JP2003255669A - Electrifying roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrifying roller which is excellent in resistance against leak and which can be more easily manufactured than a conventional one. <P>SOLUTION: The roller constituted by coating a metal core with a single resin layer, is characterized in that the resin layer contains at least a thermoplastic resin, conductive carbon and an ionomer resin. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging roller having stable electric characteristics used in copying machines and printers.

[0002]

2. Description of the Related Art FIG. 1 is a diagram schematically showing a typical image forming mechanism in an electrophotographic apparatus such as a copying machine or a printer. In image formation in an electrophotographic apparatus, as shown in FIG. 1, a charging step of uniformly charging a photoconductor,
An exposure step of exposing a charged photoconductor to an electrostatic latent image on the surface of the photoconductor, and attaching toner to the photoconductor on which the electrostatic latent image is formed, and transferring it onto paper with a transfer roller. It basically includes a transfer step of forming a toner image by heating and a fixing step of applying heat and pressure to fix the toner image on the paper. After passing through these steps, the photosensitive member is cleaned by a blade or the like to remove the residual waste toner, is discharged, and is subjected to repeated charging steps.

Conventionally, the charging of the photosensitive member in the conventional process was generally performed by corona discharge, but since ozone generated in corona discharge adversely affects the surroundings, it has been recently shown in FIG. As described above, a method using a contact type charging roller has been adopted. In the method using the charging roller, the volume resistivity of the roller is 10 ⁴ Ω · cm to 10 ⁹ Ω in order to charge the photoconductor.
・ It is desirable to be about cm. In order to obtain the above volume resistivity, conventionally, a resin material such as a thermoplastic elastomer, epichlorohydrin rubber, nitrile rubber, urethane rubber, EP (ethylene-propylene) rubber, silicone rubber or the like is blended with an appropriate amount of conductive carbon. The charging roller obtained as described above was used, but such a charging roller has a problem that leakage to the photosensitive member is likely to occur. Further, in recent research, when the amount of conductive carbon is reduced and an ionic conductive agent represented by a quaternary ammonium salt is mixed, a charging roller having desired volume resistivity and excellent leak resistance can be obtained. It is known that the characteristics of the ion conductive agent are easily influenced by the environment, and the resistance decreases as the temperature and humidity increase, and the resistance increases as the temperature and humidity decrease, so the characteristics of the roller produced by it are unstable. The phenomenon has been pointed out. Further, the ionic conductive agent has a property that it blooms on the surface of the charging roller during use, and it also has a drawback of contaminating the photoconductor. Therefore, recently, when a charging roller containing an ionic conductive agent is used, a method of preventing environmental dependence and bloom is adopted as a laminated structure including an outermost layer containing no ionic conductive agent. There is. However, such a charging roller having a laminated structure has problems such as complicated manufacture, poor dimensional stability, and unstable adhesion between layers.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a charging roller which has excellent leak resistance and can be manufactured more easily than before. Is to provide.

[0005]

The present inventors have completed the present invention as a result of intensive research to solve the above problems. That is, the present invention is as follows. (1) A roller having a metal core coated with a single resin layer, wherein the resin layer contains at least a thermoplastic resin, conductive carbon, and an ionomer resin. Charging roller to do. (2) The charging roller as described in (1) above, wherein the thermoplastic resin is an ABS resin. (3) The volume resistivity of the resin layer is 1 × 10 ⁴ Ω · cm or more.
The above (1) characterized in that it is 1 × 10 ⁹ Ω · cm
Alternatively, the charging roller according to (2).

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The charging roller of the present invention is a roller including a metal core and a single resin layer covering the metal core, the resin layer containing at least a thermoplastic resin, conductive carbon, and an ionomer resin. It is characterized by The thermoplastic resin used in the present invention is not particularly limited, and various conventionally known thermoplastic resins can be used, but the shape changes easily even after being used for a long time (30000 hours to 50000 hours). Therefore, ABS (acrylonitrile-butadiene-styrene) resin, PS (polystyrene) resin, PC (polycarbonate) resin, PPE (polyphenylene ether) resin, PBT (polybutylene terephthalate) resin, PA (polyamide) resin, PP
A (polypropylene) resin or the like is used. Among them, ABS resin is preferably used because it is excellent in physical properties such as impact resistance, creep resistance, thermal stability, and easy moldability.

The conductive carbon used in the present invention is blended for the purpose of lowering the resistance, and the kind thereof is not particularly limited, and examples thereof include Ketjen black, acetylene black, furnace black, channel black and thermal. Carbon black such as black can be used. Above all, it is preferable to use Ketjen black and / or acetylene black because high conductivity can be obtained by adding a small amount.

The amount of the electrically conductive carbon compounded is not particularly limited and may be appropriately selected depending on the type thereof. From the viewpoint of moldability, electrical properties and mechanical properties, the thermoplastic resin 100
The amount is preferably 3 to 20 parts by weight, more preferably 5 to 15 parts by weight, based on parts by weight. This is because if the content of the conductive carbon is less than 3 parts by weight based on 100 parts by weight of the thermoplastic resin, the desired conductivity tends not to be obtained, and the content of the conductive carbon is 100 parts by weight of the thermoplastic resin. This is because if the amount exceeds 20 parts by weight with respect to parts, the leak resistance tends to deteriorate.

As the ionomer resin used in the present invention, a carboxyl group of the side chain of the copolymer obtained by copolymerizing α-olefin and unsaturated carboxylic acid is neutralized and crosslinked with cation. , There is no particular limitation. The ionomer resin is one in which the ions in the resin have conductivity, and is excellent in heat resistance and impact resistance, and also has a characteristic of high breakdown voltage (excellent leak resistance). As the α-olefin, ethylene, propylene, 1-butene and the like can be preferably used. As the unsaturated carboxylic acid, acrylic acid, methacrylic acid, fumaric acid, maleic acid and the like can be preferably used. Further, as the cation, sodium, magnesium,
Potassium, aluminum, lithium, zinc, copper, cobalt, nickel, etc. can be used conveniently.

In the above ionomer resin, the ratio of α-olefin to unsaturated carboxylic acid is not particularly limited, but α-olefin: unsaturated carboxylic acid = 1: 0.05
˜1: 0.4 is preferable, and α-olefin: unsaturated carboxylic acid = 1: 0.1 to 1: 0.3 is more preferable. α-olefin: unsaturated carboxylic acid = 1:
Less than 0.05 (too little unsaturated carboxylic acid)
When it exceeds α-olefin: unsaturated carboxylic acid = 1: 0.4 (too much unsaturated carboxylic acid), it tends to become brittle (inferior in strength). The cation is preferably blended so that 90% or less of the carboxyl groups are neutralized, and more preferably 80% or less of the carboxyl groups are neutralized.

The blending amount of the ionomer resin in the present invention is not particularly limited and may be appropriately selected depending on the type, but from the viewpoint of conductivity, leak resistance, the above physical properties and workability, 100 parts by weight of the thermoplastic resin is used. On the other hand, it is preferably 5 to 20 parts by weight, more preferably 7 to 15 parts by weight. This is because if the amount of the ionomer resin blended is less than 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin, the desired conductivity tends not to be obtained, and the amount of the ionomer resin blended is 100 parts by weight of the thermoplastic resin. On the other hand, if the amount exceeds 20 parts by weight, the workability and the above physical properties tend to deteriorate.

In the charging roller of the present invention, the composition containing at least the above-mentioned thermoplastic resin, conductive carbon and ionomer resin is molded as a single resin layer covering the metal core. As the metal core forming material, metal materials such as iron, iron alloys, copper, copper alloys, aluminum, and aluminum alloys that have been conventionally used as metal core materials in the art can be used without particular limitation. Above all, it is preferable to use a metal core made of iron or an iron alloy (specifically, carbon steel or stainless steel) from the viewpoints of strength, cost, and workability.

In the present invention, as described above, by containing at least the thermoplastic resin, the conductive carbon and the ionomer resin, even if the resin layer is a single layer roller, environmental dependence and bloom are prevented. In addition, it is possible to realize a charging roller that has excellent leakage resistance. In the present invention, the above-mentioned effects can be achieved only when any of the thermoplastic resin, the conductive carbon and the ionomer resin is contained. That is, among these three, a charging roller lacking a thermoplastic resin is difficult to mold, and the molding is complicated (costly), the creep resistance is poor, and high dimensional accuracy cannot be obtained. There is. Further, in the charging roller lacking conductive carbon among the above three, in order to achieve the desired volume resistivity, a large amount of ionomer resin must be blended, which causes the above-mentioned problems. Further, among the above three, in the charging roller lacking the ionomer resin, a large amount of conductive carbon must be blended in order to obtain the desired volume resistivity, which causes a problem that leakage occurs. Since the charging roller of the present invention contains the ionomer resin, it is possible to achieve the desired volume resistivity while keeping the amount of the conductive carbon compounded to an extremely small amount such that leakage does not occur. In addition, ionomer resin absorbs moisture immediately after molding and its resistance decreases, but thereafter, the characteristics are not affected by the environment and bloom does not occur on the surface of the charging roller, so conventional ion conductive agents are used. It is not necessary to provide the outermost layer to prevent this, unlike the charging roller described above.
It is possible to realize a charging roller having excellent leak resistance with a single resin layer. Here, the "excellent leak resistance" means that the voltage when the dielectric breakdown test is conducted and the dielectric breakdown is 1200 V or more.

The method of manufacturing the charging roller of the present invention is not particularly limited, and the charging roller can be manufactured by a method known in the art. For example, a composition obtained by blending at least a thermoplastic resin, carbon black and an ionomer resin in a predetermined amount is kneaded using a known kneader such as a Banbury mixer or a roll kneader, and then a metal core is formed using a known injection molding machine. The resin layer for coating may be injection molded. As described above, according to the present invention, even a roller having a single resin layer can realize a charging roller that can prevent environmental dependence and bloom and that has excellent leak resistance. By injection molding the above, a product can be obtained by molding once, and no grinding process or the like is required, so that the product can be manufactured more easily than before. In the present invention, there is also an advantage that the manufacturing process can be carried out at a minimum as described above and the manufacturing cost can be kept low. The conditions of injection molding are not particularly limited, but usually,
Molding temperature of 200 ° C to 250 ° C, 50 mm / sec to 150
Molding is performed within each range of the injection speed of mm / sec.

Further, in the charging roller of the present invention, the volume resistivity of the resin layer is 1 × 10 ⁴ Ω · cm from the viewpoint of charging the photosensitive member.
~ 1 × 10 ⁹ Ω · cm is preferable, 1 × 10 ⁵ Ω · cm
-Cm to 1 x 10 ⁸ Ω-cm is more preferable.
This is because if the volume resistivity is less than 1 × 10 ⁴ Ω · cm, the electrification voltage is too low and the photoreceptor tends to be damaged. If the volume resistivity exceeds 1 × 10 ⁹ Ω · cm, This is because the charging efficiency tends to be too high to charge the photoconductor. The volume resistivity is calculated, for example, by winding a metal foil around the charging roller, applying a direct current from the metal core of the charging roller, and calculating the resistance value by reading the value of an ammeter connected in series to obtain the metal foil. The volume resistivity is converted from the area and the roller coating thickness (wall thickness of the resin layer). The volume resistivity of the charging roller can be adjusted by the blending amount of conductive carbon, and as described above, by blending 3 parts by weight to 20 parts by weight of conductive carbon with respect to 100 parts by weight of the thermoplastic resin, A volume resistivity of 1 × 10 ⁴ Ω · cm to 1 × 10 ⁹ Ω · cm can be realized.

The charging roller of the present invention is not particularly limited in its length, roll diameter (outer diameter), shaft diameter (inner diameter) and the like, and may be appropriately selected according to the copying machine to which it is applied.
Further, the composition for forming the charging roller of the present invention may be blended with an appropriate additive such as an inorganic filler, an antioxidant, a compatibilizer, etc. within a range that does not impair the effects of the present invention. Good.

[0017]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. Example 1 A composition in which 5 parts by weight of carbon black and 10 parts by weight of an ionomer resin were mixed with 100 parts by weight of ABS resin,
After kneading with a Banbury mixer, injection molding (temperature: 230 ° C, injection speed: 100 mm) on a stainless steel metal core
/ Sec), roll diameter 12 mm (shaft diameter: 8 mm),
A 350 mm long charging roller sample was prepared.

Example 2 A charging roller sample was prepared in the same manner as in Example 1 except that a polyester resin was used instead of the ABS resin.

Example 3 A charging roller sample was prepared in the same manner as in Example 1 except that polypropylene resin was used instead of ABS resin.

Comparative Example 1 A charging roller sample was prepared in the same manner as in Example 1 except that a composition prepared by mixing 5 parts by weight of carbon black with 100 parts by weight of ABS resin was used.

Comparative Example 2 A charging roller sample was prepared in the same manner as in Example 1 except that a composition prepared by mixing 10 parts by weight of carbon black with 100 parts by weight of ABS resin was used.

Comparative Example 3 100 parts by weight of polyester resin and 1 part of carbon black
A sample of the charging roller was prepared in the same manner as in Example 1 except that the composition containing 0 part by weight was used.

Comparative Example 4 A charging roller sample was prepared in the same manner as in Example 1 except that a composition prepared by mixing 20 parts by weight of an ionomer resin with 100 parts by weight of ABS resin was used.

[Evaluation Test] Examples 1 to 1 produced above
Regarding the samples of 3 and Comparative Examples 1 to 4, those satisfying both the criteria of the volume resistivity and the leak voltage measured by the following procedure were regarded as pass, and those not satisfying any one of them were collectively judged as fail. . (1) Volume resistivity A metal foil was wrapped around each sample, a DC voltage of 100 V was applied from the metal core, the resistance value was calculated from the reading of the value of an ammeter connected in series, and the area of the metal foil, The volume resistivity was converted from the roller coating thickness. 1.0 × 10 ⁴ Ω · cm ~
The range of 1.0 × 10 ⁹ Ω · cm was evaluated as ◯, and the range outside of the above range was evaluated as x. (2) Leak voltage A 20 mm-long metal foil was wound around each sample, connected to an AC voltage generator, and the voltage was measured when the voltage was increased and dielectric breakdown occurred. If the voltage was 1200 V or higher, ○, 1
When the voltage was less than 200 V, it was rated as x. The results are shown in Table 1.

[0025]

[Table 1]

[0026]

As is apparent from the above description, according to the present invention, it is possible to provide a charging roller which is excellent in leak resistance and can be manufactured more easily than ever before.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a typical image forming mechanism in an electrophotographic apparatus such as a copying machine or a printer.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H200 FA02 FA13 GA23 GA32 GA44                       GB12 GB13 GB22 HA03 HA12                       HA28 HB03 HB12 HB22 HB45                       HB46 JA02 LC09 MA01 MA04                       MA06 MA11 MA14 MA17 MA20                       MB01 MB04                 3J103 AA02 AA12 AA32 AA85 EA02                       EA11 FA15 GA02 GA57 GA58                       HA03 HA20 HA41 HA52

Claims (3)

[Claims] 1. A roller comprising a metal core coated with a single resin layer, the resin layer containing at least a thermoplastic resin, conductive carbon, and an ionomer resin. Characteristic charging roller. 2. The charging roller according to claim 1, wherein the thermoplastic resin is ABS resin. 3. The volume resistivity of the resin layer is 1 × 10 ⁴ Ω.
The charging roller according to claim 1 or 2, wherein the charging roller has a viscosity of 1 to 10 ⁹ Ω · cm.