JP2000206777A - Toner carrier and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner carrier capable of excellently coping with a color image and obtaining a high-quality image by preventing image defect such as spots and irregular density and further white image fogging from occurring as far as possible. SOLUTION: As for this toner carrier, an electric resistance value at the time of applying 100 V is 104 to 1010 Ω and the maximum value of surface potential after 0.35 seconds in the case of electrifying the surface of the toner carrier by applying 8 kV voltage to a corona discharger arranged at the distance of 1 mm from the surface thereof, so that corona discharge may be generated is <=90 V. The toner carrier in this method is what is obtained by forming a semiconductive elastic layer 3 on the outer periphery of a good conductive shaft 2 and further forming a semiconductive resin covering layer 3a on the layer 3 such as a roller 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a developing roller for visualizing an electrostatic latent image with a non-magnetic one-component developer in an electrophotographic apparatus such as a copying machine or a printer or an electrostatic recording apparatus. More specifically, the present invention relates to a toner carrier and an image forming apparatus such as a developing device using the toner carrier, and more particularly, to a toner carrier capable of obtaining a uniform image without fogging or unevenness of a white image, and using the toner carrier. The image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a copying machine or a printer, a non-magnetic one-component developer is supplied to a photosensitive drum or the like holding a latent image and the developer is supplied to the latent image on the photosensitive drum. A pressure development method is known as a development method for visualizing a latent image by adhering a toner (US Pat. No. 3,515,2012).
According to this method, since a magnetic material such as a carrier is not required, the apparatus can be simplified,
It is easy to miniaturize, and can handle color images because it does not contain magnetic powder.

In this pressure development method, a developing roller (toner carrier) carrying a toner (non-magnetic one-component developer) is a latent image carrier (image forming body) holding an electrostatic latent image such as a photosensitive drum. The development is carried out by bringing toner into contact with the latent image on the latent image holding member by contacting the developing roller. Therefore, it is necessary to form the developing roller with an elastic material having conductivity.

That is, in this pressure development method, as shown in FIG. 4, for example, a toner coating roller 4 for supplying toner and a photosensitive drum (image forming body) 5 holding an electrostatic latent image. Between the developing roller (toner carrier) 1
The toner 6 is supplied to the surface of the developing roller 1 by the toner applying roller 4 by rotating the developing roller 1, the photosensitive drum 5, and the toner applying roller 4 in the direction of the arrow in the drawing, respectively. The toner is arranged in a uniform thin layer by the stratification blade 7, and the developing roller 1 is rotated while being in contact with the photosensitive drum 5 in this state, so that the toner formed in the thin layer is transferred from the developing roller 1 to the photosensitive drum 5. The latent image is made visible by adhering to the image. In the drawing, reference numeral 8 denotes a transfer unit, which transfers a toner image to a recording medium such as paper. Reference numeral 9 denotes a cleaning unit, which is provided on the surface of the photosensitive drum 5 after transfer by a cleaning blade 10. The remaining toner is removed.

In this case, the developing roller 1 includes a photosensitive drum 5
It is necessary to rotate while securely maintaining a state of being in close contact with the shaft. Therefore, as shown in FIG.
It has a structure in which a semiconductive elastic body in which carbon black or metal powder is dispersed in an elastomer such as NBR, EPDM, ECO, polyurethane or the like, or a semiconductive elastic layer 3 made of a foam body formed by foaming them. . Further, a coating layer 3a made of resin or the like is formed for the purpose of controlling the chargeability and adhesion of the toner, controlling the frictional force between the developing roller and the layering blade, and preventing the photosensitive member from being contaminated by the elastic body of the developing roller. It may be formed on the surface.

Further, there has been proposed a method of forming an image by directly flying toner carried on the surface of a toner carrier through a perforated control electrode onto paper or OHP paper.

In these toner carriers, the resistance of the carrier itself is adjusted to about 10 ⁵ to 10 ⁹ Ω in order to obtain an electric field which serves as a driving force for transferring the carried toner to an image forming body such as a photoreceptor. You. In many cases, the resistance of the resin coating layer 3a covering the surface is set higher than that of the semiconductive elastic layer 3 to facilitate resistance adjustment. in this case,
As in the case of the semiconductive elastic layer 3, carbon black, metal powder, metal oxide, or the like is used for adjusting the resistance of the resin coating layer 3a.

[0008]

To consider an electrophotographic system using the developing roller (toner carrier) 1 described above,
In particular, in order to obtain a high-quality image, it is required that the developer held on the developing roller always keeps a constant charge when reaching the image forming body and has a uniform charging state.

That is, when high image quality is required for an image forming apparatus such as a printer or when an attempt is made to support a color image, if the electrical characteristics of the developing roller vary over the entire surface of the roller, image defects such as spots and density This causes a problem of unevenness and fog of a white image. Also, during continuous printing, etc., the charge amount of the developer held on the developing roller may gradually change,
In addition, when a solid black image is printed, for example, the charge amount of the developer newly held in that part may be different from that of the surrounding area, and the unevenness of the developer charge distribution caused by this may cause unevenness. An image defect may occur. These phenomena are likely to occur when the charge applied to the surface of the toner carrier hardly escapes.

In this case, it is considered that the electric charge given to the surface of the toner carrier is attenuated mainly by being grounded from the surface through the conductive shaft. For example, in a developing sleeve used for magnetic toner development, Since the substrate is made of a metal, it has extremely good conductivity, the surface charge can easily flow into the ground, and the residual surface charge hardly causes a problem. However, in the case of a toner carrier used for non-magnetic one-component toner development using a semiconductive material as a base material, since the resistance of the base material is high, the residual charge is difficult to escape and tends to remain for a long time. Inconvenience occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and aims to prevent image defects such as spots, uneven density, and white image fog as much as possible, and to cope well with color images. It is an object of the present invention to provide a toner carrier capable of reliably obtaining a high-quality image that can be obtained, and an image forming apparatus using the toner carrier.

[0012]

Means for Solving the Problems and Embodiments of the Invention The present inventors have conducted intensive studies in order to obtain a toner carrier capable of forming a high-quality image which can sufficiently cope with a color image. As a result, the electrical resistance between the metal shaft and the surface, which has been regarded as important in the conventional developing roller (toner carrier), is controlled to a constant value over the entire surface of the roller and is not only uniform, but also the charging characteristics of the toner. The surface charge retention ability on the developing roller, which determines the image quality, is maintained at a constant value over the entire surface of the roller, and by making it uniform, image defects such as spots due to residual charges, uneven density, and the occurrence of white image fog Can be prevented
In order to discover that high-quality images can be formed, and to make the toner charge amount uniform, continuous printing or partial image printing is performed by keeping the residual charge holding capacity on the roller surface below a certain value. It has been found that even in such a case, uniform toner charging can be obtained, and a high-quality image can be reliably obtained.

The present inventor has further studied the evaluation of the proper electric resistance value and the good surface charge holding ability of the toner carrier having a semiconductive resin coating layer on the surface. At 22 ° C. and 50%, the electric resistance value of the toner carrier is 10 ⁴ to 10 ¹⁰ Ω when 100 V is applied, and a voltage of 8 kV is applied to a corona discharger arranged at an interval of 1 mm from the surface to perform corona discharge. Is generated so that the maximum value of the surface potential after 0.35 seconds when the surface is charged is controlled to be 90 V or less.
It can prevent image defects such as spots due to residual charge, uneven density, and white image fogging as much as possible, and maintain good image quality even during continuous printing or partial image printing. As a result, the inventors have found that a high-quality image that can well cope with a color image can be obtained reliably and stably, and the present invention has been completed.

Accordingly, the present invention comprises a semiconductive elastic layer formed on the outer periphery of a good conductive shaft, and a nonmagnetic one-component developer carried on the surface to form a thin layer of the developer. In a toner carrier that forms a visible image on the image forming body by contacting or approaching the image forming body in a state and supplying the developer to the surface of the image forming body, a semiconductive resin is used as an outermost layer. A corona discharge is generated by applying a voltage of 8 kV to a corona discharger having a coating layer and having an electric resistance value of 10 ⁴ to 10 ¹⁰ Ω when a voltage of 100 V is applied and having a distance of 1 mm from the surface. An object of the present invention is to provide a toner carrier, wherein the maximum value of the surface potential after 0.35 seconds after charging the surface is 90 V or less, and an image forming apparatus using the toner carrier itself.

Hereinafter, the present invention will be described in more detail.
In the toner carrier of the present invention, for example, a semiconductive elastic layer 3 is formed on the outer periphery of a good conductive shaft 2 like the roller 1 shown in FIG. In the present invention, such a toner carrier has an electric resistance value of 10 ⁴ Ω to 10 ¹⁰ Ω when a voltage of 100 V is applied, and is arranged at a distance of 1 mm from the surface. When a voltage of 8 kV is applied to the corona discharger to generate a corona discharge to charge the surface, the maximum value of the surface potential after 0.35 seconds is set to 90 V or less.

Here, as the shaft 2, any shaft having good conductivity can be used, but usually, a core made of a solid metal such as iron, stainless steel, aluminum or the like is used. A metal shaft such as a metal cylinder having a hollow or hollow inside is used.

Next, the semiconductive elastic layer 3 formed on the outer periphery of the shaft 2 is made of an elastomer alone or a foam obtained by foaming the elastomer, and an electronic conductive agent such as carbon black or an ionic conductive agent such as sodium perchlorate. Is formed of a semiconductive elastic body whose resistance value is adjusted by blending the above.

Examples of the elastomer include silicone rubber, EPDM, NBR, natural rubber, SBR, butyl rubber, chloroprene rubber, acrylic rubber, epichlorohydrin rubber, EVA, polyurethane, and mixtures thereof. , EPDM and epichlorohydrin rubber polyurethane are preferably used. Further, these elastomers can be foamed chemically using a foaming agent, or can be used as a foam body formed by foaming by mechanically entraining air like polyurethane foam.

Examples of the conductive agent to be incorporated in the semiconductive elastic layer 3 include an electronic conductive agent, for example, conductive carbon such as Ketjen black and acetylene black, SAF, ISAF, HAF, FEF, and the like. GPF, SR
Rubber carbon such as F, FT, MT, etc., carbon for color (ink) subjected to oxidation treatment, pyrolytic carbon, natural graphite, artificial graphite, antimony-doped tin oxide, titanium oxide, zinc oxide, nickel, copper And metal oxides such as silver and germanium, and conductive polymers such as polyaniline, polypyrrole, and polyacetylene. The amount of the electronic conductive agent is usually 1 to 50 parts by weight, especially 5 to 100 parts by weight of the elastomer.
It is preferably used in the range of from 40 to 40 parts by weight.

Examples of the ionic conductive agent include perchlorates, chlorates, and hydrochloric acid such as tetraethylammonium, tetrabutylammonium, dodecyltrimethylammonium, hexadecyltrimethylammonium, benzyltrimethylammonium, and modified dimethylethylammonium fatty acid. Ammonium salts such as salts, bromates, iodates, borofluorides, sulfates, ethyl sulfates, carboxylates, sulfonates; alkali metals such as lithium, sodium, potassium, calcium, magnesium; Examples include alkaline earth metal perchlorates, chlorates, hydrochlorides, bromates, iodates, borofluorides, sulfates and the like. The compounding amount of these ionic conductive agents is generally suitably used in the range of 0.01 to 5 parts by weight, particularly 0.05 to 2 parts by weight, based on 100 parts by weight of the elastomer.

The above-mentioned conductive agents may be used alone or in combination of two or more. In this case, it is possible to combine an electronic conductive agent and an ionic conductive agent.

The semiconductive elastic layer 3 is not particularly limited, but may have a resistance of 10 ³ to 10 ¹⁰ Ωcm, particularly 10 ⁴ to 10 ⁸ Ωcm, by mixing the above conductive agent. preferable. Charge and the resistance value is less than 10 ³ [Omega] cm is or leak to the photosensitive drum or the like, there are cases where the toner carrying member itself or destroyed by voltage, whereas 10 ¹⁰ Omega
When it exceeds cm, ground fogging tends to occur.

A cross-linking agent and a vulcanizing agent can be added to the semiconductive elastic layer 3 to convert the elastomer into a rubbery substance, if necessary. In this case, a vulcanization aid, a vulcanization accelerator, a vulcanization acceleration aid, a vulcanization retarder, and the like can be used in both cases of organic peroxide crosslinking and sulfur crosslinking. Furthermore, in addition to the above, peptizing agents, foaming agents, plasticizers, softeners generally used as compounding agents for rubber,
Tackifiers, antiadhesives, separating agents, release agents, extenders, colorants and the like can be added.

Further, when the conductive layer 3 is formed using polyurethane or EPDM as a base material, nigrosine, triaminophenylmethane, cationic dye, and the like are used for controlling the amount of toner charge on the surface when used as a developing roller. And various fine particles such as silicone resin, silicone rubber and nylon. In this case, the amount of these additives is preferably 1 to 5 parts by weight, and the fine powder is preferably 1 to 10 parts by weight, based on 100 parts by weight of the polyurethane or EPDM.

Although the hardness of the semiconductive elastic layer 3 is not particularly limited, it is 60 ° on a JIS-A scale.
Hereinafter, it is particularly preferable to set the angle to 25 to 55 °. In this case, if the hardness exceeds 60 °, for example, when used as a developing roller, the contact area with the photosensitive drum or the like becomes small, and there is a possibility that good development cannot be performed. Further, the toner is damaged, and the toner adheres to the photoreceptor or the layered blade, and the image is likely to be defective. Conversely, if the hardness is too low, the frictional force between the photoconductor and the stratification blade increases, and image defects such as jitter may occur. In addition, since the semiconductive elastic layer 3 is used in contact with a photoreceptor, a layered blade, or the like, even when the hardness is set to be low, it is preferable that the compression set be as small as possible. Is preferably 20% or less.

The surface roughness of the semiconductive elastic layer 3 is not particularly limited, but is preferably 15 μmRz or less, particularly preferably 1 to 10 μmRz in terms of JIS 10-point average roughness. When the surface roughness exceeds 15 μmRz, the thickness of the toner layer of the one-component developer (toner) and the uniformity of charging may be impaired. However, when the surface roughness is 15 μmRz or less, the adhesion of the toner can be improved. While you can
Image deterioration due to wear of the roller during long-term use can be more reliably prevented.

As shown in FIG. 1, the toner carrier of the present invention has a density of 10 ³ to 10 ¹² on the semiconductive elastic layer 3 in order to adjust the resistance and control the charge amount and the transport amount of the toner. Ωc
m, in particular, a semiconductive resin coating layer 3a having a volume resistivity of 10 ⁴ to 10 ¹⁰ Ωcm. The resin forming the resin coating layer is not particularly limited, and may be any resin that is non-staining and does not adhere to an image forming body such as a photosensitive drum. Specifically, polyester resin, polyether resin, fluorine resin, epoxy resin, amino resin, polyamide resin, acrylic resin, acrylic urethane resin,
Examples thereof include a urethane resin, an alkyd resin, a phenol resin, a melamine resin, a urea resin, a silicone resin, and a polyvinyl butyral resin. These may be used alone or in combination of two or more. Further, modified resins in which a specific functional group is introduced into these resins can also be used.

The resin coating layer 3a may contain a conductive agent for the purpose of controlling its conductivity. Examples of the conductive agent include those exemplified as the conductive agent used in the semiconductive elastic layer 3. The same thing can be illustrated. In order to improve the mechanical strength and environmental resistance of the resin coating layer 3a, it is preferable to introduce a crosslinked structure. In this case, the introduction of the cross-linking structure includes a self-cross-linking method of cross-linking with heat, a catalyst, air (oxygen), moisture (water), ultraviolet light, or the like according to the molecular structure of the resin constituting the resin coating layer 3a; There is a method in which a crosslinking agent or another crosslinking resin is reacted.

Incidentally, various other additives can be added to the resin coating layer 3a in an appropriate amount as needed.

As a method of forming the resin coating layer 3a on the semiconductive elastic layer 3, a method of surface-treating the semiconductive elastic layer 3 with a resin solution containing the resin component and the additive is preferable. Adopted to. In this case, the surface treatment is performed after preparing a resin solution, a spray method, a roll coater method,
It can be performed by a dipping method or the like. Note that the solvent for preparing the resin solution may be any solvent as long as it dissolves the above resin, but is usually methanol, ethanol, lower alcohols such as isopropanol, acetone, methyl ethyl ketone, ketones such as cyclohexanone, Toluene, xylene and the like are preferably used.

Although the thickness of the resin coating layer 3a is not particularly limited, it is usually 3 to 50 μm, especially 5 to 30 μm.
If the thickness is less than 3 μm, it may not be possible to sufficiently secure the charging performance of the surface layer due to friction during durability. In some cases, the surface becomes hard, damaging the toner, causing the toner to adhere to an image forming body such as a photoreceptor or a layered blade, resulting in an image defect.

The toner carrier of the present invention has an electric resistance of 10 ⁴ Ω to 10 ¹⁰ Ω when a voltage of 100 V is applied, preferably 10 ⁵ Ω to 10 ⁹ Ω. In this case, if the resistance value is less than 10 ⁴ Ω, it is extremely difficult to control the gradation, and if an image forming body such as a photoreceptor has a defect, a bias leak may occur. On the other hand, when the resistance exceeds 10 ¹⁰ Ω, for example, when developing the toner on a latent image holding member such as a photoconductor, the developing bias causes a voltage drop due to the high resistance of the toner holding member itself, and the developing bias is insufficient. The developing bias cannot be secured, and a sufficient image density cannot be obtained. The measurement of this resistance value
For example, the toner carrier can be pressed against a flat or cylindrical counter electrode at a predetermined pressure, a voltage of 100 V is applied between the shaft and the counter electrode, and the current value at that time can be obtained.

As described above, it is important to properly and uniformly control the resistance value of the toner carrier in order to maintain the electric field strength for moving the toner properly and uniformly. This is a necessary condition but not a sufficient condition to make the charge amount appropriate and uniform. That is, according to the study of the present inventor, it is important to control the charge holding ability of the surface of the toner carrier in addition to this resistance value, and to maintain the uniformity, in order to optimize and equalize the toner charge amount. There was found.
In this case, the surface charge holding ability is examined by measuring a surface resistance by arranging a pair of electrodes on the surface of the toner carrier and applying a constant voltage between the two electrodes. Since it does not only flow through the carrier but also flows inside the carrier, accurate evaluation of the carrier surface cannot be performed. Although improvement in accuracy by the four-terminal method has also been proposed, particularly in the case of a laminated toner carrier, the surface layer is quite thin, and it is difficult to characterize only the surface in this method. is there. Therefore, the characteristic values obtained by these conventional measurement methods cannot accurately represent the surface charge holding ability.

Therefore, in the present invention, in addition to the above-described resistance value when 90 V is applied, a voltage of 8 kV is applied to a corona discharger arranged at a distance of 1 mm from the surface of the toner carrier to generate corona discharge. 0.3 when charged
The surface charge holding ability is evaluated based on the maximum value of the surface potential after 5 seconds, and the maximum value is set to 90 V or less, preferably 50 V or less. In this case, if the maximum value exceeds 90 V, the toner is supplied to the image forming body, and when the toner is removed from the surface of the toner carrier, the electric charge in that part stays there without escaping. Then, the charge amount of the toner charged next in the same portion becomes low. Further, when the toner is continuously rotated without being supplied to the image forming body, the toner charge gradually increases, and in some cases, the electric field generated by the toner charging exceeds a local maximum value, so that the image forming body such as a photoreceptor is formed. Discharge occurs between the first and second steps, and an image defect may occur.

The reason why the surface potential was measured 0.35 seconds after charging due to the occurrence of corona discharge is as follows. That is, it is difficult to measure the surface potential immediately after charging by corona discharge, and since the surface potential at the very beginning is unstable, it is not preferable to control the characteristic value in this portion. When considering an actual process in image formation such as development, for example, when the toner carrier is a roller shape,
The rotation speed is usually 0.35 sec / 1 rotation, and the control of residual charges on the surface may be performed during this time.

The measurement of the maximum value of the surface potential can be performed by, for example, the apparatus shown in FIG. That is,
A measurement unit in which both ends of the shaft 2 of the toner carrier 1 are gripped by the chuck 11 to support the toner carrier 1, and a small corotron discharger 12 and a surface electrometer 13 are juxtaposed at a predetermined interval. 1 mm from the surface of the toner carrier 1
The measurement units 12 and 13 are moved at a constant speed from one end to the other end of the toner carrier 1 while the toner carrier 1 is kept stationary, so that a surface charge is applied. In addition, a method of measuring the surface potential 0.35 seconds later is preferably employed.

The toner carrier of the present invention can be incorporated in an image forming apparatus such as a developing apparatus using a non-magnetic one-component developer, and more specifically, as shown in FIG. The toner carrier of the present invention is disposed as a developing roller 1 in contact with or in proximity to the photosensitive drum 5 between the coating roller 4 and the photosensitive drum 5 holding the electrostatic latent image. The toner 6 is supplied to the developing roller 1, which is formed into a uniform thin layer by a layering blade 7, and the toner is supplied from the thin layer to the photosensitive drum 5, and the toner is applied to the electrostatic latent image on the photosensitive drum 5. The latent image can be visualized by attaching it. Since the details of FIG. 2 have been described in the related art, the description thereof is omitted.

In addition to such a developing device,
For example, the image forming apparatus is preferably used in an image forming apparatus that forms an image by directly flying toner carried on a toner carrier through an aperture-shaped control electrode on an image forming body made of paper sheets. .

[0039]

EXAMPLES The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples 1 to 3 and Comparative Examples] Polyether polyol (O) having a molecular weight of 5,000 by adding propylene oxide and ethylene oxide to glycerin.
H value 33) 100 parts (parts by weight, the same applies hereinafter) to 1,4-
Butanediol 1.0 part, silicone surfactant 1.5
Parts, 0.5 parts of nickel acetylacetonate, 0.01 parts of dibutyltin dilaurate and 0.01 parts of sodium perchlorate were added and mixed with a mixer to prepare a polyol composition.

After the polyol composition was stirred and defoamed under reduced pressure, 17.5 parts of urethane-modified MDI was added, stirred for 2 minutes, and then poured into a mold heated to 110 ° C. After curing, an elastic layer was formed on the outer periphery of the metallic shaft to obtain a roller having the structure shown in FIG. The surface of the obtained roller is polished and the surface is JIS 10 point average roughness 7μ.
Adjusted to mRz.

The resin shown in Table 1 below was dissolved in methyl ethyl ketone (MEK), and the conductive agent shown in Table 1 was further added to prepare a paint. The roller was immersed in the paint, and then pulled up. , Heated and dried to form a resin coating layer, and the four types of developing rollers (toner carrier) shown in Table 1
I got The thickness of the resin coating layer was adjusted by adjusting the resin concentration in the paint as follows. Example 1
25%, Example 2: 10%, Comparative example: 30%, Example 3: 25%.

With respect to each of the obtained developing rollers (toner carrier), the resistance value when a voltage of 100 V was applied between the developing roller (toner carrier) and the counter electrode (metal drum) was measured using the rotational resistance measuring device shown in FIG. did. Table 1 shows the results.

Also, using the apparatus shown in FIG. 2, a voltage of 8 kV was applied to the roller to charge the roller surface by corona discharge, and the measuring units 12 and 13 were set to 200 mm / sec.
It moved at the speed of c, and measured the surface potential 0.35 seconds after corona charging. The shape and dimensions of the measurement unit are as shown in FIG. By this method, the entire roller surface was measured, and the maximum value was measured as the surface potential value. In addition, the difference between the maximum and the minimum among the measured values was arranged. Table 1 shows the results. The measurement environment was set at temperature 2
The temperature was controlled at 2 ° C. and the humidity was 50%.

Next, each roller is used as a developing roller 1 in FIG.
The image was mounted on the developing device (image forming device) shown in (1) and developed (image formation), and the obtained image was evaluated. Table 1 shows the results.

[0046]

[Table 1] * 1: Carbon black “printex3” manufactured by Degussa
5 "* 2: Hakusui" 23K "* 3: Resin comparison

As is apparent from the results shown in Table 1, in addition to the electric resistance, the maximum value of the surface potential 0.35 seconds after corona charging was used to optimize the surface charge holding ability of Examples 1 and 2. It was confirmed that the roller can reliably form a good image. Further, the roller of Example 3 was able to obtain an almost satisfactory image, but had a slight image unevenness due to a large difference between the maximum value and the minimum value of the surface potential.

[0048]

As described above, according to the toner carrier of the present invention and the image forming apparatus using the same, image defects such as spots, uneven density, and occurrence of white image fog are minimized. Thus, a high-quality image can be reliably obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of the toner carrier of the present invention.

FIG. 2 is a schematic diagram illustrating an example of an apparatus for measuring a surface potential of a toner carrier.

FIG. 3 is a schematic plan view showing shapes and dimensions of measurement units used in Examples and Comparative Examples.

FIG. 4 is a schematic sectional view showing an example of the image forming apparatus (developing apparatus) of the present invention.

FIG. 5 is a schematic view showing a rotational resistance measuring instrument used in Examples and Comparative Examples.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developing roller 2 shaft 3 semiconductive elastic layer 3a resin coating layer 4 toner coating roller 5 photosensitive drum (image forming body) 6 toner (non-magnetic one-component developer) 7 layering blade 8 transfer unit 9 cleaning unit 10 cleaning blade Reference Signs List 11 chuck 12 corotron discharger (corona discharger) 13 surface electrometer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takahiro Kawagoe 1302-57, Aobadai, Tokorozawa-shi, Saitama (72) Inventor Takashi Kitamura 5-36-7, Onan, Musashimurayama-shi, Tokyo F-term (reference) 2H077 AD13 AD17 EA14 EA15 EA16 FA13 FA16 FA22 FA25

Claims (3)

[Claims] 1. A semiconductive elastic layer is formed on the outer periphery of a good conductive shaft, and a nonmagnetic one-component developer is carried on the surface to form a thin layer of the developer. The toner carrier that forms a visible image on the image forming body by supplying the developer to the surface of the image forming body in contact with or in proximity to the body has a semiconductive resin coating layer as an outermost layer. And the electrical resistance value when 100 V is applied is 10 ⁴
10 is a ¹⁰ Omega, the maximum surface potential after 0.35 seconds in the case of applying a 8kV voltage to the corona discharger disposed at a distance of the surface and 1mm to generate corona discharge by charging the surface A toner carrier having a value of 90 V or less. 2. An image comprising a toner carrier which carries a non-magnetic one-component developer on its surface to form a thin layer of the developer, and which carries the developer and supplies it to the surface of the image forming body. An image forming apparatus, wherein the toner carrier according to claim 1 is used as the toner carrier in the forming apparatus. 3. The image forming member is a latent image holding member holding an electrostatic latent image on the surface, and the non-magnetic one-component developer held on the toner holding member surface is held on the latent image holding member surface. 3. The image forming apparatus according to claim 2, wherein said image forming apparatus adheres to said electrostatic latent image to visualize said electrostatic latent image.