JP7178165B2 - Elastic roller and image forming apparatus - Google Patents

Description

The present invention relates to elastic rollers and image forming apparatuses.

2. Description of the Related Art Conventionally, various elastic rollers such as developing rollers, charging rollers, fixing rollers, and heating rollers have been used in image forming apparatuses such as printers, copiers, facsimiles, and multifunctional machines thereof. These elastic rollers generally have an elastic layer containing an elastic body formed on a shaft.

As such an elastic roller, for example, Patent Document 1 discloses a pressure roller having characteristics of Asker C hardness of 45 degrees or more and surface micro hardness of 45 degrees or less.

JP-A-2000-221823

2. Description of the Related Art In recent years, image forming apparatuses are required to have elastic rollers with finer characteristics as image formation becomes more precise and faster.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an elastic roller capable of sufficiently suppressing thermal expansion in a usage environment and maintaining fine characteristics for a long period of time, and an image forming apparatus having the elastic roller.

One aspect of the present invention relates to an elastic roller comprising a shaft, a foamed elastic layer having a thickness of less than 1.5 mm provided on the outer peripheral surface of the shaft, and a coating layer provided on the foamed elastic layer. . In one embodiment, the foamed elastic layer contains silicone rubber and hollow glass beads. Further, the elastic roller has an Asker C hardness of 80 or more on the surface of the roller.

In one aspect, the hollow glass beads may have an average particle size of 60 μm or less.

In one aspect, the content of the hollow glass beads may be 5 to 20% by mass based on the total amount of the foamed elastic layer.

Another aspect of the present invention relates to an image forming apparatus including the elastic roller.

According to the present invention, an elastic roller capable of sufficiently suppressing thermal expansion under a use environment and maintaining fine characteristics for a long period of time, and an image forming apparatus provided with the elastic roller are provided.

It is a front view showing an outline of an elastic roller concerning one embodiment. FIG. 2 is a cross-sectional view showing a cross section taken along line II-II of FIG. 1; FIG. 2 is a cross-sectional view showing a cross section taken along line III-III of FIG. 1;

Preferred embodiments of the present invention will be described below with reference to the drawings. Note that the drawings are drawn in an exaggerated manner for easy understanding, and the dimensional ratios and the like are not limited to those described in the drawings.

FIG. 1 is a front view showing an outline of an elastic roller according to this embodiment. FIG. 2 is a cross-sectional view showing a cross section taken along line II-II of FIG. FIG. 3 is a cross-sectional view showing a cross-section taken along line III--III in FIG. The elastic roller 1 according to this embodiment includes a shaft 2, a foamed elastic layer 3 provided on the outer peripheral surface of the shaft 2, and a covering layer 4 provided on the foamed elastic layer 3. .

The Asker C hardness of the roller surface of the elastic roller 1 is 80 or more. In addition, in this specification, the Asker C hardness indicates a value measured by the following measuring method.

<Method for measuring Asker C hardness>
The Asker C hardness of the roll surface is measured using an Asker C type hardness tester (manufactured by Kobunshi Keiki Co., Ltd.) in accordance with SRIS (Japan Rubber Society Standard) 0101. More specifically, the Asker C hardness is the hardness measured by contacting the indenter of an Asker C hardness tester to the roll surface and applying a constant pressure load (9.8 N).

In the elastic roller 1, the upper limit of the Asker C hardness of the roller surface is not particularly limited, and may be, for example, 95 or less, or 86 or less. The Asker C hardness of the roller surface of the elastic roller 1 can be adjusted, for example, by changing the expansion ratio of the foam constituting the foamed elastic layer 3, changing the composition of the foam, and changing the molding conditions of the foam.

The shaft 2 may be a shaft used for known elastic rollers. The shaft 2 may be made of metal such as iron, aluminum, stainless steel, brass, or the like. Such a shaft 2 can be rephrased as a metal core. Moreover, the shaft 2 does not necessarily have to be made of metal, and may be made of, for example, a resin material. The resin material may be, for example, a thermoplastic resin or a thermosetting resin, or may be a conductive resin obtained by blending a conductivity-imparting agent with a thermoplastic resin or a thermosetting resin.

The shaft 2 may be made of one material, or may be made of two or more materials. The shaft 2 may be composed of, for example, a core material and an outer covering layer that covers the core material. Specifically, for example, the shaft 2 may be a metal core material that is plated.

The outer peripheral surface of the shaft 2 may be roughened in order to improve adhesion with the foamed elastic layer 3 or to improve the effect of the primer treatment described below. The roughening treatment method is not particularly limited, and may be appropriately selected from known methods according to the material of the shaft 2 and the like. Specific examples of roughening treatment methods include sandblasting and polishing.

The outer peripheral surface of the shaft body 2 may be subjected to a primer treatment for improving adhesion to the foamed elastic layer 3 . The primer treatment method is not particularly limited, and may be appropriately selected from known methods according to the material of the shaft 2, the composition of the foamed elastic layer 3, and the like. Examples of suitable primers include alkyd resins, phenol-modified and silicone-modified alkyd resins, oil-free alkyd resins, acrylic resins, silicone resins, epoxy resins, fluorine resins, phenol resins, polyamide resins, urethane resins, and the like. can be used.

The outer diameter of the shaft 2 may be appropriately changed according to the form of the image forming apparatus. The outer diameter of the shaft 2 may be, for example, 6-40 mm, preferably 10-30 mm. The length of the shaft 2 may be appropriately changed according to the form of the image forming apparatus. The length of the shaft 2 may be, for example, 100-600 mm, preferably 130-500 mm.

The foamed elastic layer 3 is provided on the outer peripheral surface of the body portion of the shaft 2 and is made of a foam containing silicone rubber and hollow glass beads. The silicone rubber may be, for example, a crosslinked product of raw silicone rubber, which will be described later.

Hollow glass beads may be hollow particles composed of various types of glass. The hollow glass beads may be spherical or irregular, but preferably spherical from the viewpoint of excellent dispersibility in silicone rubber.

The glass constituting the hollow glass beads is not particularly limited, and may be, for example, at least one selected from the group consisting of soda lime glass, low alkali glass, borosilicate glass, quartz glass and aluminosilicate glass. Among these, borosilicate glass and aluminosilicate glass are preferable because they have excellent impact resistance and low thermal expansion.

The average particle diameter of the hollow glass beads may be, for example, 60 μm or less, preferably 40 μm or less, more preferably 30 μm or less. This tends to further improve the uniformity of the foamed elastic layer 3 . The average particle size of the hollow glass beads may be 10 µm or more, or may be 20 µm or more.

In addition, in this specification, the average particle size of the hollow glass beads indicates a value measured with a scanning electron microscope (SEM).

The specific gravity of the hollow glass beads may be, for example, 0.1 or more, preferably 0.2 or more. Also, the density of the hollow glass beads may be, for example, 1.3 or less, preferably 0.5 or less.

Hollow glass beads may be prepared as appropriate and may be commercially available. Commercially available products include, for example, the product series name “Sphericel” (manufactured by Potters-Ballotini Co., Ltd.), the product name “110P8” (borosilicate glass, average particle diameter 12 μm, specific gravity 1.10 g / cm ³ ), trade name “60P18” (borosilicate glass, average particle size 18 μm, specific gravity 0.60 g/cm ³ ), trade name “34P30” (borosilicate glass, average particle size 35 μm, specific gravity 0.34 g/cm ³ ). , trade name “25P45” (borosilicate glass, average particle diameter 45 μm, specific gravity 0.25 g/cm ³ ), and the like. In addition, other commercially available products include, for example, product series names "Q-CEL", "Ceramic Multi Cellular" and "Extendospheres" (all manufactured by Potters-Ballotini Co., Ltd.), and products Series name "Glass Bubbles" (soda lime borosilicate glass) (manufactured by Sumitomo 3M Co., Ltd.) and the like are also included.

The hollow glass beads may have their surfaces treated with a silane coupling agent. As a result, the adhesiveness to the silicone rubber constituting the foamed elastic layer 3 is improved, and there is a tendency that the foamed elastic layer 3 is less likely to come off. Examples of silicone coupling agents include (meth)acryloyl group-containing (meth)acrylsilane coupling agents, amino group-containing aminosilane coupling agents, epoxy group-containing epoxysilane coupling agents, and vinyl group-containing vinylsilane coupling agents. ring agents, mercaptosilane coupling agents having a mercapto group, and the like.

Examples of (meth)acrylsilane coupling agents include 3-acryloxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane.

Examples of aminosilane coupling agents include 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylethyldiethoxysilane, 3-aminopropyldimethylethoxysilane. , 3-aminopropylmethyldiethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-( aminoethyl)-3-aminopropyltriethoxysilane, N,N-dimethylaminopropyltrimethoxysilane, N,N-diethylaminopropyltrimethoxysilane, N,N-dipropylaminopropyltrimethoxysilane, N,N-dibutyl aminopropyltrimethoxysilane, N-monobutylaminopropyltrimethoxysilane, N,N-dioctylaminopropyltrimethoxysilane, N,N-dibutylaminopropylmethyldimethoxysilane, N,N-dibutylaminopropyldimethylmonomethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N,N-dimethylaminophenyltrimethoxysilane, trimethoxysilyl-3-propylphenylamine, trimethoxysilyl-3-propylbenzylamine , trimethoxysilyl-3-propylpiperidine, trimethoxysilyl-3-propylmorpholine, trimethoxysilyl-3-propylimidazole, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-acryloxypropyltri methoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane and the like.

The content of the hollow glass beads in the foamed elastic layer 3 may be, for example, 0.8% by mass or more, preferably 4.0% by mass or more, more preferably 8.0% by mass, based on the total amount of the foamed elastic layer 3. % or more. With such a content, the thermal expansion of the foamed elastic layer 3 tends to be smaller. The content of the hollow glass beads may be, for example, 25.0% by mass or less, preferably 20.0% by mass or less, and more preferably 16.0% by mass or less based on the total amount of the foamed elastic layer 3. It's okay. Such a content tends to further improve the hardness of the foamed elastic layer 3 .

The foam may be obtained, for example, by foaming and curing a silicone composition containing raw silicone rubber, a foaming agent, a cross-linking agent, and hollow glass beads. That is, the foam may be a foamed cured product of the above silicone composition.

The silicone raw rubber is not particularly limited, and may be any known silicone raw rubber. Examples of the silicone raw rubber include vinyl group-containing silicone raw rubber (more specifically, vinyl group-containing dimethylsilicone raw rubber, vinyl group-containing phenylsilicone raw rubber, vinyl group-containing fluorosilicone raw rubber, etc.), modified products thereof, and the like. be done.

The raw silicone rubber may be, for example, a millable silicone rubber, a thermally crosslinked silicone rubber, or the like. As the silicone raw rubber, commercially available products may be used. "KE-541-U", "KE-551-U", "KE-561-U", "KE-961T-U", "KE-1541-U", "KE-1551-U", "KE -941-U", "KE-971T-U", etc. may be used.

The amount of silicone crude rubber to be blended may be, for example, 40 to 80% by mass, preferably 50 to 70% by mass, based on the total amount of the silicone composition.

The foaming agent is not particularly limited, and any known silicone rubber foaming agent may be used. As the foaming agent, organic azo foaming agents such as azobisisobutyronitrile (AIBN), azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), and hydrazodicarbonamide (HDCA) are preferably used. be able to.

The blending amount of the foaming agent may be appropriately changed according to the foaming ratio of the foam. The expansion ratio of the foam may be, for example, 110% or more, or 150% or more. Moreover, the expansion ratio of the foam may be, for example, 500% or less, or may be 350% or less. The blending amount of the foaming agent may be an amount that can achieve such an expansion ratio.

The cross-linking agent is not particularly limited, and a known cross-linking agent for silicone rubber may be used. Examples of cross-linking agents include addition reaction cross-linking agents and organic peroxide cross-linking agents. The addition reaction cross-linking agent includes, for example, organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms in one molecule. Organohydrogenpolysiloxanes may, for example, have linear, cyclic or branched alkyl groups. Examples of organic peroxide cross-linking agents include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5- Examples thereof include bis(t-butylperoxy)hexane.

The amount of the cross-linking agent may be, for example, 0.5 to 10.0% by mass, preferably 1.0 to 5.0% by mass, based on the total amount of the silicone composition.

The content of the hollow glass beads may be, for example, 0.8% by mass or more, preferably 4.0% by mass or more, and more preferably 8.0% by mass or more based on the total amount of the silicone composition. . The amount of the hollow glass beads to be blended may be, for example, 25.0% by mass or less, preferably 20.0% by mass or less, and more preferably 16.0% by mass or less, based on the total amount of the silicone composition. you can

The silicone composition may further contain components other than those mentioned above. For example, the silicone composition may further include reinforcing silica fillers such as fumed silica, precipitated silica, and the like. In addition, the silicone composition may further contain a curing aid. Curing aids may be, for example, peroxides. Examples of peroxides include benzoyl peroxide, bis-2,4-dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis(t-butyl peroxide). Oxy)hexane and the like are exemplified.

Moreover, the silicone composition may further contain a reaction inhibitor. Examples of reaction inhibitors include methylvinylcyclotetrasiloxane, acetylene alcohols, siloxane-modified acetylene alcohol, and hydroperoxide.

In addition, the silicone composition may further contain a curing accelerator. Curing accelerators include, for example, platinum catalysts. Examples of platinum catalysts include chloroplatinic acid, alcohol-modified chloroplatinic acid, platinum supported on a solid catalyst (e.g., platinum black, alumina, silica, carbon, etc.), platinum and olefin, alcohol or vinyl siloxane. complexes, and the like.

In addition, the silicone composition may further contain heat resistance improvers, non-reinforcing silica for adjusting hardness, fillers, colorants, heat conductivity improvers, and the like.

The foamed elastic layer 3 may be formed by heating a silicone composition placed on the outer peripheral surface of the shaft 2 to foam and harden it. The curing temperature may be, for example, 100-300°C, or 150-250°C.

The foamed elastic layer 3 may be formed by grinding or polishing the foamed cured product of the silicone composition formed on the outer peripheral surface of the shaft 2 to have a predetermined thickness. Grinding or polishing may be, for example, profile grinding with a cylindrical grinder.

The thickness of the foamed elastic layer 3 is less than 1.5 mm. In the present embodiment, in the elastic roller 1 having the foamed elastic layer 3 with a thickness of less than 1.5 mm, by setting the Asker C hardness and the composition of the foamed elastic layer 3 to specific values, thermal expansion under the usage environment is reduced to Sufficiently suppressed. The thickness of the foamed elastic layer 3 may be 1.3 mm or less. Moreover, the thickness of the foamed elastic layer 3 may be 0.5 mm or more, or may be 1.0 mm or more.

A covering layer 4 may be provided on the outer peripheral surface of the foamed elastic layer 3 . The coating layer 4 is a layer that covers the outer peripheral surface of the foamed elastic layer 3 to flatten the roller surface.

The composition of the coating layer 4 may be appropriately selected according to the application of the elastic roller. For example, the coating layer 4 may be a layer containing a fluororesin (a fluororesin layer).

Examples of the fluororesin include fluoroethylene-propylene copolymer (FEP), fluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTFE), and the like.

The thickness of the coating layer 4 is not particularly limited, and may be appropriately adjusted according to the type of the coating layer 4, the application of the elastic roller 1, and the like. For example, when the coating layer 4 is a fluororesin layer, the thickness of the coating layer 4 may be, for example, 15 to 150 μm, and may be 20 to 100 μm.

An adhesive layer may be further provided between the foamed elastic layer 3 and the covering layer 4 to bond them together. The adhesive layer may be a layer containing an adhesive or a cured product thereof. As the adhesive, for example, a silicone adhesive, an acrylic adhesive, or the like can be used. The thickness of the adhesive layer is not particularly limited, and may be, for example, 1 to 100 μm, or 5 to 50 μm.

As described above, in the elastic roller 1 according to the present embodiment, the thickness of the foamed elastic layer 3 is less than 1.5 mm, the foamed elastic layer 3 contains silicone rubber and hollow glass beads, and the roll surface has an Asker C hardness. is 80 or more. By having such a configuration, the elastic roller 1 is sufficiently suppressed from thermal expansion under the usage environment (for example, 150 to 200° C.). In addition, since the elastic roller 1 has the above-described structure, the thermal expansion coefficients at the roller ends and the roller center are made uniform, and even if there is a slight thermal expansion, the thermal expansion between the roller ends and the roller center distortion is reduced, and fine characteristics are maintained. Furthermore, in the elastic roller 1, the foamed elastic layer 3 containing hollow glass beads functions as a heat insulating layer, so that energy saving of the image forming apparatus can be achieved.

In conventional elastic rollers, it is necessary to increase the specific gravity of the elastic layer in order to increase the hardness. it was difficult to In contrast, the elastic roller according to the present embodiment maintains a sufficiently low coefficient of thermal expansion while being a high-hardness elastic roller with an Asker C hardness of 80 or more.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

For example, one aspect of the present invention relates to an image forming apparatus including the elastic roller 1 described above. In the image forming apparatus, the elastic roller 1 is used as, for example, a pressure roller, a fixing roller, and the like. Components of the image forming apparatus other than the elastic roller 1 may be the same as those of known image forming apparatuses.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the examples.

(Example 1)
In Example 1, 100 parts by mass of millable silicone rubber, 3.0 parts by mass of addition cross-linking agent, 3.0 parts by mass of organic peroxide cross-linking agent, 1.5 parts by mass of platinum catalyst, and hollow glass beads having an average particle size of 12 µm. A mixture of 20.0 parts by weight and 1.5 parts by weight of a chemical blowing agent (AIBN) was used as the silicone composition.

A metal shaft (SUM22 plated with electroless nickel, diameter 23 mm) was washed with toluene and coated with a primer. After applying the primer, the metal shaft was baked in a gear oven at a temperature of 180° C. for 30 minutes, and cooled at room temperature for 30 minutes or more. Then, the metal shaft and the silicone composition were integrally extruded by an extruder and heated to 220° C. in an IR furnace to foam and cure the silicone composition. After that, the outer shape was ground by a cylindrical grinder to form a foamed elastic layer having a thickness of 1.0 mm.

Next, an adhesive was applied to the outer peripheral surface of the foamed elastic layer, which was press-fitted into a PFA tube having a thickness of 50 μm and heated at a temperature of 120° C. for 1 hour to form a coating layer made of PFA. The elastic roller (A-1) of Example 1 was obtained by the above method. The Asker C hardness of the roller surface of the elastic roller (A-1) was 84.5.

The obtained elastic roller (A-1) was subjected to a thermal expansion test by the following method.

<Thermal expansion test>
First, the outer diameter of the elastic roller at room temperature (23° C.) was measured. Next, the elastic roller was heated in a constant temperature bath at 180° C., and the outer diameter of the elastic roller was measured every 10 minutes for 60 minutes after the start of heating. The coefficient of thermal expansion at each time was calculated from the difference between the initial outer diameter and the outer diameter after heating, and the maximum value was evaluated as the maximum value of the thermal expansion coefficient.

As a result of the thermal expansion test, the maximum thermal expansion coefficient of the elastic roller (A-1) was 10.0%.

(Example 2)
An elastic roller (A-2) was produced in the same manner as in Example 1, except that hollow glass beads having an average particle diameter of 35 μm were used as the hollow glass beads. The Asker C hardness of the roller surface of the elastic roller (A-2) was 84.3.

The obtained elastic roller (A-2) was subjected to a thermal expansion test in the same manner as in Example 1, and the maximum thermal expansion coefficient of the elastic roller (A-2) was 10.0%.

(Example 3)
An elastic roller (A-3) was produced in the same manner as in Example 1, except that the thickness of the foamed elastic layer was changed to 1.2 mm. The Asker C hardness of the roller surface of the elastic roller (A-3) was 83.6.

The obtained elastic roller (A-3) was subjected to a thermal expansion test in the same manner as in Example 1, and the maximum thermal expansion coefficient of the elastic roller (A-3) was 10.5%.

(Example 4)
An elastic roller (A-4) was produced in the same manner as in Example 1, except that the thickness of the foamed elastic layer was changed to 1.4 mm. The Asker C hardness of the roller surface of the elastic roller (A-4) was 83.2.

The obtained elastic roller (A-4) was subjected to a thermal expansion test in the same manner as in Example 1, and the maximum thermal expansion coefficient of the elastic roller (A-4) was 10.5%.

(Example 5)
An elastic roller (A-5) was produced in the same manner as in Example 1, except that hollow glass beads having an average particle diameter of 35 μm were used as the hollow glass beads, and the thickness of the foamed elastic layer was changed to 1.2 mm. . The Asker C hardness of the roller surface of the elastic roller (A-5) was 83.5.

The obtained elastic roller (A-5) was subjected to a thermal expansion test in the same manner as in Example 1, and the maximum thermal expansion coefficient of the elastic roller (A-5) was 10.0%.

(Example 6)
An elastic roller (A-6) was produced in the same manner as in Example 1, except that the blending amount of the hollow glass beads was changed to 10 parts by mass and the average particle diameter of the hollow glass beads was changed to 35 μm. The Asker C hardness of the roller surface of the elastic roller (A-6) was 83.0.

The obtained elastic roller (A-6) was subjected to a thermal expansion test in the same manner as in Example 1, and the maximum thermal expansion coefficient of the elastic roller (A-6) was 10.8%.

(Example 7)
An elastic roller (A-7) was produced in the same manner as in Example 1, except that the blending amount of the hollow glass beads was changed to 10 parts by mass. The Asker C hardness of the roller surface of the elastic roller (A-7) was 83.4.

The obtained elastic roller (A-7) was subjected to a thermal expansion test in the same manner as in Example 1, and the maximum value of the thermal expansion coefficient of the elastic roller (A-7) was 11.0%.

(Example 8)
The procedure was the same as in Example 1, except that the blending amount of the hollow glass beads was changed to 10 parts by mass, the average particle size of the hollow glass beads was changed to 35 μm, and the thickness of the foamed elastic layer was changed to 1.4 mm. An elastic roller (A-8) was produced. The Asker C hardness of the roller surface of the elastic roller (A-8) was 82.6.

The obtained elastic roller (A-8) was subjected to a thermal expansion test in the same manner as in Example 1, and the maximum thermal expansion coefficient of the elastic roller (A-8) was 10.5%.

(Comparative example 1)
An elastic roller (B-1) was produced in the same manner as in Example 1, except that the thickness of the foamed elastic layer was changed to 1.6 mm. The Asker C hardness of the roller surface of the elastic roller (B-1) was 79.5.

The obtained elastic roller (B-1) was subjected to a thermal expansion test in the same manner as in Example 1, and the maximum thermal expansion coefficient of the elastic roller (B-1) was 10.5%.

(Comparative example 2)
An elastic roller (B-2) was produced in the same manner as in Example 1, except that the amount of the chemical foaming agent was changed to 2 parts by mass. The Asker C hardness of the roller surface of the elastic roller (B-2) was 78.3.

The obtained elastic roller (B-2) was subjected to a thermal expansion test in the same manner as in Example 1, and the maximum thermal expansion coefficient of the elastic roller (B-2) was 9.5%.

(Comparative Example 3)
An elastic roller (B-3) was produced in the same manner as in Example 1, except that the blending amount of the hollow glass beads was changed to 0 parts by mass. The Asker C hardness of the roller surface of the elastic roller (B-3) was 79.5.

The obtained elastic roller (B-3) was subjected to a thermal expansion test in the same manner as in Example 1, and the maximum thermal expansion coefficient of the elastic roller (B-3) was 11.0%.

In the elastic rollers of Examples, it was possible to achieve a sufficiently low coefficient of thermal expansion while being a high-hardness elastic roller with an Asker C hardness of 80 or more. On the other hand, the elastic roller of the comparative example could not achieve both high hardness and low coefficient of thermal expansion.

DESCRIPTION OF SYMBOLS 1... Elastic roller, 2... Shaft, 3... Foamed elastic layer, 4... Coating layer.

Claims (4)

a shaft;
a foamed elastic layer having a thickness of less than 1.5 mm provided on the outer peripheral surface of the shaft;
a covering layer provided on the foamed elastic layer;
with
The foamed elastic layer contains silicone rubber and hollow glass beads,
An elastic roller having an Asker C hardness of 80 or more on the surface of the roller. 2. The elastic roller according to claim 1, wherein the hollow glass beads have an average particle size of 60 [mu]m or less. 3. The elastic roller according to claim 1, wherein the content of said hollow glass beads is 0.8 to 25.0% by mass based on the total amount of said foamed elastic layer. An image forming apparatus comprising the elastic roller according to any one of claims 1 to 3.

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