JP5145802B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus provided with a mechanism for transferring a toner image onto a sheet via an intermediate transfer belt.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copiers and printers uniformly charge the surface of a photoconductive drum to a predetermined potential, and then perform image exposure on the surface of the photoconductive drum to provide electrostatic information corresponding to image information. A latent image is formed, and the electrostatic latent image is developed with toner by a developing device and visualized, whereby the formed toner image is transferred and fixed on a recording sheet to form an image. .

  In the above image forming apparatus, for example, a toner image is formed on the photoreceptor in the order of yellow, magenta, and cyan, and then this superimposed toner image is transferred onto the recording paper in batch, that is, a batch transfer method. A color image forming apparatus has been proposed.

  Specifically, a charger, an exposure unit, and a plurality of, for example, cyan, magenta, yellow, and black developing units corresponding to each color, a transfer unit, and a cleaning device are arranged around the photoconductor, and 1 on the photoconductor. A color image forming apparatus is proposed in which a toner image of each color is formed one by one on each rotation, and each color toner image formed on the photoconductor is transferred onto a recording sheet in one transfer process to form a color image. ing.

  Alternatively, a plurality of recording units each including a charger, an exposure optical system, and a developing unit are arranged around the photosensitive drum, and a toner image of each color is formed on the photosensitive drum while the photosensitive drum rotates once. There has been proposed a color image forming apparatus that transfers the toner images of the respective colors onto a recording sheet in a single transfer process (for example, see Patent Document 1).

  However, in the above-described color image forming apparatus that collectively transfers the superimposed toner image, the toner image formed in the first development step, that is, the surface of the photoconductor, is in contact with the photoconductor, and the degree of adhesion to the photoconductor However, the toner image having the strongest toner image is inferior in transfer efficiency to recording paper compared to other colors.

  In other words, a superimposed toner image in which a yellow toner image, a magenta toner image, and a cyan toner image are stacked in this order on the surface of the photoconductor is stacked in the order of C, M, and Y in the transfer process, contrary to the above. Is transferred to the recording paper. However, since the uppermost Y toner image on the recording paper is not completely transferred when transferred from the photoreceptor and remains on the photoreceptor side, it has a desirable thickness compared to the M and C toner images. It will not be a thing. As a result, the Y toner layer originally has the transmittance and reflectance of the red (R), green (G), and blue (B) color components (the B component is absorbed and the R and G components are reflected). This is different from the power value, and there is a problem that color reproduction faithful to the original cannot be performed. On the other hand, in the developing device that performs the first developing operation, the transparent toner is used, so that the toner layer that cannot be completely transferred in the transfer process to the recording paper is made of a transparent toner, and the transfer property of the colored toner layer is improved. An improved color image forming apparatus has been proposed (see, for example, Patent Document 2).

  In consideration of the above-described facts, an object of the present invention is to provide an image forming apparatus that prevents a transfer failure of a colored toner image even when embossed paper or the like having a large surface unevenness is used for the paper.

The image forming apparatus according to claim 1, a colored toner image forming unit that forms a colored toner image with colored toner, a transparent toner image generating unit that forms a transparent toner image with transparent toner, the colored toner image and the transparent toner An intermediate transfer body to which a toner image is transferred, and the colored toner image layer is formed on the transparent toner image layer on the intermediate transfer body, and the transparent toner has a volume The average particle size is larger than that of the color toner, the shape factor is less than that of the color toner, and the charge amount is lower than that of the color toner.

In the present aspect, since the transparent toner to be a layer formed on the intermediate transfer member has a volume average particle diameter is larger than the color toner shape factor is less than the color toner, and a low charge quantity than the color toner, transparent A difference occurs in the adhesion force between the toner and the color toner, and transfer failure of the color toner image can be suppressed as compared with the case where the configuration of the present application is not provided .

The image forming apparatus according to claim 2, further comprising: a transparent toner mode in which a colored toner layer formed of colored toner is formed on the transparent toner image layer formed of transparent toner on the intermediate transfer member. , when the colored toner layer is composed of a plurality of color toner layer containing a black toner, when the transparent toner mode is selected, as compared with the case where the transparent toner mode is not selected, the color toner The ratio of the black toner in the layer is increased.

In the invention of the above configuration, the gray color obtained by mixing the color toners is substituted with the black toner, so that when the transparent toner mode is selected, the color toner is not compared with the case where the transparent toner mode is not selected . The total amount can be reduced. As a result, the transfer electric field to the colored toner layer at the time of transfer to the paper sufficiently acts, and the remaining of the colored toner can be suppressed.

The image forming apparatus according to claim 3, wherein the charge amount of the transparent toner layer formed on the photosensitive member or the intermediate transfer member is adjusted upstream of the colored toner layer in the conveyance direction. The charge adjusting means is provided .

In the invention of the above configuration, the property of the transparent toner interface on the intermediate transfer member is different from that of the colored toner by providing the charge adjusting means for adjusting the charge amount of the transparent toner layer, compared with the case of not having the configuration of the present application. Excellent transferability .

The image forming apparatus according to claim 4 is an intermediate transfer member to which a toner image formed by exposing an image on a surface of a photosensitive member as an exposure electrostatic image and having a toner image developed by a plurality of developing devices is transferred. A transparent toner mode in which a colored toner layer formed of colored toner is formed on a transparent toner image layer formed of transparent toner on the intermediate transfer member, and the adhesive force between the colored toners Also, the adhesive force between the colored toner and the transparent toner is lowered, so that cutting is caused at the interface between the colored toner layer and the transparent toner image layer when transferring from the intermediate transfer member to the recording medium .

In the invention with the above configuration, the adhesion of the colored toner layer formed on the transparent toner layer on the intermediate transfer member is higher than that of the transparent toner layer. Separation and transfer failure of colored toner images can be suppressed as compared with the case where the configuration of the present application is not provided .

  Since the present invention has the above-described configuration, even when embossed paper or the like having a large surface unevenness is used for the paper, an image forming apparatus that prevents transfer failure of a colored toner image can be obtained.

<Overview of image forming apparatus>
1 to 3 show an image forming apparatus according to a first embodiment of the present invention.

  FIG. 1 is a cross-sectional view showing the internal structure of the image forming apparatus according to the first embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus 10 includes an intermediate transfer belt 12 on which a toner image is transferred to the surface, image forming units 30Y to 30K that form a toner image on the surface of the intermediate transfer belt 12, and upstream in the conveying direction. An image forming unit 30T for forming a transparent toner image is provided on the side, and the main part is configured.

  The image forming units 30T to 30K form an electrostatic latent image on the photosensitive drum 32 that forms an electrostatic latent image on the surface, a charging roll 34 for primary charging that contacts and charges the photosensitive drum 32, and the photosensitive drum 32. And a developing unit 38 for developing the electrostatic latent image with toner. Toners 15Y to 15K are supplied from the toner cartridges 14Y to 14K to the developing units 38Y to 38K, respectively, and transparent toner 15T is supplied from the transparent toner cartridge 14T to the developing unit 38T. 15Y to 15K and transparent toner 15T are replenished.

  The recording paper P is accommodated in the tray 16 and conveyed along a paper conveyance path (black arrow in the figure), and the toner image is transferred from the intermediate transfer belt 12 pressed by the secondary transfer roll 17 at the nip position 12A.

  On the other hand, when a paper that is likely to cause a transfer failure in a concave portion, such as an embossed paper having a local deep concave portion, is used as the paper P, the transparent toner mode set in the image forming apparatus 10 is selected and image formation is performed. The surface of the photosensitive drum 32T, to which the surface potential is applied by the charging roll 34T in the portion 30T, is irradiated with light to a position range where an image is to be formed with the colored toner 15, and an electrostatic latent image corresponding thereto is formed. It is formed.

  The electrostatic latent image is transferred to the electrostatic latent image formed on the photosensitive drum 32T (toner development) by transferring the transparent toner 15T on the developing unit 38T to a desired position on the photosensitive drum 32T. That is, the transparent toner image 20 is formed at a location corresponding to the location where the color image is formed in the image forming units 30Y to 30K for each color.

  A primary transfer roll 31T provided at a position facing the photosensitive drum 32T and the intermediate transfer belt 12, and an intermediate transfer belt 12 driven as indicated by white arrows in the drawing while being in contact with the rotating photosensitive drum 32T. The transparent toner image 20 is transferred from the photosensitive drum 32T to the intermediate transfer belt 12 at the nip position.

  Here, since the image forming unit 30T is provided on the upstream side in the transport direction with respect to the image forming unit 30 of the other four colors, the transparent toner image 20 is directly formed on the surface of the intermediate transfer belt 12. In other words, a four-color image of Y to K is formed on the transparent toner image 20.

  As shown in FIGS. 2 and 3, after the transparent toner image 20 is formed on the surface of the photosensitive drum 32T, four color images Y to K are transferred onto the transparent toner image 20 transferred to the intermediate transfer belt 12. In the meantime, a corona discharger 39 as a charge adjusting means is provided.

  Specifically, as shown in FIG. 2, between the developing unit 38T and the primary transfer roll 31T, in the vicinity of the surface of the photosensitive drum 32T, or as shown in FIG. 3, on the downstream side in the transport direction from the nip position with the primary transfer roll 31T. A corona discharge device 39 is provided near the surface of the intermediate transfer belt 12 and a grounded metal roll 33 is provided on the back side of the intermediate transfer belt 12, and four color images Y to K are transferred onto the transparent toner image 20. The charging amount of the transparent toner image 20 is adjusted until the image is printed.

  On the other hand, in each of the image forming units 30Y to 30K, light modulated in accordance with the input image by the optical scanning device 36 as an exposure device is applied to the surface of the photosensitive drum 32 to which the surface potential is applied by the charging roll 34. Irradiated to form an electrostatic latent image according to the input image information.

  This electrostatic latent image is transferred to the electrostatic latent image formed on the photosensitive drum 32 (toner development) by transferring the toner 15 on the developing unit 38 to each color toner image on the photosensitive drum 32. It is formed.

  Next, the toner image formed on the photosensitive drum 32 is transferred to the intermediate transfer belt 12 that is driven as indicated by the white arrow in the drawing while being in contact with the rotating photosensitive drum 32, and the transfer of the respective color images Y to K is performed. By aligning the positions, a color image of four colors is finally formed at a position where the transparent toner image 20 is formed on the intermediate transfer belt 12.

  The color image is transferred onto the recording paper P nipped with the intermediate transfer belt 12 at the nip position 12A by the transfer roll 18, and the recording paper P transported along the transport path is thermally welded by the fixing device 50. The toner image is fixed. The recording paper P on which the image is formed is discharged out of the apparatus and output as an image.

  A belt cleaner 70 that cleans the intermediate transfer belt 12 is provided on the downstream side in the transport direction of the intermediate transfer belt 12 after image transfer.

  The belt cleaner unit 70 is a box-shaped member having a substantially U-shaped cross section, is in contact with the intermediate transfer belt 12 wound around the counter roll 13 at the opening 70 </ b> A, and is in contact with the counter roll 13. A blade 72 is provided for cleaning the surface while always abutting on the surface 12.

  The blade 72 cleans the residual toner remaining on the intermediate transfer belt 12 and not completely transferred onto the recording paper P. A collection auger is provided below the belt cleaner unit 70, and the blade 72 scrapes off the remaining toner collected by the belt cleaner unit 70 and discharges it to a collection unit (not shown).

The toner used in the present invention is based on the following conditions for both transparent toner and colored toner. (Refer to the toner production methods described in paragraphs [0019] to [0067] of JP-A-10-26842 for the production method of each toner.)
The toner particles of each color prepared by the above production method have substantially the same volume average particle size and particle size distribution, and the volume average particle size measured with a Coulter Counter (manufactured by Coulter Co.) is preferably 3 to 7 um. The distribution index (GSD) was 1.23.

  The shape of the toner is represented by a shape factor, and an enlarged photograph of the toner obtained with an optical microscope (Microphoto FXA; manufactured by Nikon Corporation) is subjected to image analysis with an image analyzer Luzex3 (manufactured by NIRECO), and a value calculated according to the following formula: It is.

  The toner shape factor is expressed as a ratio of the projected area of the toner to the area of a circle circumscribing the toner, and is 100 for a true sphere, and increases as the shape collapses. The shape factor is calculated for a plurality of toner particles, and the average value is used as a representative value. In the present invention, a toner having a shape factor of 138 or less was used. It is more preferable to use a toner having a shape factor of 134 or less.

The surface property of the toner is represented by a surface property index value, which is a value calculated from the following formula from a specific surface area value obtained by nitrogen adsorption measured by the BET method and a specific surface area calculated value including particle size distribution.
C = {6Σ (n × R ² )} / {ρΣ (n × R ³ )}

  Where n = number of particles in the channel in the Coulter counter, R = channel particle diameter in the Coulter counter, and ρ = toner density. In the present invention, a toner having a surface property index of 9 or less was used. The surface property index is preferably 5.1 or less.

  Further, an appropriate amount of inorganic fine particles (external additive) such as silica and titania having an average particle diameter of 10 to 150 nm was externally added to the toner and mixed with a carrier made of ferrite beads having an average particle diameter of 35 μm to obtain a developer.

  The average charge amount of the toner is −15 to −60 μC / g, preferably −35 to −45 μC / g.

  In addition to the toner prepared by this production method, it is of course possible to use toner formed by suspension polymerization, dissolution suspension, emulsion polymerization, kneading and pulverization, and the like. .

<Effect>
Since this invention was set as the said structure, it has the following outstanding effects.

  That is, as shown in FIGS. 2 and 3, the transparent toner image layer 20A on the intermediate transfer belt 12 or the photosensitive drum 32T upstream in the transport direction in the process of superimposing the colored toner layer 21A on the transparent toner image layer 20A. By providing the corona discharger 39 which is a charge adjusting means for adjusting the charge amount of the toner, the corona discharger 39 can change the charge amount (energy level, potential) at the interface of the transparent toner image layer 20A. .

  As a result, as shown in FIG. 7, the properties (interface surface property, interface adsorption force, etc.) of the interface between the transparent toner image layer 20A and the colored toner layer 21A indicated by the broken line on the intermediate transfer belt 12 are changed. The charge amount can be varied.

  For example, in FIG. 3, by applying negative discharge to the negatively charged transparent toner 15T (transparent toner image layer 20A) from the surface side of the intermediate transfer belt 12, the potential of the toner layer is made uniform and difficult to move. When the color toner layer 21A is superimposed on the sheet P and transferred onto the paper P, the color toner layer 21A is easily cut between the transparent toner image layer 20A and the color toner layer 21A.

  As a result, the adhesion between the transparent toner image layer 20A and the colored toner layer 21A that are in contact with each other can be made different, so that the transfer between the transparent toner image layer 20A and the colored toner layer 21A during transfer onto the paper P can be performed. It becomes easy to cut with. A part of the transparent toner image layer 20A remains on the intermediate transfer belt 12, but the colored toner layer 21A is transferred to the paper P side, and no transfer omission occurs.

  When a thick embossed paper is used as the paper P, a predetermined amount of toner is poorly transferred at a portion where the transfer electric field is weak, such as unevenness of the embossed paper, and remains on the intermediate transfer belt 12 side. By cutting off the adhesive force and adsorbing force between the toner image layer 20A and the colored toner layer 21A and facilitating cutting between the toner layers, the first transparent toner image layer 20A is sacrificed, and the residual transfer of the colored toner layer 21A is reduced. be able to.

  Further, the corona discharger 39 may be provided only in the image forming unit 30T (transparent toner engine), or when provided in the image forming unit 30 of all colors, the corona discharge of the image forming unit 30T (transparent toner engine) is provided. By changing the output of the electric device 39 with the corona discharge device 39 of the image forming unit 30 of another color, the charge amount (energy level) of the transparent toner 15T can be changed with the toner of the other color.

  Alternatively, in the developing unit 38, the toner charge amount in the developer may be different between the transparent toner 15T and the colored toner 15. In other words, the charging amount (energy level) of the transparent toner 15T is changed to the colored toner 15 in the preparation setting in the developing unit 38, and the charging amount of the transparent toner 15T in the developing unit 38T is lowered, so that Therefore, it is possible to weaken the bonding and facilitate cutting in the transparent toner image layer 20A.

  Further, since the amount of toner that can be transferred is the sum of the total amount of electricity of the charged toner, if the amount of charge of the transparent toner 15T is decreased, the amount of the transparent toner 15T per amount of electricity can be increased, and the intermediate transfer belt Thus, the ratio of the transparent toner 15T in the toner remaining in the toner 12 can be increased, that is, the transfer failure of the colored toner 15 can be reduced.

  Further, the toner adhesion force on the intermediate transfer belt 12 may be varied by changing any one of the toner particle size, toner shape, toner charge amount, and external additive amount in the developer. .

<Second form>
Instead of reducing the charge amount of the transparent toner 15T as employed in the first embodiment, the amount of the colored toner 15 on the intermediate transfer belt 12 may be reduced as compared with the normal time.

  That is, paper that is likely to cause transfer failure in the concave portion, such as embossed paper having a local deep concave portion, is used as the paper P, and when the transparent toner mode is selected, the colored toner 17 that forms the colored toner layer 21A is selected. By reducing the amount and the total charge amount, the color toner layer 21A is sufficiently affected by the transfer electric field to the paper P, and the transfer residual of the color toner layer 21A to the intermediate transfer belt 12 is suppressed, so that the transparent toner image layer It becomes easy to cut | disconnect at the interface with 20A.

  Specifically, for example, the amount of the colored toner 17 may be reduced by replacing, for example, three YMC toners of the colored toner 17 with K1 color.

  As shown in FIG. 8 (A), the color toner 17 of YMC three colors, that is, the color reproduced by the composite color of Y1, M1, and C1, is black in Y2, M2, and C2, as shown in FIG. 8 (B). It can be replaced by adding K2.

  This replaces the color (gray) reproduced by Y3, M3, and C3 (parts indicated by broken lines) which are equal amounts of the colored toners 17 by addition of black toner, and the color toners 17 indicated by the broken lines, that is, This “inking” makes it possible to reduce Y3, M3, and C3.

  If Y3 + M3 + C3 = K2 × 3, the amount of the colored toner 17 can be reduced to a maximum of 1/3 depending on the color to be reproduced. When “Inking” is performed, the colors are different from those in normal image formation, and the YMC3 colors are replaced with K in terms of color reproducibility, especially saturation, so inevitably the dynamic range (color gamut) of each color. May become narrower.

  However, with paper P with many surface irregularities such as embossed paper, there is a tendency to emphasize the texture of the paper over the color reproducibility and color gamut of the color image in particular, so if transfer defects with large dents on the paper P surface can be improved, It is not a big problem.

<Experimental result>
4 and 5 show the image quality evaluation results of two types of embossed sheets of toner images created by the image forming apparatuses according to the first and second embodiments of the present invention.

  The experimental conditions are as follows.

  The transfer property to embossed paper was evaluated using a 5-color or 4-color tandem engine (image forming unit) construction machine in an environment of 22 ° C. and 55% RH. Evaluation is made with a Rezak 66 white 130k (151 gsm) and a Rezac 66 white 215k (250 gsm) that are generally widely used as embossed paper. A gradation pattern chart in which the image density was changed in 10% increments from 10 to 100% was used. The transparent toner layer is formed on the entire surface with an arbitrary image structure and toner amount.

  As the toner, a polymer toner having a shape factor of 132, an average particle diameter of 5.8 um, and an average charge of 35 to 45 μC / g was used for both the transparent toner and the colored toner.

  The evaluation result ○ indicates that there is no transfer failure in all gradations / all colors (acceptable white level in the embossed paper recess), Δ indicates that there is a transfer failure in the recess portion in the tertiary color, and × indicates that there is no practical problem. Not practical due to defects (embossed embossed paper recesses with 1 to 3 primary colors). In the graph of FIG. 5, the vertical axis represents the transferability 0, Δ the transferability 1, and x the transferability 2.

  Comparative Example 1 is an image formation using YMCK four-color toner, and no image is formed using the transparent toner 15T. As a result, there is a problem because a transfer defect occurs on the embossed paper.

  Comparative example 2 has a five-color configuration in which transparent toner 15T is added as the first color to the configuration of comparative example 1, and transparent toner 15T forms a transparent toner image layer 20A. However, there is no difference in the charge amount and other conditions between the transparent toner 15T and the colored toner 17, and the transparent toner image layer 20A and the colored toner layer 21A are not easily cut at the interface. As a result, although the embossed paper transfer property of 151 gsm is improved as compared with Comparative Example 1 in which no transparent toner layer is used, a sufficient effect has not been obtained.

  The experimental results according to the embodiments of the present invention for the above comparative examples are as follows.

(1) In Example 1, in the five-color configuration including the transparent toner 15T as the first color, the colored toner 17 is transparent while the average charge amount is 35 to 45 μC / g, the shape factor is 132, and the average particle size is 5.8 μm. The toner 15T had an average charge amount of 25 to 35 μC / g, a shape factor of 120 (substantially spherical shape), and an average particle size of 6.5 μm. This is a comparison with Comparative Example 2.

  As a result, the color toner 17 and the transparent toner 15T have different particle diameters, shapes, and charge amounts, so that there is a difference in adhesion, and the transfer to the paper P is likely to be cut at the interface between the two. In particular, the average charge amount of the transparent toner 15T is as small as 25 to 35 μC / g with respect to the average charge amount of 35 to 45 μC / g of the color toner 17, and the color toner image 21 is sacrificed because the transparent toner image layer 20A is easily cut. Without being transferred, it is possible to transfer to a deep concave portion of the embossed paper.

(2) In Example 2, in the five-color configuration including the transparent toner 15T as the first color, in addition to the configuration of Example 1, the multiple color amount of the colored toner 17 is set to an upper limit of 200%. For the amount exceeding 200%, so-called inking correction was performed in which three YMC colors were replaced with K1 color equivalents.

  As a result, since the total amount of the color toner 17 in the color toner layer 21A is reduced, the total charge amount is also reduced, and the transfer electric field to the paper P sufficiently acts on the color toner layer 21A. As a result of being easily cut, the residual transfer to the intermediate transfer belt 12 side is suppressed, and the image is also transferred to a deep concave portion of the embossed paper. However, in the concave portion of embossed paper (250 gsm) having a large basis weight, the transfer electric field was weak and a slight transfer failure occurred.

(3) In the third embodiment, in the five-color configuration including the transparent toner 15T for the first color, as shown in FIG. 3, the image forming unit 30 (colored toner engine) is located downstream of the image forming unit 30T (transparent toner engine) in the transport direction. ), A corona discharger 39 (60 μm wire diameter, applied voltage DC-4 kV, AC peak-to-peak 3 kV, AC frequency 2 kHz) at a position where a metal roll 33 is provided opposite to the back surface of the intermediate transfer belt 12 and grounded. Evaluation was performed with a configuration in which a sine wave) was arranged.

  As a result, by changing the charge amount (energy level, potential) at the interface of the transparent toner layer 20A, the properties of both toner interfaces on the intermediate transfer belt 12 could be made different. By irradiating the negatively charged transparent toner 15T with negative discharge from the surface side of the intermediate transfer belt 12, the potential of the transparent toner layer 20A is made uniform and difficult to move. When the color toner layer 21A is superimposed and transferred onto the paper P, it is easily cut between the transparent toner layer 20A and the color toner layer 21A. As a result, transferability to the paper P could be improved. In addition, the paper can be used for thick embossed paper (250 gsm) having a large basis weight, and the versatility of the paper can be expanded.

<Others>
As mentioned above, although the Example of this invention was described, it cannot be overemphasized that this invention is not limited to said Example at all, and can implement in a various aspect in the range which does not deviate from the summary of this invention.

  That is, in the present embodiment, an example of an image forming apparatus that employs a tandem configuration of a five-color engine in which transparent toner is added to a color image using four-color toner of YMCK has been described as an example. It can also be applied to an image forming apparatus of two colors, three colors, or six colors or more.

  Alternatively, the present invention is not limited to the tandem type, and may be applied to an image forming apparatus having a rotary type or a cycle type engine using one photosensitive member.

1 is a conceptual diagram illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a side view showing the image forming unit according to the first embodiment of the present invention. It is a side view which shows the modification of the image formation part which concerns on 1st Embodiment of this invention. It is a table | surface which shows the transferability to the embossed paper in embodiment of this invention. It is a graph which shows the transferability to the embossed paper in embodiment of this invention. FIG. 3 is a side view showing separation / transfer of colored toner / transparent toner in the present invention. FIG. 3 is a side view showing a layered structure of color toner / transparent toner and an interface property determining factor in the present invention. FIG. 6 is a conceptual diagram illustrating a toner consumption amount when a color toner YMC in the present invention is replaced with K.

Explanation of symbols

10 Image forming apparatus 12A Nip position 12 Intermediate transfer belt (intermediate transfer member)
12C Background portion 13 Opposed roll 14 Toner cartridge 15T Transparent toner 17 Colored toner 20 Transparent toner image 20A Transparent toner layer 21 Colored toner image 21A Colored toner layer 30 Image forming unit 31 Primary transfer roll 32 Photosensitive drum (photosensitive member)
33 Metal Roll 34 Charging Roll 36 Optical Scanning Device 38 Development Unit 39 Corona Discharger (Charging Adjustment Means)
50 Fixing Device 70 Belt Cleaner 72 Blade P Recording Paper

Claims (4)

A colored toner image forming unit that forms a colored toner image with colored toner;
A transparent toner image generation unit that forms a transparent toner image with transparent toner;
An intermediate transfer body to which the colored toner image and the transparent toner image are transferred;
On the intermediate transfer member, the colored toner image layer is formed on the transparent toner image layer, and
The image forming apparatus, wherein the transparent toner has a volume average particle size larger than that of the colored toner, a shape factor smaller than that of the colored toner, and a charge amount lower than that of the colored toner. A transparent toner mode in which a colored toner layer formed of colored toner is formed on the transparent toner image layer formed of transparent toner on the intermediate transfer member;
When the colored toner layer is composed of a plurality of colored toner layers including black toner,
The ratio of the black toner in the colored toner layer is higher when the transparent toner mode is selected than when the transparent toner mode is not selected . Image forming apparatus. On the upstream side in the transport direction than the colored toner layer is formed,
3. The image forming apparatus according to claim 1, further comprising a charge adjusting unit that adjusts a charge amount of the transparent toner layer formed on the photosensitive member or the intermediate transfer member. An intermediate transfer member to which a toner image formed by exposing an image on the surface of the photosensitive member as an electrostatic exposure image and having a toner image developed by a plurality of developing devices is transferred;
A transparent toner mode in which a colored toner layer formed of colored toner is formed on the transparent toner image layer formed of transparent toner on the intermediate transfer body,
By making the adhesion between the colored toner and the transparent toner lower than the adhesion between the colored toners, cutting at the interface between the colored toner layer and the transparent toner image layer during transfer from the intermediate transfer member to the recording medium An image forming apparatus.

Images