JP5320707B2 - Development device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that is hardly influenced by operating environment and can continuously provide a high-quality print image even when performing printing of many sheets though it is compact and inexpensive. <P>SOLUTION: The developing device 30C has a developing roller 32 and a discharge member 50, wherein deflection of the developing roller is 5 to 25 &mu;m, and when a mean value of pressing force of the discharge member abutting on the developing roller is represented as Pave, and the maximum value and the minimum value thereof are represented as Pmax and Pmin respectively, they satisfy following expressions (1) and (2). The expression (1) is 0.5 kPa&le;Pave&le;50 kPa, and the expression (2) is 0.05&le;(Pmax-Pmin)/Pave&le;0.3. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a developing device used by being mounted on an electrophotographic image forming apparatus.

  In recent years, image forming technologies such as copying machines, printers, facsimiles and the like have been remarkably developed, and in particular, an image forming apparatus based on an electrophotographic system is often used. In addition, with improvements in the performance of related technologies such as personal computers, there is an increasing demand for devices capable of forming color images and compact, lightweight, low-cost image forming devices, and further improvements and improved performance are desired. .

  The electrophotographic developer used in the image forming apparatus includes a so-called two-component developer composed of a toner and a carrier and a one-component toner composed of a non-magnetic or magnetic toner. In an image forming method using the one-component toner, a carrier is used. Therefore, there is no need for a stirrer for mixing the carrier and the toner, and there is an advantage that the control for making the mixing ratio of the toner and the carrier constant is not required. Furthermore, the one-component developing method using a non-magnetic one-component toner does not require the use of a magnet on the developing roller as compared with the magnetic one-component toner, and thus is preferable for a printer which is a small electrophotographic image forming apparatus. It is used.

  Among the one-component development methods using non-magnetic toner, a non-contact development method in which development is performed by separating a photosensitive member and a developing roller is advantageous for improving image quality.

  As described above, the developing device is required to have high image quality and high durability while being small and inexpensive.

  On the other hand, as an approach for improving image quality, attempts have been made to increase the dimensional accuracy of image forming members such as a photoreceptor and a developing roller to eliminate unevenness in image density (see, for example, Patent Document 1 and Patent Document 2). .

  In particular, in a non-contact developing method in which a toner thin layer is formed on a developing roller with a regulating member and development is performed by separating the photosensitive member and the developing roller, the variation in the gap directly leads to uneven image density. In addition, the runout accuracy of the developing roller becomes important.

In order to ensure the runout accuracy of the developing roller, a conductive shaft body made of metal or the like is polished with high accuracy, and the outer periphery thereof is concavo-convex by blasting or the like, and then a developing roller having a plated layer (for example, patent document) 3), and a method in which a conductive elastic layer made of silicone rubber or the like is molded on a conductive shaft made of metal or the like with a high-precision mold to increase accuracy (for example, see Patent Document 4). .)
JP-A-8-74839 JP 2000-288879 A Japanese Patent Publication No. 3-35664 JP 2003-184862 A

  However, at present, there is no developing device that can satisfy all of the price, image quality, and durability with respect to the required level of the market.

  The developing device of the present invention can achieve high image quality while solving the market demand for a developing device that is small in size and low in price, and solves a problem related to durability.

  In order to obtain high image quality, as described above, the dimensions of the developing roller incorporated in the developing device, particularly the shake accuracy, are important.

  However, even if the shake accuracy is increased, the image quality at the initial stage of printing is a required level, but there are problems that the image quality deteriorates when the printing environment is changed or when a large number of sheets are printed.

  This is because when a toner thin layer is formed on the developing roll with the toner regulating member, the toner is stressed, and the external additive is embedded in the toner base particles due to the stress or the toner is crushed. It is assumed that the toner is deteriorated. It is considered that the deteriorated toner has a reduced charge amount, and as a result, the toner is scattered in the apparatus, and image fogging and density unevenness of the image occur, resulting in a decrease in image quality.

  In terms of increasing run-out accuracy, a developing roller that only performs surface processing on a conductive shaft such as metal is considered advantageous. However, such a developing roller tends to apply stress to the toner and shortens the durability of the toner. There was a problem.

  An object of the present invention is to provide a developing device that is small in size and low in cost, is less affected by the use environment, and can continuously obtain a high-quality print image quality even when a large number of sheets are printed.

  The above-described problems are solved by the configuration described below.

1. In a non-contact developing type developing device having a developing roller and a charge eliminating member,
The developing roller has a runout of 5 to 25 μm,
The static elimination member has at least a sheet member and a holder for fixing the sheet member, and both ends of the sheet member are fixed to the holder, and a region of the sheet member not fixed to the holder is brought into contact with the developing roller. Is,
The developing is characterized in that the following formulas (1) and (2) are satisfied, where Pave is the average value of the pressing force of the static eliminating member that contacts the developing roller, Pmax is the maximum value, and Pmin is the minimum value: apparatus.

Formula (1) 0.5kPa <= Pave <= 50kPa
Formula (2) 0.05 ≦ (Pmax−Pmin) /Pave≦0.3
2. 2. The developing device according to 1 above, wherein the developing roller is a developing roller provided with a coating layer containing a conductive agent and a resin without providing a conductive elastic layer on the outer periphery of the conductive shaft.

  The developing device of the present invention is small in size and low in cost, has little influence by the use environment, and has an excellent effect that a high quality print image quality can be continuously obtained even when a large number of sheets are printed.

  The inventor has studied a developing device that is less affected by the use environment and can continuously obtain a high-quality print image quality even when a large number of sheets are printed.

  As a result of various studies, a developing roller that is less affected by the usage environment and can continuously obtain high-quality print image quality even when many sheets are printed. It was found that it is important to keep the pressing force of the member to a specific value and make the pressing force uniform.

  If the runout accuracy of the developing roller and the pressing force of the charge eliminating member are within the range of the present invention, the charge remaining on the developing roller surface is uniformly removed at each position in the circumferential direction and the axial direction on the developing roller surface. Further, the discharged toner is replaced with new toner in the next process (scraping process and supply process), but the replacement of toner does not replace 100% new toner.

  If the charge removal amount of the remaining toner is uniform, most of the toner can obtain a desired charge amount even when the toner is conveyed again to the charging step.

  The replacement of the residual toner with a new toner depends on the amount of charge removal. Therefore, the replacement of the toner becomes important even when the toner is repeatedly used.

  The shake of the developing roller used in the developing device of the present invention is 5 μm to 25 μm, preferably 5 μm to 15 μm. By setting the runout to 5 μm or more, the yield during production is improved, so that the cost can be kept low. Further, by setting the shake to 25 μm or less, the fluctuation range of the gap (separation) between the photosensitive member and the developing roll can be suppressed to a small extent, so that the fluctuation of the image density is small, and the unevenness of static elimination by the static elimination member can be suppressed. There is no fogging.

  The average value (Pave) of the pressing force (P) of the static eliminating member that contacts the developing roller is 0.5 kPa or more and 50 kPa or less, preferably 5 kPa or more and 30 kPa or less.

  By setting Pave to 0.5 kPa or more, the remaining toner is sufficiently neutralized, the toner can be replaced, and the toner charge amount does not decrease due to the stacking of the toner that could not be replaced on the developing roller. In-machine contamination due to toner scattering or the like is eliminated. Also, by setting the Pave to 50 kPa or less, the stress on the toner does not become excessive, the charge amount of the toner does not decrease due to the embedding of the external additive or the toner cracking, and the internal contamination due to the scattering of the toner does not occur. .

  When the maximum value of the pressing force (P) is Pmax and the minimum value of the pressing force (P) is Pmin, (Pmax−Pmin) / Pave is 0.05 or more and 0.3 or less, preferably 0.08. Above, it is 0.15 or less.

  By setting (Pmax−Pmin) / Pave to be 0.05 or more, the accuracy of each part is within a range that can be easily processed, and it is easy to assemble, and the part cost and the manufacturing cost can be reduced, which meets the object of the present invention. Further, by setting (Pmax−Pmin) / Pave to 0.3 or less, it is possible to prevent the occurrence of uneven density in the printed image due to uneven pressing force.

  Note that (Pmax−Pmin) / Pave represents the variation in the pressing force when the static elimination member contacts the developing roller.

  The present invention will be described in detail below.

<Developing device>
First, the developing device of the present invention will be described.

  FIG. 1 is a schematic diagram showing an example of the developing device of the present invention.

  FIG. 1 is a schematic view showing one developing device 30C of the full-color image forming apparatus shown in FIG. 7 described below, and the other developing devices 30M, 30Y, and 30Bk have the same configuration as the developing device 30C, and a description thereof will be omitted.

  In FIG. 1, 10 is a photosensitive member, 30C is a developing device, 32 is a developing roller, 34 is a supply roller, 35 is a toner regulating member, 50 is a static eliminating member, 36 is an agitator, 37 is a bias power supply, 38 is a hopper, and 39 is The body case is shown. The developing device 30C is configured by arranging members such as a developing roller 32, a supply roller 34, a toner regulating member 35, a charge removing member 50, an agitator 36, and the like in a main body case 39 at predetermined positions. Is placed at a predetermined position in the electrophotographic recording apparatus, the developing roller 32 faces or contacts the photosensitive member 10 with a predetermined gap.

  The new toner T in the developing device 30C is agitated by the agitator 36 and conveyed to the developing roller 32 by the supply roller 34.

  Toner T is adsorbed on the surface of the developing roller 32 to form a toner layer Ts. The toner layer Ts is thinned by the toner regulating member 35 and is triboelectrically charged. The toner T on the surface of the developing roller 32 that has been frictionally charged is electrically transferred and adhered to the electrostatic latent image on the surface of the photoconductor 10, whereby the electrostatic latent image is developed. The toner remaining on the developing roller 32 after development passes through the charge removing member 50 and is discharged. The discharged toner is scraped off by the supply roller, and at the same time, new toner is supplied (scraping process, supply process), and a part of the toner is replaced with the new toner.

  The pressing force with which the toner regulating member 35 comes into contact with the developing roller 32 is preferably 3 to 250 N / m, and particularly preferably 5 to 30 N / m, as the linear pressure in the sleeve bus direction. By setting the pressing force to 3 to 250 N / m, the toner charge amount distribution becomes sharp and image fogging and scattering can be avoided.

  The toner regulating member 35 is preferably an elastic blade, an elastic roller, or the like, and is made of a friction charging material suitable for charging the toner to a desired polarity. In the present invention, metal plates such as SUS and phosphor bronze, silicone rubber, urethane rubber, styrene-butadiene rubber and the like are suitable. Furthermore, an organic resin layer such as polyamide, polyimide, nylon, melamine, melamine cross-linked nylon, phenol resin, fluorine resin, silicone resin, polyester resin, urethane resin, styrene resin may be provided. It is also possible to use conductive rubber, conductive resin, etc., or to disperse fillers such as metal oxide, carbon black, inorganic whiskers, inorganic fibers and charge control agents in the blade rubber and resin. It is preferable because it imparts charge imparting properties and can charge the toner appropriately.

《Development roller runout》
The fluctuation of the developing roller used in the present invention is in the above range (5 to 25 μm).

  The run-out of the developing roller can be caused by high-precision processing of the conductive shaft (for example, centerless polishing, cutting with a diamond tool, etc.) or polishing after forming a coating layer on the surface of the conductive shaft (for example, plunge-type rubber) For example, polishing).

  The shake of the developing roller according to the present invention can be measured under the following conditions.

Measuring device: Non-contact laser displacement sensor VG (manufactured by Keyence Corporation)
Measurement environment: 23 ° C, 60% RH
FIG. 2 is a schematic diagram of an apparatus for measuring the runout of the developing roller.

  In FIG. 2, 11 is a conductive shaft body, 32 is a developing roller, and P is a measurement unit using laser light.

  The shake is measured by the runout of the cylindrical surface when the developing roller is rotated with reference to both ends A and B of the developing roller. As for the runout accuracy of the developing roller, 11 positions obtained by dividing the image forming area into 10 parts are measured, and the difference between the maximum value and the minimum value is obtained. In the present invention, the difference between the maximum value and the minimum value is taken as the runout of the developing roller.

  The runout of the conductive shaft can be measured by the same measurement method as that for the developing roller.

《Pressing force of static elimination member》
The pressing force of the neutralizing member that contacts the developing roller includes the material, thickness and surface roughness of the sheet member constituting the neutralizing member, the material and hardness of the pressing force equalizing member, the pushing amount of the neutralizing member to the developing roller, the nip Can be controlled by width etc. The material of the sheet member is preferably adjusted mainly by the hardness and pressing amount of the pressing force equalizing member in order to prioritize the charge removal performance from the charging sequence with the toner.

  The pressing force of the neutralizing member in the present invention refers to the tensile force when a tensile test is conducted by a tensile tester with a polyester film having a width of 1 cm and a thickness of 100 μm sandwiched between the developing roller and the neutralizing member. N), the value obtained by calculating the pressing force (P) as pressing force (P) = F × 10 (kPa).

  FIG. 3 is a schematic diagram of an apparatus for measuring the pressing force.

  In FIG. 3, 32 is a developing roll, 50 is a static elimination member, 60 is a polyester film (width 1 cm, thickness 100 μm), and 100 is a tensile tester.

<Measurement equipment and conditions>
Tensile tester: HEIDON surface quality tester TYPE18L (manufactured by Shinto Kagaku)
Measurement environment: 23 ° C, 60% RH
Pulling speed: 300mm / min
Measurement range: 0.9805 N / Volt (50% full scale)
Filter: 10Hz
Divide the image forming width of the developing roller into 10 equal parts and measure the pressing force at 11 locations. The following numerical values are calculated from this data group.

Pmax: Maximum value of the pressing force (P) Pmin: Minimum value of the pressing force (P) Pave: Average value of the pressing force (P) The pushing amount referred to in the present invention is when the discharging member is pressed against the developing roller. It refers to the amount (height) that the neutralizing member is depressed and dented. The nip width refers to the width of the static eliminating member that comes into contact with the developing roller when the static eliminating member is pushed.

  FIG. 4 is a schematic diagram showing the nip width.

  In the figure, 32 is a developing roller, 50 is a static eliminating member, and 54 is a nip width.

<Development roller>
Next, the developing roller will be described.

  FIG. 5 is a schematic cross-sectional view showing an example of the configuration of the developing roller according to the present invention.

  In the figure, 11 is a conductive shaft, 20 is a coating film, 21 is a conductive elastic layer, 22 is a coating layer, 23 is a surface layer, and 32 is a developing roller.

  The developing roller according to the present invention is one in which a coating film is provided on the surface of a conductive shaft as shown in FIGS. 5 (a), 5 (b), and 5 (c).

  FIG. 5A shows a structure in which a three-layer coating film 20 including a conductive elastic layer 21, a coating layer 22, and a surface layer 23 is provided on the outer periphery of the conductive shaft body 11.

  FIG. 5B shows a case where a coating layer 22 is provided on the outer periphery of the conductive shaft body 11.

  FIG. 5C shows a case in which a two-layer coating film 20 including a coating layer 22 and a surface layer 23 is provided on the outer periphery of the conductive shaft body 11.

  The developing roller according to the present invention may have any of the above-described configurations, but the configuration in which the coating layer 22 is provided on the outer periphery of the conductive shaft body shown in FIG. 5B is preferable because it is small and can be manufactured at low cost. .

  Hereinafter, the conductive shaft body and each layer constituting the developing roller 32 will be described.

  The conductive shaft body 11 is not particularly limited, and for example, a metal hollow body or solid body is used. Examples of the material of the conductive shaft include stainless steel and aluminum. In order to improve the adhesive property of the conductive elastic layer or the coating layer, an adhesive agent, a primer, or the like may be applied to the outer peripheral surface of the conductive shaft body 11 as necessary. Primers and the like may be made conductive as necessary.

  The conductive elastic layer (base rubber layer) 21 formed on the outer periphery of the conductive shaft 11 is, for example, ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber (SBR), silicone rubber, polyurethane elastomer, and the like. Formed by. Especially, as a forming material of the said conductive elastic layer 21, it is preferable to use conductive silicone rubber from the point that the fatigue strength with respect to the elastic deformation with low hardness is high. Various additives such as a conductive agent and silicone oil are appropriately blended in this material. Examples of the conductive agent include carbon black, graphite, potassium titanate, and iron oxide. Examples of the silicone oil include various types such as dimethyl silicone oil.

  As a material for forming the coating layer 22, for example, EPDM, SBR, nitrile rubber, acrylonitrile rubber (NBR), hydrogenated nitrile rubber, polyurethane elastomer, polyester, polyamide, or the like is used. In addition to the above components, a conductive agent such as carbon black, metal oxide, quaternary ammonium salt, and borate may be appropriately added as necessary.

  And the said layer formation material is melt | dissolved etc. in the organic solvent, and is used as a coating liquid. Examples of the organic solvent include methyl ethyl ketone (MEK), methanol, toluene, isopropyl alcohol, methyl cellosolve, dimethylformamide and the like. These may be used alone or in combination of two or more. In particular, it is preferable to use methyl ethyl ketone from the viewpoint of solubility in the layer forming material.

  The material for forming the surface layer 23 is not particularly limited, and examples thereof include urethane resin, polyamide resin, acrylic resin, acrylic silicone resin, butyral resin (PVB), and the like. Used together. Of these, urethane resins are preferably used in terms of wear resistance. In addition to the above components, a conductive agent, a charge control agent and the like may be appropriately added as necessary.

  In addition, the material for forming the surface layer 23 is dissolved in an organic solvent and used as a coating solution in the same manner as the material for forming the coating layer 22. Examples of the organic solvent include tetrahydrofuran (THF) and methyl ethyl ketone (MEK).

  Next, a method for producing the developing roller will be described.

  The developing roller according to the present invention can be produced, for example, as follows.

(Preparation of conductive elastic layer)
The material (compound) for forming the conductive elastic layer is prepared by kneading and stirring each component for forming the conductive elastic layer using an apparatus such as a kneader or a mixer. Next, a cylindrical mold for forming the conductive elastic layer and a conductive shaft are prepared. Then, a wax-based release agent is applied to the inner peripheral surface of the cylindrical mold, and an adhesive, a primer, or the like is applied to the outer peripheral surface of the conductive shaft as necessary. Subsequently, the conductive shaft body is installed on the central axis of the cylindrical mold with the lower lid fitted outside, and the conductive elastic layer forming material is formed in the gap between the conductive shaft body and the cylindrical mold. After filling (compound), the upper lid is fitted on the cylindrical mold. Subsequently, the entire cylindrical mold with the lower and upper lids fitted outside is placed in an oven, heated to vulcanize the conductive elastic layer forming material (compound), and conductive on the outer periphery of the conductive shaft. An elastic layer is formed. And it demolds after that. Secondary vulcanization may be performed after demolding. Thus, a conductive elastic layer is formed on the outer peripheral surface of the conductive shaft body. In addition, as a conductive shaft body, in order to improve the adhesiveness with a conductive elastic layer, you may use what apply | coated the adhesive agent previously.

(Preparation of coating layer and surface layer forming coating solution)
The coating solution for the coating layer and surface layer forming material weighs each component forming the layer and the organic solvent, and after stirring and mixing, disperses using a mechanical disperser (ball mill, sand mill, homomixer, etc.), and further organic Prepare by adding a solvent and stirring.

  Examples of the organic solvent include methyl ethyl ketone (MEK), cyclohexanone, methanol, toluene, isopropyl alcohol, methyl cellosolve, dimethylformamide, tetrahydrofuran, and ethyl acetate. These may be used alone or in combination of two or more.

(Production roller development)
In the three-layer developing roller shown in FIG. 5A, the coating layer forming coating solution prepared above is applied onto the conductive elastic layer and dried to form a coating layer. Further, the surface layer-forming coating solution prepared above is dip-coated on the outer peripheral surface of the coating layer and dried to form a surface layer.

  The developing roller having a single-layer structure shown in FIG. 5 (b) can be produced by applying the coating layer-forming coating solution prepared above on the outer periphery of the conductive shaft and drying it to form a coating layer. it can.

  The developing roller having a two-layer structure shown in FIG. 5C is manufactured by applying a surface layer forming coating solution on the coating layer of FIG. 5B and drying to form a surface layer. can do.

  The coating solution can be applied by dip coating, roll coating, spray coating, or the like, but dip coating is preferred to obtain a stable film thickness.

  The thickness of the conductive elastic layer is not particularly limited, and is preferably set in the range of 0.1 to 10 mm, and more preferably 0.2 to 3 mm. Moreover, the thickness of a coating layer and a surface layer is not specifically limited, It is preferable to set to the range of 1-30 micrometers, Especially preferably, it is 5-20 micrometers. The thicknesses of the conductive elastic layer, the coating layer, and the surface layer can be obtained by taking a cross-sectional sample from the developing roller and measuring this micrograph.

  The conductive elastic layer contains a so-called conductive agent to exhibit conductivity. Specific examples of the conductive agent include, for example, carbon black, copper, copper alloy, silver, nickel, low-melting-point alloy (solder, etc.) metal fine particles, zinc oxide, tin oxide, indium oxide and other metal oxide fine particles, Examples thereof include conductive polymer particles such as polypyrrole and polyaniline, polymer fine particles coated with metal, copper and silver fine particles coated with noble metal, metal fibers, and carbon fibers.

As a method for detecting conductivity, it is detected by measuring the resistivity of the developing roller. That is, when the resistivity of the developing roller is 10 ³ to 10 ¹⁰ Ω · cm, preferably 10 ⁴ to 10 ⁸ Ω · cm, it indicates that the developing roller has conductivity.

  In this resistivity measurement method, a developing roller is placed horizontally on a metal plate, a load of 500 g is applied to each end of the shaft of the developing roller in the direction of the metal plate, and a DC voltage is applied between the shaft and the metal plate. It is a value measured by applying 100 volts.

<Staticizer>
As the structure of the charge removal member used in the present invention, any structure can be selected as long as the pressing force of the charge removal member in contact with the developing roller can be set within the above-described range.

  FIG. 6 is a schematic cross-sectional view illustrating an example of the configuration of the charge removal member.

  In FIG. 6, 50 is a static elimination member, 51 is a holder, 52 is a sheet wetting material, 53 is a pressing force equalizing member, 54 is a nip width, and 55 is a pushing amount.

  FIG. 6A shows a static eliminating member having a configuration in which the sheet member is fixed to the holder and the opposite side is in contact with the developing roller.

  FIG. 6B shows a static eliminating member having a structure in which the pressing force equalizing member is fixed to the holder, and the flat surface or curved surface on the anti-fixed side is in contact with the developing roller.

  FIG. 6C shows a static eliminating member having a configuration in which one side of the sheet member is fixed to the holder and the end of the sheet member is in contact with the developing roller.

  Among these, the configuration of FIG. 6B is preferable because the pressing force can be easily adjusted. FIG. 6B shows a static eliminating member having a configuration in which a portion that contacts the developing roller is a flexible sheet member, and a pressing force equalizing member (for example, a sponge-like member) is installed from the back surface of the sheet member. is there.

Examples of the sheet member include nylon, polyurethane, acrylic, polyester, vinyl chloride, silicone resin, and fluororesin. Preferably, a conductive agent such as carbon black is kneaded into fluororesin (PTFE) to impart conductivity. Sheet. The thickness of the sheet member is preferably 20 to 500 μm, particularly preferably 50 μm to 200 μm. The surface roughness of the sheet member is preferably 0.05 μm to 2.0 μm, particularly preferably 0.1 μm to 1.0 μm, in terms of centerline average roughness (Ra). The resistivity of the sheet member is preferably 10 ⁴ to 10 ⁹ Ω · cm, and particularly preferably 10 ⁵ to 10 ⁷ Ω · cm.

  The material of the pressing force equalizing member is not particularly limited as long as it can be installed on the back surface of the sheet member and the sheet member can be fixed. EPDM, urethane, nylon, silicone, PET, PTFE, PVDF, natural rubber, nitrile butadiene rubber, chloroprene rubber , Styrene butadiene rubber, butadiene rubber, isoprene rubber, maltoprene and polynorbornene rubber. Among these, maltoprene is preferable because it can fix the sheet member satisfactorily.

  The hardness of the pressing force uniformizing member is preferably 30 to 70 ° in JIS K 6253 type E hardness, and particularly preferably 40 to 60 °.

  In addition, it is preferable that the neutralizing member is set to be 0.1 to 0.8 mm into the developing roller so that the nip width between the developing roller and the neutralizing member is 0.1 to 3 mm.

  The center line average roughness (Ra) can be measured by a surface roughness measuring instrument “SURFCOM 1400D” manufactured by Tokyo Seimitsu Co., Ltd.

  The type E hardness can be measured by an Asker rubber hardness meter E type (conforming to JIS K 6253) manufactured by Kobunshi Keiki Co., Ltd.

"toner"
In the present invention, a non-magnetic one-component toner suitable for reducing the weight and size of the developing device is preferably used. The non-magnetic one-component toner is prepared by fixing an external additive such as titanium oxide or resin fine particles to the surface of the toner base particles in order to ensure fluidity and charge amount on the toner base particles having a resin and a colorant. is there.

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. Specifically, the toner base particles are prepared, and then an external additive such as titanium oxide or resin fine particles is added to fix the external additive to the toner base particles.

<Image forming apparatus>
Next, an image forming apparatus that forms an image using the developing device of the present invention will be described.

  FIG. 7 is a structural sectional view showing an example of a full-color image forming apparatus in which the developing device of the present invention can be mounted.

  In the full-color image forming apparatus shown in FIG. 7, the charging brush 11 that uniformly charges the surface of the photoconductor 10 to a predetermined potential and the toner remaining on the photoconductor 10 are scraped off around the photoconductor 10 that is driven to rotate. A cleaner 12 is provided.

  A laser scanning optical system 20 that scans and exposes the photosensitive member 10 charged by the charging brush 11 with a laser beam is provided. The laser scanning optical system 20 includes a laser diode, a polygon mirror, and an fθ optical element. Print data for each color of cyan, magenta, yellow, and black is transferred from the host computer to the controller of the laser scanning optical system 20, and the laser scanning optical system 20 outputs a laser beam based on the printing data for each color, An electrostatic latent image for each color is formed on the photoreceptor 10.

  A developing device 30 that supplies toner of each color to the photoreceptor 10 on which the electrostatic latent image is formed and performs full-color development includes cyan, magenta, yellow, and black non-magnetic one-component toner around the support shaft 33. Four accommodated developer units 30C, 30M, 30Y, and 30Bk are provided. Each of the developing devices 30C, 30M, 30Y, and 30Bk is guided to a position facing the photoconductor 10 with the support shaft 33 as a center.

  In addition, a toner regulating member 35 is pressed against the outer peripheral surface of the developing roller 32 that rotates and conveys toner to each of the developing units 30C, 30M, 30Y, and 30Bk, and is conveyed by the developing roller 32 by the toner regulating member 35. The toner amount is regulated and the toner is charged. The developing device 30 may be provided with two toner regulating members in order to appropriately regulate and charge the amount of toner conveyed by the developing roller 32.

  Each time an electrostatic latent image of each color is formed on the photoreceptor 10 by the laser scanning optical system 20, the developing device 30 rotates around the support shaft 33 to store the corresponding color toner. 30C, 30M, 30Y, and 30Bk are sequentially guided to positions facing the photoconductor 10. Then, the developing roller 32 provided in each developing device is brought into contact with the photoconductor 10, and development is performed by supplying charged toner of each color onto the photoconductor 10 on which an electrostatic latent image of each color is formed.

  Further, an endless intermediate transfer belt 40 that rotates as an intermediate transfer body 40 is provided downstream of the developing device 30 in the rotation direction of the photoreceptor 10, and the intermediate transfer belt 40 is driven to rotate in synchronization with the photoreceptor 10. . The intermediate transfer belt 40 is pressed by a rotatable primary transfer roller 41 and comes into contact with the photoreceptor 10. A secondary transfer roller 43 is rotatably provided at a portion of the support roller 42 that supports the intermediate transfer belt 40, and the transfer sheet 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 toner remaining on the intermediate transfer belt 40 is provided in a space provided between the developing device 30 and the intermediate transfer belt 40 so as to be able to contact and separate from the intermediate transfer belt 40. ing.

  Further, the paper feeding means 60 for guiding the recording material S such as plain paper to the intermediate transfer belt 40 feeds the transfer sheet S in which the transfer sheet S is accommodated and the transfer sheet S accommodated in the paper feed tray 61 one by one. And a timing roller 63 for feeding the transfer sheet S fed in synchronization with the image formed on the intermediate transfer belt 40 between the intermediate transfer belt 40 and the secondary transfer roller 43. The Thus, the transfer sheet S conveyed between the intermediate transfer belt 40 and the secondary transfer roller 43 is pressed against the intermediate transfer belt 40 by the secondary transfer roller 43, and the toner image is transferred from the intermediate transfer belt 40 to the transfer sheet S. Press transfer.

  The transfer sheet S on which the toner image is pressed and transferred is conveyed to a fixing device 70 by a conveying means 66 constituted by an air suction belt or the like, and the toner image transferred by the fixing device 70 is fixed on the transfer sheet S. After the fixing process, the transfer sheet S is transported through the vertical transport path 80 and discharged onto the upper surface of the apparatus main body 1.

  Next, a full color image forming operation performed by the full color image forming apparatus will be described in detail. First, the photoconductor 10 and the intermediate transfer belt 40 are rotationally driven in the respective directions at the same peripheral speed, and the photoconductor 10 is charged to a predetermined potential by the charging brush 11.

  A cyan image is exposed on the photosensitive member 10 thus charged by the laser scanning optical system 20 to form an electrostatic latent image of the cyan image on the photosensitive member 10. After forming the electrostatic latent image, the cyan toner charged by the toner regulating member is supplied from the developing device 30C containing the cyan toner to form a cyan toner image on the photoconductor 10. Then, the intermediate transfer belt 40 is pressed against the photoreceptor 10 on which the cyan toner image is formed by using the primary transfer roller 41, and the cyan toner image formed on the photoreceptor 10 is primarily transferred onto the intermediate transfer belt 40. Let

  After the cyan toner image is transferred onto the intermediate transfer belt 40, the developing device 30 is rotated about the support shaft 33, and the developing device 30 </ b> M containing magenta toner is guided to the position facing the photoconductor 10. An electrostatic latent image of a magenta image is formed on the laser scanning optical system 20. The formed magenta electrostatic latent image is developed with magenta toner by the developing device 30M, and the developed magenta toner image is primarily transferred from the photosensitive member 10 onto the intermediate transfer belt 40. Further, exposure, development, and primary transfer of the yellow image and the black image are sequentially performed in the same procedure, and the cyan, magenta, yellow, and black toner images are superimposed on the intermediate transfer belt 40 to form a full-color toner image.

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

  As described above, when the full-color toner image is secondarily transferred onto the transfer sheet S, the transfer sheet S is conveyed to the fixing device 70 by the conveying means 66, and the full-color toner image transferred by the fixing device 70 is transferred to the transfer sheet. Fix on top. Thereafter, the transfer sheet S on which image formation has been performed is discharged onto the upper surface of the apparatus main body 1 via the vertical conveyance path 80.

  Hereinafter, although an example is given and explained concretely, the embodiment of the present invention is not limited to this.

<Production of developing roller>
A developing roller was produced as follows.

<Preparation of conductive shaft>
The surface of the stainless steel shaft was processed to prepare the following “conductive shaft 1 to conductive shaft 5”.

Conductive shaft 1: Centerless polished SUS303 hollow cylindrical conductive shaft (outer diameter 15 mm, runout 15 μm)
Conductive shaft 2: Centerless polished SUS303 hollow cylindrical conductive shaft (outer diameter 16 mm, runout 5 μm)
Conductive shaft 3: Centerless polished SUS303 hollow cylindrical conductive shaft (outer diameter 16 mm, runout 12 μm)
Conductive shaft body 4: Centerless polished SUS303 hollow cylindrical conductive shaft body (outer diameter 16 mm, runout 22 μm)
Conductive shaft 5: SUS303 hollow cylindrical conductive shaft cut with a diamond tool (outer diameter 16 mm, runout 19 μm)
Conductive shaft 6: The surface of the conductive shaft 2 is blasted (outer diameter 16 mm, runout 27 μm, surface roughness Rz 5 μm)
The shake is a value obtained by measurement by the above method. The surface roughness Rz is a value measured using a surface roughness measuring instrument “SURFCOM 1400D” manufactured by Tokyo Seimitsu Co., Ltd.

(Preparation of conductive elastic layer forming material)
A conductive elastic layer forming material (compound) was prepared by kneading conductive silicone rubber using a kneader.

(Preparation of coating layer forming coating solution 1)
A sand mill was prepared by dissolving 6 parts by mass of Ketjen Black and 8 parts by mass of an acrylic resin having an average particle diameter of 20 μm in a solution in which 20 parts by mass of a urethane resin (Nipporan 5199, manufactured by Nippon Polyurethane) was dissolved in 100 parts by mass of methyl ethyl ketone. And dispersed for 2 hours to prepare “Coating layer forming coating solution 1”.

(Preparation of surface layer forming coating solution 1)
A reactor equipped with a stirrer, thermometer, nitrogen gas inlet tube, and reflux condenser was charged with 310 parts by mass of ε-caprolactone, 150 parts by mass of alcohol-modified siloxane oil and 0.05 parts by mass of tetrabutyl titanate, and nitrogen. The mixture was reacted at a temperature of 180 ° C. for 10 hours under an air stream to obtain a polysiloxane-polyester copolymer having a hydroxyl value of 37, an acid value of 0.40, and a number average molecular weight of 3,030.

  150 parts by mass of the copolymer and 27 parts by mass of 1,4-butanediol were dissolved in a mixed solvent of 200 parts by mass of methyl ethyl ketone and 100 parts by mass of dimethylformamide, and 91 parts by mass with good stirring at 60 ° C. Of hydrogenated diphenylmethane diisocyanate (which may be abbreviated as hydrogenated MDI or H12MDI) in 188 parts by mass of dimethylformamide was gradually added dropwise, and after completion of the addition, the reaction was carried out at 80 ° C. for 6 hours. A silicone copolymer polyurethane resin solution was obtained. This solution was very transparent and had a viscosity of 35.5 Pa · s (25 ° C.) at a solid content of 35% by mass.

  100 parts by mass of the silicone copolymer polyurethane resin obtained above and 30 parts by mass of ketjen black (carbon black) were mixed and dispersed to prepare “surface layer forming coating solution 1”.

<Preparation of developing roller 1>
(Formation of conductive elastic layer)
The outer peripheral surface of the “conductive shaft body 1” having an outer diameter of 15 mm is coated with an adhesive, set inside the roll mold, and a conductive elastic layer in the gap between the conductive shaft body and the roll inner peripheral surface. A compound as a forming material is cast, and heat vulcanization is performed at 180 ° C. for 1 hour, then demolded, and further subjected to secondary vulcanization treatment at 200 ° C. for 4 hours to form an outer periphery of the conductive shaft body. A conductive elastic layer (thickness 0.6 mm) was formed. The rubber surface of the conductive shaft body on which the conductive elastic layer was formed was polished with a plunge type cylindrical grinder (manufactured by Mizuguchi Seisakusho) so that the outer diameter after forming the conductive elastic layer was 16 mm.

(Formation of coating layer)
After coating the “coating layer forming coating solution 1” on the outer periphery of the conductive elastic layer thus obtained so that the dry film thickness becomes 15 μm, drying is performed at 120 ° C. for 30 minutes, and “coating layer 1”. Formed.

(Formation of surface layer)
After coating “surface layer forming coating solution 1” on the outer peripheral surface of the “coating layer 1” so that the dry film thickness is 5 μm, the coating is dried at 120 ° C. for 60 minutes to form a three-layer coating. “Developing roller 1” having a film was prepared. The developing roller runout was 20 μm.

<Preparation of developing roller 2>
In producing the developing roller 1, the conductive shaft 1 is changed to the “conductive shaft 2”, the “conductive elastic layer 1” is not provided, and the “coating layer 1” is directly formed on the surface of the “conductive shaft 2”. “Developing roller 2” was produced in the same manner except that “.” Was formed. The runout of the developing roller was 6 μm.

<Preparation of developing roller 3>
In the production of the developing roller 1, the conductive shaft 1 is changed to “conductive shaft 3”, and the coating layer is formed directly on the surface of “conductive shaft 3” without providing “conductive elastic layer 1”. A “developing roller 3” was produced in the same manner as described above. The runout of the developing roller was 13 μm.

<Preparation of developing roller 4>
In the production of the developing roller 1, the conductive shaft 1 is changed to the “conductive shaft 4”, the “conductive elastic layer 1” is not provided, and the “coating layer 1” is directly formed on the surface of the “conductive shaft 4”. “Developing roller 4” was produced in the same manner except that “.” Was formed. The runout of this developing roller was 25 μm.

<Preparation of developing roller 5>
In the production of the developing roller 1, the conductive shaft 1 is changed to the “conductive shaft 5”, the “conductive elastic layer 1” is not provided, and the “direct covering layer 1” is formed on the surface of the “conductive shaft 5”. “Developing roller 5” was produced in the same manner except that “.” Was formed. The developing roller runout was 20 μm.

<Preparation of developing roller 6>
A “developing roller 6” was obtained by using the “conductive shaft body 6” as it is as a developing roller. The runout of this developing roller was 27 μm.

  Table 1 shows the conductive shaft used for producing the developing roller, the layer structure, and the runout of the developing roller.

  The shake is a value obtained by measurement by the above method.

<Production of static elimination member>
<Preparation of static elimination member 1>
As a pressing force uniformizing member, a maltprene having a thickness of 5 mm and a JIS K 6253 type E hardness (hereinafter referred to as E hardness) of 50 ° was fixed to a predetermined place of the holder with a double-sided tape. A conductive Teflon (registered trademark) sheet having a thickness of 50 μm was placed thereon as a sheet member and fixed with a double-sided tape. This is referred to as “static elimination member 1”.

<Preparation of static elimination member 2>
What was produced in the same manner except that the pressing force uniformizing member used in the preparation of the static elimination member 1 was changed to a maltoprene having a thickness of 3 mm and an E hardness of 20 °, and the sheet member was changed to an insulating PET sheet having a thickness of 75 μm. It will be referred to as “static elimination member 2”.

<Preparation of static elimination member 3>
What was produced in the same manner except that the pressing force uniformizing member used in the preparation of the static elimination member 1 was changed to a urethane foam having a thickness of 10 mm and an E hardness of 70 °, and the sheet member being an insulating urethane sheet having a thickness of 100 μm. It is set as the static elimination member 3 ".

<Prepared on the static elimination member 4>
Without installing a pressing force equalizing member, both ends of a conductive Teflon (registered trademark) sheet having a film thickness of 100 μm were fixed to a predetermined place of the holder with a double-sided tape. This is referred to as “static elimination member 4”.

  Table 2 shows the sheet member and the pressing force uniformizing member used for producing the static elimination member.

  The E hardness is a value obtained by measurement by the above method.

<Adjustment of developing device>
“Developing devices 1 to 10” were prepared by mounting the developing roller and the charge eliminating member prepared above in the developing device.

  Table 3 shows the runout, pushing amount, and pressing force of each developing device.

<Evaluation>
For actual image evaluation, a color laser printer “Magicor 2430DL (manufactured by Konica Minolta Business Technologies)” using a non-magnetic one-component toner was prepared as an image forming apparatus.

  The developing device prepared above was sequentially mounted on the image forming apparatus, and printing was performed in an environment of low temperature and low humidity (10 ° C., 15% RH) and high temperature and high humidity (30 ° C., 80% RH).

  In the initial performance evaluation of the developing roller, 10 originals (A4 size) having a pixel rate of 20% (a full color mode of 5% each color of yellow, magenta, cyan, and black) were printed.

  Thereafter, 5,000 originals (A4 size) having an image rate of 2% (full color mode of 0.5% for each color of yellow, magenta, cyan, and black) were printed.

  For performance evaluation after printing 5000 sheets, 10 originals (A4 size) having a pixel rate of 20% (full color mode of 5% for each color of yellow, magenta, cyan, and black) as in the initial performance evaluation were printed. Image density unevenness, image fogging, and the state of internal contamination due to toner scattering and spillage were evaluated according to the following evaluation criteria. In addition, the evaluation is ◎ and ○ are acceptable.

(Image density unevenness)
The density unevenness of the image is printed in a low-humidity environment (10 ° C, 15% RH) and after printing 5000 sheets, a black halftone image with an image density of 0.5 is printed, and the resulting halftone image is visually observed. evaluated.

Evaluation criteria ◎: Halftone image has no density unevenness ○: Halftone image has streaky thin density unevenness, but no problem in practical use ×: Halftone image has streaky density unevenness, practical use Top problem.

(Image fog)
As for image fogging, after printing 5000 sheets in a low temperature and low humidity (10 ° C., 15% RH) environment, a white background document was printed and evaluated for image fogging. Image fogging is a phenomenon in which toner does not collect on the printed image surface but is scattered over a wide area, and the background is slightly stained, and it can be distinguished from toner spillage that causes dot-like image defects by some collected toner. The image fog density was determined by measuring an arbitrary 10 points of the relative density of the white background portion with an image density measuring device “RD-918 type” (manufactured by Macbeth Co., Ltd.) and obtaining the average value as the image fog density.

Evaluation Criteria A: Image fog density is good when it is less than 0.005 B: Image fog density is 0.005 or more and less than 0.01, and there is no practical problem ×: Image fog density is practical when 0.01 or more The level that causes problems.

(In-flight dirt)
In-machine stains were evaluated by visually observing the periphery of the developing device after completion of printing 5000 sheets in an environment of high temperature and high humidity (30 ° C., 80% RH), and visually observing toner scattering and toner spillage around the developing device.

Evaluation Criteria A: Toner spillage is not observed and good B: Toner spillage is slightly observed but has no practical problem. X: Toner spilled toner scattering is clearly observed and causes a practical problem.

  Table 4 shows the evaluation results.

  From the evaluation results of Table 4, it was confirmed that Examples 1 to 6 showed good results for all the evaluation items and exhibited the effects of the present invention. On the other hand, in Comparative Examples 1 to 4, it was confirmed that satisfactory results were not obtained for any of the evaluation items, and the effects of the present invention were not exhibited.

It is a schematic diagram which shows an example of a developing device. It is a schematic diagram of an apparatus for measuring the deflection of the developing roller. It is a schematic diagram of the apparatus which measures pressing force. It is a schematic diagram which shows nip width | variety. It is a cross-sectional schematic diagram which shows an example of a structure of the developing roller which concerns on this invention. It is a cross-sectional schematic diagram which shows an example of a structure of a static elimination member. 1 is a cross-sectional view illustrating an example of a full-color image forming apparatus in which a developing device of the present invention can be mounted.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photoconductor 30C Developing device 32 Developing roller 34 Supply roller 35 Toner regulating member 50 Static elimination member 36 Agitator 37 Bias power supply 38 Hopper 39 Main body case

Claims (2)

In a non-contact developing type developing device having a developing roller and a charge eliminating member,
The developing roller has a runout of 5 to 25 μm,
The static elimination member has at least a sheet member and a holder for fixing the sheet member, and both ends of the sheet member are fixed to the holder, and a region of the sheet member not fixed to the holder is brought into contact with the developing roller. Is,
The developing is characterized in that the following formulas (1) and (2) are satisfied, where Pave is the average value of the pressing force of the static eliminating member that contacts the developing roller, Pmax is the maximum value, and Pmin is the minimum value: apparatus.
Formula (1) 0.5kPa <= Pave <= 50kPa
Formula (2) 0.05 ≦ (Pmax−Pmin) / Pave ≦ 3   2. The developing according to claim 1, wherein the developing roller is a developing roller provided directly with a coating layer containing a conductive material and a resin without providing a conductive elastic layer on the outer periphery of the conductive shaft body. apparatus.

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