JP2018112640A - Conductive roller for electrophotography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive roller for electrophotography as a contact charging roller capable of reducing charging sounds even when used being applied with a voltage including AC voltage (AC component) while preventing deformation due to compression deformation, and a charging roller for electrophotography.SOLUTION: The conductive roller for electrophotography includes: a conductivity foamed elastic layer formed on a conductive support; and at least one conductive coating layer. The conductive roller for electrophotography is characterized in that, in dynamic viscoelasticity measurement at a frequency corresponding to the charging sound in the conductive foamed elastic layer of 1 kHz to 20 kHz, the ratio (G'/tan δ) of the storage elastic modulus G' to the loss tangent tan δ is 2 MPa or less. There are also provided a charging roller for electrophotography and a usage method thereof.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a conductive roller used in an electrophotographic apparatus, and to a charging roller used to charge the surface of an electrophotographic photosensitive member to a predetermined potential.

  In an electrophotographic apparatus such as a laser printer, the surface of a photoconductor is uniformly charged, the photoconductor is irradiated with light such as a laser beam, and the charged portion is erased to remove a latent image on the photoconductor. Form. Next, the latent image is developed with toner to form a visible image, the toner image is transferred to a recording medium such as paper, and then the toner image is fixed by heat, pressure, or the like.

  Conventionally, a corona charger has been used as a charger for initializing and charging the surface of a photoreceptor. However, the corona discharge method requires application of a high voltage of 6 to 10 kV, which is not preferable from the viewpoint of machine safety maintenance. In addition, since harmful products such as ozone are generated during corona discharge, there is also an environmental problem. Further, additional means / mechanisms for dealing with the problem are required, and there are problems that the apparatus is easily increased in size and cost.

  In recent years, a contact charging method using a charging roller or the like has been adopted as a charging method that can be charged with a lower applied voltage than corona discharge and can suppress the generation of harmful substances such as ozone. It has become to.

  In the contact charging method, a charging roller is brought into pressure contact with the surface of the photosensitive member, and a voltage is applied to the charging roller to charge the surface of the photosensitive member. As the charging roller, a roller in which a conductive elastic layer is concentrically laminated on a conductive support such as metal is usually used, and on the outer periphery of the conductive elastic layer for the purpose of imparting its surface property. A conductive roller having a conductive elastic layer formed by laminating a conductive surface layer and having two or more layers is also used as necessary.

  In order to stably maintain a uniform charging potential on the surface of the photoconductor by this contact charging method, a method of superimposing an AC voltage on a DC voltage is often used, but the charging roller and the photoconductor are in contact with each other. When an AC voltage is applied, a phenomenon occurs in which the charging roller strikes the photoreceptor due to the applied AC voltage, and a charging sound is generated. Therefore, in order to reduce the charging noise, for example, Patent Document 1 and Patent Document 2 adopt a method of reducing the hardness of the entire charging member or the elastic layer.

In order to reduce the hardness of the charging member, a method of adding a softening agent or a plasticizer to the rubber composition forming the elastic layer is known. However, bleeding of these additives occurs (bleed). This causes problems such as contamination of the photoreceptor surface. In rubbers where such problems are likely to occur, the amount of bleed-causing substance added must be reduced, and there is a limit to reducing the hardness of the charging member.
On the other hand, Patent Document 3 employs a method in which the elastic layer is a foam, but there is a limit to suppressing the charging sound by simply using the elastic layer as foamed rubber.

Furthermore, as a means for reducing the charging sound, there is one that pays attention to the loss tangent tan δ or the storage elastic modulus in the dynamic viscoelasticity measurement of the elastic layer. In Patent Document 4 and Patent Document 5, the tan δ value of the elastic layer is increased.
In Patent Document 6, the storage elastic modulus of the elastic layer is lowered and the tan δ value is controlled within a predetermined range.
In Patent Document 7, tan δ is controlled at a frequency corresponding to the charging sound.
The charging sound level of the charging member having these characteristics has been improved compared to the conventional one, but in recent years, the higher the charging sound frequency with the speeding up of the printer, the higher the sound and the harsh sound generated. There is still room for improvement before reaching a level where general users can use it satisfactorily.

  Decreasing the hardness of the elastic layer or increasing the tan δ value means that the charging member having the elastic layer contributes greatly to the viscosity characteristics, and the charging member has a large ability to absorb vibration caused by alternating current application internally. However, in the contact charging method, since the charging member is in pressure contact with the photoconductor for a long time, the charging member is likely to be deformed at the contact position, and this deformation does not return (compression permanent distortion). ). For this reason, a difference in discharge state (discharge from the charging member to the photosensitive member) occurs between a distorted portion of the charging member and a portion where the charging member does not, so that a difference in charging occurs and an image defect may occur. In addition, there are problems such as vibration accompanying deterioration of shape and deterioration of charging sound.

Japanese Patent Laid-Open No. 4-025868 Japanese Patent Laid-Open No. 7-092776 Japanese Patent Laid-Open No. 5-210281 JP-A-4-161964 JP-A-8-262835 JP-A-10-319676 WO2006 / 088237

  The present invention has been made in view of the above-described background art, and the problem thereof relates to a contact charging type charging roller, and even when a voltage including an alternating voltage (alternating current component) is applied and used, the charging noise is reduced. An electrophotographic conductive roller and an electrophotographic charging roller capable of realizing both deformation prevention by compression deformation.

  Therefore, as a result of intensive studies to solve such problems, the present inventor, in an electrophotographic charging roller provided with a conductive foamed elastic layer on a conductive support and at least one conductive coating layer thereon, A parameter (G ′ / tan δ), which is a combination of storage elastic modulus G ′ and loss tangent tan δ measured by dynamic viscoelasticity at a frequency corresponding to the charging sound of the conductive foamed elastic layer, represents the charging sound generated from the charging roller. It has been found that there is a good correlation with the strength, and it has been found that if G ′ / tan δ is set to 2 MPa or less, the charged sound can be adjusted to an acceptable level (a level that does not feel uncomfortable), and the present invention has been achieved. Note that the frequency range corresponding to the charging sound is 1 kHz to 20 kHz.

Regarding the significance of the parameter G ′ / tan δ, the storage elastic modulus G ′ has a correlation with the hardness of the elastic layer and is considered to affect the magnitude of the charged sound. The viscosity characteristic (loss elastic modulus G ″) and the elastic characteristic (storage) It is considered that tan δ, which is a ratio of the elastic modulus G ′), is a parameter that contributes to the attenuation of the charging sound. It has been made by finding that it can be quantitatively evaluated by evaluating in the form of tan δ.
This parameter (G ′ / tan δ) indicates that the foamed elastic layer has low elasticity and low viscosity, and that there is a suitable range for G ′ and tan δ in order to make the charged sound acceptable. Indicated by.
On the other hand, the prior art discloses a technique that defines the range of elastic modulus and / or tan δ, but does not discuss a parameter that combines the two, and a charging roller that essentially suppresses the charging noise is disclosed. It is considered that it cannot be specified.

  An object of the present invention is to provide a charging roller for electrophotography that can realize both reduction of charging sound and prevention of deformation due to compression deformation. It has been found that by balancing a foamed elastic layer having characteristics and a conductive coating layer thereon, both reduction of charging noise and prevention of deformation due to compression deformation can be realized more reliably, and the present invention has been achieved. .

  As described above, the foamed elastic layer having the above-mentioned parameter characteristics, the thickness of the conductive coating layer thereon, and the roller hardness are controlled within a predetermined range, so that charging even when a voltage including an AC voltage is applied is used. It has become possible to provide a charging roller that can adjust the sound intensity to an acceptable level (a level that does not feel uncomfortable) and that can prevent compression deformation after long-time pressure contact with the photoreceptor.

  That is, the present invention is an electrophotographic conductive roller in which a conductive foamed elastic layer and at least one conductive coating layer thereon are provided on a conductive support, the 1 kHz of the conductive foamed elastic layer. The ratio (G ′ / tan δ) between the storage elastic modulus G ′ and loss tangent tan δ by dynamic viscoelasticity measurement at a frequency corresponding to charged sound in ˜20 kHz is 2 MPa or less. A conductive roller is provided.

  The present invention also relates to a method for using an electrophotographic conductive roller using the electrophotographic conductive roller described above, wherein the electrophotographic conductive roller is mounted on an electrophotographic apparatus main body, brought into contact with the surface of the electrophotographic photosensitive member, and an AC component. The electrophotographic photosensitive member is charged by applying a voltage containing the electrophotographic photosensitive roller, and a method for using the electrophotographic conductive roller is provided.

  According to the present invention, an AC voltage (alternating current component) is generated by using an electrophotographic conductive roller provided with a foamed elastic layer having the above-described parameter characteristics and a conductive coating layer thereon, which solves the above problems. Even when a voltage including the voltage is applied, the charged sound intensity can be adjusted to an acceptable level (a level that does not feel uncomfortable), and compression deformation after long-time pressure contact with the photoreceptor can be prevented. .

Furthermore, the thickness of the conductive coating layer is preferably 0.05 mm to 0.25 mm, particularly preferably 0.15 mm to 0.20 mm, and the hardness (roller hardness) as a conductive roller is Asker at a load of 500 g. The C roller hardness is preferably 40 ° to 60 °, and particularly preferably 45 to 55 °, whereby the above-mentioned problem is solved more suitably.
That is, by controlling the foamed elastic layer having the above-mentioned parameter characteristics and the thickness and roller hardness of the conductive coating layer thereon in a predetermined range, in combination with the above-mentioned limitation of “G ′ / tan δ”, The charged sound intensity can be adjusted to an acceptable level, and compression deformation can be prevented.

It is a schematic cross-sectional view of the electrophotographic conductive roller of the present invention. It is a schematic longitudinal cross-sectional view of the dynamic-viscoelasticity measuring apparatus used for the dynamic-viscoelasticity measurement of the electrophotographic conductive roller of this invention. FIG. 4 is a diagram showing the relationship between “G ′ / tan δ” of the conductive foamed elastic layer of the electrophotographic conductive roller of the present invention and “peak value of charged sound [a.u. (arbitrary unit)]”.

Hereinafter, embodiments of the present invention will be described in detail.
The electrophotographic conductive roller of the present invention is an electrophotographic conductive roller in which a conductive foamed elastic layer and at least one conductive coating layer are provided on a conductive support, and the electroconductive roller The ratio (G ′ / tan δ) of the storage elastic modulus G ′ and loss tangent tan δ measured by dynamic viscoelasticity at a frequency corresponding to a charging sound within a frequency range of 1 kHz to 20 kHz of the foamed elastic layer is 2 MPa or less. And
In the present invention, the “electrophotographic conductive roller” may be simply abbreviated as “conductive roller” and the “electrophotographic charging roller” may be simply abbreviated as “charging roller”.

<Conductive roller, charging roller>
As described above, the conductive roller and the charging roller of the present invention are obtained by forming a conductive foamed elastic layer on a conductive support and at least one conductive coating layer thereon. An example of the configuration is shown in FIG. FIG. 1 shows a case where there is one conductive coating layer. In FIG. 1, 1 is a conductive support, 2 is a conductive foamed elastic layer, and 3 is a conductive coating layer.

The conductive roller used in the contact charging method needs to be smoothly rotated following the rotation of the photoconductor while the both ends are supported by the shaft. The easier one is better.
Moreover, it is necessary to maintain the rigidity of the charging roller. Therefore, the conductive support 1 is preferably a metal such as iron, an aluminum alloy, or stainless steel, and a cylindrical shape is preferably used as the shape thereof.

<< Conductive foamed elastic layer >>
The conductive foamed elastic layer 2 is preferably formed from a foamed rubber composition containing a conductive material. Specific examples of the rubber component of the foamed rubber composition include natural rubber, styrene / butadiene rubber (SBR), isoprene rubber, butadiene rubber, chloroprene rubber, acenylnitrile / butadiene rubber (NBR), and ethylene / propylene. -Diene rubber (EPDM), epichlorohydrin rubber, urethane rubber, silicon rubber, etc. are mentioned. These rubber components may be used alone or in combination of two or more. In particular, the rubber component is not limited.

  Specifically, for example, carbon black, metal, metal oxide, alkali metal salt, quaternary ammonium salt and the like are preferably used as the conductive agent to be blended in the rubber composition.

In order to charge the photosensitive member to a necessary surface potential, the value of the specific resistance (resistivity) of the charging roller is usually required to be a medium resistance region (about 10 ³ Ω · cm to 10 ⁸ Ω · cm). The use of carbon black is preferred because the resistance value is easily controlled by adjusting the amount added. The blending ratio of carbon black is adjusted according to the target resistance value of the conductive foamed elastic layer.

  As the foaming agent to be blended in the foamed rubber composition, any of various foaming agents can be used as long as gas can be generated by heating to foam the conductive rubber composition. Examples thereof include organic foaming agents such as azodicarbonamide (ADCA), 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH), N, N'-dinitrosopentamethylenetetramine (DPT). In addition, it is preferable that the mixture ratio of these foaming agents is 1 mass part or more and 8 mass parts or less per 100 mass parts of total amounts of rubber | gum as a range which can foam a rubber | gum content favorably.

Moreover, it is preferable to mix | blend a crosslinking agent and a crosslinking accelerator with a rubber composition in order to bridge | crosslink a rubber part. Examples of the crosslinking agent include sulfur-based crosslinking agents, thiourea-based crosslinking agents, triazine derivative-based crosslinking agents, and peroxide-based crosslinking agents.
Of these, sulfur-based crosslinking agents are preferred, and sulfur such as powdered sulfur is particularly preferred. The mixing ratio of the sulfur is preferably 0.2 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the total amount of rubber as a range in consideration of productivity such as a crosslinking rate.
Examples of the crosslinking accelerator include inorganic accelerators and organic accelerators such as slaked lime and magnesium oxide, and an optimal crosslinking accelerator may be selected and used according to the type of the crosslinking agent to be combined.
In addition, you may mix | blend a softener, a filler, a processing aid, etc. with a rubber composition as needed.

The thickness and specific resistance (resistivity) of the conductive foamed elastic layer 2 are appropriately set according to the use of the conductive roller, etc., but when used for the charging roller of the present invention, the thickness is 1 mm to 10 mm. Is preferable, and 4 mm to 8 mm is particularly preferable.
The specific resistance (resistivity) of the conductive roller is preferably ^{10 3 Ω · cm~10 5 Ω ·} cm.

  Type, content, crosslinking / foaming conditions, etc., of rubber component, conductive agent, foaming agent, crosslinking agent, crosslinking accelerator, softener, filler, processing aid, acid acceptor, etc. of conductive foam elastic layer 2 Determines the storage elastic modulus G ′, loss tangent tan δ, G ′ / tan δ, suitable wall thickness, suitable foaming form, suitable specific resistance (resistivity), and the like. That is, by determining the type and adjusting the amount, and by adjusting the crosslinking temperature and time, (storage elastic modulus G ′, loss tangent tan δ), G ′ / tan δ, (thickness, preferred foam form) , Suitable specific resistance) and the like can be within the scope of the present invention.

More specifically, in order to adjust G ′ / tan δ of the present invention to be small (2 MPa or less), as described above, the storage elastic modulus G ′ of the foamed elastic layer is reduced and the loss elastic modulus G ″ is also reduced. For this purpose, a polymer having a low Mooney viscosity (for example, epichlorohydrin rubber or the like) is determined, the foam cell diameter is increased, or open cells are formed.
Examples of means for increasing the foam cell diameter include adjusting the growth rate of the foam cell and the crosslinking rate by adjusting the amount of the foaming agent and adjusting the crosslinking temperature and time.
Accordingly, G ′ / tan δ can be within the scope of the present invention. In addition, G ′ / tan δ, suitable specific resistance and the like can be made within the (preferred) range of the present invention.

<< Conductive coating layer >>
The material and manufacturing method of the conductive coating layer 3 are not particularly limited. However, the conductive coating layer 3 is based on a thermoplastic resin, and is made of a material in which a conductive agent, an antioxidant, a lubricant, a processing aid or the like is added and dispersed. The seamless tube is preferably from the viewpoint of production stability.
As the thermoplastic resin, ethylene; propylene ethylene block or random copolymer; rubber or latex component; styrene / butadiene / styrene block copolymer; polyester; polyurethane;
As the conductive agent, it is preferable to use carbon black; metal or metal oxide; alkali metal salt; quaternary ammonium salt; etc. Among them, carbon black is the same as the reason for the conductive foamed elastic layer. Particularly preferred.

<Method for producing conductive roller and charging roller>
A preferable method for producing a conductive roller / charging roller is as follows.
That is, the conductive foamed elastic layer 1 is formed by extruding a rubber composition containing a conductive agent (conductivity imparting material), a foaming agent and the like into a cylindrical shape through a die of an extruder, and an extruded cylindrical body. Is continuously crosslinked and foamed, and the produced cylindrical foam rubber is further cut into a predetermined length.
A roller of a conductive foamed elastic layer is obtained by, for example, inserting a metal shaft into the cylinder manufactured through the above steps and fixing them to each other.

  Furthermore, after blending the thermoplastic resin with a necessary additive such as a conductive agent and kneading together, the seamless tube formed by, for example, an extrusion molding machine or the like is externally fitted to the roller of the conductive foamed elastic layer, and the present invention. Conductive roller and charging roller can be obtained.

In the conductive roller of the present invention, as described above, the conductive foamed elastic layer (inner side) has a role of reducing charging noise, and the conductive coating layer (outer side) has a role of preventing deformation due to compression deformation. Yes.
As a whole of the conductive roller (charging roller), it is preferable to balance the thickness of the outer conductive coating layer 3 and the roller hardness to the extent that the flexibility of the conductive foamed elastic layer 2 is not impaired.
According to this, the thickness of the conductive coating layer 3 is preferably 0.05 to 0.25 mm, more preferably 0.10 mm to 0.20 mm, and particularly preferably 0.15 mm to 0.18 mm.
Moreover, as a whole conductive roller (charging roller), the Asker C roller hardness at a load of 500 g is preferably 40 ° to 60 °, and particularly preferably 45 ° to 55 °. Although the range of the said thickness and roller hardness may be one side, it is preferable to satisfy | fill both simultaneously.

Moreover, it is preferable that the value of the specific resistance (resistivity) of the conductive coating layer 3 is higher than that of the inner conductive foam elasticity 2, specifically, 10 ⁵ Ω · cm. ~10 ⁷ Ω · cm is preferable.

<Measurement of dynamic viscoelasticity, numerical values such as G ′ / tan δ>
Storage elastic modulus G ′ by dynamic viscoelasticity measurement at a frequency corresponding to charging sound in 1 kHz to 20 kHz by adjusting the material, thickness, and specific resistance (resistivity) of conductive foamed elastic layer 2 If the ratio (G ′ / tan δ) with respect to the loss tangent tan δ is 2 MPa or less, the charging sound can be adjusted to an allowable level (a level that does not feel uncomfortable).
G ′ / tan δ is essential to be 2 MPa or less, preferably 0.001 MPa to less than 2 MPa, more preferably 0.001 MPa to 1.5 MPa, and particularly preferably 0.001 MPa to 1 MPa.

According to the present invention, “G ′ / tan δ of the conductive foamed elastic layer” at “a frequency at one point” corresponding to “the charging sound of the electrophotographic apparatus in the range of 1 kHz to 20 kHz” is 2 MPa or less. Features. “G ′ / tan δ” may be a value of G ′ / tan δ at one frequency in the range of 1 kHz to 20 kHz (although it exhibits an effect), but “an electrophotographic image using the conductive roller of the present invention” The effect of the present invention is further exhibited when the value of G ′ / tan δ at a frequency corresponding to the “charging sound unique to the apparatus main body and the contact charging device” is within the above range.
Furthermore, the range of the above value is particularly preferable over the entire frequency range of 1 kHz to 20 kHz, which is a frequency corresponding to the charging sound, in order to exhibit the effect.

  The specified temperature of the physical properties such as G ′ / tan δ of the conductive foamed elastic layer is 10 ° C. to 35 ° C., and it is within the scope of the present invention if it is satisfied at one specified temperature in this range. It is preferable to satisfy | fill, and it is especially preferable to satisfy | fill at 20 degreeC.

The measurement of the dynamic viscoelasticity of the conductive foamed elastic layer 2 is performed using a rheometer or a dynamic viscoelasticity measuring device and a fixed torsion jig 4 (see FIG. 2).
The conductive foamed elastic layer is cut into a strip shape, both ends of the sample 5 for dynamic viscoelasticity measurement are fixed, a static load of 0.3 N is applied in the length pulling direction, the storage elastic modulus G ′, and the loss elastic modulus G ″. And the loss tangent tan δ is calculated from the ratio.

In the conductive foamed elastic layer, the conductive roller, and the charging roller in the present invention, the obtained result is fitted by the WLF (Williams, Landel, Ferry) formula according to the time-temperature conversion rule, and the shift factor αT and Get the master curve.
The master curve is shifted by the shift factor at each temperature, the storage elastic modulus G ′ and the loss tangent tan δ at the frequency corresponding to the charging sound at each temperature are extracted, and the parameter “G ′ / tan δ”, which is a feature of the present invention. Ask for.

In the present invention, the electrophotographic conductive roller mounted on the electrophotographic apparatus main body is in contact with the surface of the electrophotographic photosensitive member, and the electroconductive roller is applied with a voltage containing an alternating current component. The electrophotographic conductive roller for charging the photosensitive member is preferred.
The electrophotographic conductive roller of the present invention is mounted on an electrophotographic apparatus main body and in contact with the surface of the electrophotographic photosensitive member, by applying a voltage containing an alternating current component, the electrophotographic photosensitive member is In order to achieve the above-described effects of the present invention, it is preferable that it can be charged.

In the conductive roller of the present invention, a voltage containing an AC component is applied to the conductive roller in a state where the conductive roller is in contact with the surface of the electrophotographic photosensitive member, whereby the conductive roller is It is said that the effect of the present invention described above, that is, the intensity of charged sound generated when applying a voltage containing an AC component can be adjusted to an allowable level is used for an application such as charging a photoreceptor. It is preferable because the effect is particularly achieved. The electrophotographic conductive roller of the present invention is preferably used in contact with the electrophotographic photoreceptor surface.
That is, the present invention is a method of using an electrophotographic conductive roller using the electrophotographic conductive roller described above, which is mounted on an electrophotographic apparatus main body, brought into contact with the surface of the electrophotographic photosensitive member, and an AC component. The electrophotographic photosensitive member is charged by applying a voltage containing the electrophotographic photosensitive roller, wherein the electrophotographic conductive roller is used.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples unless it exceeds the gist.
In the examples, “part” means “part by mass”. In the embodiment, only “charging roller” is described. However, since “charging roller” is “conductive roller”, it can be read as described below.

<Preparation of conductive coating layer>
<< Preparation of Conductive Coating Layers of Examples 1 and 2 and Comparative Examples 1 to 3 >>
As a material for the conductive coating layer, 100 parts of thermoplastic nylon 12 (Ube Industries: 3020A), 15 parts of carbon black (Tokai Carbon: Seast 3) as a conductive agent, calcium carbonate (Shiraishi calcium: Whiten B, BF300) 40 parts and 3 parts of antioxidant (BASF: Irgano × 1010) were kneaded at 200 ° C. using a twin screw extruder, cut with a strand cutter, and pelletized material was produced.
The obtained pellets are extruded by an extruder with an annular die (outer diameter 15 mm, inner diameter 14.5 mm), and after a cooling process, a seamless tube that becomes a conductive coating layer having an outer diameter of 12.0 mm and an inner diameter of 11.65 mm Was made.

<Preparation of conductive foamed elastic layer>
Example 1
<< Conductive Foam Elastic Layer Used in Example 1 >>
As materials for the conductive foamed elastic layer, 100 parts of epichlorohydrin rubber (Nippon ZEON: HYDRIN, T3108), 10 parts of carbon black (Mitsubishi Chemical: Diamond Black I) as a conductive agent, foaming agent (Yewa Kasei Kogyo: Binihole AC #) 3) 4 parts, acid acceptor (Kyowa Chemical Industry: DHT-4A-2) 3 parts, cross-linking agent (Tsurumi Chemical Industry: powdered sulfur) 1.5 parts, accelerator (Ouchi Shinsei Chemical Industry: Noxeller) DM) 1.5 parts, accelerator (Ouchi Shinsei Chemical Industry: Noxeller TS) 0.5 part, and accelerator assistant (Hakusitek: zinc oxide) 3 parts were blended at 80 ° C in a closed kneader. The rubber composition was prepared by kneading for 3 to 5 minutes.
The obtained rubber composition was extruded through a die of an extruder into a long cylindrical shape having an outer diameter of 10.5 mm and an inner diameter of 3.5 mm, and foamed and crosslinked in water vapor at 150 ° C. and 6.0 MPa for 60 minutes. A cylindrical foamed elastic layer was prepared. The outer diameter and inner diameter of the foamed elastic layer were about Φ15.0 mm and about Φ4.0 mm, respectively.

Example 2
<< Conductive Foam Elastic Layer Used in Example 2 >>
70 parts of epichlorohydrin rubber (Nippon ZEON: HYDRIN, T3108), 30 parts of acrylonitrile butadiene rubber (Nippon ZEON: DN401LL), carbon black as a conductive agent (Mitsubishi Chemical: Diamond Black I) 10 parts, 4 parts foaming agent (Eiwa Chemical Industries: VINYHALL AC # 3), 3 parts acid acceptor (Kyowa Chemical Industry: DHT-4A-2), 1 part cross-linking agent (Tsurumi Chemical Industry: powdered sulfur) .5 parts, 1.5 parts of accelerator (Ouchi Shinsei Chemical Industry: Noxeller DM), 0.5 part of accelerator (Ouchi Shinsei Chemical Industry: Noxeller TS), accelerator aid (Hakusui Tech: zinc oxide) A rubber composition was prepared by kneading 3 parts with a closed kneader at 80 ° C. for 3 to 5 minutes.
The obtained rubber composition was extruded through a die of an extruder into a long cylindrical shape having an outer diameter of 10.5 mm and an inner diameter of 3.5 mm, and foamed and crosslinked in water vapor at 150 ° C. and 6.0 MPa for 60 minutes. A cylindrical foamed elastic layer was prepared. The outer diameter and inner diameter of the foamed elastic layer were about Φ15.0 mm and about Φ4.0 mm, respectively.

Comparative Example 1
<< Conductive Foam Elastic Layer Used in Comparative Example 1 >>
60 parts of epichlorohydrin rubber (Nippon ZEON: HYDRIN, T3108), 40 parts of acrylonitrile butadiene rubber (Nippon ZEON: DN401LL), carbon black as a conductive agent (Mitsubishi Chemical: Diamond Black I) 20 parts, 4 parts foaming agent (Eiwa Chemical Industries: VINYHALL AC # 3), 3 parts acid acceptor (Kyowa Chemical Industry: DHT-4A-2), 1 part cross-linking agent (Tsurumi Chemical Industry: powdered sulfur) .5 parts, 1.5 parts of accelerator (Ouchi Shinsei Chemical Industry: Noxeller DM), 0.5 part of accelerator (Ouchi Shinsei Chemical Industry: Noxeller TS), accelerator aid (Hakusui Tech: zinc oxide) A rubber composition was prepared by kneading 3 parts with a closed kneader at 80 ° C. for 3 to 5 minutes.
The resulting rubber composition was extruded through a die of an extruder into a long cylindrical shape having an outer diameter of 10.5 mm and an inner diameter of 3.5 mm, and foamed and crosslinked in water vapor at 150 ° C. and 6.0 MPa for 60 minutes. A cylindrical foamed elastic layer was produced. The outer diameter and inner diameter of the foamed elastic layer were about Φ15.0 mm and about Φ4.0 mm, respectively.

Comparative Example 2
<< Conductive Foam Elastic Layer Used in Comparative Example 2 >>
70 parts of epichlorohydrin rubber (Nippon ZEON: HYDRIN, T3108), 30 parts of acrylonitrile butadiene rubber (Nippon ZEON: DN401LL), carbon black as a conductive agent (Mitsubishi Chemical: Diamond Black I) 20 parts, 4 parts foaming agent (Eiwa Chemical Industries: VINYHALL AC # 3), 3 parts acid acceptor (Kyowa Chemical Industry: DHT-4A-2), 1 part cross-linking agent (Tsurumi Chemical Industry: powdered sulfur) .5 parts, 1.5 parts of accelerator (Ouchi Shinsei Chemical Industry: Noxeller DM), 0.5 part of accelerator (Ouchi Shinsei Chemical Industry: Noxeller TS), accelerator aid (Hakusui Tech: zinc oxide) A rubber composition was prepared by kneading 3 parts with a closed kneader at 80 ° C. for 3 to 5 minutes.
The resulting rubber composition was extruded through a die of an extruder into a long cylindrical shape having an outer diameter of 10.5 mm and an inner diameter of 3.5 mm, and foamed and crosslinked in water vapor at 150 ° C. and 6.0 MPa for 60 minutes. A cylindrical foamed elastic layer was produced. The outer diameter and inner diameter of the foamed elastic layer were about Φ15.0 mm and about Φ4.0 mm, respectively.

Comparative Example 3
<< Conductive Foam Elastic Layer Used in Comparative Example 3 >>
80 parts of epichlorohydrin rubber (Nippon ZEON: HYDRIN, T3108), 20 parts of acrylonitrile butadiene rubber (Nippon ZEON: DN401LL), carbon black as a conductive agent (Mitsubishi Chemical: Diamond Black I) 20 parts, 4 parts foaming agent (Eiwa Chemical Industries: VINYHALL AC # 3), 3 parts acid acceptor (Kyowa Chemical Industry: DHT-4A-2), 1 part cross-linking agent (Tsurumi Chemical Industry: powdered sulfur) .5 parts, 1.5 parts of accelerator (Ouchi Shinsei Chemical Industry: Noxeller DM), 0.5 part of accelerator (Ouchi Shinsei Chemical Industry: Noxeller TS), accelerator aid (Hakusui Tech: zinc oxide) A rubber composition was prepared by kneading 3 parts with a closed kneader at 80 ° C. for 3 to 5 minutes.
The resulting rubber composition was extruded through a die of an extruder into a long cylindrical shape having an outer diameter of 10.5 mm and an inner diameter of 3.5 mm, and foamed and crosslinked in water vapor at 150 ° C. and 6.0 MPa for 60 minutes. A cylindrical foamed elastic layer was produced. The outer diameter and inner diameter of the foamed elastic layer were about Φ15.0 mm and about Φ4.0 mm, respectively.

<Preparation of the charging roller of Examples 1, 2 and Comparative Examples 1-3>
The obtained cylindrical foamed elastic layer was cut into a predetermined length to form a roller body. A metallic (SUS) conductive support having an outer diameter of 6 mmΦ and a length of 240 mm, having a surface coated with a conductive adhesive, was press-fitted into the cylinder of the roller main body, and the roller main body and the conductive support were fixed.
Unnecessary end foam layer was cut, and the outer peripheral surface was ground with a cylindrical grinder to produce a roller with a conductive foam elastic layer having an outer diameter of 12.0 mm.

Finally, the “seamless tube to be a conductive coating layer” prepared in <Preparation of conductive coating layer> was coated on the roller with the conductive foamed elastic layer, and a charging roller as shown in FIG. 1 was prepared. . The specific resistance (resistivity) of the conductive foamed elastic layer and the conductive coating layer was 10 ⁵ Ω · cm and 10 ⁶ Ω · cm, respectively.

Comparative Example 4
<Charging roller used in Comparative Example 4>
A charging roller comprising a conductive foamed elastic layer in which carbon black was added to EPDM and a conductive coating layer of butadiene rubber (silica blend, PMMA coat) having a thickness of 0.5 mm was used.

<Measurement example>
<< Measurement Method of Dynamic Viscoelasticity >>
The conductive foamed elastic layer of the charging roller obtained in Examples and Comparative Examples was cut into strips, and a sample 5 for dynamic viscoelasticity measurement was set as shown in FIG. 2, and a rheometer MCR302 (manufactured by Anton Paar) was used. The dynamic viscoelasticity was measured under the following conditions.
-Strain: 0.05%
・ Measurement temperature: -80 ℃ ～ 0 ℃ (in increments of 5 ℃)
・ Measurement frequency: 0.1 to 10 Hz at each measurement temperature (measurement of 5 points per digit)
Normal force: -0.3N

  The shift factor αT and the master curve were obtained by fitting the obtained results using the WLF equation based on the time-temperature conversion rule. The master curve is shifted by the shift factor at each temperature, and “storage elastic modulus G ′ and loss tangent tan δ at a frequency corresponding to charging sound” at each specified temperature (described in Table 1) is extracted. The parameter G ′ / tan δ which is

<< Method for measuring charging sound >>
The charging sound of the charging roller obtained in the examples and comparative examples was performed by the following method. Each charging roller was attached to a commercially available laser printer (AC voltage applied with a peak-to-peak voltage of 2 kV / 1600 Hz), and the charging noise when actually operating was measured. A digital camera was fixed at a location 30 cm away, and a live-action scene was shot on the spot.
Thereafter, sound data was extracted from the image data, a peak value corresponding to the frequency of the charged sound was read, and the determination was made according to the following criteria.

<< Criteria for Charging Sound >>
(Double-circle): The peak value of a charging sound is 20 or less, and it does not feel harsh at all.
○: The peak value of the charging sound is larger than 20, but 50 or less, and it does not feel harsh.
(Triangle | delta): The peak value of a charging sound is larger than 50, but is 100 or less, and it feels a little annoying (insufficient level).
X: The peak value of the charging sound is larger than 100 and feels harsh.

<< Image quality and measuring method of charging roller compression deformation >>
The measurement of compression deformation of the charging roller obtained in Examples and Comparative Examples was performed by the following method.
Each charging roller was incorporated into a commercially available process cartridge for a laser printer and left for 1 week in a harsh environment (50 ° C., 90%). Thereafter, the process cartridge was mounted on a laser printer, and it was confirmed whether or not there was an image defect at a position corresponding to the contact position between the charging roller and the photosensitive member, and the image quality was determined according to the following criteria.

<< Judgment criteria for image quality >>
(Double-circle): Image defect is not seen at all.
○: Image defect is not noticeable and does not cause a problem (allowable level).
Δ: Some image defects are observed, and the image level is insufficient.

<Result>
The results of this evaluation test are shown in Table 1. FIG. 3 shows the relationship between G ′ / tan δ and the peak value of the charging sound.

From Table 1, in the charging roller of Example 1, G ′ / tan δ of the conductive foamed elastic layer was 2 MPa or less, and the charging sound was at a sufficiently acceptable level. Further, in the measurement of compression deformation, no image defect corresponding to the contact position with the photosensitive member was confirmed, and the image quality was good.
Also in the charging roller of Example 2, G ′ / tan δ of the conductive foamed elastic layer was 2 MPa or less, and for the same reason, the charging sound was at an acceptable level and there was no problem with compression deformation.

On the other hand, Comparative Example 1 to Comparative Example 3 had no problem in the evaluation of compression deformation, but G ′ / tan δ of the conductive foamed elastic layer did not satisfy 2 MPa or less, and the charged sound was unpleasant and unacceptable. there were.
In Comparative Example 4, G ′ / tan δ of the conductive foamed elastic layer did not satisfy 2 MPa or less, and the evaluation of the charging sound was insufficient. In addition, the thickness of the conductive coating layer, the roller hardness, and the combination thereof (coexistence) do not satisfy the preferred range of the present invention, and there are some problems in the measurement result of compression deformation, and the image quality is “Δ”. there were.

  Since the conductive roller using the specific conductive foamed elastic layer of the present invention achieves reduction of charging sound and does not deteriorate image quality due to compression deformation, it can be used for electrophotography of printers, copiers, printing machines, etc. It is widely used as a charging roller for devices.

DESCRIPTION OF SYMBOLS 1 Conductive support body 2 Conductive foam elastic layer 3 Conductive coating layer 4 Fixed torsion jig 5 Sample for dynamic viscoelasticity measurement (conductive foam elastic layer)

Claims (5)

  An electrophotographic conductive roller having a conductive foamed elastic layer and at least one conductive coating layer thereon provided on a conductive support, wherein the conductive foamed elastic layer is charged at 1 kHz to 20 kHz. A conductive roller for electrophotography, wherein a ratio (G ′ / tan δ) between a storage elastic modulus G ′ and a loss tangent tan δ measured by dynamic viscoelasticity at a frequency corresponding to sound is 2 MPa or less.   The conductive coating layer provided on the conductive foamed elastic layer has a thickness of 0.05 mm to 0.25 mm, and as an electrophotographic conductive roller, the Asker C roller hardness at a load of 500 g is 40 °. The electrophotographic conductive roller according to claim 1, which is ˜60 °.   The electrophotographic conductive roller according to claim 1, wherein the electrophotographic conductive roller is an electrophotographic charging roller.   The electrophotographic conductive roller mounted on the electrophotographic apparatus main body is in contact with the surface of the electrophotographic photosensitive member, and the conductive roller charges the electrophotographic photosensitive member by applying a voltage containing an AC component. The electroconductive roller for electrophotography according to claim 1, wherein the electroconductive roller is an electroconductive roller.   5. A method of using an electrophotographic conductive roller using the electrophotographic conductive roller according to claim 1, wherein the electrophotographic photosensitive member is mounted on an electrophotographic apparatus main body. A method of using a conductive roller for electrophotography, wherein the electrophotographic photosensitive member is charged by being brought into contact with the surface of the substrate and applying a voltage containing an alternating current component.

Images