JP2006208978A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain high quality images for a long period by reducing the amount of generation of discharge products and preventing an electrostatic charge defect in an image forming apparatus in which a transfer residual toner is recovered by a developing device. <P>SOLUTION: The image forming apparatus comprises the developing device which forms an electrostatic latent image after electrostatically charging a photoreceptor 1 by an electrostatic charger 3, and develops the electrostatic latent image by the toner electrostatically charged to the same polarity as the electrostatic charge polarity of the photoreceptor, and a transfer means 6 which transfers the toner image onto an object to be transferred by forming a transfer electric field between the photoreceptor and an object to be transferred. The electrostatic charger uses an electrostatic charge roller 3a arranged in proximity to the surface of the photoreceptor and includes a transfer residual toner spray means 40 for spraying the transfer residual toner remaining on the photoreceptor surface without being transferred by the transfer means 6 to the surface of the photoreceptor. The toner of ≤10% in the ratio of ≤1 μm in the number average grain size is used. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine that forms an image by an electrophotographic process.

  Conventionally, as the image forming apparatus, an electrostatic latent image is formed on an image carrier charged by a charging device, the electrostatic latent image is converted into a toner image by a developing device, and the toner image is transferred to a transfer target by a transfer device. What is used is widely used. As the transfer device, an electrostatic apparatus that forms a transfer electric field between the image carrier and the transfer target that moves while contacting the image carrier and transfers the toner image on the image carrier to the transfer target. Are known. In the electrostatic transfer device, toner charged to a polarity opposite to the normal charging polarity is not transferred to the transfer target and remains on the surface of the image carrier. If the image carrier is subjected to the next image forming process without the transfer residual toner being removed, charging failure such as uneven charging occurs in the portion of the image carrier where the transfer residual toner remains, and the image quality deteriorates. . Therefore, a cleaning device is provided at a position facing the surface of the image carrier from the transfer area to the charging area to remove the transfer residual toner.

  However, the cleaning device requires a space for providing a waste toner tank for storing the transfer residual toner collected from the surface of the image carrier and a recycle toner transport passage for transporting the recovered transfer residual toner for reuse. Therefore, there is a problem that the image forming apparatus is increased in size. In particular, in recent years, there has been a strong demand for increasing the speed of image formation for color images, and so-called tandem type image forming apparatuses having an image carrier for each color are becoming mainstream. In this tandem type image forming apparatus, since it is necessary to individually provide a cleaning device for each color of a plurality of image carriers, an increase in the size of the device is a more significant problem.

  For example, an image forming apparatus disclosed in Japanese Patent Application Laid-Open No. 2005-228561 can be cited as a device that can cope with the problem of the enlargement of the apparatus. This image forming apparatus employs a so-called simultaneous development cleaning system in which a transfer residual toner remaining on the surface of an image carrier is collected by a developing device. In the simultaneous development cleaning method, a developing device installed for a purpose other than cleaning is used as a cleaning means, and there is no need to separately provide a conventional cleaning device. Therefore, it can greatly contribute to the downsizing of the apparatus.

  In the image forming apparatus disclosed in Patent Document 1, toner charged to the same polarity as the charged polarity of the image carrier is attached to the image carrier to form a toner image. In addition, a charging roller that contacts an image carrier is described as a charging device. As the charging device, a contact charging method in which a charging member such as a charging roller is brought into contact with the surface of the image carrier, a proximity charging method in which the charging member is brought close to the surface of the image carrier, and a charger charging method such as a corona charger. It has been known. The charger charging method has a problem in terms of environment because discharge products such as ozone and NOx are generated in large quantities. In contrast, the contact charging method and the proximity charging method are advantageous in terms of the environment because the amount of generated discharge products is small. For these reasons, the image forming apparatus disclosed in Patent Document 1 can be said to be an excellent apparatus in terms of the environment, with a small amount of discharge products generated while downsizing the apparatus.

  However, in the image forming apparatus employing the simultaneous development cleaning method and the contact charging method, the transfer residual toner and the charging roller come into contact with each other while the transfer residual toner on the image carrier is transported to the development area. . The transfer residual toner contains a lot of toner charged to a polarity opposite to the normal charge polarity of the toner, and the transfer residual toner charged to the reverse polarity adheres to the charging roller to which the charging bias is applied. As a result, uniform charging of the image carrier by the charging roller is hindered, and the surface potential of the image carrier cannot be set to a desired potential, or charging failure such as uneven charging occurs. For this reason, there has been a problem that image density is deteriorated and background stains occur, resulting in image quality deterioration.

  In addition, the transfer residual toner on the image carrier has an image pattern, and when such transfer residual toner adheres to the charging roller in a pattern, charging failure corresponding to the pattern occurs, resulting in a decrease in image density or background contamination. Etc. appear as an afterimage in a pattern. Therefore, there is provided a transfer residual toner spraying means for spraying the transfer residual toner pattern on the image carrier upstream of the contact portion with the charging roller, preventing pattern-like toner from adhering to the charging roller and making the residual image inconspicuous. The method is known.

  In addition, various proposals have been made so that the transfer residual toner can be satisfactorily removed by the developing device without degrading the charging performance of the charging roller. For example, in Patent Document 2, a charging device that applies a DC voltage to a charging member placed in contact with a surface to be charged to charge the surface to be charged to a predetermined potential, and a transfer residual toner that has been transferred from the surface to be charged to the charging member. There has been proposed an apparatus provided with a transfer means for transferring from a charging member to a charged surface during charging of the charged surface. Specifically, as the transfer means, a speed difference is provided between the peripheral speed of the charging roller as the charging member and the peripheral speed of the surface to be charged (image carrier surface), and the transfer residual toner is charged by frictional charging by rubbing. It has been proposed to apply a charge having the same polarity as the DC voltage applied to the roller so that the transfer residual toner is transferred from the charging roller side to the surface of the image carrier. Further, as a transfer means, there has been proposed an apparatus provided with a charge applying member disposed in contact with the charging member so as to apply a charge to the charged member contaminants transferred to the charging roller. This charge imparting member is made of a material having a different charge series with respect to the developer, and has the same polarity as the DC voltage applied to the transfer residual toner on the charging roller to the charging member due to frictional charging by rubbing with the charging roller. Is granted. Thus, the transfer residual toner on the charging roller is transferred from the charging roller side to the surface of the image carrier. However, it is difficult to completely charge toner that is reversely charged by frictional charging to the same polarity as the DC voltage applied to the charging roller, and it has not been possible to solve image density reduction and background stains.

  Further, in Patent Document 3, a toner scraping member is provided downstream from the contact portion of the charging roller that contacts the image carrier with the image carrier, and the charging roller controls the toner charge to the same polarity as the charging polarity of the image carrier. It has been proposed to have a polarity control agent.

  Further, in Patent Document 4, a developer charging polarity control that can move in the longitudinal direction of the image carrier upstream of the charging member and charges the developer remaining on the image carrier after the transfer process to a normal polarity. Proposed means are proposed. This is because when the developer remaining on the image carrier is charged to a normal polarity, the developer charge polarity control means is arranged in the longitudinal direction of the image carrier in order to prevent overcharge and insufficient charge of the minute transfer residual toner. It can be moved in the direction. Further, in order to make the polarity control by the developer charging polarity control means uniform, the residual developer uniformizing means for making the transfer residual toner uniform upstream from the developer charging polarity control means and downstream from the transfer device. Some have also been proposed. However, providing such a movable mechanism leads to complication of the apparatus. Further, even when such developer charging polarity control means is used, it is difficult to completely charge the reversely charged toner to the normal polarity, and it has not yet been possible to solve the reduction in image density and background stains.

  Further, Patent Document 5 proposes a toner that defines the toner circularity, carrier particle size distribution, and the like in addition to the developer charge control means. Japanese Patent Application Laid-Open No. H10-228561 proposes a developer that defines the charging roller hardness, toner molecular weight distribution, carrier particle size distribution, and the like in addition to the developer charge control means.

Japanese Patent No. 3091323 JP-A-10-213945 JP 2000-181200 A JP 2001-215799 A Japanese Patent Laid-Open No. 2002-221829 JP 2002-221830 A

  The devices disclosed in Patent Documents 2, 3, 4, 5, and 6 improve the contamination due to a large amount of untransferred toner adhering to the contact-type charging roller, and the contamination can be improved to some extent. However, it is difficult to completely remove dirt with a contact-type charging roller, and image density reduction and background dirt are still insufficient.

  The present invention has been made in view of the above background. The object is to reduce the amount of discharge products generated in an image forming apparatus that collects untransferred toner with a developing device and to prevent poor charging and obtain a high-quality image over a long period of time. An image forming apparatus is provided.

To achieve the above object, the invention of claim 1 is directed to an image carrier, a charging device for charging the image carrier, and latent image formation for forming an electrostatic latent image on the surface of the charged latent image carrier. A transfer electric field is formed between the image carrier and the transfer object, and a developing device for attaching toner charged to the same polarity as the charged polarity of the image carrier to the image carrier to form a toner image And a transfer device that transfers the toner image on the image carrier onto the transfer target, and the transfer residual toner remaining on the image carrier without being transferred by the transfer device. A transfer residual toner spraying means for spraying on the surface of the image carrier, and the charging device applies a charging bias of a predetermined polarity to a charging member disposed in the vicinity of the surface of the image carrier. The ratio of 1 μm or less in the average particle size is 10% or less It is intended to.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the charging member is made of a resin.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the charging member has a roller shape.
According to a fourth aspect of the present invention, in the image forming apparatus of the third aspect, the roller-shaped charging member has a surface roughness Ra of 0.1 μm or less.
According to a fifth aspect of the present invention, in the image forming apparatus according to the first, second, third, or fourth aspect, the image carrier and the charging member are disposed with a gap of 40 μm or more. To do.
According to a sixth aspect of the present invention, in the image forming apparatus of the first, second, third, fourth, or fifth aspect, the toner charge amount is expressed as q [fC] and the toner particle size is expressed as d [μm]. In addition, in the distribution of q / d values, the total ratio of the toner having the same polarity as the normal charging polarity of the toner and having a value of | 0.1 | [fc / μm] or less and that having the opposite polarity is 10% or less. It is characterized by.
According to a seventh aspect of the present invention, in the image forming apparatus of the sixth aspect, the charge amount of the toner additive has the same polarity as the toner, and the reverse charge ratio is 0%. It is.
According to an eighth aspect of the present invention, in the image forming apparatus of the first, second, third, fourth, fifth, sixth or seventh aspect, the charging device applies a voltage in which AC is superimposed on DC to the charging member. The image bearing member is charged.
According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the AC peak-to-peak voltage is not less than 1 KV and not more than 2 KV.
According to a tenth aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, fifth, sixth, seventh, eighth, or ninth aspect, the image carrier, the charging member, and the developing device include: The process cartridge is configured as a unit and is detachable from the main body of the image forming apparatus.

In these image forming apparatuses, by using a charging member close to the image carrier, the transfer residual toner on the image carrier and the charging member are prevented from contacting each other. Although some of the transfer residual toner on the image carrier is electrostatically transferred to and adhering to a nearby charging member, the amount thereof is much smaller than when the charging member is brought into contact.
Further, by adopting the following configuration, contamination of adjacent charging members is suppressed and charging failure is prevented.
This image forming apparatus is provided with transfer residual toner spraying means for spraying the transfer residual toner remaining on the image carrier onto the surface of the image carrier, and sprays this even if the transfer residual toner has a pattern. This prevents pattern-like toner from adhering to the charging member and suppresses the occurrence of local charging failure.
Further, a toner that hardly transfers from the image carrier to the charging member is used. This will be described in detail below. In the toner manufacturing process, a plurality of materials such as a binder resin and a pigment are mixed at a certain composition ratio and then finely divided to obtain a desired particle diameter. Is difficult and actually has a particle size distribution. Among these, the ultrafine toner does not maintain the above composition ratio and deteriorates the so-called toner uniformity, and many toners are charged to the opposite polarity without being charged to the normal normal polarity. This is because a mixture of a plurality of materials has a structure in which different materials are phase-separated, but in the process of finely pulverizing the toner, destruction at the phase-separation structure interface of different materials is likely to occur. Since the ultrafine toner is repeatedly destroyed at the interface of the phase separation structure, the composition ratio is difficult to maintain and the uniformity of the toner is deteriorated. For this reason, by reducing the amount of ultrafine toner, it is possible to reduce the amount of toner that is charged to the opposite polarity and easily transferred to the charging member. As shown in an experiment to be described later, it was confirmed that the toner adhesion to the charging member is significantly suppressed when the ratio of 1 μm or less in the number average particle diameter of the toner is 10% or less. By cutting the toner having a particle size of 1 μm or less as the ultrafine toner by classification, the original characteristics of the toner can be exhibited, the reversely charged toner is hardly generated, and the adhesion to the charging member can be greatly reduced.
As described above, by combining the above-described conditions, it is possible to suppress the transfer residual toner from adhering to the charging member and prevent charging failure. In addition, the use of a nearby charging member is advantageous in terms of the environment because the amount of generated discharge is small.

  According to the first to tenth aspects of the present invention, in the image forming apparatus that collects the transfer residual toner by the developing device, the generation amount of the discharge product is reduced and the charging failure is prevented, and a high-quality image can be obtained over a long period of time. There is an excellent effect that it can be obtained.

  Hereinafter, an embodiment in which the present invention is applied to a full-color laser printer (hereinafter simply referred to as “printer”) as an image forming apparatus will be described. FIG. 1 is a schematic configuration diagram of a printer. In this printer, four toner image forming units 2Y, 2C, 2M, and 2K of yellow, cyan, magenta, and black are arranged side by side to constitute a tandem image forming unit. In the tandem image forming unit, individual toner image forming units 2Y, C, M, and K are arranged in order from the left in the drawing. Here, the suffixes Y, C, M, and K of the respective symbols indicate members for yellow, magenta, cyan, and black, respectively. In the tandem image forming unit, the individual toner image forming units 2Y, 2C, 2M, and 2K include drum-shaped photoreceptors 1Y, 1C, 1M, and 1K as latent image carriers. Around the drum-shaped photoconductors 1Y, 1C, 1M, and 1K, a charging device, a developing device, and the like, which will be described later, are provided.

  The toner image forming units 2Y, C, M, and K for the respective colors are formed as process cartridges that can be attached to and detached from the main body. These process cartridges can be pulled out from the printer body along guide rails (not shown) fixed to the printer body. Further, the toner image forming means 2Y, 2C, 2M, and 2K can be loaded at predetermined positions by pushing the process cartridge into the printer main body.

  Here, the toner image forming units 2Y, 2C, 2M, and 2K have the same configuration and operation. Therefore, the subscripts Y, C, M, and K of the respective symbols are omitted below, and the toner image forming unit 2 will be described in detail. FIG. 2 is a schematic configuration diagram of the toner image forming unit. A charging device 3 and a developing device 5 are sequentially arranged around the photosensitive member 1 that rotates clockwise in the drawing. The charging device 3 includes a charging roller 3a as a charging member. The charging roller 3a has a surface layer provided with a conductive resin or rubber on a conductive rotation shaft, and is disposed so as to face and close to the photosensitive member 1 while maintaining a minute gap. The surface of the photoconductor 1 is uniformly charged by applying a voltage from a charging high-voltage power supply 3b connected to the rotating shaft of the charging roller 3b. The developing device 5 includes a developer accommodating portion that accommodates the developer, and a developing roller 5 a as a developer carrying member disposed so as to face and face the surface of the photoreceptor 1. A developer stirring / conveying member 5b that transports the developer to the vicinity of the developing roller 5a while stirring the developer is provided in the developer accommodating portion. The developing roller 5a is configured to carry the developer and transport it to a position facing the photoconductor 1, and to develop the toner by supplying toner to the electrostatic latent image on the photoconductor 1.

  In addition, toner bottles 31Y, 31C, 31M, and 31K filled with yellow, cyan, magenta, and black color toners are disposed at the top of the printer. Each color developing device 5 is replenished with a predetermined replenishment amount from the toner bottles 31Y, 31C, 31M, and 31K through a conveyance path (not shown).

  An exposure device 4 as a latent image forming unit is provided below the tandem image forming unit. The exposure device 20 is configured to irradiate the surface of each photoconductor 1 while scanning with laser light based on image data.

  An intermediate transfer unit 6 is provided immediately above the tandem image forming unit. The intermediate transfer unit 6 includes an endless belt-like intermediate transfer belt 10 as an intermediate transfer member. Further, primary transfer for transferring the toner images formed on the photoconductors 1Y, C, M, and K onto the intermediate transfer belt 10 and the support rollers 11, 12, and 13 that rotatably support the intermediate transfer belt 10. Rollers 14Y, C, M, and K are provided. Further, a secondary transfer roller 16 as a secondary transfer device is provided downstream of the primary transfer rollers 14Y, 14C, 14M, and 14K with respect to the driving direction of the intermediate transfer belt 10. A support roller 13 is disposed on the opposite side of the secondary transfer roller 16 and the intermediate transfer belt 10 and functions as a pressing member. Further, a belt cleaning device 15 is provided downstream of the secondary transfer roller 16 in the driving direction of the intermediate transfer belt 10.

  A lower part of the printer is provided with a paper feeding unit. The paper supply unit includes a paper supply roller 21 that conveys the recording paper P from the paper supply cassette 20 to the secondary transfer area, a registration roller 22, and the like.

  Further, a fixing device unit 23 for fixing the image on the recording medium P is provided downstream of the secondary transfer roller 16 with respect to the traveling direction of the recording medium P to which the toner image is transferred from the secondary transfer roller 16. The fixing unit 23 includes a fixing roller 23a and a pressure roller 23b, and performs fixing by applying heat and pressure to the toner image on the recording paper P.

  Next, the operation of the printer will be described. Each photoconductor 1 is rotated by the individual toner image forming means 2, and the surface of the photoconductor 1 is uniformly charged by the charging roller 3 a as the photoconductor 1 rotates. Next, the image data is irradiated with writing light by a laser from the exposure device 4 to form an electrostatic latent image on the photoreceptor 1. Thereafter, toner is attached by the developing device 5 and the electrostatic latent image is visualized to form single color images of yellow, cyan, magenta, and black on the respective photoreceptors 1. Further, the intermediate transfer belt 10 is rotated and conveyed by a drive motor (not shown), and the visible image is sequentially transferred onto the intermediate transfer belt 10 by each primary transfer device 14. As a result, a composite color image is formed on the intermediate transfer belt 10.

  Further, the leading edge of the recording paper P in the paper feed cassette 20 is fed out by the paper feed roller 21 in accordance with the timing of the image formation, and is conveyed to the registration roller 22 and temporarily stops. Then, the sheet is conveyed between the secondary transfer roller 16 and the intermediate transfer belt 10 while taking the timing with the image forming operation. Here, the intermediate transfer belt 10 and the secondary transfer counter roller 16 form a so-called secondary transfer nip across the recording medium P, and the secondary transfer roller 16 transfers the toner image on the intermediate transfer belt 16 to the recording medium P. Secondary transfer on top.

  The recording medium P after image transfer is sent to the fixing unit 23, where heat and pressure are applied by the fixing device to fix the transferred image, and the image is discharged outside the apparatus. On the other hand, the intermediate transfer belt 10 after image transfer is removed by the belt cleaning device 15 to remove residual toner remaining on the intermediate transfer belt 10 after image transfer, and is prepared for re-image formation by the tandem image forming unit.

  This printer removes residual toner remaining on the photosensitive member 1 when the visible image on the photosensitive member 1 is transferred onto the intermediate transfer belt 10 by the primary transfer device 14 between the transfer region and the charging region. No cleaning device is provided as a means to do this. A printer that does not have such a cleaning device is used as a means, and a so-called simultaneous development cleaning system is employed in which the transfer residual toner on the photoreceptor 1 is collected by the developing roller 5a.

Next, the characteristic part of this embodiment is demonstrated.
In the printer of the present embodiment, as described above, the charging roller 3a is disposed so as to face and face each other while maintaining a minute gap between the charging roller 3a and the photosensitive member 1. Therefore, the untransferred toner on the photosensitive member 1 does not come into contact with the charging roller 3a in the charging unit that passes until it is collected by the developing roller 5a. For this reason, although there are toners that are transferred and adhered to the electrostatically adjacent charging roller 3a, the amount of toner remaining on the photosensitive member 1 is smaller than that using a contact-type charging member. Further, in the case of using the charging roller 3a in the vicinity, the amount of discharge generated is smaller than that in the case of the charger charging system, which is advantageous in terms of the environment, as in the case of using the contact type charging member.

  Further, in this printer, the transfer residual toner spraying means 40 for spraying the transfer residual toner on the photoconductor 1 to the surface of the photoconductor 1 downstream of the primary transfer unit and upstream of the charging unit in the rotation direction of the photoconductor 1. Is provided. The untransferred toner spraying means 40 sprays and unpatterns the untransferred toner even when the untransferred toner is patterned by an image upstream of the charging unit. As a result, the transfer residual toner is transferred to the adjacent charging roller 3a in a pattern and is prevented from being concentrated and adhered locally, thereby suppressing the occurrence of local charging failure. As the transfer residual toner spraying means, a brush roller having a brush shape in which straight hairs or loop hairs are pasted on a core metal was used. Further, as the straight hair or loop hair of the brush, a medium resistance material is preferable, and nylon, polyester or the like is used.

Next, a method for producing toner used in the printer of this embodiment will be described.
"Synthesis of resin fine particle emulsion"
Production Example 1
In a reaction vessel equipped with a stirrer and a thermometer, 683 parts of ion exchange water, 11 parts of sodium salt of ethylene oxide methacrylate adduct sulfate (Eleminol RS-30: manufactured by Sanyo Chemical Industries), 83 parts of styrene, methacrylic acid When 60 parts, 105 parts of tert-butyl acrylate, and 1 part of ammonium persulfate were charged and stirred at 500 rpm for 30 minutes, a white emulsion was obtained. The system was heated to raise the system temperature to 80 ° C. and reacted for 6 hours. Further, 50 parts of a 1% ammonium persulfate aqueous solution was added dropwise, and the mixture was aged at 70 ° C. for 15 hours, followed by vinyl resin (styrene-methacrylic acid-tert-butyl acrylate-methacrylic acid ethylene oxide adduct sulfate sodium salt). Copolymer) aqueous dispersion [fine particle dispersion 1] was obtained. The volume average particle diameter of [fine particle dispersion 1] measured with LA-920 was 0.08 μm. A part of [fine particle dispersion 1] was dried to isolate the resin component. The resin content Tg was 62 ° C.

"Adjusting the water phase"
Production Example 2
1000 parts of ion exchange water, 83 parts of [fine particle dispersion 1], 50 parts of a 48.5% aqueous solution of sodium dodecyl diphenyl ether disulfonate (Eleminol MON-7: manufactured by Sanyo Chemical Industries) and 100 parts of ethyl acetate are mixed and stirred to give a milky white color. Obtained liquid. This is designated as [Aqueous Phase 1].
Production Example 3
1000 parts of ion-exchanged water, 83 parts of [fine particle dispersion 2], 37 parts of a 48.5% aqueous solution of sodium dodecyl diphenyl ether disulfonate (Eleminol MON-7: manufactured by Sanyo Chemical Industries) and 80 parts of ethyl acetate were mixed and stirred to give a milky white color Obtained liquid. This is designated as [Aqueous Phase 2].
Production Example 4
1000 parts of ion exchange water, silica fine particles (AEROSIL130: average particle size of primary particles is about 16 nm, manufactured by Nippon Aerosil Co., Ltd.), 48.5% aqueous solution of sodium dodecyl diphenyl ether disulfonate (Eleminol MON-7: manufactured by Sanyo Chemical Industries) 37 parts and 100 parts of ethyl acetate were mixed and stirred to obtain a milky white liquid. This is designated as [Aqueous Phase 3].
Production Example 5
1000 parts of ion exchange water, 6 parts of titanium dioxide fine particles (P-25: primary particles have an average diameter of about 21 nm, manufactured by Nippon Aerosil Co., Ltd.), 48.5% aqueous solution of sodium dodecyl diphenyl ether disulfonate (Eleminol MON-7: Sanyo Chemical) 37 parts of Kogyo Co., Ltd. and 110 parts of ethyl acetate were mixed and stirred to obtain a milky white liquid. This is designated as [Aqueous Phase 4].
Production Example 6
1000 parts of ion-exchanged water, 45 parts of [fine particle dispersion 1], 2 parts of titanium dioxide fine particles (P-25: manufactured by Nippon Aerosil Co., Ltd.), 48.5% aqueous solution of sodium dodecyl diphenyl ether disulfonate (Eleminol MON-7: Sanyo Chemical) 37 parts and 90 parts of ethyl acetate were mixed and stirred to obtain a milky white liquid. This is designated as [Aqueous Phase 5].
Production Example 7
A mixture of 1000 parts of ion-exchanged water, 83 parts of [fine particle dispersion 3], 37 parts of a 48.55% aqueous solution of sodium dodecyl diphenyl ether disulfonate (Eleminol MON-7: manufactured by Sanyo Chemical Industries) and 90 parts of ethyl acetate is mixed with milky white. Obtained liquid. This is designated as [Aqueous Phase 6].
Production Example 8
1000 parts of ion-exchanged water, 40 parts of a 48.5% aqueous solution of sodium dodecyl diphenyl ether disulfonate (ELEMINOL MON-7: manufactured by Sanyo Chemical Industries) and 100 parts of ethyl acetate were mixed and stirred to obtain a liquid containing no fine particles. This is designated as [Aqueous Phase 7].

"Synthesis of low molecular weight polyester"
Production Example 9
In a reaction vessel equipped with a condenser, a stirrer and a nitrogen inlet tube, 388 parts of bisphenol A ethylene oxide 2-mole adduct, 550 parts of bisphenol A propylene oxide 3-mole adduct, 333 parts terephthalic acid, 66 parts adipic acid and dibutyl Add 2 parts of tin oxide, react for 8 hours at 230 ° C. under normal pressure, and further react for 5 hours under reduced pressure of 10-15 mmHg, then add 54 parts of trimellitic anhydride to the reaction vessel and add 2 parts at 180 ° C. under normal pressure. The reaction was performed for a while to obtain [Low molecular weight polyester 1]. [Low molecular polyester 1] had a number average molecular weight of 2500, a weight average molecular weight of 6700, Tg of 48 ° C., and an acid value of 30.
Production Example 10
In a reaction vessel equipped with a condenser, a stirrer, and a nitrogen introduction tube, 262 parts of bisphenol A ethylene oxide 2 mol adduct, 180 parts of bisphenol A propylene oxide 2 mol adduct, 236 parts of bisphenol A propylene oxide 3 mol adduct, 266 parts of terephthalic acid, 48 parts of adipic acid and 2 parts of dibutyltin oxide were added, reacted at 230 ° C. under normal pressure for 8 hours, and further reacted at 5-15 hours under reduced pressure of 10-15 mmHg. A portion was added and reacted at 180 ° C. and normal pressure for 2 hours to obtain [Low molecular weight polyester 2]. [Low molecular polyester 2] had a number average molecular weight of 2390, a weight average molecular weight of 6010, a Tg of 58 ° C., and an acid value of 22.

"Synthesis of prepolymers with isocyanate groups"
Production Example 11
In a reaction vessel equipped with a cooling pipe, a stirrer and a nitrogen introduction pipe, 698 parts of bisphenol A ethylene oxide 2-mole adduct, 81 parts of bisphenol A propylene oxide 2-mole adduct, 283 parts of terephthalic acid, trimellitic anhydride 22 And 5 parts of dibutyltin oxide were added, reacted for 10 hours at 220 ° C. under normal pressure, and further reacted for 5 hours under reduced pressure of 10 to 15 mmHg to obtain [Intermediate Polyester 1]. [Intermediate Polyester 1] had a number average molecular weight of 2,100, a weight average molecular weight of 9,500, a Tg of 61 ° C., an acid value of 1, and a hydroxyl value of 54. Next, 450 parts of [Intermediate polyester 1], 80 parts of isophorone diisocyanate, and 500 parts of ethyl acetate are placed in a reaction vessel equipped with a cooling pipe, a stirrer and a nitrogen introduction pipe and reacted at 90 ° C. for 8 hours. Polymer 1] was obtained. [Prepolymer 1] had a free isocyanate weight% of 0.98%.

"Synthesis of ketimine"
Production Example 12
In a reaction vessel equipped with a stirrer and a thermometer, 170 parts of isophoronediamine and 75 parts of methyl ethyl ketone were charged and reacted at 40 ° C. for 10 hours to obtain [ketimine compound 1]. The amine value of [ketimine compound 1] was 356.

"Adjustment of pigment master batch"
Production Example 13
1200 parts of water, 440 parts of carbon black (Printex 60, manufactured by Dexa) and 1200 parts of low molecular weight polyester 1 are added and mixed with a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.), and the mixture is kneaded at 130 ° C. for 45 minutes using two rolls. Thereafter, it was rapidly cooled, rolled and cooled, and pulverized to 1 mmφ or less with a pulverizer to obtain [Masterbatch 1].

"Creating an oil phase"
A container equipped with a stir bar and a thermometer is charged with 400 parts of [Low molecular polyester 1], 100 parts of synthetic ester wax, 10 parts of CCA (salicylic acid metal complex E-48: manufactured by Orient Chemical Industries), and 1000 parts of ethyl acetate. The mixture was heated to 80 ° C. with stirring, maintained at 80 ° C. for 5 hours, and then cooled to 30 ° C. in 1 hour. Next, 500 parts of [Masterbatch 1] and 500 parts of ethyl acetate were charged in a container and mixed for 1 hour to obtain [Raw material solution 1].
[Raw material solution 1] Transfer 1324 parts to a container and use a bead mill (Ultra Visco Mill, manufactured by Imex Co., Ltd.) to feed liquid 1 kg / hr, disk peripheral speed 6 m / sec, 0.5 mm zirconia beads 80% by volume. Carbon black and WAX were dispersed under the conditions of filling and 3 passes. Next, 1324 parts of a 65% ethyl acetate solution of [low molecular weight polyester 1] was added, and one pass was performed with a bead mill under the above conditions to obtain [Pigment / WAX Dispersion 1]. The solid content concentration of [Pigment / WAX Dispersion 1] (130 ° C., 30 minutes) was 50%.

"Emulsification → Desolvation"
700 parts of [Pigment / WAX Dispersion 1], 1600 parts of [Prepolymer 1] and 6.0 parts of [Ketimine Compound 1] were put in a container and mixed for 1 minute at 6000 rpm with a TK homomixer (made by Tokushu Kika). Thereafter, 1200 parts of [Aqueous Phase 1] was added to the container and mixed with a TK homomixer at 13,000 rpm for 20 minutes to obtain [Emulsified Slurry 1]. [Emulsion slurry 1] was put into a container equipped with a stirrer and a thermometer, and after removing the solvent at 30 ° C. for 8 hours, aging was carried out at 40 ° C. for 8 hours to obtain [Dispersion slurry 1].

"Washing → drying"
[Emulsified slurry 1] After 100 parts of vacuum filtration,
(1): 100 parts of ion-exchanged water was added to the filter cake, mixed with a TK homomixer (rotation speed: 12,000 rpm for 10 minutes), and then filtered.
(2): 100 parts of a 10% aqueous sodium hydroxide solution was added to the filter cake of (1), mixed with a TK homomixer (30 minutes at 12,000 rpm), and then filtered under reduced pressure.
(3): 100 parts of 10% hydrochloric acid was added to the filter cake of (2), mixed with a TK homomixer (rotation speed: 12000 rpm for 10 minutes), and then filtered.
(4): 300 parts of ion-exchanged water was added to the filter cake of (3), mixed with a TK homomixer (rotation speed: 12000 rpm for 10 minutes), and then filtered twice to obtain [Filter cake 1].
[Filter cake 1] was dried at 40 ° C. for 48 hours in a circulating drier, sieved with a mesh of 75 μm, and then hydrophobic silica (hexamethyldisilazane surface-treated product, specific surface area: 100 parts of toner particles). and 200m ² /g)0.5 parts, hydrophobized rutile-type titanium oxide (isobutyltrimethoxysilane surface treated product, average primary particle diameter: 0.02 [mu] m) were mixed with 0.5 parts of a Henschel mixer, the toner a Got. At this time, mixing was performed 10 times in a cycle of stirring for 1 minute and allowing to stand for 5 minutes.

  This toner had a volume average particle size of 4.55 μm, Tg of 53 ° C., and a THF insoluble content of the resin component of 8%.

Next, 7 wt% of carbon (manufactured by Lion Akzo, Ketjen Black EC-DJ600) is dispersed for 10 minutes using a ball mill with respect to the solid content of the silicone resin (SR2411: manufactured by Toray Dow Corning Silicone). The liquid was diluted to a solid content of 10 wt% to obtain a dispersion. The above dispersion is applied at a rate of about 50 g / min in an atmosphere of 100 ° C. using a fluidized bed coating apparatus to 5 kg of magnetite powder core material having an average particle size of 30 μm, and further at 250 ° C. for 2 hours. A carrier with a thickness of 0.5 μm was obtained by heating. The film thickness was adjusted according to the amount of coating solution. The carrier had a volume resistivity of 4.3 × 10 ¹⁰ Ω · cm. The obtained carrier was degassed for 30 minutes in the final step. The carrier resistance was measured with a 4329A High Resistance Meter manufactured by Yokogawa Hewlett-Packard Co., Ltd., with a core material filled in a container having electrodes arranged in parallel at intervals of 2 mm, and a DC resistance at 1000 V between the two electrodes.

Here, as described above, in particular, a toner of 1 μm or less has an undesired component composition, and it is considered that the function as the toner cannot be satisfied. Therefore, the toner of 1 μm or less was cut by classification. The following experiment was conducted using the toner with the cut ratio changed. The developer was prepared by mixing 5 parts by weight of toner with 95 parts by weight of the carrier. Using this developer, an image was produced by the printer shown in FIG.

[Example 1]
The ratio of 1 μm or less of the used toner was 8%. A rubber roller was used as the charging roller 3a, and the charging roller 3a was not in contact with the photoreceptor 1. When an image was printed in this state, toner and additives did not adhere to the charging roller 3a, and a high-quality image could be obtained. The life of the charging roller 3a was 120K.

[Example 2]
The toner used was the same as in Example 1 and the ratio of 1 μm or less was 8%. Instead of the rubber roller used in Example 1, a resin roller was used, and the charging roller 3 a was not in contact with the photoreceptor 1. When an image was printed in this state, no toner or additive adhered to the charging roller 3a, and a high-quality image could be obtained. Further, the charging roller life was extended to 160K.

[Comparative Example 1]
The ratio of 1 μm or less of the used toner was 13%. A rubber roller similar to that in Example 1 was used, so that it was not in contact with the photoreceptor 1. When an image was printed in this state, the toner and additive adhered to the charging roller 3a member, and a high-quality image could not be obtained.

[Comparative Example 2]
The toner used was the same as in Comparative Example 1, and the ratio of 1 μm or less was 13%. The same roller made of rubber resin as in Example 1 was used and brought into contact with the photoreceptor 1. When an image was printed in this state, the toner and additive adhered to the charging roller 3a much more than in Comparative Example 1, and a high-quality image could not be obtained.

[Comparative Example 3]
The toner used was the same as in Example 1 and the ratio of 1 μm or less was 8%. The same roller made of rubber resin as in Example 1 was used and brought into contact with the photoreceptor 1. When the image was printed in this state, the toner and additive were improved on the charging roller 3a as compared with Comparative Example 2, but more adherent than Comparative Example 1 and a high-quality image could not be obtained. .

  As described above, when the charging roller 3a is brought into contact with the photosensitive member 1, a large amount of toner and additives adhere to the charging roller 3a. When the charging roller 3a is not in contact with the photoreceptor 1, the adhesion of toner and additives to the charging roller 3a can be suppressed by setting the ratio of 1 μm or less to 10% or less. Further, as the material of the charging roller 3a, it is possible to achieve a level of image quality that is made of rubber or resin, but in order to obtain an image having a longer life, the resin charging roller 3a is used. It was confirmed from experiments that this is preferable. This is presumably because the resin charging roller has a higher surface hardness than the rubber roller, and the adhesion of the toner and additives is low.

  Further, as the resin charging member, various shapes such as a flat plate shape and an uneven shape can be used in addition to the roller shape. However, in order to improve the durability of the parts and make a highly reliable system, it is effective to rotate in the form of a roller as compared with the case where the same surface always faces the photoreceptor 1. Further, it was found that the surface roughness Ra of the charging roller 3a affects the adhesion of the toner and the additive, and that the toner and the additive are more likely to adhere to the charging roller 3a as the roughness increases. Through experiments, it was confirmed that the surface roughness Ra of the charging roller 3a is 0.1 μm or less, the adhesion of the toner and additives is reduced, and a highly reliable system can be achieved.

  In addition, as described above, in order for the toner on the photosensitive member 1 not to adhere to the charging roller 3a, it is important that the charging roller 3a and the photosensitive member 1 are arranged in a non-contact manner with a gap. This will be described in detail. In order to prevent the toner on the photoreceptor 1 from adhering to the charging roller 3a, it is important to prevent the toner on the photoreceptor 1 from contacting the charging roller 3a. Here, the particle diameter of the toner has been reduced in recent years, and when a toner having an average particle diameter of 5 μm is used, the toner is about two layers in the whole solid image and the toner layer is about 10 μm. In addition, since the amount of adhesion increases in a fine line or a character image as compared with a solid image, the toner layer is about 20 μm. Considering the thickness of the toner remaining on the toner layer, the gap between the charging roller 3a and the photosensitive member 1 needs to be larger than that of the toner layer, and should be 40 μm or more, which is about twice that of the thick toner layer. Is desirable. Experimentally, the result that it is preferable to form a gap of 40 μm or more was obtained.

  In this image forming apparatus, a toner image is formed with negatively charged toner, but the toner adhering to the charging member is mostly positively charged toner. Therefore, in order not to adhere to the charging roller, the toner charge amount distribution is defined. When the charge amount of the toner is expressed as q (fC) and the particle diameter of the toner is expressed as d (μm), the distribution of q / d values is −0.1 [fC / μm] or more for a negatively charged toner. It is effective to make the ratio of the toner having the charge amount of 10% or less. An analyzer manufactured by Hosokawa Micron Co., Ltd. (trade name: “E-SPART ANALYZER”) was used to measure the toner charge amount q (fC) and the toner particle size d (μm). This analyzer employs a method that uses a dual beam frequency-shifted laser Doppler velocimeter and an elastic wave that perturbs the movement of particles in an electrostatic field. Can be used to obtain data on the particle size and charge amount of each toner. If the toner is positively charged, the ratio of toner having a charge amount of 0.1 [fC / μm] or less is set to 10% or less. In addition, it is known that not only toner but also many additives adhere to the charging member. As the toner adheres electrostatically like the toner, the charge amount of the additive is negatively charged, and the positive charge ratio is 0%, so that charging member contamination can be suppressed. became.

  In order to achieve a high-quality image, the charging device 3 that applies uniform charging as a charging method is desirable. For this purpose, AC is superimposed on DC from a charging high-voltage power source 3b on a charging roller 3a that is disposed in proximity. It is desirable to apply a voltage. Further, by increasing the AC peak-to-peak voltage, stable charging can be performed and high image quality can be achieved. However, increasing the peak-to-peak voltage is not preferable because the amount of ozone generated increases and a phenomenon that toner or the like is filmed on the photoreceptor 1 occurs. Therefore, the peak-to-peak voltage is preferably 1 KV or more at which the potential becomes uniform, and needs to be 2 KV or less in order to suppress the amount of ozone generated.

As described above, as described in the present embodiment, the charging roller 3a adjacent to the photosensitive member 1 is used so as not to come into contact with the photosensitive member 1, so that the charging member can be compared with the case using the contact type charging member. Transfer residual toner that is transferred and adhered is reduced. Further, a transfer residual toner spraying means 40 for spraying the transfer residual toner remaining on the photosensitive member 1 to the surface of the photosensitive member is provided to prevent the transfer residual toner from being locally transferred and adhered to the charging roller 3a. Gu Further, since the ratio of 1 μm or less in the number average particle diameter of the toner is 10% or less, the toner charged to a polarity opposite to the normal charging polarity of the toner is reduced, and the transfer residual toner transferred and adhered to the charging member is reduced. . By combining these conditions, it is possible to suppress the transfer residual toner from adhering to the charging roller 3a and prevent charging failure while reducing the amount of generated discharge.
In addition, by making the material of the charging roller 3a resin, the surface hardness of the charging roller 3a is higher than that of rubber, and the adhesion of the toner and additives is lowered. For this reason, it is possible to prevent the transfer residual toner from adhering to the charging roller and prevent charging failure.
Further, by forming the charging member in a roller shape, the durability of the parts can be improved and a highly reliable system can be achieved as compared with the case where the same surface always faces the photoreceptor 1.
Further, the surface roughness Ra of the charging roller 3a affects the adherence of the toner and the additive. The larger the roughness, the easier the toner and the additive adhere to the charging roller 3a. When the surface roughness Ra is 0.1 μm or less, adhesion of the toner and additives is reduced, and a highly reliable system can be achieved.
Further, the photosensitive member 1 and the charging roller 3a are arranged with a gap of 40 μm or more. This is because the particle diameter of the toner has been reduced in recent years, and when a toner having an average particle diameter of 5 μm is used, the toner is about two layers in the whole solid image and the toner layer is about 10 μm. In addition, since the amount of adhesion increases in a fine line or a character image as compared with a solid image, the toner layer is about 20 μm. Considering the thickness of the toner remaining on the toner layer, the gap between the charging roller 3a and the photosensitive member 1 needs to be larger than that of the toner layer, and should be 40 μm or more, which is about twice that of the thick toner layer. This ensures that the toner on the photoreceptor 1 does not adhere to the charging roller 3a.
In this printer, the toner image is formed with negatively charged toner, but the toner adhering to the charging member is mostly positively charged toner. For this reason, in order to prevent the toner from adhering to the charging roller 3a, when the toner charge amount is represented by q [fC] and the toner particle diameter is represented by d [μm], the toner is normally charged in the q / d value distribution. It is effective that the total ratio of those having the same polarity as that of | 0.1 | [fc / μm] or less and those having the opposite polarity is 10% or less.
Further, it is known that not only toner but also a large amount of additives adhere to the charging roller 3a. Additives adhere electrostatically in the same way as toners. For this reason, it is effective that the charge amount of the toner additive is the same polarity as that of the toner, and the reverse charging ratio is 0%.
In order to achieve a high-quality image using the proximity charging method, it is desirable to apply a voltage in which AC is superimposed on DC to the charging roller 3a.
Further, in order to achieve a high-quality image and to suppress the amount of ozone generated, it is desirable that the AC peak-to-peak voltage is 1 KV or more and 2 KV or less.
In addition, user maintenance is facilitated by using a process cartridge that is detachably attached to the printer main body and is configured by integrating the photosensitive member 1, the charging device 3, and the developing device 10.

1 is a schematic configuration diagram of a printer according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a toner image forming unit.

Explanation of symbols

1Y, C, M, K photoconductor 2Y, C, M, K toner image forming means 3 charging device 3a charging roller 3b high voltage power supply for charging 4 exposure device 5 developing device 6 intermediate transfer unit 10 intermediate transfer belt 11, 12, 13 Support roller 14Y, C, M, K Primary transfer roller 15 Belt cleaning device 16 Secondary transfer roller 20 Paper feed cassette 21 Paper feed roller 22 Registration roller 23 Fixing unit 23a Fixing roller 23b Pressure roller 24 Paper discharge roller 31Y, C, M, K toner bottle 40 Transfer residual toner spraying means

Claims (10)

An image carrier, a charging device for charging the image carrier, a latent image forming means for forming an electrostatic latent image on the surface of the charged latent image carrier, and charged to the same polarity as the charge polarity of the image carrier. A developing device that attaches the toner to the image carrier to form a toner image, and a transfer electric field is formed between the image carrier and the transfer target to transfer the toner image on the image support onto the transfer target. In an image forming apparatus provided with a transfer device for transferring to
Transfer residual toner spraying means for spraying transfer residual toner that has not been transferred by the transfer device and remains on the image carrier onto the surface of the image carrier, and the charging device is disposed close to the surface of the image carrier. An image forming apparatus for applying a charging bias of a predetermined polarity to the charged member, wherein a ratio of 1 μm or less to the number average particle diameter of the toner is 10% or less.   2. The image forming apparatus according to claim 1, wherein the charging member is made of resin.   3. The image forming apparatus according to claim 1, wherein the charging member has a roller shape.   4. The image forming apparatus according to claim 3, wherein the roller-shaped charging member has a surface roughness Ra of 0.1 [mu] m or less.   5. The image forming apparatus according to claim 1, wherein the image carrier and the charging member are arranged with a gap of 40 μm or more.   6. The image forming apparatus according to claim 1, wherein a charge amount of the toner is expressed as q [fC] and a toner particle diameter is expressed as d [μm]. An image forming apparatus characterized in that the total ratio of the toner having the same polarity as the normal charging polarity of the toner and not exceeding | 0.1 | [fc / μm] and having the opposite polarity is not more than 10%.   7. The image forming apparatus according to claim 6, wherein the charge amount of the toner additive has the same polarity as that of the toner, and the reverse charge ratio is 0%.   8. The image forming apparatus according to claim 1, wherein the charging device applies a voltage in which AC is superimposed on DC to the charging member to charge the image carrier. An image forming apparatus.   9. The image forming apparatus according to claim 8, wherein the AC peak-to-peak voltage is 1 KV or more and 2 KV or less.   The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the image carrier, the charging member, and the developing device are integrally formed to form an image. An image forming apparatus, wherein the process cartridge is detachable from the apparatus main body.

Images