Electrophotographic belt and electrophotographic image forming apparatus using the same

Abstract

To provide an electrophotography belt capable of combining flame retardancy and embossed paper transferability.SOLUTION: An electronic photographic belt having an elastic layer, the elastic layer containing at least silicone rubber, magnesium hydroxide, and silica particles modified with a hydrophilic group, the magnesium hydroxide is dispersed in the silicone rubber, a content of the magnesium hydroxide is 10 to 25 pts.mass with respect to 100 pts.mass of the silicone rubber, and the content of silica particles modified with a hydrophilic group is 2 to 9 pts.mass with respect to 100 pts.mass of the silicone rubber, an arithmetic mean value of each area of Voronoi polygons formed when a section perpendicular to a circumferential direction of the electrophotographic belt is subjected to Voronoi division using magnesium hydroxide particles exposed in the section as generating points is set to S, and a standard deviation is set to σ, the electrophotographic belt having a variation coefficient of 1.5 or less calculated by the following formula (1). Variation coefficient=σ / S formula (1).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrophotographic belt used in an electrophotographic image forming apparatus such as a copying machine or a printer, and to an electrophotographic image forming apparatus. [Background technology]

[0002] In electrophotographic image forming apparatuses, the tandem method is widely adopted in which toner images of each color of Y, M, C, and K are superimposed on an intermediate transfer belt, which is an electrophotographic belt, and then transferred all at once onto paper to obtain a full-color image. In such image forming apparatuses, there are cases where an intermediate transfer belt having at least one elastic layer (hereinafter also referred to as an elastic intermediate transfer belt) is used to further improve image quality. The elastic intermediate transfer belt is soft because it has at least one elastic layer in its layer structure, and is known to be effective in preventing the hollow toner phenomenon because it can reduce the pressure acting on the toner in the transfer section. In addition, since it has good adhesion to the paper in the secondary transfer section, it is known to have an excellent effect not only in improving the transfer efficiency for general paper, but also in the transferability for thick paper and paper with unevenness. One of the properties required for such intermediate transfer belts is flame retardancy. Patent Document 1 describes the addition of a metal hydroxide as a flame retardant as one means for inexpensively improving the flame retardancy. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-12888 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when an inexpensive metal hydroxide is added to an elastic intermediate transfer belt to impart flame retardancy, the more the amount of metal hydroxide added, the harder the elastic layer becomes, and the harder the elastic layer becomes, the smaller the effect of reducing the pressure acting on the toner in the transfer section becomes, which leads to problems such as a smaller effect of reducing the hollow phenomenon and a smaller effect of improving transferability. In addition, flame retardants such as platinum compounds and various modifiers that can impart flame retardancy at an amount of about 1 part by mass without hardening the elastic layer are commercially available, but they are expensive, costing several thousand yen or more per gram.Even if the amount of metal hydroxide flame retardants added is about 10 parts by mass, they are inexpensive, costing several thousand yen or more per kilogram, so even if a large amount is added, the cost of the flame retardant is about 1 / 100th. Therefore, an object of one aspect of the present disclosure is to provide an electrophotographic belt that is compatible with flame retardancy and embossed paper transferability. According to another aspect of the present disclosure, an object is to provide an electrophotographic image forming apparatus including the above-mentioned electrophotographic belt as an intermediate transfer belt. [Means for solving the problem]

[0005] According to one aspect of the present disclosure, An electrophotographic belt having an elastic layer, the elastic layer contains at least silicone rubber, magnesium hydroxide, and silica particles modified with a hydrophilic group; the magnesium hydroxide is dispersed in the silicone rubber, The content of the magnesium hydroxide is 10 to 25 parts by mass relative to 100 parts by mass of the silicone rubber, the content of the hydrophilic group-modified silica particles is 2 to 9 parts by mass relative to 100 parts by mass of the silicone rubber, The electrophotographic belt has a coefficient of variation of 1.5 or less, calculated by the following formula (1), where S is the arithmetic mean value of the areas of Voronoi polygons formed when a cross section of the electrophotographic belt in a direction perpendicular to the circumferential direction is divided into Voronoi polygons with the magnesium hydroxide particles exposed on the cross section as generating points, and σ is the standard deviation. Coefficient of variation = σ / S Equation (1) Effect of the Invention

[0006] According to one aspect of the present disclosure, it is possible to provide an electrophotographic belt that is compatible with flame retardancy and embossed paper transferability. According to another aspect of the present disclosure, there can be provided an electrophotographic image forming apparatus including the above-mentioned electrophotographic belt as an intermediate transfer belt. [Brief description of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view showing an example of an image forming apparatus using an elastic intermediate transfer belt of the present disclosure. [Diagram 2] 1 is a diagram illustrating a cross section of an elastic intermediate transfer belt according to the present disclosure. [Diagram 3] 1 is a SEM reflected image of an elastic layer in cross section of an elastic intermediate transfer belt of the present disclosure. [Figure 4] 4 is an example of a binarized image obtained by binarizing the image shown in FIG. 3. [Diagram 5] 5 is an example of a diagram in which the image shown in FIG. 4 is divided into Voronoi regions. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present disclosure will be described in detail. However, the scope of the present disclosure is not limited to the following embodiments. 2, the elastic intermediate transfer belt of the present embodiment is a laminated body composed of at least three layers, namely, a base layer 21, an elastic layer 22, and a surface layer 23. However, it is not limited to these three layers, and a primer layer for improving adhesion between the layers, a stress relaxation layer for suppressing cracking of the surface layer 23, and an intermediate layer for suppressing bleeding may be added.

[0009] (base layer) The base layer 21 in the present disclosure will be described. The base layer 21 in the present disclosure is a seamless cylindrical type in the form of a roll or belt, and examples of materials suitable for the base layer 21 include the following resin materials: polyether ether ketone, polyethylene terephthalate, polybutylene naphthalate, polyester, polyimide, polyamide, polyamideimide, polyacetal, polyphenylene sulfide, etc. The resin for the base layer 21 may be made conductive by adding conductive powder such as metal powder, conductive oxide powder, conductive carbon, etc. In the present disclosure, polyether ether ketone or polyimide with added carbon black is particularly preferred from the viewpoint of obtaining excellent mechanical strength and conductivity. The thickness of the base layer 21 is preferably 10 μm or more and 500 μm or less. If it is less than 10 μm, the mechanical strength is significantly reduced, and if it is more than 500 μm, the rigidity becomes too strong, making it difficult to use it as an intermediate transfer body.

[0010] (Elastic layer) Next, the elastic layer 22 in the present disclosure will be described. The elastic layer 22 needs to have a suitable degree of flexibility in order to conform to the surface shape of the recording medium. In the present disclosure, silicone rubber is used because it has a small compression set even though it is a low-hardness rubber and has excellent ozone resistance. The thickness of the elastic layer 22 is preferably 100 to 1000 μm, more preferably 200 to 500 μm. The JIS-A hardness of the elastic layer 22 is preferably 55 degrees or less, more preferably 25 degrees or less.

[0011] The intermediate transfer belt is required to be flame retardant because it conducts electricity at the transfer section. It is difficult to ensure the necessary flame retardancy without adding a flame retardant, not only for silicone rubber but also for various rubbers such as chloroprene rubber, urethane rubber, and acrylic rubber. Flame retardants include metal hydroxides such as magnesium hydroxide and aluminum hydroxide that utilize endothermic action, platinum compounds and phenolic compounds that suppress thermal decomposition, intumescent compounds that have an oxygen blocking effect, and phosphate ester condensation compounds. In this disclosure, magnesium hydroxide is used. The magnesium hydroxide is dispersed in the silicone rubber. The content of magnesium hydroxide is 10 to 25 parts by mass per 100 parts by mass of silicone rubber. By making the content of magnesium hydroxide 10 parts by mass or more per 100 parts by mass of silicone rubber, excellent flame retardancy can be obtained. By making the content of magnesium hydroxide 25 parts by mass or less per 100 parts by mass of silicone rubber, appropriate flexibility can be obtained.

[0012] Magnesium hydroxide oxidizes during combustion to generate water and act as a flame retardant, but if magnesium hydroxide aggregates in some parts of the silicone rubber, it is believed that this will result in areas without magnesium hydroxide, resulting in a decrease in flame retardancy. Therefore, the issue of flame retardancy can be resolved by improving the dispersibility of magnesium hydroxide, i.e., by reducing the coefficient of variation of the area of ​​the Voronoi polygon.

[0013] A Voronoi polygon is a polygon formed by Voronoi tessellation. Specifically, Voronoi tessellation is performed using the following procedure. For example, when there are multiple target regions within a certain field of view, all adjacent regions are connected independently with straight lines, and perpendicular bisectors are created for each line connecting two adjacent regions. When the perpendicular bisectors extending from adjacent lines are connected, a region is created in which one region is surrounded by the perpendicular bisectors. The perimeter of the region surrounded by these perpendicular bisectors forms a polygon, and this polygon is called a Voronoi polygon. In the present disclosure, the multiple regions refer to a magnesium hydroxide region (hereinafter also referred to as a first region) and other regions (hereinafter also referred to as a second region).

[0014] There are two division methods: division based on the center of gravity of the region, and division based on the edge of the region. In this disclosure, division based on the edge is used. In division based on the edge, the straight line that is the shortest distance is selected from among the straight lines connecting the edges of two adjacent first regions, and the polygon formed by the perpendicular bisector to this line becomes the Voronoi polygon.

[0015] Next, the Voronoi polygon will be specifically described. A backscattered electron image of a cross section of an electrophotographic belt in a direction perpendicular to the circumferential direction as shown in FIG. 3 is binarized using any image processing software, and the image is divided into a first region of magnesium hydroxide and a second region of the rest as shown in FIG. 4. Next, Voronoi division is performed as described above to obtain an image as shown in FIG. Next, when the arithmetic mean value of the area of ​​each Voronoi polygon formed by Voronoi tessellation using magnesium hydroxide particles as kernel points is taken as S and the standard deviation is taken as σ, the value obtained by dividing σ by S is taken as the coefficient of variation (=σ / S). If this coefficient of variation is 1.5 or less, the dispersion state of magnesium hydroxide is good, and excellent flame retardancy is obtained.

[0016] The elastic layer contains 2 to 9 parts by mass of silica particles modified with a hydrophilic group relative to 100 parts by mass of silicone rubber. It is believed that when silica particles modified with hydrophilic groups are added, the viscosity of the liquid silicone rubber increases significantly, resulting in more shear force being applied to the magnesium hydroxide when the liquid silicone rubber is kneaded, improving the dispersibility of the magnesium hydroxide.

[0017] The elastic layer 22 in the present disclosure may contain an electronic conductivity imparting agent or an ionic conductivity imparting agent within a range that does not impair the effects of the invention. Examples of the electronic conductivity imparting agent include the following: conductive carbon black such as acetylene black and ketjen black, graphite, graphene, carbon fiber, carbon nanotubes, metal powder such as silver, copper, nickel, etc., conductive zinc white, conductive calcium carbonate, conductive titanium oxide, conductive tin oxide, conductive mica, etc. Among these, conductive carbon black is preferably used from the viewpoint of ease of controlling the electrical resistance. Examples of the ionic conductivity imparting agent include lithium salts and potassium salts, as well as pyridine-based, alicyclic amine-based, and aliphatic amine-based ionic liquids.

[0018] The amount of the electronic conductivity imparting agent or ionic conductivity imparting agent blended in the elastic layer 22 is preferably 35 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of silicone rubber, from the viewpoint of obtaining excellent mechanical strength. This provides the elastic layer 22 with stable conductivity suitable for an intermediate transfer belt. In addition, the elastic layer 22 in the present disclosure may contain other additives such as a filler, a crosslinking accelerator, a crosslinking retarder, a crosslinking assistant, a scorch inhibitor, an antiaging agent, a softener, a heat stabilizer, a flame retardant, a flame retardant assistant, an ultraviolet absorber, and a rust inhibitor.

[0019] Examples of the filler include reinforcing fillers such as fumed silica, crystalline silica, wet silica, fumed titanium oxide, and cellulose nanofibers. From the viewpoint of ease of dispersion in silicone rubber, the reinforcing filler may be surface-modified with an organosilicon compound such as an organoalkoxysilane, an organohalosilane, an organosilazane, a diorganosiloxane oligomer having both molecular chain terminals blocked with silanol groups, or a cyclic organosiloxane. Furthermore, a primer layer (not shown) may be provided as necessary between the base layer 21 and the elastic layer 22. The thickness of the primer layer is preferably 0.1 μm or more and 2 μm or less from the viewpoint of reducing cohesive failure in the primer layer.

[0020] (Surface layer) In this embodiment, the electrophotographic belt is obtained by forming the surface layer 23 on the elastic layer 22. Examples of the material for the surface layer 23 include urethane resin. The Martens hardness of the obtained electrophotographic belt when pressed 10 μm was 0.05 N / mm 2 More than 0.20N / mm 2 It is preferable that: Martens hardness is 0.05N / mm 2 If the hardness is less than this, the mechanical properties deteriorate, such as an increased compression set and a decreased elongation at break, and therefore, it is preferable that the hardness be greater than this for an electrophotographic belt. Martens hardness is 0.20N / mm 2 If the thickness exceeds this value, the flexibility of the elastic layer is lost, and the elastic layer may not be able to conform sufficiently to embossed paper or the like.

[0021] (Image forming device) An example of an image forming apparatus using the electrophotographic belt of the present disclosure as an elastic intermediate transfer belt will be described with reference to Fig. 1. It should be noted that the present disclosure is not limited to the following description. The electrophotographic image forming apparatus 100 shown in FIG. 1 is a color electrophotographic image forming apparatus (color laser printer). In this electrophotographic image forming apparatus, image forming units Py, Pm, Pc, and Pk of the colors yellow (Y), magenta (M), cyan (C), and black (K) are arranged in the moving direction along a flat portion of an intermediate transfer belt 7, which is an intermediate transfer body. 1Y, 1M, 1C, and 1K respectively indicate electrophotographic photosensitive bodies. 2Y, 2M, 2C, and 2K respectively indicate roller-shaped charging members (hereinafter also referred to as charging rollers). 3Y, 3M, 3C, and 3K respectively indicate laser exposure devices. 4Y, 4M, 4C, and 4K respectively indicate developing devices. 5Y, 5M, 5C, and 5K respectively indicate primary transfer rollers. Since the basic configuration of each image forming unit is the same, the details of the image forming units will be described only for the yellow image forming unit Py.

[0022] The yellow image forming unit Py has a drum-shaped electrophotographic photosensitive member 1Y (hereinafter also referred to as a "photosensitive drum" or a "first image bearing member") as an image bearing member. The photosensitive drum 1Y is formed by laminating a charge generating layer, a charge transport layer, and a surface protective layer in this order on an aluminum cylinder as a base. Further, the yellow image forming unit Py includes a charging roller 2Y as a charging means. By applying a charging bias to the charging roller 2Y, the surface of the photosensitive drum 1Y is uniformly charged.

[0023] A laser exposure device 3Y is disposed above the photosensitive drum 1Y as an image exposure means. The laser exposure device 3Y scans and exposes the uniformly charged surface of the photosensitive drum 1Y in accordance with image information, forming an electrostatic latent image of a yellow color component on the surface of the photosensitive drum 1Y. The electrostatic latent image formed on the photosensitive drum 1Y is developed by the developing device 4Y as a developing means with toner as a developer. That is, the developing device 4Y includes a developing roller 4Ya as a developer carrier, a regulating blade 4Yb as a developer amount regulating member, and contains yellow toner as a developer. The developing roller 4Ya to which the yellow toner is supplied is lightly pressed against the photosensitive drum 1Y in the developing section, and rotates in the forward direction with a speed difference from the photosensitive drum 1Y. The yellow toner conveyed to the developing section by the developing roller 4Ya adheres to the electrostatic latent image formed on the photosensitive drum 1Y by applying a developing bias to the developing roller 4Ya. As a result, a visible image (yellow toner image) is formed on the photosensitive drum 1Y.

[0024] The intermediate transfer belt 7 is stretched around a drive roller 71, a tension roller 72, and a driven roller 73, and is moved (rotationally driven) in the direction of an arrow 74 in the figure while in contact with the photosensitive drum 1Y. A primary transfer means (primary transfer roller 5Y) is disposed opposite the photosensitive drum 1Y via the intermediate transfer belt 7. The yellow toner image formed on the photosensitive drum (first image carrier) that has reached the primary transfer portion Ty is primarily transferred onto the intermediate transfer belt 7 by the primary transfer means (primary transfer roller 5Y).

[0025] Similarly, the above image forming operation is performed in each of the magenta (M), cyan (C) and black (K) units Pm, Pc and Pk as the intermediate transfer belt 7 moves, and toner images of four colors, yellow, magenta, cyan and black, are stacked on the intermediate transfer belt 7. The stacked four color toner images are transported as the intermediate transfer belt 7 moves, and at the secondary transfer portion T', the secondary transfer roller 8 as secondary transfer means transfers the images collectively onto a transfer material S (hereinafter also referred to as "second image carrier") that is transported at a predetermined timing. In such secondary transfer, a transfer voltage of several kV is usually applied to ensure a sufficient transfer rate.

[0026] The transfer material S is supplied to a conveying path from a cassette 12 in which the transfer material S is stored by a pickup roller 13. The transfer material S supplied to the conveying path is conveyed to a secondary transfer portion T' in synchronization with the four-color toner image transferred to the intermediate transfer belt 7 by a conveying roller pair 14 and a registration roller pair 15. The toner image transferred to the transfer material S is fixed by a fixing device 9 to become, for example, a full-color image. The fixing device 9 has a fixing roller 91 equipped with a heating means and a pressure roller 92, and fixes the unfixed toner image on the transfer material S by applying heat and pressure. Thereafter, the transfer material S is discharged outside the machine by a pair of conveying rollers 16, a pair of discharge rollers 17, etc.

[0027] A cleaning unit 11 for the intermediate transfer belt 7 is disposed downstream of the secondary transfer portion T' in the driving direction of the intermediate transfer belt 7, and removes residual toner that has not been transferred to the transfer material S at the secondary transfer portion T' and remains on the intermediate transfer belt 7. As described above, the electrical transfer process of the toner image is repeated from the photoconductor to the intermediate transfer belt and from the intermediate transfer belt to the transfer material. Furthermore, by repeating recording on a large number of transfer materials, the electrical transfer process is further repeated. EXAMPLES

[0028] <Example 1> (Preparation of the base layer) The following materials were kneaded using a twin-screw kneader (product name: PCM30, manufactured by Ikegai Corporation) to obtain pellets. Polyether ether ketone (product name: VICTREX PEEK450G, manufactured by Victrex) Acetylene black (product name: Denka Black granular product, manufactured by Denka Co., Ltd.)

[0029] The materials were fed into a twin-screw kneader using a weight feeder so that the polyether ether ketone and acetylene black were 80% by mass and 20% by mass, respectively. The cylinder temperature of the twin-screw kneader was set to 320°C at the material feed section, and 360°C downstream of the cylinder and the die. The screw rotation speed of the twin-screw kneader was 300 rpm, and the material supply rate was 8 kg / h.

[0030] Next, the obtained pellets were used to obtain a belt by cylindrical extrusion molding. The cylindrical extrusion molding was performed using a single-screw extruder (product name: GT40, manufactured by Plastics Engineering Research Institute) and a cylindrical die having a circular opening with a diameter of 300 mm and a gap of 1 mm. The pellets were fed to the single-screw extruder at a feed rate of 4 kg / h using a weight feeder. The cylinder temperature of the single-screw extruder was set to 320°C at the material input section and 380°C downstream of the cylinder and the cylindrical die. The molten resin discharged from the single-screw extruder was extruded from the cylindrical die through a gear pump and taken up by a cylindrical take-up machine at a speed to give a thickness of 85 um. In the process of taking up, the resin was cooled and solidified by contacting with a cooling mandrel installed between the cylindrical die and the cylindrical take-up machine. The solidified resin was cut to a width of 460 mm by a cylindrical cutter installed below the cylindrical take-up machine, and a crystalline thermoplastic resin belt was obtained.

[0031] (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 15 parts by mass Hydrophilic fumed silica (product name: AEROSIL (registered trademark) 380, manufactured by Evonik) 3 parts by weight The above materials were mixed under the following conditions using a planetary mixer (2P-1, manufactured by Hivismix Co., Ltd.). Revolution speed: 80 rpm Rotation speed: 194 rpm Time: 30 minutes Then, 0.2 parts by mass of an ionic liquid type antistatic agent (product name: FC-4400, manufactured by 3M Japan) was added to the kneaded rubber as a conductivity imparting agent, and the mixture was stirred and degassed in the same apparatus to obtain a liquid silicone rubber mixture.

[0032] (Formation of elastic layer) The crystalline thermoplastic resin belt that becomes the base layer was attached to a cylindrical core, and a ring nozzle for discharging rubber was attached coaxially with the core. The liquid silicone rubber mixture was supplied to the ring nozzle using a liquid pump, and discharged from a slit to apply the mixture onto the base layer. At this time, the relative movement speed and the discharge amount of the liquid pump were adjusted so that the silicone rubber layer after curing had a thickness of 260 μm. The belt was placed in a heating furnace while attached to the core, and heated at 130 ° C for 10 minutes and then at 180 ° C for 60 minutes to perform rubber crosslinking. After cooling, the belt was removed from the core to obtain a belt with an elastic layer laminated thereon.

[0033] (Surface modification of elastic layer) In order to improve the adhesion between the elastic layer and the intermediate layer, the surface of the elastic layer was modified using an excimer lamp (manufactured by M.D.COM) that emits a single wavelength of 172 nm as an excimer UV irradiation unit. The transfer belt on which the elastic layer was formed was fitted into a cylindrical core and placed at a position where the distance from the surface of the excimer lamp to the surface of the elastic layer was about 1 mm. Then, while rotating the cylindrical core at a rotation speed of 5 rpm, the excimer UV light was irradiated for 30 minutes in a space where nitrogen gas and air were flowed in at a volume ratio of 29:1, to obtain a belt with a surface-modified elastic layer.

[0034] (Preparation of surface layer) 95 parts by weight of fluorine-containing polyurethane resin liquid in which polytetrafluoroethylene is dispersed in polyurethane dispersion (product name: BONDERITE S-FN T-861C, manufactured by Henkel Japan Co., Ltd.) Hardener (product name: LOCTITE TW8370C WH-1, manufactured by Henkel Japan) 5 parts by mass The above materials were stirred to prepare a urethane coating liquid for forming a surface layer. The belt with the surface-modified elastic layer was fitted into a core and rotated at 90 rpm, while the urethane coating liquid was applied using a spray gun (product name: W-101, manufactured by Anest Iwata Corporation). The amount of paint discharged during application was set so that the dry film thickness of the surface layer was 3 μm. After application, the belt was placed in a heating furnace at a temperature of 130° C. and left to stand for 30 minutes. After removing from the heating furnace and cooling, an elastic intermediate transfer belt 1 was obtained.

[0035] <Example 2> An elastic intermediate transfer belt 2 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 10 parts by weight Hydrophilic fumed silica (product name: AEROSIL (registered trademark) 380, manufactured by Evonik) 9 parts by weight

[0036] <Example 3> An elastic intermediate transfer belt 3 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 25 parts by weight Hydrophilic fumed silica (product name: AEROSIL (registered trademark) 380, manufactured by Evonik) 9 parts by weight

[0037] <Example 4> An elastic intermediate transfer belt 4 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 10 parts by weight Hydrophilic fumed silica (product name: AEROSIL (registered trademark) 380, manufactured by Evonik) 2 parts by weight

[0038] <Example 5> An elastic intermediate transfer belt 5 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 25 parts by weight Hydrophilic fumed silica (product name: AEROSIL (registered trademark) 380, manufactured by Evonik) 2 parts by weight

[0039] <Comparative Example 1> An elastic intermediate transfer belt 6 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 28 parts by weight Hydrophilic fumed silica (product name: AEROSIL (registered trademark) 380, manufactured by Evonik) 2 parts by weight

[0040] <Comparative Example 2> An elastic intermediate transfer belt 7 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 28 parts by weight Hydrophilic fumed silica (product name: AEROSIL (registered trademark) 380, manufactured by Evonik) 9 parts by weight

[0041] <Comparative Example 3> An elastic intermediate transfer belt 8 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 8 parts by weight Hydrophilic fumed silica (product name: AEROSIL (registered trademark) 380, manufactured by Evonik) 2 parts by weight

[0042] <Comparative Example 4> An elastic intermediate transfer belt 9 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 8 parts by weight Hydrophilic fumed silica (product name: AEROSIL (registered trademark) 380, manufactured by Evonik) 9 parts by weight

[0043] <Comparative Example 5> An elastic intermediate transfer belt 10 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 10 parts by weight Hydrophilic fumed silica 0 parts by weight

[0044] <Comparative Example 6> An elastic intermediate transfer belt 11 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 25 parts by weight Hydrophilic fumed silica 0 parts by weight

[0045] <Comparative Example 7> An elastic intermediate transfer belt 12 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 10 parts by weight Hydrophilic fumed silica (product name: AEROSIL (registered trademark) 380, manufactured by Evonik) 10 parts by weight

[0046] <Comparative Example 8> An elastic intermediate transfer belt 13 was obtained in the same manner as in Example 1, except that the mixing amounts of the materials were changed as follows. (Preparation of Elastic Layer Forming Material) Addition-curing liquid silicone rubber (product name: TSE3032 A / B (mass ratio A1000:B8), manufactured by Momentive Performance Materials, Inc.) 100 parts by mass Magnesium hydroxide (product name: KISMA 5P, manufactured by Kyowa Chemical Industry Co., Ltd.) 25 parts by weight Hydrophilic fumed silica (product name: AEROSIL (registered trademark) 380, manufactured by Evonik) 10 parts by weight

[0047] <Evaluation> The elastic intermediate transfer belts thus produced were evaluated as follows. (Poor appearance) The intermediate transfer belt thus produced was observed and subjected to a visual appearance inspection. Visually identifiable defects in appearance were evaluated according to the following criteria. The evaluation results are shown in Table 2. ◯: No defects in appearance were observed. ×: Chipping of the surface layer due to unevenness of the elastic layer was observed in multiple places on the entire surface.

[0048] (Method of measuring Martens hardness) A test piece was prepared by cutting the intermediate transfer belt with a cutter knife. The size of the test piece was 10 mm x 10 mm, and about 20 mL of hexadecane was applied between the test piece and the slide glass and attached. The Martens hardness was measured using a commercially available microhardness tester, a surface coating physical property tester (product name: PICODENTOR (registered trademark) HM500) from Fisher Instruments. The measurement conditions are shown below. Measuring indenter (shape, type): Vickers indenter Indenter material: Diamond Measurement environment: Temperature 23°C, relative humidity 23% Loading and unloading speed: 4mN / sec Maximum pressing load F: 40mN The indenter was pressed into the test piece under the above conditions, and the surface area in contact with the indenter was determined from the indentation depth when the maximum indentation load of 40 mN was reached, and the Martens hardness was calculated using the following formula. Martens hardness (N / mm 2 ) = F(N) / surface area in contact with the indenter (mm 2 ) The above measurement was carried out five times (for example, for five test pieces in the circumferential direction of the belt), and the arithmetic mean value of the measured values ​​was taken as the Martens hardness of the evaluation object. The measurement results are shown in Table 2. The test pieces were obtained within the image area in the width direction of the elastic intermediate transfer belt, specifically, the test pieces were obtained so as to include the central position in the width direction of each intermediate transfer belt to be evaluated.

[0049] (Method for evaluating the dispersion state of magnesium hydroxide particles) First, a test piece to be observed is prepared. The elastic intermediate transfer belt is cut into a square with a width of 10 mm and a length of 5 mm using a cutter knife and a microtome (manufactured by Leica) to prepare a test piece. The test piece is fixed to the sample stage of a Cross Section Polisher (registered trademark) SM-09010 (manufactured by JEOL Ltd.), a shielding plate is provided, and Ar ions are irradiated at an acceleration voltage of 4 eV and a current of 60 μA for 16 hours to expose the cross section of the elastic intermediate transfer belt. At this time, the current amount is controlled by adjusting the Ar flow rate.

[0050] Next, the exposed cross section is observed as a backscattered electron image at a magnification of 500x using an FE-SEM SU-8220 (Hitachi High-Technologies Corporation). Figure 3 shows the results of observing a cross section of the elastic layer of elastic intermediate transfer belt 1. The bright aggregates seen in the elastic layer are magnesium hydroxide particles, and the aggregates in which magnesium is not detected in a separate EDX mapping analysis are painted black and excluded using image processing, etc., assuming that the aggregates are silica or another filler. The dispersion state of magnesium hydroxide particles was evaluated using the coefficient of variation of the area of ​​the Voronoi polygon.

[0051] (Flame retardancy evaluation method) One method for evaluating the flame retardancy of intermediate transfer belts is the UL94 combustion test, and the UL94VTM involves a thin material vertical combustion test (ASTM D4804). In this test, a film test piece (200±5mm x 50±1mm x tmm) is rolled into a cylinder, attached vertically to a clamp, and exposed to a 20mm flame for three seconds twice, and the test is judged as VTM-0, VTM-1, VTM-2, or Not based on the combustion behavior. Table 1 shows the UL94VTM judgment criteria. Table 2 shows the judgment results.

[0052] [Table 1]

[0053] (Embossed paper transferability evaluation) The intermediate transfer belts shown in the present examples and the comparative examples were mounted on a full-color electrophotographic image forming apparatus (product name: imagePRESS C800, manufactured by Canon Inc.) and an evaluation test was carried out. The test was performed in an environment of 25°C and 55% relative humidity on A3-sized embossed paper (product name: Lezac 66 250g / m 2 A solid image of secondary colors of cyan and magenta was formed on a sheet of paper (manufactured by Tokai Tokushu Paper Co., Ltd.) to obtain Image 2. The obtained Image 2 was visually observed and evaluated according to the following criteria. The evaluation results are shown in Table 2. Rank A: No image unevenness is observed Rank B: Image unevenness in less than 20% of the embossed paper recess Rank C: Image unevenness is present in an area of ​​20% to less than 50% of the embossed paper recess. Rank D: Image unevenness in 50% or more of the embossed paper recessed area

[0054] [Table 2]

[0055] Table 2 shows the evaluation results of each prototype elastic intermediate transfer belt. From Examples 1 to 5 and Comparative Examples 1, 2, 7, and 8, the following can be seen. By adding 10 parts by mass or more of magnesium hydroxide and keeping the coefficient of variation of the area of ​​the Voronoi polygon, which indicates the dispersibility of magnesium hydroxide, to 1.5 or less, it is possible to obtain a flame retardancy rating of VTM-1 or higher in the UL94VTM test. This is thought to be because by dispersing magnesium hydroxide uniformly, even if a flame is brought close during a combustion test, the area where there is no magnesium hydroxide does not ignite or spread.

[0056] On the other hand, when the amount of magnesium hydroxide added is less than 10 parts by mass, even if the coefficient of variation of the area of ​​the Voronoi polygon is 1.5 or less, it is not possible to obtain VTM-1 or higher in the flame retardancy UL94VTM test (Comparative Examples 3 and 4). Even if the amount of magnesium hydroxide added is 10 parts by mass or more, if the coefficient of variation of the area of ​​the Voronoi polygon exceeds 1.5, it is not possible to obtain VTM-1 or higher in the flame retardancy UL94VTM test (Comparative Examples 5 and 6).

[0057] From a comparison between the elastic intermediate transfer belts 3 and 5 (Examples 3 and 5) and the elastic intermediate transfer belts 6 and 7 (Comparative Examples 1 and 2), the following can be seen. By setting the amount of magnesium hydroxide to 25 parts by mass or less, the Martens hardness is reduced to 0.20 N / mm 2 The following elastic intermediate transfer belt can be obtained: The Martens hardness of the elastic intermediate transfer belt is 0.20 N / mm 2 If it is less than this, sufficient embossed paper transferability can be obtained. It is believed that if a large amount of magnesium hydroxide is added, the flexibility of the elastic layer is impaired, and the elastic layer is unable to conform to the embossed paper sufficiently.

[0058] Furthermore, a comparison of elastic intermediate transfer belts 4 and 5 (Examples 4 and 5) with elastic intermediate transfer belts 10 and 11 (Comparative Examples 5 and 6) shows that in order to achieve VTM-1 or higher in the UL94 VTM test, it is necessary to add 2 parts by mass or more of hydrophilic silica. This is believed to be because the viscosity of the silicone composition of the elastic layer rises sharply when the amount of hydrophilic silica added is increased.When the viscosity of the silicone composition is high, the shear force applied to the magnesium hydroxide during kneading increases, and this leads to the magnesium hydroxide, which is a flame retardant, being uniformly dispersed.

[0059] Comparing Elastic Intermediate Transfer Belts 2 and 3 with Elastic Intermediate Transfer Belts 12 and 13, it was found that adding 10 parts by mass or more of hydrophilic silica caused poor appearance. This is thought to be because the addition of hydrophilic silica significantly increased the viscosity of the silicone composition in the elastic layer, causing agglomerations of hydrophilic silica. As described above in detail, by satisfying the following requirements, it is possible to obtain an electrophotographic belt that is compatible with flame retardancy and embossed paper transferability. The silicone rubber contains 10 to 25 parts by mass of magnesium hydroxide per 100 parts by mass of silicone rubber, and the coefficient of variation of the area of ​​the Voronoi polygon of magnesium hydroxide particles observed on a cross section of the elastic layer is 1.5 or less. [Explanation of symbols]

[0060] 21: Base layer 22: Elastic layer 23: Surface layer

Claims

1. An electrophotographic belt having an elastic layer, the elastic layer contains at least silicone rubber, magnesium hydroxide, and silica particles modified with a hydrophilic group; the magnesium hydroxide is dispersed in the silicone rubber, the content of the magnesium hydroxide is 10 to 25 parts by mass relative to 100 parts by mass of the silicone rubber, the content of the hydrophilic group-modified silica particles is 2 to 9 parts by mass based on 100 parts by mass of the silicone rubber, an electrophotographic belt, characterized in that, when a cross section of the electrophotographic belt in a direction perpendicular to a circumferential direction is divided into Voronoi polygons by using the magnesium hydroxide particles exposed on the cross section as generating points, an arithmetic mean value of the areas of the Voronoi polygons formed is S and a standard deviation is σ, a coefficient of variation calculated by the following formula (1) is 1.5 or less: Coefficient of variation = σ / S Equation (1).

2. Martens hardness at 10 μm indentation is 0.05 N / mm ２ 0.20N / mm or more ２ 2. The electrophotographic belt according to claim 1, wherein:

3. 3. The electrophotographic belt according to claim 1, further comprising: a base layer; the elastic layer formed on the base layer; and a surface layer formed on the elastic layer.

4. 4. An electrophotographic image forming apparatus comprising the electrophotographic belt according to claim 1 as an intermediate transfer belt.

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