JP7183026B2 - Intermediate transfer belt and image forming apparatus - Google Patents

Description

The present invention relates to an intermediate transfer belt used in image forming apparatuses such as copiers, printers, and facsimile machines using an electrophotographic method or an electrostatic recording method, and the image forming apparatus.

Conventionally, in an image forming apparatus using an electrophotographic method or the like, a toner image formed on an image bearing member such as a photoreceptor is primarily transferred onto an intermediate transfer belt, which is an endless belt-like intermediate transfer member, and then recorded on paper or the like. An intermediate transfer method for secondary transfer onto a material is widely used.

In such an image forming apparatus, an intermediate transfer belt having at least one elastic layer (hereinafter also referred to as an "elastic intermediate transfer belt") is sometimes used to further improve image quality (Patent Document 1). ). The elastic intermediate transfer belt is formed by providing an elastic layer made of an elastic material such as rubber on a base layer made of resin. Since the elastic intermediate transfer belt has at least one elastic layer, it is relatively soft and can reduce the pressure acting on the toner in the transfer section (primary transfer section, secondary transfer section). Therefore, it is known that the elastic intermediate transfer belt is effective in suppressing the hollow phenomenon in which a part of the toner image is not transferred. Also, the elastic intermediate transfer belt has good adhesion to the recording material in the secondary transfer portion. Therefore, the elastic intermediate transfer belt not only improves the transfer efficiency of toner images on general paper, but also improves the transferability of toner images on thick paper and the transferability of toner images on uneven recording materials such as embossed paper. is also known to be effective.

In order to reduce the high tackiness of the surface of the elastic layer, such an elastic intermediate transfer belt is sometimes provided with a surface layer with low tackiness or a surface layer with excellent frictional wear resistance on the outermost surface. Further, in the elastic intermediate transfer belt, an intermediate layer may be provided between the elastic layer and the surface layer in order to improve adhesion between the elastic layer and the surface layer.

Materials that are sufficiently harder than the elastic layer, such as materials with a hardness (indentation hardness measured by a method described later) of about 0.01 GPa to 0.5 GPa, are used as materials for forming the surface layer and the intermediate layer.

JP 2007-292851 A

However, since the surface layer and the intermediate layer as described above are relatively strongly crosslinked during heat curing, they tend to shrink on curing and decrease in volume. Therefore, the higher the hardness of the surface layer and the intermediate layer is compared to the hardness of the elastic layer, the more the edge of the intermediate transfer belt in the width direction moves toward the outer peripheral surface side of the intermediate transfer belt (from the elastic layer side toward the surface layer and intermediate layer side). direction) (here, also referred to as “edge warpage”).

When the intermediate transfer belt is attached to and detached from the main body of the image forming apparatus in a state in which the widthwise end portion of the intermediate transfer belt is warped toward the outer peripheral surface side, the end portion and a part of the apparatus main body interfere with each other. It may get caught and break at the end.

Further, as shown in FIG. 6, the image forming apparatus is provided with an edge position sensor for detecting the conveying position of the intermediate transfer belt in the width direction corresponding to the edge of the intermediate transfer belt in the width direction. Sometimes. In this case, if the edge in the width direction of the intermediate transfer belt is warped toward the outer peripheral surface, the edge may come into contact with the edge position sensor or become worn, resulting in erroneous detection or detection by the edge position sensor. It may lead to loss of accuracy. Further, as shown in FIG. 6, the image forming apparatus includes a home position sensor for detecting the position of the intermediate transfer belt in the circumferential direction on the inner peripheral surface side corresponding to the widthwise end of the intermediate transfer belt. may be provided. In this case, if the edge of the intermediate transfer belt in the width direction warps toward the outer peripheral surface, the distance between the intermediate transfer belt and the home position sensor increases. may lead to a decline.

Edge warpage of the intermediate transfer belt is a particular problem in the case of a configuration in which an edge position sensor is used to control (steer) the conveying position of the intermediate transfer belt. However, even in the case of a configuration in which a rib is provided on the inner peripheral surface side of the edge of the intermediate transfer belt, and the rib is abutted against a regulating member to determine the conveying position of the intermediate transfer belt, for example, the edge on the side where the rib is not provided may be used. This can be a problem when detecting the home position of the intermediate transfer belt. Interference with the device main body described above is a problem in any of the above configurations.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an intermediate transfer belt capable of suppressing edge warping in a configuration having an elastic layer and a layer harder than the elastic layer provided on the surface side of the elastic layer, and an intermediate transfer belt including the same. Another object of the present invention is to provide an image forming apparatus that is

The above objects are achieved by an intermediate transfer belt and an image forming apparatus according to the present invention. In summary, the present invention provides an intermediate transfer belt having a surface to which a toner image can be transferred, comprising: a base layer; an elastic layer provided closer to the surface than the base layer; In an intermediate transfer belt having a single outer layer or a plurality of outer layers, the hardness in an image region where a toner image in the width direction of the intermediate transfer belt can be transferred is the highest among the single outer layer or the plurality of outer layers. The average thickness of the predetermined outer layer, which is a large layer, in the image area is 2 μm or more, and the average thickness of the predetermined outer layer at the outermost end in the width direction of the intermediate transfer belt is A, from the outermost end. B is the average thickness of the predetermined outer layer at a position 5 mm inward in the width direction of the intermediate transfer belt, and B is the average thickness of the predetermined outer layer at a position 10 mm inward in the width direction of the intermediate transfer belt from the extreme end When the thickness is C and the average thickness of the predetermined outer layer at any position in the image area is D, the following formulas (1) to (4),
A<B<C<D (1)
B≦D×0.5 (2)
C≦D×0.75 (3)
A≧0 (4)
The intermediate transfer belt is characterized by satisfying the relationship of

According to another aspect of the present invention, there is provided an intermediate transfer belt having a surface onto which a toner image can be transferred, comprising: a base layer; an elastic layer provided on the surface side of the base layer; In an intermediate transfer belt having a single outer layer or a plurality of outer layers provided, hardness in an image region where a toner image in the width direction of the intermediate transfer belt can be transferred among the single outer layer or the plurality of outer layers is When the largest layer is the predetermined outer layer, the hardness of the predetermined outer layer at a position 5 mm inward in the width direction of the intermediate transfer belt from the outermost end in the width direction of the intermediate transfer belt is arbitrary within the image area. is less than the hardness of the predetermined outer layer at the position of the intermediate transfer belt.

According to another aspect of the present invention, there is provided an image forming apparatus comprising the intermediate transfer belt of the present invention.

According to the present invention, an intermediate transfer belt capable of suppressing edge warping in a configuration having an elastic layer and a layer harder than the elastic layer provided on the surface side of the elastic layer, and an image provided with the intermediate transfer belt A forming apparatus can be provided.

1 is a schematic cross-sectional view of an example of an image forming apparatus; FIG. 2 is a schematic cross-sectional view of an intermediate transfer belt; FIG. FIG. 2 is a schematic diagram of a spray coating device used for coating an intermediate layer and a surface layer of an intermediate transfer belt; 3 is a schematic cross-sectional view for explaining the layer structure of the end portion of the intermediate transfer belt in the first embodiment; FIG. FIG. 4 is a schematic diagram for explaining an apparatus for evaluating edge warpage; FIG. 5 is a schematic cross-sectional view of the vicinity of the intermediate transfer belt for explaining the problem of edge warping; 2 is a schematic partial cross-sectional perspective view of a radiant furnace used for baking an intermediate layer and a surface layer of an intermediate transfer belt; FIG. (a) It is a graph showing the relationship between the temperature of the end furnace body, the firing time, and the amount of warp in Experimental Example 1 of the second embodiment. (b) is a graph showing the relationship between the amount of warpage and the hardness of the intermediate layer at the edge in Experimental Example 1 of the second embodiment. (a) It is a graph showing the relationship between the temperature of the end furnace body, the firing time, and the amount of warp in Experimental Example 2 of the second embodiment. (b) is a graph showing the relationship between the amount of warpage and the hardness of the intermediate layer at the edge in Experimental Example 2 of the second embodiment.

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, an example of an image forming apparatus that can use the intermediate transfer belt according to the present invention will be described. FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 of this example. The image forming apparatus 100 of this example is a tandem-type laser printer that employs an intermediate transfer method and is capable of forming a full-color image using an electrophotographic method.

The image forming apparatus 100 of this example forms yellow (Y), magenta (M), cyan (C), and black (K) images along the moving direction of the flat portion of the intermediate transfer belt 1 . It has four image forming units PY, PM, PC, and PK. For elements having the same or corresponding functions or configurations in the image forming units PY, PM, PC, and PK, the suffixes Y, M, C, and K are omitted from the symbols indicating that they are elements for one of the colors. may be described in a comprehensive manner. In this example, the image forming section P includes a photosensitive drum 101, a charging roller 102, an exposure device 103, a developing device 104, a primary transfer roller 105, etc., which will be described later.

A photosensitive drum 101, which is a drum-shaped (cylindrical) photosensitive member (electrophotographic photosensitive member) as an image bearing member, is rotationally driven in the counterclockwise direction indicated by the arrow in the drawing. The photosensitive drum 101 has a structure in which a charge generating layer, a charge transporting layer and a surface protective layer are sequentially laminated on a substrate formed of an aluminum cylinder. The surface of the rotating photosensitive drum 101 is uniformly charged to a predetermined potential with a predetermined polarity (negative polarity in this example) by a charging roller 102 which is a roller-type charging member as charging means. A predetermined charging voltage (charging bias) is applied to the charging roller 102 during the charging process. The charged surface of the photosensitive drum 101 is scanned and exposed according to image information by an exposure device (laser scanner) 103 as an exposure unit, and static color components corresponding to each image forming portion P are formed on the photosensitive drum 101 . An electric image (electrostatic latent image) is formed. The electrostatic image formed on the photosensitive drum 101 is developed (visualized) by supplying toner as a developer by a developing device 104 as developing means, and a toner image (developer image) is formed on the photosensitive drum 101 . be done. The developing device 104 includes a developing container containing toner, a developing roller as a developer carrying member, a regulating blade as a developer amount regulating member for regulating the amount of toner on the developing roller, and the like. Developing devices 104Y, 104M, 104C, and 104K for yellow, magenta, cyan, and black contain yellow, magenta, cyan, and black toner, respectively. The developing roller is lightly pressed against the photosensitive drum 101 at the developing portion, and is rotationally driven with a speed difference in the forward direction with respect to the photosensitive drum 101 . The toner conveyed to the developing section by the developing roller adheres to the electrostatic image formed on the photosensitive drum 101 by applying a predetermined developing voltage (developing bias) to the developing roller. In this example, a charge having the same polarity as the charge polarity of the photosensitive drum 101 (negative polarity in this example) is applied to the exposed portion of the photosensitive drum 101 where the absolute value of the potential is lowered by exposure after being uniformly charged. Charged toner adheres.

An endless intermediate transfer belt (elastic intermediate transfer belt) 1 is arranged as an intermediate transfer member so as to be in contact with the four photosensitive drums 101Y, 101M, 101C, and 101K. The intermediate transfer belt 1 is stretched over a driving roller 121, a tension roller 122, and a secondary transfer counter roller 123 as a plurality of stretching rollers (supporting rollers) with a predetermined tension. When the drive roller 121 is rotationally driven, the intermediate transfer belt 1 is transmitted with a driving force, and rotates (circulates) in the clockwise direction indicated by the arrow in the figure. On the inner peripheral surface side of the intermediate transfer belt 1 , primary transfer rollers 105 , which are roller-type primary transfer members as primary transfer means, are arranged corresponding to the respective photosensitive drums 101 . A primary transfer roller 105 is pressed toward the photosensitive drum 101 via the intermediate transfer belt 1 to form a primary transfer portion T1 where the photosensitive drum 101 and the intermediate transfer belt 1 are in contact with each other. The toner image formed on the photosensitive drum 101 as described above is primarily transferred onto the rotating intermediate transfer belt 1 by the action of the primary transfer roller 105 at the primary transfer portion T1. During the primary transfer process, a predetermined primary transfer voltage (primary transfer bias), which is a DC voltage having a polarity opposite to the normal charge polarity of the toner (charge polarity during development), is applied to the primary transfer roller 105 . be done. For example, when a full-color image is formed, yellow, magenta, cyan, and black toner images formed on the respective photosensitive drums 101Y, 101M, 101C, and 101K are sequentially superimposed on the intermediate transfer belt 1. Primary transfer is performed.

A secondary transfer roller 108 , which is a roller-type secondary transfer member as a secondary transfer means, is arranged at a position facing the secondary transfer opposing roller 123 on the outer peripheral surface side of the intermediate transfer belt 1 . The secondary transfer roller 108 is pressed toward the secondary transfer opposing roller 123 via the intermediate transfer belt 1, forming a secondary transfer portion T2 where the intermediate transfer belt 1 and the secondary transfer roller 108 are in contact with each other. The toner image formed on the intermediate transfer belt 1 as described above is nipped and conveyed between the intermediate transfer belt 1 and the secondary transfer roller 108 by the action of the secondary transfer roller 108 at the secondary transfer portion T2. is secondarily transferred onto the recording material S. During the secondary transfer process, the secondary transfer roller 108 is applied with a predetermined secondary transfer voltage (secondary transfer bias) that is a DC voltage having a polarity opposite to the normal charge polarity of the toner. Usually, a secondary transfer voltage of several kV is applied in order to ensure sufficient secondary transfer efficiency. A recording material (recording medium, transfer material, sheet) S is accommodated in a cassette 112 and is supplied from the cassette 112 to a conveying path by a pickup roller 113 . The recording material S supplied to the conveying path is conveyed to the secondary transfer portion T2 in timing with the toner image on the intermediate transfer belt 1 by the conveying roller pair 114 and the registration roller pair 115 . The recording material S is typically paper, but may be synthetic paper made of resin such as waterproof paper, plastic sheet such as OHP sheet, or cloth.

The recording material S onto which the toner image has been transferred is conveyed to a fixing device 109 as fixing means. The fixing device 109 has a fixing roller 191 having a heating means and a pressure roller 192 that presses against the fixing roller 191 . The fixing device 109 heats and presses the recording material S bearing an unfixed toner image with a fixing roller 191 and a pressure roller 192, thereby fixing (melting or fixing) the toner image onto the recording material S. . The recording material S on which the toner image has been fixed is discharged (output) to the outside of the image forming apparatus 100 by the pair of conveying rollers 116, the pair of discharge rollers 117, and the like.

Further, the toner remaining on the photosensitive drum 101 without being transferred to the intermediate transfer belt 1 during the primary transfer process is removed from the photosensitive drum 101 by the developing device 104 and collected. Toner (secondary transfer residual toner) remaining on the intermediate transfer belt 1 without being transferred to the recording material S during the secondary transfer process and paper dust are removed by a belt cleaning device 111 as intermediate transfer body cleaning means. It is removed from the belt 1 and collected.

The image forming apparatus 100 of this embodiment is provided with the edge position sensor and the home position sensor described with reference to FIG. The image forming apparatus 100 of this embodiment is configured to control (steer) the conveying position of the intermediate transfer belt 1 using the edge position sensor. However, even if the image forming apparatus 100 is configured such that a rib is provided on the inner peripheral surface side of the end portion of the intermediate transfer belt 1, and the rib is abutted against a regulating member to determine the conveying position of the intermediate transfer belt 1. good.

By using the intermediate transfer belt 1 according to the present invention as the intermediate transfer belt 1 in such an image forming apparatus 100, warping of the end portion of the intermediate transfer belt 1 is suppressed. Therefore, when the unit including the intermediate transfer belt 1 is attached to and detached from the apparatus main body of the image forming apparatus 100 , it is possible to suppress the interference of the widthwise ends of the intermediate transfer belt 1 with the apparatus main body. It is possible to suppress the breakage of the ends of the direction. In addition, it is possible to suppress erroneous detection and deterioration of detection accuracy of the end position sensor and the home position sensor as described with reference to FIG. 6 . As a result, high-quality images can be formed over a long period of time.

2. Intermediate Transfer Belt Next, an embodiment of an intermediate transfer belt (elastic intermediate transfer belt) according to the present invention will be described. As shown in FIG. 2, the intermediate transfer belt 1 of the present embodiment is composed of a laminate having four layers: a base layer 11, an elastic layer 12, an intermediate layer 13, and a surface layer . The intermediate transfer belt 1 includes a base layer 11, an elastic layer 12, and an image area in the width direction of the intermediate transfer belt 1 (the surface of the intermediate transfer belt 1) provided on the surface side of the intermediate transfer belt 1 from the elastic layer 12. and a single or a plurality of outer layers whose hardness is greater than that of the elastic layer 12 in the region where the toner image can be transferred. It may also consist of a stack of layers.

<Base layer>
The base layer (base material) 11 will be described. The base layer 11 is a roll-shaped or belt-shaped seamless type cylindrical one. Materials suitable for forming the base layer 11 include, for example, resin materials such as polyetheretherketone, polyethylene terephthalate, polybutylene naphthalate, polyester, polyimide, polyamide, polyamideimide, polyacetal, and polyphenylene sulfide.

Conductive powder such as metal powder, conductive oxide powder, or conductive carbon may be added to the resin forming the base layer 11 to impart conductivity.

As the resin constituting the base layer 11, polyether ether ketone or polyimide to which carbon black is added is particularly preferable from the viewpoint of mechanical strength and conductivity.

The thickness (film thickness) of the base layer 11 is preferably 10 μm or more and 500 μm or less. If the thickness of the base layer 11 is less than 10 μm, the mechanical strength may be remarkably lowered. On the other hand, if the thickness of the base layer 11 is more than 500 μm, it may become difficult to use as an intermediate transfer member due to excessive rigidity.

<Elastic layer>
The elastic layer 12 will be explained. In order to follow the surface shape of the recording material S, the elastic layer 12 needs to have an appropriate elastic modulus (flexibility). The elastic material constituting the elastic layer 12 is not particularly limited as long as it has an appropriate elastic modulus. , ethylene-propylene rubber, chlorosulfonated rubber, acrylate rubber, epichlorohydrin rubber, urethane rubber, silicone rubber, fluororubber, and the like. Among these, silicone rubber is particularly preferable because of its low compression set and excellent ozone resistance.

The thickness of the elastic layer 12 is preferably 100 μm or more and 1000 μm or less, more preferably 150 μm or more and 500 μm or less, and even more preferably 200 μm or more and 500 μm or less. If the thickness of the elastic layer 12 is too thin, sufficient flexibility may not be obtained, and if the thickness of the elastic layer 12 is too thick, it may become difficult to use as an intermediate transfer body.

The hardness of the elastic layer 12 in the image area (indentation hardness measured by a method described later) is preferably about 0.001 GPa or more and 0.015 GPa or less (for example, 0.005 GPa). If the hardness of the elastic layer 12 in the image area is too low, bleeding tends to occur.

The elastic layer 12 may contain an electronic conductive agent or an ionic conductive agent as a conductive agent. Examples of the electron conductive agent include conductive carbon black such as acetylene black and ketjen black, graphite, graphene, carbon fiber, and carbon nanotube. In addition, as an electronic conductive agent, metal powder such as silver, copper, nickel, conductive zinc oxide, conductive calcium carbonate, conductive titanium oxide, conductive tin oxide, conductive zinc oxide, conductive antimony oxide, conductive Mica, etc., or a composite thereof can be exemplified. Among these, conductive carbon black is preferable from the viewpoint of ease of control of electric resistance. Examples of ion conducting agents include lithium salts, potassium salts, ammonium salts, pyridine-based, alicyclic amine-based, and aliphatic amine-based ionic liquids. Of these, ionic liquids are preferable from the viewpoint of environmental stability and suppression of polarization due to durability. Potassium salts and ammonium salts are particularly preferred from the viewpoint of electrical resistance stability. From the viewpoint of mechanical strength, the compounding ratio for the elastic layer 12 is preferably 35 parts by mass or less, more preferably 25 parts by mass or less per 100 parts by mass of the silicone rubber. Thereby, the elastic layer 12 is provided with a stable conductivity suitable for the intermediate transfer body.

In addition, the elastic layer 12 contains a filler, a cross-linking accelerator, a cross-linking retarder, a cross-linking aid, an anti-scorch agent, an anti-aging agent, a softening agent, a heat stabilizer, a flame retardant, an auxiliary flame retardant, an ultraviolet absorber, an anti- Additives such as rust agents may be included. In particular, fillers include reinforcing fillers such as fumed silica, crystalline silica, wet silica, fumed titanium oxide, cellulose nanofibers, and the like. Reinforcing fillers include organoalkoxysilanes, organohalosilanes, organosilazanes, diorganosiloxane oligomers whose molecular chain ends are blocked with silanol groups, and cyclic organosiloxanes, from the standpoint of being easily dispersed in silicone rubber. It may be surface-modified with an organosilicon compound.

<Middle layer>
The intermediate layer 13 will be explained. The intermediate layer 13 has an elastic modulus greater than that of the surface layer 14, and suppresses the occurrence of cracks in the surface layer 14 due to deformation of the intermediate layer 13 when the elastic layer 12 is deformed. . The material constituting the intermediate layer 13 is not particularly limited as long as it has an elastic modulus greater than that of the surface layer 14, but may be fluororesin, fluorinated urethane resin, fluororubber, siloxane-modified polyimide, epoxy resin, Polyamide resins, fluororesins, phenolic resins, etc. can be mentioned, and mixtures thereof can also be used. Among these, from the viewpoint of not impairing the elastic function of the elastic layer 12 and from the viewpoint of barrier properties to suppress bleeding of low-molecular-weight components contained in the elastic layer 12 to the surface of the surface layer 14, urethane resins and modified polyamides are preferred. A resin or the like is preferable. Note that if the intermediate layer 13 is not provided between the elastic layer 12 and the surface layer 14 and there is no problem from the viewpoint of cracks and bleeding, the intermediate layer 13 is not particularly necessary.

The thickness of the intermediate layer 13 is preferably 1 μm or more and 20 μm or less, more preferably 1 μm or more and 15 μm or less. When the thickness of the intermediate layer 13 is less than 1 μm, the barrier properties are weakened, and the additive of the elastic layer 12 may bleed. From this point of view, the thickness of the intermediate layer 13 is more preferably greater than 2 μm, typically 3 μm or more. Moreover, if the thickness of the intermediate layer 13 is more than 20 μm, the elastic function of the elastic layer 12 may be impaired.

Further, the hardness of the intermediate layer 13 in the image area (indentation hardness measured by a method to be described later) is generally about 0.01 GPa or more and 0.5 GPa or less (for example, 0.1 GPa).

The intermediate layer 13 may contain additives such as curing agents, plasticizers, and conductive agents, if necessary. For example, when the intermediate layer 13 contains a conductive agent, the amount of the conductive agent is set to 100 parts by mass of the main component of the intermediate layer 13 (urethane resin, modified polyamide resin, etc.) from the viewpoint of adhesion and mechanical strength. is preferably 30 parts by mass or less.

If necessary, before laminating the intermediate layer 13 on the elastic layer 12, the surface of the elastic layer 12 may be subjected to UV or plasma activation treatment (hydrophilization treatment).

A primer layer (not shown) may be provided between the elastic layer 12 and the intermediate layer 13 as necessary. From the viewpoint of not impairing the elastic function of the elastic layer 12, the thickness of the primer layer is preferably 0.1 μm or more and 2 μm or less.

<Surface layer>
The surface layer 14 will be explained. The surface layer 14 constitutes the surface of the intermediate transfer belt 1 (the surface carrying the toner image). The surface layer 14 is a layer provided to improve the transferability of the toner onto the recording material S and the releasability of the toner from the intermediate transfer belt 1, and is required to have low adhesion. be. As a material for forming the surface layer 14, any material having low adhesion can be used without any particular limitation. Such materials include fluorine resin, fluorine-containing urethane resin, fluorine rubber, and siloxane-modified polyimide. Among these, fluorine-containing urethane resin is preferable from the viewpoint of not impairing the elastic function of the elastic layer 12 . Hydrophobic fillers such as PTFE particles, PFPE particles, PFA particles, Si particles, and hydrophobized _SiO2 particles may also be added to these resins.

In recent years, in consideration of the environmental burden, the use of water-based paints using water as the main solvent is increasing in place of conventionally used solvent-based paints using organic solvents as the main solvent. A water-based paint refers to a paint in which the weight ratio of water in the solvent is 0.5 or more. Water-based paints have less environmental impact because the main component of the solvent is water, but they have lower leveling properties than solvent-based paints due to their high surface tension, and the surface of the film after drying. tends to be relatively rough.

The thickness of the surface layer 14 is preferably 1 μm or more and 10 μm or less, more preferably 1 μm or more and 4 μm or less. If the thickness of the surface layer 14 is less than 1 μm, it tends to disappear due to abrasion. Moreover, if the thickness of the surface layer 14 is more than 10 μm, the elastic function of the elastic layer 12 may be impaired.

The hardness of the surface layer 14 in the image area (indentation hardness measured by a method described later) is generally about 0.01 GPa or more and 1.0 GPa or less (for example, 0.2 GPa).

The surface layer 14 may contain a conductive agent similar to that described above, if necessary. From the viewpoint of adhesion and mechanical strength, the amount of the conductive agent is preferably 30 parts by mass or less with respect to 100 parts by mass of the main component (fluorine-containing urethane resin, etc.) of the surface layer 14 .

If the intermediate layer 13 is not provided, a primer layer (not shown) may be provided between the elastic layer 12 and the surface layer 14 as necessary. From the viewpoint of not impairing the elastic function of the elastic layer 12, the thickness of the primer layer is preferably 0.1 μm or more and 2 μm or less.

<Electrical resistance of intermediate transfer belt>
The volume resistivity of the intermediate transfer belt 1 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. It is more preferably 0×10 ¹³ Ω·cm or less.

Further, the surface resistivity of the intermediate transfer belt 1 measured from the surface layer 14 side is preferably 1.0×10 ⁶ Ω/□ or more and 1.0×10 ¹⁴ Ω/□ or less. It is more preferably 10 ⁹ Ω/□ or more and 1.0×10 ¹³ Ω/□ or less.

By setting the electric resistance of the intermediate transfer belt 1 within the range of the semiconductive region as described above, the primary transfer of the toner image from the photosensitive drum 101 and the transfer of the toner image from the intermediate transfer belt 1 to the recording material S can be performed. Secondary transfer can be stably performed.

The surface resistivity of the intermediate transfer belt 1 was measured using a circular electrode (trade name: Hiresta UP, manufactured by Mitsubishi Chemical Analytic Tech). The intermediate transfer belt 1 to be measured is placed on a plate made of an insulating material, a voltage of 1000 V is applied, and the value is read 10 seconds after the application. Measurements are taken at arbitrary 18 points within a single belt surface, and the average value thereof is taken as the surface resistivity of the intermediate transfer belt 1 to be measured. The method for measuring volume resistivity is substantially the same as the method for measuring surface resistivity, except that the object to be measured is placed on a plate made of metal and the current flowing between it and the cylindrical electrode is measured. .

<Width of intermediate transfer belt>
The width of the image area in the width direction of the intermediate transfer belt 1 (the area where the toner image on the surface of the intermediate transfer belt 1 can be transferred) is generally required to be 320 mm for office machines, and at least 330 mm, which is equivalent to an A3 stretched sheet, for production machines. be. Note that the image area in the width direction of the intermediate transfer belt 1 corresponds to an area (paper passing area) that can come into contact with the recording material P at the secondary transfer portion on the intermediate transfer belt 1 . In this embodiment, the width of the intermediate transfer belt 1 is set to 360 mm in consideration of other members. Further, in this embodiment, the width of the image area in the width direction of the intermediate transfer belt 1 is 330 mm. This image area is arranged at the center of the intermediate transfer belt 1 in the width direction with the center of the intermediate transfer belt 1 in the width direction as a reference.

<Thickness of Outer Layer at End of Intermediate Transfer Belt>
In the present embodiment, the intermediate transfer belt 1 includes a base layer 11, an elastic layer 12, and a single layer or a plurality of layers provided closer to the surface of the intermediate transfer belt 1 than the elastic layer 12 and having hardness greater than that of the elastic layer 12 in the image area. and an outer layer of Particularly, in this embodiment, the outer layer includes the surface layer 14 forming the surface of the intermediate transfer belt 1 and the intermediate layer 12 provided between the elastic layer 12 and the surface layer 14 . Here, among the plurality of outer layers, the layer having the highest hardness in the image area is defined as the predetermined outer layer. In this embodiment, this predetermined outer layer is the intermediate layer 13 . When the intermediate transfer belt 1 includes only the surface layer 14 forming the surface of the intermediate transfer belt 1 as a single outer layer, the predetermined outer layer is the surface layer 14 .

In the present embodiment, the intermediate layer 13 as the predetermined outer layer has an average thickness at the edges in the width direction of the intermediate transfer belt 1 rather than the average thickness in the image area in the width direction of the intermediate transfer belt 1 . formed to be smaller. More specifically, the average thickness of the intermediate layer 13 at the extreme end (edge) in the width direction of the intermediate transfer belt 1 is greater than the average thickness in the image area in the width direction of the intermediate transfer belt 1 . It is formed to be small, or it is formed so as not to be provided at the extreme end. As a result, at the edges of the intermediate transfer belt 1 in the width direction, the stress generated by curing shrinkage of the intermediate layer 13 during crosslinking can be alleviated, and the edge warping of the intermediate transfer belt 1 can be suppressed.

3. Specific Examples Next, the effects of the present invention will be further described using the following specific examples 1 to 9.

3-1. Measurement Method and Evaluation Method The measurement method and evaluation method will be described. This measurement method and evaluation method are the same in the second embodiment, which will be described later.

<Method for measuring the thickness of each layer>
A method for measuring the thickness of each layer of the intermediate transfer belt 1 will be described. The thickness of each layer (base layer 11, elastic layer 12, intermediate layer 13, surface layer 14) of the intermediate transfer belt 1 is determined by using a cross-section polisher to prepare a vertical section from the surface of the intermediate transfer belt 1, and then making It was obtained by observing the cut cross section with a scanning electron microscope.

Specifically, a cross section polisher (trade name: SM-09010, manufactured by JEOL Ltd.) was used to process the cross section of each sample. After that, this cross section is observed using a scanning electron microscope (trade name: S-4800, manufactured by Hitachi High-Technologies Corporation), the thickness of each layer is measured at arbitrary 10 points, and the average value is the thickness of each layer. thickness (average thickness, average film thickness).

The thickness of the elastic layer 12 is the thickness in the direction substantially perpendicular to the plane of the base layer 11 . Also, the thickness of the intermediate layer 13 is the thickness in the direction substantially orthogonal to the plane of the elastic layer 12 . Also, the thickness of the surface layer 14 is the thickness in the direction substantially orthogonal to the plane of the intermediate layer 13 .

<Method for measuring hardness of each layer>
Next, a method for measuring the hardness (film hardness) of each layer laminated on the base layer 11 of the intermediate transfer belt 1 will be described. The hardness of each layer (elastic layer 12, intermediate layer 13, surface layer 14) of the intermediate transfer belt 1 was measured by setting a test piece of each layer peeled off from the intermediate transfer belt 1 on a glass substrate and using a nanoindenter (FISCHER). The indentation hardness (indentation hardness) was measured with a PICODENTOR HM500 (manufactured). Then, the average value of the stress measured when the thickness of the layer to be measured was pushed from 10% to 20% was used as the hardness.

Incidentally, in this embodiment, the test piece is obtained from within the range of the image area in the width direction of the intermediate transfer belt 1 . Specifically, a test piece is obtained so as to include the central position in the width direction of each intermediate transfer belt 1 to be evaluated. Further, the measured value of the hardness of each layer of the intermediate transfer belt 1 to be evaluated can be represented by the average value of the measured values obtained by performing measurements a plurality of times (for example, five points in the circumferential direction of the belt).

<Evaluation of Edge Warp of Intermediate Transfer Belt>
Next, a method for evaluating edge warpage of the intermediate transfer belt 1 will be described. The edge warp of the intermediate transfer belt 1 was evaluated using a warp amount measuring device 50 shown in FIG. The intermediate transfer belt 1 to be evaluated is suspended between two rollers 51 and 52 having an outer diameter of 30 mm, and a load of 5 kgf is applied to one of the rollers 52 . Then, at the intermediate position between the two rollers 51 and 52 at this time, the difference in the amount of displacement between the central position and the edge of the image area in the width direction of the intermediate transfer belt 1 is measured by the laser displacement meter 53. The amount of warp was measured. In addition, the displacement amount of the end portion of the intermediate transfer belt 1 in the width direction was measured at a position 5 mm inward from the extreme end portion of the intermediate transfer belt 1 in the width direction.

According to the studies of the present inventors, if the amount of warp is 1.5 mm or less, the problem of interference with the apparatus main body, erroneous detection of the end position sensor and home position sensor, and deterioration of detection accuracy can be suppressed. It can be said that it is sufficient for The evaluation of edge warp was good (o) when the amount of warp was 1.5 mm or less, and bad (x) when the amount of warp exceeded 1.5 mm.

3-2. Example 1
In each specific example, the material of the mixed dispersion includes those diluted and dispersed with a solvent, but the amount (parts by mass) of each material used is the amount related to the non-volatile content unless otherwise indicated, and the solvent (volatile matter) is removed. This also applies to the second embodiment, which will be described later.

<Preparation of base layer>
The following materials were kneaded using a twin-screw kneader (trade name: PCM30, manufactured by Ikegai Co., Ltd.) to obtain pellets.
・Polyether ether ketone (trade name: VICTREX PEEK450G, manufactured by Victrex)
・Acetylene black (product name: Denka black granular product, manufactured by Denka)

The above materials were charged into a twin-screw kneader using a weight feeder so that the polyetheretherketone content was 80% by mass and the acetylene black content was 20% by mass. The set temperatures of the cylinders of the twin-screw kneader were 320° C. at the material charging section and 360° C. at the downstream side of the cylinder and the die. The screw rotation speed of the twin-screw kneader was set to 300 rpm, and the material supply amount was set to 8 kg/h.

Next, the obtained pellets were subjected to cylindrical extrusion molding to obtain a belt. Cylindrical extrusion molding was performed using a single-screw extruder (trade name: GT40, manufactured by Plastic Engineering Laboratory Co., Ltd.) and a cylindrical die having a circular opening with a diameter of 300 mm and a gap of 1 mm. Using a gravimetric feeder, the pellets were fed into the single screw extruder at a feed rate of 4 kg/h. The set temperature of the cylinder of the single-screw extruder was 320°C at the material charging portion, and 380°C at the downstream side of the cylinder and the cylindrical die. The molten resin discharged from the single-screw extruder was passed through a gear pump, extruded from a cylindrical die, and taken up at a speed of 85 μm in thickness by a cylindrical take-up machine. The molten resin was cooled and solidified by coming into contact with a cooling mandrel provided between the cylindrical die and the cylindrical take-up machine during the take-off process. The solidified resin was cut into a width of 410 mm by a cylindrical cutting machine installed at the bottom of the cylindrical take-up machine to obtain a crystalline thermoplastic resin belt.

<Preparation of elastic layer>
Tri-n-butylmethylammonium bistrifluoromethanesulfonimide (trade name: FC4400, manufactured by 3M) was used as the conductive agent. Addition curable liquid silicone rubber (trade name: TSE3450 A/B, manufactured by Momentive Performance Materials) is added at a rate of 0.2 parts by mass to 100 parts by mass of the conductive agent liquid, followed by planetary stirring and defoaming. A mixed liquid was obtained by stirring and defoaming with an apparatus (trade name: HM-500, manufactured by Keyence Corporation).

Next, the crystalline thermoplastic resin belt, which serves as the base layer 11, was attached to a cylindrical core, and a ring nozzle for ejecting rubber was attached coaxially with the core. The liquid silicone rubber mixed liquid was supplied to the ring nozzle using a liquid feed pump and discharged from the slit to apply the mixed liquid onto the base layer 11 . At this time, the relative movement speed of the ring nozzle and the discharge amount of the liquid feed pump were adjusted so that the thickness of the cured silicone rubber layer was 260 μm. The coating width of the elastic layer 12 in the width direction of the belt was set to 390 mm, and a range of 15 mm inside from the extreme end in the width direction of the belt was cut off as a thickness adjustment region. The belt coated with the mixed solution was placed in a heating furnace while attached to a core. In the cross-linking (vulcanization) step using a heating furnace, the primary firing was performed at 130° C. for 10 minutes, and the secondary firing was performed at 180° C. for 60 minutes to perform rubber cross-linking. After cooling, the belt was removed from the core to obtain a belt laminated with the elastic layer 12 .

<Preparation of intermediate layer>
As a material for the intermediate layer 13, a mixture of polyamide and phenolic resin (trade name: Maxieve, manufactured by Mitsubishi Gas Chemical Company, M-100, C-93 ratio, 1.2:10) was used. FIG. 3 shows the spray coating used for coating the intermediate layer 13 and the surface layer 14 of the intermediate transfer belt 1 in this specific example (other specific examples of this embodiment and the specific example of the second embodiment described later). 4 is a schematic diagram of the device 40. FIG. The surface of the elastic layer 12 is irradiated with excimer UV to make the surface hydrophilic, and as shown in FIG. The resin mixture was applied using a gun 42 (trade name: W-101, manufactured by Anest Iwata Co., Ltd.). The amount of paint discharged during application was set so that the thickness of the intermediate layer 13 after drying was 8 μm in the image area in the width direction of the intermediate transfer belt 1 .

FIG. 4 is a schematic cross-sectional view showing the positional relationship of each layer at the end of the belt in the width direction. When applying the paint for the intermediate layer 13, as shown in FIG. 4, the discharge amount is gradually increased toward the image area from the coating start position on one of the extreme ends in the width direction of the belt outside the image area. did. After that, at the opposite end of the belt in the width direction, after passing the image area, the discharge amount was reduced until the coating was completed. In this manner, the thickness of the intermediate layer 13 at the end portions in the width direction of the intermediate transfer belt 1 is reduced. At this time, in order to create a gripping margin, the shielding plate 43 is placed between the spray gun 42 and the core 41 so that the intermediate layer 13 is not applied in the range of 10 mm inside from the extreme end at both ends in the width direction of the belt. placed in between.

The thickness distribution of the intermediate layer 13 was set as follows. Each thickness (μm) is an average value of arbitrary 10 points in the circumferential direction of the belt. Let A (μm) be the average thickness of the intermediate layer 13 at the cutting position (most edge) a of the intermediate transfer belt 1 in the width direction. Let B (μm) be the average thickness of the intermediate layer 13 at a position b that is 5 mm inward in the width direction of the intermediate transfer belt 1 from the cutting position (most end) a. Let C (μm) be the average thickness of the intermediate layer 13 at a position c that is 10 mm inward in the width direction of the intermediate transfer belt 1 from the cutting position (most end) a. Let D (μm) be the average thickness of the intermediate layer 13 at an arbitrary position d in the image area (typically, the center position in the width direction of the intermediate transfer belt 1). At this time, it was set so as to satisfy the relationships of the following formulas (1) to (4).
A<B<C<D (1)
B≦D×0.5 (2)
C≦D×0.75 (3)
A≧0 (4)

Although A>0 in the present embodiment, A=0 may be satisfied.

After the application of the resin mixture, the belt was fitted to the core and dried naturally for 15 minutes while being rotated at 200 rpm. After natural drying, a belt laminated with the intermediate layer 13 was obtained.

<Preparation of surface layer>
As a material for the surface layer 14, a fluorine-containing polyurethane resin liquid (trade name: Emralon T-861, manufactured by Henkel Japan Ltd.) in which polytetrafluoroethylene is dispersed in a polyurethane dispersion was used. The belt laminated with the intermediate layer 13 was fitted to the core, and while rotating at 200 rpm, the urethane resin liquid was applied using a spray gun (trade name: W-101, manufactured by Anest Iwata Co., Ltd.). At this time, in order to create a grip margin, a shielding plate is placed between the spray gun and the core so that the surface layer 14 is not applied in the range of 10 mm inside from the extreme end at both ends in the width direction of the belt. did. The amount of paint discharged during application was set so that the thickness of the surface layer 14 after drying was 3 μm.

After applying the resin liquid, the substrate was placed in a heating furnace at 130° C. and left for 30 minutes. After being removed from the heating furnace and cooled, a belt having the surface layer 14 laminated thereon was obtained.

<Cutting the edge of the intermediate transfer belt>
The belt laminated with the base layer 11, the elastic layer 12, the intermediate layer 13, and the surface layer 14 is fitted to the core, and while rotating the core at 2 rpm, a tungsten steel circular blade with a blade thickness of 0.3 mm is penetrated. to cut both ends of the belt to obtain an intermediate transfer belt 1 . As shown in FIG. 4, the cutting position a of the belt was 25 mm inward from the extreme end of the belt.

The thickness of the intermediate layer 13 in Specific Example 1 was A=2 μm, B=4 μm, C=6 μm, and D=8 μm. The relation of the thickness at each position of the intermediate layer 13 in the specific example 1 satisfies the above-mentioned formulas (1) to (4).

In Specific Example 1, the elastic layer 12 has a hardness of 0.002 GPa, the intermediate layer 13 has a hardness of 0.193 GPa, and the surface layer The hardness of No. 14 was 0.0058 GPa.

In Specific Example 1, almost no edge warpage occurred.

3-3. Example 2
An intermediate transfer belt 1 of Specific Example 2 was obtained in the same manner as in Specific Example 1, except that the ejection conditions during coating of the intermediate layer 13 outside the image area were changed.

The thickness of the intermediate layer 13 in Specific Example 2 was A=2 μm, B=2 μm, C=2 μm, and D=2 μm. The relationship of the thickness at each position of the intermediate layer 13 in Specific Example 2 is A=B=C=D and A>0.

As in Specific Example 2, when the thickness of the intermediate layer 13 was 2 μm in the entire region in the width direction, almost no edge warpage occurred.

3-4. Example 3
An intermediate transfer belt 1 of Specific Example 3 was obtained in the same manner as in Specific Example 1, except that the ejection conditions during the coating of the intermediate layer 13 outside the image area were changed.

The thickness of the intermediate layer 13 in Specific Example 3 was A=1 μm, B=1.4 μm, C=2 μm, and D=3 μm. The relation of the thickness at each position of the intermediate layer 13 in Specific Example 3 satisfies the above-mentioned formulas (1) to (4).

In Specific Example 3, almost no edge warpage occurred.

3-5. Example 4
An intermediate transfer belt 1 of Specific Example 4 was obtained in the same manner as in Specific Example 1, except that the ejection conditions during the coating of the intermediate layer 13 outside the image area were changed.

The thickness of the intermediate layer 13 in Specific Example 4 was A=1 μm, B=1.4 μm, C=2.5 μm, and D=3 μm. The thickness relationship at each position of the intermediate layer 13 in Specific Example 4 is as follows:
A<B<C<D
B≦D×0.5
C>D×0.75
A > 0
It has become.

In Concrete Example 4, the edge warpage exceeded 1.5 mm.

3-6. Example 5
An intermediate transfer belt 1 of Specific Example 5 was obtained in the same manner as in Specific Example 1, except that the ejection conditions during coating of the intermediate layer 13 outside the image area were changed.

The thickness of the intermediate layer 13 in Specific Example 5 was A=1 μm, B=1.6 μm, C=2 μm, and D=3 μm. The thickness relationship at each position of the intermediate layer 13 in Specific Example 5 is as follows:
A<B<C<D
B>D×0.5
C≦D×0.75
A > 0
It has become.

In Concrete Example 5, the edge warpage exceeded 1.5 mm.

3-7. Example 6
An intermediate transfer belt 1 of Specific Example 6 was obtained in the same manner as in Specific Example 1, except that the ejection conditions during coating of the intermediate layer 13 outside the image area were changed.

The thickness of the intermediate layer 13 in Specific Example 6 was A=6 μm, B=7 μm, C=11 μm, and D=15 μm. The relation of the thickness at each position of the intermediate layer 13 in Specific Example 6 satisfies the above-mentioned formulas (1) to (4).

In Specific Example 6, the edge warp was 1.5 mm or less.

3-8. Example 7
An intermediate transfer belt 1 of Specific Example 7 was obtained in the same manner as in Specific Example 1 except that the ejection conditions during coating of the intermediate layer 13 outside the image area were changed.

The thickness of the intermediate layer 13 in Specific Example 7 was A=6 μm, B=7 μm, C=12 μm, and D=15 μm. The thickness relationship at each position of the intermediate layer 13 in Specific Example 7 is as follows:
A<B<C<D
B≦D×0.5
C>D×0.75
A > 0
It has become.

In Concrete Example 7, the edge warpage exceeded 1.5 mm.

3-9. Example 8
An intermediate transfer belt 1 of Specific Example 8 was obtained in the same manner as in Specific Example 1, except that the ejection conditions during the coating of the intermediate layer 13 outside the image area were changed.

The thickness of the intermediate layer 13 in Specific Example 8 was A=7 μm, B=8 μm, C=11 μm, and D=15 μm. The thickness relationship at each position of the intermediate layer 13 in Specific Example 8 is as follows:
A<B<C<D
B>D×0.5
C≦D×0.75
A > 0
It has become.

In Concrete Example 8, the edge warpage exceeded 1.5 mm.

3-10. Example 9
An intermediate transfer belt 1 of Specific Example 9 was obtained in the same manner as in Specific Example 1 except that the ejection conditions during coating of the intermediate layer 13 outside the image area were changed.

The thickness of the intermediate layer 13 in Specific Example 9 was A=6 μm, B=8 μm, C=12 μm, and D=15 μm. The thickness relationship at each position of the intermediate layer 13 in Specific Example 9 is as follows:
A<B<C<D
B>D×0.5
C>D×0.75
A > 0
It has become.

In Concrete Example 9, the edge warpage exceeded 1.5 mm.

Table 1 shows the thickness at each position of the intermediate layer 13 of the intermediate transfer belt 1 of each specific example, the relationship between the thickness of the image area and the edge, and the evaluation of edge warpage.

As can be seen from the results in Table 1, among the intermediate layer 13 and the surface layer 14 provided closer to the surface side of the intermediate transfer belt 1 than the elastic layer 12, the thickness of the intermediate layer 13, which has the highest hardness in the image area, in the image area is 2 μm or more, the average thicknesses A (μm), B (μm), C (μm), and D (μm) at positions a, b, c, and d in the width direction of the intermediate transfer belt 1 are calculated by the following formula ( By satisfying 1) to (4), edge warping can be suppressed.
A<B<C<D (1)
B≦D×0.5 (2)
C≦D×0.75 (3)
A≧0 (4)

At this time, from the standpoint of ease of production, typically, as in the present embodiment, intermediate transfer belt 1 is formed on the outer side of the image area in the width direction of intermediate transfer belt 1 from the image area side toward the endmost side. The average thickness of layer 13 is gradually reduced.

As described above, according to the present embodiment, the intermediate transfer belt 1 having the elastic layer 12 and the layer 13 harder than the elastic layer 12 provided on the surface side of the elastic layer 12 can be prevented from warping at the edges. Therefore, according to the present embodiment, damage to the widthwise end of the intermediate transfer belt 1 due to interference between the widthwise end of the intermediate transfer belt 1 and the apparatus main body, and erroneous detection of the end position sensor or the home position sensor can be prevented. and deterioration of detection accuracy can be suppressed.

[Second embodiment]
Next, a second embodiment of the invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Therefore, in the image forming apparatus of the present embodiment, elements having the same or corresponding functions or configurations as those of the image forming apparatus of the first embodiment are denoted by the same reference numerals as in the first embodiment. A detailed explanation is omitted.

1. Overview of this Embodiment In the first embodiment, the intermediate layer 13 as a predetermined outer layer has an average thickness at the end portions in the width direction of the intermediate transfer belt 1 rather than the average thickness in the image area in the width direction of the intermediate transfer belt 1. was formed so that the thickness of the On the other hand, in the present embodiment, the intermediate layer 13 as the predetermined outer layer has a smaller hardness at the end portions in the width direction of the intermediate transfer belt 1 than in the image area in the width direction of the intermediate transfer belt 1. is formed as More specifically, the hardness of the intermediate layer 13 at a position 5 mm inward from the extreme end in the width direction of the intermediate transfer belt 1 is smaller than the hardness in the image area in the width direction of the intermediate transfer belt 1 . is formed as Such hardness setting is typically achieved by setting the heating temperature during baking of the intermediate layer 13 to be lower at the edges than at the image area. As a result, at the edges of the intermediate transfer belt 1 in the width direction, the stress generated by curing shrinkage of the intermediate layer 13 during crosslinking can be alleviated, and the edge warping of the intermediate transfer belt 1 can be suppressed.

2. Experimental example 1
In order to examine the influence of the hardness of the intermediate layer 13 at the widthwise end of the intermediate transfer belt 1, the following Experimental Example 1 (Specific Examples 21 to 27: attached.) was evaluated.

2-1. Example 21
<Preparation of base layer>
The following materials were kneaded using a twin-screw kneader (trade name: PCM30, manufactured by Ikegai Co., Ltd.) to obtain pellets.
・Polyether ether ketone (trade name: VICTREX PEEK450G, manufactured by Victrex)
・Acetylene black (product name: Denka black granular product, manufactured by Denka)

Each of the above materials was charged into a twin-screw kneader using a weight feeder such that the polyetheretherketone content was 80% by mass and the acetylene black content was 20% by mass. The set temperatures of the cylinders of the twin-screw kneader were 320° C. at the material charging section and 360° C. at the downstream side of the cylinder and the die. The screw rotation speed of the twin-screw kneader was set to 300 rpm, and the material supply amount was set to 8 kg/h.

Next, the obtained pellets were subjected to cylindrical extrusion molding to obtain a belt. Cylindrical extrusion molding was performed using a single-screw extruder (trade name: GT40, manufactured by Plastic Engineering Laboratory Co., Ltd.) and a cylindrical die having a circular opening with a diameter of 300 mm and a gap of 1 mm. Using a gravimetric feeder, the pellets were fed into the single screw extruder at a feed rate of 4 kg/h. The set temperature of the cylinder of the single-screw extruder was 320°C at the material charging portion, and 380°C at the downstream side of the cylinder and the cylindrical die. The molten resin discharged from the single-screw extruder was passed through a gear pump, extruded from a cylindrical die, and taken up at a speed of 85 μm in thickness by a cylindrical take-up machine. The molten resin was cooled and solidified by coming into contact with a cooling mandrel provided between the cylindrical die and the cylindrical take-up machine during the take-off process. The solidified resin was cut into a width of 460 mm by a cylindrical cutting machine installed at the bottom of the cylindrical take-up machine to obtain a crystalline thermoplastic resin belt.

<Preparation of elastic layer>
Tri-n-butylmethylammonium bistrifluoromethanesulfonimide (trade name: FC4400, manufactured by 3M) was used as the conductive agent. Addition curable liquid silicone rubber (trade name: TSE3450 A/B, manufactured by Momentive Performance Materials) is added at a rate of 0.2 parts by mass to 100 parts by mass of the conductive agent liquid, followed by planetary stirring and defoaming. A mixed liquid was obtained by stirring and defoaming with an apparatus (trade name: HM-500, manufactured by Keyence Corporation).

Next, the crystalline thermoplastic resin belt, which serves as the base layer 11, was attached to a cylindrical core, and a ring nozzle for ejecting rubber was attached coaxially with the core. The liquid silicone rubber mixed liquid was supplied to the ring nozzle using a liquid feed pump and discharged from the slit to apply the mixed liquid onto the base layer 11 . At this time, the relative movement speed of the ring nozzle and the discharge amount of the liquid feed pump were adjusted so that the thickness of the cured silicone rubber layer was 260 μm.

The belt coated with the mixed solution was placed in a heating furnace while attached to a core. In the cross-linking (vulcanization) step using a heating furnace, the primary firing was performed at 130° C. for 10 minutes, and the secondary firing was performed at 180° C. for 60 minutes to perform rubber cross-linking. After cooling, the belt was removed from the core to obtain a belt laminated with the elastic layer 12 .

<Preparation of intermediate layer>
As a material for the intermediate layer 13, a polyurethane resin liquid (trade name: HYDRAN 201, a paint obtained by adding 20 parts by weight of a curing agent Bonderite WH-2 to DIC Corporation) was used. The surface of the elastic layer 12 is irradiated with excimer UV to make the surface hydrophilic, and as shown in FIG. The polyurethane resin liquid was applied using a gun 42 (trade name: W-101, manufactured by Anest Iwata Co., Ltd.). The amount of paint discharged during application was set so that the thickness of the intermediate layer 13 after drying was 8 μm at the central position in the width direction of the intermediate transfer belt 1 . At this time, in order to create a gripping margin, the shielding plate 43 is placed between the spray gun 42 and the core 41 so that the intermediate layer 13 is not applied in the range of 10 mm inside from the extreme end at both ends in the width direction of the belt. placed in between. Note that in the present embodiment, the thickness of the intermediate layer 13 is substantially the same throughout the width of the intermediate transfer belt 1 .

After the application of the resin mixture, the belt was fitted to the core and dried naturally for 15 minutes while being rotated at 200 rpm. After natural drying, a belt laminated with the intermediate layer 13 was obtained.

<Preparation of surface layer>
As a material for the surface layer 14, a fluorine-containing polyurethane resin liquid (trade name: Emralon T-861, manufactured by Henkel Japan Ltd.) in which polytetrafluoroethylene is dispersed in a polyurethane dispersion was used. The belt laminated with the intermediate layer 13 was fitted to the core, and while rotating at 200 rpm, the urethane resin liquid was applied using a spray gun (trade name: W-101, manufactured by Anest Iwata Co., Ltd.). At this time, in order to create a grip margin, a shielding plate is placed between the spray gun and the core so that the surface layer 14 is not applied in the range of 10 mm inside from the extreme end at both ends in the width direction of the belt. did. The amount of paint discharged during application was set so that the thickness of the surface layer 14 after drying was 3 μm.

<Firing of intermediate layer and surface layer>
A radiant furnace was used for baking the intermediate layer 13 and the surface layer 14 . FIG. 7 is a schematic partial cross-sectional perspective view of the radiant furnace 60 used in this experimental example. This radiant furnace 60 is of a type that directly heats an object with far infrared rays emitted from the surface of a heated furnace body 61 . This radiant furnace 60 can uniformly heat the surface by heating an annular furnace body 61 having a thickness of 10 mm with a mantle heater. In order to uniformly and efficiently radiate far-infrared rays, the inner surface of the furnace body 61 is coated with a heat-resistant black paint (manufactured by Okitsumo Co., Ltd.). The radiant furnace 60 changes the radiant heat between the belt center region corresponding to the image region in the width direction of the intermediate transfer belt 1 and the belt end regions corresponding to both width direction end portions of the intermediate transfer belt 1. Therefore, it is structured as follows. That is, the furnace body 61 has a central furnace body 61a that heats the central region whose width is set to be 10 mm larger than both ends of the image region, and both end regions that are arranged adjacent to both ends in the width direction of the central furnace body 61a. and an end furnace body 61b for heating the . Since the radiant heat is radiated obliquely to surfaces other than the facing surfaces, the temperature switching part of the two different furnace bodies 61a and 61b becomes the integrated value of the radiant heat radiated from the two different furnace bodies 61a and 61b. The temperature gradually decreases toward the ends in the width direction of the body 61 .

The belt obtained by applying the surface layer 14 to the uncured intermediate layer 13 was set in the radiant furnace 60 and left for a predetermined period of time to obtain a belt in which the intermediate layer 13 and the surface layer 14 were baked. At this time, the temperature of the central furnace body 61a for heating the central region of the belt was 130° C., the temperature of the end furnace body 61b for heating the both end regions of the belt was 70° C., and the firing time was 20 minutes. .

<Cutting the edge of the intermediate transfer belt>
The belt laminated with the base layer 11, the elastic layer 12, the intermediate layer 13, and the surface layer 14 is fitted to the core, and while rotating the core at 2 rpm, a tungsten steel circular blade with a blade thickness of 0.3 mm is penetrated. to cut both ends of the belt to obtain an intermediate transfer belt 1 .

Note that, in this embodiment, the width of the intermediate transfer belt 1 after the end portion is cut is 360 mm, as in the first embodiment. Further, in this embodiment, as in the first embodiment, the width of the image area in the width direction of the intermediate transfer belt 1 is 330 mm. This image area is arranged at the center of the intermediate transfer belt 1 in the width direction with the center of the intermediate transfer belt 1 in the width direction as a reference.

2-2. Examples 22-27
Intermediate transfer belts 1 of Specific Examples 22 to 27 were obtained in the same manner as in Specific Example 21, except that the temperature of the furnace body 61 of the radiant furnace 60 in firing the intermediate layer 13 and the surface layer 14 was changed. In Specific Examples 22 to 27, the temperature of the central furnace body 61a that heats the central region of the belt was fixed at 130° C., and the temperature and firing time of the end furnace bodies 61b that heat the both end regions of the belt are shown in Table 2. Firing was performed by shaking as shown.

The hardness of the intermediate layer 13 at the central position and the end position of the intermediate transfer belt 1, the temperature and firing time of the end furnace body 61b in firing the intermediate layer 13 and the surface layer 14, and the end Table 2 shows the evaluation of warpage. FIG. 8(a) shows the relationship between the temperature of the end furnace body 61, the firing time, and the amount of warpage in firing the intermediate layer 13 and the surface layer 14 in each specific example of Experimental Example 1. As shown in FIG. FIG. 8B shows the relationship between the amount of warp and the hardness of the intermediate layer 13 at the end position of the intermediate transfer belt 1 for each specific example of Experimental Example 1. As shown in FIG.

In the present embodiment, the test piece for hardness measurement is the image area in the width direction of the intermediate transfer belt 1 (specifically, the area including the center position in the width direction) and the width direction of the intermediate transfer belt 1. Each is obtained within a range including a position 5 mm inward from the extreme end (end position). Further, the measured values of the hardness of each layer of the intermediate transfer belt 1 to be evaluated are obtained by performing measurements a plurality of times (for example, five points in the circumferential direction of the belt) at each of the above-mentioned central position and end position. It can be represented by the mean of the values. In any of Examples 21 to 27, the hardness of the elastic layer 12 in the image area was 0.002 GPa, and the hardness of the surface layer 14 in the image area was 0.0015 GPa.

3. Experimental example 2
In order to examine the influence of the hardness of the intermediate layer 13 at the widthwise end of the intermediate transfer belt 1, the following Experimental Example 2 (Specific Examples 31 to 38: numbered.) was evaluated.

The same procedure as in Experimental Example 1 was performed except that a mixture of polyamide and phenolic resin (trade name: Maxieve, manufactured by Mitsubishi Gas Chemical Company, M-100, C-93 ratio, 1.2:10) was used as the material for the intermediate layer 13. The intermediate transfer belt 1 of each specific example of Experimental Example 2 was obtained in the same manner as the intermediate transfer belt 1 .

In Specific Examples 31 to 38, in firing the intermediate layer 13 and the surface layer 14, the temperature of the central furnace body 61a that heats the central region of the belt was fixed at 130° C., and the end furnaces that heat the both end regions of the belt were used. The body 61b was fired while varying the temperature and firing time as shown in Table 3.

The hardness of the intermediate layer 13 at the center position and the end position of the intermediate transfer belt 1, the temperature and firing time of the end furnace body 61b in firing the intermediate layer 13 and the surface layer 14, and the end Table 3 shows the evaluation of warpage. FIG. 9(a) shows the relationship between the temperature of the end furnace body 61, the firing time, and the amount of warpage in firing the intermediate layer 13 and the surface layer 14 in each specific example of Experimental Example 2. As shown in FIG. FIG. 9B shows the relationship between the amount of warpage and the hardness of the intermediate layer 13 at the edge position of the intermediate transfer belt 1 for each specific example of Experimental Example 2. As shown in FIG.

In any of Examples 31 to 38, the hardness of the elastic layer 12 in the image area was 0.002 GPa, and the hardness of the surface layer 14 in the image area was 0.0015 GPa.

4. Effect From the results of the specific examples of Experimental Examples 1 and 2 shown in Tables 2 and 3, the intermediate layer 13 and the surface layer 14 provided on the surface side of the intermediate transfer belt 1 from the elastic layer 12, in the image region. The hardness of the intermediate layer 13 having the highest hardness at a position 5 mm inward in the width direction of the intermediate transfer belt 1 from the extreme end in the width direction of the intermediate transfer belt 1 is lower than the hardness at any position within the image area. Thus, edge warping can be suppressed.

Further, as can be seen from FIGS. 8A and 9A, by adjusting the heating temperature and the firing time of the end portion of the belt during firing of the intermediate layer 13, the intermediate layer 13 at the end portion of the belt can be By adjusting the hardness of , the amount of warpage can be suppressed to a predetermined value (here, 1.5 mm) or less. At this time, from the standpoint of ease of production, typically, as in the present embodiment, intermediate transfer belt 1 is formed on the outer side of the image area in the width direction of intermediate transfer belt 1 from the image area side toward the endmost side. The hardness of layer 13 is gradually reduced. In this embodiment, the furnace body 61 of the radiant furnace 60 used for firing is divided into a central furnace body 61a and an end furnace body 61b, and a temperature gradient (the temperature gradually decreases) is generated from the central position toward the end positions. Such hardness distribution is achieved by providing

Moreover, as can be seen from Tables 2 and 3, FIG. 8B, and FIG. The hardness of the intermediate layer 13 at a position 5 mm inward in the width direction of the intermediate transfer belt 1 from the edge is preferably 0.01 GPa or less. However, the hardness of the intermediate layer 13 at a position 5 mm inward in the width direction of the intermediate transfer belt 1 from the extreme end of the intermediate transfer belt 1 is greater than the hardness of the elastic layer 12 in the image area.

As described above, according to the present embodiment, the intermediate transfer belt 1 having the elastic layer 12 and the layer 13 harder than the elastic layer 12 provided on the surface side of the elastic layer 12 can be prevented from warping at the edges. Therefore, according to the present embodiment, the edge of the intermediate transfer belt 1 in the width direction is damaged due to interference between the edge of the intermediate transfer belt 1 and the apparatus main body, and erroneous detection and detection accuracy of the edge position sensor and the home position sensor. can be suppressed.

REFERENCE SIGNS LIST 1 intermediate transfer belt 11 base layer 12 elastic layer 13 intermediate layer 14 surface layer 40 spray coating device 60 radiant furnace

Claims (8)

An intermediate transfer belt having a surface on which a toner image can be transferred, comprising a base layer, an elastic layer provided on the surface side of the base layer, and a single or multiple outer layers provided on the surface side of the elastic layer. and an intermediate transfer belt having
The average thickness in the image area of the predetermined outer layer, which is the layer having the highest hardness in the image area where the toner image in the width direction of the intermediate transfer belt can be transferred, among the single outer layer or the plurality of outer layers A is the average thickness of the predetermined outer layer at the extreme end in the width direction of the intermediate transfer belt, and the predetermined outer layer at a position 5 mm inward in the width direction of the intermediate transfer belt from the extreme end. B is the average thickness of the predetermined outer layer, C is the average thickness of the predetermined outer layer at a position 10 mm inward in the width direction of the intermediate transfer belt from the outermost end, and C is the predetermined outer layer at an arbitrary position in the image area When the average thickness of is D, the following formulas (1) to (4),
A<B<C<D (1)
B≦D×0.5 (2)
C≦D×0.75 (3)
A≧0 (4)
An intermediate transfer belt characterized by satisfying the relationship of 3. An average thickness of the predetermined outer layer is gradually reduced from the image area side toward the outermost side outside the image area in the width direction of the intermediate transfer belt. 1. The intermediate transfer belt according to 1. An intermediate transfer belt having a surface on which a toner image can be transferred, comprising a base layer, an elastic layer provided on the surface side of the base layer, and a single or multiple outer layers provided on the surface side of the elastic layer. and an intermediate transfer belt having
When the single outer layer or the layer having the highest hardness in the image region where the toner image in the width direction of the intermediate transfer belt can be transferred among the plurality of outer layers is the predetermined outer layer, the width direction of the intermediate transfer belt. wherein the hardness of the predetermined outer layer at a position 5 mm inward in the width direction of the intermediate transfer belt from the most end of the intermediate transfer belt is lower than the hardness of the predetermined outer layer at an arbitrary position within the image area. belt. 4. The method according to claim 3, wherein, outside the image area in the width direction of the intermediate transfer belt, the hardness of the predetermined outer layer gradually decreases from the image area side toward the extreme end portion side. intermediate transfer belt . 5. The outer layer according to claim 3, wherein a hardness of the predetermined outer layer at a position 5 mm inward in the width direction of the intermediate transfer belt from the most end portion of the intermediate transfer belt is 0.01 GPa or less. Intermediate transfer belt. 3. The outer layer includes a surface layer forming the surface and an intermediate layer provided between the elastic layer and the surface layer, and the predetermined outer layer is the intermediate layer. 6. The intermediate transfer belt according to any one of 1 to 5. 6. The intermediate transfer belt according to claim 1, wherein the outer layer includes a surface layer forming the surface, and the predetermined outer layer is the surface layer. An image forming apparatus comprising the intermediate transfer belt according to claim 1 .

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