JP3360432B2 - Developing member and electrophotographic apparatus using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art
In the electrophotographic process of a copier, etc., a latent image is formed by first uniformly charging the surface of a photoreceptor, projecting an image from the optical system onto the photoreceptor, and removing the charge in the light-exposed area. In addition, a method of performing copying or the like by applying toner, transferring a toner image to paper, and cleaning after transfer is also adopted.

[0003] In these processes, first, with regard to 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 the latent image. As a developing method for visualizing, a pressure developing method is known (U.S. Pat. Nos. 3,515,2012 and 3,373,11).
According to this method, no magnetic material is required, so that the apparatus can be easily simplified and downsized, and the toner can be easily colored.

In this pressure development method, a developing roller carrying a toner (a non-magnetic one-component developer) is brought into contact with a latent image holding member such as a photosensitive drum holding an electrostatic latent image, and the toner is transferred to the latent image holding member. The re-development is performed by adhering to the latent image on the holding member. For this reason, the developing roller needs to be formed of an elastic body having conductivity.

In this case, the developing roller 6 in FIG.
It is necessary to rotate while securely maintaining a state in which the photosensitive drum 5 is in close contact with the photosensitive drum 5, and therefore, a silicone rubber, NBR, EPDM
It has a structure in which a conductive material is blended into an elastic rubber or urethane foam or the like to form an elastic layer made of an elastic body provided with conductivity.

[0006]

However, the conventional developing roller has the following disadvantages 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 reduced to obtain good adhesion, the photosensitive drum may be contaminated. 2. If the elastic layer is formed of a sponge body such as urethane foam, the toner will enter the elastic layer, and if used for a long period of time, the roller will be hardened due to toner clogging, and image quality will be affected by toner contamination on the roller surface. May decrease. This tendency applies not only to the sponge body but also to a roller having a surface to which the toner easily adheres. 3. In general, when the developing roller is composed of a single layer, the coefficient of surface friction is very large.In the case of the developing roller, a large load is applied between the developing blade and the photoconductor, so that the toner conveyance becomes non-uniform or Jitter in driving tends to cause image defects.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has low hardness and good adhesiveness, without causing inconvenience such as contamination of a photoreceptor or the like, and having uneven density or fogging. It is an object of the present invention to provide a developing member capable of obtaining a high-quality image without causing deterioration in image quality even when used for a long time, and an electrophotographic apparatus using the developing member.

[0008]

The developing member of the present invention carries a developer on the surface to form a thin film of the developer, and in this state, holds the electrostatic latent image on the surface. A developing member that is brought into contact with the body to adhere the developer to the electrostatic latent image on the surface of the latent image holding member and that visualizes the electrostatic latent image, wherein the developing member is formed of an elastic base material; The surface is formed of a resin layer containing a urethane modified acrylic resin in which a urethane resin component and an acrylic resin component are chemically bonded, and the content ratio of the acrylic resin component in the urethane modified acrylic resin constituting the resin layer is 40-7
0% by weight.

Further, in the developing member of the present invention, the resin layer contains a conductive powder.

That is, in the developing member of the present invention, in a developing member used in an electrophotographic apparatus, the surface of the developing member is formed of a resin layer containing a urethane-modified acrylic resin containing 40 to 70% by weight of an acrylic resin component. By forming
Low resistance change due to environment, no photoreceptor contamination, excellent charging environment stability, and a developing member free of toner adhesion to the surface and clogging in repeated use. When the silicone component is contained in an amount of 1 to 50% by weight, there is no tackiness with the photoreceptor or the like, and when the surface resistance is adjusted by adding conductive particles, it is relatively slow depending on the amount added. Accordingly, the resistance value can be reliably adjusted to a desired resistance value, and the electrophotographic apparatus using the developing member, that is, the developing apparatus can be suitably used.

Hereinafter, the present invention will be described in more detail. An ordinary polyurethane elastomer or polyurethane resin is flexible as a film, the solution viscosity is stable, and the resistance of the film hardly changes with time. However, polyurethane generally has high adhesiveness, and when used as a skin layer of a developing member, easily adheres to a photoreceptor and peeling is not performed smoothly. In addition, toner, dust, and the like easily adhere to the developing roller, which causes poor charging of the toner.

On the other hand, an acrylic resin has low adhesiveness and good stain resistance, but generally has a high hardness and, when used as a skin layer of a developing member, increases the hardness of the entire member and makes charging nonuniform. In addition, it may damage the photoreceptor and cause toner fusion. This toner fusion phenomenon is more likely to occur as the hardness of the surface layer of the developing member is higher or the adhesiveness is higher.

As a method for modifying the acrylic resin according to the present invention with a urethane component, it is more effective to chemically bond the urethane resin and the acrylic resin component from the viewpoints of compatibility, liquid stability, film flexibility and the like. It is. Specifically, for example, 2-hydroxypropyl (meth) acrylate, 2
A reaction between a polymer in which a hydroxyl group has been introduced into an acrylic polymer and a urethane prepolymer having an isocyanate group at a molecular terminal by hydroxyethyl (meth) acrylate or the like, or at a molecular terminal as described below (one terminal or both terminals)
In this case, an acrylic component having a hydroxyl group is reacted with a urethane prepolymer having an isocyanate group at the terminal. (A: methacrylic acid, methacrylate monomer or oligomer) As the urethane prepolymer, a polyether type, a polyester type, a polyolefin type, or the like is 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.

Embedded image

[0015] The urethane-modified acrylic resin of the present invention is not limited to the above-mentioned method. In addition, a method of adding diisocyanate to an acrylic diol mixed system,
It can also be obtained by adding isocyanate polyester or polyether at both ends or one end to an acrylic monomer and polymerizing or copolymerizing the urethane acrylate. As the acrylic resin component used for the synthesis, those having a glass transition temperature Tg as a polymer from room temperature to about 80 ° C. are preferable. In addition to the above-mentioned 2-hydroxyethyl methacrylate and the like, for example, methyl (meth) (Meth) acrylates such as acrylate, ethyl (meth) acrylate, isobutyl (meth) acrylate, n-butyl (meth) acrylate, and glycidyl (meth) acrylate, acrylonitrile, acrylamide, and the like are also used. Further, a polymerizable monomer such as styrene, vinyl acetate, vinyl chloride, maleic acid and a derivative thereof may be copolymerized.
At this time, the composition of the acrylic resin component in the urethane-modified acrylic resin is 40 to 70% by weight.

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

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

The urethane-modified acrylic resin may be contained alone in the surface layer of the developing member, or two or more urethane-modified acrylic resins may be contained, and other resins may be mixed and used. In this case, as a resin other than the urethane-modified acrylic resin,
Examples include polyester, phenolic resin, polyamide, epoxy resin, urea resin, urethane resin and the like. In addition,
In this case, it is preferable that the compounding amount is not more than 50% by weight of the whole resin constituting the resin layer.

Here, the contact portion (skin layer) of the developing member is
Its volume resistivity is 10 ⁶ to 10 ¹³ Ωcm, especially 10 ⁷
It is preferably set to 10 ¹¹ Ωcm, and 10 ⁶ Ωcm
If it is too small, the developing member may be broken by voltage application, while if it is more than 10 ¹³ Ωcm, the conductivity may be reduced. The adjustment of the volume resistivity can be performed by adding a conductive material such as conductive particles to a material containing the urethane-modified acrylic resin constituting the contact portion, and the conductive particles include carbon black. In addition, metal oxide particles such as tin oxide and titanium oxide can be used, and carbon black is particularly preferably used. Furthermore, it is also possible to use a combination of carbon black and a metal oxide. In this case, the material forming the contact portion of the developing member of the present invention changes its resistance relatively slowly according to the amount of addition of these conductive particles, so that the contact portion has a desired value. The resistance value can be easily and reliably adjusted.

Further, silica, calcium carbonate, etc. may be added for the purpose of improving the ability to form a coating film and improving the sharpness and sagging when using a paint. The type is 3 μm
A hydrophobic material having a size of from 200 μm to 200 μm is preferably used. For example, Nipsil (Nippon Silica), AELO
SIL (Nippon Aerosil) and the like. The addition amount is preferably 0.5 phr to 40 phr. Further, the present resin layer may be cross-linked using a curing agent to increase the strength of the coating film. Crosslinking can be carried out by adding a reactive group such as a hydroxyl group and an isocyanate group to the main agent and the curing agent. As the curing agent, for example, a difunctional diisocyanate or a polyisocyanate having a higher functional group is used, and a group that gives flexibility to the curing agent is introduced to easily increase the elongation and elongation. The durability of the film can be improved. The curing agent may contain a silicone component for the purpose of further improving adhesion.

The thickness of the resin layer forming the contact portion (skin layer) of the developing member is 1 to 200 μm, particularly 5 to 50 μm.
It is preferable that As a method of forming these skin layers on a substrate, for example, the substrate is immersed in a coating material in which the urethane-modified acrylic resin and the conductive powder of the present invention are dissolved and dispersed, and the coating is formed by pulling up. Alternatively, the coating material may be melted to form a tube, and a substrate may be inserted into the tube to form a close contact. Further, as the coating method, a spray or the like can be used.

In the developing member of the present invention, as shown in FIGS. 1 and 2, a skin layer containing the urethane-modified acrylic resin is bonded to a substrate (FIGS. 1 and 2) made of a material having appropriate conductivity. However, the substrate may have a multilayer structure of two or more layers, or the developing member may be composed of only the layer containing the urethane-modified acrylic resin. In addition, 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. Optionally, a conductivity-imparting agent such as carbon black is added. Further, the shape of the developing member of the present invention is not limited to a roll shape as shown in FIGS. Further, the electrophotographic apparatus using the developing member of the present invention is not limited to FIG.
It can be changed as appropriate.

Hereinafter, an embodiment of the developing member of the present invention will be described. FIG. 3 is a schematic view of an image forming apparatus using the developing member of the present invention. (1) Configuration of Image Forming Apparatus (FIG. 3) 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 at 100 mm / sec in the direction of arrow a. First, a constant DC voltage or a high voltage obtained by superimposing an AC voltage on a DC voltage is applied to a charging roller or a corona charger (omitted in the figure) to uniformly charge the photoconductor. An electrostatic latent image is formed on the photosensitive drum by performing scanning exposure using a semiconductor laser or exposure using an LED, a halogen lamp, or the like. The latent image is visualized as a toner image by the developing device 7, then transferred to a transfer material 8 such as paper by a transfer roller 9 or a transfer pole, and discharged as a print through a fixing unit 13. The toner remaining on the photoreceptor after the transfer is cleaned by the cleaning roller 11 of the cleaning device 12, or
Alternatively, it is collected by a developing roller or the like after passing through the cleaning roller.

(2) Configuration of Developing Roller As shown in the sectional view of FIG.
It has a multilayer structure in which two layers are sequentially formed around a bottle metal 1 such as S. 1 is made conductive by dispersing conductive carbon in urethane foam (up to 1).
0 ⁷ Ω). Layer 2 in FIG. 2 is made of a conductive elastic material made conductive (10 ³ Ω) by dispersing conductive carbon in butadiene rubber or isoprene rubber. The layer 3 is a resistance layer, and has a resistance value controlled by dispersing conductive carbon in urethane rubber.
The skin layer (layer 4) of the present invention is provided as a coating layer on layer 2 in FIG. 1 and layer 3 in FIG.

(Example 1) A urethane-modified acrylic resin (I) in which a mixed solution of toluene-isopropyl alcohol-butanol was dissolved as a solvent
B-582, manufactured by Sanyo Chemical Co., Ltd., acrylic resin component 40% by weight) in carbon black 2400B (manufactured by Mitsubishi Chemical Corporation)
Was added to 20 phr and 15 phr of tin oxide, and mixed with Red Devil to obtain a dispersion. Resistance 10 ^{7 in} this dispersion
A roller of a polyurethane foam of Ω was immersed and dried to form a skin layer of about 10 μm on the polyurethane to produce a roller-shaped developing member having a surface roughness of 4 μmRz as shown in FIG. (roller)

Comparative Example 1 On the other hand, using a polyurethane resin (P22S, manufactured by Nippon Polyurethane Co., Ltd.), a dispersion was prepared in the same manner, and a skin layer was similarly formed on a polyurethane foam to prepare a conductive member. (roller)

When both rollers were pressed against the photosensitive drum under a load of 1 kg and left at 50 ° C. and 85% RH for 7 days, contamination occurred on the rollers. Also, when the image was mounted on the electrophotographic apparatus shown in FIG. 3 as a developing roller and 2,000 sheets of images were output at the same speed of 50 mm / sec, the toner charge amount and the image did not change in the roller. A reduction in charge amount and a reduction in image density were observed.

[0028]

As described above, according to the developing member of the present invention, defects such as contamination of the rubber roller to the photoreceptor, occurrence of black spots, fog, and toner fusion in reversal development are greatly reduced. Provided is an image forming apparatus having improved conductivity and excellent performance stability. Therefore, the developing member and the image forming apparatus of the present invention can be widely used in electrophotography and electrostatic processes such as copying machines and printers.

[Brief description of the drawings]

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

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

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

[Explanation of symbols]

 Reference Signs List 1 core metal 2 conductive elastic layer 3 resistance layer 4 skin layer 5 photosensitive drum 6 developing roller 7 developing device 8 transfer material 9 transfer roller 11 cleaning roller 12 cleaning device 13 fixing unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 15/08-15/095 G03G 15/16 G03G 15/20 G03G 21/00 F16C 3/00-9 / 06 F16C 13/00-15/00

Claims (3)

(57) [Claims] 1. A developer is carried on the surface to form a thin film of the developer, and in this state, the electrostatic latent image is brought into contact with a latent image carrier holding the surface to apply the developer to the latent image carrier. A developing member that adheres to the surface of the electrostatic latent image to visualize the electrostatic latent image, wherein the developing member is formed of an elastic base material, and the surface of the developing member is formed by a urethane resin component and an acrylic resin component. Is formed of a resin layer containing a urethane-modified acrylic resin which is chemically bonded, and the content ratio of the acrylic resin component in the urethane-modified acrylic resin constituting the resin layer is 40 to
70% by weight of the developing member. 2. The developing member according to claim 1, wherein said resin layer contains a conductive powder. 3. A developer is carried on the surface of the conductive member according to claim 1 to form a thin film of the developer, and in this state, a contact is made with a latent image holding member holding an electrostatic latent image on the surface. An electrophotographic apparatus comprising: a developing device that causes the developer to adhere to the electrostatic latent image on the surface of the latent image holding member, thereby visualizing the electrostatic latent image.