JP2006301165A - Development device for image formation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development device for image formation which will not deteriorate the charging properties of toner by preventing field concentration due to surface roughness, is free from filming phenomenon on the surface of a toner bearing member even on a long-term basis, excels in toner transport property, as well as in image uniformity, and can suppress voltage drop on the surface of a developing roller. <P>SOLUTION: The development device for image formation is a developing device for color image formation comprising the toner bearing member, wherein the toner bearing member comprises a core to which voltage can be applied, the core having a surface roughened so as to have ruggedness; and a ceramic covering layer, having high dielectric property or high resistance disposed on a roughened surface of the core, wherein the thickness (t<SB>1</SB>) of the ceramic covering layer on convex portions in the core surface is made larger than the thickness (t<SB>2</SB>) of the ceramic-covering layer on concave portions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming developing device comprising a roller-shaped toner carrier used in an electrophotographic system or an electrostatic recording system.

  In the electrophotographic system, for example, after the toner is supplied from the toner carrier (developing roller) to the photosensitive member on which the electrostatic latent image is formed, the intermediate transfer medium may or may not be used in the transfer process. The toner image on the photoconductor is transferred to a transfer paper and fixed with heat and pressure on the paper surface in a fixing process. In the one-component development system, toner is supplied to the surface of the toner carrier in the developing device, and the supplied toner is made into a thin and uniform toner layer by the layer regulating member and transports the toner to the development position. In the development position, the electrostatic latent image on the photoconductor is visualized in a contact or non-contact state with the photoconductor and in the presence of a development bias.

  As a toner carrier in such a one-component development system, the material of the surface is a metal or a rubber elastic body, but in any case, the surface of the toner carrier is The shape is intentionally uneven, and is managed by a roughness index such as Rz. However, when a bias voltage is applied to the toner carrier during development, the electric field concentrates on the convex portion of the surface of the toner carrier, and the opposite polarity is released from the opposite polarity toner or toner base particles present in the toner. The external additive particles are electrostatically adsorbed, which not only lowers the chargeability of the toner in the short term, but also causes filming on the surface of the toner carrier in the long term, thereby reducing image uniformity. is there. In order to avoid such a phenomenon, it is conceivable to provide a high-resistance layer or a high-dielectric coating on the surface of the toner carrier. However, even if the electrostatic concentration problem can be solved, there is a problem in ensuring toner transportability. In addition, in order to ensure the toner transportability, the surface needs to be roughened to have a film thickness of a certain level or more, and a voltage drop on the surface of the developing roller becomes a problem. In order to obtain, there is a problem that it is necessary to use a higher output power source.

Therefore, conventionally, a semiconductor ceramic coating layer having a specific resistance of 10 ⁴ to 10 ¹² Ω · cm and a layer thickness of 100 to 1000 μm is provided on the surface of the core of the toner carrier by plasma spraying to form a toner carrier. When the surface of the semiconductor layer is roughened as proposed (Patent Document 1), the ceramic coating layer is diamond-polished so that the Ra is 0.1 to 0.5 μm, the uneven pitch is about 10 μm, and the particle size is 10 μm. It is said that irregularities that are convenient for the transportability of the front and rear toners are formed. However, if a high-dielectric material such as silicon carbide is coated as a ceramic on a smooth toner carrier, it will be constant to roughen the surface. There is a problem that a voltage drop on the surface of the developing roller becomes a problem, and it is necessary to use a higher output power source in order to obtain a desired developing bias. In addition, when the ceramic is a low dielectric material, the problem of electric field concentration due to surface irregularities is not sufficiently improved, and not only does the toner chargeability deteriorate in the short term, but also in the long term. There is a problem that a filming phenomenon occurs on the surface of the toner carrying member and image uniformity is lowered.

In addition, the surface of the core of the toner carrier contains conductive inorganic powder such as metal boride, metal carbide, metal nitride, metal oxide, and carbon black that is not metal-plated on the surface. It has been proposed (Patent Document 2) to form a developing sleeve having a volume resistivity of 10 ⁻³ to 10 ⁴ Ω · cm by forming a coating layer having fine irregularities on the surface by electrodeposition coating. The unevenness in is formed by the particle size of the inorganic powder to be contained, and since the inorganic powder forming the surface unevenness is conductive and not a high resistance body, the problem of electric field concentration caused by the surface unevenness is There is a problem that the toner is not sufficiently improved and not only the charging property of the toner is lowered in the short term, but also the filming phenomenon on the surface of the toner carrier is caused in the long term and the image uniformity is lowered.
Japanese Patent No. 2705090 Japanese Patent No. 3262467

  The present invention prevents the occurrence of electric field concentration due to unevenness of the surface, so that the chargeability of the toner is not lowered, the filming phenomenon on the surface of the toner carrier is not long-term, and the image uniformity is excellent. An object of the present invention is to provide an image forming developing device that has excellent toner transportability and can suppress a voltage drop on the surface of the developing roller.

The image forming developing device of the present invention is an image forming developing device comprising a toner carrier, wherein the toner carrier comprises a core to which a voltage can be applied, and the surface of the core is roughened to be uneven. And a ceramic coating layer having a high dielectric or high resistance provided on the surface of the irregular core body, and having a film thickness (t ₁ ) of the ceramic coating layer on the convex portion on the core surface. It is characterized by being thicker than the film thickness (t ₂ ) of the ceramic coating layer on the recess.

  The core of the toner carrier is a metal roller, and the ceramic coating layer is a roller-like toner carrier that is a high dielectric layer having a relative dielectric constant of 100 or more.

  The core of the toner carrier is a conductive elastic roller, and the ceramic coating layer is a roller-like toner carrier that is a high resistance layer having a specific resistance of 50 μΩ · cm or more. .

The thickness (t ₁ ) of the ceramic coating layer on the convex portion on the surface of the core body is 3 μm to 10 μm, the thickness (t ₂ ) of the ceramic coating layer on the concave portion is ₁ μm to 5 μm, and t ₁ is from t ₂ . The thickness is 2 μm or more.

  The surface roughness (Rz) in the core is 5 μm to 15 μm.

  The ceramic coating layer has a surface roughness (Rz) of 2 μm to 12 μm.

  The toner has a volume average particle diameter of 4.5 μm to 9 μm and an average circularity of 0.95 to 0.99.

  The toner is a negatively chargeable toner, and is a non-magnetic one-component toner comprising toner mother particles and at least positive-polarity added particles.

  The developing device for image formation according to the present invention has a roller-like core surface that is roughened and further has a high dielectric or high-resistance ceramic coating layer on the roughened surface. By making the ceramic coating layer highly dielectric or highly resistive, it is possible to prevent concentration of the electric field, and to remove the opposite polarity from the opposite polarity toner and toner mother particles present in the toner. Since electrostatic adsorption of additive particles can be prevented, there is no decrease in toner chargeability in the short term, and filming phenomenon on the surface of the toner carrier can be prevented in the long term, resulting in excellent image uniformity. And can. Further, since the image uniformity is excellent, when the toners of the respective colors are superimposed, the color reproducibility is excellent, and it can be made suitable as a color image forming developing device.

Further, a roughening treatment such as polishing is performed by making the film thickness (t ₁ ) of the ceramic coating layer on the convex portion on the core surface larger than the film thickness (t ₂ ) of the ceramic coating layer on the concave portion. In other words, the surface of the toner carrying member can be formed into an uneven shape suitable for toner transportability. Further, since the thickness of the ceramic coating layer can be reduced, a voltage drop on the surface of the developing roller can be suppressed, and a desired developing bias can be obtained without using a high output power source.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1A is a cross-sectional view of the toner carrier (developing roller) in the image forming developing apparatus according to the present invention when the core is the metal roller 201, and the ceramic coating layer 202 is formed on the metal roller 201. Is covered. The metal roller 201 has a cylindrical shape with a thickness of 0.5 mm to 2 mm and an outer diameter of 1 cm to 5 cm made of a metal such as aluminum, SUS, or brass.

  FIG. 1B is an enlarged cross-sectional view of part A of FIG. 1A, and the outer surface of the metal roller 201 is subjected to surface roughening treatment such as sandblasting or knurling so that the surface roughness is increased. (Rz) is 5 μm to 15 μm, preferably 7 μm to 10 μm. If Rz is smaller than 5 μm, the surface of the ceramic coating layer is not sufficiently formed when the ceramic coating layer is coated, and if it is larger than 15 μm, the surface of the ceramic coating layer formed when the ceramic coating layer is coated The desired roughness cannot be obtained, and a problem occurs in toner transportability.

On the surface of the metal roller 201 subjected to the roughening treatment, a ceramic coating layer is formed by using a multi-electrode type plasma CVD method or an HCD type ion plating method. The film thickness (t ₁ ) of the ceramic coating layer can be made larger (t ₁ > t ₂ ) than the film thickness (t ₂ ) of the ceramic coating layer on the recess. The multi-electrode type plasma CVD method and HCD type ion plating method are films formed in the presence of an electric field. The electric field concentrates on the tip of the convex part on the surface of the metal roller, and the convex part is compared with the concave part by electrostatic adsorption. Thus, a thicker film can be formed, and a film can be formed in a relationship of t ₁ > t ₂ .

  Examples of the high dielectric constant ceramics include titanium nitride, titanium carbide, zirconium carbide, vanadium carbide and the like.

In order to form a silicon carbide film by a multi-electrode type plasma CVD method, Si (CH ₃ ) ₄ is used as a synthesis gas, and in order to form a titanium nitride or titanium carbide film, TiCl ₄ is used as a synthesis gas. The film can be formed under known film forming conditions such as.

To form a titanium nitride film by the HCD ion plating method, titanium is used as an evaporation source, nitrogen is used as a synthesis gas, and to form a chromium carbide film, Cr is used as an evaporation source. The film can be formed under known film formation conditions such as using C ₂ H ₂ as a synthesis gas.

The film thickness (t ₁ ) of the ceramic coating layer on the convex portion of the metal roller surface can be 3 μm to 10 μm, the film thickness (t ₂ ) of the ceramic coating layer on the concave portion can be ₁ μm to 5 μm, and t ₁ Is preferably thicker than t ₂ by 2 μm or more.

  The surface roughness (Rz) of the ceramic coating layer to be formed is 2 μm to 12 μm, preferably 5 μm to 10 μm, and the uneven pitch is 10 μm to 50 μm. As a result, the toner particles having a volume average particle diameter of 4.5 μm to 9 μm can be excellently conveyed.

  Further, the ceramic coating layer may be a high dielectric constant ceramic coating layer having a relative dielectric constant of 100 or more, whereby a coating layer in which charges are not concentrated on the convex portions can be obtained. According to the plasma CVD method or the ion plating method, since the ceramic coating layer can be made thin, even if a high dielectric layer is provided on the surface of the developing roller, a voltage drop on the surface of the developing roller can be suppressed.

  Next, FIG. 2A is a cross-sectional view when the core body is a conductive elastic roller 204 coated on a support 203, and the ceramic coating layer 202 is coated on the conductive elastic roller 204. FIG. The

The conductive elastic roller 204 is made of nitrile butadiene rubber (NBR), chloroprene rubber, fluorine rubber, nitrile rubber, urethane rubber, acrylic rubber, epichlorohydrin rubber, ethylene-propylene diene rubber (EPDM), butadiene rubber, styrene butadiene rubber ( SBR), high styrene rubber, isoprene rubber, butyl rubber, silicon rubber, natural rubber (NR), etc. are kneaded with conductive material, volume resistance is 10 ^-10 Ω · cm or less, thickness is 0.5 mm to 10 mm, outer diameter Has a cylindrical shape of 1 cm to 5 cm.

  2B is an enlarged cross-sectional view of part A of FIG. 2A. The outer surface of the conductive elastic roller 204 is roughened by sandblasting, knurling or the like, and the surface roughness ( Rz) is 5 μm to 15 μm, preferably 7 μm to 10 μm. When Rz is smaller than 5 μm, the ceramic coating layer surface is not sufficiently uneven when coated with the ceramic coating layer 202, and when it is larger than 15 μm, the ceramic coating layer surface formed when the ceramic coating layer is coated. Cannot achieve the desired roughness, resulting in a problem in toner transportability.

A ceramic coating layer may be formed by electrodeposition coating on the surface of the roughened conductive elastic roller 204, and the thickness (t ₁ ) of the ceramic coating layer on the convex portion of the conductive elastic roller surface may be set on the concave portion. It is possible to form a film thicker (t ₁ > t ₂ ) than the film thickness (t ₂ ) of the ceramic coating layer. Electrodeposition coating is film formation in the presence of an electric field, and the electric field concentrates on the tip of the convex portion on the surface of the conductive elastic roller, and can be formed thicker on the convex portion than the concave portion by electrostatic adsorption. _1> it can be deposited in the relationship of t _2.

  Electrodeposition paint is made of high resistance ceramic particles such as boron nitride (BN), silicon carbide, titanium carbide, aluminum nitride, etc., whose volume average particle size is adjusted to 0.05 μm to 1 μm, and carbon black particles, such as nylon. Dissolved and suspended in isopropyl alcohol (IPA) together with the electrodeposition resin, and co-deposited on the surface of the conductive elastic roller together with the electrodeposition resin by electrophoretic action, etc. It is.

The film thickness (t ₁ ) of the ceramic coating layer on the convex portion on the surface of the conductive elastic roller is 3 μm to 10 μm, the film thickness (t ₂ ) of the ceramic coating layer on the concave portion is ₁ μm to 5 μm, and t ₁ Is preferably thicker than t ₂ by 2 μm or more.

  The surface roughness (Rz) of the ceramic coating layer to be formed is 2 μm to 12 μm, preferably 5 μm to 10 μm, and the uneven pitch is 10 μm to 50 μm. As a result, the toner particles having a volume average particle diameter of 4.5 μm to 9 μm can be excellently conveyed.

  Further, the ceramic coating layer may be a high resistance layer having a specific resistance of 50 μΩ · cm or more, preferably 70 μΩ · cm or more, whereby a coating layer in which the electric field does not concentrate on the convex portion can be obtained. The ceramic coating layer can be made thin, and even if a high resistance layer is provided on the surface of the developing roller, the voltage drop on the surface of the developing roller can be suppressed.

  Next, the toner used in the present invention will be described. The toner in the present invention is preferably a non-magnetic single component spherical toner, and the toner particles are formed by externally adding an external additive to the toner base particles.

  The toner base particles may be obtained by any one of a pulverization method, a polymerization method, and a dissolution suspension method. As a method by the pulverization method, at least a pigment is contained in a binder resin, a release agent, a charge control agent and the like are added, mixed uniformly with a Henschel mixer, etc., melt-kneaded with a twin screw extruder, cooled, Through a pulverization-fine pulverization step, classification is performed to form toner base particles.

  Examples of the binder resin include styrene or a homopolymer or copolymer containing a styrene-substituted product, a polyester resin, and the like, and a colorant, a release agent, a charge control agent, and the like are added. Colorants for full color include carbon black, lamp black, magnetite, titanium black, chrome yellow, ultramarine, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine 6G, calco oil blue, quinacridone, benzidine yellow, rose bengal Malachite Green Lake, Quinoline Yellow, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 184, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 180, C.I. I. Solvent Yellow 162, C.I. I. Pigment blue 5: 1, C.I. I. Dye and pigment such as CI Pigment Blue 15: 3 can be used alone or in combination.

  The component ratio in the toner base particles is 0.5 to 15 parts by weight, preferably 1 to 10 parts by weight, and 1 to 10 parts by weight of the release agent with respect to 100 parts by weight of the binder resin. The charge control agent is 0.1 to 7 parts by mass, preferably 0.5 to 5 parts by mass.

  The pulverized toner is preferably spheroidized in order to improve transfer efficiency. In the pulverization process, a relatively round spherical device capable of being pulverized, for example, a turbo mill known as a mechanical pulverizer (manufactured by Turbo Kogyo Co., Ltd.). ) Can be used to increase the degree of circularity to 0.93, and the degree of circularity can be increased to 1.00 by using a hot air spheronizing device (manufactured by Nippon Pneumatic Industry) for the pulverized toner. .

  Next, the polymerization toner is obtained by a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method, or the like, and can be made suitable for a full color toner. In the suspension polymerization method, a polymerizable monomer, a color pigment, a release agent, and a complex added with a dye, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives as necessary are dissolved or dissolved. The dispersed monomer composition is added to an aqueous phase containing a suspension stabilizer (water-soluble polymer, poorly water-soluble inorganic substance) with stirring, granulated, and polymerized to obtain a desired particle size. The colored polymer toner particles are formed. In the material used for the production of the polymerization toner, as the colorant, the same material as that of the pulverized toner described above can be used. In the emulsion polymerization method, polymerization is performed by dispersing a monomer and a mold release agent, and if necessary, a polymerization initiator and an emulsifier (surfactant) in water, and then aggregating with a colorant, a charge control agent, and the like. Colored toner particles having a desired particle size are formed by adding an agent (electrolyte) or the like.

  Examples of the polymerizable monomer component include styrene or derivatives thereof, (meth) acrylic acid ester derivatives such as divinylbenzene and methyl acrylate, and the emulsifier (surfactant) includes sodium dodecylbenzene sulfate and the like. In addition, examples of the polymerization initiator include potassium persulfate, and examples of the flocculant (electrolyte) include sodium chloride.

  As a method for adjusting the circularity of the polymerization toner, the emulsion polymerization method can freely change the circularity by controlling the temperature and time during the aggregation process of the secondary particles, and its range is from 0.94 to 1. .00. In the suspension polymerization method, a true spherical toner can be produced, and the circularity can be in the range of 0.98 to 1.00. In order to set the average circularity to 0.95 to 0.99, it can be adjusted as appropriate by heat-deforming at or above the Tg temperature of the toner.

  Next, the dissolution suspension method toner will be described. As the binder resin, the binder resin described in the above section of the pulverized toner can be used, but a polyester resin is preferable from the viewpoint of color developing properties. As a polyester resin, the thing of Unexamined-Japanese-Patent No. 2003-140380 is illustrated.

  Dissolving suspension method toner mother particles are prepared by dissolving and dispersing the colorant described in the section of binder resin and pulverized toner, and if necessary, a release agent and a charge control agent in an organic solvent, and then dissolving in the organic solvent obtained. -Fine particles of the mixture can be formed by gradually introducing an aqueous medium into the dispersion and emulsifying it by phase inversion emulsification. The obtained fine particles are agglomerated and granulated into colorant-containing resin fine particles having a desired size, and can be converted into toner mother particles through separation, washing and drying steps. In the dissolution suspension method, toner mother particles can be produced while controlling emulsification and association.

  In the present invention, the toner base particles and the volume average particle size of the toner particles are preferably 9 μm or less for the pulverized toner base particles, the polymerized toner base particles, and the dissolution suspension method toner base particles, and are 8 μm to 4.5 μm. More preferably. For toner particles having a volume average particle size larger than 9 μm, even if a latent image is formed at a high resolution of 1200 dpi or higher, the reproducibility of the resolution is lower than that of a small particle size toner, and is 4.5 μm or less. As a result, the concealability by the toner decreases, and the amount of the external additive used to increase the fluidity increases, and as a result, the fixing performance tends to decrease.

  Further, the volume average particle diameter and average circularity of the toner base particles and toner particles in the present invention are values measured by a flow type particle image analyzer (FPIA2100 manufactured by Sysmex).

As the toner base particle shape, toner particles having a shape close to a true sphere are preferable. Specifically, the toner base particles are represented by the following formula:
R = L ₀ / L ₁
{However, in the formula, L ₁ (μm) is the perimeter of the projected image of the toner particles to be measured, and L ₀ (μm) is a perfect circle having an area equal to the area of the projected image of the toner particles to be measured (completely The perimeter of a geometric circle). }
The average circularity (R) represented by the formula is 0.95 to 0.99, preferably 0.972 to 0.983. As a result, the transfer efficiency is high, and even when continuous printing is performed, there is little fluctuation in the transfer efficiency, the charge amount is stabilized, and the toner has excellent cleaning properties.

  Next, examples of the external additive particles include hydrophobized external additive particles that are excellent in environmental stability. The particle diameter of the external additive particles is measured by electron microscopy, and the average particle diameter of the external additive particles is the primary average particle diameter.

  Examples of the external additive particles include negatively-charged silica fine particles and positively-charged silica fine particles for the purpose of charge adjustment. The silica fine particles are used with respect to 100 parts by mass of the toner base particles for the purpose of improving the fluidity of the toner. 0.5 to 2.0 parts by mass, preferably 0.5 to 1.5 parts by mass. The silica fine particles are preferably hydrophobized. Examples of the hydrophobic silica fine particles include commercially available RX200 (average particle size 12 nm), RX50 (40 nm) manufactured by Nippon Aerosil Co., Ltd., and the like.

  Further, as the externally added particles, fine particles of titanium oxide having a relatively small electric resistivity are exemplified. Titanium oxide has a particle size or major axis size of 10 nm to 50 nm, preferably 10 nm to 40 nm, and is added in an amount of 0.2 to 1.0 part by mass with respect to 100 parts by mass of toner base particles. The surface of the titanium oxide fine particles is hydrophobic in order to reduce the change in chargeability with respect to the change in the external environment of the toner (that is, maintain stable chargeability) and improve the fluidity of the toner. Is preferable. Hydrophobization of the titanium oxide fine particles is carried out by the same method as that of the negatively chargeable silica fine particles. Examples of the hydrophobic titanium oxide fine particles include STT-30S (average particle size 30 nm) manufactured by Titanium Industry Co., Ltd. For example, when the titanium oxide particles are released from the negatively chargeable toner, they behave as positive external additive particles.

Inorganic fine particles other than titanium oxide fine particles can also be externally added for the purpose of controlling the chargeability and improving the fluidity. For example, inorganic fine particles include aluminum oxide, strontium oxide, tin oxide, zirconia, magnesium oxide, indium oxide and other metal oxide fine particles, silicon nitride and other nitride fine particles, silicon carbide and other carbide fine particles, calcium sulfate , Fine particles of metal salts such as barium sulfate and calcium carbonate, and inorganic fine particles such as a composite thereof. Metal oxide fine particles having an electric resistance of 10 ⁹ Ωcm or less and a relatively small electric resistance are preferably used. The size of the inorganic fine particles to be added is preferably a particle size of 10 to 30 nm. These inorganic fine particles are preferably subjected to a hydrophobic treatment on the surface for the purpose of stabilizing charging characteristics.

  In order to externally add the toner base particles with the externally added particles, it is preferable to externally add the toner mother particles using a Henschel mixer, Q-type mixer or the like manufactured by Mitsui Mining Co., Ltd.

  Next, a color image forming apparatus incorporating the developing device according to the present invention will be described.

  FIG. 3 is a cross-sectional view showing the overall configuration of an image forming apparatus taking a tandem type as an example. The image forming apparatus 1 includes a housing 3, a paper discharge tray 5 formed on the top of the housing 3, and a door that opens and closes. The housing 7 is provided with an exposure unit 9, an image forming unit 11, a blower fan 13, a transfer belt unit 15, and a paper feed unit 17. A paper transport unit 19 is provided.

  The image forming unit 11 includes four image forming stations 21 in which four developing devices that store different color toners can be set. The four image forming stations 21 are for yellow, magenta, cyan, and black developing devices, and are denoted by reference numerals 21Y, 21M, 21C, and 21K in the drawing. In each of the image forming stations 21Y, 21M, 21C, and 21K, a photosensitive drum 23, a corona charging unit 25 provided around the photosensitive drum 23, and the developing device 100 of the present invention are disposed.

  The transfer belt unit 15 is stretched between a driving roller 27 that is rotationally driven by a driving source (not shown), a driven roller 29 provided obliquely above the driving roller 27, a tension roller 31, and these rollers. The intermediate transfer belt 33 is circulated and driven in the counterclockwise direction X, and the cleaning means 34 is in contact with the surface of the intermediate transfer belt 33. The driven roller 29, the tension roller 31 and the intermediate transfer belt 33 are arranged side by side so as to be inclined with respect to the drive roller 27. When the intermediate transfer belt 33 is driven by this, the belt conveyance direction X is downward. The belt surface 35 is located on the lower side, and the belt surface 37 with the conveying direction facing upward is located on the upper side.

  The photosensitive drum 23 is pressed against the belt surface 35 along the arched line and is driven to rotate in the direction indicated by the arrow in FIG. By adjusting the position of the tension roller 31, the tension of the intermediate transfer belt 33, the curvature of the arch, and the like can be controlled.

The drive roller 27 also serves as a backup roller for the secondary transfer roller 39.
Further, on the peripheral surface of the drive roller 27, for example, a rubber layer having a thickness of about 3 mm and a volume resistivity of 10 ⁵ Ω · cm or less is formed, and the secondary transfer roller is grounded through a metal shaft. The secondary transfer bias conductive path supplied via the line 39 is configured. Further, the diameter of the drive roller 27 is smaller than the diameters of the driven roller 29 and the tension roller 31, so that the recording paper after the secondary transfer can be easily peeled by the elastic force of the recording paper itself. The driven roller 29 also functions as a backup roller for the cleaning means 34.

  The cleaning unit 34 is provided on the side of the belt surface 35 facing downward in the conveyance direction, and a cleaning blade 41 that removes toner remaining on the surface of the intermediate transfer belt 33 after the secondary transfer, and a toner conveyance path that conveys the collected toner. 42. The cleaning blade 41 is in contact with a portion where the intermediate transfer belt 33 is wound around the driven roller 29. Further, the primary transfer member 43 abuts the back surface of the intermediate transfer belt 33 at a position facing the photosensitive drum 23 of each of the image forming stations 21Y, 21M, 21C, and 21K, and a transfer bias is applied to the primary transfer member 43. It has come to be.

  The exposure unit 9 is provided in a space obliquely below the image forming unit 11, and a blower fan 13 is provided obliquely above the exposure unit 9. A paper feed unit 17 is provided below the exposure unit 9. In the exposure unit 9, a scanner means 49 comprising a polygon mirror motor 45 and a polygon mirror 47 is vertically arranged on the bottom. In addition, a single f-θ lens 51 and a reflection mirror 53 are provided in the optical path B, and a plurality of folds are provided above the reflection mirror 53 so that the scanning light paths of the respective colors fold in parallel with the photosensitive drum 23. A mirror 55 is provided.

  In the exposure unit 9, an image signal corresponding to each color is emitted from the polygon mirror 47 with a laser beam modulated and formed based on a common data clock frequency, and passes through the f-θ lens 51, the reflection mirror 53, and the folding mirror 55. The photosensitive drums 23 of the image forming stations 21Y, 21M, 21C and 21K are irradiated to form latent images. The optical path length from the polygon mirror 47 of the exposure unit 9 to the photosensitive drum 23 with respect to each image forming unit 11 is configured to be substantially the same, so that the scanning width of the light beam scanned in each optical path is also substantially the same. It is the same, and no special configuration is required for forming the image signal. Accordingly, the laser light source can be modulated and formed based on a common data clock frequency in spite of being modulated in accordance with images of different colors by different image signals. Color misregistration caused by a relative difference in the scanning direction can be prevented, and a simple and inexpensive color image forming apparatus can be configured.

  The blower fan 13 functions as a cooling unit, guides air in the direction of the arrow, and performs a function of releasing heat from the exposure unit 9 and other heat generating units. As a result, the temperature rise of the polygon mirror motor 45 can be suppressed, the deterioration of the image quality can be prevented, and the life of the polygon mirror motor 45 can be extended.

  The paper feed unit 17 includes a paper feed cassette 57 in which the recording media P are stacked, and a pickup roller 59 that feeds the recording media P from the paper feed cassette 57 one by one. The paper transport unit 19 includes a gate roller pair 61 that defines the timing of feeding the recording medium P to the secondary transfer unit, a secondary transfer roller 39 that is pressed against the drive roller 27 and the intermediate transfer belt 33, and a fixing unit 63. A pair of paper discharge rollers 65 and a duplex printing conveyance path 67.

  The fixing unit 63 includes a rotatable fixing roller pair 69 containing a heating element such as a halogen heater in at least one side, and at least one roller of the fixing roller pair 69 is pressed and biased to the other side to form a secondary sheet. The secondary image transferred to the recording medium is fixed to the recording medium at a predetermined temperature at a nip portion formed by the fixing roller pair 69. Is done.

  The developing device 100 used in the present invention is of a type that circulates and uses toner, and is set in each of the image forming stations 21Y, 21M, 21C, and 21K. The construction of these developing devices is basically the same.

  FIG. 4 is a cross-sectional view of the developing device 100. The developing device 100 includes a housing 103 in which a substantially cylindrical toner accommodating portion 101 is formed. A supply roller 105 and a developing roller 107 are provided to the housing 103. In a state where the developing device 100 is set in the image forming station (see FIG. 3), the developing roller 107 is adjacent to the photosensitive drum 23 with a slight gap (for example, 100 to 300 μm). It has a function of developing the latent image formed on the photosensitive drum 23 with the toner supplied to the peripheral surface of the developing roller 107 while being rotationally driven in the direction opposite to the rotation direction (see the arrow in the drawing). Such a developing action applies a developing bias in which an AC voltage is superimposed on a DC voltage from a developing bias power source (not shown) to the developing roller 107, thereby causing an oscillating voltage to act between the developing roller and the photosensitive drum, This is performed by supplying toner from the developing roller 107 to the electrostatic latent image portion formed on the photosensitive drum 23. It is also possible to perform development by bringing the developing roller 107 into contact with the peripheral surface of the photosensitive drum 23.

  The supply roller 105 has a surface formed of urethane sponge, and can rotate in the same direction as the developing roller 107 (counterclockwise in FIG. 4) with the peripheral surface of the supplying roller 105 in contact with the developing roller 107. . A voltage equivalent to the developing bias voltage applied to the developing roller 107 is also applied to the supply roller 105.

  A regulating blade 109 is pressed against the developing roller 107 so that it is always uniform over the longitudinal direction of the peripheral surface of the developing roller 107 by the action of the leaf spring member 111 and the elastic member 112 provided below the leaf spring member 111. In addition, an excessive amount of toner adhering to the peripheral surface of the developing roller 107 is scraped off so that a certain amount of toner is carried on the peripheral surface of the developing roller 107. The regulation blade 109 also has a function of appropriately charging the toner 113.

  The toner that has been scraped off naturally falls and is mixed into the toner 113 in the toner storage unit 101, which will be described in detail later. Further, the other end side of the seal member 115 whose one end is fixed to the housing 103 is in pressure contact with the upper surface of the developing roller 107, thereby preventing the toner 113 in the housing 103 from being scattered outside. Yes.

  An agitator 119 that rotates in the clockwise direction in FIG. 4 about the rotation shaft 117 is provided in the toner storage unit 101. The agitator 119 includes two arm members 121 extending in opposite directions around the rotation shaft 117, and each arm member 121 is set to a dimension slightly shorter than the diameter of a circle in the cross section of the toner containing portion 101. A stirring fin 123 extends from the tip of each arm member 121 in the direction opposite to the rotational direction of the agitator 119. The stirring fin 123 is composed of a flexible sheet member, and the tip side thereof is in pressure contact with the inner peripheral surface of the cylindrical toner accommodating portion 101 by an elastic force resulting from the flexibility. With such a configuration, when the agitator 119 rotates, the toner 113 existing in the region 125 between the inner peripheral surface of the toner containing portion 101 and the stirring fin 123 is scraped up by the stirring fin 123 so as to be described later. It can be conveyed on a member.

  The upper surface 114 of the toner 113 accommodated in the toner accommodating portion 101 is set to be lower than the location 127 where the regulating blade 109 is in contact with the peripheral surface of the developing roller 107. This is because if the amount of toner is so large that the regulating blade 109 is buried, the toner scraped off by the regulating blade 109 exists near the regulating blade, so that the circulation path to be returned to the toner storage unit 101 is obstructed. This is because the function of the regulating blade 109 scraping off excess toner from the developing roller 107 and regulating the amount of toner conveyed to the developing area and the function of appropriately charging the toner are hindered.

  In the present embodiment, the position of the upper surface 114 of the toner 113 accommodated in the toner accommodating portion 101 is more specifically lower than the lower end of the regulating blade 109, and the leaf spring member 111, the elastic member 112, and the like. The position of the intersection 128 is set as the upper limit. If the position of the upper surface 114 of the toner 113 in the toner containing portion 101 reaches above the intersection 128, the movement of the leaf spring member 111 may be restrained, which may result in failure to obtain an appropriate regulation pressure. As a result, there is a possibility that the “function of carrying a certain amount of toner on the peripheral surface of the developing roller 107” and the “function of properly charging the toner” may be hindered. However, as described above, by setting the upper limit of the upper surface 114 position of the toner 113 to the position of the intersection point 128, it is possible to eliminate the possibility of the functions being hindered.

  The toner between the portion 127 where the regulating blade 109 is in contact with the peripheral surface of the developing roller 107 and the upper surface 114 of the toner 113 accommodated in the toner accommodating portion 101 is inclined at an angle greater than the repose angle of the toner 113. A toner guide surface 129 that is inclined obliquely toward the upper surface 114 is formed as a part of the housing 103. The toner guide surface 129 has a function of guiding the toner 113 scraped off from the peripheral surface of the developing roller 107 by the regulating blade 109 to the toner containing portion 101 side.

  The toner 113 scraped off from the peripheral surface of the developing roller 107 by the regulating blade 109 does not necessarily have to be guided to the toner storage portion 101 by the toner guide surface 129, and the toner 113 scraped off is directly applied to the toner storage portion 101. It is good also as a structure which falls in the. The toner 113 scraped off from the circumferential surface of the developing roller 107 by the regulating blade 109 is guided to the toner accommodating portion 101 below the portion 127 where the regulating blade 109 is in contact with the circumferential surface of the developing roller 107 as described above. For this purpose, a toner guide space 131 is formed.

  A toner guide member 133 is provided above the toner container 101. The toner guide member 133 is provided at an end portion 134 on the side away from the supply roller 105, and has a scraper 135 formed at an acute angle for scraping off the toner 113 conveyed by the stirring fin 123, and more than the scraper 135. On the supply roller 105 side, the upper surface side is inclined at an angle equal to or greater than the repose angle of the toner 113 and is formed in a plane, and is formed on the downstream side of the flat conveyance portion 137, and the upper surface side forms a concave curved surface. And a contact portion 143 that is in contact with an appropriate linear pressure set on the peripheral surface of the supply roller 105 on the downstream side of the bending portion 141. The surface roughness of the toner guide member 133 including the flat conveying portion 137, the curved portion 141, and the contact portion 143 is formed to be less than the average particle diameter of the toner.

  Further, the presence of the contact portion 143 prevents the toner 113 adhering to the lower surface side of the supply roller 105 from dropping due to gravity, thereby preventing a decrease in image density due to a decrease in the amount of toner that can be supplied to the developing roller. be able to. In addition, a temporary toner storage portion 139 is formed between the curved portion 141 and the peripheral surface of the supply roller 105 so that the cross section narrows in a wedge shape. Here, the wedge-shaped cross section means that the entrance side is relatively large and becomes narrower in the toner traveling direction, and is sufficiently narrow so that the toner does not slip naturally on the front end side of the wedge.

  In the toner guide member 133 having such a shape, after the toner 113 conveyed by the stirring fins 123 is scraped off by the scraper 135, the toner 113 extends along the width direction of the flat conveyance unit 137 and its inclination. Gravity falls at a uniform speed at an arbitrary point in the direction, and is temporarily stored in the temporary toner storage unit 139. In the temporary toner storage portion 139 that narrows in a wedge shape, as the toner 113 advances to a narrow region, the pressure contact force against the peripheral surface of the supply roller 105 gradually increases. And the toner 113 is easily carried on the peripheral surface. When the toner 113 is pushed out beyond the contact portion 143, the toner 113 falls down the toner guide space 131 and is guided directly or by the toner guide surface 129 and returned to the toner storage portion 101.

  The following are (1) the method for producing the toner used in the examples and the release rate of the titanium oxide externally added particles, (2) the method for measuring the surface roughness of the toner carrier obtained in the examples, and (3) the toner carrier. A method for measuring the film thickness of the holder surface will be described.

(1) Preparation of toner A monomer mixture comprising 80 parts by mass of styrene monomer, 20 parts by mass of butyl acrylate monomer, and 5 parts by mass of acrylic acid monomer was prepared. This mixture was mixed with 105 parts by weight of water, 1 part by weight of a nonionic emulsifier (New Coal 506: manufactured by Nippon Emulsifier Co., Ltd.), 1.5 parts by weight of an anionic emulsifier (Ribotac TE: manufactured by Lion Corporation), and persulfate. In addition to an aqueous solution consisting of 0.55 parts by mass of potassium, dispersion and emulsification were carried out to carry out emulsion polymerization to obtain a milky white resin emulsion having a particle size of 0.25 μm.

  200 parts by weight of the obtained resin emulsion, 20 parts by weight of polyethylene wax emulsion (manufactured by Sanyo Chemical Industries, Ltd.) and 7 parts by weight of phthalocyanine blue, 0.2 parts by weight of sodium dodecylbenzenesulfonate (surfactant) Dispersed in 500 g of contained water. Next, after adding diethylamine and adjusting pH to 5.5, 0.3 mass part of aluminum sulfate which is electrolyte was added, stirring. Subsequently, the mixture was stirred at a high speed with a TK homomixer and dispersed.

  Furthermore, 40 parts by mass of styrene monomer, 10 parts by mass of butyl acrylate, and 5 parts by mass of zinc salicylate were added together with 40 parts by mass of water, and the mixture was heated to 90 ° C. with stirring under a nitrogen stream, and hydrogen peroxide was added. For 5 hours to grow particles. After the polymerization was stopped, the temperature was raised to 95 ° C. and maintained at 95 ° C. for 5 hours while adjusting the pH to 5 or more in order to improve the bond strength of the associated particles. The obtained particles were washed with water and vacuum-dried at 45 ° C. for 10 hours. By this method, toner base particles having a volume average particle diameter of 7.0 μm were prepared. The resulting toner base particles had an average circularity of 0.97.

  1 part by mass of hydrophobic negatively chargeable silica particles “RX200” (average particle size 12 nm) manufactured by Nippon Aerosil Co., Ltd., manufactured by Nippon Aerosil Co., Ltd., hydrophobic negatively charged Add 1 part by mass of silica particles “RX50” (average particle size 40 nm), and 0.5% by mass of hydrophobic titanium oxide particles “STT-30S” (average particle size 50 nm) manufactured by Titanium Industry Co., Ltd. Using “FM20B type Henschel mixer” manufactured by Mitsui Mining Co., Ltd., stirring blade peripheral speed 30 m / sec, stirring time 5 min. Were added under the following mixing conditions to obtain negatively chargeable toner particles having a volume average particle diameter of 7.0 μm.

Further, the liberation rate of titanium oxide fine particles in the obtained toner was 2.42%. In addition, the liberation rate of the titanium oxide fine particles was measured using a PT1000 particle analyzer (manufactured by Yokogawa Electric Corporation). Details of the method for measuring the liberation rate of the external additive are described in a patent document (Japanese Patent Laid-Open No. 2002-202622, etc.). Briefly, this principle is to determine the liberation rate by introducing toner particles into plasma, exciting and emitting the toner particles, and measuring the intensity and time. That is, the isolation rate of TiO ₂ introduces toner particles TiO ₂ was externally added to the plasma, measuring the emission intensity of the TiO ₂ in the toner particles. From the emission intensity, the particle size (equivalent particle size) of TiO ₂ is obtained assuming that the toner particles to which TiO ₂ is externally added are true spherical particles. Liberated TiO ₂ also, as in the case of the toner particles, the equivalent diameter of the TiO ₂ is determined from the emission intensity. However, since the emission intensity of the free TiO ₂ is small, the equivalent particle size is small, and by comparing the equivalent particle size, the external additive added to the toner particles is distinguished from the free external additive. Is done. Therefore, when the total number of detected external additives TiO ₂ is determined and an individual having a small equivalent particle diameter is defined as the number of free external additive particles, the following expression (X) is obtained.

Release rate (%) = (number of detected free TiO ₂ ) / total number of detected TiO ₂ × 100
.... (X)
Specifically, the following measurement conditions were used.
"Particle analyzer PT1000" manufactured by Yokogawa Electric Corporation
Number of detected C (base material) in one measurement: 4,000 to 6,000 Number of scans in one sample (number of measurements): 6 times Noise cut level: 1.5 V or less Sort time: 30 digits
Gas used: He gas containing 0.1% O ₂ (2) Surface roughness measurement method on toner carrier The surface roughness was measured with a laser microscope “VK-9500” manufactured by Keyence Corporation, and an observation magnification of 1000 In accordance with JIS B-0601-1994, the average value of the line roughness at two locations in the axial direction and the peripheral direction of the developing roll is obtained.

(3) Method for measuring film thickness on toner carrier surface The film thickness of the coating film on the surface of the developing roller was measured using a “FIB (FB2000)” manufactured by Hitachi, Ltd. with a beam diameter of 1 μm and a beam current of 10 nA. And then ground and measured.

Hereinafter, toner carriers of the present invention and comparative examples will be shown as examples.
Example 1
The surface of an iron roller (SUS304, thickness 1 mm, outer diameter 18 mm) was subjected to shot blasting (blast abrasive grains: No. 100 to 200 alumina beads), and the surface roughness (Rz) was 3 μm.

Next, a multi-electrode plasma CVD apparatus (synthetic gas: Si (CH ₃ ) ₄ manufactured by Toshiba Tungaloy Co., Ltd., a synthesis temperature of 140 ° C., a gas flow rate of 500 cm ³ / min. An SiC film was formed at an internal gas pressure of 50 torr. The developing roller surface roughness (Rz) after film formation was 7 μm.

After film formation, the film thickness (average value) of the ceramic coating layer was measured. The thickness (t ₁ ) of the ceramic coating layer on the convex portion on the surface of the core (iron roller) was 7 μm, and the thickness (t ₂ ) of the ceramic coating layer on the concave portion was 3 μm.

(Example 2)
The surface of an aluminum roller (thickness 2 mm, outer diameter 18 mm) was subjected to shot blasting (blast abrasive grains: No. 100 to 200 alumina beads), and the surface roughness (Rz) was 3 μm.

Next, an HCD type ion plating apparatus (evaporation source: titanium, synthesis gas: N ₂ , reaction temperature: 300 ° C., gas flow rate: 70 cm ³ / min.) Manufactured by ULVAC Co., Ltd. on the roughened aluminum roller surface. A TiN film was formed at a gas pressure of 1 × 10 ⁻³ torr. The developing roller surface roughness (Rz) after film formation was 7 μm.

After film formation, the film thickness of the ceramic coating layer was measured. The thickness (t ₁ ) of the ceramic coating layer on the convex portion on the surface of the core (Al roller) was 8 μm, and the thickness (t ₂ ) of the ceramic coating layer on the concave portion was 3 μm.

(Example 3)
The surface of a conductive NBR rubber roller (surface resistivity 10 ⁻⁵ Ω · cm, outer diameter 18 mm) coated with NBR rubber with a thickness of 1 mm on an iron support is roughened by a polishing method, The roughness (Rz) was 3 μm.

  Next, 10 parts by mass of BN fine particles, 10 parts by mass of carbon black particles, and 80 parts by mass of nylon resin adjusted to an average particle diameter of 1 μm were dissolved and suspended in isopropanol as an electrodeposition coating on the roughened NBR rubber roller surface. The ceramic coating layer was electrodeposited using an electrodeposition coating apparatus (applied voltage: 200 V) manufactured by Iseyama Co., Ltd. The developing roller surface roughness (Rz) after film formation was 7 μm.

After film formation, the film thickness of the ceramic coating layer was measured. The thickness (t ₁ ) of the ceramic coating layer on the convex portion on the surface of the core (conductive NBR rubber roller) was 7 μm, and the thickness (t ₂ ) of the ceramic coating layer on the concave portion was 4 μm.

Example 4
Conductive silicone rubber roller (surface specific resistance 10 ^-6 Ω · cm, outer diameter 18 mm) coated with silicone rubber with a thickness of 1 mm on an iron support is roughened by traverse polishing to produce a rough surface. The degree (Rz) was 3 μm.

  Next, 10 parts by mass of SiC fine particles, 10 parts by mass of carbon black particles, and 80 parts by mass of nylon resin adjusted to an average particle diameter of 1 μm are dissolved in isopropanol as an electrodeposition coating on the roughened conductive silicone rubber roller surface. -The ceramic coating layer was electrodeposited using an electrodeposition coating apparatus (applied voltage: 150 V) manufactured by Iseyama Co., Ltd. The developing roller surface roughness (Rz) after film formation was 7 μm.

After film formation, the film thickness of the ceramic coating layer was measured. The film thickness (t ₁ ) of the ceramic coating layer on the convex portion on the surface of the core (made of conductive silicone rubber) was 5 μm, and the film thickness (t ₂ ) of the ceramic coating layer on the concave portion was 4 μm.

(Comparative Example 1)
The surface of an iron roller (SUS304, thickness 1 mm, outer diameter 18 mm) was subjected to shot blasting (blast abrasive grains: No. 150 to 300 alumina beads), and the surface roughness (Rz) was set to 3 μm.

  Next, a solution obtained by diluting silicic acid three times with water was spray-coated on the roughened iron roller surface, dried at 70 ° C., and then immersed in a 2 mol% aqueous ammonium acetate solution. This was washed with water and then dried in a hot air dryer at 140 ° C. to obtain a water glass film. The developing roller surface roughness (Rz) after film formation was 7 μm.

After film formation, the film thickness of the ceramic coating layer was measured. The thickness (t ₁ ) of the ceramic coating layer on the convex portion on the surface of the core (iron roller) was 6 μm, and the thickness (t ₂ ) of the ceramic coating layer on the concave portion was 6 μm.

(Comparative Example 2)
A conductive NBR rubber roller (surface specific resistance 10 ⁻⁶ Ω · cm, outer diameter 18 mm) coated with NBR rubber with a thickness of 1 mm on an iron support is roughened by plunge polishing, and the surface is roughened. The degree (Rz) was 3 μm.

  Next, on the roughened NBR rubber roller surface, as an electrodeposition coating material, 10 parts by mass of carbon black particles and 80 parts by mass of nylon resin were dissolved and suspended in isopropanol to obtain a solid solution of 10% solids. The electrodeposition was applied using an electrodeposition coating apparatus (applied voltage: 150 V) manufactured by Iseyama Co., Ltd. The developing roller surface roughness (Rz) after film formation was 7 μm.

After film formation, the film thickness of the ceramic coating layer was measured. The film thickness (t ₁ ) of the ceramic coating layer on the convex portion on the surface of the core (conductive NBR rubber roller) was 15 μm, and the film thickness (t ₂ ) of the ceramic coating layer on the concave portion was 10 μm.

(Evaluation)
After the toner prepared above is put into the black developing cartridge of “Color Laser Printer LP9000C” manufactured by Seiko Epson Corporation, the toner carrier (developing roller) of the present invention and the comparative example is attached, and the developing gap is 120 μm, the DC voltage The developing bias of (DC) is -200 V, the alternating voltage (AC) is 3 kHz superimposed on this, and the PP voltage is 1.5 kV. The peripheral speed of the developing roller rotating counterclockwise is a latent image carrier rotating clockwise. The peripheral speed ratio was 1.6 times that of the holder.

  Initial image uniformity due to the difference in image density between the leading and trailing edges of an A3 size monochrome solid image, and a decrease in image density when 3000 sheets of 5% toner consumption patterns are printed continuously in A4 size. The image uniformity after printing 3000 sheets was determined.

  Image uniformity was evaluated using a “528 type densitometer” manufactured by X-Rite, and the difference in image density (OD value) was within 0.1, and when it was larger than 0.1, it was displayed as x.

  Evaluation of filming at the initial stage on the surface of the developing roller and after printing 3000 sheets was made by observing the surface of the developing roller with an optical microscope (about 100 times) and observing the occurrence of rubbing marks in the rotating direction of the developing roller, The case where the generation of the rubbing trace was not visually recognized was rated as “◯”, and the case where the generation of the rubbing trace was visually recognized was marked as “X”. The results are shown in Table 1 below.

  As can be seen from Table 1, the image forming developing device of the present invention has an initial image uniformity after printing 3000 sheets, and even onto the developing roller, even if the toner contains toner particles of opposite polarity. No filming occurs, and a desired developing bias can be obtained without using a high output power source.

  According to the image forming developing device of the present invention, by preventing the occurrence of electric field concentration due to surface irregularities, the charging property of the toner is not deteriorated, and the filming phenomenon on the surface of the toner carrier can be prevented for a long time. In addition, since the image uniformity is excellent and the toner transportability is excellent, and the voltage drop on the surface of the developing roller can be suppressed, the industrial utility value is great.

FIG. 1 is a cross-sectional view of a toner carrier (developing roller) of a developing device for image formation according to the present invention, (a) is an overall view, and (b) is an enlarged cross-sectional view of part A of (a). FIG. 5 is a cross-sectional view of the toner carrier (developing roller) when the core is a metal roller. 2A and 2B are cross-sectional views of the toner carrier (developing roller) of the image forming developing device according to the present invention. FIG. 2A is an overall view, and FIG. 2B is an enlarged cross-sectional view of a portion A in FIG. FIG. 5 is a cross-sectional view when the core of the toner carrier (developing roller) is a conductive elastic roller. FIG. 3 is a cross-sectional view showing the overall configuration of a tandem type image forming apparatus. FIG. 4 is a cross-sectional view of the developing device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 23 ... Photosensitive drum, 100 ... Developing apparatus, 101 ... Toner accommodating part, 103 ... Housing, 105 ... Supply roller, 107 ... Developing roller, 109 ... Restricting blade, 111 ... Plate spring member, 112 ... Elastic member, 113 ... Toner, DESCRIPTION OF SYMBOLS 201 ... Metal roller, 202 ... Ceramic coating layer, 203 ... Support body, 204 ... Conductive elastic roller.

Claims (8)

An image-forming developing device comprising a toner carrier, wherein the toner carrier comprises a core body to which a voltage can be applied, and the core body surface is roughened into a rough surface and the concave-convex core body. A ceramic coating layer having a high dielectric or high resistance provided on the surface, and the thickness (t ₁ ) of the ceramic coating layer on the convex portion on the surface of the core is set to the thickness of the ceramic coating layer on the concave portion ( t ₂ ) An image forming developing device characterized in that it is thicker. 2. The roller-shaped toner carrier in which the core in the toner carrier is a metal roller, and the ceramic coating layer is a high dielectric layer having a relative dielectric constant of 100 or more. Image forming developing apparatus. The core of the toner carrier is a conductive elastic roller, and the ceramic coating layer is a roller-like toner carrier that is a high resistance layer having a specific resistance of 50 μΩ · cm or more. The image forming developing apparatus according to claim 1. The thickness (t ₁ ) of the ceramic coating layer on the convex portion on the surface of the core body is 3 μm to 10 μm, the thickness (t ₂ ) of the ceramic coating layer on the concave portion is ₁ μm to 5 μm, and t ₁ is from t ₂ . 2. The image forming developing device according to claim 1, wherein the developing device has a thickness of 2 [mu] m or more. 2. The image forming developing apparatus according to claim 1, wherein the surface roughness (Rz) of the core is 5 to 15 [mu] m. 2. The image forming developing apparatus according to claim 1, wherein the ceramic coating layer has a surface roughness (Rz) of 2 to 12 [mu] m. 2. The image forming developing apparatus according to claim 1, wherein the toner has a volume average particle diameter of 4.5 to 9 [mu] m and an average circularity of 0.95 to 0.99. 2. The image forming developing apparatus according to claim 1, wherein the toner is a negatively chargeable toner, and is a non-magnetic one-component toner comprising toner base particles and at least positive-polarity added particles.

Images