JP3432103B2 - Conductive tube, method for producing the conductive tube, and charging roller having the conductive tube - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a conductive tube,
The present invention relates to a method of manufacturing the conductive tube and a charging roller having the conductive tube.

[0002]

2. Description of the Related Art In order to satisfy various performances such as charging performance, charging sound, non-staining property and permanent distortion, a charging roller usually has several elastic layers laminated on a conductive cored bar. It has a combined structure. More specifically, the base layer closest to the core metal is usually thickest, and the outermost surface layer and other layers are relatively thinner than the base layer. Each layer is responsible for the performance that cannot be satisfied by one layer of elastic body. For example, when an alternating current is applied in addition to a direct current when charging an object to be charged using a charging roller, a charging sound becomes a problem, but by using a conductive sponge layer as a base layer, the charging sound is reduced. be able to. Further, since the outermost layer of the charging roller is in contact with the body to be charged, it is required to have a non-contaminating property that does not contaminate the body to be charged even if it contacts the body to be charged for a long time. Also,
Smoothness of the surface is also required for uniform charging,
A certain degree of softness is required in order to prevent toner fusion to the charged body.

Each elastic layer is formed by a method such as an in-mold forming method, a dipping method, a spray coating method and an extrusion forming method. Among them, the extrusion molding method is an effective method for reducing the cost of the charging roller because the surface layer tube and other tubes can be manufactured at low cost.

In the extrusion molding of a tube for a charging roller, first, a binder resin as a raw material is mixed with a conductive material and other fillers, heated, kneaded with a kneader, pelletized, and again heated to give a tube. Follow the process of extruding into a shape, cooling, drying and cutting to an appropriate length. Kneading and pelletization can be omitted. The resulting tube is stored until it is coated with the base layer.

Particularly, when a charging member is used in an electrophotographic process or the like, uniform charging is required in order to obtain a good image. Therefore, even as a charging roller, smooth surface property,
Accurate dimensions and uniform electric resistance are required.
It is required to manufacture a conductive tube having good manufacturing stability and uniform resistance even when manufacturing the tube.

[0006]

However, there are few resins suitable for the method of manufacturing a tube by the extrusion molding method that have tackiness, and when a resin having tackiness is selected as the material, the tube is coated on the base layer. There was a problem that tubes would stick to each other if they were temporarily bundled and stored before. If the tubes stick to each other, the two tubes can be separated by separating them, but the force applied when separating the tubes changes the delicate positional relationship between the conductive materials in the tubes, resulting in an electrical resistance value. Change and uneven charging occurs. Also, if a material with a stronger tack property is used, it will stick strongly to the member to be charged (usually an organic photoconductor (OPC) drum), so if the image is output with an electrophotographic device after long-term storage, the drum photoconductor layer will peel off and the image There is also the problem of causing defects. Further, in order to avoid toner fusion to the OPC drum, the material resin of the surface layer tube is required to be soft, but the tackiness of the tube increases as the soft resin is used, and the tube layer is different from the surface layer tube of the charging roller. There is also a problem that the OPC drum tends to stick to it.

Therefore, the present invention provides a uniform and inexpensive conductive tube which is free from sticking, has less toner fusion to the photosensitive member, a method of manufacturing the conductive tube, a charging roller having the conductive tube, and an electric resistance. It is an object of the present invention to provide a charging roller that can be uniformly charged because the values are uniform.

[0008]

The present invention has been made in view of the above circumstances, and extrudes a thermoplastic polymer mixture to which electroconductivity is added by adding electroconductive powder in a molten state at high temperature. Then, in a method for producing a conductive tube by bringing a low temperature fluid into contact with the fluid and cooling the fluid, a non-adhesive powder is mixed in the fluid.

According to a second aspect of the invention, in the first aspect of the invention, the low temperature fluid is water and the non-adhesive powder is a non-adhesive fluorine compound containing fluorinated graphite. Is characterized by.

The invention of the conductive tube described in claims 3 to 4 is obtained by the method of claims 1 to 2, and the invention of the charging roller described in claims 5 to 6 is:
A conductive core obtained by the method according to any one of claims 1 and 2 is coated on a conductive cored bar by one or a plurality of layers.

According to the present invention, there is no sticking, there is little toner fusion to the photosensitive member, a uniform and inexpensive conductive tube, a method for producing the conductive tube, a charging roller having the conductive tube, and a charging. It is possible to provide a charging roller that does not cause defects.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An example of the structure of a charging roller of the present invention is shown in FIG. The charging roller includes a conductive core metal 3, a conductive elastic layer 2, and a conductive thermoplastic polymer tube 1 in this order from the center.
It is configured in the order of. The conductive thermoplastic polymer tube may be coated with one sheet or two or more sheets.

The present invention will be described below with reference to examples. In the examples, “part” means “part by weight”.

[Example 1] A thermoplastic elastomer (styrene content; 20% by weight, ASTM, in which a polystyrene molecular chain is covalently bonded to one end of an ethylene butylene rubber molecular chain and an olefin crystal is covalently bonded to the other end thereof) D2
Specific gravity according to 97; 0.9, ASTM D1238 (23
0 ° C., 2.16 kg) MFR; 5.6 g / min, J
Tensile strength of IS K6301; 17 MPa, JIS
Elongation at break of K6301; 650%, ASTM D34
Glass transition point of 18; -45 ° C; 130 parts; carbon black (specific surface area by BET method; 800 m ² / g;
DBP oil absorption capacity: 360cc / 100g, 10MP
16 parts of powder resistance at a time; 0.1 Ω · cm), conductive titanium oxide coated with antimony-doped tin oxide (particle size: about 0.2 to 0.3 μm, powder resistance at 10 MPa; 2 to 20 parts of 5 Ω · cm), 10 parts of magnesium oxide and 1 part of calcium stearate were mixed and melt-kneaded at 200 ° C. for 10 minutes using a pressure kneader to prepare a semiconductive thermoplastic elastomer mixture. The obtained semiconductive thermoplastic elastomer mixture has a volume resistivity of 2 ×.
It was 10 ⁸ Ω · cm, JIS-A hardness was 60 degrees, and heat distortion temperature ASTM D-648 was 80 ° C.

The resulting semiconductive thermoplastic elastomer mixture was extruded with an inner diameter of 11 mm and a wall thickness of 250 μm.
It was formed into a seamless tube having a length of m and a length of 250 mm. In the extrusion step, as shown in FIG. 1, cooling water was showered on the high temperature tube extruded between the die and the nipple to cool it to near room temperature. At this time, 1% by weight of fluorinated graphite fine particles were stirred and dispersed in the cooling water. Dry air was blown onto the tube surface to remove excess water, and then the tube was cut into a length of 250 mm. This tube is referred to as Tube A (Fig. 2
(Indicated by middle 13)). In FIG. 1, 19 is a cooling water container, 20 is cooling water in which fluorinated graphite fine particles are mixed by stirring,
Reference numeral 21 is a stirring propeller, 22 is a shower port, 23 is a shower of cooling water in which fluorinated graphite fine particles are stirred and mixed, and 24
Is a conductive thermoplastic elastomer tube, 25 is a high temperature conductive thermoplastic elastomer, 26 is a nipple, and 27 is a die.

Separately from this, an ether type thermoplastic urethane (JISK7311 A hardness; 85 degrees, JISK73
11 Tensile strength; 47 MPa, glass transition temperature; -5
100 parts at 0 ° C., carbon black (specific surface area by BET method; 800 m ² / g, DBP oil absorption; 36
Powder resistance at 0 cc / 100 g, 10 MPa; 0.1Ω
-Cm) 14.5 parts, conductive titanium oxide coated with antimony-doped tin oxide (particle diameter; about 0.2 to 0.
Powder resistance at 3 μm, 10 MPa; 2-5 Ω · cm) 2
Mix 0 parts, 10 parts of magnesium oxide and 1 part of calcium stearate, and mix them with a pressure kneader at 180 ° C. for 1 hour.
The mixture was melt-kneaded for 0 minutes to prepare a semiconductive thermoplastic elastomer mixture. The obtained semiconductive thermoplastic elastomer mixture has a volume resistivity of 2 × 10 ⁶ Ω · cm,
JIS-A hardness is 70 degrees, heat distortion temperature ASTM D-6
48 was 85 ° C. The obtained semiconductive thermoplastic elastomer mixture was molded by an extruder into a seamless tube having an inner diameter of 10.5 mm, a wall thickness of 250 μm and a length of 250 mm. This tube is called Tube B
(14 in FIG. 2). Also in the molding process of the tube B, 1% by weight of fluorinated graphite fine particles (average particle diameter: 2 μm) was stirred and dispersed in the cooling water.

Next, 100 parts of EPDM rubber, 60 parts of carbon black, 90 parts of paraffin oil, 5 parts of zinc oxide, 2 parts of sulfur, 18 parts of azodicarbodiamide and 2 parts.
5 parts of mercaptobenzothiazole were kneaded with 2 rolls and extruded into a tube with a single-screw extruder.
Foam and vulcanize for 30 minutes in steam at 0.7 ° C and a diameter of about 13 mm, a length of 250 mm, a central hole diameter of 4 mm, and an average foam diameter of sponge rubber of about 200 μm.
A tubular conductive sponge rubber base layer (15 in FIG. 2) having a JIS-A hardness of 26 degrees was prepared. This sponge base layer tube was coated on a core metal (16 in FIG. 2) made of SUS and having a diameter of 6 mm and a length of 250 mm, the surface of which was coated with a conductive adhesive, followed by steam at 200 ° C. and 0.7 MPa. After vulcanizing for 30 minutes, unnecessary end rubber was cut by 1 cm each, and then tube B was covered while being inflated by air pressure, and finally tube A was covered.

The charging roller thus obtained is shown in FIG.
The contact pressure with the image carrier (photoreceptor) is 10 g at the position of the primary charger of the electrophotographic printer cartridge shown in FIG.
(Measure the force when pulling out a 1 cm wide aluminum sheet between the photoconductor and the charging roller)
After performing a severe storage test of leaving it in an environment of ℃ × 95% Rh for 30 days, in the environment of 25 ℃ × 50% Rh, an alternating voltage of 2 kV was superposed on a direct current voltage of -670 V at a frequency of 900 Hz to charge the image. Was output. In FIG. 3, 4 is a charging roller, 5 is a photosensitive drum, 6 is a developing sleeve, 7 is a toner container, 8 is a transfer roller, 9 is a cleaning blade, 10 is a waste toner container, 11 is a transfer material, and 12 is an exposure beam. Is.

As a result, there was no sticking of the charging roller to the drum, and the output image was good.

Separately from this, two uncoated tubes A are scissors between Teflon plates as shown in FIG. 4, and two tubes are compressed until the maximum diameter of one tube becomes twice the minimum diameter. The tube was left in an adhered state and kept in an environment of normal temperature and normal pressure for 30 days. In FIG. 4, 17 is a Teflon plate and 18 is a conductive thermoplastic elastomer tube.

After standing, the two tubes were not stuck at all. In addition, when the volume resistivity of the portion where the tubes were in contact with each other and the portion where they were not in contact were measured, both were 4 × 10 ⁸ Ω · cm, and the resistance increase due to the separation of the attached tubes , Not observed at all.

As the non-adhesive powder to be mixed in the cooling water, in addition to fluorinated graphite, for example, fluororubber; fluoroelastomer; fluorocarbon in which fluorine is bonded to graphite; polytetrafluoroethylene (PTFE), Fluorine resin powder such as polyvinylidene fluoride (PVDF), tetrafluoroethylene / ethylene copolymer (ETFE) and tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA); silicone resin, silicone rubber and silicone elastomer Silicone powders such as; powders of resins such as polyethylene (PE), polypropylene (PP), acrylic resins, nylon resins, phenol resins and epoxy resins and compounds and mixtures thereof; granular carbon such as spherical graphite; silica , Alumina, acid Titanium, magnesium oxide, there are inorganic powders such as tin oxide and iron oxide, it can be used singly or in combination. Further, the shape and particle size of the non-adhesive powder are not particularly limited, and any shape such as spherical, fibrous, plate-like and amorphous can be used as long as non-adhesive powder is obtained. However, the range of 0.02 to 50 μm is preferable in consideration of dispersibility and surface property. If necessary, these powders may be surface-treated within a range that does not impair the non-adhesiveness.

Other materials that can be used for the core metal include, for example, metals such as iron, aluminum, titanium, copper and nickel, alloys such as stainless steel, duralumin, brass and bronze, and carbon black and carbon. A rigid and electrically conductive material such as a composite material in which fibers are hardened with plastic can be used.

The material for the base layer is a conductive sponge rubber having a JIS-A hardness of 30 degrees or less and an electric resistivity in the range of 10 ³ to 10 ⁶ Ω · cm. Examples of the binder for the base layer rubber include butyl rubber and chloroprene. Rubber such as rubber, ethylene / propylene / diene rubber (EPDM), nitrile rubber, silicone rubber, urethane rubber, epichlorohydrin rubber and fluororubber can be used. In some cases, these rubber binders may be used alone or in combination with several kinds of conductive materials such as carbon black, graphite, carbon fiber, conductive tin oxide, conductive titanium oxide, metal powder, quaternary ammonium salt and solid electrolyte. It is possible to give a predetermined electric resistivity.
If necessary, the base layer material may be mixed with additives such as process oil and antioxidant. The base layer can be molded by using a method such as in-mold molding, extrusion molding, or foaming by heating with steam, electromagnetic waves, an electric furnace, or the like.
Can be vulcanized. In some cases, it may be vulcanized and then ground to be molded into a predetermined size.

The material of the tube has a thermoplastic elastomer as a main component, but if necessary, a thermoplastic resin or another thermoplastic elastomer may be blended and used as a polymer alloy. If necessary, the elastomer may be mixed with a conductive material or other chemical compound. Examples of thermoplastic elastomers include urethane elastomers, styrene elastomers, olefin elastomers, polyester elastomers, polyamide elastomers and fluorine elastomers. In particular, thermoplastic elastomers having a block copolymer structure in which olefin crystals or styrene chains are covalently bonded to both ends of ethylene butylene rubber, and thermoplastic urethane such as ester urethane and ether urethane are used as the main components of the surface seamless tube. Are better. Examples of thermoplastic resins include thermoplastic polymers such as polyolefins, polyamides, polyimides, fluororesins and chlorinated polyethylenes. Examples of the conductive material mixed with the surface material include, for example, conductive materials such as carbon black, graphite, carbon fiber, conductive tin oxide, conductive titanium oxide, metal powder, quaternary ammonium salt and solid electrolyte. If necessary, these may be mixed alone or in combination with the resin in a predetermined ratio to obtain a material having a desired electrical resistivity. As examples of other compounding agents, MgO, mica, synthetic mica, smectite, etc. for suppressing tackiness can be used. Further, the surface seamless tube may cover only one layer on the base layer to complete the charging roller. In order to separate functions such as contamination of the body to be charged and oil barrier property from the base layer, two layers or three layers are provided. You may use it as a charging roller by layering more than one layer and covering it.

Example 2 Instead of the fluorinated graphite fine particles used by stirring and mixing in cooling water in Example 1,
A charging roller was prepared and evaluated in the same manner as in Example 1 except that PTFE fine particles having an average diameter of 1 μm were used.

As a result, there was no sticking of the charging roller to the drum, and the output image was good.

The two tubes were not stuck at all. Furthermore, when the volume resistivity of the portion where the tubes were in contact with each other and the portion where they were not in contact were measured, both were 4 × 10 ⁸ Ω · cm, and the resistance increase due to the separation of the attached tubes , Not observed at all.

Example 3 Instead of the fluorinated graphite fine particles used by stirring and mixing in cooling water in Example 1,
A charging roller was prepared and evaluated in the same manner as in Example 1 except that ETFE fine particles having an average diameter of 1 μm were used.

As a result, there was no sticking of the charging roller to the drum, and the output image was good.

The two tubes were not stuck at all. Furthermore, when the volume resistivity of the portion where the tubes were in contact with each other and the portion where they were not in contact were measured, both were 4 × 10 ⁸ Ω · cm, and the resistance increase due to the separation of the attached tubes , Not observed at all.

[Comparative Example 1] A charging roller was prepared and evaluated in the same manner as in Example 1 except that the fluorinated graphite fine particles used by stirring and mixing in cooling water in Example 1 were not used and cooling was performed only with water. .

As a result, the charging roller was stuck to the drum. When the peeling torque was measured with the charging roller and the photoconductor drum incorporated in the cartridge for the electrophotographic printer, it was 15 N · cm. For the electrophotographic printer, the charging roller and the photoconductor drum were normally in contact with each other. The torque when rotated in the state of being incorporated in the cartridge was significantly higher than 3 N · cm.

In the output image, the contact portion of the charging roller appeared as a halftone black band image defect.

The two tubes were attached to each other over a width of 10 mm and a length of 250 mm. Stuck 2
A peeling line stress of 3 N / cm was required when the book tube was peeled off. Furthermore, when the volume resistivity of the part where the tubes were in contact with each other and the part where they were not in contact were measured, the resistivity of the part that was not in contact was 4 ×
While it was 10 ⁸ Ω · cm, the adhered portion was 5 × as high as 2 × 10 ⁹ Ω · cm.

[Comparative Example 2] Instead of the fluorinated graphite fine particles used by stirring and mixing in cooling water in Example 1,
A charging roller was prepared and evaluated in the same manner as in Example 1 except that polyvinyl acetate fine particles having an average diameter of 1 μm were used.

As a result, the charging roller was stuck to the drum. When the peeling torque was measured with the charging roller and the photoconductor drum incorporated in the cartridge for the electrophotographic printer, it was 11 N · cm. For the electrophotographic printer, the charging roller and the photoconductor drum were normally in contact with each other. The torque when rotated in the state of being incorporated in the cartridge was significantly higher than 3 N · cm.

In the output image, the contact portion of the charging roller appeared as a halftone black band image defect.

The two tubes were attached to each other over a width of 10 mm and a length of 250 mm. Stuck 2
A peeling line stress of 2 N / cm was required when the book tube was peeled off. Furthermore, when the volume resistivity of the part where the tubes were in contact with each other and the part where they were not in contact were measured, the resistivity of the part that was not in contact was 4 ×
While it was 10 ⁸ Ω · cm, the adhered portion was 1.5 × 10 ⁹ Ω · cm, which was four times as high.

[0040]

As described above, according to the present invention,
Even if a conductive tube made by extrusion molding of a thermoplastic polymer mixture, which is inexpensive to manufacture, and a charging roller with the surface of the tube being used are used, there is an effect that it does not stick to the drum and cause an image defect. . Even when the conductive tube is stored as a single unit before being covered with the roller, it is possible to prevent the phenomenon that the resistance increases when the tubes are peeled off and the resistance increases. The effect is that the tubes can be bundled and stored.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a cooling process in an extrusion molding process of a conductive thermoplastic elastomer tube according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of the charging roller according to the first exemplary embodiment of the present invention.

FIG. 3 is a schematic diagram showing a positional relationship of parts in the electrophotographic process cartridge according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram illustrating a tube-to-tube sticking test method according to Example 1 of the present invention.

FIG. 5 is a schematic cross-sectional view in the axial direction of an example of a charging roller according to the present invention.

[Explanation of symbols]

1 Conductive Thermoplastic Polymer Tube 2 Conductive Elastic Layer 3 Conductive Core Bar 4 Charging Roller 5 Photosensitive Drum 6 Developing Sleeve 7 Developing Toner Container 8 Transfer Roller 9 Cleaning Blade 10 Waste Toner Container 11 Transfer Material 12 Exposure Beam 13 Tube A 14 Tube B 15 Conductive Sponge Rubber Base Layer 16 Core Bar 17 Teflon Plate 18 Conductive Thermoplastic Elastomer Tube 19 Cooling Water Container 20 Cooling Water with Stirred Fluorinated Graphite Fine Particles 21 Stirring Propeller 22 Shower Port 23 Fluorinated Graphite Fine Particles Shower of cooling water with stirring and mixing 24 Conductive thermoplastic elastomer tube 25 High temperature conductive thermoplastic elastomer 26 Nipple 27 Dice

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Inoue 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Naoki Fuei 3-30-2 Shimomaruko, Ota-ku, Tokyo Ki (56) References JP-A-4-255332 (JP, A) JP-A-54-153291 (JP, A) JP-A-4-232005 (JP, A) JP-A-61-189920 (JP , A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B29C 47/00-47/96 G03G 13/02 B29D 1/00-29/10 B29D 31/00-31/02

Claims (6)

(57) [Claims] 1. A thermoplastic polymer mixture to which electroconductivity is added to impart electroconductivity, and the mixture is extruded in a molten state at high temperature,
Next, a method for producing a conductive tube by bringing a low temperature fluid into contact with the fluid to cool the fluid, wherein a non-adhesive powder is mixed in the fluid. 2. The method for producing a conductive tube according to claim 1, wherein the low-temperature fluid is water, and the non-adhesive powder is a non-adhesive fluorine compound containing fluorinated graphite. 3. A thermoplastic polymer mixture to which conductivity is added by adding a conductive powder, is extruded in a molten state at high temperature,
Then, in a conductive tube obtained by bringing a low temperature fluid into contact with it to cool it, a non-adhesive powder is mixed in the fluid. 4. The conductive tube according to claim 3, wherein the low-temperature fluid is water, and the non-adhesive powder is a non-adhesive fluorine compound containing fluorinated graphite. 5. A thermoplastic polymer mixture to which electroconductivity is added by adding electroconductive powder, and extruded in a molten state at high temperature,
Then, in a charging roller having a conductive tube obtained by contacting and cooling a low temperature fluid, the conductive tube obtained by mixing a non-adhesive powder in the fluid is replaced with a conductive core. A charging roller characterized by coating one or more sheets of gold. 6. The charging roller according to claim 5, wherein the low-temperature fluid is water, and the non-adhesive powder is a non-adhesive fluorine compound containing fluorinated graphite.