JP2002031946A - Toner carrier and device for image formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner carrier which is excellent in durability and can definitely reproduce images of high picture quality for a long time without causing fog in a white image, rough halftone image or irregular density in a black image even when the carrier is used for a long time. SOLUTION: In the toner carrier having a semiconducting elastic layer 3 formed around a conductive shaft 2, the semiconducting elastic layer 3 is formed by applying at least two resin coating layers on a conductive elastic substrate 31. The first resin coating layer 32 in contact with the conductive elastic substrate 31 has <=109 Ω.cm resistance, and the outermost resin coating layer 33 constituting the outermost layer essentially comprises phenol resin and has >=1010 Ω.cm resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for visualizing an electrostatic latent image by supplying toner to a photosensitive drum holding the electrostatic latent image in an electrophotographic apparatus such as a copying machine or a printer or an electrostatic recording apparatus. The toner carrier used in the case of performing image formation by directly supplying toner to an image forming body such as a paper sheet, and an image forming apparatus using the toner carrier are described in more detail below. The present invention relates to a toner carrier capable of stably obtaining high image quality for a long time even in continuous printing, and an image forming apparatus using the toner carrier.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a copying machine or a printer, toner is supplied to a photosensitive drum or the like holding a latent image, and the toner is attached to the latent image on the photosensitive drum to form the latent image. As a development method for visualizing, a pressure development method is known (U.S. Pat.
According to this method, a magnetic material such as a carrier is not required, so that the device can be simplified and downsized easily, and a color image can be handled because it does not contain a magnetic powder.

In this pressure development method, a developing roller (toner carrying member) carrying toner is brought into contact with a latent image holding member (image forming member) holding an electrostatic latent image such as a photosensitive drum, and the toner is condensed. The development is performed by attaching the latent image to the latent image on the latent image holding member. For this reason, it is necessary to form the developing roller (toner carrier) with a conductive elastic body.

That is, in this pressure development method, as shown in FIG. 4, for example, a toner applying roller 4 for supplying toner and a photosensitive drum (image forming body) holding an electrostatic latent image
5, the developing roller (toner carrier) 1 is disposed, and the developing roller 1, the photosensitive drum 5, and the toner applying roller 4 rotate in the direction of the arrow in FIG. The toner is supplied to the surface of the developing roller 1 by the coating roller 4, and the toner is adjusted to a uniform thin layer by the layering blade 7. In this state, the developing roller 1 rotates while being in contact with the photosensitive drum 5, thereby forming a thin layer. Is adhered to the latent image on the photosensitive drum 5 from the developing roller 1 to visualize the latent image. In the figure, reference numeral 8 denotes a transfer unit, which transfers a toner image onto a recording medium such as paper. Reference numeral 9 denotes a cleaning unit.
Thus, the toner remaining on the surface of the photosensitive drum 5 after the transfer is removed.

In this case, the developing roller 1 includes a photosensitive drum 5
It is necessary to rotate while firmly maintaining the state of being in close contact with the shaft. Therefore, as shown in FIG.
The conductive elastic layer 3 is formed of a conductive elastic body having a conductivity imparted by blending a conductive agent into an elastic rubber such as NBR, EPDM, polyurethane rubber, foam or the like. 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.

These toner carriers have an electric resistance of 10 ⁴ to 10 ¹⁰ 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 photosensitive member.
Adjusted to the extent. In many cases, the resistance of the resin coating layer 3a covering the surface is set higher than that of the conductive elastic layer 3 in order to facilitate resistance adjustment. in this case,
As in the case of the semiconductive elastic layer 3, a conductive agent such as carbon black, metal powder, or metal oxide is used for adjusting the resistance of the resin coating layer 3a.

[0008]

However, in recent years, image forming apparatuses such as printers have been accelerated, advanced fine image formation has been demanded, and color image formation has been demanded. The problem has become severe, and the problem that the above-described conventional toner carrier cannot sufficiently cope with the problem has become apparent. That is, the demand for image uniformity becomes more severe, and when the number of printed sheets is increased by incorporating the toner carrier into the image forming apparatus and using it for a long time, white image fog, roughness of halftone images or black There has been a problem that image defects such as uneven shading of images occur.

The present invention has been made in view of the above circumstances, and can sufficiently respond to recent demands for higher image quality. Even when used for a long period of time, white image fogging, half-tone image roughness or black image An object of the present invention is to provide a toner carrier having excellent durability and capable of reliably reproducing a high-quality image over a long period of time without causing shading and the like, and an image forming apparatus using the toner carrier.

[0010]

Means for Solving the Problems and Embodiments of the Invention The present inventor has conducted intensive studies to achieve the above object, and as a result, formed a semiconductive elastic layer on the outer periphery of a good conductive shaft to form a roller. In the case of forming a toner carrier having a shape such as a shape, at least two resin coating layers are formed on a conductive elastic substrate to constitute the semiconductive elastic layer, and the conductive elastic substrate is formed of the resin coating layer. the resistance of the first resin coating layer in contact with the 10 ⁸
Ω · cm or less, and the outermost resin coating layer constituting the outermost layer is formed mainly of a phenol resin, particularly a resol type phenol resin, and has a resistance of 10 ¹⁰ Ω · c.
m or more, a good image can be obtained for a long period of time without causing white image fog, roughness of a halftone image, unevenness of shading of a black image, etc. The present invention has been completed, and the present invention has been completed.

That is, in the toner carrier of the present invention, the phenol resin constituting the outermost resin coating layer has excellent chargeability,
In addition to exhibiting good toner carrying performance, the toner has excellent strength characteristics, has little deterioration during durability, and can maintain excellent performance over a long period of time. In this case, it is preferable that the outermost resin coating layer constituting the surface of the toner carrier does not contain conductive fine particles from the viewpoint of stabilizing the toner charging property, and in order to stably form an image over a long period of time, It is necessary to set the resistance to 10 ¹⁰ Ω · cm or more without using a conductive agent as much as possible. However, when such a high-resistance resin layer is formed alone as a coating layer on the surface of the toner carrier, , The development bias cannot be sufficiently secured, and the image density decreases. In this case, the charge-up characteristic also deteriorates and image unevenness occurs. Therefore, in the present invention, the first resin coating layer having a relatively good conductivity of 10 ⁹ Ω · cm or less is provided inside the outermost resin coating layer as a coating layer in contact with the conductive elastic base material. In this case, a sufficient developing bias is ensured, and the deterioration of the charge-up characteristic is prevented so that a good image can be reliably obtained.

Accordingly, the present invention provides a semiconductive elastic layer formed on the outer periphery of a good conductive shaft, and carries a toner on the surface to form a thin layer of the toner. In contact or close, by supplying the toner to the surface of the image forming body, in a toner carrier that forms a visible image on the image forming body, the semiconductive elastic layer is formed on a conductive elastic substrate. At least two resin coating layers are provided, and the resistance of the first resin coating layer in contact with the conductive elastic substrate is 10 ⁹ Ω · cm or less, and the outermost resin coating layer constituting the outermost layer is Phenol resin as main material and resistance is 10
^An object of the present invention is to provide a toner carrier characterized by having a resistivity of ¹⁰ Ω · cm or more.

Further, according to the present invention, as an image forming apparatus using a toner carrier, a toner is carried on the surface to form a thin layer of the toner. In an image forming apparatus including a toner carrier that forms a visible image on the surface of the image forming body by supplying the toner to the surface of the image forming body, the toner carrier of the present invention is used as the toner carrier. There is provided an image forming apparatus characterized in that it is used.

Hereinafter, the present invention will be described in more detail.
The toner carrier of the present invention is, for example, as shown in FIG.
A semiconductive elastic layer 3 composed of a conductive elastic substrate 31 and two or more (two layers in the figure) resin coating layers 32 and 33 is provided on the outer periphery of the good conductive shaft 2. In this case, In the present invention, the resistance value of the first resin coating layer 32 that is in contact with the conductive elastic substrate 31 among the resin coating layers 32 and 33 is 10 ⁹ Ω.
Cm or less, and the outermost resin coating layer 33 constituting the outermost layer is formed mainly of phenol resin, and has a resistance value of 10 ¹⁰ Ω · cm or more.

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

Next, as described above, the semiconductive elastic layer 3 formed on the outer periphery of the shaft 2 is formed on the conductive elastic base material 31 by the first resin coating layer 32 and the outermost resin coating layer 33. And at least two resin coating layers are laminated.

The conductive elastic base material 31 is a conductive elastomer obtained by blending an electronic conductive agent such as carbon black or an ionic conductive agent such as sodium perchlorate into an elastomer alone or a foam body obtained by foaming the elastomer to adjust the resistance value. It is formed of an elastic body.

Examples of the elastomer include silicone rubber, urethane rubber, polybutadiene rubber, polyisoprene rubber, natural rubber, styrene butadiene rubber, nitrile rubber, ethylene propylene rubber, acrylic rubber, epichlorohydrin rubber, chloroprene rubber, and mixtures thereof. Among these, urethane rubber,
Polybutadiene rubber, polyisoprene rubber, or the like, or a mixed rubber thereof is preferably used. Further, these elastomers can be chemically foamed by using a foaming agent, or can be used as a foam body which is foamed by mechanically entraining air like a polyurethane foam.

Examples of the conductive agent to be incorporated into the conductive elastic substrate 31 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 ion 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 conductive elastic substrate 31 is not particularly limited.
Although it is not a thing, the combination of the conductive agent
Value 10^Three-10^TenΩcm, especially 10^Four-10⁸Ωcm
Is preferred. Resistance value is 10^ThreeLess than Ωcm
Charge leaks to the photosensitive drum, etc.
-The carrier itself may be destroyed, while 10 ^Ten
If it exceeds Ωcm, ground fogging tends to occur.

The conductive elastic base material 31 has a crosslinking agent for converting the elastomer into a rubbery substance, if necessary.
Vulcanizing agents can be added. 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, 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, in order to control the amount of charge of the toner carried on the surface of the toner carrier, various charge control materials such as nigrosine, triaminophenylmethane, and cationic dye, silicone Fine powders such as resin, silicone rubber, and nylon can be added. In this case, the amount of these additives is 1 to 5 parts by weight of the charge control agent based on 100 parts by weight of the main material.
It is preferable that the weight of the fine powder is 1 to 10 parts by weight.

Here, the elastic body constituting the conductive elastic substrate 31 is not particularly limited, but its tear strength is preferably 10 kg / cm or more, particularly preferably 12 kg / cm or more. In this case, the tear strength can be adjusted by appropriately selecting the combination and the mixing ratio of the base material, the conductive agent and other additives constituting the elastic body, the vulcanization conditions, and the like. The tear strength was measured according to JIS K62.
This is a value measured according to No. 52.

The elastic material constituting the conductive elastic base material 31 has a wear amount of 0.1 cm ³ or less, especially 0.1 mm ³ in a Lambourn abrasion test according to JIS K 6264.
05cm ³ or less, more preferably at 0.03 cm ³ or less, the tear strength by adjusting as described above, it is possible to achieve such good wear resistance. The test conditions for the Lambourn abrasion test were based on JIS.
Appropriate conditions in accordance with K 6264 can be set. In this case, the test conditions such as the slip ratio can be appropriately changed according to the sample. As the specific test conditions, for example, using a No. 40 file, a slip ratio of 99%,
The load can be 4.5 kg, the sample peripheral speed can be 30 cm / sec, and the test time can be 15 seconds.

The durability of the conductive elastic substrate 31 is improved by adjusting the tear strength of the conductive elastic substrate 31 and the wear amount in the Lambourn abrasion test as described above, and the durability of the entire toner carrier is improved. And the object of the present invention can be more reliably achieved.

When the conductive elastic base material 31 is made of urethane, there is no particular limitation, but a piece mainly composed of a polyol component and an isocyanate component and having a siloxane bond in the main chain. It is preferable to form the conductive elastic substrate 31 using a polyurethane containing a terminal alcohol or an amino-modified silicone oil. By using such a polyurethane, the coefficient of friction can be reduced, and the wear resistance can be improved. In addition, the tackiness can be eliminated, and the releasability and the machinability can be improved, and good workability can be obtained.

The polyol component is not particularly limited, and various commercially available polyols can be used. Examples thereof include polyether polyol, polytetramethylene ether glycol, THF-alkylene oxide copolymer polyol, Polyester polyol, acrylic polyol, polyolefin polyol,
Partially saponified ethylene-vinyl acetate copolymers, phosphate-based polyols, halogen-containing polyols, and the like can be suitably used.

The isocyanate component is not particularly limited, and specifically, TDI, MDI, crude-MDI
(Polymeric-MDI) and general-purpose isocyanates such as modified MDI. In addition to these general-purpose isocyanates, 1,5-naphthalene diisocyanate, tolidine diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, p-phenylene diisocyanate, Transcyclohexane-
1,4-diisocyanate, xylylene diisocyanate (XDI), hydrogenated-XDI, hydrogenated-MDI, lysine diisocyanate, triphenylmethane triisocyanate, tris (isocyanate phenyl) thiophosphate, tetramethyl xylene diisocyanate, lysine ester Triisocyanate, 1,6,11-undecane triisocyanate, 1,8-diisocyanate,
Relatively special isocyanates such as 4-isocyanate methyloctane, 1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate, and trimethylhexamethylene diisocyanate can also be suitably used.

As described above, a polyurethane mainly containing the polyol component and the isocyanate component and containing a one-terminal alcohol having a siloxane bond in the main chain or an amino-modified silicone oil is preferably used. Examples of the type alcohol or amino-modified silicone oil include a side chain alcohol or amino-modified silicone oil represented by the following formula (1) and a one-terminal alcohol or amino-modified silicone oil represented by the following formula (2). In addition, the following formula (3) represents a double-ended alcohol or amino-modified silicone oil, and the following formula (4) represents a double-ended alcohol or an amino-modified silicone oil, respectively. These formulas (3) and (4) The above-mentioned effects cannot be obtained with the double-ended alcohol or amino-modified silicone oil shown.

[0032]

Embedded image (Wherein, R ^{1 to} R ⁴ all represent the same or individually different alkylene groups, X represents a hydroxyl group or an amino group,
m represents an integer of 1 or more, and n represents an integer of 0 or more. )

The molecular weight of the above-mentioned one-terminal type alcohol-modified or amino-modified silicone oil is not particularly limited, but may be from 2,000 to 6,000, particularly from 4,000 to 4,000.
Preferably it is 6000. In this case, the molecular weight is 6
Even if the amount exceeds 000, the effect is not particularly improved, while if less than 2,000, a sufficient effect may not be obtained.

The amount of the one-terminal alcohol or amino-modified silicone oil to be added is not particularly limited, but is usually 2 to 1 per 100 parts by weight of the polyol component.
0 parts by weight, particularly preferably 5 to 10 parts by weight,
In this case, even if added in an amount exceeding 10 parts by weight, no further effect can be obtained, and the cost simply increases.

The method for forming the conductive elastic substrate 31 from polyurethane is a so-called one-shot method in which the polyol component and the isocyanate component are simultaneously mixed. The so-called prepolymer method used may be used. In this case, in the one-shot method, the above-mentioned one-terminal alcohol or amino-modified silicone oil may be blended in the above-mentioned weight ratio, and in the prepolymer method, a silicone having a siloxane bond in the main chain in 100 parts by weight of the prepolymer. The prepolymer may be blended in an appropriate amount at 10 parts by weight or less.

The conductive elastic substrate 31 has various charge control agents such as nigrosine, triaminophenylmethane, and cationic dye, silicone resin, silicone rubber, and the like for the purpose of controlling the toner charge amount on the surface of the toner carrier.
Fine powder such as nylon can also be added. In this case, the additive amount of these additives is 1 to 5 parts by weight of the charge control agent and 1 to 10 parts by weight of the fine powder based on 100 parts by weight of the elastic base material such as rubber or polyurethane. Is preferred.

The hardness of the conductive elastic substrate 31 is as follows:
Although not particularly limited, the angle is preferably 85 ° or less, particularly preferably 60 to 75 ° on an Asker-C scale. In this case, if the hardness exceeds 85 °, 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. vice versa,
If the hardness is too low, the frictional force between the photoreceptor and the laminating blade increases, and image defects such as jitter may occur. Further, even when the hardness of the conductive elastic substrate 31 is set to a low hardness, it is preferable to reduce the compression set as much as possible, specifically, it is preferable to set the compression set to 20% or less.

The surface roughness of the conductive elastic substrate 31 is as follows:
Although not particularly limited, the JIS 10-point average roughness is preferably 15 μmRz or less, particularly preferably 3 to 10 μmRz. If the surface roughness exceeds 15 μmRz, the thickness of the toner layer and the uniformity of charging may be impaired.
By adjusting the thickness to 5 μmRz or less, the adhesion of the toner can be improved, and the image deterioration 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 comprises two or more resin coating layers (the first resin coating layer 32 and the outermost resin coating layer in the figure) on the conductive elastic substrate 31. 33 is formed. Among these resin coating layers, the first resin coating layer 32 that is in contact with the conductive elastic base material 31 has a resistance value of 10 ⁹ Ω · cm or less, preferably 10 ⁴ to 10 ⁸ Ω · cm. Things.

The material of the first resin coating layer 32 is not particularly limited as long as it satisfies the above-mentioned resistance value and does not contaminate a partner member 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, alkyd resin, phenol resin, melamine resin, urea resin, silicone resin, polyvinyl resin Butyral resins and the like can be mentioned, and one or more of these can be used as a mixture. In the present invention, urethane resins, polyamide resins, and the like are preferably used from the viewpoint of flexibility, coatability and the like. Urethane resins are particularly preferred.

A conductive agent can be added to the first resin coating layer 32 for the purpose of controlling the conductivity to the above-mentioned resistance value. As the conductive agent, the conductive agent used for the conductive elastic substrate 31 can be used. The same agents as those exemplified above can be exemplified.

Although the thickness of the first resin coating layer 32 is not particularly limited, it is usually 2 to 30 μm, especially 5 to 30 μm.
The thickness is preferably about 20 μm, and if the thickness is less than 2 μm, the base material cannot be sufficiently coated, resulting in an uneven surface, which may cause image unevenness. Then, cracks may occur in the surface layer.

The outermost resin coating layer 33 constitutes a surface layer of the toner carrier of the present invention, and has a resistance value of 10 ¹⁰ Ω · cm formed mainly of phenol resin.
The above is the resin coating layer.

As the phenol resin forming the outermost resin coating layer 33, any of a resol type and a novolak type can be used. More specifically, a simple phenol resin obtained by reacting phenol with formalin, Resorcinol resin using resorcinol instead of phenol,
Resins using a combination of phenol and resorcin, and various modified phenol resins such as melamine-modified, xylene-modified, and epoxy-modified can also be used. Among them are simple phenols,
Resorcinol resins and mixtures thereof are preferably used. In addition, a resol type phenol resin is particularly preferably used because a good cured film can be formed only by heating without the need for a crosslinking agent, and the productivity is excellent.

The outermost resin coating layer 33 has a high electric resistance of 10 ¹⁰ Ω · cm or more as described above, and it is not necessary to particularly mix a conductive agent. To adjust the resistance value. In this case, the conductive agent may be the same as the conductive agent used for the conductive elastic substrate 31. The outermost resin coating layer 33 has a resistance value of 10 ¹⁰ Ω · cm or more as described above, but is preferably 10 ¹¹ Ω · cm or more,
It is preferable to be about 0 ¹² to 10 ¹⁴ Ω · cm.

The outermost resin coating layer 33 is not particularly limited, but it is preferable to add a fluororesin powder to reduce the friction coefficient of the surface. That is, when the coefficient of friction between the layered blade or the like that forms the toner layer during image formation durability and the surface of the toner carrier (the outermost resin coating layer 33) is high, the surface of the toner carrier (the outermost resin coating layer 3).
3) Or, the blade contact surface is worn, which causes image unevenness. In order to prevent this problem, it is necessary to lower the friction of the surface of the toner carrier. When a fluororesin powder is added as a friction-reducing agent, the effect becomes particularly remarkable. In this case, if the particle size of the fluororesin powder used is large, the surface roughness increases, and image deterioration may occur due to an excessive amount of toner transport. The fluororesin powder used has a particle size of 2 μm or less, particularly 1 μm or less. Fine particles are preferred.

The fluororesin powder is not particularly limited, but may be polytetrafluoroethylene (P
TFE), perfluoroalkyl vinyl ether copolymer (PFA), hexafluoropropylene copolymer (F
EP), ethylene tetrafluoride-ethylene copolymer (ETF)
E), polychlorotrifluoroethylene (PCTFE)
And the like, and one or more of these can be used in combination. Of these, PTFE is particularly preferably used.

The amount of the fluororesin particles added is not particularly limited, but the phenolic resin 100
The amount is preferably 10 to 50 parts by weight, more preferably 20 to 30 parts by weight, with respect to parts by weight. If the addition amount is less than 10 parts by weight, a sufficient effect of reducing friction may not be obtained. Exceeding the weight part may make the coating film brittle.

The thickness of the outermost resin coating layer 33 is not particularly limited, but is 1 to 20 μm, particularly 3 to 10 μm.
It is preferably set to μm. In this case, if the thickness is less than 1 μm, the abrasion resistance of the roller surface becomes insufficient and it may not be able to withstand long-term use. When it comes into contact with a mating member such as a photosensitive drum without being able to follow the deformation of the elastic elastic base material 31, cracks or the like may occur, and there is a possibility that the mating member surface such as the photosensitive drum may be damaged.

The roughness of the surface of the roller on which the outermost resin coating layer 33 is formed is not particularly limited, but since it affects good toner transportability, it is generally 2 to 10 JIS 10-point average roughness Rz. It is preferable to adjust the thickness to 30 μm, particularly 5 to 15 μm. In this case, JIS 10 point average roughness R
If z is less than 2 μm, the toner transport amount may be insufficient and the image density may be reduced.
If it exceeds m, the toner may be conveyed to an uncharged toner and fog may occur in the image. The surface roughness of the roller can be adjusted by polishing the surface of the conductive elastic base material 31, and the first resin coating layer 32 and the outermost resin coating layer 33 are coated with fine polymer particles such as fluororesin and silicone resin. Also, inorganic fine particles such as silica, graphite and the like can be mixed to obtain an appropriate roughness. The hardness of the entire toner carrier on which the outermost resin coating layer 33 is formed is not particularly limited, but is preferably 60 to 85 °, particularly preferably 60 to 75 ° in Asker C hardness.

The first resin coating layer 32 and the outermost resin coating layer 33 may optionally contain additives other than those described above. The method for forming the resin coating layers 32 and 33 is not limited, and can be formed by an appropriate method. Usually, the conductive elastic base material is formed by a resin solution containing the base resin component and additives. 31 or first resin coating layer 32
Is preferably employed. 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 base resin,
Usually, lower alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, toluene and xylene are preferably used.

Here, the first resin coating layer 32 is used.
And a resin coating layer having a two-layer structure with the outermost resin coating layer 33, the resin coating layer of the toner carrier of the present invention is not limited to such a two-layer structure. Another resin coating layer may be provided between the first resin coating layer 32 and the outermost resin coating layer 33 as long as the purpose is not deviated.

Although the toner carrier of the present invention is not particularly limited, it has an electric resistance of 10 ¹⁰ Ω when a voltage of 100 V is applied.
Hereinafter, it is particularly preferable to configure so as to be 10 ⁴ to 10 ⁶ Ω. In this case, if the resistance value is less than 10 ⁴ Ω, it may be 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. In some cases, it becomes impossible to secure a developing bias, and it is impossible to obtain a sufficient image density. 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 appropriately and uniformly control the resistance value of the toner carrier in order to maintain the electric field strength for toner movement properly and uniformly. Are necessary, but not necessarily sufficient, to make the amount of charge of the toner proper and uniform. That is, in addition to the resistance value, it is important to control the charge holding ability of the surface of the toner carrier and keep it uniform, in order to make the toner charge amount appropriate and uniform. 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. Improvements in accuracy by the four-terminal method have also been proposed, but particularly in the case of a stacked toner carrier, the surface layer is a very thin layer, 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 addition to the resistance value when 100 V was applied, a voltage of 8 kV was applied to a corona discharger arranged at a distance of 1 mm from the surface of the toner carrier to generate corona discharge to charge the surface. In this case, it is effective to evaluate the surface charge retention ability based on the maximum value of the surface potential after 0.35 seconds, and set the maximum value to 100 V or less, especially 50 V
It is preferable to form the toner carrier as follows in order to reproduce a good image over a long period of time.
In this case, if the maximum value exceeds 100 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 may be low. Also, when the toner continues to rotate 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 of the photoconductor or the like is not obtained. Discharge occurs between the formed member and the formed member, and image defects may occur.

The above can be summarized as follows. In other words, if the charge holding ability of the surface of the toner carrier is too high, the reverse charge of the developed toner remains on the surface, and the conditions will be different when new toner is carried next time. For this reason, an image defect may occur in which the image density differs between the front end portion and the rear end portion of the image.
The electric resistance at the time of application of 0 V is 10 ⁴ to 10 ¹⁰ Ω, and 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 to charge the surface. By configuring the toner carrying member such that the maximum value of the surface potential after 0.35 seconds after the above is 100 V or less, such a problem does not occur.
A good image can be surely formed.

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 maximum 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. 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.

Further, the toner carrier of the present invention is not limited to such a developing device. For example, the toner carried on the toner carrier is formed on an image forming body made of paper sheets via a control electrode in the form of a hole. It is also suitably used in an image forming apparatus which forms an image by directly flying.

[0061]

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 to 5] A conductive elastic substrate, a first resin coating layer and an outermost resin coating layer were formed by the following method, and the developing roller (Table 1 and Table 2) (Toner carrier).

[Formation of Conductive Elastic Substrate] Examples 1 and Comparative Examples 1-4 Polyether polyol having a hydroxyl value of 33.0 (SBU polyol 0610, manufactured by Sumitomo Bayer Urethane Co., Ltd.) 1
00 parts by weight and a side chain alcohol-modified silicone oil having a siloxane bond in the main chain represented by the general formula (1) (manufactured by Toray Dow Corning Silicone Co., Ltd., SF8
428) 1 part by weight, dibutyltin dilaurate 0.01
Parts by weight, 1,4-B. D. 1 part by weight of (butanediol) (manufactured by Tosoh, 1,4-BD), alkyldiphenylamine (manufactured by Seiko Chemical Co., Ltd., steerer STAR)
0.5 parts by weight and 3.5 parts by weight of acetylene black (Denka Black, manufactured by Denki Kagaku Kogyo Co., Ltd.)
After defoaming under reduced pressure for 0 minutes, a urethane-modified MDI having an NCO% of 23.0 (BASF INOAC Polyurethane Co., Ltd.)
(Ipratenate MP102) was added and stirred for 3 minutes while defoaming under reduced pressure.

The obtained urethane composition was poured into a mold having an inner diameter of 22 mm on which a metal shaft was set.
After being cured for 16 hours, the mold was removed, and polished to a predetermined outer diameter and a surface roughness Rz of 5 μm to form a conductive elastic substrate made of polyurethane on the outer periphery of the shaft.

Example 2 and Comparative Example 5 65 parts by weight of polybutadiene rubber and polyisoprene rubber 3
5 parts by weight, ink carbon was added to the mixed rubber to a concentration of 15% by weight, mixed well, poured into a mold having a metal shaft set, and heated at 90 ° C. for 1 hour. After curing with sulfur, a conductive elastic substrate was formed on the outer periphery of the shaft. On the other hand, a test piece was molded from the same composition under the same vulcanization conditions, the tear strength was measured according to JIS K6252, and JIS K62 under the following test conditions.
When a Lambourn abrasion test was performed by a method based on No. 64, the tear strength was 10.59 kg / cm and the Lambourn abrasion amount was 4.85 × 10 ⁻² cm ³ . Test conditions for Lambourn abrasion test Grinding wheel: sandpaper No. 40 Slip ratio: 99% Sample peripheral speed: 30 cm / sec Load: 4.5 kg Test time: 15 sec

[Formation of First Resin Coating Layer] Examples 1 and 2 and Comparative Example 3 The polyol component was a polyester (adipic acid and 1,4
A polycondensate of butanediol) and a polyurethane in which the isocyanate is methylenebisphenyl diisocyanate (the molecular weight is Mn = 80000 in terms of polystyrene, M
w = 140000) as a binder, which was diluted with a mixed solvent of methyl ethyl ketone and dioxane,
A solution having a resin concentration of 10% by weight was prepared. To this solution was added 13 parts by weight of HFC carbon for color (specific surface area: 260 m ² / g, oil absorption: 40 ml / 100 g) based on 100 parts by weight of the above polyurethane, and dispersed and mixed by a red devil method to prepare a coating solution. did. Using this coating solution, a first resin coating layer was formed on a conductive elastic substrate by a dipping method, and dried at 100 ° C. for 1 hour.

[Formation of Outer Resin Coating Layer] Examples 1 and 2 and Comparative Examples 1 and 2 Resole type phenol resin (PR5, manufactured by Sumitomo Durez Co., Ltd.)
0781) and PTFE (LD100E, manufactured by Daikin Industries, Ltd., average particle size: 0.2 μm) as a fine powder of fluororesin so as to have a weight ratio of 3: 1. After dissolving in ethanol and adding glass beads, the mixture was shaken with a paint shaker for 6 hours to prepare a coating solution. Using the obtained coating solution, an outermost resin coating layer is formed by a dipping method.
It was dried and cured by heating at 10 ° C. for 4 hours.

Comparative Example 3 Oil-free alkyd resin (“M64” manufactured by Dainippon Ink and Chemicals, Inc.)
02 ") and a melamine resin (" L14 "manufactured by Dainippon Ink and Chemicals, Inc.)
5 ") was mixed at a weight ratio of 7: 3, and this was dissolved in methyl ethyl ketone so as to have a total amount of 15% by weight to prepare a coating solution. An outermost resin coating layer was formed by a dipping method using the obtained coating solution.

For each of the obtained toner carriers, the roller resistance, the surface roughness Rz, the surface potential after 0.35 seconds, and the Asker C hardness were measured. The results are shown in Tables 1 and 2 as physical properties. Note that the roller resistance was measured by applying a voltage of 100 V using the rotation resistance measuring instrument shown in FIG. 5, and the surface potential after 0.35 seconds was the surface potential shown in FIG. This was measured by the measuring unit shown in FIG. 3 using the measuring device under the conditions described above.

For each toner carrier, the initial roller characteristics (toner charge amount, toner transport amount),
The initial image (image density, fog, difference in front and rear edges, halftone spots), durability characteristics, blade contact marks, and photoconductor contamination were evaluated. The results are shown in Tables 1 and 2.

[Toner Charge Amount (q / m), Toner Conveyance Amount (m / a)] Each roller is attached to the developing unit shown in FIG. 2 as a developing roller, and rotated at a peripheral speed of 50 mm / sec. A uniform thin layer of toner is formed on the roller surface, and the thin layer of toner is sucked and introduced into a Faraday gauge,
The amount of charge was measured, and at the same time, the weight of the toner sucked and sucked was measured to determine the amount of toner charge per unit weight. Further, the area of the portion from which the toner was removed by suction was measured, and the toner weight per unit area was calculated to obtain the toner transport amount. [Evaluation of Image] Each roller was used as a developing roller and attached to the developing unit shown in FIG. 2, and a developing bias of -400 V and a blade bias of -600 V were used. Speed 60mm / sec
An image was formed by reversal development while rotating at a peripheral speed of, and image evaluation was performed on a white background, a halftone image, and a black background image. In this case, the tenth sheet as the initial image and the five sheets before and after the 10,000th printed image as the durable image were evaluated.
In the case of a black background image, the difference between the density at the leading edge of the printing and the density at the trailing edge of the printing was evaluated as the difference between the leading edge and the trailing edge. [Blade Pressing Mark] FIG.
Was left for one month in a state where the blade and the roller were in contact with each other at a constant pressure, and then a halftone image was printed to evaluate the presence or absence of a trace on the contact surface between the roller and the blade. [Photoconductor contamination] Each roller was set as a developing roller in the developing unit shown in FIG. 2 and left in an environment of 50 ° C. and 80% RH for 5 days while being in contact with the photoconductor. A halftone image was printed using the photoconductor after standing, and the presence or absence of a trace on the contact surface between the roller and the photoconductor was evaluated.

[0071]

[Table 1]

[Table 2]

As shown in Tables 1 and 2, it was confirmed that the toner carrier of the present invention can stably reproduce a good image over a long period of time.

[0073]

As described above, according to the toner carrier of the present invention and the image forming apparatus using the same, it is possible to sufficiently meet the demand for higher image quality, and to obtain a white image even when used for a long time. It is excellent in durability and can reliably reproduce a high-quality image over a long period of time without causing fog, roughness of a halftone image, or shading of a black image.

[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 the shape and dimensions of a measuring unit of the surface potential measuring device 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 resistance measuring instrument used in Examples and Comparative Examples.

FIG. 6 is a schematic sectional view showing an example of a conventional toner carrier.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developing roller (toner carrier) 2 shaft 3 semiconductive elastic layer 31 conductive elastic base material 32 first resin coating layer 33 outermost resin coating layer 4 toner coating roller 5 photosensitive drum (image forming body) 6 toner ( 7 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

Continued on the front page (72) Inventor Toshiaki Arai 3-5-5-843 Ogawahigashi-cho, Kodaira-shi, Tokyo F-term (reference) 2H077 AD06 AD13 AD35 AE09 EA14 EA15 EA16 FA01 FA13 FA22 FA25 3J103 AA02 AA15 AA36 AA51 AA85 BA41 FA30 GA02 GA57 GA58 HA02 HA06 HA11 HA12 HA20 HA32 HA33 HA37 HA41 HA48 HA53 4J034 CA01 CD07 DA01 DA03 DB03 DF01 DG02 DG06 DM01 DM05 DP12 DP18 HA01 HA07 HC03 HC12 HC13 HC35 QB12 QB15

Claims (8)

[Claims] 1. A semiconductive elastic layer is formed on the outer periphery of a good conductive shaft, and a thin layer of the toner is formed by carrying a toner on the surface of the shaft. In the toner carrier that forms a visible image on the image forming body by supplying the toner to the surface of the image forming body, the semiconductive elastic layer has at least two layers on a conductive elastic substrate. A resin coating layer is provided, and the resistance of the first resin coating layer in contact with the conductive elastic substrate is 10 ⁹
Ωcm or less, the outermost resin coating layer constituting the outermost layer is
A toner carrier comprising a phenol resin as a main material and having a resistance of 10 ¹⁰ Ω · cm or more. 2. The toner carrier according to claim 1, wherein the phenol resin forming the outermost resin coating layer is a resol type phenol resin. 3. The toner carrier according to claim 1, wherein said outermost resin coating layer contains fine particles of fluororesin of 2 μm or less. 4. The electric resistance when 100V is applied is 10 ⁴ -1.
0 is ¹⁰ Omega, and 0 in the case of applying a voltage of 8kV to the corona discharger disposed at an interval of the toner carrying member surface and 1mm charges the surface by generating corona discharge.
The toner carrier according to any one of claims 1 to 3, wherein the maximum value of the surface potential after 35 seconds is 100 V or less. 5. The conductive elastic base material has a tear strength of 10 k.
The toner carrier according to any one of claims 1 to 4, wherein the toner carrier is made of an elastic body having a particle size of g / cm or more. 6. The toner carrier according to claim 5, wherein the elastic body forming the conductive elastic base material has a wear amount of 0.1 cm ³ or less in a Lambourn abrasion test according to JIS K 6264. 7. The conductive elastic base material is mainly composed of a polyurethane mainly composed of a polyol component and an isocyanate component, and contains one-terminal alcohol or amino-modified silicone oil having a siloxane bond in the main chain. The toner carrier according to claim 1. 8. A toner is carried on the surface to form a thin layer of the toner.
8. An image forming apparatus comprising a toner carrier for forming a visible image on the surface of the image forming body by supplying the toner to the surface of the image forming body, wherein the toner carrier is used as the toner carrier. An image forming apparatus using the toner carrier according to claim 1.