JP2006003758A - Toner carrier, developing device, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner carrier, a developing device, a process cartridge, and an image forming apparatus which have a distribution of appropriate stable charged toner and to provide an image carrier capable of responding to environmental problems. <P>SOLUTION: The toner carrier renders an electrostatic latent image visible by holding toner thereon while rotating and by supplying the toner onto an image carrier in contact with or close to the image carrier on which the electrostatic latent image has been formed. The toner carrier has a coating layer on its substrate. The ionization potential of the coating layer is smaller than the ionization potential of the toner by 0.1eV or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a toner carrier, a developing device, a process cartridge, and an image forming apparatus for visualizing an electrostatic latent image with a non-magnetic one-component developer, such as an electrophotographic apparatus such as a copying machine or a printer, or an electrostatic recording apparatus. Is.

Conventionally, an image forming apparatus is known.
For example, “Development method and developing apparatus for electrostatic latent image” in Patent Document 1 has a problem of preventing image defects such as fogging and image memory, and a developer for charging a negatively charged developer by frictional charging. The ionization potential of the developer roller is 4.5 to 5.5 eV, the developing roller contains carbon black having a pH of 5 or more, and the ionization potential is adjusted to be lower than that of the developer (preferably 4.5 to 5.3 eV). The layer comprises one or more lubricants selected from monoester lubricants and fatty acid ester lubricants and / or ester-type nonionic surfactants, sorbitan ester-type nonionic surfactants, and sorbitan etherester-type non-layers. 1 type, or 2 or more types of nonionic surfactant chosen from an ionic surfactant is contained. Further, when the positively charged developer is charged by frictional charging, the ionization potential of the developer is 4.5 to 5.5 eV, the developing roller contains an ionic conductive agent, and the ionization potential is higher than that of the developer (preferably It is disclosed to adjust to 4.7 to 5.5 eV).
The developing device of the present invention uses a non-magnetic one-component development as a developing method, and has a configuration of a highly conductive shaft and a conductive layer (the conductive layer may be an elastic body and a surface layer, or only a surface layer. It is taught that it is possible.

  In addition, the “developing device” of Patent Document 2 contains two or more types of emulsion resin particles having different particle sizes in the toner carrier surface layer in order to increase the strength of the surface layer and appropriately charge the toner. And using a negatively chargeable toner having at least one particle size of 0.2 μm or less and another particle size ratio of 5 or less, the work function of the surface of the toner carrier is in the range of 4 to 5 eV. . The developing method of this apparatus is non-magnetic one-component development. The apparatus (toner carrier) of the present invention includes a metal body, a surface layer or a metal body, an elastic body, and a surface layer. In Comparative Example 1, the work function is 4.7 eV, but ΔID is as large as 0.4, and a stable image density cannot be provided over a long period of time. As its technical basis, it is stated that the particle size ratio is 6. Although the value of the work function is defined as 4 to 5 eV, its effect is technically unclear.

  Patent Document 3 discloses a method and an apparatus for developing an electrostatic latent image in which a negatively charged developer is charged by charge injection in order to prevent image defects caused by image memory or normal fog. The ionization potential is set to 4.5 to 5.5 eV, and the ionization potential of the developing roller not containing conductive powder is adjusted to be 0.3 eV or more higher than that of the developer. An invention is disclosed in which a conductive shaft and a conductive layer (the configuration of the conductive layer may be an elastic body, a surface layer, or only a surface layer).

  Patent Document 4 discloses a method and an apparatus for developing an electrostatic latent image. In order to prevent image defects due to image memory and normal fog, ionization of a developer is performed when a charged developer is charged by charge injection. The potential is set to 4.5 to 5.5 eV, the developing roller contains carbon black having a pH of 5 or more, and the ionization potential is adjusted to below the developer (preferably 4.5 to 5.3 eV). One or more lubricants selected from monoester lubricants and fatty acid ester lubricants and / or ester type nonionic surfactants, sorbitan ester type nonionic surfactants and sorbitan ether ester type nonionic types 1 type or 2 or more types of nonionic surfactant chosen from surfactant is contained. The developing method of the apparatus is non-magnetic one-component development, and its configuration is a highly conductive shaft and a conductive layer (the conductive layer may be an elastic body and a surface layer, or only a surface layer). It has become.

  In addition, in the “developing apparatus” of Patent Document 5, the toner carrier has an elastic layer having a hardness of 70 degrees or less and a thickness of 7 to 50 μm in order to prevent noise due to uneven image density and leakage, and is not in contact with the image carrier. Ra is 0.5 to 2.0 μm, and the work function is 4.30 to 5.00 eV. The developing method of the apparatus is non-magnetic one-component development (non-contact), and the developing unit has a metal body and an elastic layer.

  In addition, in “Liquid developer for electrostatic latent image, image forming apparatus, apparatus unit, and facsimile apparatus” of Patent Document 6, characters are thinned in a character image, and density is reduced in a halftone or solid black image. In order to prevent the fading phenomenon, γ (inclination [Y / eV]) in the work function measurement of the surface of the developer carrying member is 10 or more, and a multi-pole permanent magnet using magnetic one-component development as a developing method. It is described that the roller, the developing sleeve, the surface of the developing sleeve contain conductive fine particles and / or a solid lubricant, and the base uses a phenol resin.

  In addition, in the “developing roll and developing device” of Patent Document 7, the surface of the developing roll has a small and highly charged region where one-component developer is easily charged, and a single one in order to prevent development ghost and reduce fog in non-image areas. The minute non-charged region where the component developer is difficult to be charged is closely mixed and exposed, and the difference between the ionization potential of the developer and the average ionization potential of the developing roll is 0.2 to 1.2 eV. The difference in ionization potential between the charged area and the minute non-charged area is 0.2 to 1.2 eV. As a developing method, magnetic one-component development is performed, and as a configuration, a magnet roller, a developing sleeve, and a surface layer are formed. Yes.

  In addition, in the “image agent carrier and developing device using the same” in Patent Document 8, in order to prevent development ghost, the developer carrier surface layer is made of a conductive paint in which conductive fine particles are dispersed in a resin. The electron carrying efficiency Yield / eV of the developer carrying member is set to 5 or more and 30 or less, and the developing method is magnetic one-component development. The constitution includes a magnet roller, a developing sleeve, a surface layer It is disclosed that it consists of.

In addition, in the “one-component developer carrying method and one-component developer developing method” of Patent Document 9, a negatively chargeable developer is used to prevent uneven image density, and the work function of the developer carrier is set to 4. 0.7 eV or less, Ra is 1.0 to 2.0 μm, concavo-convex pitch is 3.8 μm or less, the effective line length is 101% or less, the developing system uses magnetic one-component development, and the configuration is metal An invention comprising a body and a resin layer is disclosed.
Japanese Patent No. 3000919 JP 2002-148936 A Japanese Patent No. 3000920 Japanese Patent Laid-Open No. 2000-066651 JP 2002-207361 A Japanese Patent No. 3005081 JP-A-9-244395 Japanese Patent Laid-Open No. 10-063088 JP 2001-296735 A

The present invention has been made in view of the following points.
1. Life of toner carrier In recent years, in electrophotographic apparatuses such as copying machines, printers, facsimiles, etc., especially in the field of small machines, the maintenance has been simplified, and development using a non-magnetic one-component developer (toner) The system has been put into practical use (FIG. 1).
In general, a toner carrying body (FIG. 7) made of an elastic material such as rubber or elastomer is used, a contact developing method for a drum or belt photoreceptor, a toner carrying body made of a metal material such as aluminum or stainless steel (FIG. 8). Various types of contact developing methods for belt photoreceptors and toner carriers used for the same have been proposed. A toner bearing member is brought into contact with the drum or belt photosensitive member on which the electrostatic latent image is formed, and the toner thinned on the surface of the toner bearing member is moved in accordance with the developing electric field to make a visible image. To do. This method has the advantage that colorization is easy without using a magnetic material for the toner. However, in the developing device as shown in FIG. 1, the surface of the toner carrying member or the toner layer is formed due to the stress on the toner at the contact portion with the toner layer forming member and the replenishing roller which are the contacting members to the toner carrying member. The toner tends to stick to the surface of the member and often takes the form of a cartridge that can be replaced with several k to several k prints due to scraping of the toner carrier or generation of scratches. In recent years, there has been a problem that cartridges have to be recycled due to environmental problems, and due to price reduction, a means has been proposed for reducing the running cost per print by keeping the developing device stationary. ing. For that purpose, it is necessary to make the developing device have a long life (e.g., equivalent to a mechanical life of about 1200 k print), and therefore it is important to improve the durability (abrasion resistance) of the toner carrier.

In order to improve the durability (wear resistance) of the toner carrier, a polyurethane resin having excellent mechanical strength is often used for the coating layer. Further, in order to further increase the mechanical strength, a condensed cross-linked product is often formed with an amino resin. However, when the coating layer does not wear at all, toner sticking is likely to occur, preventing good development and preventing providing a good image. Therefore, it is better that the coating layer of the toner carrier is appropriately worn.
The amino resin has many nitrogen groups in the molecular structure, and it is known that these nitrogen groups greatly contribute to the chargeability of the toner. However, it has been confirmed that condensation crosslinked products with amino resins tend to concentrate (localize) on the surface of the coating layer (Reference 1). Therefore, the conventional toner carrier initially has a high toner charge amount, can perform high-quality development, and can provide a high-quality image. However, as the coating layer wears over time, On the layer, the ratio of the condensation cross-linked product due to the amino resin is reduced, the chargeability of the toner is lowered, not only preventing good quality development, but also reducing the ability to electrostatically adsorb the toner, This also causes toner scattering. In order to achieve stable toner chargeability over time, it is extremely important to have a technique in which a condensation cross-linked product of an amino resin is almost stably present inside the coating layer.

2. In recent years, regarding the environmental aspect, there has been a demand for a reduction in VOC (Volatile Organic Compounds) with respect to coating, and a shift from solvent-based paints to water-based paints is being made. Even in the manufacturing process, it is important to remove the solvent in order to improve the working environment and prevent the discharge of harmful substances to the outside.

  An object of the present invention is to provide a toner carrier, a developing device, a process cartridge, and an image forming apparatus that have an appropriate and stable toner charge amount distribution, and to provide a toner carrier that can cope with environmental problems. .

As a result of intensive studies, the authors have found that there is a very important relationship between the ionization potential of the polyurethane + amino resin coating layer and the toner chargeability.
The ionization potential is the energy required to separate one electron from an atom or molecule in the ground state to infinity and dissociate it into a cation and a free electron, and ultraviolet light (4.2 to 6.2 eV). ), The photoelectrons emitted at this time are measured, and can be easily obtained from the threshold value of the power plot (normalized photon yield) of the quantum efficiency. The higher the electron donating property, the smaller the ionization potential value and the positive charging property, and the stronger the electron accepting property, the larger the ionization potential value and the tendency to exhibit the negative charging property. In other words, a smaller ionization potential is better for charging the toner more negatively. Also, the slope of the normalized photon yield (Y / eV) represents the photoelectron emission efficiency, and a larger slope (Y / eV) is better for charging the toner more negatively.

  It is an object of the present invention to provide a toner carrier having an appropriate toner charge amount. In the present invention, since a negatively chargeable toner is used, the coating layer itself needs to be positively charged with respect to the toner, and the toner needs to be negatively charged. Therefore, mention was made of the ionization potential of the coating layer and the slope of the normalized photon yield.

The second object of the present invention is to provide a toner carrier having an appropriate toner charge amount distribution and excellent wear resistance. In other words, it was mentioned that a polyurethane resin having excellent wear resistance is used as a base resin, and at least one amino resin that greatly contributes to the chargeability of the toner is added to form a condensed cross-linked product.
The object of the present invention is to provide a conductive toner carrier. That is, in the present invention, since the potential difference is used for the movement of the toner, the toner carrier must be conductive.

  Another object of the present invention is to provide a toner carrier that can cope with environmental problems. Recently, reductions in the amount of volatile solvents represented by toluene and xylene have been screamed. There are also warnings about the effects on the human body. Under such circumstances, the social mission is to actively move to water-based paints that are environmentally friendly (improvement of working environment and prevention of harmful substances to the outside). Therefore, mention was made of using a polyurethane resin composition emulsified and dispersed in water.

It is an object of the present invention to provide a toner carrier having a stable toner charge amount distribution. As the coating layer wears, the inside of the coating layer gradually becomes the toner carrying surface. Therefore, mention was made of the ionization potential inside the coating layer and the slope of the normalized photon yield.
The object of the present invention is to provide a developing device having an appropriate and stable toner charge amount distribution.

  The object of the present invention is to provide a process cartridge having an appropriate and stable toner charge amount distribution.

  It is an object of the present invention to provide an image forming apparatus having an appropriate and stable toner charge amount distribution.

  The toner carrier according to claim 1, wherein the electrostatic latent image that supplies toner on the image carrier in contact with or in proximity to the image carrier on which the electrostatic latent image is formed by carrying the toner while rotating. In the toner carrier to be visualized, the toner carrier has a coating layer on a substrate, and the ionization potential of the coating layer is 0.1 eV or more smaller than the ionization potential of the toner.

  The toner carrier according to claim 2, wherein the coating layer is formed of a condensation cross-linked product of a polyurethane resin having a carboxyl group in the molecule and one or more amino resins. To do.

  According to a third aspect of the present invention, in the toner carrier according to the first or second aspect, the coating layer contains carbon black.

  A toner carrier according to a fourth aspect is the toner carrier according to the second aspect, wherein the polyurethane resin is a polyurethane resin emulsified and dispersed in water.

  The toner carrier according to claim 5 is characterized in that, in any one of claims 1 to 4, the normalized photon yield Y and the slope (Y / eV) of the excitation energy eV are 20 or more.

  According to a sixth aspect of the present invention, in the fifth aspect, the outermost layer of the coating layer is removed.

  The toner carrier according to claim 7 is characterized in that, in claim 6, the ionization potential of the toner carrier after removing the outermost layer of the coating layer is smaller than the ionization potential before removing the outermost layer of the coating layer. To do.

  The toner carrier according to claim 8 is characterized in that, in claim 7, the inclination (Y / eV) after removing the outermost layer of the coating layer is larger than that before removing the outermost layer of the coating layer. .

  According to a ninth aspect of the present invention, in the first to fifth or eighth aspect, the ionization potential of the coating layer is approximately 5 eV.

  According to a tenth aspect of the present invention, the toner carrier according to the ninth aspect is mounted.

  The eleventh aspect is the developing device according to the tenth aspect, wherein the ionization potential of the toner is approximately 5.8 eV, and the slope of the normalized photon yield Y and the excitation energy eV (Y / eV) is approximately 50. It is characterized by being.

  A twelfth aspect is a process cartridge in which the developing device according to the eleventh aspect is mounted.

  A thirteenth aspect of the present invention is an image forming apparatus on which the process cartridge according to the twelfth aspect is mounted.

  In a toner carrier that visualizes the electrostatic latent image by supplying toner to the surface of the image carrier in contact with or close to the image carrier on which the electrostatic latent image is formed while carrying the toner. In claim 1, the toner carrier has a structure having a coating layer on a substrate, and the ionization potential of the coating layer is 0.1 eV or more smaller than the ionization potential of the toner. Since the electron donating property of the coating layer is stronger than that of the coating layer, the coating layer exhibits positive chargeability and the toner exhibits negative chargeability. Therefore, the toner is more negatively charged, and a toner carrier having an appropriate toner charge amount can be provided.

  Further, in claim 2, the coating layer is a polyurethane resin excellent in abrasion resistance in a toner carrier formed by a condensation crosslinked product of a polyurethane resin having a carboxyl group in the molecule and at least one amino resin. Further, by forming a condensation cross-linked product with an amino resin, it is possible to provide a toner carrier having further excellent wear resistance. Further, by using an amino resin that greatly contributes to the toner chargeability, it is possible to provide a toner carrier that charges the toner more negatively.

  According to a third aspect of the present invention, a conductive toner carrier can be provided at a low cost in a toner carrier in which the coating layer contains carbon black. Further, since carbon black also functions as a reinforcing agent and a lubricant for the coating film, it is possible to provide a toner carrier excellent in wear resistance.

  According to the fourth aspect of the present invention, in the toner carrier that is a polyurethane resin composition in which the polyurethane resin is emulsified and dispersed in water, VOC can be reduced, the working environment of the coating process is improved, and the burden on the environment is reduced. Reduced. Since the solution is water, the paint is easy to level and the surface of the toner carrier can be smoothed.

  According to the fifth aspect of the present invention, in the toner carrier in which the normalized photon yield Y and the slope Y / eV of the excitation energy eV at the time of ionization potential measurement are 20 or more, since the electron emission efficiency is excellent, the toner is more negatively charged. Thus, a toner carrier having an appropriate toner charge amount can be provided.

  According to the sixth aspect of the present invention, in the toner carrier from which the outermost layer of the coating layer is removed, the oxidation product formed in the outermost layer can be removed, and the condensation crosslinked product of the amino resin can be put out on the surface. A toner carrier having a toner charge amount can be provided.

  In claim 7, the ionization potential after removing the outermost layer of the coating layer is smaller than the ionization potential before removing the outermost layer of the coating layer, even if the coating layer is worn at least in the toner carrier, A toner carrier having a stable toner charge amount can be provided.

  According to the eighth aspect of the present invention, the inclination after removing the outermost layer of the coating layer is stable even when the coating layer is worn at least on the toner carrier, as compared with the inclination before removing the outermost layer of the coating layer. A toner carrier having a toner charge amount can be provided.

  According to the ninth aspect of the present invention, it is possible to provide a toner carrier having an appropriate toner charge amount in a toner carrier in which the ionization potential of the coating layer is approximately 5 eV.

  According to a tenth aspect of the present invention, in the developing device including the toner carrier according to the ninth aspect, the toner charge amount distribution on the toner carrier is appropriate and stable over time. A developing device having an appropriate and stable toner charge amount distribution can be provided. Further, it is possible to provide a developing device that does not cause toner scattering.

  According to claim 11, in the developing device according to claim 10, the ionization potential of the toner is approximately 5.8 eV, and the slope Y / eV of the normalized photon yield Y and the excitation energy eV is approximately 50. Since the toner charge amount distribution on the toner carrier is appropriate and stable over time even when the coating layer is worn, a developing device having an appropriate and stable toner charge amount distribution can be provided. it can. Further, it is possible to provide a developing device that does not cause toner scattering.

  According to a twelfth aspect of the present invention, in the process cartridge equipped with the developing device according to the eleventh aspect, since the toner charge amount distribution on the toner carrier is appropriate and stable over time, a high-quality toner image (unfixed) ) Can be provided. Further, it is possible to provide a process cartridge that does not cause toner scattering.

  According to a thirteenth aspect of the present invention, in the image forming apparatus equipped with the process cartridge according to the twelfth aspect, the toner charge amount distribution on the toner carrying member is appropriate and stable over time, so that a high-quality image is provided. be able to. Further, it is possible to provide an image forming apparatus that does not cause toner scattering.

  1, 2 and 3 are views showing an example of a developing apparatus according to the present invention. 4, 5 and 6 are views showing an example of a process cartridge according to the present invention. FIG. 4 has the developing device shown in FIG. 1 mounted thereon. FIG. 5 is a view in which the developing device of FIG. 2 is mounted. FIG. 6 has the developing device of FIG. 3 mounted thereon. The operation will be described with reference to the process cartridge.

  In the operation of FIG. 4, the toner carrier 111, the toner supply member 112 formed by forming a foam on a metal core, and the toner stirring member 113 are pivotally supported on the side plate of the case 114. The toner 116 is supplied to the surface of the toner carrier 111 via the toner stirring member 113 and the toner supply member 112. The toner supplied onto the toner carrier 111 is thinned to a predetermined amount by the toner layer regulating member 115 and charged when passing through the toner layer regulating member 115. The charged toner is conveyed to the photoreceptor 211 through the toner carrier 111. The toner carrier 111 is in contact with (bite into) the photosensitive member 211, and a bias voltage (not shown) between the charged potential of the photosensitive member 211 and the residual potential after light writing (after exposure) is applied via the electrodes. . The toner on the toner carrier 111 is conveyed to a contact portion with the photoconductor 211, and charged toner adheres to the photoconductor 211 according to the photoconductor potential and the developing electric field generated by the developing bias supplied from the bias power source 213. The electrostatic latent image is visualized. The photosensitive member 211 has a drum shape, but is not limited thereto. The charging member 212 has a roll shape, but is not limited to this. Further, the rotation direction of the toner supply member 112 may be forward or reverse (the forward direction in the figure) with respect to the rotation direction of the toner carrier 111.

  In FIG. 5, the toner layer regulating member 125 has a roller shape. The basic operation is the same as in FIG. The toner layer regulating member 125 is pressed against the toner carrier 121 by an elastic member such as a spring 127 and bites into the toner carrier 121 to form a nip. The operation of the toner layer regulating member 125 is stationary when the toner carrier 121 develops the electrostatic latent image on the photoreceptor 221 with toner (when the toner carrier 121 is rotating). After the developing operation of the carrier 121 is completed, the toner layer regulating member 125 is rotated by rotating in the reverse direction to be changed to a new contact surface.

  A one-way clutch is disposed at the end of the toner layer regulating member 125 so that it can rotate only in a predetermined direction. In addition to the intermittent rotation, the operation of the toner layer regulating member 125 can be rotated together with the toner carrier 121 at the time of development if the motor torque of the apparatus is sufficient and there is no problem such as banding. The rotation direction may be forward or reverse with respect to the rotation direction of the toner carrier 121. The toner layer regulating member 125 is desirably conductive and adjusts the resistance when applying a voltage, but may be insulating when no voltage is applied. The photosensitive member 221 has a drum shape, but is not limited to this. The charging member 222 has a roll shape, but is not limited thereto.

  In the operation of the developing device shown in FIG. 6, the toner is charged by the developer 137 and the developer toner 136 adhered to the surface of the developer supply member (magnet roller) 132 by magnetic force is supplied to the toner carrier 131 as a bias power source. The electrostatic latent image on the photosensitive member 231 is developed by the supply bias supplied from 138 and the development bias supplied from the bias power source 233.

The toner to be used is a charge control agent (CCA), a colorant, and a low softening point substance (wax) dispersed in a resin such as polyester or polyol, and a substance such as silica or titanium oxide is externally added to the surroundings. Increased fluidity. The toner is produced by a conventional pulverization method or a polymerization method such as an emulsion or suspension polymerization method.
Examples of the external additive include aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, zinc oxide and other metal oxides, nitrides such as silicon nitride, and carbides such as silicon carbide. And metal salts such as calcium sulfate, barium sulfate and calcium carbonate, fatty acid metal salts such as zinc stearate and calcium stearate, carbon black and silica. The particle size of the external additive is usually in the range of 0.1 to 1.5 μm, and the addition amount is 0.01 to 10 parts by weight, preferably 0.05 to 100 parts by weight with respect to 100 parts by weight of the toner particles. 5 parts by weight are used. These external additives may be used alone or in combination. These external additives are more preferably hydrophobized.

Examples of the colorant include carbon black, phthalocyanine blue, quinacridone, and carmine.
The range of the volume average particle size and the uniform particle size of the toner is preferably 3 to 12 μm, but in this embodiment, it is about 6.5 μm and can sufficiently cope with a high resolution image of 1200 dpi or more.
It is also possible to add a low softening substance inside the toner. Examples of the low softening point substance include paraffin wax, polyolefin wax, Fischer tropish wax, amide wax, higher fatty acid, ester wax, and derivatives thereof. And the graft / block compound. When such a low softening point substance is added, it is preferable to add about 5 to 30% by mass in the toner.

  As shown in FIG. 7, the toner carrier is formed with a rubber or elastomer elastic body 312 on a metal core shaft 311 and around its periphery in consideration of toner chargeability, wear resistance, toner adhesion, and the like. Those provided with the surface layer 313 can be used. Moreover, as shown in FIG. 8, what has a surface layer provided on the metal substrate can also be used. The toner carrier may be in the form of a roller or a belt.

  FIG. 9 is a view showing an example (color image forming apparatus) of the image forming apparatus according to the present invention. In addition to what the process cartridge has, at least an optical writing device 120, a transfer member 310, and a fixing device 400 are provided. Although the optical path from the optical writing device 120 is not shown, the optical path is secured at an appropriate position on the photosensitive member between the charging member and the toner carrier.

● Substrate of toner carrier As the toner substrate, either an elastic body or a metal body can be used.
Examples of the elastic body include polyurethane, EPDM, natural rubber, butyl rubber, nitrile rubber, NBR, epichlorohydrin rubber, polyisoprene rubber, polybutadiene rubber, silicone rubber, styrene-butadiene rubber, ethylene-propylene rubber, chloroprene rubber, acrylic rubber, and the like. A crosslinking agent and a vulcanizing agent can be added in order to use the selected one kind and a mixture of two or more of these and further form a rubbery substance by crosslinking. In this case, a vulcanization aid, a vulcanization accelerator, a vulcanization retarder, etc. can be used in both cases of organic peroxide crosslinking and sulfur crosslinking. In addition to the above, foaming agents, plasticizers, softeners, tackifiers, tackifiers, separation agents, mold release agents, extenders, colorants, etc., which are commonly used as rubber compounding agents, have characteristics. It can add in the range which does not impair.

  As the metal body, for example, aluminum, SUS (stainless steel), iron, or the like can be used. Aluminum is often used in terms of workability and lightness. In the case of aluminum, aluminum of a material such as A6063, A5056, and A3003 can be exemplified, and in the case of SUS, stainless steel such as 303, 304, and 416 can be used.

In such a toner carrier, electrical characteristics, particularly electrical resistance, are important. In the case of an elastic body, various conductivity-imparting agents can be added to adjust the resistance. As the conductive material, the powder includes conductive carbon such as ketjen black EC and acetylene black, rubber carbon such as SAF, ISAF, HAF, FEF, GPF, SRF, FT and MT, and oxidation treatment. Color carbon, pyrolytic carbon, indium-doped tin oxide (ITO), tin oxide, titanium oxide, zinc oxide, copper, silver, germanium, and other metals and conductive polymers such as metal oxides, polyaniline, polypyrrole, polyacetylene Etc. In addition, there are ionic conductive substances as conductivity imparting agents, including inorganic ionic conductive substances such as sodium perchlorate, lithium perchlorate, calcium perchlorate, and lithium chloride, as well as modified fatty acid dimethylammonium ethosulphate, stearin. There are organic ionic conductive substances such as acid ammonium acetate, lauryl ammonium acetate, and octadecyltrimethylammonium perchlorate. In the present invention, the resistance value of the elastic body is preferably 10 ³ to 10 ⁹ Ω · cm. When the resistance value is less than 10 ³ Ω · cm, the workability of the material is remarkably impaired and the hardness is increased. On the other hand, if it exceeds 10 ⁹ Ω · cm, it becomes difficult to make the resistance of the toner carrier coated with the surface layer appropriate. If the elastic body is insulative, a surface layer to be described later may have a low resistance and a bias may be taken from the surface.

  The hardness of the elastic body is not particularly limited, but when the toner carrier is in contact with the photoreceptor, it is 60 degrees or less (type A), and preferably 25 to 50 degrees. When the hardness is too high, when the photosensitive member is a drum, the nip width becomes small, and thus there is a possibility that good development cannot be performed. On the other hand, if the hardness is too low, compression set becomes large, and density unevenness occurs when the toner carrier is deformed or decentered. Moreover, since the low hardness side is greatly influenced by the intrinsic physical properties of the material, the materials that can be used are limited. Even when the hardness of the elastic layer is low, it is desirable to reduce the compression set, specifically 20% or less.

● Surface layer of toner carrier The functions required for the surface layer of the toner carrier include toner chargeability, toner non-sticking property, and abrasion resistance. A urethane resin is well known as a material that satisfies these requirements. As a result of examining several types of urethane-based materials (water-based), by cross-linking the water-based urethane resin having a carboxyl group in the molecule with an amino resin, the toner resistance (fixing property) is improved and the toner chargeability, It was confirmed that the wear resistance was improved. As the amino resin, an amino resin having a triazine ring with many nitrogen groups, which are functional groups that impart chargeability to the toner, is desirable. Specifically, a melamine resin having 6 nitrogen atoms in the molecule and a guanamine resin having 5 are desirable. The melamine resin and the guanamine resin can be optionally used, although there are various resins depending on the type and number of functional groups added to the triazine ring. Even if two or more kinds are mixed and used, the processability and characteristics are not limited. The melamine resin is a thermosetting type, and unless it is heated, there is an advantage that the pot life of the paint is also long because the curing reaction does not occur.

  Aqueous urethane resin is a resin with a molecular weight of hundreds of thousands that has been emulsion-polymerized in water. The carboxylic acid (COO group or COOH group) is grafted into the molecule, neutralized with an alkali (such as an amine), and dispersed in water. It is what.

The addition amount of the melamine resin can be added in the range of 3 to 80% by weight with respect to the polyurethane resin 100. Since the melamine resin contains a lot of nitrogen groups in the molecular structure, the toner chargeability can be improved by increasing the amount of the melamine resin added. However, since the coating film becomes harder as the addition amount is increased, it is necessary to add within a range that does not impair the physical properties of the coating film.
When the addition amount of the melamine resin is 3% by weight or less, the physical properties of the coating film cannot be sufficiently improved. Even when added above the reaction point, self-condensation is unlikely to exist as a monomer, so bleeding does not occur from the inside of the coating film.

In order to use it as a surface layer of a toner carrier, it is necessary to make the paint conductive, and conductive using a conductive agent such as carbon black. In this embodiment, the conductive is performed using general conductive carbon, and the addition amount of carbon black is 10% by weight with respect to the resin 100, but is not limited to this. Absent.
In addition, when dispersing the carbon black in the water-based paint, various additives such as a dispersant or an antifoaming agent can be appropriately added from the viewpoint of non-contamination to the toner and the photoreceptor. In the conductive water-based urethane paint used in the present invention, no additive is added.

  The film thickness of the surface layer is determined according to the amount of wear according to the life of the toner carrier, and is arbitrary. However, in order to cope with high image quality, it is desirable that the surface roughness of the toner carrier is as small as possible. As the hardness of the elastic layer is reduced (Shore hardness type A is 40 degrees or less), the surface roughness of the elastic layer is reduced. It is common that it is difficult to make it small. Therefore, in forming the surface layer, it has been necessary to smooth the roller surface. In order to solve this problem, coating is performed so as to fill the unevenness of the elastic layer with a film thickness equal to or greater than the surface roughness of the elastic layer.

  The surface layer is formed on the elastic layer by various known coating methods such as dipping, spray coating, roll coating, and the like.

Measurement Method ● Ionization potential (eV) and slope (Y / eV) are measured according to the following method using the following apparatus.
・ Measurement device: atmospheric photoelectron spectrometer AC-2 (manufactured by Riken Keiki Co., Ltd.)
・ Irradiation energy: 4.2 to 6.2 eV (ultraviolet light)
-Irradiation light diameter: 2 x 2 mm Sq
・ Power: 0.5
・ Light intensity: 505.3nW
Measurement is performed according to such conditions.
Ionization potential: Calculated from the intersection of the normalized photon yield base line and the rising line (linear approximation). Also, slope (Y / eV): calculated from the slope of the rising line (linear approximation) of the normalized photon yield.
An example of such measurement is shown in Table 1.

The toner charge amount distribution q / (the unit is fC / 10 μm and represents the toner charge amount per 10 μm particle size) was performed using the following apparatus under the following conditions.
・ Measurement device: E-Spart analyzer (Hosokawa Micron)
・ Developing device: Fig. 3
・ Carrier: Non-coated type ・ Toner: Polyester resin (base material) + charge control agent (CCA) Volume average particle size 6.5 μm
-Toner concentration: Adjusted to 5-7 wt%-Magnet roller linear speed: 621 mm / sec
・ Developing roller linear speed: 270 mm / sec
Supply bias (potential difference between magnet roller and developing roller): 100V
Procedure: Developer (carrier and toner) with toner concentration adjusted to 5 to 7 wt% is supplied to the magnet roller with the developing device (FIG. 3), and −2 to −2.5 fC / 10 μm on the magnet roller. The toner charged so as to have a peak charge amount is supplied to the developing roller, and the toner charge amount distribution on the developing roller is measured with an E-Spart analyzer.

Hereinafter, based on an Example and a comparative example, the structure of this invention is demonstrated in detail.
● Elastic layer An elastic layer of urethane elastomer is molded by a one-shot method using a polyol (Sumitomo Bayer Urethane) and isocyanate (Sumitomo Bayer Urethane) in which carbon black is dispersed around a SUS 8 mm SUS core shaft coated with an adhesive. did. Thereafter, by adjusting to φ16 mm by outer diameter grinding, an elastic layer having a thickness of 4 mm was obtained.

● Coating layer <Base resin>
20% by weight of carbon black was added and dispersed in Asahi Denka Kogyo's AM36 (water-based urethane resin) to prepare a conductive material (hereinafter referred to as AM36E).
<Amino resin>
The following six amino resins were added at 20% by weight based on the solid content of the base resin.
MX035, MX730, MX706, MX042 (above, Sanwa Chemical), M30WT, M50WT (above, Sumitomo Chemical)

Preparation and Evaluation of Test Piece and Roller A test piece was prepared by applying the above-mentioned paint on a SUS substrate with a bar coater and then heat-curing under conditions of 130 ° C. × 1 hr. In the evaluation, the ionization potential of the initial state (unpolished) and the outermost layer removal was measured. The outermost layer was removed by polishing with a polishing tape.
The roller was prepared by applying the paint to the elastic layer by spray coating and then heat-curing under conditions of 130 ° C. × 1 hr. In the evaluation, the toner charge amount distribution was measured in the initial state (unpolished), the outermost layer removal, and the 3 μm polished state.

(Examples 1-6)
The ionization potential of the coating layer is 0.1 eV or more smaller than the ionization potential of the toner. → Claim 1
-The ionization potential is smaller than the initial state after the outermost layer is removed. → Claim 7
-The ionization potential is approximately 5 eV. → Claim 9
-There are 20 or more slopes. → Claim 5
・ The slope is larger than the initial state after the outermost layer is removed. → Claim 8
The coating layer is formed of a condensation crosslinked product of a polyurethane resin having a carboxyl group in the molecule and one or more amino resins (→ Claim 2), and contains carbon black (→ Claim 3). A polyurethane resin composition emulsified and dispersed in water (→ claim 4).

The toner charge amount distribution of such a coating layer is
In the initial state, the outermost layer removal, and 3 μm polishing, the peak of the toner charge amount distribution is −0.5 fC / 10 μm, which is almost unchanged.
Even when the coating film is worn, a stable toner charge amount distribution can be obtained, but it was found that the charge amount is small and not suitable.
When an image was confirmed with an image forming apparatus equipped with the toner carrier, the image density was thin and density unevenness was observed because the toner charge amount was small. In addition, there was a background stain. In addition, toner scattering was also observed.

The toner charge amount distribution of such a coating layer (only Example 1 is shown below) is:
In the initial state, the peak of the toner charge amount distribution is −1.0 fC / 10 μm.
・ When the outermost layer was removed, the peak position shifted slightly to the minus side.
-Thereafter, the toner charge amount distribution is stable up to a coating depth of 3 μm.

It was found that an appropriate and stable toner charge distribution can be obtained even when the coating is worn.
When an image was confirmed with an image forming apparatus equipped with such a toner carrier, a good image was obtained, and problems such as toner scattering did not occur.

[Comparative Example 1]
Substrate: Aluminum roller φ26; Mitsuya tube extruded material was used as the aluminum material (A6063-T5), and a journal of φ8 was press-fitted into the aluminum inlay portion at the center of the Mitsuya tube, and finished to φ26 mm by cutting.
Coating layer: Polyester resin (20SS; Toyobo), methylated melamine resin (Cymel 325/20% by weight based on the solid content of the polyester resin), ITO conductive particles (alumina powder base / 55 wt%) combined paint by spray coating After coating, it was baked under conditions of 160 ° C. × 1 hr.

<Toner>
The polyester resin 100 is pulverized with 4 parts by weight of a charge control agent (CCA), 5 parts by weight of carbon black as a pigment, and 1 wt% of SiO 2 and 0.3 wt% of TiO 2 added externally. is there. The average particle size is 6.5 μm.
The ionization potential of the coating layer is almost equal to the ionization potential of the toner (at least 0.1 eV or more is not smaller. → Claim 1 is not satisfied.
・ Ionization potential is almost the same as the initial state after outermost layer removal. → Claim 7 is not satisfied.
-The ionization potential is approximately 5.7 eV. → Claim 9 is not satisfied.
The slope is 18.7 in the initial state and 12.6 in the outermost layer removal. → Claims 5 and 8 are not satisfied.
The coating layer is formed of a condensation cross-linked product of a polyester resin and one or more amino resins (→ does not satisfy claim 2) and does not contain carbon black (→ satisfies claim 3). Neither is the polyurethane resin composition emulsified and dispersed in water (→ does not satisfy claim 4)

  The developing device used in the present invention represents at least a toner carrier, a toner supply member, a toner layer regulating member, toner or developer. The process cartridge represents a cartridge that includes at least a developing device, an image carrier (photoconductor), and a charging unit. The image forming apparatus represents an apparatus including at least a developing device, an image carrier (photosensitive member), a charging unit (hereinafter, a process cartridge), an optical writing unit, a transfer member, and a fixing device.

It is a figure which shows the structural example of a developing device. It is another figure which shows the structural example of a developing device. FIG. 10 is still another diagram illustrating a configuration example of a developing device. FIG. 3 is a diagram illustrating a configuration example of a process cartridge equipped with a developing device. It is another figure which shows the structural example of the process cartridge carrying a developing device. FIG. 12 is still another diagram illustrating a configuration example of a process cartridge on which a developing device is mounted. FIG. 4 is a diagram illustrating a configuration example of a toner carrier including an elastic body as a configuration. It is a figure which shows the structural example of the toner carrier which contains a metal body as a structure. 1 is a diagram illustrating an example (color image forming apparatus) of an image forming apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 111 Toner carrier 112 Toner supply member 113 Toner stirring member 114 Case 115 Toner layer regulating member 116 Toner 120 Optical writing device 127 Spring 132 Developer supply member (magnet roller)
133 Developer stirring member 135 Developer layer regulating member 137 Developer (carrier, toner)
138, 223 Bias power supply (power supply)
200 Developing Device 210 Process Cartridge 211 Photoconductor 212 Charging Member 310 Transfer Member 311 Core Shaft 312 Elastic Body 313 Surface Layer 322 Metal Body 400 Fixing Device

Claims (13)

In the toner carrier for visualizing the electrostatic latent image that supplies toner on the image carrier in contact with or in proximity to the image carrier on which the electrostatic latent image is formed by carrying the toner while rotating,
The toner carrier has a coating layer on a substrate, and the ionization potential of the coating layer is 0.1 eV or less smaller than the ionization potential of the toner.   2. The toner carrier according to claim 1, wherein the coating layer is formed of a condensation crosslinked product of a polyurethane resin having a carboxyl group in the molecule and one or more amino resins.   The toner carrier according to claim 1, wherein the coating layer contains carbon black.   The toner carrier according to claim 2, wherein the polyurethane resin is a polyurethane resin emulsified and dispersed in water.   The toner carrier according to claim 1, wherein the normalized photon yield Y and the slope (Y / eV) of the excitation energy eV are 20 or more.   6. The toner carrier according to claim 5, wherein the outermost layer of the coating layer is removed.   The toner carrier according to claim 6, wherein an ionization potential of the toner carrier from which the outermost layer of the coating layer is removed is smaller than an ionization potential before the outermost layer of the coating layer is removed.   The toner carrier according to claim 7, wherein the inclination (Y / eV) after removing the outermost layer of the coating layer is larger than that before removing the outermost layer of the coating layer.   The toner carrier according to claim 1, wherein the ionization potential of the coating layer is approximately 5 eV.   A developing device equipped with the toner carrier according to claim 9.   11. The developing device according to claim 10, wherein the ionization potential of the toner is approximately 5.8 eV, and the slope of the normalized photon yield Y and the excitation energy eV (Y / eV) is approximately 50. Developing device.   A process cartridge equipped with the developing device according to claim 11.   An image forming apparatus equipped with the process cartridge according to claim 12.

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