conductive paint cut into the shape of the hatched portion in FIG.
(1.2) Power supply, insulation resistance measuring instrument and switch from (1.1.2) to (1.1.4) of “JIS K6911 5.12.1”.
(1.3) Micrometer An outer micrometer specified in JIS B 7502 or one having an accuracy equivalent to or better than this.
(1.4) Vernier caliper An outer micrometer specified in JIS B7507 or having an accuracy equivalent to or better than this.
(2) Test piece A test piece formed into a disk having a diameter of about 100 mm and a thickness of 2 mm is used.
(3) Pretreatment The test piece is pretreated at C-90 (+ 4-2) h / 20 ± 2 ° C./(65±5)% RH.
(4) Method: The thickness of the treated test piece is accurately measured to 0.01 mm with an outer macrometer, and conductive rubber is arranged as shown in FIG. Moreover, as shown in FIG. 8, it can draw on a test piece with a moisture-permeable conductive paint, and can be set as an electrode. In this case, the test piece is treated after drawing the electrode, and care is taken so that the moisture-permeable conductive paint does not peel off from the test piece during operation. The outer diameter of the inner circle of the surface electrode and the inner diameter of the annular electrode are measured to 0.02 mm with a caliper. When measuring the volume resistivity, as shown in FIG. 9A, when measuring the surface resistivity, as shown in FIG. This is further connected to the position of the test piece of the circuit similar to 5.12, charged for 1 minute, and measured for volume resistance and surface resistance. In this case, the test is performed under conditions of a temperature of 20 ± 2 ° C. and a relative humidity (65 ± 5)%.
(5) Calculation The volume resistivity and the surface resistivity are calculated by the following equations.
ρ _V = (πd ² / 4T) × R _V ,
ρ _S = {π (D + d) / (D−d)} × R _S
Here, ρv: volume resistivity [MΩcm], ρs: surface resistivity [MΩ], d: outer diameter of inner circle of surface electrode, T: thickness of test specimen [cm], Rv: volume resistivity [ MΩ], D: inner diameter [cm] of the annular electrode on the surface, Rs: surface resistance [MΩ], and π: circumferential ratio = 3.14.

(1.1) of the above “JIS K6911 5.12.1” is shown below.
FIG. 10 is a diagram showing an insulation resistance measuring device according to (1.1) of “JIS K6911 5.12.1”.
(1.1) Insulation resistance measuring device: having an electrode, a power source, a galvanometer, a universal shunt, a switch and the like as illustrated in FIG.
(1.1.1) A brass taper pin (1.1.2) having a diameter of 5 mm and having no scratch on the surface as defined in the electrode “JIS B1352” (1.1.2) A dry battery or a storage battery having a power supply DC voltage of 500V. However, a power source that has flowed alternating current may be used as long as it can be confirmed that a constant direct current voltage is maintained.
(1.1.3) Insulation resistance measuring instrument (1.1.3.1) When measuring an insulation resistance value of 1 MΩ or more and less than 10 ⁶ MΩ (comparative method) Standard resistance is 1 MΩ manganin or an accuracy equivalent to or better than that. The universal shunt shall be precise to adjust the galvanometer runout and measurement range. The galvanometer is highly sensitive with a stable 0 point, and if there is a 1 mm deflection at a distance of 1 m due to a current of 10 ⁻¹⁰ A, a resistance of less than 10 ⁶ MΩ with an accuracy of ± 10% Can be measured.
(1.1.3.2) When measuring an insulation resistance value of 5 MΩ or less, an insulation resistance meter specified in “JIS C 1302” is used.
(1.1.3.3) When measuring an insulation resistance value of 1 MΩ or more and less than 10 ⁸ MΩ Use a DC amplifier calibrated to an accuracy of ± 10%.
(1.1.4) Switch with appropriate insulation protection.

As another method for measuring electric resistance, “JISR3256 3” is shown below.
FIG. 11 is a diagram showing a surface resistance measurement method.
3. 3. Measurement method at room temperature 3.1 Test piece using measurement circuit composed of electrode-test piece system X, DC power source E, DC voltmeter V and ammeter A as shown in the principle diagram of measurement (FIG. 11) A surface resistivity is calculated from the surface resistance value obtained by applying a voltage to the surface and dividing the applied voltage by the current flowing on the surface of the test piece according to the calculation formula defined in 3.5. Note that a high insulation resistance meter is commercially available as a simple device for measuring the surface resistance in which the devices shown in FIG.
3.2 Measurement conditions and applied voltage: The test piece is left in an air-conditioned room at a temperature of 20 ± 2 ° C. and a relative humidity (50 ± 5)% for 16 hours or more, and then measured. The applied voltage to the test piece is 1000 V or less, and 500 V is the standard voltage. The voltage application time is 1 minute as a standard, and is changed depending on the material of the substrate glass.
3.3 Test piece preparation method: The test piece adjustment method is as follows.
a) Shape and dimension The test piece is a rectangle with a side of 50 mm or more or a disk with a diameter of 50 mm or more.
b) Surface condition of the test piece The test piece should be mirror-polished or have a surface condition equivalent thereto.
c) Cleaning and drying The test piece is first rubbed with a neutral detergent, then rinsed with tap water, and further ultrasonically cleaned in a solvent such as ultrapure water, acetone, ethanol, and the like. Drying may be performed using an oven or by natural drying.
d) Method for forming electrode on test piece The electrode is formed on the test piece by using a method such as vapor deposition or sputtering of a conductive material. Examples of the conductive material include gold and platinum. In this measurement method, it is desirable to use gold. Further, in this measuring method, since a high insulation resistance is measured, it is necessary to form a guard electrode in order to eliminate stray current of the electrode-test specimen system.
FIG. 12 is a diagram showing an example of a method for applying an electrode to a test piece, FIG. 12 (A) is a plan view, and FIG. 12 (B) is a front view.
e) Electrodes arranged on concentric circles as shown in the dimension drawing of the electrodes (FIG. 12) are used. In this case, the size of the main electrode can be changed in the range of about 26 to 36 mm in consideration of the sensitivity of the measuring apparatus, and the size of the gap can be adjusted.
3.4 an electrode is formed on the test piece by the procedure a) method shown in FIG. 12 of the measurement, the diameter D ₁ and the counter electrode of the main electrode inner diameter D ₂ 'JISB7507 "calipers or equivalent or more defined Measure with an accuracy of 0.05 mm using an accurate measuring device.
b) After the test piece is dried at about 120 ° C. for 2 hours or more, it is cooled in a desiccator.
c) The surface resistance is measured by the surface resistance measurement method of FIG. 11 under the measurement conditions and applied voltage defined in 3.2. The measuring device is preferably held in a shielded ultra-high resistance measurement box.
3.5 Calculation and number of measurements: The electrical resistivity of the substrate glass surface is calculated by the following formula.
ρs [Ω] = (Dmπ / g) Rs
Here, ρs: surface resistivity [Ω], Rs: surface resistance [Ω], Dm: average diameter [D ₁ + D ₂ ] / 2 [mm], D ₁ : main electrode diameter [mm], D ₂ : the inner diameter of the counter electrode [mm], g: gap _{(D 2 -D 1) [mm} ]
The measurement is performed twice, and the average value is taken as the surface resistivity measurement value.

Next, the measurement of the coefficient of static friction by the Euler method will be described.
FIG. 13 is a diagram schematically showing a method for measuring the surface friction coefficient by the Euler method. First, a piece of paper (TYPE 6200 A4 T: manufactured by Ricoh Co., Ltd.) is cut into 297 mm × 30 mm, and a thread 101 is attached to both ends to create a measurement paper piece 100. The properties of the paper pieces are as follows: weighing: 71.7 g / m2, thickness: 89 μm, density: 0.81 g / cm3, smoothness: table; 40 s, back: 37 s, volume resistance: 1.2E + 11 Ω · cm, friction coefficient: table / Back: (Rum with rubber) Tan θ, length: 0.64, width: 0.65. A piece of measuring paper 100 is placed on the photosensitive drum 1 supported by a support member 103 at one end of a table 102, a weight 104 of 0.98 N (100 g weight) is tied to one thread 101, and a digital push is applied to the other thread 101. The pull gauge 105 is connected. In this state, the digital push-pull gauge 105 pulls the measurement paper piece 100 through the thread 101, and the value of the digital push-pull gauge 105 when the measurement paper piece 100 starts moving is read. When the value at this time is F (N), the static friction coefficient μ is obtained by μ = (2 / π) × [ln (F / 0.98)].

  The belt cleaning unit 19 that can contact and separate from the intermediate transfer belt 10 includes a cleaning blade 18 and a contact / separation mechanism 26 that contacts and separates the cleaning blade from the intermediate transfer belt 10. During the primary transfer of the second, third, and fourth colors after the primary transfer of the image, the contact / separation mechanism 26 separates the surface from the surface of the intermediate transfer belt 10. The contact / separation mechanism 26 is in contact with a biasing means (not shown) that biases the cleaning unit 19 so that the cleaning blade 18 is in contact with the surface of the photosensitive member 1 and a bottom surface of the cleaning unit 19 that is swung. An eccentric cam that is rotationally driven by a control unit 200 (not shown) is used.

  Further, a belt position detection mark 23 is provided at an end in the width direction of the outer peripheral surface of the intermediate transfer belt 10, and an image forming process for each color is started at the timing when the mark 23 is detected by the mark sensor 24. Thus, accurate color superposition of each color image becomes possible. The technique of the present invention is effective in preventing color misregistration because there is no stretching distortion or change in the rotation direction of the intermediate transfer belt.

  The secondary transfer unit 15 includes a secondary transfer bias roller 14 and a contact / separation mechanism 16 that contacts and separates the secondary transfer bias roller 14 from the intermediate transfer belt 10. The contact / separation mechanism 16 includes a spring member as a biasing unit that biases the secondary transfer unit 15 so that the secondary transfer bias roller 14 is separated from the intermediate transfer belt 10, and a bottom surface on which the secondary transfer unit 15 swings. It is configured using an eccentric cam that is rotationally driven by a control unit 200 (not shown) while being in contact with the unit.

The secondary transfer bias roller 14 is configured by coating a metal core such as SUS with an elastic body such as urethane adjusted to a resistance value of 10 ⁶ to 10 ¹⁰ Ω with a conductive material. The resistance value of the secondary transfer bias roller 14 is measured by installing the secondary transfer bias roller 14 on a conductive metal plate and measuring 4.9N on one side (total of 9.8N on both sides) at both ends of the core metal. It calculated from the electric current value which flows when the voltage of 1000V is applied between a metal core and the said metal plate in the state which applied the load.

  The secondary transfer bias roller 14 is given a driving force by a drive gear (not shown), and the peripheral speed thereof is adjusted to be substantially the same as the peripheral speed of the intermediate transfer belt 10. The secondary transfer bias roller 14 is normally separated from the surface of the intermediate transfer belt 10, but collectively transfers four-color superimposed images formed on the surface of the intermediate transfer belt 10 onto a transfer sheet 22 as a transfer material. The secondary transfer bias is applied to the secondary transfer bias roller 14 by a high voltage power source (not shown) as a secondary transfer bias applying means that is pressed by the contact / separation mechanism 16 as the contact / separation means with timing. Thus, transfer from the intermediate transfer belt 10 to the transfer paper 22 is performed.

  Here, the primary transfer current supplied to the primary transfer bias roller 11 is preferably in the range of +20 to 50 μA, and the secondary transfer current supplied to the secondary transfer bias roller 14 is preferably in the range of +5 to 35 μA. .

  In the printer having the above-described configuration, the transfer paper 22 is fed by the paper feed roller 25 and the registration roller 21 at the timing when the leading end of the four-color superimposed image on the intermediate transfer belt 10 reaches the secondary transfer position. . The four-color superimposed image transferred to the transfer paper 22 is fixed by the fixing unit 17 and then discharged.

  The toner used in the printer preferably has a volume average particle size in the range of 4 to 10 μm. By reducing the particle size of the toner within the above range, toner scattering can be prevented and high-resolution image formation can be achieved. Deterioration of toner and toner aggregation can be prevented, and the occurrence of a void image can be effectively prevented.

As the binder resin used for the toner, all those conventionally used as the binder resin for toner can be applied. It is used alone or in admixture of two or more.
As the colorant used in the toner, it is possible to apply all dyes and pigments that have been conventionally used as toner colorants. In addition, generally the usage-amount of a coloring agent is 0.1-50 mass parts with respect to 100 mass parts of binder resin.

  In this embodiment, four colors of toner are used, but toner of three colors, two colors, single color, or five colors or more may be used. The color used may be any color, but it is preferable to select a color that can reproduce a full color. In particular, as described above, when the toner color is four colors of black, yellow, cyan, and magenta, the number of times of development can be reduced, and a relatively wide color tone range can be covered.

  Further, the toner may contain a charge control agent as necessary. Any known charge control agent can be used. The amount of charge control agent used is determined by the type of binder resin, the presence or absence of additives used as necessary, the toner production method including the dispersion method, etc., and is not limited uniquely. However, it is preferably used in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the binder resin. More preferably, the range of 2 to 5 parts by mass is good. Here, when the amount is less than 0.1 parts by mass, the toner is insufficiently charged and is not practical. On the other hand, when the amount exceeds 10 parts by mass, the chargeability of the toner is too high, and the electrostatic attraction force with the carrier, the developing sleeve or the like increases, and the image density is lowered due to spent or filming. If necessary, a plurality of charge control agents may be used in combination.

  The printer of this embodiment may be developed by a so-called one-component development method in which an electrostatic latent image is visualized by using toner alone as a developer, or a two-component developer obtained by mixing toner and a carrier. You may develop by the two-component developing method which visualizes an electrostatic latent image using. In the case of using the two-component development method, as the carrier to be used, conventional ones such as iron powder, ferrite and glass beads can be used. In addition, those carriers coated with resin can also be used. In any case, the mixing ratio of the toner and the carrier is generally about 0.5 to 6.0 parts by mass with respect to 100 parts by mass of the carrier.

  The toner may be mixed with an additive as necessary. Examples of the additives include fluidity imparting agents composed of inorganic fine particles such as hydrophobic silica, hydrophobic titanium oxide, and hydrophobic aluminum oxide, anti-caking agents, lubricants such as ethylene tetrafluoride resin and zinc stearate, carbon black, Conductivity imparting agents such as tin oxide, abrasives such as cerium oxide and silicon carbide, fixing aids such as low molecular weight polyolefins, and the like can be used. These may be used alone or in combination of two or more. The addition amount of these additives is desirably 0.1 to 5 parts by mass with respect to 100 parts by mass of the toner.

  In producing the toner, after mixing the constituent materials as described above in a mixer such as a Henschel mixer, the mixture is heated and kneaded in a kneader such as a continuous kneader or a roll kneader, and the kneaded product is cooled and solidified. A method of obtaining a desired average particle size by pulverization and classification is preferred. As other production methods, there are a spray drying method, a polymerization method, a microcapsule method and the like. The toner thus obtained can be sufficiently mixed with a desired additive with a mixer such as a Henschel mixer, if necessary, to produce a toner.

  The toner of this embodiment uses a polyester resin as a binder resin and a zinc salicylate derivative as a charge control agent as materials common to all colors. This zinc salicylate derivative is contained at a ratio of 4 parts by mass with respect to 100 parts by mass of the polyester resin. In addition, each color toner contains a colorant, and 5 parts by mass of carbon black in black toner and disazo type yellow pigment (CI PIGMENTYELLOW17 in yellow toner) with respect to 100 parts by mass of the polyester resin. ) Is 5 parts by weight, cyan toner contains 4 parts by weight of copper phthalocyanine blue pigment (CI PIGMENTBLUE15), and magenta toner contains quinacdrine magenta pigment (CI PIGMENTRED 184) at a ratio of 4 parts by weight. Yes.

The following ranges are preferred for the micro Vickers hardness H _T of the toner. That is, in the case of a pulverized toner that contains at least a resin, a pigment, and a charge control agent and is manufactured through a kneading process of this material, the micro Vickers hardness of the melt-solidified chip-shaped kneaded material after the kneading process is loaded. The measured value when repeatedly measured at 50 g or less is 49 [N / cm ² ] or more and 196 [N / cm ² ] or less (5 to 20 [kgf / cm ² ]), and the difference between the maximum value and the minimum value Is preferably 19.6 [N / cm ² ] (2 [kgf / cm ² ]) or more. In this case, a soft portion having a certain size exists in the uniform state of high hardness of the kneaded product. Therefore, the pulverization property is improved, and as a result, even when a toner having a small particle diameter is manufactured, the yield of the toner having a particle size distribution in a desired range is good and the manufacturing cost can be suppressed. Moreover, the filming after continuous use can be suppressed.

The toner hardness is measured with the following measuring apparatus and conditions.
Measuring equipment: “Microhardness tester DUH201” manufactured by Shimadzu Corporation
Measurement conditions: Indenter: Triangular pyramid 115 °, Weight: 1.96 × 10 ⁻² N (2.0 gf)
Sample molding: Pressurized pellet molding machine, pellet diameter 2cm,
Sample amount: 0.6g, load 6t

  In addition, this embodiment was described in order to make an understanding of this invention easy, Comprising: This invention is not limited. For example, in this embodiment, the photosensitive drum is used as the image carrier. However, the present invention is not limited to this and can be applied to all image carriers such as a photosensitive belt. In this embodiment, the photosensitive drum has a single form. However, the present invention can also be applied to a so-called quadruple tandem type full-color image forming system form using dedicated photosensitive drums for black, yellow, cyan, and magenta colors. It is. In this embodiment, the transfer roller is used as the primary transfer unit, but a contact transfer system such as a transfer brush, a transfer blade, and a transfer plate is used as well as a rotary contact transfer system such as a rotary transfer brush. The present invention is applicable to any image forming apparatus.

Next, an embodiment of an image forming apparatus (printer) provided with the intermediate transfer belt having the above configuration will be described. In the following examples, the evaluation of images on which image formation was performed was performed based on Tables 1 and 2. Here, the generation of a hollow image is evaluated by using OHP sheets and cardboard to evaluate print samples of characters and vertical and horizontal lines (both mixed patterns of single color, two colors, and three colors). Was evaluated according to the evaluation criteria shown in Table 1.

In addition, about the structure and conditions which are not prescribed | regulated specially in each Example, it was set as the following common setting.
Surface roughness Rz of the intermediate layer side surface of the base layer 130:
Lower limit: 3 μm
Upper limit: (intermediate layer thickness / 2) μm or (intermediate layer thickness−25) μm
Elastic modulus of intermediate layer 120: 10-300 MPa at 20% compression
Hardness of intermediate layer 120: 35 ± 5 degrees in JIS-A hardness Elastic modulus of surface layer 110: 500 MPa at 20% compression
Transfer pressure: 2 ± 0.5N / image width (about 30cm width)
(0.2 ± 0.05 Mdyn / image width (about 30 cm width))
(0.2 ± 0.05 kgf / image width (about 30 cm width))
Force applied to the secondary transfer bias roller 14 when applying the secondary transfer bias:
20 ± 5N / image width (about 30cm width)
(2 ± 0.5 Mdyn / image width (about 30 cm width))
(2 ± 0.5kgf / image width (about 30cm width))
Toner hardness: 9-11
Surface micro hardness of intermediate transfer belt 10: 40 ± 5 degrees Transfer bias application condition: 20 to 30 μA (primary transfer current)
25 to 35 μA (secondary transfer current)

[Examples 1-7]
Tables 3 and 4 show the configuration of the intermediate transfer belt 10 in Examples 1 to 7 and other conditions. Tables 3 and 4 also show the configuration of the intermediate transfer belt 10 in Comparative Examples 1 to 4 performed together with Examples 1 to 7 and other conditions.
Table 5 shows the evaluation results of the images obtained by image formation in Examples 1 to 7 and Comparative Examples 1 to 4.

[Examples A1, A2, B1, B2, C1, C2]
Table 6 shows the configuration of the intermediate transfer belt 10 and the other conditions in Examples A1, A2, B1, B2, C1, and C2. Table 6 also shows the configuration and other conditions of the intermediate transfer belt 10 in Comparative Examples A1, A2, B1, B2, C1, and C2 performed with Examples A1, A2, B1, B2, C1, and C2. ing.

(Example A1)
The material of the base layer (back layer) 130 of the intermediate transfer belt 10 is polyimide resin (PI) in which carbon is dispersed as a conductive filler.
The base layer 130 has a relative dielectric constant (vacuum relative dielectric constant of 1) of 11 ± 3, a tensile strength in the rotational direction of 300 MPa (speed 200 mm / min, 25 ° C.) or more, and a thickness of 40 ± 4 μm. is there.
Further, the surface roughness Rz (maximum height of JIS B 0601-2001) of the intermediate layer side surface of the base layer 130 is 3.5 ± 0.5 μm. Further, the surface roughness Rsm of the surface (average length of contour curve elements of JIS B 0601-2001. Average interval of irregularities) is 25 ± 10 μm, which is shorter than the shortest diameter of about 40 μm of the minimum pixel of the image. In order to obtain the predetermined surface roughnesses Rz and Rsm, the surface of the base layer 130 was subjected to sand blasting after molding.
As the intermediate layer (elastic layer) 120, chloroplane rubber (CR) having a thickness of 100 μm in which carbon was dispersed as a conductive filler was used.
As the surface layer 110, a PVDF elastomer having a thickness of 1.5 ± 0.5 μm, which has both ionic conductivity and releasability by itself, was used. The maximum static friction coefficient of the surface layer 110 was 0.45 on average. The maximum static friction coefficient was measured using the following friction coefficient measuring instrument.
-Measuring instrument: HEIDON portable friction meter muse (Static friction tester μs) type 94i
・ Measurement range: 0 to 1.300μs
・ Slider: Brass (hard chrome treatment) 40g
The portable tribometer muse type 94i used for the measurement is a brass (hard chrome treatment) disk with a flat slider (contactor) to be brought into contact with the intermediate transfer belt 10. The maximum static friction coefficient can be measured simply by bringing the main body slider into contact with the device under test (intermediate transfer belt 10). A force is gradually applied to the slider (contactor) installed at the bottom of the main unit, and the frictional force at the moment when the slider starts to slide on the DUT in contact can be converted and displayed. The average static friction coefficient of the number of measurements can also be displayed.

(Example A2)
The intermediate transfer belt 10 is made of the same material as in Example A1, and the surface roughness on the intermediate layer side of the base layer (back surface layer) 130 is 47 μm in Rz.

(Comparative Example A1)
The intermediate transfer belt 10 is made of the same material as in Example A1, and the surface roughness of the intermediate layer side of the base layer (back surface layer) 130 is 2.6 μm in Rz.

(Comparative Example A2)
The intermediate transfer belt 10 is made of the same material as in Example A1, and the surface roughness of the intermediate layer side of the base layer (back surface layer) 130 is 52 μm in Rz.

(Example B1)
As the base layer (back layer) 130, a foamable polyimide resin (foamed PI) in which carbon was dispersed as a conductive filler was used. The thickness of the base layer 130 was 40 ± 4 μm. The surface roughness on the intermediate layer side of the base layer (back surface layer) 130 was 3.5 ± 0.5 μm in Rz (maximum height of JIS B 0601-2001) as in Example A1.
The intermediate layer 120 and the surface layer 110 were made of the same material and thickness as in Example A1.

(Example B2)
The intermediate transfer belt 10 is made of the same material as in Example B1, and the surface roughness on the intermediate layer side of the base layer (back surface layer) 130 is 48 μm in Rz.

(Comparative Example B1)
The intermediate transfer belt 10 is made of the same material as in Example B1, and the surface roughness on the intermediate layer side of the base layer (back surface layer) 130 is 2.3 μm in Rz.

(Comparative Example B2)
The intermediate transfer belt 10 is made of the same material as in Example B1, and the surface roughness on the intermediate layer side of the base layer (back surface layer) 130 is 55 μm in Rz.

(Example C1)
As the base layer (back surface layer) 130, a polyimide in which carbon having a thickness of 40 ± 4 μm was dispersed was used as in Example A1. The surface roughness on the intermediate layer side of the base layer (back surface layer) 130 was also set to 3.5 ± 0.5 μm in Rz (maximum height of JIS B 0601-2001) as in Example A1.
As the intermediate layer (elastic layer) 120, foamed polyurethane (foamed PU) having a thickness of 100 μm in which carbon was dispersed as a conductive filler was used.
As the surface layer 110, the same type of material as that of Example A1 (PVDF elastomer having both ionic conductivity and releasability by itself) and an equivalent thickness (1.5 ± 0.5 μm) were used. Moreover, the maximum static friction coefficient of the surface layer 110 is 0.5 or less similarly to Example A1.

(Example C2)
The intermediate transfer belt 10 is made of the same material as in Example C1, and the surface roughness of the intermediate layer side of the base layer (back surface layer) 130 is 42 μm in Rz.

(Comparative Example C1)
The intermediate transfer belt 10 is made of the same material as in Example C1, and the surface roughness of the intermediate layer side of the base layer (back surface layer) 130 is 2.0 μm in Rz.

(Comparative Example C2)
The intermediate transfer belt 10 is made of the same material as in Example C1, and the surface roughness of the intermediate layer side of the base layer (back surface layer) 130 is 50 μm in Rz.

Table 7 shows images obtained by image formation and intermediate transfer in Examples A1, A2, B1, B2, C1, C2 and Comparative Examples A1, A2, B1, B2, C1, C2 with different materials and roughness Rz. The evaluation result of the adhesive strength of the belt is shown. The images were evaluated for the occurrence of abnormal images with missing characters (see Table 1) and transfer dust (see Table 2). As for the adhesive strength of the intermediate transfer belt, it is continuously used for 8 minutes at a tension 2 [N / cm] (linear speed 200 mm / sec) that is slightly more than twice the tension 1 [N / cm] per unit width in normal use. A running test was performed on the intermediate transfer belt 10 that was driven and expanded and contracted by ON-OFF, in which the tension was released when stopped for 2 minutes (OFF). Then, the driving time until peeling (floating) was confirmed between the base layer 130 and the intermediate layer 120 was evaluated as “peeling time”. As a result, in the case of Examples A1, A2, B1, B2, C1, and C2, it was found that the “peeling time” was significantly longer than in Comparative Examples A1, A2, B1, B2, C1, and C2. .

[Examples P1 to P4]
Table 8 shows the configuration of the intermediate transfer belt 10 in Examples P1 to P4, other conditions, and the image evaluation results. Table 8 also shows the configuration of the intermediate transfer belt 10 and other conditions in Comparative Examples P1 to P4 performed together with Examples P1 to P4, other conditions, and image evaluation results.

[Examples Q1-Q4]
Table 9 shows the configuration of the intermediate transfer belt 10 in Examples Q1 to Q4, other conditions, and the image evaluation results. Table 9 also shows the configuration and other conditions of the intermediate transfer belt 10 in Comparative Examples Q1 to Q4 performed together with Examples Q1 to Q4, and the image evaluation results.

[Examples R1 to R4]
Table 10 shows the configuration of the intermediate transfer belt 10 in Examples R1 to R4, other conditions, and the image evaluation results. Table 10 also shows the configuration and other conditions of the intermediate transfer belt 10 in Comparative Examples R1 to R4 performed together with Examples R1 to R4, and the image evaluation results.

[Examples S1 to S4]
Table 11 shows the configuration of the intermediate transfer belt 10 in Examples S1 to S4, other conditions, and the image evaluation results. In Table 11, the tensile strength X [MPa] is the tensile strength of the base layer 130 of the intermediate transfer belt 10, the average thickness t _B [mm] is the average thickness of the base layer 130, and the tension T _M [N / cm]. Is the maximum tension per unit length in the width direction of the intermediate transfer belt 10 supported by the roller and driven to rotate. Table 11 also shows the configuration and other conditions of the intermediate transfer belt 10 in Comparative Examples S1 to S4 performed together with Examples S1 to S4, and the image evaluation results.

As described above, according to the present embodiment, the interface portion between the base layer 130 and the intermediate layer 120 of the intermediate transfer belt 10 is so formed that the irregularities formed on the surfaces of the layers 130 and 120 that are in contact with each other are engaged with each other. Is formed. As described above, the irregularities on the surface of the base layer and the surface of the intermediate layer are fitted into each other, so that the contact area between the base layer 130 and the intermediate layer 120 increases and the maximum static friction coefficient of the intermediate layer 120 with respect to the surface of the base layer 130 is increased. growing. Accordingly, when the intermediate layer 120 does not expand and contract during the use of the intermediate transfer belt 10 and the intermediate layer 120 expands and contracts in the circumferential direction, the surface portion in contact with the base layer 130 of the intermediate layer 120 is at the interface with the base layer 130 An anchoring effect that stops the shifting in the direction along the direction is generated, and the intermediate layer 120 is difficult to peel off from the base layer 130. Therefore, when the three-layer structure of the base layer (non-stretchable), intermediate layer (stretchable), and surface layer (stretchable) is used to suppress the occurrence of abnormal images such as missing characters and worm-eating, the three-layer structure It is possible to prevent the peeling at the interface between the intermediate layer 120 and the base layer 130 constituting the structure and to extend the life.
Further, since the influence of the tension applied to the base layer 130 on the surface layer 110 can be mitigated by the presence of the stretchable intermediate layer 120, cracks generated in the surface layer 110 and retention of the cracks can be prevented. it can.
Further, according to the present embodiment, when the thickness of the intermediate layer 120 is t [μm], the maximum height Rz [μm] of the surface roughness of the base layer 130 on the intermediate layer side is 3 ≦ Rz <( It is in the range of t / 2). As shown in Examples A1, A2, B1, B2, C1, and C2 (see Tables 6 and 7), when Rz is 3 [μm] or more, the “peeling time” until the above peeling occurs is 50. Good adhesive strength over time can be achieved. In addition, when Rz is smaller than (t / 2) [μm], it is possible to reliably prevent the occurrence of abnormal images such as character dropout and transfer dust.
The upper limit of Rz may be defined as less than (t−25) [μm], that is, Rz <(t−25) [μm]. Further, when the thickness t of the intermediate layer 120 is 50 [μm], 3 [μm] ≦ Rz <25 [μm] is a preferable range.
In the present embodiment, it is preferable that at least one of the base layer 130 and the intermediate layer 120 of the intermediate transfer belt 10 is formed of a material having a foamable void. In this case, since it is possible to prevent the external additive from being stressed or buried in the transfer nip, it is possible to alleviate the stress that promotes the aggregation of the toner and the adhesion of the toner to the photoreceptor 1. effective. Therefore, transfer failure (transfer unevenness, etc.) can be suppressed by the effect of suppressing contact failure to the paper surface with low smoothness during transfer to transfer paper (secondary transfer). In addition, not only during operation but also in a stationary state, excessive compression deformation of the intermediate transfer belt 10 does not become excessive, so that it is possible to prevent problems such as character unevenness and transfer unevenness due to the impression of the intermediate transfer belt 10.
In this embodiment, the micro hardness H ₁ measured by the micro rubber hardness meter measured on the outer peripheral surface of the surface layer 110 of the intermediate transfer belt 10 is preferably 30 degrees or more and 70 degrees or less. As shown above in Example P1 to P3 (see Table 8), by microhardness H ₁ of the outer circumferential surface of the surface layer 110 of the intermediate transfer belt 10 is not less than 30 degrees, toner filming on the intermediate transfer belt 10 And surface abrasion can be prevented. Further, by microhardness H ₁ of the outer circumferential surface of the surface layer 110 is less than 70 degrees, the character in accordance with the adhesion of and pressure drop significantly applied to many places of the toner adhesion amount of the toner and the photosensitive member becomes stronger Occurrence of abnormal images such as omission can be prevented more reliably.
In this embodiment, the maximum coefficient of static friction measured by the Euler belt method measured on the outer peripheral surface of the surface layer 110 of the intermediate transfer belt 10 is preferably 0.5 or less. In this case, since the non-electrostatic adhesion force between the intermediate transfer belt 10 and the toner can be suppressed, there is little transfer residue and less cleaning residue at the time of secondary transfer. Filming can be reliably prevented.
Further, according to the present embodiment, the detent means for restricting the movement of the intermediate transfer belt 10 in the drive roller axial direction is provided. The tension (intermediate transfer belt tension) per unit length in the width direction of the intermediate transfer belt 10 supported by this roller and driven to rotate is preferably 0.5 N / cm or more and 1.1 N / cm or less. As shown in Examples Q1 to Q3 (see Table 9), when the tension of the intermediate transfer belt 10 is 0.5 N / cm or more, the tension is too weak and the running speed of the intermediate transfer belt becomes unstable. To prevent meandering. That is, if the tension of the intermediate transfer belt 10 is less than 0.5 N / cm, the running speed of the intermediate transfer belt 10 becomes unstable due to frictional resistance caused by a rubbing member such as a cleaning blade that comes into contact with the intermediate transfer belt, and it becomes easy to meander. , Belt breakage and belt end damage will occur. If the intermediate transfer belt 10 is too slack, the intermediate transfer belt 10 is detached from the detent means, causing meandering and displacement. Further, when the tension of the intermediate transfer belt 10 is 1.1 N / cm or less, the characteristic transfer with time, elongation and breakage of the intermediate transfer belt 10 can be prevented.
In the present embodiment, the intermediate transfer belt 10 is supported by a roller and driven to rotate by setting the tensile strength of the base layer 130 of the intermediate transfer belt 10 to X [MPa] and the average thickness of the base layer 130 to t _B [mm]. When the maximum tension per unit length in the width direction of 10 is T _M [N / cm], it is preferable that X · t _B ≧ 2 × T _M is satisfied. As shown above in Example S1 to S3 (see Table 11), by satisfying the above-mentioned _{X · t B ≧ 2 × T} M, the lifetime when using an intermediate transfer belt 10 is stretched 1% or more 1000 hours Further, the life of the intermediate transfer belt 10 can be extended.
Further, in this embodiment, each transfer facing in the primary transfer nip portion and the secondary transfer nip portion in which the transfer facing member is brought into contact with and opposed to the portion supported by the roller of the intermediate transfer belt 10 to perform primary transfer and secondary transfer, respectively. The contact force per unit length of the member in the width direction of the intermediate transfer belt 10 is preferably 0.05 N / cm or more and 1.0 N / cm or less. As shown in Examples R1 to R3 (see Table 10), when the contact force of each transfer facing member in the primary transfer nip portion and the secondary transfer nip portion is 0.05 N / cm or more, transfer dust and Occurrence of uneven transfer of the solid image can be prevented. Further, since the contact force of each transfer facing member at the primary transfer nip and the secondary transfer nip is 1.0 N / cm or less, it is difficult to apply excessive pressure to the toner image, and abnormal images such as missing characters are lost. Can be prevented more reliably.

1 is a schematic configuration diagram of a laser printer according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating a configuration example of an intermediate transfer belt. FIG. 3 is an enlarged cross-sectional view of the intermediate transfer belt in FIG. 2. FIG. 6 is a cross-sectional view of an intermediate transfer belt according to another configuration example. FIG. 5 is an enlarged cross-sectional view of the intermediate transfer belt in FIG. 4. FIG. 6 is a cross-sectional view of an intermediate transfer belt according to still another configuration example. FIG. 7 is an enlarged cross-sectional view of the intermediate transfer belt in FIG. 6. (A) And (B) is explanatory drawing which shows electrode arrangement | positioning in a resistivity test. (A) And (B) is explanatory drawing which shows the connection method of the electrode in the resistivity test. The schematic block diagram of an insulation resistance measuring apparatus. Explanatory drawing which shows the surface resistance measuring method. (A) And (B) is explanatory drawing which shows an example of the electrode provision method to the test piece in the surface resistance measuring method. Explanatory drawing which shows typically the measuring method of the surface friction coefficient by the Euler method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 4 Charging device 5 Exposure unit 6 Yellow developing device 7 Magenta developing device 8 Cyan developing device 9 Black developing device 10 Intermediate transfer belt 11 Primary transfer bias roller 12a, 12b Drive roller 13 Drive roller 14 Secondary transfer bias roller 110 Surface Layer 120 Intermediate layer 130 Base layer (back layer)
140 Interface

Claims (10)

It has a three-layer structure of surface layer, intermediate layer and base layer from the outer peripheral surface side in the thickness direction,
The surface layer is stretchable in the circumferential direction, the intermediate layer is stretchable in the circumferential direction and thickness direction, the base layer is non-stretchable, and the toner image on the image carrier is transferred. A transfer belt,
A transfer belt characterized in that an interface portion between the base layer and the intermediate layer is formed such that irregularities formed on the surfaces of the layers in contact with each other are fitted into each other and bite into each other. It has a three-layer structure of surface layer, intermediate layer and base layer from the outer peripheral surface side in the thickness direction,
The surface layer is stretchable in the circumferential direction, the intermediate layer is stretchable in the circumferential direction and thickness direction, the base layer is non-stretchable, and the toner image on the image carrier is transferred. A transfer belt,
When the thickness of the intermediate layer is t [μm], the maximum height Rz [μm] of the roughness of the surface of the base layer on the intermediate layer side is in the range of 3 ≦ Rz <(t / 2). A transfer belt characterized by that. The transfer belt according to claim 1 or 2,
A transfer belt, wherein at least one of the base layer and the intermediate layer is formed of a material having foamable voids. The transfer belt according to claim 1, 2 or 3,
A transfer belt, wherein the micro hardness H ₁ measured by the micro rubber hardness meter measured on the outer peripheral surface of the surface layer is 30 degrees or more and 70 degrees or less. The transfer belt according to claim 1, 2, 3 or 4,
A transfer belt having a maximum coefficient of static friction measured by the Euler belt method measured on the outer peripheral surface of the surface layer of 0.5 or less. A transfer device comprising a transfer belt supported by a plurality of support rollers including a driving roller, and a transfer material transfer means for transferring a toner image on the transfer belt to a transfer material,
A transfer device using the transfer belt according to claim 1, 2, 3, 4 or 5 as the transfer belt. The transfer apparatus according to claim 6.
A detent means for restricting movement of the transfer belt in the support roller axial direction;
A transfer device, wherein a tension per unit length in a width direction of the transfer belt supported by the support roller and driven to rotate is 0.5 N / cm or more and 1.1 N / cm or less. The transfer device according to claim 6 or 7,
The tensile strength of the base layer of the transfer belt is set to X [MPa], the average thickness of the base layer is set to t _B [mm], and the unit length in the width direction of the transfer belt supported by the support roller and driven to rotate. When the maximum tension per unit is T _M [N / cm],
X · t _B ≧ 2 × _TM
A transfer device characterized by satisfying the above. A latent image carrier, a toner image forming means for forming a toner image on the latent image carrier, and a toner image on the latent image carrier is primarily transferred to an intermediate transfer member to transfer the toner image on the intermediate transfer member to An image forming apparatus comprising an intermediate transfer means for secondary transfer to a recording medium,
9. An image forming apparatus using the transfer device according to claim 6, 7 or 8, wherein the intermediate transfer member is the transfer belt. The image forming apparatus according to claim 9.
A primary transfer nip portion and a secondary transfer nip portion of the primary transfer nip portion for performing the primary transfer and the secondary transfer, respectively, by bringing the transfer counter member into contact with and facing the portion of the intermediate transfer member supported by the support roller. An image forming apparatus, wherein the contact force per unit length in the width direction of the intermediate transfer member is 0.05 N / cm or more and 1.0 N / cm or less.

Images