JP7510315B2 - Toner supply roller and image forming apparatus - Google Patents

Description

The present invention relates to a toner supply roller and an image forming device.

Laser printers, copiers, video printers, facsimiles, and all-in-one machines employ various image forming devices that use electrophotography. Electrophotographic image forming devices are equipped with various printing sponge rollers, such as cleaning rollers, charging rollers, developing rollers, transfer rollers, pressure rollers, paper feed rollers, and fixing rollers, each of which has a shaft body and an elastic layer formed on its outer circumferential surface.

Among these sponge rollers, cleaning rollers, toner supply rollers, and developing rollers are conductive in order to attract and transport developer, and are required to have low hardness in order to reduce the load and friction on the developer when pressed against other sponge rollers.

For example, Patent Document 1 discloses an example of a sponge roller with low hardness. The roller is a toner supply roller that rotates in contact with the surface of a developing roller in a developing mechanism of an image forming device that involves a developing operation using a developer, carries and transports toner in a toner reservoir on its outer circumferential surface, and supplies toner to the surface of the developing roller. At least the outer circumferential surface is formed of a foam, and a predetermined area excluding both ends of the roller is crushed to destroy the cell membrane of the foam, and a predetermined area in the center of the roller is set to a lower hardness than both ends of the roller.

Patent document 2 also discloses a conductive roller that includes a conductive shaft and a cylindrical conductive rubber body that is conductive and provided on the outer circumferential surface of the shaft, and in which a metal fiber aggregate formed by entangling and assembling flexible metal fibers is embedded in the conductive rubber body so as to provide electrical conductivity between the shaft and the outer circumferential surface of the conductive rubber body.

JP 2007-65103 A JP 2007-256410 A

However, the sponge rollers described in Patent Documents 1 and 2 have a problem that, due to their low hardness, the elastic layer is easily distorted over time, and their durability decreases due to wear. In particular, since the toner supply roller supplies and scrapes off toner while rotating in contact with the developing roller, if the outer diameter becomes smaller due to wear, there is a problem that the toner supply and scraping off are insufficient, resulting in poor images.
The present invention has been made in consideration of the above circumstances, and aims to provide a toner supply roller that has low hardness but improved distortion characteristics and durability, and an image forming apparatus equipped with such a toner supply roller that is capable of obtaining high-quality images.

As a result of extensive research, the present inventors discovered that by incorporating silicone rubber balls instead of silica as an inorganic filler, it is possible to improve distortion characteristics while maintaining low hardness, and thus arrived at the present invention.
That is, the toner supply roller of the present invention is a toner supply roller having a shaft and a foamed elastic layer formed on the outer peripheral surface of the shaft, the foamed elastic layer being formed from a silicone rubber composition containing millable type silicone rubber, silicone rubber balls, a crosslinking agent and a chemical foaming agent, the content of silicone rubber balls in the silicone rubber composition is 2% by mass or more and 20% by mass or less, the Asker F hardness of the foamed elastic layer is 30 or more and 50 or less, and the outer diameter recovery rate of the foamed elastic layer in a compression test is 90% or more and 100% or less.

The average particle size of the silicone rubber balls is preferably 5 μm or more and 20 μm or less.

The specific gravity of the foamed elastic layer is preferably 0.13 or more and 0.3 or less.

The image forming apparatus of the present invention is equipped with the toner supply roller of the present invention.

The present invention provides a toner supply roller that has low hardness but improved distortion characteristics and durability, and an image forming apparatus that can obtain high-quality images using the toner supply roller.

1 is a schematic perspective view illustrating an embodiment of a toner supply roller of the present invention. 1 is a schematic cross-sectional view illustrating an embodiment of an image forming apparatus of the present invention. 4 is a schematic cross-sectional view showing a method for measuring an outer diameter return rate of the toner supply roller of the present invention. FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[Toner supply roller]
1, a toner supply roller 1 of the present invention has a shaft body 2 and a foamed elastic layer 3 formed on the outer peripheral surface of the shaft body 2. The components will be described in detail below.

<Shaft body>
The shaft body 2 may be a shaft body having conductive properties and used in a conventionally known elastic roller. The shaft body 2 is preferably made of at least one metal selected from the group consisting of iron, aluminum, stainless steel, and brass.

<Foamed Elastic Layer>
The foamed elastic layer 3 is made of a silicone rubber composition containing millable type silicone rubber, silicone rubber balls, a crosslinking agent and a chemical foaming agent. The silicone rubber composition in the present invention does not contain a silica-based filler.

(Silicone rubber composition)
- Millable silicone rubber -
Millable type silicone rubber is a silicone rubber compound whose pre-hardened state is similar to unvulcanized compounded rubbers such as natural rubber or ordinary synthetic rubber, and which can be plasticized and mixed using a mixing roll mill or an internal mixer.

The millable silicone rubber contains an organopolysiloxane (A) having a degree of polymerization of 100 or more and represented by the following average composition formula (I), and a conductivity imparting agent (B).
^R1aSiO _{( 4-a)/2} (I)
(In the formula, ^R1 represents the same or different unsubstituted or substituted monovalent hydrocarbon groups, and a is a positive number of 1.95 to 2.05.)

Examples of ^R1 include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl groups, cycloalkyl groups such as cyclohexyl groups, alkenyl groups such as vinyl, allyl, butenyl, and hexenyl groups, aryl groups such as phenyl and tolyl groups, and aralkyl groups such as β-phenylpropyl groups. ^R1 may also be a group in which some or all of the hydrogen atoms of these hydrocarbon groups have been substituted with a substituent. The substituent may be, for example, a halogen atom or a cyano group. Examples of the hydrocarbon group having a substituent include a chloromethyl group, a trifluoropropyl group, and a cyanoethyl group.

It is preferable that the molecular chain terminals of the organopolysiloxane (A) are blocked with a trialkylsilyl group such as a trimethylsilyl group, a dialkylaralkylsilyl group such as a dimethylvinylsilyl group, a dialkylhydroxysilyl group such as a dimethylhydroxysilyl group, or a triarylalkylsilyl group such as a trivinylsilyl group.

The organopolysiloxane (A) preferably has two or more alkenyl groups in the molecule. The organopolysiloxane preferably has 0.001 mol % or more and 5 mol % or less (more preferably 0.01 mol % or more and 0.5 mol % or less) of alkenyl groups in ^R1 . The alkenyl group contained in the organopolysiloxane is particularly preferably a vinyl group.

Organopolysiloxane (A) can be obtained, for example, by cohydrolytic condensation of one or more organohalosilanes, or by ring-opening polymerization of a cyclic polysiloxane such as a siloxane trimer or tetramer. The organopolysiloxane may basically be a linear diorganopolysiloxane, or may be partially branched. In addition, organopolysiloxane (A) may be a mixture of two or more types having different molecular structures.

The organopolysiloxane (A) preferably has a kinematic viscosity at 25°C of 100 cSt or more, and more preferably 100,000 cSt or more and 10,000,000 cSt or less. The degree of polymerization of the organopolysiloxane (A) is preferably, for example, 100 cSt or more, and more preferably 3,000 cSt or more and 10,000 cSt or less.

The conductive agent (B) is not particularly limited as long as it is a component for imparting conductivity to the foamed elastic layer 3. Examples of the conductive agent (B) include conductive powders containing conductive carbon, rubber carbons, metals, conductive polymers, etc. It is preferable to use carbon black as the conductive powder, and examples of the carbon black include furnace black such as Ketjen Black (registered trademark), acetylene black, channel black, and thermal black.

In the toner supply roller 1 of the present invention, dimethyl silicone raw rubber can also be blended with the millable silicone rubber. The blending ratio of dimethyl silicone raw rubber to 100 parts by mass of millable silicone rubber is preferably 0 parts by mass or more and 140 parts by mass or less, and more preferably 0 parts by mass or more and 100 parts by mass or less. By adjusting the blending ratio of dimethyl silicone raw rubber to millable silicone rubber in this manner, the outer diameter return rate described below can be adjusted to a predetermined range, and as a result, a toner supply roller with low hardness and high durability can be obtained.
Examples of dimethyl silicone raw rubber include KE-76VBS and KE-77VBS.

- Silicone rubber ball -
The silicone rubber balls are spherical particles made of silicone rubber and may be solid or hollow. By using the silicone rubber balls, the thickness of the cell walls of the foamed elastic layer 3 can be made uniform, and a toner supply roller with low hardness and high outer diameter return rate can be obtained.

The average particle size of the silicone rubber balls is preferably 1 μm or more and 20 μm or less, and more preferably 5 μm or more and 15 μm or less. By having the average particle size of the silicone rubber balls in the above range, a toner supply roller with high outer diameter return rate and high durability can be obtained.

The content of silicone rubber balls is 2% to 20% by mass based on 100 parts by mass of Millable silicone rubber. By having the content of silicone rubber balls in the above range, the silicone rubber balls are uniformly dispersed on the cell walls, resulting in a uniform cell diameter and a high outer diameter return rate despite low hardness.

- Crosslinking agent -
Examples of the crosslinking agent in the present invention include an addition reaction crosslinking agent and an organic peroxide crosslinking agent.
As the addition reaction crosslinking agent, for example, organohydrogenpolysiloxane, which is known as an addition reaction type crosslinking agent having two or more SiH groups (SiH bonds) in one molecule, can be preferably mentioned. The addition reaction crosslinking agent can be used alone or in combination of two or more. The amount of the addition reaction crosslinking agent is usually 0.1 parts by mass or more and 3.0 parts by mass or less per 100 parts by mass of the millable type silicone rubber.

When an addition reaction crosslinking agent is used, the organic peroxide crosslinking agent can crosslink the millable silicone rubber by itself, but when used in combination with the addition reaction crosslinking agent as an auxiliary crosslinking agent, the strength, distortion, and other physical properties of the resulting toner supply roller can be further improved. Examples of organic peroxide crosslinking agents include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, and 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane. The amount of organic peroxide crosslinking agent is usually 0.1 to 5.0 parts by mass per 100 parts by mass of millable silicone rubber. The organic peroxide crosslinking agents can be used alone or in combination of two or more.

It is preferable to use an addition reaction catalyst in combination with the addition reaction crosslinking agent. Examples of addition reaction catalysts include platinum black, platinic chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetoacetate, palladium catalysts, and rhodium catalysts. The amount of this addition reaction catalyst to be used can be a catalytic amount.

- Chemical foaming agent -
The chemical foaming agent in the present invention may be any foaming agent that has been conventionally used to form the foamed elastic layer 3. For example, inorganic foaming agents include sodium bicarbonate and ammonium carbonate, and organic foaming agents include organic azo compounds such as diazoamino derivatives, azonitrile derivatives, and azodicarboxylic acid derivatives. Among organic azo compounds, azodicarboxylic acid amide and azobis-isobutyronitrile are preferably used. In particular, azobis-isobutyronitrile is preferably used. Although unexpanded microballoons can also be used as the foaming agent, it is preferable to use only a chemical foaming agent as the foaming agent in the present invention.
The content of the chemical foaming agent in the silicone rubber composition is preferably 0.5% by mass or more and 6% by mass or less, from the viewpoint of obtaining cells of uniform size while having a low specific gravity.

-Other ingredients-
The silicone rubber composition may contain various additives. Examples of the various additives include auxiliary agents such as chain extenders, catalysts, dispersants, antioxidants, antioxidants, and fillers other than silica-based materials such as glass beads, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardant improvers, acid acceptors, thermal conductivity improvers, release agents, and solvents. These various additives may be additives that are commonly used, or may be additives that are specially used depending on the application.

(specific gravity)
The specific gravity of the foamed elastic layer 3 is preferably 0.13 or more and 0.6 or less, from the viewpoint of making the layer have a low hardness and improving the toner supplying property and the toner scraping property.

(Cell wall)
The thickness of the cell walls of the foamed elastic layer 3 is preferably 13 μm to 30 μm, more preferably 5 μm to 20 μm. By having the thickness of the cell walls in the above range, it is possible to obtain a toner supply roller having low hardness and high durability.

(Outer diameter return rate)
The outer diameter restoration rate of the foamed elastic layer 3 in a compression test is 90% or more and 100% or less. When the outer diameter restoration rate is in the above range, a toner supply roller with improved distortion characteristics can be obtained.

The outer diameter recovery rate of the foamed elastic layer 3 is measured using a compression tester 60 shown in FIG.
First, the outer diameter of the toner supply roller 1 is measured at room temperature by a laser measuring device. Next, as shown in FIG. 3, the toner supply roller 1 is sandwiched between compression plates 61 and 61, and the handle 63 is turned to tighten. The thickness of the spacer 62 (the length from the upper end surface of the spacer 62 that contacts the upper compression plate 61 to the lower end of the spacer 62 that contacts the lower compression plate 61) is 10 mm, and the handle 63 is turned to tighten according to the thickness of the spacer 62. With the toner supply roller 1 tightened by the compression tester 60, the compression tester 60 is placed in a dryer at 100° C. and heated for 8 hours. After 8 hours, the compression device is removed from the dryer, the toner supply roller 1 is immediately removed from the compression tester 60, and the outer diameter of the toner supply roller 1 is measured by a laser measuring device after leaving it at room temperature for 1 hour. The value calculated by the following formula is the outer diameter recovery rate (%).
Outer diameter recovery rate=(outer diameter of toner supply roller after compression/outer diameter of toner supply roller before compression)×100

The thickness of the foamed elastic layer 3 is not particularly limited, but is preferably 0.1 mm to 6 mm, and more preferably 1 mm to 4 mm. In this specification, the thickness refers to the thickness in the direction perpendicular to the axial direction of the toner supply roller 1.

The outer diameter of the foamed elastic layer 3 is not particularly limited, but is preferably, for example, 6 mm or more and 25 mm or less, and more preferably 7 mm or more and 21 mm or less.

The method for forming the foamed elastic layer 3 is not particularly limited. For example, the foamed elastic layer 3 may be formed by a method such as extrusion molding of a silicone rubber composition or LIMS molding. The foamed elastic layer 3 may also be formed by grinding and polishing the foamed elastic body (cured product of the silicone rubber composition) formed on the shaft body 2.

(Asker F hardness)
The foamed elastic layer 3 has an Asker F hardness of 30 or more and 45 or less. The foamed elastic layer 3 more preferably has an Asker F hardness of 35 or more and 40 or less. When the Asker F hardness is in the above range, a toner supply roller with low hardness can be obtained, and the load and friction on the developer when the rollers are pressed against each other can be reduced.
The Asker F hardness is a value obtained by pressing the center of the presser of a hardness meter against the curved surface of a roller to be measured, and reading the scale at the moment when the reference surface comes into contact with the surface of the roller. In practice, it can be measured using an "Asker Rubber Hardness Meter Type F" manufactured by Kobunshi Keiki Co., Ltd.

(Friction reduction amount)
The friction reduction amount of the foamed elastic layer 3 is preferably 0.2 g or more and 0.35 g or less, and more preferably 0.25 g or more and 0.30 g or less. When the friction reduction amount is in the above range, a toner supply roller having excellent durability can be obtained.
The amount of friction reduction was determined by pressing a metal roller (made of SUS, φ16 mm, surface roughness Ra = 0.5) longer than the axial length of the sponge roller against the sponge roller to a depth of 1 mm from the surface of the sponge roller and rotating it at a rotational speed of 120 rpm for 24 hours, and measuring the amount of rubber reduction after 24 hours.

<Method of Manufacturing Toner Supply Roller>
First, a silicone rubber composition is prepared. The method for mixing the above components of the silicone rubber composition is not particularly limited, and examples thereof include a method in which the millable silicone rubber, the chemical foaming agent, and the crosslinking agent are added sequentially or all at once under normal temperature and pressure, and mixed uniformly using a stirrer, kneader, or the like.

The silicone rubber composition can be obtained by kneading the materials at room temperature or under heating using a rubber mixer such as a two-roll mill, a three-roll mill, a roll mill, a Banbury mixer, or a dough mixer (kneader) until the materials are uniformly mixed, for example, for several minutes to several hours, preferably 5 minutes to 1 hour.

Next, the obtained silicone rubber composition is formed into a cylindrical shape by continuous heat molding such as extrusion molding on the outer surface of a shaft that will form the toner supply roller, and the cylindrical molded body is then heated together with the shaft to be vulcanized (heat curing).

It is preferable to heat the material for the primary vulcanization at 100° C. to 300° C., particularly 150° C. to 250° C., for 5 to 30 minutes, and then to heat the material for the secondary vulcanization at 180° C. to 250° C., particularly 200° C. to 230° C., for 1 to 10 hours. Heating the material multiple times in this manner is preferable because it makes it possible to control the decomposition of the chemical foaming agent, the hardening of the millable silicone rubber, and the elimination of the residual low molecular weight siloxane, as necessary.
The heating required for vulcanization can be carried out by a heating furnace such as an infrared heating furnace or a hot air furnace, or a heating machine such as a dryer.
The foamed elastic layer 3 thus obtained may further be subjected to a polishing step.

[Image forming apparatus]
Next, an embodiment of an image forming apparatus including the toner supply roller 1 of the present invention as developer supply means 43 will be described with reference to FIG.
2, the image forming apparatus 30 according to the present invention includes a rotatable image carrier 31, e.g., a photoreceptor, on which an electrostatic latent image is formed, a charging means 32, e.g., a charging roller, an exposure means 33, a developing means 40, a transfer means 34, e.g., a transfer roller, a cleaning means 37, e.g., a cleaning roller, which are arranged around the image carrier 31, and a fixing means 35 on the downstream side in the transport direction of the recording medium 36. The developing means 40 is basically formed in the same manner as a conventional developing means, and specifically, as shown in FIG. 2, includes a developer storage section 41, a developer carrier 44 which supplies developer 42 to the image carrier 31, a developer supplying means 43 which supplies developer 42 to the developer carrier 44, and a developer regulating member 45 which charges the developer 42.

As shown in FIG. 2, the fixing means 35 is a pressure heat fixing device that is rotatably supported so that the fixing roller 53 and the pressure roller 56 are in contact with each other via the endless belt 55 and is provided in a housing 50 having an opening 52 through which the recording medium 36 passes. The fixing roller 53 is supported in a freely rotatable manner so that the fixing roller 53 and the pressure roller 56 are in contact with each other or in pressure contact with each other via the endless belt 55.

The endless belt support roller 54 may be a roller normally used in an image forming apparatus, such as an elastic roller. The endless belt 55 may be a belt formed in an endless shape from a resin such as polyamide or polyamideimide, and its thickness may be adjusted appropriately to fit the fixing means 35. The pressure roller 56 is pressed against the fixing roller 53 via the endless belt 55 by a spring or other biasing means (not shown). The heating means may be a radiant heating method using a halogen heater or a reflector, a direct contact heating method in which a heater or the like is directly contacted to heat the fixing roller 53, or an induction heating method. This heating means is a member having a length approximately equal to the axial length of the fixing roller 53, and may be disposed anywhere in the fixing means 35, but it is preferable that it is disposed approximately parallel to the fixing roller 53 at a certain distance from the surface of the fixing roller 53, as shown in FIG. 2. The induction heating method uses a heating coil, which is usually made of a ferromagnetic material such as ferrite and is wound with a conductor in the typical shapes used for switching power supplies, such as I-type, E-type, and U-type. When the recording medium 36 passes through the pressure-contact gap between the endless belt 55 and the pressure roller 56, it is heated and pressurized, and the developer 42 (electrostatic latent image) transferred to the recording medium 36 can be fixed.

The image forming apparatus 30 according to the present invention operates as follows. First, in the image forming apparatus 30, the image carrier 31 is uniformly charged by the charging means 32, and an electrostatic latent image is formed on the surface of the image carrier 31 by the exposure means 33. Next, the developer 42 is supplied from the developing means 40 to the image carrier 31 to develop the electrostatic latent image, and this developer image is transferred onto the recording medium 36 transported between the image carrier 31 and the transfer means 34. The toner supply roller of the present invention can be suitably used, for example, for the developer supply means 43 and the developer carrier 44, and since it has a low hardness, the load and friction on the developer are reduced. Furthermore, since the distortion characteristics are also improved, it has excellent durability. This recording medium 36 is transported to the fixing means 35, and the developer image is fixed to the recording medium 36 as a permanent image. In this way, an image can be formed on the recording medium 36.

The fixing roller 53 or pressure roller 56 in this fixing means 35 has excellent fixing properties for fixing the developer to the recording medium and consumes little power.

The toner supply roller and image forming device according to this invention are not limited to the above-mentioned embodiments, and various modifications are possible within the scope of the invention.

For example, in the toner supply roller 1, the foamed elastic layer 3 has a single-layer structure, but in this invention it may have a multi-layer structure of two or more layers.

The image forming apparatus 30 is an electrophotographic image forming apparatus, but in this invention, the image forming apparatus is not limited to the electrophotographic type, and may be, for example, an electrostatic type image forming apparatus. Also, the image forming apparatus 30 is a monochrome image forming apparatus that contains only a single color developer 42 in the developing means 40, but in this invention, the image forming apparatus is not limited to the monochrome image forming apparatus, and may be a color image forming apparatus. Examples of color image forming apparatuses include a four-cycle type color image forming apparatus that sequentially repeats the primary transfer of a developer image carried on an image carrier to an intermediate transfer body, and a tandem type color image forming apparatus in which multiple image carriers equipped with developing means for each color are arranged in series on an intermediate transfer body or a transfer conveyor belt. The image forming apparatus 30 is, for example, an image forming apparatus such as a copier, a facsimile, or a printer.

The present invention will be described in detail below with reference to examples. Note that the present invention is not limited to the examples shown below.

[Example 1]
(Primer layer)
An electroless nickel-plated shaft (made of SUM22, diameter 10 mm, length 275 mm) was washed with ethanol, and its surface was coated with a silicone-based primer (product name "Primer No. 16", made by Shin-Etsu Chemical Co., Ltd.). The primer-treated shaft was baked in a gear oven at 150°C for 10 minutes and then cooled at room temperature for 30 minutes or more to form a primer layer on the outer circumferential surface of the shaft.

(Foamed Elastic Layer)
A foamed elastic layer was formed on the shaft body by the following method.
First, a silicone rubber composition for the foamed elastic layer was prepared by kneading 215 parts by mass of dimethyl silicone raw rubber (product name "KE-76VBS") and 25 parts by mass of a conductivity imparting agent (product name "KE-87C40PU", manufactured by Shin-Etsu Chemical Co., Ltd.) to prepare a millable type silicone rubber.
To 100 parts by mass of the above millable type silicone rubber, 10 parts by mass of silicone rubber balls (product name "KMP598", Shin-Etsu Chemical Co., Ltd., average particle size 13 μm), 2 parts by mass of an addition reaction crosslinking agent (product name "C-25B", Shin-Etsu Chemical Co., Ltd.), 5 parts by mass of a chemical foaming agent (product name AZO series AIBN, Otsuka Chemical Co., Ltd.), and 2 parts by mass of a platinum catalyst (product name "C-25A", Shin-Etsu Chemical Co., Ltd.) were added to prepare a silicone rubber composition.

Next, the shaft body with the primer layer formed and the silicone rubber composition were extruded as one unit using an extruder, and the mixture was heated at 225°C for 17 minutes in an infrared heating furnace (IR furnace) for primary vulcanization, and then the mixture was subjected to secondary vulcanization at 225°C for 7 hours in a hot air drying furnace to produce a foamed roller base body. The circumferential surface of this foamed roller base body was polished at high speed with a metal grindstone using a polishing machine manufactured by Mizuguchi Seisakusho Co., Ltd., to produce a toner supply roller with an outer diameter of 13 mm.

[Example 2]
A toner supply roller was produced in the same manner as in Example 1, except that the content of the silicone rubber balls in the silicone rubber composition was 20 parts by mass.

[Example 3]
A toner supply roller was produced in the same manner as in Example 1, except that the content of the silicone rubber balls in the silicone rubber composition was 4 parts by mass.

[Comparative Example 1]
A toner supply roller was produced in the same manner as in Example 1, except that the silicone rubber composition did not contain any silicone rubber balls.

[Comparative Example 2]
A toner supply roller was produced in the same manner as in Example 1, except that the silicone rubber composition contained 4.1 parts by mass of silica particles instead of the silicone rubber balls.

[Comparative Example 3]
A toner supply roller was produced in the same manner as in Example 1, except that the silicone rubber composition contained 8.2 parts by mass of silica particles instead of the silicone rubber balls.

For the above examples and comparative examples, the outer diameter recovery rate (%), Asker F hardness, and friction reduction were measured using the above methods. The evaluation results are shown in Table 1.

As shown in Table 1, the toner supply roller of the present invention, which has a foamed elastic layer containing silicone rubber balls, has a low rubber hardness and a high outer diameter return rate, so the occurrence of distortion is suppressed. Furthermore, since the amount of friction reduction is small, toner can be supplied and scraped off well, so good images can be obtained for a long period of time.

REFERENCE SIGNS LIST 1 Toner supply roller 2 Shaft body 3 Foamed elastic layer 30 Image forming device 31 Image carrier 32 Charging means 33 Exposure means 34 Transfer means 35 Fixing means 36 Recording body 37 Cleaning means 40 Developing means 41 Developer storage section 42 Developer 43 Developer supply means 44 Developer carrier 45 Developer regulating member 50 Housing 52 Opening 53 Fixing roller 54 Endless belt support roller 55 Endless belt 56 Pressure roller 60 Compression tester 61 Compression plate 62 Spacer 63 Handle

Claims (4)

A toner supply roller having a shaft body and a foamed elastic layer formed on an outer peripheral surface of the shaft body,
the foamed elastic layer is formed from a silicone rubber composition containing millable silicone rubber, silicone rubber balls, a crosslinking agent and a chemical foaming agent;
The content of the silicone rubber balls is 4 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the millable type silicone rubber ,
The foamed elastic layer has an Asker F hardness of 30 or more and 50 or less,
The foamed elastic layer has an outer diameter recovery rate of 90% or more and 100% or less in a compression test;
The toner supply roller has a friction reduction amount of the foamed elastic layer of 0.28 g or less, as measured by the following measurement method.
<Measurement method>
A metal roller (made of SUS, φ16 mm, surface roughness Ra = 0.5) longer than the axial length of the toner supply roller is pressed against the toner supply roller to a depth of 1 mm from the surface of the toner supply roller, and rotated at a rotation speed of 120 rpm for 24 hours. The amount of rubber loss after 24 hours is measured and this is regarded as the amount of friction loss. The toner supply roller according to claim 1, wherein the average particle size of the silicone rubber balls is 5 μm or more and 20 μm or less. The toner supply roller according to claim 1 or 2, wherein the specific gravity of the foamed elastic layer is 0.13 or more and 0.6 or less. 4. An image forming apparatus comprising the toner supply roller according to claim 1.