JP3337887B2 - Elastic members for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elastic member for electrophotography, and more particularly, to an elastic member for electrophotography such as a transfer member and a charging member used in an electrophotographic apparatus such as a copying machine or a laser beam printer.

[0002]

2. Description of the Related Art A general structure of an electrophotographic elastic member is such that a semiconductive elastic layer is provided on a conductor such as a metal core via an adhesive layer. By the way, regarding the adhesive layer, the adhesive to be used naturally affects the semiconductivity of the elastic member due to the resistance. For example, when the adhesive is used for a transfer member, the transfer efficiency with respect to the transfer agent is reduced, and uniform and excellent transfer is achieved. Problems such as inability to obtain performance occur.

In the case where the adhesive layer has uneven resistance,
Disturbance of uniform charging and uniform transfer occurs, leading to image deterioration.

Conventionally, carbon black is often used as the conductive filler mixed in the adhesive layer because it is inexpensive and can easily obtain a low resistance. In this case, however, the dispersion of the resistance due to the non-uniformity of the dispersion increases. In some cases, image defects due to resistance unevenness occurred.

[0005]

The problem to be solved is an image defect due to such uneven resistance of the adhesive layer.

[0006]

According to the present invention, there is provided an electrophotographic elastic member having a semiconductive elastic layer on a conductor via an adhesive layer, wherein the adhesive layer comprises carbon black as a conductive filler, graphite and a binder. An electrophotographic elastic member comprising a thermoplastic elastomer, wherein the semiconductive elastic layer is bonded by heating.

[0007] By blending carbon black and graphite as a conductive filler to be contained in the adhesive layer of the elastic member for electrophotography according to the present invention, uniform and good conductivity can be obtained.

[0008] This is considered to be that by mixing and dispersing the flaky graphite, conduction between the carbon blacks is connected by the flaky graphite and the dispersion due to the dispersion of the carbon black can be greatly improved. .

[0009] Carbon black is an aggregate in which fine black particles are chemically bonded. On the other hand, graphite is scaly graphite, and it is considered that a blend of both forms uniform and good conductivity.

The total amount of carbon black and graphite in the adhesive layer is preferably 20 to 80 phr, that is, 100 parts by weight of the binder. It is 20 to 80 parts by weight. Further, the ratio of carbon black to graphite is preferably 0.5 to 10 (weight ratio) of graphite to 1 of carbon black.

When the elastic member is used as an elastic roller such as a transfer roller or a charging roller, a load is applied to the interface between the elastic semiconductive layer and the rigid core metal due to the shearing force associated with the pressure rotation. By relaxing such a shear force with an elastic adhesive layer, the shear force is dispersed, and peeling of the adhesive layer caused by concentration of stress can be avoided, and there is no resistance unevenness and resistance fluctuation accompanying peeling. Can be avoided. In this regard, a thermoplastic elastomer is effective as a binder used for the adhesive layer.

[0012] Among the thermoplastic elastomers, it is preferable to use a styrene-butylene elastomer as a main component as a binder.

This is because the rubber is rich in elasticity, excellent in heat resistance, and excellent in ozone resistance and weather resistance.

Further, by modifying with various functional groups such as polar groups, it is possible to easily adhere even between poorly adhesive materials such as EPDM and SBS.

As the thermoplastic elastomer, other elastomers such as polyolefin, polyester, polyurethane, acrylic and butadiene-acrylonitrile are used.

In the method of manufacturing a roller-shaped elastic member, a core metal having an adhesive layer formed on the surface of a vulcanized tube-shaped semiconductive elastic layer may be press-fitted later. it can.

For example, after applying the above-mentioned adhesive dissolved in a solvent on a metal core which is a conductor and drying it at room temperature, a vulcanized semiconductive elastic tube is press-fitted and heated, and the roller body is heated. Is molded. At the time of press-fitting, the applied adhesive layer does not yet have an adhesive force, so that the production line can be streamlined such as by automating the press-fitting / heating bonding process.

The shape of the elastic member of the present invention may be a roller, a blade, or the like, and can be selected according to the specifications of the electrophotographic apparatus.

FIG. 1 shows a basic configuration of a roller-shaped elastic member 1. In this case, a semiconductive elastic layer 4 is formed on a cylindrical cored bar 2 via an adhesive layer 3. When the elastic member has a blade shape, a semiconductive elastic layer may be formed on a plate-shaped core metal with an adhesive layer interposed therebetween.

As the core metal, a metal such as iron, copper, stainless steel, or a metal alloy can be used.

The semiconductive elastic layer can be formed by dispersing a conductive filler such as conductive carbon, graphite and metal powder in an elastic body such as rubber and resin matrix. Particularly, a double oxide is preferable as the conductive filler.

Here, the double oxide refers to a solid solution compound composed of two or more oxides, and is therefore different from a mere metal oxide. As such a complex oxide, for example, Z
nO.Al ₂ O ₃ .SnO ₂ .Sb ₂ O ₅ , In ₂ O ₃
Such as · SnO ₂ and the like.

The characteristics of such multiple oxides are that each metal has a short atomic radius, forms a substitution-type solid solution, and has a different valence number. That is, conductivity that cannot be obtained is obtained.

The specific resistance of these double oxides is 10 ¹ Ω ·
cm〜１０10 ³ Ω · cm, higher than conductive carbon black, reinforcing carbon black, metal powders such as copper and silver, and lower than iron trioxide or tin oxide (10 ⁴ Ω · cm or more).

That is, 1 expressed by the double oxide
When using a filler of ^{0 1 Ω · cm~10 3 Ω ·} cm, a stable semiconductive properties obtained with the addition amount that does not cause problems in physical properties, excellent reproducibility and productivity stability.

Among the above-mentioned complex oxides, ZnO.A
l ₂ O ₃ is excellent. The reason for this is that the specific resistance of this filler is 10 ² Ω · cm to 10 ³ Ω · cm, which is the most ideal resistance value with respect to the resistance stability in the semiconductive region. It is easy to disperse in a molecular dispersion medium and is excellent in workability, the cost is low, and an appropriate resistance value can be achieved depending on the doping amount of Al (Al ₂ O ₃ ).

The content of the double oxide in the elastic body is 5 wt% or more.
40 wt%, especially 10 wt% to 30 wt% is preferred.

Examples of the elastic material include EPDM, polybutadiene, natural rubber, polyisoprene, SBR, CR,
Rubber such as NBR, silicone rubber, urethane rubber, epichlorohydrin rubber, RB (butadiene resin), SB
S (styrene-butadiene-styrene elastomer) and other thermoplastic elastomers such as polystyrene, polyolefin, polyester and polyurethane, polyurethane, polystyrene, PE, PP, PVC, acrylic resin, styrene-vinyl acetate copolymer, Butadiene-
A polymer material such as an acrylonitrile copolymer can be used. The elastic body can be used as a foam or as a solid rubber.

Further, other additives such as a reinforcing agent, an insulating oil, and a filler may be added to the elastic body.

The electric resistance of the semiconductive elastic layer is preferably 10 ⁴ to 10 ¹⁰ Ω in terms of the resistance from the core metal to the surface of the semiconductive layer per cm ^{2 of the} semiconductive elastic layer.

In the case where the photosensitive member is charged by using the elastic member of the present invention, for example, a voltage is externally applied to the core of the elastic member to apply a voltage to the photosensitive member in contact with the elastic member. In contrast, charging can be performed.

The charging is performed by a method in which an elastic member is brought into contact with the surface of the photoreceptor, and the surface of the photoreceptor is charged by the elastic member to which a voltage is applied. That is, the discharge is performed through the thin wedge-shaped space outside the contact portion between the photosensitive member and the elastic member. The reason why the elastic member is brought into contact with the photoconductor is to create and maintain such a small gap.

In the present invention, as shown in FIG. 2, a plurality of elements of an electrophotographic apparatus such as a photoreceptor, a charging member, a developing means and a cleaning means can be integrated into a process cartridge. By doing so, the process cartridge can be detachably attached to the apparatus main body. For example, the elastic member of the present invention used as a charging member and, if necessary, at least one of a developing unit and a cleaning unit are integrally incorporated into a process cartridge together with a photoreceptor, and a guide unit such as a rail of the apparatus body is used. It can be configured to be removable.

The elastic member for electrophotography of the present invention can be used for transfer,
In addition to primary charging and static elimination, it can also be used for conveying paper feed rollers and the like. There is a problem that the roller contact portion of the transfer material is charged due to friction between the transfer roller and the transfer material, resulting in image unevenness as a result of uneven charging of the transfer material itself. There are things to apply.

The photoreceptor which can use the elastic member of the present invention includes an OPC (organic photoconductor) photoreceptor, A-Si, Se,
Various photoconductors such as ZnO can be used.

The electrophotographic apparatus which can use the elastic member of the present invention includes a copying machine, a laser beam printer, and an LED.
A printer or an electrophotographic application device such as an electrophotographic plate making system may be used.

Hereinafter, a description will be given based on an embodiment of the present invention.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION

(Example 1) Carbon black (manufactured by Columbian Carbon, trade name: Conductex 975) 20 phr and graphite 10 to 20 µ diameter as conductive filler 3
20 phr of rosin-modified xylol resin (adhesive) per 100 phr of a styrene-butylene elastomer (trade name: Lavalon, manufactured by Mitsubishi Yuka) as a 0 phr binder
r, using a microcrystalline wax of 10 phr or more as a solvent and dissolving and dispersing in 500 phr of toluene by a ball mill to obtain an adhesive.

Using the above adhesive, a roller-shaped elastic member was produced as follows.

In EPDM, ZnO-Al _{2 is} used as a complex oxide.
O ₃ (manufactured by Hakusui Chemical Industry: conductive zinc oxide 23K-S) was added to obtain a semiconductive elastic layer forming material.

The semiconductive elastic layer forming material thus obtained is a stable semiconductive elastic layer forming material having no resistance unevenness and reproducible processing. This semiconductive elastic layer forming material was foamed with a foaming agent and vulcanized to obtain a tube. Next, a stainless steel core obtained by applying the above-mentioned adhesive with a roll coater and touch-drying was press-fitted into this tube, and was heated and bonded in an oven at 200 ° C. for 10 minutes. The surface of the semiconductive elastic layer was polished to obtain a roller-shaped elastic member. The dimensions are core diameter 6mm, outer diameter 16mm, core length 250m
m, and the length of the semiconductive elastic layer was 230 mm. The electric resistance value of this elastic member was 10 ⁹ Ω. Here, the electric resistance value represents the resistance from the core metal to the surface of the elastic member per 1 cm ^{2 of the} elastic member.

The roller-shaped elastic member manufactured in this manner was brought into contact with a stainless roller having a diameter of 40 mm.
The contact pressure is 300 g at both ends of the core of both rollers. The roller-shaped elastic member is rotated at a peripheral speed of 100 mm / sec in such a state of contact, a DC voltage of 2 kV is applied between the cores of both rollers, and the current value between the cores is measured. The maximum value / minimum value of the resistance in the circumferential direction of the shape elastic member was measured as circumferential unevenness, and as a result, it was 3%.

This elastic member was mounted as an elastic member for transfer of an electrophotographic apparatus (laser beam printer), and the image output was evaluated.

FIG. 2 shows a schematic diagram of this electrophotographic apparatus.

In this electrophotographic apparatus, an OPC drum 5 sensitized to near infrared light is used as a photoreceptor, and a negative contact charge is uniformly performed by a charging roller 6 and then modulated by an image signal to perform raster scan. The potential of the image portion is reduced by the laser light 7 thus formed, an electrostatic latent image is formed, and the image is visualized by the negative toner in the developing device 8. Thereafter, the toner image T on the drum 5 is transferred onto the transfer material P by the roller-shaped transfer elastic member 1 to which a positive voltage is applied. Further, the transfer material P to which the toner image T has been transferred is thereafter conveyed to a fixing device (not shown), where the toner image T is permanently fixed. The transfer residual toner on the OPC drum 5 is cleaned by the cleaner 9, and the same process is repeated again.

In this apparatus, an OPC drum having a diameter of 40 mm is used, the dark portion potential (V _D ) is -600 V, and the light portion potential (V
_L ) was set to -100 V, and reversal development was performed using a one-component insulating magnetic toner. Transfer material has a basis weight of 64 g / m
^Two copy papers were used. The paper feed speed is 40
mm / sec.

The charging roller 6 is provided with a semiconductive rubber layer on a cored bar, and a roller made of a 10 ⁶ Ω semiconductive urethane rubber using the above-described conductive adhesive for bonding the two. It was used. Here, the resistance represents the resistance from the core metal to the roller surface per 1 cm ^{2 of the} roller surface. The charging roller 6 is always kept in pressure contact with the surface of the OPC drum 5 with a predetermined pressure (for example, a linear pressure of 0.01 to 0.2 kg / cm), and the photosensitive member is made uniform by applying a predetermined voltage. Charge. In this embodiment, a charging roller is shown as a charging unit, but a corona charger conventionally used may be applied.

In the above electrophotographic apparatus, when the initial transfer property was evaluated, it was found that both solid black images and halftone images were uniform and excellent in transfer unevenness such as white spots (a phenomenon in which the toner density was partially reduced). Transferability was obtained. Also,
After continuous running of 200,000 sheets, there was no peeling at the interface between the semiconductive layer and the core metal even after the running, showing the same performance as the initial transferability.

(Example 2) Ethylene vinyl acetate copolymer (trade name: Duran, manufactured by Takeda Pharmaceutical Co., Ltd.) 10 as a binder
A conductive adhesive was obtained using 20 phr of hydrogenated rosin, 15 phr of paraffin wax, and the conductive filler and solvent used in Example 1 with respect to 0 phr. Except for using this adhesive, a roller-shaped elastic member was produced in the same manner as in Example 1, and the same evaluation as in Example 1 was performed.
As in the case of Example 1, uniform and good transfer characteristics were obtained in the initial stage and in continuous running of 100,000 sheets.

Comparative Example 1 10 phr of carbon black (trade name: Ketjen Black EC, manufactured by Ketjen Black International) and 20 phr of carbon black (trade name: Conductex) as conductive fillers
When the transfer characteristics of the elastic roller formed in the same manner as in Example 1 except for using No. were evaluated, white spots occurred in both the solid black image and the halftone image, resulting in image failure. The resistance value of the roller is 10Ω, and the peripheral unevenness is 45%.
Met.

As a conductive filler, graphite 50 is used.
The transferability of the elastic roller formed in the same manner as in Example 1 except that only phr was added was evaluated. As a result, the density of the solid black image was reduced and transfer failure occurred. The resistance value of this roller was 10Ω.

(Comparative Example 2) 100 phr of NBR (35% total acrylonitrile, manufactured by Nippon Synthetic Rubber Co., Ltd.)
Graphite 20 hpr, carbon black (Ketjen black) 15 phr, alkylphenol resin (tackifier) 20 phr, DBP (dibutyl phthalate-plasticizer) 50 phr, Zno 5 phr, sulfur 1.5 phr
r, 1 phr of TS (tetramethylthiuram monosulfide-vulcanization accelerator), 2 phr of DM (dibenzothiazoyl disulfide-vulcanization accelerator), and NS-6
(2,2'-methylenebis (4-methyl-6-P-butyl) phenol-antiaging agent) A 2 phr kneading mixture was dissolved in MEK by a ball mill to obtain a conductive adhesive having a solid content of 20%.

An elastic roller was formed using this adhesive. The electric resistance of this roller was 10 ⁹ Ω. The peripheral unevenness was 5%. Using this roller, the transfer characteristics were evaluated in the same manner as in Example 1. As a result, the initial transferability was such that uniform and good transferability without transfer unevenness such as a solid black image and a halftone image was obtained. Was. But 5
After continuous running of 10,000 sheets, peeling occurred at the interface between the semiconductive layer and the metal core after the running, and as a result, the electric resistance value of the roller was 10 ¹⁰ Ω, and the density of the solid black image was reduced. did. In addition, the peripheral unevenness was 40%, and a solid black image and a halftone had a marginal omission.

Example 3 An elastic roller was formed in the same manner as in Example 1 except that 10 phr of carbon black (Ketjen Black EC) and 50 phr of graphite (10 to 20 μ diameter) were used as the conductive filler. The electric resistance of this roller was 10 ⁹ Ω. The peripheral unevenness was 2.5%. When the transfer characteristics were evaluated using this roller in the same manner as in Example 1, the same results as in Example 1 were obtained.

Evaluation was performed in the same manner as in Example 1 except that an elastic roller was formed using this adhesive. As a result, the toner transfer rate was low and the image density was low.

[0056]

As described above, carbon black and graphite are dispersed in the conductor and the semiconductive elastic layer.
The elastic member for electrophotography adhered with the conductive adhesive has excellent adhesion and small resistance unevenness and variation due to the location of the elastic member.
No resistance unevenness and resistance fluctuation due to peeling due to durability.

When a styrene-butylene elastomer is used as a main component, an adhesive layer having excellent rubber elasticity, heat resistance, ozone resistance and weather resistance can be formed.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view (left figure) and a parallel sectional view (right figure) of an elastic member for electrophotography having a roller shape with respect to an axial direction.

FIG. 2 is a schematic cross-sectional view of the electrophotographic apparatus used in the present embodiment.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/02 101 G03G 15/16 103

Claims (13)

(57) [Claims] 1. An electrophotographic elastic member having a semiconductive elastic layer on a conductor via an adhesive layer, wherein the adhesive layer contains carbon black and graphite as a conductive filler and a thermoplastic elastomer as a binder.
An elastic member for electrophotography, wherein said semiconductive elastic layer is bonded by heating. 2. The electrophotographic elastic member according to claim 1, wherein the total amount of carbon black and graphite in the adhesive layer is 20 to 80 phr. 3. The electrophotographic elastic member according to claim 2, wherein the ratio of carbon black to graphite in the adhesive layer is 0.5 to 10 with respect to carbon black. 4. The electrophotographic elastic member according to claim 4, wherein the thermoplastic elastomer is a styrene-butylene elastomer. 5. An electrophotographic charging roller having a semiconductive elastic layer on a conductor via an adhesive layer, wherein the adhesive layer contains carbon black and graphite as a conductive filler, and a thermoplastic elastomer as a binder. A charging roller for electrophotography, wherein the charging roller is formed by heating and bonding a conductive elastic layer. 6. The charging roller for electrophotography according to claim 5, wherein the total amount of carbon black and graphite in the adhesive layer is 20 to 80 phr. 7. The elastic member for electrophotography according to claim 6, wherein the ratio of carbon black to graphite in the adhesive layer is 0.5 to 10 with respect to 1 carbon black. 8. The electrophotographic roller according to claim 5, wherein the adhesive layer has a thermoplastic elastomer as a binder. 9. An electrophotographic apparatus having an elastic member and an electrophotographic photosensitive member, wherein the elastic member has a semiconductive elastic layer on a conductor via an adhesive layer, and the adhesive layer serves as a conductive filler. An electrophotographic apparatus comprising carbon black, graphite, and a thermoplastic elastomer as a binder, wherein the semiconductive elastic layer is bonded by heating. 10. The electrophotographic apparatus according to claim 9, wherein the total amount of carbon black and graphite in the adhesive layer is 20 to 80 phr. 11. The transfer member according to claim 9, wherein the elastic member is a transfer member.
Electrophotographic equipment. 12. The charging member according to claim 9, wherein the elastic member is a charging member.
Electrophotographic equipment. 13. A process cartridge in which an electrophotographic photosensitive member and a charging member are integrally formed as a cartridge, and which is detachable from an image forming apparatus main body, wherein the charging member is semiconductive through an adhesive layer on a conductor. A process cartridge having a conductive elastic layer, wherein the adhesive layer contains carbon black and graphite as a conductive filler and a thermoplastic elastomer as a binder, and is formed by heating and bonding the semiconductive elastic layer.