JP5119340B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to driving of a transfer belt unit in an electrophotographic process image forming apparatus such as a copying machine, a printer, and a facsimile, in particular, an image forming apparatus having a transfer belt unit. Applications to developing devices, cleaning devices, and process cartridges are possible.

  In a conventional image forming apparatus, particularly a color image forming apparatus, each color toner image sequentially formed on a photosensitive drum is transferred onto a transfer belt unit (hereinafter referred to as an intermediate transfer belt) which is an intermediate transfer body, and the color is transferred. A configuration in which images are collectively transferred onto a transfer material (hereinafter referred to as transfer paper) is widely known.

  Regarding these intermediate transfer belts, the gripping force is obtained by selecting the driving position of the intermediate transfer belt that has a large winding angle generated by stretching the intermediate transfer belt. However, depending on the size of the unit and the arrangement of the belt, there may be cases where a predetermined belt wrap angle cannot be obtained. In such cases, a roller is arranged to bend the belt from the outside to the inside, thereby securing the wrap angle. I was trying. However, if the belt is bent inward, a large load is applied to the belt, causing problems such as the belt being easily broken.

  On the other hand, many members are in contact with the intermediate transfer belt from the outside, and the load of these members becomes a load for driving the belt, and if it exceeds the grip force of the belt, a slip or the like occurs, thereby preventing the belt from running stably. It becomes.

  In order to stabilize the belt running, Patent Document 1 proposes that a driving source is connected to a roller to which a load fluctuation is directly applied to form a belt driving roller.

  In Patent Document 1, the contact member of the drive roller is limited to the process means. However, not only the process means but also the one that causes fluctuations in the belt runnability is essentially all to stabilize the runnability most. It should be considered to cope with the load. In this prior art, there is no clear statement regarding the detailed contact method and position of the transfer roller to be brought into contact with the drive roller.

  SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to define the driving position of an intermediate transfer belt and the position of a member that contacts the transfer belt in order to obtain a stable belt.

According to the present invention, there is provided an intermediate transfer belt that is stretched by at least three rollers and carries a toner image, and transfers a transfer material in a vertical direction toward a fixing unit. An image forming apparatus comprising: a transfer unit that contacts the intermediate transfer belt to transfer a toner image onto a transfer material, wherein the three rollers are tension rollers that apply a predetermined tension to the intermediate transfer belt; A driving roller provided at a position facing the transfer unit across the intermediate transfer belt, and an inlet roller positioned upstream of the driving roller in the belt moving direction, and the tension roller is the driving roller located above the resist nip downward together with the inlet roller is positioned on the tension roller toward below than the drive rollers Also located on the tension roller side, a belt winding angle of the driving roller is smaller than the belt winding angle of the tension roller, the transfer means, the belt moving direction with respect to the center portion of the belt winding portion of said drive roller In contact with the intermediate transfer belt region that is not in contact with the drive roller, and is not in contact with the entrance roller via the intermediate transfer belt. Is solved.

It is preferable if the belt winding angle of the drive roller is 90 ° or more and 130 ° or less. It is preferable if the transfer means is a rotating body and has at least rotation in the same direction as the belt running direction. Driving the transfer means, from the drive roller, or considered to be obtained from the accompanying rotation of the intermediate transfer belt.
It is more effective if it has a cleaning means for removing the toner adhering to the surface of the intermediate transfer belt, and the cleaning means has a cleaning member that contacts the intermediate transfer belt at a position facing the tension roller. Is.

  According to the present invention, stable belt driving can be obtained even in a small unit or a restricted belt arrangement, and no unnecessary load is applied to the belt.

1 is a schematic configuration diagram of a color image forming apparatus according to the present invention. It is an enlarged view of an image station.

  Hereinafter, the present invention will be described in an electrophotographic color image forming apparatus. In the tandem type as in this example, the influence of the belt running property is more likely to occur in the image than in other methods. By applying the present invention to such a method, the belt running property is stabilized, and consequently The improvement of the image quality becomes remarkable, and on the other hand, the productivity by the tandem method can be obtained and the effect of high quality and high productivity can be obtained.

  First, a process for obtaining a color image will be described. In FIG. 1, a color image forming apparatus includes a transfer belt unit 10 having an intermediate transfer belt 11 and four image stations. Each image station has 20Y, 20C, 20M, and 20Bk as image carriers (hereinafter referred to as photosensitive drums), around which are dedicated charging devices 30Y, 30C, 30M, 30Bk, developing devices 50Y, 50C, 50M, 50Bk, primary transfer rollers 12Y, 12C, 12M, 12Bk and cleaning devices 40Y, 40C, 40M, 40Bk are provided.

FIG. 2 is an enlarged view of one of these image stations. The developing device 50 includes a developing case 55 having an opening, a developing roller 51 disposed so as to face and face the surface of the photosensitive drum 20, a developing blade 52 that regulates the developer on the developing roller 51 to a certain height, The first conveying screw 53 and the second conveying screw 54 arranged at a position facing the roller 51 are configured. The cleaning device 40 includes a cleaning case 43 having an opening, a cleaning blade 41 for cleaning residual toner on the photosensitive drum 20, a waste toner screw 42 for transporting the cleaned waste toner to a waste toner bottle (not shown), and the like. It is comprised by. The transfer belt unit 10 includes an intermediate transfer belt 11, a primary transfer roller 12 for transferring the toner image on the photosensitive drum 20 to the intermediate transfer belt 11, an intermediate transfer belt case 14 for holding these components, and the like. It is configured. Reference numeral 30 denotes a charging roller as a charging device, 31 denotes a cleaning roller for the charging roller, and L denotes laser light from the optical writing device 8.

  In FIG. 1, reference numeral 9 shown at the upper left indicates a toner bottle for replenishing toner. From left, yellow (Y), cyan (C), magenta (M), and black (Bk) toners are present. From this point, the developing devices 50Y, 50C, 50M, and 50Bk of the respective colors are replenished by a predetermined replenishment amount through a conveyance path (not shown).

  Regarding the operation for obtaining a color image, the transfer paper 2 is fed from the lower paper feed cassette 1 by the paper feed roller 3, and when the leading edge of the transfer paper 2 reaches the registration roller pair 4, it is detected by a sensor (not shown). The transfer sheet 2 is conveyed to the nip portion between the secondary transfer roller 5 and the intermediate transfer belt 11 by the registration roller pair 4 while taking a timing with a signal.

  The photosensitive drums 20Y, 20C, 20M, and 20Bk, which are uniformly charged in advance by the charging devices 30Y, 30C, 30M, and 30Bk, are exposed and scanned with laser light by the optical writing device 8, and the photosensitive drums 20Y, 20C, and An electrostatic latent image is created on 20M and 20Bk.

  The electrostatic latent images are developed by the developing devices 50Y, 50C, 50M, and 50Bk for the respective colors, and yellow, cyan, magenta, and black toner images are formed on the surfaces of the photosensitive drums 20Y, 20C, 20M, and 20Bk. .

  Next, a voltage is applied to the primary transfer rollers 12Y, 12C, 12M, and 12Bk, and the toner on the photosensitive drums 20Y, 20C, 20M, and 20Bk is sequentially transferred onto the intermediate transfer belt 11. At this time, the image forming operation for each color is executed while shifting the timing from the upstream side to the downstream side so that the toner image is transferred to the same position on the intermediate transfer belt 11.

  The image formed on the intermediate transfer belt 11 is conveyed to the position of the secondary transfer roller 5 and is secondarily transferred to the transfer paper 2. The transfer paper 2 onto which the toner images of the respective colors are transferred is conveyed to the fixing device 6 and thermally fixed, and is discharged by the paper discharge roller 7.

  The residual toner on the photoconductive drums 20Y, 20C, 20M, and 20Bk is cleaned by the respective cleaning devices 40Y, 40C, 40M, and 40Bk, and then the charging device 30Y, in which the bias of the AC component is superimposed and applied to the direct current. 30C, 30M, and 30Bk are charged at the same time as static elimination, and are prepared for the next image formation. The residual toner on the intermediate transfer belt 11 is cleaned by the intermediate transfer belt cleaning device 13 and prepared for the next image forming process.

  Next, the tension of the intermediate transfer belt 11 will be described. As can be seen in FIG. 1, there are a total of seven rollers that stretch the intermediate transfer belt 11 from the inside. That is, the transfer counter roller 100, the transfer inlet roller 101, each of the primary transfer rollers 12: four, and the cleaning counter roller 131 shown on the left in FIG. Further, as for the members that come in contact with the outer periphery of the intermediate transfer belt 11, there are the secondary transfer roller 5, four photosensitive members 20: four, and a cleaning unit (cleaning brush, cleaning blade) 13.

The transfer wrap angle is the cleaning counter roller 131 (170 °) with respect to the transfer counter roller 100 (100 °), and the gripping force of the cleaning counter roller 131 is superior as is known from the Euler type, Judging from the gripping force, it is preferable to provide the drive on the cleaning facing roller side. However, when the cleaning counter roller 131 is driven, another belt pressure (tension) roller must be provided. In that case, so the case of the transfer inlet roller 101 pressurized (tension) roller, and the transfer inlet shape becomes possible to change from time to time, may generate defective transfer becomes unstable conveyance of the transfer sheet Inconvenient . Since the transfer counter roller 100 must be fixed with respect to the transfer position, if the cleaning counter roller 131 is a driving roller, a pressure roller must be added.

However , the addition of rollers causes problems such as a complicated configuration, an increase in size of the unit itself, an increase in weight, and an increase in cost. Also, when driving at the position of the cleaning counter roller 131, the problem is the external load. In the case of FIG. 1, the pressure force generated between the member and the member that contacts the unit is 30 N at the portion of the secondary transfer roller 5, 3 N at the photosensitive member position, and 5 N at the cleaning position. The secondary transfer roller portion is the one that gives the most load to the transfer belt. If the belt running lacks stability due to these loads, image defects such as misalignment tend to occur. In this case, the stability of the belt running means that the fluctuation of the belt speed is small. Therefore, in these systems, a secondary transfer roller having a high pressure is a problem with respect to belt running performance.

Here, when there is no sliding (linear speed difference) between the transfer belt 11 and each contact member and the contact member itself has a drive, no load is generated with respect to the belt drive. It is essential, because it becomes necessary to add a configuration for its, and thus lead to complicated and large-sized devices. On the other hand, it can be considered that the secondary transfer roller 5 is configured to rotate with the belt. However, if the drive roller position and the contact position are different, a load is applied to the belt drive. It has also been found that adjusting the linear speed of the transfer to the constant speed is not good for the image, such as the occurrence of image defects such as missing characters in transfer and the like.

  If the contact member having a large pressing force against the transfer belt is installed away from the driving roller in this manner, a problem may occur in the stability of the belt running and the like, and an image defect may easily occur. In the present invention, the driving roller is the roller that generates the largest applied pressure between the opposite contact members of the stretching roller regardless of the belt winding angle for driving the intermediate transfer. As a result, the load generated by the applied pressure is not the belt speed but a load on the drive source for driving the belt, and can be handled separately from the belt running performance.

  Referring to FIG. 1, the transfer counter roller 100 is a drive roller. Further, according to the configuration, a vertical force acts between the belt and the driving roller by the transfer roller having the largest applied pressure, and a product obtained by multiplying this by a friction coefficient between the belt and the roller becomes a frictional force and becomes a driving grip force.

  In the present invention, the transfer counter roller 100 has a smaller wrapping angle than the driven roller and a smaller belt grip force, but as an effect of this configuration, a large grip force can be obtained by adding the pressure applied by the transfer roller. Can do. According to the comparison by this configuration, when the roller surface layer is made of EP rubber, the grip force (force at which the belt slips) of the transfer counter roller is improved by about 10% to 30%. It has been found that sufficient grip force can be obtained even when the winding angle is shallow due to these effects.

In addition, in the example of FIG. 1 in which the angle configuration is a sheet feeding on the lower side, a fixing on the upper side, and a vertical conveyance of the sheet on the side, it is desirable that the wrapping angle of the driving roller be 90 ° or more. In order to secure a space for arranging the primary transfer roller and the like in the apparatus and arrange the driven roller, it is desirable to make it 130 ° or less in order to reduce the size of the apparatus. If the angle is 90 ° or less, the belt is arranged with a wide angle around the driving roller. On the other hand, if the angle is 130 ° or more, the primary transfer roller cannot be arranged because of the driven roller. This is because the pitch cannot be secured.

  Next, even if there is a linear speed difference in the transfer roller, the belt and roller slip are less likely to occur compared to other rollers by obtaining a proportional grip force by the applied pressure. Moreover, the effect becomes the highest by constituting the portion with the largest applied pressure. Therefore, according to this configuration, it is possible to provide an image forming apparatus that can efficiently obtain a belt grip force and suppress a load on a belt drive such as a transfer roller. Furthermore, it is possible to reduce the size of the apparatus.

  Further, by configuring the secondary transfer roller having the highest pressure to be driven from the transfer counter roller via a gear, the linear velocity of the belt follows either the secondary transfer roller or the transfer counter roller. However, the belt is controlled by the same drive source, and the belt linear velocity can be easily adjusted.

  By rotating the transfer roller, which is a contact rotating body, with respect to the belt, the configuration of the secondary transfer drive can be eliminated, the apparatus can be simplified, and the size and cost can be reduced. . Stabilization of the belt running performance can be achieved at the same time.

In order to increase the belt grip force, the transfer roller is installed in contact with the upstream side of the center of the belt winding portion of the transfer counter roller 100 (drive roller) with the belt traveling direction as a flow. When a transfer roller or the like is in contact with the winding downstream side and the transfer roller linear speed is slower than the belt linear speed, belt deflection occurs on the upstream side of the transfer roller contact point of the belt winding portion of the drive roller, and the winding angle is Decrease in grip force. In order to alleviate this phenomenon, the present invention adopts the above configuration to prevent a decrease in the amount of winding due to deflection. This makes it possible to prevent a decrease in grip force. Further, if the transfer roller has a range in which the transfer roller is in contact with only the belt before the start point of the contact area between the drive roller and the belt (the belt winding portion of the drive roller) , the transfer roller can increase the belt winding angle with respect to the drive roller. While having the effect of increasing, it becomes possible to further increase the driving force and grip force.

  Here, the configuration of the transfer belt 11 will be described. A belt used as an intermediate transfer belt can be made of a conventionally known fluorine resin, polycarbonate resin, polyimide resin, or the like. In particular, a polyimide resin is excellent in mechanical strength and the like, and when combined with this method, performance improvement such as positional deviation can be achieved. In recent years, “elastic belts” in which the entire belt layer or a part of the belt is an elastic member have also been used. Examples of elastic belts are shown below. However, it is needless to say that the present invention is not limited to the elastic belt, and includes a single layer belt, an inelastic belt, or the like.

  As resin components of the belt, polycarbonate, fluorine resin (ETFE, PVDF), polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer Polymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-acrylic) Octyl acid copolymer and styrene-phenyl acrylate copolymer), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-phenyl methacrylate copolymer) Polymers), styrene-α-chloro Styrenic resins such as methyl acrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer (monopolymer or copolymer containing styrene or styrene substitution product), methyl methacrylate resin, butyl methacrylate resin, acrylic Ethyl acid resin, butyl acrylate resin, modified acrylic resin (silicone modified acrylic resin, vinyl chloride resin modified acrylic resin, acrylic / urethane resin, etc.), vinyl chloride resin, styrene-vinyl acetate copolymer, vinyl chloride-vinyl acetate Polymer, rosin-modified maleic resin, phenol resin, epoxy resin, polyester resin, polyester polyurethane resin, polyethylene, polypropylene, polybutadiene, polyvinylidene chloride, ionomer resin, polyurethane resin, silicone resin, ketone tree An ethylene - can be used ethyl acrylate copolymer, xylene resin and polyvinyl butyral resin, polyamide resin, one kind or two kinds or more selected from the group consisting of modified polyphenylene oxide resin. However, it is natural that the material is not limited to the above materials.

  Elastic rubbers and elastomers include butyl rubber, fluorine rubber, acrylic rubber, EPDM, NBR, acrylonitrile-butadiene-styrene rubber natural rubber, isoprene rubber, styrene-butadiene rubber, butadiene rubber, ethylene-propylene rubber, ethylene-propylene. Terpolymer, chloroprene rubber, chlorosulfonated polyethylene, chlorinated polyethylene, urethane rubber, syndiotactic 1,2-polybutadiene, epichlorohydrin rubber, ricone rubber, fluororubber, polysulfide rubber, polynorbornene rubber, hydrogenated nitrile Selected from the group consisting of rubber, thermoplastic elastomers (eg polystyrene, polyolefin, polyvinyl chloride, polyurethane, polyamide, polyurea, polyester, fluororesin) It is possible to use one kind or two or more elements. However, it is natural that the material is not limited to the above materials.

  There are no particular restrictions on the conductive agent for adjusting the resistance value. For example, carbon black, graphite, metal powder such as aluminum and nickel, tin oxide, titanium oxide, antimony oxide, indium oxide, potassium titanate, antimony oxide-tin oxide composite Conductive metal oxides such as oxides (ATO) and indium oxide-tin oxide composite oxides (ITO), and conductive metal oxides are coated with insulating fine particles such as barium sulfate, magnesium silicate and calcium carbonate But you can. Of course, the conductive agent is not limited to the above.

  There is no special limitation on the surface layer material, but it is required to reduce the adhesion of the toner to the surface of the transfer belt to improve the secondary transfer property. For example, one or more of polyurethane, polyester, epoxy resin, etc. A material that reduces surface energy and improves lubricity, for example, fluororesin, fluorine compound, powder of fluorocarbon, titanium dioxide, silicon carbide, etc., one or more kinds of particles, or particle size Different types can be dispersed and used. It is also possible to use a material with a reduced surface energy by forming a fluorine-rich layer on the surface by heat treatment, such as a fluorine-based rubber material.

  The manufacturing method of the transfer belt in the above components is not limited. Centrifugal molding method in which material is poured into a rotating cylindrical mold to form a belt, spray coating method to form a thin film on the surface, dipping method in which a cylindrical mold is dipped in a solution of the material, inner mold, outer mold There is a casting method that is poured into a mold and a method in which a compound is wound around a cylindrical mold and vulcanized and polished. However, the present invention is not limited to these, and a belt can be manufactured by combining a plurality of manufacturing methods. It is natural to be able to

  As a method of preventing elongation as an elastic belt, there are a method of forming a rubber layer in a core resin layer having a small elongation as in the above example, a method of putting a material for preventing elongation in the core layer, etc. It is not restricted to. Materials constituting the core layer for preventing elongation include, for example, natural fibers such as cotton and silk, polyester fibers, nylon fibers, acrylic fibers, polyolefin fibers, polyvinyl alcohol fibers, polyvinyl chloride fibers, polyvinylidene chloride fibers, polyurethane 1 or 2 types selected from the group consisting of synthetic fibers such as fibers, polyacetal fibers, polyfluoroethylene fibers and phenol fibers, inorganic fibers such as carbon fibers, glass fibers and boron fibers, and metal fibers such as iron fibers and copper fibers Using the above, it is used as a woven fabric or a yarn. Of course, the material is not limited to the above.

  The yarn may be twisted in any manner, such as one or a plurality of filaments twisted, one-twisted yarn, various twisted yarns, double yarn, or the like. Further, for example, fibers of a material selected from the above material group may be blended. Of course, the yarn can be used after being subjected to an appropriate conductive treatment. On the other hand, the woven fabric can be any woven fabric such as knitted fabric, and of course, a woven fabric that is interwoven can also be used, and naturally conductive treatment can be applied.

  The production method for providing the core layer is not particularly limited. For example, a method in which a woven fabric woven in a cylindrical shape is covered with a mold and a coating layer is provided thereon, a woven fabric woven in a cylindrical shape is immersed in liquid rubber or the like, and a coating layer is formed on one or both sides of the core layer. Examples thereof include a method of providing, a method of winding a thread around a metal mold or the like at an arbitrary pitch, and providing a coating layer thereon. Although the thickness of the elastic layer depends on the hardness of the elastic layer, if it is too thick, surface expansion and contraction increases, and cracks are likely to occur in the surface layer. In addition, since the amount of expansion / contraction increases, it is not preferable that the image is too thick (e.g., about 1 mm or more).

  The appropriate range of the hardness of the elastic layer is 10 ° ≦ HS ≦ 65 ° (JIS-A). The optimum hardness needs to be adjusted according to the belt layer thickness. Those having a hardness of less than 10 ° JIS-A are very difficult to mold with high dimensional accuracy. This is due to the fact that it is susceptible to shrinkage and expansion during molding. Moreover, when making it soft, it is a general method to contain an oil component in the base material, but there is a drawback that the oil component oozes out when continuously operated in a pressurized state. For this reason, it has been found that the photosensitive member in contact with the surface of the intermediate transfer belt is contaminated to generate horizontal band unevenness. In general, a surface layer is provided to improve releasability, but in order to give a complete leaching prevention effect, the surface layer has high required quality such as durability quality, material selection, characteristics, etc. It will be difficult to secure. On the other hand, those with a hardness of 65 ° JIS-A or higher can be molded accurately with the increased hardness, and the oil content can be reduced or reduced, so the contamination of the photoreceptor can be reduced. However, the effect of improving transferability, such as missing characters, cannot be obtained, and stretching on the roller becomes difficult.

  Next, the combination of the toner and the present invention will be described. By combining the present invention and the polymerized toner, it is possible to make the transfer linear velocity difference of the secondary transfer nearly zero, thereby reducing the load on the belt running performance of the secondary transfer roller and reducing the applied pressure. The grip force for driving the transfer belt can be obtained, so that more stable drive transmission is possible, and an effect of efficiently preventing misalignment is obtained. The difference in linear velocity can be reduced because the cause of missing characters is proportional to M / A (the amount of toner per unit area), and the toner is agglomerated by the secondary transfer pressurization and adheres dynamically to the belt after paper transfer. However, if a polymerized toner is used, the toner filling rate can be increased. Therefore, even with the same amount of toner, color reproducibility is improved, the amount of toner can be reduced, and the M / A can be reduced. This is possible, and the sphericity of the polymerized toner itself can be increased, so that it is difficult to aggregate.

  The toner used in the present invention will be described below. The toner is a polymerized toner made of a modified polyester. Resins used in conventional polymerization methods are mainly styrene-acrylic resins, but styrene-acrylic resins are inferior in low-temperature fixability compared to polyester resins. The cause was found to be the balance between the fixing temperature and Tg. Comparing the Tg of the toner made of styrene-acrylic resin and the toner made of polyester resin having the same fixing temperature, the Tg of the toner made of styrene-acrylic resin is clearly lower. For this reason, the heat resistant storage stability of the toner made of styrene-acrylic resin is worse than that of the toner made of polyester resin. The polyester resin used is modified with acrylic, epoxy, urethane or the like. By modifying, it becomes easy to control the physical properties of the toner and also improve the manufacturability.

It is important that the toner used in the present invention has a shape factor SF-1 of 100 to 135. The SF-1 indicating the shape factor is obtained by randomly sampling 100 toner particle images of 2 μm or more magnified 1000 times using, for example, FE-SEM (S-800) manufactured by Hitachi, Ltd. Thus, for example, it is introduced into an image analysis apparatus (Luxex III) manufactured by Nicole and analyzed, and the values obtained from the following formulas are defined as shape factors SF-1 and SF-2:
SF-1 = (MXLNG) ² / AREA * π / 4 * 100
SF-2 = (PERI) ² / AREA * 1 / 4π * 100
In the formula, MXLNG represents the absolute maximum length of the particle (the length of the circumscribed circle), PERI represents the perimeter of the particle, and AREA represents the projected area of the particle.

  The shape factor SF-1 indicates the degree of roundness of the toner particles (SF-1 increases as it is deformed from a circle (spherical shape)), and the spherical coefficient SF-2 indicates the degree of unevenness of the toner particles. In general, SF-1 affects durability, and 100 <SF-1 ≦ 135 is preferable, and 100 <SF-1 ≦ 120 is more preferable. In the case of 135 <SF-1, the toner layer moves away from the spherical shape and approaches an indeterminate shape, and the layer thickness and the surface of the toner layer are not uniform. . As a result, the transfer current increases and the discharge during separation increases.

  The toner used in the present invention preferably has an average circularity of 0.93 or more. When the average circularity of the toner is 0.93 or less, the layer thickness and the surface of the toner layer are not uniform as in SF-1, and the contact between the toner, the transfer paper, and the photosensitive member is reduced, so that the transfer efficiency is improved. descend. As a result, the transfer current increases and the discharge during separation increases.

  The average circularity can be measured using a flow type particle image analyzer FPIA-2100 manufactured by Sysmex Corporation. The measurement was adjusted to a 1% NaCl aqueous solution using primary sodium chloride and then passed through a 0.45 μm filter to 50 to 100 ml of a surfactant, preferably 0.1 to 5 ml of an alkylbenzene sulfonate as a dispersant. In addition, add 1-10 mg of sample. This was subjected to a dispersion treatment for 1 minute with an ultrasonic disperser, and measurement was performed using a dispersion liquid in which the particle concentration was adjusted to 5000 to 15000 particles / μl. The diameter of a circle having the same area as a two-dimensional image captured by a CCD camera is assumed to be the equivalent circle diameter, and the equivalent circle diameter of 0.6 μm or more is effective from the accuracy of CCD pixels, and is used for calculating the average circularity. It was. The average circularity can be obtained by calculating the circularity of each particle, adding up the circularity of each particle, and dividing by the total number of particles. The average circularity of each particle can be calculated by dividing the circumference of a circle having the same projected area as the particle image by the circumference of the particle projection image.

  Further, the weight average particle diameter: Xw / number average particle diameter: Xn of the toner used in the present invention is preferably 1.35 or less. When the toner has a weight average particle diameter: Xw / number average particle diameter: Xn of 1.35 or more, the toner layer does not have a uniform thickness and surface as in SF-1, so the toner, transfer paper, and photoconductor Contact is reduced, and transfer efficiency is reduced. As a result, the transfer current increases and the discharge during separation increases. The toner particle size was measured using Coulter MULTISIZER IIe. The aperture diameter is 100 μm.

The toner used in the present invention preferably has a small cohesive force. If the cohesive force of the toner is small, the thickness of the toner layer in the gap between the photoconductor and the transfer paper can be made uniform. Further, by making the surface uniform, the electric field exerted on each toner becomes uniform and the transfer efficiency increases. Furthermore, the charge amount of the transfer paper can be reduced, and dust caused by discharge during separation can be reduced. Here, the cohesion force of the toner can be expressed as an aggregation degree (%). The higher the cohesion value, the stronger the cohesion of the toner:
Coagulation degree measuring method Measuring apparatus: Powder tester PT-N type The operating method manufactured by Hosokawa Micron Corporation basically follows the instruction manual of "Powder Tester PT-N type", but changes the following points:
1. Use sieve: 75μm, 45μm, 22μm
2. Vibration time: 30 seconds

  The degree of aggregation of the toner is 5 to 20%, preferably 5 to 15%. When the degree of aggregation is 5% or less, the fluidity of the toner is too good and dust tends to be generated during transfer. On the other hand, if it is 20% or more, the cohesive force of the toner becomes strong and the transferability becomes poor. The OPC photoconductor used in the present invention is preferably provided with a reinforcing layer on the surface of the OPC photoconductor CTL layer. If the CTL layer of the OPC photosensitive member is thinned, the amount of charge as the photosensitive member is increased and the development amount can be increased, but the film is scraped and there is a problem in durability. Accordingly, a surface reinforcing layer represented by polycarbonate in which fine metal powder such as aluminum oxide is dispersed is provided to improve the life.

  The production method of the polymerized toner in the present invention is exemplified. The toner binder can be produced by the following method. The polyol (1) and the polycarboxylic acid (2) are heated to 150 to 280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate or dibutyltin oxide, and the generated water is distilled off as necessary. Thus, a polyester having a hydroxyl group is obtained. Next, this is reacted with polyisocyanate (3) at 40 to 140 ° C. to obtain a prepolymer (A) having an isocyanate group. Further, (A) is reacted with amines (B) at 0 to 140 ° C. to obtain a modified polyester. When reacting (3) and reacting (A) and (B), a solvent may be used as necessary. Usable solvents include aromatic solvents (toluene, xylene, etc.); ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.); esters (ethyl acetate, etc.); amides (dimethylformamide, dimethylacetamide, etc.) and ethers And those inert to the isocyanate (3), such as tetrahydrofuran (such as tetrahydrofuran). When polyester (ii) not modified with urea bond is used in combination, (ii) is produced by the same method as polyester having a hydroxyl group, and this is dissolved in the solution after completion of the reaction of (i) and mixed. To do.

(Toner production method in aqueous medium)
The aqueous medium used in the present invention may be water alone, or a solvent miscible with water may be used in combination. Examples of the miscible solvent include alcohol (methanol, isopropanol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methylcellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.) and the like.

  The toner particles may be formed by reacting a dispersion made of a prepolymer (A) having an isocyanate group in an aqueous medium with (B), or a modified polyester (i) produced in advance may be used. . As a method for stably forming a dispersion composed of the modified polyester (i) and the prepolymer (A) in the aqueous medium, the composition of the toner raw material composed of the modified polyester (i) and the prepolymer (A) in the aqueous medium is used. The method of adding a thing and making it disperse | distribute by shearing force etc. are mentioned. The prepolymer (A) and other toner compositions (hereinafter referred to as toner raw materials), a colorant masterbatch, a release agent, a charge control agent, an unmodified polyester resin, etc. are dispersed in an aqueous medium. It may be mixed at the time of formation, but it is more preferable to mix the toner raw materials in advance and then add and disperse the mixture in the aqueous medium. In the present invention, other toner materials such as a colorant, a release agent, and a charge control agent do not necessarily have to be mixed when forming particles in an aqueous medium. It may be added. For example, after forming particles containing no colorant, the colorant can be added by a known dyeing method.

  The dispersion method is not particularly limited, and known equipment such as a low-speed shear method, a high-speed shear method, a friction method, a high-pressure jet method, and an ultrasonic wave can be applied. In order to make the particle size of the dispersion 2 to 20 μm, a high-speed shearing type is preferable. When a high-speed shearing disperser is used, the rotational speed is not particularly limited, but is usually 1000 to 30000 rpm, preferably 5000 to 20000 rpm. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. The temperature during dispersion is usually 0 to 150 ° C. (under pressure), preferably 40 to 98 ° C. Higher temperatures are preferred in that the dispersion made of the modified polyester (i) or the prepolymer (A) has a low viscosity and is easy to disperse.

  The amount of the aqueous medium used relative to 100 parts of the toner composition containing the modified polyester (i) and the prepolymer (A) is usually 50 to 2000 parts by weight, preferably 100 to 1000 parts by weight. If the amount is less than 50 parts by weight, the dispersion state of the toner composition is poor, and toner particles having a predetermined particle diameter cannot be obtained. If it exceeds 20000 parts by weight, it is not economical. Moreover, a dispersing agent can also be used as needed. It is preferable to use a dispersant because the particle size distribution becomes sharp and the dispersion is stable.

  As a dispersant for emulsifying and dispersing the oily phase in which the toner composition is dispersed in a water-containing liquid, anionic surface active soot such as alkylbenzene sulfonate, α-olefin sulfonate, and phosphate ester, alkylamine salt Amine salt types such as amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, imidazoline, alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, benzethonium chloride, etc. Nonionic surfactants such as quaternary ammonium salt type cationic surfactants, fatty acid amide derivatives, polyhydric alcohol derivatives, such as alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl-N , - amphoteric surfactants, such as dimethyl ammonium betaine and the like.

  Moreover, the effect can be raised in a very small amount by using a surfactant having a fluoroalkyl group. Preferred anionic surfactants having a fluoroalkyl group include fluoroalkyl carboxylic acids having 2 to 10 carbon atoms and metal salts thereof, disodium perfluorooctanesulfonyl glutamate, 3- [omega-fluoroalkyl (C6-C11 ) Oxy] -1-alkyl (C3-C4) sodium sulfonate, 3- [omega-fluoroalkanoyl (C6-C8) -N-ethylamino] -1-propanesulfonic acid sodium, fluoroalkyl (C11-C20) carvone Acids and metal salts, perfluoroalkylcarboxylic acids (C7 to C13) and metal salts thereof, perfluoroalkyl (C4 to C12) sulfonic acids and metal salts thereof, perfluorooctanesulfonic acid diethanolamide, N-propyl-N- ( 2-hydroxyethyl) -Fluorooctanesulfonamide, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (C6-C10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (C6-C16) ethyl phosphate, etc. Is mentioned.

  Product names include Surflon S-111, S-112, S-113 (Asahi Glass Co., Ltd.), Florard FC-93, FC-95, FC-98, FC-129 (Sumitomo 3M Co., Ltd.), Unidyne DS-101. DS-102 (manufactured by Taikin Kogyo Co., Ltd.), Mega-Fac F-ll0, F-120, F-113, F-191, F-812, F-833 (Dainippon Ink Co., Ltd.), Xtop EF- 102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (manufactured by Tochem Products), and Fgentent F-100, F150 (manufactured by Neos).

  In addition, as the cationic surfactant, aliphatic quaternary ammonium salts such as aliphatic primary, secondary or secondary amic acid, perfluoroalkyl (C6 to C10) sulfonamidopropyltrimethylammonium salt which right the fluoroalkyl group, Benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts, trade names include Surflon S-121 (Asahi Glass), Florard FC-135 (Sumitomo 3M), Unidyne DS-202 (Daikin Industries) ), Megafuck F-150, F-824 (Dainippon Ink Co., Ltd.), Xtop EF-132 (Tochem Products Co., Ltd.), Footgent F-300 (Neos Co., Ltd.) and the like.

  Moreover, tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, hydroxyapatite, etc. can be used as an inorganic compound dispersant which is hardly soluble in water. Further, the dispersed droplets may be stabilized by a polymer protective colloid. For example, acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride and other (meth) acrylic monomers containing hydroxyl groups Bodies such as β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, γ-hydroxypropyl acrylate, γ-hydroxypropyl methacrylate, 3-acrylate Chloro-2-hydroxypropyl, 3-chloro-2-hydroxypropyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate, glycerol monomethacrylate, N- Methylol acrylamide, N-methylol methacrylamide, etc., vinyl alcohol or ethers with vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, etc., or esters of compounds containing vinyl alcohol and carboxyl groups, such as acetic acid Vinyl, vinyl propionate, vinyl butyrate, acrylamide, methacrylamide, diacetone acrylamide or their methylol compounds, acid chlorides such as acrylic chloride, methacrylic chloride, vinyl pyridine, vinyl pyrrolidone, vinyl imidazole, ethylene imine, etc. Homopolymers or copolymers such as those having nitrogen atoms or heterocyclic rings thereof, polyoxyethylene, polyoxypropylene, polyoxyethylene Lenalkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, polyoxyethylene nonyl phenyl ester Polyoxyethylenes such as, celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose can be used.

  In order to remove the organic solvent from the obtained emulsified dispersion, a method in which the temperature of the entire system is gradually raised to completely evaporate and remove the organic solvent in the droplets can be employed. Alternatively, the emulsified dispersion can be sprayed into a dry atmosphere to completely remove the water-insoluble organic solvent in the droplets to form toner fine particles, and the aqueous dispersant can be removed by evaporation together. . As a dry atmosphere in which the emulsified dispersion is sprayed, a gas obtained by heating air, nitrogen, carbon dioxide gas, combustion gas, or the like, in particular, various air currents heated to a temperature equal to or higher than the boiling point of the highest boiling solvent used is generally used. Sufficient quality can be obtained in a short time such as spray dryer, belt dryer or rotary kiln.

  In addition, when an acid such as calcium phosphate salt or an alkali-soluble one is used as the dispersion stabilizer, the calcium phosphate salt is removed from the fine particles by a method such as washing with water after dissolving the calcium phosphate salt with an acid such as hydrochloric acid. To do. In addition, it can be removed by an operation such as enzymatic degradation.

  When a dispersant is used, the dispersant may remain on the surface of the toner particles. However, it is preferable from the charged surface of the toner that the dispersant is washed and removed after the elongation and / or crosslinking reaction.

  Further, in order to lower the viscosity of the toner composition, a solvent in which the modified polyester (i) or (A) is soluble can be used. The use of a solvent is preferable in that the particle size distribution becomes sharp. The solvent is preferably volatile with a boiling point of less than 100 ° C. from the viewpoint of easy removal. Examples of the solvent include toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl acetate, Methyl ethyl ketone, methyl isobutyl ketone and the like can be used alone or in combination of two or more. In particular, aromatic solvents such as toluene and xylene and halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform and carbon tetrachloride are preferred. The usage-amount of the solvent with respect to 100 parts of prepolymers (A) is 0-300 parts normally, Preferably it is 0-100 parts, More preferably, it is 25-70 parts. When a solvent is used, it is removed by heating under normal pressure or reduced pressure after the elongation and / or crosslinking reaction.

  The elongation and / or crosslinking reaction time is selected depending on the reactivity of the isocyanate group structure of the prepolymer (A) and the amines (B), but is usually 10 minutes to 40 hours, preferably 2 to 24 hours. is there. The reaction temperature is generally 0 to 150 ° C, preferably 40 to 98 ° C. Moreover, a well-known catalyst can be used as needed. Specific examples include dibutyltin laurate and dioctyltin laurate.

  In order to remove the organic solvent from the obtained emulsified dispersion, a method in which the temperature of the entire system is gradually raised to completely evaporate and remove the organic solvent in the droplets can be employed. Alternatively, the emulsified dispersion can be sprayed into a dry atmosphere to completely remove the water-insoluble organic solvent in the droplets to form toner fine particles, and the aqueous dispersant can be removed by evaporation together. . As a dry atmosphere in which the emulsified dispersion is sprayed, a gas obtained by heating air, nitrogen, carbon dioxide gas, combustion gas, or the like, in particular, various air currents heated to a temperature equal to or higher than the boiling point of the highest boiling solvent used is generally used. Sufficient quality can be obtained in a short time such as spray dryer, belt dryer or rotary kiln.

  When the particle size distribution at the time of emulsification dispersion is wide and washing and drying processes are performed while maintaining the particle size distribution, the particle size distribution can be adjusted by classifying into a desired particle size distribution. In the classification operation, the fine particle portion can be removed in the liquid by a cyclone, a decanter, centrifugation, or the like. Of course, the classification operation may be performed after obtaining the powder after drying, but it is preferably performed in a liquid in terms of efficiency. The obtained unnecessary fine particles or coarse particles can be returned to the kneading step and used for forming particles. At that time, fine particles or coarse particles may be in a wet state.

The dispersant used is preferably removed from the obtained dispersion as much as possible, but it is preferable to carry out it simultaneously with the classification operation described above.
By mixing the resulting dried toner powder with dissimilar particles such as release agent fine particles, charge control fine particles, fluidizing agent fine particles, and colorant fine particles, or by giving mechanical impact force to the mixed powder By immobilizing and fusing on the surface, it is possible to prevent the detachment of the foreign particles from the surface of the resulting composite particle. Specific means include a method of applying an impact force to the mixture by blades rotating at high speed, a method of injecting and accelerating the mixture into a high-speed air stream, and causing particles or composite particles to collide with an appropriate collision plate, etc. is there. As equipment, Ong mill (manufactured by Hosokawa Micron Co., Ltd.), I-type mill (manufactured by Nippon Pneumatic Co., Ltd.) has been modified to lower the pulverization air pressure, hybridization system (manufactured by Nara Machinery Co., Ltd.), kryptron Examples include a system (manufactured by Kawasaki Heavy Industries, Ltd.) and an automatic mortar.

As the external additive for improving the fluidity of the toner, inorganic fine particles can be preferably used. The primary particle diameter of the inorganic fine particles is preferably 5 mμ to 2 μm, and particularly preferably 5 mμ to 500 mμ. Moreover, it is preferable that the specific surface area by BET method is 20-500 m < ² > / g. The proportion of the inorganic fine particles used is preferably 0.01 to 5% by weight of the toner, and particularly preferably 0.01 to 2.0% by weight. Specific examples of the inorganic fine particles include, for example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, silica sand, clay, mica, wollastonite, diatomaceous earth. Examples include soil, chromium oxide, cerium oxide, pengala, antimony trioxide, magnesium oxide, zirconium oxide, parium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride.

  In addition, polymer fine particles, such as polystyrene obtained by soap-free emulsion polymerization, suspension polymerization, and dispersion polymerization, methacrylate esters, acrylate copolymers, polycondensation systems such as silicone, benzoguanamine, and nylon, thermosetting Examples thereof include polymer particles made of a resin. Such a fluidizing agent can be surface-treated to increase hydrophobicity and prevent deterioration of flow characteristics and charging characteristics even under high humidity. For example, a silane coupling agent, a silylating agent, a silane coupling agent having a fluorinated alkyl group, an organic titanate coupling agent, an aluminum coupling agent and the like are preferable surface treatment agents.

2 Transfer Paper 5 Secondary Transfer Roller 8 Optical Writing Device 10 Transfer Belt Unit 11 Intermediate Transfer Belt 20 Photoconductor

JP 2001-343843 A

Claims (7)

An intermediate transfer belt that is stretched around at least three rollers and carries a toner image, and a transfer material is transferred in a vertical direction toward the fixing unit, and the toner image on the intermediate transfer belt is transferred to the transfer material. Therefore, the three rollers include a tension roller for applying a predetermined tension to the intermediate transfer belt, and the intermediate transfer belt between the three rollers. A driving roller provided at a position facing the transfer unit; and an inlet roller positioned upstream of the driving roller in the belt moving direction, the tension roller being positioned above the driving roller, the tension roller side than the resist nip downward together with the inlet roller is positioned on the tension roller toward below than the drive rollers Position, and a belt winding angle of the driving roller is smaller than the belt winding angle of the tension roller, said transfer means abutting on the upstream side of the belt moving direction with respect to the center portion of the belt winding portion of said drive roller And an image that is disposed so as to be in contact with an intermediate transfer belt region that is not in contact with the drive roller, and is in non-contact with the entrance roller via the intermediate transfer belt. Forming equipment.   The image forming apparatus according to claim 1, wherein a belt winding angle of the drive roller is 90 ° or more and 130 ° or less.   The image forming apparatus according to claim 1, wherein the transfer unit is a rotating body and has a rotation in at least the same direction as a belt traveling direction.   The image forming apparatus according to claim 3, wherein driving of the transfer unit is obtained from the driving roller.   4. The image forming apparatus according to claim 3, wherein driving of the transfer unit is obtained from rotation of the intermediate transfer belt.   6. The image forming apparatus according to claim 1, further comprising a cleaning unit that removes toner adhering to the surface of the intermediate transfer belt, the cleaning unit facing the tension roller. An image forming apparatus comprising a cleaning member that contacts the intermediate transfer belt at a position.   The image forming apparatus according to claim 1, wherein the image forming apparatus is a tandem type image forming apparatus including a plurality of photoconductors.

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