JP2020106765A - Electrophotographic roller, process cartridge and electrophotographic image formation device - Google Patents

Abstract

To provide an electrophotographic roller suppressing non-uniform wear-out of a photoreceptor while suppressing a spot-like image or a horizontal stripe image caused by abnormal discharge, even in an accelerated electrophotographic device.SOLUTION: An electrophotographic roller includes a conductive substrate and a conductive elastic layer as a surface layer. The conductive elastic layer has a projection part on a surface thereof. In the electrophotographic roller, a degree of orientation and a shape of a contact part of the projection part and a glass plate satisfy a prescribed relational expression. L1-1 and L1-2 respectively denote maximum lengths in a direction orthogonal to a direction along an axis, and in a direction along the axis, of the electrophotographic roller at the contact part when pressed to be 6.5 g/mm2, and L2-1 and L2-2 respectively denote maximum lengths in a direction orthogonal to a direction along an axis, and in a direction along the axis, of the electrophotographic roller at the contact part when pressed to be 14.3 g/mm2.SELECTED DRAWING: Figure 1

Description

The present invention relates to an electrophotographic roller that can be used as a charging member or the like for applying a voltage to charge a surface of an electrophotographic photosensitive member, which is a member to be charged, to a predetermined potential, a process cartridge and an electrophotographic roller using the same. The present invention relates to an image forming apparatus (hereinafter, also referred to as “electrophotographic apparatus”).

The electrophotographic apparatus adopting the electrophotographic method mainly includes an electrophotographic photosensitive member (hereinafter, also simply referred to as “photosensitive member”), a charging device, an exposure device, a developing device, a transfer device, and a fixing device. As the charging device, a contact charging device that charges the surface of the photoconductor by applying a DC voltage or a voltage obtained by superposing an AC voltage on the DC voltage to a charging member that is in contact with or close to the surface of the photoconductor is used. It is widely adopted.

In Patent Document 1, as a roller member (hereinafter, also referred to as a “charging roller”) that is brought into contact with a photosensitive member and charged, a bowl-shaped resin particle having an opening in a conductive resin layer is contained, and a bowl is provided on the surface. A roller member having an uneven shape derived from the openings and edge portions of the shaped resin particles is disclosed. According to the roller member of Patent Document 1, the contact pressure is relieved by elastic deformation of the edge portion of the bowl-shaped resin particles when they come into contact with the photoconductor, so that the photoconductor can be used even for a long period of time. It is described that uneven wear can be suppressed.

JP, 2011-237470, A

On the other hand, in recent years, as the process speed of an electrophotographic apparatus has been increased, the photoconductor is likely to vibrate when an electrophotographic image is formed. When an attempt is made to charge a vibrating photoconductor by using the roller member described in Patent Document 1, the roller member cannot follow the rotation of the photoconductor, and the roller member slips on the surface of the photoconductor ( Hereinafter, it was confirmed that "stick slip" may occur. The occurrence of stick-slip causes uneven charging on the photosensitive member, which causes horizontal stripe-shaped uneven density on the electrophotographic image. Note that, hereinafter, the horizontal stripe-shaped density unevenness generated in the electrophotographic image may be referred to as “banding”. In addition, an electrophotographic image having horizontal stripe-shaped density unevenness may be referred to as a “banding image”.

One aspect of the present invention is directed to providing an electrophotographic roller capable of sufficiently suppressing uneven wear of a photoreceptor and generation of a banding image even after long-term use. Another aspect of the present invention is directed to providing a process cartridge that contributes to the formation of a high-quality electrophotographic image. Furthermore, another aspect of the present invention is directed to providing an electrophotographic apparatus capable of forming a high-quality electrophotographic image.

According to one aspect of the invention,
An electrophotographic roller having a conductive substrate and a conductive elastic layer on the conductive substrate, wherein the elastic layer contains a binder, and a part of the surface of the electrophotographic roller has the elastic layer. It is composed by.
The surface of the electrophotographic roller has a plurality of convex portions,
A part of the surface of the electrophotographic roller is constituted by the elastic layer,
Young's modulus of each of the protrusions is 0.01 to 5000 MPa,
When the electrophotographic roller is pressed against a glass plate so that the load per unit area of the nip formed by the electrophotographic roller and the glass plate becomes 6.5 g/mm ^2. The average value S1ave of the areas of the first contact portions between the convex portion of the electrophotographic roller and the glass plate is 10 μm ² or more,
Regarding the orthographically projected image of the contact portion obtained by orthographically projecting each of the first contact portions onto the surface of the conductive substrate, the maximum length in the direction orthogonal to the direction along the axis of the electrophotographic roller is L1. -1, and the maximum length in the direction along the axis of the electrophotographic roller is L1-2, L1-1 and L1-2 satisfy the relationship of the following formula (1), and the electrophotographic roller is Of the electrophotographic roller when pressed against the glass plate so that the load per unit area of the nip formed by the electrophotographic roller and the glass plate was 14.3 g/mm ² . The average value S2ave of the areas of the second contact portions between the convex portion and the glass plate is 200 μm ² or less,
Regarding the orthographically projected image of the contact portion obtained by orthographically projecting each of the second contact portions onto the surface of the conductive substrate, the maximum length in the direction orthogonal to the direction along the axis of the electrophotographic roller is L2. -1, and the maximum length in the direction along the axis of the electrophotographic roller is L2-2, an electrophotographic roller is provided in which L2-1 and L2-2 satisfy the relationship of the following formula (2). It

According to another aspect of the present invention, a step of producing a conductive roller by forming a coating layer of a composition in which hollow resin particles are dispersed in a binder on the outer periphery of a conductive substrate,
By polishing the surface of the coating layer, part of the shell of the hollow resin particles is removed to form a bowl shape having an opening, and the edge portion of the opening of the bowl-shaped resin particle is formed on the surface of the coating layer. And a step of forming a concave portion defined by the inner wall of the resin particles, and a convex portion derived from the edge portion of the opening,
A step of heat-treating the conductive roller in an oxygen-containing atmosphere, a step of applying particles to the surface of the coating layer, and a surface finishing grinding of the coating layer rotating in a direction opposite to the polishing step by a tape polishing method. Process to perform,
There is provided a method for manufacturing the electrophotographic roller having:
According to another aspect of the present invention, there is provided the electrophotographic roller having a step of incorporating a conductive substrate in a cylindrical mold having a recessed shape elongated in a direction along a central axis and injecting a material by injection molding. A manufacturing method is provided.

According to another aspect of the present invention, there is provided a process cartridge detachably mountable to a main body of an electrophotographic image forming apparatus, the electrophotographic photosensitive member and a charging roller for charging the electrophotographic photosensitive member. , And the charging roller is the electrophotographic roller described above.
Furthermore, according to another aspect of the present invention, an electrophotographic apparatus comprising an electrophotographic photosensitive member and a charging roller for charging the electrophotographic photosensitive member, wherein the charging roller is the electrophotographic roller described above. An image forming apparatus is provided.

According to one aspect of the present invention, even in a high-speed electrophotographic image forming apparatus, an electronic device capable of providing a high-quality electrophotographic image in which uneven wear of a photoconductor is suppressed and a banding image is suppressed A photographic roller is provided. Further, according to another aspect of the present invention, there is provided a process cartridge and an electrophotographic image forming apparatus that contribute to stable formation of a high-quality electrophotographic image.

FIG. 3 is a schematic view of a contact portion pressed against a glass plate of the electrophotographic roller according to an aspect of the present invention. It is a schematic diagram showing the peripheral speed of the conventional electrophotographic roller, and the relationship of a contact part. FIG. 3 is a schematic diagram showing the relationship between the peripheral speed and the contact portion of the electrophotographic roller according to an aspect of the present invention. It is a schematic sectional drawing which shows an example of the roller for electrophotography which concerns on 1 aspect of this invention. It is an explanatory view showing an example of a cylindrical metallic mold for carrying out the present invention. It is explanatory drawing showing an example of the particle coating method for implementing this invention. It is an explanatory view showing an example of surface finish grinding for carrying out the present invention. It is a schematic sectional view showing an example of an electrophotographic image forming apparatus according to an aspect of the present invention. It is a schematic sectional drawing showing an example of the process cartridge which concerns on 1 aspect of this invention. It is a schematic diagram of a jig which makes a glass plate and the surface of a roller for electrophotography contact.

An electrophotographic roller according to an aspect of the present invention includes a conductive base and a conductive elastic layer as a surface layer on the conductive base. The elastic layer contains a binder. Further, the outer surface of the electrophotographic roller has a plurality of convex portions.

Under the following test conditions, the contact portion between the convex portion of the electrophotographic roller and the glass plate of the electrophotographic roller satisfies the following formulas (1) and (2).

Ｌ１−１及びＬ１−２は、それぞれ６．５ｇ／ｍｍ^２となるように押圧したときの接触部の電子写真用ローラの軸に沿う方向に直交する方向と軸に沿う方向の最大長さを示す。また、Ｌ２−１及びＬ２−２は、それぞれ１４．３ｇ／ｍｍ^２となるように押圧したときの接触部の電子写真用ローラの軸に沿う方向に直交する方向と軸に沿う方向の最大長を示す。なお、式（１）及び式（２）の左辺をそれぞれ下記式（１Ａ）及び（２Ａ）の通り、Ｄ１及びＤ２と定義する。
式（１Ａ）
Ｄ１＝ａｒｃｔａｎ（Ｌ１−１／Ｌ１−２）
式（２Ａ）
Ｄ２＝ａｒｃｔａｎ（Ｌ２−１／Ｌ２−２）

L1-1 and L1-2 are the maximum length in the direction orthogonal to the direction along the axis of the electrophotographic roller and the maximum length of the contact portion when pressed so as to be 6.5 g/mm ² , respectively. Show. Further, L2-1 and L2-2 are the maximum lengths of the contact portion in the direction orthogonal to the direction along the axis of the electrophotographic roller and the direction along the axis when pressed so as to be 14.3 g/mm ² , respectively. Indicates. The left sides of the equations (1) and (2) are defined as D1 and D2, respectively, as in the following equations (1A) and (2A).
Formula (1A)
D1=arctan (L1-1/L1-2)
Formula (2A)
D2=arctan (L2-1/L2-2)

(Test conditions)
The glass plate is arranged in the longitudinal direction of the electrophotographic roller, that is, over the entire width of the axis of the electrophotographic roller (direction of rotation center axis). This arrangement state is maintained, the glass plate is transmitted, and an observation image when the glass plate is not in contact is obtained. In this state, the load per unit area of the nip formed by the roller for electrophotography and the glass ^plate, 6.5 g / mm 2, and pressed so as to be 14.3 g / mm ^2, an electronic glass plate It is brought into contact with a photographic roller to obtain an observation image when the glass plate comes into contact. Further, the "nip" is a contact portion between the electrophotographic roller and the glass plate, and more specifically, in a direction (circumferential direction) orthogonal to the direction (longitudinal direction) along the axis of the electrophotographic roller. A region sandwiched by two straight lines parallel to the longitudinal direction of the electrophotographic roller passing through the respective contact points at two positions at both ends in the circumferential direction of the contact point between the electrophotographic roller and the glass plate. Further, in order to obtain the detailed shape of the contact portion with the highest convex portion in the observation image when not in contact with the glass plate as the center of the visual field, the magnification is switched to a high magnification and the detailed observation image when in contact with the glass plate is obtained.

Regarding the load per unit area of the nip, the above range was adopted from the contact load of the electrophotographic roller on the photoconductor in a general electrophotographic apparatus and the nip area when pressed by the contact load. ..
The glass plate is a model of a member such as a photoconductor to which the electrophotographic roller is brought into contact. By using the glass plate, a member such as the electrophotographic roller and the photoconductor is formed by an observation method described later. It is possible to visualize the contact state with the simulation.

The relationship between the surface structure of the elastic layer of the electrophotographic roller and the above formulas (1) and (2) when the electrophotographic roller is used as a member that rotates in contact with the photoconductor will be described below. ..

FIG. 1A is a diagram showing an example of a state in which a concavo-convex structure formed of bowl-shaped resin particles having openings held on the surface of an elastic layer is pressed against a contact plane of a glass plate. As shown in FIG. 1A, when such a concavo-convex structure is pressed against a glass plate, the edge portion derived from the opening of the bowl-shaped resin particles 11 dispersed in the binder comes into contact with one surface of the glass plate 13. ..

Next, the calculation of D1 and D2 from the contact portion between the edge portion and the glass plate will be described.
1A is a contact portion between the edge portion and the glass plate 13, and the contact portion A is taken in the direction of arrow B, that is, from the surface opposite to the contact surface with the edge portion of the glass plate. When observed at, a contact portion A as shown in FIG. 1(b) is confirmed. In the contact portion between the edge portion and the glass plate, the contact portion under a load of 6.5 g/mm ² is the first contact portion. Next, each of the first contact portions is orthographically projected onto the surface of the conductive substrate to obtain an orthographically projected image of the contact portion. The maximum length in the direction orthogonal to the direction (longitudinal direction) C along the axis of the electrophotographic roller in the obtained orthographically projected image of the contact portion is L1-1. Further, the maximum length of the electrophotographic roller in the longitudinal direction C is L1-2. The contact portion under a load of 14.3 g/mm ^{2 is referred} to as the second contact portion. Next, an orthographically projected image of the contact portion obtained by orthographically projecting each of the second contact portions onto the surface of the conductive substrate is obtained. With respect to the obtained orthographic image of the contact portion, the maximum length in the direction orthogonal to the longitudinal direction C of the electrophotographic roller is L2-1. Further, the maximum length of the electrophotographic roller in the longitudinal direction C is L2-2. L1-1, L1-2, L2-1, and L2-2 are measured from the detailed observation image at the time of contact with the glass plate obtained by the observation at high magnification at each load. The measured L1-1, L1-2, L2-1, and L2-2 are substituted into the above equations (1) and (2) to calculate D1 and D2.

As a result of diligent studies by the present inventors, the first contact portion and the second contact portion satisfy the above formulas (1) and (2), respectively, so that the stability of the driven rotation between the electrophotographic roller and the photoconductor is improved. It was found that the image quality was improved, rotation unevenness was suppressed, and banding images were suppressed. The mechanism is speculated as follows.

FIG. 2 is a schematic diagram showing the relationship between the circumferential speed of the electrophotographic roller 32 according to Patent Document 1 in the longitudinal direction and the contact portion at a specific position. The electrophotographic roller 32 is brought into contact with the photoconductor 31 by a predetermined pressing force (not shown) such as a spring and is driven to rotate. The inventors of the present invention caused a difference in peripheral speed (hereinafter, referred to as a disturbance in peripheral speed) at points Z1 and Z2 in FIG. 2 due to uneven shape and roughness of the electrophotographic roller and the photoconductor, and banding. It was confirmed that an image was generated.

On the other hand, FIG. 3 is a schematic diagram showing the relationship between the circumferential speed of the electrophotographic roller 33 according to the embodiment of the present invention in the longitudinal direction and the contact portion at a specific position. The electrophotographic roller 33 is driven to rotate as in FIG. At the positions D and D'in FIGS. 2 and 3, the contact with the photosensitive member was brought into contact with the glass plate to visualize it. The inventors have confirmed that the electrophotographic roller according to the embodiment of the present invention can reduce the disturbance of the peripheral speed. The longer the contact portion of the electrophotographic roller is in the longitudinal direction C and the shorter in the direction orthogonal to the longitudinal direction C, the more the disturbance of the peripheral speed can be reduced. The mechanism for reducing turbulence is inferred as follows.

By making the contact portion of the electrophotographic roller long in the longitudinal direction C and short in the direction orthogonal to the longitudinal direction C, that is, a shape having a small torsional rigidity with respect to the rotational direction, the electrophotographic roller has a shape shown in FIG. It has been found that the banding image is suppressed by causing the torsional deformation from the contact portions A to A′ as shown and reducing the disturbance of the peripheral speed. In order to reduce the disturbance of the peripheral speed, the maximum lengths L1-1, L2-1 and the maximum lengths L1-2, L2- in the longitudinal direction C of the contact portion of the electrophotographic roller in the direction orthogonal to the longitudinal direction C are obtained. It has been found that it is necessary that 2 satisfies the expressions (1) and (2).

Here, when the shape of the contact portion of the electrophotographic roller is a rectangular shape (La>Lb) having a maximum length La of the contact portion and a length Lb in the direction orthogonal to the maximum length, twisting of the convex portion The rigidity GJ is generally represented by the equation (3).
GJ=Gk ₂ La(Lb) ³ ... Formula (3)
Here, G is a shear elastic modulus, J is a torsion constant, and k ₂ is a coefficient which changes depending on La/Lb, and generally takes a value as shown in Table 1.

From equation (3), it is understood that the torsional rigidity can be reduced by reducing La and Lb, and particularly by reducing Lb. That is, in the minute size convex portion, a shape having a small length in a direction perpendicular to the maximum length and a large aspect ratio is likely to be twisted and deformed. Further, when the electrophotographic roller is driven to rotate by the photoconductor, the peripheral speed is likely to be disturbed in the longitudinal direction due to unevenness in shape and roughness in the electrophotographic roller and the photoconductor in the longitudinal direction. To solve this problem, by arranging the convex portion having a large aspect ratio with the maximum length along the rotation axis direction, it is possible to reduce the disturbance of the peripheral speed due to the torsional deformation of the convex portion. Based on the relationship between the shape of the convex portion that causes the torsional deformation and the orientation direction of the convex portion that reduces the peripheral speed disturbance due to the torsional deformation, the present inventors have made investigations, and when the expressions (1) and (2) are satisfied, , It was found that it is possible to suppress the peripheral speed disturbance.

The electrophotographic roller according to this aspect has at least one convex portion on the surface thereof. In order to further suppress the occurrence of a banding image, one position is provided in each of five regions obtained by dividing the longitudinal direction of the electrophotographic roller into five parts, and six positions in the circumferential direction at each position (phase 0°, 60°, (120°, 180°, 240°, and 300°), at each of 30 positions in total, when the surface layer in the region of 0.5 mm in the longitudinal direction and 0.5 mm in the circumferential direction is defined as the “measurement range”, the above formula (1) ), it is necessary that the “measurement range” in which the convex portions satisfying the formula (2) exist is 15 points (50%) or more, and more preferably 18 points (60%) or more.

Further, it is more preferable that the average values D1(ave) and D2(ave) of D1 and D2 calculated in the “measurement range” at the 30 points are 1/√3 or less, respectively. Further, each of D1 and D2 calculated in the measurement range of the above 30 points is more preferably 1/√3 or less, and further preferably 2/5 or less.

In addition, in the contact load of the electrophotographic roller on the photoconductor in a general electrophotographic apparatus, the "measurement range" at the 30 points is set so as to be driven to rotate by the contact portion derived from the electrophotographic member according to this aspect. The average value (Save) of the respective areas of the contact portions has a specific value. When the load is 6.5 g/mm ^2, the average value S1ave of each area of the first contact portions is 10 μm ² or more, and when the load is 14.3 g/mm ² , the average value S2ave of each area of the second contact portions is It is 200 μm ² or less.

The contact portion of the roller for electrophotography according to this aspect with the glass plate satisfies the formulas (1) and (2), and further, L1-1, L1-2, L2-1, and L2-2 are as follows. It is preferably in the range of.
L1-1 and L2-1 are, when the electrophotographic roller of the present invention is brought into contact with a glass plate (L1-1: load 6.5 g/mm ² ; L2-1: load 14.3 g/mm ^2). It represents the maximum length of the contact part (when loaded) in the direction perpendicular to the rotation axis. As L1-1 and L2-1 are smaller, torsional deformation is more likely to occur, and the peripheral speed turbulence reduction effect is greater. That is, L1-1 and L2-1 are preferably 1 μm or more and 10 μm or less, and particularly preferably 2 μm or more and 9 μm or less.
L1-2 and L2-2 are, when the electrophotographic roller according to the present aspect is brought into contact with the glass plate (L1-2: load 6.5 g/mm ^2, load L2-2: load 14.3 g/mm). The maximum length in the direction along the rotation axis of the contact portion under ^two loads is shown. The smaller L1-2 and L2-2 are, the more easily torsional deformation occurs. In addition, the larger L1-2 and L2-2 are, the larger the effect of reducing the peripheral speed disturbance is as compared with L1-1 and L2-1. That is, L1-2 and L2-2 are preferably 2 μm or more and 200 μm or less, and particularly preferably 10 μm or more and 150 μm or less.

<Glass plate>
As the glass plate used for the evaluation of the convex portion, for example, a glass plate having material: BK7, surface accuracy: double-sided optical polishing surface, parallelism: within 1 minute, thickness: 2 mm is used. As described above with reference to FIG. 1A, the surface formed as one flat surface of the glass plate is used as the contact surface for pressing the electrophotographic roller, and the opposite surface is used as the contact portion. Can be used as a surface for observation. As shown in FIG. 10B, the width (W2) of the glass plate is equal to or larger than the width (W1) in the axial (rotational axis) direction (that is, the longitudinal direction) of the electrophotographic roller (W1≦W2). To be done. Further, the width (W2) of the glass plate and the length (L) in the direction perpendicular to the width may be set so that the nip portion for obtaining the information necessary for the calculation of Save described above can be formed. For example, the length (L) is preferably a length in a direction perpendicular to the shaft of the electrophotographic roller, that is, an outer diameter (d) or more.

The electrophotographic roller can suppress "turbulence of peripheral speed" by having a convex portion on the surface thereof that satisfies the formulas (1) and (2). Then, in order to satisfy the above formulas (1) and (2), the method of forming a convex portion shown below is preferable. The following two methods can be exemplified as the method of forming the convex portion.
Method 1: A method in which a material is injected into a cylindrical mold having a long concave shape in the direction along the rotation axis of the electrophotographic roller and a convex portion corresponding to the concave shape of the mold is transferred.
Method 2: A method in which the surface of the coating layer is heat-treated in an oxygen-containing atmosphere (such as an air atmosphere), then powder coating is performed and surface finishing grinding is performed.

Hereinafter, manufacturing examples of the electrophotographic roller according to each of Method 1 and Method 2 will be described.
FIG. 4 is a schematic cross-sectional view showing an example of the electrophotographic roller according to this aspect. The electrophotographic roller shown in FIG. 4A has a conductive substrate 1 and a conductive elastic layer 2. The conductive elastic layer may have a two-layer structure of conductive elastic layers 21 and 22, as shown in FIG. The conductive elastic layer contains a binder. Further, in the method 2, the conductive elastic layer contains bowl-shaped resin particles, and the convex portion derived from the edge portion described later forms the convex portion satisfying the formulas (1) and (2).
The conductive substrate 1 and the conductive elastic layer 2 or layers sequentially stacked on the conductive substrate 1 (for example, the conductive elastic layers 21 and 22 shown in FIG. 4B) are bonded by an adhesive. In this case, it is preferable that the adhesive is conductive. A known adhesive can be used as the conductive adhesive. The base resin of the adhesive is a thermosetting resin or a thermoplastic resin. Known resins such as urethane-based, acrylic-based, polyester-based, polyether-based, and epoxy-based resins can be used as the conductive agent for imparting conductivity to the adhesive, which will be described in detail later. It is possible to use one kind alone or two or more kinds in combination by appropriately selecting from the conductive fine particles.

[Conductive substrate]
The conductive substrate has conductivity and has a function of supporting a conductive elastic layer provided thereon. Examples of the material include metals such as iron, copper, aluminum and nickel and alloys thereof (stainless steel etc.).

[binder]
A known rubber or resin can be used as the binder contained in the conductive elastic layer. Examples of the rubber include natural rubber, vulcanized natural rubber, and synthetic rubber. The following are mentioned as a synthetic rubber. Ethylene propylene rubber, styrene butadiene rubber (SBR), silicone rubber, urethane rubber, isopropylene rubber (IR), butyl rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butadiene rubber (BR), acrylic rubber, epichlorohydrin rubber And fluororubber.
As the resin, for example, a resin such as a thermosetting resin or a thermoplastic resin can be used. Among them, fluororesin, polyamide resin, acrylic resin, polyurethane resin, acrylic urethane resin, silicone resin and butyral resin are more preferable. These may be used alone or in combination of two or more. Further, a monomer which is a raw material of these binders may be copolymerized to obtain a copolymer. However, in Method 1, it is preferable to select a binder having high fluidity in order to accurately transfer a recessed shape which is long in the direction along the center axis of the cylindrical mold described later. Specifically, silicone rubber and NBR having a small molecular weight can be exemplified. However, the Young's modulus of the electrophotographic roller is about 0.01 to 5000 MPa, and it is necessary to select a material that can withstand torsional deformation.
In Method 1, styrene-butadiene rubber (SBR), butyl rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butadiene rubber having a double bond in the molecule and having high heat resistance are provided for the reason described later. It is more preferable to use (BR).
Further, in order to control the conductivity of the binder in the conductive elastic layer and the conductivity of the recesses derived from the bowl-shaped resin particles, it is preferable to add silicone oil to the conductive elastic layer. As the structure of the silicone oil, linear dimethyl polysiloxane is preferable. Further, the content of silicone oil is preferably 0.2 parts by mass or more and 2.0 parts by mass or less, particularly 0.4 parts by mass or more and 1.0 part by mass or less with respect to 100 parts by mass of the binder. This allows better control of the conductivity of the electrophotographic roller. Although the viscosity of the silicone oil will be described later, it is preferably 20 mm ² /s or more and 200 mm ² /s or less, and more preferably 30 mm ² /s or more and 100 mm ² /s or less.

[Conductive particles]
The volume resistivity of the conductive elastic layer is preferably 1×10 ² Ωcm or more and 1×10 ¹⁶ Ωcm or less in an environment of a temperature of 23° C. and a relative humidity of 50%. Within this range, it becomes easier to properly charge the photoconductor by discharging. Therefore, known conductive fine particles may be contained in the conductive elastic layer. Examples of the conductive fine particles include fine particles of metal oxide, metal, carbon black, and graphite. In addition, these conductive fine particles can be used alone or in combination of two or more. The content of the conductive fine particles in the conductive elastic layer is 2 to 200 parts by mass, and particularly 5 to 100 parts by mass with respect to 100 parts by mass of the binder.

[Method for forming conductive elastic layer according to method 1]
An example of a method for forming the conductive elastic layer according to Method 1 is shown in FIG. An enlarged view of the area E in FIG. 5A is shown in FIG. 5B, and an enlarged view of the area F in FIG. 5B is shown in FIG. 5C. Reference numeral 53 denotes an inner wall of the mold 51 used for forming the elastic layer, which has a concave shape 54 long in the direction along the central axis of the cylindrical mold. When the length in the direction along the central axis is K1 and the length in the direction orthogonal to the direction along the central axis is K2 in this recessed shape 54, K1 is preferably 2 μm or more and 200 μm or less, and K2 is 1 μm or more and 10 μm or less. Is preferred. Two cylindrical pieces that concentrically hold a shaft-shaped cored bar are assembled in the cylindrical mold having the recessed shape, and sandwiched and heated by a heating platen divided in parallel to the axial direction of the cylindrical mold to heat the shaft. The elastic layer has a convex shape satisfying the formulas (1) and (2) by integrally molding the above-mentioned elastic layer into a cylindrical shape around the above-mentioned core metal and transferring from the concave shape. Form on the surface.

[Method for forming conductive elastic layer according to method 2]
The method for forming the conductive elastic layer according to Method 2 will be exemplified below. First, a coating layer of a composition in which hollow resin particles are dispersed in a binder is formed on a conductive substrate. Then, by polishing the surface of the coating layer, a part of the shell of the hollow resin particles is removed to form a bowl shape having an opening, and the edge portion of the opening of the bowl-shaped resin particle and the inner wall of the resin particle are removed. And a convex portion derived from the edge portion of the opening of the bowl-shaped resin particles are formed (hereinafter, a shape including these irregularities is referred to as “a concavo-convex shape due to the opening of the bowl-shaped resin particles”). I call it). Then, the conductivity of the material present on the surface of the coating layer is adjusted by applying conductive fine particles to the recesses, heat treatment of the coating layer in an oxygen-containing atmosphere, or the like.

Hereinafter, each step of the method for forming the conductive elastic layer in the method 2 will be described in detail. The coating layer before the polishing step among the coating layers is referred to as "preliminary coating layer". In addition, the “shell of resin particles having a hollow shape” in the raw material for the electrophotographic roller is the same as the “shell of resin particles in a bowl shape” in the electrophotographic roller in which the bowl-shaped resin particles having openings are formed by the polishing treatment. It is called a bowl.

[Dispersion of resin particles in the preliminary coating layer]
First, a method of dispersing hollow resin particles in the preliminary coating layer will be described. As one method, hollow resin particles containing gas inside, a coating film of a conductive resin composition dispersed in a binder is formed on a conductive substrate, and the coating film is dried and cured. Alternatively, a method of performing crosslinking or the like can be exemplified. In addition, the conductive resin composition may contain conductive particles. As a material used for the hollow-shaped resin particles, a resin having a polar group is preferable, and a resin having a unit represented by the following chemical formula (I) is more preferable, from the viewpoint of low gas permeability and high impact resilience. .. It is more preferable to have both the unit represented by the chemical formula (I) and the unit represented by the chemical formula (II) from the viewpoint of easily controlling the polishing property.

In chemical formula (I), A is selected from a cyano group, a phenyl group, and an aminocarbonyl group, and may be the same or different in a plurality of units. R1 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

In the chemical formula (II), R2 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R3 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.

As another method, it is possible to exemplify a method of using heat-expandable microcapsules containing an encapsulating substance inside the particles and expanding the encapsulating substance by heating to form hollow resin particles. In this method, a thermally expandable microcapsule is dispersed in a binder to prepare a conductive resin composition, the conductive substrate is coated with the composition, and the composition is dried, cured, or crosslinked. In the case of this method, the encapsulating substance can be expanded by the heat at the time of drying, curing, or crosslinking of the binder used in the preliminary coating layer to form hollow resin particles. At that time, the particle size can be controlled by controlling the temperature condition.

When using heat-expandable microcapsules, it is necessary to use a thermoplastic resin as a binder. The following are mentioned as a thermoplastic resin. Acrylonitrile resin, vinyl chloride resin, vinylidene chloride resin, methacrylic acid resin, styrene resin, butadiene resin, urethane resin, amide resin, methacrylonitrile resin, acrylic acid resin, acrylic ester resin, methacrylic ester resin. Among them, it is particularly preferable to use a thermoplastic resin composed of at least one selected from acrylonitrile resin, vinylidene chloride resin, and methacrylonitrile resin, which exhibits high impact resilience, in order to form the bowl shape shown in FIG. preferable. These thermoplastic resins may be used alone or in combination of two or more. Further, a monomer which is a raw material of these thermoplastic resins may be copolymerized to obtain a copolymer.

The substance to be encapsulated in the heat-expandable microcapsules is preferably one that expands into a gas at a temperature equal to or lower than the softening point of the thermoplastic resin, and examples thereof include the following. Low boiling point liquids such as propane, propylene, butene, normal butane, isobutane, normal pentane and isopentane, high boiling point liquids such as normal hexane, isohexane, normal heptane, normal octane, isooctane, normal decane and isodecane.

The above heat-expandable microcapsules can be produced by a known production method such as a suspension polymerization method, an interfacial polymerization method, an interfacial precipitation method, or a submerged drying method. For example, in the suspension polymerization method, a polymerizable monomer, a substance to be encapsulated in the heat-expandable microcapsules, and a polymerization initiator are mixed, and the mixture is mixed in an aqueous medium containing a surfactant or a dispersion stabilizer. The method of carrying out suspension polymerization after dispersion in the above can be exemplified. A compound having a reactive group that reacts with the functional group of the polymerizable monomer and an organic filler can be added.

The following can be illustrated as a polymerizable monomer. Acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, fumaronitrile, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, vinylidene chloride, vinyl acetate; acrylic acid ester (methyl acrylate, ethyl Acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, isobornyl acrylate, cyclohexyl acrylate, benzyl acrylate), methacrylic acid ester (methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate) , Isobornyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate); styrene monomers, acrylamide, substituted acrylamide, methacrylamide, substituted methacrylamide, butadiene, ε-caprolactam, polyether, isocyanate. These polymerizable monomers may be used alone or in combination of two or more.

The polymerization initiator is not particularly limited, but an initiator soluble in the polymerizable monomer is preferable, and known peroxide initiators and azo initiators can be used. Of these, azo initiators are preferred. Examples of azo initiators are given below. 2,2'-azobisisobutyronitrile, 1,1'-azobiscyclohexane 1-carbonitrile, 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile. Of these, 2,2'-azobisisobutyronitrile is preferable. The amount of the polymerization initiator used is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the polymerizable monomer.

As the surface active agent, an anionic surface active agent, a cationic surface active agent, a nonionic surface active agent, an amphoteric surface active agent, or a polymer type dispersant can be used. The amount of the surfactant used is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the polymerizable monomer. Examples of the dispersion stabilizer include the following. Organic fine particles (polystyrene fine particles, polymethyl methacrylate fine particles, polyacrylic acid fine particles and polyepoxide fine particles), silica (colloidal silica), calcium carbonate, calcium phosphate, aluminum hydroxide, barium carbonate, magnesium hydroxide and the like. The amount of the dispersion stabilizer used is preferably 0.01 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer.

The suspension polymerization is preferably carried out in a pressure-tight container and in a closed state. Further, the polymerizable raw material may be suspended in a disperser or the like and then transferred into a pressure resistant container for suspension polymerization, or may be suspended in the pressure resistant container. The polymerization temperature is preferably 50°C to 120°C. The polymerization may be carried out at atmospheric pressure, but it may be carried out under pressure (under a pressure obtained by adding 0.1 to 1 MPa to the atmospheric pressure) in order to prevent the substance contained in the thermal expansion microcapsules from being vaporized. preferable. After completion of the polymerization, solid-liquid separation and washing may be performed by centrifugation or filtration. In the case of solid-liquid separation or washing, drying or pulverization may be performed thereafter at a softening temperature or lower of the resin constituting the thermally expanded microcapsules. Drying and pulverization can be performed by a known method, and a flash dryer, a draft dryer and a Nauta mixer can be used. Further, the drying and the pulverization can be simultaneously performed by a pulverization dryer. The surfactant and the dispersion stabilizer can be removed by repeating washing filtration after the production.

[Other components constituting the conductive elastic layer]
In addition to the above, the conductive elastic layer may contain insulating particles and additives such as a softening oil and a plasticizer for adjusting hardness. As the plasticizer, a polymer type is preferably used, and its weight average molecular weight is preferably 2000 or more, more preferably 4000 or more. Further, as a material that imparts various functions, an antiaging agent, a filler, a processing aid, a tackifier, an antitack agent, a dispersant, and resin particles other than roughening particles may be contained. Examples of the resin particles include the following. Polymethylmethacrylate particles, polyethylene particles, silicone rubber particles, polyurethane particles, polystyrene particles, amino resin particles, or phenol resin particles.

[Method of forming preliminary coating layer]
Next, a method of forming the preliminary coating layer will be described. As the method for forming the preliminary coating layer, a layer of the conductive resin composition is formed on the conductive substrate by a coating method such as electrostatic spray coating, dipping coating, or roll coating, and this layer is formed by drying, heating, crosslinking or the like. The method of hardening is mentioned. Further, a method of adhering or coating a sheet-shaped or tube-shaped layer obtained by forming a conductive resin composition to have a predetermined film thickness and curing the conductive resin composition on a conductive substrate. Further, there is a method of forming a preliminary coating layer by putting a conductive resin composition in a mold in which a conductive substrate is placed and curing the composition. Further, particularly when the binder is rubber, it can be produced by integrally extruding the conductive substrate and the unvulcanized rubber composition using an extruder equipped with a crosshead. The crosshead is an extrusion die that is used to form a coating layer for electric wires and wires and that is installed and used at the tip of the cylinder of an extruder. After that, after drying, curing, crosslinking, etc., the surface of the preliminary coating layer is polished to remove a part of the shell of the hollow resin particles to form a bowl shape. A cylindrical polishing method or a tape polishing method can be used as the polishing method. Examples of the cylindrical polishing machine include a traverse type NC cylindrical polishing machine and a plunge cut type NC cylindrical polishing machine.

(A) When the thickness of the preliminary coating layer is 5 times or less of the average particle diameter of the hollow resin particles: When the thickness of the preliminary coating layer is 5 times or less of the average particle diameter of the hollow resin particles, In many cases, convex portions derived from hollow resin particles are formed on the surface. In this case, a part of the convex portion derived from the hollow-shaped resin particles is polished into a bowl shape until the hollow inner wall of the resin particles is exposed, and an uneven shape due to the opening of the bowl-shaped resin particles can be formed. .. In this case, it is more preferable to use a tape polishing method in which the pressure applied to the preliminary coating layer during polishing is relatively small. As an example, the preferred range of polishing conditions for the preliminary coating layer when using the tape polishing method is shown below.

The polishing tape is obtained by dispersing polishing abrasive grains in a resin and applying it to a sheet-shaped substrate. Examples of the abrasive grains include aluminum oxide, chromium oxide, iron oxide, diamond, cerium oxide, corundum, silicon nitride, silicon carbide, molybdenum carbide, tungsten carbide, titanium carbide and silicon oxide. The average grain size of the polishing abrasive grains is preferably 0.01 μm or more and 50 μm or less, and more preferably 1 μm or more and 30 μm or less. The average particle diameter of the polishing abrasive grains is the median diameter D50 measured by the centrifugal sedimentation method. The preferable range of the count of the polishing tape having the above-mentioned preferable range of abrasive grains is 500 or more and 20,000 or less, and more preferably 1,000 or more and 10,000 or less.

Specific examples of the polishing tape will be given below. "MAXIMA LAP, MAXIMA T type" (product name, Reflight Co., Ltd.), "Lapica" (product name, manufactured by KOVAX), "micro-finishing film", "wrapping film" (product name, Sumitomo 3M Co., Ltd. (new company name : 3M Japan)), "Mirror film", "Wrapping film" (trade name, manufactured by Sankyo Rikagaku Co., Ltd.), "Mipox" (trade name, Mipox (former company name: Nippon Micro Coating Co., Ltd.)).
The grinding direction is preferably one direction facing the surface finishing step described later so that the contact portion having the convex shape satisfies the expressions (1) and (2).

The feed rate of the polishing tape is preferably 10 mm/min or more and 500 mm/min or less, more preferably 50 mm/min or more and 300 mm/min or less. The pressing pressure of the polishing tape on the preliminary coating layer is preferably 0.01 MPa or more and 0.4 MPa or less, more preferably 0.1 MPa or more and 0.3 MPa or less. A backup roller may be brought into contact with the preliminary coating layer via an abrasive tape in order to control the pressing pressure. Moreover, in order to obtain a desired shape, the polishing treatment may be performed plural times. The number of rotations is preferably set to 10 rpm or more and 1000 rpm or less, more preferably 50 rpm or more and 800 rpm or less. By setting the above conditions, it is possible to more easily form the uneven shape due to the opening of the bowl-shaped resin particles on the surface of the preliminary coating layer. Even if the thickness of the preliminary coating layer is out of the above range, the uneven shape due to the opening of the bowl-shaped resin particles can be formed by the method (b) described below.

(B) When the thickness of the preliminary coating layer is more than 5 times the average particle diameter of the hollow resin particles When the thickness of the preliminary coating layer is more than 5 times the average particle diameter of the hollow resin particles, In some cases, no convex portion derived from hollow resin particles is formed on the surface. In such a case, it is possible to form the uneven shape due to the opening of the bowl-shaped resin particles by utilizing the difference in the polishing property between the hollow-shaped resin particles and the material of the preliminary coating layer. The hollow resin particles have a high impact resilience because they enclose gas inside. On the other hand, as the binder of the preliminary coating layer, rubber or resin having a relatively low impact resilience and a small elongation is selected. As a result, the preliminary coating layer can be easily polished, and the hollow resin particles can be hardly polished. When the preliminary coating layer in the above state is polished, the hollow-shaped resin particles are not polished in the same state as the preliminary coating layer, and may have a bowl shape in which a part of the shell of the hollow-shaped resin particles is removed. it can. This makes it possible to form a concavo-convex shape due to the openings of the bowl-shaped resin particles on the surface of the coating layer. Since this method is a method of forming an uneven shape by utilizing the difference in the abrasiveness between the hollow-shaped resin particles and the material of the preliminary coating layer, the material (binder) used for the preliminary coating layer is rubber. Is preferred. Among these, it is particularly preferable to use acrylonitrile butadiene rubber, styrene butadiene rubber, or butadiene rubber from the viewpoint of low impact resilience and small elongation.

As a polishing method, a cylindrical polishing method or a tape polishing method can be used. However, since it is necessary to remarkably make a difference in the polishing property of the material, it is preferable to perform the polishing condition faster. From this viewpoint, it is more preferable to use the cylindrical polishing method. Among the cylindrical polishing methods, it is more preferable to use the plunge cut method from the viewpoint that the longitudinal direction of the preliminary coating layer can be simultaneously polished and the polishing time can be shortened. It is preferable that the grinding direction is one direction facing the surface finishing step described later so that the contact portion having the convex shape satisfies the expressions (1) and (2). In addition, in order to form the protruding first convex region, the spark-out process (polishing process at an intrusion speed of 0 mm/min) that has been conventionally performed from the viewpoint of making the polishing surface uniform is performed as quickly as possible. Or preferably not performed. As an example, the rotation speed of the plunge-cut type cylindrical polishing grindstone is preferably 1000 to 4000 rpm, and particularly preferably 2000 to 4000 rpm. The penetration speed into the preliminary coating layer is preferably 5 to 30 mm/min, particularly preferably 10 to 30 mm/min. At the end of the invasion step, a polishing step may be performed on the polishing surface, and it is preferable that the intrusion rate is 0.1 or more and 0.2 mm/min or less and the time is within 2 seconds. The spark-out process (polishing process at an intrusion speed of 0 mm/min) is preferably 3 seconds or less. The number of revolutions is preferably set to 50 rpm or more and 500 rpm or less, and more preferably set to 200 rpm or more. By setting the above conditions, it is possible to more easily form the unevenness due to the opening of the bowl-shaped resin particles on the surface of the preliminary coating layer. In the following description, the polishing-treated preliminary coating layer is simply referred to as "coating layer".

[Surface hardening method]
Next, the heat treatment method will be described in detail below. In the heat treatment in the oxygen-containing atmosphere, the degree of crosslinking of the resin in the bowl-shaped resin particles increases due to the progress of oxidative crosslinking. The more the oxidative crosslinking proceeds, the more the resin is cured. In order to satisfy the above formulas (1) and (2), it is preferable to cure the resin appropriately, and the degree of oxidative crosslinking can be adjusted by the heat treatment temperature and the oxygen concentration of the crosslinked portion. Regarding the heating temperature, the higher the temperature, the higher the degree of crosslinking. Regarding the oxygen concentration, the higher the oxygen concentration in the crosslinked portion, the more the oxidative crosslinking can proceed. Therefore, the hardness of the resin can be controlled by controlling the heating temperature and the oxygen concentration in the resin. At this time, as a method of controlling the oxygen concentration in the resin, it is useful to adjust the oxygen gas permeability of the bowl of resin particles having a bowl shape (shell of resin particles having a hollow shape).

Therefore, acrylonitrile resin, vinylidene chloride resin, methacrylonitrile resin, methyl methacrylate resin, and copolymers of these resins, which have low oxygen gas permeability, are used as the material for forming the bowl of bowl-shaped resin particles. It is preferable to use an acrylonitrile resin or a vinylidene chloride resin. Thereby, the hardness of the resin described above can be more easily achieved.

On the other hand, the oxidative crosslinking degree can be controlled by changing the temperature of the heat treatment, and this method is a useful method for controlling the hardness of the resin. However, the progress of oxidative crosslinking due to the heating is promoted as the temperature increases, but at the same time, the embrittlement of the resin proceeds. When the embrittlement of the resin occurs, the edge portion may be excessively removed during the surface finish grinding, and the above formulas (1) and (2) may not be satisfied. Therefore, the heating temperature is preferably controlled to 180 to 210°C, and more preferably 190 to 200°C. The heat treatment time is preferably 10 to 200 minutes.

As the heat treatment method, known means such as a hot-air continuous furnace, an oven, a near infrared heating method, a far infrared heating method can be used, but the coating is performed in an oxygen-containing atmosphere (in the presence of oxygen). The method is not particularly limited to these methods as long as the surface of the layer can be heat-treated.

As the resin as the binder, it is preferable to use a resin that promotes the effect of oxidative crosslinking when heated in an oxygen-containing atmosphere. Specifically, it has styrene-butadiene rubber (SBR) having a double bond in the molecule and high heat resistance, butyl rubber, acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butadiene rubber (BR). It is preferable to use a crosslinked product of at least one rubber selected from the group (crosslinked rubber). The conductive elastic layer preferably contains a crosslinked rubber as a binder and is formed by thermally crosslinking a layer of a conductive thermally crosslinkable rubber composition containing conductive fine particles in the presence of oxygen. However, the Young's modulus of the electrophotographic roller is about 0.01 to 5000 MPa, and it is necessary to select a material that can withstand torsional deformation.

[Particle coating]
Next, the particle coating method will be described in detail below. As an example of the particle coating method, FIG. 6 shows a schematic view of a coating apparatus for coating particles to form a surface layer. The particle coating device includes particles 60, a particle storage unit 61, a particle coating roller 62, and a particle coated member 63. By installing an electrophotographic roller as the particle coated member 63, a surface layer can be formed.

The particle coating roller 62 is an elastic sponge roller in which a foam layer is formed on the outer periphery of a conductive cored bar, and is arranged so as to form a predetermined contact area (nip portion) at a portion facing the particle coated member 63. , Rotate in the direction of the arrow shown (clockwise). At this time, the particle coating roller 62 is in contact with the particle coated member 63 with a predetermined amount of intrusion, that is, the particle coated roller 62 is concave by the particle coated member 63. When the particles are applied, the particles are rotated so as to move in opposite directions in the contact area. By this operation, the particle application roller 62 applies the particles to the particle application member 63, and the particles are applied to the particle application member 63. The particles are being stripped.

The material for the particles 60 forming the surface layer is not particularly limited, but the material may be polyethylene resin, acrylic resin, urethane resin, silicone resin, amino resin, polyester resin, polyamide resin, polycarbonate resin, epoxy resin, melamine resin. Etc. However, in the surface finishing step, since the contact portion of the convex portion of the electrophotographic roller satisfies the above formulas (1) and (2), it is necessary to provide a space in which the convex portion can be selectively processed. Therefore, the average particle size of the particles is preferably 1 μm or more and 10 μm or less, and more preferably 2 μm or more and 8 μm or less.
As a method for coating particles, known means such as electrostatic spray coating, dipping coating, and roll coating for coating a dispersion liquid in which particles are dispersed can be used, and the above formula (1) and formula ( The method is not particularly limited to these methods as long as the surface shape that satisfies 2) can be formed.

[Surface finishing grinding]
Next, the surface finish grinding method will be described in detail below. The preferred range of polishing conditions for the coating layer when the tape polishing method shown in FIG. 7 is used as an example of surface finish grinding is shown below.
The polishing tape 72 is obtained by dispersing polishing abrasive grains in a resin and applying the dispersed abrasive grains to a sheet-shaped base material. Examples of the abrasive grains include aluminum oxide, chromium oxide, iron oxide, diamond, cerium oxide, corundum, silicon nitride, silicon carbide, molybdenum carbide, tungsten carbide, titanium carbide and silicon oxide. The average grain size of the polishing abrasive grains is preferably 0.01 μm or more and 50 μm or less, and more preferably 1 μm or more and 30 μm or less. The average particle diameter of the polishing abrasive grains is the median diameter D50 measured by the centrifugal sedimentation method. The preferable range of the count of the polishing tape having the above-mentioned preferable range of abrasive grains is 500 or more and 20,000 or less, and more preferably 1,000 or more and 10,000 or less.

Specific examples of the polishing tape will be given below. "MAXIMA LAP, MAXIMA T type" (product name, Reflight Co., Ltd.), "Lapica" (product name, manufactured by KOVAX), "micro-finishing film", "wrapping film" (product name, Sumitomo 3M Co., Ltd. (new company name : 3M Japan Co., Ltd.), mirror film, wrapping film (trade name, manufactured by Sankyo Rikagaku Co., Ltd.), Mipox (trade name, manufactured by Mipox (former company name: Nippon Micro Coating Co., Ltd.)).

The pressing pressure of the polishing tape 72 against the roller member 71 having the coating layer formed thereon is preferably 0.01 MPa or more and 0.4 MPa or less, and more preferably 0.1 MPa or more and 0.3 MPa or less. A backup roller 73 may be brought into contact with the coating layer via the polishing tape 72 to control the pressing pressure, and a tape guide 74 may be used to prevent the polishing tape 72 from loosening.

A high convex shape is likely to be formed upstream of the concave portion with respect to the grinding direction in the step of forming the preliminary coating layer. Therefore, when the surface finish grinding is performed in the same direction as the grinding direction in the step of forming the preliminary coating layer, the convex shape may escape to the concave portion, and the grinding may not be sufficiently performed. From the above, the grinding direction may be one direction opposite to the grinding direction in the above-mentioned method for forming the preliminary coating layer in order that the contact portion having the convex shape satisfies the expressions (1) and (2). preferable. Moreover, in order to obtain a desired shape, the polishing treatment may be performed plural times. The rotation speed of the roller member 71 is preferably set to 500 rpm or more and 6000 rpm or less, more preferably 1000 rpm or more and 4000 rpm or less.

Under the above conditions, the edge portion hardened by the heat treatment can be cut to form a convex shape that serves as a contact portion that satisfies the formulas (1) and (2). The skewness Rsk of the roughness curve based on JIS B 0601:2001 can be used as a measure of the cutting degree of the edge portion. If Rsk is negative, it can be determined that the cutting of the edge portion has been sufficiently performed.

As for the method of surface finish grinding, known means such as a buffing method and a cylindrical grinding method can be used, but any method capable of forming a surface shape satisfying the above formulas (1) and (2) can be used. However, the method is not particularly limited to these methods.

Although the method of forming the conductive elastic layer has been described above, examples of the method of manufacturing the electrophotographic roller according to one aspect of the present invention are the following [1] to [3].

[1] Material is injected into a cylindrical mold having an inner wall having a recessed shape that is long in the direction along the center axis of the electrophotographic roller, and a convex portion corresponding to the recessed shape of the mold is transferred to the surface of the electrophotographic roller. A method for manufacturing an electrophotographic roller having a step of:

[2] A step 1 of producing a conductive roller by forming a coating layer of a composition in which hollow resin particles are dispersed in a binder on a conductive substrate.
By polishing the surface of the coating layer in one direction in the circumferential direction of the conductive roller, a part of the shell of the hollow resin particles is removed to form a bowl shape having an opening, and the bowl is formed on the surface of the coating layer. A step 2 of forming a concave portion defined by the edge portion of the opening of the shaped resin particle and the inner wall of the resin particle, and a convex portion derived from the edge portion of the opening,
Step 3 in which the conductive roller is heat-treated in an oxygen-containing atmosphere,
Step 4 of applying particles to the surface layer of the conductive roller, and
Step 5 of performing surface finish grinding of the coating layer in one direction opposite to Step 2 by a tape polishing method,
And a method for manufacturing a roller for electrophotography, which comprises:

[3] A step 1 of producing a conductive roller by forming a coating layer of a composition in which hollow resin particles are dispersed in a binder on a conductive substrate.
By polishing the surface of the coating layer in one direction in the circumferential direction of the conductive roller, a part of the shell of the hollow resin particles is removed to form a bowl shape having an opening, and the bowl is formed on the surface of the coating layer. A step 2 of forming a concave portion defined by the edge portion of the opening of the shaped resin particle and the inner wall of the resin particle, and a convex portion derived from the edge portion of the opening,
Step 3 of heat-treating the conductive roller under an oxygen-containing atmosphere, and
In a state where the distance between the conductive roller and the polishing tape is controlled so as to cut only the convex portion derived from the edge portion, the surface finishing grinding of the coating layer is performed by the tape polishing method in one direction opposite to the step 2. Step 4,
And a method for manufacturing a roller for electrophotography, which comprises:

<Electrophotographic image forming apparatus>
An electrophotographic image forming apparatus according to an aspect of the present invention includes an electrophotographic photosensitive member and a charging roller that charges the electrophotographic photosensitive member.
FIG. 8 shows a schematic configuration of an example of an electrophotographic image forming apparatus according to an aspect of the present invention. This electrophotographic apparatus includes an electrophotographic photosensitive member, a charging device that charges the electrophotographic photosensitive member, a latent image forming device that performs exposure, a developing device that develops a toner image, a transfer device that transfers to a transfer material, and an electrophotographic photosensitive member. And a fixing device for fixing the toner image. The electrophotographic roller according to an aspect of the present invention can be used as a charging roller included in the charging device of the electrophotographic image forming apparatus.

The electrophotographic photoreceptor 82 is a rotary drum type having a photosensitive layer on a conductive substrate. The electrophotographic photosensitive member is rotationally driven in the direction of the arrow at a predetermined peripheral speed (process speed).
The charging device has a contact-type charging roller 81 which is placed in contact with the electrophotographic photosensitive member 82 by being brought into contact with the electrophotographic photosensitive member 82 with a predetermined pressing force. The charging roller 81 is driven to rotate in accordance with the rotation of the electrophotographic photosensitive member 82, and charges the electrophotographic photosensitive member 82 to a predetermined potential by applying a predetermined DC voltage from the charging power source 89. As a latent image forming device (not shown) for forming an electrostatic latent image on the electrophotographic photosensitive member 82, an exposure device such as a laser beam scanner is used. An electrostatic latent image is formed by irradiating the uniformly charged electrophotographic photosensitive member 82 with exposure light 87 corresponding to image information.

The developing device has a developing sleeve or a developing roller 83 which is arranged close to or in contact with the electrophotographic photosensitive member 82. The developing device develops the electrostatic latent image by reversal development of the toner that has been electrostatically processed to have the same polarity as the charging polarity of the electrophotographic photosensitive member to form a toner image. The transfer device has a contact type transfer roller 84. The toner image is transferred from the electrophotographic photosensitive member to a transfer material P such as plain paper. The transfer material P is transported by a paper feeding system having a transport member (not shown).
The cleaning device has a blade type cleaning member 86 and a recovery container 88, and mechanically scrapes off the transfer residual toner remaining on the electrophotographic photosensitive member 82 after the developed toner image is transferred to the transfer material. to recover. Here, it is possible to omit the cleaning device by adopting the simultaneous development cleaning system in which the developing device collects the transfer residual toner. The toner image transferred onto the transfer material is fixed on the transfer material by passing between a fixing belt 85 heated by a heating device (not shown) and a roller arranged to face the fixing belt. ..

<Process cartridge>
A process cartridge according to an aspect of the present invention includes an electrophotographic photosensitive member and a charging roller that charges the electrophotographic photosensitive member, and is configured to be attachable to and detachable from a main body of an electrophotographic image forming apparatus.
FIG. 9 shows a schematic structure of the process cartridge. This process cartridge is configured such that an electrophotographic photosensitive member 92, a charging roller 91, a developing roller 93, a cleaning member 96, etc. are integrated and can be attached to and detached from the main body of the electrophotographic image forming apparatus. The electrophotographic roller according to an aspect of the present invention can be used as the charging roller 91 included in this process cartridge.

Hereinafter, the present invention will be described in more detail with reference to specific production examples and examples. Prior to Examples, Production Examples A1 to A10 (Production of Resin Particles No. 1 to No. 10), Method for Measuring Volume Average Particle Diameter of Resin Particles, Production Examples B1 to B16 (Conductive Rubber Composition No. 1 to Production of No. 16) will be described. In the following examples and comparative examples, all parts and% are based on mass unless otherwise specified.

<Production Example A1: Resin particle No. Manufacturing 1>
An aqueous mixed solution containing 4000 parts by mass of ion-exchanged water, 9 parts by mass of colloidal silica as a dispersion stabilizer, and 0.15 parts by mass of polyvinylpyrrolidone was prepared. Then, 50 parts by mass of acrylonitrile, 45 parts by mass of methacrylonitrile, and 5 parts by mass of methyl acrylate as a polymerizable monomer, 12.5 parts by mass of normal hexane as an inclusion substance, and 0 of dicumyl peroxide as a polymerization initiator. An oily mixture consisting of 0.75 parts by mass was prepared. This oily mixed solution was added to the aqueous mixed solution, and 0.4 part by mass of sodium hydroxide was further added to prepare a dispersion liquid.
The obtained dispersion was stirred and mixed using a homogenizer for 3 minutes, charged into a nitrogen-substituted polymerization reaction container, and reacted at 60° C. for 20 hours under stirring at 400 rpm to prepare a reaction product. The obtained reaction product was repeatedly filtered and washed with water, and then dried at 80° C. for 5 hours to prepare resin particles. By crushing and classifying the resin particles with a sonic classifier, the resin particle No. Got 1.

<Production Example A2: Resin Particle No. Manufacturing 2>
In Production Example A1, resin particle No. 1 was obtained by the same method except that the classification conditions were changed. Got 2.

<Production Examples A3 and A5 to A8: Resin Particle No. 3 and No. 5 to No. Manufacturing 8>
Resin particles were prepared in the same manner as in Production Example A1 except that the amount of colloidal silica used, the type and amount of polymerizable monomer used, and the number of stirring revolutions during polymerization were changed as shown in Table 2. By making and classifying, resin particle No. 3 and No. 5 to No. Got 8.

<Production Example A4: Resin Particle No. Manufacturing 4>
In Production Example A3, resin particle No. 1 was obtained by the same method except that the classification conditions were changed. Got 4.

<Production Example A9: Resin particle No. Manufacturing 9>
In Production Example A7, resin particle No. 1 was obtained by the same method except that the classification conditions were changed. Got 9.

<Production Example A10: Resin particle No. Manufacturing 10>
In Production Example A8, resin particle No. 1 was obtained by the same method except that the classification conditions were changed. Got 10.

<Measurement of volume average particle size of resin particles>
Resin particle No. 1-No. The volume average particle size of 10 was measured by a laser diffraction type particle size distribution meter (trade name: Coulter LS-230 type particle size distribution meter, manufactured by Coulter). A water-based module was used for the measurement, and pure water was used as a measurement solvent. The measurement system of the particle size distribution meter was washed with pure water for about 5 minutes, and 10 to 25 mg of sodium sulfite was added to the measurement system as an antifoaming agent to execute the background function. Next, 3 to 4 drops of the surfactant were added to 50 ml of pure water, and 1 mg to 25 mg of the measurement sample (resin particles) was added. The aqueous solution in which the sample was suspended was subjected to a dispersion treatment with an ultrasonic disperser for 1 minute to 3 minutes to prepare a test sample solution. The test sample solution is gradually added to the measurement system of the measurement device, and the test sample concentration in the measurement system is adjusted so that the polarized light scattering intensity difference (PIDS) on the screen of the device is 45% or more and 55% or less. Was measured. The volume average particle diameter Dv was calculated from the obtained volume distribution. Resin particle No. 1-No. Table 2 shows the formulation of the material of No. 10, the stirring conditions at the time of polymerization, and the volume average particle diameter of the obtained resin particles.

<Production Example B1: Conductive rubber composition No. Manufacturing 1>
To 100 parts by mass of acrylonitrile butadiene rubber (NBR) (trade name: N230SV, manufactured by JSR), other materials shown in the column of component (1) in Table 3 were added, and the mixture was adjusted to 50° C. in a closed mixer. Kneaded for 15 minutes. To this, the materials shown in the column of component (2) in Table 3 were added. Then, the mixture was kneaded for 10 minutes with a two-roll machine cooled to a temperature of 25° C., and the conductive rubber composition No. Got 1.

<Production Example B2: Conductive rubber composition No. Manufacturing method of 2>
To 100 parts by mass of acrylonitrile butadiene rubber (NBR) (trade name: N230SV, manufactured by JSR), other materials shown in the column of component (1) in Table 4 were added, and the mixture was adjusted to 50° C. in a closed mixer. Kneaded for 15 minutes. To this, the materials shown in the column of component (2) in Table 4 were added. Then, the mixture was kneaded for 10 minutes with a two-roll machine cooled to a temperature of 25° C., and the conductive rubber composition No. Got 2.

<Production Examples B3 to B8: Conductive rubber composition No. 3 to No. Manufacturing method of 8>
Conductive rubber composition No. 3 was prepared in the same manner as in Production Example B2 except that the resin particles (resin particles No. 3 to No. 8) were changed to the conditions shown in Table 6. 3 to No. Got 8.

<Production Example B9: Conductive rubber composition No. Manufacturing method of 9>
To 100 parts by mass of acrylonitrile butadiene rubber (NBR) (trade name: N230SV, manufactured by JSR), other materials shown in the column of component (1) in Table 5 were added, and the mixture was adjusted to 50° C. in a closed mixer. Kneaded for 15 minutes. To this, the materials shown in the column of component (2) in Table 5 were added. Then, the mixture was kneaded for 10 minutes with a two-roll machine cooled to a temperature of 25° C., and the conductive rubber composition No. Got 9.

<Production Examples B10 to B12: Conductive rubber composition No. 10-No. Production of 12>
Conductive rubber composition No. 6 was prepared in the same manner as in Production Example B9 except that the resin particles and carbon black described in Component (2) were changed to the conditions shown in Table 6. 10-No. I got 12.

<Production Examples B13 to B16: Conductive rubber composition No. 13-No. Manufacturing 16>
Same as Production Example B1 except that in Production Example B1, acrylonitrile butadiene rubber was changed to butadiene rubber (BR) (trade name: JSR BR01, manufactured by JSR Corporation), and resin particles and carbon black were set to the conditions shown in Table 6. Conductive rubber composition No. 13-No. 16 was obtained.
The conductive rubber composition No. 1-No. The 16 formulations are shown in Table 6.

<Example 1>
1. Conductive Substrate A thermosetting resin containing 10% by mass of carbon black was applied to a stainless steel substrate having a diameter of 6 mm and a length of 252.5 mm and dried to be used as a conductive substrate.
2. Formation of Conductive Elastic Layer Using an extrusion molding apparatus equipped with a crosshead, the conductive rubber composition No. 1 manufactured in Production Example B1 was formed into a cylindrical shape on the peripheral surface with the conductive substrate as the central axis. 1 was coated. The thickness of the conductive rubber composition was adjusted to 1.75 mm.
The roller after extrusion was vulcanized in a hot air oven at 160° C. for 1 hour, and then the end of the rubber layer was removed to a length of 224.2 mm to prepare a roller having a preliminary coating layer. The outer peripheral surface of the obtained roller was polished by using a plunge cut type cylindrical polishing machine. A vitrified grindstone was used as the abrasive grains, the abrasive grains were green silicon carbide (GC), and the grain size was 100 mesh. The rotation number of the roller was 350 rpm, and the rotation number of the polishing grindstone was 2050 rpm. The cutting speed was set to 20 mm/min, the spark-out time (time when the cut was 0 mm) was set to 0 seconds, and polishing was performed to produce a conductive roller having a conductive elastic layer (coating layer). The thickness of the conductive elastic layer was adjusted to 1.5 mm. The crown amount of this roller (the average value of the difference between the outer diameter of the central portion and the outer diameter at positions 90 mm apart from the central portion toward both ends) was 120 μm.

After polishing, post-heating treatment was performed at 180° C. for 1 hour in the air atmosphere using a hot air oven to cure the edge. Particles having a particle size of 2 μm (hereinafter referred to as spacer particles) were applied to the roller surface by the particle applying method shown in FIG. By using the surface finishing grinding device shown in FIG. 7, a conductive roller rotating at 3000 rpm is subjected to surface finishing grinding with lapping film WA abrasive grains #2000 (trade name, manufactured by Sankyo Rikagaku Co., Ltd.) to clean the surface. Electrophotographic roller No. Got 1. This electrophotographic roller has, on its surface, a convex portion derived from the edge portion of the opening of the bowl-shaped resin particle, and a concave portion defined by the edge portion of the opening of the bowl-shaped resin particle and the inner wall of the resin particle. It had a conductive elastic layer.

Table 8 shows the results of measuring the physical properties of the electrophotographic roller and the results of images, which were conducted by the following methods.
3. Evaluation of roller for electrophotography 3-1. Area and shape measurement of the contact part when the electrophotographic roller is pressed against the glass plate Glass plate (width (W2): 300 mm x length (L): 50 mm, thickness: 2 mm, material: BK7, surface accuracy: double-sided optics) Polishing, parallelism: within 1 minute) for electrophotographic roller No. It was used as a glass plate to be contacted with 1. Using the jig 102 shown in FIG. 10, the first surface as the contact surface of the glass plate 101 is covered with the width (W2) of the glass plate 101 over the entire width (W1) in the longitudinal direction of the electrophotographic roller 103, Of the electrophotographic roller 103 is arranged so that its first surface is parallel to the rotation axis of the electrophotographic roller 103. This arrangement state was maintained, the glass plate was permeated and observed through a video microscope (trade name: DIGITAL MICROSCOPE VHX-500, manufactured by Keyence Corporation) to obtain an observation image when the glass plate was not in contact. The observation magnification was 200 times. While maintaining the same field of view, a load H was applied by a spring from the conductive base portions at both ends of the electrophotographic roller 103 to press the electrophotographic roller 103 against the first surface of the glass plate 101. While maintaining this state, the contact surface between the electrophotographic roller 103 and the first surface of the glass plate 101 is opposite to the first surface of the glass plate 101 on the second surface side (direction of arrow G). The glass plate was transmitted from the side) and observed with a video microscope (trade name: DIGITAL MICROSCOPE VHX-500, manufactured by Keyence Corporation) at an observation magnification of 200 times to obtain an observed image when the glass plate was in contact. Further, the highest convex portion in the observation image when not in contact with the glass plate was used as the center of the visual field, and observation was performed at an observation magnification of 1000 times to obtain a detailed observation image when contacting the glass plate.

The load H was set so that the surface pressure M calculated from the following formula (4) was 6.5 g/mm ² .
(Equation 4)
M=2H/N
N is a roller No. for electrophotography due to load H. 1 is the area of the nip formed when 1 is pressed against the glass plate 101.

Hereinafter, the nip area N, the maximum length L1-1, L2- in the direction orthogonal to the axis of the electrophotographic roller at the contact portion between the highest convex portion and the glass plate in the observation image when not in contact with the glass plate 1, the maximum lengths L1-2 and L2-2 in the direction along the axis of the electrophotographic roller, the average value Save of each area, and D1 and D2 in the following formula (1A) formula (2A) were calculated.
(Formula 1A)
D1=arctan (L1-1/L1-2)
(Formula 2A)
D2=arctan (L2-1/L2-2)

The observed image was subjected to electrophotographic roller No. 1 using image analysis software (ImageProPlus (registered trademark): manufactured by Media Cybernetics). Only the contact portion formed between 1 and the glass plate was extracted and binarized. After that, in order to remove noise, the opening process was performed once on the binarized image, and then the closing process was performed once. The opening process is an image processing operation of contracting and expanding the same number of times, and it is possible to eliminate a very small extraction region that is considered to be noise. The closing process is an image processing work in which expansion and contraction are performed the same number of times, and it is possible to connect extraction regions that should have been originally connected as contact portions but have been divided during extraction. The opening process and the closing process make it possible to appropriately extract the contact portion.
First, a method of calculating the nip area N will be described. Electrophotographic roller No. in the observation area The electrophotographic roller No. 1 passing through each contact point at two positions at both ends in the circumferential direction of the contact point between the glass plate and the contact point of the glass plate. A region sandwiched by two straight lines parallel to the longitudinal direction of 1 was defined as a nip region, and the nip region was cut out using the software. The circumferential length of the cut-out nip area was set to the electrophotographic roller No. 1 at the central part in the longitudinal direction, at a position 45 mm apart from the central part in the direction of both ends, and at a position 90 mm apart from the central part in the direction of both ends, measuring at each of 5 positions in the longitudinal direction and the average value thereof. , Electrophotographic roller No. The nip area N was calculated by multiplying the longitudinal length of the nip where 1 and the glass plate are in contact with each other.

Next, a method of calculating Save will be described. With respect to the highest convex portion in the observation image when the glass plate was not in contact, the shape of the contact portion obtained in the detailed observation image when the glass plate was in contact was extracted by the software. Maximum lengths L1-1 and L2-1 in the direction orthogonal to the direction of the electrophotographic roller axis from the extracted shape of the contact portion, and maximum lengths L1-2 and L2 in the direction along the electrophotographic roller axis. -2 was measured. Further, the contact area S was calculated along with the extraction of the shape of the contact portion. The above operation is performed at five positions in the longitudinal direction of the electrophotographic roller at the central part in the longitudinal direction, at a position 30 mm apart from the central part in each end direction, and at a position 75 mm apart from the central part in each end direction. With respect to the electrophotographic roller, a total of 30 positions of 6 positions (phase 0°, 60°, 120°, 180°, 240°, and 300°) in the circumferential direction of the roller for electrophotography are performed. At each of those 30 locations, the maximum length in the direction orthogonal to the axis of the electrophotographic roller at the contact portion between the highest convex portion having a surface pressure of 6.5 g/mm ² and the glass plate is L1-1, Let L1-2 be the maximum length in the direction along the axis of the photographic roller, and go straight in the direction along the axis of the electrophotographic roller at the contact portion between the highest convex portion and the glass plate with a surface pressure of 14.3 g/mm ^2. The maximum length in the direction of rotation is L2-1, and the maximum length in the direction along the axis of the electrophotographic roller is L2-2. Further, the average of the area S1 of the first contact portion when the surface pressure of 6.5 g/mm ^{2 is} loaded at 30 locations is S1ave, and the average of the area S2 of the second contact portion when the surface pressure is 14.3 g/mm ^{2 is} loaded is S2ave. And
Next, D1 and D2 at each contact portion were calculated from the obtained L1-1, L1-2, L2-1, and L2-2 by the above formula (1) and formula (2). Electrophotographic roller No. Table 7 shows D1, D2, S1, S2 calculated for 1 and the average value of each value.

3-2. Image evaluation A monochrome laser printer (“LBP6700” (trade name)) manufactured by Canon Inc., which is an electrophotographic apparatus having a process cartridge having the configuration shown in FIG. 9, can be attached and detached, and the process speed of 250 mm/sec and 370 mm/sec is variable. I modified it so that I could do it. The attached charging roller was removed from the process cartridge for this printer, and instead of the electrophotographic roller No. 1 was set as a charging roller. The charging roller was brought into contact with the electrophotographic photosensitive member with a pressing force of a spring of 4.9 N at one end and a total of 9.8 N at both ends. Furthermore, a voltage was applied to the charging roller from the outside. As the applied voltage, a peak-peak voltage (Vpp) was 1800 V, a frequency (f) was 1350 Hz, and a DC voltage (Vdc) was -600 V as an AC voltage. The image resolution was 600 dpi.
The process cartridge was acclimated to a low temperature and low humidity environment having a temperature of 15° C. and a relative humidity of 10% for 24 hours and then subjected to image evaluation. Specifically, a halftone image (an image in which a horizontal line having a width of 1 dot and a spacing of 2 dots is drawn in the direction perpendicular to the rotation direction of the electrophotographic photosensitive member) is output, and the obtained image is visually observed to provide a spot-shaped The presence or absence of the image defect of No. 1 and the presence or absence of the horizontal stripe image defect due to the banding at the process speed of 250 mm/sec and 370 mm/sec were determined according to the following criteria.

[Evaluation of spot-shaped image]
Rank 1: No spot-like image defect is recognized.
Rank 2: A spot-like image defect is slightly observed.
Rank 3: It is recognized that spot-like image defects are generated in a part of the area in correspondence with the rotation pitch of the charging roller.
Rank 4: Spot-like image defects are observed in a wide range and are conspicuous.

[Evaluation of horizontal stripe image (banding)]
Rank 1: No horizontal stripe-shaped image defect is observed.
Rank 2: A slight horizontal stripe-shaped image defect is recognized.
Rank 3: It is recognized that a horizontal stripe-shaped image defect is generated in a part of the area in correspondence with the rotation pitch of the charging roller.
Rank 4: A horizontal streak-shaped image defect is recognized in a wide range and is conspicuous.

3-3. Young's modulus measurement method Based on ISO14577, it was measured using Picodenter HM500 (trade name, manufactured by Fisher Instrument Co., Ltd.). As the indenter, there was used an indenter (Vickers pyramid) having a square pyramidal diamond indenter with a square base and a facing angle of 136° with the apex interposed. The measurement was performed at the central portion and both end portions in the longitudinal direction of the electrophotographic roller (at positions of 90 mm from the central portion to both end portions). The measurement is a step of pushing the indenter at a predetermined speed until a predetermined load is applied (hereinafter, referred to as "pushing step"), and a step of unloading the load at a predetermined speed from a predetermined pushing position (hereinafter, " It is called "unloading process"). Young's modulus was calculated from the load displacement curve thus obtained. The measurement was performed under the following conditions, and the highest convex portion in the observed image was selected.
<Condition>
(Pushing process)
・Maximum load = 10mN
・Pushing time = 100 seconds (unloading process)
・Minimum load = 0.005mN
-Unloading time = 100 seconds Unloading was performed until the minimum load of the indenter was reached. Young's modulus was calculated from the slope of the tangent line of the load displacement curve obtained under the above conditions. In the electrophotographic roller, six locations were randomly selected while changing the observation position, and the average Young's modulus values are shown in Tables 8 and 9.

3-4. Measurement method of Rsk According to the standard of surface roughness according to JIS B0601-2001, measurement is performed using a surface roughness measuring instrument "SE-3500" (trade name, manufactured by Kosaka Laboratory Ltd.). Rsk is calculated by randomly selecting six measurement points of the electrophotographic roller and using the following equation (5) at each measurement point.

In the equation (5), Rq is the root mean square of the roughness curve, and lr is the reference length (1/5 of the evaluation length). Table 8-2 shows the average value of Rsk (Rsk(ave)) obtained from the six measurement points.

<Examples 2-18, 20-33>
In Example 1, the type of conductive composition, the abrasive grain size of the lapping film, and the spacer grain size were changed as shown in Tables 8-1 and 8-3. Except for those, the electrophotographic roller No. 1 is the same as in the first embodiment. 2 to No. 18, No. 20-No. 33 was produced and evaluated.
The average value (ave) of L1-1, L1-2, L2-1, and L2-2 of each roller for electrophotography, the average value (ave) of D1 and D2, and D1 of the 30 convex portions Is the number of convex portions whose 1/√3 or less and its ratio, the number of convex portions whose D2 is 1/√3 or less and its ratio, the average value (ave) of S1 and S2, the Young's modulus, and the average of Rsk. The values are shown in Table 8-1 and Table 8-3. In addition, for all 60 data of L1-1 and L2-1 measured for each electrophotographic roller, the number of data and its ratio within the range of 1 to 10 μm, and all 60 data of L2-1 and L2-2 , The number of data within the range of 2 to 200 μm and its ratio are shown in Table 8-2 and Table 8-4. Further, the results of image evaluation are shown in Table 8-2 and Table 8-4.

<Example 19>
The same conductive substrate as in Example 1 was used, and a cylindrical mold having a concave shape of K1:18 μm and K2:5 μm shown in FIG. 5 and two cylindrical pieces for holding the base in the cylindrical mold were assembled to form a cylinder. A cylindrical mold is sandwiched by a heating platen that is divided in parallel to the longitudinal direction of the mold and heated to 150° C., and a conductive silicone rubber material (product name: “DY35-11”, manufactured by Toray Dow Corning Co., Ltd.) by injection molding. ) Was poured into a cylindrical mold, heated for 15 minutes to cause a curing reaction, and then removed from the mold. Then, it was further heated in an electric furnace at 200° C. for 4 hours to complete the curing reaction, and a vulcanizing roller having a rubber layer formed on the outer peripheral surface of the substrate was obtained. The pressure during injection molding was 0.5 MPa. Air-dry at room temperature for about 30 minutes, and further in a hot-air circulation dryer at a temperature of 140° C. for 4 hours to cure the material, and electrophotographic roller No. I got 19. No polishing treatment was performed.

<Comparative Examples 1 to 8>
A polished conductive roller was produced in the same manner as in Example 1 except that the conductive rubber composition was changed to the material shown in Table 9 and the polishing conditions were changed. The surface of each conductive roller was treated by electron beam irradiation under the following conditions similar to those described in Patent Document 1, and electrophotographic roller No. C1 to No. C8 was obtained.
An electron beam irradiation apparatus (manufactured by Iwasaki Electric Co., Ltd.) having a maximum accelerating voltage of 150 kV and a maximum electron current of 40 mA was used for the irradiation of the electron beam, and a nitrogen gas purge was performed during the irradiation. The processing conditions were: acceleration voltage: 125 kV, electron current: 35 mA, processing speed: 1.27 m/min, oxygen concentration: 100 ppm.
Electrophotographic roller No. C1 to No. The results of physical property measurement and image evaluation of C8 are shown in Table 9-1 to Table 9-2.

In Examples 1 to 33, since the surface shape of the electrophotographic roller satisfies the formulas (1) and (2), good results were obtained for both the spot-like image and the horizontal streak image due to banding.
On the other hand, in Comparative Examples 1 to 8, since the surface shape of the electrophotographic roller did not satisfy the formulas (1) and (2), horizontal streak images were generated due to banding.

1: conductive substrate 2: conductive elastic layer 11: bowl-shaped resin particles 13, 101: glass plate 21: conductive elastic layer 22: conductive elastic layer 31: electrophotographic photosensitive member 32: described in Patent Document 1. Electrophotographic member 33: Electrophotographic roller 51 according to one embodiment of the present invention: Cylindrical mold 52: Electrophotographic roller 53: Mold inner wall 54: Recessed shape 60: Particle 61: Particle storage 62: Particle coating roller 63 : Particle coated member (electrophotographic roller)
71: Electrophotographic roller 72: Abrasive tape 81, 91: Charging roller 82, 92: Electrophotographic photoreceptor

Claims (12)

A roller for electrophotography, comprising a conductive substrate and a conductive elastic layer as a surface layer on the conductive substrate,
The elastic layer includes a binder,
The surface of the electrophotographic roller has a plurality of convex portions,
A part of the surface of the electrophotographic roller is constituted by the elastic layer,
Young's modulus of each of the protrusions is 0.01 to 5000 MPa,
When the electrophotographic roller is pressed against a glass plate so that the load per unit area of the nip formed by the electrophotographic roller and the glass plate becomes 6.5 g/mm ^2. The average value S1ave of the areas of the first contact portions between the convex portion of the electrophotographic roller and the glass plate is 10 μm ² or more,
Regarding the orthographically projected image of the contact portion obtained by orthographically projecting each of the first contact portions onto the surface of the conductive substrate, the maximum length in the direction orthogonal to the direction along the axis of the electrophotographic roller is L1. -1, and the maximum length in the direction along the axis of the electrophotographic roller is L1-2, L1-1 and L1-2 satisfy the relationship of the following formula (1), and the electrophotographic roller is Of the electrophotographic roller when pressed against the glass plate so that the load per unit area of the nip formed by the electrophotographic roller and the glass plate was 14.3 g/mm ² . The average value S2ave of the areas of the second contact portions between the convex portion and the glass plate is 200 μm ² or less,
Regarding the orthographically projected image of the contact portion obtained by orthographically projecting each of the second contact portions onto the surface of the conductive substrate, the maximum length in the direction orthogonal to the direction along the axis of the electrophotographic roller is L2. -1, and the maximum length in the direction along the axis of the electrophotographic roller is L2-2, L2-1 and L2-2 satisfy the relationship of the following formula (2). Roller for:

The roller for electrophotography according to claim 1, wherein the arctan (L1-1/L1-2) and the arctan (L2-1/L2-2) are 2/5 or less. The roller for electrophotography according to claim 1, wherein each of the L1-1 and the L2-1 is 1 μm or more and 10 μm or less. The roller for electrophotography according to claim 1, wherein each of the L1-1 and the L2-1 is 2 μm or more and 9 μm or less. The electrophotographic roller according to claim 1, wherein each of the L1-2 and the L2-2 is 2 μm or more and 200 μm or less. The electrophotographic roller according to claim 1, wherein each of the L1-2 and the L2-2 is 10 μm or more and 150 μm or less. The resin particles are bowl-shaped resin particles having an opening,
The elastic layer holds the resin particles in a state where the openings are exposed on the surface of the electrophotographic roller,
The surface of the electrophotographic roller has a concave portion from which the opening of the bowl-shaped resin particles originates, and
The roller for electrophotography according to claim 1, wherein the convex portion is derived from an edge of the bowl-shaped resin particles around the opening. The shell of the bowl-shaped resin particles is at least one selected from the group consisting of acrylonitrile resin, methacrylonitrile resin, vinylidene chloride resin, methyl methacrylate resin, and at least two copolymers selected from these resins. The electrophotographic roller according to claim 7, further comprising a resin. The elastic layer contains a cross-linked product of at least one rubber selected from the group consisting of styrene butadiene rubber, butyl rubber, acrylonitrile butadiene rubber, chloroprene rubber, and butadiene rubber. The described electrophotographic roller. The electrophotographic roller according to any one of claims 1 to 9, wherein the surface of the electrophotographic roller has a negative skewness Rsk of a roughness curve based on JIS B 0601:2001. A process cartridge configured to be attachable to and detachable from a main body of an electrophotographic image forming apparatus, the process cartridge including an electrophotographic photosensitive member and a charging roller that charges the electrophotographic photosensitive member,
A process cartridge, wherein the charging roller is the electrophotographic roller according to any one of claims 1 to 10. An electrophotographic photosensitive member and a charging roller for charging the electrophotographic photosensitive member,
An electrophotographic image forming apparatus, wherein the charging roller is the electrophotographic roller according to any one of claims 1 to 10.

Images