JP2003255693A - Developing roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roll having excellent toner electrification property and toner carrying property, causing no deterioration of toner and giving preferable image quality. <P>SOLUTION: The developing roller is composed of an axial body 11, a base rubber layer 12 formed on the peripheral surface of the axial body 11, an intermediate layer 13 formed on the peripheral surface of the base rubber layer 12, and further an outermost layer 14 formed on the peripheral surface of the intermediate layer 13. The outermost layer is comprised of the following resin composition (X). The resin composition (X) essentially comprising (A) polyvinylbutyral and (B) polyurethane with the proportions of the component (A) and component (B) specified to the weight ratio of (A)/(B)=95/5 to 50/50. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to a developing roll used in an electrophotographic apparatus such as a printer.

[0002]

2. Description of the Related Art Generally, copying by an electrophotographic copying machine is performed as follows. That is, a document image is formed as an electrostatic latent image on a rotating photosensitive drum, toner is attached to the electrostatic latent image to form a toner image, and the toner image is transferred to a copy sheet to perform copying. In this case, in order to form an electrostatic latent image on the surface of the photosensitive drum, the surface of the photosensitive drum is charged in advance, and a document image is projected onto this charged portion through an optical system and exposed to light. It has been practiced to create an electrostatic latent image by canceling the electrification of a part. As a developing method for developing an electrostatic latent image on a photosensitive drum to form a visible image, various methods have been conventionally proposed according to the type of developer used. As an example thereof, a one-component developing method using only toner as a developer is known.

As a developing device used in the one-component developing method, for example, a developing device 1 as shown in FIG. 5 has been proposed. In this developing device 1, a developing roll 3 carrying a one-component developer (toner) 2 is in contact with the photosensitive drum 4 and is housed inside a toner box 5 opened to the photosensitive drum 4 side. Further, the developing roll 3
Is in contact with an elastic roll 6 made of a foam made of polyurethane foam, sponge or the like, and the rotation of the elastic roll 6 in the direction of the arrow forms a layer of toner 2 on the outer periphery of the developing roll 3. It has become. On the other hand, the toner box 5 is provided with a layer forming member 7. The layer forming member 7 is in pressure contact with the outer peripheral surface of the developing roll 3.

In such a developing device 1, a toner image is formed on the outer peripheral surface of the photosensitive drum 4 as follows. That is, first, the developing roll 3 and the photosensitive drum 4 rotate as shown by the arrow. Along with this, the toner 2 is triboelectrically charged by friction between the layer forming member 7 and the outer peripheral surface of the developing roll 3, and a toner layer having a uniform thickness is formed on the outer peripheral surface of the developing roll 3. Then, the toner 2 of this toner layer is
The electrostatic attraction image (charged to the opposite polarity to the toner 2) formed on the outer peripheral surface of the photosensitive drum 4 causes the electrostatic attraction image to become a toner image. In this way, a toner image is formed on the outer peripheral surface of the photosensitive drum 4. The toner that has not participated in the toner image formation is collected in the toner box 5 and repeatedly used.

Here, in the developing roll 3, for example, a base rubber layer made of an elastic material such as silicone rubber is formed on the outer peripheral surface of a shaft body, and an outermost layer made of a resin material or a rubber material is formed on the outer peripheral surface thereof. Is configured. With such a structure, the outermost layer prevents the low molecular weight component from bleeding out from the silicone rubber or the like that is the material for forming the base rubber layer. Further, by appropriately selecting the outermost layer forming material of the developing roll 3 so as to be the outermost layer most suitable for the toner used, toner charging property, toner transporting property, toner filming resistance and the like are secured. become. And as such an outermost layer forming material,
Conventionally, urethane resin, acrylic resin, polyamide resin, etc. have been used.

[0006]

However, when the conventional outermost layer forming material as described above is used, the toner component adheres to the layer forming member 7 due to the continued use of the developing roll 3, and a uniform toner layer is formed. However, there is a problem in that the toner cannot be formed, and an image defect occurs, and the collected toner is deteriorated by heat. This is because when the above-mentioned conventional outermost layer forming material is used, the frictional resistance of the roll surface is large, and the pressure contact portion of the layer forming member 7 with the developing roll 3 locally generates heat due to continued use, and the heat It is considered that this is because the toner is fused or deteriorated. In particular, in recent years, since the melting point of toner tends to be lowered in order to achieve low power consumption, it can be said that toner deterioration due to heat generation is likely to proceed.

The present invention has been made in view of the above circumstances, and provides a developing roll which is excellent in toner charging property, toner transporting property, and the like, and which does not cause toner deterioration and can obtain good image quality. To that end.

[0008]

In order to achieve the above object, the developing roll of the present invention is a developing roll having at least one layer formed on the outer peripheral surface of a shaft, the outermost layer of which is as follows. The resin composition (X) is used. (X) The following (A) and (B) are the main components, and the content ratio of the (A) component and the (B) component is a weight ratio,
(A) / (B) = a resin composition set in the range of 95/5 to 50/50. (A) Polyvinyl butyral. (B) Polyurethane.

That is, the present inventors have conducted a series of studies to solve the above problems. In the process, it was found that the use of polyvinyl butyral (hereinafter abbreviated as “PVB”) as a material for forming the outermost layer of the developing roll can suppress the frictional resistance of the roll surface to a low level. The present inventors have conducted repeated studies to improve the frictional resistance of the roll surface, which is a drawback of conventional developing rolls, by using PVB. As a result, it was found that PVB has a high compatibility with polyurethane. It has been found that when PVB is blended in a specific ratio with respect to polyurethane and this is used as the outermost layer forming material, low friction is achieved without impairing the toner charging property and the toner transporting property. Reached

Particularly, when the coefficient of static and dynamic friction of the outermost layer surface is set in a specific range, frictional heat can be further suppressed, so that toner deterioration is less likely to occur and image quality is further improved. .

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in detail.

In the developing roll of the present invention, for example, as shown in FIG. 1, the base rubber layer 12 extends along the outer peripheral surface of the shaft body 11.
Is formed, the intermediate layer 13 is formed on the outer peripheral surface thereof, and the outermost layer 14 is further formed on the outer peripheral surface thereof. In the present invention, the outermost layer 14 contains PVB and polyurethane as main components,
Moreover, the greatest feature is that it is formed of a resin composition containing these in a specific ratio. Here, the "main component" has a great influence on the characteristics of the composition, and usually means 50% by weight or more of the whole, and includes the case where the whole is made up of only the main component.

The shaft 11 is not particularly limited as long as it has conductivity, and a cored bar made of a metal solid body or a metal cylindrical body hollowed out inside is used. To be Examples of the material of the shaft body 11 include aluminum and stainless steel. In addition, an adhesive, a primer, or the like can be applied on the shaft body 11 if necessary. In addition, the adhesive, the primer, and the like may be made conductive if necessary.

The material for forming the base rubber layer 12 formed on the outer peripheral surface of the shaft body 11 is not particularly limited, and examples thereof include silicone rubber, ethylene-propylene-diene rubber (EPDM), and styrene-butadiene rubber ( SBR), polyurethane elastomers and the like, and they may be used alone or in combination of two or more. Among them, silicone rubber is preferable because it has low hardness and little settling. In order to impart conductivity, carbon black, graphite, potassium titanate, iron oxide, c
_{-TiO 2, c-ZnO, c} -SnO 2, an ion conductive agent (quaternary ammonium salt, borate, surfactant, etc.) conventionally known conductive agent such as, the base rubber layer 12 formed material appropriately in May be added to.

The material for forming the intermediate layer 13 formed on the outer peripheral surface of the base rubber layer 12 is not particularly limited, and examples thereof include acrylonitrile-butadiene rubber (NBR) and hydrogenated acrylonitrile-butadiene rubber (H-). NBR), polyurethane elastomer, chloroprene rubber (CR), natural rubber, butadiene rubber (B
R), butyl rubber (IIR), hydrin rubber, nylon and the like, which may be used alone or in combination of two or more. Among them, H-NBR is particularly preferable from the viewpoint of adhesiveness and stability of the coating liquid.

As the material for forming the outermost layer 14 formed on the outer peripheral surface of the intermediate layer 13, as described above, a resin composition containing PVB and polyurethane as main components and containing them in a specific ratio. Things are used.

The PVB is a resin having a cyclic acetal structure obtained by reacting polyvinyl alcohol with butyraldehyde in the presence of an acid catalyst,
Apparently, it has a terpolymer structure composed of vinyl butyral units, vinyl acetate units and vinyl alcohol units.

The polyurethane is not particularly limited, and polytetramethylene ether glycol (PTMG) type, polypropylene glycol (PP) is used.
Various materials such as G) -based polyether-based, caprolactone-based, adipate-based polyester-based, polycarbonate-based, and the like can be used. Among them, excellent properties, low friction coefficient, and solvent solubility are available. In terms of etc., PT
MG type and adipate type are preferable. Further, the polyurethane is preferably a linear one, but if necessary, a functional group such as —OH, —NCO, —NH ₂ or the like is added to the terminal or side chain, and an isocyanate compound, an amine compound, an epoxy compound, etc. It may be crosslinked by.

The content ratio of PVB (component A) and polyurethane (component B) in the resin composition, which is the material for forming the outermost layer 14, is (A) / (B) = 95 /
It is set in the range of 5 to 50/50. That is, in the above proportion, if the component (A) is too much, the toner chargeability and toner transportability will be impaired.
On the other hand, if the amount of the component (A) is too small, the roll surface cannot be reduced in friction. The content ratio (weight ratio) is (A) / (B) = 90/10 to 60/4.
The range of 0 is preferable, and (A) / (B) = 80/2
More preferably, it is in the range of 0 to 70/30. That is, by setting the amount within such a range, it is possible to obtain a preferable result or a more preferable result in achieving both low friction of the roll surface and toner chargeability.

In addition to the above-mentioned components (A) and (B), other additives can be appropriately added to the special outermost layer 14 forming material, if necessary. Other additives include conductive agents such as carbon black, graphite and potassium titanate, fillers such as titanium oxide, calcium carbonate, talc, clay and silica, stabilizers, UV absorbers, charge control agents and reinforcing agents. Examples include agents, lubricants, release agents, dyes, pigments, flame retardants, oils and the like.

The developing roll of the present invention can be manufactured, for example, as follows.

That is, first, each component for the material for forming the base rubber layer 12 is kneaded with a kneader such as a kneader to prepare a material for forming the base rubber layer 12. In addition, the intermediate layer 1
3 Each component for forming material is kneaded by using a kneader such as a roll, and an organic solvent is added to this mixture and mixed and stirred to prepare a material for forming the intermediate layer 13 (coating liquid). Further, by dissolving each component for the outermost layer 14 forming material in an organic solvent and dispersing with a sand mill or the like,
A material (coating liquid) for forming the outermost layer 14 is prepared.

Then, the metal shaft 11 is set in the hollow part of the cylindrical mold, and the material for forming the base rubber layer 12 is cast into the space between the cylindrical mold and the shaft 11. rear,
The mold is covered and heated to crosslink the base rubber layer 12 forming material. After that, by removing from the cylindrical mold, the base roll having the base rubber layer 12 formed on the outer peripheral surface of the shaft body 11 is taken out. If necessary, the surface of the base roll is subjected to corona discharge treatment or plasma treatment. If necessary, a coupling agent is applied to the surface of the base roll. And of the above base roll,
The base rubber layer 12 is formed by applying a coating liquid, which is a material for forming the intermediate layer 13, to the outer periphery of the base rubber layer 12, or by immersing the base roll in the coating liquid and pulling it up, followed by drying and heat treatment. The intermediate layer 13 is formed on the outer periphery of the. Further, the outermost layer 14 forming solution is applied to the outer periphery of the intermediate layer 13. This coating method is not particularly limited, and a conventional method such as a dipping method, a spray method or a roll coating method can be applied. Then, after coating, drying and heat treatment (vulcanization treatment,
Conditions: 120 to 200 ° C. × 20 to 90 minutes) to remove the solvent in the solution for forming the outermost layer 14 and to crosslink those that crosslink. In this way
A roll having a three-layer structure as shown in FIG. 1 can be manufactured.

In this developing roll, the base rubber layer 1
The thickness of 2 is usually preferably set in the range of 0.5 to 10 mm, particularly preferably 1 to 6 mm.
The thickness of the intermediate layer 13 is preferably set in the range of 3 to 90 μm, particularly preferably 5 to 40 μm.
Is. And the thickness of the outermost layer 14 is 3 to 100 μm.
It is preferable to set in the range of, and particularly preferably, the thickness is 5 to 50 μm.

In the developing roll of the present invention thus obtained, the coefficient of dynamic friction μk of the surface of the outermost layer is μk
When <0.35, the static friction coefficient μs is preferably set to μs <0.40. More preferably, μk <0.
30 and μs <0.35. That is, when the coefficient of static and dynamic friction is set in such a range, the frictional heat on the roll surface can be further suppressed, so that toner deterioration is less likely to occur and, as a result, the image quality is further improved. is there. The static friction coefficient can be measured, for example, by a static friction coefficient meter manufactured by Kyowa Interface Science Co., Ltd.

Although an example of the developing roll of the present invention has a three-layer structure in FIG. 1, the layer formed on the outer periphery of the shaft body 11 does not necessarily have to be three layers. An appropriate number of layers are formed according to the above. However,
The outermost layer (if it is a single layer) is always the outermost layer 1 above.
4 must be formed with a forming solution.

Next, examples will be described together with comparative examples.

[0028]

[Example 1] [Base rubber layer forming material] Silicone rubber (X34-264, manufactured by Shin-Etsu Chemical Co., Ltd.).

[Intermediate Layer Forming Material] 100 parts by weight of H-NBR (Zetpol 0020, manufactured by Zeon Corporation) (hereinafter abbreviated as “part”), 0.5 part of stearic acid, and 5 parts of zinc white (ZnO). And 40 parts of carbon black (Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.), 1 part of the crosslinking accelerator BZ, 2 parts of the crosslinking accelerator CZ, and 1 part of sulfur, and then an organic solvent. To prepare an intermediate layer forming solution.

[Outermost layer forming material] 95 parts of PVB (Denka Butyral # 2000, manufactured by Denki Kagaku Kogyo Co., Ltd.), 5 parts of polyurethane (Mirasen E-34, manufactured by TSE), and carbon black (Denka Black HS-100, 10 parts of Denki Kagaku Kogyo Co., Ltd.) and then dispersed in methyl ethyl ketone to prepare an outermost layer forming solution.

[Preparation of Developing Roll] Next, a core metal made of SUS303 (diameter 10 mm) was prepared as a shaft body, and the outer peripheral surface of which was coated with an adhesive was set inside a roll mold, and The compound, which is the material for forming the base rubber layer, is cast into the space between the inner peripheral surfaces of the roll mold, heated and vulcanized (150 ° C x 30 minutes), and then demolded to form the base on the outer periphery of the shaft body. A rubber layer (thickness 4 mm) was formed.
The shaft body with the base rubber layer thus obtained is released from the mold, and the reaction is completed if necessary (200
C x 4 hours). Then, after applying a coating liquid comprising the intermediate layer forming material on the outer peripheral surface of the base rubber layer, drying and heat treatment are performed to form an intermediate layer (thickness 20 μm) on the outer peripheral surface of the base rubber layer. The outermost layer (thickness: 10 μm) is formed on the outer peripheral surface of the intermediate layer by applying a coating liquid containing the outermost layer forming material on the outer peripheral surface of the intermediate layer, and then performing drying and heat treatment to develop a three-layer structure. A roll was obtained (see Figure 1).

[0032]

Example 2 An outermost layer forming material was prepared in the same manner as in Example 1 except that the mixing ratio of PVB in the outermost layer forming material was 90 parts and the mixing ratio of polyurethane was 10 parts. Then, except for the above, a developing roll was manufactured in the same manner as in Example 1 (the manufacturing method and the thickness of each layer are also the same as in Example 1).

[0033]

Example 3 An outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 80 parts and the blending ratio of polyurethane was 20 parts. Then, except for the above, a developing roll was manufactured in the same manner as in Example 1 (the manufacturing method and the thickness of each layer are also the same as in Example 1).

[0034]

Example 4 An outermost layer forming material was prepared in the same manner as in Example 1 except that the mixing ratio of PVB in the outermost layer forming material was 70 parts and the mixing ratio of polyurethane was 30 parts. Then, except for the above, a developing roll was manufactured in the same manner as in Example 1 (the manufacturing method and the thickness of each layer are also the same as in Example 1).

[0035]

Example 5 An outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 60 parts and the blending ratio of polyurethane was 40 parts. Then, except for the above, a developing roll was manufactured in the same manner as in Example 1 (the manufacturing method and the thickness of each layer are also the same as in Example 1).

[0036]

Example 6 An outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 50 parts and the blending ratio of polyurethane was 50 parts. Then, except for the above, a developing roll was manufactured in the same manner as in Example 1 (the manufacturing method and the thickness of each layer are also the same as in Example 1).

[0037]

Comparative Example 1 An outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 100 parts (polyurethane was not included). Then, except for the above, a developing roll was manufactured in the same manner as in Example 1 (the manufacturing method and the thickness of each layer are also the same as in Example 1).

[0038]

Comparative Example 2 An outermost layer forming material was prepared in the same manner as in Example 1 except that the blending ratio of PVB in the outermost layer forming material was 40 parts and the blending ratio of polyurethane was 60 parts. Then, except for the above, a developing roll was manufactured in the same manner as in Example 1 (the manufacturing method and the thickness of each layer are also the same as in Example 1).

[0039]

Comparative Example 3 Polyurethane (Elastollan ET1040, manufactured by Mitsui Takeda Chemicals, Inc.) was used as the polymer of the outermost layer forming material. Then, except for the above, a developing roll was manufactured in the same manner as in Example 1 (the manufacturing method and the thickness of each layer are also the same as in Example 1).

[0040]

Comparative Example 4 An acrylic resin (Hyper D-100E, manufactured by Negami Kogyo Co., Ltd.) was used as the polymer for the outermost layer forming material. Then, except for the above, a developing roll was manufactured in the same manner as in Example 1 (the manufacturing method and the thickness of each layer are also the same as in Example 1).

With respect to the developing rolls thus obtained, the respective properties were compared and evaluated according to the following criteria. The results are also shown in Tables 1 and 2 below.

[Surface Hardness] The surface hardness of the developing roll was measured using a micro rubber hardness meter MD-1 type (manufactured by Kobunshi Keiki Co., Ltd.).

[Roll Electric Resistance] The roll electric resistance was measured by a metal roll electrode method using an apparatus as shown in FIG. That is, the developing roll 62 is brought into contact with the metal roll 61 made of stainless steel, both ends of the developing roll 62 are pressed with a load of 1000 g (9.8 N), and in this state, a voltage of 100 V is applied to one end of the developing roll 62. The electrical resistance was measured.

[Surface Roughness (Rz)] The surface roughness (circumferential direction) of the developing roll surface was measured by Surfcom (manufactured by Tokyo Seimitsu Co., Ltd.) in accordance with JIS B 0601. In addition,
Rz is the ten-point average roughness obtained from the roughness curve obtained by cutting off the surface waviness component longer than a predetermined wavelength from the contour (this is called a cross-section curve) appearing at the cut when cut on a plane perpendicular to the unevenness. Is shown.

[Dynamic friction coefficient (μk), static friction coefficient (μ
s)] It was measured using a static and dynamic friction coefficient meter (manufactured by Kyowa Interface Science Co., Ltd.) as shown in FIG. That is, using the resin composition which is the outermost layer forming material of the developing roll,
A coating film 11 having a thickness of 00 μm was prepared, and the coating film 11 was set on the fixed table 12 and measured under the conditions of a moving speed of 0.3 cm / sec and a load of 100 g. In FIG. 3, 13 is a pressure contactor, 14 is a zero-adjustment balance, 15 is a load cell, and 16 is a load (10
0g). 4A is a sectional view of the pressure contactor 13, and FIG. 4B is a front view of the pressure contactor 13.

[Toner Charge Amount] Q / M Measuring Device (MODE
L210HS, manufactured by Trek), the charge amount per unit weight of the toner layer-formed on the developing roll was measured.

[Toner Transport Amount] The toner formed on the developing roll was tape-transferred, and the weight per unit area of the toner was measured.

[Surface Temperature After Endurance] The obtained developing roll was idled in an actual machine for 3 hours, and the temperature change of the roll surface due to frictional heat with the layer forming member incorporated in the actual machine was measured by a radiation thermometer (IT -330, manufactured by Horiba Ltd.).

[Image Evaluation] The obtained developing roll was incorporated in an electrophotographic printer, and actual printing was performed. Then, the image quality of the printed image was visually evaluated at the initial stage and after printing 10,000 sheets (after the endurance). That is, a character was printed, and the printed image had no problem and was clearly printed down to fine lines. The result was evaluated as ◯, and in the order of good image, evaluated as Δ and ×.

[Toner Filming Property] After printing 10,000 sheets (after endurance), the presence or absence of toner filming on the developing roll was visually determined. Then, the case where the toner filming did not occur was evaluated as ◯, and the case where the toner filming occurred was evaluated as x.

[Toner Sticking] After the 10,000 sheets were printed (after running), the presence or absence of toner sticking to the layer forming member in the electrophotographic printer was visually determined. The evaluation was evaluated as ◯ when toner adhesion did not occur, Δ when slight toner adhesion occurred but no problem in practical use, and x when toner adhesion occurred.

[0052]

[Table 1]

[0053]

[Table 2]

From the results in the above table, all the example products
It can be seen that the toner is excellent in toner charging property and toner transporting property, toner filming does not occur, and the printed image is hardly deteriorated even after the endurance. On the other hand, in Comparative Example 1 product in which the outermost layer was formed only from PVB, it was found that the surface hardness was too high and a clear printed image could not be obtained. Further, it can be seen that in the product of Comparative Example 2 in which the PVB content is low, the temperature of the roll surface rises due to friction, which causes toner deterioration and adversely affects the image quality after endurance. Also, in the case of the comparative example 3 product in which the outermost layer is made only of urethane and the comparative example 4 product made of only acrylic,
It can be seen that the image quality after endurance is poor.

[0055]

As described above, the developing roll of the present invention is
The outermost layer is formed of a resin composition containing PVB and polyurethane as main components and containing them in a specific ratio. Therefore, low friction can be achieved without impairing the toner charging property and the toner transporting property, which are the performance of the developing roll. As a result, since the generation of heat due to friction with the layer forming member is suppressed, even if the toner is continuously used, the toner is not fused to the layer forming member due to heat, and thermal deterioration does not occur, It becomes possible to obtain an excellent printed image. Also,
Even when a toner having a low melting point is used, the above-mentioned fusion and the like do not occur, so that it is possible to achieve low power consumption without causing image defects.

In particular, when the coefficient of static and dynamic friction of the surface of the outermost layer is set within a specific range, frictional heat can be further suppressed, so that toner deterioration is less likely to occur and a better printed image can be obtained. You can

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a developing roll of the present invention.

FIG. 2 is an explanatory diagram showing a method for measuring roll electric resistance.

FIG. 3 is an explanatory diagram showing a measurement state of a friction coefficient by a static-dynamic friction coefficient meter.

FIG. 4A is a cross-sectional view of a pressure contactor used for measuring the friction coefficient, and FIG. 4B is a front view of the pressure contactor.

FIG. 5 is an explanatory diagram showing a usage state of the developing roll.

[Explanation of symbols]

11 axis 12 Base rubber layer 13 Middle class 14 outermost layer

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H077 AD06 FA13                 3J103 AA02 AA15 AA23 FA30 GA02                       GA57 GA58 GA60 HA03 HA04                       HA48

Claims (2)

[Claims] 1. A developing roll having at least one layer formed on the outer peripheral surface of a shaft body, wherein the outermost layer is formed of the following resin composition (X). . (X) The following (A) and (B) are the main components, and the content ratio of the (A) component and the (B) component is a weight ratio,
(A) / (B) = a resin composition set in the range of 95/5 to 50/50. (A) Polyvinyl butyral. (B) Polyurethane. 2. The dynamic friction coefficient μk of the outermost surface is such that μk <
2. The developing roll according to claim 1, wherein the coefficient of static friction μs is set to 0.35 and μs <0.40.