JP2023128396A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can prevent occurrence of fixing offset and transfer blurring and suppress a change in a hue of an image.SOLUTION: An image forming apparatus performing image formation on a recording medium comprises: an image forming unit that has electrifying means each applying an electrification bias to electrify an image carrier, exposure means irradiating the image carriers with light to form electrostatic latent images and capable of changing a quantity of exposure light, and developing means each applying a development bias to develop the electrostatic latent image, and has image forming means corresponding to respective colors including at least cyan, magenta, and yellow; detection means that detects the color of the recording medium; and control means that, according to a result of detection performed by the detection means, changes an amount of attachment of toners in cyan, magenta, and yellow by changing at least one or more of the electrification bias, the quantity of exposure light, and the development bias.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus.

2. Description of the Related Art Conventionally, an image forming apparatus is known that forms a K (black) image by superimposing C (cyan), M (magenta), and Y (yellow) toners.

Patent Document 1 discloses a printing device that can print black either as a single color black or as a mixed color black formed by a plurality of colors.

Furthermore, a method is also known in which a special color toner such as white toner, IR stealth toner, or clear toner is mounted instead of the K toner image forming unit. In this case, as described above, a K image is created by superimposing C, M, and Y toners. New added value has also been created, such as white images that could not be expressed with conventional C, M, Y, and K image forming devices, and the embedding of information that can only be read by shining special light onto the image. It becomes possible to attach. In this case, if K is simply expressed by overlapping three colors of C, M, and Y toners, the amount of toner adhering to the paper (transfer paper) will be larger than usual, resulting in fixation offset and uneven transfer. There are challenges.

Patent Document 2 discloses that a color toner image made of at least one color toner among yellow, magenta, and cyan and a special toner image made of a special toner are formed on the same recording medium, and the color toner image and the special toner are formed on the same recording medium. In an image forming apparatus that forms an image by fixing an image on the recording medium by a fixing means, in the case of a special image forming operation of forming the color toner image and the special toner image, the special toner image is not formed. An image forming apparatus is disclosed in which the amount of color toner per unit area on the recording medium is smaller than that in a normal image forming operation in which the same color toner image is formed on the recording medium.

However, the configuration disclosed in Patent Document 2 has a problem in that when the paper is colored, a color variation occurs in the K image formed by overlapping three colors depending on the color.

In order to solve the above-mentioned problems, the invention according to claim 1 provides an image forming apparatus that forms an image on a recording medium. It has an exposure means that forms an electrostatic latent image by irradiating the image carrier with light and can change the amount of exposure light, and a developing means that develops the electrostatic latent image by applying a developing bias. , an image forming unit having an image forming unit corresponding to at least each color of cyan, magenta, and yellow, a detection unit that detects the color of the recording medium, and a detection result of the detection unit that determines the charging bias, The image forming apparatus further includes a control unit that changes the adhesion amount of the cyan, magenta, and yellow toners by changing at least one of the exposure light amount and the development bias.

According to the present invention, it is possible to provide an image forming apparatus that can prevent the occurrence of fixing offset and transfer blur, and suppress variations in the color tone of an image.

FIG. 1 is an explanatory diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view of an image forming unit according to an embodiment of the present invention. FIG. 1 is a block diagram related to control in a copying machine according to an embodiment of the invention. 1 is a flowchart showing the flow of image forming operations according to an embodiment of the present invention. FIG. 3 is an explanatory diagram when a black image is formed on white paper. FIG. 3 is an explanatory diagram when the paper is colored and the toner adhesion amounts of three colors cyan, magenta, and yellow are reduced by the same amount and overlapped to form a black image. FIG. 7 is an explanatory diagram when the paper is colored and the toner adhesion amounts of two of the three colors cyan, magenta, and yellow are greatly reduced and superimposed to form a black image. FIG. 7 is an explanatory diagram showing another example in which a black image is formed on color paper. An explanatory diagram when the paper color is black and a black image is formed. FIG. 3 is an explanatory diagram when a gray image is formed on white paper. FIG. 3 is an explanatory diagram when the paper is colored and a gray image is formed. FIG. 3 is an explanatory diagram when a gray image is formed on black paper. FIG. 3 is a diagram illustrating an example of a toner adhesion amount adjustment table for each paper color.

Embodiments of the present invention will be described below using the drawings.

First, an embodiment of a tandem color copying machine (hereinafter referred to as copying machine 500) as an image forming apparatus to which the present invention is applied will be described.

In the embodiment of the present invention, a special color (hereinafter referred to as SP) toner is used instead of black (hereinafter referred to as K) toner. As a result, a K image is created by overlapping cyan (hereinafter referred to as C) toner, magenta (hereinafter referred to as M) toner, and yellow (hereinafter referred to as Y) toner. is forming. The following explanation is based on this premise.

FIG. 1 is a schematic configuration diagram of a copying machine 500. Further, FIG. 2 is an enlarged view of the image forming unit C. Here, although FIG. 2 shows the image forming unit 6C as a representative, M, Y, and SP also have a similar configuration.

In FIG. 1, a copying machine 500 is a main body of an image forming apparatus, and includes a document reading section 4 and a document transport section 3, which are reading means for reading images, above a printer section 100 of an image forming section. Further, below the printer section 100, a paper feed section 7 is provided. The document transport section 3 transports the document to the document reading section 4 . The document reading unit 4 reads image information of the transported document. The paper feed section 7 includes a paper feed cassette 26 that accommodates paper (transfer paper) P that is a recording medium, and a paper feed roller 27 that feeds the paper P in the paper feed cassette 26 toward the printer section 100. Note that in FIG. 1, a dashed line indicates a conveyance path of paper P within the copying machine 500.

The upper part of the printer section 100 is a paper discharge tray 30 on which paper P on which an output image is formed is stacked. Further, the paper P is discharged onto the paper discharge tray 30 by the paper discharge roller 25. The printer section 100 includes four image forming units 6 (C, M, Y, SP) as image forming sections that form toner images of each color (C, M, Y, SP), and an intermediate transfer unit 10. Equipped with

Each image forming unit 6 (C, M, Y, SP) includes a drum-shaped photoreceptor 1 (C, M, Y, SP) as an image carrier on which a toner image of each color is formed, and each photoreceptor. A charging device 2, which is a charging means, has a charging roller 12 that charges the surface of each photoreceptor 1 (C, M, Y, SP), and irradiation light L is directed toward each photoreceptor 1 (C, M, Y, SP). An exposure device 13, which is an exposure means that forms an electrostatic latent image by irradiation and exposure, and a developer that transfers the electrostatic latent image formed on the surface of each photoreceptor 1 (C, M, Y, SP). The developing device 5 (Y, M, C, K) is a developing means having a developing roller 51 that performs development with toner.

The intermediate transfer unit 10 includes an intermediate transfer belt 8 and primary transfer bias rollers 9 (C, M, Y, SP). The intermediate transfer belt 8 is an intermediate transfer member on which the toner images of each color formed on the surface of each photoreceptor 1 (C, M, Y, SP) are transferred in a superimposed manner to form a color toner image on the surface. . Further, the primary transfer bias roller 9 (C, M, Y, SP) is used for primary transfer to transfer the toner image formed on the surface of each photoreceptor 1 (C, M, Y, SP) to the intermediate transfer belt 8. It is a means.

The printer section 100 includes a secondary transfer bias roller 19 for transferring the color toner image on the intermediate transfer belt 8 onto the paper P. It also includes a pair of registration rollers 28 that adjust the timing of conveying the paper P sent out by the paper feed roller 27 to a secondary transfer nip where the intermediate transfer belt 8 and the secondary transfer bias roller 19 face each other.

Furthermore, the printer section 100 includes a fixing device 20 that fixes the unfixed toner image on the paper P above the secondary transfer nip.

Toner containers 11 for each color (C, M, Y, SP) are arranged below the paper discharge tray 30 in the printer section 100 and above the intermediate transfer unit 10 . The toner containers 11 (C, M, Y, SP) of each color contain toner of each color (C, M, Y, SP) to be supplied to each developing device 5 (Y, M, C, SP). Further, in this embodiment, white (hereinafter referred to as white) toner is used as the SP toner. Note that although white toner is used as the SP toner in this embodiment, the present invention is not limited to this, and IR stealth toner, clear toner, etc. may also be applied.

Next, features of the present invention will be explained.

In the present invention, a K image is formed by superimposing C, M, and Y toners. At that time, the paper used for printing may be colored. At this time, the color of the paper on which the K image is to be formed is checked.

For example, when a user prints a K image using red paper, the K image is created by superimposing C, M, and Y toners, so the image has a reddish tint. Sometimes it looks like Therefore, the detailed method will be described later, but by adjusting the amount of toner adhesion of M and Y, which are the color components of the paper, by taking the color of the paper into account, and then layering the three colors to create a K image. This prevents redness.

Based on this, the present invention employs a method of detecting (extracting) the color of paper, which includes the following methods.

First, there is a method in which the color of the paper is detected by having the document reading unit 4 read the paper used for printing by the user.

In this case, when the user prints, the document reading section 4 reads the paper used for printing once, and the user sets printing conditions before printing. Specifically, after the user reads the color (R, G, B) of paper to be printed and converts it to C, M, Y, the adhesion of C, M, Y toner related to this color component is performed. After adjusting the amount so that the K image does not have that color tone, printing is performed. In addition, in this specification, "related to a component of this color" shall mean "a component that forms this color." Note that although here, the color of the paper was read using the original reading unit 4 of the copying machine 500, the present invention is not limited to this, and a reading device that is not included in the copying machine 500 may be used.

Also, a method different from this will be explained. In this method, a table (hereinafter referred to as a paper color toner adhesion amount adjustment table) that associates the paper type such as the paper color with the toner adhesion amount adjustment method for the corresponding color is stored in advance. Then, there is a method in which the control unit 130 automatically forms an image based on this toner adhesion amount adjustment table for each paper color. Specifically, the color of the paper is detected, and the amount of toner adhesion of C, M, and Y related to that color and the components of that color is set so that the color of the paper is not applied to the K image. make a table. FIG. 13 shows the toner adhesion amount adjustment table for each paper color. Note that the table shown in FIG. 13 is an example. Then, the toner adhesion amount adjustment table for each paper color is stored in the storage unit 132 of the control unit 130 in advance. As a result, when the user prints, the control unit 130 adjusts the amount of toner adhesion for C, M, and Y based on this toner adhesion amount adjustment table for each paper color so that the color tone of the paper does not appear on the K image. Then, you will print. Note that this toner adhesion amount adjustment table for each paper color is also applied to the above-mentioned case where "the document reading unit 4 reads the paper used for printing once, the user sets the printing conditions, and then prints." Is possible.

Furthermore, another method will be explained. One possible method for this is to provide a sensor or the like inside the copying machine 500 to detect the color of the paper and form a K image by detecting the color of the paper. Specifically, for example, an optical sensor is provided in the paper feed section 7 of the copying machine 500, and detects the color of the paper fed at the start of printing. Then, based on the detected color of the paper, the amount of C, M, and Y toner adhesion related to the color components is adjusted so that the color of the paper does not appear on the K image, and then printing is performed. become. It should be noted that the above-mentioned toner adhesion amount adjustment table for each paper color may be provided, and the toner adhesion amount may be adjusted by comparing the results detected by the optical sensor with the table.

Next, FIG. 3 will be explained. FIG. 3 is a block diagram related to control in a copying machine according to an embodiment of the present invention.

The control unit 130 in the embodiment of the present invention includes a main control unit 131, a storage unit 132 as a storage unit, a color conversion/separation processing unit 133, a gamma correction unit 134, a toner amount adjustment unit 135, and a color conversion/separation processing unit 133. It has a key conversion section 136. Note that the control unit is an example of a control means.

The main control unit 131 is composed of a CPU, RAM, ROM, etc., and performs image processing and overall control of the printer by executing various programs. Furthermore, the storage unit 132 stores various data and programs used in each part of the control unit 130, the above-described toner adhesion amount adjustment table for each paper color, and the like.

The color conversion/separation processing unit 133 uses the color conversion/separation table stored in the storage unit 132 to convert the color information (RGB) of the input image information into C, M, and Y colors, which are color information for the printer. It converts into information, decomposes it, and generates image information for each C, M, and Y. Furthermore, if the input image information includes spot color image information, the spot color image information is extracted from the input image information and generated. Then, when the paper is read or the color of the paper is detected using an optical sensor or the like, the color information (RGB) of the paper is also converted and separated into C, M, and Y color information.

In order to achieve appropriate gradation on paper, the gamma correction unit 134 uses the gamma correction table stored in the storage unit 132 to correct C, M, and Y image information, and as necessary. SP image information and the like are also subjected to γ (gamma) correction processing.

Under the control of the main control section 131, the toner amount adjustment section 135 performs toner amount adjustment control for adjusting the amount of toner per unit area using the toner adhesion amount conversion table stored in the storage section 132. Specifically, the toner amount adjustment unit 135 uses the toner adhesion amount conversion table to calculate the toner adhesion amount of C, M, and Y toners per unit area in order to form the input image on the paper. The total amount (hereinafter referred to as "toner total amount") is calculated. After the calculation, toner adhesion amount conversion processing (image processing) for each image information of C, M, and Y is performed.

For this calculation, once the paper is read or the color of the paper is detected using an optical sensor, etc., the paper color components related to the converted and separated color information are determined using the toner adhesion amount conversion table. The amount of color associated with is converted into the amount of C, M, Y toner adhesion. Then, the converted toner adhesion amount is taken into consideration in the calculation. Alternatively, when calculating the above, if a toner adhesion amount adjustment table for each paper color has been created, the C, M, and Y toner adhesion amounts based on the toner adhesion amount adjustment table for each paper color should be taken into account in the calculation. Make it. At this time, toner adhesion amount conversion processing (image processing) may also be performed on the SP image information. In this embodiment, the toner adhesion amount adjustment table for each paper color and the toner adhesion amount conversion table are separate, but they may be combined into one table.

The gradation conversion unit 136 uses the dither pattern data stored in the storage unit 132 to perform gradation conversion processing that converts each image information of C, M, Y, and SP into a dither pattern according to the halftone density. etc.

The image forming control unit 140 controls each charging device 2, exposure device 13, and developing device 5 for C, M, Y, and SP based on the C, M, and Y image information. Adjust (change) bias, exposure light amount, and development bias.

Here, the charging bias refers to the voltage applied to the charging roller 12 shown in FIG. 2. When this voltage is increased, the amount of toner adhesion increases, and when the voltage is decreased, the amount of toner adhesion is decreased.

Further, when the amount of exposure light, which is the amount of light irradiated toward the photoreceptor 1 from the exposure device 13, is increased, the amount of toner adhesion increases, and when the amount of exposure light is decreased, the amount of toner adhesion is decreased.

The developing bias refers to the voltage applied to the developing roller 51 shown in FIG. When this voltage is increased, the amount of toner adhesion increases, and when the voltage is decreased, the amount of toner adhesion is decreased.

The image forming control unit 140 controls at least one of the charging bias, the exposure light amount, and the developing bias to adjust the increase/decrease in the amount of toner adhesion. In order to appropriately adjust the increase/decrease in the amount of toner adhesion, it is more desirable to control the charging bias, the exposure light amount, and the developing bias to change them at the same time.

Next, FIG. 4 is a flowchart showing the flow of an image forming operation in an embodiment of the present invention.

The control unit 130 acquires input image information, paper color information, etc. from the document reading unit 4, a personal computer, etc. (S1).

Thereafter, the control unit 130 uses the color conversion/separation table stored in the storage unit 132 to cause the color conversion/separation processing unit 133 to convert the color information (RGB) of the input image information into printer color information. It is converted and decomposed into C, M, and Y color information (S2). Further, when the paper is read or the color of the paper is detected using an optical sensor or the like, the color information (RGB) is also converted and separated into C, M, and Y color information. Then, the gamma correction unit 134 executes gamma correction processing on each of the C, M, and Y image information, etc. (S3).

Next, based on the C, M, and Y image information after the gamma correction process, the control unit 130 causes the toner amount adjustment unit 135 to calculate the amount of toner adhesion necessary for the K image portion of the image based on the image information. calculate. Then, based on the calculation, the amount of C, M, and Y toner adhesion necessary for the K image is determined (S4).

Here, since the embodiment according to the present invention does not include an image forming unit that uses K toner, it is necessary to form an image by overlapping C, M, and Y toners for the K image portion. At this time, the total amount of toner per unit area becomes large, and there is a possibility that it exceeds the fixable upper limit. Furthermore, there is a possibility that the color tone of the K image varies depending on the color of the paper.

Therefore, we calculated the amount of C, M, and Y toner adhesion required to form a K image without exceeding the fixable upper limit value and based on the detected paper color or the toner adhesion amount adjustment table for each paper color. do.

After the calculation, the gradation conversion unit 136 executes gradation conversion processing (S5). Thereafter, the C, M, and Y image information outputted from the gradation conversion section 136 is sent to the image formation control section 140. The image forming control section 140 controls one or more of the charging bias, the exposure light amount, and the developing bias. Then, after adjusting the toner adhesion amount of each color, an image forming operation is executed (S6).

Next, a method of forming a K image by detecting the color of the paper described above and combining toner of a color related to the detected color component and superimposing C, M, and Y toner images. Details will be explained below.

In the embodiments of the present invention, the total toner amount per unit area is, for example, a relative value of the toner adhesion amount per unit area of each color, with the target toner adhesion amount when forming a monochrome solid image as 100%. In the case indicated by , it is assumed that the upper limit value that can be fixed is set to 220%. Furthermore, here, the term "paper color component" refers to the amount when the amount of color related to the color component of the paper is converted into the amount of toner adhesion. The numerical values and the like described in this embodiment are merely examples.

First, the case of "forming a K image on white paper" will be described using FIG. 5. At this time, the paper on which the K image is to be formed is assumed to be P1. Here, if the K image is formed by superimposing the toner adhesion amount of 100% of each of C, M, and Y, the fixable upper limit value will be exceeded, which may cause transfer/fixing failure.

Therefore, the C, M, and Y toner adhesion amounts are adjusted to be reduced to, for example, 70%. At this time, since the color of the paper P1 is white, there is not much variation in color with respect to the K image. Therefore, when adjusting the amount of C, M, and Y toner adhesion, it is not necessary to take into consideration the color of the paper.

Then, the reduced C, M, and Y toner images are superimposed to form a K image on the paper P1.

By doing so, even if a K image is formed by overlapping three colors, the fixable upper limit of 220% will not be exceeded, so that fixing/transfer defects can be prevented from occurring. In this embodiment, the maximum amount of toner adhesion for each color when forming a K image is set to 70% of this amount. If the paper is colored, adjustments are made to reduce the amount of toner adhesion based on this 70%, taking into account the color of the paper. I will discuss this later.

Next, a case will be described in which "the paper is colored and a K image is formed". Here, for example, assume that the color of paper P2A is red. In addition, color refers to colors other than white and black, such as red, blue, green, and yellow. At this time, as shown in FIG. 6, the toner adhesion amounts for C, M, and Y are reduced to the same amount (for example, 70%) for the three colors, as in the case of white paper P1, and then these are overlapped. Suppose that a K image is also formed on paper P2A. On the other hand, as it is, since the color of the paper P2A is red, the K image will appear reddish when printed.

Therefore, in the embodiment of the present invention, when reducing and adjusting the amount of toner adhesion for C, M, and Y and superimposing them, the amount of toner adhesion for C, M, and Y is adjusted by taking into account the color of the paper. We are making adjustments to reduce it. Specifically, as shown in FIG. 7, since the color of paper P2A is red, the amount of M and Y toner adhesion, which are these components, is calculated by taking into account the color of the paper (for example, 20%). (including), respectively, by, for example, 50%. Further, the amount of C toner adhesion is reduced to, for example, 70%. That is, the M and Y toner adhesion amounts are reduced by more than the C toner adhesion amount, which has been reduced to the standard. Then, the reduced C, M, and Y toner images are superimposed to form a K image on the paper P2A.

By doing so, it is possible to prevent fixing/transfer failures due to an increase in the amount of toner adhering to the paper. Further, it is also possible to prevent the color tone of the K image from changing.

Another example will be explained using FIG. 8. For example, assume that an image is formed on paper P2B, which has a red paper color like paper P2A. On the other hand, assume that the color of the paper P2B is lighter than that of the paper P2A in terms of the depth (density) of the red color.

In this case, when forming a K image on paper P2B, the amount of toner adhesion of M and Y, which are red components, is calculated by the amount of toner adhesion of C, taking into account the color of the paper (for example, 10%). Try to reduce by more. Since the paper P2B is a lighter red than the paper P2A, the amount to be reduced is, for example, by Z2 (for example, 40%), which is smaller than Z1 (for example, 50%) shown in FIG. It will be a good thing. That is, it is sufficient to reduce the amount of M and Y toner adhesion to, for example, 60%. Note that the amount of toner adhesion for C is reduced to, for example, 70%, as in the case of paper P2A. Then, the reduced C, M, and Y toner images are superimposed to form a K image on the paper P2B.

In other words, in the embodiment of the present invention, depending on the color of the paper, the amount of toner adhesion of a color related to the component of that color is adjusted to be reduced by a larger amount by taking into account the color of the paper. The three colors are superimposed to form a K image. Furthermore, the amount to reduce the amount of attached toner of a color related to the component of that color is determined according to the color depth (density) of the paper. This makes it possible to prevent fixation/transfer failure due to an increase in the amount of toner adhering to the paper, and to prevent variations in the color tone of the K image.

Although we have explained the case where the paper color is red, for example, if the paper color is blue, when forming a K image by superimposing three colors, the blue components C and M What is necessary is to reduce the amount of toner adhesion as much as possible. Further, if the color of the paper is green, when forming a K image by superimposing three colors, the amount of adhered toner of Y and C, which are green components, may be reduced by a larger amount.

Further, the present invention is not limited to being applied only to the case where two colors are reduced by a large amount or to the case where two colors are reduced by the same amount. Here's another example. If the paper color is yellow, when three colors are superimposed to form a K image, the amount of toner adhesion of the other two colors is reduced to the standard by taking into account the color of the paper. You should try to reduce it by more than the amount. Furthermore, to give another example, if the color of the paper is red with a strong yellowish tint, of the components M and Y that are related to the color of the paper, the toner adhesion amount of Y, which has a strong tint, will be higher. You should try to reduce it by more. Specifically, for example, reduce the toner adhesion amount of C to 70%, reduce the toner adhesion amount of M to 60%, reduce the toner adhesion amount of Y to 50%, and then overlap the three colors to create K. It is sufficient to form an image of

Next, a case will be described in which "the color of the paper is black and a K image is formed". Note that this case can be applied when printing a security code or the like when it is desired to embed security information on paper.

Here, it is assumed that the color of the paper P3 shown in FIG. 9 is black (RGB components are close to 0). As for the method of forming a K image, the amount of C, M, and Y toner adhesion is reduced to 70%, for example, in the same way as in the case of forming a K image on white paper as described above. Do it like this. Further, at this time, since the color of the paper is black, there is not much variation due to color in the K image. Therefore, when adjusting the amount of C, M, and Y toner adhesion, it is not necessary to take into consideration the color of the paper. Then, the reduced C, M, and Y toner images are superimposed to form a K image on the paper P3.

By doing so, it is possible to prevent fixing/transfer failures due to an increase in the amount of toner adhering to the paper.

Furthermore, in the present invention, it is also possible to form a gray image as a modification of the K image formation. This will be explained below.

Here, a case will be described in which "the paper color is white and a gray image is formed". In this case, the amount of toner adhesion for C, M, and Y, taking into account the amount of toner adhesion for C, M, and Y, the method of overlapping the three color toners to form a K image, and the color of the paper, The point of adjustment is basically the same as in the above-mentioned "case where the paper color is white and a K image is to be formed".

The difference is that, as shown in FIG. 10, K images are formed on paper P4 at predetermined intervals to form a halftone image. Thereby, a gray image can be formed on the paper P4.

By doing so, it is possible to prevent fixing/transfer failures due to an increase in the amount of toner adhering to the paper.

Next, a case will be described in which "the paper is colored and a gray image is formed". Here, it is assumed that the paper P5 to be printed is, for example, the same red color as the paper P2A, and its color density is also the same as that of the paper P2A. In this case, the amount of toner adhesion for C, M, and Y, taking into account the amount of toner adhesion for C, M, and Y, the method of overlapping the three color toners to form a K image, and the color of the paper, The point of adjustment is basically the same as in the above-mentioned case of "forming a K image on color paper".

The difference is that, as shown in FIG. 11, K images are formed on paper P5 at predetermined intervals to form a halftone image. In addition, in FIG. 11, the amount of toner adhesion for M and Y is reduced to, for example, 50%, and the amount of toner adhesion for C is reduced to, for example, 70%, and then the three colors are superimposed to form a K image. This shows the case where As a result, a gray image can be formed on the paper P5.

By doing so, it is possible to prevent fixing/transfer failures due to an increase in the amount of toner adhering to the paper. Further, it is also possible to prevent the color tone of a gray image from changing.

Further, when the SP toner is a white toner, it can also be used to form a gray image.

Here, a case will be described in which "the paper color is black and a gray image is formed". At this time, it is also possible to form a K image by overlapping C, M, and Y toners, and then form a gray image by creating a halftone image. However, in this case, there is a possibility that a gray image cannot be accurately expressed.

Therefore, a gray image is formed by using white toner as SP toner without using C, M, and Y toners. Specifically, as shown in FIG. 12, a white image is formed by applying white toner on the paper P6 at predetermined intervals to form a halftone image. Thereby, a gray image can be formed on the paper P6.

By forming an image using a single color of white toner in this manner, it is possible to prevent fixing/transfer failures due to an increase in the amount of toner adhering to the paper. Further, even on black paper, it is possible to form a gray image without any color variation.

Note that since a single color of white toner is used on the paper P6, a white image may be formed by setting the toner adhesion amount of the white toner to 100%, but it may also be formed by reducing it to, for example, 70%.

What has been described above is just an example, and the present invention provides unique effects in each of the following aspects.

The first aspect is an image forming apparatus that forms an image on a recording medium (for example, paper P), and a charging unit (for example, charging device 2), an exposure means (e.g. exposure device 13) that irradiates light onto the image carrier to form an electrostatic latent image and is capable of changing the amount of exposure light; An image comprising a developing means (e.g., developing device 5) for developing a latent image, and image forming means (e.g., image forming unit 6) corresponding to at least each color of cyan, magenta, and yellow. A forming unit, a detection means for detecting the color of the recording medium, and at least one of the charging bias, the exposure light amount, and the development bias are changed according to the detection result of the detection means, thereby changing the cyan color and the color of the recording medium. An image forming apparatus comprising: a control unit (for example, a control unit 130) that changes the adhesion amount of magenta and yellow toners.

The second aspect is an image forming apparatus that forms an image on a recording medium (for example, paper P), and a charging unit (for example, charging device 2), an exposure means (e.g. exposure device 13) that irradiates light onto the image carrier to form an electrostatic latent image and is capable of changing the amount of exposure light; An image comprising a developing means (e.g., developing device 5) for developing a latent image, and image forming means (e.g., image forming unit 6) corresponding to at least each color of cyan, magenta, and yellow. a forming unit; a storage unit that stores a table that associates the color of a recording medium with a method of forming an image to be formed on the recording medium; The present invention is characterized by comprising a control means (for example, a control section 130) that changes the adhesion amount of the cyan, magenta, and yellow toners by changing at least one of the toners.

A third aspect is that in the first aspect, the detection means is a reading means (for example, document reading unit 4) that reads an image formed on the recording medium and detects the color of the recording medium. It is characterized by:

In a fourth aspect, based on the first aspect, the image forming apparatus includes a paper feeding section (for example, paper feeding section 7) that feeds the recording medium to the image forming section, and the detection means includes an optical The present invention is characterized in that it is a sensor and is provided in the paper feeding section.

In a fifth aspect, in the first to fourth aspects, the charging bias is a voltage applied to a charging roller included in the charging means, and changing the charging bias means increasing or decreasing the voltage. The image forming apparatus according to any one of claims 1 to 4.

A sixth aspect is that in the first to fifth aspects, changing the amount of exposure light is characterized in that the amount of light that the exposure means irradiates to the image carrier is increased or decreased. It is characterized by certain things.

In a seventh aspect, in the first to sixth aspects, the developing bias is a voltage applied to a developing roller included in the developing means, and changing the developing bias means increasing or decreasing the voltage. It is characterized by the fact that

An eighth aspect is that in the first to seventh aspects, the control means superimposes the cyan, magenta, and yellow toners to form a black image. It is something.

In a ninth aspect, in the first to seventh aspects, when the color of the recording medium is white or color, the control means superimposes the cyan, magenta, and yellow toners. It is characterized by forming a gray image by combining the dots and forming a halftone image.

In a tenth aspect, in the eighth aspect, when the color of the recording medium is white or black, the control means makes a change to reduce the adhesion amount of the cyan, magenta, and yellow toners. It is characterized by the fact that

In an eleventh aspect, in the eighth aspect or the ninth aspect, when the color of the recording medium is color, the control means controls the adhesion amount of the cyan, magenta, and yellow toners. The reduced toner adhesion amount is determined by reducing the amount of any one or more of the cyan color, the magenta color, or the yellow color related to the color components of the recording medium to the toner adhesion amount. It is characterized in that it includes the amount when converted.

In a twelfth aspect, in the ninth aspect, when the color of the recording medium is white, the control means performs a change to reduce the adhesion amount of the cyan, magenta, and yellow toners. It is characterized by:

A thirteenth aspect is the image forming unit according to the first to seventh aspects, wherein the image forming section has an image forming means corresponding to a spot color, and the spot color is white. be.

A fourteenth aspect is the thirteenth aspect, wherein the control means forms a gray image using white toner when the color of the recording medium is black.

According to the first to fourteenth aspects, it is possible to form a black image with a reduced amount of toner adhesion while taking into account the color of the recording medium. Therefore, it is possible to prevent the occurrence of fixing offset and transfer blur, and to suppress variations in the color tone of the image.

1 Photoreceptor 2 Charging device 3 Original transport section 4 Original reading section 5 Developing device 6 Image forming unit 7 Paper feeding section 8 Intermediate transfer belt 9 Primary transfer bias roller 10 Intermediate transfer unit 11 Toner container 12 Charging roller 13 Exposure device 19 Secondary Transfer bias roller 20 Fixing device 25 Paper ejection roller 26 Paper feed cassette 27 Paper feed roller 28 Registration roller pair 30 Paper ejection tray 51 Developing roller 100 Printer section 130 Control section 131 Main control section 132 Storage section 133 Color conversion/separation processing section 134 Gamma correction section 135 Toner amount adjustment section 136 Tone conversion section 140 Image formation control section 500 Copying machine

Japanese Patent Application Publication No. 2005-96339 Japanese Patent Application Publication No. 2019-117371

Claims (14)

In an image forming apparatus that forms an image on a recording medium,
A charging device that charges an image carrier by applying a charging bias, an exposure device that forms an electrostatic latent image by irradiating the image carrier with light and can change the amount of exposure light, and applies a developing bias. an image forming section having a developing means for developing the electrostatic latent image, and having image forming means corresponding to at least cyan, magenta, and yellow colors;
detection means for detecting the color of the recording medium;
A control means for changing the adhesion amount of the cyan, magenta, and yellow toners by changing at least one of the charging bias, the exposure light amount, and the developing bias according to the detection result of the detection means. An image forming apparatus comprising: In an image forming apparatus that forms an image on a recording medium,
A charging device that charges an image carrier by applying a charging bias, an exposure device that forms an electrostatic latent image by irradiating the image carrier with light and can change the amount of exposure light, and applies a developing bias. an image forming section having a developing means for developing the electrostatic latent image, and having image forming means corresponding to at least cyan, magenta, and yellow colors;
a storage unit that stores a table that associates the color of a recording medium with a method of forming an image formed on the recording medium;
control means for changing the adhesion amount of the cyan, magenta, and yellow toners by changing at least one of the charging bias, the exposure light amount, and the developing bias according to the table; An image forming apparatus characterized by: The image forming apparatus according to claim 1, wherein the detection means is a reading means that reads an image formed on the recording medium and detects a color of the recording medium. The image forming apparatus includes a paper feed unit that feeds the recording medium to the image forming unit,
The image forming apparatus according to claim 1, wherein the detection means is an optical sensor and is provided in the paper feed section. 5. The charging bias is a voltage applied to a charging roller of the charging means, and changing the charging bias means increasing or decreasing the voltage. The image forming apparatus described in . According to any one of claims 1 to 5, the changing of the exposure light amount is characterized in that the exposure means increases or decreases the amount of light irradiated to the image carrier. The image forming apparatus described above. 7. The developing bias is a voltage applied to a developing roller included in the developing means, and changing the developing bias means increasing or decreasing the voltage. The image forming apparatus described in . 8. The image forming apparatus according to claim 1, wherein the control unit forms a black image by overlapping the cyan, magenta, and yellow toners. When the color of the recording medium is white or color, the control means forms a gray image by overlapping the cyan, magenta, and yellow toners and forming a halftone image. The image forming apparatus according to any one of claims 1 to 7. 9. The control means performs a change to reduce the adhesion amount of the cyan, magenta, and yellow toners when the color of the recording medium is white or black. Image forming device. When the color of the recording medium is color, the control means makes a change to reduce the adhesion amount of the cyan, magenta, and yellow toners,
The reduced toner adhesion amount is the amount when the amount of any one or more of the cyan color, the magenta color, or the yellow color related to the color components of the recording medium is converted into the toner adhesion amount. The image forming apparatus according to claim 8 or 9, characterized in that the image forming apparatus includes: 10. The image according to claim 9, wherein when the color of the recording medium is white, the control means performs a change to reduce the adhesion amount of the cyan, magenta, and yellow toners. Forming device. The image forming section has an image forming means corresponding to a spot color,
The image forming apparatus according to any one of claims 1 to 7, wherein the special color is white. 14. The image forming apparatus according to claim 13, wherein the control means forms a gray image using white toner when the color of the recording medium is black.