JPH08286470A - Conductive member and electrophotographic device using same - Google Patents

Abstract

PURPOSE: To obtain a stable image of high quality by using a polymer material containing a conductive powder as a conductive member and moveover, dispersing silica fine particles in the polymer material. CONSTITUTION: The developer roller 1 consists of a shaft 2 of a good conductive material such as a metal and an elastic layer 3 (conductive member) of an elastic material to which conductivity is imparted. The conductive member 3 consists of a polymer material containing a conductive powder, and further, silica fine particles are dispersed in the polymer material. For example, an elastomer or formed material such as polyurethane and EPDM is used as the base material, and a conductive powder such as carbon black, metal or metal oxide is added to the base material to control the conductivity to a medium resistance region which is the optimum for the use. Further, by using positive charge silica having amino groups on the surface as the silica particles, the resistance can be more stably controlled.

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 for charging, developing, transferring, cleaning and the like in an electrophotographic device, an electrostatic recording device and the like, and an electrophotographic device using the conductive member. The present invention uses a conductive member and a developing member as a developing member for visualizing an electrostatic latent image with a non-magnetic one-component developer, particularly in electrophotographic devices such as copying machines and printers. A developing roller (conductive member) capable of easily adjusting a resistance region thereof, having excellent resistance stability, and reliably obtaining a good image, and
The developing device using this is mainly described in detail, but it is originally used as a conductive member of the present invention or various devices using the same, that is, for a charging member, a transfer member, a cleaning member, or the like. The electroconductive member or the electrophotographic apparatus using the electroconductive member is not limited to the developing device or the developing device.

[0002]

2. Description of the Related Art Conventionally, in a conductive member, for example, in an electrophotographic device such as a copying machine or a printer, an electrostatic recording device, etc., a non-magnetic one-component developer is supplied to a photosensitive drum or the like holding a latent image to form a photosensitive drum. A pressure developing method is known as a developing method for visualizing the latent image by adhering the developer to the latent image (see US Pat. Nos. 3,152,2012 and 3,731).
No. 146, 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 holding member 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.

That is, in this pressure developing method, as shown in FIG. 2, for example, between the toner coating roller 4 for supplying toner and the photosensitive drum 5 holding the electrostatic latent image, The developing roller 1 is arranged in a state of being in contact with the photosensitive drum 5 and slightly separated from the toner applying roller 4, and the developing roller 1, the photosensitive drum 5 and the toner applying roller 4 are respectively arranged in the arrow directions in the drawing. As the toner 6 rotates, the toner 6 is supplied to the surface of the developing roller 1 by the toner applying roller 4, and this toner is adjusted to a uniform thin layer by the stratifying blade 7. In this state, the developing roller 1 contacts the photosensitive drum 5. By rotating while rotating, the toner formed in a thin layer adheres from the developing roller 1 to the latent image on the photosensitive drum 5 so that the latent image becomes visible. In addition,
In the figure, reference numeral 8 is a transfer portion, which is adapted to transfer a toner image onto a recording medium such as paper, and 9 is a cleaning portion, which remains on the surface of the photosensitive drum 5 after being transferred by the cleaning blade 10. It is designed to remove toner.

In this case, the developing roller 1 is the photosensitive drum 5
It is necessary to rotate while firmly maintaining the state of being in close contact with, and as shown in FIG. 1, silicone rubber is attached to the outer periphery of the shaft 2 made of a metal or other good conductive material.
It has a structure in which an elastic layer 3 is formed of an elastic body in which a conductive agent is mixed with elastic rubber such as NBR or EPDM or urethane foam. Further, it has been proposed to provide a surface layer having conductivity by blending conductive powder on the elastic layer 3 for the purpose of improving the surface friction property and the image quality.

[0006]

However, the above-mentioned conventional conductive developing roller has the following drawbacks. (1) The resistance of the conductive elastic layer is 10 ⁵ to 1 depending on the application.
It is necessary to set the resistance to about ^{9 9} Ωcm, and it is difficult to control the resistance. (2) When the electroconductivity is controlled by the electroconductive powder, the resistance tends to be partially non-uniform, so that density unevenness occurs in a halftone or the like. (3) To make the resistance uniform, it is possible to control it by adding an ionic conductive agent, but in this case, the resistance level fluctuates greatly due to the effect of humidity in particular, and stable quality is achieved in all environments. Can't get The present invention has been made in view of the above circumstances, it is easy to control the resistance range, further there is little variation in resistance, the resistance is stable even in environmental changes, so a stable high-quality image can be obtained. It is an object of the present invention to provide a conductive member to be used, and an electrophotographic apparatus using the conductive member.

[0007]

The present invention relates to a conductive member used for electrophotography and the like, wherein the conductive member is made of a polymer material containing conductive powder, and silica fine particles are contained in the polymer material. It was found that the dispersion raises the resistance level. It has been found that the resistance region can be easily controlled by the number of parts of the silica fine particles to be mixed, and that a conductive member having a small resistance variation can be obtained even in a medium to high resistance region where the resistance becomes unstable only with a normal conductive powder. . Further, they have found that the use of positively chargeable silica having an amino group on the surface as the silica fine particles to be used enables more stable resistance control, and has arrived at the present invention.

The present invention will be described in detail below. The base material in the present invention uses an elastomer such as polyurethane or EPDM or a foam material as a base material, and conductive powder such as carbon black, metal or metal oxide powder is mixed into the base material to make it conductive. It is preferable that the property is adjusted to the optimum medium resistance region 10 ³ to 10 ⁷ Ωcm according to the application.

In this case, the base material is polyurethane, natural rubber, butyl rubber, nitrile rubber, polyisoprene rubber,
Examples thereof include polybutadiene rubber, silicone rubber, styrene-butadiene rubber, ethylene-propylene rubber, chloroprene rubber, acrylic rubber, and mixtures thereof, but polyurethane and EPDM are particularly preferable.

First, polyurethane will be described. The polyurethane elastomer and the foam material may be produced by various methods. For example, a method in which carbon black or the like is blended in a polyurethane prepolymer and the prepolymer is subjected to a crosslinking reaction, a polyol. It can be obtained by a method of blending a conductive powder with the above and reacting this polyol with polyisocyanate by the one-shot method.

The urethane used as the base material of the conductive material layer is, as a polyhydroxyl compound, a polyol used in the production of general flexible polyurethane foam or urethane elastomer, for example, a polyether polyol having a polyhydroxyl group at the terminal, In addition to polyester polyols and mixtures of both,
A general polyol such as a polyolefin polyol such as polybutadiene polyol or polyisoprene polyol, a so-called polymer polyol obtained by polymerizing an ethylenically unsaturated monomer in the polyol can be used. Further, as the polyisocyanate compound, similarly, polyisocyanates used for producing general flexible polyurethane foams and urethane elastomers, that is, tolylene diisocyanate (TDI), crude TDI, 4,4-diphenylmethane diisocyanate (MDI), crude polyisocyanate MDI, C2-C18 aliphatic polyisocyanate, C4-C1
The alicyclic polyisocyanate of 5 and a mixture or modified product of these polyisocyanates, such as a prepolymer obtained by partially reacting with a polyol, are used.

On the other hand, EPDM is a terpolymer composed of ethylene, propylene and a third component in this case, and the third component is not particularly limited, but includes dicyclopentadiene, ethylidene norbornene, 1,4-hexadiene and the like are preferably used. The ratio of ethylene, propylene and the third component is not particularly limited, but the ethylene content is 5 to 95.
It is preferable that the content of propylene is 5 to 95% by weight, and the content of the third component is 0 to 50 in terms of iodine value. It should be noted that two or more kinds of EPDM having different iodine values can be mixed and used. Silicone rubber, silicone-modified EPDM, or both of them may be blended with the EPDM. In this case, the mixing amount of silicone rubber and silicone-modified EPDM is EP
It can be 5 to 80 parts by weight with respect to 100 parts by weight of DM. The silicone-modified EPDM refers to a hybrid rubber in which the bonding force between both EPDM and silicone polymers is increased through a silanol compound or siloxane.

Further, a crosslinking agent and a vulcanizing agent may be added to crosslink the elastic layer into a rubber-like substance. In this case, a vulcanization aid, a vulcanization accelerator, a vulcanization acceleration aid, a vulcanization retarder, etc. can be used in both cases of organic peroxide crosslinking and sulfur crosslinking. Furthermore, in addition to the above, a peptizer, a foaming agent, which is commonly used as a rubber compounding material,
A plasticizer, a softening agent, a tackifier, an anti-tacking agent, a separating agent, a release agent, a filler, a coloring agent and the like can be added.

The elastic layer mainly composed of polyurethane or EPDM has various charges such as nigrosine, triaminophenylmethane, and cationic dye for the purpose of controlling the toner charge amount on the surface when used as a developing member. A fine powder such as a control agent, silicone resin, silicone rubber or nylon can be added. In this case, the amount of these additives added is the above-mentioned polyurethane or EPDM1.
1 to 5 parts by weight of the charge control agent with respect to 00 parts by weight,
The fine powder is preferably 1 to 10 parts by weight.

Examples of the conductive powder include conductive carbon such as Ketjen Black EC and acetylene black, and SA.
F, ISAF, HAF, FEF, GPF, SRF, F
Carbon for rubber such as T and MT, carbon for color (ink) that has been subjected to oxidation treatment, pyrolytic carbon, natural graphite, artificial graphite, antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper, silver, Examples thereof include metals such as germanium and metal oxides, and conductive polymers such as polyaniline, polypyrrole, and polyacetylene. Among them, carbon black is inexpensive and whose conductivity can be easily controlled with a small amount. Normally, taking urethane as an example, it is 0.5 per 100 parts by weight of urethane.
It is preferably used in the range of ˜50 parts by weight, particularly 1 to 30 parts by weight, but in order to further stabilize the variation of resistance when the resistance level is increased by mixing silica fine particles, the added conductive powder is It is desirable to increase the number of parts to be added until it is sufficiently percolated.

As the silica fine particles, silica fine particles having a normal surface with a hydrophilic functional group and those having a hydrophobic surface are preferably used. Particularly, the silica surface is treated with a coupling agent containing an amino group as a functional group. Positively charged silica as described above is preferably used. When urethane is used as an example of the base material, the amount of addition is preferably 0.01 to 10 parts by weight, particularly 0.1 to 5 parts by weight, per 100 parts by weight of urethane. The mechanism by which the silica fine particles are added to increase the resistance level is not always clear, but it is considered that the silica fine particles have an effect of enhancing the dispersibility of the conductive powder in the base material. Particularly, in the case of positively charged silica, since it has a positively charged functional group on the surface, electrical interaction with the conductive powder may occur, and the dispersibility of the conductive powder may be altered. The method of adding the silica fine particles is not particularly limited, but it is usually mixed and kneaded in the base material at the same time as the conductive powder.

[0017]

EXAMPLES Hereinafter, the conductive member of the present invention and the device using the member will be described in more detail with reference to examples, but the invention is not limited thereto. [Example 1] Silica fine particles having an average particle size of 6 µm were surface-treated with an aminosilane coupling agent to prepare positively chargeable silica fine particles. Here, the formulation used in this example is as follows. Propylene oxide and ethylene oxide are added to glycerin to give a molecular weight of 5000, and a polyether polyol (OH value 33) (Asahi Glass Co., Ltd., Exenol 828) 100 parts, urethane-modified MDI (NCO% = 2)
3% ・ Sumitomo Bayer Urethane Co., Ltd. ・ Sumijour P
F) 25.0 parts, 1,4-butanediol 2.5 parts, dibutyltin dilaurate 0.01 part, HAF carbon (manufactured by DEGUSSA) 9.0 parts, positively charged silica 1.0 part. This was agitated according to the above formulation, then poured into a mold heated to 110 ° C. and cured for 2 hours to form a conductive layer on the outer circumference of a metal shaft to obtain a conductive member. The surface of the obtained conductive member was dry-polished to form a roller.

The roller volume resistance was measured as follows. The conductive roller is pressed against a roller-shaped aluminum counter electrode having a diameter of 5 cm with a load of 500 g on one side, and the aluminum counter electrode is rotated at 6 rpm.
Simultaneously with the rotation, the DC voltage of 100 V was applied to the conductive roller, and the volume resistance of the entire roller was converted from the current value flowing at that time. Further, the same measurement was performed using a divided counter electrode having a width of 1 cm, and the partial resistance in the conductive roller was measured to calculate the maximum value and the minimum value of the partial resistance, which was used as an index of the variation in the resistance of the conductive roller. The measurement results are shown in Table 1.

[0019]

[Table 1]

[Example 2] A conductive roller was prepared in the same manner as in Example 1 except that hydrophobic silica (SS20, manufactured by Nippon Silica Industry Co., Ltd.) was used in place of the positively chargeable silica in Example 1, and a resistance value was obtained. Was measured. The measurement results are shown in Table 1.

[Example 3] Denka black (manufactured by Denka Industry Co., Ltd.) in place of HAF carbon in Example 1.
A conductive roller was prepared and the resistance value was measured in the same manner as in Example 1 except that 5 parts and 2 parts of positively charged silica were used. The measurement results are shown in Table 1.

Comparative Example 1 A conductive roller was prepared in the same manner as in Example 1 except that the positively chargeable silica was removed, and the resistance value was measured. The measurement results are shown in Table 1.

[Comparative Example 2] A conductive roller was prepared and a resistance value was measured in the same manner as in Example 1 except that the number of HAF carbon parts was changed to 3 and the resistance region was the same as in Example 1. . The results of these measurements are shown in Table 1.

[Comparative Example 3] In Comparative Example 1, except that 0.25 parts of a quaternary ammonium salt (KS-555 manufactured by Kao Corporation), which is an ion conductive material, was added in place of HAF carbon. A conductive roller was prepared in the same manner as 1 and the resistance value was measured. Moreover, the environmental stability of the resistance was measured by changing the temperature and humidity, and the results are shown in Table 2.

[0025]

[Table 2]

[Comparative Example 4] A roller-shaped member was produced in the same manner as in Example 1 except that HAF carbon was removed. When the volume resistance of this roller was measured, no current flowed and it was shown to be an insulating body.

The case in which each roller is used will be described in detail below. [Evaluation of developing roller image] The roller obtained in Example 1;
Image evaluation was performed by using the roller obtained in Comparative Example 1 and incorporating it in a developing cartridge of a commercially available laser beam printer (manufactured by IBM 4029), and printing a black solid image and a 12% printed portion image. As shown in Table 3, with the roller of Example 1, a high-quality image was obtained.

[0028]

[Table 3]

[Evaluation of Charging Roller Image] Acrylic modified urethane resin (manufactured by Sanyo Kasei Co., Ltd., IB) prepared by dissolving a toluene-isopropyl alcohol-butanol mixed solution as a solvent.
20 phr of carbon black 2400B (manufactured by Sanyo Kasei Co., Ltd.) was added to -582, acrylic resin component 40% by weight) and mixed with red devil to obtain a dispersion liquid. The roller obtained in Example 3 was immersed in this dispersion liquid to form a skin layer of about 50 μm on the roller to prepare a charging roller. This roller and the photoconductor drum are placed facing each other, and between them-
A voltage in which an alternating current of 1.5 KV was superposed on a direct current of 0.75 KV was applied to measure the charging potential of the photoconductor. as a result,
The charging voltage was −630 V, which shows that good charging was performed without unevenness. This roller is a commercially available laser beam printer (HP Laeser Jet).
4L), the image was printed and good image quality was obtained.

[Comparative Example 5] A conductive roller was prepared in the same manner as in Example 3 except that the positively chargeable silica was removed, and the resistance value was measured. The results are shown in Table 4. Using the roller prepared in Comparative Example 5,
Similarly, when a charging roller was formed and an image was printed, it was shown that a defective image with a sand pattern was partially generated on a white background, and a defective charging was partially caused.

[0031]

[Table 4]

Example 4 Using the positively charged silica prepared in Example 1, a conductive roller was prepared with the following composition. Propylene oxide and ethylene oxide were added to glycerin to give a molecular weight of 5000. Polyether polyol (OH value 33) (Asahi Glass Co., Ltd., Excene 828) 100 parts by weight 1,4-butanediol 6.56 parts by weight Tri Diisocyanate 22 parts by weight Silicone-based surfactant 2 parts by weight Dibutyltin dilaurate 0.01 parts by weight Acetylene black 2.5 parts by weight Positively charged silica 1.0 parts by weight

The above components were mixed with a hand mixer, air was introduced into a mold heated to 110 ° C., and the mixture was cured for 2 hours to form a conductive layer on the outer circumference of a metal shaft to obtain a conductive member of foam material. It was The surface of the obtained conductive member was dry-polished to form a roller. The resistance value of this conductive roller is
It was measured by the method of Example 1. Table 5 shows the results.

[Comparative Example 6] A conductive roller was produced in the same manner as in Example 4, except that the positively charged silica was removed.
The resistance value of this conductive roller was measured by the method of Example 1.
Table 5 shows the results.

[0035]

[Table 5]

[Evaluation of transfer roller image] A commercially available laser beam printer (Star Precision LS55T) was used by using the roller obtained in Example 4 and the roller obtained in Comparative Example 6.
The image was evaluated by incorporating it in the transfer portion of T) and printing a black solid image. As shown in Table 6, with the roller of Example 4, a high-quality image was obtained. In Comparative Example 6, an image defect, which is considered to be a transfer defect due to insufficient transfer bias, occurred particularly in a portion having high resistance.

[0037]

[Table 6]

[0038]

As described above, and as described with reference to Examples and Comparative Examples, according to the present invention, in a conductive member used for electrophotography, etc., the conductive member contains a conductive powder. It has been found that the resistance level is increased by being composed of a molecular material and further dispersing fine silica particles in the polymeric material. It has been found that the resistance region can be easily controlled by the number of parts of the silica fine particles to be mixed, and that a conductive member having a small resistance variation can be obtained even in a medium to high resistance region where the resistance becomes unstable only with a normal conductive powder. . Further, they have found that the use of positively chargeable silica having an amino group on the surface as the silica fine particles to be used enables more stable resistance control, and has arrived at the present invention.

[Brief description of drawings]

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

FIG. 2 is a schematic sectional view of an electrophotographic apparatus showing an example of the present invention.

[Explanation of symbols]

 1 Developing Roller 2 Shaft 3 Elastic Body (Conductor) 4 Toner Applying Roller 5 Photosensitive Drum 6 Toner (Non-magnetic Single-Component Developer) 7 Layering Blade 8 Transfer Section 9 Cleaning Section 10 Cleaning Blade 11 Charging Section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Kawagoe 1302-57 Aobadai, Tokorozawa, Saitama Prefecture

Claims (13)

[Claims] 1. A conductive member used in an electrophotographic apparatus or the like, wherein the conductive member is made of a polymer material containing conductive powder, and silica fine particles are dispersed in the polymer material. Conductive member. 2. The conductive member according to claim 1, wherein the silica fine particles are hydrophobic silica fine particles. 3. The conductive member according to claim 1, wherein the silica fine particles are positively chargeable silica fine particles. 4. The conductive member according to claim 1, wherein the silica fine particles have their silica surfaces treated with a coupling agent containing an amino group. 5. The roller according to claim 1, wherein the roller is formed on the conductive shaft.
The conductive member according to the item. 6. The conductive member according to claim 1, wherein the conductive member is brought into contact with a member to be charged and a voltage is applied between the member and the member to be charged to charge the member to be charged. What is a charging member. 7. The conductive member according to claim 1, wherein the conductive member carries a developer on a surface thereof to form a thin film of the developer, and the thin film is used as a latent image developer. A developer carrying member that is attached to the surface of a latent image carrier to visualize the electrostatic latent image. 8. The conductive member according to claim 1, wherein the conductive member charges the transfer paper and transfers the developer from the electrostatic latent image carrier visualized by the developer to the transfer paper. What is a member. 9. The conductive member according to claim 1, wherein the conductive member is a cleaning member for cleaning and removing residual toner on the photoconductor after transfer. 10. The charging device according to claim 1, wherein the conductive member is brought into contact with a member to be charged and a voltage is applied between the member and the member to be charged to charge the member. An electrophotographic apparatus characterized by having. 11. The conductive member according to claim 1, wherein the conductive member carries a developer on a surface thereof to form a thin film of the developer, and the thin film is used to form the latent image developer. An electrophotographic apparatus comprising a developing device which is attached to the surface of a latent image carrier to visualize the electrostatic latent image. 12. The transfer device according to claim 1, wherein the conductive member charges the transfer paper and transfers the developer from the electrostatic latent image holding member visualized by the developer to the transfer paper. An electrophotographic apparatus comprising: 13. The electrophotographic apparatus according to claim 1, wherein the conductive member has a cleaning device for cleaning and removing residual toner on the photoconductor after the transfer.