JPH07310732A - Conductive member and electrophotographic device using the member - Google Patents

Abstract

PURPOSE:To prevent the contamination of a photosensitive member or the like by forming the surface of a conductive member out of a resin layer containing urethane modified acrylic resin having the the specified amount of an acrylic resin component. CONSTITUTION:A conductive roller has a multilayer structure with twp layers sequentially formed around a mandrel 1 of stainless steel or the like. A substrate is a conductive elastic layer 2 made electrically conductive through the dispersion of conductive carbon in urethane rubber, urethane foam or ethylene- propylene rubber, and a skin layer 4 is formed as a coating layer on the layer 2. The layer 4 is formed of a resin layer containing urethane modified acrylic resin having an acrylic resin component between 5 and 80wt.%. As a result, a conductive member can be provided, ensuring a less resistance change due to environment, freedom from the contamination of a photosensitive member, high stability against charging environment, and further freedom from toner deposition on surface, clogging or the like, due to a repeated service.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive member used in a developing device, a transfer device, a cleaning device or the like used in an electrophotographic or electrostatic recording process, and an electrophotographic device such as a copying machine or a printer having the conductive member. .

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
In the electrophotographic process of a copying machine or the like, first the surface of the photoconductor is uniformly charged, and then an image is projected from the optical system on the photoconductor to erase the charge on the exposed part to form a latent image. In addition, a method of performing copying or the like by further adhering toner, transferring a toner image to paper, and cleaning after the transfer is used.

In these processes, first, regarding development, a non-magnetic one-component developer is supplied to a photosensitive drum or the like holding a latent image, and the developer is attached to the latent image on the photosensitive drum to form a latent image. A pressure developing method is known as a developing method for visualization (U.S. Pat. Nos. 3,152,2012 and 37311).
No. 46, etc.), this method does not require a magnetic material, so that the apparatus can be simplified and downsized, and the toner can be colored easily.

In this pressure developing method, a developing roller carrying a toner (non-magnetic one-component developer) is brought into contact with a latent image carrier such as a photosensitive drum which holds an electrostatic latent image, and the toner is transferred to the latent image. Development is carried out by adhering the latent image on the holding member. Therefore, it is necessary to form the developing roller with an elastic body having conductivity.

In this case, the developing roller 6 in FIG.
It must rotate while securely holding the state in which it is in close contact with the photosensitive drum 5. Therefore, silicone rubber, NBR, EPDM is attached to the outer periphery of the shaft made of a material having good conductivity such as metal.
This is a structure in which an elastic layer made of an elastic body in which a conductive material is added to elastic rubber such as urethane foam or the like is added with conductivity.

In the conventional transfer device, a corona charger is generally used. However, corona discharge has problems such as generation of ozone and necessity of high voltage power source. As a transfer device that solves these problems, a transfer device using a bias roller made of a conductive rubber is known, but in this method, in order to obtain a high transfer efficiency and a transferred image without unevenness, It is necessary to set a constant nip width between them, to lower the pressure between the roller and the drum, and to use fairly soft conductive rubber.

More recently, in a multicolor electrophotographic copying apparatus as shown in FIG. 4, development is carried out for each developer of yellow, magenta, cyan and black, and each image is brought into contact with the photoconductor either sequentially or collectively. A method has been proposed in which four color full color development is possible by transferring onto an intermediate transfer roller.
As a member used for the surface layer of the intermediate transfer roller 10 used in this formula, it is preferable to use a soft conductive rubber or the like from the viewpoints of preventing image color misregistration, unevenness, and improving durability.

On the other hand, as a cleaning device for cleaning the toner left on the photosensitive member after the transfer, a conventional one is one in which the edge of a blade made of urethane rubber or the like is pressed against the photosensitive member to scrape off the toner. However, when such a blade is used, the frictional force with the photoconductor is large, the driving force is large, the photoconductor is easily damaged by the edge, and when the rubber blade is damaged, cleaning may not be possible. As one of the solutions to such a problem, in FIG. 3, there is a cleanerless method in which a cleaning roller to which a voltage can be applied is attached and cleaning is performed by the cleaning roller, or toner is forcibly charged and the toner is collected by a developing roller or the like. Proposed. This cleaning roller is also required to have the same characteristics as the transfer roller and the like.

[0009]

However, each of the conventional rollers described above has the following drawbacks due to the characteristics of the elastic layer. 1. When the elastic layer is formed of an elastic rubber such as silicone rubber, NBR or EPDM, if the hardness is lowered to obtain good adhesion, the photosensitive drum may be contaminated. 2. When the elastic layer is formed from a sponge such as urethane foam, if the toner enters the elastic layer and is used for a long period of time, the roller will become hard due to clogging of the toner, or the image of the roller surface will be contaminated by the toner. May decrease. This tendency is the same not only in the case of the sponge body but also in the case of a roller having a surface to which toner is easily attached. 3. In general, when the developing roller is composed of a single layer, the surface friction coefficient is very large. Therefore, in the case of the developing roller, a large load is applied between the developing blade and the photoconductor to make the toner conveyance uneven or Image defects are likely to occur due to driving jitter. Further, also in the transfer drum, the increase in frictional force causes the transfer material to be displaced or distorted, resulting in deterioration of image quality.

The present invention has been made in view of the above circumstances, has a low density and good adhesion, and does not cause inconvenience such as contaminating a photoconductor or the like, and has no uneven density or background fog. It is an object of the present invention to provide a conductive member that can obtain a high-quality image without causing deterioration of image quality even when used for a long period of time, and an electrophotographic apparatus using the conductive member.

[0011]

The conductive member of the present invention is a conductive member used in an electrophotographic apparatus, wherein the surface of the conductive member is a urethane-modified acrylic resin containing 5 to 80% by weight of an acrylic resin component. It is characterized in that it is formed of a resin layer containing.

Further, the conductive member of the present invention is characterized in that the surface of the conductive member is formed of a resin layer containing 1 to 50% by weight of a silicone component in a urethane-modified acrylic resin. Furthermore, the conductive member of the present invention is characterized in that the resin layer contains conductive powder.

That is, the conductive member of the present invention is a conductive member used in an electrophotographic apparatus, wherein the surface of the conductive member is formed of a resin layer containing a urethane-modified acrylic resin containing 5 to 80% by weight of an acrylic resin component. By doing so, there is little resistance change due to the environment, there is no contamination of the photoconductor, the stability of the charging environment is excellent, and it is possible to obtain a conductive member that does not have toner adhered to the surface or clogging during repeated use. 1 silicone component in acrylic resin
When contained in an amount of ˜50% by weight, there is no adhesiveness to the photoreceptor, and when the surface resistance is adjusted by adding conductive particles, the resistance value changes relatively slowly according to the addition amount. Therefore, the resistance value can be surely adjusted to a desired resistance value, and moreover, it can be widely used in electrophotographic devices using a conductive member, that is, developing devices, transfer devices, cleaning devices and the like.

The present invention will be described in more detail below. An ordinary polyurethane elastomer or polyurethane resin is flexible as a film, the solution viscosity is stable, and the resistance of the film does not change with time. However, polyurethane is generally highly adhesive, and when it is used as a skin layer of a conductive member, it easily adheres to the photoreceptor and cannot be peeled off smoothly. In addition, toner, dust, and the like are likely to adhere to the developing roller and the cleaning roller, which causes toner, and the transfer roller causes charging failure of paper and the like.

On the other hand, an acrylic resin has low tackiness and good stain resistance, but generally has high hardness, and when used as a skin layer of a conductive member, it increases hardness of the entire member and makes charging nonuniform. Not only that, it may damage the photoreceptor and cause toner fusion. Toner fusion here means, for example, when a cleaning roller is used as the conductive member in the electrophotographic apparatus shown in FIG. 3, the residual toner on the photoconductor after transfer is brought into contact with the photoconductor by the cleaning roller 11 to carry an image. The phenomenon of being pressed against the body and being fused to the surface of the image carrier. This toner fusion phenomenon is more likely to occur as the hardness of the surface layer of the conductive member is higher or the tackiness is higher than the above-mentioned generation mechanism.

As a method for modifying the acrylic resin with a urethane component according to the present invention, it is more effective to chemically bond the urethane resin and the acrylic resin component from the viewpoint of compatibility, liquid stability, film flexibility and the like. Is. Specifically, for example, 2-hydroxypropyl (meth) acrylate, 2
-Reaction between a polymer having a hydroxyl group introduced into an acrylic polymer and a urethane prepolymer having an isocyanate group at the molecular end with hydroxyethyl (meth) acrylate, or at the molecular end as described below (one end or both ends)
It is synthesized by reacting an acrylic component having a hydroxyl group with a urethane prepolymer having an isocyanate group at the end. (A: Methacrylic acid, methacrylic acid ester monomer or oligomer) As the urethane prepolymer, polyether type, polyester type, polyolefin type and the like are used.

In the polymer thus obtained, the urethane chain and the acrylic chain may be bonded to each other in a block type or a graft type.

[Chemical 1]

The urethane-modified acrylic resin of the present invention is not limited to the above-mentioned method, but other than this, a method of adding diisocyanate to an acrylic diol mixed system,
It can also be obtained by a method in which an acrylic monomer is added to both-end or one-end isocyanate polyester, polyether, etc., and the urethane acrylate is polymerized or copolymerized. Further, as the acrylic resin component used in these syntheses, those having a glass transition temperature T _g as a polymer from room temperature to about 80 ° C. are preferable, and in addition to 2-hydroxyethyl methacrylate and the like, for example, methyl (meth ) (Meth) acrylic acid esters such as acrylate, ethyl (meth) acrylate, isobutyl (meth) acrylate, n-butyl (meth) acrylate, glycidyl (meth) acrylate, acrylonitrile and acrylamide are also used. Further, a polymerizable monomer such as styrene, vinyl acetate, vinyl chloride, maleic acid and a derivative may be copolymerized with these. At this time, the composition of the acrylic resin component in the urethane-modified acrylic resin is preferably 5 to 80% by weight, particularly preferably 50 to 70% by weight.

Since the urethane component and the acrylic component are chemically bonded to each other in the urethane-modified acrylic resin, various physical properties such as hardness, adhesiveness and frictional property can be arbitrarily adjusted by changing their composition ratio. This is the reason why the urethane-modified acrylic resin is preferable as compared with other resins or elastomer materials.

Further, a silicone component may be contained in the urethane-modified acrylic resin from the viewpoint of improving the adhesion to the photoreceptor. Specifically, for example, a method of synthesizing by reacting a urethane prepolymer using a polyol containing a silicone chain as a raw material with an acrylic component can be considered. In this case, the composition of the silicone component in the urethane prepolymer is 2 to 80% by weight, especially 5 to 50%.
It is preferably in the weight%. The composition of the silicone component in the urethane-modified acrylic resin after the reaction is preferably 1 to 50% by weight, particularly 3 to 30% by weight.

The urethane modified acrylic resin may be contained alone or in combination of two or more kinds in the surface layer of the conductive member, and other resins may be mixed and used. In this case, as the resin other than the urethane-modified acrylic resin,
Examples thereof include polyester, phenol resin, polyamide, epoxy resin, urea resin and urethane resin. In addition,
The compounding amount at this time is preferably 50% by weight or less based on the entire resin constituting the resin layer.

Here, the contact portion (skin layer) of the conductive member is
The volume resistivity is 10 ⁶ to 10 ¹³ Ωcm, especially 10 ⁷ to
It is preferably 10 ¹¹ Ωcm, and if it is less than 10 ⁶ Ωcm, the conductive member may be destroyed by the voltage application, while if it is more than 10 ¹³ Ωcm, the conductivity may decrease. The volume resistivity can be adjusted by adding a conductive material such as conductive particles to the material containing the urethane-modified acrylic resin forming the contact portion, and the conductive particles include carbon black. Although metal oxide particles such as tin oxide and titanium oxide can be used, carbon black is particularly preferably used.
Furthermore, it is possible to use carbon black and a metal oxide together. In this case, the material forming the abutting portion of the conductive member of the present invention has a resistance value that relatively slowly changes depending on the addition amount of the conductive particles due to the addition of these conductive particles. The resistance value can be adjusted easily and reliably.

Further, silica, calcium carbonate and the like may be added for the purpose of improving the coating film forming ability and improving the sharpness and sagging when the paint is used. The particle size is 3 μm
A hydrophobic one having a size of from 200 μm to 200 μm is preferably used. For example, Nipsil (Nippon Silica) AELOS
IL (Japan Aerosil) etc. are mentioned. The addition amount is preferably 0.5 phr to 40 phr. Further, the resin layer may be crosslinked with a curing agent to increase the strength of the coating film. The cross-linking can be performed by allowing the main agent and the curing agent to contain a hydroxyl group and a reactive group such as an isocyanate group. As the curing agent, for example, bifunctional diisocyanates or polyisocyanates having more than two functional groups are used, and by introducing a group that imparts flexibility to the curing agent, the strength and elongation can be easily increased to obtain a coating agent. The durability of the film can be improved. Further, the curing agent may contain a silicone component for the purpose of further improving the adhesiveness.

The thickness of the resin layer forming the contact portion (skin layer) of the conductive member is 1 to 200 μm, and particularly 5 to 50 μm.
It is preferable that As a method for forming these skin layers on a substrate, for example, the substrate may be dipped in a coating material in which the urethane-modified acrylic resin of the present invention and a conductive powder are dissolved / dispersed, and the substrate may be pulled up to form a coating. Alternatively, the coating material may be melted, and the substrate may be inserted into a tubular shape to form a close contact. Further, this coating method can be used for sprays and the like other than the roller as in the present invention.

The conductive member of the present invention is usually obtained by bonding a skin layer containing the above urethane-modified acrylic resin onto a substrate (FIGS. 1 and 2) made of a material having appropriate conductivity as shown in FIGS. However, the substrate may have a multi-layered structure of two or more layers, and the conductive member may be composed of only the layer containing the urethane-modified acrylic resin. Examples of the material of the base include metal, urethane, natural rubber, butyl rubber, nitrile rubber, polyisoprene rubber, polybutadiene rubber, silicone, styrene-butadiene rubber, ethylene-propylene rubber, chloroprene rubber, and foams thereof. A conductivity imparting agent such as carbon black is appropriately added. Further, the shape of the conductive member of the present invention is not limited to the roll shape as shown in FIGS. 1 and 2, and may be various shapes such as a plate shape, a square block shape, a spherical shape, and a brush shape. However, it is usually preferable to use a roll shape or a brush shape. Further, an electrophotographic apparatus using the conductive member of the present invention is also shown in FIG.
The present invention is not limited to this, and can be changed as appropriate.

[0026]

EXAMPLE An example of the conductive member of the present invention will be described in detail below. FIG. 3 is a schematic view of an image forming apparatus using the charging device of the present invention. (1) Configuration of Image Forming Apparatus (FIGS. 3 and 4) FIG. 3 shows an example of the configuration of a monocolor electrophotographic apparatus. Reference numeral 5 denotes a photosensitive drum 5 as a drum type electrophotographic photosensitive member, which rotates in the direction of arrow a at 100 mm / sec. First, a constant DC voltage or a high voltage obtained by superimposing an AC voltage on a DC voltage as needed is applied to a charging roller or a corona charger (not shown) to uniformly charge the photoconductor. An electrostatic latent image is formed on the photosensitive drum by scanning exposure with a semiconductor laser or exposure with an LED, a halogen lamp, or the like. The latent image is visualized as a toner image by the developing device 7, then transferred onto a transfer material 8 such as paper by a transfer roller 9 or a transfer pole, and discharged through a fixing unit 13 as a print. The toner remaining on the photoreceptor after the transfer is cleaned by the cleaning roller 11 of the cleaning device 12, or
Alternatively, after passing through the cleaning roller, it is collected by a developing roller or the like.

FIG. 4 shows an example of the structure of a full-color electrophotographic apparatus. In this apparatus, the toner image formed on the photosensitive drum 1 by each of the cyan, magenta, yellow, and black developing devices 7 is transferred onto the intermediate transfer roller by the voltage of the opposite polarity to the toner applied to the intermediate transfer roller 10. Transferred, and a four-color superimposed toner image is formed. After that, when the transfer material 8 is inserted into the nip region between the photosensitive drum 5 and the intermediate transfer roller, a voltage having the same polarity as the toner is applied to the intermediate transfer roller, and the four-color toner image is transferred to the transfer material. After that, it is similarly fixed and discharged as a print. Further, a small copying machine may be attached around each of the intermediate transfer rollers 10, and four colors may be superposed on the rollers to form a toner image. The intermediate transfer roller 10
Defines the surface roughness according to JIS in order to form a toner image.
The 10-point average roughness is preferably 15 μm or less.

(2) Construction of Conductive Roller The conductive roller of the present embodiment, as shown in the sectional views of FIGS. 1 and 2, has two or three layers in sequence around a core metal 1 of iron, SUS or the like. It has a multilayer structure formed. The substrate 2 in FIG. 1 is a conductive elastic layer which is made conductive (-10 ⁷ Ω) by dispersing conductive carbon in urethane rubber, urethane foam or ethylene-propylene rubber. Layer 2 in FIG. 2 is a conductive elastic layer which is made conductive (10 ³ Ω) by dispersing conductive carbon in butadiene rubber or isoprene rubber. Layer 3 is a resistance layer, and is a resistance value controlled by dispersing conductive carbon in urethane rubber. On the layer 2 in FIG. 1 and the layer 3 in FIG. 2, the skin layer (layer 4) of the present invention is provided as a coating layer.

Example 1 [Developing Roller] A urethane-modified acrylic resin (I) prepared by dissolving a toluene-isopropyl alcohol-butanol mixed solution as a solvent.
B-582, Sanyo Chemical Co., Ltd., acrylic resin component 40% by weight) in carbon black 2400B (Mitsubishi Chemical Co., Ltd.)
20 phr and tin phr 15 phr were added and mixed with red devil to obtain a dispersion. The resistance in this dispersion is 10 ⁷
A roller of polyurethane foam of Ω was dipped and dried to form a skin layer of about 10 μm on the polyurethane to prepare a roller-shaped conductive member having a surface roughness of 4 μmRz as shown in FIG. (roller)

Comparative Example 1 On the other hand, a polyurethane resin (P
22S, manufactured by Nippon Polyurethane Industry Co., Ltd.), a dispersion was prepared in the same manner, and a skin layer was similarly formed on the polyurethane foam to prepare a conductive member. (roller)

When both rollers were pressed against the photosensitive drum with a load of 1 kg and left at 50 ° C. and 85% RH for 7 days, contamination occurred on the rollers. Further, when the electrophotographic apparatus shown in FIG. 3 was installed as a developing roller and 2000 sheets of images were output at the same speed of 50 mm / sec, there was no change in the toner charge amount or the image on the roller, but the toner on the roller was changed. A decrease in charge amount and a decrease in image density were observed.

(Embodiment 2) [Case of Transfer Roller] In Embodiment 1, urethane modified acrylic resin is used as EAU.
-2B (manufactured by Asia Kogyo Co., Ltd., 60% by weight of acrylic resin component), and a conductive roller was prepared in the same manner as in Example 1 except that the conductive powder was only carbon black 2400B.
(roller)

Comparative Example 2 A polyurethane foam roller before forming a skin layer on the roller was prepared.
(roller)

When both rollers were subjected to the photoreceptor contamination test in the same manner as in Example 1, the rollers slightly contaminated. Further, when the transfer roller was mounted on the electrophotographic apparatus shown in FIG. 3 and 5,000 sheets of images were similarly output, no problem occurred in the roller, but in the roller, the toner on the roller surface was not generated. Due to dirt and the like, missing characters in the image and dirt on the back surface occurred.

(Example 3) [In case of cleaning roller] A roller (roller) having a skin layer was prepared in the same manner as in Example 2 except that the roller diameter was different.

Comparative Example 3 In the same manner as in Example 3, a roller having no skin layer was prepared.

Slight photoreceptor contamination likewise occurred on the rolls. Further, both rollers were mounted as the cleaning rollers of the electrophotographic apparatus shown in FIG. 3, a voltage of the same polarity as that of the toner was applied, and 5000 images were output by the method of cleaning with the developing roller. No problem occurred on the image, but white background fog occurred on the roller due to poor cleaning.

(Example 4) [In the case of intermediate transfer roller] A pipe-shaped core metal having an outer diameter of 100 mm was coated with 10 ⁷ Ω urethane foam similar to that used in Example 1 to a thickness of about 8 mm, and further, The urethane-modified acrylic resin dispersion liquid used in Example 2 was applied thereon to obtain a roller.

(Comparative Example 4) In the same manner as in Example 4, a roller was obtained by similarly applying the urethane resin dispersion liquid instead of the urethane modified acrylic resin dispersion liquid.

When the contamination of the photoconductor was confirmed for both rollers in the same manner as in Example 1, the contamination occurred on the rollers. Both rollers were attached to the electrophotographic apparatus shown in FIG. 4 as an intermediate transfer roller, and four color images were output, and no problems occurred with the rollers.
On the roller, image disturbance due to poor transfer and color mixing and image stain due to poor cleaning of toner on the intermediate transfer roller occurred.

[0041]

As described above, according to the conductive member of the present invention, the drawbacks such as the contamination of the rubber roller on the photosensitive member, the generation of black spots, fog and toner fusion during reversal development are greatly improved. Provide a conductive device having excellent conductive characteristics and performance stability. Therefore, the conductive member and the conductive device of the present invention can be widely used for electrophotography and electrostatic processes such as copying machines and printers.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a conductive roller of the present invention.

FIG. 2 is a schematic sectional view showing an example of a conductive roller of the present invention.

FIG. 3 is a schematic view showing an example of an image forming apparatus using the conductive device of the present invention.

FIG. 4 is a schematic view showing an example of a full-color electrophotographic apparatus using the conductive device of the present invention.

[Explanation of symbols]

 1 Core Metal 2 Conductive Elastic Layer 3 Resistive Layer 4 Skin Layer 5 Photosensitive Drum 6 Developing Roller 7 Developing Device 8 Transfer Material 9 Transfer Roller 10 Intermediate Transfer Roller 11 Cleaning Roller 12 Cleaning Device 13 Fixing Section

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G03G 21/10 // C09D 175/00 PHR 175/16 PDZ

Claims (6)

[Claims] 1. A conductive member used in an electrophotographic apparatus, wherein the surface of the conductive member is formed of a resin layer containing a urethane-modified acrylic resin containing an acrylic resin component in an amount of 5 to 80% by weight. Element. 2. The conductive member according to claim 1, wherein the urethane-modified acrylic resin contains a silicone component in an amount of 1 to 50% by weight. 3. The conductive member according to claim 1, wherein the resin layer contains conductive powder. 4. A latent image in which a developer is carried on the surface of the conductive member according to claim 1 to form a thin film of the developer, and an electrostatic latent image is held on the surface in this state. An electrophotographic apparatus, comprising: a developing device which is brought into contact with a holding body to adhere the developer to the electrostatic latent image on the surface of the latent image holding body to visualize the electrostatic latent image. 5. A transfer device is provided which charges the transfer paper with the conductive member according to claim 1 and transfers the developer from the electrostatic latent image visualized by the developer to the transfer paper. Characteristic electrophotographic device. 6. An electrophotographic apparatus comprising a cleaning device for removing the developer remaining on a member to be charged by the conductive member according to any one of claims 1 to 3.