JP2008233157A - Developing roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller on the surface of which the occurrence of filming is suppressed, and which forms a high-quality toner image having high density and free from fogging, and does not cause soiling in a device, for example, even when consecutive print of 5,000-sheet level is performed, in a non-magnetic one-component developing type printer. <P>SOLUTION: The developing roller forms a covering layer having conductivity on the outer circumference of a conductive shaft, carries non-magnetic one-component developer on the surface of the covering layer, to form the thin layer of the non-magnetic one-component developer, and sticks the non-magnetic one-component developer to an electrostatic latent image on the surface of a latent image holding body which holds the electrostatic latent image on its surface from the thin layer without coming into contact with the latent image holding body in such a state, to make the electrostatic latent image visible. When a resin thin film composed of only resin which forms the covering layer is electrified by an electrifier, assuming that the surface potential of the resin thin film one second after that is Rv1 and that ten seconds after that is Rv2, the developing roller has relation; 0.01≤Rv2/Rv1≤0.20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a developing roller incorporated in an image forming apparatus employing an electrophotographic system such as a copying machine, a printer or a facsimile receiver, and more particularly to a developing roller used in a developing apparatus employing a nonmagnetic one-component developing system. It is.

  In the non-magnetic one-component developing method, the non-magnetic one-component developer (hereinafter also referred to as toner) held on the surface of the developing roller is thinned when passing between the developer layer regulating member (toner regulating blade). Is done.

  At this time, the toner is frictionally charged by being brought into contact with the surface of the developing roller and the toner regulating blade, so that electric charge is applied. As described above, the developing roller used in the non-magnetic one-component developing system has a function of transporting the toner to the developing portion, but is required to have a charge imparting performance to the toner.

  The toner charged on the developing roller and transported to the developing unit is required to be always in a uniformly charged state and a constant transport amount.

  However, during continuous printing, the charge amount of toner held on the developing roller may become unstable.

  For example, the toner in the non-developed portion (the portion that has not contributed to image formation) on the developing roller retains an excessive amount of charge due to continuous frictional charging, and is caused to adhere from the developing roller to the photoreceptor. The ability to visualize is reduced, and it is difficult to remove the toner on the developing roller by the static eliminator blade, and it is difficult to replace the toner on the developing roller, which may cause an image defect (for example, insufficient image density).

  In addition, in the developing portion (the portion where toner is consumed by contributing to image formation), new toner is supplied to the consumed portion, but the remaining toner not contributing to image formation is newly supplied. The charge amount may differ from toner, and image defects (for example, fogging) may occur due to non-uniformity of the charge amount distribution caused by the charge amount.

  All of the above problems are greatly related to the surface potential of the developing roller. When the surface potential of the developing roller is high, the ability to make the toner adhere to the photosensitive member from the developing roller is reduced. Also, if the surface potential of the developing roller is high, it becomes difficult to remove the toner when the toner is removed by the static elimination blade. Even if the toner is removed, if the surface potential is high, the charge on the developing roller does not escape and stays there. Therefore, the charge amount of the toner charged next at the same portion becomes low.

  If the surface potential of the developing roller decreases to a constant potential after a lapse of a certain time and the surface potential of the developing roller is constant, the toner is charged well, and the toner is removed by the static elimination blade. It can be removed well, no toner is continuously attached to the surface of the developing roller, filming on the surface of the developing roller can be prevented, and a stable toner image without image defects (for example, insufficient image density or fogging) can be obtained. can get.

For the purpose of preventing the occurrence of insufficient image density and fogging and obtaining a high-quality toner image, a semiconductive resin coating layer in which a conductive agent is blended with the outermost resin layer of the developing roller is provided, and the electric resistance when 100 V is applied. Is 1 × 10 ⁴ to 1 × 10 ¹⁰ Ω, 0.35 seconds when the surface is charged by applying a voltage of 8 kV to a corona charger disposed at a distance of 1 mm from the surface to generate a corona discharge. A developing roller in which the maximum value of the subsequent surface potential is 90 V or less has been studied (for example, see Patent Document 1).

Further, for the purpose of preventing the occurrence of fogging and insufficient image density, a voltage of 8 kV is applied to a corona charger arranged at a distance of 1 mm from the surface to generate a corona discharge to charge the surface. A developing roller in which an ultraviolet curable resin or an electron beam curable resin is mixed with a conductive agent is studied so that the absolute value of the surface potential decay rate from 0.1 to 0.2 seconds after charging is 0.1 V / sec or less. (For example, see Patent Document 2).
JP 2000-206777 A JP 2000-352084 A

  However, the developing roller manufactured using the above-mentioned proposed resin is mounted on a non-magnetic one-component developing type printer, and when a large number of sheets are continuously printed, filming occurs on the surface of the developing roller, resulting in insufficient image density. There was a problem that fogging occurred or dirt inside the machine was generated.

  The present invention is a non-magnetic one-component development type printer, and even when a large number of sheets (for example, continuous 5000 sheets) are printed, the occurrence of filming on the surface of the developing roller is suppressed, and high density and no fogging are caused. An object of the present invention is to provide a developing roller that can obtain a high-quality toner image and that does not cause in-machine contamination.

  The present invention is achieved by adopting the following configuration.

1. A conductive coating layer is formed on the outer periphery of the conductive shaft, and a non-magnetic one-component developer is carried on the surface of the coating layer to form a thin layer of the non-magnetic one-component developer. The non-magnetic one-component developer is attached from the thin layer to the electrostatic latent image on the surface of the latent image holding member without contacting the latent image holding member holding the electrostatic latent image on the surface, thereby visualizing the electrostatic latent image. In the developing roller
When the developing roller is charged by a charger with a resin thin film made of only the resin forming the coating layer, the surface potential of the resin thin film after 1 second is Rv1, and the surface potential of the resin thin film after 10 seconds is Rv2
0.01 ≦ Rv2 / Rv1 ≦ 0.20
A developing roller having the following relationship:

  According to the present invention, for example, even when a large number of continuous 5000 sheets are printed, the occurrence of filming on the surface of the developing roller can be suppressed, and a high-quality toner image with high density and no fogging can be obtained. It is now possible to perform excellent image formation that does not generate any of the above.

  The present inventors examined characteristics required for a developing roller that can be used for non-contact image formation using a non-magnetic one-component developer.

  The inventors of the present invention paid attention to the attenuation characteristics at the surface potential after the coating layer of the developing roller was charged. That is, the surface potential of the developing roller is preferable even when a large number of sheets are printed continuously by selecting a resin whose surface potential attenuates to a specific value after a certain time has elapsed after charging the coating layer of the developing roller. I guessed it could be controlled to the range.

  As a result of various studies, when a thin film made only of a resin (hereinafter also referred to as a resin thin film) is charged with a charger, the surface potential of the resin thin film after 1 second of charging is represented by Rv1, and the surface potential of the resin thin film after 10 seconds is represented by Rv2. When Rv1 and Rv2 used the resin which has the attenuation | damping characteristic which satisfy | fills following formula, it discovered that the subject of this invention was eliminated.

formula
0.01 ≦ Rv2 / Rv1 ≦ 0.20
That is, in the developing roller formed using a resin in which the surface potential of the resin thin film satisfies the above relationship, charge is imparted to the toner satisfactorily, and the toner can be satisfactorily removed by the static elimination blade. New toner is supplied uniformly. As a result, toner does not continuously adhere to the surface of the developing roller, filming on the surface of the developing roller can be prevented, and a stable toner image without image defects can be obtained.

  Examples of the resin exhibiting such damping characteristics include thermoplastic elastomers.

  Thermoplastic elastomers are composed of soft segments and hard segments. Soft segments and hard segments are incompatible with each other and exist in a microphase-separated state, and form a crystalline phase by intermolecular cohesive forces mainly consisting of hydrogen bonds. A high-order structure consisting of a matrix with high mobility is formed by a hard segment domain and a weak intermolecular force mainly composed of a soft segment.

  The cohesive strength of microdomains is indicated by the magnitude of the molecular cohesive energy of the organic bonds that make up the microdomains.

  Urethane bonds and amide bonds have higher molecular cohesive energy than other organic functional groups. In thermoplastic elastomers having these bonds, active hydrogen tends to form hydrogen bonds with oxygen of the carbonyl group by aggregation, so that charges are polarized in the molecule and carrier ions are generated. It is considered that the charge is attenuated by the movement of the carrier ions.

  Table 1 shows the cohesive energy of the organic functional group described in the document “JOURNAL OF POLYMER SCIENCE VOL. XVI, Pages 323-343 (1955)”.

  Hereinafter, the present invention will be described in detail.

<< Surface potential (Rv1, Rv2) of resin thin film, attenuation characteristics (Rv2 / Rv1) >>
The surface potential (Rv1, Rv2) and attenuation characteristic (Rv2 / Rv1) of the resin thin film can be measured and calculated by the following method.

Preparation of measurement sample A solution obtained by dissolving 20 parts by mass of resin in 100 parts by mass of methyl ethyl ketone was applied onto an aluminum plate using an applicator, dried at 130 ° C. for 1 hour, and a measurement sample (resin thin film) having a dry film thickness of 30 μm. Is made.

  The measurement sample prepared above was obtained by measuring the surface potential (Rv1) after 1 second charging and the surface potential (Rv2) after 10 seconds charging under the following conditions using the measuring apparatus shown in FIG. An attenuation characteristic (Rv2 / Rv1) is calculated from the values of Rv1 and Rv2.

Measurement conditions Measurement environment Normal temperature and humidity (20 ℃, 50% RH)
Potential measurement device "REPA-8300A" (manufactured by Kawaguchi Electric)
Charging device Corona charger Charging wire Tungsten Distance between charging wire and corona charger back plate 5mm
Applied voltage 4 kV
Distance between resin thin film and charging wire of corona charger 10mm
Charging speed 2 cm / second Time until measurement after charging 1 second FIG. 1 shows an example of an apparatus for measuring the surface potential of a resin and its attenuation characteristics.

  In the figure, 1 is an aluminum plate, 2 is a resin thin film, 3 is a corona charger, 4 is a probe of a potential measuring device, 5 is an aluminum plate provided with a resin thin film, and 6 is a probe of a corona charger and a potential measuring device. Indicates the rail to be moved.

  In the measurement, the resin thin film 2 formed by coating on the aluminum plate 1 is charged by the corona charger 3 under the above conditions, and a charging decay curve from 1 second to 10 seconds after charging is attached 20 mm away from the charger. Measurement is performed by the probe 4 of the obtained potential measuring device. Randomly change the measurement location, measure 20 points, and obtain Rv1 and Rv2 from the average value. Rv2 / Rv1 is calculated from the values of Rv1 and Rv2.

  FIG. 2 is a graph showing a state in which the surface potential of the resin decays with the elapsed time after charging.

  In the figure, the vertical axis represents the surface potential of the resin, and the horizontal axis represents the elapsed time after charging. Rv1 indicates the surface potential after 1 second of charging, and Rv2 indicates the surface potential after 10 seconds of charging.

  The resin used in the present invention satisfies 0.01 ≦ Rv2 / Rv1 ≦ 0.20.

  For example, if the surface potential (Rv1) after 1 second of charging is −500V, a resin whose surface potential (Rv2) after 10 seconds is −5V ≦ Rv2 ≦ −100V is applicable.

  Next, the configuration, material, and manufacturing method of the developing roller will be described.

<Configuration of developing roller>
The developing roller of the present invention has a configuration in which a conductive coating layer is provided on the outer periphery of the conductive shaft.

  FIG. 3 is a schematic cross-sectional view showing an example of the developing roller of the present invention.

  In the figure, 32 is a developing roller, 11 is a conductive shaft, 12 is a coating layer, and 12b is an adhesive layer.

  In the developing roller of the present invention, even if the coating layer 1 is directly provided on the conductive shaft as shown in FIG. 3A, an adhesive layer is provided on the conductive shaft as shown in FIG. It may be a laminate of two or more layers provided with layers.

"material"
The developing roller of the present invention is obtained by forming a conductive coating layer on the outer periphery of the conductive shaft.

  The coating layer contains a resin according to the present invention (a resin having a specific attenuation characteristic) and a conductive agent imparting conductivity (for example, an electronic conductive agent or an ionic conductive agent), and if necessary, a non-conductive filler. Is added to form.

《Conductive shaft》
Since the conductive shaft also serves as a member that leaks charges accumulated on the surface of the developing roller, the conductive shaft is preferably made of a conductive metal having a volume resistance of 10 ⁻³ Ω · cm or less. Typical examples include conductive metals such as stainless steel (for example, SUS304) having a diameter of 1 to 30 mm, iron, aluminum, nickel, aluminum alloy, and nickel alloy, and may be formed of a conductive resin.

<Coating layer>
The coating layer is formed by applying a coating liquid obtained by appropriately blending the resin according to the present invention and various additives such as a conductive agent and a non-conductive filler to the outer peripheral surface of the conductive shaft and drying it. can do. The conductivity of the coating layer is imparted by a conductive agent blended in the coating layer.

<resin>
The resin according to the present invention can be used without any particular limitation as long as it exhibits a specific attenuation characteristic as described above.

  A thermoplastic elastomer is preferable as the resin having the above-mentioned damping characteristics.

  Specific examples include thermoplastic polyurethane elastomers and thermoplastic polyamide elastomers. Among these, the thermoplastic polyurethane elastomer is a rubber-like elastic body obtained by a reaction between polyester or polyether and isocyanate, and is generally called urethane rubber. The structure of the thermoplastic polyurethane elastomer is composed of a part A constituting a soft segment and a part B constituting a hard segment as shown below.

  Among these, urethane resin, polyamide resin, and the like are preferably used from the viewpoint of toner chargeability and the like. Among these, it is particularly preferable to use a urethane resin from the viewpoint of obtaining good wear resistance and elasticity.

  Examples of the urethane resin include those obtained by reacting a urethane raw material containing a polyhydroxy compound and an isocyanate compound, for example, those obtained by a method in which a prepolymer is subjected to a crosslinking reaction, and polyols obtained by polyisocyanate by a one-shot method. What was obtained by the method of making it react with soot is mentioned.

  In this case, as a polyhydroxyl compound used when obtaining a urethane resin, a polyol used for production of a general flexible polyurethane foam or a urethane elastomer, for example, a polyether polyol having a polyhydroxyl group at a terminal, a polyester polyol, or a polyether In addition to polyester polyols, general polyols such as polyolefin polyols such as polybutadiene polyol and polyisoprene polyol, and so-called polymer polyols obtained by polymerizing ethylenically unsaturated monomers in polyols can be used. As the isocyanate compound, polyisocyanate used in the production of general flexible polyurethane foam and urethane elastomer, that is, tolylene diisocyanate (sometimes referred to as TDI), crude TDI, 4,4'-diphenylmethane. Diisocyanates (sometimes referred to as MDI), crude MDI, aliphatic polyisocyanates having 2 to 18 carbon atoms, alicyclic polyisocyanates having 4 to 15 carbon atoms, and mixtures and modified products of these polyisocyanates, such as partially polyols A prepolymer obtained by reacting with a polymer can be used. In particular, the mixing ratio of the polyisocyanate may be lowered for the purpose of reducing the universal hardness of the coating layer.

  Moreover, the urethane resin may be prepared using a one-pack type or two-pack type urethane raw material containing a polyhydroxyl compound and a polyisocyanate, and an epoxy resin or a melamine resin is used as a crosslinking agent as necessary. Also good.

  Polyamide resins include polyamide resins typified by nylon 6,6,6,6,10,6,12,11,12,12,12, and polyamides obtained from polycondensation between different types of polyamide monomers. In view of workability, alcohol-soluble ones are preferred. For example, those obtained by adjusting the molecular weight of a polyamide terpolymer or quaternary copolymer, or those obtained by methoxymethylating nylon 6 or nylon 12 to be soluble in alcohol or water.

<Conductive agent>
Examples of the conductive agent include an electronic conductive agent and an ionic conductive agent. In the present invention, it is preferable to adjust the volume resistance of the coating layer to 1 × 10 ⁴ to 1 × 10 ¹⁰ Ω · cm by adding a conductive agent to the coating layer.

(Electronic conductive agent)
Examples of the electronic conductive agent include various conductive metals or alloys such as carbon black, graphite, aluminum, copper, tin, and stainless steel, tin oxide, zinc oxide, indium oxide, titanium oxide, tin oxide antimony monoxide solid solution, tin oxide Various conductive metal oxides such as indium oxide solid solution, and fine powders such as insulating substances coated with these conductive materials can be used. Among these, carbon black is preferably used because it can be obtained relatively easily and good chargeability can be obtained.

  The type of carbon black is not particularly limited, and various conventionally known carbon blacks such as ketjen black, channel black, and furnace black can be used. The blending amount of carbon black is not particularly limited because it varies depending on the type of carbon black to be used. Usually, it is preferably 5 to 50 parts by mass, more preferably 10 to 40 parts by mass with respect to 100 parts by mass of the resin component. In the range of the part, it is appropriately set according to the conductivity and universal hardness required for the coating layer.

  When the blending amount of carbon black is 50 parts by mass or less, the conductivity and universal hardness of the developing roller become appropriate, and further, the uniformity of distribution within the resin layer increases, so the uniformity of conductivity is also improved. To do. On the other hand, when the blending amount of carbon black is 5 parts by mass or more, a preferable level of conductivity can be ensured.

(Ionic conductive agent)
As the ionic conductive agent, conventionally known inorganic ionic salts and organic ionic salts can be appropriately selected and used. Specifically, alkali metal halides such as Li, LiCl, NaI, NaBr, and KI, perchlorates such as LiClO ₄ , KClO ₄ , and CuC ₁₂ Mg (ClO ₄ ) ₂ , and thiocyanic acids such as LiSCN, NaSCN, and CsSCN Inorganic ion salts such as salts, aliphatic sulfonates, higher all sulfates, higher alcohol phosphates, higher alcohol ethylene oxide addition sulfates, higher alcohol ethylene oxide addition phosphates, quaternary Mention may be made of organic ion salts such as ammonium salts and betaines. Among these, quaternary ammonium salts such as trimethyloctadecyl ammonium perchlorate, tetramethylammonium chloride, and benzyltrimethylammonium chloride are particularly preferable. These ionic conductive agents may be used alone or in combination of two or more.

  The compounding amount of the ionic conductive agent is not particularly limited and is appropriately selected according to various situations, but is preferably 0.001 to 5 parts by mass with respect to 100 parts by mass of the resin component forming the coating layer, and 0.05 to 2 Part by mass is more preferable.

<Non-conductive filler>
Examples of the non-conductive filler include diatomaceous earth, quartz powder, dry silica, wet silica, titanium oxide, zinc oxide, aluminosilicate, calcium carbonate, and resin particles. Among these, resin particles are preferable, and as the resin particles, crosslinked acrylic resin particles and crosslinked urethane resin particles are particularly preferable. The non-conductive filler is added for the purpose of imparting roughness to the surface of the developing roller and facilitating the toner conveyance of the developing roller.

<Production of developing roller>
As a means for providing the coating layer on the outer peripheral surface of the conductive shaft, a method of applying a coating solution in which the above constituent materials are dissolved and dispersed in an organic solvent onto the conductive shaft is effectively employed. The resin component concentration of the coating solution is not particularly limited and may be appropriately adjusted according to the required layer thickness. However, the resin component concentration is 10% by mass or more from the dispersibility and stability of various additives in the coating solution. It is preferable that The solvent used for preparing the coating solution may be any solvent as long as it can dissolve the resin component, for example, lower alcohols such as methanol, ethanol and isopropanol, ketones such as methyl ethyl ketone, cyclohexane, Toluene, xylene and the like are preferably used.

  Examples of the method for forming the coating layer include dipping, spraying, roll coating, brushing, and the like depending on the viscosity of the resin component constituting the coating layer, but the present invention does not particularly limit this forming method. Absent.

  Further, the surface roughness (arithmetic average roughness Ra) of the developing roller of the present invention is preferably 0.3 to 3.0 μm. By setting the amount within this range, the toner conveyance amount can be made suitable. The surface roughness of the developing roller can be adjusted by adding a non-conductive filler in the coating layer.

  The arithmetic average roughness Ra (hereinafter also simply referred to as Ra) will be described (same as JIS B 0601).

  In the present invention, Ra is extracted from the roughness curve by the reference length Lr in the direction of the average line, the x-axis is taken in the direction of the average line of the extracted portion, the y-axis is taken in the direction of the vertical magnification, and the roughness curve is obtained. When represented by y = f (x), the value obtained by the following formula (1) is represented by micrometers (μm).

  The measuring instrument is a surface roughness meter “Surfcom 1400D” (manufactured by Tokyo Seimitsu Co., Ltd.). However, other measuring instruments may be used as long as the measuring instrument produces the same result within the error range.

Surface roughness measurement conditions Measurement length L: 4.0 mm
Reference length Lr: 0.8 mm
Cut-off wavelength λc: 0.8 mm
Stylus tip shape: tip angle 60 ° cone Stitch tip radius: 2 μm
Measurement speed: 0.3 mm / sec
Measurement magnification: 10000 times In addition, each sample was measured at a total of 9 points, 3 points at equal intervals in the axial direction and 3 points at equal angles in the circumferential direction, and the average value is an arithmetic average roughness Ra defined by the present invention. And

  The thickness of the coating layer is preferably set in the range of 1 to 30 μm, particularly preferably 5 to 20 μm. The thickness of the resin layer is measured from a cross-sectional sample including the resin layer taken from the developing roller and from a micrograph of the cross-sectional sample.

  The resin layer formed around the conductive shaft may have a multilayer structure having a plurality of layers such as a surface layer and an intermediate layer.

  Next, a developing device, an image forming method, an image forming device, and a developer using the developing roller of the present invention will be described.

<Developing device>
FIG. 4 is a schematic cross-sectional view showing an example of a developing device (developing device) used with the developing roller of the present invention attached.

  In FIG. 4, reference numeral 10 denotes a latent image holding member (hereinafter also referred to as a photosensitive drum), and latent image formation is performed by electrophotographic process means or electrostatic recording means (not shown). A developing roller 32 is provided with a coating layer on a conductive shaft made of aluminum or stainless steel.

  The toner T is stored in the hopper 6 and is supplied onto the developing roller by the supply roll 4. The supply roll is made of a foam material such as polyurethane foam, and rotates with a relative speed in the forward or reverse direction with respect to the developing roller 32. Together with the toner supply, the developed toner on the developing roller (undeveloped toner) We are also stripping off. A uniform toner thin layer is formed on the toner supplied onto the developing roller 32 by a toner regulating blade 5 which is a kind of member that performs toner thinning and charging.

  The contact pressure between the toner regulating blade and the developing roller is 3 to 250 N / m, preferably 10 to 30 N / m, as the linear pressure in the developing roller bus direction. When the contact pressure is less than 3 N / m, it is difficult to form a uniform toner thin layer, and the toner charge amount distribution becomes broad, which may cause fogging or scattering. On the other hand, if the contact pressure exceeds 250 N / m, a large pressure is applied to the toner and the toner deteriorates, which is not preferable because toner aggregation occurs. Further, it is not preferable because a large torque is required to drive the developing roller. That is, by adjusting the contact pressure to 3 to 250 N / m, it is possible to effectively loosen the toner of the present invention, and it is possible to instantaneously raise the charge amount of the toner.

  Examples of the member that forms and charges a uniform thin toner layer include an elastic blade and an elastic roller, and is formed of a material capable of charging the toner to a desired polarity by frictional charging.

  In the case of non-magnetic one-component toner in which a thin layer of toner is coated on the developing roller with a blade, the thickness of the toner layer on the developing roller is set to be opposite between the developing roller and the photosensitive drum in order to obtain a sufficient image density. It is preferable that the gap length is smaller than that of the so-called non-contact development method, and an alternating electric field is applied to the gap. A gap of 50 to 500 μm, more preferably 100 to 300 μm, is provided between the photoreceptor surface and the developing roller surface. On the other hand, the toner layer provided on the developing roller overlaps with about 1 to 3 toner particles. A toner layer of ˜30 μm is preferable. Note that the film thickness of the toner layer on the developing roller can be obtained by microscopic observation.

  That is, a developing cartridge loaded in an actual image forming apparatus is irradiated with parallel light from the cross-sectional direction of the developing process, and a high-speed, high-resolution camera (for example, Phototron: FASTCAM MAX, photographing speed 100,000 (FPS)) It can measure from what image | photographed by and visualized the behavior of the image development part.

  The film thickness (a) of the toner thin layer on the developing roller is determined by the gap (b) between the toner layer on the developing roller and the photosensitive member in the area close to the photosensitive member, and the developing nip sandwiched between the developing roller and the photosensitive member. The center distance (c) is measured, and the difference (a = c−b) is obtained.

  4 is applied between the developing roller 32 and the photosensitive drum 10 by applying a developing bias in which an alternating electric field or a DC electric field is superimposed on the alternating electric field, from above the developing roller to the photosensitive drum. Therefore, it is possible to easily move the toner and to obtain a high-quality image.

<Image formation>
FIG. 5 is a schematic sectional view showing an example of a full-color image forming apparatus in which the developing roller of the present invention is used.

  In the full-color image forming apparatus shown in FIG. 5, a charging brush 111 that uniformly charges the surface of the photosensitive drum 10 to a predetermined potential around the photosensitive drum 10 that is rotationally driven, and the surface of the photosensitive drum 10. A cleaner 112 for scraping off the remaining toner is provided.

  Further, a laser scanning optical system 20 for scanning and exposing the photosensitive drum 10 charged by the charging brush 111 with a laser beam is provided. The laser scanning optical system 20 includes a laser diode, a polygon mirror, and an fθ optical element. As is well known, print data for each of yellow, magenta, cyan, and black is transferred from the host computer to the control unit. The laser scanning optical system 20 sequentially outputs the laser beam as a laser beam based on the print data for each color, scans and exposes the photosensitive drum 10, and thereby the static image for each color is formed on the photosensitive drum 10. Electro latent images are sequentially formed.

  In addition, the full-color developing device 30 that supplies full-color development to the photosensitive drum 10 on which the electrostatic latent image is formed in this manner, performs yellow, magenta, cyan, and black around the support shaft 33. Four color-developing units 31Y, 31M, 31C, and 31Bk each containing non-magnetic one-component toner are provided. The developing units 31Y, 31M, 31C, and 31Bk rotate around the support shaft 33, and the developing units 31Y, 31M, 31C, and 31Bk are rotated. It is guided to a position facing the photosensitive drum 10.

  Further, in each of the developing devices 31Y, 31M, 31C, and 31Bk in the full color developing device 30, as shown in FIG. 5, the toner is formed on the outer peripheral surface of the developer carrier (developing roller) 32 that rotates and conveys the toner. A regulating member is in pressure contact, and the toner regulating member regulates the amount of toner conveyed by the developing roller 32 and charges the conveyed toner. In the full-color developing device 30, two toner regulating members may be provided in order to appropriately regulate and charge the toner conveyed by the developing roller.

  Then, whenever the electrostatic latent image of each color is formed on the photosensitive drum 10 by the laser scanning optical system 20 as described above, the full-color developing device 30 is rotated around the support shaft 33 as described above. Then, the developing devices 31Y, 31M, 31C, and 31Bk containing toner of the corresponding colors are sequentially guided to positions facing the photosensitive drum 10, and the developing rollers 32 in the developing devices 31Y, 31M, 31C, and 31Bk are moved. Development is performed by sequentially supplying charged toner of each color onto the photosensitive drum 10 in which the electrostatic latent images of the respective colors are sequentially formed as described above without contact with the photosensitive drum 10. It has become.

  Further, an endless intermediate transfer belt 40 that is rotationally driven is provided as an intermediate transfer body 40 at a position downstream of the full-color developing device 30 in the rotation direction of the photosensitive drum 10. Is driven to rotate in synchronization with the photosensitive drum 10. The intermediate transfer belt 40 is pressed by a rotatable primary transfer roller 41 so as to come into contact with the photosensitive drum 10, and a portion of a support roller 42 that supports the intermediate transfer belt 40 includes: A secondary transfer roller 43 is rotatably provided, and the recording material S such as recording paper is pressed against the intermediate transfer belt 40 by the secondary transfer roller 43.

  Further, a cleaner 50 that scrapes off the toner remaining on the intermediate transfer belt 40 is provided in a space between the full-color developing device 30 and the intermediate transfer belt 40 so as to be able to contact with and separate from the intermediate transfer belt 40. ing.

  Further, the paper feeding means 60 that guides the recording material S such as plain paper to the intermediate transfer belt 40 includes a paper feeding tray 61 that accommodates the recording material S and the recording material S that is accommodated in the paper feeding tray 61 one by one. The recording material S fed in synchronization with the paper feed roller 62 for feeding paper and the image formed on the intermediate transfer belt 40 is sent between the intermediate transfer belt 40 and the secondary transfer roller 43. The recording material S sent between the intermediate transfer belt 40 and the secondary transfer roller 43 in this way is pressed against the intermediate transfer belt 40 by the secondary transfer roller 43. The toner image is pressed and transferred from the intermediate transfer belt 40 to the recording material S.

  On the other hand, the recording material S on which the toner image is pressed and transferred as described above is guided to the fixing device 70 by the conveying means 66 constituted by an air suction belt or the like, and is transferred by the fixing device 70. The toner image is fixed on the recording material S, and then the recording material S is discharged onto the upper surface of the apparatus main body 100 through the vertical conveyance path 80.

  Next, the operation of forming a full color image using this full color image forming apparatus will be specifically described.

  First, the photosensitive drum 10 and the intermediate transfer belt 40 are rotationally driven in the respective directions at the same peripheral speed, and the photosensitive drum 10 is charged to a predetermined potential by the charging brush 11.

  The photosensitive drum 10 thus charged is exposed to a yellow image by the laser scanning optical system 20 to form an electrostatic latent image of a cyan image on the photosensitive drum 10. The yellow image is developed by supplying the yellow toner charged by the toner regulating member as described above from the developing device 31Y in which the yellow toner is accommodated in the photosensitive drum 10, and the yellow toner image is thus formed. The intermediate transfer belt 40 is pressed against the body drum 10 by the primary transfer roller 41, and the yellow toner image formed on the photosensitive drum 10 is primarily transferred to the intermediate transfer belt 40.

  After the yellow toner image is transferred to the intermediate transfer belt 40 in this way, the full-color developing device 30 is rotated around the support shaft 33 as described above, and the developing device 31M containing magenta toner is exposed to light. As in the case of the yellow image described above, the magenta image is exposed to the photosensitive drum 10 charged by the laser scanning optical system 20 to form an electrostatic latent image. The electrostatic latent image is developed by a developing device 31M containing magenta toner, and the developed magenta toner image is primarily transferred from the photosensitive drum 10 to the intermediate transfer belt 40. Black image exposure, development and primary transfer are sequentially performed, and yellow, magenta, cyan, and black toner images are sequentially superimposed on the intermediate transfer belt 40. To form a toner image of Rukara.

  When the final black toner image is primarily transferred onto the intermediate transfer belt 40, the recording material S is fed between the secondary transfer roller 43 and the intermediate transfer belt 40 by the timing roller 63, and the secondary transfer roller. The recording material S is pressed against the intermediate transfer belt 40 by 43, and the full color toner image formed on the intermediate transfer belt 40 is secondarily transferred onto the recording material S.

  When the full-color toner image is secondarily transferred onto the recording material S in this way, the recording material S is guided to the fixing device 70 by the conveying means 66, and the full-color toner transferred by the fixing device 70 is transferred. The image is fixed on the recording material S, and then the recording material S is discharged onto the upper surface of the apparatus main body 1 through the vertical conveyance path 80.

  As the non-magnetic one-component developer, a heat-fixable non-magnetic one-component toner is used.

  As the resin constituting the nonmagnetic one-component toner, it is preferable to use a resin having a relative dielectric constant of 2 to 4.

The median diameter (D ₅₀ ) diameter of the nonmagnetic one-component toner on the volume basis is preferably 3 to 9 μm from the viewpoint of obtaining a high-quality toner image.

  Specific examples of the resin constituting the nonmagnetic one-component toner include polyester resin and acrylic resin.

  The production method of the non-magnetic one-component toner is not particularly limited, and can be produced by a known polymerization method or pulverization method.

  The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited to these examples.

<Preparation of resin for coating>
Eight types of resins were prepared as coating resins.

Urethane A: Thermoplastic polyurethane elastomer (soft segment A: hard segment B = 60 parts by mass: 40 parts by mass)
Urethane B: Thermoplastic polyurethane elastomer (soft segment A: soft segment B = 80 parts by mass: 20 parts by mass)
The urethane A and the urethane B have the following structural formula.

Amide C: Thermoplastic polyamide elastomer (soft segment C: soft segment D = 60 parts by mass: 40 parts by mass)
Amide D: Thermoplastic polyamide elastomer (soft segment C: soft segment D = 80 parts by mass: 20 parts by mass)
The amide C and amide D have the following structural formula.

Acrylic resin: Thermoplastic acrylic resin “SUMIPEX LG” (manufactured by Sumitomo Chemical Co., Ltd.)
Polycarbonate resin: Polycarbonate film “Racron (R)” (made by International Chemical Co., Ltd.) Thickness 30 μm
Polyester resin: Polyethylene terephthalate film “Mylar” (manufactured by Teijin DuPont Co., Ltd.) Thickness 30 μm
Polythiophene resin: Poly (3-hexylthiophene) film 30 μm thick

  Table 2 shows the results of measuring and calculating Rv1, Rv2, and Rv2 / Rv1 of the eight types of prepared resins by the above method.

<Production of developing roller>
A developing roller was produced using the resin prepared above.

(Conductive shaft)
As a conductive shaft of the developing roller, a hollow cylindrical conductive shaft of SUS303 was prepared. This is referred to as “shaft 1”.

<Preparation of developing roller 1>
(Coating layer forming coating solution 1)
Carbon black “Ketjen Black EC300J” (manufactured by Lion Corporation) as an electronic conductive agent in a solution obtained by dissolving 100 parts by mass of “urethane A” which is a thermoplastic polyurethane elastomer in 500 parts by mass of methyl ethyl ketone, as an ionic conductive agent A coating solution for forming a coating layer was prepared by dispersing 2.0 parts by mass of tetramethylammonium chloride and 10 parts by mass of crosslinked acrylic resin particles having a median diameter (D ₅₀ ) of 5 μm on a volume basis using a sand mill for 2 hours. This is designated “Coating Layer Forming Coating Solution 1”.

(Coating layer formation)
“Coating layer forming coating solution 1” is spray-coated on the outer peripheral surface of “shaft 1” and then dried at 120 ° C. for 1 hour to form a coating layer having a dried film thickness of 30 μm. Was made.

<Preparation of developing roller 2>
A “developing roller 2” was prepared in the same manner except that the resin “urethane A” used in the development of the developing roller 1 was changed to “amide C” which is a thermoplastic polyamide elastomer.

<Preparation of developing roller 3>
(Coating liquid 3 for coating layer formation)
Carbon black “Ketjen Black EC300J” (manufactured by Lion Corporation) as an electronic conductive agent in a solution in which 100 parts by mass of “urethane B”, which is a thermoplastic polyurethane elastomer, is dissolved in 500 parts by mass of methyl ethyl ketone. A coating solution for forming a coating layer was prepared by dispersing 10 parts by mass of a crosslinked acrylic resin particle having a diameter (D ₅₀ ) of 5 μm for 2 hours using a sand mill. This is designated as “Coating Layer Forming Coating Liquid 3”.

(Coating layer formation)
“Coating layer forming coating solution 3” is spray coated on the outer peripheral surface of “Shaft 1” and then dried at 120 ° C. for 1 hour to form a coating layer having a thickness of 30 μm after drying. Was made.

<Preparation of developing roller 4>
(Coating layer forming coating solution 4)
Carbon black “Ketjen Black EC300J” (manufactured by Lion Corporation) as an electronic conductive agent in a solution obtained by dissolving 100 parts by mass of “amide D”, which is a thermoplastic polyamide elastomer, in 500 parts by mass of methyl ethyl ketone, median on a volume basis A coating solution for forming a coating layer was prepared by dispersing 10 parts by mass of a crosslinked acrylic resin particle having a diameter (D ₅₀ ) of 5 μm for 2 hours using a sand mill. This is designated as “Coating Layer Forming Coating Liquid 4”.

(Coating layer formation)
“Coating layer forming coating solution 4” is spray-coated on the outer peripheral surface of “shaft 1” and then dried at 120 ° C. for 1 hour to form a coating layer having a thickness of 30 μm after drying. Was made.

<Preparation of developing rollers 5-8>
“Developing rollers 5 to 8” were produced in the same manner except that the resin “urethane A” used in the production of the developing roller 1 was changed to the resin shown in Table 1.

  Table 3 shows the type of resin used for the development roller production and the conductive agent (electronic conductive agent, ionic conductive agent).

<Evaluation>
Evaluation of the developing roller was performed by sequentially mounting the developing roller produced above on a color laser printer “Magicor 2300DL” (manufactured by Konica Minolta Business Technologies), and in a normal temperature and humidity (20 ° C., 55% RH) environment, a large number of sheets (continuous 5000). Sheet) printed.

The initial performance evaluation of the developing roller is that 10 sheets of A4 size original are printed on high-quality paper (64 g / m ² ) at a pixel rate of 20% (full color mode of 5% for each color of yellow, magenta, cyan, and black), and the toner The image quality and the residual potential of the developing roller were evaluated.

  Thereafter, continuous 5000 sheets were printed using a document with an image ratio of 2% (full color mode of 0.5% for each color of yellow, magenta, cyan, and black).

The performance evaluation after printing 5000 sheets is the same as the initial performance evaluation, but the A4 size document is printed on high-quality paper (64 g / m ² ) with a pixel rate of 20% (full color mode of 5% for each color of yellow, magenta, cyan, and black). Then, the toner image quality, the residual potential of the developing roller, the occurrence of scratches and the contamination in the machine were evaluated.

<Toner charge amount>
The charge amount of the toner on the developing roller was measured as follows.

Method for measuring charge amount The mass: W1 (g) of the toner collecting unit equipped with filter paper (T100A047A: manufactured by Advantech) is measured with an analytical balance “cp224S type (manufactured by Sartorius)”.
2. Attach the toner collection unit to the suction pump.
3. The toner in the area of about 7 cm ^{2 on} the surface of the developing roller in the developing device is collected on the filter paper by a suction pump, and the charge amount of the collected toner transferred to the toner collecting unit: Q (μC) is a digital electrometer. It is determined by the charge amount measurement mode of “R8252 type (manufactured by ADC Corporation)”.
4). The toner collecting unit is removed from the suction pump, and the mass of the toner collecting unit after collecting the toner: W2 (g) is measured.
5. The toner charge amount Q / M (μC / g) is obtained from Equation 1.

Formula 1 Charge amount = Q / M = Q / (W2-W1)
Evaluation Criteria The toner charge amount is evaluated by measuring the initial charge amount after printing 10 sheets in a developing unit and the charge amount after continuous 5000 sheets print, and the initial charge amount and the charge amount after 5000 sheets print. A difference of ± 5 μC / g or less is regarded as a problem-free level.

<Image density>
For the image density, the density of the solid black image portion after the initial printing and 5000 sheets printing was measured at 12 points using a reflection densitometer “RD-918” (manufactured by Macbeth), and the average value was evaluated. The density of the solid black image portion is 1.20 or higher.

<Cover>
The fog (white solid image density) is measured by measuring the density of copy paper (white paper) at 20 locations using the Macbeth reflection densitometer “RD-918” at the absolute image density, and the average value is defined as the white paper density. Next, 20 white solid images of the copied image were similarly measured at 20 absolute image densities, and a value obtained by subtracting the white paper density from the average density was evaluated as a fog (white solid image density).

Evaluation criteria ◎: Fog is good when 0.005 or less ○: Fog exceeds 0.005 and 0.01 or less is practically no problem ×: Fog exceeds 0.01 and is practically problematic .

<Filming on developing roller surface>
Filming on the surface of the developing roller was evaluated by visual observation of the filming state on the surface of the developing roller after continuous printing of 5000 sheets and the degree of image contamination due to filming of the toner image obtained by printing. .

Evaluation criteria A: No filming was observed on the surface of the developing roller. O: A slight filming was observed on the surface of the developing roller, but the print image was found to have image contamination due to filming. No problem level for practical use ×: Level at which filming occurs on the surface of the developing roller, and image contamination due to filming is observed in the printed image, causing a problem in practical use.

  Table 4 shows the evaluation results.

  From the results of Table 4, it can be seen that "Examples 1 to 4" of the present invention are excellent in any evaluation items. However, it was found that “Comparative Examples 1 to 4” outside the present invention had a problem with at least one of the evaluation items.

An example of an apparatus for measuring the surface potential of a resin and its attenuation characteristic is shown. It is a graph which shows the attenuation state by the charge amount of the resin surface by the elapsed time after charging. It is a cross-sectional schematic diagram showing an example of the developing roller of the present invention. FIG. 3 is a schematic cross-sectional view showing an example of a developing device to which the developing roller of the present invention is attached and used. 1 is a schematic cross-sectional view illustrating an example of a full-color image forming apparatus.

Explanation of symbols

4 Supply Roll 5 Toner Regulation Blade 6 Hopper 7 Bias Power Supply T Toner 11 Conductive Shaft 12 Coating Layer 12b Adhesive Layer 32 Developing Roller

Claims (1)

A conductive coating layer is formed on the outer periphery of the conductive shaft, and a non-magnetic one-component developer is carried on the surface of the coating layer to form a thin layer of the non-magnetic one-component developer. The non-magnetic one-component developer is attached from the thin layer to the electrostatic latent image on the surface of the latent image holding member without contacting the latent image holding member holding the electrostatic latent image on the surface, thereby visualizing the electrostatic latent image. In the developing roller
When the developing roller is charged by a charger with a resin thin film made of only the resin forming the coating layer, the surface potential of the resin thin film after 1 second is Rv1, and the surface potential of the resin thin film after 10 seconds is Rv2
0.01 ≦ Rv2 / Rv1 ≦ 0.20
A developing roller having the following relationship:

Images