JP2000181190A - Electrifying member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying member which enables energy saving in a production process and recycling and, further, eliminates problems such as image defects. SOLUTION: A semiconductive elastic layer 203 composed of a thermoplastic elastomer in which perchloric acid lithium is dispersed as an ion conductive material is formed on a conductive support (core shaft) 201 made of stainless steel, further, the surface of the elastic layer 202 is coated with a protective layer 203, and thus an electrifying roller is obtained. The protective layer 203 is formed of a mixture of fluororesin, isocyanate curing agent, epichlorohydrin rubber, and silica. It is preferable that the constituents of the thermoplastic elastomer contain a polyether chain or polyester chain, the resistance value of the protective layer 203 be higher than the resistance value of the semiconductive elastic layer 202, a difference in resistance value between the protective layer 203 and the semiconductive elastic layer 202 be 103 Ωcm or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a charging member (such as a charging roller) for performing a charging process on a photosensitive member in an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art A charging roller type image forming apparatus 110 will be described with reference to FIG. The charging roller is the most general charging member used in the image forming apparatus. In FIG. 4, reference numeral 101 denotes a photosensitive drum on which an electrostatic latent image is formed, and reference numeral 102 denotes a charging roller that contacts the photosensitive drum 101 and performs a charging process. Reference numeral 103 denotes exposure of laser light or light reflected from a document. Reference numeral 104 denotes a developing roller for attaching toner to the electrostatic latent image on the photoreceptor 101;
Reference numeral 05 denotes a power pack for applying a voltage to the charging roller 102, reference numeral 106 denotes a transfer roller, and reference numeral 107 denotes a recording sheet conveyed from a sheet feeding unit. The transfer roller 106 transfers the toner image on the photosensitive drum 101 to the recording paper 107. Reference numeral 108 denotes a cleaning device for the surface of the photoconductor drum, and reference numeral 109 denotes a surface voltmeter for measuring the surface potential of the photoconductor drum 101. In FIG. 4, functional units normally required in other electrophotographic processes are not shown.

The image forming apparatus 11 configured as described above
The basic image forming operation at 0 will be described. By applying a voltage from a power pack 105 to a charging roller 102 which is in contact with the photosensitive drum 101, the surface of the photosensitive drum 101 is uniformly charged to a high potential. Immediately thereafter, when image light (exposure 103) is irradiated on the surface of the photosensitive drum 101, the irradiated portion has a lower potential. Since the image light has a light amount distribution corresponding to the black / white of the image, the potential distribution corresponding to the recorded image, that is, an electrostatic latent image is formed on the surface of the photosensitive drum 101 by the irradiation of the image light.

The portion where the electrostatic latent image is formed is the developing roller 1
After passing through 04, toner adheres according to the level of the potential, and a toner image is formed by visualizing the electrostatic latent image.
The recording paper 107 is conveyed to the portion where the toner image is formed by a registration roller (not shown) at a predetermined timing, and overlaps the toner image. This toner image is transferred to a transfer roller.
After being transferred to the recording paper 107 by the roller 106, the recording paper 107 is separated from the photosensitive drum 101. The separated recording paper is conveyed through a conveyance path, is fixed by heat and pressure by a fixing unit (not shown), and is discharged outside the apparatus. After the transfer, the photosensitive drum 10
The surface of 1 is cleaned by a cleaning device 108, and residual charges are erased by a quenching lamp (not shown), so that the surface is prepared for the next image forming process.

[0005] The mechanism of charging the surface of the photosensitive drum 101 by the charging roller 102 is as follows.
2. It is known that the discharge is in accordance with Paschen's law in a minute space between the photosensitive drums 101. The contact-type charging roller 102 abuts on the photosensitive drum 101 made of a metal substrate with a predetermined pressing force, and the photosensitive drum 101
When the charging roller 102 does not have sufficient flexibility, a floating occurs between the charging roller 102 and the photosensitive drum 101 in a slight depression on the surface. Because of the variation, charging failure occurs.

For this reason, in the charging roller 102, the semiconductive elastic layer is provided on the conductive support to prevent the photosensitive drum 101 from floating. Ethylene-propylene-diene rubber (EPD)
M), vulcanized rubber materials such as urethane rubber, silicone rubber and epichlorohydrin rubber are generally used.

In recent years, environmental protection activities have been increasing worldwide, and companies are also demanding environmentally conscious activities such as reduction of energy consumption during manufacturing and reduction of waste. However, the vulcanized rubber material used to form the above-described semiconductive elastic layer consumes energy in the vulcanization step during production and, once vulcanized, cannot be recycled by re-molding. For this reason, it cannot be denied that the material is extremely disadvantageous from the viewpoint of environmental protection. Therefore, it is conceivable to apply a thermoplastic elastomer material to the formation of the semiconductive elastic layer as an alternative to the vulcanized rubber material. Since thermoplastic elastomers can be molded in the same manner as thermoplastic resins, they have merits in terms of environmental protection, such as omitting the vulcanization step and recycling. However, when this thermoplastic elastomer is applied to a charging member, it is important to make the thermoplastic elastomer semiconductive.

Japanese Patent Application Laid-Open No. 7-121006 proposes a charging member used in an electrophotographic image forming apparatus using a thermoplastic elastomer in which a conductive pigment (for example, carbon black) is dispersed.

[0009]

However, when a conductive pigment is used, if the charging member is set in a semiconductive region (resistance value is about 10 ⁴ to 10 ⁹ Ωcm), the resistance value varies. And an image defect such as a partial charging failure occurs. This is because it is difficult to uniformly disperse the conductive pigment in the thermoplastic elastomer, resulting in poor dispersion.

The present invention has been made in view of the above problems of the prior art, and a first object of the present invention is to use a thermoplastic elastomer material in which an ion conductive material is dispersed as a material for forming an elastic layer. Another object of the present invention is to provide a charging member that can reduce energy in a manufacturing process, can be recycled, and does not cause the above-described problems such as image defects.

In order to achieve the first object, the present inventors have:
As described later, a charging member in which a semiconductive elastic layer made of a thermoplastic elastomer in which an ionic conductive material was dispersed was formed on a conductive support was examined. In the thermoplastic elastomer in which the ionic conductive material is dispersed, the dispersion of the resistance value is small unlike the thermoplastic elastomer in which the conductive pigment is dispersed, and partial charging failure does not occur from the viewpoint of image quality.

However, in a charging roller having a semiconductive elastic layer formed of a thermoplastic elastomer of the ionic conductive material dispersion type, the ionic conductive material becomes semiconductive by pressing against the photosensitive drum and leaving it for a long time. A problem of bleeding (bleeding) on the surface of the elastic layer was confirmed.
This bleed causes contamination of the photosensitive drum, causing deterioration of the photosensitive drum and image defects. In addition, since toner adheres to the charging roller, charging failure due to the accumulation of toner also occurs at the same time.

Accordingly, a second object of the present invention is to solve the problem that the ionic conductive material in the semiconductive elastic layer bleeds to the surface by forming a protective layer on the surface of the semiconductive elastic layer. Is to do.

Also, in the case of a charging roller having a semiconductive elastic layer formed of a normal thermoplastic elastomer material, if the charging roller is brought into contact with the photosensitive member with a predetermined pressing force, the surface of the photosensitive member is contaminated. was there. The reason is that the thermoplastic elastomer material that forms the semiconductive elastic layer generally contains an oily low molecular weight substance to impart flexibility, and this low molecular weight substance bleeds onto the surface of the charging roller. However, there is a possibility that the toner migrates to the surface of the photoconductor. Contaminated portions on the photoreceptor are less likely to be charged, so that a toner image is not formed, resulting in an abnormal image.

As a means for eliminating the above problem, it is conceivable to provide a protective layer having a barrier function on the surface of the semiconductive elastic layer. This protective layer is required to be thin, uniform, and have good surface properties so as not to impair the function as a charging roller. Therefore, formation of the protective layer is generally performed by dissolving the resin in a solvent and spraying or dipping this solution.

However, it has been found that even in a charging roller having a protective layer formed by such means, the low molecular weight substance from the semiconductive elastic layer bleeds on the surface of the protective layer, thereby contaminating the surface of the photoreceptor. . The bleed occurs because a low molecular weight substance existing in the semiconductive elastic layer is extracted when forming the protective layer. The properties required for the semiconductive elastic layer include a roller hardness and a compression set, and are required to have excellent low-temperature and high-temperature properties enough to withstand a general storage environment including the actual internal temperature.

Accordingly, a third object of the present invention is to provide a charging member capable of preventing contamination of the surface of a photoreceptor and obtaining excellent image quality by preventing bleeding of a low molecular weight substance on the surface of a protective layer. Is to do.

[0018]

In order to achieve the first object, the charging member according to claim 1 is a charging member having a semiconductive elastic layer formed on a conductive support, The material forming the semiconductive elastic layer is a thermoplastic elastomer in which an ionic conductive material is dispersed.

A charging member according to a second aspect is characterized in that, in the first aspect, a polyether chain or a polyester chain is contained as a component of the thermoplastic elastomer.

According to a third aspect of the present invention, in the charging member according to the first or second aspect, a protective layer is formed on a surface of the semiconductive elastic layer.

According to a fourth aspect of the present invention, in the charging member according to the third aspect, the resistance value of the protective layer is larger than the resistance value of the semiconductive elastic layer.

According to a fifth aspect of the present invention, in the charging member according to the fourth aspect, the difference in resistance between the protective layer and the semiconductive elastic layer is 10%.
^{It is 3} Ωcm or less.

According to a sixth aspect of the present invention, in order to achieve the second object,
The charging member according to (1), forms a semiconductive elastic layer made of a thermoplastic elastomer in which an ion conductive material is dispersed on a conductive support, and forms a protective layer made of a silicone resin on the surface of the semiconductive elastic layer. It is characterized by having done.

In the charging member according to the sixth aspect, it is desirable that the thermoplastic elastomer contains a polyether chain or a polyester chain as a constituent component, thereby facilitating the movement of ions. A smaller charging member exhibiting stable conductivity can be obtained. In the charging member of the sixth aspect, it is desirable to disperse the conductive particles in the resin of the protective layer, and the charging efficiency of the charging member is improved.

According to a seventh aspect of the present invention, in the charging member according to the sixth aspect, the resistance value of the protective layer is larger than the resistance value of the semiconductive elastic layer.

[0026] To achieve the third object, the present invention provides a method according to claim 8.
The charging member according to the above, characterized in that a semiconductive elastic layer made of a thermoplastic elastomer was formed on the conductive support, and a protective layer made of a polyester resin was formed on the surface of the semiconductive elastic layer. .

It is preferable to add a hydroxyl group or a carboxyl group to the main chain of the polyester resin and to add a curing agent to the resin, thereby improving the film strength of the protective layer and the adhesion to the semiconductive elastic layer. Further, it is desirable to disperse a conductive agent in the protective layer, whereby the charging member becomes semiconductive, and good charging ability is secured. Further, it is desirable that the resistance value of the protective layer is larger than the resistance value of the semiconductive elastic layer, so that voltage concentration on the photoconductor pinhole and abnormal discharge (leakage) can be avoided.

In order to achieve the third object, a ninth aspect is provided.
Is a charging member in which each layer is formed in the order of a semiconductive elastic layer and a protective layer on a conductive support, and the semiconductive elastic layer is made of an olefin-based or styrene-based thermoplastic elastomer. It is characterized by the following.

The charging member according to claim 10 is the charging member according to claim 9.
Wherein the resistance value of the protective layer is larger than the resistance value of the semiconductive elastic layer.

The charging member according to the eleventh aspect is the ninth aspect.
Alternatively, the resin material for forming the protective layer in the method described in 10 is polyvinyl butyral resin.

The charging member according to the twelfth aspect is the ninth aspect.
Alternatively, the resin material for forming the protective layer in the method described in 10 is a polyamide resin.

A charging member according to a thirteenth aspect is characterized in that, in the ninth, tenth, eleventh or twelfth aspect, the protective layer is formed by dispersing conductive particles in a resin.

[0033]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 (Claim 1) FIG. 1 is a cross-sectional view showing a configuration of a charging roller as a representative example of a charging member. This charging roller is electrically conductive support 2
The semiconductor device has a structure in which a semiconductive elastic layer 202 is formed (covered) on the substrate 01. The semiconductive elastic layer 202 is formed of a thermoplastic elastomer in which an ion conductive material (ion conductive agent) is dispersed.

The dispersion of the ionic conductive agent in the thermoplastic elastomer can be easily carried out by using means such as a twin-screw kneader or a kneader. Also, the conductive support 2
When coating 01 with a thermoplastic elastomer composition, by using means such as an extrusion molding machine or an injection molding machine,
The thickness and shape of the semiconductive elastic layer (coating layer) 202 can be arbitrarily finished without going through a vulcanization step required for the rubber composition.

Examples of the ionic conductive agent include alkali metal peroxides such as lithium peroxide, perchlorates such as lithium perchlorate, quaternary ammonium salts such as tetrabutylammonium salt, and phosphate ester salts. Regarding the compounding amount of the ionic conductive agent, since it is necessary to adjust the resistance value of the semiconductive elastic layer 202 to a predetermined range (about 10 ⁵ to 10 ⁹ Ωcm), 100 parts by weight of the base material (the thermoplastic elastomer) is used. It is preferable to mix the ionic conductive agent in the range of 1 to 10 parts by weight with respect to (1).

The ionic conductive agent forms a kind of coordination bond with an atom having an unpaired electron in the thermoplastic elastomer.
It is uniformly dispersed at the molecular level in the elastomer. Therefore, there is no variation in resistance value due to poor dispersion as seen in an elastomer in which a conductive pigment is dispersed (see the above-mentioned patent publication), and there is no occurrence of image defects due to partial charging failure and the like.

The thermoplastic elastomer for forming the semiconductive elastic layer 202 only needs to have the flexibility required for the charging roller, and the kind of the elastomer is not particularly limited, but is preferably used. In the case of an elastomer containing a polyether chain or a polyester chain as a component, the movement of ions becomes easier, so that the variation in the resistance value of the semiconductive elastic layer 202 is reduced, and a stable conductivity is obtained. The charging roller shown is obtained.

Second Embodiment (Claim 3) As shown in FIG. 1, when a charging roller is formed by forming only a semiconductive elastic layer 202 on a conductive support 201, the surface of the semiconductive elastic layer 202 If the chargeability is not good, the uniformity of charging may be poor. As shown in FIG. 2, such a defect is caused by further adding a protective layer 20 on the semiconductive elastic layer 202.
By forming 3, it can be eliminated. Protective layer 20
Examples of the material for forming 3 include a polyamide resin, a fluorine resin, and a polyvinyl butyral resin.

By making the resistance value of the protective layer 203 larger than that of the semiconductive elastic layer 202, voltage concentration on the photoconductor pinhole and abnormal discharge (leakage) can be avoided. However, if the resistance value of the protective layer 203 is too high, the charging efficiency is reduced. Therefore, the difference between the resistance values of the protective layer 203 and the semiconductive elastic layer 202 is preferably set to 10 ³ Ωcm or less. In this case, the resistance value of the protective layer 203 can be adjusted by blending various kinds of conductive agents with the raw material resin.

Embodiment 3 (Claim 6) When a charging roller having only a semiconductive elastic layer formed on a conductive support is used, the uniformity of charging may be poor due to poor surface properties. This defect is, as shown in FIG.
This can be solved by providing a protective layer 203 around the semiconductive elastic layer 202. Also, the semiconductive elastic layer 202
In the thermoplastic elastomer used for, as described above,
There is a problem that the ion conductive material bleeds. Therefore, the protective layer 203 needs to exert a barrier effect against the bleed.

A resin material is generally used to improve the surface properties, obtain a barrier property against bleed, and follow the elastic layer as an underlayer. However, since these resins are electrically insulative, if the protective layer 203 is formed singly, characteristics as a charging member cannot be obtained. Therefore, the resistance of the protective layer is reduced by blending various conductive agents with the resin. Commonly used conductive agents include carbon black and metal oxides.

It is not sufficient that the resistance value of the protective layer 203 is low. The charging roller is in contact with the photoconductor drum, but if there is a pinhole or defect in the photoconductor drum, the resistance of the charging roller, especially when the surface resistance is low,
Concentrated leakage of current to the pinhole or the like occurs, and charging is not performed in the vicinity thereof. Further, when the concentration is severe, a large current causes damage to the charging roller and the photosensitive drum. For this reason, the protective layer 203 has anisotropy in electrical resistance such that the charging current flows in the direction to the photosensitive drum (radial direction of the charging roller) but does not flow in the circumferential direction and the axial direction. It is necessary to have. In other words, the material for forming the protective layer is required to have low volume resistance (resistance in the film thickness direction) and high surface resistance.

The volume resistivity of the protective layer 203 is 10 ¹⁰ Ωcm
By setting the thickness to about 10 μm, the current can easily flow sufficiently in the radial direction and can hardly flow in the circumferential direction and the axial direction. By doing this,
Concentrated leakage of charging current to the photoconductor drum pinhole can be prevented.

In the present invention, a silicone resin is used as a material for forming the protective layer. This silicone resin is represented by the following [Chemical Formula 1]

[0045]

Embedded image

As shown in the figure, a siloxane bond (—Si—
O-), and this skeletal structure is known to be excellent in heat resistance. Further, by introducing an organic group into this skeleton structure, it is possible to simultaneously impart inorganicity and organicity. In the above [Chemical formula 1], R ₁ and R ₂ are a methyl group, a phenyl group or the like.

The above silicone resin is excellent in heat resistance, low in surface tension, excellent in water repellency, and excellent in releasability, weather resistance and chemical resistance. Furthermore, a composite having excellent characteristics having the performance of each material can be obtained by using a silicone resin and various resins having a functional group. The recycling of the charging member provided with such a protective layer can be carried out by dissolving and removing the protective layer with a solvent or by polishing and removing.

Embodiment 4 (Claim 8) As shown in FIG.
A semiconductive elastic layer made of a thermoplastic elastomer on 1
No. 02 is formed, and a protective layer 203 made of a polyester resin is formed on the surface of the semiconductive elastic layer 202. The semiconductive elastic layer 202 is formed of a thermoplastic elastomer in which an ion conductive material (ion conductive agent) is dispersed.

The dispersion of the ionic conductive agent in the thermoplastic elastomer can be easily carried out by using means such as a twin-screw kneader or a kneader. Further, when the conductive support is coated with the thermoplastic elastomer composition, by using a means such as an extruder or an injection molding machine, the semiconductive material is not subjected to the vulcanization step required for the rubber composition. The thickness and shape of the elastic layer (coating layer) can be arbitrarily set. After this coating, the charging roller is subjected to grinding in order to obtain the required surface accuracy. After these processes, a protective layer is formed by a coating process such as spray coating or dipping.

The thermoplastic elastomer for forming the semiconductive elastic layer only needs to have the flexibility required for the charging roller, and the kind of the elastomer is not particularly limited. An elastomer containing a polyether chain or a polyester chain as a constituent component facilitates the movement of ions, so that the variation in the resistance value of the semiconductive elastic layer is reduced,
A charging roller exhibiting stable conductivity is obtained.

Examples of the ionic conductive agent include alkali metal peroxides such as lithium peroxide, perchlorates such as lithium perchlorate, quaternary ammonium salts such as tetrabutylammonium salt, and phosphate ester salts. About the compounding amount of the ionic conductive agent, it is necessary to adjust the resistance value of the semiconductive elastic layer to a predetermined range (about 10 ⁵ to 10 ⁹ Ωcm), so that 100 parts by weight of the base material (thermoplastic elastomer) It is preferable to mix the ionic conductive agent in the range of 1 to 10 parts by weight. -Examples of the electronic conductive agent include carbon black, metal oxides (such as titanium oxide, tin oxide, and zinc oxide), graphite, and metal powder.

The ionic conductive agent forms a kind of coordination bond with an atom having an unpaired electron in the thermoplastic elastomer.
It is uniformly dispersed at the molecular level in the elastomer. Therefore, there is no variation in resistance value due to poor dispersion as seen in an elastomer in which a conductive pigment is dispersed (see the above-mentioned patent publication), and there is no occurrence of image defects due to partial charging failure and the like.

The bleed prevention effect can be enhanced by forming the protective layer with a polyester resin.
This is because the high crystallinity of the polyester resin provides a low molecular weight substance shielding effect and suppresses the migration of the low molecular weight substance to the surface of the protective layer. Therefore, according to the charging roller, an image of excellent quality can be stably formed.

As the polyester resin, a resin containing a polyester component, for example, a polyester polyurethane can also be used. Further, a mixture of a polyester resin and a polyurethane resin can also be employed as the material for forming the protective layer. Further, by introducing a hydroxyl group or a carboxyl group into the main chain of the polyester resin and adding a curing agent such as an isocyanate-based, melamine-based, or epoxy-based resin, the film strength of the protective layer and the adhesion to the base are improved.

Since these resins are electrically insulative, when a protective layer is formed of a single resin, the charging ability is reduced. In order to prevent this, it is desirable to blend these resins with various conductive agents to make them semiconductive. Examples of the conductive agent include carbon black and metal oxide. Further, by making the electric resistance value of the protective layer larger than the resistance value of the semiconductive elastic layer, voltage concentration on the photoconductor pinhole and abnormal discharge (leakage) can be avoided.

Fifth Embodiment (Claim 9) As shown in FIG. 2, this charging roller
1 is covered with a semiconductive elastic layer 202 and a protective layer 203. The semiconductive elastic layer is formed of an olefin or styrene thermoplastic elastomer.

Conductive agent (ionic conductive agent, electronic conductive agent) for olefin-based or styrene-based thermoplastic elastomer
Can be easily performed by using a means such as a twin-screw kneader or a kneader. The coating of the thermoplastic elastomer composition on the support can be formed into an arbitrary shape by means such as extrusion molding or injection molding without going through a vulcanization step required for the rubber composition.

As described above, the olefin-based or styrene-based thermoplastic elastomer using the semiconductive elastic layer 202 also has a problem of photoconductor contamination. The protective layer 203 needs to exert a barrier effect on the bleed. Examples of a material that achieves both improvement in surface properties and barrier property against bleed include polyamide resin and polyvinyl butyral resin. But,
Since these resins are electrically insulating, if the protective layer 203 is formed by itself, the characteristics as a charging member cannot be obtained. Therefore, the resistance of the protective layer is reduced by blending various conductive agents with the resin. As the conductive agent, the same material as that used for the above-described semiconductive elastic layer can be employed.

The lower the resistance value of the protective layer 203 is, the better. The charging member is in contact with the photoconductor drum, but if there is a pinhole or a defect in the photoconductor drum, if the resistance of the charging member is low, particularly if the surface resistance is low, current leaks to the pinhole or the like. Occurs, and charging is not performed in the vicinity thereof. Furthermore, when this concentration is severe, the charging member,
The photoconductor drum is damaged. Therefore, the protective layer 203
Is the direction to the photosensitive drum (radial direction of the charging roller)
It is necessary to have anisotropy in electric resistance such that a charging current is passed in the circumferential direction and the charging current is not passed in the circumferential direction and the axial direction. In other words, the protective layer 203 needs to have low volume resistance (resistance in the thickness direction) and high surface resistance.

In the present invention, the material itself does not have such characteristics, but by setting the volume resistivity of the protective layer 203 to about 10 ¹⁰ Ωcm and the thickness to about 10 μm, it is sufficient in the radial direction. However, the current is hard to flow in the circumferential and axial directions. As a result, it is possible to prevent the charging current from leaking into the photoconductor drum pinholes. The recycling in the case where the protective layer is provided can be carried out by dissolving and removing the protective layer with a solvent or by removing by polishing.

[0061]

EXAMPLES Examples of the present invention and comparative examples will be described below. Example 1 A charging roller having a structure shown in FIG. 1 in which a stainless steel core shaft (conductive support having a diameter of 6 mm) was covered with a semiconductive elastic layer was produced. As a material of the semiconductive elastic layer, a composition obtained by mixing 0.5 parts by weight of lithium perchlorate with 100 parts by weight of a thermoplastic elastomer containing a polyester component (Elastage ES5000A, manufactured by Tosoh Corporation) is used, and this material is extruded. Molded by a molding machine to cover the core shaft, φ1
A 4 mm charging roller was obtained. The surface hardness of this charging roller was 50 ° according to JIS-A, and the resistance value was 4 × 10 ⁸ Ωcm.

Example 2 A charging roller having the structure shown in FIG. 2 was prepared by coating a protective layer on the semiconductive elastic layer of the charging roller manufactured in the same manner as in Example 1. As a material for the protective layer, a mixture (resistance value: 3 × 10 ¹⁰ Ωcm) composed of a fluororesin (Lumiflon LF-600, manufactured by Asahi Glass Co., Ltd.), an isocyanate-based curing agent, epichlorohydrin rubber, and silica was used. Coated to 7 μm.

Example 3 The thermoplastic elastomer composition used as the material for forming the semiconductive elastic layer in Example 1 was pulverized into pellets of about 5 mm square, and a new thermoplastic resin was obtained so that the recycled content was 50% by weight. By blending with the elastomer composition, a charging roller having a diameter of 14 mm was produced in the same manner as in Example 1. The surface hardness of this charging roller was 51 ° according to JIS-A, and the resistance value was 4 × 10 ⁸ Ωcm, which was almost the same as the case where no recycled component was included.

Comparative Example 1 A charging roller having a structure in which a core shaft (conductive support having a diameter of 6 mm) made of stainless steel was covered with a semiconductive elastic layer was manufactured. As a material of the semiconductive elastic layer, 12% by weight of conductive carbon black (Ketjen Black EC: Ketjen Black International) was blended with an olefin-based thermoplastic elastomer (Millastomer 5030N: manufactured by Mitsui Petrochemical Industries, Ltd.). Using the composition, this material was molded by an extrusion molding machine to cover the core shaft, and φ14 mm
Was obtained. The surface hardness of this charging roller is JI
The SA was 60 ° and the resistance was 4 × 10 ⁷ Ωcm.

With respect to the above charging roller, image evaluation was performed using the image forming apparatus shown in FIG. In this case, the voltage applied to the charging roller was set to -1600 V of DC.
The evaluation results are shown in [Table 1]. In the evaluation of an abnormal image caused by voltage concentration on the photoconductor pinhole and abnormal discharge, the following ranking was performed. Rank 1: No white spots have occurred on the image due to abnormal discharge, or the diameter of the white spots is less than 2 mm. Rank 2: A blank spot My diameter is 2 mm or more, but it is not streaked. Rank 3: Streak-like white spots have occurred on the image.

[0066]

[Table 1]

Example 4 On a core shaft (φ6 mm) made of stainless steel, as a semiconductive elastic layer, 100 parts by weight of a thermoplastic elastomer containing a polyester component (Elastage ES5000A, manufactured by Tosoh Corporation) was mixed with 100 parts by weight of lithium perchlorate. The composition containing 0.5 part by weight was coated by extrusion molding to have an outer diameter of φ14. On this semiconductive elastic layer, as a protective layer, a mixture of epoxy-modified silicone resin and carbon black (10 wt% based on the total solid content) (resistance value is 3 × 10 ¹⁰
Ωcm) to a thickness of about 7 μm to obtain a charging roller.

Example 5 On a core shaft (φ6 mm) made of stainless steel, as a semiconductive elastic layer, 100 parts by weight of a thermoplastic elastomer containing a polyester component (Elastage ES5000A, manufactured by Tosoh Corporation) was mixed with 100 parts by weight of lithium perchlorate. The composition containing 0.5 part by weight was coated by extrusion molding to have an outer diameter of φ14. On this semiconductive elastic layer, as a protective layer, an epoxy-modified silicone resin and tin oxide (60% of the total solid content)
wt%) (resistance value is 3 × 10 ¹⁰ Ωcm)
Was coated to a film thickness of about 7 μm to obtain a charging roller.

Example 6 On a core shaft (φ6 mm) made of stainless steel, as a semiconductive elastic layer, 100 parts by weight of a thermoplastic elastomer containing a polyester component (Elastage ES5000A, manufactured by TOSOH CORPORATION) was added with lithium perchlorate 0%. The composition containing 0.5 part by weight was coated by extrusion molding to have an outer diameter of φ14. On this semiconductive elastic layer, as a protective layer, a mixture of acrylic modified silicone resin and carbon black (10 wt% with respect to the total solid content) (resistance value 3 × 10 ¹⁰
Ωcm) to a thickness of about 7 μm to obtain a charging roller.

Example 7 On a core shaft (φ6 mm) made of stainless steel, 100 parts by weight of a thermoplastic elastomer containing a polyester component (Elastage ES5000A, manufactured by Tosoh Corporation) was added as a semiconductive elastic layer. The composition containing 0.5 part by weight was coated by extrusion molding to have an outer diameter of φ14. On this semiconductive elastic layer, an acrylic modified silicone resin and tin oxide (60
wt%) (resistance value is 3 × 10 ¹⁰ Ωcm)
Was coated to a film thickness of about 7 μm to obtain a charging roller.

Example 8 The thermoplastic elastomer composition used for the elastic layer of Example 4 was pulverized into pellets of about 5 mm square, and this was added to a new thermoplastic elastomer composition so that the recycled content was 50 wt%. By blending, a charging roller of φ14 was obtained in the same manner as in Example 4. Surface hardness is 5 according to JIS-A
At 1 °, the resistance value was 4 × 10 ⁸ Ωcm, which was almost the same as the case where the recycled content was not included.

Comparative Example 2 On a core shaft (φ6 mm) made of stainless steel, 100 parts by weight of a thermoplastic elastomer containing a polyester component (Elastage ES5000A, manufactured by Tosoh Corporation) was used as a semiconductive elastic layer. The composition containing 0.5 parts by weight was coated by extrusion molding to obtain a charging roller of φ14. The surface hardness of this charging roller is 5 according to JIS-A.
0 ° and the resistance value was 4 × 10 ⁸ Ωcm.

Comparative Example 3 An olefin thermoplastic elastomer (Millastomer 5030N, manufactured by Mitsui Petrochemical Industry Co., Ltd.) and conductive carbon black (Ketjen Black EC) were formed on a core shaft (φ6 mm) made of stainless steel as a semiconductive elastic layer. , Ketchen Black International)
t% is coated by extrusion molding,
m of the charging roller was obtained. The surface hardness of this charging roller is J
IS-A was 60 ° and the resistance was 4 × 10 ⁷ Ωcm.

With respect to the above charging roller, image evaluation was performed using the image forming apparatus shown in FIG. In this case, the voltage applied to the charging roller was set to -1600 V of DC.
The evaluation results are shown in [Table 2] and [Table 3]. In the evaluation of abnormal images caused by voltage concentration on the photoconductor pinholes and abnormal discharge, the same ranking as in Examples 1 to 4 and Comparative Example 1 was performed.

[0075]

[Table 2]

[0076]

[Table 3]

Example 9 A charging roller having the structure shown in FIG. 2 was obtained by coating a stainless steel core shaft (conductive support having a diameter of 6 mm) with a semiconductive elastic layer and forming a protective layer on the surface thereof. Produced. As a material of the semiconductive elastic layer, a thermoplastic elastomer containing a polyester component (Elastage ES500)
(0A, manufactured by Tosoh Corporation) 100 parts by weight of a composition in which 0.5 part by weight of lithium perchlorate was blended, and this material was molded by an extruder to cover the core shaft. Then, it was finished to an outer diameter of φ14 by grinding. Next, a dispersion of tin oxide (60 wt% based on the total solid content) as a conductive agent in a polyester resin (Vylon 20SS, manufactured by Toyobo) (resistance value 1 × 10 ¹⁰ Ωcm) was applied to the semiconductive elastic layer. The surface was coated to a thickness of about 7 μm to form a protective layer, which was used as a charging roller. The surface hardness of this charging roller is J
IS-A was 50 ° and the resistance was 5 × 10 ⁶ Ωcm.

Example 10 A protective layer was coated on the semiconductive elastic layer of the charging roller manufactured in the same manner as in Example 9 by the following method to manufacture a charging roller having the structure shown in FIG. As a material of the protective layer, polyester urethane (Vylon UR1400, manufactured by Toyobo) was added to tin oxide (60% based on the total solid content) as a conductive agent.
wt%) (resistance value is 1 × 10 ¹⁰ Ωcm)
Was used to coat to a film thickness of about 7 μm. The surface hardness of this charging roller is 50 ° according to JIS-A, and the resistance value is 5 × 1.
0 was ^{6 Ωcm.}

Example 11 A protective layer was coated on the semiconductive elastic layer of the charging roller manufactured in the same manner as in Example 9 by the following method to manufacture a charging roller having the structure shown in FIG. As a material for the protective layer, a polyester resin (Vylon 20SS, manufactured by Toyobo) in which an isocyanate-based curing agent and tin oxide (60 wt% based on the total solid content) as a conductive agent are dispersed (resistance value is 1 × 10 ^10). Ωcm) to a thickness of about 7 μm. The surface hardness of this charging roller was 50 ° according to JIS-A, and the resistance value was 5 × 10 ⁶ Ωcm.

Example 12 A protective layer was coated on the semiconductive elastic layer of the charging roller manufactured in the same manner as in Example 9 by the following method to manufacture a charging roller having the structure shown in FIG. As a material for the protective layer, polyester urethane (Vylon UR1400, manufactured by Toyobo) in which an isocyanate-based curing agent and tin oxide (60 wt% based on the total solid content) as a conductive agent are dispersed (resistance value is 1 × 10 ^10). Ωcm) and a film thickness of about 7 μm
Coated. The surface hardness of this charging roller is JI
The SA was 50 ° and the resistance was 5 × 10 ⁶ Ωcm.

Comparative Example 4 A protective layer was coated on the semiconductive elastic layer of the charging roller manufactured in the same manner as in Example 9 by the following method to obtain a charging roller. As a material for the protective layer, a polyvinyl butyral resin (3000-K, manufactured by Denki Kagaku Kogyo Co., Ltd.) in which an isocyanate-based curing agent and tin oxide (60 wt% based on the total solid content) as a conductive agent are dispersed (resistance value is 1x1
0 ¹⁰ Ωcm) to a thickness of about 7 μm. The surface hardness of this charging roller is 50 ° according to JIS-A,
The resistance value was 5 × 10 ⁶ Ωcm.

With respect to the above charging roller, image evaluation was performed using the image forming apparatus shown in FIG. In this case, the voltage applied to the charging roller was set to -1600 V of DC.
Next, a photoreceptor contamination test was performed by the method shown in FIG.
The charging roller 102 was pressed against the photoreceptor 101 with a force of 6.5 N, and left for 5 days in an environment at a temperature of 30 ° C. and a humidity of 90% RH. Thereafter, the photoreceptor was set in the image forming apparatus shown in FIG. 4 and image evaluation was performed. If the photoconductor is contaminated, the contaminated portion is not charged, and this portion appears as an abnormal image (white spots). Therefore, it was confirmed whether or not this white spot occurred. Further, regarding the film strength of the protective layer and the adhesion between the protective layer and the underlayer, JIS K54008.5.5.3: X
The evaluation was performed based on the cut tape method. The above evaluation results are shown in [Table 4].

[0083]

[Table 4]

The charging potential of the photoreceptor was in the range of -930 to -960 V in all of Examples 9 to 12 and Comparative Example 4, and was OK. These values are appropriate as the charging potential, and the difference between -930 V and -960 V does not cause a significant problem. Further, in Comparative Example 4, bleeding of a low molecular weight substance in the semiconductive elastic layer was observed, and when an image was formed using this charging roller, partial charging failure (image unevenness) and photosensitive Body contamination (image white spots) was observed. With respect to the film strength of the protective layer and the adhesion to the base, rank evaluation was performed based on Table 19 of the X-cut tape method, and as a result, Examples 9 and 10 were ranked 4 (△) and Examples 11 and 12 were evaluated. Is rank 8 (○), comparative example 4 is rank 2
(△ to ×).

Comparative Example 5 A urethane thermoplastic elastomer 1 was formed as a semiconductive elastic layer on a core shaft (φ8 mm) made of stainless steel.
A composition obtained by mixing 15 parts by weight of conductive carbon black (Ketjen Black EC: Ketjen Black International) in 00 parts by weight was coated by injection molding to obtain a φ14 charging roller [same configuration as in FIG. so,
Surface hardness (JIS-A) 90 °, resistance value 4 × 10 ⁸
Ωcm].

Comparative Example 6 100 parts by weight of a vinyl chloride thermoplastic elastomer was used as a semiconductive elastic layer on a core shaft (φ8 mm) made of stainless steel, and conductive carbon black (Ketjen Black EC: manufactured by Ketjen Black International) ) Is blended in an amount of 15 parts by weight [surface hardness (JIS-
A) was coated at 50 ° and the resistance value was 4 × 10 ⁶ Ωcm] by extrusion to obtain a charging roller having a diameter of 14 mm.

Comparative Example 7 On a core shaft (φ8 mm) made of stainless steel, 100 parts by weight of an olefin-based thermoplastic elastomer (Millastomer: manufactured by Mitsui Petrochemical) was added as a semiconductive elastic layer to conductive carbon black (Ketjen Black EC). : Ketjen Black International Co., Ltd.) was coated with 15 parts by weight (surface hardness (JIS-A) of 50 °, resistance value of 1 × 10 ⁶ Ωcm) by extrusion molding, and φ1
A 4 mm charging roller was obtained.

Comparative Example 8 100 parts by weight of a styrene-based thermoplastic elastomer (Elastomer AR: manufactured by Aron Kasei Co., Ltd.) was used as a semiconductive elastic layer on a core shaft (φ8 mm) made of stainless steel, and conductive carbon black (Ketjen Black EC) was used. : Ketjen Black International Co., Ltd.) was coated with 15 parts by weight of a composition [surface hardness (JIS-A) is 45 °, resistance value is 2 × 10 ⁶ Ωcm] by extrusion molding, and φ
A 14 mm charging roller was obtained.

Comparative Example 9 A polyamide resin (Diamid T-1) was used as a protective layer on the semiconductive elastic layer of the charging roller manufactured in the same manner as in Comparative Example 8.
71: a mixture (resistance value: 3 × 10) composed of tin oxide (80 wt% based on the total solid content), manufactured by Daicel Huels Co., Ltd.
⁵ Ωcm) to a thickness of about 7 μm (FIG. 2).
And the same configuration). In addition, coating (molding) of the olefin-based or styrene-based thermoplastic elastomer material on the support can be easily performed by means such as extrusion molding or injection molding.

Example 13 As a protective layer on a semiconductive elastic layer of a charging roller produced in the same manner as in Comparative Example 7, a polyvinyl butyral resin (Denka Butyral 3000-K: manufactured by Denki Kagaku Kogyo KK), an isocyanate-based curing agent, Mixture of carbon black (10 wt% based on the total solid content) (resistance value: 3 × 10 ¹⁰ Ω)
cm) was coated to a thickness of about 7 μm (same configuration as in FIG. 2).

Example 14 As a protective layer on a semiconductive elastic layer of a charging roller produced in the same manner as in Comparative Example 8, a polyvinyl butyral resin (Denka butyral 3000-K: manufactured by Denki Kagaku Kogyo KK), an isocyanate-based curing agent, Tin oxide (60w based on total solids)
t%) (resistance value: 3 × 10 ¹⁰ Ωcm) was coated to a film thickness of about 7 μm (same configuration as in FIG. 2).

Example 15 A polyamide resin (Diamid T-1) was used as a protective layer on the semiconductive elastic layer of the charging roller manufactured in the same manner as in Comparative Example 7.
71: a mixture (resistance value: 10 wt% based on the total solid content) of carbon black (manufactured by Daicel Huels Co., Ltd.)
3 × 10 ¹⁰ Ωcm) to a thickness of about 7 μm (same configuration as in FIG. 2).

Example 16 A polyamide resin (Diamid T-1) was used as a protective layer on the semiconductive elastic layer of the charging roller manufactured in the same manner as in Comparative Example 8.
71: a mixture (resistance value: 3 × 10) composed of tin oxide (60 wt% based on the total solid content), manufactured by Daicel Huels Co., Ltd.
¹⁰ Ωcm) to a film thickness of about 7 μm (FIG. 2).
And the same configuration).

With respect to the above charging roller, image evaluation was performed using the image forming apparatus shown in FIG. On this occasion,
The voltage applied to the charging roller was DC-1600V.
Next, a photoreceptor contamination test was performed by a method as shown in FIG. 6.5 N charging roller 102 on photosensitive drum 101
And left for 5 days in an environment of a temperature of 30 ° C. and a humidity of 90% RH. Thereafter, the photosensitive drum 101 is moved to the position shown in FIG.
(1) and image evaluation was performed. If the photoconductor is contaminated, the contaminated area is not charged and appears as an abnormal image (white spots). It was checked whether the white spots occurred. The above results are shown in [Table 5] and [Table 6].

[0095]

[Table 5] * -1: The resistance value of the protective layer of Comparative Example 9 is smaller than that of the semiconductive elastic layer. * -2: PVB indicates polyvinyl butyral

[0096]

[Table 6]

A 10K paper-passing run was performed using the image forming apparatus shown in FIG. In this case, the charging roller is kept in constant contact with the photoconductor (load 500 g).
The image forming apparatus was placed in an environment of a temperature of 10 ° C. and a humidity of 18% RH, and a paper passing run of 5K was performed. Then, the image forming apparatus was placed in an environment of a temperature of 28 ° C. and a humidity of 70% RH, and a paper passing run of 5K was performed. Was done.

In Comparative Example 5, abnormal noise was generated at 10 ° C. and 18% RH, and in Comparative Example 6,
The deformation of the charging roller (presumably due to the large compression set) occurred after 10K with the generation of abnormal noise,
In Comparative Examples 7 and 8 and Examples 13 to 16, neither abnormal noise nor deformation occurred. From the above results, it can be seen that the olefin-based and styrene-based semiconductive elastic layers have excellent low-temperature and high-temperature characteristics enough to withstand a general storage environment including the actual internal temperature.

[0099]

As apparent from the above description, the following effects can be obtained according to the present invention. (1) Claim 1 In this charging member, the material forming the semiconductive elastic layer is a thermoplastic elastomer in which an ionic conductive material is dispersed. The resistance value does not vary, and image defects due to partial charging failure and the like do not occur. In addition, energy can be reduced in the manufacturing process and recycled.

(2) Claim 2 In the charging member, since a polyether chain or a polyester chain is included as a component of the thermoplastic elastomer forming the semiconductive elastic layer, ions can be easily moved. Therefore, the variation of the resistance value is smaller,
It shows stable conductivity.

(3) Claim 3 In this charging member, the uniformity and surface properties of charging are improved by forming the protective layer on the surface of the semiconductive elastic layer.

(4) Claim 4 In this charging member, since the resistance value of the protective layer is larger than the resistance value of the semiconductive elastic layer, voltage concentration on the photoconductor pinhole and abnormal discharge can be avoided. .

(5) Claim 5 In this charging member, since the difference in resistance between the protective layer and the semiconductive elastic layer is 10 ³ Ωcm or less, a decrease in charging efficiency can be prevented.

(6) A semiconductive elastic layer made of a thermoplastic elastomer in which an ionic conductive material is dispersed on a conductive support, and a photosensitive drum or toner is formed on the surface of the semiconductive elastic layer. Since the protective layer made of a silicone resin having excellent non-adhesiveness to the toner is formed, a charging member that does not cause a charging failure due to contamination of the photosensitive drum or toner fixation in addition to the above-described effects of the charging member of claim 1 can be obtained.

(7) In the charging member according to claim 6, since the resistance value of the protective layer is larger than the resistance value of the semiconductive elastic layer, voltage concentration on the photoconductor pinhole and abnormal discharge are avoided. be able to.

(8) Claim 8 In this charging member, a semiconductive elastic layer made of a thermoplastic elastomer is formed on a conductive support, and a protective layer made of a polyester resin is provided on the surface of the semiconductive elastic layer. As a result, it is possible to prevent the low molecular weight substance in the thermoplastic elastomer from bleeding to the surface of the protective layer, so that contamination of the surface of the photoreceptor can be avoided and excellent image quality can be obtained.

(9) Claim 9 Since the material for forming the semiconductive elastic layer is an olefin-based or styrene-based thermoplastic elastomer, the low-temperature and high-temperature excellent enough to withstand a general storage environment including the temperature in an actual machine. With characteristics, a roller of low hardness can be easily obtained, and
It has the advantage that energy can be reduced in the manufacturing process and that it can be recycled. In addition, since the periphery of the semiconductive elastic layer is covered with a protective layer made of a material having excellent non-adhesiveness to the photosensitive drum and toner, a charging member free from contamination of the photosensitive drum and poor charging due to toner adhesion is obtained. Can be

(10) Since the resistance value of the protective layer is made larger than the resistance value of the semiconductive elastic layer, voltage concentration on the photoconductor pinhole and abnormal discharge can be avoided.

(11) Claim 11 Since the polyvinyl butyral resin is excellent in non-adhesiveness to the photosensitive drum and the toner, by using this as a resin material for the protective layer, the photosensitive drum is contaminated and the charging failure due to the adhesion of the toner. Can be prevented.

(12) Claim 12 Since the polyamide resin is excellent in non-adhesion to the photosensitive drum and toner, by using this as a resin material for the protective layer, contamination of the photosensitive drum and poor charging due to toner adhesion are prevented. Can be prevented.

(13) Claim 13 In general, since the resin is insulative, if it is used as it is as a protective layer material, sufficient charging efficiency cannot be obtained. However, in the charging member of the present invention, a conductive material is contained in the resin. Since the protective layer is formed of a material in which particles are dispersed, charging efficiency is improved. In addition, the charging member according to claims 1 to 13 is PP.
The present invention can be effectively applied to an electrophotographic image forming apparatus such as C, LBP, and facsimile.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a charging roller according to the present invention.

FIG. 2 is a cross-sectional view showing another example of the charging roller according to the present invention.

FIG. 3 is an explanatory view showing a test method of photoreceptor contamination.

FIG. 4 is an explanatory diagram illustrating a configuration of an image forming apparatus using a charging roller.

[Explanation of symbols]

 Reference Signs List 101 photosensitive drum 102 charging roller 103 exposure 104 developing roller 105 power pack 106 transfer roller 107 recording paper 108 cleaning device 109 surface voltmeter 110 image forming device 201 conductive support member 202 semiconductive elastic layer 203 protective layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Koji Kamiya 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Hiroyuki Kitano 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H003 AA12 BB11 CC05 DD03 EE11 3J103 AA02 AA13 AA14 AA51 BA41 FA15 FA20 GA02 GA52 HA12 HA20 HA41 HA42 HA43 HA44 HA45 HA46 HA47 HA53

Claims (13)

[Claims] 1. A charging member comprising a conductive support and a semiconductive elastic layer made of a thermoplastic elastomer in which an ion conductive material is dispersed. 2. The charging member according to claim 1, wherein the thermoplastic elastomer contains a polyether chain or a polyester chain as a constituent component. 3. The charging member according to claim 1, wherein a protective layer is formed on a surface of said semiconductive elastic layer. 4. The charging member according to claim 3, wherein a resistance value of the protective layer is larger than a resistance value of the semiconductive elastic layer. 5. The charging member according to claim 4, wherein a difference in resistance between said protective layer and said semiconductive elastic layer is 10 ³ Ωcm or less. 6. A semiconductive elastic layer made of a thermoplastic elastomer in which an ion conductive material is dispersed on a conductive support, and a protective layer made of a silicone resin is formed on the surface of the semiconductive elastic layer. A charging member characterized by the above-mentioned. 7. The charging member according to claim 6, wherein a resistance value of the protective layer is larger than a resistance value of the semiconductive elastic layer. 8. A charging member characterized in that a semiconductive elastic layer made of a thermoplastic elastomer is formed on a conductive support, and a protective layer made of a polyester resin is formed on the surface of the semiconductive elastic layer. . 9. A charging member having a semiconductive elastic layer and a protective layer formed on a conductive support in this order, wherein the semiconductive elastic layer is made of an olefin-based or styrene-based thermoplastic elastomer. Characteristic charging member. 10. The resistance value of the protective layer is higher than the resistance value of the semiconductive elastic layer.
The charging member as described in the above. 11. The charging member according to claim 9, wherein the resin material forming the protective layer is a polyvinyl butyral resin. 12. The resin material for forming the protective layer is a polyamide resin.
0 charging member. 13. The protective layer according to claim 9, wherein the protective layer is formed by dispersing conductive particles in a resin.
Or the charging member according to 12.