JP2007323025A - Development device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development device which allows development with a transparent toner and with which miniaturization of an apparatus, suppression of cost increase and reduction in increase of the number of consumables are possible and improvement of transferability and enhancement of gloss can be achieved, and to provide an image forming apparatus. <P>SOLUTION: The development device 7a comprises: a developer housing section 8a housing a developer; a developer bearing member 5a which bears and transports the developer to develop an electrostatic latent image formed on an image bearing member 1a: and a developer supply means 13a to supply the developer to the developer bearing member 5a, wherein the developer includes a mixture of a first toner Tp which is charged to positive polarity and a second toner Tn which is charged to negative polarity, wherein at least one of the toners is a transparent toner. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention generally relates to a developing device and an image forming apparatus used in an image forming apparatus using an electrophotographic system or an electrostatic recording system such as a printer, a facsimile machine, and a copying machine. More specifically, the present invention relates to a developing device and an image forming apparatus that can perform development using a developer containing transparent toner in addition to colored toner.

  Conventionally, as an electrophotographic image forming apparatus, for example, an intermediate transfer type image forming apparatus is known. In this type of image forming apparatus, a toner image formed on a drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) as an image carrier is temporarily transferred onto an intermediate transfer member. The transfer is repeated a plurality of times to superimpose a plurality of color toner images on the intermediate transfer member to form a color toner image. Thereafter, these color toner images are collectively transferred onto a transfer material such as paper.

  FIG. 10 shows an example of an image forming apparatus using an intermediate transfer member.

  The image forming apparatus of this example includes a photosensitive drum 101 that is rotatably supported in the direction of arrow R1. Around the photosensitive drum 101, there are four developing units 105 and 106 each containing four color toners, that is, black (K), magenta (M), cyan (C), and yellow (Y). , 107 and 108 are arranged. Among these developing devices, one used for developing the electrostatic latent image on the photosensitive drum 101 is configured to abut on the photosensitive drum 101 by contact / separation means (not shown).

  The photosensitive drum 101 is uniformly charged by a charger 102, and an electrostatic latent image is formed by scanning light (laser light) 104 by a laser exposure optical system 103 or the like. Next, the electrostatic latent image is developed as a toner image with toner attached thereto by the above-described developing device 105 or the like, and is sequentially primary transferred onto an intermediate transfer belt 109 as an intermediate transfer member by a primary transfer roller 110 sequentially.

  The formation, development, and primary transfer of the electrostatic latent image described above are sequentially performed on the four color toners by the developing units 105 to 108 and the like, thereby forming a four-color color toner image on the intermediate transfer belt 109. Is done. Subsequently, these toner images are secondarily transferred collectively to a transfer material 118 that is nipped and conveyed by the secondary transfer roller 111 and the intermediate transfer belt 109.

  The above-described primary transfer and secondary transfer will be further described in detail.

First, when the photosensitive drum 101 is, for example, an OPC (organic optical semiconductor) photosensitive member having a negative charging characteristic, negative toner is used when developing the exposed portion of the laser light 104 with the developing units 105 to 108. . Accordingly, a positive transfer bias is applied to the primary transfer roller 110 by the bias power source 120. Conventionally, the intermediate transfer belt 109 has a thickness of 100 to 200 μm and a volume resistivity of about 10 ¹¹ to 10 ¹⁶ Ω · cm, such as PVdF (polyvinylidene fluoride), nylon, PET (polyethylene terephthalate), polycarbonate, and other resin films (if necessary In this case, the resistance is adjusted to be endless. Then, it is wound around the back roller 112, the driving roller 115, the tension roller 116, and the like, and is driven to rotate in the direction of the arrow.

As the primary transfer roller 110, a low resistance roller having a volume resistivity of 10 ⁵ Ω · cm or less was used. Thus, by using a thin film as the intermediate transfer belt 109, a large capacitance of several hundreds to several thousand pF can be secured in the primary transfer nip portion N1. Therefore, a stable transfer current can be obtained.

  With the above configuration, the primary transfer roller 110 and the bias power source 120 constitute a primary transfer unit.

  Next, the secondary transfer of the toner image onto the transfer material 118 is performed by secondary transfer means constituted by the secondary transfer roller 111, the back roller 112, the bias power source 121, and the like.

  In other words, the secondary transfer unit has the low resistance back roller 112 to which the ground or an appropriate bias is applied arranged as an opposing electrode inside the intermediate transfer belt 109, and the low resistance secondary transfer roller arranged on the outside. The secondary transfer nip portion N2 is configured by sandwiching the intermediate transfer belt 109 with the belt 111. With the above configuration, a positive transfer bias is applied to the secondary transfer roller 111 by the bias power supply 121, and the secondary transfer roller 111 is brought into contact with the back surface of the transfer material 118 to perform secondary transfer. .

  The primary transfer residual toner remaining on the surface of the photosensitive drum 101 after the above-described primary transfer is removed and collected by the cleaner 119, and the residual charge is further removed by the exposure device 117, and used for the next image formation.

  On the other hand, after the secondary transfer residual toner is removed by the cleaner 113, the surface of the intermediate transfer belt 109 on which the above-described secondary transfer has been completed is discharged by a charge removing charger (charge removing means) 114. As the charge eliminating charger 114, AC corona charging is often used. In order to increase the charge removal efficiency, a counter electrode (not shown) is generally provided inside the intermediate transfer belt 109.

  However, the above-described conventional example has the following problems.

  In the primary transfer, the toner transferred onto the intermediate transfer belt 109 bounces on the intermediate transfer belt 109 and is retransferred, so that the toner image is likely to be scattered and the image quality is deteriorated.

  In the secondary transfer, when smooth paper with small surface irregularities is used as the transfer material 118, all the toner images on the intermediate transfer belt 109 can be transferred to the transfer material. However, when plain paper having a large surface unevenness compared to smooth paper or rough paper having a large unevenness is used, there are the following problems.

  That is, at a portion corresponding to a low density portion of a monochromatic image, fine lines, fine character details, or the like, a toner image and a transfer material are in contact with each other, or a portion of a toner image that is not in contact at all is generated. Accordingly, there is a problem that the toner image is not transferred to the transfer material and is transferred.

  For example, Patent Documents 1 and 2 describe techniques for suppressing such transfer defects.

  In Patent Document 1, an elastic layer is provided on an intermediate transfer member. With this configuration, the elastic layer of the intermediate transfer member serves as a cushion during primary transfer to reduce the impact of toner. As a result, an effect of suppressing toner scattering on the intermediate transfer member is obtained. At the time of secondary transfer, there is an effect of increasing the contact area between the transfer material and the intermediate transfer member and suppressing transfer loss.

On the other hand, Patent Document 2 obtains the toner adhesion area of each pixel of a toner image based on image information carried on an image carrier. Next, a transparent toner is selectively applied to the obtained pixel having a small toner adhesion area, and then the image carrier and the recording medium are overlapped to transfer and fix the toner image together with the transparent toner on the recording medium. The With this configuration, a transparent toner is applied to the toner image, the toner image and the recording medium are in sufficient contact, and the toner image can be reliably transferred to the recording medium. Therefore, it is possible to form a high-quality image with little density unevenness and transfer loss without being affected by the surface properties of the recording medium.
Japanese Patent Laid-Open No. 10-186893 JP 2001-109208 A

  However, the above prior art has the following drawbacks.

  In the configuration in which the elastic layer is provided on the intermediate transfer member, it is necessary to uniformly form the thickness and electrical resistance of the elastic layer, and when these conditions are not satisfied, density unevenness occurs due to transfer unevenness. In addition, the durability is inferior to that of a general intermediate transfer belt using a resin film (resistance is adjusted if necessary) such as PVdF (polyvinylidene fluoride), nylon, PET (polyethylene terephthalate), and polycarbonate. . In addition, the number of manufacturing man-hours increases, leading to cost increases including material costs.

  In the configuration for transferring the toner image to the recording medium together with the transparent toner, it is necessary to add one developing unit for the transparent toner. Therefore, the cost of the image forming apparatus is increased and the apparatus is enlarged. Further, there is a problem that the printing speed required for the image forming process of the transparent toner is lowered. In addition, the number of consumables increases, leading to a decrease in usability.

  Accordingly, an object of the present invention is to enable the development of transparent toner, to reduce the size of the apparatus, to suppress the increase in cost, to reduce the increase in the number of consumables, and to improve transferability and increase gloss. It is an object to provide a developing device and an image forming apparatus.

The above object is achieved by the developing device and the image forming apparatus according to the present invention. In summary, according to the first aspect of the present invention, the developer containing portion that contains the developer and the developer that carries and conveys the developer to develop the electrostatic latent image formed on the image carrier. In a developing device comprising a developer carrier, and a developer supply means for supplying a developer to the developer carrier.
The developer includes a mixture of a first toner charged to a positive polarity and a second toner charged to a negative polarity, and one of the toners is a colorless transparent toner. An apparatus is provided.

According to a second aspect of the present invention, at least one image carrier on which an electrostatic latent image is formed, and at least one developing device that develops the electrostatic latent image on the image carrier into a toner image. A transfer unit that transfers the toner image directly to a transfer material conveyed by a transfer material conveyance unit or to an intermediate transfer member;
At least one of the developing devices is a developing device containing the transparent toner, and an image forming apparatus is provided.

According to the third aspect of the present invention, at least one image carrier on which an electrostatic latent image corresponding to image information is formed, and at least the electrostatic latent image on the image carrier is developed into a toner image. In an image forming apparatus comprising: one developing device; and a transfer unit that transfers the toner image directly to a transfer material conveyed by a transfer material conveyance unit or to an intermediate transfer member.
At least one of the developing devices is a developing device containing the transparent toner, and a developing device containing transparent toner and black toner as a developer.
Having color separation means for performing color separation without using a black color plate by separating the black and gray colors of image information into process black and process gray;
By performing color separation without using the black plate in the color separation means, development in the developing device containing the mixed toner can be performed with only transparent toner.
An image forming apparatus is provided.

  According to the present invention, image formation is performed using a developing device including a mixed developer in which at least a transparent toner and other toner are mixed, thereby reducing the size of the device, suppressing an increase in cost, and reducing the increase in the number of consumable items. It is possible to improve transferability and increase gloss.

  Hereinafter, the developing device and the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Example 1
FIG. 1 shows a schematic cross section of an embodiment of an image forming apparatus according to the present invention.

  First, the overall configuration of the image forming apparatus of this embodiment will be described. The image forming apparatus 100 according to the present exemplary embodiment is a laser beam printer that can form an image on a transfer material such as a recording paper, an OHP sheet, or a cloth using an electrophotographic method. The image forming apparatus 100 receives image information from an external host device such as a personal computer or a document reading device connected to the apparatus main body so as to be communicable, and forms an image according to the image input data.

  In particular, the image forming apparatus 100 according to the present exemplary embodiment uses an intermediate transfer capable of forming a full-color image using four color toners of yellow (Y), magenta (M), cyan (C), and black (K). This is an image forming apparatus of the type.

  The image forming apparatus 100 of the present embodiment includes a first image forming station Pa, a second image forming station Pb, a third image forming station Pc, and a fourth image forming station Pd as the image forming unit P. Each image forming station P (Pa, Pb, Pc, Pd) has a drum-type electrophotographic photosensitive member as an image carrier, that is, a photosensitive drum 1 (1a, 1b, 1c, 1d). Then, a developer image (toner image) is formed on the photosensitive drum 1.

  The developer images (toner images) formed on the respective photosensitive drums 1 are transferred onto an intermediate transfer belt 17 as an intermediate transfer member and synthesized thereon to form a color toner image. This synthetic toner image is further transferred to a transfer material P to obtain a recorded image.

  In this embodiment, each image forming station P (Pa, Pb, Pc, Pd) is provided with a developing device 7 (7a, 7b, 7c, 7d) as a developing means, and yellow ( It contains four color toners of Y), magenta (M), cyan (C), and black (K).

  In the present embodiment, any one of the developing devices described above is such that the developing device 7a includes a transparent toner in addition to a colored toner as a developer, and includes two types of developers (toners). Can be supplied.

  Therefore, according to the image forming apparatus of the present embodiment, the image forming unit can form an image by superimposing a total of five types of developers, that is, the above-described four color toners and transparent toners.

  Next, the configuration of each image forming station P will be further described.

  Since each image forming station P (Pa, Pb, Pc, Pd) has the same configuration, the following description will be made comprehensively without adding the suffixes a to d to each component.

  The photosensitive drum 1 is rotationally driven in the direction indicated by the arrow in the figure. Around the photosensitive drum 1, a charging roller 2 as a charging unit is provided. The charging roller 2 receives power from a charging high-voltage power supply (not shown) and uniformly charges the surface of the rotating photosensitive drum 1 to a constant potential. The surface of the charged photosensitive drum 1 is irradiated with a laser beam E emitted from a laser scanner 4 as an exposure means, reflected by a reflection mirror 3. As a result, the electrostatic potential of the portion of the photosensitive drum 1 that has received the exposure E fluctuates, and an electrostatic latent image corresponding to the desired color-separated image information is formed on the photosensitive drum 1.

  Next, at the facing portion (development position) G between the developing device 7 and the photosensitive drum 1, the electrostatic latent image is developed with toner of a desired color and visualized as a toner image.

  The toner image formed on the photosensitive drum 1 is transferred to the intermediate transfer belt 17 at the primary transfer portion N1 where the primary transfer roller 9 as a primary transfer unit contacts the photosensitive drum 1 via the intermediate transfer belt 17. In the primary transfer portion N1, a transfer bias having a desired polarity and potential is applied to the primary transfer roller 9.

  Excess toner remaining on the photosensitive drum 1 after the primary transfer process is scraped off by the cleaning blade 10 serving as a cleaning unit, and is stored in the cleaner container 14 as waste toner 16. The photosensitive drum 1 thus cleaned is again used for the next image forming process.

  Next, a full color image forming method by the image forming apparatus will be described.

  In FIG. 1, the developing devices 7b, 7c, and 7d provided in the second, third, and fourth image forming stations Pb, Pc, and Pd have a negatively charged yellow developer, a magenta developer, and a cyan developer, respectively. That is, negatively chargeable toner is stored.

  However, in this embodiment, the developing device 7a provided in the first image forming station Pa includes a positively charged transparent developer (positively charged toner) and a negatively charged black developer (negatively charged toner). Is housed.

  First, the developing device 7a of the first image forming station Pa will be described.

  In the developing device 7a in which positive and negative bipolar toners are mixed, an image defect called “fogging” in which toner that should not be supplied is supplied to the image portion on the photosensitive drum 1a to be developed is avoided. There is a need to. Therefore, it is desirable to extract positive and negative bipolar toners and develop them selectively. A specific means for coating a developing roller, which is a developer carrying member, with a toner having a proper polarity is described in Japanese Patent Application Laid-Open No. 2004-252420.

  According to the method described in this patent document, an electric field is provided between the developing roller and a supply roller for supplying toner onto the developing roller. Further, the toner blade upper layer on the main developing roller is peeled off by a relatively small mechanical adhesion force by the regulating blade as the developer regulating member. Then, a lower-layer toner having a proper polarity with an electrical mirror image force as a main adhesion force is selectively supplied to the development position G.

  In this embodiment, the method described in the above-mentioned patent document was used as a selective coating means for the developer onto the developing roller.

  FIG. 2 shows a schematic cross section of the developing device 7a of this embodiment.

  In the present embodiment, the developing device 7a includes a developing container 8a that is a developer accommodating portion that accommodates toner that is an insulating nonmagnetic one-component developer. The toner is formed by mixing a positively chargeable toner Tp (black circle, first toner in the figure) and a negatively chargeable toner Tn (white circle, second toner in the figure). Hereinafter, a mixture of the positively chargeable toner Tp and the negatively chargeable toner Tn is collectively referred to as a mixed developer (mixed toner) T.

  A developing roller 5a as a developer carrying member is rotatably disposed so as to be partly exposed from the developing container 8a at an opening portion of the developing container 8a facing the photosensitive drum 1a. The developing roller 5a plays a role of supplying toner held on the surface with rotation to the photosensitive drum 1a provided outside the developing container 8a.

  The developing roller 5a is not limited to this, but can be an elastic roller in which a conductive rubber 5B made of silicone rubber is formed on the outer periphery of the metal core 5A, and a urethane coating 5C is applied to the outermost layer. .

  A developing bias power source 12 as a voltage applying unit is connected to the developing roller 5a. A bias applied from the developing bias power source 12 to the developing roller 5a so that the toner on the developing roller 5a is peeled off by an electric field provided between the developing roller 5a and the photosensitive drum 1a and moves to the photosensitive drum 1a. The voltage is adjusted.

  A supply roller 13a is in contact with the developing roller 5a as a developer supply means. The supply roller 13a is rotationally driven in the direction of the arrow in the figure. The developing roller 5a and the supply roller 13a are rotated so that the surface movement directions are opposite to each other (counter direction) at the contact portion, and the positively chargeable toner Tp is positively frictionally charged, and the negatively chargeable toner Tn. Is negatively triboelectrically charged.

  The supply roller 13a is not limited to this, but can be configured by molding a conductive rubber (sponge layer) 13B made of urethane foam on the outer periphery of the metal core 13A.

  A supply bias power source 11 as a voltage applying unit is connected to the supply roller 13a. The voltage of the supply bias power supply 11 is variable, and the polarity of the potential difference between the supply roller 13a and the developing roller 5a can be switched. That is, the supply bias power supply 11 selectively selects a potential difference (electric field) such that one of the positively chargeable toner Tp and the negatively chargeable toner Tn is directed to the developing roller 5a (and therefore the other is directed to the supply roller 13a). It works as a switching means that can be set by switching. By switching the polarity of the potential difference with respect to the developer, the main toner carried on the developing roller 5a can be switched from two types of toner. Accordingly, it is possible to selectively change the type of toner used for development and supply a plurality of types of toner from one developing roller 5a to the photosensitive drum 1a to be developed.

  For example, when the negatively chargeable toner Tn is supplied from the supply roller 13a to the developing roller 5a (when the developing operation with the negatively chargeable toner Tn is performed), a negative voltage is generated between the developing roller 5a and the supply roller 13a. A potential difference (for example, a developing roller (developing bias): −400 V, a supply roller (supply bias): −800 V) is provided. That is, the potential difference between the developing roller 5a and the supply roller 13a is set by the supply bias power supply 11 and the development bias power supply 12. Here, the main toner carried on the developing roller 5a is a negatively chargeable toner, but a layer in which the negatively chargeable toner Tn and the positively chargeable toner Tp are mixed is formed on the upper layer of the toner layer. That is, as the toner layer supplied from the supply roller 13a to the developing roller 5a, a layer of the negatively chargeable toner Tn is formed in the lower layer, and a layer in which the negatively chargeable toner Tn and the positively charged toner Tp are mixed is formed in the upper layer.

  In the developing container 8a, a plate-like stirring member 15a is provided, and a flexible plate-like member such as Mylar is attached to a resin rotating shaft. The agitating member 15a rotates in the direction of the arrow in the drawing, and conveys and supplies the mixed developer T accommodated in the developing container 8a toward the developing roller 5a and the supply roller 13a.

  Further, in order to make the toner on the surface layer of the developing roller 5a a uniform thin layer, a regulating blade 6a as a developer regulating member is in contact with the developing roller 5a. The regulating blade 6a is fixed to the toner container 8a so as to contact the developing roller 5a with a relatively uniform contact pressure.

  The toner layer adhering to the surface layer (upper layer) is mainly mechanically adhering. Compared with the electric adhesion force due to the mirror force or Coulomb force of the lowermost toner layer in contact with the surface layer of the developing roller 5a, the adhesion force is weak. As a result, only the toner on the surface layer having a relatively weak adhesive force is scraped off by the regulating blade 6a. That is, the upper layer in which the negatively chargeable toner Tn and the positively chargeable toner Tp are mixed is separated by the regulating blade 6a, and the lower layer made of the negatively charged toner Tn passes through the regulating blade 6a. In other words, toner (positively charged toner) other than the main toner (negatively charged toner) can be separated by the regulating blade 6a.

  In this way, the regulating blade 6a selectively selects a toner layer (lower layer (one type of toner layer)) having the same polarity from the toner layer (upper layer and lower layer) formed on the developing roller 5a by the supply roller 13a. Acts as separation means for passing (separating).

  According to the present embodiment, the developing device 7a configured as described above has high developer separation efficiency. By using the developing device 7a configured as described above, “fogging” due to poor developer separation can be suppressed. In addition, even if “fogging” occurs due to toner with reversed polarity, since one of the mixed developers is a transparent toner, there is a “color fog” that occurs when toners of different hues and saturations are mixed together. It does not occur.

  Next, development and transfer to the photosensitive drum will be described.

  In this embodiment, a contact development method is used which is performed under the condition that the toner formed on the developing roller 5a and the electrostatic latent image are in contact with each other. In addition, a transparent toner image is transferred onto the photosensitive drum 1a by a regular development method (here, the developer is transferred to an unexposed portion of the photosensitive drum 1a charged to a polarity (negative polarity) opposite to the charging polarity of the developer). Is formed. The transparent toner image is transferred to the intermediate transfer belt 17 by a primary transfer roller 9a to which a negative bias is applied from a primary transfer bias power supply 41 that can generate a positive or negative bias voltage.

  The toner image of the positively charged transparent toner on the intermediate transfer belt 17 faces the corona charging portion 19 as the developer charging means and the intermediate transfer belt 17 as the intermediate transfer belt 17 rotates (rotates). Reach the part to be. Then, the toner image is negatively charged by the corona charging unit 19 to which the negative polarity bias is applied from the corona charging unit bias power supply 43, and thereafter becomes a negatively charged toner image.

  Thereafter, at the first image forming station Pa, the latent image formation is switched to reversal development, the timing is changed, the supply bias power supply 11 is changed, and black toner is supplied from the supply roller 13a to the development roller 5a. Then, in synchronism with the movement of the transparent toner image on the intermediate transfer belt 17, reversal development in contact with the photosensitive drum 1 a (here, an image carrier charged to the same polarity (negative polarity) as the developer charging polarity). Then, a toner image is transferred to the exposed portion of the toner), and a black (negatively chargeable toner) toner image is formed. This black toner image is superimposed and transferred onto the transparent toner image on the intermediate transfer belt 17.

  Further, toner images are also formed at the second, third, and fourth image forming stations Pb, Pc, and Pd, and transferred onto the toner images on the intermediate transfer belt 17 in an overlapping manner.

  That is, the developing devices 7b, 7c, and 7d of the second, third, and fourth image forming stations Pb, Pc, and Pd are configured similarly to the developing device 7a. However, as described above, only the negatively charged yellow developer, the magenta developer, and the cyan developer, that is, the negatively chargeable toner are accommodated as the developers. Accordingly, in these developing devices 7b, 7c, and 7d, unlike the developing device 7a, the voltage of the supply bias power supply 11 connected to the supply rollers 13b, 13c, and 13d is variable, and the potential difference from the developing rollers 5b, 5c, and 5d. There is no need to switch the polarity.

  Accordingly, in the photosensitive drums 1b, 1c, and 1d of the second, third, and fourth image forming stations Pb, Pc, and Pd, magenta toner (negatively chargeable toner), yellow toner (negatively chargeable toner), and cyan are obtained by reversal development. A toner (negatively charged toner) image is formed.

  As described above, the color toner images of black, magenta, yellow, and cyan formed at each image forming station P are primary to which a positive bias is applied from the primary transfer bias power sources 41, 42b, 42c, and 42d. Transfer is performed on the intermediate transfer belt 17 by the transfer rollers 9a, 9b, 9c, and 9d. In this way, a full color image is formed on the intermediate transfer belt 17 by superimposing the four color toner images on the transparent toner image.

  The transfer material P is conveyed with the movement and timing of the full-color toner image, and the opposite portion (secondary) between the conveying roller 18 disposed inside the intermediate transfer belt 17 and the corona charging unit 19 serving as a secondary transfer unit. The full color image is secondarily transferred onto the transfer material P at the transfer portion N2. At this time, a bias having a polarity (positive polarity) opposite to that of the toner on the intermediate transfer belt 17 is applied to the corona charging unit 19 from the secondary transfer bias power source 43. As described above, the corona charging unit 19 also functions as a charging unit that adjusts the charging polarity of the toner on the intermediate transfer belt 17 and a transfer unit that secondarily transfers the toner image from the intermediate transfer belt 17 to the transfer material P. The transfer material P is transported from the cassette 20 serving as a transfer material storage portion to the secondary transfer portion N2 by transport means such as a pickup roller 21, a transport roller pair 22, and a registration roller pair 23.

  The transfer material P on which the full-color toner image is placed on the transparent toner image is further conveyed and fixed on the transfer material P by the roller fixing device 24 serving as a fixing unit. Thereafter, the transfer material P on which the image is fixed is discharged from the image forming apparatus 100.

  In the above description, the negatively chargeable toner is black toner and the positively chargeable toner is transparent toner. However, the positively chargeable toner may be black toner and the negatively chargeable toner may be transparent toner.

  In this embodiment, the transparent toner is mixed with the black toner. However, in a full-color printer, other colored (cyan, magenta, yellow) toner and a transparent toner having a polarity different from that of the colored toner may be mixed. In particular, when mixed with yellow toner, even if yellow toner fog occurs on the transparent toner printing portion, it is difficult to recognize.

  In addition, the transparent toner as a base is desirably a sphere and has a small particle size, so that the smoothness of the transparent toner layer is increased, and the effect of suppressing scattering of other color toners transferred after the transparent toner is improved. growing.

  Specifically, in the toner-based circle equivalent diameter-circularity scattergram measured by the flow type particle image measuring apparatus, the toner equivalent circle average diameter is 2 to 10 μm, and the toner average circularity is Is 0.920 to 0.995, and the circularity standard deviation is preferably less than 0.040. A cleaning failure that is likely to deteriorate due to the use of a true sphere is a colorless transparent toner, and thus is tolerated more than other colored toners.

  The effects specific to this embodiment are as follows.

  That is, conventionally, for example, five developing devices have been required to form a transparent toner image on a four-color toner image, but four developing devices can be obtained by using the developing device of this embodiment having high developer separation efficiency. It is possible to add a transparent toner image to a full-color image of four colors by using at least one of the apparatuses as a developing device for transparent toner. Therefore, it is possible to reduce the size of the apparatus, suppress the cost increase, and reduce the increase in the number of consumables.

  Regarding the image quality, the transparent toner can be printed, so that a high gloss image can be formed. In addition, by placing transparent toner on the ground or overlapping a minute pattern or fine line, the degree of adhesion between the transfer material and the toner at the time of secondary transfer is increased, and the secondary transfer efficiency is increased. Further, with respect to the order of forming the image on the intermediate transfer belt 17, by transferring the transparent toner to the intermediate transfer belt first, it is possible to transfer other toner onto the transparent toner layer, and the elasticity of the transparent toner. Due to the effect of the body, scattering of the primary transfer is suppressed.

  Since one of the toners to be mixed is a transparent toner, even if “fogging” occurs due to a toner whose polarity is reversed, a “color fog” that occurs when mixed with toners of different hues and saturations does not occur.

  In the above embodiment, the mixed toner developing device 7a is arranged at the most upstream in the moving direction of the intermediate transfer belt 17, but the order may not be the most upstream.

  By constructing the developing device that changes the polarity of the toner and develops the mixed toner that requires two developments as the most downstream, that is, the developing device 7d of the fourth image forming station Pd as in this embodiment, the first print is performed. The out time can be shortened. Further, by reducing the number of times that the toner image initially formed on the intermediate transfer belt passes through the transfer nip, it is possible to suppress deterioration in transfer efficiency due to retransfer.

  In the above-described embodiment, the developer supply from the developing roller to the photosensitive drum is described as using the contact developing method, but a non-contact developing method may be used.

  Further, the supply of the developer to the developing roller is mainly composed of a mirror image force or a Coulomb force by an electric field, that is, a non-magnetic toner has been described. However, the other toner that is not the transparent toner of the mixed developer may have magnetism and be supplied with development by magnetic force under a magnetic field.

  Further, a developing method based on two-component contact development may be used using a mixed developer obtained by mixing three types of developer including a magnetic carrier, a colored toner, and a transparent toner having a polarity different from that of the colored toner.

  Further, in this embodiment, a so-called in-line image forming apparatus of a tandem type is used. However, the present invention is similarly applied to an image forming apparatus having a configuration as shown in a modified embodiment shown below, and the above-described embodiment. The same effect as Example 1 can be achieved.

Modified example 1
The modified embodiment shown in FIG. 3 is an image forming apparatus including the photosensitive drum and the four developing devices arranged around the photosensitive drum described above with reference to FIG.

  That is, the image forming apparatus according to the present modified embodiment is different from the image forming apparatus according to the first embodiment described with reference to FIG. 1 in that one image carrier, that is, one photosensitive drum 1 is arranged around the image forming apparatus. The configuration differs in that a plurality of developing devices are juxtaposed. The configuration of the developing device that characterizes the present invention is the same. Accordingly, members having the same functions and actions are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this modified embodiment, the image forming apparatus includes a photosensitive drum 1 that is rotatably supported in the direction of arrow R1. Around the photosensitive drum 1, four developing devices 7 (each having four color toners, ie, black (K), magenta (M), cyan (C), and yellow (Y), are stored. 7a, 7b, 7c, 7d) are arranged. Among these developing devices, those used for developing the electrostatic latent image on the photosensitive drum 1 are configured to abut against the photosensitive drum 1 by contact / separation means (not shown).

  In this modified embodiment, the developing device 7a contains a mixed developer containing transparent toner in addition to the black toner, as in the above-described embodiment. The image forming device and the developing device 7a It operates in the same way as the embodiment.

  That is, the photosensitive drum 1 is uniformly charged by the charger 2, and an electrostatic latent image is formed by the scanning light (laser light) E by the laser exposure optical system 4 or the like. Next, the electrostatic latent image is developed as a toner image with toner attached thereto by any of the developing devices 7, and sequentially transferred onto an intermediate transfer belt 17 as an intermediate transfer member by a primary transfer roller 9.

  The formation, development, and primary transfer of the electrostatic latent image described above are performed by the developing device 7 (7a, 7b, 7c, 7d) for the transparent toner and the four color toners in the same manner as described in the above embodiment. As a result, four color toner images are formed on the intermediate transfer belt 17. Next, these toner images are secondarily transferred onto the transfer material P all at once by the secondary transfer means 19.

  Also in this modified embodiment, it is desirable from the viewpoint of improving the primary transfer property that the developing operation color order is to first print a transparent toner image and form the transparent toner on the intermediate transfer belt 17 as a base. Further, the transparent toner may be mixed with at least one of the plurality of developing devices. However, it is not limited to this.

Modified embodiment 2
The modified example shown in FIG. 4 differs from the image forming apparatus according to the modified example 1 only in a configuration in which a rotary developing device equipped with a plurality of developing devices is arranged in parallel to face the photosensitive drum 1. It is. Accordingly, members having the same functions and actions are denoted by the same reference numerals, and detailed description thereof is omitted.

  In other words, the rotary developing device 7 includes four toners each containing toner of each color, that is, black (K), magenta (M), cyan (C), and yellow (Y). The developing devices 7a, 7b, 7c and 7d are mounted. Among these developing devices, the one that is used for developing the electrostatic latent image on the photosensitive drum 1 is moved to a developing position G that faces the photosensitive drum 1.

  In this modified embodiment, the developing device 7a contains a mixed developer containing transparent toner in addition to the black toner, as in the above embodiment, and operates in the same manner as in the above embodiment.

  That is, the electrostatic latent image formation, development, and primary transfer described above are performed by the developing device 7 (7a, 7b, 7c, 7d) for the transparent toner and the four colored toners in the same manner as described in the above embodiment. This is performed sequentially, whereby a four-color color toner image is formed on the intermediate transfer belt 17. Next, these toner images are secondarily transferred onto the transfer material P all at once by the secondary transfer means 19.

  Also in this modified embodiment, it is desirable from the viewpoint of improving the primary transfer property that the developing operation color order is to first print a transparent toner image and form it on the intermediate transfer belt with the transparent toner as a base. However, it is not limited to this.

Modified embodiment 3
In the present modified embodiment shown in FIG. 5, the image forming apparatus 100 has the same configuration as the in-line four-color full-color electrophotographic image forming apparatus described in the first embodiment with reference to FIG. However, in the image forming apparatus 100 according to the first exemplary embodiment, the toner image formed at each image forming station P (Pa, Pb, Pc, Pd) is transferred to the intermediate transfer belt 17 at one end, and then on the intermediate transfer belt. The combined color toner images were transferred onto the transfer material P all at once. On the other hand, in this modified embodiment, the toner image formed on the surface of the photosensitive drum 1 at each image forming station P (Pa, Pb, Pc, Pd) is transported by a transport belt 27 as a transfer material transport unit. The only difference is that the color image is recorded by being directly and sequentially transferred to the transfer material P transported by the printer.

  Therefore, members having the same configuration and function as those of the image forming apparatus of the above embodiment are denoted by the same reference numerals, and the description of the first embodiment is used, and the description thereof is omitted here.

  Also in this modified embodiment, it is desirable from the viewpoint of improving the primary transfer property that the transparent toner image is first printed and formed on the transfer material with the transparent toner as a base in the developing operation color order. However, it is not limited to this.

  In each of the first, second, and third modified examples, the developing device for mixed toner is disposed on the most upstream side, but the order may not be the most upstream. Also in the above modified embodiments, the developing method may be a contact developing method or a non-contact developing method.

  Further, the supply of the developer to the developing roller is mainly based on the mirror image force and the Coulomb force due to the electric field, that is, the non-magnetic toner has been described, but the other toner that is not the transparent toner of the mixed developer is used. May be provided with magnetism, and development may be supplied by magnetic force under a magnetic field.

  A developing method based on two-component contact development may be used using a mixed developer in which three kinds of developers, a magnetic carrier, a colored toner, and a transparent toner having a polarity different from that of the colored toner are mixed.

Modified embodiment 4
In the image forming apparatuses described in the first embodiment and the first to third modified embodiments, a color image can be formed using only a transparent toner without using a black color.

  That is, the image forming apparatus according to the fourth modified embodiment includes a color separation unit that performs color separation without using a black color plate by separating the black color and gray color of image information into process black and process gray. Yes. Then, color separation without using a black plate is performed by the color separation unit, whereby development in the developing device including the mixed toner is performed using only the transparent toner.

  In other words, as described above, in a full-color image forming apparatus using a mixed toner in which a black toner and a transparent toner having a different polarity are mixed in a black developing device, the black color, gray color, and shadow portion of image information are processed in process gray. And process black.

  With the image forming apparatus configured as described above, a black color is not used for color separation of image information, and development by the developing device using the mixed toner is developed with only transparent toner, and a full color image can be obtained. .

  The image forming apparatus of the present modified embodiment 4 is particularly like the image forming apparatus of the embodiment 1 described with reference to FIG. 1 and the image forming apparatus of the above modified embodiment 3 described with reference to FIG. This can be suitably implemented with an in-line image forming apparatus.

  In other words, according to the present modified example 4, in an inline-type full-color image forming apparatus including a developing device that accommodates a mixed developer and performs development twice, image formation of black color, gray color, shadow portion, etc. One-pass printing is made possible by printing only with transparent toner without using black toner.

  Further, the developing device including the mixed developer can be positioned on the most upstream side or the most downstream side with respect to the moving direction of the transfer material or the intermediate transfer member.

Example 2
The overall configuration of the image forming apparatus of this embodiment shown in FIG. 7 is the same as that of the image forming apparatus of Embodiment 1 shown in FIG. 1, except for the configuration of the developing apparatus provided with the mixed developer.

  That is, the developing device 7a including the mixed developer of Example 1 sequentially develops electrostatic latent images having different polarities using developers having different polarities. However, according to the developing device of the present example, static images having different polarities are developed. The difference is that the electrostatic latent image is developed at a time.

  In the following description, members having the same configurations and functions as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The in-line image forming apparatus and developing apparatus in this embodiment will be described.

  FIG. 7 shows the overall configuration of the image forming apparatus 100 of this embodiment, and FIG. 6 shows the configuration of an image forming station Pa provided with a developing device 7a having a configuration according to this embodiment.

  In this embodiment, the developing device having a specific configuration may be provided in any image forming station P. In this embodiment, the developing device is a developing device 7a provided in the first image forming station Pa. . The developing devices 7b to 7d provided in the other image forming stations 7b to 7d have the same configuration as described in the first embodiment.

  In this embodiment, the developing device 7a includes a developing container 8a that contains toner that is an insulating non-magnetic one-component developer. The toner contains a mixed developer T in which a positively charged transparent toner Tp and a negatively charged black toner Tn are mixed. According to the present embodiment, two developing rollers 25 and 32 as developer carriers are disposed in the developing container 8a.

  Further, the mixed developer T accommodated in the developing container 8a is conveyed toward the developing rollers 25 and 32 and the supply roller 13a by the stirring member 15a in the developing container 8a. The developing rollers 25 and 32 and the supply roller 13a can have the same configuration as the developing roller 5 and the supply roller 13 in the first embodiment.

  A supply roller 13a is in contact with the developing roller 25 and the developing roller 32 as a common supply member. The supply roller 13a is rotationally driven in the direction of the arrow in the figure, and the two developing rollers 25 and 32 and the supply roller 13a are rotated so that the surface movement directions are opposite to each other (counter direction) at the contact portion. ing. As a result, the positively chargeable toner Tp is positively frictionally charged, and the negatively chargeable toner Tn is negatively frictionally charged. The supply roller 13a is connected to a supply bias power source 37 as voltage applying means.

  The developing roller 25 and the developing roller 32 are respectively disposed so as to be rotatable in the direction of the arrow so as to be partially exposed from the developing container 8a at the opening of the developing container 8a facing the photosensitive drum 1. The developing roller 25 and the developing roller 32 play a role of supplying toner held on the surface with rotation to the photosensitive drum 1. A developing bias power source 38 and a developing bias power source 39 as voltage applying means are connected to the developing roller 25 and the developing roller 32, respectively. The bias voltages applied to the two developing rollers 25 and 32 from the developing bias power supplies 38 and 39 are moved to the photosensitive drum 1 as the toner on the developing roller is peeled off by an electric field provided between the developing drums 25 and 32. To be adjusted.

  In the first image forming station Pa, latent image formation is performed by scanning laser light from a semiconductor laser (not shown) by rotation of the polygon mirror 4 and reflecting the scanning light by the reflecting mirror 3a to expose the surface of the photosensitive drum 1a. It is done by doing. The photosensitive drum 1a is charged to a potential level Vh by receiving power from a charging high voltage power source (not shown) by the charging roller 2a. The exposed portion changes to the potential level VL. Further, by adjusting the light amount and light emission timing of the semiconductor laser and performing exposure, a latent image having an intermediate potential level Vm is provided in the vicinity of the middle between the exposed portion potential VL and the non-exposed portion potential Vh.

  Next, an example of the developing operation will be described in detail with reference to FIG.

  When the colored toner, that is, the negatively chargeable toner Tn is supplied to the developing roller 25 and the transparent toner, that is, the positively charged toner Tp is supplied to the developing roller 32, the following potential setting can be made.

  That is, a negative potential difference (for example, the developing roller (developing bias Vd1 = −400 V), the supplying roller (supply bias Vrs = −800 V)) is set between the developing roller 25 and the supply roller 13a. Further, a positive potential difference (for example, a developing roller (developing bias Vd2 = −1200 V) and a supplying roller (supply bias Vrs = −800 V)) is set between the developing roller 32 and the supply roller 13a.

  As in the first embodiment, the developing blade 25 is in contact with the regulating blade 26, and the developing roller 32 is in contact with the regulating blade 36. These regulating blades 26 and 36 are fixed to the developing container 8a so as to come into contact with the developing rollers 25 and 32 with a relatively uniform contact pressure. Then, only the toner on the surface layer of the developing rollers 25 and 32 is scraped off, whereby the developing roller 25 is selectively coated with the negatively chargeable toner Tn and the developing roller 32 is selectively coated with the positively chargeable toner Tp.

  In this embodiment, the photosensitive drum 1a is negatively charged by the voltage applied by the charging roller 2a. The toner is transferred from the developing roller 25 to the electrostatic image of the potential level Vh on the photosensitive drum 1a to a non-exposed portion of the photosensitive drum charged with a contact-type normal developing method (here, a polarity opposite to the charging polarity of the developer Thus, a positively chargeable toner image is formed. Further, the developer is transferred from the developing roller 32 to the electrostatic image of the potential level VL on the photosensitive drum 1a to the contact type reversal developing method (exposed portion of the photosensitive drum charged with the same polarity as the toner charging polarity). ) To form a negatively chargeable toner image. Further, toner is not supplied to the electrostatic image at the potential level Vm on the photosensitive drum 1a.

In this embodiment, the magnitude relationship between each developing bias and the potential level of the photosensitive drum surface is as shown in FIG.
VL (about 0 V)> Vd1 (−400 V)> Vm (about −800 V)> Vd2 (−1200 V)> Vh (−1600 V)
Is set.

  That is, a negatively chargeable black toner is developed on the exposed portion of the potential VL, a positively charged transparent toner is developed on the non-exposed portion of the potential Vh, and no toner is developed on the exposed portion of the potential Vm.

  The developed positively charged transparent toner is negatively charged by injecting a negative charge when passing through the corona charger 34, and can be handled as a negatively charged toner in the subsequent processes.

  The multiple developed toner image formed on the photosensitive drum 1a by the black toner and the transparent toner is transferred to the intermediate transfer belt 17 by the primary transfer roller 9a to which a positive bias is applied from the primary transfer bias power source 41.

  The method for selectively applying the transparent toner to the area other than the black toner printing portion has been described above. However, in order to increase the gloss and make the gloss uniform by applying some transparent toner to the entire image area and coating the entire image with the transparent toner, exposure for creating a latent image level of the potential Vm. The transparent toner may be applied to the entire area other than the black toner printing portion.

  In the in-line full-color image forming apparatus 100 that holds the yellow, magenta, and cyan developing devices 7b, 7c, and 7d of the present embodiment shown in FIG. 7, five types of developer including transparent toner are transferred to the intermediate transfer belt. 17 can be printed by one rotation.

  Further, as described above, according to the present embodiment, it is possible to add a transparent toner image to a full-color image of four colors by the four developing devices 7 (7a, 7b, 7c, 7d). In this case, gloss control and transferability can be improved.

  In general, in order to form a full-color image, the color separation toner images of CMYK color toner and transparent toner are overlapped. In this embodiment, a developing device that holds a mixed developer containing transparent toner is disposed at the most upstream. As a result, it becomes possible to form a CMY color toner image with transparent toner as a base. Thereby, for example, by using image processing that selectively applies transparent toner to a fine pattern of CMY colors or an image boundary, it is possible to suppress transfer scattering and transfer failure.

  As described above, as an effect peculiar to the present embodiment, by simultaneously developing transparent toner and black toner as a mixed developer, five types of developer including transparent toner are printed at high speed with one rotation of the intermediate transfer belt. A full-color printer can be realized.

  In the above-described embodiment, the mixed toner developing device is disposed on the most upstream side, but the order may not be the most upstream.

  In the above-described embodiment, the developer supply from the developing roller to the photosensitive drum has been described using the contact developing method, but a non-contact developing method may be used.

  Further, the supply of the developer to the developing roller is mainly based on the mirror image force and the Coulomb force due to the electric field, that is, the non-magnetic toner has been described, but the other toner that is not the transparent toner of the mixed developer is used. May be provided with magnetism, and development may be supplied by magnetic force under a magnetic field.

  A developing method based on two-component contact development may be used using a mixed developer in which three kinds of developers, a magnetic carrier, a colored toner, and a transparent toner having a polarity different from that of the colored toner are mixed.

  Further, in this embodiment, the inline image forming apparatus is used. However, the present invention is similarly applied to an image forming apparatus having a configuration as shown in the following modified embodiment, and the same operation as that of the second embodiment. An effect can be achieved.

  For example, according to the modified embodiment shown in FIG. 9, the image forming apparatus 100 has the same configuration as the in-line four-color full-color electrophotographic image forming apparatus described in the second embodiment with reference to FIG. The However, in the image forming apparatus 100 according to the second embodiment, the toner image formed at each image forming station P (Pa, Pb, Pc, Pd) is transferred to the intermediate transfer belt 17 at one end, and then on the intermediate transfer belt. The combined color toner images were transferred onto the transfer material P all at once. On the other hand, in the present modified embodiment, each image forming station P (Pa, Pb, Pc, Pd) is provided in the same manner as in the modified embodiment 3 in the previous embodiment 1 described with reference to FIG. Thus, the toner images formed on the surface of the photosensitive drum 1 are sequentially and directly transferred onto the transfer material P conveyed by the conveying belt 27 to record a color image.

  Accordingly, members having the same configuration and function as those of the image forming apparatus according to the second embodiment are denoted by the same reference numerals, and the description of the second embodiment and the modified third embodiment in the first embodiment is referred to here. The re-explanation will be omitted.

  Also in this modified embodiment, the order of the developing operation color is to first print a transparent toner image and a black toner image, and to form on the transfer material with the transparent toner as a base, transfer scattering is suppressed, and the primary transfer property is improved. From the viewpoint of However, it is not limited to this.

  Further, also in the second embodiment, a configuration in which a plurality of developing devices are arranged opposite to the photosensitive drum can be employed, as in the case of the first modified embodiment of the first embodiment shown in FIG. With such a configuration, the developing device is switched to sequentially form monochromatic toner images on the photosensitive drum, and monochromatic toner images are sequentially formed on the intermediate transfer belt. Similarly to the above embodiment, the developing device 7a contains a mixed developer containing transparent toner in addition to black toner, and operates in the same manner as in the above embodiment.

  Further, similarly to the modified example 2 in the example 1 shown in FIG. 4, a rotary developing device equipped with a plurality of developing devices can be arranged in parallel to face the photosensitive drum 1. With such a configuration, the developing device is switched to sequentially form monochromatic toner images on the photosensitive drum, and monochromatic toner images are sequentially formed on the intermediate transfer belt. As in the above embodiment, the developing device 7a contains a mixed developer containing transparent toner in addition to black toner, and operates in the same manner as in the above embodiment.

  In each of the above-described modified embodiments, the developing device including the mixed developer is disposed on the most upstream side, but the order may not be the most upstream. The developing device containing the mixed developer may be at least one of a plurality of developing devices.

  Also in the above modified embodiments, the developing method may be a contact developing method or a non-contact developing method.

  Further, the supply of the developer to the developing roller is mainly based on the mirror image force and the Coulomb force due to the electric field, that is, the non-magnetic toner has been described, but the other toner that is not the transparent toner of the mixed developer is used. May be provided with magnetism, and development may be supplied by magnetic force under a magnetic field.

  A developing method based on two-component contact development may be used using a mixed developer in which three kinds of developers, a magnetic carrier, a colored toner, and a transparent toner having a polarity different from that of the colored toner are mixed.

1 is a schematic cross-sectional view of an embodiment of an image forming apparatus of the present invention. 2 is a schematic cross-sectional view of an embodiment of the developing device of the present invention. It is a schematic sectional drawing of the other Example of the image forming apparatus of this invention. It is a schematic sectional drawing of the other Example of the image forming apparatus of this invention. It is a schematic sectional drawing of the other Example of the image forming apparatus of this invention. It is a schematic sectional drawing of the developing apparatus of another Example of this invention, and exposure and a transfer part. It is a schematic sectional drawing of the other Example of the image forming apparatus of this invention. It is a figure explaining the electric potential structure in the image development apparatus of the Example shown to FIG. 6, FIG. 7 of this invention. It is a schematic sectional drawing of the other Example of the image forming apparatus of this invention. It is a schematic sectional view of an image forming apparatus using a conventional intermediate transfer member.

Explanation of symbols

1 (1a, 1b, 1c, 1d) Photosensitive drum (image carrier)
2 (2a, 2b, 2c, 2d) Charging roller (charging means)
4 Laser scanner (exposure means)
5 (5a, 5b, 5c, 5d) Developing roller (developer carrier)
6 (6a, 6b, 6c, 6d) regulating blade (developer regulating member, separating means)
7 (7a, 7b, 7c, 7d) Developing device 8 (8a, 8b, 8c, 8d) Developer container (developer container)
9 (9a, 9b, 9c, 9d) Primary transfer roller (primary transfer means)
11 Supply bias power supply (switching means, voltage applying means)
12 Development bias power supply (switching means, voltage application means)
13 Supply roller (developer supply means)
15 Stirring member 17 Intermediate transfer belt (intermediate transfer member)
19 Corona charger (secondary transfer means)
25, 32 Development roller (developer carrier)
26, 36 Regulating blade (separation means)
27 Conveying belt (transfer material conveying means)
34 Corona charger 37 Supply bias power supply (separation means, voltage application means)
38, 39 Development bias power supply (separation means, voltage application means)
41 Primary transfer bias power source 42 (42b, 42c, 42d) Primary transfer bias power source 43 Secondary transfer bias power source 50 Boundary of latent image level Tn Negatively chargeable toner (colored toner)
Tp Positively chargeable toner (transparent toner)
T Mixed developer P Transfer material

Claims (17)

A developer container that contains the developer; a developer carrier that carries and conveys the developer to develop an electrostatic latent image formed on the image carrier; and a developer that is applied to the developer carrier. A developer supply means for supplying the developer,
The developer includes a mixture of a first toner charged to a positive polarity and a second toner charged to a negative polarity, and one of the toners is a colorless transparent toner. apparatus. The developer carrier is one developer carrier,
Switching means for selectively switching main toners to be carried on the developer carrier from the first and second toners;
Separating means for separating toner other than the main toner carried on the developer carrying member;
The developing device according to claim 1, further comprising:   The separating means is a developer regulating member that regulates the developer layer carried on the developer carrying body in order to separate the upper layer of the developer layer formed on the developer carrying body, and the switching means Is a voltage application means for applying a voltage between the developer carrier and the developer supply means in order to switch the polarity of the potential difference between the developer carrier and the developer supply means with respect to the developer. The developing device according to claim 2, wherein:   4. The developing device according to claim 2, wherein a developing operation using a transparent toner is first performed among the first and second toners. The developer carrier is two developer carriers,
2. The separation device according to claim 1, further comprising: a separating unit that separates toner carried on the one developer carrying member and toner carried on the other developer carrying member from the first and second toners. Development device.   Each of the developer regulating members for regulating the developer layer carried on each developer carrier in order to separate the upper layer of the developer layer formed on each developer carrier; and Voltage application means for applying a voltage between each developer carrier and the developer supply means in order to change the polarity of the potential difference between each developer carrier and the developer supply means with respect to the developer. The developing device according to claim 5, wherein:   7. The developing device according to claim 5, wherein a developing operation using the transparent toner and a developing operation using another toner can be performed simultaneously.   The transparent toner has a toner equivalent circle average diameter of 2 to 10 μm and a toner average circle in a scattergram based on the number equivalent circle of the toner measured by a flow type particle image measuring apparatus. The developing device according to claim 1, wherein the developing device is a toner having a degree of 0.920 or more and a circularity standard deviation of less than 0.040. At least one image carrier on which an electrostatic latent image is formed, at least one developing device for developing the electrostatic latent image on the image carrier into a toner image, and transferring the toner image to a transfer material conveying unit In an image forming apparatus provided with a transfer unit that transfers directly to a transfer material conveyed by the transfer to an intermediate transfer member,
An image forming apparatus, wherein at least one of the developing devices is a developing device including the transparent toner according to claim 1.   The image forming apparatus according to claim 9, wherein a plurality of the developing devices are arranged around one image carrier.   11. The image forming apparatus according to claim 10, wherein the developing device located on the most upstream side or the most downstream side with respect to the rotation direction of the image carrier is a developing device containing a transparent toner.   A rotating body equipped with a plurality of the developing devices is provided facing one image carrier, and each of the developing devices develops an electrostatic latent image on the image carrier sequentially by driving the rotating body. The image forming apparatus according to claim 9, wherein the image forming apparatus is moved to a developing position.   The image forming apparatus according to claim 9, further comprising a plurality of the image carriers, wherein the developing device is arranged corresponding to each of the image carriers.   The developing device provided corresponding to the image carrier located on the most upstream side or the most downstream side with respect to the moving direction of the transfer material or the intermediate transfer member is a developing device containing transparent toner. The image forming apparatus according to claim 13. At least one image carrier on which an electrostatic latent image corresponding to image information is formed, at least one developing device that develops the electrostatic latent image on the image carrier into a toner image, and the toner image In an image forming apparatus comprising a transfer unit that transfers directly to a transfer material conveyed by a transfer material conveyance unit or to an intermediate transfer member,
At least one of the developing devices is the developing device according to any one of claims 1 to 3, wherein the developing device includes a transparent toner and a black toner as a developer.
Having color separation means for performing color separation without using a black color plate by separating the black and gray colors of image information into process black and process gray;
By performing color separation without using the black plate in the color separation means, development in the developing device containing the mixed toner can be performed with only transparent toner.
An image forming apparatus.   16. The image forming apparatus according to claim 15, further comprising a plurality of the image carriers, wherein the developing device is arranged corresponding to each of the image carriers.   The developing device provided corresponding to the image carrier located on the most upstream side or the most downstream side with respect to the moving direction of the transfer material or the intermediate transfer member is a developing device containing transparent toner. The image forming apparatus according to claim 16.

Images