JP2019032463A - Intermediate transfer belt and image forming apparatus - Google Patents

Abstract

To provide an intermediate transfer belt that can provide good transferability and has improved durability, and an image forming apparatus including the same.SOLUTION: An intermediate transfer belt 7 used in an image forming apparatus 100 has a base layer 7a, an elastic layer 7b, an intermediate layer 7c, and a surface layer 7d laminated in this order, where the elongation at break of the intermediate layer 7c is largest among the elongation at break of the layers 7a, 7b, 7c, and 7d.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an intermediate transfer belt used in an image forming apparatus such as a copying machine, a printer, and a facsimile apparatus using an electrophotographic system or an electrostatic recording system, and the image forming apparatus.

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic method, a toner image formed on an image carrier such as a photosensitive member is temporarily transferred to an intermediate transfer member and then transferred to a transfer material (recording medium) such as a recording sheet. Some have adopted an intermediate transfer method for secondary transfer. As the intermediate transfer member, an intermediate transfer belt composed of an endless belt is widely used.

  In such an image forming apparatus, an intermediate transfer belt having at least one elastic layer (herein, also referred to as “elastic intermediate transfer belt”) may be used. The elastic intermediate transfer belt is softer than the resin intermediate transfer belt that does not have an elastic layer, and can reduce the pressure acting on the toner in the primary transfer portion and the secondary transfer portion. This is effective in suppressing a phenomenon called “spotting”. In addition, the elastic intermediate transfer belt has good adhesion to the transfer material in the secondary transfer portion, so that it is effective not only in improving the transfer efficiency for plain paper but also in the transferability for thick paper and uneven paper. is there.

  The elastic intermediate transfer belt is often provided with a surface layer formed of a resin on the outermost surface for the purpose of reducing the tackiness of the surface. Patent Document 1 discloses that transferability, wear resistance, and crack resistance are improved by defining the mechanical properties of the surface layer.

JP2015-125226A

  However, in recent years, from the viewpoint of cost reduction and the like, further improvement in durability of the intermediate transfer belt has been demanded. According to the study by the present inventors, the conventional elastic intermediate transfer belt has insufficient durability. It turns out that there may not be.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an intermediate transfer belt having good transferability and improved durability, and an image forming apparatus including the intermediate transfer belt.

  The above object is achieved by the intermediate transfer belt and the image forming apparatus according to the present invention. In summary, according to the present invention, in an intermediate transfer belt used in an image forming apparatus, a base layer, an elastic layer, an intermediate layer, and a surface layer are overlapped in this order, and the base layer, the elastic layer, the intermediate layer, and the The intermediate transfer belt is characterized in that the intermediate layer has the largest breaking elongation among the respective breaking elongations of the surface layer.

  According to another aspect of the present invention, there is provided an image carrier that carries a toner image, and the intermediate transfer belt of the present invention that conveys the toner image transferred from the image carrier to be transferred to a transfer material. An image forming apparatus is provided.

  According to the present invention, it is possible to provide an intermediate transfer belt having good transferability and improved durability, and an image forming apparatus including the intermediate transfer belt.

1 is a schematic sectional view of an image forming apparatus. FIG. 3 is a schematic cross-sectional view of an intermediate transfer belt.

  Hereinafter, the intermediate transfer belt and the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

[First Embodiment]
1. Image Forming Apparatus First, the overall configuration and operation of the image forming apparatus 100 of this embodiment will be described. FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 of the present embodiment.

  The image forming apparatus 100 according to the present embodiment is a tandem type laser printer that employs an intermediate transfer method that can form a full-color image using an electrophotographic method. The image forming apparatus 100 includes first, second, third, and third images that form yellow (Y), magenta (M), cyan (C), and black (K) images as a plurality of image forming units, respectively. 4 image forming units (stations) PY, PM, PC, PK. For elements having the same or corresponding functions or configurations provided for each color, the Y, M, C, and K at the end of the symbol indicating that it is an element for each color will be omitted and described comprehensively. There is. In the present embodiment, the image forming unit P includes a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a primary transfer roller 5, and the like which will be described later.

  The image forming apparatus 100 includes a photosensitive drum 1 that is a drum-type (cylindrical) electrophotographic photosensitive member (photosensitive member) as a rotatable image carrier that supports a toner image. The photosensitive drum 1 is configured by laminating a charge generation layer, a charge transport layer, and a surface protective layer in this order on an aluminum cylinder as a conductive substrate. The photosensitive drum 1 is rotationally driven at a predetermined peripheral speed (process speed) in the direction of arrow R1 (counterclockwise) in the drawing. The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential having a predetermined polarity (negative polarity in this embodiment) by a charging roller 2 which is a roller-type charging member as a charging unit. A predetermined charging voltage (charging bias) is applied to the charging roller 2 during the charging process. The charged surface of the photosensitive drum 1 is scanned and exposed in accordance with image information by an exposure device 3 as an exposure unit, and an electrostatic image (electrostatic latent image) is formed on the photosensitive drum 1. In the present embodiment, the exposure apparatus 3 is a laser scanner apparatus using a semiconductor laser.

  The electrostatic image formed on the photosensitive drum 1 is developed using a toner as a developer by a developing device 4 as a developing unit, and a toner image is formed on the photosensitive drum 1. The developing device 4 includes a developing container containing toner, a developing roller as a developer carrying member rotatably supported by the developing container, and a regulating blade as a developer amount regulating member. The developing roller is brought into contact with the photosensitive drum 1 at a developing portion which is a portion facing the photosensitive drum 1. The developing roller is rotationally driven with a peripheral speed difference between the developing roller and the peripheral speed of the photosensitive drum 1 so as to move forward with the photosensitive drum 1 in the developing unit. The toner carried on the developing roller and conveyed to the developing unit adheres to the surface of the photosensitive drum 1 according to the electrostatic image formed on the photosensitive drum 1. As a result, a toner image is formed on the photosensitive drum 1. During the developing process, a predetermined developing voltage (developing bias) is applied to the developing roller. In the present embodiment, the surface of the photosensitive drum 1 having the same polarity as the charging polarity of the photosensitive drum 1 (in this embodiment) is exposed to an exposed portion where the absolute value of the potential is reduced by exposure after being uniformly charged. Negatively charged toner adheres.

  An intermediate transfer belt 7 composed of an endless belt is disposed facing each of the photosensitive drums 1Y, 1M, 1C, and 1K. The intermediate transfer belt 7 is an example of an intermediate transfer member that conveys the toner image transferred from the image carrier to transfer the toner image to a transfer material. The intermediate transfer belt 7 is stretched around a driving roller 71, a tension roller 72, and a secondary transfer counter roller 73 as a plurality of stretching rollers. The intermediate transfer belt 7 rotates (circulates) in the direction of the arrow R2 (clockwise) in the figure as the drive roller 71 is driven to rotate. A primary transfer roller 5, which is a roller-type primary transfer member serving as a primary transfer unit, is disposed on the inner peripheral surface side of the intermediate transfer belt 7 corresponding to each photosensitive drum 1. The primary transfer roller 5 is pressed toward the photosensitive drum 1 via the intermediate transfer belt 7 to form a primary transfer portion T1 where the photosensitive drum 1 and the intermediate transfer belt 7 are in contact with each other. The toner image formed on the photosensitive drum as described above is primarily transferred onto the rotating intermediate transfer belt 7 by the action of the primary transfer roller 5 in the primary transfer portion T1. During the primary transfer process, the primary transfer roller 5 has a primary transfer voltage which is a DC voltage having a polarity (positive in this embodiment) opposite to the toner charging polarity (normal toner charging polarity) during development. (Primary transfer bias) is applied. For example, when forming a full-color image, yellow, magenta, cyan, and black toner images formed on the respective photosensitive drums 1 are sequentially primary-transferred so as to be superimposed on the intermediate transfer belt 7.

  On the outer peripheral surface side of the intermediate transfer belt 7, a secondary transfer roller 8 that is a roller-type secondary transfer member as a secondary transfer unit is disposed at a position facing the secondary transfer counter roller 73. The secondary transfer roller 8 is pressed toward the secondary transfer counter roller 73 via the intermediate transfer belt 7 to form a secondary transfer portion T2 where the intermediate transfer belt 7 and the secondary transfer roller 8 are in contact with each other. As described above, the toner image formed on the intermediate transfer belt 7 is conveyed by being sandwiched between the intermediate transfer belt 7 and the secondary transfer roller 8 by the action of the secondary transfer roller 8 in the secondary transfer portion T2. Secondary transfer is performed on a transfer material (recording medium, sheet) S such as recording paper. During the secondary transfer process, the secondary transfer roller 8 is applied with a secondary transfer voltage (secondary transfer bias) that is a DC voltage having a polarity (positive in this embodiment) opposite to the normal charging polarity of the toner. The In the present embodiment, a secondary transfer voltage of several kV is applied to the secondary transfer roller 8 so that sufficient transfer efficiency can be obtained in the secondary transfer.

  The transfer material S is stored in the cassette 12 and is sent out from the cassette 12 to the conveyance path by the pickup roller 13. The transfer material S sent to the conveyance path is conveyed to the registration roller pair 15 by the conveyance roller pair 14. Then, the transfer material S is supplied to the secondary transfer portion T2 at the same timing as the toner image on the intermediate transfer belt 7 by the registration roller pair 15. Further, the transfer material S on which the toner image is transferred is conveyed to a fixing device 9 as a fixing unit. The transfer material S is heated and pressed by the fixing device 9 to fix (fix) the toner image, and then the transfer material S is mounted on the main body of the image forming apparatus 100 by the conveying roller pair 16 and the discharge roller pair 17. It is discharged (output) to the outside.

  On the other hand, the toner remaining on the photosensitive drum 1 without being transferred onto the intermediate transfer belt 7 during the primary transfer process (primary transfer residual toner) is charged by the charging roller 2 and then partially developed by the developing device 4. The other part constitutes a subsequent toner image. Further, a belt cleaning unit 11 as an intermediate transfer member cleaning unit is disposed downstream of the secondary transfer portion T2 and upstream of the most upstream primary transfer portion T1Y in the rotation direction of the intermediate transfer belt 7. In the present embodiment, the belt cleaning unit 11 is disposed at a position facing the driving roller 71 on the outer peripheral surface side of the intermediate transfer belt 7. The toner remaining on the intermediate transfer belt 7 without being transferred onto the transfer material S in the secondary transfer step (secondary transfer residual toner) is removed from the intermediate transfer belt 7 by the belt cleaning unit 11 and collected. The belt cleaning unit 11 collects the secondary transfer residual toner from the surface of the moving intermediate transfer belt 7 by a blade-like or brush-like cleaning member in contact with the intermediate transfer belt 7 and collects it in a collection container.

2. Intermediate Transfer Belt Next, the intermediate transfer belt 7 of this embodiment will be described. FIG. 2 is a schematic cross-sectional view of the intermediate transfer belt 7 of the present embodiment.

  In the present embodiment, the intermediate transfer belt (elastic intermediate transfer belt) 7 is an endless belt composed of a laminate in which four layers of a base layer 7a, an elastic layer 7b, an intermediate layer 7c, and a surface layer 7d overlap in this order. It is. The base layer 7a is a layer that supports upper layers such as the elastic layer 7b, the intermediate layer 7c, and the surface layer 7d. The elastic layer 7 b is a layer for imparting elasticity to the intermediate transfer belt 7 and enhancing the followability of the intermediate transfer belt 7 to the surface shape of the transfer material S. The intermediate layer 7 c is a layer for preventing the crack from growing in the thickness direction of the intermediate transfer belt 7 when a crack occurs in the surface layer 7 d. The surface layer 7d is a layer constituting the outermost surface (outermost layer) of the intermediate transfer belt 7, and is a layer for imparting hardness to the surface of the intermediate transfer belt 7 and improving transferability. In the present embodiment, it is sufficient that the intermediate layer 7c is provided between the elastic layer 7b and the surface layer 7d, and the base layer 7a and the elastic layer 7b may each be composed of a plurality of layers.

  In the present embodiment, the intermediate transfer belt 7 has the largest breaking elongation of the intermediate layer 7 among the breaking elongations of the base layer 7a, the elastic layer 7b, the intermediate layer 7c, and the surface layer 7d.

  By providing the soft elastic layer 7b, the followability of the intermediate transfer belt 7 with respect to the surface shape of the transfer material S is increased (that is, the contact property (adhesion) between the intermediate transfer belt 7 and the transfer material S is increased), Transferability can be improved. Further, by providing the hard surface layer 7d, the toner is buried in the intermediate transfer belt 7 at the time of primary transfer, and the non-electrostatic adhesion force of the toner is increased, thereby suppressing the transfer efficiency from being lowered at the time of secondary transfer. be able to. However, the hard surface layer 7d tends to crack due to repeated expansion and contraction due to repeated use of the intermediate transfer belt 7. This crack grows in the thickness direction of the intermediate transfer belt 7, and causes a defect such as when the depth reaches 10 μm or more, the transfer residual toner that has entered there passes through the cleaning member to cause a cleaning failure. May be.

  On the other hand, by providing the intermediate layer 7c, even if a crack occurs in the surface layer 7d due to repeated expansion and contraction of the surface layer 7d, the intermediate layer 7c having a high elongation at break expands and contracts. The growth of cracks in the thickness direction can be suppressed.

  That is, in the intermediate transfer belt 7 of the present embodiment, generally, the function of following the surface shape of the transfer material S is the elastic layer 7b, the function of improving the durability is the intermediate layer 7c, and the function of reducing the adhesion force of the toner. Can be provided to each of the surface layers 7d to separate the functions. Thus, in the present embodiment, by providing the intermediate transfer belt 7 with the intermediate layer 7c having a high elongation at break, durability can be improved while obtaining good transferability.

3. Examples and Comparative Examples Next, the effects of the present invention will be further described with reference to the results of comparative tests on the examples according to the present embodiment and the comparative intermediate transfer belt 7 as a comparative object. The method for manufacturing the intermediate transfer belt 7 described below shows a preferable example, and the method for manufacturing the intermediate transfer belt 7 is not limited to this.

<Example 1>
(Base layer)
In this embodiment, the base layer 7a is a roll-type or belt-shaped seamless type cylindrical type. In this example, the base layer 7a was formed by cylindrical extrusion. In this example, the base layer 7a was produced as follows.

The following materials were kneaded using a biaxial kneader (trade name: PCM30, manufactured by Ikekai Co., Ltd.) to obtain pellets.
・ Polyetheretherketone (trade name: VICTREX PEEK450G, manufactured by Victrex)
・ Acetylene black (trade name: Denka Black granular product, manufactured by Denka)

  The polyether ether ketone is 80% by mass (the total of the two materials is 100% by mass), and the acetylene black is 20% by mass (the total of the two materials is 100% by mass). Using a weight feeder, it was put into a twin-screw kneader. The cylinder set temperature of the biaxial kneader was 320 ° C. at the material charging part, and 360 ° C. at the downstream of the cylinder and the die. The screw rotation speed of the biaxial kneader was 300 rpm, and the material supply rate was 8 kg / h.

  Next, a belt was obtained by cylindrical extrusion using the pellets obtained as described above. Cylindrical extrusion was performed using a single screw extruder (trade name: GT40, manufactured by Plastic Engineering Laboratory) and a cylindrical die having a circular opening with a diameter of 300 mm and a gap of 1 mm. Using a weight feeder, the pellets were fed to a single screw extruder at a feed rate of 4 kg / h. The cylinder set temperature of the single-screw extruder was 320 ° C. at the material charging part, and 380 ° C. at the cylinder downstream and the cylindrical die. The molten resin discharged from the single-screw extruder was extruded from a cylindrical die through a gear pump, and taken out at a speed of 85 μm by a cylindrical take-up machine. In the process of being taken up, the resin was cooled and solidified by contacting a cooling mandrel provided between the cylindrical die and the cylindrical take-up machine. The solidified resin was cut to have a width of 460 mm by a cylindrical cutting machine installed at the lower part of the cylindrical take-up machine, and a crystalline thermoplastic resin belt was obtained.

  The material for forming the base layer 7a is not limited to that of this embodiment, and examples thereof include resin materials such as polyethylene terephthalate, polybutylene naphthalate, polyester, polyimide, polyamide, polyamideimide, polyacetal, and polyphenylene sulfide. .

  The material forming the base layer 7a may be imparted with conductivity by adding, for example, conductive powder such as metal powder, conductive oxide powder, or conductive carbon as a conductive agent.

  The thickness (film thickness) of the base layer 7a is preferably 10 μm or more and 500 μm or less, and more preferably 30 μm or more and 150 μm or less from the viewpoint of strength, manufacturing cost, and the like. In addition, the thickness of the base layer 7a can be represented by an average value of measured values at a plurality of locations.

  Moreover, in this example, the base layer 7a had a tensile strength of 75.0 Mpa and a breaking elongation of 10% in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127).

  The tensile strength and breaking elongation of the base layer 7a were measured using a test piece formed from the single base layer 7a produced as described above. The tensile strength can be obtained by measuring the maximum tensile force when the specimen is pulled until it is cut. The elongation at break is determined by measuring the length of the test piece before pulling and the length when it breaks (when cracks start to enter).

(Elastic layer)
In this embodiment, the elastic layer 7b is formed by applying a coating for the elastic layer 7b to the surface of the base layer 7a. It is important that the elastic layer 7b has an appropriate elastic modulus in order to express the followability of the intermediate transfer belt 7 with respect to the surface shape of the transfer material S. In this example, the elastic layer 7b was produced as follows.

  Addition of 0.2 parts by mass of the following conductive agent liquid to 100 parts by mass of addition-curable liquid silicone rubber (trade name: TSE3450 A / B, manufactured by Momentive Performance Materials) The mixture was obtained by stirring and defoaming with a foaming device (trade name: HM-500, manufactured by Keyence Corporation).

The following conductive agent liquid was used as the conductive agent.
Potassium bis (trifluoromethanesulfonyl) imide (trade name: EF-N112, manufactured by Mitsubishi Materials Electronics Chemical Co., Ltd.): 5% by mass (the total amount of the conductive agent is 100% by mass)
PEG-3 dimethicone (trade name: KF-6015, manufactured by Shin-Etsu Silicone): 95% by mass (the total amount of the conductive agent is 100% by mass)

  Next, a crystalline thermoplastic resin belt to be the base layer 7a formed as described above was attached to a cylindrical core, and a ring nozzle for discharging rubber was attached coaxially with the core. The liquid silicone rubber mixed solution was supplied to the ring nozzle using a liquid feed pump, and discharged from the slit to apply the mixed solution on the belt. At this time, the relative movement speed of the nozzle and the belt and the discharge amount by the liquid feed pump were adjusted so that the cured silicone rubber layer had a thickness of 280 μm. The belt coated with silicone rubber was put in a heating furnace with the core attached to the core, and heated at 130 ° C. for 15 minutes and further at 180 ° C. for 60 minutes to crosslink the rubber. After cooling, the belt was removed from the core to obtain a belt on which the elastic layer 7b was laminated.

  The material of the elastic layer 7b is not limited to that of this embodiment, but natural rubber, styrene / butadiene rubber, butadiene rubber, isoprene rubber, nitrile rubber, chloroprene rubber, butyl rubber, ethylene / propylene rubber, chlorosulfonated rubber. Acrylate rubber, epichlorohydrin rubber, urethane rubber, silicone rubber, fluorine rubber and the like. Of these, silicone rubber is preferred from the viewpoint of exhibiting characteristics from low temperature to high temperature and from the viewpoint of excellent ozone resistance.

  The thickness (film thickness) of the elastic layer 7b is preferably 100 μm or more and 1000 μm or less, and more preferably 200 μm or more and 500 μm or less from the viewpoint of sufficiently utilizing its flexibility. The thickness of the elastic layer 7b can be represented by an average value of measured values at a plurality of locations.

  The material forming the elastic layer 7b may contain a conductive agent such as an electronic conductive agent or an ionic conductive agent as necessary. Examples of the electronic conductive agent include conductive carbon black such as acetylene black and ketjen black, graphite, graphene, carbon fiber, and carbon nanotube. Moreover, metal powders, such as silver, copper, nickel, electroconductive zinc white, electroconductive calcium carbonate, electroconductive titanium oxide, electroconductive tin oxide, electroconductive mica etc. can be illustrated. Among these, conductive carbon black is preferable from the viewpoint of easy control of electric resistance. Examples of the ionic conductive agent include liquids containing ions such as lithium salts, potassium salts, and ammonium salts. Of these, potassium salts are preferred from the viewpoints of environmental stability and electrical resistance stability. The blending amount of the conductive agent with respect to the material forming the elastic layer 7b is preferably 35 parts by mass or less and more preferably 25 parts by mass or less with respect to 100 parts by mass of the silicone rubber from the viewpoint of mechanical strength. Thereby, stable conductivity suitable for the intermediate transfer belt 7 is imparted to the elastic layer 7a.

  The material forming the elastic layer 7b is a filler, a crosslinking accelerator, a crosslinking retarder, a crosslinking aid, a scorch inhibitor, an antiaging agent, a softening agent, a heat stabilizer, a flame retardant, a flame retardant aid, an ultraviolet ray. Other additives such as an absorbent and a rust inhibitor may be included. In particular, examples of the filler include reinforcing fillers such as fumed silica, crystalline silica, wet silica, fumed titanium oxide, and cellulose nanofiber. Reinforcing fillers include organoalkoxysilanes, organohalosilanes, organosilazanes, diorganosiloxane oligomers in which both molecular chain ends are blocked with silanol groups, and cyclic organosiloxanes from the viewpoint of being easily dispersed in silicone rubber. The surface may be modified with an organosilicon compound.

  In this example, the elastic layer 7b had a breaking elongation of 80% in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127). In this example, the elastic layer 7b had a compression set of 5% based on the JIS method (K6262).

  The breaking elongation of the elastic layer 7b was measured using a test piece formed from a finished product of the intermediate transfer belt 7 in which the base layer 7a, the elastic layer 7b, the intermediate layer 7c, and the surface layer 7d were laminated. The elongation at break of the elastic layer 7b can be obtained by measuring the length of the elastic layer 7b in the test piece before pulling and the length when the elastic layer 7b is broken (when cracks start to enter). The compression set of the elastic layer 7b was measured using a test piece of a finished product of the intermediate transfer belt 7 in which the base layer 7a, the elastic layer 7b, the intermediate layer 7c, and the surface layer 7d were laminated. The compression set of the elastic layer 7b can be obtained by measuring the thickness of the elastic layer 7b in the test piece before compression of the test piece, after compression / holding / opening. The measurement of the elongation at break and compression set of the intermediate layer 7c and the surface layer 7d, which will be described later, is the same as that of the elastic layer 7b except that the measurement objects are the intermediate layer 7c and the surface layer 7d, respectively. It is.

(Middle layer)
In this embodiment, the intermediate layer 7c is formed by applying a coating for the intermediate layer 7c on the surface of the elastic layer 7b. In this example, the intermediate layer 7c was produced as follows.

  As a material for forming the intermediate layer 7c, a polyurethane resin liquid (trade name: HydRzn 201, manufactured by DIC Corporation) was used. Excimer UV irradiation was performed on the surface of the elastic layer 7b formed as described above to hydrophilize the surface. Then, the polyurethane resin liquid was applied using a spray gun (trade name: W-101, manufactured by Anest Iwata Co., Ltd.) while fitting the belt on which the elastic layer 7b was laminated to the core and rotating the belt at 200 rpm. The amount of paint discharged during application was set such that the thickness (film thickness) after drying of the intermediate layer 7c was 8 μm. After application, the belt was naturally dried for 15 minutes while being rotated at 200 rpm with the belt fitted into the core. After natural drying, a belt on which the intermediate layer 7c was laminated was obtained.

  The material for the intermediate layer 7c is not limited to that of the present embodiment, and examples thereof include fluororesin, fluorine-containing urethane resin, fluororubber, and siloxane-modified polyimide. Among these, from the viewpoint of suppressing cracks generated in the surface layer 7d from growing in the thickness direction of the intermediate transfer belt 7, a urethane resin having a high elongation at break is preferable.

  The thickness (film thickness) of the intermediate layer 7c is preferably 1 μm or more and 15 μm or less. If the thickness of the intermediate layer 7c is less than 1 μm, it tends to disappear due to wear. Further, if the thickness of the intermediate layer 7c is larger than 15 μm, there is a concern that the elastic function of the elastic layer 7b is hindered. The thickness of the intermediate layer 7c can be represented by an average value of measured values at a plurality of locations.

  The material for forming the intermediate layer 7c may contain a conductive agent such as an electronic conductive agent or an ionic conductive agent as necessary. Examples of the conductive agent include those described above with respect to the elastic layer 7b. The blending amount of the conductive agent with respect to the material forming the intermediate layer 7c is 30 parts by mass with respect to 100 parts by mass of the resin material forming the intermediate layer 7c from the viewpoint of adhesion between the intermediate layer 7c and other layers and mechanical strength. The following is preferable.

  Moreover, you may provide a primer layer between the elastic layer 7b and the intermediate | middle layer 7c as needed. The thickness (film thickness) of the primer layer is preferably 0.1 μm or more and 2 μm or less from the viewpoint of not inhibiting the elastic function of the elastic layer 7b.

  In this example, the intermediate layer 7c had a breaking elongation of 800% in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127). Further, in this example, the intermediate layer 7c had a compression set of 20% based on the JIS method (K6262).

(Surface layer)
In this example, the surface layer 7d was formed by applying a coating material for the surface layer 7d on the surface of the intermediate layer 7c. In this example, the surface layer 7d was manufactured as follows.

  A fluorine-containing polyurethane resin liquid (trade name: Emallon T-861, manufactured by Henkel Japan) in which polytetrafluoroethylene is dispersed in a polyurethane dispersion was prepared. The above-described urethane resin solution is applied using a spray gun (trade name: W-101, manufactured by Anest Iwata Co., Ltd.) while fitting the belt laminated up to the intermediate layer 7c as described above to the core and rotating at 200 rpm. Applied. The amount of paint discharged at the time of application was set so that the thickness (film thickness) after drying of the surface layer 7d was 3 μm. After coating, the belt was placed in a heating furnace at 130 ° C. and left for 30 minutes. The belt was taken out from the heating furnace, and after cooling, an intermediate transfer belt 7 was obtained.

  The surface layer 7d is a layer for releasing the toner from the intermediate transfer belt 7 and transferring it to the transfer material S, and low adhesion to the toner is required. The material for forming the surface layer 7d is not particularly limited as long as it has a sufficiently low adhesion to the toner, and examples thereof include fluororesin, fluorine-containing urethane resin, fluororubber, and siloxane-modified polyimide. Among these, a fluorine-containing urethane resin is preferable from the viewpoint of not inhibiting the elastic function of the elastic layer 7b.

  In recent years, due to considerations for environmental impact, water-based paints using water as a main solvent are increasingly used instead of solvent-based paints using an organic solvent as a main solvent. Here, the water-based paint refers to a paint whose weight ratio of water in the solvent is 0.5% or more. Water-based paints have a low environmental impact because the main component of the solvent is water, while the surface tension of the paint is high, so the leveling property is low compared to solvent-based paints. Tends to be relatively rough.

  The thickness (film thickness) of the surface layer 7d is preferably 1 μm or more and 4 μm or less. If the thickness of the surface layer 7d is less than 1 μm, it tends to disappear due to wear. Further, if the thickness of the surface layer 7d is larger than 4 μm, there is a concern that the elastic function of the elastic layer 7d is hindered. In addition, the thickness of the surface layer 7d can be represented by an average value of measured values at a plurality of locations.

  The material for forming the surface layer 7d may contain a conductive agent such as an electronic conductive agent or an ionic conductive agent as necessary. Examples of the conductive agent include those described above with respect to the elastic layer 7b. The blending amount of the conductive agent with respect to the material forming the surface layer 7d is 30 parts by mass with respect to 100 parts by mass of the resin material forming the surface layer 7d from the viewpoint of adhesion between the surface layer 7d and other layers and mechanical strength. The following is preferable.

  In this example, the surface layer 7d had a breaking elongation of 50% in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127). Further, in this example, the surface layer 7d had a compression set of 30% based on the JIS method (K6262).

(Intermediate transfer belt)
The volume resistivity of the intermediate transfer belt 7 is preferably 1.0 × 10 ⁶ Ω · cm or more and 1.0 × 10 ¹⁴ Ω · cm or less, and 1.0 × 10 ⁸ Ω · cm or more. More preferably, it is 0 × 10 ¹³ Ω · cm or less. The surface resistivity measured from the surface layer 7d side of the intermediate transfer belt 7 is preferably 1.0 × 10 ⁶ Ω / □ or more and 1.0 × 10 ¹⁴ Ω / □ or less, and 1.0 × More preferably, it is 10 ⁹ Ω / □ or more and 1.0 × 10 ¹³ Ω / □ or less. By setting the electric resistance value of the intermediate transfer belt 7 within the range of the semiconductive region as described above, the primary transfer of the toner image from the photosensitive drum 1 to the intermediate transfer belt 7 and the transfer material from the intermediate transfer belt 7 are performed. The secondary transfer of the toner image to S can be performed stably.

  In this embodiment, the intermediate transfer belt 7 has a hardness of 55 °. The hardness of the intermediate transfer belt 7 was measured by pressing the surface of the intermediate transfer belt 7 with a type A indenter of a micro rubber hardness meter MD-1 (manufactured by Kobunshi Keiki Co., Ltd.) in accordance with JIS method (K6253-3). (Here, it is also referred to as “type A durometer hardness”).

  Further, in this example, when the intermediate transfer belt 7 was subjected to a tensile test in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127), it was confirmed that the base layer 7a was first broken. It was. Then, it was confirmed that the surface layer 7d and the elastic layer 7b were broken in this order, and the intermediate layer 7c was finally broken. This is because the intermediate layer 7c has the highest elongation at break in each of the layers 7a, 7b, 7c, and 7d. The elongation when the intermediate layer 7c finally broke was 800%.

<Example 2>
In this example, the heating temperature for crosslinking the elastic layer 7b was changed from that in Example 1, and the mechanical characteristics of the elastic layer 7b and the intermediate transfer belt 7 were made different from those in Example 1. Other points are substantially the same as those of the first embodiment.

(Elastic layer)
In this example, the elastic layer 7b had a breaking elongation of 60% in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127). In this example, the elastic layer 7b had a compression set of 3% in accordance with the JIS method (K6262).

(Intermediate transfer belt)
In this example, the hardness (type A durometer hardness) of the intermediate transfer belt 7 was 45 °.

  Further, in this example, when the intermediate transfer belt 7 was subjected to a tensile test in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127), it was confirmed that the base layer 7a was first broken. It was. Then, it was confirmed that the surface layer 7d and the elastic layer 7b were broken in this order, and the intermediate layer 7c was finally broken. This is because the intermediate layer 7c has the highest elongation at break in each of the layers 7a, 7b, 7c, and 7d. The elongation when the intermediate layer 7c finally broke was 800%.

<Example 3>
In this example, the heating temperature for crosslinking the elastic layer 7b was changed from that in Example 1, and the mechanical characteristics of the elastic layer 7b and the intermediate transfer belt 7 were made different from those in Example 1. Other points are substantially the same as those of the first embodiment.

(Elastic layer)
In this example, the elastic layer 7b had a breaking elongation of 90% in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127). Moreover, in this example, the elastic layer 7b had a compression set of 10% based on the JIS method (K6262).

(Intermediate transfer belt)
In this embodiment, the intermediate transfer belt 7 has a hardness (type A durometer hardness) of 75 °.

  Further, in this example, when the intermediate transfer belt 7 was subjected to a tensile test in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127), it was confirmed that the base layer 7a was first broken. It was. Then, it was confirmed that the surface layer 7d and the elastic layer 7b were broken in this order, and the intermediate layer 7c was finally broken. This is because the intermediate layer 7c has the highest elongation at break in each of the layers 7a, 7b, 7c, and 7d. The elongation when the intermediate layer 7c finally broke was 800%.

<Example 4>
In this example, the material of the intermediate layer 7c was changed from that of Example 1, and the mechanical properties of the intermediate layer 7c and the intermediate transfer belt 7 were made different from those of Example 1 as follows. Other points are substantially the same as those of the first embodiment.

(Middle layer)
In this example, a polyurethane resin liquid (trade name: HydRzn 213, manufactured by DIC Corporation) was used as a material for forming the intermediate layer 7c.

  In this example, the intermediate layer 7c had a breaking elongation of 350% in a dumbbell specimen JIS1 (JIS K6251) based on the JIS method (K7127). In this example, the intermediate layer 7c had a compression set of 30% in accordance with the JIS method (K6262).

(Intermediate transfer belt)
In this embodiment, the intermediate transfer belt 7 has a hardness (type A durometer hardness) of 55 °.

  Further, in this example, when the intermediate transfer belt 7 was subjected to a tensile test in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127), it was confirmed that the base layer 7a was first broken. It was. Then, it was confirmed that the surface layer 7d and the elastic layer 7b were broken in this order, and the intermediate layer 7c was finally broken. This is because the intermediate layer 7c has the highest elongation at break in each of the layers 7a, 7b, 7c, and 7d. The elongation when the intermediate layer 7c was finally broken was 350%.

<Example 5>
In this example, the material of the surface layer 7d was changed from Example 1, and the mechanical properties of the surface layer 7d and the intermediate transfer belt 7 were made different from those of Example 1 as follows. Other points are substantially the same as those of the first embodiment.

(Surface layer)
In this example, a fluorine-containing polyurethane resin liquid (trade name: Emalon 820, manufactured by Henkel Japan) in which polytetrafluoroethylene is dispersed in a polyurethane dispersion was used as a material for forming the surface layer 7d.

  In this example, the surface layer 7d had a breaking elongation of 10% in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127). In this example, the surface layer 7d had a compression set of 40% in accordance with the JIS method (K6262).

(Intermediate transfer belt)
In this embodiment, the intermediate transfer belt 7 has a hardness (type A durometer hardness) of 55 °.

  Further, in this example, when the intermediate transfer belt 7 was subjected to a tensile test in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127), it was confirmed that the base layer 7a was first broken. It was. Then, it was confirmed that the surface layer 7d and the elastic layer 7b were broken in this order, and the intermediate layer 7c was finally broken. This is because the intermediate layer 7c has the highest elongation at break in each of the layers 7a, 7b, 7c, and 7d. The elongation when the intermediate layer 7c finally broke was 800%.

<Comparative Example 1>
In this comparative example, the intermediate transfer belt 7 is an endless belt composed of a laminate in which three layers of a base layer 7a, an elastic layer 7b, and a surface layer 7d overlap in this order. In this comparative example, the intermediate transfer belt 7 is not provided with the intermediate layer 7c, but the other points are substantially the same as those of the first embodiment.

(Intermediate transfer belt)
In this comparative example, the intermediate transfer belt 7 had a hardness (type A durometer hardness) of 55 °.

  Further, in this comparative example, when the intermediate transfer belt 7 was subjected to a tensile test in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127), it was confirmed that the base layer 7a was first broken. It was. Then, it was confirmed that the surface layer 7d and the elastic layer 7b were broken in this order. This is because the elastic layer 7b has the highest elongation at break in each of the layers 7a, 7b, and 7d. The elongation when the elastic layer 7b was finally broken was 80%.

<Comparative example 2>
In this comparative example, a curing agent was added to the material forming the intermediate layer 7c, and the mechanical characteristics of the intermediate layer 7c and the intermediate transfer belt 7 were made different from those of Example 1 as follows. Other points are substantially the same as those of the first embodiment.

(Middle layer)
In this comparative example, as a material for forming the intermediate layer 7c, a polyurethane resin liquid (trade name: HydRzn 201, manufactured by DIC Corporation) added with a curing agent was used.

  In this comparative example, the intermediate layer 7c had a breaking elongation of 70% in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127). Moreover, in this comparative example, the compression set based on JIS method (K6262) was 35%.

(Intermediate transfer belt)
In this comparative example, the intermediate transfer belt 7 had a hardness (type A durometer hardness) of 55 °.

  Further, in this comparative example, when the intermediate transfer belt 7 was subjected to a tensile test in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127), it was confirmed that the base layer 7a was first broken. It was. Next, it was confirmed that the surface layer 7d and the intermediate layer 7c were broken in this order, and the elastic layer 7b was finally broken. This is because the elastic layer 7b has the highest elongation at break in each of the layers 7a, 7b, 7c, and 7d. The elongation when the elastic layer 7b was finally broken was 80%.

<Comparative Example 3>
In this comparative example, the material of the intermediate layer 7c in Example 1 was used as the material of the elastic layer 7b, and the mechanical characteristics of the elastic layer 7b and the intermediate transfer belt 7 were made different from those in Example 1. Other points are substantially the same as those of the first embodiment.

(Elastic layer)
In this comparative example, the elastic layer 7b had a breaking elongation of 800% in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127). In this comparative example, the elastic layer 7b had a compression set of 20% based on the JIS method (K6262).

(Intermediate transfer belt)
In this comparative example, the intermediate transfer belt 7 had a hardness (type A durometer hardness) of 40 °.

  Further, in this comparative example, when the intermediate transfer belt 7 was subjected to a tensile test in a dumbbell test piece JIS No. 1 (JIS K6251) based on the JIS method (K7127), it was confirmed that the base layer 7a was first broken. It was. Then, it was confirmed that the surface layer 7d, and finally the elastic layer 7b and the intermediate layer 7c break almost simultaneously. This is because, in each of the layers 7a, 7b, 7c, and 7d, the elastic layer 7b and the intermediate layer 7c have the largest breaking elongation, and the elastic layer 7b and the intermediate layer 7c have substantially the same breaking elongation. . The elongation at the time when the elastic layer 7b and the intermediate layer 7c were finally broken was 800%.

<Comparison test>
In place of the intermediate transfer belt 7 attached to the image forming apparatus (trade name: imagePRESS C800, manufactured by Canon Inc.) according to the present embodiment, the intermediate transfer belts 7 of Examples 1 to 5 and Comparative Examples 1 to 3 are attached, respectively. did. First, in an environment of 30 ° C./80%, embossed paper, Rezak 66 250 g A3 size paper, was used, and secondary color solid images of cyan and magenta were output to evaluate transferability. Specifically, the degree of occurrence of “missing” in the secondary color solid image is visually confirmed. If it does not occur, “◎”. If it occurs rarely, there is no problem in practical use. “○”, the case where it occurred at a level that could cause a problem was evaluated as “x”. Next, an endurance test in which A4 size plain paper (trade name: CS814, manufactured by Canon Inc.) was continuously passed was performed, and a cleaning failure caused by a crack in the intermediate transfer belt 7 was confirmed. Specifically, in an endurance test, the number of sheets passing through which the transfer residual toner on the intermediate transfer belt 7 slips through the belt cleaning unit 11 may occur at a level that may cause a problem (the number of occurrences of cleaning defects). ). The results are shown in Table 1.

  First, good transfer results were obtained with all intermediate transfer belts 7 except Comparative Example 3. The reason why the transferability of Comparative Example 3 is poor is thought to be because the compression set is large and the follow-up performance with respect to uneven paper is lost.

  Next, the number of occurrences of defective cleaning by the durability test was greatly improved in Examples 1 to 6. That is, the number of defective cleanings is at most about 1050K in Comparative Example 1 and Comparative Example 2, whereas it is at least about 1350K in Examples 1 to 6, and more than 1500K in the case of large numbers. It was. When the intermediate transfer belt 7 after the endurance test was observed, in Examples 1 to 6, although a small crack was generated in the surface layer 7d, the depth was limited to about 4 μm. On the other hand, in Comparative Example 1 and Comparative Example 2, the depth of the crack generated in the surface layer 7d reached about 50 μm, and toner, paper powder, and the like were captured in the crack. In the first to sixth embodiments, the reason why the number of occurrences of defective cleaning is improved is that the small cracks generated in the surface layer 7d grow in the thickness direction of the intermediate transfer belt 7, and the intermediate layer 7c having a high elongation at break. This is thought to be due to suppression.

  Moreover, it turns out that it is preferable that the breaking elongation of the intermediate | middle layer 7c is 350% or more and 800% or less based on the comparative test of Examples 1-5 and Comparative Examples 1-3. If the breaking elongation of the intermediate layer 7c is less than 350%, there is a concern that cracks generated in the surface layer 7d cannot be sufficiently suppressed from growing in the thickness direction of the intermediate transfer belt 7. Moreover, when the elongation at break of the intermediate layer 7c is greater than 800%, there is a concern that the transferability is lowered.

  Moreover, it turns out that it is preferable that the compression set of the elastic layer 7b is 10% or less based on the comparative test of Examples 1-5 and Comparative Examples 1-3. If the compression set of the elastic layer 7b is larger than 10%, there is a concern that the transferability is lowered. Note that the compression set of the elastic layer 7b is often 3% or more, and typically 5% or more.

  Moreover, based on the comparative test of Examples 1-5 and Comparative Examples 1-3, it turns out that it is preferable that the hardness (type A durometer hardness) of the intermediate transfer belt 7 is 45 degrees or more and 75 degrees or less. If this hardness is less than 45 ° or greater than 75 °, there is a concern that transferability may be reduced.

  As described above, according to the present embodiment, it is possible to provide the intermediate transfer belt 7 in which good transferability is obtained and durability is improved. In addition, according to the present embodiment, the image forming apparatus 100 including the intermediate transfer belt 7 can obtain a good transferability for a long time and can output a good image for a long time.

7 Intermediate transfer belt 7a Base layer 7b Elastic layer 7c Intermediate layer 7d Surface layer 100 Image forming apparatus

Claims (5)

In the intermediate transfer belt used in the image forming apparatus,
The base layer, the elastic layer, the intermediate layer, and the surface layer are overlapped in this order, and the intermediate layer has the highest breaking elongation among the respective breaking elongations of the base layer, the elastic layer, the intermediate layer, and the surface layer. An intermediate transfer belt that is large.   The intermediate transfer belt according to claim 1, wherein the elongation at break of the intermediate layer is 350% or more and 800% or less.   The intermediate transfer belt according to claim 1 or 2, wherein the compression set of the elastic layer is 10% or less.   The intermediate transfer belt according to any one of claims 1 to 3, wherein the hardness (type A durometer hardness) is 45 ° or more and 75 ° or less. An image carrier for carrying a toner image;
The intermediate transfer belt according to any one of claims 1 to 4, wherein the toner image transferred from the image carrier is transported for transfer to a transfer material;
An image forming apparatus comprising:

Images