JPH11147267A - Production of foam roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and inexpensively produce a foam roller of high accuracy having no difference in level in its superposed part. SOLUTION: A foam roller is produced by forming a rubber 13 into a cylindrical shape on a core metal 12 in a non-foamed state and winding a thermoplastic sheet-like film 14 around the cylindrical non-foamed rubber so that the winding start part and winding terminal part thereof are superposed on one another and fitting the whole in a tubular mold in this state to heat the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging roller, a transfer roller, a developing roller, a conveying roller, a fixing roller, and a charging roller used in an image forming apparatus utilizing an electrophotographic process.
The present invention relates to a method of manufacturing a foam roller used for an intermediate transfer member or the like.

[0002]

2. Description of the Related Art Heretofore, in an electrophotographic process, a charging / transferring process has been performed using corona discharge. However, there is a problem that harmful ozone is generated at the time of corona discharge, a problem that deterioration of the photoreceptor surface progresses due to the ozone, a problem that a stain on a wire that performs corona discharge affects an image and causes image white spots and black streaks. there were.

Accordingly, contact charging / transfer techniques have been actively studied. FIG. 1 is a schematic cross-sectional view of a configuration diagram of an electrophotographic apparatus using a contact charging / transferring member. The photoconductor 1 is a photoconductor used in a drum type electrophotographic process, and is an image carrier as a member to be charged. It consists of two layers, a conductive base layer using aluminum and a photoconductive layer formed on the outer peripheral surface thereof.

The charging roller 2 is a charging member that comes into contact with the photoconductor and uniformly charges the photoconductor surface to a predetermined potential.
This charging roller is composed of a central metal core and a layer of a conductive elastic body formed on the outer periphery thereof. This charging roller is
The photosensitive member 1 is pressed against the photosensitive member 1 with a predetermined pressing force by a pressing member such as a spring, and is rotated by the rotation of the photosensitive member 1. Further, by applying a DC + AC (or DC only) bias to the cored bar, the photoconductor 1 is contact-charged to a predetermined potential. In order to obtain a good copy image, a uniform contact state and conductivity are required.

[0005] The surface of the photoreceptor 1 charged to a predetermined potential by contact with the charging roller 2 is exposed to image information by exposure means 3 such as a laser or an LED to form an electrostatic latent image corresponding to the target image information. Form.

Next, the latent image is visualized as a toner image 9 by the developing means 4. The toner image on the surface of the photoreceptor 1 is transferred to the front surface of the transfer material 5 by charging the transfer material 6 from the back of the transfer material 5 with a polarity opposite to that of the toner. The transfer material 5 to which the toner image has been transferred is separated from the photoreceptor 1 and fixed by heat and pressure by a fixing member 7. Further, the surface of the photoconductor 1 after the image transfer is removed by the cleaning unit 8 to remove the adhered matter such as residual toner at the time of transfer, and the surface is cleaned, so that the photoconductor can be repeatedly used for image formation.

The charging roller and the transfer roller used in such a process are constituted by a core metal rotatably supported at both ends and a conductive elastic body provided in a column shape around the core metal. As the elastic body used for such a roller, a foam having a low hardness is often used in order to obtain a uniform contact state without damaging the photoconductor.

[0008] Further, the conductive elastic body is coated with a conductive tube adjusted to a desired resistance, and the conductive elastic body is coated with a conductive paint to adjust the roller resistance. is there.

Heretofore, the following methods have been employed as methods for producing these multi-layered foam rollers.

First, as a method of forming a foamed layer of a roller having a multilayer structure, a rubber material before foaming is extruded into a tube shape, and is heated and vulcanized / foamed to obtain a tubular foamed material. A method of inserting gold and polishing to a desired outer diameter in this state is used. Other methods include wrapping rubber before vulcanization and foaming on a core metal, or molding a rubber material on a core metal using a crosshead to create a charged shape, and then inserting it into a cylindrical pipe mold. And heating to perform vulcanization and foaming to obtain a foamed roller.

After a foam layer as a base layer is formed on a core metal by using these means, the foam layer is coated on the foam layer by a coating method such as tube coating, dip coating, spray coating or roll coating. By forming the surface layer, a roller having a multilayer structure was formed.

[0012] Here, the tube used for coating the tube is conventionally formed by extruding hot-melt molding represented by an inflation method, by melting a resin or its pre-driving body, and applying the resin on the inner and outer surfaces of a tubular mold. Casting method in which a solvent is removed and then peeled off, JP-A-8-1877
It has been obtained by, for example, a method of fusing a sheet as shown in JP-A-73-73 to form a tube.

[0013]

However, as a method for coating the surface layer on the foam layer, when a liquid material such as a dip coat is applied to the surface, the accuracy of the outer diameter is poor.
There were problems such as surface defects. In particular, in the case of coating on a polished surface, there was a case where defects such as dents and holes were caused without being able to completely fill the pores formed by foaming on the surface by polishing.

Further, as a problem in the case of performing tube coating, first, the inflation method involves a problem such as deterioration of accuracy due to deformation at the time of film winding.
As for the casting method, a demolding step is required, and there is a problem in that the processing costs are high in the steps of controlling the concentration of the solution to obtain a uniform thickness, controlling the drying atmosphere, and the like.

An object of the present invention is to provide a method for stably producing a high-precision multilayered foam roller at low cost.

[0016]

SUMMARY OF THE INVENTION According to the present invention, after forming an unfoamed rubber into a cylindrical shape on a cored bar, a thermoplastic sheet-like film is wound around the cylindrical unfoamed rubber. Are wound so as to partially overlap each other, and in this state, they are fitted into a tubular mold and heated to produce a foamed roller.

In the present invention, a thermoplastic sheet-like film (sometimes simply referred to as a sheet-like film) is used.
A film made of thermoplastic resin, usually about 1 m
m or less.

According to the present invention, as the foaming of the unfoamed rubber formed into a cylindrical shape by heating progresses, the gap with the tubular mold is filled, and further the foaming is attempted. Rise. At the same time, since the thermoplastic sheet-like film is in a molten state by heating, a pressure due to expansion of the foam is applied to the overlapping portion, and the state is maintained for a predetermined time, so that the overlapping portion of the sheet-like film is Are joined. Therefore, it is possible to form a smooth and uniform multilayered foam roller having no steps on the surface.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a state in which a thermoplastic sheet-like film is wound around a cylindrical unfoamed rubber so as to be overlapped so that the start and end portions thereof partially overlap each other, and fitted into a tubular mold. An example of a state is schematically shown. The metal mold 10 is provided with a metal core holding member 11 for holding the metal core on a concentric axis at an end of the metal mold so that an unfoamed rubber material is molded around the metal core 12. I have. Further, the core metal holding member also serves to regulate the flow of the material in the longitudinal direction, and further has a hole for venting gas.

As shown in FIG. 2, a sheet-like film 14 is overlapped on an unfoamed rubber material 13 so as to partially overlap, and inserted into a tubular mold 10. FIG. 3 is a schematic diagram three-dimensionally showing how to wind a sheet-like film.

Further, as schematically shown in FIG. 4, a cavity having the same inner diameter as the outer diameter of the tubular mold 10 is provided.
Heating plate 1 divided in parallel to the axial direction of a cylindrical molding die
Heat using 5.

As the heating method, in addition to the method using the heating plate, a method using an electric furnace, a method using induction heating,
A method using a vulcanizer, a method using far / near infrared rays, a method using microwaves, or the like may be used.

Here, as a means for forming the unfoamed rubber into a cylindrical shape on the core metal, a method of simultaneously extruding the core metal with a crosshead, a method of molding using a split mold, and a method of forming a sheet on the core metal For example, a method of winding a rubber in the shape of a letter can be used.

Further, by using a plurality of sheet-like films made of different materials and winding each of the sheet-like films so that the beginning and the end thereof partially overlap, a foam having a multilayer surface layer is used. It is also possible to form rollers.

As the thermoplastic resin material used for the sheet-like film, polyethylene, polypropylene, polymethylpentene-1, polystyrene, polyamide, polycarbonate, polysulfone, polyarylate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene sulfide, polyether sulfone ,
Any of polyether nitrile, thermoplastic polyimide-based material, polyether ether ketone and the like may be used.

Further, in order to impart conductivity, heat resistance, and heat conductivity to the surface layer, the above-mentioned thermoplastic resin material may be made of an organic,
Inorganic fine powder can also be blended.

The organic powder is preferably a condensation type polyimide or the like. Examples of the inorganic powder include inorganic spherical fine particles such as carbon black powder, magnesium oxide powder, magnesium fluoride powder, silicon oxide powder, aluminum oxide powder, and titanium oxide powder; carbon fiber, potassium titanate (potassium hexatitanate, octitanate). Whisker-like powders such as potassium, etc.), silicon carbide and silicon nitride are preferred. It is preferable to select and use these powders as appropriate according to the purpose of conductivity, heat resistance, heat conductivity and the like.

As the rubber material used for the foam layer,
Natural rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, ethylene-propylene rubber (EP
M, EPDM), butyl rubber, silicone rubber, urethane rubber, fluorine rubber, chlorine rubber and the like. Further, for the purpose of imparting conductivity to the rubber material, carbons such as carbon black and conductive carbon; metal powder; conductive fiber; or semiconductive metal oxide powder such as tin oxide; And the like can be blended.

In order to form a foam layer, a foaming agent is added to and mixed with the above rubber material, and the rubber material is foamed by heating. Examples of the foaming agent include ADCA (azodicarbonamide), OBSH (oxybisbenzenesulfenyl hydrazide), sodium hydrogen carbonate, water and the like. These are appropriately selected and used depending on the type of rubber.

The foamed roller of the present invention can be used as a charging roller and a transfer roller of an electrophotographic apparatus by imparting conductivity. In addition, it can be used for various applications that require smoothness and uniformity of the surface. However, as a member of the electrophotographic apparatus, it can be used for a developing roller, a transport roller, a fixing roller, an intermediate transfer member, and the like.

[0031]

The present invention will be described in more detail with reference to the following examples.

Example 1 A charging roller used in an electrophotographic apparatus was manufactured by the following method. First, EP
Ketjen Black (carbon black powder) in DM
And an organic blowing agent such as ADCA or OBSH.

Next, the obtained rubber is simultaneously coaxially extruded into a cylindrical shape around the core metal using a crosshead, and the end is cut. Is obtained. As shown in FIG. 6, this is fixed inside the mold with a cored metal holding member, and a sheet-like film 2 having the same length as the longitudinal direction of the cavity of the mold.
0 is overlapped so that it partially overlaps, and in this state, it is inserted into the gap between the tubular mold and the unfoamed rubber material.

The sheet-like film used in this embodiment is made of a styrene-based elastomer, has a thickness of 150 μm, and has carbon black dispersed therein as a conductive filler.
The resistance was adjusted to around 10 ⁷ Ω.

A tubular mold charged with the unfoamed rubber and the sheet-like film formed on the cored bar was heated for 30 minutes with a heating plate heated to 180 ° C., and vulcanization / foaming and joining were simultaneously performed.

After heating, cooling and demolding, secondary vulcanization was performed in an electric furnace at 160 ° C. for 30 minutes. As a result, the length of the roller portion was 240 mm, and the resistance value of the roller was 1
Is 0 ⁷ Omega obtain a charging roller having a uniform two-layer structure.

When the deflection of this charging roller was measured with a non-contact type laser length measuring device, it was 0.71 mm. When the roller was cut, the average diameter of the pores of the foam was 15 mm.
0 μm, and the thickness of the surface layer was 150 μm ± 15 μm.

Next, in order to examine the uniformity of the conductivity of the charging roller, the resistance was measured using an apparatus schematically shown in FIG.

After the charging roller 16 is pressed against the cylindrical aluminum drum 17 and then rotated, a DC voltage of 100 V is applied to the core of the charging roller using a power source 18 to rotate the charging roller 16 in series with the aluminum drum 17. The variation in the resistance of the charging roller in the circumferential direction was determined from the voltage applied to the resistor 19 connected to the charging roller. Table 1 shows the ratio between the maximum value and the minimum value of the resistance value.

As a result of incorporating the charging roller obtained in this embodiment into an actual electrophotographic apparatus and outputting an image, problems such as image defects considered to be caused by a step at a joint portion and a variation in resistance in a circumferential direction are obtained. There was no outbreak.

As described above, in the present embodiment, since the foaming pressure is applied to the place where the sheet-like film is softened, the step of the surface layer is eliminated when the overlapped portions are welded and joined, and the surface is smoothed and uniformized. I understand.

Further, when the material of the sheet-like film and the foam used in the present embodiment is used, the adhesion between the sheet-like film and the foam is firmly made by heat and pressure even if there is no primer treatment or an adhesive. Turned out to be done.

[Embodiment 2] FIG. 7 schematically shows how to wind the sheet-like film 21 in this embodiment.

The sheet-shaped film 21 is made of a styrene-based elastomer, has a thickness of 80 μm, and has a resistance value of 10 by dispersing carbon black as a conductive filler.
Using wound ⁷ Omega those adjusted back and forth in duplicate.

As used in this example, the film having a thickness half that of the sheet-like film of Example 1 was double-wound and joined to obtain a difference in the overlapped portion before joining. Is about half that of a single one.

Using this winding method, the run-out and resistance variation of the charging roller prepared in the same manner as in Example 1 were measured in the same manner as in Example 1. Table 1 shows the results.

As a result, as compared with the first embodiment, since the step before joining is small, the magnitude of the run-out is small,
Further, it can be seen that the variation in the resistance has been reduced.

[Embodiment 3] FIG. 8 schematically shows how the sheet-like film 22 is wound in this embodiment. FIG.
Is a schematic diagram three-dimensionally showing how to wind the sheet-like film 22.

The sheet-like film is made of a styrene-based elastomer, has a thickness of 150 μm, and has carbon black dispersed therein as a conductive filler, and has a resistance of 10 μm.
Using wound ⁷ Omega those adjusted back and forth in duplicate.

When the sheet-like film is wound spirally as shown in this embodiment, when the roller is pressed, the step portion does not concentrate on the pressed portion, so that the variation in resistance is reduced.

Using this winding method, the run-out and resistance variation of the charging roller prepared in the same manner as in Example 1 were measured in the same manner as in Example 1. Table 1 shows the results.

As a result, it can be seen that, as compared with the first embodiment, the step portion does not concentrate on the press contact portion, so that the variation in resistance is reduced.

Embodiment 4 FIG. 10 schematically shows how to wind a sheet-like film in this embodiment. FIG.
FIG. 3 is a schematic diagram three-dimensionally showing how to wind a sheet-like film.

After the unfoamed rubber is formed in a cylindrical shape on the core metal, the first thermoplastic sheet-like film 23 is wound around the cylindrical unfoamed rubber so that the start and end portions thereof partially overlap. Part of the beginning and end of the winding of the thermoplastic second sheet film 24 so that the overlapping portion of the first sheet film does not overlap the outside of the first sheet film. Are superimposed so as to overlap.

The first sheet-like film used in this example is made of a urethane-based elastomer for preventing seepage from the base layer, has a thickness of 150 μm, and has carbon black dispersed therein as a conductive filler. the is obtained by adjusting the front and rear 10 ⁶ Omega, second sheet-like film with a styrene-based elastomer as a resistance adjusting layer, 80 [mu] m in thickness, by dispersing carbon black as the conductive filler, the resistance 10 Adjusted to around ⁷ Ω.

Using this winding method, the shape of the charging roller prepared in the same manner as in Example 1 was measured in the same manner as in Example 1. Table 1 shows the results.

As a result, the variation in resistance and the like are not so different from those in the first embodiment. However, the roller of the present embodiment is pressed against the drum and subjected to high temperature and high humidity conditions (40 ° C., 90 ° C.).
%) For a long period (3 months), a roller was obtained which did not seep out oil or the like on the drum surface from the roller.

[0058]

[Table 1]

[0059]

According to the present invention, it is possible to manufacture a high-precision foam roller stably without any step at the overlapping portion and at a low cost.

Further, since the surface layer and the foam layer are heat-sealed, it is not necessary to use a primer treatment, an adhesive or the like for the adhesion between the foam layer and the surface layer, and the process can be shortened and the cost can be reduced. it can.

The foam roller manufactured according to the present invention is excellent in stability and reliability as a product.

[Brief description of the drawings]

FIG. 1 schematically shows a configuration of an electrophotographic apparatus using a contact charging / transfer member.

FIG. 2 is a schematic representation of the production method of the present invention, in which a thermoplastic sheet-like film is wound around an unfoamed rubber material formed into a cylindrical shape around a cored bar and charged into a mold. FIG.

FIG. 3 is a schematic diagram three-dimensionally showing how to wind a sheet-like film.

FIG. 4 is a view showing a heating step of the present invention.

FIG. 5 is a schematic diagram of a charging roller resistance measuring device.

FIG. 6 is a schematic view showing how to wind the sheet-like film of Example 1.

FIG. 7 is a schematic diagram showing how to wind a sheet-like film of Example 2.

FIG. 8 is a schematic diagram showing how to wind a sheet-like film of Example 3.

FIG. 9 is a schematic diagram three-dimensionally showing how to wind a sheet-like film of Example 3.

FIG. 10 is a schematic diagram showing how to wind a sheet-like film of Example 4.

FIG. 11 shows how to wind the sheet-like film of Example 4 to 3
FIG. 3 is a schematic diagram shown in a dimensional manner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoreceptor of electrophotographic apparatus 2 Charging roller 3 Exposure means 4 Developing means 5 Transfer material 6 Transfer roller 7 Fixing member 8 Cleaning member 9 Toner image 10 Mold 11 Core holding member 12 Core metal 13 Unfoamed rubber material 14 Sheet Film 15 Heating plate 16 Prepared charging roller 17 Aluminum drum 18 DC power supply 19 Resistance 20 Sheet film of Example 1 21 Sheet film of Example 22 Sheet film of Example 3 23 First of Example 4 Sheet-like film 24 Second sheet-like film of Example 4

Claims (9)

[Claims] An unfoamed rubber is formed in a cylindrical shape on a cored bar, and then a thermoplastic sheet-like film is wound around the cylindrical unfoamed rubber so that the start and the end thereof partially overlap. A method for producing a foamed roller, wherein the foamed roller is fitted in a tubular mold and heated in this state. 2. The method for producing a foam roller according to claim 1, wherein when the sheet-like film is wound around the cylindrical unfoamed rubber, the start and the end are overlapped by winding a plurality of times. . 3. The sheet-like film has a shape in which both ends are cut obliquely, and when the sheet-like film is wound around the cylindrical unfoamed rubber, the overlapping portions of both ends of the sheet-like film are formed. The method for producing a foamed roller according to claim 1, wherein the roller is wound into a spiral shape. 4. After forming an unfoamed rubber in a cylindrical shape on a cored bar, a plurality of thermoplastic sheet films are wound around the cylindrical unfoamed rubber at the start of winding of each sheet film. A method for producing a foamed roller, characterized in that winding is performed so that the ends are partially overlapped, and in this state, it is fitted into a tubular mold and heated. 5. The method according to claim 4, wherein the number of the sheet films is two. 6. A conductive foam roller is produced by dispersing conductive particles in the unfoamed rubber.
5. The method for producing a foamed roller according to any one of the above items 5. 7. A foam roller manufactured by the manufacturing method according to claim 1. 8. The electrophotographic photosensitive member is manufactured by the manufacturing method according to claim 6, and is disposed so as to be in contact with the surface of the electrophotographic photosensitive member.
A foam roller used as a charging roller for charging the surface of the electrophotographic photosensitive member. 9. A foam produced by the production method according to claim 6, which is disposed so as to be in contact with the surface of the electrophotographic photosensitive member, and is used for a transfer roller for transferring a toner image on the surface of the electrophotographic photosensitive member to a transfer material. Body roller.