Conductive rolls, transfer devices, process cartridges, and image forming apparatuses

Abstract

To provide a conductive roll that is used to press its outer peripheral surface against an opposing roll to form an insertion part into which a recording medium is inserted and transfer an image to the recording medium at the insertion part, and can easily increase the parallelism of the image transferred to the recording medium and is excellent in electrification maintainability.SOLUTION: A conductive roll has a support member, an elastic layer arranged on an outer peripheral surface of the support member, and a surface layer arranged on an outer peripheral surface of the elastic layer. The elastic layer includes a cylindrical elastic foam and a conductive coating layer that covers an exposed surface of the elastic foam, and has a volume resistance value of 105 Ω or less at the application of a voltage of 10 V. The content of conductive particles in the elastic foam is 1 mass% or less based on the total mass of the elastic foam.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a conductive roll, a transfer device, a process cartridge, and an image forming apparatus .

Background Art

[0002] Patent Document 1 discloses a semiconductive member containing an alkali metal salt represented by the following general formula (1) in a surface layer thereof. (M)n n ·X···(1) provided that n is equal to the anionic valence of X. M: Na + , K + , Li + X: Cl - , Br - , I - , F - , CH3COO - , CF3COO - , CH(COOH)CHCOO - , (CHCOO - )2, CH2(COOH)CH2COO - , (CH2COO - )2, (HOOC)Ar(COO - ), Ar(COO - )2, (HOOC)2Ar(COO - ), (HOOC)Ar(COO - )2, Ar(COO - )3, (HOOC)3Ar(COO - ), (HOOC)2Ar(COO - )2, (HOOC)Ar(COO - )3, Ar(COO - )4, Ar-SO3 - , Ar(SO3 - )2, an oligomer or polymer having an acrylic acid anion unit, or an oligomer or polymer having a methacrylic acid anion unit Ar represents a benzene ring, a naphthalene ring, or a biphenyl ring.

Prior Art Literature

[0003] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2010-139832 Summary of the Invention Problem to be Solved by the Invention

[0004] The present disclosure relates to a conductive roll used for pressing an outer peripheral surface against an opposing roll to form an insertion portion through which a recording medium is inserted, and transferring an image onto the recording medium at the insertion portion, wherein the content of conductive particles in an elastic foam constituting an elastic layer is more than 1% by mass relative to the total mass of the elastic foam, and the volume resistance value of the elastic layer when a voltage of 10 V is applied is 10 5 An object of the present invention is to provide a conductive roll that更容易 improves the parallelism of an image transferred onto a recording medium and is excellent in charge retention property, compared to a case where the volume resistance value is Ω or less. Means for Solving the Problem

[0005] Specific means for solving the above problem include the following aspects.

[0006] <1> A conductive roll comprising: a support member; an elastic layer disposed on an outer peripheral surface of the support member; and a surface layer disposed on an outer peripheral surface of the elastic layer,[ ] the elastic layer comprises a cylindrical elastic foam and a conductive coating layer that covers an exposed surface of the elastic foam, and has a volume resistance value of 10 when a voltage of 10 V is applied 5 Ω or less,[ ] wherein a content of conductive particles in the elastic foam is 1% by mass or less relative to a total mass of the elastic foam.

[0007] <2> The surface layer comprises: an intermediate layer disposed on an outer peripheral surface of the elastic layer; and a outermost surface layer disposed on an outer peripheral surface of the intermediate layer,[ ] a volume resistance value of the intermediate layer when a voltage of 50 V is applied is 10 4 Ω or more and 10 10It is less than or equal to Ω, <1> The conductive roll described above. <3> The intermediate layer contains an ion conductive agent. <2> The conductive roll described above. <4> The volume resistance when a voltage of 1000V is applied is 10 4 Ω or more 10 12 It is less than or equal to Ω. <1> ~ <3> A conductive roll as described in one of the following. <5> The ratio (Y / X) of the thickness Y of the elastic layer to the total thickness X of the elastic layer and the surface layer is 0.66 or more and 0.95 or less. <1> ~ <4> A conductive roll as described in one of the following. <6> The elastic foam has an open-cell structure, <1> ~ <5> A conductive roll as described in one of the following. <7> The density of the elastic foam is 35 kg / m³. 3 More than 90kg / m 3 It is less than or equal to %. <6> The conductive roll described above. <8> The rebound stress of the elastic layer when compressed by 10% is 12 kPa or less. <1> ~ <7> A conductive roll as described in one of the following.

[0008] <9> <1> ~ <8> A transfer apparatus comprising a conductive roll as described in any one of the following. <10> Image holder and <9> A process cartridge comprising the transfer apparatus described above, which is attached to and detached from an image forming apparatus. <11> Image holder and, A charging device for charging the surface of the image holder, An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the charged image holder, A developing apparatus that develops an electrostatic latent image formed on the surface of an image holder using a developer containing toner to form a toner image, The toner image is transferred to the surface of the recording medium. <9> The transfer apparatus described above, An image forming apparatus equipped with the following features. [Effects of the Invention]

[0009] <1> According to the invention, a conductive roll is used to press its outer surface against an opposing roll, form an insertion portion for inserting a recording medium, and transfer an image to the recording medium at the insertion portion, wherein the content of conductive particles in the elastic foam constituting the elastic layer is more than 1% by mass relative to the total mass of the elastic foam, and the volume resistivity of the elastic layer when a voltage of 10V is applied is 10 5 Compared to cases where the resistance is Ω or less, a conductive roll is provided that makes it easier to improve the parallelism of the image transferred to the recording medium and also has excellent charge retention properties.

[0010] <2> According to the invention, the surface layer is composed of an intermediate layer disposed on the outer surface of the elastic layer and a surface layer disposed on the outer surface of the intermediate layer, and the volume resistivity of the intermediate layer when a voltage of 50V is applied is 10 10 A conductive roll is provided that exhibits superior charge retention compared to cases with a resistance of Ω or higher. <3> According to the invention, a conductive roll is provided that exhibits superior resistance uniformity and charge retention compared to a case where the intermediate layer contains an electronically conductive agent. <4> According to the invention, the volume resistance value when a voltage of 1000V is applied is 10 4 Less than Ω or 10 12 Compared to cases where the resistance is greater than Ω, a conductive roll is provided that makes it easier to increase the parallelism of the image transferred to the recording medium and also has excellent charge retention properties. <5> According to the invention, a conductive roll is provided that makes it easier to increase the parallelism of the image transferred to the recording medium and has excellent charge retention compared to the case where the ratio (Y / X) is less than 0.66. <6> According to the invention, a conductive roll is provided that makes it easier to improve the parallelism of the image transferred to the recording medium compared to the case where the elastic foam has a closed-cell structure. <7> According to the invention relating to this invention, the density of the elastic foam is 35 kg / m³ 3 Less than 90 kg / m 3 Compared to the case of a non-conductive roll, a conductive roll is provided that makes it easier to increase the parallelism of the image transferred to the recording medium and also has excellent charge retention properties. <8> According to the invention, a conductive roll is provided that makes it easier to improve the parallelism of the image transferred to the recording medium compared to the case where the elastic layer has a rebound stress of more than 12 kPa when compressed by 10%.

[0011] <9> , <10> , or <11> According to the invention, a conductive roll is used to press its outer surface against an opposing roll, form an insertion portion for inserting a recording medium, and transfer an image to the recording medium at the insertion portion, wherein the content of conductive particles in the elastic foam constituting the elastic layer is more than 1% by mass relative to the total mass of the elastic foam, and the volume resistivity of the elastic layer when a voltage of 50V is applied is 10 3 A transfer apparatus, process cartridge, or image forming apparatus is provided that has a conductive roll that makes it easier to increase the parallelism of the image transferred to the recording medium and has excellent charge retention compared to the case where the value is Ω or less. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram illustrating the parallelism of an image transferred to a recording medium. [Figure 2] This is a schematic perspective view showing an example of a conductive roll according to this embodiment. [Figure 3] This is a schematic cross-sectional view showing an example of a conductive roll according to this embodiment, and is a cross-sectional view AA of Figure 2. [Figure 4] This is a schematic diagram showing an example of an image forming apparatus according to this embodiment. [Figure 5] This is a schematic diagram showing another example of the image forming apparatus according to this embodiment. [Modes for carrying out the invention]

[0013] The embodiments of this disclosure are described below. These descriptions and embodiments are illustrative and do not limit the scope of the embodiments.

[0014] In this disclosure, the numerical range indicated using "~" represents a range that includes the numbers before and after "~" as the minimum and maximum values, respectively.

[0015] In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples.

[0016] In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved.

[0017] When embodiments are described in this disclosure with reference to the drawings, the configuration of such embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the sizes of the components are not limited thereto.

[0018] In this disclosure, each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition in this disclosure, if there are multiple types of the substance corresponding to each component in the composition, it means the total amount of those multiple types of substances present in the composition unless otherwise specified.

[0019] <Conductive Roll> The conductive roll according to this embodiment comprises a support member, an elastic layer disposed on the outer circumferential surface of the support member, and a surface layer disposed on the outer circumferential surface of the elastic layer, wherein the elastic layer is composed of a cylindrical elastic foam and a conductive coating layer covering the exposed surface of the elastic foam, and the volume resistivity when a voltage of 10V is applied is 10 5 The conductive roll has a capacitance of Ω or less, and the content of conductive particles in the elastic foam is 1% by mass or less relative to the total mass of the elastic foam.

[0020] The conductive roll according to this embodiment is not particularly limited in its application, as long as it is a conductive roll used to press its outer surface against an opposing roll, form an insertion portion for inserting a recording medium, and transfer an image to the recording medium through the insertion portion. In other words, the conductive roll according to this embodiment is used to press its outer surface against an opposing roll, to insert a recording medium through the pressing area which serves as an insertion portion, and to transfer an image to the recording medium through this insertion portion. The conductive roll according to this embodiment is suitably used, for example, as a transfer roll in an electrophotographic image forming apparatus. However, the applications of the conductive roll according to this embodiment are not limited to those described above, and include charging rolls, developing rolls, paper feeding rolls, and the like.

[0021] When the outer surface of a conductive roll is pressed against an opposing roll to form an insertion section through which a recording medium is inserted, and an image is transferred to the recording medium through this insertion section, the parallelism of the image transferred to the recording medium may decrease. Here, the parallelism of the transferred image refers to the degree of parallelism of the image with respect to the direction perpendicular to the transport direction of the recording medium P in the insertion section (arrow Y direction in Figures 1(a) and (b)) (arrow X direction in Figures 1(a) and (b)). Specifically, the parallelism of the transferred image refers to, for example, when attempting to form a rectangular image G1 on the recording medium P, as shown in Figure 1(a), composed of sides parallel to each side of the recording medium P, the line image length L at one end in the direction of arrow X (labeled Front in Figure 1), as shown in Figure 1(b), which is generated in the image G2 actually transferred onto the recording medium P. Front The line image length L at the other end (labeled "Rear" in Figure 1) Rear The difference ΔL(=L) Front -L Rear This is shown by ).

[0022] One method for correcting the above ΔL is to adjust the amount the conductive roll is pressed against the opposing roll at both ends in the axial direction of the conductive roll, thereby creating a difference in the amount of recording medium transported in a direction perpendicular to the transport direction of the recording medium. In the case of conventional conductive rolls, the elastic foam constituting the elastic layer contains many conductive particles, resulting in high hardness of the elastic layer, and thus the correction of ΔL using the above method was insufficient.

[0023] In the conductive roll according to this embodiment, the content of conductive particles in the elastic foam is 1% by mass or less relative to the total mass of the elastic foam. This is presumed to result in a lower hardness of the elastic layer, making it easier to correct ΔL using the method described above and thus easier to improve the parallelism of the image transferred to the recording medium. Furthermore, the conductive roll according to this embodiment has an elastic layer in which the exposed surface of the elastic foam is covered with a conductive coating layer. With an elastic layer of this configuration, the increase in hardness and Young's modulus can be suppressed compared to when conductive particles (e.g., carbon black) are added to the elastic foam, so it is presumed that a large amount of conductive particles can be incorporated, and the charge retention properties are also excellent.

[0024] The conductive roll according to this embodiment will be described with reference to the drawings. Figure 2 is a schematic perspective view showing an example of a conductive roll according to this embodiment. Figure 3 is a cross-sectional view AA of Figure 2, which is a cross-sectional view of the conductive roll shown in Figure 2, cut radially.

[0025] As shown in Figure 2, the conductive roll 100 is a roll member comprising a cylindrical support member 110 and a layered material 120, including an elastic layer and a surface layer, disposed on the outer circumferential surface of the support member 110. Furthermore, as shown in Figure 3, the layer structure of the conductive roll 100 includes an elastic layer 122 disposed on the outer circumferential surface of the cylindrical support member 110, an intermediate layer 124 disposed on the outer circumferential surface of the elastic layer 122, and a surface layer 126 disposed on the outer circumferential surface of the intermediate layer 124. In the conductive roll according to this embodiment, the surface layer is composed of the intermediate layer 124 and the surface layer 126. The conductive roll according to this embodiment is not limited to the configuration shown in Figures 2 and 3. For example, adhesive layers may be appropriately provided between the support member 110 and the elastic layer 122, between the elastic layer 122 and the intermediate layer 124, and between the intermediate layer 124 and the surface layer 126.

[0026] The following describes the materials of each layer constituting the conductive roll according to this embodiment.

[0027] [Support member] In the conductive roll according to this embodiment, the support member can be any member that functions as a support member for the conductive roll. The support member may be a hollow member (i.e., a cylindrical member) or a solid member (i.e., a columnar member). Furthermore, when forming an electric field between a conductive roll and an opposing roll, it is preferable that the support member be a conductive support member.

[0028] Examples of conductive support members include metal members such as iron (free-cutting steel, etc.), copper, brass, stainless steel, aluminum, and nickel; resin members or ceramic members with a plated outer surface; and resin members or ceramic members containing a conductive agent.

[0029] The outer diameter of the support member should be determined according to the application of the conductive roll. For example, if the conductive roll according to this embodiment is a secondary transfer roll, the outer diameter of the support member may be 3 mm or more and 30 mm or less.

[0030] [Elastic layer] In the conductive roll according to this embodiment, the elastic layer comprises a cylindrical elastic foam and a conductive coating layer that covers the exposed surface of the elastic foam. Furthermore, the content of conductive particles in the elastic foam is 1% by mass or less relative to the total mass of the elastic foam.

[0031] (Elastic foam) The elastic foam that constitutes the elastic layer is a foam containing an elastic material (also called a rubber material).

[0032] Examples of elastic materials include isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, polyurethane, silicone rubber, fluororubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer rubber, ethylene-propylene-diene terpolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), natural rubber, and rubbers made by mixing these materials.

[0033] Examples of foaming agents for obtaining elastic foams include water; azo compounds such as azodicarbonamide, azobisisobutyronitrile, and diazoaminobenzene; benzenesulfonyl hydrazides such as benzenesulfonyl hydrazide, 4,4'-oxybisbenzenesulfonyl hydrazide, and toluenesulfonyl hydrazide; bicarbonates such as sodium bicarbonate that generate carbon dioxide gas by thermal decomposition; mixtures of NaNO2 and NH4Cl that generate nitrogen gas; and peroxides that generate oxygen. To obtain a foamed elastic layer, foaming aids, foam stabilizers, catalysts, etc., may be used as needed.

[0034] The content of conductive particles in the elastic foam is 1% by mass or less, preferably 0.5% by mass or less, and more preferably 0% by mass, relative to the total mass of the elastic foam. In other words, the fewer conductive particles in the elastic foam, the better. Even if the elastic foam contains conductive particles, the content of the conductive particles must be 1% by mass or less relative to the total mass of the elastic foam.

[0035] Examples of conductive particles in conductive foam include electronically conductive agents. Examples of electronically conductive agents include powders such as carbon black (e.g., Ketjenblack, acetylene black); pyrolytic carbon, graphite; metals or alloys such as aluminum, copper, nickel, and stainless steel; conductive metal oxides such as tin oxide, indium oxide, titanium oxide, tin oxide-antimony oxide solid solution, and tin oxide-indium oxide solid solution; and materials obtained by treating the surface of an insulating material to make it conductive. Within the above-mentioned range of content, the electronically conductive agent may be used alone or in combination of two or more types.

[0036] Other additives include, for example, known materials that can be added to elastic materials, such as ionic conductive agents, softeners, plasticizers, curing agents, vulcanizing agents, vulcanization accelerators, antioxidants, surfactants, coupling agents, and fillers (silica, calcium carbonate, etc.). Furthermore, if the elastic foam contains granular materials such as the conductive particles and fillers mentioned above, the hardness of the elastic layer increases, and the effect of improving the parallelism of the image transferred to the recording medium tends to decrease. For this reason, it is preferable to have as few granular materials as possible in the elastic foam, and even if the elastic foam contains granular materials, it is preferable that the total content of the granular materials be 1% by mass or less relative to the total mass of the elastic foam.

[0037] In elastic foams, a continuous cell structure is more preferable from the viewpoint of ease of forming a conductive coating layer and from the viewpoint of easily improving the parallelism of the image transferred to the recording medium. Here, an open-cell structure refers to a structure in which adjacent cells (i.e., bubbles) are connected, and a portion of the connected cells is exposed (open) on the surface. Furthermore, the elastic foam is preferable to have a low closed-cell ratio, and the closed-cell ratio is preferably, for example, 50% or less (more preferably 30% or less).

[0038] From the viewpoint of ease of forming a conductive coating layer and ease of improving the parallelism of images transferred to the recording medium, the density of the elastic foam should be 35 kg / m². 3 More than 90kg / m 3Preferably, it is 50 kg / m 3 More than 85kg / m 3 It is more preferable that the following is 60 kg / m 3 More than 80kg / m 3 The following is even more preferable:

[0039] Here, the cell diameter (bubble diameter), closed-cell ratio, and density of the elastic foam are determined as follows. First, a cross-section of the elastic layer (elastic foam within the elastic layer) in the thickness direction is prepared using a razor. A total of four cross-sections are prepared, parallel to the axial direction of the conductive roll and at 90° intervals in the circumferential direction. The axial center of the cross-section is photographed with a laser microscope (Keyence Corporation, VK-X200) to acquire an image. The image is analyzed with image analysis software (Media Cybernetics Corporation, Image-Pro Plus) to measure the maximum diameter and area of ​​the cells (bubbles). Furthermore, if the elastic foam layer has an open-cell structure, the continuity (connection) state of the cells (bubbles) is estimated from the shape of the open cells, each connected cell is virtually separated, and the maximum diameter of the separated cell is determined. That is, if the open cell is estimated to be, for example, a shape of five connected bubbles, the five cells are virtually separated into five, and the maximum diameter of the five separated cells is measured. The cell diameter is determined by calculating the arithmetic mean of the largest diameters of 100 randomly selected cells in the analyzed cross-sectional image, and then calculating the arithmetic mean of the four cross-sections based on the obtained value. The closed-cell ratio is calculated as (total area of ​​closed cells in the analyzed cross-sectional image) / (total area of ​​cells in the analyzed cross-sectional image × 100). Here, a closed-cell bubble is defined as a bubble in the cross-sectional image that is entirely surrounded by walls. Density is measured as follows: The elastic layer (elastic foam within the elastic layer) is cut using a razor to create a cube. Making the foam as large as possible allows for more accurate measurements. Next, the length, width, and height of the cube are measured to calculate its volume, its mass is measured, and its density is determined by dividing its mass by its volume.

[0040] -Formation of elastic foam- There are no particular restrictions on the method for forming the cylindrical elastic foam, and known methods can be used. For example, one method involves preparing a composition containing an elastic material, a foaming agent, and other components used as needed (e.g., a vulcanizing agent), extruding the composition into a cylindrical shape, and then heating the molded product to vulcanize and foam it; or cutting a cylindrical shape from a large foam mass. Alternatively, after forming a cylindrical elastic foam, a central hole for inserting a support member may be formed to obtain a cylindrical elastic foam. Furthermore, after obtaining the cylindrical elastic foam, the shape may be further refined or post-processing such as surface polishing may be performed as needed.

[0041] (Conductive coating layer) The conductive coating layer constituting the elastic layer is a conductive layer that covers the exposed surface of the elastic foam (i.e., the contact surface of the elastic foam with the atmosphere, including the inner circumferential surface, outer circumferential surface, and cell wall surface of the cylindrical elastic foam). The exposed surface of the elastic foam may be entirely covered with a conductive coating layer, or only partially covered.

[0042] The conductive coating layer is formed using a processing solution containing a conductive agent and a resin. Examples of conductive agents used in the processing solution include electronic conductive agents and ionic conductive agents, with electronic conductive agents being preferred. The conductive agent contained in the processing solution may be one type or two or more types. Here, examples of electronically conductive agents are the same as those contained in elastic foams, and preferred embodiments are also the same.

[0043] The resin used in the processing solution is not particularly limited as long as it can form a coating layer on the exposed surface of the elastic foam, and examples include acrylic resin, urethane resin, fluororesin, and silicone resin. These resins are preferably used as latex. Examples of latex include, in addition to the resin latex mentioned above, natural rubber latex, butadiene rubber latex, acrylonitrile-butadiene rubber latex, acrylic rubber latex, polyurethane rubber latex, fluororubber latex, and silicone rubber latex.

[0044] The processing solution preferably contains a conductive agent, a resin, and water, that is, an aqueous dispersion containing a conductive agent and a resin. The concentrations of the conductive agent and resin in the processing solution should be determined according to the ease of forming the conductive coating layer, the required resistance value of the elastic layer, and other factors.

[0045] -Formation of conductive coating layer- The conductive coating layer is formed by applying a treatment solution to the elastic foam and then heating and drying it. Methods for applying the treatment solution to the elastic foam include applying the treatment solution to the elastic foam by spray coating or the like, and immersing the elastic foam in the treatment solution. These methods allow the treatment solution to penetrate the surface and interior of the bubbles in the elastic foam. Subsequently, the applied treatment solution is dried by heating or other means to form a conductive coating layer.

[0046] As the conductive coating layer, for example, a coating layer and a method for forming the same described in Japanese Patent Publication No. 2009-244824 may be used.

[0047] As described above, the elastic layer of the conductive roll according to this embodiment is formed by forming a conductive coating layer on the exposed surface of the elastic foam.

[0048] (Volume resistivity of the elastic layer) In the conductive roll according to this embodiment, the volume resistivity of the elastic layer when a voltage of 10V is applied is 10 5 It is less than or equal to Ω, and 1Ω or more and 10 4 Preferably, it is less than or equal to Ω, and 10Ω or more. 3 It is even more preferable that it be less than or equal to Ω.

[0049] Here, the volume resistivity of the elastic layer is measured as follows. First, a roll member is fabricated with the elastic layer to be measured on the outer circumference of a conductive support member, and the volume resistivity of the elastic layer is measured using the obtained roll member. Note that if the conductive roll according to this embodiment includes a conductive support member, the roll member obtained by peeling off the surface layer from such a conductive roll may also be measured. The roll member is placed on a metal plate such as a copper plate, with a load of 500g applied to each end of the roll member. A voltage of 10V (V) is applied between the conductive support member of the roll member and the metal plate using a microcurrent measuring instrument (Advantest R8320), and the current value I(A) after 5 seconds is read and calculated using the following formula. Formula: Volume resistivity Rv(Ω) = V / I The measurements will be taken under conditions of 22°C and 55% RH humidity.

[0050] (Young's modulus of the elastic layer) In the conductive roll according to this embodiment, it is preferable that the elastic layer is soft, from the viewpoint of easily increasing the parallelism of the image transferred to the recording medium. Specifically, the Young's modulus of the elastic layer is preferably 150 kPa or less, and more preferably 35 kPa or more and 150 kPa or less.

[0051] Here, the Young's modulus of the elastic layer is measured as follows. The method for measuring the Young's modulus of each layer basically conforms to ISO 527. For the intermediate layer and elastic layer, dumbbell-shaped tensile test specimens with a gauge spacing of 50 mm and a thickness of 5 mm were prepared. The stress (σ)-strain (ε) curves were determined at a tensile speed of 5 mm / min using a benchtop precision universal testing machine (AGS-X; manufactured by Shimadzu Corporation), and the stress at 0.05% to 0.25% strain was measured. Young's modulus was then determined from Δσ / Δε. For the Young's modulus of the surface layer, a dumbbell-shaped tensile test specimen with a thickness of 0.2 mm is prepared and used; otherwise, it can be determined using the same method as for measuring the Young's modulus of the intermediate layer and the elastic layer.

[0052] (Rebound stress when the elastic layer is compressed by 10%) In the conductive roll according to this embodiment, the rebound stress when the elastic layer is compressed by 10% is preferably 15 kPa or less, more preferably 10 kPa or less, even more preferably 9 kPa or less, and particularly preferably 1 kPa or more and 9 kPa or less, from the viewpoint of easily improving the parallelism of the image transferred to the recording medium.

[0053] In this embodiment, the rebound stress when the elastic layer is compressed by 10% shall be measured by the following method. The rebound stress at 10% compression was measured according to JIS K 6400-2(2004) Method B, and the value obtained from the SS curve during indentation was taken as the value at 10% compression.

[0054] (Thickness of the elastic layer) In the conductive roll according to this embodiment, the thickness of the elastic layer may be determined according to the application of the conductive roll. For example, if the conductive roll according to this embodiment is a secondary transfer roll, the thickness of the elastic layer may be 1 mm or more and 10 mm or less.

[0055] Furthermore, in the conductive roll according to this embodiment, a thicker elastic layer is preferable from the viewpoint of easily increasing the parallelism of the image transferred to the recording medium. Specifically, the ratio of the thickness Y of the elastic layer to the total thickness X of the elastic layer and surface layer (Y / X) is preferably 0.66 or more and 0.95 or less, and more preferably 0.75 or more and 0.92 or less.

[0056] [Surface layer] In the conductive roll according to this embodiment, a surface layer is arranged on the outer circumferential surface of the elastic layer. The surface layer is the outermost layer of the conductive roll and consists of one or more layers. In particular, in the conductive roll according to this embodiment, it is preferable that the surface layer comprises an intermediate layer disposed on the outer circumferential surface of the elastic layer and a surface layer disposed on the outer circumferential surface of the intermediate layer.

[0057] (Middle class) The intermediate layer is a layer placed on the outer surface of the elastic layer. The intermediate layer is a layer that contributes to adjusting the resistance of the conductive roll, and the volume resistivity of the intermediate layer, which is placed on the outer surface of the elastic layer, when a voltage of 100V is applied is 10 4 Ω or more 10 10 Ω or less (more preferably 10) 6 Ω or more 10 9 It is preferable that the value is less than or equal to Ω. The volume resistivity of the intermediate layer is measured using the same method as the volume resistivity of the elastic layer.

[0058] The intermediate layer preferably contains a conductive agent in order to achieve the above-mentioned volume resistivity. Both electronic and ionic conductive agents can be used as conductive agents, but among them, ionic conductive agents are preferred from the viewpoint of improving charge retention. In other words, it is preferable that the intermediate layer contains an ionic conductive agent. The ionic conductive agent may be used individually or in combination of two or more types.

[0059] Examples of ionic conductive agents included in the intermediate layer include quaternary ammonium salts (e.g., lauryltrimethylammonium, stearyltrimethylammonium, octadodecyltrimethylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, or perchlorates, chlorates, hydrofluoric acid salts, sulfates, ethosulfate salts, benzyl bromide salts or benzyl chloride salts of modified fatty acid dimethylethylammonium), aliphatic sulfonates, higher alcohol sulfate esters, higher alcohol ethylene oxide-added sulfate esters, higher alcohol phosphate esters, higher alcohol ethylene oxide-added phosphate esters, betaine, higher alcohol ethylene oxide, polyethylene glycol fatty acid esters, polyhydric alcohol fatty acid esters, and the like.

[0060] Furthermore, the ion conductive agent may be a polymer material having ion conductivity, such as epichlorohydrin rubber, epichlorohydrin-ethylene oxide copolymer rubber, or epichlorohydrin-ethylene oxide-allyl glycidyl ether ternary copolymer rubber. Furthermore, the ionic conductive agent may be a compound in which an ionic conductive agent is bonded to the ends of a polymer material such as a resin.

[0061] The amount of ionic conductive agent should be within a range that allows the above-mentioned volume resistivity to be achieved. Furthermore, if the intermediate layer contains a binder material, the content of the ion conductive agent is preferably 0.1 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.5 parts by mass or more and 3.0 parts by mass or less, per 100 parts by mass of the binder material.

[0062] The intermediate layer may contain a binder material in addition to the ionic conductive agent. There are no particular restrictions on the binding material, and examples include resins and elastic materials that can form an intermediate layer. Examples of resins used for the intermediate layer include urethane resins, acrylic resins, epoxy resins, and silicone resins.

[0063] The intermediate layer may contain other additives depending on the required physical properties of the intermediate layer.

[0064] (Young's modulus of the middle class) The Young's modulus of the intermediate layer is preferably 5 MPa or higher, and more preferably 5 MPa to 10 MPa. The Young's modulus of the intermediate layer is measured using the same method as the Young's modulus of the elastic layer.

[0065] (Thickness of the intermediate layer) In the conductive roll according to this embodiment, the thickness of the intermediate layer can be determined according to the application of the conductive roll, and from the viewpoint of easily improving the parallelism of the image transferred to the recording medium, it is preferable that it be thinner than the elastic layer. Specifically, the thickness of the intermediate layer is preferably 1 / 20 to 1 / 2 of the thickness of the elastic layer, and more preferably 1 / 10 to 1 / 3. For example, if the conductive roll according to this embodiment is a secondary transfer roll, the thickness of the intermediate layer may be 0.5 mm or more and 5 mm or less.

[0066] There are no particular restrictions on the method of forming the intermediate layer. For example, one method involves applying an intermediate layer forming coating solution onto an elastic layer and then drying the resulting coating film.

[0067] (Surface layer) The surface layer is a layer positioned on the outer circumferential surface of the intermediate layer and constitutes the outermost surface of the conductive roll. Since the surface layer comes into contact with the medium, it is preferable that it has release properties.

[0068] The surface layer is preferably a layer containing resin. There are no particular restrictions on the resin included in the surface layer, but examples include urethane resin, polyester resin, phenolic resin, acrylic resin, epoxy resin, and cellulose resin.

[0069] The surface layer preferably contains a conductive agent. Examples of conductive agents included in the surface layer include electronically conductive agents and ionic conductive agents. The electronic conductive agent used in the surface layer is the same as the electronic conductive agent used in the conductive coating layer. Furthermore, the ionic conductive agent used in the surface layer is the same as the ionic conductive agent used in the intermediate layer.

[0070] The surface layer may contain other additives depending on the required physical properties of the surface layer.

[0071] (Young's modulus of the surface layer) The Young's modulus of the surface layer is preferably 10 MPa or more, preferably 10 MPa to 400 MPa, and more preferably 50 MPa to 400 MPa. The Young's modulus of the surface layer is measured using the same method as for the Young's modulus of the elastic layer. However, a dumbbell-shaped tensile test specimen with a thickness of 0.2 mm is used. This dumbbell test specimen is obtained by analyzing the composition of the surface layer of the conductive roll in question, placing a surface layer forming material with the same composition as the composition obtained from the analysis into a highly release resin mold such as polytetrafluoroethylene (PTFE), heat-curing it, and then demolding it.

[0072] (Thickness of the surface layer) In the conductive roll according to this embodiment, the thickness of the surface layer may be determined according to the application of the conductive roll. For example, if the conductive roll according to this embodiment is a secondary transfer roll, the thickness of the surface layer may be 0.01 mm or more and 0.05 mm or less.

[0073] (Volume resistivity of the surface layer) The volume resistance of the surface layer when a voltage of 10V is applied is 10 4 Ω or more 10 14 Preferably it is less than or equal to Ω, 10 5 Ω or more 10 11 It is more preferable that it be less than or equal to Ω.

[0074] The volume resistivity of the surface layer is measured as follows, in accordance with JIS K 6911:1995. First, a single-layer sheet is fabricated using the surface layer material, and the volume resistivity is measured using the obtained single-layer sheet material. A single-layer sheet thickness of 0.2 mm is appropriate. The volume resistivity is calculated by applying a voltage of 10 V between the surface electrode and the back electrode of the single-layer sheet material using a microcurrent measuring instrument (Advantest R8320) between circular electrodes, reading the current value I (A) after 5 seconds, and calculating it using the following formula. Formula: Volume resistivity Rv(Ω) = V / I The measurements will be taken under conditions of 22°C and 55% RH humidity.

[0075] There are no particular restrictions on the method of forming the surface layer. For example, one method involves applying a surface layer forming solution onto the intermediate layer and then drying the resulting coating film.

[0076] [Volume resistivity of conductive rolls] The conductive roll according to this embodiment has a volume resistance of 10 when a voltage of 1000V is applied. 4 Ω or more 10 12 Preferably it is less than or equal to Ω, 10 5 Ω or more 10 11 It is more preferable that it be less than or equal to Ω, 10 6 Ω or more 10 10 It is even more preferable that it be less than or equal to Ω. The volume resistivity of a conductive roll is measured in the same way as the volume resistivity of an elastic layer.

[0077] <Image forming apparatus, transfer apparatus, process cartridges> Figure 4 is a schematic diagram showing a direct transfer type image forming apparatus, which is an example of an image forming apparatus according to this embodiment.

[0078] The image forming apparatus 200 shown in Figure 4 comprises a photoreceptor 207 (an example of an image holder), a charging roll 208 (an example of a charging means) for charging the surface of the photoreceptor 207, an exposure apparatus 206 (an example of a static charge image forming means) for forming a static charge image on the charged surface of the photoreceptor 207, a developing apparatus 211 (an example of a developing means) for developing the static charge image formed on the surface of the photoreceptor 207 as a toner image using a developer containing toner, and a transfer roll 212 (an example of a transfer means, an example of a transfer apparatus according to this embodiment) for transferring the toner image formed on the surface of the photoreceptor 207 to the surface of a recording medium. Here, the conductive roll according to this embodiment is applied to the transfer roll 212, which presses its outer surface against the photoreceptor 207, which corresponds to the opposing roll, and forms an insertion portion through which the recording paper 500 is inserted.

[0079] The image forming apparatus 200 shown in Figure 4 further includes a cleaning device 213 for removing toner remaining on the surface of the photoreceptor 207, a static elimination device 214 for removing static electricity from the surface of the photoreceptor 207, and a fixing device 215 (an example of a fixing means) for fixing the toner image onto a recording medium.

[0080] The charging roll 208 may be charged using a contact charging method or a non-contact charging method. Voltage is applied to the charging roll 208 from the power supply 209.

[0081] The exposure apparatus 206 uses a light source such as a semiconductor laser or an LED (light-emitting diode). One example of an optical device that can be equipped with it is the optical device itself.

[0082] The developing device 211 is a device that supplies toner to the photoreceptor 207. The developing device 211, for example, brings a roll-shaped developer holder into contact with or close to the photoreceptor 207, thereby depositing toner onto the electrostatic image on the photoreceptor 207 and forming a toner image.

[0083] The transfer roll 212 is a transfer roll that is in direct contact with the surface of the recording medium and is positioned opposite the photoreceptor 207. Recording paper 500 (an example of a recording medium) is supplied via a supply mechanism into the gap where the transfer roll 212 and the photoreceptor 207 are in contact. When a transfer bias is applied to the transfer roll 212, an electrostatic force from the photoreceptor 207 toward the recording paper 500 acts on the toner image, and the toner image on the photoreceptor 207 is transferred onto the recording paper 500.

[0084] Examples of fixing devices 215 include a heating fixing device that includes a heating roll and a pressure roll that presses against the heating roll.

[0085] The cleaning device 213 may include a device equipped with cleaning components such as blades, brushes, and rolls.

[0086] The static elimination device 214 is, for example, a device that irradiates light onto the surface of the photoreceptor 207 after transfer to eliminate the residual potential of the photoreceptor 207.

[0087] The photoreceptor 207 and the transfer roll 212 may be integrated into a single housing, for example, in a cartridge structure (process cartridge according to this embodiment) that can be attached to and detached from an image forming apparatus. This cartridge structure (process cartridge according to this embodiment) may further include at least one selected from the group consisting of a charging roll 208, an exposure device 206, a developing device 211, and a cleaning device 213.

[0088] The image forming apparatus may be a tandem-type image forming apparatus in which a photoreceptor 207, a charging roll 208, an exposure device 206, a developing device 211, a transfer roll 212, and a cleaning device 213 are arranged in a single image forming unit, and multiple such image forming units are mounted side by side.

[0089] Figure 5 is a schematic diagram showing an intermediate transfer type image forming apparatus, which is an example of an image forming apparatus according to this embodiment. The image forming apparatus shown in Figure 5 is a tandem type image forming apparatus in which four image forming units are arranged in parallel.

[0090] In the image forming apparatus shown in Figure 5, the transfer means for transferring the toner image formed on the surface of the image holder to the surface of the recording medium is configured as a transfer unit (an example of a transfer apparatus according to this embodiment) comprising an intermediate transfer body, a primary transfer means, and a secondary transfer means. The transfer unit may also be a cartridge structure that can be attached to and detached from the image forming apparatus.

[0091] The image forming apparatus shown in Figure 5 comprises a photoreceptor 1 (an example of an image holder), a charging roll 2 (an example of a charging means) for charging the surface of the photoreceptor 1, an exposure apparatus 3 (an example of a static charge image forming means) for forming a static charge image on the charged surface of the photoreceptor 1, a developing apparatus 4 (an example of a developing means) for developing the static charge image formed on the surface of the photoreceptor 1 as a toner image using a developer containing toner, an intermediate transfer belt 20 (an example of an intermediate transfer body), a primary transfer roll 5 (an example of a primary transfer means) for transferring the toner image formed on the surface of the photoreceptor 1 to the surface of the intermediate transfer belt 20, and a secondary transfer roll 26 (an example of a secondary transfer means) for transferring the toner image transferred to the surface of the intermediate transfer belt 20 to the surface of a recording medium. Here, the conductive roll according to this embodiment is applied to the secondary transfer roll 26, which presses its outer surface against the support roll 27, which corresponds to the opposing roll, and forms an insertion portion through which the recording paper P is inserted.

[0092] The image forming apparatus shown in Figure 5 further comprises a fixing device 28 (an example of fixing means) for fixing the toner image onto a recording medium, a photoreceptor cleaning device 6 for removing toner remaining on the surface of the photoreceptor 1, and an intermediate transfer belt cleaning device 30 for removing toner remaining on the surface of the intermediate transfer belt 20.

[0093] The image forming apparatus shown in Figure 5 includes first to fourth electrophotographic image forming units 10Y, 10M, 10C, and 10K that output images of yellow (Y), magenta (M), cyan (C), and black (K) based on color-separated image data. These image forming units 10Y, 10M, 10C, and 10K are arranged side by side, spaced apart horizontally. Each of the image forming units 10Y, 10M, 10C, and 10K may be a process cartridge that can be attached to and detached from the image forming apparatus.

[0094] An intermediate transfer belt 20 extends above each image forming unit 10Y, 10M, 10C, and 10K, passing through each image forming unit. The intermediate transfer belt 20 is wound around a drive roll 22 and a support roll 24, which are in contact with the inner surface of the intermediate transfer belt 20, and is configured to travel in the direction from the first image forming unit 10Y to the fourth image forming unit 10K. The support roll 24 is subjected to a force moving away from the drive roll 22 by a spring or the like (not shown), and tension is applied to the intermediate transfer belt 20 wound around both. An intermediate transfer belt cleaning device 30 is provided on the image holding surface side of the intermediate transfer belt 20, facing the drive roll 22.

[0095] Each image forming unit 10Y, 10M, 10C, and 10K has a developing unit 4Y, 4M, 4C, and 4K, respectively, which is supplied with yellow, magenta, cyan, and black toner contained in toner cartridges 8Y, 8M, 8C, and 8K.

[0096] Since the first to fourth image forming units 10Y, 10M, 10C, and 10K have equivalent configurations and operations, when describing the image forming units below, the first image forming unit 10Y will be described as representative.

[0097] The first image forming unit 10Y includes a photoreceptor 1Y, a charging roll 2Y for charging the surface of the photoreceptor 1Y, a developing device 4Y for developing the electrostatic charge image formed on the surface of the photoreceptor 1Y as a toner image using a developer containing toner, a primary transfer roll 5Y for transferring the toner image formed on the surface of the photoreceptor 1Y to the surface of the intermediate transfer belt 20, and a photoreceptor cleaning device 6Y for removing toner remaining on the surface of the photoreceptor 1Y after primary transfer.

[0098] The charging roll 2Y charges the surface of the photoreceptor 1Y. The charging roll 2Y may use a contact charging method or a non-contact charging method.

[0099] A laser beam 3Y is shone from the exposure device 3 onto the surface of the charged photoreceptor 1Y. As a result, an electrostatic image of a yellow image pattern is formed on the surface of the photoreceptor 1Y.

[0100] The developing device 4Y contains, for example, an electrostatic image developer including at least yellow toner and a carrier. The yellow toner is triboelectrically charged by being agitated inside the developing device 4Y. As the surface of the photoreceptor 1Y passes through the developing device 4Y, the electrostatic image formed on the photoreceptor 1Y is developed as a toner image.

[0101] The primary transfer roll 5Y is positioned inside the intermediate transfer belt 20 and opposite the photoreceptor 1Y. A bias power supply (not shown) for applying the primary transfer bias is connected to the primary transfer roll 5Y. The primary transfer roll 5Y transfers the toner image on the photoreceptor 1Y onto the intermediate transfer belt 20 by electrostatic force.

[0102] On the intermediate transfer belt 20, toner images of each color are transferred in order from the first to fourth image forming units 10Y, 10M, 10C, and 10K. The intermediate transfer belt 20, on which the toner images of the four colors have been transferred through the first to fourth image forming units, proceeds to a secondary transfer means consisting of a support roll 24 and a secondary transfer roll 26.

[0103] The secondary transfer roll 26 is a transfer roll that is in direct contact with the surface of the recording medium and is positioned outside the intermediate transfer belt 20, facing the support roll 24. Recording paper P (an example of a recording medium) is supplied via a supply mechanism into the gap where the secondary transfer roll 26 and the intermediate transfer belt 20 are in contact. When a secondary transfer bias is applied to the secondary transfer roll 26, an electrostatic force from the intermediate transfer belt 20 toward the recording paper P acts on the toner image, and the toner image on the intermediate transfer belt 20 is transferred onto the recording paper P.

[0104] The recording paper P onto which the toner image has been transferred is fed to the contact section (nip section) of a fixing device 28 consisting of a pair of rolls, and the toner image is fixed onto the recording paper P.

[0105] The toner and developer used in the image forming apparatus according to this embodiment are not particularly limited, and any known electrophotographic toner and developer can be used. The recording medium used in the image forming apparatus according to this embodiment is not particularly limited and includes, for example, paper used in electrophotographic photocopiers and printers; OHP sheets; and the like. [Examples]

[0106] The embodiments of the invention will be described in detail below with reference to examples, but the embodiments of the invention are not limited to these examples.

[0107] [Formation of an elastic layer] Using EP70 (manufactured by Inoac Corporation), which does not contain conductive particles, we polished and molded it into a cylindrical shape with an outer diameter of 26 mm, an inner diameter of 14 mm, and a length of 350 mm to obtain a cylindrical elastic foam (the elastic foam does not contain conductive particles). The resulting elastic foam has an open-cell structure, a cell diameter of 400 μm, and a density of 70 kg / m³. 3 That was the case.

[0108] (Formation of conductive coating layer) As a treatment solution, a conductive treatment solution was obtained by mixing an aqueous dispersion containing 40% by mass of carbon black with an acrylic emulsion (manufactured by Nippon Zeon Co., Ltd., product name "Nipol LX852") in a 1:1 mass ratio. The elastic foam was immersed in the obtained conductive treatment solution at 20°C for 10 minutes. Subsequently, the elastic foam with the treatment solution adhering to it was heated in a curing furnace set to 100°C for 60 minutes to dry it, removing moisture and crosslinking the acrylic resin. The acrylic resin hardened by crosslinking formed a conductive coating layer containing carbon black on the exposed surface of the elastic foam. As described above, an elastic layer was obtained, comprising an elastic foam and a conductive coating layer covering the exposed surface of the elastic foam. Next, a conductive support member (made of stainless steel, 14 mm in diameter) with adhesive applied to its surface was inserted into the resulting elastic layer to form a roll member.

[0109] [Formation of the intermediate layer] A coating solution for forming an intermediate layer was prepared by mixing 70 parts by mass of urethane oligomer (manufactured by Nippon Synthetic Chemical Co., Ltd., urethane acrylate UV3700B), 30 parts by mass of urethane monomer (manufactured by Kyoeisha Chemical Co., Ltd., isomiristyl acrylate), 0.5 parts by mass of polymerization initiator (manufactured by IGM Resins BV, 1-hydroxycyclohexyl phenyl ketone: Omnirad 184 (formerly Irgacure 184)), and 3 parts by mass of alkyltrimethylammonium perchlorate (ionic conductive agent, quaternary ammonium salt, trade name "LXN-30", manufactured by Daiso Co., Ltd.). The prepared coating solution for forming an intermediate layer was applied to an elastic layer using a die coater and rotated while being exposed to UV irradiation at an intensity of 700 mW / cm². 2 The coating was then irradiated with UV light for 5 seconds. This process formed an intermediate layer with a thickness of 1 mm.

[0110] [Formation of the surface layer] A surface layer forming coating solution was obtained by adding 5% by mass of a hardener (WH-1, manufactured by Henkel Japan Ltd.) to a urethane resin paint (EMRALON T-862A, manufactured by Henkel Japan Ltd.) and mixing the mixture. The obtained surface layer forming coating solution was applied to the intermediate layer by spray application, and the coating film was heat-cured at 120°C for 20 minutes to form a surface layer with a thickness of 20 μm.

[0111] As described above, the volume resistivity is 10 6.6 A conductive roll with a resistance of Ω (measured when 1000V is applied) was obtained.

[0112] <Example 2> In forming the elastic layer, a conductive roll 2 was obtained in the same manner as in Example 1, except that an aqueous dispersion containing 25% by mass of carbon black was used to obtain the conductive treatment solution.

[0113] <Example 3> A conductive roll 3 was obtained in the same manner as in Example 1, except that a cylindrical elastic foam was obtained using RR26 low density (manufactured by Inoac Corporation) which does not contain conductive particles, in the formation of the elastic layer.

[0114] <Example 4> A conductive roll 4 was obtained in the same manner as in Example 1, except that a cylindrical elastic foam was obtained using RR26 medium density (manufactured by Inoac Corporation) which does not contain conductive particles, in the formation of the elastic layer.

[0115] <Example 5> A conductive roll 5 was obtained in the same manner as in Example 1, except that a cylindrical elastic foam was obtained using SP80 (manufactured by Inoac Corporation) which does not contain conductive particles, in the formation of the elastic layer.

[0116] <Example 6> A conductive roll 6 was obtained in the same manner as in Example 1, except that a cylindrical elastic foam was obtained using RR90 high density (manufactured by Inoac Corporation) which does not contain conductive particles, in the formation of the elastic layer.

[0117] <Example 7> A conductive roll 7 was obtained in the same manner as in Example 2, except that the amount of alkyltrimethylammonium perchlorate used as an ionic conductive agent in the formation of the intermediate layer was changed to 0.3 parts by mass.

[0118] <Example 8> In forming the elastic layer, a conductive roll 8 was obtained in the same manner as in Example 1, except that an aqueous dispersion containing 15% by mass of carbon black was used to obtain the conductive treatment solution.

[0119] <Example 9> A conductive roll 9 was obtained in the same manner as in Example 1, except that the thickness of the intermediate layer was set to 2.0 mm and the thickness of the surface layer was set to 50 μm.

[0120] <Example 10> A conductive roll 10 was obtained in the same manner as in Example 1, except that the thickness of the intermediate layer was set to 0.5 mm and the thickness of the surface layer was set to 10 μm.

[0121] <Example 11> A conductive roll 11 was obtained in the same manner as in Example 1, except that the thickness of the intermediate layer was set to 3.0 mm and the thickness of the surface layer was set to 50 μm.

[0122] <Comparative Example 1> A comparative conductive roll 1 was obtained in the same manner as in Example 1, except that a cylindrical elastic foam was obtained using medium-density Endure (manufactured by Inoac Corporation) containing carbon black in the formation of the elastic layer, and a conductive coating layer was not formed.

[0123] [evaluation] (Parallelism of images transferred to a recording medium) The conductive rolls from each example were mounted as secondary transfer rolls on the evaluation machine, a Fuji Xerox ApeosPort VII C6688. In this evaluation machine, the pressing amount of the secondary transfer roll against the opposing intermediate transfer belt was set to 0.2 mm for the rear and 0.8 mm for the front, and the secondary transfer roll was installed with a difference of 0.6 mm between the pressing amount (Rear) and (Front). A rectangular line measuring 280 mm x 400 mm was imaged on the intermediate transfer belt, and this was transferred to A3 size paper in the secondary transfer section and fixed in the fixing device. The image line lengths (L) on the rear and front sides of the output image were then measured. Rear , L Front ) is measured, and the image length difference (L Front )-(L Rear The ΔL value was calculated by determining the parallelism of the image. A larger ΔL value indicates that the conductive roll is more easily used to improve the parallelism of the image (easier to adjust the parallelism of the image). -Evaluation Criteria- S(◎):ΔL≧2mm A(〇): 1.5mm ≤ ΔL < 2.0mm B(△): 0.5mm ≤ ΔL < 1.5mm C(×): 0.5mm > ΔL

[0124] (Static resistance) The conductive rolls from each example were mounted as secondary transfer rolls on the evaluation machine, a Fuji Xerox ApeosPort VII C6688. The evaluation machine was used to print 300,000 halftone images with an image density of 20% on A4 paper (specifically, 150,000 images were printed under a 28°C 85%RH environment, followed by another 150,000 images under a 10°C 15%RH environment). The 150,000th image printed under the 10°C 15%RH environment (i.e., the 300,000th image in total) was visually inspected for density unevenness and evaluated according to the following criteria. Less density unevenness indicates superior charge retention. A(◎): No unevenness in density is observed. B(○): Slight unevenness in density is visible to the naked eye. C(△): Some unevenness in density is visible, but it is within an acceptable range. D(×): Unacceptable unevenness in concentration is observed.

[0125] [Table 1]

[0126] Table 1 shows that the conductive roll of this embodiment is effective in increasing the parallelism of the image transferred to the recording medium and also exhibits excellent charge retention.

[0127] <Example 12> [Formation of an elastic layer] EP70 (manufactured by Inoac Corporation) was used as the elastic foam material. This was polished and molded into a cylindrical shape with an outer diameter of 28 mm, an inner diameter of 15 mm, and a length of 350 mm to obtain a cylindrical elastic foam material. As a treatment solution, a conductive treatment solution was prepared by mixing an aqueous dispersion containing 36% by mass of carbon black with an acrylic emulsion (manufactured by Nippon Zeon Co., Ltd., product name "Nipol LX852") in a 1:1 ratio by mass, and the material was immersed in this solution at 20°C for 10 minutes. The elastic foam obtained by the above method was then immersed at 20°C for 10 minutes. Subsequently, the elastic foam with the treatment solution adhering to it was heated in a curing furnace set to 100°C for 60 minutes to dry it, removing moisture and crosslinking the acrylic resin. The crosslinked and hardened acrylic resin formed a conductive coating layer containing carbon black on the exposed surface of the elastic foam. As described above, an elastic layer was obtained, comprising an elastic foam and a conductive coating layer covering the exposed surface of the elastic foam. Next, a conductive support member (made of stainless steel, 15 mm in diameter) with adhesive applied to its surface was inserted into the resulting elastic layer to form a roll member. The rebound stress of the elastic layer when compressed by 10% was 8.6 kPa.

[0128] [Formation of the intermediate layer] A coating solution for forming an intermediate layer was prepared by mixing 70 parts by mass of urethane oligomer (manufactured by Nippon Synthetic Chemicals Co., Ltd., urethane acrylate UV3700B), 30 parts by mass of urethane monomer (manufactured by Kyoeisha Chemicals Co., Ltd., isomiristyl acrylate), 0.5 parts by mass of polymerization initiator (manufactured by Ciba Specialty Chemicals Co., Ltd., 1-hydroxycyclohexyl phenyl ketone Irgacure 184), and 3 parts by mass of alkyltrimethylammonium perchlorate (product name "LXN-30", manufactured by Daiso Co., Ltd.). The prepared coating solution for forming an intermediate layer was applied to an elastic layer using a die coater and rotated while being exposed to UV irradiation at an intensity of 700 mW / cm². 2 The coating was then irradiated with UV light for 5 seconds. This process formed an intermediate layer with a thickness of 1 mm.

[0129] [Formation of the surface layer] A surface layer forming coating solution was obtained by adding 5% by mass of a hardener (WH-1, manufactured by Henkel Japan Ltd.) to a urethane resin paint (EMRALON T-862A, manufactured by Henkel Japan Ltd.) and mixing the mixture. The obtained surface layer forming coating solution was applied to the intermediate layer by spray application, and the coating film was heat-cured at 120°C for 20 minutes to form a surface layer with a thickness of 20 μm.

[0130] In this way, a conductive roll 12 was obtained using an elastic layer having a rebound stress of 8.6 kPa when compressed by 10%.

[0131] <Example 13> A conductive roll 13 was obtained in the same manner as in Example 12, except that RR80 (manufactured by Inoac Corporation) was used as the elastic foam. The rebound stress of the elastic layer when compressed by 10% was 10 kPa.

[0132] <Example 14> A conductive roll 14 was obtained in the same manner as in Example 12, except that RR90 high density (manufactured by Inoac Corporation) was used as the elastic foam. The rebound stress of the elastic layer when compressed by 10% was 13 kPa.

[0133] [evaluation] (Parallelism of images transferred to a recording medium) The evaluation was conducted using the same method as described above.

[0134] [Table 2]

[0135] As shown in Table 2, an elastic layer with a rebound stress of 10 kPa or less when compressed by 10% makes it easier to improve the parallelism of the image transferred to the recording medium. [Explanation of Symbols]

[0136] 100 Conductive roll, 110 Support member, 122 Elastic layer, 124 Intermediate layer, 126 Surface layer, 200 Image forming apparatus, 206 Exposure apparatus, 207 Photoreceptor, 208 Charging roll, 209 Power supply, 211 Developing apparatus, 212 Transfer roll, 213 Cleaning apparatus, 214 Static eliminator, 215 Fixing apparatus, 500 Recording paper 1Y, 1M, 1C, 1K Photoreceptor, 2Y, 2M, 2C, 2K Charging roll, 3 Exposure apparatus, 3Y, 3M, 3C, 3K Laser beam, 4Y, 4M, 4C, 4K Developing apparatus, 5Y, 5M, 5C, 5K Primary transfer roll, 6Y, 6M, 6C, 6K Photoreceptor cleaning apparatus, 8Y, 8M, 8C, 8K Toner cartridge, 10Y, 10M, 10C, 10K Image forming unit, 20 intermediate transfer belt, 22 drive roll, 24 support roll, 26 secondary transfer roll, 28 fixing device, 30 intermediate transfer belt cleaning device, P recording paper

Claims

1. It comprises a support member, an elastic layer disposed on the outer circumferential surface of the support member, and a surface layer disposed on the outer circumferential surface of the elastic layer, The elastic layer comprises a cylindrical elastic foam and a conductive coating layer covering the exposed surface of the elastic foam, and the volume resistivity when a voltage of 10V is applied is 10 ５ It is less than or equal to Ω, The surface layer comprises an intermediate layer disposed on the outer circumferential surface of the elastic layer and an outermost layer disposed on the outer circumferential surface of the intermediate layer. The volume resistance of the aforementioned intermediate layer when a voltage of 50V is applied is 10 ４ Ω or more 10 １０ It is less than or equal to Ω, The volume resistance of the outermost layer when a voltage of 10V is applied is 10 ４ Ω or more 10 １４ It is less than or equal to Ω, A conductive roll in which the content of conductive particles in the elastic foam is 1% by mass or less relative to the total mass of the elastic foam. The volume resistivity of the elastic layer is measured as follows. An elastic-layered roll member, which has the elastic layer on the outer circumference of a conductive support member, is placed on a copper plate with a load of 500g applied to each end of the elastic-layered roll member. A voltage of 10V (V) is applied between the conductive support member of the elastic-layered roll member and the copper plate using a microcurrent measuring instrument (Advantest R8320), and the current value I (A) after 5 seconds is read and calculated using the following formula. Formula: Volume resistivity Rv (Ω) = V / I The volume resistivity of the intermediate layer is measured as follows. An intermediate-layered roll member, which has the elastic layer and the intermediate layer on the outer circumference of a conductive support member, is placed on a copper plate with a load of 500g applied to each end of the intermediate-layered roll member. A voltage of 50V (V) is applied between the conductive support member of the intermediate-layered roll member and the copper plate using a microcurrent measuring instrument (Advantest R8320), and the current value I (A) after 5 seconds is read and calculated using the following formula. Formula: Volume resistivity Rv (Ω) = V / I The volume resistivity of the elastic layer or the intermediate layer is measured under conditions of 22°C and 55% RH. The volume resistivity of the outermost layer is measured as follows. First, a single-layer sheet with a thickness of 0.2 mm is fabricated using the outermost layer material, and the volume resistivity is measured using the obtained single-layer sheet member. A voltage of 10 V (V) is applied between the surface electrode and the back electrode of the single-layer sheet member using a microcurrent measuring instrument (R8320, manufactured by Advantage Inc.), and the current value I (A) after 5 seconds is read and calculated using the following formula. Formula: Volume resistivity Rv (Ω) = V / I The volume resistivity of the outermost layer is measured under conditions of 22°C and 55% RH.

2. The conductive roll according to claim 1, wherein the intermediate layer contains an ionic conductive agent.

3. The volume resistance of the conductive roll when a voltage of 1000V is applied is 10 ４ Ω or more 10 １２ A conductive roll according to claim 1 or claim 2, wherein the impedance is less than or equal to Ω.

4. A conductive roll according to any one of claims 1 to 3, wherein the ratio of the thickness Y of the elastic layer to the total thickness X of the elastic layer and the surface layer (Y / X) is 0.66 or more and 0.95 or less.

5. The conductive roll according to any one of claims 1 to 4, wherein the elastic foam has an open-cell structure.

6. The density of the elastic foam is 35 kg / m ３ or more and 90 kg / m ３ or less, the conductive roll according to claim 5.

7. The conductive roll according to any one of claims 1 to 6, wherein the rebound stress of the elastic layer when compressed by 10% is 12 kPa or less.

8. A transfer apparatus comprising a conductive roll according to any one of claims 1 to 7.

9. A process cartridge comprising an image holder and the transfer device described in claim 8, which is attached to and detached from an image forming apparatus.

10. Image holder and, A charging device for charging the surface of the image holder, An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the charged image holder, A developing apparatus that develops an electrostatic latent image formed on the surface of an image holder using a developer containing toner to form a toner image, A transfer apparatus according to claim 8, which transfers the toner image onto the surface of a recording medium, An image forming apparatus equipped with the following features.

Images