JP6790593B2 - Image forming device and image forming program - Google Patents

Description

The present invention relates to an image forming apparatus and an image forming program.

Patent Document 1 describes that in an image forming apparatus capable of forming an image by using a metallic toner together with a process color toner, an image is formed by using the process color toner and the metallic toner for the metallic color of the input image data. Metallic color conversion means for converting to the metallic color signal of the above, process color conversion means for converting the input image data other than the metallic color into a process color signal for forming an image using the process color toner, and the metallic. The screen means for performing screen processing on the metallic color signal converted by the color conversion means or the process color signal converted by the process color conversion means, and the process color toner and the process color toner according to the process color signal or metallic color signal after the screen processing. An image forming apparatus comprising an image forming means for forming an image using a metallic toner, wherein the screen means performs a screen processing different from the process color signal as a screen processing on the metallic color signal. It is disclosed.

Patent Document 2 describes a first metallic color material layer made of a metallic color material, one or more process color material layers made of one or more process color color materials, and a second metallic color material layer made of a metallic color material. A color material layer forming means for forming the first metallic color material layer, the process color material layer, and the second metallic color material layer on the surface of the print medium so as to be closer to the surface of the print medium in this order. The first metallic color material layer and the second metallic color material layer formed by the color material layer forming means according to the total amount of the color materials of the one or more process colors in the one or more process color material layers. A first distribution control means for controlling the distribution of the metallic color material between the two, and increasing the distribution of the second metallic color material layer as the total amount of the color materials of the one or more process colors increases. An image processing apparatus including a distribution control means having a function of executing the control of the above is disclosed.

Japanese Unexamined Patent Publication No. 2006-50347 Japanese Unexamined Patent Publication No. 2014-35419

In recent years, toners (development) called chromatic colors such as yellow (Y), magenta (M), cyan (C), and black (K), which have been conventionally used in an image forming apparatus for forming a color image, are so-called process colors. In addition to (also referred to as an agent), special color toners such as white (W), gold, silver, and transparent color may be used.

Whereas process color toner forms a user-specified image (user image), spot color toner forms a base or coating of the user image, or forms an image with a color that is difficult to achieve with process color toner. Etc. are used.

Further, the special color toner may be used for an application of giving a metallic luster to a user image, and in this case, a special color toner containing a metal pigment such as gold, silver, and white is used.

However, since toner containing a metal pigment is more likely to take up electric charge than a toner having a process color that does not contain a metal pigment, the charge polarity of the toner becomes opposite due to charge injection accompanying transfer of the toner to an intermediate transfer body, for example. Alternatively, the charge amount of the toner may be less than the predetermined charge amount.

Therefore, the transfer efficiency in the secondary transfer of the toner containing the metal pigment transferred to the intermediate transfer body may be lower than the transfer efficiency in the secondary transfer of the toner of the process color, for example, and the image quality may be deteriorated.

In the present invention, an image is obtained in a state where the developer containing a metal pigment becomes less than a predetermined charge amount due to transfer, or the charge polarity of the developer containing a metal pigment becomes opposite to the predetermined polarity. The deterioration of the image quality is suppressed as compared with the case of forming.

In order to achieve the above object, the image forming apparatus according to claim 1 is photosensitive with a first developing agent containing no metal pigment and a second developing agent containing a metal pigment, both of which are charged to the same polarity. An image forming means for developing an electrostatic latent image formed on the body and forming an image on the photoconductor, and a current for generating a voltage having a charge polarity opposite to that of the first developer and the second developer. supplied, the the transfer body is conveyed to a nip portion formed between the photosensitive member, a transfer unit that transfers the image formed on the photosensitive member, when it is transferred to the transfer medium by the transfer unit By injecting a positive charge at the nip portion, the charge distribution on the transfer body tends to be more biased toward the positive side than the charge distribution of the first developer. Is provided with a control means for controlling the charge distribution of the second developer so as to approach the charge distribution of the first developer transferred to the transfer body.

In the invention according to claim 2, when the control means transfers an image formed by the second developer to the transfer body, the magnitude of the current supplied to the transfer means is the magnitude of the first development. When the image formed by the agent is transferred to the transfer body, the supply amount of the current is controlled so as to be larger than the magnitude of the current supplied to the transfer means.

In the invention according to claim 3, the image forming means further includes a third developer that does not contain a metal pigment and has a color different from that of the first developer, and the first developer and the second developer. An image with the third developer is formed in a place at least partially different from the image formed on the photoconductor, and the control means performs the third development after the image formed by the second developer. The transfer means is controlled so that the image formed by the agent is transferred to the transfer body.

In the invention according to claim 4, the offset angle representing the amount of deviation between the position of the photoconductor and the position of the transfer means in the transport direction of the transfer body is the discharge generated between the photoconductor and the transfer body. The photoconductor and the transfer means are arranged so that the discharge amount is included in a predetermined angle range in which the discharge amount is larger than the reference discharge amount.

In the invention according to claim 5, the color of the second developer is gold, silver, or white.

The image forming program according to claim 6 causes a computer to function as a control means for the image forming apparatus according to any one of claims 1 to 5.

According to the inventions of claims 1 and 6, the developer containing a metal pigment becomes less than a predetermined charge amount due to transfer, or the charge polarity of the developer containing a metal pigment becomes a predetermined polarity. It is possible to suppress deterioration of image quality as compared with the case where the image is formed in a state of having the opposite polarity.

According to the second aspect of the present invention, when the developer is transferred to the transfer body, the magnitude of the current supplied to the transfer means is the same for the transfer of any developer. Deterioration of image quality can be suppressed.

According to the third aspect of the invention, deterioration of image quality can be suppressed as compared with the case where the second developer containing a metal pigment is transferred to the transfer body after the third developer.

According to the invention of claim 4, deterioration of image quality is suppressed as compared with the case where the photoconductor and the transfer means are arranged so as not to generate an electric discharge on the downstream side in the transport direction of the transfer body from the nip portion. be able to.

According to the invention of claim 5, the color gamut to be expressed can be widened as compared with the case where an image is formed by the first developing agent.

It is a schematic side view which shows the example of composition of the main part of the image forming apparatus which concerns on 1st Embodiment. It is a schematic diagram explaining the color visibility state when the Si toner layer is formed on the process color toner layer. It is a schematic diagram explaining the color visibility state when the process color toner layer is formed on the Si toner layer. It is a figure which shows the example of the composition of the main part of the electric system of an image forming apparatus. It is a flowchart which shows an example of the flow of the image formation processing which concerns on 1st Embodiment. It is a figure which showed an example of the secondary transfer rate for each toner color when the image forming part which forms the Si color toner image is arranged on the most downstream side in the transport direction. It is a figure which shows an example of the charge distribution of each toner image in Si color and C color when the image forming part which forms the Si color toner image is arranged on the most downstream side in the transport direction. When the image forming portion for forming the Si color toner image is arranged on the most downstream side in the transport direction, and when the image forming portion for forming the Si color toner image is formed on the downstream side in the transport direction, the CR color toner image is formed. It is a figure which shows an example of the charge distribution of the Si color toner image in each case where a part is arranged. It is a figure which showed an example of the secondary transfer rate for each toner color when the image forming part which forms a CR color toner image is arranged on the downstream side in the transport direction of the image forming part which forms a Si color toner image. .. It is a figure which shows an example of the image quality quality result of the image formed by the image forming apparatus which concerns on 1st Embodiment. It is a schematic side view which shows the example of composition of the main part of the image forming apparatus which concerns on 2nd Embodiment. It is a flowchart which shows an example of the flow of the image formation processing which concerns on 2nd Embodiment. It is a figure which shows an example of the image quality quality result of the image formed by the image forming apparatus which concerns on 2nd Embodiment. It is a schematic side view which shows the example of the main part structure of the image forming apparatus which concerns on 3rd Embodiment. It is a schematic diagram which shows an example of the arrangement of the primary transfer device of the image forming apparatus which concerns on 3rd Embodiment. It is a schematic side view which shows the example of composition of the main part of the image forming apparatus which concerns on 4th Embodiment. It is a flowchart which shows an example of the flow of the image formation processing which concerns on 4th Embodiment. It is a schematic side view which shows the example of composition of the main part of the image forming apparatus which concerns on 5th Embodiment. It is a flowchart which shows an example of the flow of the image formation processing which concerns on 5th Embodiment. It is a figure which shows an example of the image quality quality result of the image formed by the image forming apparatus which concerns on 5th Embodiment.

Hereinafter, examples of embodiments for carrying out the technique of the present disclosure will be described in detail with reference to the drawings. It should be noted that the components and processes having the same function or function are given the same code throughout the drawings, and duplicate description is omitted.

Regarding the color display, yellow is "Y", magenta is "M", cyan is "C", black is "K", white including metal pigment is "W", and metallic gloss is included. The indicated color (for example, metallic color such as gold and silver) is represented by "Si", a predetermined color different from the above color, and as an example, red (custom red) represented by a specific RGB value is represented by "CR". .. The use of CR color will be described later. Further, "R" is a symbol representing red, "G" is a symbol representing green, and "B" is a symbol representing blue.

When it is necessary to explain each member or image separately for each color, a color code (Y, M, C, K, W, Si, CR) corresponding to each color is added to the end of the name or code. Distinguish. On the other hand, when each member or image is described collectively without distinguishing each member or image, the color code added to the end of the name or code is omitted.

<First Embodiment>
FIG. 1 shows an example of a schematic side view showing a main configuration of an image forming apparatus 200 using an electrophotographic method according to the disclosed technique. The image forming apparatus 200 is equipped with an image forming function of receiving image data via a communication line (not shown) and forming an image (user image) based on the received image data on a recording medium such as paper. ..

The image forming apparatus 200 includes six photoconductors 1Y, 1M, 1C, 1K, 1Si, and 1CR that rotate in the direction of arrow A in the drawing for each color of Y, M, C, K, Si, and CR. It includes chargers 2Y, 2M, 2C, 2K, 2Si, and 2CR that charge the surface of each photoconductor 1 by supplying a charging bias.

Further, the image forming apparatus 200 exposes the surface of the charged photoconductor 1 with light modulated based on the image information of each color, and forms an electrostatic latent image on the photoconductor 1 laser output units 3Y and 3M. It includes 3C, 3K, 3Si, and 3CR, and developing rolls 34Y, 34M, 34C, 34K, 34Si, and 34CR that hold the developer (toner) of each color.

Further, the image forming apparatus 200 develops an electrostatic latent image on the photoconductor 1 with toner of each color by supplying a development bias to the developing rolls 34 of each color by a development bias power supply (not shown), and puts the electrostatic latent image on the photoconductor 1 on the photoconductor 1. Developers 4Y, 4M, 4C, 4K, 4Si, and 4CR that form toner images, and primary transfer devices 5Y, 5M, 5C that transfer each color toner image on the photoconductor 1 to the intermediate transfer belt 6 as an example of a transfer body. It includes 5, 5K, 5Si, and 5CR.

Further, the image forming apparatus 200 is transferred to the paper accommodating portion T for storing the paper, which is an example of the recording medium, the secondary transfer device 7 for transferring the toner image on the intermediate transfer belt 6 to the paper P, and the paper P. A fixing device 9 for fixing the toner image to the paper P and a belt cleaner 8 for removing the toner remaining on the surface of the intermediate transfer belt 6 after the toner image is transferred to the paper P by the secondary transfer device 7 are provided.

Further, the image forming apparatus 200 includes a cleaner (not shown) for cleaning the surface of each photoconductor 1 and a static eliminator (not shown) for removing the residual charge on the surface of each photoconductor 1.

The photoconductor 1, the charger 2, the laser output unit 3, and the developer 4 including the developing roll 34 for each of Y, M, C, K, Si, and CR cooperate with each other to apply toner to the intermediate transfer belt 6. The image forming unit 15 is an example of an image forming unit 15 that forms an image, and the image forming unit 15 is an example of an image forming means. The primary transfer device 5 is an example of a transfer means.

In the following, each color of Y, M, C, and K may be collectively referred to as "process color", and each toner (process color toner) corresponding to the process color is an example of the first developer. The toner corresponding to the Si color is an example of a spot color toner and also an example of a second developer. The toner corresponding to the CR color is an example of a special color toner that does not contain a metal pigment, and is also an example of a third developer.

A toner corresponding to W color may be used instead of a toner corresponding to Si color, but here, as a typical example of a toner containing a metal pigment, a toner corresponding to Si color will be described. That is, the toner corresponding to the W color is also an example of the spot color toner and also an example of the second developer.

Here, the CR color is not a color expressed by superimposing at least two colors of toner among process color toners and special color toners, but a color expressed by a dedicated toner mixed with a predetermined color. .. For example, in the case of a color that is considered to be used in a relatively large number of situations, such as a color used for a company logo mark, the logo mark, etc., is used in advance rather than being created by superimposing process color toner and special color toner each time. The time required for image formation can be shortened by using a special toner mixed with the color. Therefore, the image forming apparatus 200 includes a dedicated image forming unit 15CR that forms a toner image corresponding to the CR color on the intermediate transfer belt 6.

Next, the image forming operation in the image forming apparatus 200 shown in FIG. 1 will be described.

First, for example, image data corresponding to a user image to be image-formed is output to the image forming apparatus 200 from a terminal device such as a personal computer (not shown) via a communication line (not shown).

When a user image is input to the image forming apparatus 200, the image forming apparatus 200 supplies a charging bias to the charging device 2 to charge the surface of the photoconductor 1 to the negative electrode.

On the other hand, the user image is input to the control unit 60 of the image forming apparatus 200. The control unit 60 decomposes the user image into image data of each of the process colors, Si, and CR, and then outputs a modulation signal based on the image data of each color to the laser output unit 3 of the corresponding color. The laser output unit 3 outputs the laser beam 11 modulated according to the input modulation signal.

Each of the modulated laser beams 11 irradiates the surface of the photoconductor 1. The surface of the photoconductor 1 is in a state of being charged to the negative electrode by the charger 2, but when the surface of the photoconductor 1 is irradiated with the laser beam 11, the charge of the portion irradiated with the laser beam 11 disappears and the photoconductor 1 is irradiated. Electrostatic latent images corresponding to the image data of each color are formed on the 1.

Further, each color developer 4 contains a toner colored in Y, M, C, K, Si, and CR and charged on the negative electrode, and a developing roll 34 for adhering each toner to the surface of the photoconductor 1. ..

When the electrostatic latent image formed on the photoconductor 1 reaches the developing device 4, the developing bias is supplied to the developing roll 34 in the developing device 4 by a developing bias power supply (not shown). Then, the toners of each color held on the peripheral surfaces of the developing rolls 34 adhere to the electrostatic latent image of the photoconductor 1 of the corresponding color, and the color represented by the image data on each of the photoconductors 1 is obtained. Corresponding toner images are formed respectively.

Further, the rollers 12A, 12D, 12E, and the backup roll 7A of the secondary transfer device 7 are rotated by a motor (not shown), so that the intermediate transfer belt 6 is conveyed in the direction of the arrow 14, and the primary transfer device 5 and the photoconductor 1 are conveyed. The intermediate transfer belt 6 is pressed against the photoconductor 1 at each of the nip portions formed by the above. At this time, a primary transfer bias is supplied to the primary transfer device 5 from a primary transfer bias power supply (not shown), and the toner images of each color formed on the photoconductor 1 are transferred to the intermediate transfer belt 6 (primary transfer).

In the photoconductor 1 on which the toner image is transferred to the intermediate transfer belt 6, deposits such as residual toner adhering to the surface of the photoconductor 1 are removed by a cleaner (not shown), and residual charges are removed by a static eliminator (not shown).

On the other hand, the secondary transfer device 7 includes a backup roll 7A for stretching the intermediate transfer belt 6 and a secondary transfer roll 7B, and the secondary transfer roll 7B comes into contact with the intermediate transfer belt 6 to contact the intermediate transfer belt 6 and the intermediate transfer belt 6 It rotates following the transport of.

Further, when the paper transport roller 13 is rotated by a motor (not shown), the paper P in the paper accommodating portion T is formed by the secondary transfer roll pair obtained by combining the backup roll 7A and the secondary transfer roll 7B of the secondary transfer device 7. It is conveyed to the formed secondary transfer nip.

Then, when the paper P is pressed against the intermediate transfer belt 6 in a state of facing the surface of the intermediate transfer belt 6 on which the toner image is formed in the secondary transfer nip portion, the secondary transfer bias power supply is used for the secondary transfer bias. A secondary transfer bias is supplied to the transfer roll pair, and the toner image formed on the intermediate transfer belt 6 is transferred to the paper P (secondary transfer). The toner image transferred on the paper P is heated and pressurized by the fixing device 9 and fixed on the paper P.

The intermediate transfer belt 6 on which the toner image is transferred to the paper P is removed by the belt cleaner 8 from deposits such as residual toner adhering to the surface.

As described above, the user image is formed on the paper P, and the image forming operation is completed. The configuration of the image forming apparatus 200 shown in FIG. 1 is an example, and as long as the image forming operation shown above is executed, for example, the transport path of the paper P may be arranged in any way.

When the surface of the paper P is viewed, when the Si toner layer 21 formed by the Si toner is formed above the process color toner layer 22 formed by the process color toner, the Si toner contains a metal pigment. Since it is contained, the light 23 is more likely to be reflected than the process color toner. Therefore, as shown in FIG. 2, the light 23 is reflected on the surface of the Si toner layer 21 and is represented by the process color toner layer 22. The color is hard to see.

On the other hand, when looking at the surface of the paper P, when the Si toner layer 21 formed by the Si toner is formed below the process color toner layer 22 formed by the process color toner, as shown in FIG. Since the light 23 passes through the process color toner layer 22 and is reflected by the Si toner layer 21 underneath, the original color of the user image represented by the process color and the Si color is visually recognized as compared with the situation of FIG. It will be easier.

Therefore, as shown in FIG. 1, in the image forming apparatus 200, the image forming unit 15Y, the image forming unit 15M, the image forming unit 15C, and the image forming unit 15K are used in the intermediate transfer belt 6 from the upstream side to the downstream side in the transport direction. By arranging the image forming unit 15Si and the image forming unit 15CR, the Si toner layer 21 is formed below the process color toner layer 22 when the user image is formed on the paper P. Hereinafter, the upstream side of the intermediate transfer belt 6 in the transport direction is simply referred to as the “upstream side in the transport direction”, and the downstream side of the intermediate transfer belt 6 in the transport direction is simply referred to as the “downstream side in the transport direction”.

As described above, the CR color toner is used for forming an image corresponding to a logo mark of a company or the like. Such a logo mark is formed as a stamp in a place such as a header or footer of paper P that does not overlap with or partially overlaps with the toner image formed by the image forming unit 15 corresponding to the process color and the Si color. Will be done. It should be noted that the CR color toner image partially overlaps the toner image formed by the image forming unit 15 corresponding to the process color and the Si color, that is, at least a part of the CR color toner image is a CR color toner image. A state in which the entire image does not overlap with the toner image formed by the image forming unit 15 corresponding to the process color and the Si color and is formed in a different place. That is, it means a state in which the entire CR color toner image is not formed so as to overlap with the toner image formed by the image forming unit 15 corresponding to the process color and the Si color.

Therefore, even if the image forming portion 15CR is arranged on the downstream side of the image forming portion 15Si in the transport direction, the Si toner layer 21 does not cover the entire CR toner layer on the paper P as shown in FIG. , The visibility of the toner image formed by the CR toner is ensured.

Next, with reference to FIG. 4, the configuration of a main part of the electrical system of the image forming apparatus 200 according to the disclosed technique will be described.

The image forming apparatus 200 according to the disclosed technique includes a CPU (Central Processing Unit) 30 in a control unit 60 that controls the operation of the image forming apparatus 200. Further, the image forming apparatus 200 includes a ROM (Read Only Memory) 31 in which various programs and various parameters are stored in advance, and a RAM (Random Access Memory) 32 used as a work area or the like when the CPU 30 executes various programs. Be prepared.

The CPU 30, ROM 31, and RAM 32 are connected to each other by the bus 37 of the image forming apparatus 200. The bus 37 supplies the primary transfer bias power supply 33 that supplies the primary transfer bias to each of the laser output unit 3 corresponding to each color, the primary transfer device 5 corresponding to each color, and the secondary transfer bias to the secondary transfer device 7. The secondary transfer bias power supply 38 is connected. Further, the bus 37 drives a rotating body included in the image forming unit 15 such as the photoconductor 1, various rollers for transporting the intermediate transfer belt 6, a fixing device 9, a paper transport roller 13 for transporting the paper P, and the like. The motor group 35 and the fixing power supply 36 for heating the fixing device 9 are connected.

The members and the like connected to the bus 37 are not limited to these members, and for example, a communication device connected to a communication line (not shown), an input device for receiving user's instructions, an output for notifying the operating state of the image forming apparatus 200, and the like. You may connect the device. Further, the control unit 60 is an example of the control means according to the disclosed technology, and a computer can be used.

Next, the operation of the image forming apparatus 200 will be described with reference to FIG. FIG. 5 is a flowchart showing an example of a flow of image formation processing by an image formation program executed by the CPU 30 when the CPU 30 receives a user image to be image-formed.

The image forming program is stored in ROM 31 in advance, and it is assumed that a toner image corresponding to each color is already formed on each photoconductor 1 by the operation of the image forming unit 15.

First, in step S10, the CPU 30 controls the primary transfer device 5Y to transfer the Y color toner image to the intermediate transfer belt 6.

Specifically, the CPU 30 receives a predetermined current I from the primary transfer bias power supply 33 when the toner image formed on the photoconductor 1Y passes through the nip portion formed by the primary transfer device 5Y and the photoconductor 1Y. By controlling the primary transfer bias power supply 33 so as to supply ₀ , a discharge is generated in the nip portion. In this case, a positive voltage is applied to the primary transfer device 5Y.

As described above, since the toner of each color is charged in the negative electrode in advance, the Y color formed on the photoconductor 1Y is formed by applying the voltage of the positive electrode, which is opposite to the charging polarity of the toner, to the primary transfer device 5Y. Toner image is attracted to the primary transfer device 5Y side. Therefore, the Y-color toner image formed on the photoconductor 1Y is easily peeled off from the photoconductor 1Y, so that the Y-color toner image is different from the case where the current I ₀ is not supplied from the primary transfer bias power supply 33 at the time of transfer. The toner image is easily transferred to the intermediate transfer belt 6.

Hereinafter, in steps S20 to S60, the CPU 30 performs the same processing as in step S10 on the primary transfer device 5 corresponding to each color of M, C, K, Si, and CR, respectively, and M, C, K, The toner images corresponding to the respective colors of Si and CR are sequentially transferred to the intermediate transfer belt 6.

Then, in step S70, the CPU 30 controls the secondary transfer device 7 to transfer the toner image on the intermediate transfer belt 6 to the paper P.

Specifically, the CPU 30 determines the secondary transfer bias when the toner image and the paper P formed on the intermediate transfer belt 6 pass through the secondary transfer nip portion formed by the backup roll 7A and the secondary transfer roll 7B. By controlling the secondary transfer bias power supply 38 so as to supply _a predetermined current I _a from the power supply 38, a discharge is generated in the secondary transfer nip portion. In this case, since the voltage of the positive electrode is applied to the secondary transfer roll 7B, the toner image on the intermediate transfer belt 6 charged on the negative electrode is attracted to the secondary transfer roll 7B side, and the toner image on the intermediate transfer belt 6 is displayed. Transferred to paper P.

The magnitudes of the current I ₀ and the current I _a are preset to the magnitude at which the transfer rate of the toner image is highest. Here, the transfer rate of the toner image indicates, for example, the ratio of the amount of toner forming the toner image transferred to the transfer destination to the amount of toner forming the toner image at the transfer source before transfer. The higher the transfer rate of the toner image, the smaller the amount of toner at the transfer source that remains without being transferred, so that deterioration of image quality is suppressed.

FIG. 6 shows a secondary transfer in the case where the image forming unit 15CR is not installed on the downstream side of the image forming unit 15Si in the conveying direction in the image forming apparatus 200, but is installed on the upstream side of the image forming unit 15Y in the conveying direction, for example. It is a figure which showed the transfer rate in the secondary transfer device 7 with respect to the bias, that is, the secondary transfer rate for each color. In FIG. 6, “PK” represents black color formed by superimposing Y, M, and C color toners. Further, "B + Si" represents a blue color in which metallic colors are superimposed to give a metallic luster.

In this case, for example, when a secondary transfer bias of about 3 kv is applied to the secondary transfer device 7 by the secondary transfer bias power supply 38, each secondary transfer rate in the toner image of each color other than Si color is determined by the user. It is 90% or more, which is the standard value at which deterioration of the quality of the toner begins to be confirmed. However, since the secondary transfer rate of the Si-colored toner image is about 75%, the functional index indicating the metallic luster in the toner image is lowered, and the image quality may be deteriorated.

This is because Si-colored toner contains a metal pigment, so its resistance value is lower than that of process-colored toner that does not contain a metal pigment. Therefore, the Si-colored toner is more likely to be positively charged at the nip portion of the primary transfer device 5 than the process-colored toner, so that the charge polarity of the Si-colored toner image on the intermediate transfer belt 6 is positive. The charge amount of the negative electrode of the Si color toner image on the intermediate transfer belt 6 is lower than the charge amount of the negative electrode of the Si color toner in the developer 4Si. May occur.

FIG. 7 shows the charge distribution 24 of the Si-color toner image formed on the photoconductor 1Si, the charge distribution 25 of the C-color toner image formed on the photoconductor 1C, and the Si-color toner transferred to the intermediate transfer belt 6. It is a figure which showed an example of the charge distribution 26 of the image, and the charge distribution 27 of the C color toner image transferred to the intermediate transfer belt 6. The horizontal axis of FIG. 7 shows the charge amount per 1 μm of toner, and the vertical axis shows the abundance ratio of the toner having each charge amount in the toner image of each color.

As shown in FIG. 7, when paying attention to the charge distribution 24 of the Si color toner image and the charge distribution 25 of the C color toner image formed on the photoconductor 1, for example, the charge amounts having the largest abundance ratio are both. It shows a value around -0.5 [fC / μm].

On the other hand, when paying attention to the charge distribution 26 of the Si color toner image transferred to the intermediate transfer belt 6 and the charge distribution 27 of the C color toner image, as described above, the Si color toner is more than the C color toner image. Since the image is more likely to be reversed or decharged, the charge distribution 26 has a charge distribution containing a larger amount of positive charge than the charge distribution 27. That is, in FIG. 7, the charge distribution 26 is distributed on the right side of the charge distribution 27, and the charge amount having the largest abundance ratio in the charge distribution 26 is about −0.25 [fC / μm], whereas the charge distribution 27 The amount of charge having the largest abundance ratio is about -0.7 [fC / μm]. As described above, the charge distributions 26 and 27 have a larger difference in the amount of charge having the largest abundance ratio than the charge distributions 24 and 25, and are opposite poles with respect to the Si color toner image of the intermediate transfer belt 6. It can be seen that there is a decrease in charge or a decrease in charge.

When the Si color toner image on the intermediate transfer belt 6 is reversed or decharged, even if the secondary transfer bias of the positive electrode is applied to the secondary transfer roll 7B of the secondary transfer device 7, the color other than Si color is applied. Compared to toner images of other colors, the proportion of the amount of Si-colored toner attracted to the secondary transfer roll 75B side is smaller, and as a result, the secondary transfer rate of the Si-colored toner image is reduced. ..

The electric discharge during transfer by the primary transfer device 5 is located not only in the nip portion formed by the photoconductor 1 and the primary transfer device 5 but also on the downstream side in the transport direction of the nip portion, and the intermediate transfer belt 6 is exposed to light. It also occurs in the range (post-nip portion) where it no longer contacts the body 1. That is, the post-nip portion is located on the downstream side in the transport direction of the nip portion, within the range where the intermediate transfer belt 6 does not come into contact with the photoconductor 1, and the electric discharge is generated between the photoconductor 1 and the intermediate transfer belt 6. It is the range that occurs.

Since the photoconductor 1 charges the negative electrode with respect to the intermediate transfer belt 6 due to the primary transfer bias, unlike the nip portion, the charge of the negative electrode is taken into the toner image on the intermediate transfer belt 6 by electric discharge at the post-nip portion. become. However, since the amount of charge of the positive electrode taken into the Si color toner image by the charge injection of the nip portion is large, even if the negative electrode charge is applied by the discharge of the post nip portion, the reverse electrode of the Si color toner image on the intermediate transfer belt 6 is applied. It is difficult to eliminate the low charge or low charge.

However, in the image forming apparatus 200 according to the disclosed technique, after the Si color toner image is transferred to the intermediate transfer belt 6 by the primary transfer device 5Si, the CR color toner image is further transferred to the intermediate transfer belt 6 by the primary transfer device 5CR. Transfer.

Therefore, the Si-colored toner image is further generated by the discharge generated by the photoconductor 1CR and the intermediate transfer belt 6 generated in the post-nip portion located on the downstream side in the transport direction of the nip portion formed by the photoconductor 1CR and the primary transfer device 5CR. It will take in the charge of the negative electrode.

In FIG. 8, as in the image forming apparatus 200 shown in FIG. 1, an image forming unit 15CR for forming a CR color toner image is arranged on the downstream side in the transport direction of the image forming unit 15Si for forming a Si color toner image. It is a figure which shows an example of the charge distribution in the case of this, and an example of the charge distribution in the case where the image forming unit 15CR is not arranged.

The charge distribution 41 is formed on the photoconductor 1Si when there is no image forming portion 15CR on the downstream side of the image forming portion 15Si in the conveying direction and the image forming portion 15Si is located on the most downstream side in the conveying direction (case 1). An example of the charge distribution of the Si color toner image is shown. Further, the charge distribution 42 represents an example of the charge distribution of the Si color toner image transferred to the intermediate transfer belt 6 in the above-mentioned case 1.

On the other hand, the charge distribution 43 is an example of the charge distribution of the Si color toner image formed on the photoconductor 1Si when the image forming portion 15CR is arranged on the downstream side of the image forming portion 15Si in the transport direction (case 2). Represents. Further, the charge distribution 44 represents an example of the charge distribution after the Si-colored toner image transferred to the intermediate transfer belt 6 has passed through the post-nip portion of the image forming portion 15CR in the above-mentioned case 2.

As shown in FIG. 8, the charge distribution 44 tends to contain a larger amount of charge on the negative electrode as compared with the charge distribution 42. That is, the discharge generated in the post-nip portion of the image forming unit 15CR imparts a negative electrode charge to the Si-colored toner image transferred to the intermediate transfer belt 6, and the charge distribution 44 of the Si-colored toner image on the intermediate transfer belt 6 However, for example, the charge distribution 27 of the C color toner image on the intermediate transfer belt 6 shown in FIG. 7 is approached.

Therefore, as shown in FIG. 1, the image forming unit 15CR is arranged on the downstream side of the image forming unit 15Si in the transport direction, the Si color toner image is transferred to the intermediate transfer belt 6, and then the CR color toner image is transferred. By doing so, the secondary transfer rate of the Si color toner image will increase.

FIG. 9 shows a case where the image forming unit 15CR is arranged on the downstream side of the image forming unit 15Si in the transport direction, the Si color toner image is transferred to the intermediate transfer belt 6, and then the CR color toner image is transferred. It is a figure which showed an example of the secondary transfer rate of a toner image.

As shown in FIG. 9, for example, when a secondary transfer bias of about 3 kv is applied to the secondary transfer device 7 by the secondary transfer bias power supply 38, the quality of the toner image of any color is deteriorated by the user. It can be seen that it is 90% or more, which is the reference value that begins to be confirmed.

<Image quality evaluation result 1>
In order to evaluate the image quality of the user image formed on the paper P by the image forming apparatus 200 according to the technique of the present disclosure, the image quality of the user image formed on the paper P is evaluated by a plurality of evaluation image forming apparatus including the image forming apparatus 200. The results are shown in FIG.

In FIG. 10, “◯” indicates that the image quality of the user image is not deteriorated and the image quality is good, and “x” indicates that the image quality is deteriorated. Further, "-" indicates that the image quality cannot be evaluated because the user image of the corresponding color cannot be formed.

The image quality evaluation result of the configuration 1 of FIG. 10 shows the image forming unit 15CR, the image forming unit 15Y, the image forming unit 15M, the image forming unit 15C, and the image forming unit from the upstream side to the downstream side in the transport direction of the intermediate transfer belt 6. The image quality evaluation result when the image forming part 15 is arranged in the order of 15K and the image forming part 15Si is shown.

The image quality evaluation result of the configuration 2 shows the image forming unit 15Y, the image forming unit 15M, the image forming unit 15C, the image forming unit 15K, the image forming unit 15Si, and the image forming unit 15Y from the upstream side to the downstream side in the transport direction of the intermediate transfer belt 6. The image quality evaluation result when the image forming part 15 is arranged in the order of the image forming part 15CR is shown. The evaluation image forming apparatus having the configuration 2 is an example of the image forming apparatus 200.

The image quality evaluation result of the configuration 3 shows the image forming unit 15CR, the image forming unit 15Y, the image forming unit 15M, the image forming unit 15C, the image forming unit 15K, and the image forming unit 15CR from the upstream side to the downstream side in the transport direction of the intermediate transfer belt 6. The image quality evaluation result when the image forming part 15 is arranged in the order of the image forming part 15W is shown. The image forming unit 15W is an image forming unit that forms a W-color toner image, and corresponds to the image forming unit 15Si replaced with the image forming unit 15W with respect to the configuration 1 of FIG.

The image quality evaluation results of the configuration 4 show the image forming unit 15Y, the image forming unit 15M, the image forming unit 15C, the image forming unit 15K, the image forming unit 15W, and the image forming unit 15Y from the upstream side to the downstream side in the transport direction of the intermediate transfer belt 6. The image quality evaluation result when the image forming part 15 is arranged in the order of the image forming part 15CR is shown. The configuration 4 corresponds to the configuration 2 of FIG. 10 in which the image forming portion 15Si is replaced with the image forming portion 15W, and the evaluation image forming apparatus having the configuration 4 is an example of the image forming apparatus 200.

The image quality evaluation result is a visual evaluation of color charts of Y, M, C, K, CR, Si, W, B, B + W, and B + Si formed on uncoated paper having a size of about 50 × 50 mm. Got the way.

Here, "B + W" represents a multi-order color image in which a B color image expressed by superimposing C color and M color is arranged on a W color base, and "B + Si" means B color. This is a multi-order color image in which a Si-color toner image is further superimposed on the image to add a metallic luster. The reason for using the B color image as the multi-order color image is that the brightness difference between the B color and the C color is larger than the brightness difference of other colors such as the G color and the C color, so that the M color is used on the paper P. This is because when a part of the toner does not adhere to the color B and color loss occurs, it is easy to recognize it as color unevenness. Therefore, the image quality is evaluated more accurately than when the R color or the G color is used as the multi-order color image.

When the user image was evaluated, the temperature was about 28 ° C. and the humidity was about 85%, and the process speed of each evaluation image forming apparatus was about 524 mm / s. The characteristics of each member included in the evaluation image forming apparatus are as follows.

The primary transfer device 5 was an elastic roll having an elastic layer made of, for example, silicone rubber or the like and having a diameter of about 28 mm, a resistance value of about 7.7 logΩ, and an Asuka C hardness of about 30 °.

The intermediate transfer belt 6 is an endless belt in which carbon is added to a resin material such as polyimide, and has a volume resistivity of 12.5 logΩcm.

The secondary transfer roll 7B is an elastic roll having an elastic layer formed of, for example, silicone rubber or the like and having a diameter of about 28 mm. The backup roll 7A has a surface resistance of about 7.3 logΩ / □ and an Asuka C hardness of about 53. An elastic roll with a diameter of about 28 mm was used.

For each YMCK process color toner, use one having an average particle size of about 4.7 μm containing an organic pigment, and for CR color toner, use one having an average particle size of about 5.8 μm containing an organic pigment. There was. Further, the Si color toner uses a toner having an average particle diameter of about 10 μm containing a metal pigment such as aluminum, and the W color toner uses a toner having an average particle diameter of about 5.8 μm containing a metal pigment such as titanium oxide. Was used.

Then, the primary transfer bias power supply 33 is controlled so that the current supplied to the primary transfer device 5 becomes a constant current (about 54 μA), and the secondary transfer bias of the secondary transfer bias power supply 38 is set to the secondary transfer device. The voltage value at which the secondary transfer rate at No. 7 was 90% or more, specifically, the voltage value at which the current supplied to the secondary transfer device 7 was about 120 μA was set.

As shown in FIG. 10, an image forming portion 15Si for forming a Si-colored toner image is arranged at the most downstream of the intermediate transfer belt 6 in the transport direction, and the toner image is transferred to the intermediate transfer belt 6; In the configuration 3 in which the image forming unit 15W for forming the color toner image is arranged at the most downstream of the intermediate transfer belt 6 in the transport direction and the toner image is transferred to the intermediate transfer belt 6, the Si color or W color user image is displayed. Unevenness occurred in the metallic luster, and deterioration of image quality was observed.

On the other hand, the image forming unit 15Si for forming the Si color toner image is arranged upstream in the transport direction of the image forming unit 15CR to form the configuration 2 for transferring the toner image to the intermediate transfer belt 6 and the W color toner image. In the configuration 4 in which the image forming unit 15W is arranged upstream in the transport direction of the image forming unit 15CR and the toner image is transferred to the intermediate transfer belt 6, the user image of each color including Si color or W color has color unevenness or color unevenness. No uneven metallic luster was observed, and the result was that the image quality was good.

As described above, the image forming apparatus 200 according to the first embodiment is an example of a dedicated color prepared in a predetermined color other than the process color after the toner image containing the metal pigment is transferred to the intermediate transfer belt 6. In addition, by transferring the CR color toner image that does not contain the metal pigment to the intermediate transfer belt 6, it is possible to suppress the repolarization and hypocharging of the toner image that contains the metal pigment, and the secondary transfer device 7 is used. The deterioration of the quality of the image formed on the paper P is suppressed by preventing the next transfer rate from becoming less than the reference value.

<Second Embodiment>
In the second embodiment, unlike the image forming apparatus 200 according to the first embodiment, even when the toner image containing the metal pigment is finally transferred to the intermediate transfer belt 6, the image quality is suppressed from being deteriorated. The forming device 201 will be described.

FIG. 11 shows an example of a schematic side view showing a main configuration of the image forming apparatus 201 according to the second embodiment. The image forming apparatus 201 transfers the image forming unit 15CR forming the CR color toner image and the CR color toner image formed by the image forming unit 15CR from the image forming apparatus 200 according to the first embodiment to the intermediate transfer belt 6. It has a configuration removed with a primary transfer device 5CR that transfers to.

Further, the image forming apparatus 201 has the same configuration as the main part configuration of the electrical system of the image forming apparatus 200 according to the first embodiment shown in FIG.

When the amount of charge of the negative electrode applied to the Si-colored toner image of the intermediate transfer belt 6 by the discharge generated in the post-nip portion formed by the image forming unit 15 and the primary transfer device 5 was verified, it was supplied to the primary transfer device 5. It was found that the amount of charge on the negative electrode applied to the Si-colored toner image tends to increase as the magnitude of the current increases. This is because as the magnitude of the current supplied to the primary transfer device 5 increases, the potential of the photoconductor 1 with respect to the potentials of the primary transfer device 5 and the intermediate transfer belt 6 increases relatively toward the negative electrode side, so that the post-nip portion It is considered that this is because more negative electrode charges are applied to the toner image from the photoconductor 1 side due to the discharge generated in.

Therefore, in the image forming apparatus 201 according to the second embodiment, the magnitude of the current supplied from the primary transfer bias power supply 33 to the primary transfer device 5 is controlled to suppress deterioration of image quality.

Next, the operation of the image forming apparatus 201 will be described in detail with reference to FIG. FIG. 12 is a flowchart showing an example of a flow of image formation processing by an image formation program executed by the CPU 30 when the CPU 30 receives a user image to be image-formed. In the following description, it is assumed that a toner image corresponding to each color is already formed on each photoconductor 1 by the operation of the image forming unit 15 of each color.

The difference between the image forming process shown in FIG. 12 and the image forming process according to the first embodiment shown in FIG. 5 is that the processes of steps S5, S15, S25, S35, and S45 are added, and step S60 is deleted. It is a point that was done.

In step S5, the CPU 30 controls the primary transfer bias power supply 33 to set the magnitude of the current supplied from the primary transfer bias power supply 33 to the primary transfer device 5Y to a predetermined current I ₀ . Then, in step S10, the CPU 30 supplies the current I ₀ from the primary transfer bias power supply 33 to the primary transfer device 5Y to transfer the Y-color toner image to the intermediate transfer belt 6.

In steps S15, S25, and S35, the CPU 30 controls the primary transfer bias power supply 33 to set the magnitude of the current supplied from the primary transfer bias power supply 33 to the primary transfer units 5M, 5C, and 5K to the current I ₀ , respectively. Set. Then, in steps S20, S30, and S40, the CPU 30 supplies currents I ₀ from the primary transfer bias power supply 33 to the primary transfer units 5M, 5C, and 5K, respectively, and toners corresponding to the respective colors are supplied to the intermediate transfer belt 6. Transfer the image.

In step S45, the CPU 30 controls the primary transfer bias power supply 33, and sets the magnitude of the current supplied from the primary transfer bias power supply 33 to the primary transfer device 5Si in steps S5, S15, S25, and S35. Set the current I ₁ to greater than ₀ . As a result, when the Si-colored toner image is transferred to the intermediate transfer belt 6 in step S50, the current I ₀ is supplied to the primary transfer device 5Si in the post-nip portion formed by the image forming unit 15Si and the primary transfer device 5Si. If this is the case, more negative electrode charge will be injected into the Si-colored toner image. Therefore, the repolarization and decharge of the Si color toner image on the intermediate transfer belt 6 are corrected.

<Image quality evaluation result 2>
In order to evaluate the image quality of the user image formed on the paper P by the image forming apparatus 201 according to the technique of the present disclosure, the image quality of the user image formed on the paper P is evaluated by a plurality of evaluation image forming apparatus including the image forming apparatus 201. The result is shown in FIG. In the image quality evaluation shown in FIG. 13, Si color and W color toners were used as the toner containing the metal pigment.

The meanings of the symbols “◯”, “×”, and “−” in FIG. 13 are the same as the meanings of the symbols shown in FIG.

No. 13 in FIG. 1-No. 4 is an image forming unit 15Y, an image forming unit 15M, an image forming unit 15C, an image forming unit 15K, and an image forming unit 15Si in this order from the upstream side to the downstream side in the transport direction of the intermediate transfer belt 6, respectively. The image quality evaluation result when 15 is arranged (configuration 5) is shown.

Of these, No. Reference numeral 1 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5Si when the Si color toner image is first transferred is set to about 54 μA. No. Reference numeral 2 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5Si when the Si color toner image is first transferred is set to about 56.7 μA. No. Reference numeral 3 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5Si when the Si color toner image is first transferred is set to about 59.4 μA. No. Reference numeral 4 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5Si when the Si color toner image is first transferred is set to about 64.8 μA.

In addition, No. 13 in FIG. 5-No. 8 is an image forming unit 15Y, an image forming unit 15M, an image forming unit 15C, an image forming unit 15K, and an image forming unit 15W in this order from the upstream side to the downstream side in the transport direction of the intermediate transfer belt 6, respectively. The image quality evaluation result when 15 is arranged (configuration 6) is shown.

Of these, No. Reference numeral 5 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5W is set to about 54 μA when the W color toner image is first transferred. No. Reference numeral 6 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5W is set to about 56.7 μA when the W color toner image is first transferred. No. Reference numeral 7 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5W is set to about 59.4 μA when the W color toner image is first transferred. No. Reference numeral 8 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5W is set to about 64.8 μA when the W color toner image is first transferred. Configuration 6 replaces the image forming unit 15Si with the image forming unit 15W with respect to the configuration 5, and the evaluation image forming apparatus having the configuration 6 is an example of the image forming apparatus 201.

No. 13 shown in FIG. 1-No. In each configuration of No. 8, when the toner image of the process color is first transferred, the magnitude of the current supplied to the primary transfer device 5 corresponding to the process color is set to about 54 μA.

The image quality evaluation result is the color of each color of Y, M, C, K, CR, Si, W, B, B + W, and B + Si formed on uncoated paper having a size of about 50 × 50 mm, as in FIG. The chart was visually evaluated. The environmental conditions, the process speed, and the characteristics of each member included in the evaluation image forming apparatus when the image quality evaluation is performed shown in FIG. 13 are the same as those when the image quality evaluation is performed shown in FIG. It is set.

As shown in FIG. 13, in the configuration 5 in which the Si color toner is used as the special color toner containing the metal pigment, No. 1 and No. In the case of 2, unevenness occurred in the metallic luster of the Si-colored user image, and deterioration of image quality was observed. On the other hand, the magnitude of the current supplied to the primary transfer device 5Si is increased by about 10% or more from the magnitude of the current supplied to each of the primary transfer devices 5 corresponding to the process color. 3 and No. In the case of 4, no color unevenness or metallic luster unevenness was observed in the user image of each color including the Si color, and the result was obtained that the image quality was good.

Further, in the configuration 6 in which the W color toner is used as the special color toner containing the metal pigment, No. In the case of 5, unevenness occurred in the metallic luster of the W color user image, and deterioration of the image quality was observed. On the other hand, the magnitude of the current supplied to the primary transfer device 5W is increased by about 5% or more from the magnitude of the current supplied to each of the primary transfer devices 5 corresponding to the process color. 6, No. 7 and No. In the case of 8, no color unevenness or metallic luster unevenness was observed in the user image of each color including the W color, and the result was obtained that the image quality was good.

It should be noted that the magnitude of the current supplied to each of the primary transferers 5 corresponding to the process color for the evaluation of good image quality is the magnitude of the current supplied to the primary transferor 5 corresponding to the toner containing the metal pigment. The rate of increase of the toner is about 5% or more for the W color and about 10% or more for the Si color. This is because the Si-colored toner image is more likely to be reversed or decharged than the W-colored toner image, so the magnitude of the current supplied to the primary transfer device 5Si during the primary transfer is increased to the primary transfer device 5W. The charge of the negative electrode given to the Si color toner image by the post-nip portion of the photoconductor 1 and the primary transfer device 5 is made larger than the magnitude of the supplied current to be larger than the charge of the negative electrode given to the W color toner image. Because it is necessary to do.

As described above, in the image forming apparatus 201 according to the second embodiment, the magnitude of the current supplied to the primary transfer device 5 at the time of the primary transfer of transferring the toner image containing the metal pigment to the intermediate transfer belt 6 is set by the metal pigment. By making the magnitude of the current supplied to the primary transfer device 5 larger than the magnitude of the current supplied to the primary transfer device 5 when the toner image containing no metal pigment is first transferred, it is possible to suppress the polarization and decharge of the toner image containing the metal pigment, and the secondary transfer device 7 The deterioration of the quality of the image formed on the paper P is suppressed by preventing the secondary transfer rate of the above from becoming less than the reference value.

<Third Embodiment>
In the third embodiment, the image forming apparatus 202 that suppresses deterioration of image quality by adjusting the position of the primary transfer device 5 that transfers the toner image containing the metal pigment to the intermediate transfer belt 6 will be described.

FIG. 14 shows an example of a schematic side view showing a main configuration of the image forming apparatus 201A according to the third embodiment. The primary transfer device 5Si of the image forming apparatus 201A is arranged on the upstream side in the transport direction from the primary transfer device 5Si of the image forming apparatus 201 according to the second embodiment. Hereinafter, the arrangement of the primary transfer device 5Si of the image forming apparatus 201A will be described in detail with reference to FIG.

The primary transfer device 5 corresponding to each color is arranged so as to be offset to the downstream side in the transport direction with respect to the photoconductor 1. For example, as shown in FIG. 15, the primary transfer device 5Y, which is an example of the primary transfer device 5, has a line segment 45 connecting the rotation center of the primary transfer device 5Y and the rotation center of the photoconductor 1Y, and the rotation center of the photoconductor 1Y. Is arranged at a position where the angle (offset angle) formed by the vertical line 46 passing through the vertical direction is θ ₁ .

This is because, for example, as compared with the case where the rotation center of the primary transfer device 5Y is arranged on the perpendicular line 46, that is, the offset angle is set to 0 degrees, the discharge generated in the post-nip portion is suppressed, and the discharge causes the intermediate transfer belt. This is because the phenomenon that color loss or the like occurs in the toner image on 6 is suppressed. Therefore, in the image forming apparatus 201A, the primary transfer device 5M, the primary transfer device 5C, and the primary transfer device 5K are also arranged at positions where the offset angle is θ ₁ .

As described above, in order to correct the repolarization or hypocharging that occurs in the Si-colored toner image on the intermediate transfer belt 6, the amount of discharge generated in the post-nip portion of the primary transfer device 5Si should be increased. Just do it.

Therefore, in the image forming apparatus 201A, the primary transfer device 5Si is arranged at a position where the offset angle of the primary transfer device 5Si is θ _{2 which} is smaller than θ ₁ . Specifically, the offset angle θ ₂ is set in advance so that the discharge amount is larger than the discharge amount (reference discharge amount) of the discharge generated in each of the photoconductors 1 and the intermediate transfer belt 6 corresponding to the process color. It is set within the specified angle range. The predetermined angle is obtained in advance by, for example, an experiment using an actual image forming apparatus 201A or a computer simulation based on the design specifications of the image forming apparatus 201A.

In FIG. 15, when the primary transfer device 5Si is arranged so that the rotation center of the primary transfer device 5Si is on the right side of the perpendicular line 46, the amount of discharge generated at the post-nip portion of the primary transfer device 5Si is conversely reduced. (The offset angle in this case is represented by a negative value). Therefore, it is preferable to arrange the primary transfer device 5Si so that the center of rotation of the primary transfer device 5Si is not on the right side of the perpendicular line 46 (offset angle θ ₂ ≧ 0).

Further, with respect to the above-mentioned image forming apparatus 201A, an image forming portion 15CR for forming, for example, a CR color toner image is arranged on the downstream side of the image forming portion 15Si as in the image forming apparatus 200 according to the first embodiment. Then, after forming the Si color toner image on the intermediate transfer belt 6, the CR color toner image may be formed.

Further, with respect to the image forming apparatus 201A described above, the magnitude of the current supplied to the primary transfer device 5Si, as in the image forming apparatus 201 according to the second embodiment, is set to the primary transfer devices 5Y, 5M, 5C, and 5K. It may be made larger than the magnitude of the current supplied to each of the above.

As described above, in the image forming apparatus 201A according to the third embodiment, the offset angle of the primary transfer device 5 for transferring the toner containing the metal pigment to the intermediate transfer belt 6 is transferred to the intermediate transfer belt 6 for the toner not containing the metal pigment. By making it smaller than the offset angle of the primary transfer device 5, it is possible to suppress the repolarization and low charge of the toner image containing the metal pigment so that the secondary transfer rate of the secondary transfer device 7 does not fall below the reference value. The deterioration of the quality of the image formed on the paper P is suppressed.

<Fourth Embodiment>
In the first to third embodiments, tandem image forming apparatus 200, 201, 201A that suppresses deterioration of image quality using a toner containing a metal pigment has been described. In the fourth embodiment, a rotary development type image forming apparatus 202 that suppresses deterioration of image quality using a toner containing a metal pigment will be described.

FIG. 16 shows an example of a schematic side view showing a main configuration of the image forming apparatus 202 according to the fourth embodiment. In the image forming apparatus 202, for example, a plurality of image forming units 15 and a plurality of primary transfer devices 5 arranged for each toner color in the image forming devices 200, 201, and 201A are combined into one image forming unit 15 and the primary transfer device 5. The replacement, the image forming unit 15 and the primary transfer device 5 are commonly used for the toners of the respective colors.

Therefore, the image forming apparatus 202 uses a developing device 4 including developing rolls 34Y, 34M, 34C, 34K, 34Si, and 34CR corresponding to each color, for example, each color of Y, M, C, K, Si, and CR. Be prepared. Other configurations are the same as those of the image forming apparatus 200, 201, 201A.

The image forming unit 15 first forms an electrostatic latent image corresponding to the designated color on the photoconductor 1, and rotates the developer 4 so that the developing roll 34 corresponding to the designated color comes into contact with the photoconductor 1. Toner of the specified color is adhered to the electrostatic latent image in step 2, and a toner image of the specified color is formed on the photoconductor 1.

The toner image formed on the photoconductor 1 is transferred to the intermediate transfer belt 6 by the primary transfer device 5.

The image forming apparatus 202 repeats the above-mentioned image forming operation for each designated toner color to superimpose the toner images of each color on the intermediate transfer belt 6 to form a toner image corresponding to the user image. Then, the image forming apparatus 202 transfers the toner image on the intermediate transfer belt 6 to the paper P by the secondary transfer device 7, and forms an image corresponding to the user image on the paper P.

The image forming apparatus 202 has the same configuration as the main part configuration of the electrical system of the image forming apparatus 200 according to the first embodiment shown in FIG.

Next, the operation of the image forming apparatus 202 will be described in detail with reference to FIG. FIG. 17 is a flowchart showing an example of a flow of image formation processing by an image formation program executed by the CPU 30 when the CPU 30 receives a user image to be image-formed.

First, in step S100, the CPU 30 decomposes the received user image into components for each color of the toner, controls the laser output unit 3, and converts an electrostatic latent image corresponding to any process color into the photoconductor 1. Form. It is assumed that the color components obtained by decomposing the user image include, for example, at least one process color, Si color, and CR color, but a toner containing a metal pigment instead of Si color is used. Other colors to be expressed, such as W color, may be included.

In step S110, the CPU 30 rotates the developer 4 to a position where the developing roll 34 of the color corresponding to the electrostatic latent image formed in step S100 comes into contact with the photoconductor 1, and the electrostatic latent image is a designated process color. Is developed to form a toner image on the photoconductor 1.

In step S120, the CPU 30 controls the primary transfer bias power supply 33 to set the magnitude of the current supplied to the primary transfer device 5 to I ₀ .

In step S130, the CPU 30 outputs a current I ₀ from the primary transfer bias power supply 33 when the toner image on the photoconductor 1 passes through the nip portion formed by the photoconductor 1 and the primary transfer device 5, and intermediate The toner image of the process color specified on the transfer belt 6 is transferred.

In step S140, the CPU 30 determines whether or not the color component obtained by decomposing the user image in step S100 includes a process color that has not yet formed an electrostatic latent image.

In the case of an affirmative determination, the process proceeds to step S100. Then, by selecting an unselected process color in step S100 and repeatedly executing each process of steps S100 to S140, the toner image corresponding to each process color among the color components included in the user image is intermediately transferred. Transfer to belt 6.

On the other hand, when the toner image corresponding to each process color is transferred to the intermediate transfer belt 6 and the determination process in step S140 is a negative determination, the process proceeds to step S150.

In step S150, the CPU 30 acquires the Si color component obtained by decomposing the user image in step S100, controls the laser output unit 3, and forms an electrostatic latent image corresponding to the Si color on the photoconductor 1. To do.

In step S160, the CPU 30 rotates the developer 4 to a position where the developing roll 34Si comes into contact with the photoconductor 1, develops an electrostatic latent image with Si-colored toner, and forms a Si-colored toner image on the photoconductor 1. To do.

In step S170, the CPU 30 controls the primary transfer bias power supply 33 to set the magnitude of the current supplied to the primary transfer device 5 to I ₀ .

In step S180, the CPU 30 outputs a current I ₀ from the primary transfer bias power supply 33 when the Si-colored toner image on the photoconductor 1 passes through the nip portion formed by the photoconductor 1 and the primary transfer device 5. Then, the Si color toner image is transferred to the intermediate transfer belt 6.

In step S190, the CPU 30 acquires the CR color component obtained by decomposing the user image in step S100, controls the laser output unit 3, and forms an electrostatic latent image corresponding to the CR color on the photoconductor 1. To do.

In step S200, the CPU 30 rotates the developer 4 to a position where the developing roll 34CR comes into contact with the photoconductor 1, develops an electrostatic latent image with CR color toner, and forms a CR color toner image on the photoconductor 1. To do.

In step S210, the CPU 30 controls the primary transfer bias power supply 33 to set the magnitude of the current supplied to the primary transfer device 5 to I ₀ .

In step S220, the CPU 30 outputs a current I ₀ from the primary transfer bias power supply 33 when the CR color toner image on the photoconductor 1 passes through the nip portion formed by the photoconductor 1 and the primary transfer device 5. Then, the CR color toner image is transferred to the intermediate transfer belt 6.

At this time, the electric discharge generated in the post-nip portion formed by the photoconductor 1 and the primary transfer device 5 imparts a negative electrode charge to the Si-colored toner image formed on the intermediate transfer belt 6 in step S180. Therefore, the repolarization and decharge of the Si color toner image on the intermediate transfer belt 6 are corrected.

Even in the image forming apparatus 202 using the rotary development method as described above, after transferring the toner image containing the metal pigment to the intermediate transfer belt 6, the toner image containing the metal pigment and the process color toner image and the metal pigment are transferred. By transferring the toner image formed at least in a different place from the toner image containing the metal pigment, the repolarization and decharge of the toner image containing the metal pigment are suppressed. As a result, the secondary transfer rate in the secondary transfer device 7 becomes equal to or higher than the reference value, and deterioration of the quality of the image corresponding to the user image formed on the paper P is suppressed.

<Fifth Embodiment>
In the fifth embodiment, the rotary development type image forming apparatus 203 that suppresses the deterioration of the image quality even when the toner image containing the metal pigment is finally transferred to the intermediate transfer belt 6 will be described.

FIG. 18 shows an example of a schematic side view showing a main configuration of the image forming apparatus 203 according to the fifth embodiment. The image forming apparatus 203 differs from the image forming apparatus 202 according to the fourth embodiment shown in FIG. 16 in that it is provided with the developer 4A from which the CR color developing roll 34CR is removed, and the other is that the image forming apparatus is provided. It has the same configuration as 202. Further, the image forming apparatus 203 has the same configuration as the main part configuration of the electrical system of the image forming apparatus 200 according to the first embodiment shown in FIG.

Next, the operation of the image forming apparatus 203 will be described in detail with reference to FIG. FIG. 19 is a flowchart showing an example of a flow of image formation processing by an image formation program executed by the CPU 30 when the CPU 30 receives a user image to be image-formed.

The difference between the image forming process shown in FIG. 19 and the image forming process according to the fourth embodiment shown in FIG. 17 is that step S170 is replaced with step S170A and the CR color toner image is transferred to the intermediate transfer belt 6. This is a point where the processes of S190 to S220 have been deleted.

In a situation where a Si-colored toner image is formed on the photoconductor 1, in step S170A, the CPU 30 controls the primary transfer bias power supply 33 to set the magnitude of the current supplied to the primary transfer device 5 to I ₁ . .. Here, the current I ₁ is a current larger than the current I ₀ set in step S120 when the process color toner image is transferred to the intermediate transfer belt 6.

As a result, when the Si-colored toner image is transferred to the intermediate transfer belt 6 in step S180, the Si-colored toner on the intermediate transfer belt 6 is formed in the post-nip portion formed by the image forming unit 15 and the primary transfer device 5. More negative electrode charge will be applied to the image than when the current supplied to the primary transfer device 5 is set to I ₀ . Therefore, the repolarization and decharge of the Si color toner image on the intermediate transfer belt 6 are corrected.

<Image quality evaluation result 3>
FIG. 20 shows the result of evaluating the image quality of the user image formed on the paper P by the image forming apparatus 203 according to the technique of the present disclosure. In the image quality evaluation shown in FIG. 20, Si color and W color toners were used as the toner containing the metal pigment.

The meanings of the symbols “◯”, “×”, and “−” in FIG. 20 are the same as the meanings of the symbols shown in FIG.

No. 20 in FIG. 1-No. Reference numeral 4 denotes an image quality evaluation result when the developing device 4A of the image forming apparatus 203 is provided with developing rolls 34Y, 34M, 34C, 34K, and 34Si (configuration 7).

Of these, No. Reference numeral 1 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5 is set to about 23 μA when the Si color toner image is first transferred. No. Reference numeral 2 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5 is set to about 24.2 μA when the Si color toner image is first transferred. No. Reference numeral 3 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5 is set to about 25.3 μA when the Si color toner image is first transferred. No. Reference numeral 4 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5 is set to about 27.6 μA when the Si color toner image is first transferred.

In addition, No. 20 in FIG. 5-No. Reference numeral 8 denotes an image quality evaluation result when the developing device 4A of the image forming apparatus 203 is provided with the developing rolls 34Y, 34M, 34C, 34K, and 34W (configuration 8). Here, the developing roll 34W is a developing roll that adheres a W-colored toner to an electrostatic latent image to form a W-colored toner image on the photoconductor 1. That is, the configuration 8 replaces the developing roll 34Si of the configuration 7 with the developing roll 34W, and the image forming apparatus having the configuration 8 is also an example of the image forming apparatus 203.

Of these, No. Reference numeral 5 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5 is set to about 23 μA when the W color toner image is first transferred. No. Reference numeral 6 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5 is set to about 24.2 μA when the W color toner image is first transferred. No. Reference numeral 7 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5 is set to about 25.3 μA when the W color toner image is first transferred. No. Reference numeral 8 denotes an image quality evaluation result when the magnitude of the current supplied to the primary transfer device 5 is set to about 27.6 μA when the W color toner image is first transferred.

The image quality evaluation results are the same as <Image quality evaluation result 1> and <Image quality evaluation result 2>, Y, M, C, K, Si, W, B formed on uncoated paper having a size of about 50 × 50 mm. , B + W, and B + Si color charts were visually evaluated.

When the user image was evaluated, the temperature was about 28 ° C., the humidity was about 85%, and the process speed of the image forming apparatus 203 was about 220 mm / s. The characteristics of each member included in the image forming apparatus 203 are as follows.

The primary transfer device 5 was an elastic roll having an elastic layer made of, for example, silicone rubber or the like and having a diameter of about 20 mm, a resistance value of about 7.7 logΩ, and an Asuka C hardness of about 30 °.

The intermediate transfer belt 6 is an endless belt in which carbon is added to a resin material such as polyimide, and has a volume resistivity of 12.5 logΩcm.

The secondary transfer roll 7B is, for example, a roll member in which a rubber layer having a thickness of about 450 μm and a volume resistance of about 8.7 logΩ is formed on an elastic roll having a resistance of about 6.3 logΩ and a diameter of about 28 mm. As the backup roll 7A, an elastic roll having a surface resistance of about 7.3 logΩ / □ and an Asuka C hardness of about 53 ° and a diameter of about 20 mm was used.

As the toner of each process color of YMCK, a toner having an average particle size of about 4.7 μm containing an organic pigment was used. Further, the Si color toner uses a toner having an average particle diameter of about 10 μm containing a metal pigment such as aluminum, and the W color toner uses a toner having an average particle diameter of about 5.8 μm containing a metal pigment such as titanium oxide. Was used.

No. 20 shown in FIG. 1-No. In each configuration of No. 8, the magnitude of the current supplied to the primary transfer device 5 when the process color toner image was first transferred was set to about 23 μA. Further, the magnitude of the current supplied to the secondary transfer device 7 is a value such that the transfer efficiency of the toner image of the multi-order color formed by superimposing the process color single color and the process color is 90% or more (as an example). , Approximately 50 μA).

As shown in FIG. 20, in the configuration 7 in which the Si color toner is used as the special color toner containing the metal pigment, No. 1 and No. In the case of 2, unevenness occurred in the metallic luster of the Si-colored user image, and deterioration of image quality was observed. On the other hand, the magnitude of the current supplied to the primary transfer device 5 when transferring the Si color toner image is about 10% or more of the magnitude of the current supplied to the primary transfer device 5 when transferring the process color toner image. Increased No. 3 and No. In the case of 4, no color unevenness or metallic luster unevenness was observed in the user image of each color including the Si color, and the result was obtained that the image quality was good.

Further, in the configuration 8 in which the W color toner is used as the special color toner containing the metal pigment, No. In the case of 5, unevenness occurred in the metallic luster of the W color user image, and deterioration of the image quality was observed. On the other hand, the magnitude of the current supplied to the primary transfer device 5 when transferring the W color toner image is about 5% or more of the magnitude of the current supplied to the primary transfer device 5 when transferring the process color toner image. Increased No. 6, No. 7 and No. In the case of 8, no color unevenness or metallic luster unevenness was observed in the user image of each color including the W color, and the result was obtained that the image quality was good.

It should be noted that even in the image quality evaluation result using the image forming apparatus 203, the metal pigment with respect to the magnitude of the current supplied to the primary transfer device 5 when transferring the process color toner image in order to evaluate the image quality as good. The rate of increase in the magnitude of the current supplied to the primary transfer device 5 when transferring the toner image containing the above is about 5% or more for the W color and about 10% or more for the Si color.

As described above, in the image forming apparatus 201 according to the fifth embodiment, the magnitude of the current supplied to the primary transfer device 5 at the time of the primary transfer of transferring the toner image containing the metal pigment to the intermediate transfer belt 6 is set by the metal pigment. By making the magnitude of the current supplied to the primary transfer device 5 larger than the magnitude of the current supplied to the primary transfer device 5 when the toner image containing no metal pigment is first transferred, it is possible to suppress the repolarization and decharge of the toner image containing the metal pigment in the secondary transfer device 7. The deterioration of the quality of the image formed on the paper P is suppressed by preventing the secondary transfer rate of the above from becoming less than the reference value.

The primary transfer device 5 in which the offset angle is set to θ ₂ in advance may be applied to the image forming devices 202 and 203 of the rotary development method shown in the fourth embodiment and the fifth embodiment. Further, when the process color toner image is first transferred, the offset angle of the primary transfer device 5 is set to θ _1, and when the toner image containing the metal pigment is first transferred, the offset angle of the primary transfer device 5 is set to θ 1. as the _2, it may be to control the position of the primary transfer unit 5.

Although the disclosed technology has been described above using the embodiments, the disclosed technology is not limited to the scope described in each embodiment. Various changes or improvements can be made to each embodiment without departing from the gist of the disclosed technology, and the modified or improved forms are also included in the technical scope of the disclosed technology. For example, the order of processing may be changed without departing from the gist of the disclosed technology.

Further, in each embodiment, an embodiment in which the image forming process in the control unit 60 is realized by software has been described as an example, but the process is equivalent to the flowcharts shown in FIGS. 5, 12, 17, and 19. May be processed by hardware. In this case, the processing speed can be increased as compared with the case where the processing in the control unit 60 is realized by software.

Further, in the embodiment, the mode in which the image forming program is installed in the ROM 31 has been described, but the present invention is not limited to this. The image forming program according to the disclosed technique can also be provided in a form recorded on a computer-readable recording medium. For example, the image forming program according to the disclosed technology shall be provided in a form recorded on a portable recording medium such as a CD (Compact Disc) -ROM, a DVD (Digital Versatile) -ROM, or a USB (Universal Serial Bus) memory. Is also possible. Further, the image forming program according to the disclosed technique can also be provided in a form recorded in a semiconductor memory such as a flash memory.

1 (1Y, 1M, 1C, 1K, 1Si, 1CR) ... Photoreceptor 2 (2Y, 2M, 2C, 2K, 2Si, 2CR) ... Charger 3 (3Y, 3M, 3C, 3K, 3Si, 3CR) ... Laser output unit 4 (4Y, 4M, 4C, 4K, 4Si, 4CR), 4A ... Developer 5 (5Y, 5M, 5C, 5K, 5Si, 5CR, 5W) ... Primary transfer Vessel 6 ... Intermediate transfer belt 7 ... Secondary transfer device 8 ... Belt cleaner 9 ... Fixer 15 (15Y, 15M, 15C, 15K, 15Si, 15CR, 15W) ... Image forming unit 30 ... CPU
31 ... ROM
32 ... RAM
33 ... Primary transfer bias power supply 34 (34Y, 34M, 34C, 34K, 34Si, 34CR, 34W) ... Development roll 38 ... Secondary transfer bias power supply 60 ... Control unit 200 (201, 201A, 202, 203) ・ ・ ・ Image forming device P ・ ・ ・ Paper

Claims (6)

An electrostatic latent image formed on the photoconductor was developed using a first developing agent containing no metal pigment and a second developing agent containing a metal pigment, both of which were charged to the same polarity, and an image was formed on the photoconductor. Image forming means for forming
The photoconductor is supplied to a transfer body that supplies a current that generates a voltage having a polarity opposite to the charging polarity of the first developer and the second developer and is conveyed to a nip portion formed between the photoconductor and the photoconductor. A transfer means for transferring the image formed in the
When transferred to the transfer body by the transfer means , the charge distribution on the transfer body is biased toward the positive electrode side with respect to the charge distribution of the first developing agent by injecting a positive charge at the nip portion. A control means for controlling the charge distribution of the second developer so that the charge distribution of the second developer, which is easily distributed, approaches the charge distribution of the first developer transferred to the transfer body.
An image forming apparatus comprising. When the control means transfers the image formed by the second developer to the transfer body, the magnitude of the current supplied to the transfer means determines the image formed by the first developer. The image forming apparatus according to claim 1, wherein the amount of supply of the current is controlled so as to be larger than the magnitude of the current supplied to the transfer means when transferring to a transfer body. The image forming means further includes a third developer that does not contain a metal pigment and has a color different from that of the first developer, and is formed on the photoconductor by the first developer and the second developer. An image with the third developer is formed in a place at least partially different from the image.
Claim 1 or claim, wherein the control means controls the transfer means so that the image formed by the third developer is transferred to the transfer body after the image formed by the second developer. Item 2. The image forming apparatus according to item 2. The offset angle representing the amount of deviation between the position of the photoconductor and the position of the transfer means in the transport direction of the transfer body is larger than the reference discharge amount of the discharge generated between the photoconductor and the transfer body. The image forming apparatus according to any one of claims 1 to 3, wherein the photoconductor and the transfer means are arranged so as to be included in a predetermined angle range. The image forming apparatus according to any one of claims 1 to 4, wherein the color of the second developer is gold, silver, or white. An image forming program for causing a computer to function as a control means of the image forming apparatus according to any one of claims 1 to 5.

Images