JP2023095571A - Electrophotographic belt, electrophotographic image forming apparatus, and conductive resin mixture - Google Patents

Abstract

To provide an electrophotographic belt that has sufficiently small unevenness of surface resistivity and is excellent in durability.SOLUTION: An electrophotographic belt has a conductive base layer. The base layer includes crystalline polyester, an acrylonitrile-butadiene-styrene copolymer, and carbon black. The base layer has a matrix-domain structure having a matrix including the crystalline polyester, and domains including the acrylonitrile-butadiene-styrene copolymer. The carbon black is unevenly distributed in the domains. The crystalline polyester has a structure part of a styrene-ethylene-butadiene-styrene copolymer in a molecule.SELECTED DRAWING: None

Description

The present disclosure relates to an electrophotographic belt, an electrophotographic image forming apparatus equipped with the electrophotographic belt, and a conductive resin mixture.

2. Description of the Related Art In an electrophotographic image forming apparatus, an electrophotographic belt made of thermoplastic resin and having an endless shape is used as a transfer belt for conveying a transfer material and an intermediate transfer belt. Such electrophotographic belts are required to be inexpensive, have high strength, and provide high-definition printed images.
Patent Document 1 discloses an electronic device formed from a semiconductive resin mixture having a sea-island structure in which nylon regions in which nylon and carbon black are dispersed are dispersed in the sea of polyphenylene sulfide (hereinafter also referred to as “PPS”). A photographic belt is disclosed. It is disclosed that an electrophotographic belt having such a structure can suppress resistance unevenness (variation in surface resistivity).

Moreover, Patent Document 2 discloses the following method.
A method for producing a conductive electrophotographic belt by biaxially stretching a preform formed from a resin mixture containing a crystalline polyester and at least one selected from polyetheresteramide and polyetheramide.

JP 2010-195957 A JP 2010-054942 A

According to the method described in Patent Document 2, an electrophotographic belt can be manufactured at low cost. The semiconductive resin mixture according to Patent Document 1 uses carbon black as a conductive agent. Therefore, compared with the electrophotographic belt disclosed in Patent Document 2, which uses an ionic conductive agent such as polyether ester amide as a conductive agent, the electrophotographic belt is superior in that the conductivity is less dependent on the environment. Therefore, the present inventors attempted to produce an electrophotographic belt by biaxial stretching molding using the semiconductive resin mixture having the sea-island structure described in Patent Document 1.

However, the preform formed from the semiconductive resin mixture according to Patent Document 1 could not be biaxially stretched.

One aspect of the present disclosure is directed to providing an electrophotographic belt that can be manufactured at low cost, has sufficiently low surface resistivity unevenness, and has low environmental dependence of conductivity. Another aspect of the present disclosure is directed to providing an electrophotographic image forming apparatus capable of forming a high-quality electrophotographic image. Yet another aspect of the present disclosure is directed to providing a conductive resin mixture that can be used in biaxial stretch molding.

According to one aspect of the present disclosure,
An electrophotographic belt,
having a conductive base layer,
the base layer comprises crystalline polyester, acrylonitrile-butadiene-styrene copolymer, and carbon black;
the base layer has a matrix-domain structure having a matrix containing the crystalline polyester and domains containing the acrylonitrile-butadiene-styrene copolymer;
The carbon black is unevenly distributed in the domain,
The crystalline polyester provides an electrophotographic belt having a structural portion of a styrene-ethylene-butadiene-styrene copolymer in the molecule.
Further, according to another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including the above electrophotographic belt as an intermediate transfer belt. Yet another aspect of the present disclosure provides a conductive resin mixture that can be used in a biaxial stretch molding process.

According to one aspect of the present disclosure, it is possible to obtain an electrophotographic belt that can be manufactured at low cost, has sufficiently small surface resistivity unevenness, and has low environmental dependence of conductivity. Further, according to another aspect of the present disclosure, it is possible to obtain an electrophotographic image forming apparatus capable of forming high-quality electrophotographic images. Furthermore, according to another aspect of the present disclosure, a conductive resin mixture that can be used in biaxial stretching molding can be obtained.

1 is a schematic cross-sectional view showing an example of a full-color electrophotographic image forming apparatus using an electrophotographic process; FIG. 1 is a schematic cross-sectional view of an injection molding apparatus used in Examples; FIG. 1 is a schematic cross-sectional view of a primary blow molding apparatus used in Examples. FIG. It is a schematic cross-sectional view of a secondary blow molding apparatus used in Examples. 1 is an explanatory diagram of a configuration example of an electrophotographic belt according to the present disclosure; FIG. FIG. 2 is a diagram showing a reaction scheme between a maleic acid-modified moiety in the molecule of m-SEBS and a hydroxy group at the terminal of the raw material polyester (when cPES is PET).

In the present disclosure, the descriptions “XX or more and YY or less” and “XX to YY” representing numerical ranges mean numerical ranges including the lower and upper limits, which are endpoints, unless otherwise specified. In addition, when numerical ranges are described stepwise, any combinations of the upper and lower limits of each numerical range are disclosed.

The present inventors presume as follows why the preform using the semiconductive resin mixture according to Patent Document 1 could not be biaxially stretched. That is, the domain according to Patent Document 1 contains nylon and carbon black. Since nylon is a crystalline resin, when a heated preform is stretched for biaxial stretching molding, spherulites of nylon rapidly develop with carbon black as crystal nuclei, resulting in high hardness. As a result, the domain cannot be stretched to follow the stretching of the matrix.
Based on these considerations, the present inventors used a crystalline polyester that can exhibit excellent strength as a constituent material of the matrix, and as a constituent material of the domain, have low compatibility with the crystalline polyester and have a crystal structure. An acrylonitrile-butadiene-styrene copolymer (hereinafter also referred to as "ABS") having low resistance was selected and examined repeatedly.

As a result, a conductive resin mixture in which ABS containing carbon black was dispersed in crystalline polyester was as follows. That is, it had a matrix-domain structure having a matrix containing crystalline polyester and a domain containing ABS, and carbon black was unevenly distributed in the domains. However, minute cracks were observed at the interface between the matrix and the domains. When a preform formed using such a resin mixture is biaxially stretched, there is a concern that the interface between the matrix and the domain may break as the preform is stretched. Therefore, the present inventors have proposed a technique for preventing the occurrence of cracks at the interface between the matrix and the domains of the resin mixture in order to obtain an electrophotographic belt by biaxial stretching molding using the resin mixture. Recognized the need for development.

Based on such recognition, as a result of repeated further studies, the following facts were found. That is, when the crystalline polyester as a raw material is melt-kneaded with ABS in which carbon black is dispersed, a maleic acid-modified styrene-ethylene-butadiene-styrene copolymer is further added to the matrix and the interface. It is possible to obtain a resin mixture in which cracks are effectively prevented from occurring. In this specification, hereinafter, the crystalline polyester as a raw material may be referred to as "raw material polyester". Also, the maleic acid-modified styrene-ethylene-butadiene-styrene copolymer is sometimes referred to as "m-SEBS".

The present inventors consider the reason why the use of m-SEBS in the preparation of the resin mixture prevents the occurrence of cracks at the interface between the matrix and the domains as follows. there is That is, since m-SEBS has a styrene block in its molecule, it has a high affinity with the styrene block in the ABS molecule. On the other hand, the maleic acid-modified portion in the molecule of m-SEBS reacts with the terminal hydroxy group of the raw material polyester during the melt-kneading process with the raw material polyester (see FIG. 6). As a result, an SEBS-modified crystalline polyester having SEBS as a structural portion is obtained. As a result, in the resin mixture according to the present disclosure, the structural part of SEBS that the crystalline polyester in the matrix has in the molecule interacts with the styrene block of the ABS in the domain, and the affinity with the interface between the matrix and the domain improves. As a result, the occurrence of cracks between the matrix and the domains is thought to be suppressed. In the present disclosure, the crystalline polyester as a component of the resin mixture refers to the SEBS-modified crystalline polyester described above.

Hereinafter, the resin mixture according to one aspect of the present disclosure will be described in detail. Note that the present disclosure is not limited to the following aspects.

1. Conductive Resin Mixture A resin mixture according to one aspect of the present disclosure includes a crystalline polyester, an acrylonitrile-butadiene-styrene copolymer, and carbon black. It has a matrix-domain structure having a matrix containing the crystalline polyester and domains containing the acrylonitrile-butadiene-styrene copolymer. Also, the carbon black is unevenly distributed in the domains. Furthermore, the crystalline polyester has a structural portion of styrene-ethylene-butadiene-styrene copolymer (SEBS) in the molecule. That is, it is an SEBS-modified crystalline polyester.
Such a resin mixture can be produced, for example, by mixing a mixture of crystalline polyester and m-SEBS as raw materials with ABS in which carbon black is dispersed, followed by melt-kneading. Hereinafter, the mixture of crystalline polyester and m-SEBS may be referred to as "masterbatch A", and ABS with carbon black dispersed therein may be referred to as "masterbatch B".

1-1. Crystalline polyester (raw material polyester)
Crystalline polyester as a raw material can be obtained by polycondensation of dicarboxylic acid and diol, polycondensation of oxycarboxylic acid or lactone, or polycondensation using a plurality of these components. Additional polyfunctional monomers may be used in combination. The crystalline polyester may be a homopolyester containing one ester bond or a copolyester (copolymer) containing a plurality of ester bonds.

Preferred examples of the crystalline polyester include at least one selected from the group consisting of polyalkylene terephthalates and polyalkylene naphthalates that have high crystallinity and excellent heat resistance. Copolymers of polyalkylene naphthalate and polyalkylene isophthalate can also be preferably used.
The number of alkylene carbon atoms in polyalkylene terephthalate, polyalkylene naphthalate and polyalkylene isophthalate is preferably 2 or more and 16 or less from the viewpoint that high crystallinity and heat resistance can be obtained. More specifically, preferred crystalline polyesters are polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, and copolymers containing these. It is also possible to use one of these types alone, or to use two or more types in combination.

1-2. Acrylonitrile-butadiene-styrene copolymer (ABS)
ABS can be obtained by chain polymerization of acrylonitrile, butadiene and styrene. Alternatively, it can be obtained by compounding acrylonitrile-styrene copolymer with butadiene rubber. In addition, the properties shown vary depending on the ratio of each component. When a large amount of acrylonitrile is contained, excellent heat resistance and mechanical strength are obtained. When a large amount of butadiene is contained, excellent impact resistance is obtained. When a large amount of styrene is contained, excellent glossiness and workability are obtained. In the present invention, considering the use as an electrophotographic belt, the belt preferably contains a large amount of acrylonitrile, which has excellent mechanical strength, but is not particularly limited.

1-3. Carbon Black As carbon black, the following can be used. Examples include acetylene black, furnace black, channel black and thermal black.
Carbon black has a wide variety of crystallinity and connection states, and has characteristics in shape and size depending on various production methods and pulverization methods. These may be used singly or in combination of two or more. The content of carbon black in the base layer is preferably 1 mass % or more based on the base layer from the viewpoint of imparting conductivity to the electrophotographic belt. In addition, from the viewpoint of suppressing physical deterioration such as cracks and wear due to rubbing with other sliding members (such as transfer rollers and tension rollers), the content of carbon black in the base layer is is preferably 30% by mass or less. Also, the content of carbon black can be obtained from the amount of residue after dissolving the electrophotographic belt with a solvent or the like.
Further, "carbon black is unevenly distributed in the domain" means that the domain uneven distribution index of carbon black, which will be described later, is 80% or more.
The domain uneven distribution index is preferably 85% or more.

1-4. Maleic acid-modified styrene-ethylene-butadiene-styrene copolymer (m-SEBS)
m-SEBS can be obtained by modifying a styrene-ethylene-butadiene-styrene copolymer with maleic acid. SEBS copolymers can be obtained by chain polymerization of styrene, ethylene and butadiene. Alternatively, it can be obtained by partially hydrogenating the butadiene portion ( _--CH.sub.2 --CH.dbd.CH-- _CH.sub.2-- ) of the styrene-butadiene-styrene copolymer. When a large amount of styrene, which is a hard segment, is contained, the thermal stability is excellent, and when a large amount of ethylene and butadiene, which are soft segments, are contained, the flexibility and impact resistance are excellent. In the present invention, since it is used as an interface reinforcing agent, the ratio of each component is not particularly limited, but from the viewpoint of obtaining excellent mechanical strength, it is preferable that a large amount of styrene is contained. Also, from the viewpoint of good compatibility with the styrene portion of the ABS copolymer, it is preferable that the styrene content is large. Specifically, the content of styrene contained in the m-SEBS copolymer is preferably 20% by mass or more.

1-4. Additives Other components may be added to at least one of masterbatch A and masterbatch B within a range that does not impair the effects of the present disclosure. Examples of other components include antioxidants, ultraviolet absorbers, organic pigments, inorganic pigments, pH adjusters, cross-linking agents, compatibilizers, release agents, coupling agents, lubricants, and the like. These additives may be used singly or in combination of two or more. The amount of the additive to be used can be set appropriately and is not particularly limited.

The conductive resin mixture produced by the method according to the present disclosure can be applied to known molding methods such as injection molding, extrusion molding, blow molding, compression molding, and injection compression molding. shape can be manufactured. For example, when manufacturing a seamless belt, a blow molding method, an extrusion method, or the like is suitable. Since the conductive resin mixture produced by the method disclosed in the present invention has a matrix-domain structure, a molded article made of the conductive resin mixture also has the matrix-domain structure.

The conductive resin mixture according to the present disclosure can be used not only for the seamless belt but also for solar cell substrates and the like. In addition to this, households represented by electronic equipment parts such as generators, electric motors, voltage regulators, rectifiers, sensors, LED lamps, semiconductors, computers, printed circuit boards, lighting parts, refrigerator parts, air conditioner parts, copier parts・It can be used for various molded products such as office equipment parts, automobile-related parts, films, containers, pipes, tubes, hoses, and fibers.

2. Electrophotographic Belt An electrophotographic belt according to one aspect of the present disclosure has at least a conductive base layer.
FIG. 5(a) shows a perspective view of an electrophotographic belt 500 having an endless belt shape according to one aspect of the present disclosure. As an example of the layer structure, as shown in FIG. 5(b-1), the cross section taken along the line AA' in FIG. A layer (monolayer) structure may be mentioned. In this case, the outer surface 500-1 of the base layer 501 becomes the toner carrying surface (outer surface) of the electrophotographic belt.

As another example of the layer structure, the cross section taken along the line AA' is shown in FIG. and those having a laminated structure. When the second layer 502 is provided, the outer surface 500-1 of the second layer 502 becomes the toner bearing surface of the electrophotographic belt. One of the functions of the second layer is to improve toner releasability.

Examples of the second layer include a layer having excellent abrasion resistance, which contains a cured product of an active energy ray-curable resin. Such a second layer can be provided, for example, by applying a composition containing an active energy ray-curable resin such as a photocurable resin onto the outer peripheral surface of the base layer and curing the composition. As an example of the active energy ray-curable resin, for example, an acrylic resin is preferably used. Conductive particles may also be added to adjust the surface resistivity of the second layer. Examples of conductive particles include carbon black, graphite, carbon nanotubes, carbon microcoils, zinc oxide, and zinc antimonate.
Also, a third layer (not shown) covering the inner peripheral surface of the base layer 501 may be provided. Examples of the third layer include a resin layer for reinforcing the first layer and a conductive layer for making the inner peripheral surface of the electrophotographic belt conductive.

2-1. Base Layer A base layer having an endless shape, according to one aspect of the present disclosure, comprises a crystalline polyester, an acrylonitrile-butadiene-styrene copolymer, and carbon black. The base layer has a matrix-domain structure having a matrix containing the crystalline polyester and domains containing the acrylonitrile-butadiene-styrene copolymer. In addition, the carbon black is unevenly distributed in the domains, and the crystalline polyester has a styrene-ethylene-butadiene-styrene copolymer structural portion in the molecule.

The transferability of the toner basically depends on the electrical properties of the base layer. In order to obtain high-quality electrophotographic images, the surface resistivity of the base layer is preferably, for example, 1.0×10 ³ Ω/□ to 1.0×10 ¹³ Ω/□. If the surface resistivity is 1.0×10 ³ Ω/□ or more, the resistance can be prevented from being significantly lowered, the transfer electric field can be easily obtained, and the occurrence of omissions and roughness of the image can be effectively suppressed. can do. If the surface resistivity is 1.0×10 ¹³ Ω/□ or less, it is possible to more effectively suppress the transfer voltage from becoming excessive, and to effectively suppress the increase in size and cost of the power supply. can.

The thickness of the base layer is not particularly limited. However, since it is arranged in an electrophotographic image forming apparatus in a bent state, it is preferably 40 μm to 500 μm, particularly 50 μm to 100 μm, from the viewpoint of ensuring flexibility.
Then, the base layer can be manufactured by using the conductive resin mixture described above, for example, through the following steps (i) to (iii).

Step (i): A test tube-shaped preform is obtained from the conductive resin mixture described above.
Step (ii): The preform is stretched in its longitudinal direction and a gas is introduced into the preform to biaxially stretch and mold in the longitudinal and circumferential directions to obtain a biaxially stretched molded product (hereinafter referred to as “bottle ”) is obtained (biaxial stretch blow molding).
Step (iii): Both ends of the bottle are cut to obtain an endless biaxially stretched cylindrical film.

Regarding step (i), first, a masterbatch A containing crystalline polyester and m-SEBS as raw materials and a masterbatch B containing ABS in which carbon black is dispersed are prepared.
Next, as a method for preparing masterbatch A, the crystalline polyester and m-SEBS as raw materials are mixed, and the mixture is melted and kneaded. The temperature at this time is, for example, 220° C. or higher and 330° C. or lower, and the time is preferably, for example, 3 to 5 minutes. This is because the reaction between the raw material polyester and m-SEBS can be sufficiently advanced and the thermal deterioration of the resin can be prevented. The obtained masterbatch A is preferably pelletized.

In addition, and masterbatch B is obtained by mixing ABS and a predetermined amount of carbon black, followed by heat-melting and kneading. The temperature at this time is preferably 190° C. or higher and 270° C. or lower, and the time is preferably 3 to 5 minutes, for example. The obtained masterbatch B is preferably pelletized.
After masterbatch A and masterbatch B are prepared in advance in this way, it is preferable to mix masterbatch A and masterbatch B to prepare the resin mixture according to the present disclosure. Thereby, in the resin mixture, the carbon black can be more reliably unevenly distributed in the domains containing the ABS. That is, in the resin mixture according to the present disclosure, it is preferable that the carbon black is unevenly distributed in the domains containing the ABS so that the carbon black is not brought into direct contact with the crystalline polyester. As a result, when the preform formed from the resin mixture is biaxially stretched, the formation of crystalline polyester spherulites with carbon black as the nucleus can be prevented, and stretching defects due to an increase in hardness of the matrix portion can be prevented. .

The masterbatch A and masterbatch B thus obtained are melted to prepare a resin mixture according to the present disclosure. Then, the obtained resin mixture is used to form a test tube-shaped preform. The preform molding method is not particularly limited, and examples thereof include the following methods. As shown in FIG. 2, an injection molding apparatus 201 is used to inject the melt of the resin mixture into a preform molding mold comprising a cavity mold 203 and a core mold 207. to form a preform 205 having a predetermined shape. At this time, it is preferable that the temperature of the preform molding die into which the melt is injected is, for example, 40° C. or less. The melt injected into the mold is cooled and solidified in the mold, but rapid cooling at this time can prevent the crystallization of the crystalline polyester from progressing. By suppressing the crystallization of the crystalline polyester in the preform, the biaxial crystal orientation of the crystalline polyester in the stretch blow molding in step (ii) can be controlled more accurately. Note that when molding a preform by injection molding, the resin mixture according to the present disclosure and the molding of the preform proceed simultaneously. That is, the resin mixture according to the present disclosure is prepared in the process of heating and melt-kneading masterbatch A and masterbatch B in an extruder of an injection molding apparatus, and the resin mixture in a molten state is used as a molding metal. Injected into the mold cavity. As a result, a preform made of the resin mixture is molded.

Next, in step (ii), the preform is subjected to biaxial stretch blow molding. First, as shown in FIG. 3(a), the preform 205 is placed in a heating furnace 301 and heated to a stretchable temperature. The heating time at this time is preferably within 1 minute. By setting the heating time within 5 minutes, it is possible to prevent the progress of crystallization of the crystalline polyester in the preform during heating. A heated preform is transported in the direction of arrow 305 . Next, by combining the left mold 303-1 and the right mold 303-2, the blow mold 303 having a cylindrical cavity 303-3 formed therein is moved in the direction of the arrow 307 from directly above the heated preform 205. lower. Then, as shown in FIG.

In addition, it is preferable to place the heated preform at the opening of the blow mold within a short period of time (for example, within 20 seconds) so that the temperature of the heated preform does not drop before the start of the next biaxial stretching step. This can prevent the progress of crystallization of the crystalline polyester in the preform due to slow cooling of the preform. The heating temperature of the preform is calculated, for example, by using a differential scanning calorimeter (DSC) in advance for the resin mixture, which is the constituent material of the preform, and looking at the endothermic peak and baseline shift during temperature rise. may be determined from the glass transition temperature (Tg).

The heated preform 205 placed in the blow mold 303 is stretched in the longitudinal direction of the preform 205 by driving the stretching rod 309 in the direction of the arrow 311 as shown in FIG. 3(c). This stretching is called primary stretching. Also, in synchronism with the driving of the stretching rod 309, gas is caused to flow into the preform from the mouth of the preform 205 (arrow 313) to expand the preform in its circumferential direction. This is called secondary stretching. Examples of blown gases include air, nitrogen, carbon dioxide, and argon. As a result, the preform 205 expands in the directions indicated by the arrows 315 in FIG. 3(c), closely contacts the inner wall of the cavity 303-3, and is cooled and solidified in this state. Next, by separating the right mold 303-1 and the left mold 303-2 of the blow mold 303, a bottle-shaped molded product (hereinafter also referred to as “blow bottle”) is taken out from the blow mold 303.

Then, as shown in FIG. 3(d), the obtained blow bottle 317 is cut at the mouth portion side and the upper end portion opposite to the mouth portion side, and a biaxially stretched film serving as a base layer is obtained. A cylindrical film 319 is obtained.
Before cutting the blow bottle 317, heat treatment may be performed as necessary to adjust the surface roughness of the outer peripheral surface of the blow bottle and finely adjust the crystallinity of the crystalline polyester. Specifically, for example, as shown in FIG. 4, a blow bottle 317 is placed in a cylindrical mold 401, and then the inside of the blow bottle is filled with gas. Then, in order to prevent the gas inside the blow bottle from leaking, the mold 401 is moved by roller-shaped heaters 403 which are brought into contact with the outer peripheral surface of the mold 401 in a state in which outer molds are attached to the upper and lower parts of the mold 401 . Heat while rotating. The heating temperature is, for example, about 130 to 190.degree.

Applications of the electrophotographic belt according to the present disclosure are not limited to intermediate transfer belts, but are also suitable for, for example, transport transfer belts.

<Electrophotographic image forming apparatus>
An example of an electrophotographic image forming apparatus using an electrophotographic belt according to an aspect of the present disclosure as an intermediate transfer belt will be described below. As shown in FIG. 1, this electrophotographic image forming apparatus has a so-called tandem type configuration in which electrophotographic stations of a plurality of colors are arranged side by side in the rotational direction of an intermediate transfer belt. In the following description, suffixes Y, M, C, and k are attached to the reference numerals for the respective colors of yellow, magenta, cyan, and black, but the suffixes are omitted for similar configurations. sometimes.

In FIG. 1, charging devices 2Y, 2M, 2C and 2k, exposure devices 3Y, 3M, 3C and 3k, developing devices 4Y, 4M, 4C, 4k, and an intermediate transfer belt (intermediate transfer member) 6 are arranged. The photosensitive drum 1 is rotationally driven in the direction of arrow F (counterclockwise direction) at a predetermined peripheral speed (process speed). The charging device 2 charges the peripheral surface of the photosensitive drum 1 to a predetermined polarity and potential (primary charging). A laser beam scanner as the exposure device 3 outputs a laser beam that is on/off modulated in accordance with image information input from an external device such as an image scanner (not shown) or a computer, thereby charging the photosensitive drum 1. The surface is scanned and exposed. This scanning exposure forms an electrostatic latent image on the surface of the photosensitive drum 1 according to the desired image information.

The developing devices 4Y, 4M, 4C, and 4k contain toners of yellow (Y), magenta (M), cyan (C), and black (k) color components, respectively. Then, 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 to visualize the electrostatic latent image as a toner image. In this embodiment, a reversal development method is used in which toner is adhered to the exposed portion of the electrostatic latent image for development. Further, the charging device, the exposure device, and the development device constitute electrophotographic image forming means.

The intermediate transfer belt 6 is composed of an electrophotographic belt having an endless shape. The intermediate transfer belt 6 is stretched by a plurality of rollers 20 , 21 and 22 so that the outer peripheral surface of the intermediate transfer belt 6 contacts the surface of the photosensitive drum 1 . In this embodiment, the roller 20 is a tension roller configured to control the tension of the intermediate transfer belt 6 to be constant, the roller 22 is a drive roller for the intermediate transfer belt 6, and the roller 21 is a counter roller for secondary transfer. Then, the intermediate transfer belt 6 rotates in the direction of arrow G as the roller 22 is driven. Primary transfer rollers 5Y, 5M, 5C, and 5k are arranged at primary transfer positions facing the photosensitive drum 1 with the intermediate transfer belt 6 interposed therebetween.

The unfixed toner image of each color formed on the photosensitive drum 1 is transferred to the primary transfer roller 5 by applying a primary transfer bias having a polarity opposite to the charged polarity of the toner to the primary transfer roller 5 from a constant voltage source or constant current source (not shown). The images are sequentially electrostatically primary-transferred onto the intermediate transfer belt 6 . Then, a full-color image is obtained on the intermediate transfer belt 6 by superposing unfixed toner images of four colors. The intermediate transfer belt 6 rotates while bearing the toner image transferred from the photosensitive drum 1 in this manner. The surface of the photosensitive drum 1 is cleaned of transfer residual toner by the cleaning device 11 each time the photosensitive drum 1 rotates after the primary transfer, and the image forming process is repeated.

At the secondary transfer position of the intermediate transfer belt 6 facing the conveying path of the recording material 7 as a transfer medium, a secondary transfer roller (transfer portion) 9 is placed in pressure contact with the toner image bearing surface of the intermediate transfer belt 6 . are doing. Further, on the back side of the intermediate transfer belt 6 at the secondary transfer position, a counter roller 21, which serves as a counter electrode for the secondary transfer roller 9 and to which a bias is applied, is arranged. When the toner image on the intermediate transfer belt 6 is transferred to the recording material 7, a bias having the same polarity as that of the toner is applied to the opposing roller 21 by the transfer bias applying means 28, for example, -1000 to -3000 V, and the voltage is -10 to -. A current of 50 μA flows. The transfer voltage at this time is detected by the transfer voltage detection means 29 . Furthermore, a cleaning device (belt cleaner) 12 for removing toner remaining on the intermediate transfer belt 6 after the secondary transfer is provided downstream of the secondary transfer position.

The recording material 7 passes through a conveying guide 8, is conveyed in the direction of arrow H, and is introduced to the secondary transfer position. The recording material 7 introduced to the secondary transfer position is nipped and conveyed at the secondary transfer position, and at that time, the opposing roller 21 of the secondary transfer roller 9 is controlled to a predetermined value by the secondary transfer bias applying means 28. A constant voltage bias (transfer bias) is applied. By applying a transfer bias having 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 portion is collectively transferred onto the recording material 7, and transferred onto the recording material. A full-color unfixed toner image is formed. The recording material 7 to which the toner image has been transferred is introduced into a fixing device (not shown) and heated and fixed.

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these. Materials used for manufacturing electrophotographic belts according to Examples and Comparative Examples are shown below.

(Method for measuring physical property value, evaluation method)
Methods for measuring and evaluating characteristic values of electrophotographic belts according to Examples and Comparative Examples are as described in (1) to (5) below.
(Evaluation 1) Evaluation of Surface Resistivity The surface resistivity of the base layer of the electrophotographic belt was measured according to JIS-K6911. As a measuring device, a high resistance meter (trade name: Hiresta UP MCP-HT450, manufactured by Mitsubishi Chemical Analytic Co., Ltd.) has a main electrode with an inner diameter of 50 mm, a guard ring electrode with an inner diameter of 53.2 mm, and an outer diameter of A 57.2 mm probe (trade name: UR-100, manufactured by Mitsubishi Chemical Analytic Co., Ltd.) was used. The surface resistivity is defined as the surface resistance value per unit area (1 cm ² ) of the electrophotographic belt, and the unit is [Ω/□].

The produced electrophotographic belt base layer was allowed to stand for 24 hours in an environmental test chamber controlled at a temperature of 23° C. and a relative humidity of 50%. Thereafter, a voltage of 250 V was applied to the electrophotographic belt for 10 seconds under an environment of a temperature of 23° C. and a relative humidity of 50%, and the surface resistivity of the electrophotographic belt base layer was measured at four points in the circumferential direction. The average value of the obtained surface resistivities was used as an index of the surface resistivity at normal temperature and normal humidity.
The surface resistivity unevenness was a value obtained by taking the logarithm of the ratio of the maximum value and the minimum value in the measured surface resistivity values. That is, the surface resistivity unevenness is represented by Log ₁₀ (maximum value/minimum value).

(Evaluation 2) Carbon Black Domain Uneven Distribution Index The ratio of carbon black present in the domain portion to the carbon black contained in the entire electrophotographic belt is defined as the carbon black domain uneven distribution index. The domain maldistribution index of carbon black was calculated using a thermogravimetry device (trade name: TGA/DSC3+, manufactured by Mettler Toledo).
First, the mass _WD&M of a sample cut out from the electrophotographic belt was measured.
Next, the sample was heated from 25° C. to 380° C. at a heating rate of 10° C./min, and held at 380° _C. for 4 hours.
The mass calculated by (W _D&M - W _CBD&CBM ) is the mass decreased due to decomposition of the resin in the matrix part and the resin in the domain part.
A value (%) calculated by (W _CBD&CBM /W _D&M )×100 was taken as the mass ratio A of carbon black contained in the entire electrophotographic belt.

Also, the ratio of carbon black existing in the domain portion was calculated by the following method.
First, a sample cut out from an electrophotographic belt was immersed in an alkaline solution overnight to dissolve the crystalline polyester in the matrix portion, washed with pure water, dried, and then the mass _WD of the domain portion was measured.
Next, the sample was heated from 25° C. to 380° C. at a heating rate of 10° C./min, held at 380° C. for 4 hours, and then the mass of carbon black in the domain (W _CBD ) was measured.
A value (%) calculated by (W _CBD /W _D )×100 was taken as the mass ratio B of carbon black contained in the domain portion.
A value (%) calculated by (W _CBD /W _CBD&CBM )×100 is defined as the domain uneven distribution index of carbon black (CB). The closer the domain maldistribution index is to 100%, the more maldistributed the carbon black is in the domain portion.

(Evaluation 3) Evaluation of cracks Evaluation of cracks is carried out using a scanning electron microscope (trade name: Ultra55, manufactured by Carl Zeiss) to evaluate the cross section of the resin molding (test tube-shaped preform before biaxial stretching) and A cross section of the electrophotographic belt was observed and an image of the cross section was acquired. The presence or absence of cracks in the resin molding and the presence or absence of cracks in the electrophotographic belt (that is, the presence or absence of cracks after blow molding) were determined from the acquired images. A cryomicrotome (trade name: UC6, manufactured by Leica) was used to expose the observation surface. To distinguish between the matrix and the domains, a cryomicrotome was used to expose the observation surface, followed by vapor staining with a 4% _OsO4 aqueous solution to stain the butadiene component. From this staining, it was judged that the part where the butadiene component was present was the ABS copolymer.

(Evaluation 4) Evaluation of durability In accordance with JIS P8115, the test piece was cut into a size of 10 mm in width and 100 mm in length, and an MIT type folding endurance tester (Yasuda Seiki Seisakusho Co., Ltd. No. 307 MIT type endurance Using a folding tester), the number of times until breakage was measured under the following conditions.
Measurement conditions: bending speed 180 times/min, bending angle left and right 135°, tensile load 9.8N.

(Evaluation 5) Digital Reproducibility of Electrophotographic Image Forming Apparatus Using the electrophotographic image forming apparatus having the configuration shown in FIG. placed in an environmental test chamber controlled at 24 hours. Thereafter, an unfixed image at the time when the thin line image (30 lines/5 mm) was transferred onto the paper was output, and was fixed in an oven at 100° C. without pressure to obtain an image. The image was observed using a magnifying glass to confirm the presence or absence of toner scattering on each fine line image, and evaluated according to the following criteria.
<Evaluation Criteria>
Rank A: No thin line image with toner scattering.
Rank B: 1 to 5 thin line images with toner scattering.
Rank C: 6 to 10 thin line images with toner scattering.
Rank D: 11 or more thin line images with toner scattering.

[Example 1]
(Preparation of base layer)
<Pre-blend sample 1, pre-blend sample 2>
Various materials were pre-blended in advance so as to achieve the material blending ratios listed in Table 5A.
Specifically, ABS1 and CB1 were preblended to obtain preblend sample 1 (masterbatch B).
Preblend sample 2 (masterbatch A) was obtained by preblending cPES1 and m-SEBS1.

<Amorphous thermoplastic resin mixture 1>
Next, the preblend sample 1 was hot-melt kneaded using a twin-screw extruder (trade name: TEX30α, manufactured by The Japan Steel Works, Ltd.) to prepare an amorphous thermoplastic resin mixture. The hot-melt kneading temperature was adjusted to be in the range of 190° C. or higher and 270° C. or lower, and the hot-melt kneading time was about 3 to 5 minutes. The resulting amorphous thermoplastic resin mixture was pelletized to obtain amorphous thermoplastic resin mixture 1 .
<Crystalline thermoplastic resin mixture 1>
Similarly, the preblend sample 2 was hot-melt kneaded using a twin-screw extruder (trade name: TEX30α, manufactured by The Japan Steel Works, Ltd.) to prepare a crystalline thermoplastic resin mixture. The hot-melt kneading temperature was adjusted to be in the range of 220° C. or higher and 330° C. or lower, and the hot-melt kneading time was about 3 to 5 minutes. The resulting crystalline thermoplastic resin mixture was pelletized to obtain a crystalline thermoplastic resin mixture 1 .

Next, the obtained amorphous thermoplastic resin mixture 1 was dried at a temperature of 90° C. for 10 hours, and the crystalline thermoplastic resin mixture 1 was dried at a temperature of 140° C. for 10 hours. The pelletized amorphous thermoplastic resin mixture 1 and the crystalline thermoplastic resin mixture 1 were placed in an injection molding machine (trade name: SE180D, Sumitomo Heavy Industries, Ltd.) so that the material blending ratio shown in Table 5A was obtained. ) made). Then, the cylinder set temperature was set to 250 to 300° C., and injection molding was performed in a test tube-shaped mold whose temperature was controlled to 30° C. to prepare a preform. The resulting preform had the shape of a test tube with an outer diameter of 50 mm, an inner diameter of 46 mm, and a length of 150 mm.

Next, the above preform was biaxially stretched in its longitudinal direction and circumferential direction using a biaxial stretching molding device. First, as shown in FIG. 3A, the preform 205 is placed in a heating device 301 equipped with a non-contact heater (not shown) for heating the preform 205, and the heater heats the preform. Heating was performed so that the outer surface temperature was 120 to 160°C. Next, the blow mold 303 kept at a mold temperature of 30° C. is lowered against the heated preform 205 in the direction of the arrow 307 , and the heated preform 205 is placed at the mouth of the blow mold 303 . (Fig. 3(b)). Next, as shown in FIG. 3(c), the stretching rod 309 is driven in the direction of the arrow 311, and as shown by the arrow 313 in FIG. The air temperature-controlled to 23° C. was introduced into the chamber. Thus, the preform 205 was biaxially stretched and brought into close contact with the inner wall of the blow mold. Next, the right mold 303 - 1 and the left mold 303 - 2 of the blow mold 303 were separated, and a bottle-shaped molding (blow bottle) 317 was taken out from the blow mold 303 .

Next, the obtained blow bottle 317 was set in a nickel cylindrical mold 401 made by electroforming shown in FIG. 4, and an outer mold 405 was attached. An air pressure of 0.1 MPa was applied to the inside of the blow bottle, and the outer peripheral surface of the blow bottle 317 was brought into close contact with the inner peripheral surface of the cylindrical mold by adjusting so as not to leak air to the outside. Furthermore, while rotating the nickel cylindrical mold 401, it was heated to 130 to 190.degree.

After that, air at a temperature of 25° C. is blown against this nickel cylindrical mold to cool it down to room temperature (25° C.) over 1 minute. Thus, a blow bottle 317 with improved was obtained. From the dimensions of the preform 205 and the blow bottle 317, the biaxial draw ratio was 4.0 times for the transverse draw ratio (perpendicular direction) Lp and 4.3 times for the longitudinal draw ratio (perpendicular to the circumferential direction) La. .
Next, as shown in FIG. 3(d), the blow bottle 317 is cut at the mouth portion side and the portion opposite to the mouth portion side, and an electron beam having a circumference of 630 mm, a width of 250 mm, and a thickness of 70 μm is cut. A base layer for a photographic belt was prepared.

(Preparation of coating solution for surface layer)
The acrylic resin mixture described in Table 4 was weighed at a ratio of AN / PTFE / GF / SL / IRG = 66 / 20 / 1.0 / 12 / 1.0 (mass ratio in terms of solid content), and coarsely dispersed. was dispersed using the following high-pressure emulsifying disperser.
High-pressure emulsifying disperser, trade name: Nanoveita, manufactured by Yoshida Kikai Kogyo Co., Ltd. This dispersing treatment was carried out until the 50% average particle size of the contained PTFE reached 200 nm. The resulting dispersion was used as a surface layer coating liquid.

(Formation of surface layer)
The base layer is fitted on the outer periphery of a cylindrical mold (perimeter of 630 mm), the ends are sealed, and the mold is immersed in a container filled with the surface layer coating liquid, and the liquid surface of the curable composition and the The electrophotographic belt substrate was pulled up so that the relative velocity was constant. Thus, a coating film made of the coating liquid was formed on the surface of the electrophotographic belt base layer. Depending on the desired thickness of the surface layer, the pulling speed (relative speed between the liquid surface of the curable composition and the electrophotographic belt base layer) and the solvent ratio of the curable composition can be adjusted.

In this example, the lifting speed was set to 10 to 50 mm/sec, and the film thickness of the surface layer was adjusted to about 3 μm. In this embodiment, the coating direction means the direction opposite to the direction in which the electrophotographic belt base layer is pulled up. That is, the place where it is pulled up from the coating liquid first becomes the most upstream. The electrophotographic belt base layer coated with the coating solution was removed from the cylindrical mold and dried for 1 minute at 23° C. under exhaust. The drying temperature and drying time are appropriately adjusted depending on the type of solvent, solvent ratio, and film thickness. Thereafter, the coating film was cured by irradiating the coating film with ultraviolet rays using a UV irradiator (trade name: UE06/81-3, manufactured by Eyegraphic Co., Ltd.) until the integrated light quantity reached 600 mJ/cm ² .

The thickness of the surface layer was determined by a destructive test in which an electrophotographic belt base layer separately prepared under the same conditions was cut and the cross section was observed with an electron microscope (trade name: XL30-SFEG, manufactured by FEI). A destructive test revealed that the thickness of the surface layer was 2.8 μm. Thus, an electrophotographic belt having a surface layer formed on the outer peripheral surface of the base layer was obtained.
This electrophotographic belt was subjected to the above (Evaluation 1) to (Evaluation 5). The evaluation results are shown in Table 6A.

[Examples 2 to 16]
An electrophotographic belt was produced and evaluated in the same manner as in Example 1, except that the material types and blending amounts were as shown in Tables 5A and 5B below. These evaluation results are shown in Tables 6A and 6B.

[Comparative Examples 1 to 6]
An electrophotographic belt was produced and evaluated in the same manner as in Example 1, except that the material types and compounding amounts were as shown in Table 5B below. These evaluation results are shown in Table 6B.
In Comparative Example 1, no m-SEBS copolymer as an interfacial reinforcing agent was included. It was also confirmed that cracks were present at the interface between the crystalline polyester and the ABS copolymer.
In Comparative Example 2, the carbon black content is too small. Therefore, the surface resistivity was 1×10 ¹⁴ [Ω/□], which was out of the range suitable for an electrophotographic belt.

Comparative Example 3 does not contain an ABS copolymer. It is considered that the reason why the blow molding could not be performed was that when the preform was heated during the primary blow, spherulization was promoted with the carbon black as the crystal nucleus, and the preform became hard.
Comparative Example 4 does not contain crystalline polyester. The reason why the blow molding could not be performed is considered to be that when the preform was biaxially stretched, the high strength due to the oriented crystallization did not occur, and the locally thinned portion was broken.
Comparative Example 5 was the same as Example 2, except that a styrene-ethylene-butadiene-styrene copolymer not modified with maleic acid was used as the interfacial reinforcing agent. Since a styrene-ethylene-butadiene-styrene copolymer not modified with maleic acid was used as the interfacial reinforcing agent, a sufficient interfacial reinforcing effect could not be obtained, and cracks were present in the resin molding. Therefore, as shown in Table 6, the number of times until failure in the MIT test was lower than in Example 2.

Reference Signs List 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 drive roller 28 transfer bias applying means 29 transfer high pressure detection means 205 preform 303 blow mold 309 stretching bar 317 blow bottle

Claims (7)

An electrophotographic belt,
having a conductive base layer,
the base layer comprises crystalline polyester, acrylonitrile-butadiene-styrene copolymer, and carbon black;
the base layer has a matrix-domain structure having a matrix containing the crystalline polyester and domains containing the acrylonitrile-butadiene-styrene copolymer;
The carbon black is unevenly distributed in the domain,
An electrophotographic belt, wherein the crystalline polyester has a structural portion of a styrene-ethylene-butadiene-styrene copolymer in its molecule. 2. The electrophotographic belt of claim 1, wherein the base layer has a surface resistivity of 1.0×10 ³ Ω/□ to 1.0×10 ¹³ Ω/□. 3. The electrophotographic belt according to claim 1, wherein a content of said carbon black in said base layer is 1% by mass or more and 30% by mass or less with respect to said base layer. 4. The electrophotographic belt according to claim 1, wherein the carbon black contained in the base layer has a domain uneven distribution index of 80% or more. The electron according to any one of claims 1 to 4, wherein the crystalline polyester is at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, and copolymers containing these. photo belt. An electrophotographic image forming apparatus comprising the electrophotographic belt according to any one of claims 1 to 5 as an intermediate transfer belt. A conductive resin mixture,
crystalline polyester, acrylonitrile-butadiene-styrene copolymer, and carbon black;
having a matrix-domain structure having a matrix containing the crystalline polyester and domains containing the acrylonitrile-butadiene-styrene copolymer;
The carbon black is unevenly distributed in the domain,
A conductive resin mixture, wherein the crystalline polyester has a structural portion of a styrene-ethylene-butadiene-styrene copolymer in its molecule.

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