JP5071017B2 - Developing device, developing method, and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device used for electrophotographic image formation, a developing method, and an image forming apparatus.

  Non-magnetic one-component development is a development method having excellent characteristics such as a simple development device structure and compatibility with color development, and therefore has been widely used in recent years.

  The developing roller used in this developing method is often made of a polymer material (resin), especially in its coating layer, and usually contains a conductive agent and, if necessary, a charging agent in order to properly charge the toner. A control agent is added and mixed (for example, see Patent Document 1).

  The following structures are known as typical examples of these developing devices. The toner regulating member is in pressure contact with a roller-type toner carrier (developing roller) disposed close to or in contact with an electrostatic latent image forming body (mostly a photosensitive body, and sometimes referred to as a photosensitive body). A toner supply roller is disposed upstream of the toner regulating member in the surface movement direction of the toner carrier.

  In the development, the toner supply roller (also referred to as a supply roller) supplies a one-component developer (toner) onto the development roller, and the supplied toner is made into a toner thin layer having a predetermined layer thickness by a toner regulating member. Then, the toner is conveyed to a developing area that is frictionally charged and faces the electrostatic latent image forming body. Using this toner, a developing bias is applied to the toner carrying member to develop the electrostatic latent image formed on the photosensitive member, and the toner on the developing roller that has not been subjected to the development is transferred by the toner supply roller. Remove. That is, the toner supply roller not only supplies toner to the developing roller, but also serves to remove toner remaining without being subjected to development on the toner carrier (see, for example, Patent Document 2).

  However, for example, in a restricting portion that uses a metal blade such as stainless steel (SUS) that has been widely used as a restricting member to form a toner layer in a thin layer, the toner layer cannot be charged sufficiently. It was difficult to secure the level. For this reason, the toner charge amount distribution is wide, and low charge amount toner, reverse charge amount toner, or overcharge amount toner increases, and it is difficult to obtain a uniformly charged toner. Especially in high-temperature and high-humidity environments and low-temperature and low-humidity environments, the chargeability is not stable, causing toner scattering and toner adhesion to non-image areas on the photoreceptor, causing fogging, and uniform and stable developability over a long period of time (development) In many cases, it is difficult to ensure high durability.

In particular, a so-called baseless developing roller (coating roller) in which a developing roller does not have an elastic layer and a coating layer (also referred to as a surface layer) is directly formed on a conductive shaft has been developed ( In this case, the above tendency is particularly remarkable.
Japanese Patent Laid-Open No. 10-186836 JP 2006-64774 A Japanese Patent Laid-Open No. 2005-77869

  The present invention has been made to solve the above problems.

  That is, the object of the present invention is to obtain a uniformly charged toner, and the charging property is stable even in a high-temperature and high-humidity environment or a low-temperature and low-humidity environment, and the toner scatters and adheres to the non-image area on the photoreceptor. Development device capable of ensuring uniform and stable developability (high development durability) over a long period of time without causing fogging, and a non-magnetic single component suitable for non-contact development using the same. A developing method and an image forming apparatus are provided.

  As a result of intensive studies by the present inventors, it has been found that the object of the present invention can be achieved by adopting the following configuration.

(1)
At least the toner is carried and conveyed to develop the electrostatic latent image on the electrostatic latent image forming body, and the toner is supplied onto the developing roller surface before development, and the toner is scraped off from the developing roller surface after development. In the developing device having a supply roller having a role, the developing roller has a configuration in which a coating layer containing at least a conductive agent and a resin is directly formed on the outer periphery of the conductive shaft body,
The supply roller is made of a rubber foam in which a single-bubble part having closed cells and an open-cell part having open cells are mixed,
The rubber foam has 400 to 1100 cells / cm ² per unit area , an average cell diameter of 300 to 500 μm, and a foaming ratio of 0.4 to 0.9.
A developing device having a scraping rate (Tr) by a supply roller from a developing roller represented by the following formula (1): 0.10 to 0.50.

Formula (1) Tr = (A−B) / A
A: Amount of toner (mg / cm ² ) on the developing roller surface before passing through the closest area to the supply roller surface
B: Amount of toner (mg / cm ² ) on the developing roller surface after passing through the region closest to the supply roller surface
(2)
2. The developing device according to (1), wherein the moving direction of the supply roller surface and the moving direction of the developing roller surface are opposite to each other in a region closest to each other.

(3)
(1) A developing method comprising performing non-magnetic one-component development using the developing device according to (2).

(4)
The developing method according to (3), wherein the developing method is non-contact development.

(5)
An image forming apparatus using the developing method according to (3) or (4).

  According to the present invention, it is easy to obtain a uniformly charged toner, the charging property is stable even in a high-temperature and high-humidity environment and a low-temperature and low-humidity environment, and there is no toner scattering and toner adhesion to a non-image area on the photoreceptor. Development apparatus capable of ensuring uniform and stable developability (high development durability) over a long period of time, and a non-magnetic one-component development method and image suitable for non-contact development using the same A forming apparatus can be provided.

  The present invention provides a developing roller for carrying and conveying at least toner and developing an electrostatic latent image on an electrostatic latent image forming body, supplying toner onto a developing roller surface before development, and from a developing roller surface after development. The present invention relates to a developing device having a supply roller having a role of scraping off toner. The developing roller used in the developing stand according to the present invention has a configuration in which a coating layer containing at least a conductive agent and a resin is directly formed on the outer periphery of the conductive shaft, and is represented by the following formula (1). The developing device has a scraping rate (Tr) by the supply roller from 0.10 to 0.50.

Formula (1) Tr = (A−B) / A
A: Amount of toner [mg / cm ² ] on the developing roller surface before passing the closest region to the supply roller surface
B: Amount of toner [mg / cm ² ] on the developing roller surface after passing through the region closest to the supply roller surface
The amount of toner on the developing roller surface was measured by the following method.

  Prepare a toner collecting unit equipped with filter paper (T100A047A: manufactured by Advantech), and measure the mass of the toner collecting unit: W1 [mg] with an analytical balance (CP224S: manufactured by Sartorius) before collecting the toner. went.

This toner collecting unit is attached to a hose connected to a suction pump, the surface of the developing roller in the developing device is covered with a mask having a window of 7.0 cm ² , and the toner in this area is placed on the filter paper by the suction pump. I collected it.

  The toner collection unit was removed from the hose connected to the suction pump, and the mass of the toner collection unit after toner collection: W2 [mg] was measured with the same analytical balance as before the collection.

  Finally, the amount of toner on the developing roller surface was determined by the following formula.

Amount of toner on the developing roller surface [mg / cm ² ] = (W2−W1) /7.0
Next, measurement of the toner amount A on the developing roller surface before passing through the closest region to the supply roller surface and the toner amount B on the developing roller surface after passing through the closest region to the supply roller surface will be described.

  First, the developing device is incorporated in the electrophotographic apparatus, and after the image forming operation is performed for one blank sheet, the toner amount on the developing roller is measured by the above method, and the developing roller surface before passing through the closest region to the supply roller surface The upper toner amount A was used.

  Next, the developing device was incorporated into the electrophotographic image forming apparatus, and after performing the image forming operation, the developing roller was once removed from the developing device while the toner layer was formed on the developing roller. Next, after the toner remaining in the developing device and the toner adhering to the supply roller were removed, the developing roller on which the toner layer removed earlier was mounted again on the developing device.

  In this state, the developing device is incorporated in the electrophotographic image forming apparatus, and after the image forming operation is performed for one blank sheet, the toner amount on the developing roller is measured by the above method and after passing through the closest area to the supply roller surface. Toner amount B on the developing roller surface.

  In this case, if the toner scraping rate Tr is higher than 0.5, excessive toner replacement leads to a decrease in the toner charge amount, which causes fogging and in-machine contamination. On the other hand, if the toner scraping rate Tr is lower than 0.1, toner replacement is too small and toner spillage occurs due to overcharging and runaway of the toner conveyance amount.

  That is, the developing device having this configuration is illustrated and described as shown in FIG.

  The electrostatic latent image 2 formed on the electrostatic latent image forming body (photoconductor) 10 is developed with the toner T that has been transported in a thin layer formed on the developing roller 3. The toner T is first supplied onto the surface of the developing roller by the supply roller 4 having a role of supplying toner onto the surface of the developing roller before development and scraping off the toner from the surface of the developing roller after development. The supplied toner is pressed onto the developing roller 3 by the regulating member 5 to form a thin layer so that the toner is charged as uniformly as possible. In the present invention, the closest region includes a portion where the distance between the developing roller 3 and the supply roller 4 indicated by D in the drawing is the shortest.

  Further, in a preferred embodiment of the present invention, as shown in FIG. 1, the moving direction of the supply roller surface and the moving direction of the developing roller surface are opposite in the closest region.

  The electrostatic latent image 2 formed on the electrostatic latent image forming body (photoreceptor) 10 is developed with the toner formed on the developing roller 3 and transported in a thin layer. Remains on the developing roller surface facing only the so-called non-image portion where there is no electrostatic latent image to be developed, and the toner formed as a thin layer remains as it is.

  Although the residual toner on the developing roller after the development is scraped off by the supply roller, it has been considered that it is desirable that the residual toner is completely scraped off by the supply roller. Therefore, the inventions so far have pursued a measure of how to completely scrape off.

  However, the inventor of the present invention did not completely scrape, but rather left a certain amount of residual toner without scraping, and found that the characteristics were improved, leading to the present invention.

  Originally, a developing roller (which may be referred to as a coating roller hereinafter) in which a coating layer containing at least a conductive agent and a resin is formed on the outer periphery of a conductive shaft body without an elastic layer is a portion having no elastic layer. Manufacturing costs can be kept low, and variations among lots of developing rollers and variations in layer thickness within the same developing roller can be kept small, which is desirable in that sense.

  However, since there is no elastic layer, when the toner remaining on the roller surface is to be scraped off, there is no cushioning layer, so mechanical stress is applied, and toner deterioration tends to proceed. In this case, the deterioration of the toner appears as a decrease in chargeability mainly due to the influence of the buried external additive. In order to solve this problem, it is necessary to reduce the stress by appropriately scraping off the toner by the supply roller.

  There are several methods for changing the scraping rate. For example, by changing the material of the developing roller and / or the supply roller, the friction coefficient, surface energy, hardness, etc. can control the adhesion force to the toner and the amount of aggregation by pressing, thereby changing the scraping property of the toner. Can do.

  Also, the surface profile (maximum roughness, average crest interval, number of foam cells, average cell diameter, foaming rate, etc.) of the developing roller and / or supply roller is adjusted to adjust the contact area with the toner and the amount of toner taken in. The toner scraping property can be changed.

  Furthermore, a method of applying a voltage to the developing roller and / or the supply roller to adsorb the toner with an electrostatic attractive force to change the scraping property of the toner can be adopted. Alternatively, the relative positional relationship between the developing roller and the supply roller is changed so that the supply roller overlaps the developing roller (hereinafter also referred to as the biting amount. The biting amount is the distance between the supply roller shaft center and the developing roller shaft center. L, where the outer diameter of the supply roller is Ds and the outer diameter of the developing roller is Dd, the amount of biting is defined as Ds / 2 + Dd / 2−L), and the toner pressing force and the nip width are changed to adjust the toner. It is possible to change the scraping property.

  Changing the rotation speed and direction of the developing roller and supply roller to change the relative speed of the periphery of the developing roller and supply roller to change the time to pass through the nip and the energy applied to the toner, thereby changing the toner scraping property. It is also possible to make it.

  For the developing roller, performances other than scraping properties, such as toner chargeability and transportability, are also important, and usually the developing roller rotation speed, rotation direction, and applied bias are determined from the viewpoint of developability. As a method of changing the scraping rate, it is preferable to adjust by the material of the supply roller, the surface profile, the amount of biting into the developing roller, and the relative speed with the developing roller.

  In addition, reducing the replacement of the toner on the developing roller by the supply roller is considered to have an effect of sufficiently charging the toner that is still insufficiently charged by recharging. That is, the toner on the developing roller is charged at the same time as a thin toner layer is formed by the regulating member. In this case, the toner layer formed on the developing roller is a stack of at least several toners. Therefore, even if the electrification is sufficiently charged in the case where it is in sufficient contact friction with the regulating member near the surface of the toner layer, the toner below it, particularly the toner just above the developing roller surface, may be insufficient. There were many.

  Therefore, when the toner layer on the developing roller is all scraped off each time by the supply roller and a new toner layer is formed, the toner immediately above the developing roller surface is always in a state of insufficient charging. However, if the toner in this portion is not scraped off and a new toner layer is formed thereon, it is presumed that the insufficiently charged toner can be charged to a sufficient level by recharging.

  Therefore, in the configuration of the present invention, the toner on the developing roller by the supply roller can be prevented from being excessively stressed, and the toner fatigue such as the burying of the external additive can be suppressed. It can be charged enough.

  Next, the configuration of the developing roller and the supply roller, the developing method, the image forming apparatus and the like according to the present invention will be described below.

[Development roller]
As described above, the developing roller of the present invention is a developing roller in an electrophotographic image forming method, and is particularly suitable for non-magnetic one-component development using a non-contact developing method.

(Development roller configuration)
The configuration of the developing roller of the present invention includes, for example, a conductive shaft (also referred to as a shaft core or shaft body) 15 and an outer peripheral surface of the shaft body 15 as shown in a schematic cross-sectional view in FIG. And a coating layer 16 having a normal film thickness of 100 μm or less to be formed (however, an intermediate layer 17 may be provided therebetween). In the developing roller of the present invention, the developing roller is not provided with an elastic layer (usually having a film thickness of about 500 μm to 6.0 mm (6,000 μm)). In the present invention according to claim 1, “the developing roller has a configuration in which a coating layer containing at least a conductive agent and a resin is directly formed on the outer periphery of the conductive shaft body”. This means that the developing roller does not have an elastic layer.

  An adhesive layer may be further provided between the conductive shaft and the covering layer or intermediate layer. Furthermore, the developing roller of the present invention is not limited to the above two-layer structure. In short, if the layer (resin layer) of at least one polymer material is formed as a coating layer on the conductive shaft. Good.

(Conductive shaft)
What is necessary is just to use what has been conventionally used as an axial center of a developing roller for a conductive shaft. For example, a rod or hollow cylinder made of metal having a diameter of about 5.0 to 30 mm is used. Examples of the material include aluminum, stainless steel, and iron obtained by plating the surface. In addition, a conductive resin rod or the like can also be used. A metal rod such as stainless steel is typical, but the material is not particularly limited.

(Middle layer)
The material for forming the intermediate layer that may be formed on the outer peripheral surface of the conductive shaft is not particularly limited, but any conventionally known material such as a resin material used for the coating layer and an appropriate amount of a conductive agent may be added. Such materials can be used.

That is, in the resin material, for example, carbon black (furnace black, acetylene black, ketjen black), TiO ₂ , ZnO, SnO ₂ , metal oxides such as iron oxide, graphite, potassium titanate, quaternary ammonium salt, The thing which mix | blended electrically conductive agents, such as a borate and a lithium salt, is mention | raise | lifted. Among these, the film thickness is about 0.5 to 10 μm, which is selected from the viewpoint of good adhesion to the material for forming the coating layer.

(Coating layer)
The main constituent material of the coating layer is a non-conductive polymer material (resin), and a resin conventionally used for the coating layer of the developing roller can be used. Examples thereof include a mixture of urethane and acrylic urethane, an acrylic silicone copolymer, and the like. And when using the mixture of the said urethane and acrylic urethane, it is preferable to set the mixing ratio of both in the range of urethane / acryl urethane = 10 / 90-90 / 10 by mass ratio.

  The coating layer is desirably set to have a thickness of 100 μm or less, preferably 3 to 100 μm, and more preferably 5 to 50 μm. That is, when the thickness of the coating layer exceeds 100 μm, the charge imparting property to the toner is hardly lowered even by a slight wear, so that the wear resistance of the charging roller is practically improved. However, the contact portion with the layer forming blade (regulating member) is likely to be deformed, and the restoration of the deformed portion may be delayed due to the thick film thickness. Furthermore, in general, application with a thick film thickness makes it difficult to form a uniform film and a film having surface smoothness.

  The coating layer can be applied by various coating methods such as dipping coating, roller coating, and spray coating.

  The coating layer preferably contains inorganic fine particles, particularly inorganic fine particles that have been surface-treated with any of a surface treatment agent having a cationic group, a silane coupling agent, or a silicone oil having a cationic group.

[Supply roller]
The supply roller 4 is provided so that the peripheral surface thereof is in contact with the peripheral surface of the developing roller 3, and is supported so as to be rotatable, for example, in the direction of an arrow in FIG.

A typical example of the supply roller 4 is formed of a continuous single-cell rubber foam having at least the surface thereof having a cell number per unit area of 400 cells / cm ² or more, preferably 400 to 1100 cells / cm ^2. . The open-cell foamed rubber foam means a rubber foam in which a single-bubble part having closed cells and an open-cell part having open cells are mixed. When such a continuous single foam rubber foam is used, since closed cells and open cells are mixed, the surface hardness of the supply roller does not become too high as in the case of closed cells alone, Various inconveniences due to the increased surface hardness are not generated. Further, as in the case of continuous bubbles alone, the toner remains in the bubbles and does not increase the surface hardness of the supply roller 4, so that toner filming on the developing roller 3, toner deterioration, the supply roller 4 Generation of wear and the like is prevented.

  Therefore, by forming at least the surface of the supply roller 4 with a continuous single foam rubber foam having a specific number of cells and cell diameter, the surface hardness of the supply roller 4 is very long (at least several years). An appropriate amount of toner can be supplied to the developing roller 3 while preventing the toner from rising. FIG. 2A shows a perspective view of the supply roller, wherein 11 is an axial center and 12 is a rubber foam layer.

  The continuous single foam rubber foam constituting the supply roller 4 preferably has an average cell diameter of 500 μm or less, more preferably 300 to 500 μm. When the average cell diameter is in this range, the effect of the present invention is more remarkably exhibited. The average cell diameter was measured with a microscope by taking an enlarged photograph of the cross section in the extrusion direction (MD direction) of the rubber foam, the direction perpendicular to it (TD direction), and the thickness direction (VD direction) perpendicular to both directions. In the photograph, the number of bubbles on a straight line (length L) is counted and obtained from the length L and the number of bubbles.

  The rubber foam constituting the supply roller 4 preferably has a foaming rate (void ratio) of 0.4 to 0.9. Within this range, the toner carrying amount, and hence the toner supply amount to the developing roller is sufficient, the followability is good, and image blurring does not occur in a high-print image. Further, the hardness of the supply roller 4 is increased, the driving torque is increased, and there is little possibility that streaks (density unevenness) occur in the driving gear pitch of the developing roller 3 and the supply roller 4. In addition, the cell diameter becomes too large, and the cell and the cell wall on the surface of the supply roller 4 are torn with the passage of time, and the number of cells holding the toner is reduced, so that the supply of toner onto the developing roller 3 is lowered. However, the followability is deteriorated and there is little fear of image blurring in a high-printed image.

In this case, the foaming rate (void ratio) is obtained as follows. A rubber foam of volume V (mm ³ ) is submerged under the surface of a water tank having an inner dimension of 1000 mm in length × 1000 mm in width, and the height h (mm) at which the water level has risen is measured and calculated according to the following formula: did.

Foaming rate (%) = [(V−1000 × 1000 × h) / V] × 100%
The rubber material used as the material of the continuous single foam rubber foam constituting the supply roller 4 is not particularly limited. For example, ethylene propylene rubber (ethylene-propylene-diene copolymer synthetic rubber, EPDM), chloroprene rubber, nitrile Examples thereof include rubber, butadiene rubber, styrene-butadiene rubber, nitrile-butadiene rubber, isoprene rubber, and isobutylene-isoprene rubber. Among these, EPDM is preferable.

  The supply roller 4 includes, for example, a continuous single-bubble EPDM foam and is formed in a cylindrical shape. For parts other than the surface, a support base made of metal, synthetic resin, or the like can be used as the core metal.

  The supply roller 4 can be manufactured according to a known method. For example, an unvulcanized foaming rubber composition containing a rubber material, a foaming agent, a conductive agent, a filler, a softening agent, a vulcanizing agent, a vulcanization accelerator and the like is prepared. The blending amount of each component is not particularly limited, and is appropriately selected from a wide range according to the type and blending amount of other components, the vulcanization conditions of a vulcanizer used for vulcanization foaming, and the like. Each component is mixed by, for example, kneading with a general rubber kneader kneader and a roll. The unvulcanized foaming rubber composition thus obtained is extruded into a tube shape by an extruder, and the tube is continuously heated by a hot air vulcanizer, whereby the foam vulcanization proceeds. A conductive foam tube is obtained. The conductive foam tube is cut to a predetermined length. A core metal having an adhesive applied to the peripheral surface thereof is press-fitted into the tube to bond the tube and the core metal. Furthermore, pressure is applied to the tube by a pressure means such as a pressure roll to break some of the closed cells and convert them into open cells. Rubber foam with the desired foaming rate (void ratio) and average cell diameter Let it be the body. Further, the bonded body of the rubber foam and the core metal is subjected to grinding and adjusted to a desired value such as its diameter and surface roughness. Thereby, the supply roller 4 having a structure in which a layer containing a rubber foam is formed on the peripheral surface of the cored bar is obtained.

  As an apparatus for vulcanizing and foaming an unvulcanized foaming rubber composition, a UHF continuous vulcanizing apparatus is preferable. In this apparatus, for example, the UHF output is set to 0.1 to 1.5 kW, the UHF tank temperature is set to 200 to 240 ° C., and the HAV tank is set to a range of 200 to 230 ° C., and vulcanization foaming is performed. By carrying out the pressure operation, it is possible to obtain a rubber foam having a mixture of open cells and closed cells and having a foaming rate (void ratio) and an average cell diameter in the above-mentioned range. In addition, when using a UHF continuous vulcanization | cure apparatus, the rubber-like foam used by this invention may be obtained even if it does not implement the pressurization operation after vulcanization foaming.

  By observing the cross section of the foam obtained by the above method with a scanning microscope, it can be confirmed that the foam is a continuous single-cell rubber foam in which open cells and closed cells are mixed. In the rubber foam used in the present invention, the ratio between open cells and single cells is not particularly limited, and when the cut surface of the rubber foam is observed with a scanning electron microscope, open cells and single cells can be visually recognized. Although it is good, the open cell ratio indicating the ratio of open cells is preferably 5% or more, more preferably 10% or more, and particularly preferably 10 to 60%.

  FIG. 3 to be described later is a schematic cross-sectional view of the developing device. The supply roller 4 rotates in the direction of the arrow, and the toner stored in the hopper 6 that stores toner (developer) is supplied to the periphery of the developing roller 3. Supply to the surface.

  The nip width W between the developing roller 3 and the supply roller 4 is preferably in the range of 2.0 to 4.0 mm. When the nip width W is less than 2.0 mm, an excessive amount of toner layer is formed on the developing roller 3, a ghost is generated in synchronization with the rotation cycle of the developing roller 3, and background fogging occurs in a non-image area. Defects can occur. When the nip width W exceeds 4.0 mm, the driving torque increases, and there is a possibility that streaks (density unevenness) occur in the driving gear pitch of the developing roller 3 and the supply roller 4.

[Development method]
An example of a non-magnetic one-component developing method using the toner of the present invention will be described, but it is not necessarily limited thereto.

  FIG. 3 is a schematic cross-sectional view illustrating a developing device for developing non-magnetic one-component toner.

  An electrostatic latent image forming member (photosensitive member) 10 is formed by electrophotographic process means or electrostatic recording means (not shown). A developing roller 3 has a coating layer applied to a conductive shaft made of aluminum or stainless steel.

  The toner T is stored in the hopper 6 and is supplied onto the developing roller by the supply roller 4. The supply roll is made of a foam material such as polyurethane foam, and rotates with a relative speed in the forward or reverse direction with respect to the developing roller 3 to supply toner after development (undeveloped toner) on the developing roller. We are also stripping off. The toner supplied onto the developing roller 3 is uniformly and thinly applied by a toner regulating blade which is a kind of the regulating member 5 that performs toner thinning and charging.

  The contact pressure between the toner regulating member and the developing roller is 3 to 250 N / m, preferably 10 to 100 N / m, as the linear pressure in the direction of the developing roller bus. When the contact pressure is less than 3 N / m, it is difficult to uniformly apply the toner, and the toner charge amount distribution becomes broad, which may cause fogging or scattering. On the other hand, if the contact pressure exceeds 250 N / m, a large pressure is applied to the toner and the toner deteriorates, which is not preferable because toner aggregation occurs. Further, it is not preferable because a large torque is required to drive the developing roller.

  The material of the regulating member that thins and charges the toner is formed of a material that can charge the toner to a desired polarity by frictional charging. Specific examples include metal elastic materials such as stainless steel, aluminum, and phosphor bronze, and rubber elastic materials such as silicone rubber, urethane rubber, and styrene-butadiene rubber. Alternatively, a composite layer in which a polyamide resin, a polyimide resin, a melamine resin, a phenol resin, a fluorine resin, a silicone resin, a polyester resin, a urethane resin, a styrene resin, or the like is laminated on the above-described material layer may be formed. Furthermore, by adding conductive rubber, conductive resin, fillers such as metal oxides, carbon black, inorganic whiskers, inorganic fibers, and charge control agents to the elastic material described above, it is possible to improve the charge imparting property. It is. In addition to the elastic blade, an elastic roller can also be used as a regulating member for thinning and charging the toner.

  In non-magnetic one-component development in which a thin layer of toner is coated on the developing roller with a blade, the thickness of the toner layer on the developing roller is set to be opposite between the developing roller and the photosensitive drum in order to obtain a sufficient image density. It is preferable that the gap length is smaller than that of the so-called non-contact development method, and an alternating electric field is applied to the gap. A gap of 40 to 300 μm, more preferably 60 to 170 μm, is provided between the photoreceptor surface and the developing roller surface. On the other hand, the toner layer provided on the developing roller overlaps with about 2 to 5 toner particles. A toner layer of ˜30 μm is preferable.

  3 is applied between the developing roller 3 and the photosensitive member 10 by applying a developing electric field or a developing bias in which a DC electric field is superimposed on the alternating electric field to the photosensitive drum from the developing roller. It is possible to easily move the toner and to obtain a good quality image.

[Image Forming Method and Image Forming Apparatus]
An example of a full-color image forming apparatus that forms a full-color image using each color toner will be specifically described with reference to FIG.

  In the full-color image forming apparatus shown in FIG. 4, the charging brush 111 for uniformly charging the surface of the photoconductor 10 to a predetermined potential around the photoconductor 10 to be rotated and the photoconductor 10 remaining on the photoconductor 10. A cleaner 112 that scrapes off the toner is provided.

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

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

  Further, in each of the developing devices 31Y, 31M, 31C, and 31Bk in the full-color developing device 30, as shown in FIG. 3, the toner is formed on the outer peripheral surface of the developer carrying member (developing roller) 3 that rotates and conveys the toner. The regulating member 5 is in pressure contact, and the toner regulating member regulates the amount of toner conveyed by the developing roller 3 and charges the conveyed toner. In the full-color developing device 30, two toner regulating members may be provided in order to appropriately regulate and charge the toner conveyed by the developing roller.

  As described above, each time an electrostatic latent image of each color is formed on the photoreceptor 10 by the laser scanning optical system 20, the full-color developing device 30 is rotated about the support shaft 33 as described above. The developing devices 31Y, 31M, 31C, and 31Bk containing toner of the corresponding colors are sequentially guided to positions facing the photoconductor 10, and the developing roller 3 in each of the developing devices 31Y, 31M, 31C, and 31Bk is set to the photoconductor. 10, the toner of each color is sequentially supplied onto the photoconductor 10 on which the electrostatic latent images of each color are formed in order as described above, and development is performed. .

  Further, an endless intermediate transfer belt 40 that is rotationally driven is provided as an intermediate transfer member at a position downstream of the full-color developing device 30 in the rotation direction of the photosensitive member 10, and the intermediate transfer belt 40 is photosensitive. It is configured to be driven to rotate in synchronization with the body 10. The intermediate transfer belt 40 is pressed by a rotatable primary transfer roller 41 so as to come into contact with the photosensitive member 10, and a portion of the support roller 42 that supports the intermediate transfer belt 40 includes 2 A secondary transfer roller 43 is rotatably provided, and the secondary transfer roller 43 presses the recording material S such as recording paper against the intermediate transfer belt 40.

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

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

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

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

  First, the 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.

  The photosensitive member 10 thus charged is exposed to a yellow image by the laser scanning optical system 20 to form an electrostatic latent image of the yellow image on the photosensitive member 10, and then the photosensitive member. A yellow toner is developed by supplying the yellow toner charged by the toner regulating member as described above from the developing unit 31Y containing the yellow toner in the toner 10, and the yellow toner image is thus formed on the photoconductor 10 formed thereon. On the other hand, the intermediate transfer belt 40 is pressed by the primary transfer roller 41, and the yellow toner image formed on the photoconductor 10 is primarily transferred to the intermediate transfer belt 40.

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

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

  When the full-color toner image is secondarily transferred onto the recording material S in this way, the recording material S is guided to the fixing device 70 by the conveying means 66, and the full-color toner transferred by the fixing device 70 is transferred. The image is fixed on the recording material S, and then the recording material S is discharged onto the upper surface of the apparatus main body 100 through the vertical conveyance path 80.

[Non-magnetic one-component developer (toner)]
The toner according to the present invention is not particularly limited in its production method, composition and the like. Here, an example is shown as a representative example.

  The developer that can be used in the present invention is preferably a non-magnetic one-component developer. As the toner constituting the non-magnetic one-component developer, a chemical toner typified by a polymerized toner obtained through a step of polymerizing a polymerizable monomer in an aqueous medium to form resin particles is preferably used.

  The particle diameter of the developer (toner) used in the present invention is preferably 3 to 9 μm in terms of volume-based median diameter (volume D50% diameter). The ratio of the developer (toner) having a volume-based particle size of 4 μm or less is preferably 25% or less, and the ratio of the developer (toner) having a particle diameter of 12 μm or more is preferably 1% or less.

  The present invention will be further described with reference to embodiments. However, of course, the embodiments of the present invention are not limited to these. In the text, “part” means “part by mass”.

[Production roller development]
(Conductive shaft)
As a developing roller shaft, a hollow cylindrical conductive shaft made of SUS303 having an outer diameter of 16 mm was prepared. This is the shaft 1.
In addition, a SUS303 hollow cylindrical conductive shaft body made of SUS303 was prepared for a comparative sample. This is the shaft 2.

<Developing roller 1>
(Coating layer forming coating solution 1)
Carbon black “Ketjen Black EC300J” (Lion Corporation) 20 parts, average particle size 5 μm in a solution of urethane resin “Nipporan 5199” (manufactured by Nippon Polyurethane Co., Ltd.), which is a thermoplastic elastomer, in 500 parts of methyl ethyl ketone. 10 parts of the crosslinked acrylic resin particles were dispersed using a sand mill for 2 hours to prepare a coating solution for forming a coating layer. This is designated as coating liquid 1 for forming a coating layer.

(Coating layer formation)
After coating the coating liquid 1 for forming a coating layer on the outer peripheral surface of the shaft 1, drying was performed at 120 ° C. for 1 hour to form a coating layer having a thickness of 15 μm after drying, and the developing roller 1 was produced.

<Developing roller 2>
(Coating layer forming coating solution 2)
100 parts of an alkoxy group-containing silane-modified polyurethane resin obtained by the method described in JP-A-2002-220431 and having an Si content of 6.0% by mass in terms of silica mass is 400 parts of methyl ethyl ketone and 300 parts of isopropyl alcohol. In a mixed solvent. In this solution, 30 parts of carbon black “Ketjen Black EC300J” and 20 parts of a crosslinked urethane resin having a number average primary particle diameter of 10 μm were mixed and dispersed to prepare a coating liquid 2 for forming a coating layer.

(Coating layer formation)
The coating layer forming coating solution 2 was spray-coated on the outer peripheral surface of the shaft 1 and then dried at 130 ° C. for 1 hour to form a coating layer having a dried film thickness of 10 μm. Thus, the developing roller 2 was produced.

<Developing roller 3>
(Intermediate layer forming coating solution 1)
150 parts of polyamide resin Amilan CM-8000 (manufactured by Toray Industries, Inc.) was dissolved in a mixed solvent of 700 parts of methanol and 100 parts of 1-butanol. 70 parts of carbon black “Ketjen Black EC300J” was mixed and dispersed in this solution to prepare a coating liquid 1 for forming an intermediate layer.

(Coating liquid 3 for coating layer formation)
In a reactor equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a reflux condenser, 300 parts of ε-caprolactone, 140 parts of alcohol-modified silicone oil X-22-160AS (manufactured by Shin-Etsu Chemical Co., Ltd.) and tetrabutyl titanate 04 parts were charged and reacted at a temperature of 180 ° C. under a nitrogen stream for 12 hours 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 2,920.

  140 parts of the above copolymer and 28 parts of 1,4-butanediol are dissolved in a mixed solvent of 210 parts of methyl ethyl ketone and 90 parts of dimethylformamide, and hydrogenated diphenylmethane diisocyanate (hydrogenated MDI) with good stirring at 60 ° C. Or it may be abbreviated as H12MDI). 92 parts dissolved in 188 parts dimethylformamide were gradually added dropwise, and after completion of the addition, reacted at 80 ° C. for 6 hours to obtain a silicone copolymer polyurethane resin solution. This solution was very transparent and had a viscosity of 33.5 Pa · s (25 ° C.) at a solid content of 35%.

  100 parts of the silicone copolymer polyurethane resin thus obtained, 30 parts of carbon black “Ketjen Black EC300J”, and 40 parts of a cross-linked urethane resin having a number average primary particle diameter of 15 μm are mixed and dispersed to form a coating. A coating solution 3 for layer formation was prepared.

(Coating layer formation)
The intermediate layer forming coating solution 1 was spray-coated on the outer peripheral surface of the shaft 1 and then dried at 90 ° C. for 30 minutes to form an intermediate layer 1 having a thickness of 5 μm after drying. Subsequently, the coating liquid 3 for coating layer formation was dip coated on the outer peripheral surface of the intermediate layer 1 and then dried at 130 ° C. for 1 hour to produce a developing roller 3 having a coating layer thickness of 10 μm.

<Developing roller 4> (for comparison)
(Base rubber layer forming material 1)
X-34-424: 100 parts of A / B (silicone rubber, manufactured by Shin-Etsu Chemical Co., Ltd.), X-34-387: 100 parts of A / B (silicone rubber, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed and dispersed. 80 parts of chain black was added to prepare Base Rubber Layer Forming Material 1.

  Next, the shaft 2 is set inside the roller mold, and the base rubber layer forming material 1 obtained above is injected into the gap between the shaft 2 and the inner peripheral surface of the roller mold, followed by heat vulcanization (180 ° C. × 1 hour) The base rubber layer 1 (thickness 0.5 mm) was formed on the outer periphery of the shaft 2 by performing secondary vulcanization treatment (200 ° C. × 4 hours).

  The shaft with base rubber layer thus obtained is removed from the mold, sprayed with the coating layer forming coating solution 1 on the outer peripheral surface of the base rubber layer 1, and then dried at 120 ° C. for 1 hour. Then, a coating layer having a thickness of 15 μm after drying was formed, and the developing roller 4 was produced.

  Table 1 below shows the configuration of the developed developing roller.

[Production of supply roller]
<Supply roller 1>
A through hole into which a shaft member having a diameter of 4 mm can be inserted is formed in the substantially central portion of a rectangular block of conductive ethylene propylene rubber foam (580 cells / cm ² , average cell diameter 410 μm, foaming ratio 0.7). After cutting to a predetermined length, insert a shaft member coated with a hot melt adhesive on the outer peripheral surface to the through-hole, and further heat and cool the shaft member to bond, and then perform cutting to remove A supply roller 1 having a diameter of 11.6 mm was obtained.

<Supply roller 2>
A through hole into which a shaft member having a diameter of 4 mm can be inserted is formed in the substantially central portion of a rectangular block of conductive ethylene propylene rubber foam (number of cells: 1020 / cm ² , average cell diameter: 500 μm, foaming ratio: 0.8). After cutting to a predetermined length, insert a shaft member coated with a hot melt adhesive on the outer peripheral surface to the through-hole, and further heat and cool the shaft member to bond, and then perform cutting to remove A supply roller 2 having a diameter of 11.6 mm was obtained.

<Supply roller 3>
A through-hole into which a shaft member having a diameter of 4 mm can be inserted is formed at a substantially central portion of a rectangular parallelepiped block of conductive urethane rubber foam (420 cells / cm ² , average cell diameter 340 μm, foaming rate 0.5). Insert a shaft member that has been cut into a predetermined length and coated with a hot melt adhesive on the outer peripheral surface of the through hole. The supply roller 3 was 11.6 mm.

  Table 2 below shows the configuration of the manufactured supply roller.

(Characteristic evaluation)
As an evaluation apparatus, a color laser printer “Magiccolor 2300DL” (5 sheets / A4 longitudinal feed) (manufactured by Konica Minolta Business Technologies) was used. This evaluation apparatus is an image forming apparatus that employs a non-magnetic one-component non-contact developing method.

  Using the developing roller and the supply roller prepared as described above, the amount of biting of the supply roller into the development roller was adjusted. To adjust the biting amount, the supply roller bearing portion of the developing device is modified so that it can operate in the direction perpendicular to the developing roller shaft, and the relative distance between the supply roller bearing portion and the developing roller shaft becomes the desired biting amount. It was done by adjusting as follows.

  The biting amount is measured when the distance between the center of the supply roller shaft and the developing roller shaft is L, the outer diameter of the supply roller is Ds, and the outer diameter of the developing roller is Dd, “biting amount = Ds / 2 + Dd / 2−. L ". The distance L between the supply roller shaft center and the development roller shaft center, the supply roller outer diameter Ds, and the development roller outer diameter Dd were all measured with an M-type standard caliper N made by Mitutoyo.

  Using the developing device set in this way, the toner amount on the developing roller before passing through the supply roller proximity region and the toner amount on the developing roller after passing through the supply roller proximity region are measured and scraped as shown in Table 1. When the conditions were set so that the amount to be taken was changed, the following results were obtained.

<Performance evaluation>
The performance of the developing device was evaluated by continuously printing 5000 sheets of A4 size originals with a pixel rate of 20% (full color mode of 5% for each color of yellow, magenta, cyan, and black) in a normal temperature and humidity (23 ° C, 50% RH) environment. It was printed and evaluated by fogging on the white paper and dirt / spillage in the evaluation machine.

(Fog)
A white background document was printed at the time of printing 5000 sheets, and the fog was evaluated. The fog is a phenomenon in which the 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 the toner spill that becomes a dot-like image defect by some aggregated toner. In addition, the fog was determined as the fog density 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.).

Evaluation criteria A: Good when fog density is less than 0.005 B: Practical problem when fog density is 0.005 or more and less than 0.01 ×: Practical problem when fog density is 0.01 or more Level to be.

(In-flight dirt / spillage)
After the completion of printing 5000 sheets, the periphery of the developing device was visually observed, and the in-machine contamination / spillage state by toner around the developing device was visually observed and evaluated.

Evaluation Criteria ◎: Toner spillage is not observed and good ○: Toner spillage is slightly observed but practically no problem ×: Toner spillage is clearly observed and becomes a stain in the machine and causes a practical problem.

  Table 3 shows the evaluation results.

  From the evaluation results in Table 3, it was confirmed that all of Examples 1 to 9 had good results and exhibited the effects of the present invention. In addition, from the results of Examples 7 and 9, it was confirmed that reversing the rotation direction of the developing roller and the supply roller is more effective in preventing fogging. On the other hand, in Comparative Examples 1 to 5, it was confirmed that satisfactory results were not obtained in any of the evaluation items, and the effects of the present invention were not exhibited.

1 is a schematic diagram illustrating a configuration of a developing device. FIG. 3 is a schematic cross-sectional view showing a configuration of a roller of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a developing device for developing non-magnetic one-component toner. 1 is a configuration cross-sectional view of an example of a full-color image forming apparatus.

Explanation of symbols

2 Electrostatic latent image 3 Developer carrier (developing roller)
4 Supply roller 10 Electrostatic latent image forming body (photoconductor)
15 Conductive shaft (rotating shaft)
16 coating layer 20 laser scanning optical system 30 full color developing device 31, 31Y, 31M, 31C, 31Bk developing device 33 spindle 40 intermediate transfer belt 50 cleaner 60 paper feeding means 70 fixing device 80 vertical conveying path S recording material

Claims (5)

At least the toner is carried and conveyed to develop the electrostatic latent image on the electrostatic latent image forming body, and the toner is supplied onto the developing roller surface before development, and the toner is scraped off from the developing roller surface after development. In a developing device having a supply roller having a role,
The developing roller has a configuration in which a coating layer containing at least a conductive agent and a resin is directly formed on the outer periphery of the conductive shaft,
The supply roller is made of a rubber foam in which a single-bubble part having closed cells and an open-cell part having open cells are mixed,
The rubber foam has 400 to 1100 cells / cm ² per unit area , an average cell diameter of 300 to 500 μm, and a foaming ratio of 0.4 to 0.9.
A developing device having a scraping rate (Tr) by a supply roller from a developing roller represented by the following formula (1): 0.10 to 0.50.
Formula (1) Tr = (A−B) / A
A: Amount of toner (mg / cm ² ) on the developing roller surface before passing through the closest area to the supply roller surface
B: Amount of toner (mg / cm ² ) on the developing roller surface after passing through the region closest to the supply roller surface 2. The developing device according to claim 1, wherein the moving direction of the supply roller surface and the moving direction of the developing roller surface are opposite to each other in a region closest to each other. A developing method comprising performing non-magnetic one-component development using the developing device according to claim 1. 4. The developing method according to claim 3, wherein the developing method is non-contact development. An image forming apparatus using the developing method according to claim 3.

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