Developing roller

Abstract

To provide a developing roller which can suppress toner leakage and fogging, and is also excellent in stability of image density.SOLUTION: A developing roller includes a shaft member, an intermediate layer arranged outside in a radial direction of the shaft member, and a surface layer positioned on the outermost side, wherein the intermediate layer is formed by dispersing an aggregate A composed of particles into a resin, the surface layer is formed by dispersing one or more granules B selected from particles and an aggregate composed of particles into a resin, and an average diameter dB of the granule B is 1 μm or more and 10 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a developing roller. [Background technology]

[0002] In electrophotographic image forming devices such as copiers and printers, a developing method is often adopted in which toner is supplied to a photosensitive drum holding a latent image, and the toner is attached to the latent image on the photosensitive drum to make the latent image visible. Specifically, in such a developing method, for example, after the photosensitive drum is charged to a constant potential, an electrostatic latent image is formed on the photosensitive drum by an exposure device, and further, a developing roller carrying toner is brought into contact with the photosensitive drum holding the electrostatic latent image, and the toner is attached to the latent image on the photosensitive drum to perform development.

[0003] The above-mentioned developing roller generally has a structure in which an elastic layer made of a semiconductive elastic body in which a conductive agent is dispersed in an elastomer such as polyurethane, or a foam made by foaming these materials, is formed on the outer periphery of a shaft member that is axially supported at both ends in the length direction. In addition, in the above-mentioned developing roller, a surface layer made of a resin or the like may be formed on the outside of the elastic layer for the purpose of controlling the chargeability and adhesion to the toner and preventing contamination of the photosensitive drum (for example, see Patent Document 1).

[0004] Furthermore, in the layer (including the above-mentioned surface layer) disposed on the radially outer side of the developing roller, irregularities may be formed by blending fine particles. For example, Patent Document 2 discloses that the toner supplying ability is improved by providing one or more resin layers on the radially outer side of a shaft member made of a metal pipe, and dispersing fine particles in at least one of the resin layers to form surface roughness. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-352072 A [Patent Document 2] JP 2011-065188 A Summary of the Invention [Problem to be solved by the invention]

[0006] Here, considering the surface roughness (unevenness) of the developing roller, if the height of the protrusions on the surface is relatively high, it is possible to suppress damage to the members (developing blade, etc.) that come into contact with the developing roller and toner leakage from the end seal members of the image forming device. Moreover, the height of the protrusions on the surface can be increased by forming a layer using fine particles with a relatively large particle size.

[0007] However, when using fine particles with a large particle size, it becomes difficult to disperse the fine particles uniformly in the layer, which may cause uneven toner transport during development and ultimately fogging of the image.

[0008] On the other hand, if fine particles with a relatively small particle size are used, they can be dispersed uniformly. However, in this case, the height (height of the protrusion) becomes insufficient, and an appropriate space cannot be provided between the surface of the developing roller and the contact member such as the developing blade, which may cause problems such as toner leakage. In other words, toner leakage and fogging are essentially in a trade-off relationship.

[0009] Furthermore, if the fine particles used are hard, the fine particles are likely to fall off in the same shape as they are during continuous or long-term operation of the image forming apparatus. In this case, there is a concern that the image density may fluctuate due to a significant change in roughness.

[0010] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a developing roller which is capable of suppressing toner leakage and fogging and is excellent in stability of image density. [Means for solving the problem]

[0011] That is, the gist of the developing roller of the present invention that solves the above problems is as follows.

[0012] [1] A developing roller comprising a shaft member, an intermediate layer disposed radially outward of the shaft member, and a surface layer located at an outermost position, The intermediate layer is formed by dispersing aggregate A composed of particles in a resin, The surface layer is formed by dispersing granular material B, which is one or more selected from particles and aggregates composed of particles, in a resin, and the average diameter d B is 1 μm or more and 10 μm or less, A developing roller comprising:

[0013] [2] The average diameter d of the aggregates A in the intermediate layer A The developing roller according to [1], wherein the thickness of the developing roller is 10 μm or more and 35 μm or less.

[0014] [3] The developing roller according to [1] or [2], wherein the content of the particles in the intermediate layer is 10 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the resin.

[0015] [4] The developing roller according to any one of [1] to [3], wherein the content of the particles in the surface layer is 15 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the resin.

[0016] [5] The average diameter d of the aggregate A A The developing roller according to any one of [1] to [4], wherein the thickness of the intermediate layer is greater than the thickness of the intermediate layer.

[0017] [6] Average diameter d of the granular material B B The developing roller according to any one of [1] to [5], wherein the thickness of the surface layer is greater than the thickness of the surface layer.

[0018] [7] The developing roller according to any one of [1] to [6], further comprising an elastic layer between the shaft member and the intermediate layer.

[0019] [8] The developing roller according to any one of [1] to [7], further comprising an outer intermediate layer between the intermediate layer and the surface layer. Effect of the Invention

[0020] According to the present invention, it is possible to provide a developing roller capable of suppressing toner leakage and fogging and having excellent stability in image density. [Brief description of the drawings]

[0021] [Figure 1] FIG. 2 is a cross-sectional view of a developing roller according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] (Developing roller) The developing roller of the present invention will be described in detail below with reference to the embodiments.

[0023] Fig. 1 is a cross-sectional view of a developing roller according to one embodiment of the present invention (hereinafter, may be referred to as "the developing roller of this embodiment"). The developing roller 1 shown in Fig. 1 comprises a shaft member 2, an elastic layer 3 disposed radially outward of the shaft member 2, an intermediate layer 4 disposed radially outward of the elastic layer 3, and a surface layer 5 disposed radially outward of the intermediate layer 4. Note that the elastic layer 3 is not an essential component of the developing roller of the present invention. Also, although the developing roller 1 shown in Fig. 1 comprises only one elastic layer 3, the developing roller of the present invention may comprise two or more elastic layers.

[0024] In the developing roller 1 of this embodiment, the intermediate layer 4 is formed by dispersing aggregates A made of particles in a resin, and the surface layer 5 is formed by dispersing granular bodies B, which are one or more selected from particles and aggregates made of particles, in a resin. The average diameter d B The particle size is 1 μm or more and 10 μm or less. Note that, in FIG. 1, the particles and aggregates are not shown.

[0025] As described above, the aggregates A are dispersed in the intermediate layer 4 of the developing roller 1 of this embodiment. Here, the aggregates usually have a certain size. Therefore, the aggregates A in the intermediate layer 4 bring about appropriate unevenness (appropriately high convex portions) on the outer circumferential surface of the developing roller 1, which not only suppresses toner leakage but also suppresses damage to members (developing blades, etc.) that come into contact with the developing roller. Furthermore, since the medium dispersed in the intermediate layer 4 is an aggregate, even when an image forming apparatus equipped with the developing roller 1 is operated continuously or for a long period of time, the aggregate A will only be partially scraped off, rather than falling off as a whole. This prevents a significant change in surface roughness, and allows the image density to remain stable. Furthermore, the surface layer 5 of the developing roller 1 of this embodiment is made of granular material having a relatively small particle size, specifically, an average diameter d B In this case, granules B having a particle size of 10 μm or less are dispersed. Since the granules have a relatively small particle size, the dispersion can be made more uniform. Therefore, by providing a layer containing the granules B as a surface layer, fogging of the image during development can be suppressed. Therefore, the developing roller 1 of this embodiment can suppress toner leakage and fogging, and is also excellent in stability of image density.

[0026] <Shaft material> As described above, the developing roller 1 of this embodiment includes the shaft member 2. The shaft member 2 preferably has good electrical conductivity. Specifically, examples of the material of the shaft member 2 include metals such as iron, stainless steel, aluminum, and alloys containing these metals, as well as plastics with good electrical conductivity. The shaft member 2 may be a solid material or a hollow material (pipe). The shaft member 2 may include shaft portions that constitute both ends of the shaft member 2 in the length direction so that the shaft member 2 is supported by a roller support portion of the image forming apparatus.

[0027] <Middle Class> As described above, the developing roller 1 of this embodiment includes the intermediate layer 4 disposed radially outward of the shaft member 2. The intermediate layer 4 is formed by dispersing aggregates A made of particles in a resin.

[0028] The resin constituting the intermediate layer 4 is not particularly limited, and examples thereof include ultraviolet curing resins and electron beam curing resins. Specific examples of the resin include polyester resins, polyether resins, fluororesins, epoxy resins, amino resins, polyamide resins, acrylic resins, acrylic urethane resins, urethane resins, alkyd resins, phenolic resins, melamine resins, urea resins, silicone resins, and polyvinyl butyral resins. These resins may be used alone or in combination of two or more. Among these, the resin constituting the intermediate layer 4 is preferably an ultraviolet curing resin, and more preferably a urethane resin (ultraviolet curing urethane resin). The urethane resin is obtained by reacting a polyol component with a polyisocyanate component, and has the property of being cured by heat.

[0029] The intermediate layer 4 is required to have aggregates A made up of particles dispersed therein. If the dispersion medium is non-aggregated, the non-aggregated particles will fall off as a unit when an image forming apparatus including the developing roller 1 is operated continuously or for a long period of time, resulting in poor stability of image density.

[0030] The particles constituting the aggregate A dispersed in the intermediate layer 4 are not particularly limited, and examples thereof include particles of organic materials such as silicone rubber, acrylic resin, styrene resin, acrylic / styrene copolymer, fluororesin (polytetrafluoroethylene (PTFE), etc.), urethane elastomer, urethane acrylate, melamine resin, and phenol resin. These particles may be used alone or in combination of two or more types. Among these, fluororesin is preferred as the particles constituting the aggregate A from the viewpoints of cohesiveness and availability.

[0031] The deformation strength (σ 10%) is preferably 1 MPa or less. 10% If the pressure is 1 MPa or less, damage to the photosensitive drum is suppressed, and fogging can be more effectively suppressed. In addition, the deformation strength of the particles (σ 10% ) is the deformation strength against a compressive displacement of 10% of the particle diameter, and can be measured by the procedure described in the Examples.

[0032] The average diameter d of aggregates A dispersed in the intermediate layer 4 A The average diameter d is preferably 10 μm or more and 35 μm or less. A If the average diameter d is 10 μm or more, the effect of suppressing toner leakage can be further improved and the stability of image density can be maintained for a longer period of time. A From the same viewpoint, if the average diameter d of the aggregate A is 35 μm or less, the unevenness of the image density can be suppressed and the effect of suppressing fogging can be further improved. A It is more preferable that the thickness is 15 μm or more, and more preferably 30 μm or less. The average diameter of aggregate A is d A can be measured by the procedure described in the Examples.

[0033] The average diameter d of aggregates A dispersed in the intermediate layer 4 A is preferably greater than the thickness (resin thickness) of the intermediate layer 4. That is, when forming the intermediate layer 4 by applying a resin composition containing a resin and aggregate A, it is preferable to apply the resin composition to a thickness that causes the aggregate A to partially protrude. This makes the unevenness on the outer peripheral surface of the developing roller 1 more pronounced, making it possible to more effectively suppress toner leakage. Note that the thickness (resin thickness) of the intermediate layer 4 can actually be, for example, 2 μm or more and 10 μm or less.

[0034] The diameter (average primary particle diameter) of the particles constituting the aggregate A is preferably 0.1 μm or more and 1 μm or less. If the average primary particle diameter is 0.1 μm or more, when an image forming apparatus equipped with the developing roller 1 is operated continuously or for a long period of time, the aggregate A is gradually more easily scraped off, and the stability of the image density can be more effectively maintained. Furthermore, if the average primary particle diameter is 1 μm or less, the desired aggregate A is easily formed.

[0035] The content of the particles in the intermediate layer 4 is preferably 10 parts by mass or more and 30 parts by mass or less relative to 100 parts by mass of the resin. If the content is 10 parts by mass or more, the density of the aggregate A is sufficiently high, and the effect of suppressing toner leakage can be further improved. Furthermore, if the content is 30 parts by mass or less, coating unevenness during the preparation of the intermediate layer 4 can be suppressed. From the same viewpoint, the content of the particles in the intermediate layer 4 is more preferably 15 parts by mass or more and more preferably 25 parts by mass or less relative to 100 parts by mass of the resin.

[0036] The intermediate layer 4 may contain other components such as a conductive agent in addition to the aggregate A constituted by the resin and the particles.

[0037] <Surface layer> As described above, the developing roller 1 of this embodiment includes the outermost surface layer 5. The surface layer 5 is formed by dispersing granular material B, which is one or more selected from particles and aggregates composed of particles, in a resin.

[0038] The resin constituting the surface layer 5 is not particularly limited, but includes those mentioned above as the resin constituting the intermediate layer 4. These resins may be used alone or in combination of two or more. Among these, the resin constituting the surface layer 5 is preferably an ultraviolet curable resin, and more preferably a urethane resin (ultraviolet curable urethane resin). The resin constituting the surface layer 5 and the resin constituting the intermediate layer 4 may be the same or different. However, from the viewpoint of manufacturing efficiency, it is preferable that the resin constituting the surface layer 5 and the resin constituting the intermediate layer 4 are the same.

[0039] The particulate material B dispersed in the surface layer 5 may be in the form of individual particles (non-agglomerates), or may be in the form of aggregates made up of particles, or may be in the form of both.

[0040] The particles constituting the granular body B dispersed in the surface layer 5 are not particularly limited, but include those mentioned above as the particles constituting the aggregate A dispersed in the intermediate layer 4. These particles may be used alone or in combination of two or more types. Among these, fluororesin is preferred as the particles constituting the granular body B from the viewpoints of aggregability and availability. The particles constituting the granular body B and the particles constituting the aggregate A may be the same or different. However, from the viewpoint of production efficiency, it is preferred that the particles constituting the granular body B and the particles constituting the aggregate A are the same.

[0041] The average diameter d of the granular material B dispersed in the surface layer 5 B The average diameter d of the granular material B must be 1 μm or more and 10 μm or less. B When the granular body B is a non-agglomerate, d refers to the average primary particle diameter, and when the granular body B is an agglomerate, d refers to the average secondary particle diameter or agglomerate diameter. B If the average diameter d of the granules B is less than 1 μm, the granules B may be too small to obtain the desired effect. B If the average diameter d of the granular material B exceeds 10 μm, there is a possibility that the fogging cannot be suppressed. B From the viewpoint of more reliably obtaining the desired effect, the thickness is preferably 3 μm or more, and from the viewpoint of more effectively suppressing fogging, the thickness is preferably 8 μm or less. The average diameter of the granular material B is d B can be measured by the procedure described in the Examples.

[0042] Average diameter of granular material B d B is the average diameter d of the aggregates A dispersed in the intermediate layer 4 A That is, the average diameter d of the aggregate A is preferably smaller than d AAverage diameter d of granular material B B The ratio (average diameter d B / average diameter d A ) is preferably less than 1.0. In this regard, when the particles constituting the granular body B and the particles constituting the aggregate A are the same, the granular body B can be easily obtained by pulverizing the aggregate A using a dispersant or the like. In addition, the above ratio (average diameter d B / average diameter d A ) is more preferably 0.7 or less, and even more preferably 0.4 or less.

[0043] The average diameter d of the granular material B dispersed in the surface layer 5 B is preferably greater than the thickness (resin thickness) of the surface layer 5. That is, when forming the surface layer 5 by applying a resin composition containing a resin and granules B, it is preferable to apply the resin composition to a thickness that causes the granules B to partially protrude. This makes the unevenness on the outer peripheral surface of the developing roller 1 more pronounced, making it possible to more effectively suppress toner leakage. In addition, the thickness (resin thickness) of the surface layer 5 can actually be, for example, 1 μm or more and 5 μm or less. Also, the thickness (resin thickness) of the surface layer 5 may be smaller than the thickness (resin thickness) of the intermediate layer 4.

[0044] The content of the particles in the surface layer 5 is preferably 15 parts by mass or more and 35 parts by mass or less relative to 100 parts by mass of the resin. If the content is 15 parts by mass or more, the density of the granular body B is sufficiently high, and effects such as improved toner supplying ability can be obtained. Furthermore, if the content is 35 parts by mass or less, coating unevenness during preparation of the surface layer 5 can be suppressed, and the fogging suppression effect can be further improved. From the same viewpoint, the content of the particles in the surface layer 5 is more preferably 20 parts by mass or more and more preferably 30 parts by mass or less relative to 100 parts by mass of the resin.

[0045] The surface layer 5 may contain, in addition to the resin and the particles B, other components such as a conductive agent.

[0046] <Elastic layer> 1, the developing roller 1 of this embodiment preferably further includes an elastic layer 3 between the shaft member 2 and the intermediate layer 4. This gives elasticity to the developing roller 1, and can ease the stress applied to the surface layer 5 when the surface layer 5 of the developing roller 1 is pressed against a photosensitive drum or a developing blade, thereby maintaining the durability of the surface layer 5 favorably.

[0047] The elastic layer 3 is preferably made of an elastomer, and more preferably made of an elastomer foam. Examples of the elastomer include polyurethane, silicone rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), polynorbornene rubber, butyl rubber (IIR), chloroprene rubber (CR), acrylic rubber, epichlorohydrin rubber (ECO), and ethylene-vinyl acetate copolymer (EVA). These elastomers may be used alone or in combination of two or more. Among these elastomers, polyurethane is particularly preferred for the elastic layer 3.

[0048] The elastomer foam can be produced by chemically foaming the elastomer using a foaming agent, or by mechanically foaming the elastomer by entraining air as in polyurethane foam. When the elastic layer 3 is formed from an elastomer foam, the foam preferably has an expansion ratio in the range of 1.5 to 50 times and a density of 0.05 to 0.9 g / cm. 3 It is preferable that the range is 100%.

[0049] The cells in the foam are preferably closed cells, which can improve the compression set performance of the elastic layer 3. A suitable method for forming closed cells in the foam is to mechanically stir the elastomer raw material to foam the foam.

[0050] The elastic layer 3 preferably contains a conductive agent. This allows the electrical conductivity of the elastic layer 3 to be adjusted. Examples of the conductive agent include an electronic conductive agent and an ionic conductive agent. The conductive agent may be used alone or in combination of two or more. Furthermore, the conductive agent may be used in combination of an electronic conductive agent and an ionic conductive agent.

[0051] Examples of the electronic conductive agent include conductive carbon such as Ketjen black and acetylene black; carbon black for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT; carbon black for coloring that has been subjected to oxidation treatment or the like; pyrolytic carbon black, natural graphite, artificial graphite, metal oxides such as antimony-doped tin oxide, ITO, tin oxide, titanium oxide, and zinc oxide; metals such as nickel, copper, silver, and germanium; conductive polymers such as polyaniline, polypyrrole, and polyacetylene; and conductive whiskers such as carbon whiskers, graphite whiskers, titanium carbide whiskers, conductive potassium titanate whiskers, conductive barium titanate whiskers, conductive titanium oxide whiskers, and conductive zinc oxide whiskers.

[0052] Examples of the ion conductive agent include ammonium salts such as perchlorates, chlorates, hydrochlorides, bromates, iodates, hydrofluoroborates, sulfates, ethyl sulfates, carboxylates, and sulfonates, such as tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, and modified fatty acid dimethylethylammonium; and perchlorates, chlorates, hydrochlorides, bromates, iodates, hydrofluoroborates, sulfates, trifluoromethyl sulfates, and sulfonates, of alkali metals and alkaline earth metals such as lithium, sodium, potassium, calcium, and magnesium.

[0053] <Other layers> The developing roller 1 of this embodiment may include, in addition to the intermediate layer 4, the surface layer 5, and the elastic layer 3 described above, further layers.

[0054] For example, the developing roller 1 of this embodiment may further include an outer intermediate layer (not shown) on the radially outer side of the intermediate layer 4, more specifically, between the intermediate layer 4 and the surface layer 5. Such an outer intermediate layer may be only one layer or may be two or more layers. Such an outer intermediate layer may function as an adhesive layer, and by including the outer intermediate layer, the adhesion between the intermediate layer 4 and the surface layer 5 can be increased, thereby increasing the durability of the developing roller 1.

[0055] The resin constituting the outer intermediate layer is not particularly limited, but includes those mentioned above as the resin constituting the intermediate layer 4. These resins may be used alone or in combination of two or more. The thickness of the outer intermediate layer (per layer) may be, for example, 1 μm or more and 5 μm or less.

[0056] The developing roller 1 of this embodiment may further include an inner intermediate layer (not shown) radially inward of the intermediate layer 4, more specifically, between the intermediate layer 4 and the shaft member 2 or the elastic layer 3. Such an inner intermediate layer may be only one layer or may be two or more layers. Such an inner intermediate layer may function as an adhesive layer, and by including the inner intermediate layer, the adhesion between the intermediate layer 4 and the shaft member 2 or the elastic layer 3 can be increased, thereby improving the durability of the developing roller 1.

[0057] The resin constituting the inner intermediate layer is not particularly limited, but includes those mentioned above as the resin constituting the intermediate layer 4. These resins may be used alone or in combination of two or more. The thickness of the inner intermediate layer (per layer) may be, for example, 1 μm or more and 5 μm or less.

[0058] <Manufacturing Method of Developing Roller> The developing roller of the present embodiment is not particularly limited in the manufacturing method, and can be manufactured according to a conventional method. For example, each layer such as the intermediate layer 4 and the surface layer 5 can be formed by preparing a resin composition (coating liquid) containing a resin, particles and / or aggregates, and other components as appropriate, applying the coating liquid to the surface, and then curing the coating liquid by optionally irradiating it with ultraviolet rays or electron beams.

[0059] The method for applying the resin composition (coating liquid) is not particularly limited, and examples thereof include a dipping method, a roll coating method, and a spray coating method, from which an appropriate method can be selected depending on the situation.

[0060] <Applications of developing rollers> The developing roller of the present invention can be used in various electrophotographic image forming devices such as copiers, facsimiles, and laser beam printers (LBPs). The image forming device usually includes a photosensitive drum holding an electrostatic latent image, a charging member located near the photosensitive drum for charging the photosensitive drum, a toner supply roller for supplying toner, a transfer member located near the photosensitive drum, and a cleaning member disposed adjacent to the photosensitive drum, and further includes a developing roller between the toner supply roller and the photosensitive drum. In addition, a developing blade (also called a "layered blade") is usually provided near the developing roller.

[0061] In an image forming apparatus, a voltage is applied between a photosensitive drum and a charging member to charge the photosensitive drum to a constant potential, and then an exposure machine forms an electrostatic latent image on the photosensitive drum. Next, toner is sent from a toner supply roller to a developing roller and then to the photosensitive drum. At this time, the toner on the developing roller is arranged into a uniform thin layer by a developing blade, and as the developing roller and the photosensitive drum rotate while in contact with each other, the toner adheres from the developing roller to the electrostatic latent image on the photosensitive drum, and the latent image becomes visible. The toner adhered to the latent image is transferred to a recording medium such as paper by a transfer member, and the toner remaining on the photosensitive drum after transfer is removed by a cleaning member.

[0062] By using the developing roller of the present invention in an image forming apparatus, toner leakage and fogging can be suppressed, and the image density can be kept stable even when the image forming apparatus is operated continuously or for a long period of time. EXAMPLES

[0063] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples and can be modified as appropriate without departing from the gist of the present invention.

[0064] Example 1 A developing roller was produced by forming an elastic layer, an intermediate layer, an outer intermediate layer (adhesive layer), and a surface layer in this order on a shaft member made of an aluminum pipe. The intermediate layer was formed by applying a resin composition, in which an aggregate of polytetrafluoroethylene particles was blended with a urethane resin, onto the elastic layer by roll coating (the main conditions of the intermediate layer are as shown in Table 1). The adhesive layer was formed by applying a resin composition (coating liquid, purchased product) onto the intermediate layer by roll coating. The surface layer was formed by spraying a resin composition (dispersion liquid), in which an aggregate of polytetrafluoroethylene particles was blended with a solvent containing a urethane resin, onto the adhesive layer by a spray (the main conditions of the surface layer are as shown in Table 1).

[0065] In Example 1, the particles constituting the agglomerates in the intermediate layer and the particles constituting the agglomerates in the surface layer were the same, and the agglomerates in the surface layer were made even finer than the agglomerates in the intermediate layer by using a dispersant or the like.

[0066] The average diameter d of the aggregate A (or particle) dispersed in the intermediate layer A was measured in the following manner. That is, after the intermediate layer was formed, a surface image of the longitudinal center of the intermediate layer was obtained using a laser microscope (Keyence Corporation, "VK-X3000"). Next, 100 aggregates A (or particles) were counted from the surface image, and their outer diameter data was obtained. Then, using the outer diameter data, D50 was calculated as the average diameter dA It was calculated as:

[0067] In addition, the average diameter of the granular material B dispersed in the surface layer is d B was measured in the following manner. That is, after forming the surface layer, a surface image of the longitudinal center of the surface layer was obtained using a laser microscope (Keyence Corporation, "VK-X3000"). Next, 100 granular bodies B were counted from the surface image, and their outer diameter data was obtained. Then, using the outer diameter data, D50 was calculated as the average diameter d B It was calculated as:

[0068] In addition, the deformation strength of the particles (σ 10% ) was measured by the following procedure. That is, a microparticle crushing force measuring device (manufactured by Nano Seeds, "NS-A100") was used to calculate the crushing force according to the following formula. σ 10% =F 10% / A σ 10% : Deformation strength against compression displacement of 10% of particle diameter (Pa) F 10% : Test force for compressive displacement of 10% of particle diameter (N) A: Representative area (area of ​​the circle equivalent to the particle diameter measured before compression) (m 2 )

[0069] Other Examples and Comparative Examples A developing roller was produced in the same manner as in Example 1, except that the conditions of the intermediate layer and / or the surface layer were changed as shown in Table 1.

[0070] The developing rollers of the respective examples prepared as described above were subjected to the following evaluations. The results are shown in Table 1.

[0071] (1) Initial image density The developed roller was installed in a Brother monochrome laser printer "HL-L6400DW" and a solid black image was printed. The image density at five points on the paper surface of the obtained image was measured using an X-Rite spectrodensitometer "eXact Basic". The average value (average density) and the difference between the maximum and minimum values ​​(density difference) were calculated for the density at the five points and evaluated according to the following criteria. A (very good): Average density is 1.2 or more and density difference is 0.2 or less B (Good): Average density is 1.2 or more and density difference is less than 0.2 C (Poor): Average density is less than 1.2

[0072] (2) Image density after durability test (stability of image density) After measuring the initial image density as described above, a durable print (printing of approximately 20,000 solid black images) was performed. The image density at five points on the paper surface of the final image was measured using an X-Rite spectrodensitometer "eXact Basic." The average value (average density) and the difference between the maximum and minimum values ​​(density difference) for the five densities were calculated and evaluated according to the following criteria. A (very good): Average density is 1.2 or more and density difference is 0.2 or less B (Good): Average density is 1.2 or more and density difference is less than 0.2 C (Poor): Average density is less than 1.2

[0073] (3) Covering The developed roller was installed in a Brother monochrome laser printer "HL-L6400DW" and a durability test was carried out under an LL environment (10°C, 15% RH). The images obtained after that were evaluated according to the following criteria. A (very good): No toner adhesion is observed in areas of the image where toner should not be present. B (Good): Some toner adhesion is observed in areas of the image where toner should not be present. C (Poor): Toner adhesion is observed over a wide area in areas of the image where toner should not be present.

[0074] (4) Toner leakage The developed roller was installed in a Brother monochrome laser printer "HL-L6400DW" and durability tests were performed in an LL environment (10°C, 15% RH) and an HH environment (30°C, 80% RH). The toner condition around the developed roller was then evaluated according to the following criteria. A (very good): No toner was seen coming out from the end of the developing roller, and no dirt was seen on the seal. B (Good): No toner was observed coming out from the end of the developing roller, but dirt was observed on the seal. C (Poor): Toner is seen coming out from the end of the developing roller and the seal is dirty.

[0075] [Table 1]

[0076] It can be seen from Table 1 that the developing rollers of the examples according to the present invention can suppress toner leakage and fogging, and are also excellent in the stability of image density. [Industrial Applicability]

[0077] The developing roller of the present invention can be used in various electrophotographic image forming apparatuses such as copying machines, facsimiles, and laser beam printers (LBPs). [Explanation of symbols]

[0078] 1: developing roller; 2: shaft member; 3: elastic layer; 4: intermediate layer; 5: surface layer

Claims

1. A developing roller including a shaft member, an intermediate layer disposed radially outward of the shaft member, and a surface layer located at an outermost position, The intermediate layer is formed by dispersing aggregate A composed of particles in a resin, The surface layer is formed by dispersing granular bodies B, which are one or more selected from particles and aggregates composed of particles, in a resin, and the average diameter d Ｂ is 1 μm or more and 10 μm or less, A developing roller comprising:

2. The average diameter d of the aggregates A in the intermediate layer Ａ 2. The developing roller according to claim 1, wherein the thickness of the developing roller is from 10 μm to 35 μm.

3. 3. The developing roller according to claim 1, wherein a content of the particles in the intermediate layer is 10 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the resin.

4. 3. The developing roller according to claim 1, wherein the content of the particles in the surface layer is 15 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the resin.

5. The average diameter d of the aggregate A Ａ The developing roller according to claim 1 or 2, wherein the thickness of said intermediate layer is greater than the thickness of said intermediate layer.

6. The average diameter d of the granular material B Ｂ The developing roller according to claim 1 or 2, wherein the thickness of the surface layer is greater than the thickness of the surface layer.

7. The developing roller according to claim 1 , further comprising an elastic layer between the shaft member and the intermediate layer.

8. The developing roller according to claim 1 or 2, further comprising an outer intermediate layer between the intermediate layer and the surface layer.

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