JP2007178715A - Toner for electrostatic latent image development and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner which maintains a moderate charge amount as a magnetic monocomponent toner, so that it can retain good image properties over a prolonged period of time, which effectively prevents dielectric breakdown on a photoreceptor while retaining good image properties, and which has such properties as to ensure a moderate charge amount even in a state where a charge amount is less liable to rise, such as in a high temperature and high humidity environment, and an image forming apparatus using the toner. <P>SOLUTION: The magnetic monocomponent toner for electrostatic latent image development is obtained by incorporating a magnetic powder into at least a binder resin and externally adding a magnetic powder, and develops a latent image formed on an amorphous silicon photoreceptor on which an elastic blade for residual toner removal is pressed. The externally added magnetic powder has a particle shape based on a hexahedron which is a convex polyhedron framed by six quadrangles, each vertex and ridge of the hexahedron have a curved surface shape, the magnetic powder has portions seen as straight lines at the circumference of a projected image of the hexahedron, and an isolation rate of the magnetic powder is set to 10-25%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic one-component toner in which magnetic powder is contained in a binder resin, and an image forming apparatus that visualizes a latent image on a latent image carrier into a toner image using the magnetic one-component toner. Is.

  In recent years, in image forming apparatuses such as laser printers using electrostatic photography, electrostatic copying machines, plain paper facsimile machines, and complex machines of these, printing speed is increased, machine size is reduced, and machine life is increased. Durability is remarkably advanced. In addition, high resolution, high image quality, and high durability are naturally demanded as performance, but by increasing the printing speed, in order to obtain improved image characteristics and durability that match the printing speed. The toner with the stable charging characteristics is indispensable, forms a stable toner thin layer over a long period of time, and does not affect the steps of each process. Such a toner is desired.

  In image forming apparatuses such as laser printers, electrostatic copying machines, plain paper facsimile machines, and composite machines using these electrophotographic methods, first, the surface of the latent image carrier (photosensitive member) is used. It is uniformly charged by a charging means, then exposed by an exposure means such as a semiconductor laser or a light emitting diode to form a latent image, and then the latent image is developed or reversely developed by a developing means to be visualized as a toner image. Then, the toner image is directly transferred to the surface of the printed material such as paper by the transfer means, or transferred to the surface of the intermediate transfer body and then re-transferred to the surface of the printed material such as paper, and then the fixing means. In this way, a series of image forming steps is completed.

  There are roughly two types of development methods for developing such an electrostatic latent image into a toner image. There are two types of development methods, dry and wet. Currently, dry development methods are widely used. This dry development method is based on the type of toner used, and a development method using magnetic toner in which magnetic powder is encapsulated in toner particles made of a binder resin (a one-component development method using magnetic toner alone, a magnetic toner) A two-component development method using a mixture of toner and magnetic carrier in a certain ratio), a development method using a non-magnetic toner not containing magnetic powder (a one-component development method using a non-magnetic toner alone, a non-magnetic toner And a two-component development method in which a magnetic carrier and a magnetic carrier are mixed at a certain ratio.

  The two-component development method can provide a relatively stable and high-quality image in the initial stage. However, when used over a long period of time, the toner deteriorates due to the spent phenomenon in which the toner adheres to the carrier surface, and the carrier is charged. There are problems such as a problem that the imparting ability is reduced and a good quality image cannot be obtained, and the mixing ratio of the toner and the carrier is difficult to keep constant, so that the long-term durability is insufficient.

  On the other hand, in the one-component developing method using a one-component developer composed only of toner, the problem of lack of long-term durability in the two-component developer can be solved because no carrier is used. Can be made very small and simple. Among the one-component development systems, a magnetic one-component development system that employs a toner containing magnetic powder is generally well known and used.

  In this magnetic one-component development system, the magnetic toner is supplied while being thinned onto a toner carrier incorporating a fixed magnet so as to face the latent image carrier, and the latent image on the latent image carrier is transferred to the magnetic toner. Develop with. The magnetic one-component development method includes a development method using a magnetic toner having conductivity and a development method called a magnetic one-component jumping development method using an insulating magnetic toner. Jumping development methods are widely used.

  In this magnetic one-component jumping development system, first, magnetic toner is triboelectrically charged by passing through a gap between a rotating toner carrier incorporating a fixed magnet and a magnetic blade disposed close to the toner carrier. Then, a thin layer of magnetic toner is formed on the surface of the toner carrier by being supplied to the surface of the toner carrier and held by the magnetic force of a built-in fixed magnet.

  Then, this toner carrier is opposed to the latent image carrier while keeping a gap so as not to contact the formed thin layer, and an AC or DC bias voltage is applied, whereby a thin film formed on the toner carrier is formed. The magnetic toner charged from the layer is allowed to fly to the surface of the latent image carrier, and the latent image is visualized as a toner image.

  In this magnetic one-component jumping development method, since the insulating magnetic toner is used, it is impossible to use the conductive toner. It is possible to transfer to the surface of the printed material, and it is also possible to prevent the latent image carrier from being destroyed by electrical leakage.

  Insulating magnetic toner is easy to be charged, can sufficiently rub against the toner carrier while holding the magnetic toner by magnetic force, and can develop the latent image in a non-contact state with the latent image. There is also an advantage that an image having excellent image quality can be formed by preventing the occurrence of background fogging in which toner adheres to the printed portion and the margin portion.

  As the latent image carrier used in the magnetic one-component jumping development method, various organic and inorganic electrophotographic photosensitive members can be used as in the case of other development methods. An a-Si photosensitive member in which an amorphous silicon (hereinafter abbreviated as a-Si) photosensitive layer is formed on a conductive substrate is preferable. This a-Si photosensitive member has a high durability of about 10 times or more in terms of the number of images formed, for example, compared with an organic photosensitive member having an organic photosensitive layer containing a pigment, a charge transport agent, or the like in a binder resin. This is because the speed at which the thickness of the photosensitive layer is reduced by rubbing against the substrate to be printed or the elastic blade described below is about 1/100 or less that of the organic photosensitive layer. This is because it is difficult to do.

  However, the greatest disadvantage of the a-Si photosensitive member is its low productivity. That is, the a-Si photosensitive member is manufactured by forming an a-Si photosensitive layer on the surface of a conductive substrate by a vapor phase growth method such as a CVD method. Compared to an organic photosensitive layer formed by simply applying a coating liquid containing a coating on a conductive substrate and drying it, it takes much longer to form a photosensitive layer having a predetermined thickness, and vapor phase growth is performed. Since the method is batch-type and cannot be continuously produced, productivity is inevitably lowered.

  Therefore, by utilizing the fact that the a-Si photosensitive layer is less likely to wear than the organic photosensitive layer as described above, the thickness of the a-Si photosensitive layer can be made smaller than before and the productivity of the a-Si photosensitive member can be improved. It is becoming common. That is, an a-Si photosensitive member having a thickness of 30 μm or less and a thin film type a-Si photosensitive member, which has been about 30 to 60 μm so far, is beginning to spread.

  Needless to say, the main merit of such a thin film type a-Si photoreceptor is that it is more productive than the conventional one, but further, the resolution of the formed image is improved when the film thickness is reduced. There are also benefits.

  On the other hand, after the toner image is transferred to the surface of the printed material such as paper, the toner remaining on the surface of the a-Si photosensitive member is removed by a cleaning unit. In order to reduce the size of the forming apparatus and simplify the mechanism, an elastic blade pressed against the surface of the a-Si photosensitive member is preferable.

  After the toner image is transferred to the surface of the printing material, most of the magnetic toner remaining on the surface of the a-Si photosensitive member is scraped and removed from the surface of the photosensitive member by the elastic blade. That is, the magnetic powder or resin piece as toner particles or fragments thereof, or a part of the external additive such as silica that is externally added to the magnetic toner in order to improve fluidity, chargeability, etc. That is, it stays in the pressure contact portion with the a-Si photosensitive member.

  When these stays are rubbed with the elastic blade and the a-Si photosensitive member for a long period of time, a so-called charge-up that is overcharged to a predetermined charge amount or more is generated, and the charge amount is a limit value, that is, When the breakdown voltage value of the a-Si photosensitive layer is exceeded, discharge (single point discharge) is performed toward a very small area of the photosensitive member, and the a-Si photosensitive member may be dielectrically broken to cause an irreparable defect. This discharge is mainly generated at the ridge line portion of the tip portion of the elastic blade.

  Since the a-Si photosensitive member is inherently vulnerable to dielectric breakdown, the dielectric breakdown is likely to occur. For this reason, when image formation by magnetic one-component jumping development is repeated using an a-Si photosensitive member, an elastic blade, and magnetic toner, abnormal discharge (single point discharge, spark discharge) is generated in a short period of time by the above mechanism, and a There is a possibility that the Si photoconductor is broken down and causes defects. If image formation is continued using an a-Si photosensitive member in which such a defect has occurred, the carrier blocking layer is destroyed and the defect portion cannot be charged in the charging step. There is a problem of producing.

  This problem becomes a big problem especially in the a-Si photosensitive member of the thin film type. That is, the occurrence of defects in the a-Si photosensitive layer due to dielectric breakdown largely depends on the needle pressure resistance (V) of the photoreceptor, but the withstand voltage value is lower than usual in a thin-film a-Si photoreceptor. The thinner the thickness, the easier it is for defects due to dielectric breakdown.

  Therefore, with respect to the dielectric breakdown in such an a-Si photoconductor, it is one method for avoiding the toner design so that excessive charging is not accumulated in the toner used, but the dielectric breakdown of the photoconductor is avoided. For this reason, if the toner is a toner whose charge amount is difficult to accumulate, that is, the toner whose charge is easy to escape, the image density becomes low due to insufficient charge amount. The effect is significant.

  Conventionally, various countermeasures have been considered for the dielectric breakdown in the photoreceptor. For example, Patent Document 1 proposes to define the film thickness and specific resistance of the surface protective layer of the photoconductor and to further define the number of free magnetic powder in the toner in order to prevent dielectric breakdown of the photoconductor. Yes.

  Further, in Patent Document 2, the thickness of the charge injection blocking layer of the photoconductor is predetermined, and even if the surface protective layer is damaged by the peeling discharge when the residual toner is peeled off by the cleaning device, it is caused by the dielectric breakdown of the charge injection blocking layer. An electrophotographic apparatus that can reduce image defects has been proposed.

  However, the free magnetic powder in Patent Document 1 is the one in which the internally added magnetic powder is dropped from the toner, so that it is actually difficult to quantitatively control the release. Further, in this document, the breakdown is prevented by the effect of the improvement of the photoreceptor itself rather than the toner.

  In addition, the electrophotographic apparatus disclosed in Patent Document 2 has no special provision regarding toner, and since it does not take measures against toner that should originally cause insulation breakdown, when a toner having different characteristics is used in the future. There is another concern about dielectric breakdown of the photoreceptor.

  As described above, the dielectric breakdown in the photoconductor is greatly related to the charge amount of the toner. In other words, if the toner is overcharged at the blade portion, the toner is discharged toward the photoconductor, causing dielectric breakdown of the photoconductor. Therefore, as a fundamental countermeasure, it is necessary to take a countermeasure with the toner itself, not a countermeasure with respect to the photoreceptor, and it is required to appropriately control the toner charge amount. In magnetic one-component toners, the amount of toner charge varies greatly depending on the magnetic powder added internally. Therefore, various types of magnetic powder have been studied.

  At present, as the magnetic powder to be internally added to the toner, a hexahedron (cube, cuboid) shape that is a convex polyhedron surrounded by six squares, or an octahedron shape that is a convex polyhedron surrounded by eight triangles. Polyhedral magnetic powders and spherical magnetic powders such as those are generally used.

  Of these, magnetic toners using polyhedral magnetic powders tend to release charges from the sharp apexes of the magnetic powder exposed on the surface of the toner particles and the sharp ridges between adjacent surfaces. Even if it stays at the tip of the elastic blade and is rubbed for a long period of time, before the a-Si photosensitive layer undergoes dielectric breakdown, the charged charge is released through the apex and ridgeline, and the toner particles are excessively charged. Can be prevented. Therefore, dielectric breakdown of the a-Si photosensitive layer is unlikely to occur.

  However, on the other hand, electric charge is likely to be discharged from the pointed apex of magnetic powder and the pointed ridgeline between adjacent surfaces, so that charge leakage is more likely to occur than necessary, and polyhedral magnetic powder has low fluidity. Since the dispersibility with respect to the binder resin is poor, it is difficult to uniformly disperse in the binder resin. For this reason, the dispersion state of the magnetic powder in each toner particle is likely to vary. Therefore, the ease of charging and the charge amount of each magnetic toner are likely to vary, and the magnetic toner using polyhedral magnetic powder is used. The charge amount is difficult to rise quickly and the charge amount itself is low.

  On the other hand, magnetic toner using spherical magnetic powder does not have a sharp apex or ridge line, and charges are unlikely to be released from the magnetic powder exposed on the surface of the toner particles. In addition, since the spherical magnetic powder is excellent in fluidity and dispersibility with respect to the binder resin as compared with the polyhedral one, it can be easily dispersed uniformly in the binder resin and can be easily obtained in individual magnetic toners. There is no variation in the dispersion state of the magnetic powder, and the ease of charging and the amount of charge can be made uniform. However, on the contrary, since the charge is excessively accumulated, the toner is overcharged more than a predetermined charge amount, so that so-called charge-up easily occurs. If the charge amount exceeds the withstand voltage value, the a-Si photosensitive layer is insulated as described above. It will be destroyed, and minute black spots will be generated in the subsequent formed image.

  Therefore, when the thin film type a-Si photosensitive member, the elastic blade, and the conventional magnetic toner containing spherical magnetic powder are combined, the a-Si photosensitive layer can be charged in a very short period of time. May break down.

  For this reason, it is preferable to use a polyhedral magnetic powder in consideration only of prevention of charge-up, but this polyhedral magnetic powder has a sharp point of the magnetic powder exposed on the surface of the toner particles as described above. Charges are likely to be released from the apexes and sharp ridge lines between adjacent surfaces, and charge leakage is likely to occur. Polyhedral magnetic powder has low fluidity and poor dispersibility with respect to the binder resin, so that it is difficult to uniformly disperse in the binder resin. Therefore, the dispersion state of the magnetic powder in the individual toner particles tends to vary, and the ease of charging and the charge amount of the individual magnetic toners also vary.

  Therefore, the magnetic toner using the polyhedral magnetic powder is difficult to quickly rise, and the charge amount itself is low, and as a result, image defects such as a decrease in image density and occurrence of fogging are likely to occur. There's a problem. In addition, since the ease of charging and the amount of charge are likely to vary depending on the temperature and humidity environment during image formation, the above-described image defects are more likely to occur, particularly in environments that are difficult to charge, such as high temperatures and high humidity environments. There is also a problem.

  Therefore, in order to make use of the advantages of both the spherical magnetic powder and the polyhedral magnetic powder, for example, in Patent Document 3, the apexes and ridge lines of the polyhedron such as the hexahedron and the octahedron are smaller planes than the respective surfaces constituting the polyhedron. Discloses a magnetic powder having a particle shape which is so-called chamfered. Patent Document 6 discloses a magnetic powder having a particle shape in which each vertex and ridge line are curved with respect to a cube, and also describes that the magnetic powder is internally added to toner particles.

  However, even in the magnetic powder shown in Patent Document 3, there is still a sharp ridge line between the surface constituting the polyhedron and the small chamfered plane, and the charge is easily released from this ridge line. There is a tendency similar to that of polyhedral magnetic powder, and when such magnetic powder is used, charge leaks, and there is a possibility that an image defect such as a decrease in image density may occur in the one-component development portion.

  In addition, the magnetic powder described in Patent Document 4 has a curved surface by making the ridge line a curved surface, and since there are no sharp vertices or ridge lines as charge discharge points, it is similar to a spherical one. There is a tendency that electric charges are not easily released, and the toner may be overcharged to cause dielectric breakdown of the photoreceptor.

  As described above, magnetic powders having various shapes have been studied in the past. However, it is also possible to control the toner charge amount by adding these magnetic powders externally instead of internally. At present, when magnetic powder is used as an external additive, it is mainly used for the purpose of preventing toner adhesion to a photoreceptor or a toner carrier and a polishing effect.

  For example, Patent Document 5 proposes a toner externally added with magnetic powder in order to solve the problem of photoconductor drum filming caused by wax, and Patent Document 6 cleans by adding octahedral magnetic powder as an external additive. Toners with improved effects have been proposed.

Patent Document 7 includes two types of external additives having different specific resistances, and the release rate of the external additive having a low specific resistance is set larger than the release rate of the external additive having a high specific resistance. There has been proposed a toner in which the charge of the toner can be appropriately adjusted with an external additive having a low resistance.
JP 2003-149857 A JP 2002-287391 A Japanese Patent Laid-Open No. 11-153882 Japanese Patent Laid-Open No. 9-59024 JP-A-9-73186 JP 2003-66647 A JP 2003-280254 A

  However, when the toner of Patent Document 5 is subjected to thermal stress or stress over time, the external additive is buried in the toner particles and the fluidity is lowered. There is. In addition, only 50,000 sheets of toner in Patent Document 6 and only 1000 sheets of toner in Patent Document 7 are evaluated, and various problems may occur if evaluation is performed by printing a large number of sheets. Therefore, the performance has not been confirmed at all for the long life as currently required, and various problems are expected to occur.

  In other words, the polyhedral magnetic powder, which is generally considered to have a high polishing effect, has the effect of its shape when it is externally added in the same way as when it is internally added, and the toner charge amount is lowered, so that the charge amount is insufficient. This causes a problem of causing a decrease in image density. Further, although the octahedral and cubic shaped magnetic powders have a high polishing effect due to their sharp apexes, there is also a problem in that the photosensitive drum is damaged when printing is performed over a long period of time.

  Furthermore, there is a possibility that the magnetic powder detached from the toner adheres to the toner carrier or the photoreceptor and causes a fatal image defect. Therefore, it is required to control the magnetic powder so that the toner is appropriately surface-treated. It is done.

  Therefore, in the present invention, as a magnetic one-component toner, it is possible to maintain an appropriate charge amount and maintain good image characteristics over a long period of time, and to maintain the good image characteristics while maintaining insulation in the photoreceptor. Providing toner that has characteristics that can effectively prevent destruction and that can provide an appropriate amount of charge even when the amount of charge is difficult to rise, such as in a high-temperature and high-humidity environment, and an image forming apparatus using the toner It is a problem to do.

  As a result of intensive studies to solve the above-mentioned problems, attention is paid to the shape and release rate of the external additive of magnetic one-component toner in an electrophotographic system using a thin film amorphous silicon (a-Si) photoreceptor and an elastic cleaning blade. Thus, the present invention has been completed.

  That is, a latent image carrier composed of an amorphous silicon photoconductor and a fixed magnet are built in to face each other with a gap so as not to contact the latent image carrier, and the surface is a magnetic one component for developing an electrostatic latent image. A toner carrier that holds and rotates toner, and a magnetic one-component toner for developing an electrostatic latent image held on the surface of the toner carrier fly to a latent image formed on the surface of the latent image carrier and develop. A means for forming a toner image; and a cleaning means using an elastic blade for cleaning the toner remaining on the surface of the latent image carrier after the toner image is transferred to a recording medium and pressed against the latent image carrier. In an image forming apparatus having a developing process, the magnetic monocomponent toner contains at least a magnetic powder in a binder resin, and the particle shape is based on a polyhedron, and each vertex and ridge line are curved, and A magnetic blade having a portion that can be regarded as a straight line on the outer peripheral portion of the projected image and having a liberation rate of 10 to 25% is configured to be externally added, so that the toner remaining after the toner image is transferred to the recording medium is removed by the cleaning blade. Even if an attempt is made to charge up by accumulating on the tip of the cleaning blade and triboelectrically charging the tip of the cleaning blade, discharge occurs before reaching the potential causing dielectric breakdown of the a-Si photosensitive member by the free magnetic powder. It has been found that even if an a-Si photosensitive member having a thickness of 30 μm or less is used, the occurrence of abnormal images due to dielectric breakdown of the photosensitive member can be prevented.

  In addition, when the toner for developing an electrostatic latent image according to the present invention is used, it is possible to prevent a decrease in image density due to insufficient charge amount even in an environment where the charge amount tends to be low such as high temperature and high humidity.

  In other words, the magnetic powder having the above-mentioned particle shape has a curved vertex and no ridges or ridges that easily release charges, so that excessive charge leakage occurs when externally added to the toner. It is thought that it can be made difficult to cause. Moreover, since the basic shape of this magnetic powder is a hexahedron, either the apex or the adjacent surface sandwiching the ridge line constituting the hexahedron or the adjacent ridge line sandwiching the apex must be an acute angle of less than 90 °. Since the charges tend to concentrate on the vertices where the surfaces or ridge lines intersect at an acute angle and the ridge lines where the surfaces intersect at an acute angle, the vertices and ridge lines are curved so that excessive charge leakage is less likely to occur. Nevertheless, it is thought that excessive charges are hardly caused by discharging charges at an appropriate rate mainly from the apexes and ridge lines where the charges tend to concentrate.

  However, even with the above-mentioned particle shape, if the curvatures of the apexes and ridgelines that are curved are too large, the effect of preventing charge-up of the magnetic toner by discharging charges at an appropriate rate cannot be obtained. Therefore, the inventor studied to define the range of the radius of curvature of the apex and the ridgeline formed into a curved surface from the projected image of the magnetic powder taken using, for example, a transmission electron microscope.

  As a result, the curvature radius of the curved vertices and ridge lines is too large, and the curved surfaces of adjacent vertices and ridge lines are connected to each other so that the magnetic powder close to a spherical shape does not have a portion that can be regarded as a straight line on the outer periphery of the projected image. The magnetic powder having the effect of preventing the charge-up of the magnetic toner as in the case of the toner is not obtained, whereas each vertex and ridge line of the hexahedron is a curved surface, and the outer periphery of the projected image has a portion that can be regarded as a straight line. The ridges and vertices where adjacent surfaces intersect are composed of curved surfaces, but the curvature radius of the curved surface is smaller than the curvature radius of spherical magnetic powder with the same particle size, so that the charge tends to concentrate The charge can be discharged from the ridgeline at an appropriate rate, and when the magnetic powder is externally added to the magnetic toner, excessive charge leakage occurs compared to the case of using magnetic powder whose vertices and ridgelines are not curved. Start While Rinikuku, yet found that can prevent excessive charging of the magnetic toner.

  In addition, it was found that not only the shape but also the release rate of the externally added magnetic powder is important, and the release rate of the externally added magnetic powder needs to be within a range of 10 to 25%.

  That is, when the liberation rate is lower than 10%, even if the magnetic powder having the shape as described above is used, the amount of the free magnetic powder is too small to effectively release the charge of the toner, and the photoconductor. It is not possible to prevent the dielectric breakdown of. On the other hand, when the liberation rate is higher than 25%, the charge amount of the toner can be greatly reduced to prevent dielectric breakdown, but the image density is lowered. In addition, the released magnetic powder adheres to the developing roll, causing a poor formation of the toner thin layer, resulting in a fatal image defect.

  Therefore, the toner for developing an electrostatic latent image according to the present invention develops a latent image formed by electrophotography on an amorphous silicon photoreceptor to which an elastic blade for cleaning residual toner is pressed, and at least in a binder resin. A magnetic one-component toner for developing an electrostatic latent image, which contains magnetic powder and externally added magnetic powder, wherein the externally-added magnetic powder is a hexahedron that is a convex polyhedron surrounded by six squares. In which each apex and ridge line of the hexahedron is a curved surface, has a portion that can be regarded as a straight line on the outer periphery thereof, and the release rate of the magnetic powder is 10 to 25% A magnetic one-component toner for developing an electrostatic latent image.

  The image forming apparatus using the electrostatic latent image developing toner has a latent image carrier composed of an amorphous silicon photosensitive member and a fixed magnet so as to keep a distance from contacting the latent image carrier. Then, a toner carrier that rotates while holding a magnetic one-component toner for developing an electrostatic latent image on the surface, and a magnetic one-component toner held on the surface of the toner carrier are formed on the surface of the latent image carrier. A means for forming a toner image by flying on the developed latent image, and a cleaning using an elastic blade which is pressed against the latent image carrier and cleans the toner remaining after the toner image is transferred to a recording medium The magnetic monocomponent toner for developing an electrostatic latent image contains at least a magnetic powder in a binder resin, and each vertex and ridge are curved based on a hexahedron particle shape. In Jo, wherein the magnetic powder liberation percentage has a portion that can be regarded as a straight line it is 10% to 25% is constituted by externally added to the outer peripheral portion of the projected image.

  In the present invention, the binder resin, the internally added magnetic material, the dye, the pigment, the charge adjusting agent, the fluidizing agent and the like are not particularly limited, and the externally added magnetic powder is included in all magnetic one-component toners. It can be applied to.

  According to the present invention, even in a system using a thin film a-Si having a film thickness of 30 μm or less as a latent image carrier and using an elastic blade as its cleaning method, a thin layer can be stably formed on the toner carrier. However, it is possible to stably obtain a clear image without abnormal images due to dielectric breakdown of the photoconductor for a long period of time, and a good image density can be obtained even in an environment where the charge amount tends to be low, such as a high temperature and high humidity environment. The obtained toner and an image forming apparatus using the toner can be provided.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

FIG. 2 is a diagram showing an outline of the structure of an image forming apparatus for carrying out the magnetic toner of the present invention and an image forming method using the magnetic toner, and FIG. 3 is a photosensitive drum (electrostatic latent image carrier) 11 used in the present invention. FIG. 4 is a graph showing the relationship between the film thickness of the amorphous silicon photoconductor and the needle pressure resistance that causes dielectric breakdown. In the figure, a photoconductive drum 11 made of amorphous silicon (hereinafter abbreviated as a-Si) is made up of a positively charged a-Si photoconductor, for example, a φ30 drum. charger 12 using an exposure device 13, an internal stationary magnet facing holds interval so as not to contact with the latent image carrier, developing with toner carrier 14 ₁ which holds and rotates the toner to the surface A transfer roller 15 as a transfer means, a cleaning blade (elastic body, rubber, etc.) 16 as a cleaning means, and a static elimination lamp 17 as a static elimination device are arranged along the rotation direction of the photosensitive drum 11. A transfer material (not shown) such as paper or an OHP film is passed between the transfer roller 15 and the transfer roller 15, and a fixing device (not shown) is placed on a downstream transfer material discharge path. It is provided.
(Charger configuration)
The charger 12 used in the image forming apparatus of the present invention is, for example, a scorotron charger 12, which includes a shield case, a corona wire, and a grid. The charging width is 12.0 mm in the circumferential direction and 242 mm in the drum axis direction. Thus, the distance between the wire and the grid is preferably set to 5.8 mm. The distance between the grid and the a-Si photosensitive member is preferably 0.4 to 0.8 mm. If the distance is less than 0.4, there is a possibility of spark discharge, and if it is 0.8 mm or more, the charging ability is high. It will be lower.
(Configuration of a-Si Photosensitive Drum)
For example, as shown in FIG. 4, an amorphous silicon photosensitive layer 19 is formed on the surface of a conductive substrate 21 formed in a predetermined shape such as a drum shape. In particular, a thin film type amorphous silicon photoconductor having a thickness of the photosensitive layer 19 of 10 to 30 μm is suitable.

The amorphous silicon-based photosensitive layer 19 includes a carrier blocking layer 20, a surface in addition to a single layer or two or more photosensitive layers 19 that actually function as the photosensitive layer 19 on a roll of a conductive substrate 21 such as aluminum. It may have a protective layer 18 or the like, and in the case of these multi-layered photosensitive layers, the total film thickness is preferably in the range of 10 to 30 μm. Such a thin film type amorphous silicon photoconductor is advantageous in that it is excellent in productivity and can form an image with high resolution as described above.
(Photoreceptor film thickness)
In the present embodiment, the film thickness of the a-Si photoconductor means the film thickness from the surface of the substrate 21 to the surface of the photoconductor opposite to the substrate 21 in the a-Si photoconductor. , The total of the surface protective layer 18. In the a-Si photosensitive member of the present embodiment, the film thickness of the photosensitive layer 19 on the conductive substrate 21 is in the range of 10 to 30 μm because the charging ability as the photosensitive member is less than 10 μm. This is because it becomes difficult to obtain a predetermined surface potential, and the laser beam is irregularly reflected on the surface of the conductive substrate 21 to cause a problem that interference fringes are generated in the half pattern.

  On the other hand, when the film thickness of the photosensitive member is 30 μm or more, the moving speed of the heat carrier is increased, so that the dark attenuation characteristic is deteriorated. It will cause a drop. It is well known that not only the a-Si photoreceptor but also the OPC photoreceptor, the thinner the photoreceptor film, the higher the resolution. In terms of cost, the longer the film thickness, the longer the film formation time. The longer the film formation time, the higher the probability of adhesion of foreign substances and the like, and the worse the yield. Therefore, the thinner the film thickness of the photoconductor, the lower the cost and the more stable the quality.

  Therefore, the total film thickness of the photoreceptor is preferably used in the range of 10 to 30 μm or less in view of charging ability, withstand voltage, dark decay characteristics, manufacturing cost, and quality. More preferably, the thickness of the surface protective layer is preferably 20000 mm or less, more preferably 5000 to 15000 mm.

  This is because when the thickness of the surface protective layer is less than 5000 mm, the pressure resistance characteristic is reduced against the negative current flowing from the transfer roller, and as a result, the SiC layer is deteriorated at an early stage of 15000 sheets or less. This is because if the thickness of the surface protective layer exceeds 20000 mm, the film formation time becomes long and the cost becomes disadvantageous.

On the other hand, the occurrence of leaked black spots on the amorphous silicon photosensitive member in question largely depends on the needle pressure resistance (V) of the amorphous silicon photosensitive member. That is, as shown in FIG. 5, the voltage required for dielectric breakdown increases as the film thickness increases, and the voltage required for dielectric breakdown decreases as the film thickness decreases. Therefore, when a thin film a-Si photosensitive member having a thickness of 30 μm or less is used, leakage to the photosensitive member becomes noticeable with a slight charge-up. In FIG. 5, the horizontal axis represents the film thickness of the amorphous silicon photoreceptor, and the vertical axis represents the needle pressure resistance that causes discharge breakdown.
(Photoreceptor material)
The amorphous silicon-based photosensitive layer 19 can be formed, for example, by a vapor phase growth method such as a glow discharge decomposition method, a sputtering method, an ECR method, or a vapor deposition method. it can. Further, in order to adjust the characteristics of the photoreceptor, elements such as C, N, and O may be included, or a group 13 element or a group 15 element in the periodic table (long period type) may be included.

Specifically, the photosensitive layer 19 can be formed of various photoconductive materials such as a-SiC, amorphous silicon-based materials such as a-SiC, a-SiO, and a-SiON. In particular, to use a-SiC Preferably, in which case the _{Si 1-x C} x of the value of x 0.3 ≦ x <1.0, more preferably set to 0.5 ≦ x ≦ 0.95 It is good. Within this range, the a-SiC layer can have a higher resistance than the a-Si layer while maintaining good carrier transport, and the photosensitivity characteristics of the photoreceptor can be improved. As group 13 elements and group 15 elements, B and P are desirable in that they are excellent in covalent bonding properties, can change semiconductor characteristics sensitively, and can provide excellent photosensitivity.

This is because such a-SiC has a high resistance of 10 < ¹² > to 10 < ¹³ > [Omega] cm, there is little flow of latent image charge in the direction of the photoreceptor surface, and the electrostatic latent image maintaining ability and moisture resistance are reduced. It is because it is also excellent.
(Features to distinguish between OPC and amorphous)
In general, an OPC photoreceptor has a surface resistance on the order of 10 ¹³ Ω / cm, which is extremely higher than that of an a-Si photoreceptor (on the order of 10 ⁸ Ω / cm), and is characterized by being difficult to break down. Therefore, the OPC photosensitive member is less susceptible to leak black spots.
(Photoreceptor surface potential)
The charging potential of the amorphous silicon photoreceptor when forming an image is not particularly limited, but is preferably set to a value within the range of +200 to + 500V. When the surface potential of the photoreceptor is less than +200 V, the developing electric field is insufficient, and it is difficult to ensure the image density. On the other hand, when the voltage exceeds +500 V, there are problems that charging ability is insufficient depending on the film thickness of the photosensitive member, black spots are easily generated due to dielectric breakdown, or the amount of ozone generated is increased. In particular, when the film thickness is reduced, the charging ability of the photoreceptor tends to decrease correspondingly. Therefore, from the viewpoint of the balance between the developability and the charging ability of the photoreceptor, the surface potential value is preferably set to a value within the range of +200 V to +500 V, and more preferably the surface potential is set to +200 V to +300 V ( Developer)
A developing device 14 using the electrostatic latent image developing toner according to the present invention, the toner carrying member 14 ₁ is disposed consisting of a developing sleeve incorporating a magnet roller therein provided opposite to the photosensitive member 11, the and the toner thin layer is carried on the toner carrier 14 _first surface, the voltage supplied from the AC or DC bias power source (not shown) serving as means for the toner to fly to the photosensitive member is applied, a magnetic one-component jumping developing scheme The electrostatic latent image formed on the photoconductor 11 is visualized as a toner image.

The toner carrying member surface is rough, and conveys the toner by the rotation of the toner carrying member, by passing the gap between the magnetic blade and the toner carrier 14 ₁ which is not shown, the surface of the toner carrier 14 ₁ A thin toner layer is formed. Sleeve surface of the toner carrying member 14 ₁ has to be less than ten-point average roughness Rz = 2.0 .mu.m or more ～6.0Myuemu.

  When the ten-point average roughness Rz is less than 2.0 μm, the image density is not satisfactory due to a decrease in toner conveying force. When the ten-point average roughness Rz is more than 6.0 μm, the image quality is deteriorated and the protrusion on the sleeve surface is deteriorated. Leaks from the toner to the photosensitive drum, resulting in black spots on the image and the image quality is impaired. These ten-point average roughness Rz can be measured using a surface roughness measuring instrument manufactured by Kosaka Laboratory Ltd., Surfcoder SE-30D.

As a material used for the developing sleeve, for example, aluminum, SUS, or the like can be used. When considering high durability, it is preferable to use SUS as the sleeve material to be used, and for example, SUS303, SUS304, SUS305, SUS316, or the like can be used. Moreover, it is more preferable to use SUS305 which has weak magnetism and is easy to process.
(Transfer roller)
In order to hold the latent image on the surface of the amorphous silicon photoconductor 11 as the latent image carrier, the surface of the photoconductor drum 11 is uniformly charged by the charger 12 using a scorotron charger or the like, as in the past. Thereafter, exposure is performed by an exposure device 13 such as a semiconductor laser or a light emitting diode to remove the charge in the exposed portion. In order to transfer the toner image formed on the surface of the amorphous silicon photoreceptor 11 onto the surface of the printing material, for example, a corona charger, a sawtooth electrode, a transfer roll, or the like is used, and the transfer roller 15 is particularly preferable.

The transfer roller 15 is preferably rotated with a linear speed difference of 3 to 5% with respect to the surface of the photosensitive member in contact with the surface of the amorphous silicon photosensitive member. There is a possibility that the transferability of the toner image is deteriorated, resulting in a lack of characters and the like. . The transfer roller 15 is preferably a roller made of a soft foam such as foamed EPDM. When a foam roller is used, the toner attached to the transfer roll when a paper jam or the like occurs is the foam By entering the air bubbles, it is possible to prevent the back side of the printing material from being stained when the operation is resumed. Therefore, cleaning of the transfer roll becomes unnecessary, and the initial cost and running cost can be reduced. Further, the hardness of the transfer roll made of a soft foam is preferably 30 to 40 ° in terms of Asker C hardness. If it is softer than this range, there is a possibility that transfer failure may occur. If it is harder than the range, the nip between the photosensitive member and the photoconductor may be small, and the conveyance force of the substrate may be reduced.
(Cleaning device)
The toner remains on the surface of the photoconductor after the toner image formed on the surface of the photoconductor drum 11 composed of the amorphous silicon photoconductor is transferred to a printing material such as paper. As a cleaning means for removing the residual toner by cleaning, it is preferable to use an elastic blade pressed against the surface of the amorphous silicon photoreceptor. As the elastic blade, various conventionally known elastic blades made of rubber, soft resin, or the like can be used. Specifically, for example, an elastic blade made of silicone rubber, fluorine rubber, urethane rubber, urethane resin or the like can be used. The elastic blade is preferably pressed at a linear pressure of 10 to 50 g / cm, considering that the magnetic toner is satisfactorily cleaned and the surface of the amorphous silicon photoreceptor is free from pressure marks.

The outline of the operation of the image forming apparatus according to the present invention will be briefly described. The amorphous silicon photosensitive drum 11 as a latent image carrier and a fixed magnet are rotated and a thin layer of magnetic toner is formed on the surface thereof. The toner carrier (developing sleeve 14 ₁ ) to be held is opposed to the thin layer and the amorphous silicon photosensitive member so as not to contact each other, and the photosensitive layer 19 of the photosensitive drum 11 is uniformly formed by the charger 12. Then, the exposure device 13 irradiates the surface of the photosensitive drum with dot light corresponding to the document by reflected light of the document or an electric signal from a computer, etc., and the potential of the light irradiation portion is attenuated to electrostatically attenuate the electrostatic latent image. Form.

This electrostatic latent image is toner thin layer carried on the toner carrier 14 ₁ surface as described above is, of the toner carrier 14 ₁ and is not shown is applied between the photoconductor AC or DC A toner image is formed on the surface of the photosensitive drum 11 by developing the magnetic single component jumping development method by flying to the photosensitive member 11 with a voltage from the bias power source. The toner image is transferred to the transfer material by the transfer roller 15, conveyed to a fixing device (not shown), and fixed on the surface of the transfer material by heat and pressure. On the other hand, after the toner image is transferred onto the transfer material, the toner remaining on the surface of the photosensitive drum 11 is scraped off and collected by a cleaning blade 16 constituting a cleaning device, and light emitted by a static elimination lamp 17 serving as a static elimination device. The surface charge is removed by irradiation, and the next image forming process is performed.
(toner)
The toner of the present invention can be obtained by externally adding magnetic powder to a toner obtained by dispersing various toner compounding agents such as a colorant in a binder resin. The type of the binder resin used for the toner in the present invention is not particularly limited. For example, styrene resin, acrylic resin, styrene-acrylic copolymer, polyethylene resin, polypropylene resin, vinyl chloride. It is preferable to use thermoplastic resins such as resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether resin, N-vinyl resin, styrene-butadiene resin.

  More specifically, the polystyrene resin may be a styrene homopolymer or a copolymer with another copolymerizable monomer copolymerizable with styrene. As copolymerizable monomers, p-chlorostyrene; vinyl naphthalene; ethylene unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl acetate, propion Vinyl esters such as vinyl acrylate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, acrylic (Meth) acrylic acid esters such as phenyl acid, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate; other acrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; Vinyl ethers such as nylmethyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidene, etc. N-vinyl compounds of These may be used alone or in combination of two or more with a styrene monomer.

  Moreover, as the polyester resin, any resin obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component can be used. The following are mentioned as a component used when synthesize | combining a polyester-type resin. First, as a bivalent or trivalent or higher alcohol component, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4 -Diols such as butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; bisphenol A, hydrogenated Bisphenols such as bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pe Taerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4- Examples thereof include trivalent or higher alcohols such as butanetriol, trimethylolethane, trimethylolpropane and 1,3,5-trihydroxymethylbenzene.

  As the divalent or trivalent or higher carboxylic acid component, a divalent or trivalent carboxylic acid, an acid anhydride or a lower alkyl ester thereof is used. Maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid Phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, Divalent carboxylic acids such as alkyl or alkenyl succinic acid such as n-octyl succinic acid, n-octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid and isododecenyl succinic acid; , 4-Benzenetricarboxylic acid (trimellitic acid), 1,2,5 Benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl -2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empole trimer acid Examples thereof include trivalent or higher carboxylic acids and the like. Moreover, it is preferable that the softening point of a polyester-type resin is 110-150 degreeC, More preferably, it is 120-140 degreeC.

  Further, the binder resin may be a thermosetting resin. By introducing a partially crosslinked structure in this way, it is possible to further improve the storage stability, form retention, and durability of the toner without deteriorating the fixability. Therefore, it is not necessary to use 100 parts by mass of the thermoplastic resin as the toner binder resin, and it is also preferable to add a cross-linking agent or to partially use a thermosetting resin. Therefore, an epoxy resin, a cyanate resin, or the like can be used as the thermosetting resin. More specifically, one or more of bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, novolac type epoxy resin, polyalkylene ether type epoxy resin, cycloaliphatic type epoxy resin, cyanate resin, etc. Combinations are listed.

  The magnetic toner of the present invention may contain various conventionally known additives such as a colorant, a charge control agent, and wax. Among these, examples of the colorant include pigments such as carbon black and dyes such as acid violet in order to adjust the color tone. The content of the colorant is preferably about 1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  Charge control agents are formulated to significantly improve the charge level and charge rise characteristics (indicator of whether to charge to a constant charge level in a short time) and to obtain excellent durability and stability characteristics. is there. That is, when the toner is positively charged and used for development, a positively chargeable charge control agent can be added. When the toner is negatively charged and used for development, a negatively chargeable charge control agent can be added.

  Such a charge control agent is not particularly limited. For example, as specific examples of the positively chargeable charge control agent, pyridazine, pyrimidine, pyrazine, orthooxazine, metaoxazine, paraoxazine, orthothiazine, metathiazine. , Parathiazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6-oxadiazine 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1,2 , 4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline, quinoxaline and other azine compounds; Direct dyes composed of azine compounds such as FC, azine fast red 12BK, azine violet BO, azine brown 3G, azine light brown GR, azinda kugreen BH / C, azine dip black EW and azine black 3RL; nigrosine, Nigrosine compounds such as nigrosine salts and nigrosine derivatives; acid dyes comprising nigrosine compounds such as nigrosine BK, nigrosine NB and nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; benzylmethylhexyldecylammonium, decyl Quaternary ammonium salts such as trimethylammonium chloride can be exemplified, and these can be used alone or in combination of two or more. In particular, the nigrosine compound is optimal for use as a positively chargeable toner from the viewpoint of obtaining a quicker start-up property.

  Further, a quaternary ammonium salt, a carboxylate, or a resin or oligomer having a carboxyl group as a functional group can also be used as a positively chargeable charge control agent. More specifically, a styrene resin having a quaternary ammonium salt, an acrylic resin having a quaternary ammonium salt, a styrene-acrylic resin having a quaternary ammonium salt, a polyester resin having a quaternary ammonium salt, a carboxylic acid Styrene resin with salt, acrylic resin with carboxylate, styrene-acrylic resin with carboxylate, polyester resin with carboxylate, polystyrene resin with carboxyl group, acrylic with carboxyl group 1 type, or 2 or more types, such as resin, the styrene-acrylic resin which has a carboxyl group, and the polyester-type resin which has a carboxyl group, are mentioned.

  In particular, a styrene-acrylic copolymer resin having a quaternary ammonium salt as a functional group is optimal from the viewpoint that the charge amount can be easily adjusted to a value within a desired range. In this case, preferred acrylic comonomers to be copolymerized with the styrene units include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, Examples include (meth) acrylic acid alkyl esters such as 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, and iso-butyl methacrylate. As the quaternary ammonium salt, a unit derived from a dialkylaminoalkyl (meth) acrylate through a quaternization step is used. Examples of the derived dialkylaminoalkyl (meth) acrylate include di (amino) ethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate and the like ( Lower alkyl) aminoethyl (meth) acrylate; dimethylmethacrylamide, dimethylaminopropylmethacrylamide are preferred. Further, hydroxy group-containing polymerizable monomers such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and N-methylol (meth) acrylamide can be used in combination during polymerization.

  As the charge control agent exhibiting negative chargeability, for example, organometallic complexes and chelate compounds are effective, and examples thereof include aluminum acetylacetonate, iron (II) acetylacetonate, chromium 3,5-di-tert-butylsalicylate. In particular, acetylacetone metal complexes, salicylic acid metal complexes or salts are preferable, and salicylic acid metal complexes or salicylic acid metal salts are particularly preferable.

  The positively or negatively chargeable charge control agent described above is generally in an amount of 1.5 to 15 parts by weight, preferably 2.0 to 8.0 parts by weight, and most preferably 3.0 to 7.0 parts by weight. And is preferably contained in the toner (the total amount of toner is 100 parts by mass). If the addition amount of the charge control agent is smaller than the above range, it tends to be difficult to stably charge the toner to a predetermined polarity, and the electrostatic latent image is developed using the toner to develop an image. When forming, the image density tends to be low and the durability of the image density tends to be low. In addition, the charge control agent tends to be poorly dispersed, causing so-called fogging, and the contamination of the photoreceptor is apt to occur. On the other hand, when the charge control agent is used in a larger amount than the above range, it tends to cause defects such as environmental resistance, particularly poor charging under high temperature and high humidity and defective images, and contamination of the photoreceptor.

  The waxes used for improving the fixing property and the offset property are not particularly limited. For example, polyethylene wax, polypropylene wax, tetrafluoroethylene wax, Fischer-Tropsch wax, paraffin wax, ester wax It is preferable to use montan wax, rice wax or the like. Two or more of these waxes may be used in combination. By adding such wax, offset property and image smearing can be more efficiently prevented.

  The above-described waxes are not particularly limited, but generally, the wax is preferably blended in the toner (the total amount of the toner is 100 parts by mass) in an amount of 1 to 5 parts by mass. If the added amount of the wax is less than 1 part by mass, there is a tendency that the offset property and image smearing cannot be effectively prevented. On the other hand, if it exceeds 5 parts by mass, the toners are fused and stored stably. Tend to decrease.

  In the toner of the present invention, a magnetic powder is blended in a binder resin to form a magnetic one-component developer. Examples of the magnetic powder internally added to such a toner are those known per se, such as ferrite and magnetite. Ferromagnetic metals such as iron, cobalt, nickel, etc., or alloys, compounds containing these elements, or ferromagnetic elements that do not contain ferromagnetic elements but are subjected to appropriate heat treatment. An alloy, chromium dioxide, etc. can be mentioned.

  These magnetic powders are uniformly dispersed in the above-described binder resin in the form of fine powder having an average particle diameter of 0.1 to 1 μm, particularly 0.1 to 0.5 μm. The magnetic powder can also be used after being subjected to a surface treatment with a surface treatment agent such as a titanium coupling agent or a silane coupling agent. Further, the magnetic powder is preferably contained in the toner in an amount of 35 to 60 parts by mass, particularly 40 to 60 parts by mass (the total amount of the toner is 100 parts by mass). When the magnetic powder is used in a larger amount than the above range, the durability of the image density is deteriorated, and the fixability tends to be extremely lowered. When the amount is smaller than the above range, the fog in the image density durability is deteriorated. End up.

  The toner of the present invention is prepared by mixing the above-described binder resin and various toner compounding agents such as a charge control agent, melt-kneading using a kneader such as an extruder, and then cooling, pulverizing and classifying the mixture. Is obtained. The obtained toner particles preferably have an average particle diameter of 5.0 to 10.0 μm. If it is larger than this range, fluidity is lowered and fogging is caused. If it is larger than this, the image quality will deteriorate.

  In the present invention, external additive fine particles are externally added to the surface of the toner particles thus obtained to form a one-component developer. At this time, magnetic powder is used as an external additive, and the shape of the magnetic powder 2 is based on a hexahedron 1 that is a convex polyhedron surrounded by six squares as shown in FIG. Is a magnetic powder having a curved surface, and is characterized in that there are no sharp vertices or ridgelines as charge discharge points. In addition, even if the vertex and ridge are curved, the curvature radius is too large and the curved surfaces of adjacent vertices and ridges are connected, so that it is close to a sphere that does not have a straight line on the outer periphery of the projected image. As shown in FIG. 1, it is also a feature that a feature as a hexahedron in which a portion that can be regarded as a straight line remains is left in the outer peripheral portion of the projected image.

  Further, the liberation rate of the magnetic powder is preferably 10 to 25%. Here, the liberation rate is obtained from the analysis result of the particle analyzer described later, and is the ratio of the iron atoms derived from the magnetic powder to the carbon atoms derived from the toner mother particles.

By externally adding such magnetic powder to the toner, there is an effect of preventing dielectric breakdown in the a-Si photoreceptor 11, but when the magnetic powder is largely released from the toner base particles, the toner carrier 14 is used. ₁ may become a nucleus and cause a thin layer formation failure, resulting in a fatal image failure. Therefore, it is necessary to suppress the release of the magnetic powder.

  On the other hand, if the release of the magnetic powder is extremely suppressed, the toner is overcharged, and the dielectric breakdown occurs despite the addition of the magnetic powder for the purpose of preventing the dielectric breakdown of the a-Si photoreceptor 11. Occurs and the effect of external addition of magnetic powder cannot be obtained.

  Therefore, it is necessary that the magnetic powder be free from the toner base particles in a range where defects such as poor thin layer formation do not occur. The effect of the free magnetic powder suppresses toner overcharge, and a-Si photosensitive. It is necessary to effectively prevent the dielectric breakdown of the body 11, and this free range is 10 to 25% as described above.

  The method for measuring the liberation rate shown here is disclosed in the Annual Meeting of the Electrophotographic Society (95 times in total), Japan Hardcopy '97 paper collection, “Toner Analysis by New External Additive Evaluation Method Particle Analyzer”. Can be done in any way. In this toner analysis method, toner particles are excited by introducing the toner particles into plasma, and an emission spectrum associated with the excitation is detected, and analysis is performed. In this analysis method, excitation of multiple elements is performed. The accompanying emission spectrum can be detected simultaneously, and the emission spectrum periodicity can also be measured.

  More specifically, the magnetic particles are internally added to the resin resin particles of the toner as described above, and the toner particles obtained by externally adding the octahedral magnetic powder having a curved vertex and ridge are added to the plasma. When introduced, the toner base particles and the magnetic powder are simultaneously introduced into the plasma, so that the toner base particles and the magnetic powder emit light simultaneously. Therefore, when the toner base particles and the magnetic powder emit light at the same time, it is assumed that the toner base particles and the magnetic powder are in a synchronized state, indicating that the magnetic powder is not attached to the toner base particles and released. It will be.

  On the other hand, toner base particles to which magnetic powder is not attached, and magnetic powder released from the toner base particles (this free magnetic powder includes not only externally added magnetic powder but also internally removed magnetic powder) When the toner is introduced into the plasma, both the toner base particles and the magnetic powder emit light in the same manner as described above. At this time, the toner base particles and the magnetic powder are introduced into the plasma at different times. The mother particles and the magnetic powder emit light at different times. For example, when the toner base particles are introduced into the plasma before the magnetic powder, the toner base particles emit light first, and then the magnetic powder emits light after a delay.

  Thus, in a state where the toner base particles and the magnetic powder emit light at different times, the toner base particles and the magnetic powder are not synchronized, that is, in an asynchronous state, and the magnetic powder is the toner base particles. This means that it is not attached to and is in a free state.

  Furthermore, as a specific measurement method, DP-1000 (Horiba Seisakusho Co., Ltd. particle analyzer) is used, and the number of detected carbon atoms in one measurement is 2500 to 3000 as measurement conditions, and the analysis wavelength is carbon atoms (C From the synchronism of light emission of iron atoms based on carbon atoms obtained as atoms) 247.86 nm and iron atoms (Fe atoms) 239.56 nm, A is the liberation rate of Fe atoms (%), N is C atom The release rate of the magnetic powder was determined by applying the following formula (1) as the count number of Fe atoms that did not emit light simultaneously and M as the count number of Fe atoms that emitted light simultaneously with C atoms.

A (%) = N × 100 / (N + M) (1)
The effect as described above can be obtained by setting the liberation rate thus obtained to 10 to 25% as described above.

  The magnetic powder desirably has an average particle size of 0.01 to 0.50 μm. The magnetic powder having an average particle diameter of less than 0.01 μm is likely to adhere to the developing roll, which may cause a problem that a toner thin layer formation defect on the developing roll is caused. On the other hand, the magnetic powder having an average particle diameter exceeding 0.50 μm tends to damage the photosensitive drum, which may cause a fatal defect in a highly durable system.

  In consideration of the balance of the effects, the average particle diameter of the magnetic powder is preferably 0.05 to 0.35 μm, more preferably 0.15 to 0.30 μm, even within the above range. .

  The average particle size of the magnetic powder is the Martin diameter (equivalent circle diameter) measured for 300 magnetic powders photographed with a transmission electron microscope (magnification 10,000 times) magnified 4 times. Average value.

  As magnetic powder, metals such as iron, cobalt, nickel, etc., alloys thereof, compounds containing these elements, or ferromagnetic elements that do not contain ferromagnetic elements, but exhibit ferromagnetism by appropriate heat treatment. In particular, an alloy made of chromium dioxide or the like is preferable, and magnetic powder made of ferrite or magnetite is preferable. In particular, in consideration of imparting good magnetic properties to the magnetic toner, the magnetic powder is from 0.1 to 10 atomic% of Mn, Zn, Ni, Cu, Al, Ti, and Si with respect to Fe. It is preferable to use magnetic powder formed of magnetite containing at least one selected element.

  The magnetic powder comprising the magnetite, each of the vertices and ridgelines of the hexahedron is curved, and has a portion that can be regarded as a straight line on the outer periphery of the projected image, and the average particle diameter is defined within the above range, For example, it can be produced by the following method.

That is, a ferrous salt aqueous solution 26.7 l sulfuric acid containing ^{Fe 2+} of 1.5 mol / liter, with respect to the prepared 3.4N aqueous sodium 23.6 l hydroxide ^{(Fe 2+} in advance into the reaction vessel 1. Ferrous oxide containing ferrous hydroxide colloid by heating to 90 ° C. and adjusting the pH to 8-10 with a 3.4 N aqueous sodium hydroxide solution. A salt suspension is produced.

  Next, while maintaining the liquid temperature of the suspension at 90 ° C., air is blown to cause an oxidation reaction until the oxidation reaction rate of the ferrous salt reaches 60%.

  Next, an aqueous sulfuric acid solution was added to the upper suspension so that the pH was 6.5, and then air was blown into the suspension while maintaining the liquid temperature at 90 ° C. Generate.

  The produced magnetite particles are washed with water by a conventional method, filtered, dried, and then agglomerated magnetite particles are pulverized. Then, a magnetic powder composed of magnetite particles whose particle shape is basically a hexahedron and whose apexes and ridges are curved is synthesized.

  As a preferred range for carrying out the present invention, the pH during the first stage reaction is from 8 to 10, but if the pH during the first stage reaction is not maintained from 8 to 10, the hexahedral shape do not become. The hexahedron is produced by carrying out the first stage reaction in the range of 8 to 9.5.

  In this synthesis reaction, in order to adjust the curvature of the magnetic powder, the roundness varies depending on the reaction rate during the oxidation reaction of the first stage oxidation. When the amount is less than 50%, the edge appears, and when it exceeds 50%, the edge becomes round.

  In addition, when performing the above synthesis reaction, various water-soluble metal compounds such as water-soluble silicates are added to an aqueous alkali hydroxide solution or an aqueous ferrous salt reaction solution containing ferrous hydroxide colloid, respectively. When added in a proportion of 0.1 to 10 atomic% with respect to Fe, the magnetic powder synthesized is Mn, Zn, It consists of magnetite containing at least one element selected from Ni, Cu, Al, Ti, and Si.

  The ratio of the externally added magnetic powder to 100 parts by mass of toner base particles is preferably 0.1 to 5.0 parts by mass. If the ratio of the magnetic powder is less than this range, the effect of containing the magnetic powder cannot be obtained. On the other hand, if the blending ratio exceeds this range, the charge amount of the toner may be significantly reduced to lower the image density.

  In addition to the magnetic powder described above, the toner in the present invention is treated with colloidal silica, hydrophobic silica, titanium oxide, alumina, silicon carbide or the like for the purpose of maintaining the fluidity and storage stability of the toner. can do.

  In addition, these external additives may be subjected to surface treatment such as aminosilane, chicone oil, hexamethyldisilazane, titanate coupling agent, and silane coupling agent, if necessary.

  The fine particle external additive is used to improve fluidity, storage stability, cleaning properties and the like by surface treatment of the toner. The silica fine particles and titanium oxide are externally added by stirring and mixing with a magnetic toner in a dry manner. This stirring and mixing is performed by a Henschel mixer, a Nauter mixer, or the like so that the fine particles are not embedded in the toner. It is better to use. However, it is necessary to carry out the stirring and mixing so that the above-described release rate of the magnetic powder can be achieved.

  Hereinafter, the present invention will be described based on examples. Needless to say, the following description exemplifies the present invention, and the scope of the present invention is not limited to the following description.

  First, the binder resin used in the present invention was produced as follows. In a reactor equipped with a thermometer, a stirrer, and a nitrogen introduction tube, 300 parts of xylene were placed, and under a nitrogen stream, a mixed monomer of 845 parts of styrene and 155 parts of n-butyl acrylate and di-tert-butyl peroxide ( Polymerization initiator) A mixed solution of 8.5 parts and 125 parts of xylene was added dropwise at 170 ° C. over 3 hours. After dripping, it was made to react at 170 degreeC for 1 hour, and superposition | polymerization was completed. Thereafter, the solvent was removed to obtain a binder resin.

  In 49 parts by mass of the styrene-acrylic copolymer binder resin (low molecular weight peak molecular weight 7000, high molecular weight peak molecular weight 140,000, glass transition point Tg of 55 ° C.) thus produced, magnetic powder (spherical 45 parts by mass, average particle size 0.20 μm), 3 parts by mass of wax (Sazol Wax H1, manufactured by Sazol) as a release agent, quaternary ammonium salt (Bontron P-51, Orient Chemical Co., Ltd.) as a positive charge control agent 3 parts by mass were mixed with a Henschel mixer, melt kneaded with a twin screw extruder, cooled, and coarsely pulverized with a hammer mill. Further finely pulverized by a mechanical pulverizer was classified by an airflow classifier to obtain a magnetic toner having a volume average particle size of 8.0 μm.

  2.0 parts by mass of titanium oxide (ST-100, manufactured by Titanium Industry Co., Ltd.) and silica (RA-200H, manufactured by Nippon Aerosil Co., Ltd.) with respect to 100 parts by mass of the toner powder (magnetic toner) base particles obtained above. 1.0 part by mass of the above-mentioned magnetic powder for external addition, and externally added using a Henschel mixer (manufactured by Mitsui Miike Chemicals, FM10C / I) under the conditions of a rotational speed of 3000 rpm and a stirring time of 4 min. A magnetic one-component positively charged developer was prepared by adhering to the surface of the magnetic toner powder (this is referred to as the toner of Example 1).

  In this developer, the liberation rate of the magnetic powder with respect to the toner base particles was 15.6%. The magnetic powder for external use used is a hexagonal shape that is a convex polyhedron surrounded by six quadrangles, and the vertex and ridge are curved and have a mean particle diameter of 0.2 μm. is there.

  Next, as shown in the list of external additives in Table 1, after the toner powder was produced in the same manner as the toner of Example 1, the magnetic particles for external addition having an average particle diameter of 0.20 μm used in Example 1 were also used. The powder was externally added with the Henschel mixer at a rotation speed of 3500 rpm and a stirring time of 5 minutes, and at a rotation speed of 2000 rpm and a stirring time of 4 minutes, respectively, and the release rates were 10.7 (%) and 24.1 (%) in Example 2. The developer of Example 3 was obtained. Further, the magnetic powder for external addition having an average particle size of 0.22 μm was externally added by the Henschel mixer under the conditions of a rotation speed of 2000 rpm and a stirring time of 5 min, and the developer of Example 4 having a liberation rate of 21.0 (%). Obtained.

Comparative Example 1
Further, after the toner powder was manufactured in the same manner as the toner of Example 1, unlike Example 1, the particle shape is an octahedral shape that is a convex polyhedron surrounded by eight triangles, and its apex and Using the same amount of magnetic powder having a ridge line that is not curved and having an average particle size of 0.22 μm, externally added with the Henschel mixer at a rotational speed of 3000 rpm and a stirring time of 4 minutes, and a release rate of 13.3 (%). The developer of Comparative Example 1 was obtained.

Comparative Example 2
Further, after the toner powder was manufactured in the same manner as the toner of Example 1, the particle shape is an octahedral shape that is a convex polyhedron surrounded by eight triangles, and the apexes and ridge lines thereof are those shown in FIG. 6 (b), the same amount of magnetic powder having an average particle diameter of 0.20 μm chamfered by a plane smaller than each face constituting the octahedron was used, and the rotation speed was 3000 rpm. The developer of Comparative Example 2 having a liberation rate of 14.2 (%) was obtained by externally adding under the conditions of stirring time of 4 min.

Comparative Example 3
In addition, after the toner powder was produced in the same manner as the toner of Example 1, the same amount of magnetic powder having a cubic shape, a vertex and a ridge line not curved, and an average particle size of 0.22 μm were used. The developer of Comparative Example 3 having a liberation rate of 12.1 (%) was obtained by using the Henschel mixer and externally adding at a rotation speed of 3000 rpm and a stirring time of 4 min.

Comparative Example 4
Further, after the toner powder is manufactured in the same manner as the toner of Example 1, the cube is formed so that the particle shape is a cube and the apexes and ridge lines thereof are shown in FIG. The same amount of magnetic powder chamfered by a plane smaller than each surface and having an average particle diameter of 0.20 μm was used, and externally added by the Henschel mixer at a rotational speed of 3000 rpm and a stirring time of 4 min. (%) Of the developer of Comparative Example 4 was obtained.

Comparative Example 5
Further, after the toner powder was produced in the same manner as the toner of Example 1, the same amount of magnetic powder having a spherical particle shape and an average particle diameter of 0.22 μm was used, and the rotation speed was measured by the Henschel mixer. The developer of Comparative Example 5 having a liberation rate of 18.0 (%) was obtained by external addition at 3000 rpm with a stirring time of 4 min.

Comparative Example 6
In addition, after the toner powder was produced in the same manner as the toner of Example 1, the same particle shape as that of the magnetic powder of Example 1 was a hexahedral shape that is a convex polyhedron surrounded by six squares, and its apex Further, the same amount of magnetic powder having a curved ridgeline and an average particle diameter of 0.22 μm was used and externally added with the Henschel mixer at a rotation speed of 3700 rpm and a stirring time of 6 min. %) Of the developer of Comparative Example 6 was obtained.

Comparative Example 7
In addition, after the toner powder was produced in the same manner as the toner of Example 1, the same particle shape as that of the magnetic powder of Example 1 was a hexahedral shape that is a convex polyhedron surrounded by six squares, and its apex Further, the same amount of magnetic powder having a curved ridgeline and an average particle diameter of 0.20 μm was used, and externally added by the Henschel mixer at a rotation speed of 1800 rpm and a stirring time of 3 min, and the release rate was 26.5. (%) Of the developer of Comparative Example 7 was obtained.

  Using these developers, a page printer FS-3820N made by Kyocera Mita equipped with an a-Si photosensitive member was used for evaluation, and 100,000 sheets were continuously printed in a normal temperature and humidity environment (20 ° C., 65% RH) (printing rate 5). %), And the dielectric breakdown state and surface state, the toner thin layer state on the sleeve, image characteristics, and developer charging characteristics were evaluated. Similarly, 100,000 sheets were continuously printed (printing rate 5%) in a high-temperature and high-humidity environment (33 ° C., 85%), and image characteristics were evaluated.

  The shape of the magnetic powder used and the liberation rate of the magnetic powder of the obtained developer are shown in Table 1, and the evaluation results are shown in Table 2 and Table 3. Moreover, the code | symbol in the column of the particle shape of the magnetic powder shown in Table 1 is as follows, and the evaluation method of each characteristic was described below.

  Six-circle: Cubic shape with vertices and ridges curved.

  Hexagonal shape: a cubic body and the vertices and ridges are not curved. Normal cube.

  6-plane: Cubic and chamfered with a small plane having apexes and ridgelines (see FIG. 7 of JP-A-11-153882).

Octagon: An octahedron shape whose vertices and ridge lines are not curved. Normal octahedron Octahedron: Octahedron-shaped and chamfered by a small plane with apexes and ridges Sphere: Spherical.

(Photoconductor breakdown condition)
Using the above page printer, the number of black spots generated by dielectric breakdown on the photoreceptor when 100,000 sheets were printed was measured and measured using a dot analyzer (DA-5000S, manufactured by Oji Scientific Instruments Co., Ltd.). The number of dielectric breakdowns of the photoreceptor film, that is, the number of black spots on the printing paper was measured. The measurement range of the measured number of black spots was an area of 5 mm × 210 mm in the A4 horizontal direction.
(Photoreceptor surface)
Using the printer, the presence or absence of scratches on the photoreceptor when 100,000 sheets were printed was visually observed. Evaluation criteria of photoreceptor contamination The following criteria were used.

○: No flaws are observed on the surface Δ: Very small flaws are seen ×: Clear flaws are seen (toner thin layer state)
The toner thin layer state on the toner carrying member 14 _1, and confirm visually the state of the sleeve after 100,000 sheets printing evaluation used the following criteria.

○: A thin layer is uniformly formed, and there is no adhesion or unevenness on the sleeve. Δ: There is a portion where the layer thickness is thick, and it is slightly uneven depending on the location (partial thin layer formation failure).
×: Unevenness or adhesion to the sleeve has occurred, and the thin layer is not uniform (thin layer formation failure)
(Image characteristics)
In a normal temperature and humidity environment (20 ° C., 65% RH), an image evaluation pattern is printed by the page printer at the initial stage to obtain an initial image, and then 100,000 sheets are continuously passed to print the image evaluation pattern again. The solid images were measured using a Macbeth reflection densitometer (RD914) and evaluated for image characteristics. The image density was 1.30 or higher.
(Charging characteristics)
The charge quantity of the magnetic toner in the toner carrying member 14 on _one of the page printer, measured using TRek Co. suction type charge amount measuring device (Q / M Meter210HS), from the weight change at that time, per developer 1g The charge amount μC / g of was determined. It should be noted that the charge amount measured after forming an image with the developer using the page printer and outputting an image for initial image characteristic evaluation is the initial charge amount, 100,000 sheets of continuous paper passing (printing rate 5%) The charge amount of the toner after the toner was taken as the charge amount after the endurance.

  As shown in Tables 2 and 3, in Examples 1 to 4, the particle shape is basically a hexahedron that is a convex polyhedron surrounded by six squares, and the apexes and ridges are curved. Since the magnetic powder was externally added and the liberation rate was 10.7 to 24.1 (%), there were no problems in any of image characteristics, photoconductor dielectric breakdown, toner thin layer state, and the like. This is the same even in a high-temperature and high-humidity environment, and no decrease in concentration was observed.

  On the other hand, Comparative Example 1 using magnetic powder with octahedral and vertex and ridge lines not curved, Comparative Example 2 using magnetic powder with chamfered vertices and ridge lines with octahedral shape, vertex and hexahedral with In the magnetic toner externally added in Comparative Example 3 using magnetic powder whose ridgeline is not curved, and Comparative Example 4 using hexagonal magnetic powder whose apex and ridgeline are chamfered with a small plane, both the magnetic powders are sharp. Since the shape is such that vertices and ridgelines exist, leakage from these vertices and ridgelines caused the charge amount to decrease and the image density to decrease. This was particularly noticeable in a high temperature and high humidity environment, and in addition, scratches were observed on the surface of the photoreceptor after printing.

  Further, in Comparative Example 5 using the spherical magnetic powder, the dielectric breakdown occurred in the photosensitive member despite the addition of the spherical magnetic powder, and in addition, a thin layer formation defect occurred.

  Furthermore, despite the external addition of magnetic powder whose shape is basically a hexahedron, which is a convex polyhedron surrounded by six squares, and whose apexes and ridges are curved, the release rate is 8. In Comparative Example 6 having a low value of 8% and Comparative Example 8 having a high value of 26.5%, the release rate in Comparative Example 7 is small, so that the dielectric breakdown occurs. In Comparative Example 7, the release rate is too high. Adhesion to the toner carrier occurred, resulting in poor thin layer formation. In addition, there is a decrease in image density accompanying a decrease in charge amount, and this tendency is particularly remarkable in a high temperature and high humidity environment.

  From the above results, the magnetic powder to be externally added is basically a hexahedron, which is a convex polyhedron surrounded by six quadrangles, and each vertex and ridge line of the hexahedron is curved, and the projected image It turns out that the magnetic powder which has a part which can be regarded as a straight line in an outer peripheral part is preferable, and it is preferable that the release rate of this magnetic powder is 10-25%.

  According to the present invention, an appropriate charge amount can be maintained and good image characteristics can be maintained over a long period of time, and dielectric breakdown in the photoreceptor can be effectively prevented while maintaining those good image characteristics. Furthermore, it is possible to provide a toner having such characteristics that an appropriate charge amount can be obtained even in a state where the charge amount does not easily rise, such as in a high temperature and high humidity environment.

It is a schematic diagram which shows the shape of the magnetic powder which becomes this invention. 1 is a diagram showing an outline of the structure of an image forming apparatus for carrying out a magnetic toner of the present invention and an image forming method using the magnetic toner. It is sectional drawing of the amorphous silicon photoreceptor drum used for this invention. It is the graph which showed the relationship between the film thickness of an amorphous silicon photoreceptor, and the needle | hook pressure resistance which causes a dielectric breakdown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hexahedron 2a Ridge line 2b Vertex 2c Straight line part 11 Photoconductor drum 12 Charging device 13 Exposure device 14 Development device 14 ₁ Toner carrier (development sleeve)
15 Transfer roll 16 Cleaning means (cleaning blade)
17 Static eliminator 18 Surface protective layer 19 Photosensitive layer 20 Carrier blocking layer 21 Conductive substrate

Claims (2)

The latent image formed by the electrophotographic method is developed on an amorphous silicon photoreceptor pressed with an elastic blade for cleaning residual toner, and at least electrostatic powder with magnetic powder added to the binder resin and magnetic powder added externally. A magnetic one-component toner for developing a latent image,
The externally added magnetic powder is basically a hexahedron, which is a convex polyhedron surrounded by six quadrangles, and each vertex and ridge of the hexahedron are curved, and a straight line is formed on the outer periphery of the projected image. A magnetic one-component toner for developing an electrostatic latent image, which has a portion that can be regarded and has a liberation rate of the magnetic powder of 10 to 25%. A latent image carrier composed of an amorphous silicon photosensitive member and a fixed magnet are built in to face each other while keeping a gap so as not to contact the latent image carrier, and a magnetic one-component toner for developing an electrostatic latent image is applied to the surface. And a toner carrier that rotates while being held, and a means for causing the magnetic one-component toner held on the surface of the toner carrier to fly to the latent image formed on the surface of the latent image carrier and developing the toner image. An image forming apparatus comprising a cleaning unit using an elastic blade that is pressed against the latent image carrier and cleans toner remaining after the toner image is transferred to a recording medium,
The magnetic one-component toner for electrostatic latent image development is based on a hexahedron that is a convex polyhedron containing at least a magnetic powder in a binder resin and surrounded by six squares, and each of the hexahedrons. The apex and the ridge are curved, and the outer periphery of the projected image has a portion that can be regarded as a straight line, and is composed of externally added magnetic powder having a free rate of 10 to 25%. Image forming apparatus.