JP2000206779A - Toner carrier and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner carrier capable of coping with high speed operation and obtaining a high-quality image by keeping toner in a highly charged state and preventing the occurrence of white image fogging as much as possible. SOLUTION: This toner carrier is provided with a resin covering layer whose volume resistivity is >=1012 Ωcm as an outermost layer, its electric resistance value at the time of applying 100 V is 104 to 108 Ω and the minimum value of surface potential after 0.35 seconds when charging 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 is generated is 100 V to 1 kV. The toner carrier in this method is a roller 1, for example, obtained by forming a semiconductive layer 3 on the outer periphery of a good conductive shaft 2 and further forming the resin covering layer 3a on the layer 3.

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 a toner carrier capable of obtaining a uniform image without fogging or unevenness of a white image, and an image forming apparatus such as a developing device using the toner carrier. The present invention relates to an image forming apparatus used.

[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 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, image defects such as image fogging often occur particularly when the charge amount of toner is low. In particular, when conductive fine particles are contained on the surface of the roller, charging leakage occurs during charging of the toner, so that the toner charging amount cannot be maintained at a sufficiently high level, and such a problem is likely to occur.

In this case, a method has been proposed in which various charge control agents (CCA) are added to the surface of the developing roller in order to improve the charge amount of the toner, and the surface roughness is increased in order to improve the triboelectric charging characteristics. However, if the photoconductor is contaminated by CCA or the surface roughness is large, problems such as an increase in the amount of toner transport and an excessive supply of the developer may occur.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and maintains a high charge of a toner, further prevents the occurrence of white image fog as much as possible, and produces a high-quality image that can withstand high speed operation. An object of the present invention is to provide a toner carrier that can be reliably obtained, and an image forming apparatus using the toner carrier.

[0012]

The present inventor has conducted intensive studies to obtain a toner carrier capable of forming a high quality image. The electrical resistance between the metal shaft and the surface, which has been regarded as important in the body, is an important factor for the development characteristics. In particular, a roller having a resin coating layer (insulating layer) having a volume resistivity exceeding 10 ¹² Ωcm on the surface. In this case, the charge holding ability on the roller surface has a greater effect on the toner charge amount than this electric resistance, and the electric resistance value is controlled to a constant value over the entire surface of the roller and is not only uniform, but also uniform. By optimizing the charge holding ability on the developing roller, which affects the charging characteristics of the toner, it is possible to prevent image defects such as spots, uneven density, and the occurrence of white image fog. I found it.

The present inventor has further studied the evaluation of a proper electric resistance value and a good charge holding ability of the toner carrier. As a result, the toner carrier having an insulating layer on the outermost surface has a temperature of 22 ° C. , 50% RH, the electric resistance of the toner carrier is 10
A surface potential of 0.35 seconds after applying a voltage of 8 kV to a corona discharger arranged at a distance of 1 mm from the surface to generate a corona discharge and charge the surface at ⁴ to 10 ⁸ Ω. By controlling the minimum value to be equal to or less than 100 V to 1 kV, the toner is kept highly charged, and furthermore, the occurrence of white image fog is prevented as much as possible, and a high quality image which can withstand high speed operation is obtained. They have found that they can be reliably obtained, and have completed the present invention.

Accordingly, the present invention comprises a semiconductive layer formed on the outer periphery of a good conductive shaft, a nonmagnetic one-component developer carried on the surface to form a thin layer of the developer, and in this state, By supplying the developer to the surface of the image forming body in contact with or in close proximity to the image forming body, the outermost layer has a volume resistivity of 10 ¹² Ωcm as the outermost layer in the toner carrier that forms a visible image on the image forming body. Having a resin coating layer of more than
When the electric resistance value at the time of applying 00V is 10 ⁴ to 10 ⁸ Ω, and a voltage of 8 kV is applied to a corona discharger arranged at a distance of 1 mm from the surface to generate corona discharge and charge the surface. A toner carrier having a minimum surface potential after 0.35 seconds from 100 V to 1 kV, 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, a semiconductive layer 3 is formed on the outer periphery of a good conductive shaft 2 like a roller 1 shown in FIG. 1, and a resin coating layer is further formed on the semiconductive layer 3. According to the present invention, in such a toner carrier, the electric resistance value when 100 V is applied is set to 10 ⁴ to 10 ⁸ Ω, and a voltage of 8 kV is applied to a corona discharger arranged at a distance of 1 mm from the surface. The minimum value of the surface potential when the surface is charged by generating a corona discharge by applying the voltage is 100 V to 1
kV.

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 layer 3 formed on the outer periphery of the shaft 2 is prepared by blending an electronic conductive agent such as carbon black or an ionic conductive agent such as sodium perchlorate into a single elastomer or a foam obtained by foaming the elastomer. It is formed of a semiconductive elastic body whose resistance value is adjusted.

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 layer 3 include an electronic conductive agent, for example, conductive carbon such as Ketjen black and acetylene black;
F, ISAF, HAF, FEF, GPF, SRF, F
Rubber carbon such as T, 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, silver And metals such as germanium and metal oxides, and conductive polymers such as polyaniline, polypyrrole, and polyacetylene. The amount of these electronic conductive agents is usually 1 to 50 parts by weight, especially 5 to 4 parts by weight, per 100 parts by weight of the elastomer.
It is suitably used in the range of 0 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.

Although the semiconductive layer 3 is not particularly limited, it has a resistance value of 10 by mixing the above conductive agent.
It is preferably from ³ to 10 ¹⁰ Ωcm, particularly preferably from 10 ⁴ to 10 ⁸ Ωcm. If the resistance value is less than 10 ³ Ωcm, electric charges may leak to the photosensitive drum or the like, or the toner carrier itself may be broken by the voltage. On the other hand, if the resistance value exceeds 10 ¹⁰ Ωcm, fogging tends to occur. .

If necessary, a crosslinking agent and a vulcanizing agent can be added to the semiconductive layer 3 to convert the elastomer into a rubbery substance. In this case, in any case of organic peroxide crosslinking and sulfur crosslinking, a vulcanization aid, a vulcanization accelerator,
Vulcanization accelerators, vulcanization retarders and the like can be used. Furthermore, peptizing agents, foaming agents, plasticizers, softeners, tackifiers, antiblocking agents, separating agents, release agents, extenders, and coloring agents that are commonly used as rubber compounding agents in addition to the above. Etc. 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.

The hardness of the semiconductive layer 3 is not particularly limited, but is not more than 60 ° on a JIS-A scale.
Particularly, it is 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 layer 3 is used in contact with a photoreceptor, a laminating blade, or the like, it is preferable that the compression set be as small as possible even when the hardness is set to a low hardness. % Is preferable.

Although the surface roughness of the semiconductive layer 3 is not particularly limited, it is 15 μm in JIS 10 point average roughness.
mRz or less, particularly preferably 1 to 10 μmRz. If 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.
The adhesion of the toner can be improved, and the deterioration of the image due to the 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 an insulating resin coating layer 3a on the semiconductive layer 3 in order to adjust the resistance and control the amount of toner charge and the amount of conveyance.
Is formed. The resin forming the resin coating layer 3a 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, urethane resin,
Examples thereof include an alkyd resin, a phenol resin, a melamine resin, a urea resin, a silicone resin, and a polyvinyl butyral resin, and one or more of these can be used in combination. Further, modified resins in which a specific functional group is introduced into these resins can also be used.

The resin coating layer 3a may be a single layer or a multilayer structure of two or more layers. When the resin coating layer 3a has a multilayer structure of two or more layers, at least the outermost layer may have an insulating property. A conductive agent can be added to the inner layer to impart conductivity. In this case, as the conductive agent, those similar to the conductive agents used for the semiconductive layer 3 can be exemplified. In the present invention, if the volume resistivity is 10 ¹² Ωcm or more, it is considered to be insulating.

Further, it is preferable to introduce a crosslinked structure into the resin coating layer 3a in order to improve mechanical strength and environmental resistance. 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 for forming the resin coating layer 3a on the semiconductive layer 3, a method in which the surface of the semiconductive layer 3 is treated with a resin solution containing the resin component and the additive is suitably adopted. . In this case, after preparing the resin solution, the surface treatment can be performed by a spray method, a roll coater method, a dipping method, or the like. The solvent for preparing the resin solution may be any solvent as long as it dissolves the resin, but is usually methanol, ethanol, lower alcohols such as isopropanol, acetone,
Ketones such as methyl ethyl ketone and 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, the charging performance of the surface layer may not be sufficiently secured due to abrasion during durability. On the other hand, if the thickness exceeds 50 μm, the surface of the toner carrier becomes hard. When the toner is damaged, the toner may adhere to an image forming body such as a photoreceptor or a layered blade, resulting in an image defect.

In the toner carrier of the present invention, the electric resistance when 100 V is applied is 10 ⁴ to 10 ⁸ by the resin coating layer 3a.
And preferably 10 ⁵ to 10 ⁷ Ω. In this case, if the resistance value is less than 10 ⁴ Ω,
Gradation control becomes extremely difficult, 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 value exceeds 10 ⁸ 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 resistance value can be measured, for example, by pressing the toner carrier against a flat or cylindrical counter electrode at a predetermined pressure, applying a voltage of 100 V between the shaft and the counter electrode, and measuring the current value at that time. it can.

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 and keep it uniform in addition to the resistance value in order to optimize and equalize the toner charge amount. 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 100 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. The surface charge holding ability is evaluated based on the minimum value of the surface potential when is charged, and the minimum value is set to 100 V to 1 kV. in this case,
If the minimum value is less than 100 V, the charge on the roller surface is removed very quickly, and a sufficient amount of toner charge cannot be obtained, so that the object of the present invention cannot be achieved. Also, 1
When the voltage exceeds kV, the resistance of the carrier often substantially exceeds the above range in many cases. However, in this case, the toner charge amount becomes too high, and the effective developing bias of the photoconductor is reduced in the developing process. Exceeds the potential of the high potential part,
A phenomenon in which toner is developed on a white background, that is, a so-called high voltage fog occurs.

In order to increase the charge holding ability of the surface, it is effective to coat the surface of the carrier with the above-mentioned insulating resin of 1012 Ωcm or more, but on the other hand, the resistance of the carrier also increases. As described above, a sufficient developing bias cannot be ensured, which may cause an image defect.
In this case, the resistance of the carrier may be adjusted to the range of 10 ⁴ to 10 ⁸ Ω by adjusting the thickness of the resin coating layer 3a.

Thus, in the toner carrier of the present invention,
It is important to control the thickness of the outermost insulating resin layer in order to adjust the resistance value of the toner carrier to the above-mentioned 10 ⁴ to 10 ⁸ Ω. The surface roughness of the layer 3 greatly affects the surface, and the surface roughness becomes rough. In this case, the toner conveyance amount becomes excessive, which is not appropriate particularly when high image quality such as a color image is assumed. For this reason, as described above, the resin coating layer is composed of two or more layers, a conductive resin layer is formed as an inner coating layer between the semiconductive layer 3 and the outermost insulating layer, and the surface roughness is reduced. It is preferable to lower it. Although not particularly limited, the surface roughness of the toner carrier of the present invention is determined according to JIS.
The 10-point average roughness Rz is preferably 5 μm or less, particularly preferably 3 μm or less.

The minimum value of the surface potential can be measured 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. A method of measuring the surface potential while arbitrarily is adopted.

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. .

[0041]

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 and 2 and Comparative Examples 1 and 2 Glycerin was added with propylene oxide and ethylene oxide to give 100 parts (parts by weight, hereinafter the same) of polyether polyol (OH value: 33) having a molecular weight of 5000. , 1,
1.0 part of 4-butanediol, 1.5 parts of a silicone surfactant, 0.5 parts of nickel acetylacetonate, 0.01 parts of dibutyltin dilaurate and 0.01 parts of sodium perchlorate are added, and the mixture is mixed. By mixing, a polyol composition was prepared.

After stirring and defoaming the polyol composition under reduced pressure, 17.5 parts of urethane-modified MDI was added, and the mixture was stirred for 2 minutes. Then, the mixture was poured into a mold heated to 110 ° C. and stirred for 2 hours. 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.

A resin shown in Table 1 below was dissolved in methyl ethyl ketone (MEK), and a 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
15% (outside), 20% (inside), Example 2: 10%,
Comparative Example 1: 30%, Comparative Example 2: 35%. The surface roughness of each of the obtained rollers was as shown in Table 1.

The resistance value of each of the obtained developing rollers (toner carrier) when a voltage of 100 V was applied between the developing roller (toner carrier) and the counter electrode (metal drum) using the rotational resistance measuring device shown in FIG. 5 was measured. 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
The substrate was moved at a speed of c and the surface potential after corona charging was measured. The shape and dimensions of the measurement unit are as shown in FIG. By this method, the entire surface of the roller was measured, and the minimum value was measured as the value of the surface potential. 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 a temperature of 22 ° C and a humidity of 50.
%.

Next, each roller is used as a developing roller 1 as shown 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.

[0048]

[Table 1] * 1: "L6" manufactured by Degussa * 2: "CM8000" manufactured by Toray * 3: Compared with resin

As is evident from the results shown in Table 1, the rollers of Examples 1 and 2 in which the surface charge holding ability was optimized by the minimum value of the surface potential after corona charging, in addition to the electric resistance, were excellent. It was confirmed that a perfect image could be reliably formed.

[0050]

As described above, according to the toner carrier of the present invention and the image forming apparatus using the same, the toner is maintained at a high charge, and the occurrence of white image fog is prevented as much as possible. As a result, a high-quality image that can withstand high-speed operation 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]

 DESCRIPTION OF SYMBOLS 1 Developing roller 2 Shaft 3 Semiconductive layer 3a Resin coating layer 4 Toner application 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 11 Chuck 12 Corotron discharger (Corona discharger) 13 Surface potentiometer

 ──────────────────────────────────────────────────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 AD06 AD11 AD17 DB12 EA11 FA01 FA13

Claims (4)

[Claims] 1. A semiconductive 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. By supplying the developer to the surface of the image forming body in contact with or in close proximity thereto, the outermost layer of the toner carrier that forms a visible image on the image forming body has a volume resistivity of 10 ¹² Ωc.
a resin coating layer exceeding 100 m and an electric resistance value of 10 ⁴ to 10 ⁸ Ω when a voltage of 100 V is applied, and further applying a voltage of 8 kV to a corona discharger arranged at a distance of 1 mm from the surface to form a corona discharger. The minimum value of the surface potential after 0.35 seconds when the surface is charged by generating a discharge is 100 V to 1 kV.
A toner carrier. 2. The surface roughness is determined according to JIS 10-point average roughness Rz.
The toner carrier according to claim 1, wherein the particle size is 5 μm or less. 3. An image comprising a toner carrier which carries a non-magnetic one-component developer on the 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 or 2 is used as the toner carrier in the forming apparatus. 4. 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. 4. The image forming apparatus according to claim 3, wherein said image forming apparatus adheres to said electrostatic latent image to visualize said electrostatic latent image.