JPH0658324A - Conductive roll - Google Patents

Abstract

PURPOSE:To provide an excellent conductive film layer by means of a simple method by forming the conductive film layer out of thermoplastic resin whose volume resistance at a temperature 25 deg.C and relative humidity 50% RH is 10mu10<7>-1. 0X10<11>OMEGA.cm. CONSTITUTION:On the outer periphery of a shaft 1 consisting of an excellent conductive material such as stainless steel, iron that has undergone plating processing, and conductive plastic, a base layer 2 consisting of a conductive elastic material is provided, and in addition on this outer periphery surface, a conductive film layer 3 consisting of conductive thermoplastic resin whose volume resistance is 1, 0X1-<7>-1.0X10<11>OMEGA.cm is formed in covering. A non-foam or foam conductive rubber formation combined with a conductive material and conductive polyurethane foam can be used as a conductive elastic material. The conductive thermoplastic resin possesses predetermined volume resistance in itself, and its electric resistance value is not regulated by combining a conductive material. Accordingly, there is no need of electric resistance regulation, and also extrusion molding is possible, so the excellent conductive layer film 3 can be constituted by means of simple operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roll for applying an electric potential of a predetermined polarity to an object to be charged such as a photosensitive drum or a recording medium in an electrophotographic recording device or the like.

[0002]

2. Description of the Related Art An electrophotographic recording apparatus widely used in a copying machine, a laser beam printer, etc., is generally equipped with a drum-shaped photosensitive member (hereinafter referred to as a photosensitive drum),
The photosensitive drum is charged and exposed to form an electrostatic latent image, and then toner is attached and developed according to the latent image on the photosensitive drum, and then the toner on the photosensitive drum is used for recording paper or the like. The recording medium is transferred to another recording medium for transfer, and then the photosensitive drum is discharged to a predetermined potential and the toner remaining on the photosensitive drum is cleaned to prepare for the next recording. Further, the toner carried on the recording medium by the transfer is melted and pressure-bonded to be fixed on the recording medium, whereby a series of recording operations is completed.

In this case, with respect to the photosensitive drum of the electrophotographic recording apparatus, a charging roll that applies a predetermined potential to the charging area, a developing roller that conveys toner to the photosensitive drum, and a recording medium that has been conveyed to the transfer area are used. As a conductive roll such as a transfer roll for imparting a predetermined potential or a charge eliminating roll for uniformizing the charged area of the photosensitive drum after transfer to a constant potential, a conductive shaft is usually provided and a conductive shaft provided on the outer periphery thereof is preferably provided. A base layer made of conductive rubber,
In order to adjust the electric resistance of the roll and prevent contamination of the photosensitive drum and the recording medium, it is composed of a single layer or a plurality of conductive film layers coated on the base layer.

As the conductive film layer, a conductive carbon is dispersed in a thermosetting rubber such as epichlorohydrin or thermoplastic polyurethane, which has a volume resistance of 1.0 × 10 ⁷ to 1. 0x10
^The one adjusted to ¹¹ Ω · cm is used.

Further, such a conductive roll is installed in a state in which it is pressed against the photosensitive drum through a bearing which is normally supported by a spring (urging force of about 200 to 800 g), whereby To maintain contact.

[0006]

However, it is difficult to form epichlorohydrin used as the above-mentioned conductive film layer material by a simple method such as extruding the conductive film layer into a thin film tube shape, and an organic solvent such as dipping is used. In addition to the necessity of employing a complicated wet coating method, which is necessary and complicated, since it is a thermosetting resin, it is necessary to crosslink it in a subsequent step. In addition, the thermoplastic polyurethane has a complicated lamination process and is technically difficult to adjust in volume resistance, and its resistance value may be slightly changed depending on the compounding amount of the conductive powder, the dispersion method, the film coating method, and the like. Therefore, the formation of these conductive film layers is one of the factors that increase the manufacturing cost of the conductive roll.

In order to satisfactorily charge the photosensitive drum with the conductive roll, the contact width of the conductive roll with respect to the photosensitive drum (hereinafter referred to as the nip width) must be uniform along the axial direction of the roll. preferable. However, as described above, since the conductive roll is pressed against the photosensitive drum at both ends by the bearings supported by the springs, the conductive roll has a force to lift the central part with the both ends as fulcrums. Therefore, the conventional conductive roll also has a problem that the nip width at both end portions tends to be wider than that at the central portion.

The present invention has been made in view of the above circumstances.
A first object of the present invention is to provide a conductive roll which can form a good conductive film layer by a simple method and can be manufactured at low cost. It is a second object of the present invention to provide a conductive roll that can be manufactured at low cost as described above, can obtain a uniform nip width with the photosensitive drum, and can surely perform uniform charging. To do.

[0009]

In order to achieve the above-mentioned first object, the conductive roll of the present invention comprises a shaft, a conductive base layer provided on the outer periphery of the shaft, and the base layer. A conductive roll having a conductive film layer provided thereon and applying a potential of a predetermined polarity to the charged body while being in contact with the charged body,
Volume resistance at a temperature of 25 ° C. and relative humidity of 50% RH, such as Pebax (trade name) of Atochem Japan Co., Ltd. and Alculin (trade name) of Dupont Mitsui Polychemical Co., Ltd.
By forming the conductive resin layer from 0 × 10 ^{7 to} 1.0 × 10 ¹¹ Ω · cm, it is not necessary to adjust the electric resistance value when forming the conductive film layer, and moreover, the conductive material can be easily conductive by extrusion molding. The film layer can be formed.

That is, the conductive film layer of the conductive roll of the present invention is
1.0 × 10 ⁷ to which volume resistance is suitable as a conductive roll
Since it is made of a thermoplastic resin in the range of 1.0 × 10 ¹¹ Ω · cm, when forming this conductive film layer on the base layer, conductive carbon is added to adjust the electric resistance value. Since it is made of a thermoplastic resin that can be extruded and does not require a heat-curing (crosslinking) step, it is not necessary to adopt a wet coating method that is complicated in operation, and can be extruded directly from a raw material resin to perform better. Can be formed. Therefore, the coating process of the conductive film layer, which has been a complicated process in the past, can be simplified and the manufacturing cost can be reduced.

In order to achieve the above-mentioned second object, the conductive roll according to one embodiment of the present invention is such that when the conductive film layer is formed of the above-mentioned thermoplastic resin, the film thickness of the conductive film layer is changed. By forming the central portion thicker than both end portions, and forming the outer diameter of the roll central portion larger than the outer diameter of both end portions, when the conductive roll is pressed against the photosensitive drum, along the axial direction of the roll. The nip width is made uniform.

That is, by making the outer diameter of the central portion of the conductive roll larger than the outer diameter of both ends of the roll, when the conductive roll is pressed against the photosensitive drum by the bearing supported by the spring, both ends of the roll are fulcrum points. As a result, the nip width at the center of the roll does not become small even if a force to lift the central part acts, and a uniform nip width can be obtained along the axial direction of the roll. The charging area can be made uniform to a predetermined potential.

The present invention will be described in more detail below.
As described above, the conductive roll of the present invention is provided with a conductive base layer on the outer periphery of the shaft, and further has a volume resistance of 1.0 × 10 ⁷ at a temperature of 25 ° C. and a relative humidity of 50% RH on the surface of the base layer. It is formed by coating a conductive film layer made of a thermoplastic resin of up to 1.0 × 10 ¹¹ Ω · cm, and specifically, a roll having the configuration shown in FIG. 1 is exemplified.

That is, FIG. 1 shows an example of the conductive roll of the present invention, which is used as a charger of an electronic copying machine. This conductive roll is made of stainless steel,
A base layer 2 made of a conductive elastic material is provided on the outer circumference of a shaft 1 made of a good conductive material such as plated iron, brass, and conductive plastic, and a volume resistance of 1.0 is provided on the outer peripheral surface of the base layer 2. × 10 ^{7 to} 1.0 × 10 ¹¹ Ω · cm
The conductive film layer 3 made of the conductive thermoplastic resin is formed by coating.

Here, as the elastic material having conductivity which composes the base layer 2, a non-foamed or foamed conductive rubber composition and a conductive polyurethane foam mixed with a conductive material can be used.

As the rubber component constituting the non-foamed conductive rubber composition, nitrile butazine rubber, chloroprene rubber, styrene butadiene rubber, butadiene rubber, ethylene propylene rubber, isoprene rubber, polynorbornene rubber, etc. Thermoplastic rubbers such as styrene-butadiene-styrene (SBS) and styrene-butadiene-styrene water additive (SEBS) can be used, and are not particularly limited, but these rubbers, particularly solid butadiene rubber / Liquid polyisoprene rubber 10
It is preferable that the base layer 2 is formed by mixing it at a ratio of about 90/50 to 50/50 and mixing it with a conductive material to form the base layer 2. This makes it possible to obtain the base layer 2 having a low hardness and a small compression set. The adhesiveness between the roll and the member to be charged such as the photosensitive drum can be improved.

The foamed conductive rubber is not particularly limited, but ethylene propylene rubber blended with a conductive material, a foamed copolymer rubber of epichlorohydrin and ethylene oxide, or epichlorohydrin and ethylene oxide. It is possible to preferably use a foamed product obtained by mixing the copolymer rubber of (1) with a conductive material.

As the conductive material to be added to these rubber compositions, conductive powder such as carbon black, graphite, metal, various conductive metal oxides (tin oxide, titanium oxide, etc.), carbon fiber, metal oxide, etc. Various conductive fibers such as short fibers of the above can be used. The compounding amount is 3 to 100 parts by weight, particularly 5 to 50 parts by weight based on 100 parts by weight of all rubber components.
The volume resistance of the base layer 2 is preferably adjusted to about 10 ¹ to 10 ⁷ Ω · cm. The base layer 2 can be formed by a known vulcanization molding method, and the thickness thereof is appropriately set according to the application of the roll and the like, but is usually 1 to 20 mm, and its hardness is Asker C 20-90 °, especially 30-70
It is preferable to set to °.

When the resistance value of the base layer 2 is R ₁ , the resistance value of the conductive film layer 3 is R _2, and a voltage V is applied to the roll, the voltage applied to the base layer 2 and the conductive film layer 3 is: {R ₁ / (R ₁ + R ₂ )} V and {R ₂ / (R ₁ +) respectively
R ₂ )} · V, and if the base layer 2 has a high resistance value,
As a result, the voltage that the conductive film layer 3 bears becomes lower. Therefore, by increasing the resistance value of the base layer 2 to some extent, voltage breakdown of the conductive film layer 3 is less likely to occur, and the film thickness of the conductive film layer 3 can be reduced correspondingly, so that the hardness of the entire roll is reduced. Can be lowered. In this case, as a conductive material for adjusting the resistance value of the base layer 2, for example, when highly conductive carbon such as Lion Corporation, trade name Ketjen Black EC is used, an extremely low resistance value of 10 ⁴ Ω or less is obtained. SA is a normal carbon for rubber
F, ISAF, HAF, FEF, GPF, SRF, F
By blending T and MT in the range of 10 to 40 parts by weight with respect to 100 parts by weight of the rubber component, a relatively high desired resistance value can be easily adjusted.

For example, when solid butadiene / liquid polyisoprene rubber / HAF are mixed at a ratio of 60/40/24 parts by weight or a ratio of 70/30/24 parts by weight to form the base layer 2, a resistance value of 2 × A base layer 2 of 10 ⁵ Ω is obtained, and a volume resistance of 1 × 10 ⁹ is provided on the base layer 2.
A resistance value of 4 × 10 ⁵ Ω is obtained by covering the conductive film layer 3 of Ω · cm.
In the case of obtaining the conductive roll of, the thickness of the conductive film layer 3 is 100
On the other hand, the resistance value is 4 × 10 ⁵ Ω by coating the same conductive film layer on a base layer of 10 ⁴ Ω or less obtained by using highly conductive carbon such as Ketjenblack EC.
When obtaining the conductive roll of No. 2, a thickness of 200 μm is required. The resistance value of the base layer 2 in the case of the 20 parts by weight of HAF is ^{3 × 10 5 Ω, 1 ×} 10 4 Ω in case of the 25 parts by weight, 30 parts by weight and if you 1 × 10 ⁴ Ω
In each case, a base layer having a relatively high resistance value is obtained, and the hardness of the base layer 2 when HAF is 20 parts by weight is Asker C53 °, and when it is 30 parts by weight, Asker C57 °. Thus, by using ordinary carbon such as HAF, the resistance value can be reduced to 1 with a small amount of compounding.
Since it can be controlled to about 0 ⁴ to 10 ⁶ Ω, a good base layer can be obtained without making the roll too hard. As shown in FIG. 8, the resistance value is obtained by winding a copper plate 12 having a width of 1 cm on the outer peripheral surface of the conductive roll 6 and applying a voltage of 1000 V between the shaft 1 and the copper plate 12 at this time. The resistance value R is obtained from the current value I by the formula R = V / I.

The electroconductive roll of the present invention has the base layer 2
Volume resistance 1.0 × 10 ^{7 to} 1.0 × 10 ¹¹ Ω · cm on top
In this case, the conductive thermoplastic resin constituting the conductive film layer 3 itself is 1.0 × 10 ^{7 to} 1.0. ×
It has a volume resistance of 10 ¹¹ Ω · cm, and is not one in which a conductive material is mixed to adjust the electric resistance value. Therefore,
In forming the conductive film layer 3, it is not necessary to mix a conductive material to adjust the electric resistance, and since it is made of an extrudable thermoplastic resin, it is not necessary to adopt a wet coating method which is complicated in operation. By extruding the raw material resin as it is, the conductive film layer 3 can be favorably formed by a simple operation. The volume resistance value of the conductive thermoplastic resin of 1.0 × 10 ^{7 to} 1.0 × 10 ¹¹ Ω · cm is
It is a value at a temperature of 25 ° C. and a relative humidity of 50% RH.

Specific examples of such conductive thermoplastic resin include Pebax 4011, MX1723, MX1074, MX under the trade name of Elf Atchem Japan Co., Ltd.
1041 (volume resistance 1.0 × 10 ^{8 to} 1.0 × 10 ¹⁰ Ω
・ Cm), a trade name of DuPont Mitsui Polychemicals Co., Ltd., Alculin (volume resistance 1.0 × 10 ^{7 to} 1.0 × 10 ¹⁰ Ω
.Cm) and the like, but in addition to these, the electric resistance value is 1.0 × 10 ^{7 to} 1.0 × 10 ¹¹ Ω · cm.
Any electrically conductive thermoplastic resin in the range can be used.

The method of forming the conductive film layer 3 is not particularly limited, and it can be formed by various methods such as extrusion molding and painting, but the conductive film layer 3 is formed simply and inexpensively. An extrusion molding method capable of being used can be preferably adopted.

The method for forming the conductive film 3 by extrusion molding will be described in detail. For example, as shown in FIG. 5, a substantially ring-shaped die 4 having an extrusion passage 4a formed on the peripheral wall as shown in FIG. 4 is used. As described above, the roll 6 having the base layer 2 formed on the outer periphery of the shaft 1 (not shown) is passed through the hollow portion of the die 4, and the thermoplastic resin 5 is formed into a tube shape from the extrusion passage 4a of the die 4. The conductive film layer 3 can be formed by extruding the roll 6 onto the base layer 2 and moving the roll 6 in one direction to cover the entire outer peripheral surface of the base layer 2 of the roll 6 with the thermoplastic resin 5. it can. In this case, as shown in FIG. 9, the conductive film layer 3 at the roll end portion is obliquely processed together with the base layer 2 (the left end portion in the figure),
It is possible to make the conductive film layer 3 longer than the base layer 2 so as to be obliquely processed (right end portion in the drawing).

Further, as shown in FIG. 6, a roll 6 composed of only the base layer 2 formed by the molding machine 7 into a thick-walled tube is crosslinked with rubber or foamed rubber from the molding machine 7 through a heating tank, and then directly. The conductive film layer 3 is passed through the hollow portion of the base 4.
And cutting it to a predetermined length with a cutting machine 8, and then inserting the shaft 1 into the center of the base layer 2 as shown in FIG.
If necessary, it can be fixed with an adhesive.
Further, in this case, as shown by reference numerals 9 and 10 in FIG. 6, after the conductive film layer 3 is formed by coating, various modified nylons such as methoxymethylated nylon, various modified urethanes such as fluorinated urethane, and soluble fluorine. A coating material such as resin is sprayed from the spray coater 9 onto the surface of the conductive film layer 3, or the coating material 13 is applied using a rubber instrument 11 having a conical shape as shown in FIG. A contamination prevention layer 10 for preventing contamination of an object to be charged such as a photosensitive drum can be formed thereon.

As described above, in the conductive roll of the present invention, the conductive film layer can be formed by a relatively simple extrusion molding method without adjusting the resistance value, and the manufacturing cost can be saved. It is possible.

Further, in the conductive roll of the present invention, as shown in FIG. 2, when the conductive film layer 3 is formed of the above-mentioned thermoplastic resin, the film thickness of the conductive film layer 3 is set from both ends of the roll. It is also possible to form the central portion thicker so that the outer diameter D ₁ of the central portion of the roll is larger than the outer diameter D _{2 of} both end portions of the roll, whereby when the conductive roll is pressed against the photosensitive drum, A uniform nip width can be reliably obtained along the axial direction of the roll.

In this case, the outer diameter D at the center of the roll₁And low
Outer diameter of both ends D₂Difference ΔD (ΔD = D₁− D₂) Is
There is no particular limitation, and the roll is pressed onto the photosensitive drum.
Base layer 2 and the extent to which the center of the roll floats up when contacted
Designed from the degree of flexibility of between the roll and the photosensitive drum
So that the nip width is uniform along the axial direction of the roll
To do.

For example, a roll body having a length L is formed on a metal shaft 1 having a length of 245 mm and a diameter of 7 mm.
If a force of 800 g is applied to both ends of the roll to press it against the photosensitive drum, normally, the difference ΔD between the outer diameter D _{1 at the} center of the roll and the outer diameter D _{2 at} both ends of the roll satisfies the following equation. When set to, a substantially uniform nip width can be obtained. 5 × 10 ^-5 <ΔD / L <5 × 10 ^-3

However, if the hardness of the base layer 2 is extremely low or if the shaft 1 flexes extremely greatly, a uniform nip width may not be obtained even if the above expression is satisfied. In such a case, as described above, ΔD may be appropriately changed in consideration of the degree to which the central portion of the roll floats and the degree of flexibility of the base layer 2.

The method of forming the conductive film layer 3 to have a large thickness at the central portion of the roll and a small thickness at both end portions in this manner is not particularly limited, and any method may be used. When the conductive film layer 3 is formed in FIGS. 5 and 6), the feed or take-up speed of the roll 6 is gradually decreased from one end to the center of the roll, and gradually from the center to the other end. It can be easily formed by increasing the speed.

The conductive roll shown in FIG. 2 is formed so that the outer diameter gradually increases from both ends of the roll toward the center, but the present invention is not limited to this and, for example, as illustrated in FIG. , Both ends of which are tapered and have a large diameter part with a uniform diameter in the central part (FIG. A), those in which the central part bulges in an arcuate cross section (FIG. B), A small diameter portion is formed and a large diameter portion having a uniform diameter is formed in the central portion (Fig. C).

As described above, the conductive roll of the present invention is
Since it is not necessary to adjust the resistance value of the conductive film layer and the conductive film layer can be formed by a relatively simple extrusion molding, the manufacturing cost can be saved, and the film thickness of the conductive film layer can be adjusted to the axis of the roll. By changing along the direction, the outer diameter of the roll central portion is formed to be larger than the outer diameter of both ends of the roll, when the roll is pressed against the photosensitive drum,
A uniform nip width can be reliably obtained along the axial direction of the roll, and the photosensitive drum can be reliably charged to a uniform potential. The method for producing the conductive roll of the present invention is preferably the above-mentioned method in which the conductive film layer is formed by extrusion molding, but the method is not limited to this and can be obtained by various other production methods. You can

[0034]

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

[Example 1] A base layer having a thickness of 3 mm was formed on a steel shaft using a conductive rubber composition having the following formulation.
It was formed thick. In this case, the vulcanization conditions were 160 ° C. × 5 minutes. The hardness of the obtained base layer was Asker C50, and the volume resistance thereof was 8 × 10 ² Ω · cm. Conductive rubber composition formulation cis-1,4-polybutadiene 60% by weight (BR02LL manufactured by Japan Synthetic Rubber Co., Ltd.) Liquid polyisoprene 40% by weight (Kuraray Isoprene LIR30 manufactured by Kuraray Co., Ltd.) Ketjen Black EC 10% by weight Zinc Hua 10% by weight Organic peroxide 0.8% by weight

Next, Elf Atchem Japan Co., Ltd.
Made Pebax 4011 (volume resistance 1.0 × 10 ⁸ ~
1.0 × 10 ¹⁰ Ω · cm) using the base shown in FIG.
By the method shown in FIG. 5, extrusion molding was performed on the above base layer under the following conditions to form a conductive film layer, and a conductive roll having the following dimensions and characteristics was obtained. Extrusion molding conditions Extruder: Plavender φ20 extruder (manufactured by Toyo Seiki) Extrusion conditions: Die 170 ° C Crosshead 170 ° C Screw 170 ° C Hopper 160 ° C Screw rotation speed 60rpm Extrusion rate: 1kg / Hr Drawing speed: 5m / min Extruded film Thickness: 250 μm Roll size and characteristics Roll length: 240 to 340 mm Roll diameter: φ10 to 20 mm Roll electrical resistance: 5 × 10 ⁵ Ω (measurement width 1 cm, H10K1 by the method shown in FIG. 8
Use MΩ tester, measured with applied voltage 1000V) Withstand voltage 1.5kV Hardness Asker C 60 °

The obtained conductive roll was set in a laser beam printer as a charging roll, and the temperature was 15 ° C. and the relative humidity was 10% RH in a low temperature and low humidity environment (L / L) and a temperature of 3.
High temperature and high humidity environment (H / 2.5 ° C, relative humidity 85% RH)
In H), when the copy test was performed 20 times in succession,
Both L / L and H / H had good image-extracting properties, and there was no occurrence of charring on the roll.

[Example 2] A conductive rubber sponge having the following formulation was extruded in a hose shape by 2 to 2.5 times and foamed to form a base layer. The vulcanization conditions were 230 ° C. and 3 minutes. Conductive rubber sponge composition prescription EPDM 100% by weight (Nippon Synthetic Rubber Co., Ltd. T7201EF) Oil 70% by weight (Idemitsu Petroleum Co., Ltd. PW380) Polyethylene glycol 1% by weight (Nippon Oil & Fats PEG4000) Foaming agent 3% by weight (Vinyl Hall AC No. 3 or Neocerbon N5000 manufactured by Eiwa Co., Ltd.)

Next, Alculine (volume resistance 1.0 × 10 ^{7 to} 1.0 × 10 ¹⁰ ) manufactured by DuPont Mitsui Polychemicals Co., Ltd.
Ω · cm) was extruded on the base layer under the following conditions by the method shown in FIG. 5 using the die shown in FIG. 4 to form a conductive film layer. Extrusion molding conditions Extruder: Prabender φ20 extruder (manufactured by Toyo Seiki) Extrusion conditions: Die 160 ° C Crosshead 160 ° C Screw 160 ° C Hopper 150 ° C Screw rotation speed 60rpm Extrusion rate: 1kg / Hr Drawing speed: 5m / min Extruded film Thickness: 250 μm

Then, an N-methoxymethylated nylon layer having a thickness of 5 μm was formed as a pollution prevention layer on the conductive film layer, cut into a predetermined length, and a steel shaft was inserted into the base layer for adhesion. Then, a conductive roll having the following dimensions and characteristics was obtained. Dimensions and characteristics Roll length: 240 to 340 mm Roll diameter: φ10 to 20 mm Roll electric resistance: 6 × 10 Ω (measurement width 1 cm, H10K1 by the method shown in FIG. 8
(MΩ tester used, measured at applied voltage of 1000V) Withstand voltage: 1.5kV Hardness: Asker C60 °

The conductive roll thus obtained was set as a charging roll in a laser beam printer, and a copying test was conducted in the same manner as in Example 1. It was found that both L / L and H / H had good image-drawing properties, and the roll was used as a roll. There was no occurrence of charring.

Example 3 A conductive film layer was formed on the same base layer as in Example 1 under the same extrusion molding conditions as in Example 1. At this time, the feeding or take-up speed of the conductive roll was controlled so as to be slow from the end to the center and fast from the center to the end to obtain the conductive roll having the shape shown in FIG. In addition, D ₁ is 14 mm and D ₂ is 13.76.
mm, L = 240, ΔD = D ₁ −D ₂ = 0.24 m
m, ΔD / L = 1 × 10 ⁻³ . The roll characteristics were similar to those of the example.

A force of 800 g was applied to both ends of the shaft 1 of the obtained conductive roll, the roll was pressed against the photosensitive drum, and the nip width was measured while rotating both rolls.
A uniform nip width was always obtained along the axial direction of the roll.

[0044]

As described above, in the conductive roll of the present invention, the conductive film layer covering the base layer has a volume resistance of 1.0.
By forming the conductive film with a thermoplastic resin of 10 ^{7 to} 1.0 10 ¹¹ Ω · cm, it is not necessary to adjust the electric resistance value when forming the conductive film layer, and the conductive film can be easily formed by extrusion molding. Thus, the layer can be formed, and therefore the coating process of the conductive film layer, which has been a complicated process in the past, can be simplified and the manufacturing cost can be reduced.

Further, by changing the film thickness of the conductive film layer along the axial direction of the roll so that the outer diameter of the central portion of the roll is larger than the outer diameter of both end portions of the roll, the roll is formed. When pressed against, the uniform nip width can be reliably obtained along the axial direction of the roll, and the photosensitive drum can be reliably charged to a uniform potential.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a conductive roll of the present invention.

FIG. 2 is a sectional view showing another example of the conductive roll of the present invention.

3A to 3C are side views each showing another example of the conductive roll of the present invention.

FIG. 4 is a cross-sectional view showing a die for coating a conductive film layer used for manufacturing the conductive roll of the present invention.

FIG. 5 is a schematic partial cross-sectional view showing a method of coating a conductive layer on a base layer using the same die.

FIG. 6 is a schematic partial cross-sectional view showing an example of a method for producing a conductive roll of the present invention.

FIG. 7 is a cross-sectional view showing another example of the conductive roll of the present invention.

FIG. 8 is a schematic perspective view showing a method for measuring the electric resistance of a roll.

FIG. 9 is a cross-sectional view showing a roll end treatment.

FIG. 10 is a perspective view showing an example of a method for forming a pollution prevention layer.

[Explanation of symbols]

 1 Shaft 2 Base Layer 3 Conductive Layer 4 Base 5 Thermoplastic Resin 6 Conductive Roll

Claims (2)

[Claims] 1. A charged body having a shaft, a conductive base layer provided on the outer periphery of the shaft, and a conductive film layer provided on the base layer, the charged body being in contact with the charged body. In a conductive roll that applies a potential of a predetermined polarity to,
The conductive film layer has a volume resistance of 1.0 × 10 ^{7 to} 1.0 × 10 ¹¹ Ω · cm at a temperature of 25 ° C. and a relative humidity of 50% RH.
A conductive roll formed by the thermoplastic resin of. 2. The outer diameter of the roll central portion is formed larger than the outer diameter of both end portions of the roll by forming the conductive film layer so that the central portion of the roll is thicker than both end portions of the roll. Conductive roll.