JP2005345758A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which keeps the surface state of a photoreceptor preventing image deletion or toner melt sticking, even if magnetic or nonmagnetic toner is used, which is significantly improved in reliability and which can cope with even if the productivity is significantly increased. <P>SOLUTION: The image forming apparatus comprises at least a photoreceptor 2, a charging means 1, an exposing means 3, a developing means 31 to 34, a transfer means and a cleaning means 50, wherein the surface of the photoreceptor shows gradual decrease in the surface roughness Rz of the photoreceptor, due to repetition of the above steps, and a cleaning blade 52 as the cleaning means has different peak values of tanδ in a neighboring part of the cleaning blade edge and in an area other than the same. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to a full color image forming apparatus using an amorphous silicon photoconductor as an image carrier.

  In recent years, as an electrophotographic image forming apparatus, a multifunction peripheral having all output terminals such as a copying machine, a printer, and a fax machine has been widely accepted in the market. An electrophotographic system is widely accepted as such a network-compatible output terminal, but one of the major problems is the duty cycle of the main body. DutyCycle is the limit number of sheets that the main body can continue to operate normally without service maintenance, and the life of the photosensitive drum is increased as one of the largest rate limiting factors of DutyCycle.

  Further, from the viewpoint of ecology, it has become an absolute challenge for the inventors to eliminate waste, that is, to reduce consumables, extend the life of consumables, and improve reliability.

  In addition, with the advance of digitization from conventional analog devices, it has become an absolute challenge to make the body cost analog equivalent or less. Further, in recent years, black and white machines have been the mainstream for copying machines and printers, but full color printing of manuscripts or output files is also rapidly increasing in offices. Not only the analog equivalent digital machine, but also the main body cost and running cost black and white equivalent full color printer has become our absolute issue. For this purpose, a technology that can dramatically reduce TCO (total cost required from the user's perspective) is desired.

Under such circumstances, an amorphous silicon photoconductor as an image carrier is increasingly used because of its high hardness (JIS standard Vickers hardness of 1000 kg / m ² or more) and excellent durability, heat resistance, and environmental stability. In particular, it has become indispensable for high-speed machines that require high reliability. Amorphous silicon photoconductors have a replacement life that is one or more orders of magnitude higher than OPC photoconductors commonly used in recent years. That is, the life of the main body is equivalent, and there is an effect of reducing waste. In addition, there is no need for labor such as recovery and recovery as in a process cartridge using an OPC photosensitive member.

  If the technology using the amorphous silicon photoreceptor mounted on such a high-speed machine can be mounted on a full-color printer, for monochrome printing, a high-speed machine DutyCycle, a device that can realize a low running cost and can take a color print We thought it was feasible. In particular, for users with a high use ratio of black and white prints, it is essential to mount an amorphous silicon photoconductor on a one-drum full-color printer using a rotating developer in order to realize a high-speed DutyCycle and low running costs. I thought.

  However, in this type of apparatus, it is not only the toner that adheres to the surface of the image carrier and affects the image quality, but also fine paper dust generated from paper that is mostly used as a transfer material, Foreign matter adhering to the surface of the image carrier due to components, corona products generated due to the presence of high-pressure members in the device, etc., lowers the resistance especially in a high humidity environment and prevents the formation of a clear electrostatic latent image. It is considered to be a factor causing image quality degradation. It is known that the image degradation phenomenon as described above is likely to occur in the case of an amorphous silicon photoreceptor that is formed by glow discharge decomposition of silanes.

  In order to avoid such drawbacks, particularly when using a one-component magnetic toner, a cleaning roller is provided with a magnet roller on the upstream side of the cleaning blade as viewed in the traveling direction of the image carrier. A part of the toner collected in the apparatus forms a magnetic brush, which is brought into contact with the surface of the image carrier and re-supplied with the magnetic toner. There has been proposed one configured so as to remove rubbing.

  Compared to the method of rubbing the surface of the image carrier with a separately prepared polishing member such as a web or a rubber roller, the means using such a magnetic brush may cause the polishing action to be locally biased on the surface of the image carrier. There is little deterioration of the surface of the image carrier. In the above method, for example, by providing a heater on the image carrier and using accompanying means such as reducing the humidity of the surface of the image carrier by reducing ambient humidity at night and during standby, It has a certain effect to prevent image degradation due to the causes.

  In an image forming apparatus that repeats the process of transferring a transferable toner image formed on the surface of an image carrier to a transfer material mainly composed of paper, residual toner remaining on the image carrier without transferring to the transfer material is transferred during transfer. It is essential to remove them sufficiently each time.

  For this reason, many proposals have been made as cleaning means. However, a cleaning blade made of an elastic material such as urethane rubber is used to scrape off the residual toner, which is simple, compact and inexpensive. Moreover, since it has an excellent toner removal function, it is widely used. As a rubber material for the cleaning blade, urethane rubber which is high in hardness and rich in elasticity and is excellent in wear resistance, mechanical strength, oil resistance and ozone resistance is generally used.

  However, several problems are pointed out when an amorphous silicon photoreceptor is mounted on a one-drum full-color printer using a rotary developing device as described above.

  The first is the occurrence of filming. Amorphous silicon photoconductors tend to have low surface resistance. For this phenomenon, as described above, a magnetic brush is formed, brought into contact with the surface of the image carrier, and magnetic toner is re-supplied. It is effective to remove the rubbing. However, since full-color toner is generally a non-magnetic material, the apparatus configured as described above is an effective means for magnetic toner, but is less effective for non-magnetic toner.

  Factors that cause a reduction in the resistance of the surface of the photosensitive member include toner, fine paper dust generated from paper used in most cases as a transfer material, organic components precipitated from the paper, and high energy from the high-pressure member in the apparatus. During corona discharge, various metal oxides and oxygen compounds are generated, and nitrogen in the air is oxidized to form nitrate ions. This film is formed by durability and absorbs moisture in a high-humidity environment to reduce resistance, thereby preventing the formation of a clear electrostatic latent image, which causes degradation of image quality such as image flow.

  In order to remove the filming film due to the durability, it was necessary to improve the rubbing ability with respect to the surface of the photoreceptor. However, for example, when an elastic roll as a rubbing means is brought into contact with the surface of the photosensitive member with a difference in peripheral speed and rubbed, the toner locally adheres to the surface of the photosensitive member. Toner fusing locally occurs on the surface of the elastic roll, and that portion scrapes off the surface of the photoreceptor, resulting in uneven shaving and image defects.

  When trying to avoid the above problem, it is necessary to further increase the rubbing property by the elastic roll on the surface of the photosensitive member, and even the amorphous silicon increases the amount of wear and decreases the reliability. In addition, with the above settings, there is a problem in that the elastic roll itself also increases the amount of wear and decreases reliability.

  The filming film layer with durability is confirmed to be about 30 to 80 mm by an optical method in our experiment. However, the filming layer could be confirmed when measured by a reflection spectroscopic interferometer (MCDP2000 manufactured by Otsuka Electronics Co., Ltd.) in the initial durability in this experiment. The filming layer reached about 30 to 80 mm, and after that, there was almost no change in film thickness, but as the durability progressed, the image deterioration was eliminated by dry wiping, water wiping, and alcohol wiping at the beginning. However, it became clear that it was not solved.

The surface of the drum, which has been repeatedly subjected to adhesive wear and has advanced in such a state, must be polished with a dispersion of abrasive grains such as cerium oxide (CeO ₂ ) of about 0.3 to ₂ μm in alcohol. As a result, it was found that image degradation could not be resolved. This occurs particularly when the drum heater is not installed.

In addition, we have intensively studied, and the surface of the initial photosensitive member and the photosensitive member after the endurance with various surface shapes are subjected to AFM (Atomic Force Microscope: Digital Instruments, NanoScope IIIa Dimension 3000 / scanning mode tapping mode / scanning range 20 μm × 20 μm probe (Si cantilever). The surface of the photoreceptor after endurance seemed to be almost smooth due to abrasion compared to the initial stage. The surface of the photoreceptor after the endurance was heated (70 to 80 ° C., 30 minutes) in a 5% aqueous solution of sodium peroxodisulfate (Na ₂ S ₂ O ₈ ), and ultrasonically cleaned (about 1 minute) in acetone. Rinse with ethanol / pure water. As a result, the amount of filming in the recesses on the surface of the photoreceptor was particularly large.

  Secondly, there is an increase in frictional force due to filming. In our experiment, it was newly discovered that the frictional force between the transfer residual toner by the cleaning blade and the drum has increased due to durability. This is because the filming film formed by durability increases the adhesion and affinity between the cleaning blade and the drum surface, the transfer residual toner and the drum surface, and increases the frictional force between the transfer residual toner and the drum. Yes.

  The increase in the frictional force is considered to increase the shear stress of the cleaning blade, the shear stress between the toners, and the shear stress near the drum surface. As a result, chipping of the cleaning blade (local edge chipping), permanent distortion, generation of toner fusion due to increased heat generation due to increased shear stress, and increased fatigue wear due to increased internal stress of the drum are considered to have occurred. It is done.

  Thirdly, there is toner fusing accompanying an increase in continuous operation time. In recent years, image forming apparatuses have been widely used not only as a function of a copying machine as described above but also as a printer. In addition, applications such as a feeder function and a sorter function have been enhanced, and a continuous operation of 4000 or more jobs can be performed at one time. For example, in the case of 50 sheets / A4 machine, continuous operation is performed for 80 minutes or more even if it is simply estimated. Under such circumstances, the ambient temperature in the vicinity of the photoconductor reaches nearly 50 ° C., and it is considered that the temperature is higher than that at the contact (nip) portion between the cleaning blade and the photoconductor. As a result, the frequency of toner fusing on the photoreceptor has increased.

  Fourthly, when a two-component developer is used, an appropriate protective measure cannot be taken. The toner for full color is generally a non-magnetic material, and when the magnetic brush cleaning method that has been frequently used in conventional black and white machines is applied to a full color printer, it is necessary to hold the magnetic carrier in the cleaner unit in advance. Problems arise in both reliability and durability.

  The present invention has been made to cope with such problems, and maintains the surface state of the photoconductor that does not cause image flow or toner fusion even when non-magnetic toner is used, and the reliability is greatly improved. In addition, an object of the present invention is to provide an image forming apparatus that can cope with even if the productivity jumps dramatically.

According to the present invention, as means for achieving the above object, a photoconductor, a charging unit for applying a charge to the outer surface of the photoconductor, and an image to be formed by irradiating the charged photoconductor with light are used. An exposure unit that forms an electrostatic latent image on the photosensitive member, a plurality of developing units that supply a developer to the photosensitive member on which the electrostatic latent image is formed to form a toner image, and a toner image formed on the photosensitive member In an electrophotographic image forming apparatus having a transfer unit that transfers the toner to a transfer material, and a cleaning unit that removes toner remaining on the photoreceptor after transfer,
The surface of the photoconductor is gradually reduced in the photoconductor surface roughness Rz (ten-point average roughness: JIS) by repeating the above steps, and the cleaning means is at least a cleaning blade. The tan δ peak value is different between the vicinity of the blade edge portion and the other portions.

  The cleaning blade is a cleaning blade in which an isocyanate compound is impregnated in the vicinity of an edge portion that comes into contact with the toner carrying member and then cured to form a cured layer, and the thickness of the processing portion is 0.12 mm or more and 1.2 mm or less. It is preferable to be characterized by this.

  In the image forming apparatus of the present invention, it is preferable that the photoconductor is an amorphous silicon photoconductor from the viewpoints of forming a high-quality image, durability, and cleaning properties.

The image forming apparatus of the present invention is configured to sensitize an electrostatic latent image corresponding to an image to be formed by irradiating light to the photosensitive member, a charging unit that applies an electric charge to the outer surface of the photosensitive member, and light. An exposure unit that forms on the body, a plurality of developing units that form a toner image by supplying a developer to the photoconductor on which the electrostatic latent image is formed, and a toner image formed on the photoconductor is transferred to a transfer material In an electrophotographic image forming apparatus having a transfer unit and a cleaning unit for removing toner remaining on the photoreceptor after transfer,
The cleaning means is at least a cleaning blade, and the peak value of tan δ is different between the vicinity of the cleaning blade edge and the other, and at least the friction coefficient of the cleaning blade edge with respect to the PET film is 1.0 or less, A cleaning blade in which an isocyanate compound is impregnated in the vicinity of an edge portion in contact with the toner carrying member and then cured to form a hardened layer. The thickness of the treatment portion is 0.12 mm or more and 1.2 mm or less. Even if magnetic toner is used, the surface state of the photoconductor that does not cause image flow or toner fusion is maintained, reliability is greatly improved, and it is possible to cope with a breakthrough in productivity.

  Further, when the image forming apparatus of the present invention is configured to have a plurality of developing means in addition to the above configuration, it can form a full color image.

  The image forming apparatus of the present invention is configured to sensitize an electrostatic latent image corresponding to an image to be formed by irradiating light to the photosensitive member, a charging unit that applies an electric charge to the outer surface of the photosensitive member, and light. An exposure unit that forms on the body, a plurality of developing units that form a toner image by supplying a developer to the photoconductor on which the electrostatic latent image is formed, and a toner image formed on the photoconductor is transferred to a transfer material In an electrophotographic image forming apparatus having a transfer unit and a cleaning unit that removes toner remaining on the photoconductor after transfer, the surface of the photoconductor is formed by repeating the above steps. The roughness Rz (ten-point average roughness: JIS) gradually decreases, and the cleaning means is at least a cleaning blade, and the peak value of tan δ differs between the vicinity of the edge of the cleaning blade and the rest. With this configuration, the surface state of the photoconductor that does not cause image flow or toner fusion even when non-magnetic toner is used is maintained, reliability is greatly improved, and productivity is dramatically improved. Even if you can.

  The image forming apparatus of the present invention includes a photoreceptor, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit. The developer includes at least non-magnetic toner particles and a magnetic carrier, and a magnetic toner. An electrophotographic image forming apparatus using a developer containing at least a toner, wherein a cleaning blade as a cleaning means is impregnated with an isocyanate compound in the vicinity of an edge portion in contact with a toner carrying member and then cured to form a cured layer The cleaning blade having a thickness of 0.12 mm or more and 1.2 mm or less prevents the filming due to durability on the photosensitive member. Hereinafter, the image forming apparatus of the present invention will be described in more detail.

  The cleaning blade pays attention to the urethane bond group having active hydrogen originally present in the polyurethane, and bonds the isocyanate compound and urethane firmly through allophanate bond, and further removes the excess isocyanate compound that does not react with the active hydrogen compound. It is characterized by self-polymerization. According to this method, the number of steps is less than in the prior art and the cost is low in that a surface hardened layer can be formed by containing isocyanate without impregnation with an active hydrogen compound. In addition, since the tip of the cleaning blade is covered with a hardened layer with low friction, there is little deformation due to frictional force with the object to be contacted, and the edge always maintains a sharp shape, so minute toner or spherical toner In particular, it is remarkably improved for achieving both the cleaning properties of different types of toner.

  Since the electrophotographic cleaning blade is made of polyurethane having a JIS-A hardness of 60 to 80 degrees as a base material, the blade as a whole is flexible and flies elastically. As the polyurethane forming the blade substrate of the present invention, a product obtained by reacting a polymer polyol, polyisocyanate, and a curing agent can be used. When curing, a catalyst usually used for urethane curing may be used.

  Examples of the polymer polyol include polyester polyol, polyether polyol, caprolactone ester polyol, polycarbonate ester polyol, and silicone polyol. A molecular weight of 500 to 5000 is usually used. It is not limited to these.

  Examples of the isocyanate include diphenylmethane diisocyanate (MDI), tolylene diisocyanate, naphthalene diisocyanate, and hexamethylene diisocyanate. It is not limited to these.

  Examples of the crosslinking agent include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, trimethylolpropane and the like. Examples of the catalyst include triethylenediamine. It is not limited to these.

  For forming the blade, the above components are mixed at once and cast into a mold or a centrifugal molded cylindrical mold. The one-shot method is used, or the isocyanate and polyol are reacted in advance to form a prepolymer, and then a crosslinking agent. Are mixed into a mold or a centrifugal molded cylindrical mold, or a pre-polymer method in which molding is performed, or a semi-prepolymer obtained by reacting a polyol with isocyanate and a curing agent obtained by adding a polyol to a cross-linking agent is reacted with the mold. A semi-one-shot method can be used in which casting is performed by casting in a mold or a centrifugal mold.

  In general, the blade formed in this manner preferably has a JISA hardness of 60 to 85 degrees. When the JISA hardness is less than 60 degrees, the pressure contact force against the object is weak, and when it exceeds 85 degrees, the object may be damaged.

  The cleaning blade manufacturing method of the present invention is characterized in that a cured film is formed from the surface of urethane toward the inside by impregnating the whole or a part of the cleaning blade formed as described above with an isocyanate compound and curing by heating. And

  In the present invention, a part of the blade may be impregnated with the isocyanate compound either by a single blade member or by joining a support member. Further, a sheet before cutting or cutting the cleaning blade or a support member may be used.

  When impregnating only a part, it is possible to take a method such as masking a part not desired to be impregnated with a chemical-resistant tape or dipping only a part to be impregnated.

  The position where the cleaning blade is impregnated with the isocyanate compound is at least a portion where the cleaning blade and the toner carrier are in contact with each other, and it is better to impregnate the periphery with a margin. This is because the contact portion with the toner carrier is deformed by the rotation or movement of the toner carrier during sliding, and the peripheral portion at rest may touch the toner carrier. The deformation is smaller as the thickness of the impregnation is larger, and the deformation is larger as the thickness is smaller.

  In the present invention, the thickness range is set from 0.12 mm to 1.2 mm, and at the maximum value, the length of the contact portion at the tip of the cleaning blade is L1 = 0.2 mm, L2 = 0.2 mm. It is. Therefore, the length of the processing unit needs to be L1 ≧ 0.2 mm and L2 ≧ 0.2 mm.

  On the other hand, when the length L1 of the processing portion is 30% or more of the free length, the entire cleaning blade tends to be hard and lose rubber elasticity, and therefore followability to the toner carrier is poor. In addition, the increase of the linear pressure with respect to the approach amount becomes steep and it is difficult to obtain a stable linear pressure, so L1 ≦ 50% of the free length. Thereby, the followability to the toner carrier and the stability of the linear pressure are ensured. L2 can be up to the thickness of the cleaning blade.

  As a method for impregnating the blade member with the isocyanate compound, for example, the temperature is such that the polyisocyanate compound is in a liquid state, and the blade member is immersed therein. Further, a method of impregnating a fibrous or porous material with an isocyanate compound and applying it to a blade member can be employed. Moreover, you may apply | coat by spray. Similarly, the temperature of each isocyanate compound during immersion, during application, and after application is preferably a temperature at which the isocyanate compound is liquid. In this way, the urethane is impregnated with the isocyanate compound, and after a certain time, the isocyanate compound remaining on the urethane surface is wiped off. The thickness of the cured layer formed by adding isocyanate to the blade is preferably 0.12 mm or more. If it is less than 0.12 mm, the effect on the reduction of the friction coefficient due to filming on the surface of the photoreceptor is small, and the wear resistance is not good. If it exceeds 1.2 mm, the time required for impregnation becomes long and thermal deterioration of the starting isocyanate proceeds, which is not practical.

  The isocyanate compound impregnated in the blade has one or more isocyanate groups in the molecule, and those having one isocyanate group can be aliphatic monoisocyanates such as octadecyl isocyanate, aromatic monoisocyanates and the like.

  Those having two isocyanate groups are 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethazine Isocyanate (MDI), m-phenylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 4,4 ', 4 "-triphenylmethane triisocyanate, 2,4', 4" -biphenyl triisocyanate, 2,4,4 " -Diphenylmethane triisocyanate, etc. The present invention is not particularly limited, and those having three or more isocyanate groups and those having two or more isocyanate groups are used. sell.

  Of these, aliphatic monoisocyanates having a small steric hindrance and MDI having a low molecular weight are preferred from the viewpoint of permeability.

  The multimerization catalyst used with the isocyanate compound can use a quaternary ammonium salt, a carboxylate, or the like. These catalysts contain a hydroxyl group but function as a polymer for isocyanate, and are not themselves involved in the crosslinked structure. Since these catalysts are very viscous or crystallized in a state where they are not dissolved in a solvent, it is preferable to add them to an isocyanate compound after being dissolved in a solvent. Specifically, MEK, toluene, tetrahydrofuran, ethyl acetate and the like can be used. The dilution factor is preferably about 1.5 to 10 times. The addition rate of the catalyst with respect to the isocyanate compound is preferably 1 ppm to 1000 ppm. Moreover, since a polymerization reaction is accelerated when a catalyst is mixed with isocyanate, it is preferable to mix immediately before impregnation. The temperature of the isocyanate compound when impregnated may be liquid at the lower limit, and the upper limit is preferably about 90 ° C. in order to prevent the isocyanate compound from deteriorating during the treatment.

  The blade surface is impregnated with an isocyanate compound by dipping or coating for several minutes to several hours, and excess isocyanate is wiped off, followed by heat treatment in an atmosphere of 50 to 140 ° C. for several minutes to several hours. In the structure of the polyurethane, there is a urethane bond having active hydrogen, which can react with an isocyanate group. That is, it reacts with the active hydrogen of the urethane group in the polyurethane to generate an allophanate bond, thereby forming a three-dimensional branched structure.

  An isocyanate compound having two or more isocyanate groups undergoes a polymerization reaction due to urea bonds mediated by water in the environment, forms a network structure together with the above three-dimensional branched structure, and forms a cured layer .

  In the case of using a multimerization catalyst, the multimerization reaction also proceeds. This reaction does not require moisture in the environment, and the isocyanate groups react with each other, so that the reaction is completed quickly. In addition, since a cross-linked structure is formed by the trimerization reaction, a cleaning blade with high strength and high durability can be manufactured.

  In an isocyanate compound having one isocyanate group, when the isocyanate group reacts with the urethane group to form an allophanate bond, the free end is oriented toward the outside of the polyurethane surface, so that the urethane and the photoreceptor surface are in direct contact with each other. Can be reduced, and the friction can be reduced. The impregnating property is better when the molecular weight is small, and it is easy to form a cured film having a high isocyanate density. Moreover, it can control from a thin film to a thick film. A material having a large molecular weight is inferior in impregnation property but is a long chain, so that a molecular chain protrudes from the surface of the polyurethane, and the cured layer is relatively thin, but is effective in reducing the frictional force.

  An amorphous silicon photoreceptor is a photoreceptor having a photosensitive layer formed of a non-single crystal material (a-Si) having silicon atoms as a base. a-Si includes other atoms such as hydrogen atoms, halogen atoms, carbon atoms, oxygen atoms, atoms classified into Group 3B of the periodic table such as boron, and atoms classified into Periodic Table 5B such as nitrogen. May be included. In addition, the photosensitive layer is preferably configured by stacking a plurality of layers having different functions. As such a plurality of layers, a photoconductive layer composed of a lower blocking layer, a charge transport layer, a charge generation layer, and the like, a buffer layer, a surface layer, and the like can be exemplified.

  The amorphous silicon photoconductor has a surface layer formed of hydrogenated amorphous carbon on the outermost surface, from the viewpoint of improving the hardness of the photoconductor surface and improving the lubricity of the photoconductor surface. preferable. Hydrogenated amorphous carbon is a non-single crystal material containing a carbon atom as a base (a-C: H), and contains other atoms similar to the above-described a-Si. There may be. Note that a-C: H mainly represents amorphous carbon having intermediate properties between graphite and diamond, but a-C: H partially contains microcrystals and polycrystals. Also good.

  The amorphous silicon photoconductor including the surface layer can be manufactured by a conventionally known method. As such a manufacturing method, for example, a conductive substrate is installed in the system, and A manufacturing method (for example, plasma CVD method) in which an atom supply gas (raw material gas) containing the generated atoms is introduced into the system, plasma is generated in the system to decompose the raw material gas, and atoms are deposited on a conductive substrate. It can be illustrated. The film thickness and strength of the formed photosensitive layer (including the surface layer) can be adjusted by the concentration of the raw material gas, the high frequency power used for the discharge, or the like. The source gas may be diluted with hydrogen or a rare gas (inert gas).

  The charging unit is a unit that applies a charge to the outer surface of the photoconductor. As the charging means, various conventionally known charging means can be used. As such a charging means, for example, a corona discharge charging device that charges the photosensitive member by corona discharge or a conductive roller member is used. A roller charging device that charges the photoconductor in contact or non-contact state, a conductive brush charging device that charges the photoconductor in contact with a conductive brush, or a magnetic brush that forms a magnetic brush on the roller by magnetic force Examples thereof include a magnetic brush charging device that charges the photosensitive member in a contact state.

  The exposure unit is a unit that forms an electrostatic latent image on the photosensitive member according to an image to be formed by irradiating the charged photosensitive member with light. Various conventionally known exposure means can be used as the exposure means. Examples of such exposure means include gas lasers such as He-Ne lasers, semiconductor lasers, LEDs, and LCDs. can do.

  The developing means has a developing sleeve that carries a two-component developer by magnetic force to form a magnetic brush and is rotatable in the counter direction with respect to the photoreceptor, and the two-component developer is generally used in a full-color image forming apparatus. However, in the present invention, a full-color image can be formed when a plurality of the developing means are provided.

  In addition to the developing sleeve, the developing means includes a developing container for storing the developer, a developer regulating member for regulating the developer carried on the developing sleeve, and stirring for stirring the developer contained in the developing container. A member, a replenishing means for replenishing nonmagnetic toner particles, and the like can be provided.

  In the case where a plurality of developing means are provided, the image forming apparatus of the present invention may be configured such that a single developing means is disposed on a single photosensitive member, and a plurality of these sets are provided. As such a configuration, for example, a plurality of image forming units having a photosensitive member, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit are provided, and transfer materials are sequentially conveyed to the transfer unit of these units. A configuration for receiving the transfer of the toner image can be exemplified.

  In the case where a plurality of developing units are provided, the image forming apparatus of the present invention may be configured such that a plurality of developing units are disposed at the slidable position with respect to an integral photosensitive member. As such a configuration, for example, a photosensitive member and a drum-like rotatable developing unit having a plurality of developing units are provided, and the developing unit arranges the developing unit at the rubbing position by rotation. Can do.

  The developing sleeve is not particularly limited as long as it forms a magnetic brush by supporting a two-component developer by a magnetic force, and various conventionally known configurations can be adopted. As such a developing sleeve, for example, a non-magnetic and conductive rotating sleeve formed of aluminum, stainless steel or the like, and a magnetic field generating means such as a magnet having a plurality of magnetic poles and fixed inside the rotating sleeve. Examples of the configuration may be given.

  The photoconductor surface polishing rate per 1000 rotations of the photoconductor can be determined by measuring the amount of wear of the photoconductor after a predetermined number of rotations, dividing the amount of wear by the predetermined number of rotations, and multiplying this by 1000. . The polishing depth can be measured by a reflection spectroscopic interferometer (MCDP2000 manufactured by Otsuka Electronics Co., Ltd.).

  The transfer means is means for transferring a toner image formed on the photosensitive member to a transfer material. As the transfer means, various conventionally known transfer means can be used, and electrostatic transfer type transfer means can be more preferably used. Examples of such transfer means include a corona transfer device and a bias roller transfer device.

  The transfer unit is not limited to a unit that directly transfers a toner image from the photosensitive member to the transfer material. In the present invention, a transfer unit that transfers the toner image from the photosensitive member to the transfer material via the intermediate transfer unit is also suitable. Used for. As such a transfer unit, for example, an intermediate transfer unit that is arranged in contact with the photoconductor to transfer the toner image of the photoconductor, and a secondary that is arranged in contact with the intermediate transfer unit and transfers the toner image of the intermediate transfer unit to a transfer material. A configuration having transfer means can be exemplified. Examples of the intermediate transfer unit include a roller-type transfer unit and a belt-type transfer unit.

  In the case of having a plurality of developing means and using the above-described intermediate transfer means, each transfer of the toner image formed by the developing means is received by the intermediate transfer means, and transferred to the transfer material by the secondary transfer means each time. Alternatively, the transfer from the photosensitive member may be received by the intermediate transfer unit so that all the toner images formed by the developing unit overlap, and the toner images may be collectively transferred to the transfer material by the secondary transfer unit. good.

  The above-described electrostatic transfer type transfer means is preferably constituted by a member having an appropriate surface resistance value or volume resistance value. As the member having the resistance value, for example, a resin body containing conductive fine powder such as carbon black can be exemplified, and the resistance value can be adjusted depending on the type and content of the conductive fine powder. it can. Preferred examples of the resin body include silicone rubber, urethane rubber, EPDM (ethylene propylene diene monomer), and foams thereof.

  Further, it is also preferable that the transfer unit forms the surface layer of the transfer unit with a material having a high release property in order to improve the release property of the transferred toner. Examples of such a material include fluorine resins such as tetrafluoroethylene (TFE), hexafluoropropylene copolymer (FEP), and perfluoroalkoxy resin (PFA).

  The cleaning means is means for removing toner remaining on the photoconductor after transfer. As the cleaning means, various conventionally known cleaning means can be used, but a cleaning means having an elastic blade (cleaning blade) which is formed of urethane or the like and is brought into contact with the photosensitive member is preferable.

  The cleaning blade preferably has an appropriate hardness in order to remove toner without damaging the photoreceptor. In addition, it is preferable that the cleaning blade has an appropriate resilience in order to prevent the toner from slipping through and absorb fine vibration caused by friction with the photoreceptor. The cleaning blade preferably has an appropriate modulus from the viewpoint of extending the life due to wear resistance. These physical properties relating to the cleaning blade are measured by a measuring method defined by JIS.

  The image forming apparatus of the present invention preferably has a charge eliminating unit that removes the electrostatic latent image remaining on the photoreceptor after cleaning. As the static elimination means, various conventionally known static elimination means can be used. For example, as a means for canceling a residual electrostatic latent image by irradiating light to a photoconductor after cleaning, a gas laser, a semiconductor laser, Examples include LEDs and LCDs.

  In addition to the above-described means, the image forming apparatus of the present invention includes a fixing means for fixing an unfixed toner image on a transfer material, and a transfer for removing toner and paper dust adhering to and remaining on the transfer means. A cleaning means or the like can be provided as necessary.

  Next, the two-component developer used in the image forming apparatus of the present invention will be described.

  The two-component developer used in the present invention includes at least non-magnetic toner particles and a magnetic carrier, and the non-magnetic toner particles have a substantially spherical shape.

  In the present invention, the shape of the magnetic toner particles can also be confirmed by observation with an electron microscope or the like, but the nonmagnetic toner particles have a shape factor SF-1 of 100 to 140 and SF-2 of 100 to 120. Substantially spherical toner particles are preferable in order to maintain high transfer efficiency. By using toner particles having a shape factor in the above range, a primary transfer efficiency of 95% or more can always be secured.

  SF-1 and SF-2 are defined by the following formulas using the projected area of toner particles, the absolute maximum length of toner particles, and the circumference of toner particles in an image (such as an electron micrograph) of non-magnetic toner particles. The

  The shape factors SF-1 and SF-2 are obtained by obtaining an image of non-magnetic toner particles, sampling an appropriate number of toner particles in the image, analyzing the sampled toner particle image, and substituting the obtained numerical values into the above formula. , By calculating. More specifically, the shape factors SF-1 and SF-2 were obtained by sampling 100 toner particles randomly using a scanning electron microscope FE-SEM (S-800) manufactured by Hitachi, Ltd. The image information is obtained by introducing the image information into an image analysis apparatus (Luzex 3) manufactured by Nireco Co., Ltd. via an interface, performing analysis, and calculating by the above formula.

  The nonmagnetic toner particles preferably have a weight average particle diameter of 6 to 10 μm for forming a good image. If the weight average particle size is larger than the above range, resolution may be deteriorated and a clear and high-quality image may not be formed. On the other hand, when the weight average particle size is smaller than the above range, the adhesive force and the cohesive force are stronger than the electrostatic force, which may cause various troubles.

  The weight average particle diameter of the non-magnetic toner particles can be measured by various methods such as a sieving method, a sedimentation method, and a photon correlation method. In the present invention, a Coulter Multisizer (manufactured by Coulter, Inc.) is used as a measuring device. A 1% NaCl aqueous solution is prepared using special grade or first grade sodium chloride (for example, ISOTON-II manufactured by Coulter Scientific Japan Co., Ltd.), and a surfactant as a dispersant in 100 to 150 mL of the electrolytic aqueous solution. Preferably, 0.1 to 5 mL of alkylbenzene sulfonate is added, 2 to 20 mg of toner as a measurement sample is added, and the electrolytic solution in which the sample is suspended is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and a 100 μm aperture is obtained. Is used to measure the volume and number of toners, to calculate the volume distribution and number distribution, and to calculate the weight average particle according to the present invention. It can be a determining from said body integral fabric (used as the representative value for each channel the median of each channel) to measure the weight average particle size of the non-magnetic toner particles by.

  The nonmagnetic toner particles can be manufactured by a conventionally known manufacturing method. The non-magnetic toner particles can be produced by a pulverization method in which the constituent materials are made uniform by heating and melting, solidified by cooling, and pulverized to produce toner particles. Since the toner particles are generally indeterminate, it is necessary to perform mechanical, thermal, or some special treatment to obtain a substantially spherical shape. To obtain a weight average particle size within the above range, the spheronization treatment is required. It is necessary to classify the later toner particles. Therefore, in the present invention, it is preferable to employ a polymerization method as a preferred method for producing the above-mentioned nonmagnetic toner particles.

  Various production methods are known as a production method of the polymerized toner, and examples thereof include an emulsion polymerization method, a soap-free emulsion polymerization method, a two-stage swelling polymerization method, a dispersion polymerization method, and a suspension polymerization method. . In the present invention, in the case of producing toner particles having a desired particle size in one stage of the polymerization reaction, the two-stage swelling polymerization method, the dispersion polymerization method, and the suspension polymerization method are excellent. The suspension polymerization method is more excellent from the viewpoint of the quality of the manufactured product.

  The suspension polymerization method is a production method suitable for producing the nonmagnetic toner particles used in the present invention. In the suspension polymerization method, an oily material constituting toner particles is introduced into an aqueous dispersion medium containing an appropriate dispersion stabilizer to form monomer-based droplet particles in the aqueous dispersion medium. In this method, the monomer system is polymerized to produce toner particles. In the monomer system, the material constituting the toner particles includes, for example, a polymerizable monomer, a colorant, and, if necessary, a polymerization initiator, a crosslinking agent, a release agent, a plasticizer, a charge control agent, and others. Of additives.

  At the time of suspension, it is preferable to use a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser at a stretch to obtain a desired toner particle size in order to sharpen the particle size distribution of the obtained toner particles. The polymerization initiator may be added to the monomer system simultaneously with other additives, or may be added to the monomer system or aqueous dispersion medium before or after droplet particle granulation. Alternatively, the polymerization initiator may be added after being dissolved in a monomer system or an appropriate solvent.

  After granulation by monomer polymerization, stirring may be performed using an ordinary stirrer to such an extent that the particle state is maintained and particle suspension and sedimentation are prevented.

  When the polymerization is completed, nonmagnetic toner particles can be obtained by filtration, washing, and drying by a known method. In addition, it is one of preferred modes for producing the non-magnetic toner particles to include a classification step in the production process to cut coarse powder and fine powder. In the classification step, the obtained toner particles can be classified into predetermined particle diameters, and toner particles having different particle diameters can be mixed to adjust toner particles having a desired particle size distribution.

  As the polymerizable monomer, conventionally known various polymerizable monomers can be used. Examples of such polymerizable monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, and pn. -Butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy styrene , Styrene derivatives such as p-chlorostyrene, 3,4-dichlorostyrene, m-nitrostyrene, o-nitrostyrene, p-nitrostyrene; ethylene and unsaturated monoolefins such as ethylene, propylene, butylene, isobutylene; Unsaturated diolefins such as butadiene and isoprene; vinyl chloride, vinylidene chloride, odor Vinyl halides such as vinyl and vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate; methacrylic acid and methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, methacrylic acid Α-methylene aliphatic monocarboxylic esters such as isobutyl acid, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, and phenyl methacrylate; acrylic acid and methyl acrylate, ethyl acrylate , N-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, acrylic acid Acrylic acid esters such as phenyl; maleic acid, maleic acid half ester; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone; N -N-vinyl compounds such as vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone; vinyl naphthalenes; acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; acroleins, etc. Of these, one or more are used.

  As the colorant, various conventionally known colorants can be used. When a full-color image is formed, yellow, cyan, magenta, and black dyes and pigments can be used.

  Examples of the colorant for yellow include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 83; I. Examples include bat yellow 1, 3, 20 and the like.

  Examples of the colorant for cyan include C.I. I. Pigment blue 2, 3, 15, 16, 17; I. Bat Blue 6; C.I. I. Examples include Acid Blue 45, or a copper phthalocyanine pigment having a structure in which 1 to 5 phthalimidomethyl groups are substituted on the phthalocyanine skeleton.

  Examples of the colorant for magenta include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 88, 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209; I. Pigment violet 19; C.I. I. Magenta pigments such as Vat Red 1, 2, 10, 13, 15, 23, 29, 35; I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121; I. Disper thread 9; I. Solvent violet 8, 13, 14, 21, 27; C.I. I. Oil-soluble dyes such as disperse violet 1, C.I. I. B. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40; I. Basic dyes such as basic violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, and 28 can be exemplified.

  Examples of the black colorant include carbon black.

  Various conventionally known polymerization initiators can be used as the polymerization initiator. Examples of such a polymerization initiator include di-t-butyl peroxide, benzoyl peroxide, lauroyl peroxide, t-butyl peroxylaurate, 2,2′-azobisisobutyronitrile, 1,1. -Bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 1,4-bis (t-butylperoxycarbonyl) cyclohexane, 2,2 -Bis (t-butylperoxy) octane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane, 1,3-bis (t -Butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl- , 5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, di-t-butyldiperoxyisophthalate, 2,2-bis (4 4-di-t-butylperoxycyclohexyl) bropan, di-t-butylperoxy-α-methylsuccinate, di-t-butylperoxydimethylglutarate, di-t-butylperoxyhexahydroterephthalate, di -T-butylperoxyazelate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, diethylene glycol-bis (t-butylperoxycarbonate), di-t-butylperoxytrimethyladipate , Triazine, tris (t-butylperoxy) triazine, vinyltris (t-butylperoxy) Examples thereof include orchid, cumin perbivalate, dicumyl peroxide, azobis-isobutyronitrile, and dimethylazoisobutyrate.

  As the crosslinking agent, various conventionally known crosslinking agents can be used. Examples of such a crosslinking agent include divinylbenzene, divinylnaphthalene, bis (4-acryloxypolyethoxyphenyl) propane, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, and 1,4-butylene glycol diacrylate. 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol # 200, # 400, # 600 diacrylates, dipropylene glycol diacrylate, polypropylene glycol diacrylate, polyester type diacrylate (MANDA day Kayaku), and more acrylate can be exemplified such that instead of the methacrylate.

  Waxes are used as the release agent and plasticizer. In general, a release agent having a high melting point and low solubility in a polymerizable monomer is preferably selected. A plasticizer having a low melting point and high solubility in the polymerizable monomer is preferably selected. The melting point can be determined by measuring the glass transition point, and the solubility in the polymerizable monomer can be determined by the dispersion state (for example, the presence or absence of cloudiness) when dispersed in the polymerizable monomer. .

  Examples of waxes used as a mold release agent or plasticizer include paraffin wax and derivatives thereof, montan wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax and derivatives thereof, and the like. Derivatives include oxides, block copolymers with vinyl monomers, and graft modified products. Polyolefin waxes include homopolymers and copolymers of linear and branched α-olefins such as ethylene, propylene, butene, pentene, hexene, heptene, octene, nonene, and decene, alcohols, fatty acids, and acid amides. And esters, ketones, hydrogenated castor oil and derivatives thereof, vegetable waxes, animal waxes, mineral waxes, petrolactams and the like.

  As the charge control agent, various conventionally known charge control agents of negative chargeability and positive chargeability can be used.

  As the charge control agent for controlling the toner particles to be negatively charged, for example, organometallic compounds and chelate compounds are effective, and monoazo metal compounds, acetylacetone metal compounds, aromatic hydroxycarboxylic acids, aromatic dicarboxylic acid-based metals. Compounds, aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts and anhydrides, esters, phenol derivatives such as bisphenol, urea derivatives, metal-containing salicylic acid compounds, metal-containing naphthoic acid compounds, boron Examples include compounds, quaternary ammonium salts, calixarene, silicon compounds, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-acrylic-sulfonic acid copolymers, and non-metal carboxylic acid type compounds. it can.

  Examples of the charge control agent for controlling the toner particles to be positively charged include, for example, modified products of nigrosine and fatty acid metal salts, guanidine compounds, imidazole compounds, tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutyl Quaternary ammonium salts such as ammonium tetrafluoroborate, and onium salts such as phosphonium salts that are analogs thereof and lake pigments thereof, triphenylmethane dyes and lake lake pigments (as rake agents include phosphotungstic acid, Phosphomolybdic acid, phosphotungstic molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, ferrocyanide, etc.), metal salts of higher fatty acids; dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide Of diorganotin oxide; dibutyl tin borate, dioctyl tin borate, diorgano tin borate such as dicyclohexyl tin borate; can be used in combination singly or two or more.

  The other additive is not particularly limited, and as the other additive, for example, a resin compound selected from various materials can be exemplified in order to control the physical properties of the toner particles, and more specifically, Examples thereof include non-vinyl condensation resins such as polyester resins, epoxy resins, phenol resins, urea resins, polyurethane resins, polyimide resins, cellulose resins, and polyether resins, or mixtures of these with the binder resins.

  The aqueous dispersion medium is a medium containing water as a main component. Specific examples include water itself, water added with a small amount of a surfactant, water added with a pH adjuster, water added with an organic solvent, and the like. As the surfactant, for example, a nonionic surfactant such as polyvinyl alcohol is preferable. Examples of the pH adjuster include inorganic acids such as hydrochloric acid.

  The dispersion stabilizer is used to realize good granulation in an aqueous dispersion medium, and various dispersion stabilizers known in the art can be used as the dispersion stabilizer. Examples of such dispersion stabilizers include tricalcium phosphate, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, and sulfuric acid. Inorganic compounds such as calcium, barium sulfate, bentonite, silica and alumina, polyvinyl alcohol, gelatin, methylcellulose, methylhydroxypropyl cellulose, ethylcellulose, sodium salt of carboxymethylcellulose, polyacrylic acid and its salts, organic compounds such as starch, dodecyl Sodium benzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, potassium stearate Beam and the like, and the like can be exemplified surfactants such as calcium oleate.

The nonmagnetic toner particles used in the present invention preferably have a specific gravity of (1.3 g / cm ³ ) or less. If the specific gravity of the toner particles greatly exceeds (1.4 g / cm ³ ), the share of the toner particles increases, which is not preferable from the viewpoint of deterioration of the toner particles. The specific gravity of the toner particles can be adjusted according to the type (specific gravity) of the material to be used, the blending amount, and the like, and can be measured by various measurement methods such as using a measuring device such as AccuPick 1330 manufactured by Shimadzu Corporation. .

  The two-component developer used in the present invention contains at least a magnetic carrier in addition to the nonmagnetic toner particles described above. The magnetic carrier is not particularly limited as long as it carries a nonmagnetic toner and forms a magnetic brush on the developing sleeve, and various conventionally known magnetic carriers can be used.

  The magnetic carrier may be a magnetic material adjusted to a desired particle size, but in the present invention, a magnetic material-dispersed magnetic carrier in which a magnetic material is dispersed in a resin can be preferably used. The magnetic dispersion carrier can be freely adjusted in magnetic force, electrical resistance, particle size, etc., can reduce specific gravity, and can obtain a wide range of characteristics by selecting materials and adjusting the composition ratio. It can be said that it is suitable for an image quality carrier.

  The magnetic material-dispersed carrier can be produced according to the polymerization method described above, and the resin is a resin formed by polymerization of the polymerizable monomer described above, and a resin described as the other additive. Examples thereof include a mixture with a compound and a copolymer. If necessary, the above-mentioned various materials can be used for the non-magnetic toner particles.

  The magnetic carrier includes a magnetic material. Examples of such a magnetic material include ferromagnetic metals such as iron, cobalt, and nickel, and alloys or compounds containing elements exhibiting ferromagnetism such as iron, cobalt, and nickel, such as ferrite, magnetite, and hematite. It is done. In addition, the said magnetic body may use only 1 type and may use 2 or more types together. The magnetic material may be surface-treated with silicone oil or the like.

  The average particle diameter of the magnetic material-dispersed carrier is preferably in the range of 10 to 60 μm. If the average particle size is less than 10 μm, the carrier is likely to adhere to the photoconductor, and the photoconductor may be scratched and cause image deterioration. On the other hand, if the average particle size exceeds 60 μm, the share of the developer in the developing means increases, causing the deterioration of the developer, in particular, the peeling of the external additive of the toner particles and the shape change, causing image deterioration. Sometimes. Furthermore, since the specific surface area is small when the particle size is large, the amount of toner that can be retained when forming as a developer is reduced, and an image lacking fineness is easily formed.

The specific resistance of the magnetic material-dispersed carrier is preferably in the range of 10 ⁷ to 10 ¹⁵ Ω · cm. If it is less than 10 ⁷ Ω · cm, in the developing method in which a bias voltage is applied, current leaks from the sleeve to the photoreceptor surface in the developing region, and a good image may not be obtained. On the other hand, if it exceeds 10 ¹⁵ Ω · cm, a charge-up phenomenon may be caused under conditions such as low humidity, which may cause image deterioration such as thin image density, poor transfer, and fog.

  The average particle diameter of the magnetic carrier can be measured by various measuring methods. For example, the magnetic carrier is photographed as an electron micrograph, a predetermined number of the photographed carriers are extracted, and the maximum chord length of the extracted carrier is calculated. It can be obtained by calculating an average. The specific resistance of the magnetic carrier can be measured by various methods, but can be measured by a so-called tablet method. In other words, the magnetic carrier to be measured is put in an aluminum ring of 40φ (mm), pressure-molded with 2500 N, and a 4-terminal probe is used with a resistivity meter Loresta AP or Hiresta IP (both manufactured by Mitsubishi Yuka). Measure the specific resistance.

  The image forming apparatus of the present invention can be exemplified by the configuration as shown in FIG. 1, and a cleaning blade as a cleaning means is impregnated with an isocyanate compound in the vicinity of an edge portion in contact with the toner carrier, and then cured. This is a cleaning blade with a hardened layer. By setting the thickness of the processing section to 0.12 mm or more and 1.2 mm or less, foreign matters such as paper dust and corona products that cause durability on the photoreceptor can be fixed. Is prevented. Therefore, according to the image forming apparatus of the present invention, even in a full-color image forming apparatus using a two-component developer, it is possible to prevent deterioration in image quality due to filming and to form a high-quality image. It becomes. FIG. 2 shows the viscoelasticity of the cleaning blade.

  Examples of the present invention will be described below. However, the present invention is not limited to the following examples.

<Example 1>
FIG. 1 is an overall explanatory view of an image forming apparatus in the present embodiment.

  The image forming apparatus in this embodiment includes a photosensitive member 2, a charger 1 as a charging unit, a ROS (latent image writing device) 13 as an exposure unit, and four units of developing units 31 to 34 as developing units. The apparatus includes a roll 4, an intermediate transfer belt 40 and a secondary transfer device 48 as transfer means, a cleaner 50 as a cleaning means, a pre-exposure device 3 as a discharging means, a fixing device 64, a paper supply / discharge system, and the like.

  The photosensitive member 2 is a negatively charged amorphous silicon photosensitive member, and is formed by forming an amorphous silicon photosensitive layer having a thickness of 30 μm on an aluminum cylinder having a diameter of 80 mm and a thickness of about 3 mm by glow discharge or the like. As the surface layer of the photoconductor 2 in this example, 8000 mm of SiC: H (hydrogenated amorphous silicon carbide) was used.

  The charger 1 is a corona discharge type charger, and includes a discharge wire formed of tungsten or the like, and a U-shaped casing that opens toward the photoreceptor 2.

  The ROS 13 includes a laser generator that generates a laser beam according to the read image. In the optical path of the laser beam L, an imaging lens, a mirror, and the like are appropriately disposed.

  The image reading means includes a platen glass 10, a light source 11 that emits light toward the platen glass 10, and reflected light from the platen glass 10 in red (R), green (G), and blue (B). A CCD to be converted into an electrical signal, and the RGB electrical signals input from the CCD are received and converted into black (K), yellow (Y), magenta (M), and cyan (C) image data, and the converted image. And an IPS (image processing system) for outputting an electrical signal corresponding to the above to the laser generator.

  The developing device 31 regulates a developing container 37a that stores a two-component developer of K, a developing sleeve 35a that is rotatably provided in the opening of the developing container 37a, and a developer carried on the developing sleeve 35a. A regulating blade 36a for regulating the height of the magnetic brush formed on the sleeve, a rotating rod for stirring the developer in the developing container 37a, and a power source (not shown) for applying a voltage to the developing sleeve 35a during development. ). A magnet body (not shown) having a plurality of magnetic poles is fixed in the developing sleeve 35a. The developing device 32 contains a Y developer, the developing device 33 contains an M developer, and the developing device 34 contains a C developer. The developing device 32 is the same as the developing device 31 except for the contained developer. It is configured.

  The developing devices 31 to 34 are provided on a rotatable developing roll 4. The developing roll 4 has a rotary shaft 30 and is a roll that rotates so as to convey a developing unit corresponding to the color data of the electrostatic latent image to the developing area B during development, and constitutes a rotary developing means. . With this developing roll 4, the developing sleeves 35 a to 35 d are arranged so that the closest area to the photoreceptor 2 is about 400 μm at least during development, and the magnetic brush on the developing sleeve is located with respect to the photoreceptor 2. It arrange | positions so that an electrostatic latent image can be developed in the state which contacts.

  Below the surface of the photoreceptor 2, a plurality of belt support rolls including an intermediate transfer belt 40, a belt drive roll 45, a tension roll 43, idler rolls 46 and 47, a secondary transfer backup roll 44, and a primary transfer roll 42. Although not shown, a belt frame for supporting them and a blade-type belt cleaner 49 for removing residual toner and the like adhering to the intermediate transfer belt 40 before transfer are provided. The intermediate transfer belt 40 is rotatably supported by the belt support roll.

  A position sensor 41 that detects a home position provided in a non-transfer portion of the intermediate transfer belt is provided at a position separated from the intermediate transfer belt 40. Further, a secondary transfer device 48 for transferring the intermediate transferred toner image to a recording sheet as a transfer material is provided at a position facing the secondary transfer backup roll 44 via the intermediate transfer belt 40. Yes.

The intermediate transfer belt 40 has a two-layer structure of a polyimide layer and a cyanoresin layer (high dielectric constant layer). The intermediate transfer belt 40 is manufactured as follows. In the thermosetting seamless belt in which the carbon black of the base layer is dispersed, the carbon black is mixed with Ube Industries, Ltd. polyimide varnish U for heat-resistant coating and mixed with a mixer or the like. This undiluted solution is poured into a cylindrical mold and centrifugally molded while being heated. After demolding in a semi-cured state, the demolded belt is placed on an iron core and heated to 400 to 450 ° C. for main curing (imidization reaction), surface resistivity 10 ¹² Ω / □, volume resistivity A seamless belt having a thickness of 10 ¹⁰ Ωcm and a thickness of 75 μm is obtained.

On the other hand, the layer configuration of the backup roll 44 that is a support roll of the intermediate transfer belt 40 and that forms the counter electrode of the secondary transfer roll 48 may be either a single layer or a multilayer. For example, in the case of a single layer, it is composed of a roll in which an appropriate amount of conductive fine powder such as carbon black is blended in silicone rubber, urethane rubber, EPDM (ethylene propylene diene monomer) or the like. In the case of the two-layer structure, the backup roll 44 has a core layer made of a foamed material such as silicone rubber, urethane rubber, EPDM (ethylene propylene diene monomer) with appropriately adjusted volume resistivity, and a conductive layer on the outer peripheral surface thereof. It is comprised with the skin layer formed by mix | blending electrically conductive agents, such as carbon black, with silicone rubber, urethane rubber, EPDM (ethylene propylene diene monomer), etc. The volume resistivity of the backup roll 44 is preferably in the range of 10 ⁷ Ω · cm to 10 ⁹ Ω · cm.

The layer configuration of the secondary transfer roll 48 is not particularly limited. For example, in the case of a two-layer structure, the secondary transfer roll 48 includes a core layer and a coating layer covering the surface thereof. The core layer is made of silicone rubber, urethane rubber, EPDM (ethylene propylene diene monomer) or the like in which conductive powder is dispersed, or a foam thereof. The coating layer is preferably composed of a fluororesin material obtained by dispersing conductive powder. Examples of the fluororesin include tetrafluoroethylene (TFE), hexafluoropropylene copolymer (FEP), and perfluoroalkoxy resin (PFA). The volume resistivity of the secondary transfer roll 48 is preferably in the range of 10 ⁶ to 10 ⁹ Ω · cm.

  The cleaner 50 includes a cleaning blade 52 that comes into contact with the surface of the photoreceptor 2 and a cleaning container 51 that holds the cleaning blade 52 and stores toner particles and the like removed by the blade.

The cleaning blade 52 has a mass ratio of 1,4-butanediol and trimethylolpropane to a prepolymer of 7.0% NCO% produced from an ethylene butylene adipate polyester polyol having a molecular weight of 2000 and 4,4′-diphenylmethane diisocyanate. A hardness of 70 degrees (JISA) rebound resilience 15 (%) was prepared by mixing a cross-linking agent containing a triethylenediamine catalyst mixed at 65:35 at a molar ratio of hydroxyl group / isocyanate group of 0.9. A cleaning blade made of urethane with a rebound resilience of 25% at 40 ° C. and a modulus of 200% (kg / cm ² ) (both according to JIS standards) is a chemical resistant tape so that L1 = L2 = 3 mm. Mask with, soak in an MDI bath at 80 ° C for 30 minutes, and add excess isocyanate. The mask was removed, and the masking was removed, followed by curing in an oven at 130 ° C. for 60 minutes. The coefficient of friction against the PET film was 0.6 (HEIDON surface property tester / width 50 mm, load 20 g / 10 mm, moving speed 10 cm / min). Moreover, the hardened part of the cross section was cloudy, and the thickness of the hardened part was 0.7 mm by microscopic observation. The hardness of the cured part was 80 degrees (JISA). The cleaning blade 52 is disposed on the photosensitive member 2 at a contact angle of 24 ° and a contact pressure of 20 (g / cm). The cleaning blade 52 has a plate thickness of 2 mm, and a SUS plate (plate thickness of 1.0 mm) is provided as a back plate. The free length of the cleaning blade is 3 mm. Note that the tan δ peak values in the vicinity of the cleaning blade edge portion and other portions were different.

The pre-exposure device 3 is a light emitting diode (element GaAlAs) mainly having a peak wavelength of 660 nm. The pre-exposure device 3 has a half width of about 25 nm, which is ½ of the peak wavelength, and an exposure amount is 20 μJ / cm ² . The moving time of the surface of the photoreceptor 2 from the pre-exposure device 3 to the charger 1 is about 50 mm · sec.

  The fixing device 64 includes a heating roll 64a and a pressure roll 64b disposed to face the heating roll 64a.

  The sheet feeding / discharging system includes a sheet feeding tray 60 for storing the recording sheet S, a pickup roll 61 for taking out the recording sheets in the tray one by one from the tray, and a recording sheet in time with the secondary transfer unit 48. A pair of registration rollers 62 that conveys the sheet, a sheet conveyance belt 63 that conveys the recording sheet subjected to the secondary transfer toward the fixing device 64, and a recording sheet discharge that conveys the recording sheet that has undergone image fixing by the fixing device 64. A tray 65.

The two-component developer used in this example is a mixture of polymerized toner, which is non-magnetic toner particles prepared by suspension polymerization, resin magnetic carrier prepared by polymerization, and abrasive particles. Four color toner particles were prepared using each colorant. The T / D ratio, which is the mass ratio of the toner particles to the sum of the toner particles and magnetic carrier of the obtained developer, was 8%. The magnetic carrier had a specific resistance of 10 ¹³ Ω · cm. The non-magnetic polymer toner is a substantially spherical toner having a smooth surface with a shape factor SF-1 of 115 and SF-2 of 110, a weight average particle diameter of 8 μm, and a specific gravity of 1.05 g. The average charge amount per unit mass of / cm ³ was 25 μC / g. The abrasive particles were alumina, the Mohs hardness was 9, the average particle size was 1.2 μm, and the amount added to the nonmagnetic toner particles was 1% by mass.

  Note that the maximum image width in the image forming apparatus according to the present embodiment is about 320 mm obtained by adding a length corresponding to Nobi to the side of A4. Further, the peripheral speed of the photosensitive member 2 in this embodiment is 300 mm / sec.

  In FIG. 1, reflected light from an original G placed on an original platen glass 10 is converted into electrical signals of R (red), G (green), and B (blue) by a CCD 12 via an exposure optical system. . An IPS (image processing system) temporarily converts the R, G, and B electrical signals input from the CCD 12 into K (black), Y (yellow), M (magenta), and C (cyan) image data. And the image data is output to a laser drive circuit (not shown) as image data for forming a latent image at a predetermined timing. The laser drive circuit outputs a laser drive signal (not shown) to the ROS 13 according to the input image data.

  The photosensitive member 2 rotates in the direction of the arrow Da, and the surface thereof is uniformly charged by the charger 1 and then exposed and scanned by the laser beam L (main wavelength 655 nm) of the ROS 13 at the latent image writing position A. An electrostatic latent image is formed. When forming a full-color image, electrostatic latent images corresponding to four color images of K (black), Y (yellow), M (magenta), and C (cyan) are sequentially formed. Only the electrostatic latent image corresponding to the (black) image is formed.

  The latent image writing on the surface of the photoreceptor 2 by the laser beam L is started after a predetermined time has elapsed since the belt position sensor 41 detects the home position provided in the non-image portion of the intermediate transfer belt 40. In the case of a full-color image, since the respective colors are superimposed, the time from the position sensor 41 detecting the home position to the start of latent image writing by the laser beam L is the same for each color.

  The surface of the photosensitive member 2 on which the electrostatic latent image is formed rotates and moves sequentially through the development area B and the primary transfer area D. The developing units 31 to 34 are transported to the developing position by the rotation of the developing roll 4 and convert the electrostatic latent image on the surface of the photoreceptor 2 that passes through the developing area B into a toner image.

  Here, the developing process by the two-component magnetic brush method in this embodiment will be described. First, the developer pumped up at the N2 pole of the magnet body with the rotation of the developing sleeve 35a is transferred by the regulating blade 36a arranged perpendicular to the developing sleeve 35a in the process of being transported from the S2 pole to the N1 pole. A thin layer is formed on the developing sleeve 36a. Here, when the developer formed in a thin layer is conveyed to the development main pole S1, the spikes are formed by the magnetic force, and a magnetic brush by a magnetic carrier is formed on the development sleeve 35a.

  The spike-shaped developer rubs the surface of the photoreceptor 2. At this time, the toner particles move to the photoreceptor 2 to develop the electrostatic latent image. The magnetic carrier forming the magnetic brush and the abrasive particles do not actively move to the photoreceptor 2 but remain on the developing sleeve 35a. Thereafter, the developer on the developing sleeve 35a is returned into the developing container 37a by the repulsive magnetic fields of the N3 pole and the N2 pole.

  A DC voltage and an AC voltage are applied to the developing sleeve 35a from a power source (not shown). In this embodiment, with respect to the photoreceptor surface potentials Vd-450V and Vl-50V, -300V as the DC voltage and Vpp = 1500V as the AC voltage. Vf = 2000 Hz is applied. In general, in the two-component development method, when an AC voltage is applied, the development efficiency increases and the image becomes high-quality, but conversely, there is a risk that fogging easily occurs. For this reason, in general, it is possible to prevent fogging by providing a potential difference between the DC voltage applied to the developing sleeve 35a and the surface potential of the photosensitive drum 2.

  In this embodiment, the developing sleeves 35a to 35d were rotated at a peripheral speed of 450 mm / sec in the counter direction with respect to the photosensitive body peripheral speed of 300 mm / sec. The rotational load torque of the developing sleeve 35a with respect to the surface of the photoreceptor is 0.038 N · m. The rotational load torque as a rubbing function by the magnetic brush on the developing sleeve against the photosensitive member is preferably 0.02 to 0.06 N · m.

  When forming a full-color image, an electrostatic latent image of the first color is formed at the latent image writing position A, and a toner image of the first color is formed at the development region B. When the toner image passes through the primary transfer region D, the toner image is electrostatically primary transferred onto the intermediate transfer belt 40 by the primary transfer roll 42. Thereafter, in the same manner, the toner images of the second color, the third color, and the fourth color are sequentially superimposed and transferred onto the intermediate transfer belt 40 carrying the first color toner image, and finally the full-color multiple toner. An image is formed on the intermediate transfer belt 40. When forming a monochrome monochrome image, only the developing device 31 is used, and the monochrome toner image is primarily transferred onto the intermediate transfer belt 40.

  After the primary transfer, residual toner on the surface of the photoreceptor 2 is removed by the cleaning blade 52.

  The recording sheet S accommodated in the paper feed tray 60 is taken out by the pickup roll 61 at a predetermined timing and conveyed to the registration roll pair 62. The registration roll 62 conveys the recording sheet S to the secondary transfer area E in synchronization with the timing of the primary toner image or the single color toner image moving to the secondary transfer area E. In the secondary transfer region E, the secondary transfer device 48 electrostatically and collectively transfers the toner image on the intermediate transfer belt 40 onto the recording sheet S. The intermediate transfer belt B after the secondary transfer is cleaned by a belt cleaner 47, and residual toner on the belt is removed. Note that the secondary transfer roll 48 and the belt cleaner 47 are disposed so as to be separated from (contacted with and separated from) the intermediate transfer belt 40, and when a color image is formed, an unfixed toner image of the final color. Is separated from the intermediate transfer belt 40 until it is primarily transferred to the intermediate transfer belt 40.

  The recording sheet S on which the toner image has been secondarily transferred is conveyed to the fixing device 64 by the sheet conveying belt 63 and is heated and fixed by the fixing device 64. The recording sheet S on which the toner image is fixed is discharged to the recording sheet discharge tray 65.

  In this example, an image was formed in an environment of high temperature and high humidity (32.5 ° C./85%) using the above image forming apparatus. As a result, in this embodiment, no image flow occurred even after the endurance of 3 million sheets or in an environment of high temperature and high humidity. Further, no problems such as chipping occurred at the cleaning blade edge.

  As a result of inspecting the photoreceptor 2 after endurance, problems such as fusion, partial filming film generation, and rubbing scratches did not occur at all even after endurance of 3 million sheets. The amount of wear was also 0.12 nm / 1,000 rotations. The initial surface roughness Rz of the photoreceptor 2 was 0.32 μm [AFM: investigation range 20 μm × 20 μm], and the surface roughness Rz of the photoreceptor after durability of 3 million sheets was 0.12 μm.

<Example 2>
In this example, the cleaning blade used was urethane rubber having a hardness of 70 ° and a rebound resilience of 35%, and the edge was cured in the same manner as in Example 1. The coefficient of friction against the PET film was 0.7. Even in the photosensitive member 2, problems such as fusion, partial filming film, and rubbing scratches after the endurance of 3 million sheets do not occur at all, and the surface roughness after the endurance of 3 million sheets is also Rz0. It was 15 μm. Note that the tan δ peak values in the vicinity of the cleaning blade edge portion and other portions were different.

<Example 3>
In this example, a durability test was performed with the same configuration as in Example 1 except that 1000% of aC: H (hydrogenated amorphous carbon) was laminated on the surface layer instead of SiC: H. It has been confirmed by the inventors that hydrogenated amorphous carbon has a smaller friction coefficient than the conventional SiC: H surface layer. The Vickers hardness of the surface of the photoreceptor 2 in this example was (1100 kg / m ² ). Note that the tan δ peak values in the vicinity of the cleaning blade edge portion and other portions were different.

  In this embodiment, no image blur occurred even after the endurance of 3 million sheets in an environment of high temperature and high humidity (32.5 ° C./85%). Further, no problems such as chipping occurred at the cleaning blade edge. Further, Rz after durability of 3 million sheets was 0.11 μm with respect to the initial surface roughness Rz of 0.22 μm of the photoreceptor 2. Also in the photosensitive member 2, no problems such as fusion, partial filming film, and rubbing scratches occurred in the image even after the endurance of 3 million sheets, and no filming layer was confirmed.

  Further, the wear amount of the photosensitive member 2 in this example was 0.02 mm / 1000 rotations. Moreover, the coefficient of friction after durability was also smaller than that of the SiC: H surface layer. This is because the surface free energy of hydrogenated amorphous carbon is smaller than that of SiC: H, and organic substances such as ozone products and toner paper powder are less likely to adhere to and adhere to the surface of the photoconductor. Presumed.

<Comparative Example 1>
This was carried out in the same manner as in Example 1, immersed in an MDI bath for 5 minutes, wiped off excess isocyanate, and cured in an oven at 130 ° C. for 60 minutes. The thickness of the cured film at the cross section was 0.1 mm. The coefficient of friction measured by the same method as in Example 1 was 1.5. Further, the durability test was performed in the same manner as in Example 1, but a cleaning failure occurred at the initial 300,000.

<Comparative example 2>
In this comparative example, the same urethane rubber as in Example 2 was used without being treated. The coefficient of friction measured by the same method as in Example 1 was 3.0. In the durability test, fusion occurred at the time of 50,000 sheets.

1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention. It is a figure showing the viscoelasticity of the cleaning blade of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Charger 2 Photoconductor 3 Pre-exposure device 4 Developing roll 10 Manuscript table glass 11 Light source 12 CCD (solid-state image sensor)
13 ROS (Latent image writing device)
30 Rotating shafts 31 to 34 Developing devices 35a to 35d Developing sleeves 36a to 36d Restricting blades 37a to 37d Developing container 40 Intermediate transfer belt 41 Position sensor 42 Primary transfer roll 43 Tension roll 44 Secondary transfer backup roll 45 Belt drive roll 46, 47 idler roll 48 secondary transfer device 49 belt cleaner 50 cleaner 51 cleaning container 52 cleaning blade 60 paper feed tray 61 pickup roll 62 registration roll pair 63 sheet conveying belt 64 fixing device 64a heating roll 64b pressure roll 65 recording sheet discharge tray A latent Image writing position B Development area D Primary transfer area Da Arrow indicating rotation direction of photoconductor E Secondary transfer area G Document L Laser beam S Recording sheet

Claims (3)

A photoconductor, a charging unit for applying a charge to the outer surface of the photoconductor, an exposure unit for forming an electrostatic latent image on the photoconductor according to an image to be formed by irradiating the charged photoconductor with light, A plurality of developing means for supplying a developer to the photosensitive member on which the electrostatic latent image is formed to form a toner image, a transferring means for transferring the toner image formed on the photosensitive member to a transfer material, and the photosensitive material after transfer In an electrophotographic image forming apparatus having cleaning means for removing toner remaining on the body,
The surface of the photoreceptor is gradually reduced in surface roughness Rz (ten-point average roughness: JIS) by repeating the above steps, and the cleaning unit is at least a cleaning blade, An image forming apparatus, wherein a peak value of tan δ is different between the vicinity of the edge portion of the cleaning blade and the other portion.   The cleaning blade is a cleaning blade in which an isocyanate compound is impregnated in the vicinity of an edge portion in contact with the toner carrying member and then cured to form a cured layer, and the thickness of the processing portion is 0.12 mm or more and 1.2 mm or less. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided. The image forming apparatus according to claim 1, wherein the photoconductor is an amorphous silicon photoconductor.

Images