Developing roller

Abstract

Provided is a developing roller capable of suppressing toner leakage and fogging and having excellent stability of image density. The developing roller comprises a shaft member, an intermediate layer arranged on the outer side in the radial direction of the shaft member, and an outer surface layer located furthest to the outside, the developing roller characterized in that, in the intermediate layer, an aggregate A composed of particles is dispersed in a resin, the outer surface layer is obtained by dispersing a granular body B which is one or more selected from particles and aggregates composed of particles in a resin, and the average diameter dB of the granular body B is 1 μm to 10 μm inclusive.

Description

Developing roller

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

[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, the photosensitive drum is charged to a constant potential, and then an electrostatic latent image is formed on the photosensitive drum by an exposure device, and a developing roller carrying toner is brought into contact with the photosensitive drum holding the electrostatic latent image, thereby causing the toner to attach to the latent image on the photosensitive drum, thereby performing development.

[0003] The above-mentioned developing roller generally has a structure in which an elastic layer made of a semiconductive elastic material, in which a conductive agent is dispersed in an elastomer such as polyurethane, or a foam made of such a material, is formed on the outer periphery of a shaft member that is attached and journaled at both ends in the longitudinal direction. Furthermore, 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 purposes of controlling the chargeability and adhesion of toner and preventing contamination of the photosensitive drum (see, for example, Patent Document 1).

[0004] Furthermore, the layer disposed on the radially outer side of the developing roller (including the above-mentioned surface layer) may be blended with fine particles to form irregularities. For example, Patent Document 2 discloses that the toner supply capacity can be 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.

[0005] JP 2005-352072 A JP 2011-065188 A

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

[0007] However, when large particle diameter fine particles are used, it becomes difficult to disperse the fine particles uniformly in the layer, which may cause uneven toner transport during development and eventually fog in 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 convex portion) becomes insufficient, and an appropriate space cannot be provided between the surface of the developing roller and a contact member such as a developing blade, which can cause problems such as toner leakage. In other words, toner leakage and fogging are essentially in a trade-off relationship.

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

[0010] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a developing roller that can suppress toner leakage and fogging and also has excellent stability in image density.

[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 the outermost position, wherein the intermediate layer is formed by dispersing aggregates A composed of particles in a resin, and the surface layer is formed by dispersing granular materials B, which are one or more selected from particles and aggregates composed of particles, in a resin, and the average diameter d of the granular materials B is Ｂ A developing roller characterized in that the surface roughness is 1 μm or more and 10 μm or less.

[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] The 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.

[0020] According to the present invention, it is possible to provide a developing roller that can suppress toner leakage and fogging and has excellent stability in image density.

[0021] FIG. 2 is a cross-sectional view of a developing roller according to an embodiment of the present invention.

[0022] (Developing Roller) The developing roller of the present invention will be described in detail below by way of example based on an embodiment thereof.

[0023] FIG. 1 is a cross-sectional view of a developing roller according to one embodiment of the present invention (hereinafter, sometimes referred to as the "developing roller of this embodiment"). The developing roller 1 shown in FIG. 1 includes 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. Furthermore, although the developing roller 1 shown in FIG. 1 includes only one elastic layer 3, the developing roller of the present invention may include two or more elastic layers.

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

[0025] As described above, aggregates A are dispersed in the intermediate layer 4 of the developing roller 1 of this embodiment. Here, the aggregates typically have a certain size. Therefore, the aggregates A in the intermediate layer 4 create moderate unevenness (moderately high protrusions) on the outer peripheral surface of the developing roller 1, thereby suppressing toner leakage and preventing damage to components (such as a developing blade) that contact the developing roller. Furthermore, because 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, only partial scraping of the aggregates A is required, rather than total detachment. Therefore, significant changes in surface roughness are suppressed, and image density can be maintained with stability. Furthermore, the surface layer 5 of the developing roller 1 of this embodiment is made up of granular materials with a relatively small particle size, specifically, particles with an average diameter d as described above. Ｂ The developing roller 1 of this embodiment is therefore capable of suppressing toner leakage and fogging, and is also excellent in stability of image density.

[0026] <Shaft Member> As described above, the developing roller 1 of this embodiment includes the shaft member 2. The shaft member 2 preferably has good electrical conductivity. Specific examples of materials for the shaft member 2 include metals such as iron, stainless steel, aluminum, and alloys containing these, 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 also include shaft portions that constitute both longitudinal ends of the shaft member 2 so that the shaft member 2 is supported by a roller support portion of an image forming apparatus.

[0027] <Intermediate Layer> 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 made of a resin in which aggregates A made of particles are dispersed.

[0028] The resin constituting the intermediate layer 4 is not particularly limited, but examples thereof include ultraviolet-curable resins and electron beam-curable resins. Specific examples of such resins 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, ultraviolet-curable resins are preferred as the resin constituting the intermediate layer 4, and urethane resins (ultraviolet-curable urethane resins) are more preferred. 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 dispersed therein aggregates A made up of particles. If the dispersion medium is non-aggregates, the non-aggregates 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 (e.g., polytetrafluoroethylene (PTFE)), urethane elastomer, urethane acrylate, melamine resin, and phenolic resin. These particles may be used alone or in combination of two or more. Among these, fluororesin is preferred as the particles constituting the aggregate A from the viewpoints of cohesiveness and ease of availability.

[0031] The deformation strength (σ １０％ ) is preferably 1 MPa or less. １０％ If the deformation strength (σ) of the particles is 1 MPa or less, damage to the photosensitive drum is suppressed, and fogging can be more effectively suppressed. 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 the 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 enhanced, and the stability of image density can be maintained for a longer period of time. Ａ From the same viewpoint, when the average diameter d of the aggregate A is 35 μm or less, unevenness in image density can be suppressed and the effect of suppressing fogging can be further enhanced. Ａ is more preferably 15 μm or more, and more preferably 30 μm or less. Ａ can be measured by the procedure described in the Examples.

[0033] The average diameter d of the aggregates A dispersed in the intermediate layer 4 Ａis 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 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. In practice, the thickness (resin thickness) of the intermediate layer 4 can 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 including the developing roller 1 is operated continuously or for a long period of time, the aggregate A becomes easier to gradually scrape off, and the stability of the image density can be maintained more favorably. 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 per 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, uneven application during production 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 per 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 made up of resin and 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, in a resin, granular materials B, which are one or more selected from particles and aggregates composed of particles.

[0038] The resin constituting the surface layer 5 is not particularly limited, but examples thereof include 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-aggregates), or may be in the form of aggregates made up of particles, or may be both of these.

[0040] The particles constituting the granules B dispersed in the surface layer 5 are not particularly limited, but include those mentioned above as the particles constituting the aggregates 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 granules B from the viewpoints of aggregability and ease of availability. The particles constituting the granules B and the particles constituting the aggregates A may be the same or different. However, from the viewpoint of production efficiency, it is preferred that the particles constituting the granules B and the particles constituting the aggregates 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 material B is a non-agglomerate, d denotes the average primary particle diameter, and when the granular material B is an agglomerate, d denotes 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 achieve the desired effect. Ｂ If the average diameter d of the granules B is more than 10 μm, there is a risk that the fogging cannot be suppressed. Ｂis preferably 3 μm or more from the viewpoint of more reliably obtaining the desired effect, and is preferably 8 μm or less from the viewpoint of more effectively suppressing fogging. Ｂ can be measured by the procedure described in the Examples.

[0042] Average diameter d of granular material B 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 Ａ Average diameter d of granular material B Ｂ The ratio of the 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 practice, the thickness (resin thickness) of the surface layer 5 can be, for example, 1 μm or more and 5 μm or less. Furthermore, 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 per 100 parts by mass of the resin. If the content is 15 parts by mass or more, the density of the granular material B is sufficiently high, resulting in effects such as improved toner supply capacity. Furthermore, if the content is 35 parts by mass or less, coating unevenness during the preparation of the surface layer 5 can be suppressed, and the fogging suppression effect can be further enhanced. 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 per 100 parts by mass of the resin.

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

[0046] 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 provides elasticity to the developing roller 1, making it possible to alleviate stress applied to the surface layer 5 of the developing roller 1 when the surface layer 5 is pressed against the photosensitive drum or the developing blade, and thus maintaining the durability of the surface layer 5 at a good level.

[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. Of 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 entraining air in the same way as 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 in the range of 0.05 to 0.9 g / cm. ３ It is preferable that the range is:

[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 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, antimony-doped tin oxide, metal oxides such as 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, hydrofluoroborate, sulfates, ethyl sulfates, carboxylates, and sulfonates of tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, and modified fatty acid dimethylethylammonium; and perchlorates, chlorates, hydrochlorides, bromates, iodates, hydrofluoroborate, 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 further layers in addition to the intermediate layer 4, the surface layer 5, and the elastic layer 3 described above.

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

[0055] The resin constituting the outer intermediate layer is not particularly limited, but examples thereof include those resins described above as 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 consist of only one layer or two or more layers. Such an inner intermediate layer may function as an adhesive layer, and the provision of such an inner intermediate layer can increase the adhesion between the intermediate layer 4 and the shaft member 2 or the elastic layer 3, thereby improving the durability of the developing roller 1.

[0057] The resin constituting the inner intermediate layer is not particularly limited, but includes the resins described 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] <Method for Manufacturing Developing Roller> The manufacturing method of the developing roller of this embodiment is not particularly limited, and it 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 optionally curing it by irradiating it with ultraviolet light or an electron beam.

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

[0060] <Uses of Developing Roller> 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 typically 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. Furthermore, a developing roller is typically provided between the toner supply roller and the photosensitive drum. A developing blade (also called a "layered blade") is also typically 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 electrostatic latent image is formed on the photosensitive drum using an exposure device. Next, toner is delivered from a toner supply roller to a developing roller and then to the photosensitive drum. During this process, the toner on the developing roller is uniformly formed into a thin layer by a developing blade. As the developing roller and the photosensitive drum rotate while in contact with each other, the toner from the developing roller adheres to the electrostatic latent image on the photosensitive drum, making the latent image visible. The toner adhering to the latent image is transferred to a recording medium such as paper using a transfer member, and any 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.

[0063] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to the following examples and can be modified as appropriate within the scope 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 containing a urethane resin and an aggregate of polytetrafluoroethylene particles onto the elastic layer by roll coating (the main conditions for 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) containing a urethane resin and an aggregate of polytetrafluoroethylene particles onto the adhesive layer by spraying (the main conditions for 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 aggregates A (or particles) dispersed in the intermediate layer Ａ was measured by the following procedure. That is, after forming the intermediate layer, a surface image of the longitudinal center portion 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 d Ａ It was calculated as:

[0067] In addition, the average diameter d of the granular material B dispersed in the surface layer Ｂ was measured by the following procedure. That is, after forming the surface layer, a surface image of the longitudinal center portion of the surface layer was obtained using a laser microscope (Keyence Corporation, "VK-X3000"). Next, 100 granules 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 and the crushing force was calculated according to the following formula: σ １０％ =F １０％ / A σ １０％ : Deformation strength (Pa) against compression displacement of 10% of particle diameter １０％ : Test force (N) for a compressive displacement of 10% of the particle diameter A: Representative area (area of ​​a circle equivalent to the particle diameter measured before compression) (m ２ )

[0069] Other Examples and Comparative Examples Developing rollers were 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 examples prepared as described above were evaluated as follows. The results are shown in Table 1.

[0071] (1) Initial Image Density The prepared developing 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) for the densities at these five points were calculated and evaluated according to the following criteria: A (very good): average density of 1.2 or more and density difference of 0.2 or less B (good): average density of 1.2 or more and density difference of less than 0.2 C (poor): average density of less than 1.2

[0072] (2) Image density after durability (image density stability) After measuring the initial image density as described above, durability printing (printing of approximately 20,000 black solid images) was performed. For the finally obtained image, the image density was measured at five points on the paper using a spectrodensitometer "eXact Basic" manufactured by X-Rite. For the densities at these five points, the average value (average density) and the difference between the maximum and minimum values ​​(density difference) were calculated and evaluated according to the following criteria: A (very good): average density of 1.2 or more and density difference of 0.2 or less B (good): average density of 1.2 or more and density difference of less than 0.2 C (poor): average density less than 1.2

[0073] (3) Fog The developed roller was assembled into a Brother monochrome laser printer "HL-L6400DW" and subjected to a durability test under an LL environment (10°C, 15% RH). The images obtained thereafter were evaluated according to the following criteria: A (very good): no toner fixation was observed in areas of the image where toner should not be present; B (good): some toner fixation was observed in areas of the image where toner should not be present; C (poor): toner fixation was observed over a wide area in areas of the image where toner should not be present.

[0074] (4) Toner Leakage The developed roller was assembled into a Brother monochrome laser printer "HL-L6400DW" and subjected to durability tests under 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): Neither toner spilling from the end of the developed roller nor staining of the seal part was observed. B (good): No toner spilling from the end of the developed roller was observed, but staining of the seal part was observed. C (poor): Both toner spilling from the end of the developed roller and staining of the seal part were observed.

[0075]

[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.

[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).

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

Claims

1. A developing roller comprising a shaft member, an intermediate layer disposed radially outward of the shaft member, and a surface layer located on the outermost side, wherein the intermediate layer is made of a resin in which aggregates A made of particles are dispersed, and the surface layer is made of a resin in which granular bodies B, which are one or more selected from particles and aggregates made of particles, are dispersed, and the average diameter d of the granular bodies B is Ｂ A developing roller, characterized in that the surface roughness is 1 μm or more and 10 μm or less.

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

4. The developing roller according to claim 1 or 2, wherein the content of said particles in said surface layer is 15 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of said 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. 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 or 2, further comprising an elastic layer between said shaft member and said intermediate layer.

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

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