JPH0844149A - Conductive roller and device formed by using the same - Google Patents

Abstract

PURPOSE:To make it possible to obtain high-quality images which have low hardness and good adhesion property and are free from unequal density and surface fogging, etc., by forming very small recessed grooves of which the longitudinal direction is aligned nearly to the rotating direction of a conductive roller on the surface of an elastic layer. CONSTITUTION:A developing roller 1 which is one example of the conductive roller is obtd. by forming an elastic layer 3 having an electrical conductivity on the outer periphery of a good conductive shaft 2. The very small recessed grooves of which the longitudinal direction is aligned nearly to the rotating direction of the conductive roller 1 are formed on the surface of the elastic layer 3. The shape of the recessed grooves are preferably such that the depth thereof is 0.1 to 30mum the width 0. l to 50mum and the average spacing of the adjacent recessed grooves in the axial direction of the roller is 0.1 to 100mum. As a result, the friction resistance between the developing roller 1 and a later forming blade or toners is decreased and the thin layer of the toners on the roller 1 is made uniform. The electrostatic charge quantity of the toners is stabilized as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to various conductive rollers in electrophotographic devices such as copying machines and printers, electrostatic recording devices, and more specifically, charging rollers, developing rollers, transfer rollers, and the like, and uses them. The present invention relates to a charging device, a developing device, a transfer device, and the like, and particularly to a developing roller, a conductive roller suitable for use as a developing device, and an apparatus using the conductive roller.

[0002]

2. Description of the Related Art In recent years, with the progress of electrophotographic technology, there has been an increasing demand for a conductive member used in each electrophotographic process, and in particular, a developing roller used in a developing device has been attracting attention. The characteristic required for such a developing roller is not only a predetermined electric resistance value, but also a characteristic suitable for various developing mechanisms needs to be added.

Conventionally, as a developing method in the case of using a non-magnetic one-component developer as a developer (hereinafter referred to as toner), toner is supplied to a photosensitive drum holding a latent image to form a latent image on the photosensitive drum. A developing method (pressure developing method) in which a toner is attached to visualize a latent image is known. According to this method, since a magnetic material is unnecessary, the device can be simplified and downsized, and It is easy to color toner.

In this pressure developing method, a developing roller carrying toner is brought into contact with an electrostatic holding member holding an electrostatic latent image, such as a photosensitive drum, and toner is attached to the latent image on the electrostatic holding member. Therefore, it is necessary to form the developing roller with an elastic body having conductivity.

That is, in this pressure developing method, for example, as shown in FIG.
As shown in FIG. 3, the developing roller 1 is in contact with the photosensitive drum 5 between the toner applying roller 4 for supplying toner and the photosensitive drum 5 holding the electrostatic latent image. By rotating the developing roller 1, the photosensitive drum 5 and the toner applying roller 4 in the direction of the arrow in the figure, the toner 6 is supplied to the surface of the developing roller 1 by the toner applying roller 4, and this toner is formed by the layering blade 7 To form a uniform thin layer, and in this state, the developing roller 1 rotates while contacting the photosensitive drum 5, so that the toner formed in the thin layer adheres from the developing roller 1 to the latent image on the photosensitive drum 5. , The latent image is made visible.
In the figure, reference numeral 8 denotes a transfer section, which is adapted to transfer a toner image onto a recording medium such as paper, and 9 denotes a cleaning section, which is cleaned by a cleaning blade 10 on the surface of the photosensitive drum 5 after transfer. It is designed to remove the residual 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 made of an elastic body provided with conductivity is formed by mixing a conductive agent into a sponge body such as an elastic rubber such as NBR or EPDM or a urethane foam.

[0007]

However, the above-mentioned conventional developing roller, particularly the developing roller composed of a single elastic layer, does not have sufficient charge rise characteristics of toner on the roller, and the friction resistance with the photosensitive drum or the layering blade is not sufficient. Is large, and problems such as poor cleaning due to fog selective development due to poor charging of toner and reduction in print density are likely to occur, and there is a problem that the printing quality is significantly deteriorated due to continuous printing for a long period of time. This phenomenon is particularly remarkable in a high temperature and high humidity environment.

The present invention has been made in view of the above circumstances, and by improving the surface condition of the roller, it has a low hardness, good adhesion, and a high-quality image free from uneven density or background fog. An object of the present invention is to provide an obtained developing roller and a developing device using the same.

[0009]

A conductive roller according to claim 1 of the present invention is a conductive roller in which a conductive elastic layer is formed on the outer periphery of a good conductive shaft.
The surface of the elastic layer is characterized by forming a minute groove whose longitudinal direction is substantially along the rotational direction of the conductive roller.

Further, the conductive roller according to claim 2 of the present invention is characterized by being obtained by polishing.

Further, according to a third aspect of the present invention, there is provided a conductive roller according to JIS in the rotating direction of the conductive roller of the elastic layer.
The 10-point average roughness Rz is smaller than that in the axial direction.

Further, in the electroconductive roller according to claim 4 of the present invention, the concave groove has a depth of 0.1 to 30 μm and a width of 0.1.
It is characterized in that the average distance between the concave grooves adjacent to each other in the axial direction of the conductive roller is 0.1 to 100 μm.

As a result of earnest studies on the surface condition of the developing roller, the inventors of the present invention processed the surface of the developing roller so as to form a groove whose longitudinal direction is substantially along the rotational direction of the roller. It has been found that a high-quality image having high adhesion and free from uneven density (uneven halftone, etc.) and background fog can be obtained.

That is, in the developing method using the non-magnetic one-component developer, the elastic layer surface is formed with minute concave grooves whose longitudinal direction is substantially aligned with the rotating direction of the conductive roller. Since it is possible to reduce the frictional resistance with the toner, it becomes easier to form a thin layer of toner uniformly as compared with a roller in which minute irregularities are randomly formed by simply processing without considering the surface condition of the roller. As a result, a high-quality image without density unevenness or background fog can be obtained.

The present invention will be described in more detail below.
The developing roller, which is an example of the conductive roller of the present invention, is shown in FIG.
As shown in FIG. 2, the elastic layer 3 having conductivity is formed on the outer circumference of the good conductive shaft 2. Here, if the shaft 2 has good conductivity,
Although any of these may be used, a metal shaft such as a metal core made of a solid metal body or a metal cylindrical cylinder having a hollow hollow inside is usually used.

As the elastic layer 3, an elastomer such as conductive rubber or polyurethane or a foam material can be used as a base material.

First, the case where the elastic layer 3 is a conductive rubber will be described. In this case, as the rubber material forming the non-foamed conductive rubber, nitrile butadiene rubber, natural rubber, butyl rubber, nitrile rubber, isoprene rubber, polybutadiene rubber, silicone rubber, styrene-butadiene rubber, ethylene-propylene rubber, ethylene- Ordinary rubber such as propylene-diene terpolymer rubber (EPDM), chloroprene rubber, acrylic rubber, polynorbornene rubber or styrene-butadiene-styrene (SB
S), styrene-butadiene-styrene hydrogenated product (SEB
It is possible to use thermoplastic rubbers such as S) and mixtures thereof. Further, as the foamed conductive rubber, ethylene-propylene-diene terpolymer rubber (EPD) is used.
M), chloroprene rubber, chlorosulphonated polyethylene mixed with a conductive material, epichlorohydrin-ethylene oxide copolymer rubber foam or epichlorohydrin-ethylene oxide copolymer rubber mixed with a conductive material is preferable. Can be used for

As a conductive material to be blended with these rubber compositions, powdery conductive carbon such as Ketjen Black EC or acetylene black, SA can be given as an example.
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. The compounding amount thereof may be 3 to 100 parts by weight, particularly 5 to 50 parts by weight, based on 100 parts by weight of all rubber components, whereby the volume resistance of the elastic layer 3 is 10 ² to 10 ¹⁰ Ω.
・ Can be adjusted to cm.

Next, the case where the elastic layer 3 is polyurethane will be described. In this case, the polyurethane foam or the elastomer material may be any one manufactured by various methods. For example, a method in which carbon black is mixed into a polyurethane prepolymer, and the prepolymer is subjected to a crosslinking reaction, and a conductive material is mixed into a polyol. Then, this polyol can be obtained by a method such as a method of reacting this polyol with polyisocyanate by a one-shot method.

The urethane used as the base material of the elastic layer 3 is, as a polyhydroxyl compound, a polyol used in the production of general flexible polyurethane foams and urethane elastomers, for example, a polyether polyol having a polyhydroxyl group at the end, a polyester. In addition to polyols and polyether polyols which are copolymers of both, polyolefin polyols such as polybutadiene polyols and polyisoprene polyols, so-called polymer polyols obtained by polymerizing ethylenically unsaturated monomers in polyols, etc. Common polyols can be used. Further, as the polyisocyanate compound, similarly, polyisocyanates used for producing general flexible polyurethane foams and urethane elastomers, that is, tridiisocyanate (TDI), crude TDI, 4,4-diphenylmethane diisocyanate (MDI), crude MDI. , Aliphatic polyisocyanates having 2 to 18 carbon atoms, alicyclic polyisocyanates having 4 to 15 carbon atoms, and mixtures and modified products of these polyisocyanates, for example, prepolymers obtained by partially reacting with polyols, Used.

As the conductive material to be blended with these polyurethanes, the same conductive material as in the case of the above rubber composition and an ionic conductive material composed of an inorganic ionic substance such as lithium perchlorate or an organic ionic substance such as a quaternary ammonium salt are used. Materials, cationic surfactants, anionic surfactants, amphoteric ion surfactants such as various betaines, and nonionic antistatic agents such as hydrophilic polyethers and polyesters may be used in combination. In the case of urethane, it is also preferable that the polyol component is prepolymerized with isocyanate.
The blending amount is 0.5 to 100 parts by weight of urethane.
It may be 50 parts by weight, particularly 1 to 30 parts by weight, whereby the volume resistance of the elastic layer 3 is 10 ² to 10 ¹⁰ Ω · cm.
Can be adjusted to. Note that other conductive materials may be blended with an electron accepting substance capable of forming a charge transfer complex such as tetracyanoethylene, tetracyanoquinodimethane, benzoquinone, chloranil, anthraquinone, anthracene, dichlorodicyanobenzoquinone, ferrocene, and phthalocyanine. The compounding amount in that case can be 0.001 to 20 parts by weight, particularly 0.01 to 1 part by weight, relative to 100 parts by weight of urethane.

The hardness of the elastic layer is not particularly limited, but J
It is preferably 70 ° or less, particularly 10 to 60 ° on the IS-A scale. In this case, if the hardness exceeds 70 °, the contact area with the photosensitive drum and the like may be small, and good development may not be possible. When the roller is deformed or eccentric, uneven density of the image occurs. Therefore, even when the hardness of the elastic layer is low, it is preferable to reduce the compression set as much as possible.
Specifically, it is preferably 20% or less.

The method of forming the minute groove on the surface of the elastic layer is not particularly limited, but the minute groove is previously formed on the inner surface of the mold, and the base material is injected into the groove to form the conductive roller. Examples thereof include a molding method (injection molding method and the like) and a method of molding the conductive roller by polishing the elastic layer using a grindstone or the like.

The method for polishing the elastic layer is not particularly limited, but generally includes a wet method or a dry method. For example, in the wet method, a lubricant such as water or oil is used between the grindstone and the elastic layer. Although a method of polishing while spraying can be adopted, water is preferable as the lubricant because of the problem of contamination of the photosensitive drum. When the dry polishing method is adopted, the grinding speed, the type of the grindstone, etc. may be taken into consideration, but the wet method is preferably used from the viewpoint of workability.

The direction of the surface roughness of the present invention will be described with reference to the schematic view of FIG. The JIS 10-point average roughness Rz in the rotating direction of the developing roller is a value obtained by sweeping the surface of the elastic layer in the direction (1) of FIG. 3 using a contact-type surface roughness meter described later. . on the other hand,
The JIS 10-point average roughness Rz in the axial direction is a value obtained by sweeping at right angles to the direction (2) in FIG. 3, that is, the direction (1).

The surface roughness of the roller obtained by the above-described measuring method is the JIS 10-point average roughness Rz in the roller rotating direction,
By making it smaller than that in the axial direction, the frictional resistance with the photosensitive drum is reduced, and as a result, the toner charge amount conveyed is stabilized. The shape of the groove has a depth of 0.
1 to 30 μm, the width is 0.1 to 50 μm, and the average interval between the concave grooves adjacent to each other in the axial direction of the roller is 0.1 to 100 μm.
It is preferred that

As described above, since the surface of the developing roller of the present invention is formed with minute grooves whose longitudinal direction is substantially along the rotational direction of the conductive roller, the surface of the elastic layer (the roller surface condition is 4 and 5 shown in Examples below), the frictional resistance between the developing roller and the layering blade or toner is reduced, the thin layer of toner on the roller becomes uniform, and the toner charge amount is also It seems to be stable.

The conductive roller of the present invention can be incorporated in an ordinary developing device using a non-magnetic one-component developer as a developing roller. Specifically, as shown in FIG. 2, toner for supplying toner is used. Between the application roller 4 and the photosensitive drum 5 holding the electrostatic latent image, the developing roller 1 of the present invention is in contact with the photosensitive drum 5 and the toner application roller 4
And the developing roller 1, the photosensitive drum 5, and the toner applying roller 4 rotate in the direction of the arrow in the figure, so that the toner 6 is transferred to the developing roller 1 by the toner applying roller 4. The toner supplied to the surface is adjusted to a uniform thin layer by the stratifying blade 7, and the developing roller 1 is rotated in contact with the photosensitive drum 5 in this state, so that the toner formed in the thin layer is developed. The image is attached to the latent image on the photosensitive drum 5 to visualize the latent image. For details of FIG.
Since it has been described in the related art, its description is omitted.

[0029]

The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. [Example 1] 100 parts of polyether polyol (OH number 33) (Exenol (registered trademark) 828 manufactured by Asahi Glass Co., Ltd.) having a molecular weight of 5000 by adding propylene oxide and ethylene oxide to glycerin MDI NCO% = 23% (Sumijour (registered trademark) PF manufactured by Sumitomo Bayer Urethane Co., Ltd.) 25.0 parts ・ 1,4-butanediol 2.5 parts ・ Dibutyltin dilaurate 0.01 part

These were stirred and then poured into a mold heated to 110 ° C. and cured for 2 hours to form an elastic layer on the outer circumference of a metal shaft to obtain a developing roller. The surface of the obtained roller was wet-polished, and the surface state was observed with an electron microscope. As a result, the elastic layer surface had minute grooves whose longitudinal direction was substantially along the rotational direction of the conductive roller. It was confirmed (the electron micrograph of FIG. 4 [500
Double]).

[Example 2] Propylene oxide and ethylene oxide were added to glycerin to give a polyether polyol (OH value 33) (Exenol (registered trademark) 828 manufactured by Asahi Glass Co., Ltd.) having a molecular weight of 5000. 100 parts of polyether prepolymer prepolymerized with diisocyanate (TDI-80, NCO% = 23% (manufactured by Sumitomo Bayer Urethane Co., Ltd.), Asahi Thermal FT Class (manufactured by Asahi Carbon Co., Ltd.) 3.0 Part ・ 1,4-butanediol 6.9 part ・ dibutyltin dilaurate 0.05 part ・ quaternary ammonium salt (Kao Co., Ltd., KS-555) 0.2 part

These were stirred and then poured into a mold heated to 110 ° C. and cured for 2 hours to form an elastic layer on the outer circumference of a metal shaft to obtain a developing roller. The surface of the obtained roller was wet-polished, and the surface state was observed with an electron microscope. As a result, the elastic layer surface had minute grooves whose longitudinal direction was substantially along the rotational direction of the conductive roller. It was confirmed (the electron micrograph of FIG. 5 [500
Double]).

[Comparative Example 1] The developing roller obtained by the formulation of Example 1 was dry-polished, and the surface condition was observed with an electron microscope. As a result, the elastic layer surface was found to have wavy projections extending parallel to the axial direction. Was confirmed (the electron micrograph of FIG. 6 [50
0 times]).

[Comparative Example 2] The developing roller obtained by the formulation of Example 2 was dry-polished and the surface condition was observed with an electron microscope. As a result, the elastic layer surface was found to have wavy projections extending parallel to the axial direction. Was confirmed (the electron micrograph of FIG. 7 [50
0 times]).

The following characteristic tests were conducted on the developing rollers obtained in Examples 1 and 2 and Comparative Examples 1 and 2. The results are shown in Table 1. (1) Surface Roughness For each roller, a surface roughness meter Surfcom 570A (manufactured by Tokyo Seimitsu Co., Ltd.) was used. (2) Concavo-convex shape It was calculated based on the measured values and electron micrographs obtained in (1). (3) Hardness A sheet-shaped sample prepared under the same conditions as each roller was measured according to JIS-K6301 (A type). (4) Contamination of Photoreceptor Using each roller as a developing roller, it is pressed against a photosensitive drum for printer PC-PR1000E / 4, manufactured by NEC, with a load of 500 g, and left at 50 ° C. and 85% RH for 72 hours, and the surface of the photosensitive drum The contamination was visually confirmed. (5) Image output Each roller is installed as a developing roller in the developing unit section shown in FIG. 2, and non-magnetic one-component toner having an average particle size of 7 μm is used, and it is reversed while being rotated at a peripheral speed of 60 mm / sec. The image was developed by development, and the image quality (sharpness, density), fogging, and toner dust generation at the initial stage and after 2000 prints were evaluated. The results are shown in Table 1. (6) Toner charge amount Each roller is attached as a developing roller to the developing unit shown in FIG. 2 and rotated at a peripheral speed of 50 mm / sec to form a uniform thin toner layer on the surface of the developing roller. Suction the thin layer with air and introduce it into the Faraday gauge,
The charge amount was measured. (7) Electric resistance Apply a load of 500g to each end of each shaft and set each roller to 3
The resistance value (Ω) when a voltage of 2000 V was applied was measured under an environmental condition of 0 ° C. and 85% RH.

[Table 1]

[0036]

As described above, according to the present invention, a conductive roller having a low hardness and a good adhesion and capable of obtaining a high-quality image without density unevenness or background fog, and an apparatus using the same are provided. The purpose is to provide.

[Brief description of drawings]

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

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

FIG. 3 is a schematic view of the surface roughness direction of the present invention.

FIG. 4 is an electron micrograph of the surface of the developing roller (of Example 1).

FIG. 5 is an electron micrograph of the surface of the developing roller (of Example 2).

FIG. 6 is an electron micrograph of the surface of the developing roller (comparative example 1).

FIG. 7 is an electron micrograph of the surface of a developing roller (comparative example 2).

[Explanation of symbols]

 1 Developing Roller 2 Shaft 3 Elastic Body 4 Toner Application Roller 5 Photosensitive Drum (Latent Image Holding Body) 6 Toner (Non-Magnetic One-Component Developer) 7 Layering Blade 8 Transfer Section 9 Cleaning Section 10 Cleaning Blade

Claims (8)

[Claims] 1. A conductive roller having an elastic layer having conductivity formed on the outer periphery of a good conductive shaft or the like, wherein the surface of the elastic layer has a longitudinal direction that is substantially along the rotational direction of the conductive roller. A conductive roller having a groove formed therein. 2. The conductive roller according to claim 1, wherein the conductive roller is obtained by polishing. 3. The conductive roller according to claim 1, wherein JIS 10 point average roughness Rz of the elastic layer in the rotating direction of the conductive roller is smaller than that in the axial direction. 4. The groove has a depth of 0.1 to 30 μm,
The width is 0.1 to 50 μm, and the average distance between the concave grooves adjacent to each other in the axial direction of the conductive roller is 0.1 to 100 μm.
The conductive roller according to claim 1, wherein the conductive roller is 5. The charging roller according to claim 1, wherein the conductive roller is a charging roller that contacts a member to be charged and applies a voltage between the member and the member to be charged to charge the member to be charged. The conductive roller according to item 1. 6. A latent image carrier in which the conductive roller carries a non-magnetic one-component developer on the surface of an elastic body to form a thin film of the developer and holds an electrostatic latent image on the surface in this state. 5. The conductive roller according to claim 1, which is a developing roller that makes the electrostatic latent image visible by contacting the electrostatic latent image with the developer from the thin film on the surface of the latent image carrier. Sex laura. 7. The transfer roller according to claim 1, wherein the conductive roller is a transfer roller that charges the transfer paper and transfers the developer from the electrostatic latent image visualized by the developer to the transfer paper. Conductive roller. 8. An apparatus comprising the conductive roller according to claim 1.