JP2005099394A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the coating defects of a downstream sleeve, to match the development characteristics of upper and lower sleeves, to improve a gradation property and gradation stability and to make a sleeve service life be in common in a twin development sleeve developing device for regulating toner coating of the downstream sleeve in the upstream sleeve. <P>SOLUTION: In the developing device for making electrostatic latent images formed on an electrostatic latent image carrier into visible images by a negative polarity developer, the developing device is provided with a plurality of developer carriers and the developer layer thickness of a downstream developer carrier is regulated to the rotating direction of the electrostatic latent image carrier by an upstream developer carrier. In the developing device, the plurality of developer carriers are provided with a magnetic member inside, the surface is coated with a coating member by phenol resin, and a developer is developed on the electrostatic latent image carrier. Also, the coating member surface of the developer carrier has quaternary ammonium salt only in the downstream developer carrier. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing device used for a copying machine, a laser beam printer, a facsimile, a printing apparatus, and the like using an electrophotographic system.

  Conventionally, after the electrostatic latent image carrier is uniformly charged, image exposure is performed by analog exposure or semiconductor laser or LED, and an electrostatic latent image is formed on the electrostatic latent image carrier. An image forming apparatus that visualizes a developer image by a developing device, transfers the visible image to a transfer material, and then separates the transfer material from the electrostatic latent image carrier and outputs the image as a fixed image by a fixing device. Are known. The process will be described with reference to FIG. The image forming apparatus has, for example, a photosensitive drum 1 as an electrostatic latent image carrier, and the photosensitive drum 1 has a photoconductive layer such as OPC or a-Si on its surface and is rotated in the direction of arrow A. The surface of the photosensitive drum 1 is uniformly charged to, for example, −700 V by the primary charger 3. Next, image exposure 12 based on the image signal information is performed to attenuate the surface potential of the exposed portion on the photosensitive drum 1 to, for example, −200 V, and a latent image corresponding to the image signal of the image is formed on the photosensitive drum 1. For the image exposure 12, for example, a semiconductor laser or an LED array is used. Next, the latent image is developed by the developing device 2 which is a one-component developing device, and visualized as a toner image. A developing device using a dry one-component developer is simple and does not require replacement of a carrier or the like, and thus has a high durability and a long life. For example, there is a jumping development using a magnetic one-component toner. The developing device 2 uses negatively charged black toner. At the time of development, a DC bias of about −500 V is applied as a developing bias to the developer carrying member to reversely develop the latent image. Thereafter, a transfer pretreatment is performed using a charger 10 as necessary, and the image is transferred onto a transfer material supplied to the photosensitive drum 1 (usually combined with application of corona by DC or AC, or light neutralization). Transfer is performed by the charger 4. Thereafter, the toner image is sent to the fixing device 7 to fix the toner image. On the other hand, the toner remaining on the photosensitive drum 1 is removed by the cleaning device 11 to prepare for the next image formation. As for the speedup of the image forming apparatus, the developing apparatus can cope with a plurality of developing rolls of the developing apparatus using a two-component magnetic brush, as described in JP-A-03-204084. As described in Kaihei 02-188778, the distance between the sleeve and the photosensitive member is made closer to the downstream sleeve so as to equalize the toner replenishment amount from the sleeve. Further, as a developing device having a plurality of downsized developing sleeves, a developing device as shown in Japanese Patent Publication No. 3-5579 has been proposed.

  On the other hand, Japanese Patent Application Laid-Open No. 1-112253, Japanese Patent Application Laid-Open No. 2-284158, and the like propose to use a toner having a small particle diameter in order to achieve high image quality and high definition. In such a negatively charged toner having such a small particle size, the surface area per unit weight is large, so that the surface charge tends to be large, and the toner is fixed to the developer carrying member by a so-called charge-up phenomenon. The developer newly supplied onto the developer carrying member becomes difficult to be charged, and the charge amount of the developer tends to be non-uniform. For this reason, a sleeve ghost is likely to occur on the image, and the obtained image tends to be a non-uniform image such as a streak-like image or a haze-like image such as a solid image or a halftone image.

  On the other hand, in JP-A-1-277256, JP-A-3-36570, etc., the generation of the developer having such an excessive charge and the strong adhesion of the developer to the developer carrier are prevented. Therefore, a method has been proposed in which a film made of a resin composition in which a conductive material such as carbon or graphite or a solid lubricant is dispersed in a resin is formed on a developer carrier.

  However, a developing device having a plurality of developer carriers (developing sleeves) is excellent in terms of density maintenance, and a device that does not have a separate toner layer thickness regulating member between the developing sleeves is excellent in compactness and saves space. These development systems have the following problems.

  1. In the developing method in which the toner layer thickness of the downstream developing sleeve is regulated by the upstream developing sleeve, similarly, the layer thickness regulation of the upstream developing sleeve and the layer thickness regulating method of the downstream developing sleeve are different, and the downstream is counter-rotated with the rotating upstream sleeve. In order to regulate the layer thickness, the toner was rubbed vigorously, and even with the same toner, the toner tribo was different between the upstream and downstream developing sleeves. Therefore, in the downstream developing sleeve, when a toner of 7 μm or less is used in accordance with the recent improvement in image quality, a toner coat defect occurs and the toner layer cannot be formed uniformly.

  2. Also, the downstream is higher than the upstream, so the developability differs between the upstream development sleeve and the downstream development sleeve, and if a common development bias is used for space saving and cost reduction, the developability differs for each development sleeve. Therefore, it was difficult to control the concentration. This is in contradiction to the recent demand for gradation and stability of digital images corresponding to digital images and graphics, and this phenomenon is caused when negative polarity toner with a relatively large toner charge amount is used. Especially terrible.

  3. In the developing device having a plurality of developing sleeves described above, a magnetic blade or the like is used for regulating the toner layer thickness of the upstream sleeve, whereas the downstream developing sleeve regulates the toner layer thickness with the upstream developing sleeve. Therefore, since the upstream developing sleeve performs the toner layer thickness regulation once again in addition to the normal layer thickness regulation, the number of times it passes through the toner layer thickness regulating member is larger than that of the downstream development sleeve. The degree of friction received increased, and as a result, the surface of the downstream sleeve was easily scraped, and the life was different between downstream and upstream. Therefore, the development sleeve replacement maintenance interval is different, and it is necessary for the service person to visit the user frequently, and the service cost is wasted.

  It was difficult to satisfy the above simultaneously.

  A first object of the present application is to prevent a toner coat defect of a downstream sleeve in a small developing device having a plurality of developing sleeves.

  The second object of the present application is to satisfy the demands of gradation and gradation stability of digital images and images corresponding to recent graphics by preventing development properties from being different for each developing sleeve. is there.

  A third object of the present application is to make the life of the developing sleeve common in a developing device having a plurality of developing sleeves, and to reduce the service cost by eliminating the maintenance work of a serviceman.

  According to the present invention, in a developing device that visualizes an electrostatic latent image formed on an electrostatic latent image carrier with a negative developer, the developing device includes a plurality of developer carriers. In the developing device in which the developer layer thickness of the downstream developer carrier is regulated by the upstream developer carrier relative to the rotation direction of the electrostatic latent image carrier, the plurality of developer carriers have a magnetic member inside. The surface of the developer carrier is coated with a phenol resin coating member, and the developer is developed on the electrostatic latent image carrier, and the coating member surface of the developer carrier is only on the downstream developer carrier. By having a quaternary ammonium salt, in the small developing device having a plurality of developing sleeves which is the first object of the present application, it is possible to prevent toner coating defects on the downstream sleeve.

  By satisfying the requirements of gradation and gradation stability of digital images and images corresponding to recent graphics by preventing development performance from differing among the development sleeves, which is the second object of this application, .

  In the developing apparatus having a plurality of developing sleeves, which is the third object of the present application, the service life of the developing sleeve is made common, and the service cost is also reduced by eliminating the maintenance work of the service person.

  It succeeded in realizing the above simultaneously.

  As described above, according to the present invention, in the small-sized developing device having a plurality of developing sleeves which is the first object of the present invention, it is possible to prevent a toner coat defect of the downstream sleeve.

  By satisfying the requirements of gradation and gradation stability of digital images and images corresponding to recent graphics by preventing development performance from differing among the development sleeves, which is the second object of this application, .

  In the developing apparatus having a plurality of developing sleeves, which is the third object of the present application, the service life of the developing sleeve is made common, and the service cost is also reduced by eliminating the maintenance work of the service person.

  We succeeded in realizing the above simultaneously.

(Example 1)
FIG. 2 schematically shows an image forming apparatus according to the present invention.

  The image forming apparatus used an OPC drum photoconductor of φ108 as the photoconductor. The process speed is 500 mm / sec and 102 black and white digital copying machines per minute.

  The photosensitive member is uniformly charged to, for example, −600 V by the charger 3 and then subjected to image exposure 12 at 600 dpi. The image exposure 12 is a laser beam modulated by a first image signal using a semiconductor laser as a light source. The laser beam is polarized by a polygon mirror that is rotated at a constant rotational speed by a motor, passes through an imaging lens, and is turned back into a mirror. Then, the photosensitive member 1 is raster-scanned and the surface potential of the exposed portion is attenuated to, for example, -200 V to form an image-like latent image. The wavelength is 780 nm. Thereafter, development is performed, and the toner is negatively charged by the post charger 10 and the adsorption force between the photosensitive member and the toner is weakened to facilitate transfer and separation. Thereafter, the image is transferred to a transfer material proceeding in the direction of the arrow by the transfer charger 4 and sent to the fixing device 7 to fix the toner image. In this embodiment, development is performed using a black magnetic one-component developer which is a simple and highly durable development system that does not require maintenance up to 1,000 developing sleeves. In this embodiment, reversal development is performed using a plurality of developer carriers (developing sleeves). In the toner replenishment operation, when the toner near 2B in FIG. 1A runs out, the piezoelectric element 22 signal outputs a signal for rotating the mag roll 24, and the rotation of the mag roll 24 supplies the toner from the hopper 9B into the developing device.

  Next, the developing device 2 used in this embodiment will be described in detail.

As the developer, a one-component magnetic toner having a negative polarity with high durability, high reliability, and high productivity was used. The toner has a particle size of 6.8 μm and is coated with 1.0% of SiO ₂ as an external additive. As shown in FIG. 1A, there are two developing sleeves, and the first developer carrier (developing sleeve) 20 is blasted with FGB # 300 on φ30 aluminum A2017, which is a nonmagnetic member. The coating is performed as shown in 1B. The same applies to the second sleeve. The developer carrying member (developing sleeve) 30 was blasted with FGB # 300 on φ30 aluminum A2017, which is a non-magnetic member, and coated as shown in FIG. 1b. This coating is to increase the durability of the sleeve surface. (It is a film that protects the surface of A1)
Next, the magnetic seal member will be described. As shown in FIG. 5, the first developing sleeve is a developing sleeve having a magnetic pole of 6 poles inside, and the second developing sleeve is a developing sleeve having a polarity of 6 poles. As shown in FIG. 6, magnetic seal members made of Moldaroy (KN plating, permeability 10-6) mainly made of iron for the two-shaped sleeves were provided in the vicinity of both ends of the developing sleeve. The gap between the surface of the developing sleeve and the magnetic seal member was set to 420 μm ± 100 μm so that the entire circumference was formed.

  The first magnet length was L1 = 305 mm, and the second magnet length was L2 = 305 mm. As for the magnetic seal mounting position, it is most preferable that the position of the outer end of the appropriate magnetic seal with respect to the magnet matches the end of the magnet. This is because when the magnet comes out from the outside of the magnetic seal, a magnetic force is also present in the longitudinal direction, so that the toner is carried out by the magnetic force and causes toner leakage. On the other hand, if the end of the magnet enters too much into the outer end of the magnetic seal, the magnetic seal that originally forms a magnetic brush between the magnetic seal and the magnet to eliminate toner leakage is In spite of the absence of magnetic force at the outer end, the outer toner leaks to the end and the toner layer thickness increases to form a magnetic brush with the width of the magnetic seal on the sleeve. Sometimes it falls. In addition, since there is a backlash in the longitudinal direction due to the relationship between the sleeve and the magnet, the end of the magnetic seal is located at a position 1 mm inside from the end of the magnet as shown in FIG. I made it.

  A fixed magnet having a six-pole magnetic field pattern as shown in FIG. 3 and Table 1 is provided inside the first developing sleeve. The developing sleeve rotates at a speed of 120% with respect to the counter drum. The layer thickness of the toner was regulated by a magnetic blade, and S-Bgap was 250 μm. The distance S-Dgap between the first developing sleeve and the photosensitive drum was 250 μm, and a DC bias of −500 V and a rectangular wave of Vpp 1500 V and frequency 2.7 kHz were applied to the developing sleeve as an AC bias as shown in FIG. Component non-contact development is performed. Accordingly, the development contrast is 300V in the flight direction, and the fog removal contrast is 100V.

As the second developing sleeve 30, a developer carrier (developing sleeve) having a film formed on φ30 aluminum A2017 which is a nonmagnetic member is used. Inside, a magnet having a six-pole magnetic field pattern shown in FIG. A DC bias of -500 V and a rectangular wave of Vpp 1500 V and frequency 2.7 kHz are applied to the developing sleeve as shown in FIG. Since it is the same as the first developing sleeve, it is common, and since only one power source is required, there is an advantage that the cost is reduced and the space for the power source can be reduced. The developing sleeve rotates at a speed of 120% with respect to the counter drum. The blade is a plate-like magnetic blade having a thickness of 1.0 mm for the first developing sleeve, and the toner layer thickness on the second developing sleeve is regulated by the upstream developing sleeve. The distance between the first developing sleeve and the second developing sleeve was 500 μm. This is a value for making the toner supply amounts of the first and second developing sleeves equal. In this way, the toner coat amount (M / S) on the sleeve was about 1.0 mg / cm ² . The S-Dgap of the second developing sleeve is 250 μm. Aligning the toner supply amount per unit time is the most important in making it possible to control the development characteristics of a plurality of development sleeves to be consistent and to stabilize the gradation.

In addition, it is important to match the first and second development characteristics in order to meet the demands of gradation and stability of gradation corresponding to recent digital images and graphics. . As described above, the toner supply amount per unit time is equal. Further, the developing electrode of the first developing sleeve is N ₂ , the developing electrode of the second developing sleeve is N ₂ , and the half width is as much as possible. However, the development characteristics after the endurance of 1000 sheets are different as shown in FIG. (Upper is second development, lower is first development) This will be described.

This is because the first developing sleeve is regulated by toner with a magnetic blade, whereas the second developing sleeve is regulated by the first developing sleeve, and the first developing sleeve is in the direction opposite to the toner traveling direction at the toner regulating portion. Rotate. For this reason, the toner is rubbed strongly between the second developing sleeve and the first developing sleeve, and the triboelectric charging ability of the toner becomes higher than that of the normal magnetic blade regulation. That is, the tribo (Q / M) is larger in the second development than in the first development. In general, since the development characteristics depend on tribo (Q / M), the difference in Q / M appears in the VD curve as the difference in development characteristics. This tendency is conspicuous when the development time is not sufficient as in a high-speed machine having a process speed of 400 mm / s or more, and when the developing sleeve rotation speed is high and the frictional force on the toner is large at the toner layer thickness regulating member. It is. This difference causes the difference in development characteristics (at the time of 1k sheets) in FIG. (In FIG. 9, the horizontal axis is called the VD characteristic where the horizontal axis is the contrast potential and the vertical axis is the density.) Also, depending on the choice of toner, the tribo of the downstream sleeve is too high, and there are some toners that are extremely charged. The toner coat was poor and non-uniform, resulting in extreme density unevenness in terms of image. Here, a magnetic toner in which magnetic particles are dispersed in a resin is used. Table 6 shows the level of toner coat failure in a normal case where the toner resin is polyester and the amount of SiO ₂ is changed from 0.5% to 1.0% with respect to the toner of 90 parts by weight of the magnetic material. Level is a subjective assessment. In addition, as shown in Table 5, this phenomenon is remarkable when the toner particle size is 7 μm or less. In order to improve the image quality, it is desired to reduce the particle size in the future, and solving this will be an important theme. The present embodiment was implemented in view of the above.

  The film was formulated by mixing a phenol resin, crystalline graphite and carbon on the surface of the Al sleeve and curing the film in a 150 ° C. environment with a film thickness of 10 μm. The thickness of the film is about 20 μm for forming a stable and uniform film. In this case, the P / B ratio is 1 / 2.5. B represents the weight of the resin, and P represents the weight of the material other than the resin (crystalline graphite + carbon).

  When the upstream sleeve and the toner coating amount are regulated in the upstream sleeve as in this configuration, the charge characteristic for the negative polarity toner is too high, so that only the second sleeve has 070 parts by weight of a quaternary ammonium salt. Resin was used.

  When added, the quaternary ammonium salt compound is uniformly dispersed in the phenolic resin, and further taken into the structure of the phenolic resin when it is cured by heating to form a film. The resin composition itself changes to a material having negative chargeability. Therefore, if a developer carrier having a coating layer formed using such a material is used, the developer can be suitably charged positively.

  Examples of the quaternary ammonium salt compound having the functions described above that are preferably used in the present invention include compounds represented by the following general formula.

(In the formula, R ₁ , R ₂ , R ₃ and R ₄ represent an alkyl group which may have a substituent, an aryl group which may have a substituent, and an aralkyl group, respectively, and R _{1 to} R ₄ may be the same or different, and X ⁻ represents an anion of an acid.)
In the above general formula, X ^- Specific examples of the acid ions, organic sulfate ions, organic sulfonate ions, organic phosphate ions, molybdate ions, tungstate ions, such as heteropoly acid containing molybdenum atoms or tungsten atoms Can be mentioned.

  When a coating layer is formed using a resin composition obtained by adding a specific quaternary ammonium salt compound used in the present invention to a phenol resin as in (1), as described above, it is a binder resin. When the phenol resin is cured by heating to form a coating layer, the quaternary ammonium salt compound is incorporated into the structure of the phenol resin. For this reason, unlike the case of the particle addition system such as the negative silica particles or the negative Teflon (registered trademark) particles described above, positive frictional charge is imparted to the positively chargeable developer as a whole, not partially, as the coating layer. Improves. Further, unlike the particle-added coating, the processability is not impaired and the strength of the coating layer is not reduced.

  Specific examples of the quaternary ammonium salt compound suitably used in the present invention include the following, but the present invention is of course not limited thereto.

  As the phenol resin constituting the binder resin used in the present invention, a quaternary ammonium salt compound is used in the production process, particularly when a quaternary ammonium salt compound is used during the heat curing. It was found that it was easy to be incorporated into the structure of the toner and preferable for preventing charge-up of the toner. Therefore, in the present invention, if a phenol resin having such an action and produced using a nitrogen-containing compound as a catalyst in the production process is used as one of the materials constituting the coating layer on the developer carrier. Therefore, it is possible to realize a developing device that prevents the toner from being charged up.

  Examples of the nitrogen-containing compound used as a catalyst in the phenol resin production process that can be suitably used in the present invention include, for example, ammonium sulfate, ammonium phosphate, ammonium sulfamate, ammonium carbonate, ammonium acetate, and ammonium maleate. Examples of the basic catalyst include ammonia, dimethylamine, diethylamine, diisopropylamine, diisobutylamine, diamylamine, trimethylamine, triethylamine, tri-n-butylamine, triamylamine, dimethylbenzylamine. , Diethylbenzylamine, dimethylaniline, diethylaniline, N, N-di-n-butylaniline, N, N-diamilaniline, N, N-di-t-amylaniline N-methylethanolamine, N-ethylethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, ethyldiethanolamine, n-butyldiethanolamine, di-n-butylethanolamine, triisopropanolamine, ethylenediamine, hexamethylene Amino compounds such as tetramine, pyridine, α-picoline, β-picoline, γ-picoline, pyridine such as 2,4-lutidine, 2,6-lutidine and derivatives thereof, quinoline compounds, imidazole, 2-methylimidazole, 2, Imidazo such as 4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole And nitrogen-containing heterocyclic compounds such as derivatives.

  In this invention, in order to adjust the resistance value of a coating layer to said value, it is preferable to contain the electroconductive substance mentioned below in a coating layer. Examples of the conductive material used at this time include metal powders such as aluminum, copper, nickel, and silver, metal oxides such as antimony oxide, indium oxide, and tin oxide, carbon fiber, carbon black, and graphite. Examples include carbon materials. In the present invention, among these, carbon black, in particular conductive amorphous carbon, is particularly excellent in electrical conductivity, and it can be filled with a polymer material to impart conductivity, or only by controlling the amount of addition. Since arbitrary conductivity can be obtained to some extent, it is preferably used.

  The final film formulation is 90 parts by weight of graphite with an average particle size of 6.5 μm, 10 parts by weight of carbon, and 70 parts of quaternary ammonium with respect to 250 parts by weight of phenol resin. Incidentally, the ratio of graphite to carbon is preferably at least 3 times that of carbon in order to stabilize the resistance of the entire film. The film is applied to the sleeve by spraying and then dried at 150 ° C. for 30 minutes.

  The result is shown as Example 1 in Table 6. Thus, it can be seen that the toner coat defect does not occur not only at room temperature / normal humidity but also at room temperature / low temperature, which is severe for charging up the toner. Table 3 shows the tribo with a durability of 1000 sheets in the conventional system. In contrast, Table 4 shows the case of this example. In this way, the tribo value could be made substantially the same, and a uniform and high-quality image without a toner coat defect could be obtained. As a result, the development characteristics (VD curve) can be made to be quite close to the upstream and downstream sleeves as shown in FIG.

(Q / M (tribo) was measured by the following method for the measurement of the suction method tribo value on the developer carrier: a metal suction port was attached along the shape of the surface of the developer carrier. Using a measuring container having a cylindrical filter paper, the suction pressure is adjusted so that the developer layer on the surface of the developer carrier immediately after image formation can be uniformly sucked without excess or deficiency, and the surface of the developer carrier is adjusted. The developer is sucked in. The charge Q of the developer sucked at this time is measured with a 616 digital electrometer (manufactured by KEITHLEY), and the mass M of the developer is measured by Q / M (μC / g). The tribo value of the developer was calculated.)
With the above configuration, in a small-sized developing device compatible with a high-speed machine, the first purpose is to prevent a toner coat failure of the downstream sleeve, and the second purpose is that developability differs depending on the developing sleeve. By preventing this, it has been possible to satisfy the demands of gradation and gradation stability of images corresponding to recent digital images and graphics, and to provide a developing device having a high density and a stable density. .
(Example 2)
Next, the life of the developing sleeve will be described. From Table 7, the upstream sleeve is composed of 250 parts by weight of P / B 1: 2.5 phenolic resin, 90 parts by weight of graphite, and 10 parts by weight of carbon, and the downstream is 70 parts by weight of a quaternary ammonium salt. It is. Although the coating material containing the quaternary ammonium salt is slight, it can be seen that there is much film scraping due to durability compared to a system in which nothing is added. The developing system of the present invention has a more compact configuration because there is no member between the developing sleeves. This makes the coating life (sleeve life) different between the first development and the second development. Therefore, the life of one sleeve still has to be replaced first, and then the other sleeve must be replaced. After that, replacing another sleeve increases the cost of service personnel, and makes the life of the developing sleeve common. desired.

  In this embodiment, the durability is shared. Therefore, a coating material containing spherical particles carbonized or graphitized was used in order to prevent the durability of the sleeve from decreasing due to durability.

The carbonized or graphitized spherical particles are carbon micro beads (PC) manufactured by Nippon Carbon Co., Ltd., and in this example, have a particle diameter of 5 μm and a resistance of 10 ⁻⁴ −10 ⁻² Ωcm when measured as shown in FIG. The particle size was measured with a Coulter counter and expressed as a weight average particle size (D4).

  Next, the form of a present Example is demonstrated.

  The image forming apparatus according to the present invention is the same as that of the first embodiment.

  Next, the developing device 2 used in this embodiment will be described in detail.

  As the developer, a negative-polarity one-component magnetic toner was used.

  The developer used for the evaluation was obtained by melt-kneading, pulverizing and dispersing the following constituent materials.

Polyester resin (Tg 58 ° C.) 100 parts by mass Magnetite 90 parts by mass Negative charge control agent 2 parts by mass As shown in FIG. 1A, the development sleeve is composed of two, and the first developer carrier (development sleeve) 20 Is a non-magnetic member of φ20 aluminum A2017 subjected to plasting with FGB # 600 and then coated. The same applies to the second sleeve. The developer carrying member (developing sleeve) 30 was blasted with FGB # 600 on φ20 aluminum A2017, which is a nonmagnetic member, and coated. This coating is for preventing the sleeve ghost image generated at the sleeve cycle and enhancing the durability of the sleeve surface.

  The first developing sleeve rotates at a speed of 120% with respect to the counter drum. The layer thickness of the toner was regulated by a magnetic blade, and S-Bgap was 250 μm. The distance S-Dgap between the first developing sleeve and the photosensitive drum was 250 μm, and a DC bias of −500 V and a rectangular wave of Vpp 1500 V and frequency 2.7 kHz were applied to the developing sleeve as an AC bias as shown in FIG. Component non-contact development is performed. Accordingly, the development contrast is 300V in the flight direction, and the fog removal contrast is 100V.

  As the second developing sleeve 30, a developer carrier (developing sleeve) having a film formed on φ20 aluminum A2017 which is a nonmagnetic member is used. A DC bias of -500 V and a rectangular wave of Vpp 1500 V and frequency 2.7 kHz are applied to the developing sleeve as shown in FIG. Since it is the same as the first developing sleeve, it is common, and since only one power source is required, there is an advantage that the cost is reduced and the space for the power source can be reduced. The developing sleeve rotates at a speed of 120% with respect to the counter drum. The blade is the same as in Example 1.

  Next, features of the present embodiment will be described.

  The materials used in this example were 250 parts of phenol resin (320 parts in total) having 70 parts of quaternary ammonium salt (of formula 5) as the resin (B) as the upstream coating material, and carbon 10 as the pigment (P). 90 parts by weight of small-sized graphite having an average particle diameter of 3 μm and 75 parts by weight of carbonized or graphitized spherical particles having an average particle diameter of 5 μm were used.

  The difference in durability effect is as shown in Table 7. This is because the spherical particles are microscopically formed into a skeleton within the film, and the resin and carbon are dispersed between the spheres. Therefore, it is considered that the durability is improved. In addition, since it is spherical, it has good dispersibility within the coat, and a structure that becomes a skeleton for these durability is made uniformly. The particle size of the spherical particles is preferably 1-10 μm.

  In this way, the value of Q / M (tribo), which is an index of development characteristics, can be made substantially equal, and the VD curves, which are development characteristics, can be made almost the same curve.

  This makes it possible to control the gradation of the image and the stability of the gradation, and to share the durability life.

With the above configuration, the development system is compatible with a high-speed machine, and in the small development device, the first purpose is to prevent toner coat failure of the downstream sleeve, and the second purpose is development for each development sleeve. By preventing the difference in characteristics, it is possible to satisfy the demands of gradation and gradation stability of recent digital images and images corresponding to graphics, and a plurality of developing sleeves, which is the third purpose In the developing apparatus having the above, the service life of the developing sleeve is made common, and the service cost can be reduced by eliminating the maintenance work of the serviceman, and the density is high and stable and space saving is achieved. It was possible to provide a developing device having a life of 1 million sheets.
(Example 3)
The feature of this example is that the coating graphite is MoS2 compared to Example 1. As shown in FIG. 14, it was found that not only the quaternary ammonium salt but also the graphite, although slightly effective in preventing charge-up of the negative polarity toner, is more desirable. This is shown in FIG. FIG. 14 is a work function of graphite and MoS ₂ . The work function was measured with a RIKEN surface analyzer (AC-1). This measures photoelectrons by ultraviolet excitation.

When this work function is large, the material tends to be negative, that is, it prevents the toner in contact from being negatively charged. Therefore, graphite is also effective in preventing charge-up of the negative polarity toner, although it is slight. Utilizing this fact, the material used in this example is a film having a weight of 320: 90: 10 of phenol resin having a quaternary ammonium salt (chemical formula 2) on the surface of Al sleeve, crystalline MoS ₂ and carbon. A film that was mixed at a specific ratio and cured in a 150 ° C. environment with a film thickness of 20 μm was used. The configuration of the main body is the same as that of the first embodiment. As a result, a uniform and high-quality image without a toner coat defect could be obtained.

  As a result, similar to the development characteristics (VD curve), it was possible to make the characteristics quite similar to the upstream and downstream sleeves.

With the above configuration, in a small-sized developing device compatible with a high-speed machine, the first purpose is to prevent a toner coat failure of the downstream sleeve, and the second purpose is that developability differs depending on the developing sleeve. By preventing this, it has been possible to satisfy the demands of gradation and gradation stability of images corresponding to recent digital images and graphics, and to provide a developing device having a high density and a stable density. .
Example 4
The feature of this embodiment is that the developing device of the present invention is applied to the image forming apparatus. Since the Ruus toner is basically a waste toner that is not transferred and is collected by cleaning, the developing toner is deteriorated due to deterioration and the developing performance is reduced compared to the New toner. The degree of aggregation is increased, the share of S-Bgap is increased, and the film is shaved. This is the development characteristic of the Ruth diameter. It can be seen that the density is lower overall compared to the case of New toner, and the difference between the developing sleeves is larger. The present embodiment was implemented in view of these matters.

  In this embodiment, an analog copying machine using an a-Si drum as a photoreceptor in the image forming system shown in FIG. 10 will be described. The process speed is 120 mm / min at 600 mm / s. The surface of the photosensitive drum 201 is uniformly charged to +500 V by the primary charger 203. Next, analog exposure 212 is performed to form an electrostatic latent image on the photosensitive drum 201. Next, regular development is performed by the developing device 202 and the toner image is visualized. The developer is a jumping development using a magnetic one-component positive toner. The toner particle size is 6.0 μm. In the case of the conventional two-component developer, since the serviceman must perform the carrier exchange every 100,000 sheets, the advantage of Ruth cannot be prosperous. On the other hand, a dry magnetic one-component toner having infinite durability and no maintenance is used. As the developing bias, a bias voltage obtained by superimposing a DC voltage of +200 V on an AC voltage of 2400 Hz, 1500 Vpp, and Duty 50% is applied to both the first and second developing biases. The first S-Bgap was 250 μm, and both S-Dgap were 250 μm. Thereafter, the toner image is charged by supplying a total current of −200 μA with a post charger, and then transferred to a transfer material proceeding in the direction of the arrow by the transfer charger 204 and sent to the fixing device 7 to fix the toner image. On the other hand, the transfer residual toner on the photosensitive drum 1 is removed and collected by the cleaning device 206, and the waste toner (reuse toner) is returned to the developing hopper 209B through the transport pipe 208. The conveying pipe has a screw-like conveying member inside, and carries the toner by rotating. More specifically, the loose toner conveyed as shown in FIG. 10 is put into the developing hopper 209B and reused. Separately, New toner is put into the hopper 209A, and each toner is attracted by the magnetic force by the mag rollers 21A and 21B, and the toner is carried into the developing device by rotating the mag rollers 21A and 21B. In this embodiment, the method of mixing the Ruth toner and the New toner in the developing device is adopted, but a space for mixing in the hopper may be provided and mixed. The toner mixed in the developing device is sent again to the developing sleeve and developed on the photoreceptor. The normal rotation speed of the mag roller 21A is 2 rotations / minute, and the rotation speed of the mag roller 21B is changed. The mag roller rotation signal does not apply the toner's own weight to the piezo sensor (made by TDK) in the developing unit, and a toner supply signal is generated when it vibrates. Normally, the mag roller 21B is 10/90 (mag roller 21A: mag roller 21B = 9: 1) with respect to the mag roller 21A.

  The configuration of the developing device of this example is the same as that of Example 2, and is a film using phenol resin, crystalline graphite, carbon, and spherical carbon particles, and the sleeve diameter is both φ20.

  By applying this method to the Ruth system, the development performance is usually low, and the development characteristics are further different as shown in FIG. 12, but the overall density is slightly lower as shown in FIG. The tribo (Q / M) of the sleeve can be made the same level as in the first development, and the hole in the downstream sleeve and coating failure can be prevented. Incidentally, the first is 9.0 μC / g and the second is 9.4 μC / g. In this way, the value of Q / M (tribo) that is an index of development characteristics can be made substantially equal, and as a result, the VD curves that are development characteristics can be made substantially the same curve. did it. Since the Ruus system is initially developed with only New toner, a state where waste toner and New toner are mixed has low chargeability. By implementing this method on development systems with such a large difference, it is possible to prevent poor coating, match development characteristics up and down, and reduce the service cost by making the upstream and downstream sleeves substantially the same in durability. We were able to.

  As a result, it was possible to control the gradation of the image and the stability of the gradation, and it was possible to obtain a Ruth system that can share the durability life.

  With the configuration as described above, the development system is compatible with a slime, and in a small-sized developing device, the first purpose is to prevent the toner coating failure of the downstream sleeve, and the second purpose is developability for each developing sleeve. By preventing the difference in image quality, it is possible to satisfy the demands of gradation and stability of gradation corresponding to recent digital images and graphics, and a plurality of developing sleeves, which is the third purpose, are provided. In the developing device, the life of the developing sleeve is made common, the service cost can be reduced by eliminating the maintenance work of the service man, the density is high and stable, and space saving is achieved. We were able to provide a developing device with excellent environmental characteristics.

A is a block diagram for explaining the developing device of the first embodiment, and B is a block diagram for explaining the developing sleeve of the first embodiment. The figure for demonstrating the image forming apparatus used by 1st Example and 2nd Example The figure for demonstrating the magnetic pole arrangement | positioning of the image development sleeve used in 1st Example. The figure for demonstrating the developing bias used in 1st Example The figure for demonstrating the relationship between the multiple sleeves and seal of a present Example The figure for demonstrating the relationship of the longitudinal direction of the some sleeve and seal of a present Example Diagram for explaining how to measure the resistance of powder Diagram for explaining the exposure amount and charge amount of graphite Diagram for explaining conventional development characteristics FIG. 6 is a diagram for explaining a image forming apparatus according to a third embodiment. FIG. 6 is a view for explaining development characteristics improved in Example 1; Diagram for explaining the development characteristics of a conventional Ruth system The figure for demonstrating the development characteristic of the Ruus system of Example 3. Diagram for explaining work function of graphite and MoS ₂ The figure for demonstrating the conventional image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drum photoreceptor 2 Developer 3 Primary charger 4 Transfer charger 5 Separation charger 6 Cleaning device 7 Fixing device 9 Developer hopper 10 Post charger 12 Image exposure 20 First developing sleeve 30 Second developing sleeve

Claims (4)

  In a developing device that visualizes an electrostatic latent image formed on an electrostatic latent image carrier with a negative developer, the developing device has a plurality of developer carriers, and the electrostatic latent image carrier In the developing device in which the developer layer thickness of the downstream developer carrier is regulated by the upstream developer carrier relative to the rotation direction, the plurality of developer carriers have a magnetic member inside, and the surface thereof is a phenol resin. The electrostatic latent image bearing member is coated with the coating member, and the developer is developed on the electrostatic latent image bearing member, and the coating member surface of the developer bearing member has a quaternary ammonium salt only in the downstream developer bearing member. A developing device.   2. The developing device according to claim 1, wherein the coating member surface of the developer carrying member has spherical particles carbonized or graphitized on the downstream developer carrying member.   3. The spherical carbonized or graphitized spherical particles present in the resin film formed on the surface of the downstream developer carrying member according to claim 1, wherein the average particle size is 1 to 10 μm. Development device. 4. A developing device according to claim 1, wherein the developer has a weight average particle size of 7 [mu] m or less.

Images