JP2010151974A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that maintains the transparency of transparent toner for a long time, compared with the case where the agitating capability of the agitating means of a transparent developing means is set equal to or higher than the agitating capability of the agitating means of a color developing means. <P>SOLUTION: The image forming apparatus includes: an image carrier 10 that is rotated and driven and used for forming an electrostatic latent image on its surface according to image information; color developing means 10Y, 10M, and 10C that develop the electrostatic latent image, formed on the image carrier, with two-component developer composed of color toner and carrier, while agitating the two-component developer; and a transparent developing means 10T for developing the electrostatic latent image, formed on the image carrier, while agitating the two-component developer by use of the agitating means set lower in agitating capability than the agitating means of the color developing means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

Japanese Patent Laid-Open No. 5-323782 JP-A-6-95497

    Conventionally, as the image forming apparatus, by using a transparent toner together with colored toners such as yellow, magenta, cyan, and black, a watermark by the transparent toner is applied as an application, or gloss is partially given to a color image. Various proposals have been made to form images and the like.

  By the way, in such an image forming apparatus, a developing device using colored toners such as yellow, magenta, cyan, and black, and a developing device using transparent toner are basically the same except that the color of the toner used is different. It is configured.

  As a technique for improving the stirrability of the developer in the developing device, for example, those disclosed in Japanese Patent Application Laid-Open Nos. 5-323882 and 6-95497 have already been proposed.

  The developing device according to the above Japanese Patent Laid-Open No. 5-323882 is a developing device having a rotating paddle for agitating a developer composed of toner and carrier, and is stored in the rotating paddle at the lower part of the developing device case. A magnet that attracts the developer magnetically is provided.

    Further, the developing device according to the above-mentioned JP-A-6-95497 has a first paddle screw and a second paddle screw that are rotatably mounted in parallel in the developing device, and a communication port provided between the two paddle screws. In the agitation mechanism for agitating the toner replenished from one end of the first paddle screw in an endless state to be a two-component developer by the partition plate having the first paddle screw, The control block is configured to cover the paddle screw and the second paddle screw with a predetermined gap from the upper part of the outer peripheral edge, and to provide a restriction block formed to narrow the communication port on the other end side.

  By the way, the problem to be solved by the present invention is that transparent toner is compared with the case where the stirring ability of the stirring means of the transparent developing means is set to be equal to or greater than (or equal to or larger than) the stirring ability of the stirring means of the color developing means. It is an object of the present invention to provide an image forming apparatus capable of maintaining the transparency of the image over a long period of time.

That is, the invention described in claim 1 is an image carrier that is driven to rotate and an electrostatic latent image corresponding to image information is formed on the surface;
Color developing means for developing the electrostatic latent image formed on the image carrier while stirring the two-component developer composed of the color toner and the carrier by the stirring means;
The electrostatic latent image formed on the image bearing member is developed while stirring the two-component developer composed of the transparent toner and the carrier by the stirring unit whose stirring ability is set smaller than that of the stirring unit of the color developing unit. An image forming apparatus comprising: a transparent developing unit.

  The invention described in claim 2 is characterized in that the rotational speed of the stirring means of the transparent developing means is set smaller than the rotational speed of the stirring means of the colored developing means. The image forming apparatus described in the above.

  Further, the invention described in claim 3 is that the stirring means of the transparent developing means includes a stirring blade spirally formed on the outer periphery of the rotation shaft, and at least one of the diameter and the pitch of the stirring blade. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus is set smaller than a stirring unit of the color developing unit.

According to a fourth aspect of the present invention, there is provided one or a plurality of image carriers on which electrostatic latent images corresponding to a colored image and a transparent image are formed based on image information;
Among the single or plural image carriers, the electrostatic latent image of the color image formed on the corresponding image carrier is developed while stirring the two-component developer composed of the color toner and the carrier by the stirring means. Color developing means;
Among the single or plural image carriers, the electrostatic latent image of the transparent image formed on the corresponding image carrier is stirred by a stirring unit whose stirring ability is set smaller than that of the stirring unit of the color developing unit. An image forming apparatus comprising: a transparent developing unit that develops a two-component developer composed of a transparent toner and a carrier while stirring.

  According to the first aspect of the present invention, the transparent toner is more transparent than the case where the stirring ability of the stirring means of the transparent developing means is set to be equal to or greater than (equivalent or larger) the stirring ability of the stirring means of the color developing means. It is possible to maintain the transparency of this for a long time.

  According to the second aspect of the present invention, it is possible to prevent the transparent toner from being deteriorated by receiving stress from the stirring means without making the configurations of the transparent developing means and the colored developing means different.

  Further, according to the third aspect of the present invention, it is possible to suppress the transparent toner from being deteriorated by receiving stress from the stirring means only by exchanging the stirring means of the transparent developing means and the color developing means.

  According to the fourth aspect of the present invention, it is possible to prevent the transparent toner from being deteriorated due to stress from the stirring means, regardless of whether the image carrier is single or plural.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1
FIG. 1 is a block diagram showing a color image forming apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the color image forming apparatus 1 is roughly divided into a document reading device 2 that reads an image of a color document, a color image read by the document reading device 2, a personal computer (not shown), and the like. Based on predetermined image processing and color image image information, image information for forming an image with color toner and transparent toner is generated for the color image data and the transparent image data. Based on the image processing device 3 and the image information processed by the image processing device 3, a color toner image using at least yellow (Y), magenta (M), and cyan (C) color (colored) toner is obtained. An image output device serving both as a color toner image forming means for forming and a transparent toner image forming means for forming a transparent toner image made of transparent toner It is configured with a 4.

  The document reader 2 is configured to illuminate a document 5 placed on a platen glass (not shown) with an illumination lamp 6 and read a reflected light image from the document 5 with a color CCD 7 at a predetermined dot density. ing.

  The reflected light image of the document 5 read by the document reading device 2 is, for example, the image processing device 3 as document reflectance data of three colors of red (R), green (G), and blue (B) (each 8 bits). In this image processing apparatus 3, a predetermined image such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color / moving editing, etc. is applied to the reflectance data of the document 5. As processing is performed, three colors of yellow (Y), magenta (M), and cyan (C) (each 8 bits), or yellow (Y), magenta (M), cyan (C), and black (K) ( Each image data is converted into 4-bit image data of 8 bits). In the image processing apparatus 3, when image data of a transparent image is sent in addition to color image data from a personal computer (not shown) or the like, image processing based on the image data of the transparent image is performed. As the image data of the transparent image, for example, a part of the color image that is partially glossy or a color image that includes a watermark made of transparent toner is used as an application. However, the present invention is not limited to this, and image data in which a transparent image made of a transparent toner is added to a part or all of a color image may be used. Further, a specific image of the color or monochrome document 5 read by the document reading device 2 may be printed as a transparent image. Such processing is instructed and executed by a user interface (not shown) of the color image forming apparatus or a printer driver installed in a personal computer (not shown).

  An image output device 4 capable of forming a color toner image of three colors of yellow (Y), magenta (M), and cyan (C) and a transparent toner image is disposed in the color image forming apparatus 1. Yes. The image output device 4 mainly includes an image exposure device 9 as image writing means, a photosensitive drum 10 as an image carrier on which an electrostatic latent image is formed, and a static image formed on the photosensitive drum 10. A rotary type developing device 11 as developing means capable of developing a toner image of three colors of yellow (Y), magenta (M), and cyan (C) and a transparent toner image by developing the electrostatic latent image, and a photoconductor An intermediate transfer belt 13 serving as an intermediate transfer body on which three color toner images of yellow (Y), magenta (M), and cyan (C) and a transparent toner image sequentially formed on the drum 10 are sequentially transferred. The transfer corotron 14 as transfer means for transferring toner images of different colors sequentially formed on the photosensitive drum 10 onto the intermediate transfer belt 13, and the color toner image and the like from the intermediate transfer belt 13. Recording in which the color toner image and the transparent toner image are transferred at the secondary transfer position 15 where the transparent toner images are collectively transferred onto the recording paper 12 as a recording medium. A fixing device having a paper conveying belt 18 for conveying the paper 12 to the fixing device 19, and a heating roll 20 and a pressure roll 21 for fixing the toner image on the recording paper 12 on which the color toner image and the transparent toner image are transferred. 19.

  Image data that has been subjected to predetermined image processing by the image processing apparatus 3 as described above is transparent as described later in addition to image data of three colors of yellow (Y), magenta (M), and cyan (C). It is converted into toner (T) image data, and these image data are sent to the image exposure device 9.

  As shown in FIG. 2, the image exposure apparatus 9 modulates the semiconductor laser 8 in accordance with the image data, and the semiconductor laser 8 emits a laser beam LB modulated in accordance with the image data. The laser beam LB emitted from the semiconductor laser 8 is deflected and scanned by a rotating polygon mirror (not shown), and is scanned and exposed on the photosensitive drum 10 through an optical system including an f · θ lens and a reflecting mirror.

  The photosensitive drum 10 on which the laser beam LB is scanned and exposed by the image exposure device 9 is driven to rotate at a predetermined speed in the direction of the arrow by a driving means (not shown). The surface of the photosensitive drum 10 is charged in advance with a predetermined polarity (for example, negative polarity) and potential by a charging roll 22 for primary charging, and then yellow (Y) and magenta (M) according to image data. The laser beam LB corresponding to each color of cyan, (C) and transparent toner (T) is sequentially scanned and exposed to form an electrostatic latent image. The electrostatic latent image formed on the photoconductor drum 10 includes four color developing devices 11Y, 11M, 11C, and 11T of yellow (Y), magenta (M), cyan (C), and transparent toner (T). By the rotary developing device 11 provided, for example, the toner is reversely developed with toner charged to a negative polarity that is the same as the charged polarity of the photosensitive drum 10 to form a toner image of a predetermined color. The rotary developing device 11 may be configured to include a black (K) developing device.

  Examples of the color toner used in the developing device 11 include powder particles including at least a binder resin and a colorant, such as yellow toner, magenta toner, and cyan toner. The composition, average particle size, and the like of these color toners are appropriately selected from a range that does not impair the object of the present invention.

  Examples of the binder resin include those exemplified as the binder resin in the transparent toner described later. The binder resin is preferably a polyester having a weight average molecular weight of 5000 to 12000. The colorant is not particularly limited as long as it is a colorant usually used for toners, and can be selected from known yellow pigments or dyes, magenta pigments or dyes, cyan pigments or dyes.

  Examples of the colorant include benzidine yellow, quinoline yellow, and hansa yellow as yellow (Y), rhodamine B, rose bengal, and pigment red as magenta (M), and phthalocyanine blue, aniline blue, and pigment as cyan (C). As black (K) such as blue, carbon black, aniline black, a blend of color pigments, and the like are used.

  In order to obtain more preferable color tone reproducibility, the colorant has a primary particle diameter in the range of 0.01 to 1 μm, preferably in the range of 0.1 to 1 μm, and the same size as the primary particle diameter. It is preferable to use one that is melt-dispersed in the resin. The colorant melt-dispersed in the resin referred to here is obtained by kneading a resin melted by heating or in a solvent and a colorant wet cake obtained in the coloring material process. It is dispersed in a primary particle state in a resin, solidified by cooling or removing a solvent, and then pulverized.

  When developing a color toner, for example, inorganic powder may be adhered as fine particles imparting fluidity to the toner particle surface. As the inorganic powder, those composed of silica, titanium oxide, tin oxide, aluminum oxide or the like generally used in the industry and having a particle diameter of 0.001 to 0.1 μm can be used.

  The inorganic powder adhered to the toner particles may be treated with various treatment agents in order to impart charging environment stability and the like.

  The particle diameter of the color toner is not particularly limited, but is preferably 3 μm or more and 10 μm or less considering that it has a function capable of faithfully reproducing the electrostatic latent image by the image exposure device 9. If it is less than 3 μm, fogging due to low-charged toner tends to occur, and if it exceeds 10 μm, it is difficult to obtain an image with little noise and good graininess.

  In the present invention, the color toner may be appropriately prepared or may be a commercially available product.

  The color toner is used after being combined with an appropriately selected carrier known per se to be a developer. In addition, as the one-component developer, a unit that is triboelectrically charged with a developing sleeve or a charging member to form a charged toner and develops in accordance with the electrostatic latent image may be applied.

  The toner images of the respective colors sequentially formed on the photosensitive drum 10 are transferred in multiple onto the intermediate transfer belt 13 disposed below the photosensitive drum 10 by the transfer corotron 14 serving as transfer means. This intermediate transfer belt 13 is made of a synthetic resin film such as polyimide or polyamideimide formed in an endless belt shape, and is circulated and driven along the arrow direction at the same moving speed as the peripheral speed of the photosensitive drum 10. It has become so.

  On the intermediate transfer belt 13, all or one of the three colors yellow (Y), magenta (M), and cyan (C) sequentially formed on the photosensitive drum 10 according to the color of the image to be formed. Part of the toner image is transferred by the transfer corotron 14 in a sequentially superposed state. A black image is formed by superimposing three color toner images of yellow (Y), magenta (M), and cyan (C). As described above, a black developer is provided separately. Of course, a black image may be directly formed.

  In this embodiment, a transfer method using electrostatic force is used as a method of transferring the powder toner image formed on the photosensitive drum 10 as the image carrier onto the intermediate transfer belt 13. Of course, a transfer method using both force and pressure may be used. Further, a method in which the powder toner image formed on the photosensitive drum 10 as the image carrier is directly transferred onto a recording sheet may be used. Furthermore, when transferring the powder toner image formed on the photosensitive drum 10 as the image carrier onto the transfer member via a belt-like or drum-like intermediate transfer member, the image carrier The number of the photosensitive drums is not limited to one, but may be configured so as to correspond to the number of color toners to be formed and the transparent toner.

  For example, a photosensitive drum is used as the image carrier. However, the image carrier is not limited thereto, and a dielectric drum or the like used in an electrostatic recording method may be used. In this case, means for forming an electrostatic latent image directly on the dielectric drum by ion flow or the like is used as the image writing means.

  In this embodiment, a transparent toner image made of transparent toner is formed on the photosensitive drum 10 as an image carrier. However, in particular, when a plurality of image carriers are provided, the transparent toner is used. Another image carrier that forms a transparent toner image may be provided.

  As shown in FIG. 1, the recording paper 12 onto which the toner image is transferred is fed from a paper feed tray (not shown), and the toner images are collectively transferred from the intermediate transfer belt at the secondary transfer position 15. Is done.

  As the recording medium 12 used in this embodiment, it is preferable to use a recording medium in which a transparent resin layer or a white resin layer is provided on the surface of uncoated paper / coated paper at least on the image transfer surface. Formation of the resin layer on uncoated paper / coated paper can be performed by applying a resin dissolved in a solvent using an applicator or a wire bar. When the resin forming the resin layer is a polyester resin, a known solvent capable of dissolving the polyester resin, such as tetrahydrafuran or methyl ethyl ketone, can be used.

  Further, as a method of forming a resin layer on uncoated paper / coated paper other than coating formation, it is possible to use a method in which a resin layer previously formed on a plastic film is heated and pressed and transferred onto uncoated paper or coated paper. However, any method may be used as long as the resin layer can be formed on uncoated paper or coated paper by other methods.

  Further, in this embodiment, a glossy sheet having surface smoothness, heat resistance and releasability is superimposed on the recording medium 12, the transfer body and the glossy sheet are heated and pressurized, and the image receiving material and It is also possible to use fixing by a cooling and peeling device characterized in that after the gloss sheet is cooled, the gloss sheet is peeled from the transfer body.

  As described above, the recording paper 12 onto which the toner image of a predetermined number of colors has been transferred is separated from the intermediate transfer belt 13 and conveyed to the fixing device 19 by the conveyance belt 18. In the fixing device 19, a color toner image and a transparent toner image are fixed on the recording paper 12 by heat and pressure by the heating roll 20 and the pressure roll 12, and a color image having a transparent toner image at least partially is obtained. .

  In the above embodiment, the toner image transfer process and the fixing process are performed separately. However, the toner image transfer process and the fixing process may be performed simultaneously.

  Meanwhile, the transparent toner used in this embodiment is configured to contain at least a thermoplastic binder resin.

Examples of the binder resin include styrene resin, acrylic resin, styrene-acrylic resin, styrene-butadiene resin, vinyl chloride resin, vinyl acetate resin, polyester resin, polyurethane resin, polyamide resin, and epoxy resin. However, considering the fixability of the powder toner image on the transfer material 12, a powder toner having a viscosity of 10 ² Pa · s or more and 10 ⁵ Pa · s or less at the time of fixing is preferably used. Can do. When the viscosity of the powder toner at the time of fixing is less than 10 ² Pa · s, there is a possibility that an offset to the heating roll 20 may occur when fixing with the heating roll 20 of the fixing device 19. Further, when the viscosity of the powder toner at the time of fixing exceeds 10 ⁵ Pa · s, the powder toner is not melted and softened when it is fixed by the heating roll 20, and adhesion to the recording medium 12 and toner Adhesion between them becomes insufficient, so that sufficient fixing strength is difficult to obtain.

  When developing the transparent toner, for example, an inorganic powder may be adhered as fine particles that impart fluidity to the surface of the toner particles, similarly to the color toner. As the inorganic powder, those composed of silica, titanium oxide, tin oxide, aluminum oxide or the like generally used in the industry and having a particle diameter of 0.001 to 0.1 μm can be used.

  The inorganic powder adhered to the toner particles may be treated with various treatment agents in order to impart charging environment stability and the like.

  Further, the average particle size of the transparent toner used in this embodiment is desirably 3 μm or more and 15 μm or less. If it is less than 3 μm, fogging due to low-charged toner is likely to occur, and a transparent toner image is formed at a place other than the periphery of the desired pixel. If it exceeds 15 μm, it becomes difficult to control the amount of the transparent toner image formed around the pixel.

  The transparent toner is used after being combined with an appropriately selected carrier known per se to be a developer. In addition, as the one-component developer, a unit that is triboelectrically charged with a developing sleeve or a charging member to form a charged toner and develops it according to the electrostatic latent image can be applied.

  Further, in this embodiment, from the viewpoint of toner production, the color toner and the transparent toner may have the same particle diameter in order to enable production under the same conditions using the same equipment.

  By the way, in this embodiment, as shown in FIG. 1, as the developing devices 11Y, 11M, 11C, and 11T, toner images of three colors of yellow (Y), magenta (M), and cyan (C) and a transparent toner image are used. A rotary type developing device 11 is used. The rotary type developing device 11 includes color developing units 11Y, 11M, and 11C using three color toners of yellow (Y), magenta (M), and cyan (C) along the circumferential direction, and transparent toner. The rotary developing device 11 is rotated in accordance with the color for developing the electrostatic latent image formed on the photosensitive drum 10, and the developing device for the corresponding color is provided. Development is performed by moving 11Y, 11M, 11C, and 11T to a development position facing the photosensitive drum 10.

  The three color developing units 11Y, 11M, and 11C of yellow (Y), magenta (M), and cyan (C) and the transparent developing unit 11T basically have the same structure. For example, FIG. As shown in FIG. 2, the lower housing 30 is formed as a substantially rectangular box with the upper end surface opened entirely, and the upper housing 31 is a lid provided so as to close the upper end opening surface of the lower housing 30. A developing device housing 32 is provided. In the developing device housing 32, an opening 34 is provided along the longitudinal direction (direction perpendicular to the drawing) facing the developing region 33 facing the photosensitive drum 10. Inside, a developing roll 35 as a developer carrying member is disposed at a position facing the opening 34.

  The developing roll 35 includes a magnet roll 36 disposed in a state of being fixed to the developing device housing 32 therein, and a developing sleeve 37 disposed on the outer periphery of the magnet roll 36 so as to be rotatable along an arrow direction. It is composed of As will be described later, the developer 39 is supplied to the developing roll 35 by the supply auger 40, and the developer 39 supplied to the surface of the developing roll 35 is supplied to the developer roll 35 by the layer thickness regulating member 38. After the layer thickness is regulated, the two-component developer 39 composed of toner and carrier is spiked and conveyed to the developing region 33 facing the photosensitive drum 10, and formed on the surface of the photosensitive drum 10. The electrostatic latent image and the rise of the developer 39 composed of toner and carrier come into contact with each other, and a developing bias voltage is applied to the developing sleeve 37 to develop the electrostatic latent image on the surface of the photosensitive drum 10. Thereafter, the developer 39 remaining on the surface of the developing roll 35 is once separated from the surface of the developing roll 35 by a repulsive magnetic pole (not shown) of the magnet roll 36, and then a new developer 39 is supplied by the supply auger 40. A development process is performed.

  The amount of the developer 39 conveyed to the developing region 33 by the developing roller 35 is set to be a predetermined amount by the layer thickness regulating member 38, and the ears of the developer 39 composed of toner and carrier are set. In the standing state, the electrostatic latent image on the surface of the photosensitive drum 10 is developed while being rubbed against the surface of the photosensitive drum 10 in the developing region 33.

  Further, as shown in FIG. 2, a two-component developer 39 composed of toner and a carrier is accommodated in the developing device housing 32, and a stirring member that conveys the two-component developer 39 while stirring. A supply auger 40 and a transport auger 41 are rotatably arranged obliquely below the back side of the developing roll 35 (the side opposite to the photosensitive drum 10). As shown in FIGS. 3 and 4, the supply auger 40 and the transfer auger 41 include rotating shafts 42 and 44 and conveying blades 43 and 45 spirally provided on the outer periphery of the rotating shafts 42 and 44. The supply auger 40 and the transport auger 41 are configured to be opposite to each other along the axial direction, and the supply auger 40 is directed from the right end to the left end in FIG. 3 conveys the developer 39 while stirring from the left end to the right end in FIG. 3, and is provided at both ends of the partition wall 46 provided between the two along the developer transport direction. The developer 39 is delivered and circulated through the passages 47 and 48, and the developer auger 40 supplies the developer 39 substantially uniformly along the axial direction to the surface of the developing roll 35 as shown in FIG. To do It is configured.

  As shown in FIG. 3, the supply auger 40 and the transport auger 41 are rotationally driven by a drive motor (not shown) via gears 50 and 51 attached to one end portions of the rotary shafts 42 and 44. The developing roll 35 is rotationally driven by a driving motor (not shown) through a gear (not shown) attached to the rotating shaft 33a. As for the rotation direction of the photosensitive drum 10 and the developing roll 35, in FIG. 2, the photosensitive drum 10 is clockwise and the developing roll 35 is counterclockwise. In the color developing units 11Y, 11M, and 11C, the rotation speeds of the supply auger 40 and the conveyance auger 41 are set to 530 rpm, for example.

  On the other hand, the transparent developing unit 11T has the same basic configuration as the color developing units 11Y, 11M, and 11C described above. However, the transparent developing unit 11T is more than the stirring unit of the color developing unit. A two-component developer composed of a transparent toner and a carrier is developed while being stirred by a stirring means having a small stirring ability.

  In this embodiment, the rotational speeds of the supply auger 40 and the transport auger 41 of the transparent developing device 11T are set to about 1/2 the rotational speed of the color developing devices 11Y, 11M, and 11C, and the supply auger 40 and the transport auger 41 are transported. The auger 41 is set so as to reduce the stirring ability. However, also in the transparent developing device 11T, the rotation speed of the developing roll 35 is set to the same value as that in the color developing devices 11Y, 11M, and 11C, and the developing performance itself is basically the same.

  Specifically, the rotational speeds of the supply auger 40 and the transport auger 41 of the transparent developing device 11T are slightly larger than about ½ while the rotational speeds of the color developing devices 11Y, 11M, and 11C are 530 rpm. Set to 288 rpm. Note that these values are examples, and other values may of course be set.

  In the above configuration, in the color image forming apparatus according to this embodiment, the transparent toner is used in the image forming apparatus provided with the developing device using the transparent toner in addition to the developing device using the colored toner as follows. Compared to the developer configured using the same developer as the developer using colored toner, or the developer transport performance of the developer using transparent toner set higher than that of the developer using colored toner. Thus, it is possible to suppress the deterioration of the transparent toner due to stress from the stirring means, maintain the transparency of the transparent toner over a long period of time, and improve the image quality of the transparent image.

  That is, in the color image forming apparatus according to this embodiment, as shown in FIG. 1, the electrostatic latent image formed on the photosensitive drum 10 is converted into yellow (Y), magenta (M), and cyan (C). As shown in FIGS. 1 and 2, when developing with the rotary developing device 11 having the four color developing devices 11Y, 11M, 11C, and 11T of transparent toner (T), the corresponding color developing devices Is rotated to a developing position facing the photosensitive drum 10, and the electrostatic latent image on the surface of the photosensitive drum 10 is developed by the developing device.

  At that time, the developing devices 11Y, 11M, 11C, and 11T of the rotary developing device 11 are connected to a driving motor (not shown) for the first time when the developing devices 11Y, 11M, 11C, and 11T are moved to the developing position, and the developing roller 35 is rotationally driven. The supply auger 40 and the transport auger 41 are rotated, the two-component developer 39 composed of toner and carrier in the developing device housing 32 is agitated and transported, and development is performed by the developing roll 35.

  By the way, the two-component developer 39 composed of toner and carrier in each of the developing devices 11Y, 11M, 11C, and 11T of the yellow (Y), magenta (M), cyan (C), and transparent toner (T) is illustrated in FIG. As shown in FIGS. 2 and 3, when transported while being agitated by the supply auger 40 and the transport auger 41, the stirring force of the transport blades 43 and 45 of the supply auger 40 and the transport auger 41 causes shearing force, pressing force, etc. In order to receive an external force (stress), the carrier is rubbed against a carrier made of magnetic powder such as ferrite.

  As a result, the transparent toner having no colorant is strongly rubbed with the carrier made of magnetic powder such as ferrite when the stress received from the supply auger 40 and the transport auger 41 is large. The color adheres and gradually becomes darker, resulting in a decrease in transparency.

  Therefore, in this embodiment, the rotational speeds of the supply auger 40 and the transport auger 41 of the transparent developing device 11T are set to be about ½ smaller than those of the color developing devices 11Y, 11M, and 11C. The stress applied to the toner by the supply auger 40 and the conveyance auger 41 is reduced.

  Therefore, in the color image forming apparatus, even when used for a long period of time, it is possible to avoid that the transparent toner deteriorates due to stress and becomes a dark color, and the transparency of the transparent toner is maintained over a long period of time. It is possible to improve the image quality of transparent images.

Experimental example 1
In order to confirm the effect of the above-described embodiment, the present inventor accommodates a transparent toner instead of a color toner in a color developing device in a normal color image forming apparatus, and as a recording sheet as shown in FIG. Using OKTC (basis weight 127 gsm), A4 size SEF, which is a coated paper manufactured by OK Co., a square transparent toner portion is formed at a density of 100% on a total of 5000 recording papers, and the transparent toner is formed every 1000 sheets. The density of the area and the density L ^* a ^* b ^* of the non-image area of the recording paper were measured using a spectrophotometer (X-Rite 938 or 968), respectively.

Then, the L ^* a ^* b ^* value of the non-image portion of the recording paper and the Lp ^* ap ^* bp ^* value of the transparent toner portion (patch portion) as the image portion were obtained, and the color difference (ΔE) was obtained. . The color difference (ΔE) was calculated based on the following formula.
ΔE = SQRT {(L ^* −Lp ^* ) ² + (a ^* −ap ^* ) ² + (b ^* −bp ^* ) ² }
Here, SQRT indicates an operation for obtaining a square root. FIG. 6 is a graph showing the difference in reflectance detected by the spectrophotometer when the color difference is 1.2 and 4.0.

  FIG. 7 is a graph showing the results of Experimental Example 1.

  As is apparent from FIG. 7, when the rotational speed of the supply auger 38 and the transport auger of the transparent developer is 288 rpm, even if 5000 sheets are printed on the recording paper, the transparent toner portion and the non-image portion of the recording paper The color difference (ΔE) of the toner can be maintained at 3 or less, which is a visual recognition limit that can be visually discerned by human eyes, and the transparent aggregator supply auger 38 and the conveyance auger can reduce the stress of the transparent toner. It can be seen that it is possible to prevent the transparent toner from deteriorating and darkening and visually observing an image that should be transparent.

  On the other hand, as is clear from FIG. 7 above, when the rotational speed of the supply auger 38 and the transport auger of the transparent developer is 530 rpm, the non-image of the transparent toner portion and the recording paper is printed when 2000 sheets are printed on the recording paper. The color difference (ΔE) from the toner image exceeds the visual recognition limit of 3 that can be visually discerned by human eyes, the transparent toner is stressed by the supply auger 38 and the transport auger of the transparent developer, and the transparent toner is deteriorated. It turns out that it will be visually recognized by darkening.

  Further, as is clear from FIG. 7 above, when the rotation speed of the supply auger 38 and the transport auger of the transparent developer is 720 rpm, when the 1000 sheets are printed on the recording paper, the transparent toner portion and the recording paper are not in contact with each other. The color difference (ΔE) from the image portion exceeds the visual recognition limit of 3 that can be visually discerned by human eyes, the transparent toner is stressed by the supply auger 38 and the transport auger of the transparent developer, and the transparent toner It has been found that the color difference (ΔE) is close to 7 at the time when 5000 sheets are printed on the recording paper, and the color is visually recognized remarkably when the sheet is deteriorated and darkened.

  Although not shown as data as described above, even when the rotation speeds of the supply auger 38 and the transport auger of the transparent developer are set to 288 rpm, the developer is stirred well and the solid image is followed. There was no problem with sex.

Embodiment 2
FIG. 8 shows a second embodiment of the present invention. The same reference numerals are given to the same parts as those in the first embodiment. In the second embodiment, the stirring means of the transparent developing means is shown in FIG. Rather than setting the rotational speed smaller than the stirring means of the color developing means, the stirring means of the transparent developing means sets the diameter of the stirring blade smaller than that of the stirring means of the color developing means. It is configured.

  That is, in the second embodiment, as shown in FIG. 8B, the diameters of the supply auger 40 of the color developing devices 11Y, 11M, and 11C and the conveying blades 43 and 45 of the conveying auger 41 are set to 18 mm. On the other hand, in the transparent developing device 11T, the diameters of the supply blades 43 and 45 of the supply auger 40 and the transfer auger 41 are set to 12 mm. As a result, in the second embodiment, as shown in FIG. 8, when the developer 39 is transported by the supply auger 40 and the transport auger 41 of the transparent developing device 11T, the diameter of the transport blades 43 and 45 is 12 mm. Since it is set small, the conveying force exerted on the developer 39 is small, and the stress applied to the transparent toner in the developer 39 is reduced.

Experimental example 2
In order to confirm the effect of the above-described embodiment, the present inventor, as shown in FIGS. 8 (a) and 8 (b), is transparent with the diameters of the conveying blades 43 and 45 of the supply auger 40 and the conveying auger 41 set to 12 mm As shown in FIG. 5, similarly to Experimental Example 1, the developing unit 11T and the color developing units 11Y, 11M, and 11C in which the diameters of the conveyance blades 43 and 45 of the supply auger 40 and the conveyance auger 41 are set to 18 mm are used. In addition, using the OKTC (basis weight 127 gsm), A4 size SEF, which is a coated paper manufactured by OK, as the recording paper 12, a square transparent toner portion is formed at a density of 100% on a total of 5000 recording papers 12, every 1000 sheets of the density of the non-image area of the density and the recording sheet of the transparent toner portion L ^* a ^* b ^* using a spectroscopic optical meter (X-Rrite938 or 968) were measured, recorded Determined the value of L ^* a ^* b ^* of the non-image area of the paper, the transparent toner portion is an image portion of the value of Lp ^* ap ^* bp ^* of (patch section) was determined color difference (Delta] E).

  FIG. 9 is a graph showing the results of Experimental Example 2.

  As can be seen from FIG. 9, when the diameters of the supply auger 40 of the transparent developing device 11T and the conveying blades 43 and 45 of the conveying auger 41 are set to 12 mm, the transparent toner can be printed even if 5000 sheets are printed on the recording paper. The color difference (ΔE) between the image forming portion and the non-image portion of the recording paper can be maintained at 3 or less, which is a visual recognition limit that can be visually recognized by human eyes, and is transparent by the supply auger 38 and the conveyance auger of the transparent developer. It can be seen that it is possible to reduce the stress of the toner, and it is possible to prevent the transparent toner from deteriorating and darkening and visually observing an image that should be transparent.

  On the other hand, as apparent from FIG. 9, when the diameters of the supply auger 40 of the color developing units 11Y, 11M, and 11C and the conveying blades 43 and 45 of the conveying auger 41 are set to 18 mm, 2000 sheets are printed on the recording paper. At that time, the color difference (ΔE) between the transparent toner portion and the non-image portion of the recording paper exceeds 3 which is a visual recognition limit that can be visually recognized by human eyes, and the transparent auger supply auger 38 and the conveyance It can be seen that the transparent toner is stressed by the auger, and the transparent toner is deteriorated and darkened so that it is visually recognized.

  FIG. 10 is a graph confirming the followability of the toner amount when a solid image is developed.

The followability of a solid image is evaluated by the amount of decrease in the amount of toner on a recording sheet when 100 sheets are continuously output on an A4 size recording sheet at a density Cin of 100%. When the toner amount is less than 3 g / m ² , various problems such as reduction in gloss and generation of toner cloud occur.

As can be seen from FIG. 10, even when the diameters of the supply auger 40 of the transparent developing device 11T and the conveyance blades 43 and 45 of the conveyance auger 41 are set to 12 mm, the toner amount at the time of continuous printing of 100 sheets is 3 .6g / m is about ^2, well above the 3 g / m ^2, it can be seen that no problem occurs in the follow-up of the solid image.

  Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

Embodiment 3
FIG. 11 shows a second embodiment of the present invention. The same reference numerals are given to the same parts as those in the first embodiment. In the third embodiment, the stirring means of the transparent developing means is shown in FIG. Rather than setting the rotational speed smaller than the stirring means of the color developing means, the stirring means of the transparent developing means sets the pitch of the stirring blades smaller than that of the stirring means of the color developing means. It is configured.

  That is, in the third embodiment, as shown in FIG. 11, the pitch P1 of the supply auger 40 of the color developing units 11Y, 11M, and 11C and the conveyance blades 43 and 45 of the conveyance auger 41 is set to 20 mm. On the other hand, in the transparent developing device 11T, the pitch P2 of the conveying blades 43 and 45 of the supply auger 40 and the conveying auger 41 is set to 50 mm, which is twice or more. As a result, in the third embodiment, as shown in FIG. 11A, when the developer 39 is transported by the supply auger 40 and the transport auger 41 of the transparent developer 11T, the pitch of the transport blades 43 and 45 is increased. Since P2 is set as large as 50 mm, the time during which the developer 39 receives the transport force from the transport blades 43 and 45 is short, and the stress applied to the transparent toner in the developer 39 is reduced.

Experimental example 2
In order to confirm the effect of the above embodiment, the present inventor, as shown in FIG. 11, a transparent developing device 11T in which the pitch P2 of the conveying blades 43 and 45 of the supply auger 40 and the conveying auger 41 is set to 50 mm; As shown in FIG. 5, using the color developing units 11Y, 11M, and 11C in which the pitch P1 of the conveying blades 43 and 45 of the supply auger 40 and the conveying auger 41 is set to 20 mm, as shown in FIG. 12 using OKTC (basis weight 127 gsm), A4 size SEF, which is a coated paper made by OK Co., and forming a square transparent toner portion with a density of 100% on a total of 5000 recording papers, the non-image portion of the density L ^* a ^* b ^* of the concentration and the recording sheet of the transparent toner portion with a spectral photometer (X-Rrite938 or 968) were measured, for recording The value of L ^* a ^* b ^* of the non-image portion of the transparent toner portion is an image portion of the value of Lp ^* ap ^* bp ^* of (patch section) was determined and calculated color difference (Delta] E).

  FIG. 12 is a graph showing the results of Experimental Example 2.

  As can be seen from FIG. 12, when the pitch P2 of the supply blades of the supply auger 40 and the transfer auger 41 of the transparent developing device 11T is set to 50 mm, even if 5000 sheets are printed on the recording paper, The color difference (ΔE) with respect to the non-image portion of the recording paper can be maintained at about 3 which is a visual recognition limit that can be visually recognized by human eyes, and is transparent by the supply auger 40 and the conveyance auger 41 of the transparent developing device 11T. It can be seen that it is possible to reduce the stress of the toner, and it is possible to prevent the transparent toner from deteriorating and darkening and visually observing an image that should be transparent.

  On the other hand, as apparent from FIG. 12, when the pitch P1 of the feed blades 43 and 45 of the transparent auger 11T and the feed auger 41 is set to 20 mm, 2000 sheets are printed on the recording paper. The color difference (ΔE) between the transparent toner portion and the non-image portion of the recording sheet exceeds 3, which is the visual recognition limit that can be visually recognized by human eyes, and the supply auger 40 and the conveyance auger 41 of the transparent developing device 11T. As a result, the transparent toner is stressed, and the transparent toner deteriorates and darkens, so that it is visually recognized.

  FIG. 13 is a graph confirming the followability of the toner amount when a solid image is developed.

As apparent from FIG. 13, even when the pitch P2 of the conveying blades of the supply auger 40 and the conveying auger 41 of the transparent developing device 11T is set to 50 mm, the toner amount at the time of continuous printing of 100 sheets is about 3. It is about ² g / m ² and exceeds 3.0 g / m ² , and it can be seen that there is no problem in the followability of the solid image.

  Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

FIG. 1 is a block diagram showing a color image forming apparatus as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a longitudinal sectional view showing the developing device of the color image forming apparatus as the image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a cross-sectional view showing a developing device of the color image forming apparatus as the image forming apparatus according to Embodiment 1 of the present invention. FIG. 4 is a block diagram showing an auger of the developing device. FIG. 5 is a schematic diagram showing a sample for measuring the transparency of a transparent toner image. FIG. 6 is a graph showing a measurement result of a sample spectrophotometer for measuring the transparency of the transparent toner image. FIG. 7 is a graph showing the results of Experimental Example 1. FIG. 8 is a cross-sectional view showing a main part of a developing device of a color image forming apparatus as an image forming apparatus according to Embodiment 2 of the present invention. FIG. 9 is a graph showing the results of Experimental Example 2. FIG. 10 is a graph showing the results of Experimental Example 2. FIG. 11 is a cross-sectional view showing a main part of a developing device of a color image forming apparatus as an image forming apparatus according to Embodiment 3 of the present invention. FIG. 12 is a graph showing the results of Experimental Example 3. FIG. 13 is a graph showing the results of Experimental Example 3.

Explanation of symbols

  11Y, 11M, 11C: color developing unit, 11T: transparent developing unit, 35: developing roll, 40: supply auger, 41: transport auger.

Claims (4)

An image carrier that is driven to rotate and forms an electrostatic latent image according to image information on the surface;
Color developing means for developing the electrostatic latent image formed on the image carrier while stirring the two-component developer composed of the color toner and the carrier by the stirring means;
The electrostatic latent image formed on the image bearing member is developed while stirring the two-component developer composed of the transparent toner and the carrier by the stirring unit whose stirring ability is set smaller than that of the stirring unit of the color developing unit. An image forming apparatus comprising: a transparent developing unit. 2. The image forming apparatus according to claim 1, wherein the rotation speed of the stirring means of the transparent developing means is set smaller than the rotation speed of the stirring means of the colored developing means. The stirring means of the transparent developing means includes stirring blades formed in a spiral shape on the outer periphery of the rotating shaft, and at least one of the diameter or pitch of the stirring blades is smaller than that of the color developing device. The image forming apparatus according to claim 1, wherein the image forming apparatus is set. A single or a plurality of image carriers on which electrostatic latent images corresponding to a colored image and a transparent image are formed based on image information;
Among the single or plural image carriers, the electrostatic latent image of the color image formed on the corresponding image carrier is developed while stirring the two-component developer composed of the color toner and the carrier by the stirring means. Color developing means;
Among the single or plural image carriers, the electrostatic latent image of the transparent image formed on the corresponding image carrier is stirred by a stirring unit whose stirring ability is set smaller than that of the stirring unit of the color developing unit. An image forming apparatus comprising: a transparent developing unit that develops a two-component developer composed of a transparent toner and a carrier while stirring.

Images