JP7753076B2 - Electrophotographic belt and electrophotographic image forming apparatus - Google Patents

Description

This disclosure relates to an electrophotographic belt and an electrophotographic image forming apparatus.

Patent Document 1 discloses an electrophotographic intermediate transfer belt having a base layer made of a thermoplastic resin composition containing a thermoplastic polyester resin and a polyetheresteramide (hereinafter also referred to as "PEEA"), an ionic conductive agent, and a surface layer on the base layer. Patent Document 1 also discloses that the intermediate transfer belt contains a carbodiimide compound to prevent bleed-out of components derived from PEEA when a voltage is applied to the intermediate transfer belt.

JP 2010-139650 A

The intermediate transfer belt disclosed in Patent Document 1 may have experienced partial peeling of the surface layer when used for forming electrophotographic images over a long period of time. After detailed investigation into the peeling of the surface layer, it was found that the partial peeling of the surface layer was caused not at the interface between the surface layer and the base layer but within the base layer.
Therefore, one aspect of the present disclosure is to provide an electrophotographic belt that prevents the occurrence of peeling of the surface layer due to peeling of the base layer even after long-term use.
Another aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus that contributes to the stable formation of high-quality electrophotographic images.

According to one aspect of the present disclosure, there is provided an electrophotographic belt having a base layer containing a first resin and a second resin that is incompatible with the first resin, wherein the first resin is a crystalline polyester, and the base layer further contains a cyclic carbodiimide compound, the cyclic carbodiimide compound having a ring structure and at least a portion of the ring structure having a carbodiimide group. According to another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus that includes the above-mentioned electrophotographic belt as an intermediate transfer belt.

According to one aspect of the present disclosure, an electrophotographic belt can be obtained that prevents peeling of the surface layer due to peeling of the base layer even after long-term use. Furthermore, according to another aspect of the present disclosure, an electrophotographic image forming apparatus can be obtained that contributes to the stable formation of high-quality electrophotographic images.

1 is a schematic cross-sectional view showing an example of a full-color electrophotographic image forming apparatus that utilizes an electrophotographic process. FIG. 2 is a schematic cross-sectional view of an injection molding device used in the examples. FIG. 2 is a schematic cross-sectional view of a primary blow molding device used in the examples. FIG. 2 is a schematic cross-sectional view of a secondary blow molding device used in the examples. 1 is an explanatory diagram illustrating an example of the configuration of an electrophotographic belt according to the present disclosure. 1 is an explanatory diagram of the reaction mechanism between polyester and carbodiimide, where (a) shows the case where the carbodiimide is a chain carbodiimide, and (b) shows the case where the carbodiimide is a cyclic carbodiimide.

Unless otherwise specified, the expressions "XX to YY" or "XX to YY" representing a range of values mean a range of values including the lower and upper limits, which are the endpoints. When a range of values is described in stages, the upper and lower limits of each range can be combined in any way.

The present inventors investigated the cause of the base layer peeling, which caused the surface layer peeling, in the intermediate transfer belt disclosed in Patent Document 1. Here, the base layer contains a thermoplastic polyester resin and PEEA as an ion conductive agent, and the thermoplastic polyester resin and PEEA are incompatible with each other. Therefore, the base layer has a matrix-domain structure consisting of a thermoplastic polyester resin matrix and a domain containing PEEA. Further observation of the peeled portion of the base layer revealed large voids at the interface between the domain and the matrix. While it has been known that peeling can occur at the interface between the thermoplastic polyester resin matrix and the domain containing PEEA, the occurrence of such large voids at the interface has not been observed until now. Therefore, after further investigation to identify the cause of the large voids at the interface, the inventors concluded that the carbodiimide compound used in Patent Document 1 was responsible for the voids.

Carbodiimides are known as hydrolysis inhibitors for polyesters. Carbodiimide compounds inhibit the hydrolysis of polyesters by capturing acid, but they decompose when capturing acid. The carbodiimide compound used in Example 1 of Patent Document 1, "Carbodilite LA-1" (trade name, manufactured by Nisshinbo Industries, Inc.), has a chain structure. Carbodiimide compounds with a chain structure generate an isocyanate compound by capturing acid, as shown in Figure 6(a). Because this isocyanate compound is a gas at room temperature, it is believed that this compound caused the voids in the base layer.

Based on this speculation, the inventors believed that using a carbodiimide compound that does not produce decomposition products even when reacted with polyester could prevent the formation of voids in the base layer. Based on this consideration, they used a cyclic carbodiimide compound in which a carbodiimide group represented by "-N=C=N-" constitutes at least part of the ring structure. As a result, they found that it was possible to prevent the formation of large voids in the base layer and also to prevent peeling of the surface layer due to peeling of the base layer.

As shown in Figure 6(a), when a linear carbodiimide compound decomposes at the carbodiimide group, one molecule binds with acid and the other molecule becomes gas. In contrast, in the case of a cyclic carbodiimide compound in which the carbodiimide group constitutes at least a part of the ring structure, as shown in Figure 6(b), even if decomposition occurs at the carbodiimide group, the compound remains a single molecule due to its ring structure, and therefore does not generate gas even when it binds with acid. Based on this, the present inventors discovered that by using a cyclic carbodiimide compound in which the carbodiimide group constitutes at least a part of the ring structure, peeling is less likely to occur even during long-term use, and have arrived at the present invention.
An electrophotographic belt according to one embodiment of the present disclosure will be described in detail below, although the present disclosure is not limited to the following embodiment.

Structure of the Electrophotographic Belt FIG. 5( a) shows a perspective view of an electrophotographic belt 500 having an endless belt shape according to one embodiment of the present disclosure. An example of the layer structure is a monolayer structure formed solely of a base layer 501, as shown in FIG. 5( b-1) in the cross section taken along line A-A' in FIG. 5( a). In this case, the outer surface 500-1 of the base layer serves as the toner-carrying surface (outer surface) of the electrophotographic belt. Another example is a laminated structure formed as shown in FIG. 5( b-2) in the cross section taken along line A-A', which has a base layer 501 and a surface layer 502 covering the outer peripheral surface of the base layer. When the surface layer 502 is provided, the outer surface 500-1 of the surface layer 502 serves as the toner-carrying surface of the electrophotographic belt. Yet another example is a laminated structure formed as shown in FIG. 5( b-3) which has a base layer 501 and a back surface layer 503 covering the inner peripheral surface of the base layer. Further, there is also mentioned a three-layer structure (not shown) having a surface layer covering the outer peripheral surface and a back surface layer covering the inner peripheral surface of the base layer 501. The surface layer 502 and the back surface layer 503 may be a resin layer and/or a metal layer.

＜＜Base layer＞＞
First, the base layer, which is the main part of the present invention, will be described. The base layer contains a first resin and a second resin. The second resin is incompatible with the first resin.

<First Resin: Crystalline Polyester>
The polyester resin can be obtained by polycondensation of a dicarboxylic acid and a diol, polycondensation of an oxycarboxylic acid or a lactone, or polycondensation of a combination of these components. A polyfunctional monomer may also be used. The polyester resin may be a homopolyester containing one type of ester bond, or a copolyester (copolymer) containing multiple ester bonds.

From the viewpoint of strength and flex resistance, aromatic polyesters having aromatic rings in their skeletons are preferred as polyester resins. Among these, at least one selected from the group consisting of polyalkylene terephthalate and polyalkylene naphthalate is a suitable example, as they have high crystallinity and excellent heat resistance. Copolymers of polyalkylene terephthalate and polyalkylene isophthalate can also be used. The copolymer may be in the form of a block copolymer or a random copolymer.

From the viewpoint of high crystallinity and heat resistance, the number of carbon atoms in the alkylene in the polyalkylene terephthalate, polyalkylene naphthalate, and polyalkylene isophthalate is preferably 2 or more and 16 or less. More specifically, any one or a mixture of two or more selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate is preferred.
The intrinsic viscosity of the polyester resin is preferably 1.4 dL/g or less, more preferably 0.3 dL/g or more and 1.2 dL/g or less. A polyester resin with an intrinsic viscosity of 1.4 dL/g or less has excellent fluidity during hot melt kneading. An intrinsic viscosity of 0.3 dL/g or more can more easily improve the strength and durability of an electrophotographic belt. The intrinsic viscosity of the polyester resin is a value measured using o-chlorophenol as a diluent solvent for the polyester resin, with the concentration of the o-chlorophenol solution of the polyester resin at 0.5% by mass and at a temperature of 25°C.
Furthermore, from the viewpoint of mechanical properties, the content of the polyester resin is preferably 50% by mass or more and 90% by mass or less, more preferably 60% by mass or more and 85% by mass or less, and even more preferably 70% by mass or more and 80% by mass or less, relative to the total mass of the resin composition.

<Incompatible Second Resin>
For the electrophotographic belt, a resin incompatible with the first resin is added for the purposes of imparting ionic conductivity, improving mechanical properties such as flex resistance, and improving stretchability during molding.
The greater the difference in solubility parameters (SP values), the more likely they are to be incompatible, and if the difference in SP values is 0.9 ((J/cm ³ ) ^(½) ) or more, they become incompatible. Specifically, polyether ester amide and ABS resin are suitable for use. The Hansen Solubility Parameter software Hansen Solubility Parameter in Practice (HSPiP) ver. 5.1.08 was used to determine the SP value.
The content of the second resin in the base layer is not particularly limited, but from the viewpoint of imparting conductivity to the base layer and improving mechanical properties, it is preferable that the content be, for example, 5% by mass or more and 20% by mass or less, and particularly 10% by mass or more and 15% by mass or less, relative to the base layer.

・Polyetheresteramide (PEEA)
Examples of polyetheresteramides include compounds whose main component is a copolymer of polyamide block units, such as nylon 6, nylon 66, nylon 11, or nylon 12, and polyetherester units. Examples include copolymers derived from lactams (e.g., caprolactam and lauryllactam) or salts of aminocarboxylic acids, polyethylene glycol, and dicarboxylic acids. Specific examples of dicarboxylic acids include terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, undecanoic diacid, and dodecanoic diacid. PEEA can be produced by known polymerization methods, such as melt polymerization. Of course, PEEA is not limited to these. PEEA may also be a blend or alloy of two or more types.

ABS resin is a copolymer of acrylonitrile, butadiene, and styrene, and can be obtained by polymerizing a vinyl monomer in the presence of rubber latex, or by blending the resulting copolymer with AS resin (a copolymer of acrylonitrile and styrene). It can be produced by known methods such as emulsion polymerization and suspension polymerization.

<Cyclic carbodiimide compound>
It has one carbodiimide group (-N=C=N-), and the two nitrogen atoms are linked by a linking group. One cyclic structure has only one carbodiimide group, but if there are multiple cyclic structures in the molecule, they may have multiple carbodiimide groups as long as each cyclic structure has one carbodiimide group.

The linking group connecting the two nitrogen atoms of the carbodiimide group is an aliphatic group, an alicyclic group, an aromatic group, or a combination thereof. Each linking group may contain a heteroatom and a substituent. A linking group having the required number of carbon atoms to form a cyclic structure is selected. An example of a combination is a structure in which an alkylene group and an arylene group are bonded.
The number of atoms in the cyclic structure is preferably 10 to 30, and more preferably 10 to 15. If the number of atoms is too small, the stability of the compound may decrease, and if the number of atoms is too large, the synthesis may become more difficult. Specific examples of cyclic carbodiimide compounds include the following.

The content of the cyclic carbodiimide compound in the base layer is preferably 0.1% by mass or more and 5.0% by mass or less. A content of 0.1% by mass or more can effectively prevent a decrease in strength due to hydrolysis of the polyester. Furthermore, a content of 5.0% by mass or less can effectively maintain the excellent flex resistance inherent to polyester.

<Amide Compound Having at Least Two Amide Groups in One Molecule>
By containing an amide compound having at least two amide groups in one molecule, the compatibility between the polyester and the polyetheresteramide can be improved, and peeling can be further suppressed.
The compound having at least two amide groups in one molecule is preferably a compound that melts at the heating temperature during hot melt kneading, and has a melting point of preferably 70°C or higher and lower than 200°C, more preferably 100°C or higher and lower than 170°C.

As a compound having at least two amide groups in one molecule, a fatty acid bisamide can be used. The fatty acid bisamide contains a fatty acid group (preferably a long-chain fatty acid group) and an amide group in the molecule, has excellent compatibility with thermoplastic polyester resins, and is relatively stable thermally and chemically. From the viewpoints of compatibility with thermoplastic polyester resins and thermal and chemical stability, the carbon number of the long-chain fatty acid group is preferably in the range of 7 to 23.
Alternatively, an aromatic bisamide may be used as the compound having at least two amide groups in one molecule. The aromatic bisamide contains a fatty acid group and an amide group in the molecule, and the amide groups are bonded to each other via an aromatic hydrocarbon.
Examples of the fatty acid bisamide include alkylene fatty acid bisamides such as ethylene bisfatty acid amide. Specific examples include methylene _bisstearic acid amide ( _{C17H35CONHCH2NHCOC17H35} , Tm (melting point): ₁₄₂ °C), ethylene biscapric acid amide _{( C9H19CONHCH2CH2NHCOC9H19} , _Tm : ₁₆₁ °C), _and ethylene bislauric _{acid amide ( C11H23CONHCH2CH2NHCOC11H23} , _{Tm :} 157 _° C _{) .}

<Additives>
Other components may be added to the thermoplastic resin composition as long as they do not impair the effects of the present invention. Examples of other components include ionic conductive agents, conductive polymer compounds, antioxidants, UV absorbers, organic pigments, inorganic pigments, pH adjusters, crosslinking agents, compatibilizers, release agents, crosslinking agents, coupling agents, lubricants, insulating fillers, and conductive fillers. These additives may be used alone or in combination of two or more. The amount of additive used can be set appropriately and is not particularly limited.

<Molding method>
The above-mentioned base layer material is hot-melt kneaded, pelletized, and molded into an endless belt shape using a known molding method such as continuous melt extrusion molding, injection molding, stretch blow molding, or inflation molding, to obtain an electrophotographic belt.
The thermoplastic resin composition is preferably molded into an endless belt shape by continuous melt extrusion or stretch blow molding, for example, a downward extrusion method using an internally cooled mandrel, which allows for highly accurate control of the inner diameter of the extruded tube, or a vacuum sizing method.
The method for manufacturing an electrophotographic belt by stretch blow molding includes the following steps: a step of molding a preform made of a base layer material; a step of heating the preform; a step of placing the heated preform in a mold for molding an endless belt and then injecting gas into the mold to perform stretch blow molding; and a step of cutting the stretch-molded product obtained by stretch blow molding to obtain an endless belt.

<<Electrophotographic Belts>>
As described above, the specific configuration of the electrophotographic belt may be a base layer only, or may include an additional layer on the outer peripheral surface and/or inner peripheral surface.
The thickness of the electrophotographic belt is preferably 40 μm or more and 500 μm or less, particularly preferably 50 μm or more and 100 μm or less. Furthermore, in order to improve the appearance of the surface of the electrophotographic belt or to enhance the releasability of toner, etc., the surface may be coated with a treating agent or subjected to a surface treatment such as polishing. When using the electrophotographic belt with a separate layer provided on the outer peripheral surface and/or inner peripheral surface, the outermost layer can be provided, for example, by applying and curing an active energy ray-curable resin composition such as a photocurable resin to the surface of the base layer. Alternatively, the outermost layer may be provided on the surface of the thermoplastic resin composition layer by sputtering or the like.

The electrophotographic belt is not particularly limited in its application, but is suitably used, for example, as an intermediate transfer belt for temporarily transferring and holding a toner image, or as a transport transfer belt for transporting a recording material as a transfer material. It is particularly suitable for use as an intermediate transfer belt. Furthermore, when the electrophotographic belt is used as an intermediate transfer belt, it is preferable that the surface resistivity of the electrophotographic belt be 1×10 ³ Ω/□ or more and 1×10 ¹² Ω/□ or less. A surface resistivity of 1×10 ³ Ω/□ or more prevents the resistance from decreasing, makes it easy to obtain a transfer electric field, and effectively prevents image omissions and roughness. A surface resistivity of 1×10 ¹² Ω/□ or less effectively prevents the transfer voltage from increasing, effectively preventing the power supply from becoming larger and the cost from increasing.

<<Electrophotographic Image Forming Apparatus>>
An example of an electrophotographic image forming apparatus using an electrophotographic belt according to one embodiment of the present invention as an intermediate transfer belt will be described below. This electrophotographic image forming apparatus has a so-called tandem configuration in which electrophotographic stations of multiple colors are arranged side by side in the rotation direction of the intermediate transfer belt, as shown in Fig. 1. In the following description, the reference numerals for components of yellow, magenta, cyan, and black are suffixed with Y, M, C, and k, respectively, but the suffixes may be omitted for similar components.

In FIG. 1, photosensitive drums (photoconductors, image carriers) 1Y, 1M, 1C, and 1k are surrounded by charging devices 2Y, 2M, 2C, and 2k, exposure devices 3Y, 3M, 3C, and 3k, developing devices 4Y, 4M, 4C, and 4k, and an intermediate transfer belt (intermediate transfer body) 6. Photosensitive drum 1 rotates in the direction of arrow F (counterclockwise) at a predetermined peripheral speed (process speed). Charging device 2 charges the peripheral surface of photosensitive drum 1 to a predetermined polarity and potential (primary charging). Exposure device 3, a laser beam scanner, outputs on/off-modulated laser light in response to image information input from an external device such as an image scanner or computer (not shown), scanning and exposing the charged surface of photosensitive drum 1. This scanning and exposure forms an electrostatic latent image on the surface of photosensitive drum 1 corresponding to the desired image information.

Developing devices 4Y, 4M, 4C, and 4k each contain toner of the color components yellow (Y), magenta (M), cyan (C), and black (k). The developing device 4 to be used is selected based on the image information, and developer (toner) is developed on the surface of the photosensitive drum 1, visualizing the electrostatic latent image as a toner image. This embodiment uses a reversal development method in which toner is deposited on the exposed portion of the electrostatic latent image for development. These charging devices, exposure devices, and developing devices constitute an electrophotographic image forming means.

The intermediate transfer belt 6 is an endless belt that is arranged to contact the surface of the photosensitive drum 1 and is stretched over multiple tension rollers 20, 21, and 22. It rotates in the direction of arrow G. In this embodiment, tension roller 20 is a tension roller that keeps the tension of the intermediate transfer belt 6 constant, tension roller 22 is a drive roller for the intermediate transfer belt 6, and tension roller 21 is an opposing roller for secondary transfer. Furthermore, primary transfer rollers 5Y, 5M, 5C, and 5k are disposed at primary transfer positions facing the photosensitive drum 1 across the intermediate transfer belt 6.

The unfixed toner images of each color formed on the photosensitive drum 1 are electrostatically transferred sequentially onto the intermediate transfer belt 6 by applying a primary transfer bias of opposite polarity to the toner's charge polarity to the primary transfer roller 5 using a constant voltage or constant current source. A full-color image is then obtained on the intermediate transfer belt 6, with the four unfixed toner images superimposed on top of each other. The intermediate transfer belt 6 rotates while carrying the toner images transferred from the photosensitive drum 1 in this way. After each rotation of the photosensitive drum 1 after the primary transfer, the surface of the photosensitive drum 1 is cleaned of any residual toner by a cleaning device 11, and the image formation process is repeated.

At the secondary transfer position of the intermediate transfer belt 6 facing the transport path of the recording material 7, a secondary transfer roller (transfer unit) 9 is positioned in pressure contact with the toner image-bearing surface of the intermediate transfer belt 6. Also, on the back side of the intermediate transfer belt 6 at the secondary transfer position, an opposing roller 21, which serves as the opposing electrode for the secondary transfer roller 9 and to which a bias is applied, is disposed. When the toner image on the intermediate transfer belt 6 is transferred to the recording material 7, a bias of the same polarity as the toner is applied to the opposing roller 21 by a transfer bias application unit 28. For example, -1000 to -3000 V is applied, resulting in a current of -10 to -50 μA. The transfer voltage at this time is detected by a transfer voltage detection unit 29. Furthermore, a cleaning device (belt cleaner) 12 is provided downstream of the secondary transfer position to remove toner remaining on the intermediate transfer belt 6 after secondary transfer.

The recording material 7 passes through a transport guide 8 and is transported in the direction of arrow H, arriving at the secondary transfer position. Once introduced into the secondary transfer position, the recording material 7 is nipped and transported at the secondary transfer position, at which point a constant voltage bias (transfer bias) controlled to a predetermined value is applied from a secondary transfer bias application means 28 to the opposing roller 21 of the secondary transfer roller 9. By applying a transfer bias of the same polarity as the toner to the opposing roller 21, the four-color full-color image (toner image) superimposed on the intermediate transfer belt 6 at the transfer site is transferred all at once to the recording material 7, forming an unfixed full-color toner image on the recording material. After the toner image has been transferred, the recording material 7 is introduced into a fixing unit (not shown) where it is heated and fixed.

EXAMPLES The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these.
The materials shown in Tables 1 to 5 were used to manufacture the electrophotographic belts according to the examples and comparative examples.

<Evaluation method>
Presence or absence of voids A cross section was prepared using a cross section polisher (product name: SM-09010, manufactured by JEOL Ltd.) and the cross section was observed with a scanning electron microscope (SEM, product name: XL-300-SFEG, manufactured by FEI) to determine the presence or absence of voids in the base layer.

Number of Printed Sheets at Which Peeling Occurs The electrophotographic belt to be evaluated was mounted as an intermediate transfer belt in a color laser printer (product name: Satera LBP 712Ci; manufactured by Canon Inc.), images were formed, and the presence or absence of peeling on the surface of the electrophotographic belt due to peeling of the base layer was confirmed every 10,000 sheets. "Vitality" (product name, manufactured by Xerox Corporation) was used as the paper.

[Example 1]
A preblend sample was prepared by mixing the PEN, PEEA, cyclic NCN, conductive agent, and colorant listed in Tables 1 to 3 and Table 5 in the blending ratios listed in Table 8. This preblend sample was hot-melt kneaded using a twin-screw extruder (product name: TEX44α, manufactured by The Japan Steel Works, Ltd.) to prepare a pellet-shaped resin composition. The hot-melt kneading temperature was adjusted to be within the range of the melting point of the polyester or higher and the melting point plus 40°C or lower, and the hot-melt kneading time was approximately 3 minutes.
The resulting pellet-shaped resin composition was dried for 6 hours at a temperature about 20° C. higher than the glass transition temperature of the polyester.

Next, the dried resin composition in pellet form was charged into hopper 48 of an injection molding machine (product name: SE180D, manufactured by Sumitomo Heavy Industries, Ltd.) having the configuration shown in FIG.
The cylinder temperature was set to a temperature approximately 20°C to 30°C higher than the melting point of the polyester, and the polyester was melted in screws 42 and 42A and injection-molded into a mold (not shown) through nozzle 41A to produce preform 104 (see FIG. 3). The injection mold temperature was 30°C. The obtained preform had a test tube shape with an outer diameter of 50 mm, an inner diameter of 48 mm, a length of 150 mm, and a thickness of 2.0 mm.

Next, the preform 104 was placed in the heating device 107 of the primary blow molding device shown in Figure 3 at a temperature of 500°C and softened, and the preform 104 was heated to 500°C. Then, in a blow mold 108, with the mold temperature maintained at room temperature, the preform was blown using a stretch rod 109 and air force at a preform temperature of 160°C, an air pressure of 0.3 MPa, and a stretch rod speed of 1000 mm/s to obtain a blown bottle 112. The blown air was injected through the injection section 110.

Next, the resulting blow bottle 205 was set into the electroformed nickel cylindrical mold 201 of the secondary blow molding device shown in Figure 4, and the outer mold 203 was attached. An air pressure of 0.1 MPa was applied to the inside of the blow bottle 205, and the pressure was adjusted so that no air leaked to the outside, thereby transferring the blow bottle 205 to the inner surface of the mold. Then, while rotating the nickel cylindrical mold 201, it was uniformly heated by the heater 202 to a temperature approximately 70°C higher than the glass transition temperature of the polyester for a total of 60 seconds.

Thereafter, the nickel cylindrical mold was cooled to room temperature by blowing air onto it, the pressure applied inside the blown bottle was released, and a blown bottle with improved dimensions was obtained by annealing. Both ends of the blown bottle were cut to obtain an endless belt with a thickness of 70 μm.
This endless belt was used as a base layer, and an outermost layer made of an acrylic resin, which is an active energy ray curable resin, was provided as follows, with the aim of improving adhesion with other contact members such as a photosensitive drum and a cleaning blade, and improving toner releasability.

The materials shown in Table 6 were mixed as raw materials for the outermost acrylic resin layer.

This mixture was then diluted with methyl ethyl ketone to a resin solids concentration of 6% by mass and stirred with a stirrer to obtain a uniform mixture for forming an acrylic resin outermost layer. This mixture was uniformly applied to the outer peripheral surface of the base layer by a spray method, dried at 60°C for 1 minute to remove the solvent, and then cured by irradiating with ultraviolet light. In this manner, an electrophotographic belt was obtained in which an acrylic resin outermost layer having a thickness of 2 μm was formed on the outer peripheral surface of the base layer. An ultraviolet irradiation device (product name: UE06/81-3, manufactured by iGraphics Co., Ltd.) was used as the ultraviolet light source, and ultraviolet light was irradiated until an integrated light intensity of 1000 mJ/ ^cm2 was reached, thereby UV curing the acrylic resin outermost layer. The evaluation results of the obtained electrophotographic belt are shown in Table 9.

[Examples 2 to 5]
An electrophotographic belt was produced and evaluated in the same manner as in Example 1, except that the compounding ratios of PEN, PEEA, cyclic NCN, conductive agent, and colorant were as shown in Table 8. The evaluation results are shown in Table 9.
[Example 6]
An electrophotographic belt was produced and evaluated in the same manner as in Example 1, except that ABS was used instead of PEEA. The evaluation results are shown in Table 9.

[Examples 7 to 9]
An electrophotographic belt was produced and evaluated in the same manner as in Example 1, except that the polyester type was changed to that shown in Table 8. The evaluation results are shown in Table 9.
[Example 10]
An electrophotographic belt was produced and evaluated in the same manner as in Example 1, except that the compounding ratio of PEN and amide (material 9) was as shown in Table 8. The evaluation results are shown in Table 9.

In Examples 1 to 9, no voids were observed in the cross section of the base layer. Peeling occurred after printing 310,000 or 320,000 sheets, indicating that peeling was unlikely to occur. Peeling was suppressed by using a cyclic carbodiimide compound.
In Example 10, no voids were observed in the cross section of the base layer. The number of printed sheets on which peeling occurred was 450,000, and the result was that peeling was extremely unlikely to occur. Peeling was suppressed by using an amide compound having at least two amide groups in one molecule in addition to a cyclic carbodiimide compound.

[Example 11]
An endless belt consisting of a base layer and an outermost layer was obtained in the same manner as in Example 1, and then an inner surface layer made of an acrylic resin, which is an active energy ray-curable resin, was provided in the following manner in order to reduce wear on the inner peripheral surface and improve conductivity.

The materials shown in Table 7 were mixed to form the acrylic resin inner layer.

This mixture was then diluted with methyl ethyl ketone to a resin solids concentration of 6% by mass and stirred with a stirrer to obtain a uniform mixture for forming an acrylic resin inner surface layer. This mixture was uniformly applied to the inner circumferential surface of the base layer by a spray method, dried at 60°C for 1 minute to remove the solvent, and then cured by irradiating with ultraviolet light. In this manner, an electrophotographic belt was obtained in which an acrylic resin outermost layer having a thickness of 2 μm was formed on the inner circumferential surface of the base layer. An ultraviolet irradiation device (product name: UE06/81-3, manufactured by iGraphics Co., Ltd.) was used as the ultraviolet light source, and ultraviolet light was irradiated until an integrated light intensity of 1000 mJ/ ^cm2 was reached, thereby UV curing the acrylic resin inner surface layer. The evaluation results of the obtained electrophotographic belt are shown in Table 9.

In Example 11, no voids were observed in the cross section of the base layer. Peeling occurred after 320,000 printed sheets, demonstrating that peeling is unlikely to occur. Peeling is suppressed by using a cyclic carbodiimide compound.

[Comparative Examples 1 to 3]
An electrophotographic belt was produced in the same manner as in Example 1, except that the types and amounts of materials were as shown in Table 8 below. The evaluation results are shown in Table 9.
In Comparative Examples 1 to 3, voids were present in the cross section of the base layer. Peeling occurred after printing 130,000 sheets, and peeling was relatively likely to occur. It is believed that the use of a chain carbodiimide compound caused voids, which were the starting points for peeling.

1 Photosensitive drum 2 Charging device 3 Exposure device 4 Developing device 5 Primary transfer roller 6 Intermediate transfer belt 7 Recording material 9 Secondary transfer roller 11 Cleaning device (drum cleaner)
12 Cleaning device (belt cleaner)
20 tension roller 21 opposing roller 22 driving roller 28 transfer bias applying means 29 transfer high voltage detecting means

Claims (12)

An electrophotographic belt having a base layer containing a first resin and a second resin incompatible with the first resin,
the first resin is a crystalline polyester;
The electrophotographic belt is characterized in that the base layer further contains a cyclic carbodiimide compound, the cyclic carbodiimide compound having a ring structure and a carbodiimide group in at least a part of the ring structure. 2. The electrophotographic belt according to claim 1, wherein the difference between the SP value of said first resin and the SP value of said second resin is 0.9 ((J/cm ^<3> ) ^(1/2) ) or more. The electrophotographic belt according to claim 1 or 2, wherein the second resin is polyether ester amide. The electrophotographic belt according to claim 1 or 2, wherein the second resin is an ABS resin. The electrophotographic belt according to any one of claims 1 to 4, wherein the crystalline polyester is an aromatic polyester. The electrophotographic belt according to any one of claims 1 to 5, wherein the crystalline polyester is one or a mixture of two or more selected from the group consisting of polyethylene naphthalate, polyethylene terephthalate, polybutylene naphthalate, and polybutylene terephthalate. The electrophotographic belt according to any one of claims 1 to 6, wherein the content of the cyclic carbodiimide compound in the base layer is 0.1% by mass to 5.0% by mass. The electrophotographic belt according to any one of claims 1 to 7, further comprising an amide compound having at least two amide groups in one molecule. The electrophotographic belt according to any one of claims 1 to 8, wherein the electrophotographic belt has an endless shape. The electrophotographic belt according to any one of claims 1 to 9, further comprising a surface layer covering the outer peripheral surface of the base layer. The electrophotographic belt according to any one of claims 1 to 10, further comprising a backing layer covering the inner peripheral surface of the base layer. 12. An electrophotographic image forming apparatus comprising the electrophotographic belt according to claim 1 as an intermediate transfer belt.