JP4842729B2 - Image forming apparatus control method and image forming apparatus - Google Patents

Description

The invention also relates to a method of controlling an image forming apparatus of an electrophotographic system, a copying machine provided with a control method thereof, printers, plotters, facsimile or image forming equipment such as a complex machine thereof.

  An image carrier made up of a photoconductor and the like is uniformly charged by a charging unit, and a latent image is formed on the surface of the image carrier by a latent image forming unit such as an optical writing device. An electrophotographic image is formed by developing with the toner of the developing means to form a toner image, and transferring the toner image formed on the image carrier onto the transfer material directly or via an intermediate transfer body by the transfer means. Forming apparatuses are known, and are widely used as copiers, printers, plotters, facsimiles, or complex machines of these.

  In such an image forming apparatus, in order to improve the image quality, the toner used for development is reduced in particle size and increased in circularity. Since the toner manufactured by the pulverization method has limitations in these characteristics, a polymerized toner manufactured by a suspension polymerization method, an emulsion polymerization method, or a dispersion polymerization method capable of reducing the particle size is being adopted.

  In general, toner with a high degree of circularity is known to have poor cleaning properties. This is due to the fact that the toner rolls without being caught by the edge of the cleaning blade, so that the cleaning blade is easily slipped through. Such toners with poor cleaning properties tend to stain the contact charging type charging means (for example, a charging roller), and an abnormal image due to uneven charging occurs with time.

  In order to solve this problem, it is possible to remove dirt on the charging roller by mounting a cleaner on the charging roller (see, for example, Patent Document 1), or to make the charging roller less likely to become dirty by using non-contact charging or proximity charging. Has been devised (for example, see Patent Document 2). On the other hand, there has been little contrivance for preventing abnormal images due to contamination of the charging roller on the control surface.

JP 2004-361916 A JP 2004-170527 A

  There is a problem in that an abnormal image is generated when foreign matters such as toner, toner external additives, paper powder, and photoconductor lubricant adhere to the charging roller. To deal with this problem, remove the foreign matter adhering to the charging roller by placing a cleaner on the charging roller as described above, a non-contact charging method in which the charging roller and the photosensitive member are not in contact, or slightly This can be improved by using a proximity charging system that makes contact, and making it difficult for foreign matter to adhere to the charging roller. However, recently, it has become necessary to further extend the life of the unit in terms of the environment, and a greater effect than the above-described measures is required. Further, there is a demand for speeding up of the machine. When the background potential, which is the difference between the charging potential and the developing bias, is constant, an abnormal image due to contamination of the charging roller appears more clearly when the speed is increased. Increasing the background potential can reduce abnormal images and background contamination due to contamination of the charging roller, but increases carrier adhesion to the photoreceptor.

  The present invention has been made in view of the above circumstances, and by changing the background potential of the image carrier under a predetermined condition, an abnormal image due to contamination of the charging means can be obtained while minimizing carrier adhesion to the image carrier. Providing a control method that can prevent the occurrence of background stains and extend the life of the charging means, and the provision of the control method can prevent the occurrence of abnormal images and background stains, resulting in higher image quality. And a process cartridge that is provided in the image forming apparatus and that can improve convenience when replacing an image carrier, charging means, and the like. In addition, the toner used in the image forming apparatus has characteristics that can improve image quality, improve cleaning properties, extend the life of the charging means, and the like. An object of the present invention is to provide.

In order to achieve the above object, the present invention employs the following technical means.
The first means of the present invention includes an image carrier, a charging unit for charging the image carrier, a latent image forming unit for forming a latent image on the surface of the charged image carrier, and the latent image forming unit. Developing means for developing the latent image formed on the image carrier with toner to form a toner image; and transfer means for transferring the toner image formed on the image carrier on the transfer material by the developing means; a method of controlling an image forming apparatus having a linear velocity of the image bearing member is variable, a target value or setpoint for background potential of said image bearing member, Ru changed by the linear velocity of the image bearing member the control method of images forming device, the absolute value of the target value or set value of the background potential, characterized in that the faster the linear speed of the image bearing member is high.

According to a second means of the present invention, in the control method of the image forming apparatus of the first means, when the transfer current that the transfer means passes to the transfer material changes , the target value of the background potential of the image carrier is changed. Alternatively, the set value is changed by a transfer current that the transfer unit passes through the transfer material.
The third aspect of the present invention is a control method for an image forming apparatus of the second means, the higher the transfer current value, wherein the absolute value is higher target value or set value of the background potential And

According to a fourth means of the present invention, in the control method of the image forming apparatus of the first means, the target value or setting value of the background potential of the image carrier is determined by the number of rotations of the image carrier and / or the transfer material. It is variable according to the number of passing sheets.
According to a fifth means of the present invention, in the method for controlling an image forming apparatus according to the fourth means, the target value or set value of the background potential is the one having a larger number of rotations of the image carrier and / or a transfer material. The larger the number of passing sheets, the larger the absolute value of the target value or set value of the background potential.

According to a sixth means of the present invention, in the control method of the image forming apparatus of the fourth or fifth means, if the transfer current that the transfer means passes through the transfer material changes , the target value of the background potential or The set value is changed by a transfer current that the transfer means passes through the transfer material.
Further, according to a seventh means of the present invention, in the method of controlling an image forming apparatus according to any one of the first to sixth means, when setting the target value or setting value of the background potential, the image potential is changed by the image. It is a charging bias of charging means for charging the carrier.

The eighth means of the present invention comprises an image carrier, a charging means for charging the image carrier, a latent image forming means for forming a latent image on the surface of the charged image carrier, and the latent image forming means. Developing means for developing the latent image formed on the image carrier with toner to form a toner image; and transfer means for transferring the toner image formed on the image carrier on the transfer material by the developing means; Is provided with a method for controlling any one of the first to seventh means.

According to a ninth means of the present invention, in the image forming apparatus of the eighth means, the charging means is a charging roller.
According to a tenth means of the present invention, in the image forming apparatus according to the ninth means, the charging roller is disposed in a non-contact manner with respect to the image carrier.
Further, according to an eleventh means of the present invention, in the image forming apparatus according to the ninth or tenth means, an alternating current (AC) voltage is superimposed on the charging roller and applied to the charging roller. .

According to a first reference means of the present invention, in the process cartridge provided in the image forming apparatus of any one of the eighth to eleventh means, at least the image carrier and the charging means are integrated. It is characterized by being.

A second reference unit of the present invention is a toner used in the image forming apparatus of any one of the eighth to eleventh units, and has an average circularity of 0.93 or more.
The third reference means of the present invention is a toner used in the image forming apparatus of any one of the eighth to eleventh means, and has a volume average particle size (Dv) of 3 to 8 μm, The ratio (Dv / Dn) of the volume average particle size (Dv) and the number average particle size (Dn) is in the range of 1.00 to 1.40.
Furthermore, a fourth reference means of the present invention is a toner used in the image forming apparatus of any one of the eighth to eleventh means, and the shape factor SF-1 is in the range of 100 to 180, and the shape factor SF-2 is in the range of 100 to 180.

The fifth reference means of the present invention is a toner used in the image forming apparatus of any one of the eighth to eleventh means, and the ratio of the major axis to the minor axis (r2 / r1) is 0.5. The ratio of thickness to minor axis (r3 / r2) is in the range of 0.7 to 1.0,
Long axis r1 ≧ short axis r2 ≧ thickness r3
It is characterized by satisfying the relationship.
According to a sixth reference means of the present invention, there is provided a toner used in the image forming apparatus according to any one of the eighth to eleventh means, a polyester prepolymer having a functional group containing a nitrogen atom, polyester, coloring A toner composition containing an agent and a release agent is crosslinked and / or elongated in an aqueous medium in the presence of resin fine particles.

In the image forming apparatus according to the present invention, when the target value or setting value of the background potential (background portion charging potential-development bias) of the image carrier is fixed, abnormal images and background stains due to contamination of the charging unit are A difference due to the linear velocity of the image carrier occurs. This is because the actual background potential value differs from the target background potential value depending on the linear velocity. Therefore, the control method of the first means is characterized in that the target value or setting value of the background potential of the image carrier is changed depending on the linear velocity of the image carrier, and the target value or setting value of the background potential is previously determined. By changing according to the linear velocity of the carrier, it is possible to target the actual background potential, reduce abnormal images due to contamination of the charging means and the linear velocity difference between background contamination, and prevent them from occurring be able to.
Also, if the target value or setting value of the background potential is fixed, abnormal images and background contamination due to contamination of the charging means become worse when the linear velocity of the image carrier is higher. Therefore, in the control method of the first means, the absolute value of the target value or set value of the ground skin potential, are characterized by higher in fast linear velocity of the image carrier, the background potential of the linear speed is faster conditions By raising the target value from that under the condition where the linear velocity is low, it is possible to prevent the occurrence of abnormal images or background contamination due to the contamination of the charging means under the condition where the linear velocity is high.

In the image forming apparatus according to the present invention, when the transfer current is increased, the potential of the image carrier after passing through the transfer unit is increased. Therefore, it becomes difficult to recharge the image carrier, the actual background potential is lowered, and abnormal images and background contamination due to contamination of the charging means are likely to occur. Therefore, in the control method of the second means, in the control method of the first means, when the transfer current passed through the transfer material by the transfer means changes , the target value or set value of the background potential of the image carrier is The transfer means changes according to the transfer current that flows through the transfer material, and the target value of the background potential is made variable by the transfer current value, so that abnormal images and dirt due to the dirt of the charging means under each transfer current condition. Can be prevented.
Further, the control method of the third means is characterized in that, in the control method of the second means, the higher the transfer current value is, the higher the absolute value of the target value or set value of the background potential is. By increasing the target value of the background potential under high conditions, it is possible to prevent abnormal images and background contamination due to contamination of the charging means under each transfer current condition.

In the image forming apparatus according to the present invention, an abnormal image is generated over time due to contamination of the charging unit. Therefore, in the control method of the fourth means, in the control method of the first means, the target value or setting value of the background potential of the image carrier can be varied depending on the number of rotations of the image carrier and / or the number of passing of the transfer material. It is characterized by the fact that over time, the target value or setting value of the background potential is raised from the initial stage, so that it is possible to prevent the occurrence of abnormal images and background contamination due to contamination of the charging means.
Further, the control method of the fifth means, the control method of the fourth means, the target value or setpoint for background potential is one with a lot of pass number of the rotation speed there are more and / or the transfer medium of the image carrier However, it is characterized in that the absolute value of the target value or setting value of the background potential increases, and over time, abnormal images and background contamination due to contamination of the charging means can be obtained by increasing the target value or setting value of the background potential from the initial value. Can be prevented.

In the image forming apparatus including the charging unit according to the present invention, abnormal images are generated over time due to contamination. Therefore, in the control method of the fourth or fifth means, a linear velocity of the image bearing member variable can change the target value or set value of the background potential by the linear velocity of the image carrier, in time, the initial In addition, by raising the absolute value of the target value or setting value of the background potential, it is possible to prevent the occurrence of abnormal images and background contamination due to contamination of the charging means.
In addition, the difference in abnormal image or background stain due to the contamination of the charging means occurs depending on the linear velocity of the image carrier, because the actual background potential differs from the target value or set value of the background potential depending on the linear velocity. . Therefore, as described above, the actual background potential can be aimed by changing the target value or setting value of the background potential in advance according to the linear velocity. Therefore, it is possible to reduce the difference due to the linear velocity at the time of the diameter with respect to the abnormal image or the ground stain due to the stain of the charging means, and to prevent the occurrence thereof.

In the image forming apparatus including the charging unit according to the present invention, abnormal images are generated over time due to contamination. Therefore, in the control method of the sixth means, in the control method of the fourth or fifth means, when the transfer current flowing through the transfer material by the transfer means changes, the target value or setting value of the background potential is transferred. It is characterized in that the means changes according to the transfer current that flows through the transfer material, and over time, the target value or setting value of the background potential is raised from the initial stage to prevent the occurrence of abnormal images and background dirt due to the dirt of the charging means. be able to.
In addition, when the transfer current is increased, the image carrier potential after passing through the transfer unit is increased, so that it is difficult to recharge the image carrier, the actual background potential is lowered, and abnormal images due to contamination of the charging unit are reduced. Dirt is likely to occur. Therefore, as described above, the target value or setting value of the background potential is made variable according to the transfer current value, thereby preventing abnormal images and background stains due to contamination of the charging means under each transfer current condition over time. be able to.

In the control method of the seventh means, in setting the target value or setting value of the background potential in the control method of any one of the first to sixth means, the charging means for charging the image carrier is changed. The charging bias is changed when the target value or setting value of the background potential is changed and the developing bias is fixed, so that the toner can be stably developed on the image carrier. .

The image forming apparatus of the eighth means is characterized by including a control method for any one of the first to seventh means, and the same effect as described above can be obtained.
In the image forming apparatus of the ninth means, in the image forming apparatus of the eighth means, since the charging means is a charging roller, generation of ozone can be suppressed, and nitrogen oxide oxide (NOx) or the like can be suppressed. It is possible to reduce the discharge product from adhering to the image carrier.
Further, in the image forming apparatus of the tenth means, in the image forming apparatus of the ninth means, the charging roller is arranged in a non-contact manner with respect to the image carrier, so that the toner adhering to the charging roller and the toner external additive It is possible to make it difficult to adhere foreign matter such as paper dust.
Further, in the image forming apparatus of the eleventh means, in the image forming apparatus of the ninth or tenth means, the charging roller is applied with an alternating current (AC) voltage superimposed on a direct current (DC) voltage, thereby carrying the image. The body surface can be more uniformly charged.

In the process cartridge of the first reference means, at least the image carrier and the charging means are integrated, so that the user can easily replace the image buffing body and the charging means integrally. Exchange is possible, and convenience when exchanging the image carrier and the charging means can be improved.

The toner of the second reference means is characterized in that the average circularity is 0.93 or more, and in the range where the average circularity is 0.93 or more, the surface of the toner particles is smooth, Since the contact area between the toner particles and the image carrier is small, the transferability is excellent and high quality image quality can be obtained. However, toner having a large average circularity is difficult to clean and easily contaminates the charging means. However, if it is used in the image forming apparatus of any one of the eighth to eleventh means, the life of the charging means can be extended.
The toner of the third reference means has a volume average particle size (Dv) of 3 to 8 μm, and a ratio (Dv / Dn) of the volume average particle size (Dv) to the number average particle size (Dn). It is characterized by being in the range of 1.00 to 1.40. By using a small particle size toner, the toner can be densely attached to the latent image. Further, by narrowing the particle size distribution, the toner charge amount distribution becomes uniform, a high-quality image with little background fogging can be obtained, and the transfer rate can be increased. Since the transfer rate is increased, input to the cleaning blade is reduced, so that the life of the cleaning blade can be extended. Further, since the amount of the reversely charged toner can be reduced, contamination of the charging device can be reduced and the life can be extended.

By the way, if the toner shape factors SF-1 and SF-2 are small, the toner easily enters between the cleaning blade and the image carrier, and the cleaning performance is lowered, and the life of the blade, the image carrier, and the charging unit is shortened. On the other hand, if SF-1 and SF-2 are large, the toner is scattered on the image and the image quality is lowered. Therefore, the toner of the fourth reference means is characterized in that the shape factor SF-1 is in the range of 100 to 180 and the shape factor SF-2 is in the range of 100 to 180. By satisfying the above conditions, It is possible to achieve both high image quality and cleanability, and the life of the charging means can be extended.

In the toner of the fifth reference means, the ratio of the major axis to the minor axis (r2 / r1) is in the range of 0.5 to 1.0, and the ratio of the thickness to the minor axis (r3 / r2) is 0. In the range of 7 to 1.0,
Long axis r1 ≧ short axis r2 ≧ thickness r3
This condition is satisfied, and by satisfying the above conditions, it is possible to achieve both high image quality and cleanability, and to extend the life of the charging means.
In the toner of the sixth reference means, a toner composition containing a polyester prepolymer having a functional group containing a nitrogen atom, polyester, a colorant, and a release agent is crosslinked and / or in the presence of resin fine particles in an aqueous medium. The toner is characterized by an elongation reaction, and the toner produced by the polymerization method has the same charge-to-charge mass ratio for each toner particle, so that the transfer efficiency can be increased. Therefore, since the amount of toner input to the cleaning blade on the image carrier is small, the cleaning property is improved, the contamination of the charging unit is reduced, and the life of the charging unit can be extended.

  Hereinafter, the best mode for carrying out the present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a schematic overall configuration diagram of an image forming apparatus showing an embodiment of the present invention, which is an example in which the present invention is applied to a tandem type full color printer. Although FIG. 1 shows an example of a full-color printer, it can also be used as a full-color plotter, and is equipped with an image reading device (scanner) on the upper part of the apparatus main body 1 and an image processing unit in the apparatus main body. By providing it, a full-color copying machine that also serves as a printer can be obtained. Furthermore, by adding a communication function and connecting to a telephone line, optical cable, LAN, etc., it can function as a full-color facsimile or a full-color multifunction peripheral.

  In FIG. 1, in an apparatus main body 1, photosensitive body units 2A, 2B, 2C and 2D, which are four image carrier units, are detachably attached to the apparatus main body 1, respectively. In the center of the apparatus main body 1, a transfer unit in which the transfer belt 3 is rotatably mounted in a direction indicated by an arrow A between a plurality of rollers is disposed. Inside the transfer belt 3, four transfer brushes 57 are provided corresponding to the four image carriers (photosensitive members) 5, respectively. The photoconductor 5 provided in each of the photoconductor units 2A, 2B, 2C, and 2D is arranged so as to contact the upper surface of the transfer belt 3. In correspondence with the photoreceptor units 2A to 2D, developing devices 10A to 10D having different toner colors are arranged.

  The developing devices 10A to 10D have the same configuration, and are two-component developing type developing devices that differ only in the color of the toner used. The developing device 10A uses magenta (M) toner, the developing device 10B uses cyan (C) toner, the developing device 10C uses yellow (Y) toner, and the developing device 10D. Respectively use black (Bk) toner. In each color developing device, a two-component developer composed of toner and carrier is contained.

  Each of the developing devices 10A to 10D includes a developing roller that faces the photoreceptor 5, a screw that conveys and stirs the developer, a toner concentration sensor, and the like. The developing roller is composed of an outer rotatable sleeve and a plurality of magnets (or a magnet roller magnetized with a plurality of magnetic poles) fixed inside the sleeve. Further, toner is supplied from a toner supply device (not shown) according to the output of the toner density sensor.

  An optical writing unit 6 that is a latent image forming unit is disposed above the photoreceptor units 2A to 2D, and a duplex unit 7 is disposed below the transfer belt 3. This printer is equipped with a reversing unit 8 on the left side of the apparatus main body, which reverses and discharges the transfer paper P after image formation, or transports it to a duplex unit.

  The optical writing unit 6 includes four laser diode (LD) light sources prepared for each color and a first optical system (a beam shaping optical system including a coupling lens, an aperture, a cylindrical lens, etc.) A pair of polygon scanners (for example, six faces) and a polygon motor composed of a polygon motor, and a second optical system (fθ lens, long barrel-type toroidal lens (arranged from the polygon scanner to each photoconductor) ( WTL) and other optical systems for scanning and imaging composed of lenses and mirrors. The laser light emitted from each light source (laser diode) is shaped by the first optical system, then deflected and scanned by the polygon scanner, and is condensed into a minute spot light by the second optical system and is applied to each photoconductor. Irradiated.

  The duplex unit 7 includes a pair of conveyance guide plates 45a and 45b and a pair of (four sets in this example) conveyance rollers 46. In the double-sided image formation mode in which images are formed on both sides of the transfer paper P, Then, the transfer paper P on which an image is formed on one side and conveyed to the reversal conveyance path 54 of the reversing unit 8 and switched back is received, and conveyed to the paper feeding unit.

  The reversing unit 8 includes a plurality of paired transport rollers and a plurality of paired transport guide plates. As described above, the reversing unit 8 reverses the transfer paper P when double-sided image formation is carried out to the double-sided unit 7. The transfer paper P after image formation is discharged out of the machine in the same orientation, or the paper is reversed outside and turned out of the machine. Separating paper feeding units 55 and 56 for separating and feeding the transfer paper P one by one are provided in the paper feeding unit provided with the paper feeding cassettes 11 and 12, respectively.

  A fixing device 9 is provided between the transfer belt 3 and the reversing unit 8 to fix the image on the transfer paper P onto which the image has been transferred. A reverse paper discharge path 20 is branched and formed on the downstream side of the fixing device 9 in the transfer paper conveyance direction, and the transfer paper P conveyed there can be discharged onto a paper discharge tray 26 by a pair of paper discharge rollers 25. Yes.

  In the lower part of the apparatus main body 1, paper feed cassettes 11 and 12 that can store transfer papers P of different sizes are arranged in two upper and lower stages. Further, a manual feed tray 13 is provided on the right side surface of the apparatus main body 1 so as to be openable and closable in the direction indicated by the arrow B, and the manual feed tray 13 is opened so that manual feeding can be performed therefrom.

  The photoconductor units 2A to 2D are units having the same configuration, the photoconductor unit 2A forms an image corresponding to magenta (M) color, and the photoconductor unit 2B displays an image corresponding to cyan (C) color. The photoconductor unit 2C forms an image corresponding to the yellow (Y) color, and the photoconductor unit 2D forms an image corresponding to the black (Bk) color.

Next, the operation of the image forming apparatus (color printer) configured as shown in FIG. 1 will be described.
First, the operation of the image forming apparatus during full color image formation will be described. When this image forming apparatus receives full-color image data, each photoconductor 5 rotates in the clockwise direction in FIG. The surface of each photoconductor 5 is uniformly charged by the charging roller. The photoconductor unit 2A receives laser light corresponding to a magenta image by the optical writing unit 6, and the photoconductor unit 2B receives laser light corresponding to a cyan image from the photoconductor unit 2C. A laser beam corresponding to a yellow image is irradiated onto the photoconductor of the photoconductor, and a laser beam corresponding to a black image is irradiated onto the photoconductor of the photoconductor unit 2D, thereby forming a latent image corresponding to the image data of each color. Is done. Each latent image reaches the position of the developing devices 10A, 10B, 10C, and 10D by the rotation of the photosensitive member 5, where it is developed with magenta, cyan, yellow, and black toners, and a four-color toner image is obtained. Become.

  On the other hand, the transfer paper P is fed from the paper feed cassette 11 or 12 by the separation paper feeding unit 55 or 56, and is formed on each photoconductor by the registration roller pair 59 provided immediately before the transfer belt 3. The toner image is conveyed at a timing coincident with the toner image. The transfer paper P is charged to a positive polarity by a paper suction roller 58 disposed in the vicinity of the entrance of the transfer belt 3, and thereby electrostatically attracted to the surface of the transfer belt 3. Then, while the transfer paper P is conveyed while adsorbed to the transfer belt 3, magenta, cyan, yellow, and black toner images are sequentially transferred to form a four-color superimposed full-color toner image. The

  The transfer paper P on which the full-color toner image is formed (transferred) is melted and fixed by applying heat and pressure by the fixing device 9, and then passes through the paper discharge system corresponding to the designated mode. When the paper is reversed and discharged to the paper discharge tray 26 at the upper part of the apparatus main body, straightly passes from the fixing device 9 and passes straight through the reversing unit 8, or the double-sided image forming mode is selected. In the image forming section in which the photosensitive member units 2A to 2D are provided after being fed into the reversing conveyance path 54 in the reversing unit 8 and then switched back and conveyed to the duplex unit 7, and re-feeded therefrom. In the same manner as described above, the image is discharged after the image is formed on the back surface. Thereafter, when two or more image formations are instructed, the above-described image forming process is repeated.

  Next, the operation of the image forming apparatus when forming a monochrome image will be described. When the image forming apparatus receives black and white image data, the driven roller supporting the transfer belt 3 moves downward so as to face the paper suction roller 58, and the transfer belt is separated from the magenta, cyan, and yellow photoconductors. To do. The black photoconductor rotates clockwise in FIG. 1, and the surface of the black photoconductor is uniformly charged by the charging roller. Further, the photoreceptor of the photoreceptor unit 2D is irradiated with laser light corresponding to the black image to form a latent image. When the latent image reaches the position of the developing device 10D, the latent image is developed with black toner to become a toner image. At this time, the image forming units for the three colors other than black are stopped, and unnecessary wear is prevented.

  On the other hand, the transfer paper P is fed from the paper feed cassette 11 or 12 by the separation paper feed unit 55 or 56, and is formed on the black photosensitive member by the registration roller pair 59 provided immediately before the transfer belt 3. The toner image is conveyed at a timing coincident with the toner image. The transfer paper P is charged by a paper suction roller 58 disposed near the entrance of the transfer belt 3, and thereby electrostatically attracted to the surface of the transfer belt 3. Since the transfer paper P is conveyed while adsorbed to the transfer belt 3, even if the transfer belt 3 is separated from the magenta, cyan, and yellow photoconductors, the transfer paper P is conveyed to the black photoconductor and the black toner image. Is transcribed. In order to stably transfer and transfer the transfer paper P, the transfer belt 3 needs to be made of a material having at least a surface layer having a high resistance. The transfer paper P is fixed by the fixing device 9 as in the case of a full-color image, and processed through a paper discharge system corresponding to the designated mode. Thereafter, when two or more image formations are instructed, the above-described image forming process is repeated.

  As a material of the transfer belt 3, a resin material such as polyvinylidene fluoride, polyimide, polycarbonate, polyethylene terephthalate, etc. can be molded into a seamless belt and used. These materials can be used as they are, or the resistance can be adjusted with a conductive material such as carbon black. Further, using these resins as a base layer, a surface layer may be formed by a method such as spraying or dipping to form a laminated structure.

Next, FIG. 2 is a cross-sectional view showing a configuration example of a photosensitive unit (process cartridge) provided in the image forming apparatus (full color printer) shown in FIG. As shown in FIG. 2, the photoreceptor units 2A to 2D include a charging roller 17, a photoreceptor 5 on which an electrostatic latent image is formed, a brush roller 15 that cleans the surface of the photoreceptor 5, a cleaning blade 47, The flicker device 19 for blowing off the toner on the brush roller 15 and a solid lubricant 16 are included. A charging cleaning roller 49 for cleaning the roller surface is in contact with the charging roller 17. The brush roller 15 rotates and holds toner scraped off by the cleaning blade 47 and is moved to the toner transport auger 48 side by the flicker device 19 to rotate the toner transport auger 48. The waste toner collected in this way is conveyed to the waste toner storage unit 18 shown in FIG. In this embodiment, the diameter of the photoconductor 5 is 30 mm, and each photoconductor rotates in the direction of arrow C at a linear velocity of 162 mm / sec.
The brush roller 15 is disposed so as to face the photoconductor 5, is scraped off by the cleaning blade 47, discharges the toner accumulated in the portion E to the toner transport auger 48, and scrapes the solid lubricant 16 to remove the photoconductor 5. It has the function to apply to.

  The charging roller 17 serves to charge the photoconductor 5 so as to face the photoconductor 5. The charging roller 17 is in pressure contact with the surface of the photosensitive member 5 via the gap management member 14, and the charging roller 17 opens a minute gap G (gap) from the surface of the photosensitive member 5. Located in a non-contact state. A metal such as stainless steel is used for the core of the charging roller 17. If the mandrel is too thin, the influence of the deflection when the charging roller 17 is cut or when the photosensitive member 5 is pressed cannot be ignored, and it is difficult to obtain the required gap accuracy. Further, when the core bar is too thick, there is a problem that the charging roller 17 becomes large or the mass becomes heavy. Therefore, the diameter of the core bar is preferably about 6 to 10 mm.

The charging roller 17 is preferably made of a material having a volume resistance of 10 ⁴ to 10 ⁹ Ωcm. If the resistance is too low, charging bias leaks easily when the photoreceptor 5 has defects such as pinholes. If the resistance is too high, the discharge is not sufficiently generated and a uniform charging potential cannot be obtained.
The charging roller 17 is connected to a power source (not shown), and a predetermined voltage is applied. The voltage may be only a direct current (DC) voltage, but is preferably a voltage obtained by superimposing an alternating current (AC) voltage on a DC voltage. By applying an AC voltage, the surface of the photoreceptor 5 can be more uniformly charged.

  The charging roller 17 becomes dirty over time due to foreign matters such as toner, external additives, and paper dust that have passed through the cleaning blade 47. Therefore, a charging cleaning roller 49 is disposed above the charging roller 17 as a member for cleaning the charging roller 17. The electrifying cleaning roller 49 is formed by bonding a roller made of an insulating sponge material called melamine foam to a core metal having a diameter of 5 mm. The charging cleaning roller 49 is rotatably in contact with the charging roller 17 only by its own weight, and cleans the surface of the charging roller 17 while rotating in the accompanying direction as the charging roller 17 rotates.

However, the cleaning capability of the charging cleaning roller 49 is limited. In the following, a specific control method for preventing abnormal images due to charging roller contamination over time in the present embodiment will be described.
At a position corresponding to a normal image area portion, the charging roller 17 charges the photosensitive member 5 so that the potential of the photosensitive member 5 becomes a value VD determined by a control value. Then, the optical writing unit 6 irradiates the photosensitive member 5 with the writing light modulated and controlled in accordance with the image signal, and the photosensitive member potential is attenuated to VL in the portion with the strongest light amount. In the developing device, a developing bias of VB is applied to the developing roller (developing sleeve). As a result, the electrostatic latent image formed on the photosensitive member 5 is negative / positive (N / P) by the potential (potential difference) between the developing bias and the photosensitive member latent image potential by the negatively charged toner in the developing device. ) Developed and visualized.

  Here, the difference (120 V in absolute value) between the charging potential VD and the developing bias VB of the photoconductor 5 is defined as a background potential, and this background potential electrostatically makes it difficult for toner to adhere to the photoconductor. However, when the photosensitive member 5 has a plurality of photosensitive member linear velocities and the target value (target value) of the background potential (or the value set in advance as the target (setting value)) is constant, The charged potential of the photosensitive member 5 varies depending on the linear velocity, and the faster the linear velocity, the lower the charged potential and the lower the background potential. This is because the higher the linear velocity of the photosensitive member 5 is, the lower the charging response of the photosensitive member 5 and the lower the charging potential. When the background potential is low, vertical black streaks are generated due to uneven charging due to contamination of the charging roller 17, or background toner adheres to the photoreceptor. Therefore, by changing the target value (or set value) of the background potential for each linear velocity of the photoconductor 5, it is possible to prevent abnormal images due to background contamination or contamination of the charging roller 17 under conditions where the linear velocity is high.

  Table 1 below shows the target value (or set value) of the background potential. At this time, the charged potential is changed. An abnormal image due to contamination of the charging roller 17 when 90,000 sheets are passed under the condition in which the target value (or set value) of the background potential is made constant at 120 V as an absolute value regardless of the conditions and linear velocity in Table 1. The background level is shown in Tables 2 and 3 below (in Tables 2 and 3, “K sheets” means “thousand sheets” and 90K sheets = 90,000 sheets) The same applies to 4, 5). When the target value (or set value) of the background potential is constant (120 V) regardless of the linear speed, as shown in Table 2, before the 90,000 sheets are passed, An abnormal image occurred (Δ in Table 2: partially abnormal image, ×: abnormal image). On the other hand, under the conditions in Table 1, as shown in Table 3, an abnormal image due to contamination of the charging roller 17 did not occur even after passing 90,000 sheets (◯: no abnormal image).

  Here, the background potential is changed by the linear velocity of the photoconductor 5, but the background potential may be changed by a transfer current. As the transfer current increases, the surface potential of the photoconductor 5 after transfer increases, and it becomes difficult for the charging roller 17 to recharge the photoconductor 5. Therefore, the actual background potential is lowered, and abnormal images and background contamination due to contamination of the charging roller 17 are likely to occur. Therefore, the higher the transfer current, the higher the target value (or set value) of the background potential.

  On the other hand, when the background potential is increased, carrier adhesion to the photoreceptor 5 increases. Therefore, it is not preferable to raise the background potential more than necessary. Therefore, by increasing the background potential in stages over time when the charging roller 17 becomes dirty, it is possible to prevent abnormal images due to the charging roller 17 from being stained while minimizing carrier adhesion. Table 4 below shows the conditions for gradually increasing the target value (or set value) of the background potential over time, and Table 5 below shows abnormal images due to contamination of the charging roller 17 when 90,000 sheets are passed under the conditions at that time. The effect of the present invention is shown by indicating the level of.

The photoreceptor 5 is an organic photoreceptor in which an undercoat layer, a charge generation layer mainly composed of a charge generation material, and a charge transport layer mainly composed of a charge transport material are laminated on a conductive support. (OPC).
As the conductive support, a conductive support having a volume resistance of 10 ⁴ Ωcm or less, for example, a metal tube such as aluminum or stainless steel, or a metal such as nickel processed into an endless belt is used.

  In general, the undercoat layer is mainly composed of a resin. However, considering that the photosensitive layer is applied using a solvent, the resin is a resin having high resistance to general organic solvents. Is desirable. Examples of such resins include water-soluble resins such as polyvinyl alcohol, alcohol-soluble resins such as copolymer nylon, and curable resins that form a three-dimensional network structure such as polyurethane, alkyd-melamine, and epoxy. Further, a fine powder of metal oxide such as titanium oxide, silica, or alumina may be added to the undercoat layer in order to prevent moire and reduce residual potential. This undercoat layer can be formed using an appropriate solvent and coating method. The thickness of the undercoat layer is suitably from 0 to 5 μm.

  The charge generation layer is a layer mainly composed of a charge generation material, and representative examples include a monoazo pigment, a disazo pigment, a trisazo pigment, and a phthalocyanine pigment. These charge generation materials can be formed by dispersing together with a binder resin such as polycarbonate using a solvent such as tetrahydrofuran or cyclohexanone and applying a dispersion. Application is performed by dip coating, spray coating, or the like. The thickness of the charge generation layer is usually 0.01 to 5 μm.

  The charge transport layer can be formed by dissolving or dispersing the charge transport material and the binder resin in a suitable solvent such as tetrahydrofuran, toluene, dichloroethane, and applying and drying the solution. Among charge transport materials, low molecular charge transport materials include electron transport materials and hole transport materials. Examples of the electron transport material include chloroanil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 1, Examples include electron-accepting substances such as 3,7-trinitrodibenzothiophene-5,5-dioxide. Examples of hole transport materials include oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, phenylhydrazones, α-phenylstilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, thiophene derivatives, etc. These electron donating substances are listed. The binder resin used in the charge transport layer together with the charge transport material is thermoplastic such as polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, polyester, polyarylate, polycarbonate, acrylic, epoxy, melamine, phenol, etc. Or a thermosetting resin is mentioned. The thickness of the charge transport layer may be appropriately selected in the range of 5 to 30 μm according to desired photoreceptor characteristics.

  Further, a protective layer can be formed on the surface of the photoreceptor for the purpose of protecting the photosensitive layer and improving durability. As a constitution of the protective layer, mechanical durability can be improved by dispersing a filler in a binder resin. The amount of the filler added to the protective layer is 10 to 70 parts by weight, preferably 20 to 50 parts by weight with respect to 100 parts by weight of the binder resin. When the amount of the filler is less than 10 parts by weight, the wear is large and the durability is inferior. As the filler added to the protective layer, fine powders of metal oxides such as titanium oxide, silica, and alumina can be used. When the particle size of the filler is too large, the exposure light is scattered by the protective layer, so that the resolution is lowered and the image quality is inferior. Moreover, when the particle size of a filler is too small, it is inferior to abrasion resistance. Therefore, the particle size of the filler added to the protective layer is suitably 0.1 to 0.8 μm. The protective layer can be formed by dispersing filler and binder resin using a suitable solvent and applying the dispersion by spray coating. The binder resin used for the protective layer, the solvent can be the same material as the charge transport layer, and as the binder resin, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, polyester, polyarylate, There are thermoplastic or thermosetting resins such as polycarbonate, acrylic, epoxy, melamine, and phenol, and tetrahydrofuran, toluene, dichloroethane, and the like can be used as the solvent. The thickness of the protective layer is preferably 3 to 10 μm in order to improve the durability and not impair the electrostatic characteristics of the photosensitive layer. Furthermore, a charge transport material, an antioxidant, or the like can be added to the protective layer.

The charging device (charging roller 17 and charging cleaning roller 49) and the photosensitive member 5 that operate using the control method of the image forming apparatus of the present invention described above are integrally supported in one unit, and the image forming apparatus main body. 1 can be a process cartridge formed detachably. For example, the photosensitive unit 2A to 2D having the configuration shown in FIG. 2 is an example of the process cartridge. The photosensitive unit 5, the charging roller 17, the charging cleaning roller 49, and cleaning means (brush roller 15, cleaning blade 47, flicker). The device 19, the solid lubricant 16 and the like are integrally supported in one unit. In addition, the process cartridge may include a developing unit.
Even in an image forming process in which development using a toner having a high circularity and a small particle diameter is performed by this process cartridge, the image quality is deteriorated by preventing abnormal images due to contamination of the charging roller 17. The number of process cartridges can be reduced, which leads to an improvement in process cartridge life and user maintenance.

Next, a toner suitably used in the image forming apparatus of the present invention will be described. The toner according to the reference example of the present invention preferably has an average circularity of 0.93 to 1.00. In the present invention, the value obtained from the following formula (1) is defined as circularity.
Circularity a = L ₀ / L (1)
(However, L ₀ indicates the perimeter of a circle having the same projected area as the particle image, and L indicates the perimeter of the projected image of the particle.)
The circularity a is an index of the degree of unevenness of the toner particles, and indicates 1.00 when the toner is perfectly spherical, and the circularity a becomes smaller as the surface shape becomes more complicated.

When the average circularity is in the range of 0.93 to 1.00, the surface of the toner particles is smooth, and the contact area between the toner particles and between the toner particles and the photoreceptor 5 is small, so that the transferability is excellent.
On the other hand, toner with a high degree of circularity enters the gap between the photosensitive member 5 and the cleaning blade 47 in the blade type cleaning, and is easily slipped through. However, an abnormal image due to the contamination of the charging roller 17 can be suppressed by preventing the background contamination by the control method of the present invention.

  The volume average particle diameter (Dv) of the toner is 3 to 8 μm, and the ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) is 1.00 to 1.40. Good cleaning properties can also be obtained by using a toner having a small particle size and a narrow particle size distribution in the range. By narrowing the particle size distribution of the toner, the charge distribution becomes uniform, a high-quality image with little background fogging can be obtained, and the transfer rate can be increased. Such toners having a small particle diameter tend to have a relatively high content of external additive fine particles and the like, so that they are easily detached from the toner and slip through the cleaning blade 47. However, an abnormal image due to the contamination of the charging roller 17 can be suppressed by preventing the background contamination by the control method of the present invention.

The toner shape factor SF-1 is preferably in the range of 100 to 180, and the shape factor SF-2 is preferably in the range of 100 to 180. The shape factor SF-1 indicates the ratio of the roundness of the toner shape, and is represented by the following formula (2). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting toner onto a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (2)
When the value of SF-1 is 100, the shape of the toner is a true sphere, and becomes larger as the value of SF-1 increases.

The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (3). This is a value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner onto the two-dimensional plane by the figure area AREA and multiplying by 100 / 4π.
SF-2 = {(PERI) ² / AREA} × (100 / 4π) (3)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.

Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated.
When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photosensitive member becomes a point contact, so that the adsorbing force between the toners becomes weak, and thus the fluidity becomes high. The attracting power with the body also becomes weaker, and the transfer rate becomes higher. On the other hand, spherical toner tends to slip through the cleaning blade 47. However, an abnormal image due to the contamination of the charging roller 17 can be suppressed by preventing the background contamination by the control method of the present invention.
Note that if any of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate decreases, which is not preferable.

The toner according to the reference example of the present invention has a substantially spherical shape, and can be represented by the following shape rule.
When a substantially spherical toner is defined by a major axis r1, a minor axis r2, and a thickness r3 (where r1 ≧ r2 ≧ r3), the toner of the present invention has a ratio of the major axis to the minor axis (r2). / R1) is preferably 0.5 to 1.0 and the ratio of thickness to minor axis (r3 / r2) is preferably in the range of 0.7 to 1.0. When the ratio of the major axis to the minor axis (r2 / r1) is less than 0.5, the dot reproducibility and transfer efficiency are inferior because of being away from the true spherical shape, and high-quality image quality cannot be obtained. On the other hand, if the ratio of thickness to minor axis (r3 / r2) is less than 0.7, the shape is close to a flat shape, and a high transfer rate like a spherical toner cannot be obtained. In particular, when the ratio of the thickness to the minor axis (r3 / r2) is 1.0, the rotating body has a major axis as a rotation axis, and the fluidity of the toner can be improved.
In addition, r1, r2, r3 can be measured by the following method, for example. That is, the toner is uniformly dispersed and adhered on a smooth measurement surface, and 100 particles of the toner are magnified 500 times by a color laser microscope “VK-8500” (manufactured by Keyence Corporation). The major axis r1 (μm), the minor axis r2 (μm), and the thickness r3 (μm) of the particles can be measured and obtained from their arithmetic average values.

  The toner suitably used in the image forming apparatus of the present invention includes a toner material liquid in which at least a polyester prepolymer having a functional group containing a nitrogen atom, a polyester, a colorant, and a release agent are dispersed in an organic solvent. A toner obtained by crosslinking and / or elongation reaction in an aqueous solvent. Hereinafter, the constituent material and the manufacturing method of the toner will be described.

(polyester)
The polyester is obtained by a polycondensation reaction between a polyhydric alcohol compound and a polycarboxylic acid compound.
Examples of the polyhydric alcohol compound (PO) include dihydric alcohol (DIO) and trihydric or higher polyhydric alcohol (TO). (DIO) alone or a mixture of (DIO) and a small amount of (TO) preferable. Examples of the dihydric alcohol (DIO) include alkylene glycol (ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.); alkylene ether glycol (diethylene glycol) , Triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, etc.); alicyclic diols (1,4-cyclohexanedimethanol, hydrogenated bisphenol A, etc.); bisphenols (bisphenol A, bisphenol) F, bisphenol S, etc.); alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) adduct of the above alicyclic diol; Alkylene oxide bisphenol (ethylene oxide, propylene oxide, butylene oxide, etc.), etc. adducts. Among them, preferred are alkylene glycols having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols, and particularly preferred are alkylene oxide adducts of bisphenols and alkylene glycols having 2 to 12 carbon atoms. It is a combined use. The trihydric or higher polyhydric alcohol (TO) includes 3 to 8 or higher polyhydric aliphatic alcohols (glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, etc.); trihydric or higher phenols (Trisphenol PA, phenol novolak, cresol novolak, etc.); and alkylene oxide adducts of the above trivalent or higher polyphenols.

Examples of the polyvalent carboxylic acid (PC) include divalent carboxylic acid (DIC) and trivalent or higher polyvalent carboxylic acid (TC). (DIC) alone and (DIC) with a small amount of (TC) Mixtures are preferred.
Divalent carboxylic acids (DIC) include alkylene dicarboxylic acids (succinic acid, adipic acid, sebacic acid, etc.); alkenylene dicarboxylic acids (maleic acid, fumaric acid, etc.); aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid) And naphthalenedicarboxylic acid). Of these, preferred are alkenylene dicarboxylic acids having 4 to 20 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms. Examples of the trivalent or higher polyvalent carboxylic acid (TC) include aromatic polycarboxylic acids having 9 to 20 carbon atoms (such as trimellitic acid and pyromellitic acid). In addition, as polyhydric carboxylic acid (PC), you may make it react with polyhydric alcohol (PO) using the above-mentioned acid anhydride or lower alkyl ester (Methyl ester, ethyl ester, isopropyl ester, etc.).

The ratio of the polyhydric alcohol (PO) to the polycarboxylic acid (PC) is usually 2/1 to 1/1, preferably as the equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] and the carboxyl group [COOH]. Is 1.5 / 1 to 1/1, more preferably 1.3 / 1 to 1.02 / 1.
The polycondensation reaction between polyhydric alcohol (PO) and polycarboxylic acid (PC) is heated to 150 to 280 ° C. in the presence of a known esterification catalyst such as tetrabutoxytitanate or dibutyltin oxide, and the pressure is reduced as necessary. The produced water is distilled off to obtain a polyester having a hydroxyl group. The hydroxyl value of the polyester is preferably 5 or more, and the acid value of the polyester is usually 1 to 30, preferably 5 to 20. By giving the acid value, it tends to be negatively charged, and when fixing to the transfer paper P, the affinity between the transfer paper P and the toner is good and the low-temperature fixability is improved. However, when the acid value exceeds 30, there is a tendency to deteriorate with respect to the stability of charging, particularly environmental fluctuation.
The weight average molecular weight is 10,000 to 400,000, preferably 20,000 to 200,000. A weight average molecular weight of less than 10,000 is not preferable because offset resistance deteriorates. On the other hand, if it exceeds 400,000, the low-temperature fixability is deteriorated.

  In addition to the unmodified polyester obtained by the above polycondensation reaction, the polyester preferably contains a urea-modified polyester. The urea-modified polyester is obtained by reacting a terminal carboxyl group or hydroxyl group of the polyester obtained by the above polycondensation reaction with a polyvalent isocyanate compound (PIC) to obtain a polyester prepolymer (A) having an isocyanate group. It is obtained by cross-linking and / or extending the molecular chain by the reaction of the amine with amines.

  Examples of the polyvalent isocyanate compound (PIC) include aliphatic polyisocyanates (tetramethylene diisocyanate, hexamethylene diisocyanate, 2,6-diisocyanatomethylcaproate, etc.); alicyclic polyisocyanates (isophorone diisocyanate, cyclohexylmethane diisocyanate, etc.) ); Aromatic diisocyanates (tolylene diisocyanate, diphenylmethane diisocyanate, etc.); araliphatic diisocyanates (α, α, α ′, α′-tetramethylxylylene diisocyanate, etc.); isocyanates; Those blocked with caprolactam or the like; and combinations of two or more of these.

  The ratio of the polyvalent isocyanate compound (PIC) is usually 5/1 to 1/1, preferably as an equivalent ratio [NCO] / [OH] of the isocyanate group [NCO] and the hydroxyl group [OH] of the polyester having a hydroxyl group. 4/1 to 1.2 / 1, more preferably 2.5 / 1 to 1.5 / 1. When [NCO] / [OH] exceeds 5, low-temperature fixability deteriorates. When the molar ratio of [NCO] is less than 1, when a urea-modified polyester is used, the urea content in the ester is lowered and hot offset resistance is deteriorated.

The content of the polyvalent isocyanate compound (PIC) component in the polyester prepolymer (A) having an isocyanate group is usually 0.5 to 40 wt%, preferably 1 to 30 wt%, more preferably 2 to 20 wt%. . If it is less than 0.5 wt%, the hot offset resistance deteriorates, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability. On the other hand, if it exceeds 40 wt%, the low-temperature fixability deteriorates.
The number of isocyanate groups contained per molecule in the polyester prepolymer (A) having an isocyanate group is usually 1 or more, preferably 1.5 to 3 on average, more preferably 1.8 to 2 on average. Five. If it is less than 1 per molecule, the molecular weight of the urea-modified polyester will be low, and the hot offset resistance will deteriorate.

  Next, as amines (B) to be reacted with the polyester prepolymer (A), a divalent amine compound (B1), a trivalent or higher polyvalent amine compound (B2), an amino alcohol (B3), an amino mercaptan (B4) ), Amino acid (B5), and amino acid block of B1 to B5 (B6).

  Examples of the divalent amine compound (B1) include aromatic diamines (phenylenediamine, diethyltoluenediamine, 4,4′-diaminodiphenylmethane, etc.); alicyclic diamines (4,4′-diamino-3,3′-dimethyldicyclohexyl). Methane, diamine cyclohexane, isophorone diamine, etc.); and aliphatic diamines (ethylene diamine, tetramethylene diamine, hexamethylene diamine, etc.) and the like.

Examples of the trivalent or higher polyvalent amine compound (B2) include diethylenetriamine and triethylenetetramine. Examples of amino alcohol (B3) include ethanolamine and hydroxyethylaniline. Examples of amino mercaptan (B4) include aminoethyl mercaptan and aminopropyl mercaptan.
Examples of the amino acid (B5) include aminopropionic acid and aminocaproic acid. Examples of the compound (B6) obtained by blocking the amino group of B1 to B5 include ketimine compounds and oxazolidine compounds obtained from the amines of B1 to B5 and ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). Among these amines (B), preferred are B1 and a mixture of B1 and a small amount of B2.

The ratio of amines (B) is equivalent to the equivalent ratio [NCO] / [NHx] of isocyanate groups [NCO] in the polyester prepolymer (A) having isocyanate groups and amino groups [NHx] in amines (B). Is usually 1/2 to 2/1, preferably 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 1 / 1.2.
When [NCO] / [NHx] is more than 2 or less than 1/2, the molecular weight of the urea-modified polyester is lowered, and the hot offset resistance is deteriorated.
The urea-modified polyester may contain a urethane bond together with a urea bond. The molar ratio of the urea bond content to the urethane bond content is usually 100/0 to 10/90, preferably 80/20 to 20/80, and more preferably 60/40 to 30/70. When the molar ratio of the urea bond is less than 10%, the hot offset resistance is deteriorated.

  The urea-modified polyester is produced by a one-shot method or the like. Water produced by heating polyhydric alcohol (PO) and polyhydric carboxylic acid (PC) to 150 to 280 ° C. in the presence of a known esterification catalyst such as tetrabutoxy titanate or dibutyltin oxide, and if necessary, reducing the pressure. Is distilled off to obtain a polyester having a hydroxyl group. Subsequently, at 40-140 degreeC, this is made to react with polyvalent isocyanate (PIC), and the polyester prepolymer (A) which has an isocyanate group is obtained. Further, this (A) is reacted with amines (B) at 0 to 140 ° C. to obtain a urea-modified polyester.

When reacting (PIC) and when reacting (A) and (B), a solvent may be used if 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 isocyanates (PIC), such as tetrahydrofuran (such as tetrahydrofuran).
In addition, in the crosslinking and / or extension reaction between the polyester prepolymer (A) and the amines (B), a reaction terminator can be used as necessary to adjust the molecular weight of the resulting urea-modified polyester. Examples of the reaction terminator include monoamines (diethylamine, dibutylamine, butylamine, laurylamine, etc.), and those obtained by blocking them (ketimine compounds).

  The weight average molecular weight of the urea-modified polyester is usually 10,000 or more, preferably 20,000 to 10,000,000, and more preferably 30,000 to 1,000,000. If it is less than 10,000, the hot offset resistance deteriorates. The number average molecular weight of the urea-modified polyester or the like is not particularly limited when the above-mentioned unmodified polyester is used, and may be a number average molecular weight that can be easily obtained to obtain the weight average molecular weight. When the urea-modified polyester is used alone, its number average molecular weight is usually 2000-15000, preferably 2000-10000, more preferably 2000-8000. When it exceeds 20000, the low-temperature fixability and the glossiness when used in a full-color apparatus are deteriorated.

By using unmodified polyester and urea-modified polyester in combination, low-temperature fixability and gloss when used in the image forming apparatus (full-color printer) of FIG. 1 are improved, so that urea-modified polyester is used alone. preferable. The unmodified polyester may include a polyester modified with a chemical bond other than a urea bond.
The unmodified polyester and the urea-modified polyester are preferably at least partially compatible with each other in terms of low-temperature fixability and hot offset resistance. Therefore, it is preferable that the unmodified polyester and the urea-modified polyester have a similar composition.

  The weight ratio of unmodified polyester to urea-modified polyester is usually 20/80 to 95/5, preferably 70/30 to 95/5, more preferably 75/25 to 95/5, and particularly preferably 80 /. 20-93 / 7. When the weight ratio of the urea-modified polyester is less than 5%, the hot offset resistance is deteriorated, and it is disadvantageous in terms of both heat-resistant storage stability and low-temperature fixability.

The glass transition point (Tg) of the binder resin containing unmodified polyester and urea-modified polyester is usually 45 to 65 ° C, preferably 45 to 60 ° C. If it is less than 45 ° C., the heat resistance of the toner deteriorates, and if it exceeds 65 ° C., the low-temperature fixability becomes insufficient.
In addition, since the urea-modified polyester is likely to be present on the surface of the obtained toner base particles, the heat-resistant storage stability tends to be good even when the glass transition point is low as compared with known polyester-based toners.

(Coloring agent)
As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher , Yellow lead, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR, A, RN, R), pigment yellow L, benzidine yellow (G, GR), permanent yellow (NCG), Vulcan fast yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Dan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Phi Sayred, Parachlor Ortonito Aniline Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine B, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R , Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thio Indigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red Polyazo Red, Chrome Vermillion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Lid Russian nin green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The content of the colorant is usually 1 to 15% by weight, preferably 3 to 10% by weight, based on the toner.

  The colorant can also be used as a master batch combined with a resin. As a binder resin to be kneaded together with the production of the master batch or the master batch, a polymer of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyl toluene or the like, or a copolymer of these and a vinyl compound, Polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, fat Aromatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes and the like can be mentioned, and these can be used alone or in combination.

(Charge control agent)
Known charge control agents can be used, such as nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine-modified 4 Secondary ammonium salts or compounds, tungsten simple substances or compounds, fluorine activators, salicylic acid metal salts, and metal salts of salicylic acid derivatives. Specifically, Bontron 03 of a nigrosine dye, Bontron P-51 of a quaternary ammonium salt, Bontron S-34 of a metal-containing azo dye, E-82 of an oxynaphthoic acid metal complex, E-84 of a salicylic acid metal complex , Phenolic condensate E-89 (above, Orient Chemical Industries, Ltd.), quaternary ammonium salt molybdenum complex TP-302, TP-415 (above, Hodogaya Chemical Co., Ltd.), quaternary ammonium salt copy Charge PSY VP2038, copy blue PR of triphenylmethane derivative, copy charge of quaternary ammonium salt NEG VP2036, copy charge NX VP434 (manufactured by Hoechst), LRA-901, LR-147 which is a boron complex (Nippon Carlit) Manufactured), copper phthalocyanine, perylene, quinacridone, azo series Fee, a sulfonic acid group, a carboxyl group, and polymer compounds having a functional group such as quaternary ammonium salts. Of these, substances that control the negative polarity of the toner are particularly preferably used.

  The amount of charge control agent used is determined by the type of binder resin, the presence or absence of additives used as necessary, and the toner production method including the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. The range of 0.2 to 5 parts by weight is preferable. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, the effect of the charge control agent is reduced, the electrostatic attraction with the developing roller is increased, the developer fluidity is lowered, and the image density is lowered. Invite.

(Release agent)
As the release agent, a low melting point wax having a melting point of 50 to 120 ° C. works between the fixing roller 17 and the toner interface more effectively as a release agent in the dispersion with the binder resin, thereby fixing. The roller 17 is effective against high temperature offset without applying a release agent such as oil. Examples of such a wax component include the following. Examples of waxes and waxes include plant waxes such as carnauba wax, cotton wax, wood wax, rice wax, animal waxes such as beeswax and lanolin, mineral waxes such as ozokerite and cercin, and paraffin, microcrystalline, And petroleum waxes such as petrolatum. In addition to these natural waxes, synthetic hydrocarbon waxes such as Fischer-Tropsch wax and polyethylene wax, and synthetic waxes such as esters, ketones, and ethers can be used. Furthermore, fatty acid amides such as 12-hydroxystearic acid amide, stearic acid amide, phthalic anhydride imide, chlorinated hydrocarbon, and low molecular weight crystalline polymer resin, poly-n-stearyl methacrylate, poly-n- A crystalline polymer having a long alkyl group in the side chain such as a homopolymer or copolymer of polyacrylate such as lauryl methacrylate (for example, a copolymer of n-stearyl acrylate-ethyl methacrylate, etc.) can also be used. .
The charge control agent and the release agent can be melt-kneaded together with the master batch and the binder resin, and of course, they may be added when dissolved and dispersed in the organic solvent.

(External additive)
Inorganic fine particles are preferably used as an external additive for assisting the fluidity, developability and chargeability of the toner particles. The primary particle diameter of the inorganic fine particles is preferably 5 × 10 −3 to 2 μm, and particularly preferably 5 × 10 −3 to 0.5 μm. Moreover, it is preferable that the specific surface area by BET method is 20-500 m <2> / g. The use ratio of the inorganic fine particles is preferably 0.01 to 5 wt% of the toner, and particularly preferably 0.01 to 2.0 wt%.

  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, quartz sand, clay, mica, wollastonite, diatomaceous earth. Examples include soil, chromium oxide, cerium oxide, bengara, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride. Among these, as the fluidity imparting agent, it is preferable to use hydrophobic silica fine particles and hydrophobic titanium oxide fine particles in combination. In particular, when stirring and mixing are performed using particles having an average particle size of 5 × 10-2 μm or less, the electrostatic force and van der Waals force with the toner are remarkably improved. Even when stirring and mixing inside the developing device is performed, a fluidity-imparting agent is not detached from the toner, a good image quality that does not cause fireflies and the like is obtained, and a reduction in residual toner is further achieved. .

Titanium oxide fine particles are excellent in environmental stability and image density stability, but have a tendency to deteriorate the charge rise characteristics. Therefore, if the amount of titanium oxide fine particles added is larger than the amount of silica fine particles added, this side effect is affected. It can be considered large.
However, when the addition amount of the hydrophobic silica fine particles and the hydrophobic titanium oxide fine particles is in the range of 0.3 to 1.5 wt%, the charge rise characteristics are not greatly impaired, and the desired charge rise characteristics can be obtained. Even if the above is repeated, stable image quality can be obtained.

  Next, a toner manufacturing method will be described. Here, although a preferable manufacturing method is shown, it is not limited to this.

(Toner production method)
(1) A toner material solution is prepared by dispersing a colorant, unmodified polyester, a polyester prepolymer having an isocyanate group, and a release agent in an organic solvent.
The organic solvent is preferably volatile with a boiling point of less than 100 ° C. from the viewpoint of easy removal after toner base particle formation. Specifically, 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 preferable. The usage-amount of an organic solvent is 0-300 weight part normally with respect to 100 weight part of polyester prepolymers, Preferably it is 0-100 weight part, More preferably, it is 25-70 weight part.

(2) The toner material liquid is emulsified in an aqueous medium in the presence of a surfactant and resin fine particles.
The aqueous medium may be water alone or an organic solvent such as alcohol (methanol, isopropyl alcohol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.). It may be included.
The amount of the aqueous medium used relative to 100 parts by weight of the toner material liquid 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 material liquid is poor, and toner particles having a predetermined particle diameter cannot be obtained. Moreover, when it exceeds 2000 weight part, it is not economical.

Further, in order to improve the dispersion in the aqueous medium, a dispersant such as a surfactant and resin fine particles is appropriately added.
As surfactants, anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, alkylamine salts, amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt types such as imidazoline, Quaternary ammonium salt type cationic surfactants such as alkyltrimethylammonium salts, dialkyldimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, benzethonium chloride, fatty acid amide derivatives, polyhydric alcohols Nonionic surfactants such as derivatives, for example, amphoteric surfactants such as alanine, dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl-N, N-dimethylammonium betaine And the like.

Further, by using a surfactant having a fluoroalkyl group, the effect can be increased in a very small amount. 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- [ω-fluoroalkyl (C6-C11 ) Oxy] -1-alkyl (C3-C4) sodium sulfonate, 3- [ω-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) Perful Olooctanesulfonamide, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (C6-C10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (C6-C16) ethyl phosphate, etc. Can be 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 Daikin Industries, Ltd.), Megafac F-110, F-120, F-113, F-191, F-812, F-833 (manufactured by Dainippon Ink, Inc.), 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, examples of the cationic surfactant include aliphatic quaternary ammonium salts such as aliphatic primary, secondary or secondary amine acids having a fluoroalkyl group, and perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salts. , Benzalkonium salt, benzethonium chloride, pyridinium salt, imidazolinium salt, trade names include Surflon S-121 (manufactured by Asahi Glass), Florard FC-135 (manufactured by Sumitomo 3M), Unidyne DS-202 (Daikin Industries) Manufactured), MegaFuck F-150, F-824 (Dainippon Ink Co., Ltd.), Xtop EF-132 (Tochem Products), Footgent F-300 (Neos), and the like.

The resin fine particles are added to stabilize the toner base particles formed in the aqueous medium. For this reason, it is preferable to add so that the coverage existing on the surface of the toner base particles is in the range of 10 to 90%. For example, polymethyl methacrylate fine particles 1 μm and 3 μm, polystyrene fine particles 0.5 μm and 2 μm, poly (styrene-acrylonitrile) fine particles 1 μm, trade names are PB-200H (manufactured by Kao Corporation), SGP (manufactured by Soken Co., Ltd.), Techno Examples include polymer SB (manufactured by Sekisui Chemical Co., Ltd.), SGP-3G (manufactured by Sokensha), and micropearl (manufactured by Sekisui Fine Chemical Co., Ltd.).
In addition, inorganic compound dispersants such as tricalcium phosphate, calcium carbonate, titanium oxide, colloidal silica, and hydroxyapatite can also be used.

As a dispersant that can be used in combination with the above resin fine particles and inorganic compound dispersant, 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 acrylic acid-β-hydroxyethyl, methacrylic acid-β-hydroxyethyl, acrylic acid-β-hydroxypropyl, methacrylic acid-β-hydroxypropyl, acrylic acid-γ-hydroxypropyl, methacrylic acid-γ-hydroxy Propyl, acrylic acid-3-chloro-2-hydroxypropyl, methacrylic acid-3-chloro-2-hydroxypropyl, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate, glycerol monomethacrylate Luric acid esters, 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, or compounds containing vinyl alcohol and a carboxyl group Esters such as vinyl acetate, vinyl propionate, vinyl butyrate, acrylamide, methacrylamide, diacetone acrylamide or their methylol compounds, acid chlorides such as acrylic acid chloride, methacrylic acid chloride, vinyl pyridine, vinyl pyrrolidone, vinyl Nitrogen compounds such as imidazole and ethyleneimine, or homopolymers or copolymers such as those having a heterocyclic ring thereof, polyoxyethylene, poly Xoxypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonylphenyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, polyoxy Polyoxyethylenes such as ethylene nonylphenyl ester, celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose can be used.

  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. Among these, the high-speed shearing method is preferable in order to make the particle size of the dispersion 2 to 20 μm. 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.

(3) At the same time as the preparation of the emulsion, the amines (B) are added to cause a reaction with the polyester prepolymer (A) having an isocyanate group.
This reaction involves molecular chain crosslinking and / or elongation. The reaction time is selected depending on the reactivity between the isocyanate group structure of the polyester prepolymer (A) and the amines (B), but is usually 10 minutes to 40 hours, preferably 2 to 24 hours. 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.

(4) After completion of the reaction, the organic solvent is removed from the emulsified dispersion (reactant), washed and dried to obtain toner base particles.
In order to remove the organic solvent, the temperature of the entire system is gradually raised in a laminar stirring state, and after giving strong stirring in a certain temperature range, the solvent base is removed to produce spindle-shaped toner base particles. . Further, when an acid such as calcium phosphate salt or an alkali-soluble material is used as the dispersion stabilizer, the calcium phosphate salt is dissolved from the toner base particles by a method such as dissolving the calcium phosphate salt with an acid such as hydrochloric acid and washing with water. Remove. It can also be removed by operations such as enzymatic degradation.

(5) A charge control agent is injected into the toner base particles obtained above, and then inorganic fine particles such as silica fine particles and titanium oxide fine particles are externally added to obtain a toner.
The injection of the charge control agent and the external addition of the inorganic fine particles are performed by a known method using a mixer or the like.
Thereby, a toner having a small particle size and a sharp particle size distribution can be easily obtained. Furthermore, by giving strong agitation in the process of removing the organic solvent, the shape between the true spherical shape and the rugby ball shape can be controlled, and the surface morphology is also controlled between the smooth shape and the umeboshi shape. be able to.

1 is a schematic overall configuration diagram of an image forming apparatus showing an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a configuration example of a photoreceptor unit (process cartridge) provided in the image forming apparatus (full color printer) illustrated in FIG. 1.

Explanation of symbols

1: Image forming apparatus main body 2A to 2D: Photosensitive unit (process cartridge)
3: Transfer belt 5: Photoconductor (image carrier)
6: Optical writing unit (latent image forming means)
7: Duplex unit 8: Reversing unit 9: Fixing device 10A to 10D: Developing device (developing means)
11, 12: Paper feed cassette 13: Manual feed tray 15: Brush roller 17: Charging roller (charging means)
20: Reverse paper discharge path 25: Paper discharge roller pair 26: Paper discharge tray 47: Cleaning blade 48: Toner transport auger 49: Charging cleaning roller 55, 56: Separation paper feeding unit 57: Transfer brush (transfer means)
58: Paper adsorption roller 59: Registration roller pair P: Transfer paper (transfer material)

Claims (11)

An image carrier, a charging unit for charging the image carrier, a latent image forming unit for forming a latent image on the surface of the charged image carrier, and the latent image forming unit formed on the image carrier. A control method for an image forming apparatus, comprising: developing means for developing a latent image with toner to form a toner image; and transfer means for transferring a toner image formed on the image carrier by the developing means onto a transfer material. Because
In the control method of an image forming apparatus in which the linear velocity of the image carrier is variable and the target value or setting value of the background potential of the image carrier is changed according to the linear velocity of the image carrier, the target value of the background potential Alternatively, the absolute value of the set value is higher when the linear velocity of the image carrier is higher. The method of controlling an image forming apparatus according to claim 1.
When a transfer current flowing through the transfer material by the transfer unit changes, a target value or a set value of a background potential of the image carrier is changed by a transfer current that the transfer unit passes through the transfer unit. Control method for image forming apparatus. The method of controlling an image forming apparatus according to claim 2,
The method for controlling an image forming apparatus, wherein a higher transfer current value has a higher target value or set value of the background potential. The method of controlling an image forming apparatus according to claim 1.
A control method for an image forming apparatus, wherein a target value or a set value of the background potential of the image carrier is variable depending on the number of rotations of the image carrier and / or the number of passages of a transfer material. The method of controlling an image forming apparatus according to claim 4.
As for the target value or setting value of the background potential, the absolute value of the target value or setting value of the background potential increases as the number of rotations of the image carrier and / or the number of passing sheets of the transfer material increases. And a control method for the image forming apparatus. In the control method of the image forming apparatus according to claim 4 or 5,
An image forming apparatus characterized in that, when a transfer current flowing through the transfer material by the transfer unit changes, a target value or a set value of the background potential is changed by a transfer current passed through the transfer material by the transfer unit. Control method. In the control method of the image forming device according to any one of claims 1 to 6,
A method for controlling an image forming apparatus, wherein when setting the target value or set value of the background potential, the charging bias of a charging unit that charges the image carrier is changed. An image carrier, a charging unit for charging the image carrier, a latent image forming unit for forming a latent image on the surface of the charged image carrier, and the latent image forming unit formed on the image carrier. An image forming apparatus comprising: a developing unit that develops a latent image with toner to form a toner image; and a transfer unit that transfers a toner image formed on the image carrier onto the transfer material by the developing unit.
An image forming apparatus comprising the control method according to claim 1. The image forming apparatus according to claim 8.
The image forming apparatus, wherein the charging unit is a charging roller. The image forming apparatus according to claim 9.
The image forming apparatus, wherein the charging roller is disposed in a non-contact manner with respect to the image carrier. The image forming apparatus according to claim 9 or 10, wherein:
An image forming apparatus, wherein a direct current (DC) voltage is applied to the charging roller so as to be superimposed on a direct current (DC) voltage.

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