JP2007004066A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and an image forming method by which an excellent transfer image is obtained on a recording medium having at least two areas different in electric resistance. <P>SOLUTION: The image forming apparatus 100 is equipped with an image unit 1T for forming a transparent toner image in addition to an image unit for forming a color toner image. The image forming apparatus 100 has an image processing part F1, an image data decomposing part F2, an area discrimination part F3 and an exposure data generation part F4. The area discrimination part F3 discriminates between a low resistance area and a high resistance area based on the resistance distribution data of a transfer body. Then, image data for forming the transparent toner image in the low resistance area is formed. Therefore, the transparent toner image is formed at a position equivalent to the low resistance area of the transfer body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus and an image forming method. More specifically, the present invention relates to an image forming apparatus and an image forming method for forming an image on a recording medium using transparent toner and having regions having different electric resistances in the same plane.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a roller transfer method, a corona transfer method, and the like are known as methods for transferring a toner image to a recording medium. In these systems, the toner image is transferred by an electric force by generating an electric field in the direction in which the toner is transferred between the toner image carrier (for example, a photosensitive drum) and the recording medium.

  The strength of the transfer electric field has an optimum range depending on the charge amount and adhesion amount of the toner. If it is lower than this range, the toner transfer force is insufficient, resulting in a transfer failure. On the other hand, if it is stronger than that range, a leak occurs and a transfer failure occurs.

  In recent years, recording media that combine different media are used as one recording medium. For example, a card sending mount with a card used for the purpose of mailing a card is a recording medium in which a card made mainly of PET (polyethylene terephthalate) is pasted on a paper mount. Yes. In recent image forming apparatuses, those capable of printing such a recording medium, for example, printing a mount and a card in a lump are put into practical use.

When printing on such a recording medium composed of a plurality of members, there is a problem that optimum transfer conditions differ for each region of the members. As a technique focusing on this problem, for example, Patent Document 1 uses a transparent color toner (hereinafter referred to as “transparent toner”) in order to suppress variations in transfer conditions caused by irregularities on the surface of the recording medium. A method is disclosed.
JP 2002-108039 A

  However, the conventional image forming apparatus described above has the following problems. That is, in a recording medium composed of two or more members, the electrical resistance differs for each region of the members. Therefore, such a recording medium has a high resistance region and a low resistance region. Variations in transfer conditions are caused not only by variations in the surface shape of the recording medium but also by differences in the electrical resistance of the transfer body.

  That is, the electrical resistance of a transfer medium such as a recording medium is one of the factors that greatly affects the strength of the transfer electric field. If the transfer bias is fixed at a constant value, it is known that the transfer electric field increases when the electric resistance of the transfer member is small, and the transfer electric field decreases when the electric resistance is large. Therefore, when transferring to a recording medium in which a region having a high electrical resistance (card portion) and a region having a low electrical resistance (mounting portion) are mixed, such as a mount with a card as shown in FIG. The strength of the transfer electric field is different, and transfer failure occurs in at least one region.

  The present invention has been made to solve the problems of the conventional image forming apparatus described above. That is, an object of the present invention is to provide an image forming apparatus and an image forming method capable of obtaining a good transfer image on a recording medium having at least two regions having different electric resistances.

  An image forming apparatus for solving this problem is an image forming apparatus that generates an electric field between a toner image carrier and a transfer member, and transfers the toner image onto the transfer member by an electric action. An area extraction unit that acquires an electrical resistance distribution in the surface of the transfer body, extracts an area in the surface of the transfer body that has an electrical resistance smaller than the electrical resistance of other areas by a predetermined value or more, and an area; In the region extracted by the extraction unit, a transparent toner image forming unit for forming a toner image with a transparent color toner is provided.

  That is, in the image forming apparatus of the present invention, the electric resistance distribution of the transfer body is acquired by the region extraction unit. The electrical resistance distribution is a distribution of electrical resistance within the same surface of the transfer body, and may be obtained from measured values of a dielectric relaxation measuring device or the like, or the electrical resistance distribution of the transfer body is stored in a database in advance. You may select from a database. Then, a low electric resistance region (low resistance region) in the surface of the transfer body is extracted from the electric resistance distribution. As a method for extracting the low resistance region, for example, a region where a difference from the electric resistance of a reference region (for example, a region having the highest electrical resistance) is a predetermined value or more may be set as the low resistance region. Alternatively, when a reference electrical resistance (for example, electrical resistance of the mount) is set and a region having a higher electrical resistance than the electrical resistance by a predetermined value (high resistance region) is extracted, a region within the predetermined value is reduced to a low resistance. It may be extracted as a region.

  Then, a transparent toner image forming unit forms a toner image (hereinafter referred to as “transparent toner image”) with transparent toner in the extracted low resistance region. The transparent toner image is transferred to the transfer body prior to the transfer of the colored toner image or simultaneously with the transfer of the colored toner image. As a result, the transparent toner image acts as a high electrical resistance layer during the transfer of the colored toner image. Therefore, the electric field strength in the low resistance region in the transfer body can be weakened during transfer, and the electric field strength difference can be reduced.

  The image forming apparatus according to the present invention further includes a colored region extracting unit that extracts a region carrying colored toner, and the transparent toner image forming unit forms a toner image at least in the region extracted by the colored region extracting unit. Better to do. In other words, in order to avoid image noise due to transfer defects, it is only necessary to reduce variations in electric field strength in the area carrying colored toner. For this reason, a transparent toner image is formed at least in a region carrying colored toner. That is, instead of forming a transparent toner layer over the entire low-resistance region, a transparent toner image is formed only at or around the portion where the colored toner exists. As a result, the amount of transparent toner used and the amount of waste toner can be reduced.

  In addition, the transparent toner image forming unit of the image forming apparatus of the present invention preferably determines the thickness of the toner image according to the electric resistance of each region of the transfer body. That is, the electrical resistance varies depending on the difference in electrical resistance (for example, the difference in the material of the transfer body and the difference in thickness even if the same material is used). The appropriate development amount of transparent toner (weight per unit area of toner) varies depending on the difference in electrical resistance. In addition, when there are three or more regions having different electric resistances in the same plane, an appropriate transparent toner thickness cannot be determined as one. Therefore, by determining the thickness of the toner image according to the electric resistance of each region of the transfer body, it is possible to deal with various transfer bodies.

Specifically, for example, a transfer comprising a high resistance material having a volume resistivity of 10 ¹³ Ωcm or more and a low resistance material having a volume resistivity of 10 ¹¹ Ωcm or less, and having a low resistance region constituted by the low resistance material. When an image is formed on a body, a transparent toner image is formed in the low resistance region, and the thickness of the transparent toner image is determined by the following equation (A).
dt = α × εt / εh × dh (A)
dt: thickness of transparent toner image α: coefficient 0.5 <α <2.0
εt: dielectric constant of transparent toner εh: dielectric constant of high resistance material dh: thickness of high resistance material portion

In addition to this, for example, when an image is formed on a transfer body made of a high resistance material having a volume resistivity of 10 ¹³ Ωcm or more and having two or more regions having different thicknesses, the transfer body is thin. A transparent toner image is formed in the region, and the thickness of the transparent toner image is determined by the following equation (B).
dt = α × εt / εh × Δd (B)
dt: thickness of transparent toner image α: coefficient 0.5 <α <2.0
εt: dielectric constant of transparent toner εh: dielectric constant of high resistance material Δd: difference compared to the thickest portion of the transfer body

  According to the present invention, by forming a transparent toner image in the low resistance region, the electric field strength in the low resistance region can be weakened during transfer, and the difference in electric field strength from the high resistance region can be alleviated. Therefore, a good transfer image can be obtained for a recording medium having at least two regions having different electric resistances.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an image forming apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to a tandem type color printer.

  The image forming apparatus 100 of the present embodiment is a tandem full-color printer, and has five image forming units arranged in parallel as shown in FIG. Specifically, the color printer 100 of the present embodiment includes colored image forming units 1K, 1C, 1M, and 1Y and a transparent image forming unit 1T. In addition, an intermediate transfer belt 8, a secondary transfer device 9, a fixing device 10, a cleaning blade 11, a paper feed cassette 12, and the like are provided. Further, primary transfer units 5K, 5C, 5M, 5Y, and 5T are arranged to face each image forming unit through the intermediate transfer belt 8. Further, neutralizing members 7K, 7C, 7M, 7Y, and 7T are disposed on the downstream side of each primary transfer device in the moving direction of the intermediate transfer belt 8.

  Each image forming unit forms a toner image of each color. Each image forming unit corresponds to each color of black (K) for the image forming unit 1K, cyan (C) for the image forming unit 1C, magenta (M) for the image forming unit 1M, and yellow (Y) for the image forming unit 1Y. ing. The arrangement of the image forming units is not limited to the above order. In addition to the colored image forming unit, the image forming apparatus 100 includes an image forming unit 1T that forms a toner image of transparent toner (T). On the intermediate transfer belt 8, a toner image of transparent toner is superimposed on a toner image of four colors K, C, M, and Y. As the transparent toner, for example, a toner that is normally used as a binder resin (binder resin) for the toner may be used.

  Further, the image forming unit 1K has a photosensitive drum 2 that carries a toner image as shown in FIG. The photosensitive drum 2 is rotated at a constant speed in the direction of the solid line arrow in FIG. Further, around the photosensitive drum 2, a cleaning member 6, a charging device 3, and a developing device 4 are sequentially arranged along the rotation direction. An exposure unit (a dotted arrow in FIG. 2) where a latent image is formed is provided between the charging device 3 and the developing device 4. The other image forming units have the same configuration.

  The charging device 3 uniformly charges the surface of the photosensitive drum 2. The charging device 3 is of a scorotron type, and is attached so as to face the photosensitive drum 2 in a direction orthogonal to the rotation direction of the photosensitive drum 2. A bias having the same polarity as that of the toner is applied, and a uniform potential is applied to the surface of the photosensitive drum 2 by corona discharge. As the charging device 3, in addition to a non-contact type charging device that is charged by corona discharge, a contact-type charging device that contacts and charges the surface of the photosensitive drum 2 with a conductive contact charging member can be applied.

  An exposure optical system for forming a latent image in the exposure unit includes a linear exposure element in which LEDs (light emitting diodes) as light emitting elements are arranged in an array parallel to the axial direction of the photosensitive drum 2, and a unity coupling element. And an optical unit mounted on a holder. As the exposure element, a plurality of light emitting elements such as FL (phosphor light emission), EL (electroluminescence), and PL (plasma discharge) may be arranged in an array in addition to the LED.

  The developing device 4 has a function of applying toner onto the latent image. The developing device 4 may be a contact type or a non-contact type. Further, the developing method may be a two-component developing method including toner and a carrier, or a one-component developing method not including a carrier. In this embodiment, negatively charged toner is used. However, positively charged toner may be used as long as the toner image can be developed.

  The primary transfer units 5K, 5C, 5M, 5Y, and 5T corresponding to the respective colors form a transfer electric field with the photosensitive drum 2. A DC electric field having a polarity opposite to that of toner (plus polarity in this embodiment) is applied to each primary transfer device to form a transfer electric field. A neutralizing member constituted by a corona discharger is provided on the downstream side of each primary transfer unit in the moving direction of the intermediate transfer belt 8, and the intermediate transfer belt 8 charged by the primary transfer unit is provided. Perform static elimination.

  A colored or transparent toner image is formed by the image forming unit corresponding to each color. These toner images are transferred so as to be superimposed on the intermediate transfer belt 8. The toner remaining on the photosensitive drum 2 after the transfer is recovered by a cleaning member 6 that recovers the toner mechanically or electrically.

The intermediate transfer belt 8 is an endless belt member that carries a toner image of each color. The volume resistivity is 10 ¹⁰ Ωcm to ^{10 15} Ωcm. For example, a material in which a conductive material is dispersed in an engineering synthetic resin such as modified polyimide, thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, and nylon alloy is applicable. The intermediate transfer belt 8 has a two-layer structure in which a fluorine coating having a thickness of 5 μm to 50 μm is applied to the outside of a semiconductor film substrate having a thickness of 0.1 mm to 1.0 mm as a layer for preventing toner filming. have. As the substrate of the intermediate transfer belt 8, a semiconductor rubber belt having a thickness of 0.5 mm to 2.0 mm in which a conductive material is dispersed in silicon rubber or urethane rubber is also applicable.

  The intermediate transfer belt 8 is stretched around the drive roller, the tension roller, and the backup roller. During image formation, the drive roller rotates and the intermediate transfer belt 8 rotates in the direction of the arrow in FIG.

  Next, an operation when an image is formed by the image forming apparatus 100 of this embodiment will be described. First, the surface of the photosensitive drum 2 is uniformly charged to a predetermined potential by the negative bias applied to the charging device 3. Next, a latent image is formed in the exposure unit.

  Next, the developing device 4 performs development with negative polarity toner, and a toner image of the first page is formed on the photosensitive drum 2. Next, the toner image of the first page is transferred onto the intermediate transfer belt 8 by the primary transfer unit 5. That is, the toner on the photosensitive drum 2 is transferred to the intermediate transfer belt 8 by the positive polarity bias of the primary transfer unit 5. At this time, a part of the toner remains on the photosensitive drum 2 without being transferred and becomes residual toner. Further, a part of the residual toner is shifted to positive polarity. The residual toner is electrically collected by the cleaning member 6 to which the negative polarity bias is applied. Thereafter, the surface of the photosensitive drum 2 is charged again by the charging device 3.

  Such an operation is repeated for each image forming unit, and the toner images of the respective colors are superimposed on the intermediate transfer belt 8. Then, a color image is formed on the intermediate transfer belt 8 by superimposing the four-color toner image and the transparent toner image. The color image moves to the secondary transfer position, and is transferred onto the recording paper P by the secondary transfer unit 9 at once.

  The recording paper P on which the toner image obtained by superimposing the four-color toner image and the transparent toner image is discharged by the discharging electrode 13 formed of a sawtooth electrode and is conveyed to the fixing device 10. Then, heat and pressure are applied between the fixing roller and the pressure roller in the fixing device 10, and the toner image is fixed on the recording paper P. Then, the recording paper P on which the toner image is fixed is discharged to a tray outside the apparatus.

  The toner remaining on the intermediate transfer belt 8 after the secondary transfer is conveyed to a cleaning blade 11 disposed opposite the driven roller with the intermediate transfer belt 8 interposed therebetween. Then, it is collected by the cleaning blade 11.

  Next, the system configuration of the image forming apparatus of this embodiment will be described. As shown in FIG. 3, the image forming apparatus 100 according to this embodiment includes an image processing unit F1 that performs various image processing, an image data decomposition unit F2 that decomposes color image data into image data of each color, and a high-resistance image region. An area determination unit F3 for determining an area and a low resistance area, and an exposure data creation unit F4 provided for each color are included.

  Print image data is input to the image processing unit F1 in response to a print instruction from a personal computer. The print image data is sent from the memory of the scanner or printer itself as well as received from the personal computer. In the image processing unit F1, image processing such as color space conversion, black generation, and color correction is performed based on the print image data.

  Next, the image data after image processing is sent to the image data decomposing unit F2. Then, the image data decomposing unit F2 decomposes the image data into image data for each color toner (K, C, M, Y in this embodiment). That is, monochrome image data of each color is acquired from the color image data.

  Next, the image data created by the image data decomposition unit F2 is sent to the exposure data creation unit F4. The exposure data creation unit F4 performs γ correction, MTF correction, PWM modulation, and the like on the toner. As for PWM modulation, it is preferable to form a large dot so as to improve dot reproduction in the highlight area (low density area) and to increase the recording unit. The image data after PWM modulation is output to the exposure optical system. Then, image exposure is performed on the photosensitive drum 2 by the exposure optical system.

  On the other hand, the area discriminating unit F3 acquires resistance distribution data of the transfer body. Then, based on the acquired resistance distribution data, a region is discriminated into a high resistance region and a low resistance region, and region data recording the result is created. The resistance distribution data can be obtained by measuring the dielectric constant of the transfer body using an existing dielectric relaxation measuring device or the like and calculating the electrical resistance distribution from the measurement result. In addition, it is possible to generate a resistance distribution data by analyzing a transfer of a uniform test image over the entire area of the transfer body without using transparent toner, and estimating a resistance distribution from the information.

  It is also possible to obtain resistance distribution data without performing measurement by a dielectric relaxation measuring device or test printing. For example, if the electrical characteristics of the material composing the transfer body are known, the material has arrangement information, and the image forming apparatus 100 has the information as a database, it is selected from the database. It is possible to acquire resistance distribution data of the transfer body.

The criterion for discriminating between the low resistance region and the high resistance region is that a region having an insulation resistance difference of 10 ¹² Ω or more per 1 cm ^{2 in} the thickness direction is a high resistance region, and other regions are low resistance regions. The threshold values for the low resistance region and the high resistance region are not particularly limited, and may be set for each image forming unit. Further, the threshold value is not limited to one and may be two or more. That is, the image area may be classified into a plurality of types of resistance areas.

  Next, the area data created by the area discriminating unit F3 is sent to the exposure data creating unit F4 for transparent toner. The exposure data creation unit F4 for transparent toner performs control of toner development amount, PWM modulation, and the like. The image data after PWM modulation is output to the exposure optical system for transparent toner. Then, the exposure optical system exposes the image onto the photosensitive drum 2 of the transparent toner image forming unit 1T.

  In the transparent toner image forming unit 1T, as shown in FIG. 4, a transparent color toner image ('T' in FIG. 4) is formed in an area determined to be a low resistance area. This transparent toner layer acts as a layer of a high resistance material during transfer. Therefore, the electric field strength in the low resistance region can be weakened during transfer, and the difference in electric field strength from the high resistance region is alleviated.

  Note that the image formation of the transparent toner is not necessarily performed on the entire low resistance region. That is, the present invention aims to obtain a good transfer image regardless of the electric resistance difference of the transfer body. Therefore, the transparent toner image is not formed on the entire low resistance area, but as shown in FIG. The image may be formed only in the low resistance region and in the region where the image of at least one color is formed among the colored toners. In this case, the image data of each color created by the image data decomposing unit F2 is sent to the region determining unit F3 (see the dotted line in FIG. 3). Then, the area determination unit F3 extracts an area in which an image of at least one color is formed out of colored toners in the low resistance area. This mode is preferred for reducing the amount of transparent toner used and the amount of waste toner.

  Further, in the form of FIG. 5, it is considered that the control is difficult because the exact match between the position of the colored toner and the position of the transparent toner is required. For this reason, it is better to form an image in a region that is expanded by 1 or 2 dots than the region in which the colored toner is imaged. That is, by allowing the deviation between the colored toner and the transparent toner, the difference in electric field strength from the high resistance region can be surely reduced.

  The developing amount of the transparent toner may be uniformly the same in all the areas to be imaged, or may be controlled by the electric resistance difference from the reference high resistance area. If the development amount of the transparent toner is the same in all regions, it is preferable that the amount of the toner resin is 0.5 to 2.0 in order to uniformly cover the transfer body.

  If the electrical characteristics of the material constituting the transfer body are known, it is preferable to control the development amount of the transparent toner based on the information. Hereinafter, a method for determining the developing amount of the transparent toner will be described with reference to FIGS.

FIG. 6 is composed of a low resistance material (for example, a paper mount) having a volume resistivity of 10 ¹¹ Ωcm or less and a high resistance material (for example, a card mainly made of PET) having a volume resistivity of 10 ¹³ Ωcm or more. FIG. 3 is a conceptual cross-sectional view when a transparent toner image is transferred to a transfer body having a region (low resistance region) composed only of a low resistance material.

In this case, the development amount of the transparent toner imaged in the low resistance region, that is, the thickness dt of the development layer of the transparent toner is determined by the following equation (1).
dt = α × εt / εh × dh (1)
In Expression (1), εt represents the dielectric constant of the transparent toner, εh represents the dielectric constant of the high resistance material, and dh represents the thickness of the high resistance material portion.

FIG. 7 is a conceptual diagram of a cross-section when a transparent toner is transferred to a transfer body made of a high-resistance material (for example, PET) having a volume resistivity of 10 ¹³ Ωcm or more and having a different thickness depending on the region. It is. In this transfer body, the thin portion is the low resistance region, and the thick portion is the high resistance region.

In this case, the development amount of the transparent toner imaged in the low resistance region, that is, the thickness dt of the development layer of the transparent toner is determined by the following equation (2).
dt = α × εt / εh × Δd (2)
In equation (2), εt represents the dielectric constant of the transparent toner, εh represents the dielectric constant of the transfer member, and Δd represents the difference in thickness of the transfer member (difference compared to the thickest portion).

  In the equations (1) and (2), the range of the coefficient α is preferably 0.5 <α <2.0, and more preferably 0.8 <α <1.2. Further, the relative dielectric constant of PET is generally known as about 3.2.

[Application example]
The image forming apparatus 200 according to the application example is a tandem full-color printer as in the previous embodiment, and has five image forming units arranged in parallel as shown in FIG. The image forming apparatus 200 of the application example superimposes the toner image on the recording paper P without using an intermediate transfer member. This is different from the previous embodiment (see FIG. 1) in which the intermediate transfer belt 8 is provided and the toner images are superimposed on the intermediate transfer belt and then transferred onto the recording paper P in a lump.

  In the image forming apparatus 200 of the application example, the recording paper P is transported onto the transport belt 14 in synchronization with the formation of the toner image on each image forming unit. The recording paper P transported to the transport belt 14 is charged to the same polarity as the toner by the paper charger 15 and transported in close contact with the rotating transport belt 14.

  Next, the transparent toner image formed by the image forming unit 1T is transferred to the recording paper P. In the image forming apparatus 200, a transparent toner image as a base is first transferred to the recording paper P. That is, since each image forming unit directly transfers a toner image onto the recording paper P, it is necessary to first transfer a transparent toner image that acts as an electric field relaxation layer. For this reason, the image forming unit 1T for transparent toner is positioned at the uppermost stream in the conveyance direction of the recording paper P.

  After the transfer of the transparent toner image, the colored toner image formed on each image forming unit is overlaid on the recording paper P to form a color toner image. The recording paper P carrying the color toner image is discharged by the separation electrode 16, separated from the transport belt 14, and transported to the fixing device 10. Thereafter, the toner image is fixed by the fixing device 10 and discharged to a tray outside the device.

  Also in the image forming apparatus 200 of the application example, the transparent toner image acts as a high resistance region at the time of transfer. Therefore, nonuniformity of the transfer electric field strength between the high resistance region and the low resistance region can be alleviated.

  As described above in detail, in the image forming apparatus 100 according to the embodiment, the region determination unit F3 determines the low resistance region and the high resistance region based on the resistance distribution data of the transfer body. Then, in order to form a transparent toner image in the low resistance region, image data of transparent color is formed. Then, a transparent toner image is formed at a position corresponding to the low resistance region by the image forming unit 1T. Then, a colored toner image is superimposed on the transparent toner image and transferred onto the recording paper P in a lump. This transparent toner image acts as a high resistance layer when the toner image is transferred onto the recording paper P. Therefore, the electric field strength in the low resistance region in the recording paper P can be weakened during transfer to the recording paper P, and the difference in electric field strength from the high resistance region can be reduced. Therefore, an image forming apparatus and an image forming method capable of obtaining a good transfer image with respect to a recording medium having at least two regions having different electric resistances, particularly, regions having different electric resistances in the scanning direction are realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, the present invention can be applied to various image forming apparatuses such as a color printer, a monochrome printer, a copier, and a facsimile.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment. 1 is a schematic diagram illustrating a configuration of an image forming unit according to an embodiment. 1 is a block diagram illustrating a system configuration of an image forming apparatus according to an embodiment. FIG. 4 is a first diagram illustrating an image of an image forming area of a transparent toner. FIG. 6 is a second diagram illustrating an image of an image forming area of a transparent toner. FIG. 6 is a first diagram illustrating a method for determining a developing amount of a transparent toner. FIG. 6 is a second diagram illustrating a method for determining a developing amount of transparent toner. It is the schematic which shows the structure of the color printer which concerns on an application example. It is a figure which shows an example of the recording medium which consists of a some member.

Explanation of symbols

1T image forming unit (transparent toner image forming unit)
2 Photosensitive drum 3 Charging device 4 Developing device 5 Primary transfer device 8 Intermediate transfer belt 100 Image forming device 1F Image processing unit 2F Image data decomposition unit (colored region extraction unit)
3F area discriminator (area extractor)
4F Exposure data creation part

Claims (6)

In an image forming apparatus that generates an electric field between a toner image carrier and a transfer member, and transfers the toner image onto the transfer member by electrical action.
An area extraction unit that obtains an electrical resistance distribution in the surface of the transfer body and extracts an area in the surface of the transfer body that has an electrical resistance that is smaller than a predetermined value by an amount compared to the electrical resistance of other areas;
An image forming apparatus comprising: a transparent toner image forming unit that forms a toner image of a transparent toner in the region extracted by the region extracting unit. The image forming apparatus according to claim 1,
A colored area extracting unit for extracting an area carrying colored toner;
The image forming apparatus, wherein the transparent toner image forming unit forms a toner image in at least the region extracted by the colored region extracting unit. The image forming apparatus according to claim 1, wherein:
The transparent toner image forming unit determines the thickness of the toner image according to the electric resistance of each region of the transfer body. In an image forming method for forming an image on a transfer body having two or more regions having different electric resistances in the same plane,
An area extraction step of obtaining an electrical resistance distribution in the surface of the transfer body, and extracting an area in the surface of the transfer body in which the electrical resistance is smaller than the electrical resistance of other areas by a predetermined value or more;
A transparent toner image forming step for forming a toner image with a transparent toner in the region extracted in the region extracting step;
An image forming step of superimposing the transparent toner image formed in the transparent toner image forming step and the colored toner image;
An image forming method comprising: a transfer step of generating an electric field between the toner image bearing member and the transfer member, and transferring the toner image superimposed in the image forming step onto the transfer member by electrical action; Method. The image forming method according to claim 4,
A colored region extracting step for extracting a region carrying colored toner;
In the transparent toner image forming step, a toner image is formed at least in the region extracted in the colored region extracting step. The image forming method according to claim 4 or 5, wherein:
In the transparent toner image forming step, the thickness of the toner image is determined in accordance with the electric resistance of each region of the transfer body.

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