JP5338049B2 - Intermediate transfer member and image forming apparatus - Google Patents

Description

  The present invention forms an electrostatic latent image on an electrostatic latent image bearing member, develops the electrostatic latent image to form a toner image, primarily transfers the toner image to an intermediate transfer member, The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine, a combination machine combining two or more of these, and an intermediate transfer body used in the image forming apparatus, capable of secondary transfer from a transfer body to a recording medium.

  In an electrophotographic image forming apparatus or the like, an electrostatic latent image is formed on an electrostatic latent image carrier such as a photoconductor, and the electrostatic latent image is developed to form a toner image. In particular, it can be transferred and fixed on a recording medium such as recording paper.

  For example, in a monochrome image forming apparatus, a toner image developed and formed on an electrostatic latent image carrier is usually directly transferred to a recording medium and fixed, but the toner image is temporarily transferred to an intermediate transfer member. After the transfer, the intermediate transfer member may be secondarily transferred to a recording medium and fixed.

  In a color image forming apparatus capable of forming a multicolor image such as a full color image using a plurality of developing devices each holding a responsible color toner, such as a so-called tandem full color image forming apparatus or a four-cycle full color image forming apparatus, The toner image developed and formed on the electrostatic latent image carrier is primarily transferred to the intermediate transfer member, and is secondarily transferred from the intermediate transfer member to the recording medium and fixed.

  More specifically, even a color image forming apparatus capable of forming a multicolor image such as a full-color image can normally form a monochrome image. When a monochrome image is formed, one developing device is used.

  However, when forming a multicolor image, each color toner image is formed on the electrostatic latent image carrier using a plurality of developing units each holding toner of different colors, and these toner images are transferred to the intermediate transfer member. The multiple toner images are transferred onto the recording medium by secondary transfer from the intermediate transfer member to the recording medium.

In any case, such an intermediate transfer body generally has a structure in which a surface layer such as a fluororesin layer or a silicon oxide (SiO ₂ ) layer having a higher hardness than the elastic layer is provided on the surface of the elastic layer made of a rubber elastic body. It has a form such as an endless belt or a drum.

  For example, in JP-A-2004-34029, an elastic layer is provided with a fluororesin-containing surface layer, and the surface layer is provided on the elastic layer via a silicon-acrylic copolymer resin layer in order to suppress cracking. A belt-type intermediate transfer member is described.

  Such an intermediate transfer member uses an elastic layer substrate, whereby the toner is transferred between the surface of the intermediate transfer member on which the toner image to be transferred is formed and the recording medium on which the toner image is to be secondarily transferred therefrom. A sufficient nip width for image transfer can be secured.

In addition, by adopting a surface layer such as a fluororesin layer or silicon oxide (SiO ₂ ) layer, the releasability is improved and the friction coefficient is reduced, which makes unnecessary toner to the intermediate transfer member. The occurrence of toner filming due to adhesion is suppressed, and the secondary transfer efficiency of the toner image is improved.
As a result, the secondary transfer efficiency can be improved as a whole.

JP 2004-34029 A

While Shigashi, for the secondary transfer efficiency improvement and filming of suppression, high fluorocarbon resin layer hardness, the case of providing a surface layer, such as Si0 ₂ layer, conversely, the intermediate transfer from the electrostatic latent image bearing member The primary transfer efficiency of the toner image onto the body may decrease.

In particular, there may be a case where an image defect (missing) is likely to occur in the line image.
This point will be further described. When the toner image on the electrostatic latent image carrier is primarily transferred to the intermediate transfer member, the intermediate transfer member is generally attached to the electrostatic latent image by a transfer member such as a primary transfer roller. The toner image is electrostatically transferred to the intermediate transfer member by applying pressure to the image carrier and applying an electric field.

  As described above, when the intermediate transfer member is pressed and contacted with the electrostatic latent image carrier by the transfer member during the primary transfer of the toner image, a surface layer having a high hardness is formed on the elastic layer as described above. If the provided one is adopted, the softness inherent to the elastic layer is hindered by the surface layer, and the rigidity of the intermediate transfer member is increased accordingly.

Therefore, the deformation of the intermediate transfer member due to the pressing force of the transfer member in the primary transfer region is reduced, and the pressing force by the transfer member is concentrated on a limited portion of the intermediate transfer member. The toner sandwiched between the electrostatic latent image carrier and that portion of the intermediate transfer member aggregates, the charge density increases in the aggregated toner group, discharge occurs inside the toner group, and the toner polarity changes. is there.
Due to such reasons, the line image may be hollow out.

  Therefore, the present invention forms an electrostatic latent image on an electrostatic latent image carrier, develops the electrostatic latent image to form a toner image, primarily transfers the toner image to an intermediate transfer member, An intermediate transfer body for an image forming apparatus capable of secondary transfer from an intermediate transfer body to a recording medium, without reducing the secondary transfer efficiency in secondary transfer of a toner image from the intermediate transfer body to the recording medium, It is a first object to provide an intermediate transfer member that can suppress image defects in a primary transfer toner image from an electrostatic latent image carrier on the intermediate transfer member.

The present invention also forms an electrostatic latent image on the electrostatic latent image carrier, develops the electrostatic latent image to form a toner image, primarily transfers the toner image to an intermediate transfer member, An image forming apparatus capable of performing secondary transfer from an intermediate transfer body to a recording medium, without reducing the secondary transfer efficiency in secondary transfer of a toner image from the intermediate transfer body to the recording medium. A second object is to provide an image forming apparatus capable of suppressing image loss in a primary transfer toner image from an electrostatic latent image carrier and forming a good image as much.

In order to solve the first problem, the present invention provides:
An electrostatic latent image is formed on the electrostatic latent image carrier, the electrostatic latent image is developed to form a toner image, the toner image is primarily transferred to the intermediate transfer member, and recorded from the intermediate transfer member a intermediate transfer member for an image forming apparatus capable of the secondary transfer to the medium, the rotation drive can be wrapped around the roller, made endless belt of a laminated structure comprising at least two layers, the outermost layer of the endless belt The hardness of the outermost layer is higher than the hardness of the layer below the outermost surface layer, and the outermost surface layer is one or two or more dividing lines extending in the belt running direction, each of which is continuously extended in the belt running direction. Provided is an intermediate transfer member that is divided.

In order to solve the second problem, the present invention
An electrostatic latent image is formed on the electrostatic latent image carrier, the electrostatic latent image is developed to form a toner image, the toner image is primarily transferred to the intermediate transfer member, and recorded from the intermediate transfer member Provided is an image forming apparatus capable of secondary transfer onto a medium, wherein the intermediate transfer body according to the present invention is employed as the intermediate transfer body.

  The intermediate transfer member according to the present invention is composed of an endless belt, and can be wound around a roller (for example, a plurality of rollers) and driven to rotate for primary transfer and secondary transfer of a toner image. In the primary transfer area, the endless belt is pressed against the surface of the electrostatic latent image carrier from the inside of the belt by a primary transfer member such as a primary transfer roller, and the electrostatic latent image is carried under application of the primary transfer voltage. The toner image on the body can be primarily transferred onto the endless belt.

  In the secondary transfer region, for example, a secondary transfer member such as a secondary transfer roller is faced from the outside of the belt to the belt surface that is wound around the roller and is convex toward the outside of the belt. The primary transfer toner image on the endless belt can be secondarily transferred to the recording medium while the recording medium is passed through the transfer nip with the secondary transfer member while being applied with the secondary transfer voltage.

  Here, the hardness of the outermost surface layer of the endless belt (in other words, the hardness of the material forming the outermost surface layer of the endless belt) is the hardness of the layer below the outermost surface layer (in other words, the outermost layer). Higher than the hardness of the material forming the layer below the surface layer).

  That is, an endless belt as an intermediate transfer member has a layer (typically an elastic layer) below the outermost surface layer that is softer than the outermost surface layer. Therefore, a nip width for smooth secondary transfer of the toner image can be ensured between the toner image and the recording medium to which the toner image is to be transferred.

  Further, the outermost surface layer of the endless belt is harder than the layer below the endless belt, has better releasability than the lower layer, and has a reduced friction coefficient. As a result, toner filming caused by unnecessary toner adhesion to the endless belt is suppressed. The secondary transfer efficiency of the toner image is also improved.

The outermost surface layer of the endless belt is divided into a plurality of portions, but in the secondary transfer region, it can be wound around a roller and used as the outermost surface layer of the belt portion in a convex state. The influence of the outermost surface layer division on the outermost surface layer hardness of the belt portion subjected to secondary transfer is negligible.
As a result, the secondary transfer efficiency can be kept good as a whole.

  On the other hand, since the outermost surface layer that is harder than the lower layer is divided into a plurality of parts, the primary transfer member is used to transfer the endless belt to the electrostatic latent image carrier in the primary transfer of the toner image from the electrostatic latent image carrier to the endless belt. When the endless belt is not divided according to the pressing force of the primary transfer member even though the hardness of the outermost surface layer of the belt is higher than the hardness of the layer below the outermost surface layer. It can bend more easily and a large nip width for smooth primary transfer of a toner image can be obtained between the electrostatic latent image carrier and the electrostatic transfer from the electrostatic latent image carrier to the endless belt. Occurrence of image defects such as voids in the toner image can be suppressed.

Thus, the image of the primary transfer toner image from the electrostatic latent image carrier on the endless belt (intermediate transfer member) without lowering the secondary transfer efficiency in the secondary transfer of the toner image from the endless belt to the recording medium. Defects can be suppressed .

  According to the image forming apparatus of the present invention, since the intermediate transfer member (endless belt) according to the present invention is employed as the intermediate transfer member, 2 in the secondary transfer of the toner image from the intermediate transfer member to the recording medium. Without lowering the secondary transfer efficiency, it is possible to suppress the image defect in the primary transfer toner image from the electrostatic latent image carrier on the intermediate transfer body and to form a better image.

  As described above, according to the present invention, an electrostatic latent image is formed on the electrostatic latent image carrier, the electrostatic latent image is developed to form a toner image, and the toner image is transferred to the intermediate transfer member. The intermediate transfer member for an image forming apparatus capable of performing the second transfer and the second transfer from the intermediate transfer member to the recording medium, and has a secondary transfer efficiency in the secondary transfer of the toner image from the intermediate transfer member to the recording medium. It is possible to provide an intermediate transfer member that can suppress image defects in the primary transfer toner image from the electrostatic latent image carrier on the intermediate transfer member without lowering.

According to the invention, an electrostatic latent image is formed on the electrostatic latent image carrier, the electrostatic latent image is developed to form a toner image, and the toner image is primarily transferred to an intermediate transfer member. An image forming apparatus capable of performing secondary transfer from the intermediate transfer member to a recording medium, on the intermediate transfer member without reducing the secondary transfer efficiency in the secondary transfer of the toner image from the intermediate transfer member to the recording medium. It is possible to provide an image forming apparatus capable of suppressing the image defect in the primary transfer toner image from the electrostatic latent image carrier and forming a good image accordingly.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of an image forming apparatus employing an example of an intermediate transfer member (endless intermediate transfer belt) according to the present invention. The image forming apparatus shown in FIG. 1 is a tandem type full color printer.

The printer P has a drive roller 81 and an endless intermediate transfer belt 8 wound around a roller 82 facing the drive roller 81. The transfer belt 8 is rotated counterclockwise in the figure (arrow direction in the figure) by a driving roller 81 driven by a belt driving unit (not shown).
The transfer belt 8 will be described in detail later.

  The secondary transfer roller 9 faces the drive roller 81. A cleaning device 83 that removes and cleans secondary transfer residual toner and the like on the transfer belt 8 with a cleaning blade faces the facing roller 82. The toner or the like collected by the cleaner 83 is sent to a waste container by a conveying means (not shown). Instead of the cleaning blade, the cleaning device 83 may use a cleaning fur brush, a cleaning roller, or other cleaning members.

  The surface layer portion of the secondary transfer roller 9 is formed of an elastic material [for example, a conductive rubber material (for example, foamed EPDM rubber imparted with conductivity by including conductive carbon or the like), and is not illustrated. The pressing means presses the portion of the intermediate transfer belt 8 supported by the drive roller 81 that also functions as a backup roller, forms a nip portion with the intermediate transfer belt 8, and is driven by the rotation of the intermediate transfer belt 8. Alternatively, as described later, the recording medium S fed into the nip portion can be rotated following the movement of the recording medium S. A secondary transfer bias having a polarity opposite to the charging polarity of the toner can be applied to the secondary transfer roller 9 from a power supply (not shown).

  A fixing device FX is disposed above the intermediate transfer belt 8 and the secondary transfer roller 9, a timing roller pair TR is disposed below, and a recording medium S such as recording paper is accommodated below the fixing device FX. The recording medium storage cassette 10 is disposed.

The fixing device FX includes a fixing heating roller incorporating a heat source such as a halogen lamp heater and a pressure roller pressed against the fixing heating roller.
The recording medium (recording paper or the like) S stored in the recording medium storage cassette 10 can be pulled out one by one by the medium supply roller 101 and supplied to the timing roller pair TR.

  Between the rollers 81 and 82 around which the intermediate transfer belt 8 is wound, the yellow image forming unit Y, the magenta image forming unit M, the cyan image forming unit C, and the rollers 82 to 81 are moved along the transfer belt 8. Black image forming portions K are arranged in this order.

  Each of the image forming units Y, M, C, and K includes a drum-type photoreceptor 1 as an electrostatic latent image carrier, and a charger 2, an image exposure device 3, and a developer 4 around the photoreceptor. The primary transfer roller 5, the cleaning device 6, and the static eliminator 7 are arranged in this order.

The photoconductor 1 in each image forming unit is a negatively chargeable photoconductor here, and can be driven to rotate clockwise in the drawing by a photoconductor drive motor (not shown).
The charger 2 in each image forming unit is not limited to this, but is a scorotron charger in this example, and a charging voltage is applied from a power supply (not shown) at a predetermined timing.

  The exposure device 3 can perform image exposure on the photosensitive member 1 using a laser beam in accordance with image information provided from a personal computer (not shown) or the like.

  The developing device 4 in each image forming unit is not limited thereto, but in this example, a developing bias is applied to the electrostatic latent image formed on the photoreceptor 1 from a power source (not shown) using negatively chargeable toner. The reversal development can be performed by the developing roller 41.

  The primary transfer roller 5 has at least a surface layer portion formed of an elastic material [for example, a conductive rubber material (for example, foamed EPDM rubber imparted with conductivity by including conductive carbon, etc.), The belt 8 is opposed to the photoconductor 1 with the belt 8 in between, the belt 8 is brought into press contact with the photoconductor 1, and is driven to rotate as the belt runs. To the primary transfer roller 5, a primary transfer bias having a polarity opposite to the toner charging polarity for primary transfer of the toner image formed on the photoreceptor 1 to the belt 8 can be applied from a power supply (not shown). .

According to the printer P, an image can be formed using one or more of Y, M, C, and K image forming units.
Taking a case where a full color image is formed using all of the image forming portions Y, M, C, and K as an example, first, a yellow toner image is formed in the yellow image forming portion Y, and this is formed on the transfer belt 8 as a primary. Transcript.

  That is, in the yellow image forming portion Y, the photosensitive member 1 is rotationally driven in the clockwise direction in the drawing, and the surface is uniformly charged to a predetermined potential by the charger 2, and the image exposure device 3 applies the yellow image for the yellow image. The yellow electrostatic latent image is formed on the photoreceptor 1. The electrostatic latent image is developed by a developing roller 41 to which a developing bias of a developing unit 4 having yellow toner is applied to become a visible yellow toner image, and the toner image is transferred onto a transfer belt 8 by a primary transfer roller 5. Primary transfer is performed. At this time, a primary transfer bias is applied to the primary transfer roller 5 from a power supply (not shown).

  Similarly, a magenta toner image is formed in the magenta image forming unit M and transferred to the transfer belt 8. A cyan toner image is formed in the cyan image forming unit C and transferred to the transfer belt 8. In the black image forming unit K. A black toner image is formed and transferred to the transfer belt 8.

Yellow, magenta, cyan, and black toner images are formed at the timing when these toner images are transferred onto the intermediate transfer belt 8.
Thus, the multiple toner image formed on the transfer belt 8 moves toward the secondary transfer roller 9 by the rotation of the transfer belt 8.

  On the other hand, the recording medium S is pulled out from the recording medium accommodating cassette 10 by the medium supply roller 101, supplied to the timing roller pair TR, and is on standby.

  Thus, the recording medium S waiting at the timing roller pair TR7 is supplied to the nip portion between the transfer belt 8 and the secondary transfer roller 9 in accordance with the multiple toner image sent by the intermediate transfer belt 8. The multiple toner image is secondarily transferred onto the recording medium S by a secondary transfer roller 9 to which a secondary transfer bias is applied from a power supply (not shown). Thereafter, the recording medium S is passed through the fixing device FX, where the multiple toner images are fixed on the recording medium S under heat and pressure. The recording medium S is continuously discharged to the discharge tray DT by the discharge roller pair DR.

In the primary transfer of the toner image to the belt 8, transfer residual toner or the like remaining on the photosensitive member 1 is cleaned by a cleaning device 6, and the residual charge on the photosensitive member 1 is transferred to a static eliminator (in this example, an optical static eliminator) 7. And is prepared for the next image formation.
The secondary transfer residual toner remaining on the belt 8 by the secondary transfer is cleaned by the cleaning device 83. Each of these cleaned and removed toners is sent to a waste container by a conveying means (not shown).

  As described above, the image is formed, but the intermediate transfer belt 8 of the printer P does not reduce the secondary transfer efficiency in the secondary transfer of the toner image from the belt 8 to the recording medium S, and the photoreceptor 1 Image defects in the primary transfer toner image on the belt 8 from the toner can be suppressed.

As shown in FIG. 2, the transfer belt 8 has a surface layer 8a formed on an elastic layer 8b, and the surface layer 8a is divided into a plurality of parts by a dividing line ct extending in the belt running direction α .
The surface layer 8a provides a primary transfer surface of the toner image.
As shown in FIG. 2, the surface layer 8a is divided into a plurality of portions each extending continuously in the belt traveling direction α by a dividing line ct.

As the elastic layer 8b, for example,
(1) Rubber materials such as chloroprene rubber, polybutadiene rubber, isoprene rubber, urethane rubber, EPDM, acrylic rubber, silicone rubber, (2) polyamide resin, polycarbonate resin, PVDF (polyvinylidene fluoride), polyalkylene phthalate, etc. Thermoplastic resin materials,
(3) PC (polycarbonate) / PAT (polyalkylene terephthalate) blend material,
ETEF (ethylene-tetrafluoroethylene copolymer) / PC blend material,
Conductive agent particles such as carbon black and various metal powders are blended with materials such as thermoplastic resin materials such as ETFE / PAT blend materials, and the volume resistance ranges from 10 ^8.5 Ω · cm to 10 ^11.5 Ω · cm. Can be mentioned those made of the material adjusted.

  As shown in FIG. 3, the transfer belt 8 may be provided with a base layer 8 c below the elastic layer 8 b in order to further give rigidity in the circumferential direction (rotation direction) of the belt 8.

As the base layer 8c, for example,
(1) Thermoplastic resin materials such as polyamide resin, polycarbonate resin, PVDF (polyvinylidene fluoride), polyalkylene phthalate,
(2) PC (polycarbonate) / PAT (polyalkylene terephthalate) blend material,
ETEF (ethylene-tetrafluoroethylene copolymer) / PC blend material,
It can be formed from a thermoplastic resin material such as an ETFE / PAT blend material.
Furthermore, a base layer made of such a material and having a volume resistance adjusted to a range of 10 ^8.5 Ω · cm to 10 ^11.5 Ω · cm by blending conductive agent particles such as carbon black and various metal powders can be exemplified. .

  In any case, the elastic layer 8b of the intermediate transfer belt 8 preferably has a hardness (JIS A) of 75 degrees or less. If the hardness is too large, the primary transfer nip width between the belt 8 and the photoreceptor 1 (nip width in the belt running direction) due to the pressing of the primary transfer roller 5 in the primary transfer area, or recording in the secondary transfer area. It becomes difficult to ensure that the secondary transfer nip width between the medium S and the belt 8 can be made smooth to achieve good primary transfer or secondary transfer, and transfer efficiency decreases or image loss ( In particular, there is a risk that a line image may be omitted), or belt driving by the roller 81 may be difficult.

However, if the hardness (JIS A) of the elastic layer 8b is too small, for example, the recording medium S may be damaged when it is passed between the belt 8 and the secondary transfer roller 9. Can be illustrated.
From the viewpoint of strength, the thickness of the elastic layer 8b may be, for example, approximately 100 μm to 500 μm, or 150 μm to 500 μm.

As the outermost surface layer 8a of the intermediate transfer belt 8,
Polytetrafluoroethylene (PTEF), tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymerization (FEP), polychlorotrifluoroethylene (PCTFE), ethylene / tetrafluoro Examples include fluoropolymers such as ethylene copolymer (ETFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), and ceramics such as SiO _2. it can.

In any case, a material having a higher hardness than that of the elastic layer 8b is adopted as the material constituting the surface layer 8a.
By adopting such a surface layer 8a, the durability of the intermediate transfer belt 8 is improved, and the toner release to the surface of the belt 8 is suppressed by improving the releasability, thereby improving the cleaning property.

The surface layer 8 a has a volume resistance in the range of 10 ¹⁰ Ω · cm to 10 ¹³ Ω · cm, and suppresses variations in surface resistance, and the primary transfer roller 5 and the secondary transfer roller 9 are used. It is preferable for effective transfer of all toner images. Furthermore, the thickness of the surface layer 8a is preferably in the range of 0.05 μm to 10 μm in order to obtain the effect of the lower elastic layer.

  When the surface layer 8a is formed using a fluororesin, it may be formed by any one of the above fluororesins, but since the fluororesin film is inferior in film formability, polyurethane resin, polyolefin resin Polyester resin, polyamide resin, polystyrene resin, acrylic resin, styrene-acrylic copolymer resin, polycarbonate resin, vinyl chloride resin, polyurethane resin, etc. It is preferably formed by dispersing in a binder and applying to the surface of the elastic layer 8b.

  In this case, although content of a fluororesin is not specifically limited, In order to ensure a desired low friction coefficient and mold release property, it is preferable that content shall be 10 weight% or more. About an upper limit, about 50 weight% can be illustrated on intensity | strength.

  Such a surface layer can be formed, for example, by dissolving and dispersing a binder resin and a fluororesin in an appropriate solvent, applying the solution, and baking.

The ceramic surface layer such as SiO ₂ can be formed as a uniform thin layer on the surface of the elastic layer 8b by using a plasma CVD method or an atmospheric pressure plasma CVD method.

As described above, the surface layer 8a is divided into a plurality of portions.
Generally speaking, the surface layer 8a can be divided by using, for example, heat shrinkage. By heating the belt 8 itself and then rapidly cooling it, it is possible to shrink the surface layer 8a and thereby split the surface layer into cracks.
As another method, division using laser processing, cutting with a diamond blade, microblast processing, or the like can be exemplified. The dividing line ct illustrated in FIG. 2 can be formed by, for example, laser processing or cutting with a diamond blade.

4 and 5 show other examples of belt division as reference examples.
Each of FIGS. 4 and 5 is a schematic perspective view of a part of a reference example of the belt 8.
4 is a belt composed of a surface layer 8a, an elastic layer 8b, and a base layer 8c. A dividing line ct extending in the belt traveling direction is formed on the surface layer 8a by a diamond blade or the like, and then the entire belt 8 is heated to a predetermined temperature. The surface layer 8a is divided by forming a dividing line ct 'due to shrinkage cracking in a direction other than the belt running direction by heating for a predetermined time and continuing cooling.
The belt 8 in FIG. 5 is a belt composed of a surface layer 8a, an elastic layer 8b, and a base layer 8c. The entire belt 8 is heated at a predetermined temperature for a predetermined time and then continuously cooled to form a dividing line ct ″. The surface layer 8a is divided.

In any case, the intermediate transfer belt 8 is thus an endless belt having a laminated structure including at least two layers 8a and 8b, and the hardness of the outermost surface layer 8a is higher than the hardness of the elastic layer 8b below the surface layer.
That is, the belt 8 has an elastic layer 8b below the outermost surface layer that is softer than the outermost surface layer 8a. Due to the presence of the elastic layer 8b, the belt 8 is provided between the surface of the belt 8 and the recording medium S on which the toner image is to be transferred. In addition, a sufficient nip width for smooth secondary transfer of the toner image can be secured.

  Further, the outermost surface layer 8a of the belt 8 is harder than the elastic layer 8b, has better releasability than the elastic layer 8b, and has a reduced coefficient of friction. As a result, occurrence of toner filming due to unnecessary toner adhesion to the belt 8 is suppressed.

Although the outermost surface layer 8a of the belt 8 is divided into a plurality of portions, in the secondary transfer region, it can be wound around the roller 81 and used as the outermost surface layer of the convex belt portion. The influence of the outermost surface layer division on the outermost surface layer hardness of the belt portion subjected to secondary transfer is negligible.
As a result, the secondary transfer efficiency can be kept good as a whole.

  On the other hand, since the outermost surface layer 8a that is harder than the elastic layer 8b is divided into a plurality of parts, the primary transfer roller 5 is used to transfer the belt 8 to the photosensitive member 1 during the primary transfer of the toner image from the photosensitive member 1 to the intermediate transfer belt 8. The belt 8 bends more easily than the case where it is not divided according to the pressing force of the transfer roller 5, although the hardness of the surface layer 8a is higher than the hardness of the elastic layer 8b below the surface layer 8a. A large nip width for smooth primary transfer of the toner image with the photoreceptor 1 can be obtained. Accordingly, it is possible to suppress the occurrence of image defects such as voids in the primary transfer toner image on the belt 8.

  Thus, image loss in the primary transfer toner image from the photoreceptor 1 on the belt 8 can be suppressed without lowering the secondary transfer efficiency in the secondary transfer of the toner image from the intermediate transfer belt 8 to the recording medium S.

Next, a specific example (example belt) of the intermediate transfer belt 8 will be described together with a reference belt and a comparative belt. Each of the belts is a belt having a three-layer structure including the base layer 8c shown in FIG. 3, and the belt width (belt width in a direction crossing the belt rotation direction to the running direction α) is 350 mm. The resistance of the elastic layer and the base layer is adjusted as described above.

<Example belt 1>
Surface layer 8a: SiO ₂ layer, thickness 500 nm
Elastic layer 8b: urethane rubber layer, thickness 150 μm
Base layer 8c: Polyamide resin layer, thickness 100 μm
The surface layer 8a is divided into 500 pieces with a substantially equal width ("width" is a width in a direction crossing the belt running direction) by a dividing line cut and formed by a diamond blade in the belt running direction.

<Example belt 2>
Surface layer 8a: PTFE layer, thickness 1 μm
Elastic layer 8b: chloroprene rubber layer, thickness 300 μm
Base layer 8c: PVDF resin layer, thickness 120 μm
The surface layer 8a is divided into 500 pieces with a substantially equal width ("width" is a width in a direction crossing the belt running direction) by a dividing line cut and formed by a diamond blade in the belt running direction.

<Example belt 3>
Surface layer 8a: PFA layer, thickness 4 μm
Elastic layer 8b: silicon rubber layer, thickness 100 μm
Base layer 8c: PC resin layer, thickness 200 μm
The surface layer 8a is divided into 500 pieces with a substantially equal width ("width" is a width in a direction crossing the belt running direction) by a dividing line cut and formed by a diamond blade in the belt running direction.

< Reference example belt 1 >
Surface layer 8a: SiO2 layer, thickness 50 nm
Elastic layer 8b: chloroprene rubber layer, thickness 200 μm
Base layer 8c: polyetherimide layer, thickness 100 μm
The surface layer 8a is divided into approximately equal widths ("width" is a width in a direction crossing the belt traveling direction) by dividing lines that are formed by cutting with a diamond blade and extend in the belt traveling direction. It was further divided by forming a dividing line in a direction other than the belt running direction by heating at 300 ° C. for 30 minutes and then cooling.

< Reference example belt 2 >
Surface layer 8a: SiO2 layer, thickness 50 nm
Elastic layer 8b: chloroprene rubber layer, thickness 200 μm
Base layer 8c: polyetherimide layer, thickness 100 μm
The surface layer 8a was divided by generating a dividing line by heating the entire belt in a constant temperature layer at 300 ° C. for 30 minutes and then cooling.

<Comparative belt 1>
In the example belt 1, the surface layer 8a is not divided.
<Comparative belt 2>
In Example Belt 2, the surface layer 8a is not divided.
<Comparative belt 3>
In the embodiment belt 3, the surface layer 8a is not divided.

Each of the example belt, the reference belt, and the comparative belt is mounted as an intermediate transfer belt on a color image forming apparatus Bizhub C550 manufactured by Konica Minolta Business Technologies, Inc., and an image is formed using an image forming unit C that forms an image with cyan toner. Formed and evaluated for belt performance.

In the primary transfer, evaluation of image dropout and solid image transfer efficiency was evaluated, and in the secondary transfer, transfer efficiency of solid image was evaluated.
The transfer efficiency [%] for primary transfer is [(toner amount on transfer belt by primary transfer / toner amount on photoreceptor before transfer) × 100].
The secondary transfer is [(toner amount on recording paper by secondary transfer / toner amount on belt before transfer) × 100].

The evaluation of hollowing out is performed by visual observation.
Rank 5 “R5” when there is no void
Rank 4 "R4", when the void is slightly recognized but practically negligible
Rank 3 “R3” is acceptable when practically acceptable but still acceptable in practice.
Rank 2 “R2” is acceptable when it is difficult to tolerate
When there were many voids and it was not acceptable at all, it was evaluated as Rank 1 “R1”.

Primary transfer Secondary transfer
Cavity Transfer efficiency [%] Transfer efficiency [%]
Example belt 1 R5 99 97
Example belt 2 R4 99 95
Example belt 3 R4 98 96
Reference belt 1 R5 99 98
Reference belt 2 R5 98 96
Comparative belt 1 R2 99 97
Comparative belt 2 R2 98 96
Comparative belt 3 R2 99 95

As can be seen from the evaluation results, in Example Belts 1 to 3 and Reference Examples 1 and 2 in which the surface layer 8a is divided according to the present invention, image loss can be suppressed while maintaining high transfer efficiency. In contrast, in the comparative example belt that did not divide the surface layer 8a, the transfer efficiency can be able to maintain a high, it can be seen that substantial results are images deficiency.

  The present invention is an intermediate transfer member for an image forming apparatus, and performs primary transfer on the intermediate transfer member without reducing secondary transfer efficiency in secondary transfer of a toner image from the intermediate transfer member to a recording medium. The present invention can be used to provide an intermediate transfer member that can suppress image defects in a toner image and to provide an image forming apparatus that can form an excellent image by adopting the intermediate transfer member.

1 is a diagram schematically illustrating a configuration of an example of an image forming apparatus according to the present invention. FIG. 3 is a partial perspective view of an example of an intermediate transfer member according to the present invention. FIG. 6 is a partial cross-sectional view of another example of an intermediate transfer member according to the present invention. It is a fragmentary perspective view of one example of an intermediate transfer body as a reference example. FIG. 10 is a partial perspective view of another example of an intermediate transfer member as a reference example .

Explanation of symbols

P Printer Y Yellow image forming unit M Magenta image forming unit C Cyan image forming unit K Black image forming unit 1 Photoconductor 2 Charger 3 Image exposure device 4 Developer 41 Developer roller 5 Primary transfer roller 6 Cleaning device 7 Charger 8 Intermediate transfer belt 8a which is an example of an intermediate transfer member Surface layer ct, ct ', ct "Dividing line 8b Elastic layer 8c Base layer 81 Driving roller 82 Opposing roller 83 Cleaning device 9 Secondary transfer roller 10 Recording medium supply cassette 101 Medium supply roller TR Timing Roller pair FX Fixing device DR Recording medium discharge roller pair DT Recording medium discharge tray S Recording medium

Claims (2)

An electrostatic latent image is formed on the electrostatic latent image carrier, the electrostatic latent image is developed to form a toner image, the toner image is primarily transferred to the intermediate transfer member, and recorded from the intermediate transfer member a intermediate transfer member for an image forming apparatus capable of the secondary transfer to the medium, the rotation drive can be wrapped around the roller, made endless belt of a laminated structure comprising at least two layers, the outermost layer of the endless belt The hardness of the outermost layer is higher than the hardness of the layer below the outermost surface layer, and the outermost surface layer is one or two or more dividing lines extending in the belt running direction, each of which is continuously extended in the belt running direction. An intermediate transfer member characterized by being divided. An electrostatic latent image is formed on the electrostatic latent image carrier, the electrostatic latent image is developed to form a toner image, the toner image is primarily transferred to the intermediate transfer member, and recorded from the intermediate transfer member An image forming apparatus capable of secondary transfer onto a medium, wherein the intermediate transfer member according to claim 1 is employed as the intermediate transfer member .