JPH05134515A - Electrifying body - Google Patents

Abstract

PURPOSE:To to decrease the fluctuations in electric resistance so that a photosensitive body can be uniformly electrified by providing a semiconductor elastic material layer contg. a conductive material and a specific dispersion stabilzer into an elastic material matrix polymer. CONSTITUTION:The semiconductor elastic material layer 2 contg. the conductive material and the dispersion stabilizer having a chemical interaction with the conductive material in the elastic material matrix polymer is concentrically formed on the outside surface of a core rod 1. As a result, the the surface of the conductive material is coated with the dispersion stabilizer or the conductive material and the matrix polymer are crosslinked, by which the interaction between the conductive materials is weakened. The dispersion of the conductive material in the matrix polymer is facilitated and simultaneously, the reflocculation thereof is substantially prohibited. The formation of conductive paths by the dispersion stabilizer is inhibited but the way that formation is inhibited is uniform and the resistance stable as a whole is obtd. Consequently the electric resistance of the semiconductor elastic material layer 2 is stable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member used for uniformly charging a photosensitive drum or a transfer / conveying belt used in an electrophotographic copying machine or the like.

[0002]

2. Description of the Related Art In an electrophotographic copying machine, an original image is formed as an electrostatic latent image on the surface of a photoconductor, and toner is attached to this to form a toner image.
Copying is performed by transferring this toner image onto a recording sheet. In this case, the electrostatic latent image is formed on the surface of the photoconductor by charging the surface of the photoconductor in advance, projecting the original image on the charged portion through the optical system, and eliminating the charge on the light-transmitted portion. Has been done.

As a method of charging the surface of the photosensitive member prior to the formation of the electrostatic latent image, a corona discharge method has conventionally been adopted in which a corona discharge is applied to the surface of the photosensitive member from a corona discharger to perform a charging process. .. In this method, generally 5 to
Since a high-voltage power supply of 10 kV is used, it is necessary to take thorough safety measures, and there is the drawback that harmful ozone is generated during discharge.

Therefore, at present, as disclosed in US Pat. No. 2,934,650, a photosensitive member is charged by using a roller-shaped charging member (charging roller) or a belt-shaped charging member (charging belt). The contact charging method is adopted. This method is, as shown in FIG. 5 or 6, 1-2 kV
Charging roller with a DC voltage of approx.
This is a method of charging the photosensitive layer 12 to a predetermined potential by bringing the charging belt 10 or the charging belt 14 into contact with the surface of the photosensitive layer 12 of the drum-shaped electrophotographic photosensitive member 11 which is the member to be charged. In some cases, a blade-shaped charging body is used.

5 and 6 are schematic sectional views of a contact charging device of an electrophotographic copying machine to which a charging roller or a charging belt is applied. In the device shown in FIG. 5, the drum-shaped electrophotographic photosensitive member 11 has an arrow a. The surface of the photosensitive layer 12 is moved at a predetermined speed in the direction indicated by, while the charging roller 10 is brought into contact with the photosensitive layer 12 with a predetermined pressure. The power supply 13 applies a DC voltage or a voltage obtained by superposing a DC voltage and an AC voltage to the charged body.

In the apparatus shown in FIG. 6, when a voltage is applied to the rotary shaft 15, the photosensitive layer 12 on the surface of the drum-shaped electrophotographic photosensitive member 11 is charged via the charging belt 14 to be charged.

The photosensitive layer 12 formed on the surface of the photoconductor is made of a photoconductive semiconductor material containing organic semiconductor, amorphous silicon, selenium, zinc oxide and the like, and the stability of charging of the photoconductive layer affects the image quality. Since it has a great influence, it is necessary that the charging roller, the charging belt and the like are in stable contact with the photoconductor.

In the method using the charging roller, an elastic body or the like is used on the surface to increase the contact area with the photosensitive member so that the surface is stably charged. For this reason, it is desirable that the hardness of the elastic body that constitutes the roller is low.

Further, in the method using the charging belt, the contact area with the photosensitive member is increased by placing the charging belt driven by a plurality of rotating shafts on the photosensitive member. It is desirable that the charging belt be in close contact with the photoconductor and have a low hardness so as not to damage the photoconductor.

That is, both when using the charging roller and when using the charging belt, the material is required to have flexibility, and it is desirable that the hardness is low. An elastic material such as rubber is generally used as the material satisfying the flexibility and the low hardness.

Further, one of the performances required of the material forming the charged body (hereinafter, also referred to as a charging member) is electric resistance. This is deeply related to the level of charging and the uniformity of charging, and if the resistance is too high, it will not be charged, and if the resistance is too low, it will cause dielectric breakdown of the photoconductor or unstable charging. In addition to unevenness in the image, if there is a pinhole on the photoconductor, the current concentrates on that portion, causing leakage, and as a result, streaks appear in the image. For this reason, the electric resistance of the charging member varies depending on the photoconductor and the system used, but it must be set within a fairly narrow range of a semiconductive region of approximately 10 ⁶ to 10 ⁹ Ω.

As described above, it is generally suitable to use, as the charging member, an elastic material having an electric resistance in a preferable range, in other words, having semiconductivity.

As a method for obtaining the semiconductive elastic material, it is general to disperse fine particles having conductive properties in the elastic material, and carbon black is generally used as such conductive fine particles. ..

At this time, if graphite, inorganic conductive fine particles, metal fine particles, or the like is used instead of carbon black to attain a predetermined semiconductive property, it is necessary to highly fill them, and the elastic body becomes hard. In addition, there is a problem that it becomes brittle without reinforcement.

However, it is very difficult to adjust the electric resistance to the above-mentioned level of semiconductivity by using carbon black for the following reason.

That is, generally, the region of this electric resistance is
This is an area in which the resistance changes drastically with a slight difference in the amount of carbon black, and the resistance changes drastically with the difference in the processing method even with the same compounding amount, and it is a very difficult area to make.
Further, when the viscosity decreases during vulcanization, once dispersed carbon black particles cause reaggregation, and this effect also causes variations in electrical resistance.

As described above, it is theoretically easy to obtain an elastic material whose electric resistance is adjusted to a level of semiconductivity, but actually producing a stable product involves variations within a lot and between lots. It's big and very difficult.

In order to solve this problem, a material having an electric resistance smaller than the intended electric resistance is used as an axis, and another thin layer having a larger electric resistance is formed on the outer layer thereof.
There is an idea to obtain a desired electric resistance by forming multiple layers.

However, this method complicates the configuration. Also, when controlling the electrical resistance in a multilayer, the polymer used for the outer layer must be one having a low electrical resistance among the polymers,
Typical examples of such a polymer having a relatively low volume resistivity of about 10 ¹⁰ Ωcm include nylon, polyurethane, polyacrylonitrile, and their copolymers. However, all of these polymers are highly polar polymers, and are very susceptible to temperature, humidity, etc., and have the drawback that the electrical resistance changes depending on the installation environment.

When a general polymer having a volume resistivity of about 10 ¹⁶ Ωcm such as polyethylene is used,
No matter how thinly used, it is impossible to set the electric resistance from the shaft to the outermost layer to about 10 ⁶ to 10 ⁹ Ω.

Due to the above circumstances, it is very difficult to stably obtain a charged body of stable quality at present, it has a preferable electric resistance value, is hardly affected by temperature and humidity, and The reality is that the appearance of a charged body that can be stably produced is highly desired.

[0022]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in view of the above circumstances, and as a result, have developed an elastic body having a preferable electrical resistance in which a conductive substance is uniformly dispersed and stabilized in a matrix polymer. Succeeded in stable production, and completed the present invention.

That is, the present invention provides a semiconductive elastic material containing an electroconductive substance and a substance having a chemical interaction with the electroconductive substance as a dispersion stabilizer of the electroconductive substance in an elastic matrix polymer. The present invention relates to a charged body having a body layer.

[0024]

[Function] When a substance having a chemical interaction with a conductive substance (dispersion stabilizer) is contained in the elastic matrix polymer together with the conductive substance, the surface of the conductive substance is covered with the dispersion stabilizer, The conductive substance and the matrix polymer are bridged, and the interaction between the conductive substances is weakened, so that the conductive substance is easily dispersed in the matrix polymer, and at the same time, it is difficult to re-aggregate. Further, the dispersion stabilizer hinders the formation of the conductive passage,
The inhibition is uniform, and stable resistance is obtained as a whole. As a result, a semiconductive elastic body layer having stable electric resistance is formed.

[0025]

EXAMPLE A charged body of the present invention has a semiconductive elastic body layer containing an electrically conductive substance and a dispersion stabilizer having a chemical interaction with the electrically conductive substance in an elastic matrix polymer. is there.

The conductive substance is dispersed in the matrix polymer to give it proper conductivity, and carbon black is mainly used. this is,
Since carbon black has a small particle size and a structure develops to form a conductive passage, conductivity can be obtained at a low filling rate by selecting an appropriate material, and it is also excellent in reinforcing property and low cost. This is because

Some of the above carbon blacks have various sizes and characteristics depending on their raw materials, manufacturing methods, etc., but in the present invention, functional groups such as phenolic hydroxyl groups, carboxyl groups and double bonds are present on the surface. In particular, conductive carbon is preferable because it has a well-developed structure, has a relatively small particle size, and has a small amount of conductivity.

As the conductive substance, in addition to carbon black, if necessary, metal powder, inorganic semiconductive fine particles,
You may use together the material which has general electroconductivity, such as electroconductive fiber. In this case, it is preferable that the amount of use is 500 parts or less with respect to 100 parts of carbon black (parts by weight;

The substance having a chemical interaction with the conductive substance (dispersion stabilizer) means a chemical bond (covalent bond, hydrogen bond, ionic bond, etc.) with the conductive substance as described above. It has a function of preventing the re-aggregation of the conductive substance dispersed in the matrix polymer, stabilizing the dispersion, and facilitating the adjustment of the electric resistance. Specific examples of such substances include, for example, two types shown in (1) and (2) below.

(1) Polymers, oligomers and the like (hereinafter also referred to as modified polymers) containing a functional group less than or within the molecular chain.

Since the functional group of the modified polymer or the like has a chemical interaction, preferably a strong interaction, with the functional group of the surface of the conductive material, the modified polymer or the like covers the surface of the conductive material, so that The aggregation of the conductive substances dispersed in each other is prevented. Furthermore, it is preferable to select a modified polymer having a high affinity such as having compatibility with the matrix polymer, and as a result, the interaction between the matrix polymer and the conductive substance is indirectly increased. The dispersion of the conductive material is even more stabilized.

As the functional group existing in the molecular chain of the modified polymer or oligomer such as less than or within the molecular chain, for example, when the conductive substance is carbon black, the functional group on the carbon black surface is a phenolic hydroxyl group or a carboxyl group. Therefore, any substance that has a chemical interaction with, for example, reacts with, these functional groups may be used.
Specific examples of such a functional group include a hydroxyl group, a carboxyl group, an amino group and a nitro group.

The modified polymer or oligomer has a molecular structure in which the polymer other than the functional group or the main chain of the oligomer is as similar to the matrix polymer as possible from the viewpoint of dispersion stability of the conductive material, that is, a highly compatible molecular structure. Those are preferable.

The molecular weight of the modified polymer or oligomer is preferably 1000 or more (the oligomer includes several thousands of molecular weight). If the molecular weight is smaller than this, it becomes difficult to cover the surface of the conductive material so as to form a uniform layer.

Examples of the modified polymer, oligomer, etc., when the conductive substance is carbon black, for example, terminal hydroxyl group polyolefin such as terminal hydroxyl group polyethylene, terminal hydroxyl group polypropylene and terminal hydroxyl group polybutadiene, terminal amino group polyolefin, terminal Examples include carboxyl group polyolefins,
Other sulfone groups, halogenated allyl groups, halogenated alkyl groups, halogenated acyl groups, nitro groups, amide groups,
Polymers or oligomers having a urethane group, an ether group, a carbonyl group, an imino group, a cyano group, an epoxide group, a group of these homologous groups, or ions of these can also be used. Further, a polymer having a polar group or a reactive group at the terminal other than the above may be used.

When carbon black and, for example, inorganic conductive particles other than carbon black are used together as the conductive material, the same material is used. In any case,
Those having a strong interaction with the functional groups appearing on the surface of the conductive substance are preferable.

(2) A coupling agent which can be chemically bonded to a conductive substance and can be chemically and / or physically bonded to a matrix polymer.

The above-mentioned type of substance may be a general coupling agent, but it is preferable that it reacts with the functional group on the surface of the conductive substance, and specific examples include commercially available coupling agents such as silane type and titanium type. Can be given. Furthermore, those that chemically react with both the conductive substance and the matrix polymer to form a crosslinked structure are more preferable.

Specific examples of such a substance include dinitrodiamine when the conductive substance is carbon black. Dinitrodiamine cleaves radicals at high temperatures around 140 ° C to produce biradicals, which chemically bond and crosslink with the matrix polymer and carbon black to prevent reaggregation.
It is believed to improve the dispersion stability. When a conductive substance other than carbon black is used in combination with, for example, inorganic conductive particles, a general silane coupling agent or titanium coupling agent can be used.

The substance of type (1) and the substance of type (2) may be used in combination, or each may be used alone.

FIG. 3 is an explanatory view of the mechanism of dispersion stabilization when a polymer having a functional group is used as the dispersion stabilizer and carbon black is used as the conductive substance. As shown in FIG. 3, when the carbon black particles 5 and the dispersion stabilizer 6 are dispersed in the matrix polymer 9, the functional groups on the surface of the carbon black particles 5 and the functional groups in the dispersion stabilizer 6 are dispersed in the matrix polymer 9. As a result of chemically and strongly interacting with the group 7, the dispersion stabilizer 6 becomes carbon black 5.
The main chain 8 of the dispersion stabilizer 6 that covers the surface of the
Is dispersed in the matrix polymer 9 due to its high affinity with the surrounding matrix polymer 9, and as a result, the carbon black 5 is dispersed.

FIG. 4 is an explanatory view of the dispersed state of the carbon black 5 in the matrix polymer 9 when the dispersion stabilizer is not used. In this case, as a result of re-aggregation of the carbon black particles 5 with each other, the dispersion state becomes very bad.

The elastic matrix polymer used in the present invention is selected from a wide range of materials having rubber elasticity in consideration of use environment, use conditions, compatibility with a dispersion stabilizer, reactivity and the like.

Examples of the matrix polymer include natural rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, butadiene rubber, isoprene rubber, chloroprene rubber, butyl rubber, ethylene-propylene rubber and the like. Among these, it is preferable to select a rubber material having low crystallinity in consideration of hardness and the like.

A plasticizer or the like may be added in order to reduce the hardness, but as long as it does not cause deposition of a substance that may contaminate the photoreceptor due to aging and environmental changes, it does not occur. Preference is given to using. Further, if the permanent distortion of the rubber due to compression is large and the pressing time against the photoconductor becomes long, the shape of the outer circumferential circle of the roller may change. , NBR, vulcanized rubber, etc.) are preferably used.

The electric resistance of the semiconductive elastic body used in the present invention is generally 10 ⁵ to 10 ¹⁰ Ωcm, preferably 10 ⁶ to 10 ⁸ Ωcm.
Is set to. However, this value varies considerably depending on the conditions under which the charging is performed, for example, the type of the photosensitive member and the voltage between the photosensitive member and the charging member, and is appropriately selected according to each condition. Basically, the electric resistance is adjusted by changing the amount of the conductivity imparting material.

Further, it is desirable that the hardness of the semiconductive elastic body be as small as possible so as to enhance the adhesion to the photoconductor and not damage the photoconductor, and the hardness is 70 degrees (JIS A) or less,
Among them, 40 degrees or less is preferable.

The content of the conductive substance in the semiconductive elastic body is determined by the type of the conductive substance, the property (type of functional group, amount, etc.), the shape (surface area, etc.), and the type of dispersion stabilizer used in combination. It depends on the situation, so it cannot be said in a nutshell. In the case of carbon black, about 10 to 30 parts is often preferable with respect to 100 parts of the matrix polymer, but there are cases where about 100 parts are required. For example, if the carbon black has an arithmetic mean particle size of 25 nm, a DBP oil absorption of 155 ml / 100g, and a N ₂ adsorption specific surface area of 215 m ² / g (for example, Tokai Black # 5500 manufactured by Tokai Carbon Co., Ltd.) Partial size, but arithmetic mean particle size
55nm, DBP oil absorption 140ml / 100g, N ₂ adsorption specific surface area 32m ²
In the case of / g (for example, Tokai Black # 4300 manufactured by Tokai Carbon Co., Ltd.), about 40 to 60 parts are used.

The amount of the dispersion stabilizer used in the semiconductive elastic body cannot be generally stated as in the case of the conductive substance. When the substance of the type (1) is used and the conductive substance is carbon black, it is usually in the range of 0.1 to 10 parts, preferably 0.5 to 5 parts per 100 parts of carbon black. For example, carbon black to Talker Black # 5
When a molecular end NH-modified wax is used as a dispersion stabilizer when 500 is used, 1 to 10 parts are used per 100 parts of carbon black.

In the case of the substance of the type (2), usually 0.1 to 10 parts, preferably 1 to 5 parts is used with respect to 100 parts of the conductive agent, but depending on the kind and the kind of the conductive material. Since it can take various values, it is not necessarily within this range. As a specific example, if Sumifine 1162 is used as a dispersion stabilizer for carbon black (Toker Black # 5500) with an arithmetic average particle diameter of 25 nm, DBP oil absorption of 155 ml / 100 g, and N ₂ adsorption specific surface area of 215 m ² / g. Carbon black
Used in 10 to 30 parts per 100 parts, arithmetic average particle size 55
nm, DBP oil absorption 140ml / 100g, N ₂ adsorption specific surface area 32m ² / g
When using carbon black (Toker Black # 4300), the range is 40 to 60 parts.

Generally, it is preferable that the dispersion stabilizer is effective even if it is used in a small amount.
It is not preferable because it may lead to deterioration of physical properties of the semiconductive elastic body.

The method for preparing the semiconductive elastic body containing the conductive substance and the dispersion stabilizer in the matrix polymer depends on the type of the dispersion stabilizer.

For example, when a substance of the type (1) is used as a dispersion stabilizer and carbon black is used as a conductive substance, both need only be added to the matrix polymer at the same time and kneaded. When a dispersion stabilizer is mixed and the dispersion stabilizer is adsorbed on the surface of the carbon black and then dispersed in the matrix polymer, the dispersion stabilizer is more effectively adsorbed on the surface of the carbon black. ..

When a coupling agent, which is a substance of the type (2), is used as a dispersion stabilizer and carbon black is used as a conductive substance, the coupling agent together with carbon black is incorporated into the matrix polymer as described above. It may be put in and kneaded, but first, the carbon black, a small amount of the matrix polymer, and the coupling agent are kneaded, and the temperature is raised to cause a reaction to form a crosslinked structure, which is then re-formed in the matrix polymer. Is more preferable.

The charged body of the present invention having the semiconductive elastic layer has, for example, the shape of a charging roller as shown in FIG. 1 or a charging belt as shown in FIG. The charged body is not limited to these shapes, and may be, for example, a blade shape suitable for the place of use.

In the charging roller shown in FIG. 1, the semi-conductive elastic body layer 2 is concentrically formed on the outer surface of the core rod 1.
In the case of a charging roller, the thickness of the semiconductive elastic body layer is usually 1
~ 10 mm.

The core rod 1 is made of metal or a conductor similar thereto.

For the roller-shaped charged body, for example, a conductive adhesive is applied to the outer circumference of a metal shaft, placed in a mold, and the composition to be the semiconductive elastic body is added. It is manufactured by vulcanizing, demolding, and polishing.

In the belt-shaped charged body shown in FIG. 2, the conductive layer 3 is provided inside the belt, and the semiconductive elastic body layer 2 is provided on the outer periphery thereof. The belt is driven by two or more rotary shafts 4, and a voltage can be applied to the belt by making the rotary shafts 4 partially conductive.

The thickness of the semiconductive elastic body layer 2 forming the outer periphery of the conductive layer 3 is determined by the electric resistance required for the belt and the electric resistance of the material forming the semiconductive elastic body layer. It is essentially unaffected by other factors. However, in practice it is necessary to consider the occurrence of wear and scratches, so
It is preferable that the thickness is 0.5 mm or more. Further, the electric resistance of the semiconductive elastic body layer 2 of the belt-shaped charged body is 10 ⁵ to
It is preferably about 10 ¹² Ωcm.

As the conductive layer 3, a layer made of metal, plastic in which conductive filler or the like is dispersed, or rubber material may be appropriately used. The conductive layer 3 is not essential to have a film-like smoothness, and may be, for example, a woven fabric of conductive fibers or a cord-shaped material wound in a spiral shape. Also,
Either a joint belt or a seamless belt may be used.

The charging belt may be a belt having a two-layer structure as shown in FIG. 2 or a belt having a single layer structure without the conductive layer 3.

As a method for producing the belt-shaped semiconductive elastic body layer, a general extrusion molding method or the like may be used, but it is preferable to eliminate seams or steps of seams as much as possible.

As described above, in the semiconductive elastic body layer used for the charged body of the present invention, when a dispersion stabilizer composed of a modified polymer or oligomer is used as the dispersion stabilizer, they are electrically conductive. Of a conductive substance by covering it with a conductive substance, repulsion between the covered conductive substances, affinity between the modified polymer and the matrix polymer, and when a coupling agent is used as a dispersion stabilizer. Due to the bridging action with the matrix polymer, re-aggregation of the conductive substances is prevented and a stable dispersion state is achieved. As a result, a stable semiconductive electric resistance can be obtained as a whole. Therefore, the initial performance could be obtained without taking the multi-layer structure as in the prior art.

As described above, when the charged body of the present invention having one layer of the semiconductive elastic body layer having stable electric resistance is used, stable and uniform charging of the charged amount is realized on the photosensitive member, for example, electrophotography. When used in a copying machine, unevenness in the image does not occur, and it is possible to prevent dielectric breakdown to the photoconductor caused by too low electric resistance.

Hereinafter, the charged body of the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

Example 1 100 parts of EPDM (manufactured by Japan Synthetic Rubber Co., Ltd., EP-11), carbon black (manufactured by Tokai Carbon Co., Ltd., Toka Black #)
5500) 25 parts, molecular end modified wax (MP-1049 manufactured by Sanyo Kasei Co., Ltd.) as a dispersion stabilizer, 5 parts, and Percumyl D (dicumyl peroxide) 2.7 parts as a vulcanizing agent and acrylic ester ED (ethylene glycol). 2.0 parts of dimethacrylate) was kneaded at 50 to 80 ° C. for 10 minutes to prepare a rubber composition. Then, apply a conductive adhesive to the outer circumference of the stainless steel shaft with a diameter of 6 mm and a length of 238 mm, excluding the protruding part, wrap the rubber composition over it, put it in a mold, and leave it at 160 ° C for 20 minutes. It was vulcanized in. After that, it was removed from the mold and polished to prepare a charging roller having a semiconductive elastic body layer having a length of 224 mm and a thickness of 3 mm. Similarly, a total of 6 charging rollers were manufactured.

The electric resistance of each charging roller thus obtained was examined by measuring the volume resistance between the shaft and the surface using an insulation resistance meter, and the variation was determined. The electric resistance in the shaft axial direction and the circumferential direction was then obtained. As shown in Table 1, the variation of No. 1 was within one digit.

From the following experiment, it can be said that the dispersion stabilizer and the carbon black chemically interact with each other in the semiconductive charging member layer of the charging roller of this embodiment.

(A) A kneaded product of carbon black, rubber and a dispersion stabilizer was dissolved in a solvent (hot toluene when the rubber was EPDM) without vulcanization, and only carbon black was taken out. A lot of solvent was used and carbon black cleaning was included.

When the obtained carbon black was mixed again with the new solvent, the sedimentation rate of carbon black was lower than that of the carbon black obtained by the same system treatment containing no dispersion stabilizer. This indicates that the dispersion stabilizer is bound to the surface of carbon black in a state where it is not removed by the solvent, that is, by chemical interaction.

(B) Further, a mixture of carbon black and a molecular terminal modified wax as a dispersion stabilizer was added to the wax solvent. The addition amount was such that each of carbon black and wax was less than 1%. The sedimentation rate of carbon black at this time was 1/10 or less as compared with carbon black without the addition of the dispersion stabilizer. This indicates that there is a bond due to a strong interaction between the carbon black and the molecular terminal-modified wax that is the dispersion stabilizer.

The charging roller thus obtained was actually attached to an electrophotographic printer (LX manufactured by Canon Inc.),
When the image quality was examined, as shown in Table 1, stable image quality was obtained in the initial image.

Example 2 Natural rubber (ribbed smoked sheet, RSS-3) 100
Part, carbon black (the same as in Example 1) 27 parts, and a dispersion stabilizer (Sumitomo Chemical Co., Ltd., Sumifine
1162) 2 parts were kneaded at 140 ° C for 10 minutes, then the temperature was lowered, and 3 parts zinc oxide as a vulcanizing agent, 1.5 parts sulfur, a vulcanization accelerator CZ (N-cyclohexyl-2-benzothiazole sulfenamide) A rubber composition was prepared by adding 1.0 part and kneading at 50 to 80 ° C. for 10 minutes.

The fact that the carbon black and the dispersion stabilizer in this example are bound to each other by interaction means that
It was confirmed by the following experiment.

The composition of Example 2 and the composition of Example 2 containing no dispersion stabilizer were evaluated for viscoelastic properties at 60 ° C. after vulcanization.

RSA-II (manufactured by Rheometrics) was used to measure viscoelasticity.
According to

From the measured values of E ′ and E ″, according to the equation (1),
tan δ was calculated.

[0079]

[Equation 1]

No dispersant used Dispersant tan δ 0.070 0.057 E ′ (× 10 ⁷ N / m ² ) 1.38 1.43 E ″ (× 10 ⁶ N / m ² ) 0.97 0.82 However, tan δ: Loss normal cut E ′: Storage elasticity Modulus E ″: loss elastic modulus E ′ is larger when the dispersant is used,
It is shown that due to the increased interaction between the carbon and the polymer, the mobility of the polymer is restricted and, as a result, the elasticity of the polymer is increased.

The smaller value of E ″ when the dispersant is used indicates that the mobility of the polymer is restricted due to the increased interaction between the carbon and the polymer, and as a result, the viscosity of the polymer is lowered. ..

The value of tan δ when the dispersant is used is smaller than that when the dispersant is not used, as is clear from the formula (1), because the interaction between the carbon black and the polymer is increased through the coupling agent. This is because the energy loss generated on the surface of carbon black was reduced.

Using the rubber composition thus obtained, a charging roller was produced in the same manner as in Example 1 and evaluated in the same manner as in Example 1. As a result, variations in electric resistance in the shaft axial direction and the circumferential direction are shown in Table 1. As shown in, both were within one digit.

When used in the electronic printer, stable image quality was obtained in the initial image.

Comparative Examples 1-2 A charging roller was prepared and evaluated in the same manner as in Examples 1-2, except that the dispersion stabilizer was removed during the preparation of the rubber compositions in Examples 1-2. As shown in Table 1, the variations in the electrical resistance in the axial direction of the shaft and the circumferential direction were at least two digits.

Further, when used in an electronic printer, as shown in Table 1, a black uneven portion was generated in the image, or a small scratch on the photoconductor caused a leak to cause a black streak.

[0087]

[Table 1]

[0088]

EFFECT OF THE INVENTION The charged body of the present invention has a small variation in electric resistance and can uniformly charge the photosensitive body. For example, when it is used in an electrophotographic copying machine, a stable quality image can be obtained. Be done. Since the charged body of the present invention is a single layer having a uniform electric resistance, it can be easily manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view of a roller-shaped charged body.

FIG. 2 is a cross-sectional view of a belt-shaped charged body.

FIG. 3 is an explanatory diagram of a mechanism of a dispersed state of carbon black particles and a dispersion stabilizer in a matrix polymer.

FIG. 4 is an explanatory diagram of a dispersed state of carbon black particles when a dispersion stabilizer is not used in a matrix polymer.

FIG. 5 is a schematic sectional view of a contact charging device using a roller-shaped charging member.

FIG. 6 is a schematic cross-sectional view of a contact charging device using a belt-shaped charging body.

[Explanation of symbols] 2 semi-conductive elastic layer 5 carbon black particles 6 dispersion stabilizer 7 functional group 8 main chain 9 matrix polymer

Claims (5)

[Claims] 1. A semiconductive elastic body layer containing a conductive substance and a substance having a chemical interaction with the conductive substance as a dispersion stabilizer of the conductive substance, in an elastic matrix polymer. Charged body. 2. The charged body according to claim 1, wherein the conductive substance is carbon black. 3. The charged body according to claim 1, wherein the conductive substance is a mixture of carbon black and a conductive substance other than carbon black. 4. The charged body according to claim 1, wherein the substance having a chemical interaction with the conductive substance is a polymer or an oligomer having a functional group at the terminal or in the molecular chain. 5. The coupling agent, wherein the substance having a chemical interaction with the conductive substance is a coupling agent capable of chemically bonding with the conductive substance and chemically and / or physically with the matrix polymer. The charged body according to claim 1.