JP2007293121A - Toner supply roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner supply roller restraining toner packing while securing toner supply property. <P>SOLUTION: The toner supply roller is equipped with a foaming elastic body layer 32 provided on the outer peripheral surface of a core bar, and particulates 34 are imparted to the outermost surface of the foaming elastic body layer 32 and the inner surfaces of cells 33 opening on the outermost surface. Furthermore, the permeability (based on a JIS-L1096A method) of the foaming elastic body layer 32 obtained after imparting the particulates 34 is set within a range from 70 to 150 ml/cm<SP>2</SP>/sec. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a toner supply roller that is incorporated in a developing device of an electrophotographic image forming apparatus and supplies toner to a developing roller.

  In image forming apparatuses such as copying machines, printers, facsimiles, etc., developing devices that develop and visualize electrostatic latent images formed on image carriers such as electrophotographic photosensitive members and electrostatic recording dielectrics are used. Has been. Development devices are roughly classified into a two-component development method in which development is performed using a two-component developer mainly composed of toner and a carrier, and a one-component development method in which development is performed mainly using a one-component developer.

  The developing device of the one-component developing system includes a developing roller that conveys toner to an image carrier (for example, a photosensitive drum), a regulating member that regulates the layer thickness of the toner layer on the developing roller and frictionally charges the toner, A toner supply roller that contacts the developing roller to supply toner onto the developing roller and peels off toner remaining on the developing roller after development; The developing roller is rotatably supported by spacer members provided at both end portions thereof, and is disposed so as to face the photosensitive drum in the axial direction. Further, the toner supply roller is disposed so as to strongly contact the developing roller by a biasing member such as a spring.

The toner supply roller has both a toner supply function and a toner peeling function. For this reason, the surface layer of the toner supply roller is made of a foamed elastic body, and the developer is held by the cells (bubbles) on the surface, or the toner is scraped off at the edges of the cells, so that the toner supply and scraping properties are improved. (For example, patent document 1, patent document 2).
JP 2002-70839 A JP 2003-287951 A

  However, the conventional developing device described above has the following problems. That is, when the toner supply roller is used for a long period of time, toner packing (clogging) occurs due to toner aggregation in the cells on the surface of the toner supply roller. When toner packing occurs, the surface hardness of the roller increases, leading to fluctuations in the driving torque of the roller, image defects due to a decrease in the function of toner supply, and an increase in deteriorated toner.

  As a countermeasure against the aforementioned toner packing, it is conceivable to use a foamed elastic body having a high density and a small cell diameter. High density and small cell diameter suppresses toner entering the cell. However, while toner packing is suppressed, toner supply performance is reduced. Further, once the toner enters, it becomes difficult to discharge the toner. As a result, toner packing occurs. On the other hand, if a foamed elastic body having a low density and a large cell diameter is used, the toner entering the cell becomes excessive, and the discharge cannot catch up.

  In recent years, in order to meet the demand for higher image quality and higher speed, it is inevitable to use toner that has a small particle size and can be fixed at low temperature. When such toner is used, the toner easily enters the cell and is not easily discharged. Therefore, toner packing is more likely to occur.

  Up to now, focusing on toner supply and scraping properties, the surface of the foamed elastic body is provided with an additive (for example, Patent Document 1), or the surface of the foamed elastic body has irregularities formed at a predetermined pitch. (For example, Patent Document 2) is disclosed, but does not sufficiently suppress toner packing.

  The present invention has been made to solve the problems of the conventional developing device described above. That is, the problem is to provide a toner supply roller that suppresses toner packing while ensuring toner supply.

A toner supply roller for solving this problem is a toner supply roller including a core material and a foamed elastic layer located on the outer peripheral surface of the core material. Is added, and the surface of the cell opened at the outermost surface of the foamed elastic layer is made uneven by the fine particles, and the air permeability of the foamed elastic layer (conforming to JIS-L1096A method) is from 70 ml / cm ² / sec. It is characterized by being in the range of 150 ml / cm ² / sec.

  In the toner supply roller of the present invention, fine particles are added to the foamed elastic layer, and the surface of the cell forms a rough surface by the fine particles. For this reason, the toner retainability is high, and the toner supply performance is better than that in which no fine particles are added.

Further, when the foamed elastic layer to which fine particles are added has a gas permeability of less than 70 ml / cm ² / sec, the amount of toner entering the cell opened at the outermost surface of the foamed elastic layer is small. On the other hand, the amount of toner discharged is small. For this reason, toner stays in the cell, resulting in toner packing. Further, in the case of a foam having an air permeability of more than 150 ml / cm ² / sec, the amount of intrusion of toner increases and toner discharge cannot catch up. Therefore, toner packing occurs. Therefore, the toner supply roller of the present invention can avoid toner packing by setting the air permeability of the foamed elastic layer to 70 ml / cm ² / sec or more and 150 ml / cm ² / sec or less.

  In the toner supply roller of the present invention, the ratio of the area occupied by the fine particles in the surface of the cell opened at the outermost surface of the foamed elastic layer is preferably in the range of 20% to 90%. .

  When the ratio of the area occupied by the fine particles is less than 20% in the surface of the cell opened at the outermost surface of the foamed elastic layer, the supply effect by the fine particles is not exhibited. That is, when an image that constantly supplies toner (an image with a high printing rate, such as a solid image) is printed, the image density decreases from the leading edge to the trailing edge of the paper. That is, the so-called solid image density followability deteriorates. On the other hand, when the ratio exceeds 90%, the ratio of the fine particles in the cell becomes too large, so that the amount of toner held in the cell is reduced and the external additive of the toner or the toner itself is buried in the gap between the fine particles. Similarly, the followability of the solid image density is deteriorated. Therefore, in the toner supply roller of the present invention, the ratio of the area occupied by the fine particles in the surface of the cell opened on the outermost surface of the foamed elastic layer is 20% or more and 90% or less, thereby changing the image density. Can be suppressed.

  In the toner supply roller of the present invention, the average volume particle size of the fine particles is preferably in the range of 0.05 μm to 10 μm.

  When the average volume particle size of the fine particles added to the foamed elastic layer is less than 0.05, the fine particles are easily buried by the toner that has entered the cell. For this reason, the effect of supplying fine particles is not exhibited, and the absolute value of the toner supply amount decreases. On the other hand, when the average volume particle diameter exceeds 10 μm, the fine particles are cracked or detached as they are used. Therefore, the toner supply roller of the present invention can exert the effect of fine particles over a long period of time when the average volume particle size of fine particles is 0.05 μm or more and 10 μm or less.

  According to the present invention, a toner supply roller that suppresses toner packing while ensuring toner supply is realized.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings. In the present embodiment, the present invention is applied to an electrophotographic image forming apparatus provided with a developing device for storing and supplying non-magnetic one-component toner.

  As shown in FIG. 1, the image forming apparatus 100 according to the embodiment includes a photosensitive drum 11 that is an image carrier, and the surface of the photosensitive drum 11 is uniformly charged around the photosensitive drum 11. A charging device 12, an exposure device 13 for forming an electrostatic latent image on the surface of the photosensitive drum 11, and an electrostatic latent image on the photosensitive drum 11 to be a visible image (toner image). The developing device 14, the transfer device 15 for transferring the toner image on the photosensitive drum 11 to the sheet, and the cleaning device 16 for removing the transfer residual toner from the photosensitive drum 11. In line with. Further, a timing roller 17 for adjusting the timing of conveying the sheet to the transfer position and a fixing device 18 for fixing the transferred toner image on the sheet are provided in the sheet conveying path. In this embodiment, the charging device 12, the transfer device 15, and the fixing device 18 are all roller-shaped. The cleaning device 16 uses a cleaning blade.

  Next, an image forming operation by the image forming apparatus 100 will be briefly described. The image forming apparatus 100 starts operation by receiving a start signal, image data, and the like. The photosensitive drum 11 is rotationally driven in the direction of the arrow in FIG. Then, it is uniformly charged by the charging roller at a position facing the charging device 12. Next, exposure is performed by the exposure device 13, and an electrostatic latent image based on the image data is formed on the surface.

  Next, when the electrostatic latent image reaches the position of the developing device 14, the toner charged by the electric field formed between the developing bias voltage applied to the developing roller and the electrostatic latent image on the photosensitive drum 11 moves. Then, the electrostatic latent image is developed with toner.

  On the other hand, the paper transported through the paper transport path is timed by the timing roller 17 to the front end position of the image, and is transported between the photosensitive drum 11 and the transfer device 15. Then, the toner image on the photosensitive drum 11 is transferred to a sheet by the transfer device 15. Further, the sheet holding the transferred toner image is further conveyed, and heat and pressure are applied by the fixing device 18 to fix the toner image on the sheet. Further, the transfer residual toner which is not transferred onto the sheet by the transfer device 15 and remains on the photosensitive drum 11 is scraped off by the cleaning device 16. Thereby, the image formation for one sheet is completed.

  Next, the developing device 14 will be described in detail. As shown in FIG. 2, the developing device 14 includes a developing container 1 that contains non-magnetic toner that is a one-component developer, a developing roller 2 that carries the toner and conveys the toner toward the photosensitive drum 11, A toner supply roller 3 that supplies toner to the developing roller 2 and scrapes off the toner on the developing roller 2, a toner amount regulating member 4 that regulates the thickness of the toner on the developing roller 2, and prevents toner leakage. And a toner neutralizing member 5 for neutralizing toner remaining on the developing roller 2 after development. Further, a power source is connected to the developing roller 2 and a bias for development is applied.

  In the developing device 14, the toner in the developing container 1 is transferred from the toner supply roller 3 to the development roller 2 by the potential difference between the toner supply roller 3 and the development roller 2 and the mechanical conveyance force of the toner supply roller 3 whose surface is foam. Transport. The toner supplied to the developing roller 2 is thinned while being frictionally charged by the toner amount regulating member 4 as the developing roller 2 rotates, and the electrostatic latent image is visualized at a portion facing the photosensitive drum 2. .

  As shown in FIG. 3, the toner supply roller 3 includes a cored bar 31 and a foamed elastic layer 32 that is located around the cored bar 31 and is made of a foamed member. A material such as iron, stainless steel, aluminum, or resin is used for the core 31. In addition, as the metal core 31, any metal that has been subjected to rust prevention treatment is applicable. The foamed elastic layer 32 is formed of a foam of thermosetting resin such as polyurethane, epoxy resin, or acrylic resin. Further, it can be formed from a rubber foam of a thermoplastic resin such as polyethylene or polystyrene, but a polyurethane foam excellent in durability is preferred. In this embodiment, polyurethane foam was used. In this embodiment, a non-conductive material is used. However, the foamed elastic layer 32 may contain a conductive substance as necessary.

  Further, the surface shape of the foamed elastic layer 32 is cylindrical. It should be noted that, for example, the grooves along the axial direction of the roller are formed in a stripe shape at a predetermined pitch, the grooves are formed with a plurality of cuts in the axial direction at a predetermined pitch, or the shape is a polygonal column. The surface shape of the foamed elastic body is not limited.

  Further, as shown in FIGS. 4 to 5, fine particles 34 are provided on the surface of the foamed elastic layer 32 in the cells 33 opened on the surface of the foamed elastic layer 32. For this reason, the inner surface of the cell 33 opened at the outermost surface of the foamed elastic layer 32 forms a rough surface with fine particles 34. As the fine particles 34, nylon powder, polymethyl methacrylate (PMMA), silicon powder, or the like can be applied. A plurality of materials may be mixed. In this embodiment, PMMA is used as the material of the fine particles 34 and pulverized to adjust the desired average volume particle size. Details of the average volume particle size will be described later.

  The toner supply roller 3 applies at least one kind of fine particles 34 to the foamed elastic layer 32 and is fixed to the foamed elastic layer 32 so that the fine particles 34 are not detached even when contacting the toner or the developing roller 2. In the final form. The application method or fixing method of the fine particles 34 is not limited. For example, after forming the foamed elastic layer 32 together with the material of the foamed elastic layer 32, the surface of the foamed elastic layer 32 is cut or polished, or a solvent in which the particles 34 are dispersed in a binder resin or the like is formed. There are a method of applying and heating to the surface of the foamed elastic layer 32, and a method of applying and heating the resin fine particles 34 directly on the foamed elastic layer 32 after molding when the fine particles 34 are made of resin.

  In this embodiment, the fine particles 34 are fixed by the following method in order to make the fine particles 34 more effective. First, a polymer emulsion is spray-coated on the surface of the foamed elastic layer 32 as an adhesive layer between the foamed elastic layer 32 and the resin fine particles 34. Thereafter, a predetermined amount of fine particles 34 is applied and dried at 100 ° C. in a hot air circulation type drying furnace. As a result, as shown in FIG. 6, an adhesive layer 35 made of a polymer emulsion is formed on the surface of the cell 33, and the fine particles 34 are fixed to the adhesive layer 35. Thus, in the fixing method in which the fine particles are applied after the adhesive layer is applied, the fine particles protrude from the surface of the foamed elastic layer 32 and the cell surface as compared with the fixing method in which the fine particles are dispersed in the raw material and foamed. Since it can be fixed in a state, the effect of adding fine particles can be exhibited more. The fine particles are not limited to one type, and a plurality of types of fine particles may be provided. For example, as shown in FIG. 7, two types of fine particles 34 and 36 may be provided.

[Evaluation of Embodiment]
Next, the evaluation result of the developing roller according to the embodiment will be described. In this evaluation, “magicolor5440” (hereinafter referred to as “evaluation machine”) manufactured by Konica Minolta was used, and the configuration of the toner supply roller was changed for evaluation. Except for the fourth evaluation, toner for evaluation machine (average volume particle diameter: 6.5 μm, softening point: 110 ° C., hereinafter referred to as “A” type toner) was used.

  In this evaluation, the urethane foam is cut into a 40 mm × 40 mm × 300 mm rectangular parallelepiped, and a hole with a diameter of 2 mm is inserted into the urethane foam to insert a core metal. Then, an iron core bar having a diameter of 3 mm to which a hot melt adhesive has been applied in advance is passed through the urethane foam. Thereafter, the core metal is heated by an electromagnetic induction heater, and the adhesive is melted to bond the urethane foam and the core metal. After cooling the core metal and completing the bonding, the urethane foam is cut so that the outer diameter becomes 11.6 mm.

To the surface of the foamed elastic layer thus obtained, PMMA fine particles having an adjusted average volume particle size and added amount were applied by the above-described fixing method, and a toner supply roller for evaluation was prepared. As urethane foam, ECA which is urethane foam manufactured by Inoac Corporation (ordinary foam, density: 26 ± 2 [kg / m ³ ], hardness: 127.5 ± 24.5 [N]), EMM ( Hard type foam, density: 52 ± 3 [kg / m ³ ], hardness: 225.6 ± 39.2 [N]), EFF (soft type foam, density: 21 ± 2 [kg / m ³ ] , Hardness: 58.8 ± 19.6 [N]), EFS (super soft type foam, density: 20 ± 2 [kg / m ³ ], hardness: 19.6 ± 9.8 [N]) 4 types were prepared.

  In this evaluation, the “breathability”, “coverage”, and “average volume particle size” of the foamed elastic layer of the toner supply roller were evaluated. “Breathability” was measured according to JIS-L1096A method (air permeability at a differential pressure of 125 Pa using a fragile tester). “Coverage” means the ratio of the area occupied by fine particles on the cell surface when 20 or more cells located on the surface of the foamed elastic layer are observed with a scanning electron microscope (SEM). The “average volume particle size” was measured by FPIA-2100 manufactured by Sysmex Corporation.

[First evaluation]
In the first evaluation, evaluation related to toner aggregation was performed. In this evaluation, after measuring the initial weight A of each toner supply roller, a 100 ml toner container containing 30 g of toner is prepared. In the container, the toner supply roller is disposed in pressure contact with a developing roller for an evaluation machine. Thereafter, with the container sealed, only the toner supply roller was driven for 30 minutes, and then the weight B of the toner supply roller was measured. Subsequently, only the toner supply roller was placed in the toner container in which the toner was emptied, stirred for 15 minutes, and the weight C of the toner supply roller was measured again. Then, the remaining amount of toner in the toner supply roller was calculated with the clogging rate (%) expressed by the following equation (1).
Clogging rate (%) = (C−A) / (B−A) × 100 (1)

  The evaluation results of the first evaluation are shown in FIG. In this agglomeration evaluation, the clogging rate shown in the above formula (1) is less than 20%, ◎, 20% or more and less than 35%, ◯, 35% or more and less than 50%, and 50% or more. . In FIG. 8, the examples are those that have good evaluation results, and the comparative examples are those that are poor.

In Examples 1 to 11, there was little toner entering and packing, and good results were obtained. On the other hand, in Comparative Examples 1 to 11, the toner that entered the cells on the surface of the roller caused packing and became clogged. That is, when no fine particles were applied (Comparative Example 8 to Comparative Example 11), good results were not obtained. Even when fine particles are applied, the air permeability is smaller than 70 ml / cm ² / sec (Comparative Examples 1 to 4), or the air permeability is larger than 150 ml / cm ² / sec (Comparative Example 5). Even in Comparative Example 7), good results were not obtained. From this evaluation result, it was found that toner packing is suppressed by applying fine particles. Further, it was found that toner packing is suppressed when the air permeability is in the range of 70 ml / cm ² / sec to 150 ml / cm ² / sec.

FIG. 9 shows the evaluation results shown in FIG. 8 rearranged for each urethane foam material. As shown in FIG. 9, in any of the materials, if the air permeability is in the range of 70 ml / cm ² / sec to 150 ml / cm ² / sec, toner packing is suppressed, and if out of the range, clogging occurs. You can see that it has occurred. This indicates that the difference in the material of the foamed elastic layer does not affect the evaluation results.

  The air permeability of the foamed elastic layer can be adjusted by the amount of fine particles added. Therefore, even if the roller cannot be used due to problems such as toner supply and scraping properties without adding fine particles, the air permeability can be adjusted by adding the fine particles so that the roller can be used. That is, the use range of the toner supply roller can be expanded. On the other hand, even if the air permeability is within the above range, if fine particles are not added (Comparative Examples 8 and 9), the toner enters the cell. Therefore, it was found that good results could not be obtained unless fine particles were added.

[Second evaluation]
In the second evaluation, an evaluation was made regarding the supply performance of the toner supply roller. In this evaluation, the color toner cartridge for the evaluation machine is attached to the external drive unit for the evaluation machine using the toner supply roller at the initial stage and after the endurance (after the blank image print number of 5000 sheets), and the system speed is set according to the specification of the evaluation machine. As a triple state, a thin toner layer was formed on the developing roller. Then, the weight of the toner thin layer was measured.

The evaluation results of the second evaluation are shown in FIG. In this supplyability evaluation, the toner thin layer weight is less than 3 g / m ² ×, 3 g / m ² or more and less than 6 g / m ² △, 6 g / m ² or more and less than 8 g / m ² ◯, 8 g / m ² Above, it was set as ◎. In FIG. 10, the examples are those that have good evaluation results, and the comparative examples are those that are poor.

  In Examples 12 to 18, high supply performance was shown and good results were obtained. On the other hand, in Comparative Examples 11 to 17, the result was that the weight of the toner thin layer was small after the endurance. In particular, in Comparative Examples 14, 15, and 17, the weight of the toner thin layer was low even in the initial stage, and unevenness was observed in the toner thin layer. This is presumed that the ability to supply toner is reduced because the average volume particle size of the fine particles is too small, 0.03 μm or less. Therefore, it was found that the average particle size of the fine particles must be 0.05 μm or more.

  Further, in the second evaluation, evaluation of the detachability of the fine particles was also performed. In this fine particle detachment evaluation, 5000 blank paper images were printed with an evaluation machine, and the toner supply roller thereafter was observed with an SEM. In this evaluation of particle detachment, X is indicated when detachment / cracking of the particle is detected, and ◯ is indicated when neither detachment / cracking is detected.

  In Examples 12 to 18, there was no separation or cracking of fine particles, and good results were obtained. Good results were also obtained in Comparative Examples 14, 15, and 17 in which the size of the fine particles was small. On the other hand, in Comparative Examples 12, 13, and 16 in which the size of the fine particles was large, separation / cracking of the fine particles was confirmed. Therefore, it was found that the average particle size of the fine particles must be 10 μm or less. From this second evaluation, it was found that the average volume particle diameter of the fine particles is preferably in the range of 0.05 μm or more and 10 μm or less.

[Third evaluation]
In the third evaluation, the solid image followability was evaluated. In this evaluation, at the initial stage and after printing 50,000 blank images, a solid image was printed with the bias between the toner supply roller and the developing roller of the evaluation machine at the same potential. Then, the transmission density change rate between the leading edge and the trailing edge of the solid image was obtained.

  The evaluation results of the third evaluation are shown in FIG. In this solid image follow-up evaluation, the transmittance density change rate is less than 20%, ◯, 20% or more and less than 50%, Δ, 50% or more and ×. In FIG. 11, the examples are those that have good evaluation results, and the comparative examples are those that are poor.

  In Examples 19 to 25, high solid image followability was shown, and good results were obtained. On the other hand, in Comparative Examples 18 to 23, the transmission density change rate was high, and the solid image followability was low. Specifically, in Comparative Examples 18 and 19, since the coverage was 10% or less (that is, a small amount of fine particles), it was found that the effect of the fine particles was not exhibited. Further, as in Comparative Examples 20 and 21, when the coverage was 95% or more (that is, a large amount of fine particles), good results were not obtained with a solid image following property after printing 50,000 sheets. This is presumed that the external additive of the toner or the toner itself is buried in the space between the fine particles, and as a result, the effect of the fine particles is not exhibited. From this third evaluation, it was found that the coverage of fine particles on the inner surface of the cell is preferably in the range of 20% to 90%.

[Fourth evaluation]
In the fourth evaluation, the same evaluation as the first evaluation was performed using a toner different from the first evaluation. Specifically, in this evaluation, the toner (average volume particle size: 4.5 μm, softening point: 100 ° C., below) that can be fixed at a low temperature and with a smaller particle size than the A type toner used in the first evaluation. "B" type toner) was used. Toner for small particle size and low temperature fixing tends to cause more toner packing.

The result of the fourth evaluation is shown in FIG. In FIG. 12, the examples are those that gave good evaluation results, and the comparative examples that were bad. In Examples 26 to 29, there was little toner entering and packing, and good results were obtained. On the other hand, in Comparative Examples 24-27, the toner that entered the cells on the surface of the roller caused packing and became clogged. That is, good results are obtained when the air permeability is smaller than 90 ml / cm ² / sec (Comparative Examples 24 and 25) or when the air permeability is larger than 130 ml / cm ² / sec (Comparative Examples 26 and 27). I couldn't. From the results of the evaluation, when using a small particle diameter and low temperature fixing toner, as long as it is within the range breathability of ^{90ml / cm 2 / sec~130ml / cm} 2 / sec, that the toner packed is suppressed all right.

[Fifth evaluation]
In the fifth evaluation, two types of fine particles having different average volume particle diameters were applied, and the same evaluation as the first evaluation, the second evaluation, and the third evaluation was performed. Note that nylon powder was used as the material for the fine particles C, and polymethyl methacrylate was used as the material for the fine particles D.

The result of the fifth evaluation is shown in FIG. In Examples 30 to 33, good results were obtained in all of the evaluation of aggregation, evaluation of supply, evaluation of fine particle detachment, and evaluation of solid followability. These examples are all breathable range specified in the first evaluation ^{(70ml / cm 2 / sec~150ml /} cm 2 / sec), range of the average volume particle size of the fine particles as defined in the second evaluation (0.05 μm to 10 μm), which satisfies the range of coverage (20% to 90%) defined in the third evaluation. On the other hand, Comparative Examples 28 and 31 do not satisfy the air permeability range. Therefore, the result of aggregation evaluation is bad. In Comparative Example 29, the average volume particle size of the fine particles is larger than the specified range. For this reason, the results of evaluation of the detachability of the fine particles are bad. In Comparative Example 30, the average volume particle size of the fine particles is smaller than the specified range. For this reason, the results of supplyability evaluation are bad. From these results, it was found that even when a plurality of types of fine particles were applied, good results could be obtained if the ranges defined in the first evaluation, the second evaluation, and the third evaluation were satisfied.

  As described above in detail, the toner supply roller 3 of the present embodiment includes the cored bar 31 and the foamed elastic layer 32 provided on the outer peripheral surface of the cored bar 31, and the outermost surface of the foamed elastic layer 32. The fine particles 34 are applied to the inner surface of the cell 33 that opens at the outermost surface. That is, the surface of the cell 33 is roughened by the fine particles 34. For this reason, the toner retainability is high, and the toner supply performance is better than that in which no fine particles are added.

Further, the air permeability of the foamed elastic layer 32 after application of the fine particles 34 is in the range of 70 ml / cm ² / sec to 150 ml / cm ² / sec. In the case of a foam having an air permeability of less than 70 ml / cm ² / sec, the amount of toner entering the cell 33 is small, but the amount of toner discharged is also small. Therefore, the toner stays in the cell 33, resulting in toner packing. Further, in the case of a foam having an air permeability of more than 150 ml / cm ² / sec, the amount of intrusion of toner increases and toner discharge cannot catch up. Therefore, toner packing occurs. Therefore, toner packing (toner aggregation) can be avoided by setting the air permeability of the foamed elastic layer 32 after application of the fine particles 34 to 70 ml / cm ² / sec or more and 150 ml / cm ² / sec or less.

  Further, the coverage of the fine particles 34 in the surface cells 33 of the foamed elastic layer 32 is in the range of 20% to 90%. When the coverage is less than 20%, the supply effect by the fine particles is not exhibited. That is, when an image that constantly supplies toner (an image with a high printing rate, such as a solid image) is printed, the image density decreases from the leading edge to the trailing edge of the paper. On the other hand, when the coverage ratio exceeds 90%, the proportion of the fine particles 34 in the cell 33 is excessively increased, so that the amount of toner held in the cell 33 is reduced and an external additive or toner is added to the gap between the fine particles 34. The image itself is buried, and the solid image density followability is similarly deteriorated. Therefore, the fluctuation of the image density can be suppressed by setting the coverage of the fine particles 34 in the surface cells 33 of the foamed elastic layer 32 to 20% or more and 90% or less.

  The average volume particle size of the fine particles 34 applied to the foamed elastic layer 32 is in the range of 0.05 μm to 10 μm. When the average volume particle diameter is less than 0.05, the fine particles 34 are easily buried by the toner that has entered the cell 33. For this reason, the supply effect of the fine particles 34 is not exhibited, and the absolute value of the toner supply amount decreases. On the other hand, when the average volume particle diameter exceeds 10 μm, the fine particles 34 are cracked or detached as they are used. Therefore, when the average volume particle size of the fine particles 34 applied to the foamed elastic layer 32 is 0.05 μm or more and 10 μm or less, the effect of the fine particles 34 can be exhibited over a long period of time.

In addition, small particle size / low temperature fixing toner tends to decrease fluidity and increase cohesion, and toner packing is likely to occur. Therefore, when such a toner is used, the air permeability of the foamed elastic layer 32 after the application of the fine particles 34 is set to 90 ml / cm ² / sec or more and 130 ml / cm ² / sec or less to form the toner packing. (Toner aggregation) can be avoided.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the present invention can be applied to various image forming apparatuses such as a color printer, a monochrome printer, a copier, and a facsimile.

  Further, although a roller-shaped photosensitive drum is used as the image carrier, a belt-shaped photosensitive belt may be used. In addition to the roller charging method, the charging device may use a corona discharge charging charger, blade, brush, or the like. The exposure apparatus may be a laser or LED. The transfer device may use a transfer charger in addition to the transfer roller. Alternatively, in addition to a method of directly transferring a toner image from a photosensitive member to a sheet, a method of providing an intermediate transfer member and performing transfer in two or more stages may be used. In addition to the cleaning blade, the cleaning device may be a cleaning brush, a cleaning roller, or a combination thereof. Alternatively, the transfer residual toner may be collected by a developing device. In addition to the fixing roller, the fixing device may use a fixing belt or a non-contact type.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment. 1 is a diagram illustrating a schematic configuration of a developing device according to an embodiment. FIG. 2 is a diagram illustrating a schematic configuration of a toner supply roller according to an embodiment. FIG. 4 is an enlarged view of a portion X in FIG. 3. It is a figure which shows the cell inner surface from the Y viewpoint of FIG. It is a figure (one type of microparticles | fine-particles) which shows the detail of the foaming elastic-body layer of a toner supply roller. It is a figure (2 types of microparticles | fine-particles) which shows the detail of the foaming elastic-body layer of a toner supply roller. It is a figure which shows the evaluation result of 1st evaluation. It is a figure which shows the evaluation result (by the material of a urethane foam) of 1st evaluation. It is a figure which shows the evaluation result of 2nd evaluation. It is a figure which shows the evaluation result of 3rd evaluation. It is a figure which shows the evaluation result of 4th evaluation. It is a figure which shows the evaluation result of 5th evaluation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing container 2 Developing roller 3 Toner supply roller 31 Core metal (core material)
32 Elastic foam layer 33 Cell 34 Fine particle 11 Photosensitive drum 14 Developing device 100 Image forming device

Claims (3)

In a toner supply roller comprising a core material and a foamed elastic layer located on the outer peripheral surface of the core material,
Fine particles are added to the foamed elastic layer,
The surface of the cell opened at the outermost surface of the foamed elastic layer is uneven by the fine particles,
A toner supply roller, wherein the foamed elastic layer has air permeability (based on JIS-L1096A method) in a range of 70 ml / cm ² / sec to 150 ml / cm ² / sec. The toner supply roller according to claim 1,
The toner supply roller according to claim 1, wherein a ratio of an area occupied by the fine particles in a cell surface opened at an outermost surface of the foamed elastic layer is in a range of 20% to 90%. In the toner supply roller according to claim 1 or 2,
The toner supply roller, wherein an average volume particle diameter of the fine particles is in a range of 0.05 μm to 10 μm.

Images