JP2023172549A - Resin member and image forming apparatus - Google Patents

Abstract

To provide a resin member that can achieve both prevention of a reduction in electric resistance and prevention of molding failure.SOLUTION: A resin member is used for an electrophotographic image forming apparatus. The resin member contains thermoplastic resin and carbon black. The thermoplastic resin contains polyether ether ketone resin and second resin different from the polyether ether ketone resin. A value of the structure volume of the carbon black is 50-250 nm2 ml/100 g. The content ratio of the carbon black in the resin member is 19.0-30.0 mass%. The content ratio of the second resin in the thermoplastic resin is 16.0 mass% or more. A temperature-falling crystallization temperature of the resin member measured in differential scanning calorimetry is 299.0°C or more.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a resin member used in an image forming apparatus such as a copying machine, a printer, or a facsimile machine using an electrophotographic method or an electrostatic recording method, and an image forming apparatus equipped with the resin member as an intermediate transfer belt.

In an electrophotographic image forming apparatus, the method of transferring a toner image onto a transfer material is to primarily transfer the toner image formed on a photoreceptor onto a belt-like intermediate transfer belt, and then transfer the toner image. Some use an intermediate transfer method that performs secondary transfer onto a material.

In order to accurately electrostatically transfer the toner image on the surface of the photoreceptor onto the transfer material, the electrophotographic belt used as the intermediate transfer belt has a volume resistivity in a semiconductive region, and It is preferable that the variation in volume resistivity depending on the location of the member is small. Therefore, it is required that the plane involved in image formation be substantially uniform. The electrical resistance value of the intermediate transfer belt is adjusted to, for example, a volume resistivity of 1×10 ⁸ to 1×10 ¹³ Ω・cm and a surface resistivity of 1×10 ⁹ to 1×10 ¹⁵ Ω/□. are often used. As the target range of the electrical resistance value, an optimum range is selected according to the configuration of the transfer section of the image forming apparatus in which the intermediate transfer belt is used and the charging characteristics of the toner particles.

Patent Document 1 discloses a belt obtained by extruding polyetheretherketone (PEEK) containing a conductive filler into a tubular film and then cutting the film in a direction perpendicular to the axial direction. Further, it is disclosed that the volume electrical resistance value of each part of the belt is 10 ⁸ to 10 ¹⁷ Ω·cm.

Japanese Patent Application Publication No. 06-254941

However, when an electrophotographic belt is made to exhibit electrical conductivity using a conductive filler, its electrical resistance may decrease if it is used for forming an electrophotographic image over a long period of time.
Furthermore, it has been found that in intermediate transfer belts containing conductive fillers, the thickness of the belt becomes unstable during molding into a cylindrical belt, resulting in molding defects.
One aspect of the present disclosure is directed to a resin member that can both suppress a decrease in electrical resistance and suppress molding defects. Further, the present disclosure is directed to an image forming apparatus including the resin member as an intermediate transfer belt.

According to one aspect of the present disclosure,
A resin member used in an electrophotographic image forming apparatus,
The resin member contains a thermoplastic resin and carbon black,
The thermoplastic resin includes a first resin and a second resin different from the first resin,
The first resin is polyetheretherketone,
The structure volume value of the carbon black is 50 to 250 nm ² ml/100 g,
The content ratio of the carbon black in the resin member is 19.0 to 30.0% by mass,
The content rate of the second resin in the thermoplastic resin is 16.0% by mass or more,
A resin member is provided, in which the cooling crystallization temperature of the resin member measured in differential scanning calorimetry is 299.0° C. or higher.

According to other aspects of the disclosure:
a first image carrier carrying an unfixed toner image;
an intermediate transfer belt to which the toner image formed on the first image carrier is primarily transferred;
a secondary transfer means for secondarily transferring the toner image primarily transferred onto the intermediate transfer belt onto a second image carrier;
Equipped with
An image forming apparatus is provided in which the intermediate transfer belt is the resin member described above.

According to the present disclosure, it is possible to provide a resin member that can both suppress a decrease in electrical resistance and suppress molding defects.

Schematic diagram of a cross section of an image forming apparatus using an electrophotographic belt as an intermediate transfer belt Schematic diagram of the thickness measurement point of an electrophotographic belt

In the present disclosure, the descriptions of "XX to YY" and "XX to YY" expressing a numerical range mean a numerical range including the lower limit and upper limit, which are the endpoints, unless otherwise specified. When numerical ranges are described in stages, the upper and lower limits of each numerical range can be arbitrarily combined.

Hereinafter, an electrophotographic belt as an example of a resin member according to the present disclosure, a method for manufacturing the electrophotographic belt, and an electrophotographic image forming apparatus (hereinafter also simply referred to as "image forming apparatus") will be described with reference to the drawings. do.

1. Image Forming Apparatus First, an embodiment of an image forming apparatus according to one aspect of the present disclosure using an electrophotographic belt having an endless shape as an intermediate transfer belt will be described. FIG. 1 is a schematic cross-sectional view of an image forming apparatus 100 of this embodiment. The image forming apparatus 100 of this embodiment is a tandem color laser printer that employs an intermediate transfer method and is capable of forming full-color images using an electrophotographic method.

The image forming apparatus 100 includes first, second, third, and fourth image forming sections PY, PM, PC, and PK as a plurality of image forming sections. These first, second, third, and fourth image forming units PY, PM, PC, and PK are arranged in this order along the moving direction of a flat portion (image transfer surface) of the intermediate transfer belt 7, which will be described later. There is. For elements having the same or corresponding functions or configurations in the first, second, third, and fourth image forming units PY, PM, PC, and PK, a code indicating that the element is for one of the colors is used. In some cases, the suffixes Y, M, C, and K may be omitted to provide a comprehensive explanation. In this embodiment, the image forming section P includes a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, and a primary transfer roller 5, which will be described later.

The image forming section P includes a photosensitive drum 1 that is a drum-shaped (cylindrical) photosensitive member (electrophotographic photosensitive member) and serves as an image carrier (first image carrier) that carries an unfixed toner image. The photosensitive drum 1 is, for example, formed by laminating a charge generation layer, a charge transport layer, and a surface protection layer in this order on an aluminum cylinder as a base.
The photosensitive drum 1 is rotationally driven in the direction of arrow R1 (counterclockwise) in the figure. The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of a predetermined polarity (negative polarity in this embodiment) by a charging roller 2, which is a roller-shaped charging member serving as a charging means. During the charging process, a predetermined charging bias (charging voltage) containing a negative direct current component is applied to the charging roller 2. The charged surface of the photosensitive drum 1 is scanned and exposed according to image information by an exposure device (laser scanner) 3 serving as an exposure means, and an electrostatic image (electrostatic latent image) is formed on the photosensitive drum 1. .

The electrostatic image formed on the photosensitive drum 1 is developed (visualized) by supplying toner as a developer by a developing device 4 serving as a developing means, and an unfixed toner image (developer image) is formed on the photosensitive drum 1. ) is formed. During the development process, a predetermined development bias (development voltage) containing a negative polarity DC component is applied to the development roller 4a as a developer carrier included in the development device 4. In this embodiment, the exposed area (image area) on the photosensitive drum 1, whose absolute value has decreased by being exposed to light after being uniformly charged, has the same polarity as the charged polarity of the photosensitive drum 1 (in this embodiment). Toner charged to a negative polarity (negative polarity) adheres to the toner.

An intermediate transfer belt 7, which is an endless belt, is arranged so as to face the four photosensitive drums 1. The intermediate transfer belt 7 is stretched around a plurality of tension rollers, such as a drive roller 71, a tension roller 72, and a secondary transfer opposing roller 73, with a predetermined tension. The intermediate transfer belt 7 contacts the photosensitive drum 1 and rotates (circularly moves) in the direction of arrow R2 (clockwise) in the figure as the drive roller 71 is rotationally driven.
On the inner peripheral surface side of the intermediate transfer belt 7, a primary transfer roller 5, which is a roller-shaped primary transfer member serving as a primary transfer means, is arranged corresponding to each photosensitive drum 1. The primary transfer roller 5 is pressed toward the photosensitive drum 1 via the intermediate transfer belt 7, and forms a primary transfer portion (primary transfer nip) T where the photosensitive drum 1 and the intermediate transfer belt 7 are in contact. The unfixed toner image formed on the photosensitive drum 1 as described above is primarily transferred onto the rotating intermediate transfer belt 7 by the action of the primary transfer roller 5 in the primary transfer portion T.
During the primary transfer process, the primary transfer roller 5 is applied with a primary transfer bias (primary transfer voltage ) is applied. The primary transfer roller 5 is composed of a metal rotating shaft and an elastic layer formed on the outer peripheral surface of the rotating shaft, and is often adjusted to a desired resistance value. The roller may be made of composite free-cutting steel (composite free-cutting steel) or SUS (stainless steel), and may be configured with a metal roller having a straight shape in the thrust direction.

On the outer peripheral surface side of the intermediate transfer belt 7, a secondary transfer roller 8, which is a roller-shaped secondary transfer member serving as a secondary transfer means, is arranged at a position facing the secondary transfer opposing roller 73. The secondary transfer roller 8 is pressed toward the secondary transfer opposing roller 73 via the intermediate transfer belt 7, and the secondary transfer portion (secondary transfer nip) where the intermediate transfer belt 7 and the secondary transfer roller 8 come into contact Form T'.
The toner image formed on the intermediate transfer belt 7 as described above is conveyed by being sandwiched between the intermediate transfer belt 7 and the secondary transfer roller 8 by the action of the secondary transfer roller 8 in the secondary transfer portion T'. The image is secondarily transferred to the second image bearing member. The second image carrier is a recording material (sheet, transfer material) S such as paper. During the secondary transfer process, a secondary transfer bias (secondary transfer voltage), which is a DC voltage with a polarity opposite to the normal charging polarity of the toner, is applied to the secondary transfer roller 8. In secondary transfer, a transfer voltage of several kV is usually applied to ensure sufficient transfer efficiency.
The recording material S is supplied to the conveyance path by a pickup roller 13 from a cassette 12 in which the recording material S is stored. The recording material S supplied to the conveyance path is conveyed to the secondary transfer portion T' by a pair of conveyance rollers 14 and a pair of registration rollers 15 in synchronization with the toner image on the intermediate transfer belt 7.

The recording material S onto which the toner image has been transferred is conveyed to a fixing device 9 as a fixing means. The fixing device 9 includes a pressure roller 91 and a heating roller 92. The fixing device 9 fixes (melts, fixes) the toner image on the recording material S by heating and pressurizing the recording material S carrying the unfixed toner image. The recording material S with the toner image fixed thereon is discharged (output) to the outside of the main body of the image forming apparatus 100 by a pair of transport rollers 16, a pair of discharge rollers 17, and the like.

Toner remaining on the surface of the photosensitive drum 1 without being transferred to the intermediate transfer belt 7 in the primary transfer process (primary transfer residual toner) is collected at the same time as development by the developing device 4, which also serves as the photosensitive member cleaning means 4b.
Further, toner remaining on the surface of the intermediate transfer belt 7 without being transferred to the recording material S in the secondary transfer process (secondary transfer residual toner) is removed from the intermediate transfer belt 7 by a belt cleaning device 11 serving as an intermediate transfer belt cleaning means. removed from the surface and collected. The belt cleaning device 11 is arranged downstream of the secondary transfer section T' and upstream of the most upstream primary transfer section Ty (in the present embodiment, at a position facing the drive roller 71) in the rotational direction of the intermediate transfer belt 7. .
The belt cleaning device 11 scrapes and collects secondary transfer residual toner from the surface of the rotating intermediate transfer belt 7 using a cleaning blade as a cleaning member arranged so as to come into contact with the surface of the intermediate transfer belt 7. It is stored in the container 11b.

In this manner, in the image forming operation, the electrical transfer process of the toner image from the photosensitive drum 1 to the intermediate transfer belt 7 and from the intermediate transfer belt 7 to the recording material S is repeatedly performed. Further, by repeating image formation on a large number of recording materials S, the electrical transfer process is further repeated.

2. Intermediate Transfer Belt The intermediate transfer belt 7 includes at least a base layer (base material), and may be a laminate including a plurality of layers, further including a surface layer (surface layer). As explained below, the base layer is a semiconductive film made of a resin containing a conductive filler.

2-1. Structure and Characteristics of Intermediate Transfer Belt In order to stabilize the conductivity of a conductive electrophotographic belt, the present inventors use carbon black having a structure volume in the range of 50 to 250 nm ² ml/100 g. We have obtained knowledge that this is effective. Therefore, a resin composition in which carbon black having a structure volume within the above numerical range was dispersed in a thermoplastic resin was melt-extruded from a cylindrical die to produce an endless-shaped resin member.
However, the obtained resin members had variations in film thickness. Therefore, in order to obtain an electrophotographic belt whose conductivity does not easily change even after long-term use by using carbon black with a structure volume within the above numerical range, the present inventors sought to improve the thickness unevenness. I realized that I needed to do more.

Here, the present inventors speculate as follows why film thickness unevenness occurs in a cylindrical extrusion molded product of a resin composition containing carbon black whose structure volume is within the above numerical range. That is, the thickness of a cylindrical resin member molded by the cylindrical extrusion method is adjusted when the resin composition is extruded in a molten state from a cylindrical die and drawn downward.
The present inventors confirmed that the cooling crystallization temperature of the resin composition containing the carbon black is lower than that of a resin composition containing carbon black with a structure volume larger than the above numerical range. did. When the crystallization temperature is low, the resin material extruded from the cylindrical die is taken off without being sufficiently crystallized, so that no force is transmitted in the taking-off direction and the thickness becomes thin.
As the thickness decreases, material accumulates at the exit of the cylindrical die, but because it is pushed out from behind, the material is pushed out all at once at a certain timing, increasing the thickness. It is thought that this repetition caused the thickness unevenness.

According to studies by the present inventors, it has been found that thickness unevenness is particularly likely to occur when the cooling crystallization temperature is lower than 299.0°C. Therefore, in order to obtain an electrophotographic belt that has both stable conductivity and uniform film thickness at a high level, it is necessary to crystallize a resin composition containing carbon black with a structure volume within the above numerical range. It was recognized that it is important to keep the temperature at 299.0°C or higher.

The cooling crystallization temperature of the resin member needs to be 299.0°C or higher, preferably 299.0 to 380°C, more preferably 299.5 to 360.0°C, and more preferably 300. More preferably, the temperature is 0 to 340.0°C.
The cooling crystallization temperature of the resin member can be controlled by the type and content of the second resin.

<Method for measuring cooling crystallization temperature>
In a differential scanning calorimeter (DSC), the peak temperature detected during the process of cooling from a molten state is defined as the cooling crystallization temperature.
The cooling crystallization temperature was determined by cutting the resin member into pieces of about 2 to 3 mg, setting the sample in a DSC (Q2000, manufactured by TA Instruments Japan Co., Ltd.), and increasing the temperature to 400°C at a rate of 10°C/min. Then, the peak temperature that appears when the temperature is lowered to room temperature at 10° C./min is measured.

<Resin material>
A thermoplastic resin is used as a resin material for a resin member such as an intermediate transfer belt composed of a single layer. The thermoplastic resin includes a first resin and a second resin different from the first resin. The first resin is polyetheretherketone (PEEK). Intermediate transfer belts made of PEEK resin do not stretch easily even when subjected to long-term tension loads, and their surfaces are not easily abraded due to rubbing by a cleaning blade.
The content ratio of the thermoplastic resin in the resin member is preferably 70.0 to 81.0% by mass, more preferably 75.0 to 80.0% by mass.
The content ratio of PEEK in the thermoplastic resin is preferably 84.0% by mass or less, more preferably, for example, 35.0 to 84.0% by mass, 50.0 to 8.0% by mass, 60.0% by mass. 0 to 8.0% by mass, and 70.0 to 8.0% by mass.

<Second resin material>
The thermoplastic resin contains a second resin different from the polyetheretherketone. The second resin is preferably a resin that exhibits a cooling crystallization temperature higher than that of the PEEK resin while maintaining physical properties equivalent to those of the PEEK resin.
The cooling crystallization temperature of the second resin is, for example, preferably 299.0 to 350.0°C, more preferably 300.0 to 330.0°C.
In addition to PEEK resin, examples of thermoplastic resins include polyaryletherketone (PAEK), polyetherketoneketone (PEKK), and polyetherketone (PEK). Preferably, the second resin is polyetherketone (PEK). Furthermore, two or more of these resins may be selected and mixed as necessary. That is, the thermoplastic resin further contains a third resin, a fourth resin, etc. different from the PEEK resin and the second resin.
- May contain an n-th resin.

<Content ratio of second resin>
The content rate of the second resin in the thermoplastic resin is 16.0% by mass or more from the viewpoint of increasing the cooling crystallization temperature. The content ratio of the second resin in the thermoplastic resin is more preferably, for example, 16.0 to 65.0% by mass, 16.0 to 50.0% by mass, 16.0 to 40.0% by mass, It is 16.0 to 30.0% by mass.

<Measurement of content ratio of each resin in thermoplastic resin in resin member>
The content ratio of each resin in the thermoplastic resin can be measured based on known means.
For example, when the thermoplastic resin is PEEK and PEK, the cooling crystallization temperature changes depending on the content ratio of PEEK and PEK. Therefore, by obtaining a calibration curve from the relationship between the content ratios of PEEK and PEK and the cooling crystallization temperature, the content ratio of each resin can be calculated based on the cooling crystallization temperature. In this way, after understanding the resin components contained in the thermoplastic resin by known means, the content ratio of each resin can be calculated from the cooling crystallization temperature.

<Conductive filler>
At least one type of conductive filler such as carbon black or fine metal particles is blended into the resin material for the purpose of imparting conductivity to the intermediate transfer belt. In this disclosure, carbon black is used from the viewpoint of mechanical properties. That is, the resin member contains carbon black. Carbon black has various names depending on its manufacturing method and raw materials. Specifically, these include Ketjen black, furnace black, acetylene black, thermal black, and gas black.

Various known carbon blacks can be used. Specific examples include Ketjen black, furnace black, acetylene black, thermal black, and gas black. Among these, acetylene black and furnace black are preferred because they contain few impurities, have a low frequency of foreign particle defects when molded into a film shape with the above-mentioned thermoplastic resin, and can easily obtain the desired conductivity. Furnace black is more preferred.

Specific examples of acetylene black include the following. The following are all product names. "Denka Black" series (manufactured by Denka Corporation), "Mitsubishi Conductive Filler" series (manufactured by Mitsubishi Chemical Corporation), "Vulcan" series (manufactured by Cabot Corporation), "Brintex" series (manufactured by Degussa Corporation), " SRF” (manufactured by Asahi Carbon Co., Ltd.).
Specifically, furnace blacks include the "Mitsubishi Carbon Black" series (manufactured by Mitsubishi Chemical Corporation), the "Toka Black" series (manufactured by Tokai Carbon Co., Ltd.), and the "Asahi Carbon Black" series (manufactured by Asahi Carbon Co., Ltd.). ) and the "Niteron" series (manufactured by Nippon Steel Carbon Co., Ltd.).

<Content ratio of carbon black>
The content ratio of carbon black is selected in consideration of the ability to impart necessary electrical conductivity to the belt member, mechanical strength such as bending resistance and elastic modulus, and thermal conductivity of the belt member.
The content of carbon black in the resin member is 19.0 to 30.0% by mass. By setting the content of carbon black within the above range, it is possible to ensure conductivity suitable for resin members such as intermediate transfer belts and sufficient mechanical strength. When the content of carbon black in the resin member is less than 19.0% by mass, white spots are likely to occur.
The content of carbon black in the resin member is preferably 20.0 to 28.0% by mass, more preferably 20.0 to 25.0% by mass, and even more preferably 21.0 to 24.0% by mass. Mass%.

<Measurement method of carbon black content ratio>
A cut piece of the resin member is dissolved in 20 ml of concentrated sulfuric acid to obtain a cut piece solution. The cut fragment solution is neutralized with an appropriate alkaline solution (for example, 1 mol/L sodium hydroxide aqueous solution) to obtain a neutralized cut fragment solution. After diluting the cut fragment dissolving neutralization liquid twice with water, the content ratio of carbon black to be contained in the resin member can be estimated from the mass of the residual portion obtained by drying the diluted liquid.

2-2. Method for Manufacturing Intermediate Transfer Belt The method for manufacturing a resin member such as an intermediate transfer belt is not particularly limited, and any known method may be employed. The base layer of an intermediate transfer belt consisting of a single layer or the base layer of an intermediate transfer belt consisting of at least two layers is manufactured through the following steps (1) and (2).
(1) A mixing step in which a resin material (thermoplastic resin) and a conductive filler are mixed in a temperature environment where the temperature of the resin material is equal to or higher than the glass transition point of the resin material to obtain a resin composition. A molding step of melting the resulting resin composition at a temperature higher than the melting temperature of the resin material and molding it into a cylindrical tube shape. Each step of (1) and (2) will be described below.

<Mixing process>
In the mixing step, a thermoplastic resin and a conductive filler are mixed in an environment at a temperature equal to or higher than the glass transition point of the thermoplastic resin to obtain a resin composition. As the mixer used in the mixing step, for example, a twin-screw kneader having two screws in a barrel or cylinder can be used.

The mixture of materials supplied from the supply hole of the supply section is moved forward toward the die by the rotation of the screw, and is heated by shearing due to friction between the barrel or cylinder, the screw, and the raw material, and is melted and mixed. It is preferable to control the temperature of the raw material so that it does not become too high by cooling the barrel or cylinder from the outside, adjusting the temperature, adjusting the rotational speed of the screw, etc.

From the viewpoint of improving the dispersion state of the conductive filler and obtaining a resin composition with excellent mechanical, electrical and optical properties, the temperature during kneading is preferably 300 to 400°C, and more preferably Preferably it is 340-380°C. A strand die is usually installed at the tip of the twin-screw kneader, and the resin composition is extruded into a rod shape, cooled in air, and then cut to produce a pellet-shaped resin composition. The amount of extrusion and the rotation speed of the device during kneading may be appropriately set from the viewpoint of uniformly mixing the resin composition.

Note that, before the mixing step, a pre-mixing step may be provided in which the thermoplastic resin and the conductive filler are mixed using a flow mixer under a temperature environment below the glass transition point of the thermoplastic resin. Various known fluid mixers that have a mechanism for mixing by utilizing fluid motion of solids can be used, but concrete mixers such as Henschel mixers, ribbon mixers, and planetary mixers can be used. Can be used.
Among these, it is preferable to use a Henschel mixer from the viewpoint of mixing efficiency. Further, the rotation speed, processing time, processing amount, etc. of the fluidized mixer may be appropriately selected depending on the material.

<Molding process>
In the molding step, the resin composition obtained in the mixing step is molded into a resin member. For example, it is molded into a resin member in the shape of an endless belt, such as a cylindrical tube shape. For molding, methods such as extrusion molding and inflation molding can be selected depending on the resin used, but it is preferable to use cylindrical extrusion molding from the viewpoint of productivity. The resin member is preferably an extrusion molded product.
As the extruder in the extrusion molding method, any single-screw extruder having one screw in a barrel or cylinder or a multi-screw extruder combining two or more screws can be used. The pellet-shaped resin composition supplied from the supply hole of the supply section receives thermal energy from the barrel or cylinder and mechanical energy from the screw while advancing toward the die by the rotation of the screw, and is substantially completely compressed. It is melted and fed in a fixed amount to the tip of the extruder. A cylindrical die is installed at the tip of the extruder, and the resin composition is molded into a cylindrical tube shape by extruding it downward from the cylindrical die and taking it out from below.
The temperature during extrusion molding (for example, die temperature) is not particularly limited, but is preferably 300 to 400°C, more preferably 340 to 380°C.

Note that the thickness of the base layer (that is, the thickness of the resin member) of the intermediate transfer belt composed of a single layer or the intermediate transfer belt composed of at least two layers is not particularly limited, but is preferably 10 to 500 μm. about 50 to 200 μm, more preferably about 50 to 200 μm.

2-3. Reduction in resistance of intermediate transfer belt When carbon black (hereinafter referred to as CB), which is a conductive filler, is added to a thermoplastic resin, kneaded, and the kneaded product is formed into a sheet shape to develop conductivity as a sheet, the resin contains A plurality of conductive paths formed by connecting a large number of CBs exist from the front surface to the back surface of the sheet. At this time, the electric resistance value of the conductive path is the sum of the electric resistance value of the conductive part made of CB and the electric resistance value of the contact part when the CBs are connected.

For example, in the case of an intermediate transfer belt that uses a conductive filler to exhibit conductivity, as described above, the electrical resistance may decrease when used for forming an electrophotographic image over a long period of time. This is considered to be because electric discharge occurs between the secondary transfer roller and the intermediate transfer belt during printing. In such a case, the load due to energization on the intermediate transfer belt is concentrated, and the electrical resistance value of the intermediate transfer belt decreases over time, resulting in deterioration of image quality such as occurrence of white spots.

More specifically, when a gap occurs between the inner peripheral surface of the intermediate transfer belt and the primary transfer roller in the primary transfer section, electric discharge occurs between the intermediate transfer belt and the primary transfer roller, causing local The electrical resistance of the intermediate transfer belt decreases. In this case, toner is not transferred to the areas where the electrical resistance has decreased, resulting in an image that looks like white spots (white spots).
Furthermore, in the secondary transfer section, when a gap is generated between the outer peripheral surface of the intermediate transfer belt and the paper, electric discharge occurs between the intermediate transfer belt and the paper. It is thought that the charged polarity of the toner on the intermediate transfer belt is reversed due to discharge, and the toner cannot be transferred to paper, resulting in white spots. These phenomena are particularly noticeable when the dispersibility of CB is low or in a low humidity environment.

This is because the electrical resistance value of the conductive path formed by connecting a large number of CBs has decreased. Looking more closely, it is not that the electrical resistance value of the CB part (conductive part) in the conductive path has decreased, but rather that the electrical resistance value of the contact part when CB and CB are connected has decreased. It can be assumed that a discharge occurs.
It is thought that an electric field was concentrated at the contact part between the CBs due to voltage application during printing, and heat generation due to the electric field concentration during long-term printing carbonized the resin around the contact part, causing dielectric breakdown. Therefore, in order to prevent a decrease in the electrical resistance value of the conductive path, it is important to suppress heat generation due to electric field concentration and to prevent the resin around the contact portion from carbonizing.

The amount of heat generated Q at the contact portion when CB and CB in the conductive path are connected is shown by equation (1). In order to reduce the amount of heat generated, the voltage (V) must be lowered or the resistance value (R It is necessary to increase the
Q=V×V×t/R...(1)
Q: Amount of heat generated V: Voltage flowing during the pass R: Resistance value of the contact portion t: Time Since the voltage (V) is determined by printing conditions, the voltage cannot be lowered.

On the other hand, the resistance value R of the contact portion between CB particles is expressed by equation (2). In order to increase the resistance value R of the contact portion, it is necessary to reduce the structure volume a of the CB.
R=ρ/(2×a×n)...(2)
R: Resistance value of contact part ρ: Specific resistance value of carbon black a: Structure volume of carbon black n: Number of contact points

2-7. Structure Volume CB has a structure in which a plurality of spherical primary particles are randomly fused together. This structure is called a structure as the minimum structure of CB, and is one of the characteristics that expresses the connected state of CB particles.
A volume index value α correlated to the structure volume of the CB is expressed by equation (3).
α=( ^d2 )×(D×c1+c2)...(3)
d: Number average particle diameter of primary particles (nm)
D: DBP oil absorption (mL/100g)
c1, c2: constant

As the volume index value α becomes smaller, the structure volume of the CB also becomes smaller, so the resistance value R of the contact area between the CB particles increases, the heat generation amount Q of the contact area is suppressed, and the load due to energization of the intermediate transfer belt is reduced. It is thought that the decrease in electrical resistance value over time due to concentration can be suppressed.

The structure volume of carbon black is evaluated by the method described below and is 50 to 250 nm ² ·ml/100g. When the structure volume exceeds 250 nm ² ·ml/100 g, the resistance of the intermediate transfer belt is likely to decrease due to electric field concentration at the contact portion between the CBs. Furthermore, if the structure volume is less than 50 nm ² ml/100 g, the cohesive force between CBs becomes too large, making it difficult to maintain a good dispersion state of the conductive filler inside the intermediate transfer belt. .

The structure volume of carbon black is preferably 70 to 230 nm ² ·ml/100g, more preferably 100 to 220 nm ² ·ml/100g.
The structure volume of carbon black is an evaluation value calculated from the primary particle size of carbon black and the DBP oil absorption amount, and varies depending on the type of carbon black. Therefore, in order to obtain the desired structure volume, it is sufficient to select a carbon black that meets the conditions.

There is a degree of freedom regarding the constants c1 and c2 between the structure volume (structural volume) a and the volume index value α, as shown in equation (3). On the other hand, the structure volume a according to the present disclosure is calculated by equation (4).
a=(1/3)×π×(d ² /2)×(0.0046×D+0.1435) ...(4)
d: Number average particle diameter of primary particles of carbon black (nm)
D: DBP oil absorption amount of carbon black (mL/100g)

2-4. Number average particle size of primary particles of carbon black The number average particle size of primary particles of carbon black is preferably 10 to 30 nm. When the number average particle diameter of the primary particles is 10 nm or more, reagglomeration of the filler is less likely to occur. More preferably, it is 20 to 28 nm.
On the other hand, when the number average particle diameter of the primary particles is 30 nm or less, the dispersibility is less likely to decrease even when agglomerates are formed, and it is easier to suppress a decrease in resistance of the intermediate transfer belt due to discharge. Therefore, by using carbon black in which the number average particle diameter of primary particles is within the above range, better resistance maintenance properties can be obtained.

2-5. Method for evaluating the number average particle diameter of primary particles of carbon black contained in a resin member Observation of carbon black contained in a resin member is performed using a scanning electron microscope (SEM). Preparation of a thin sectioned sample before observation is performed by the following method. The resin member was cut using "ULTRACUT-S" manufactured by Leica, and a cut piece sample with a thickness of 40 nm for observation was collected. Specifically, a sample was taken from the region of the resin member in contact with the recording material and subjected to the above treatment.
Then, a SEM image was obtained using a scanning electron microscope (SEM) S-4700 manufactured by Hitachi, Ltd. under the measurement condition of an accelerating voltage of 3 kV. For analysis of the obtained SEM images, "ImageJ" (free software) was used as image analysis software. Then, the diameters of 50 primary particles of carbon black were measured, and the number average value was taken as the number average particle diameter of the primary particles.
The specific operation of "ImageJ" is to import the SEM image into ImageJ, remove noise, and then perform binarization processing (Otsu's binarization method, IEEE TRANSACTIONS ON
SYSTEMS, MAN, AND CYBERNETICS, VOL. SMC-9, NO. 1, JANUARY 1979, PP. 62-66) to extract the carbon black portion, and the particle size (maximum diameter) of each carbon black was calculated using a measurement function (Analyze Particles).

2-6. Method for evaluating DBP (dibutyl phthalate) oil absorption of carbon black contained in resin member The DBP (dibutyl phthalate) oil absorption of carbon black contained in the intermediate transfer belt to be measured can be confirmed as follows.
Carbon black contained in the intermediate transfer belt can be observed using a transmission electron microscope (TEM). Preparation of a thin sectioned sample before observation is performed by the following method. The resin member was cut using "ULTRACUT-S" manufactured by Leica, and a cut piece sample with a thickness of 40 nm for observation was collected. Specifically, a sample was taken from the area of the resin member that was in contact with the recording material.
As a transmission electron microscope (TEM), H-7100FA manufactured by Hitachi, Ltd. was used. Then, a TEM image was obtained under measurement conditions such as TE mode, acceleration voltage of 100 kV, and magnification such that one side of the image was 3 μm or less. Since the minimum structural unit of carbon black is a primary aggregate in which primary particles are connected, the distribution of the maximum Feret diameter in the carbon black primary aggregate was analyzed from the obtained TEM image. The maximum Feret diameter corresponds to the length of the longest side of a rectangle circumscribing the carbon black primary aggregate.

To analyze the maximum Feret diameter from the obtained TEM image, "ImageJ" (free software) is used to binarize and extract the carbon black, thereby determining the maximum Feret diameter of the primary carbon black aggregates scattered in the image. Diameter distribution can be analyzed. Specifically, after removing noise from the acquired TEM image, we performed binarization processing (Otsu's binarization method) to extract the primary carbon black aggregates, and then used the particle analysis function to extract Ferret's The diameter was calculated.
At this time, it is known that there is a correlation between the peak top position of the maximum Feret diameter and the DBP oil absorption amount, which is an index of the size of the primary aggregate of carbon black. By checking the number and peak top position of the maximum Feret diameter, it is possible to check the types of carbon blacks with different DBP oil absorption amounts and the DBP oil absorption amounts of each carbon black.
For example, the peak top position of the maximum Feret diameter distribution is 100 to 160 nm, and the DBP oil absorption is 93 to 127 ml/100 g.

According to one aspect of the present disclosure, it is possible to obtain a resin member for use in an electrophotographic image forming apparatus that has excellent moldability into an intermediate transfer belt or the like, and is capable of suppressing a decrease in electrical resistance and suppressing molding defects. . That is, it is preferable that the resin member is an intermediate transfer belt.
Further, according to another aspect of the present disclosure, it is possible to provide an image forming apparatus using the resin member.
The image forming device is
a first image carrier carrying an unfixed toner image;
an intermediate transfer belt to which the toner image formed on the first image carrier is primarily transferred;
a secondary transfer means for secondarily transferring the toner image primarily transferred onto the intermediate transfer belt onto a second image carrier;
The intermediate transfer belt is an image forming apparatus in which the above-mentioned resin member is used.

The present disclosure will be specifically described below using Examples. Note that the present disclosure is not limited to only the configurations embodied in the examples. Further, the number of parts in Examples and Comparative Examples is based on mass unless otherwise specified.

[Example 1]
The materials described below were melted and kneaded using a twin-screw kneading extruder (Ikegai Co., Ltd., PCM43) under the following conditions to produce a resin composition.
Resin material: PEEK resin (product name: 450G; manufactured by Victrex) Cooling crystallization temperature: 298.0°C
Second resin: PEK resin (product name: HTP45PF; manufactured by Victrex) Cooling crystallization temperature: 320.0°C
Conductive filler: Carbon black (product name: #44; manufactured by Mitsubishi Chemical Corporation)
The blending amounts were as follows, with the total belt material being 100 parts.
・PEEK resin: 62.4 parts (resin: 100 parts: 80 parts)
・PEK resin: 15.6 parts (resin: 100 parts: 20 parts)
・Carbon black: 22.0 parts (22.0% by mass in the resin member)
The conditions of the twin-screw kneading extruder were as follows.
Extrusion amount: 6kg/h
Screw rotation speed: 225rpm
Barrel control temperature: 360℃

Next, using a single screw extrusion molding machine (Plastics Engineering Research Institute Co., Ltd.) equipped with a spiral cylindrical die (inner diameter: 285 mm, slit width 1.1 mm) at the tip of the prepared resin composition, the following steps were performed: Melt extrusion was performed under the following conditions to produce a tubular tube-shaped electrophotographic belt (φ280 mm, thickness 60 μm) according to this example.
The conditions of the single screw extruder were as follows.
Extrusion amount: 6kg/h
Dice temperature: 360℃

[Comparative Examples 1 to 5]
An electrophotographic intermediate transfer belt was produced in the same manner as in Example 1, except that the type and amount of the second resin and the type and amount of carbon black were as shown in Table 1 below.
As the polyaryletherketone (PAEK), AV-651 (Solvay Specialty Polymers Japan Co., Ltd.) was used, and the cooling crystallization temperature was 285.0°C.

The following evaluations 1 and 2 were conducted on the electrophotographic intermediate transfer belts according to Example 1 and Comparative Examples 1 to 3. The results are shown in Table 2.

[Evaluation 1]
The thickness of each of the produced electrophotographic intermediate transfer belts according to Example 1 and Comparative Examples 1 to 3 was measured using a thickness measuring device Digimatic Indicator ID-C125B (manufactured by Mitutoyo Co., Ltd.).
As shown in FIG. 2, the thickness measurement points 200 are five in the direction a in FIG. There were 8 locations (8 locations at every 45 degrees when the belt 7 was placed in a circle) for a total of 40 locations (for convenience, 15 of the 40 locations are shown in Figure 2). be). The standard deviation σ of the thickness at 40 locations was calculated, and the value obtained by dividing σ by the average thickness was used as the thickness unevenness evaluation value. Since a thickness unevenness evaluation value of 0.1 or more results in poor molding, less than 0.08 was evaluated as moldability A, and 0.08 or more was evaluated as moldability B.

That is, when the thickness of the resin member is measured at 40 locations using a thickness measuring device, the value obtained by dividing the standard deviation σ of the thickness by the average thickness is preferably less than 0.08.

表中、ＣＢ粒径は、カーボンブラックの個数平均粒径である。 [Evaluation 2]
Each electrophotographic intermediate transfer belt according to Example 1 and Comparative Examples 1 to 3 was installed as an intermediate transfer belt in an electrophotographic image forming apparatus (product name: imageRUNNER-ADVANCE-C5540; manufactured by Canon Inc.) shown in FIG. did. Using this electrophotographic image forming apparatus, 600,000 solid white images were produced on A3 size plain paper (product name: CS068; manufactured by Canon Inc.) in a low humidity environment (temperature 23°C/relative humidity 5%). Outputted.
In the process, for every 10,000 solid white images, five full black halftone images were successively output. The resulting 60th set, that is, 5 full-page halftone images output after forming 600,000 white solid images, were visually observed and evaluated based on the following criteria.
Rank A: No white spots were observed in all five halftone images. (The intermediate transfer body is less likely to decrease its electrical resistance, that is, it has a high resistance maintenance property.)
Regarding rank B:, white spots were observed in one or more of the five halftone images.

In the table, the CB particle size is the number average particle size of carbon black.

In Example 1, no white spots were observed, and good resistance maintenance was obtained. In addition, the intermediate transfer belt had good moldability and was able to achieve both resistance maintenance and moldability.

In Comparative Examples 1 and 2, although the resistance maintenance property was good, the moldability was low and the molding was defective. This is considered to be because the cooling crystallization temperature of both formulations was lower than 299.0°C, which caused the thickness unevenness.

In Comparative Example 3, the moldability was good, but due to the large structure volume, it is considered that the electric field concentration at the contact portion between the carbons caused a decrease in the resistance of the intermediate transfer belt.
In Comparative Example 4, the content ratio of carbon black was low and the distance between CBs was large, so the electric field was concentrated during discharge and the resin was carbonized, which is thought to have caused a decrease in the resistance of the intermediate transfer belt. . Moreover, if the content of carbon black is small, the conductivity required for the belt member cannot be obtained.
In Comparative Example 5, the structure volume was small, the cohesive force of carbon black was large, and the dispersibility was reduced, which is considered to have caused the resistance of the intermediate transfer belt to decrease.

The present disclosure relates to the following configurations.
(Configuration 1)
A resin member used in an electrophotographic image forming apparatus,
The resin member contains a thermoplastic resin and carbon black,
The thermoplastic resin includes a first resin and a second resin different from the first resin,
The first resin is polyetheretherketone,
The structure volume value of the carbon black is 50 to 250 nm ² ml/100 g,
The content ratio of the carbon black in the resin member is 19.0 to 30.0% by mass,
The content rate of the second resin in the thermoplastic resin is 16.0% by mass or more,
A resin member characterized in that the cooling crystallization temperature of the resin member measured in differential scanning calorimetry is 299.0° C. or higher.
(Configuration 2)
The resin member according to configuration 1, wherein the cooling crystallization temperature of the second resin is higher than the cooling crystallization temperature of the polyetheretherketone.
(Configuration 3)
The resin member according to configuration 1 or 2, wherein the second resin is polyetherketone.
(Configuration 4)
The resin member according to any one of configurations 1 to 3, wherein the content of the polyetheretherketone in the thermoplastic resin is 35.0 to 84.0% by mass.
(Configuration 5)
The resin member according to any one of configurations 1 to 4, wherein the primary particles of the carbon black have a number average particle size of 10 to 30 nm.
(Configuration 6)
6. The resin member according to any one of configurations 1 to 5, wherein the resin member has an endless belt shape.
(Configuration 7)
The resin member according to any one of configurations 1 to 6, wherein the resin member is an electrophotographic belt. (Configuration 8)
a first image carrier carrying an unfixed toner image;
an intermediate transfer belt to which the toner image formed on the first image carrier is primarily transferred;
a secondary transfer means for secondarily transferring the toner image primarily transferred onto the intermediate transfer belt onto a second image carrier;
Equipped with
An image forming apparatus, wherein the intermediate transfer belt is the resin member according to any one of configurations 1 to 7.

1 Photosensitive drum, 2 Primary charging device, 3 Exposure device, 4 Developing device, 5 Primary transfer roller, 7 Intermediate transfer belt, 8 Secondary transfer outer roller, 9 Fixing device, 12 Cassette, 13 Pick-up roller, 15 Registration roller, 71 Intermediate transfer belt tension roller (drive roller), 72 Intermediate transfer belt tension roller (tension roller), 73 Intermediate transfer belt tension roller (secondary transfer inner roller), 10 Base layer, 11 Surface layer, 100 Image forming device, 200 Thickness measurement point

Claims (8)

A resin member used in an electrophotographic image forming apparatus,
The resin member contains a thermoplastic resin and carbon black,
The thermoplastic resin includes a first resin and a second resin different from the first resin,
The first resin is polyetheretherketone,
The structure volume value of the carbon black is 50 to 250 nm ² ml/100 g,
The content ratio of the carbon black in the resin member is 19.0 to 30.0% by mass,
The content rate of the second resin in the thermoplastic resin is 16.0% by mass or more,
A resin member characterized in that the cooling crystallization temperature of the resin member measured in differential scanning calorimetry is 299.0° C. or higher. The resin member according to claim 1, wherein the cooling crystallization temperature of the second resin is higher than the cooling crystallization temperature of the polyetheretherketone. The resin member according to claim 1, wherein the second resin is polyetherketone. The resin member according to claim 1, wherein the content of the polyetheretherketone in the thermoplastic resin is 35.0 to 84.0% by mass. The resin member according to claim 1, wherein the primary particles of the carbon black have a number average particle diameter of 10 to 30 nm. The resin member according to claim 1, wherein the resin member has an endless belt shape. The resin member according to claim 6, wherein the resin member is an electrophotographic belt. a first image carrier carrying an unfixed toner image;
an intermediate transfer belt to which the toner image formed on the first image carrier is primarily transferred;
a secondary transfer means for secondarily transferring the toner image primarily transferred onto the intermediate transfer belt onto a second image carrier;
Equipped with
An image forming apparatus, wherein the intermediate transfer belt is the resin member according to any one of claims 1 to 7.

Images