Image forming apparatus and program

Abstract

To expand a selection range of a charging condition compared with the case in which interference of an image is suppressed by changing a screen angle and the number of screen lines as the charging condition.SOLUTION: An image forming apparatus includes a first image formation part 30A for forming an image on a first image holding body 31A by adhering a developer onto the first image holding body 31A after performing charging of the first image holding body 31A, a second image formation part 30B for forming an image on a second image holding body 31B by adhering a developer onto the second image holding body 31B after performing charging of the second image holding body 31B, and a processor 21b for setting a first charging condition including a first frequency in the first image formation part 30A and a charging condition in the second image formation part 30B, being a second charging condition including a second frequency different from the first frequency on the basis of information on at least either developer between the developer used in the first image formation part 30A and the developer used in the second image formation part 30B.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus and a program. [Background technology]

[0002] For example, Patent Document 1 discloses an image forming apparatus capable of forming an image using metallic toner together with process color toner, the image forming apparatus comprising: metallic color conversion means for converting metallic colors in input image data into metallic color signals for forming an image using process color toners and metallic toners; process color conversion means for converting colors other than the metallic colors in the input image data into process color signals for forming an image using process color toners; screening means for performing screening processing on the metallic color signals converted by the metallic color conversion means or the process color signals converted by the process color conversion means; and image forming means for forming an image using process color toners and metallic toners in accordance with the process color signals or metallic color signals after screening, the screening means performing screening processing on the metallic color signals that is different from that performed on the process color signals. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-50347 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an image forming apparatus including a first image forming unit that charges a first image carrier and then deposits a developer on the first image carrier to form an image on the first image carrier, and a second image forming unit that charges a second image carrier and then deposits a developer on the second image carrier to form an image on the second image carrier, there is a risk that interference may occur between the images depending on the combination of developers. If an attempt is made to change the screen angle or screen ruling included in the first charging condition in the first image forming unit and the second charging condition in the second image forming unit in order to suppress such interference, the selection range of the charging conditions will be narrowed. An object of the present invention is to widen the range of options for charging conditions, as compared with the case where image interference is suppressed by changing the screen angle or screen ruling as a charging condition. [Means for solving the problem]

[0005] The invention described in claim 1 is an image forming apparatus comprising: a first image forming unit that charges a first image holder and then adheres a developer onto the first image holder to form an image on the first image holder; a second image forming unit that charges a second image holder and then adheres a developer onto the second image holder to form an image on the second image holder; and a processor that sets first charging conditions including a first frequency in the first image forming unit and second charging conditions that are charging conditions in the second image forming unit and include a second frequency different from the first frequency, based on information about at least one of the developer used in the first image forming unit and the developer used in the second image forming unit. The invention described in claim 2 is the image forming apparatus described in claim 1, characterized in that one of the first frequency and the second frequency is an integer multiple of the other. An invention described in claim 3 is the image forming apparatus described in claim 2, characterized in that the second frequency is higher than the first frequency. The invention described in claim 4 is the image forming apparatus described in claim 3, characterized in that the second frequency is set high when the developer in the second image forming unit satisfies predetermined conditions. The invention described in claim 5 is the image forming apparatus described in claim 3, characterized in that the amplitude of the second frequency is set large when the developer in the second image forming unit satisfies predetermined conditions. The invention described in claim 6 is the image forming apparatus described in claim 1, characterized in that the screen ruling included in the second charging condition is greater than the screen ruling included in the first charging condition. The invention described in claim 7 is the image forming apparatus described in claim 1, characterized in that the second frequency is an integer multiple of the first frequency, and a screen angle included in the first charging condition and a screen angle included in the second charging condition are the same. The invention described in claim 8 is the image forming apparatus described in claim 7, characterized in that the developer of the first image forming unit and the developer of the second image forming unit are of the same color. The invention described in claim 9 is the image forming apparatus described in claim 8, characterized in that the developer in the second image forming unit is lighter in color than the developer in the first image forming unit. The invention described in claim 10 is the image forming apparatus described in claim 8 or 9, characterized in that the screen ruling included in the second charging condition is greater than the screen ruling included in the first charging condition. The invention described in claim 11 is the image forming apparatus described in claim 7, characterized in that the developer of the first image forming unit is a developer of a color that is used frequently among YMCK colors. The invention described in claim 12 is the image forming apparatus described in claim 1, characterized in that the developer of the first image forming unit is any color of YMCK, and the developer of the second image forming unit is a color other than YMCK. The invention described in claim 13 is an image forming device comprising a first image forming unit that charges a first image holder and then adheres a developer onto the first image holder to form an image on the first image holder, and a second image forming unit that charges a second image holder and then adheres a developer onto the second image holder to form an image on the second image holder, and based on information about at least one of the developer used in the first image forming unit and the developer used in the second image forming unit, charging is performed under first charging conditions including a first frequency in the first image forming unit, and charging is performed under second charging conditions that are charging conditions in the second image forming unit that include a second frequency different from the first frequency. The invention described in claim 14 is a program that causes a processor of an image forming apparatus including a first image forming unit that charges a first image holder and then adheres a developer onto the first image holder to form an image on the first image holder, and a second image forming unit that charges a second image holder and then adheres a developer onto the second image holder to form an image on the second image holder, to realize a function of acquiring information about at least one of the developer used in the first image forming unit and the developer used in the second image forming unit, and a function of setting a first charging condition including a first frequency in the first image forming unit, and a second charging condition that is a charging condition in the second image forming unit and includes a second frequency different from the first frequency. Effect of the Invention

[0006] According to the invention of claim 1, the range of options for charging conditions can be expanded compared to the case where image interference is suppressed by changing the screen angle or screen ruling as the charging conditions. According to the invention of claim 2, it is possible to easily create a screen with a high line ruling, compared to a case where one of the first frequency and the second frequency is not an integer multiple of the other. According to the invention of claim 3, the second frequency is higher than the first frequency, so that a screen with a high ruling can be produced more easily than in a case where the second frequency is not provided. According to the invention of claim 4, the occurrence of white spots in the image can be suppressed compared to a case in which the second frequency is not configured to be set high when the developer in the second image forming unit satisfies predetermined conditions. According to the invention of claim 5, the amplitude of the second frequency can be suppressed from occurring in an image in comparison with a case where the configuration is not provided in which the amplitude is set large when the developer in the second image forming unit satisfies a predetermined condition. According to the invention of claim 6, the occurrence of blank areas in an image can be suppressed compared to a case where the screen ruling included in the second charging condition is greater than the screen ruling included in the first charging condition. According to the invention of claim 7, the second frequency is an integer multiple of the first frequency, and image interference can be suppressed compared to a case where the screen angle included in the first charging condition and the screen angle included in the second charging condition are not the same. According to the invention of claim 8, the developer in the first image forming unit and the developer in the second image forming unit can suppress image interference compared to a case in which the developer is not of the same color. According to the invention of claim 9, the developer in the second image forming unit is lighter in color than the developer in the first image forming unit, and image interference can be suppressed compared to a case where the developer is not lighter in color than the developer in the first image forming unit. According to the invention of claim 10, image interference can be suppressed more effectively than in the case where the screen ruling included in the second charging condition is not greater than the screen ruling included in the first charging condition. According to the invention of claim 11, the developer of the first image forming unit can suppress image interference compared to a case where the developer is not configured to be a developer of a frequently used color among YMCK colors. According to the invention of claim 12, the range of options for charging conditions can be expanded compared to a case in which the developer of the first image forming unit is one of the colors YMCK and the developer of the second image forming unit is a color other than YMCK. According to the invention of claim 13, the range of options for charging conditions can be expanded compared to the case where image interference is suppressed by changing the screen angle or screen ruling as the charging conditions. According to the invention of claim 14, the range of options for charging conditions can be expanded compared to the case where image interference is suppressed by changing the screen angle or screen ruling as the charging conditions. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an image forming apparatus. [Diagram 2] FIG. 2 illustrates an example of the hardware configuration of a control unit of the image forming apparatus. [Diagram 3] FIG. 2 is a schematic diagram illustrating image formation in the image forming apparatus. [Figure 4] 10 is a flowchart showing a processing procedure including setting of charging conditions. [Diagram 5] 5A and 5B are diagrams for explaining image formation according to the first embodiment, in which FIG. 5A shows charging conditions, and FIG. 5B shows an image developed by image formation. [Figure 6] 10A and 10B are diagrams for explaining image formation according to a second embodiment, in which FIG. 10A shows charging conditions, and FIG. 10B shows an image developed by image formation. [Figure 7] 13A and 13B are diagrams for explaining image formation according to a third embodiment, in which (a) shows charging conditions, and (b) shows an image developed by image formation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a diagram illustrating an image forming apparatus 1. As shown in FIG. The image forming apparatus 1 according to this embodiment includes a paper feed unit 1A, a printing unit 1B, and a paper discharge unit 1C. The paper feed unit 1A includes a first paper storage section 11 to a fourth paper storage section 14 for storing paper P as an example of a recording medium. The paper feed unit 1A also has feed rolls 15-18 that correspond to the first paper storage section 11 to the fourth paper storage section 14, respectively, and feed the paper P stored in each paper storage section to a transport path connected to the printing unit 1B.

[0009] The printing unit 1B includes an image forming section 20 that forms an image on a sheet P. The printing unit 1B also includes a control section 21 that controls each section of the image forming apparatus 1. The printing unit 1B also includes an image processing section 22. The image processing section 22 performs image processing on image data transmitted from the image reading device 4 and the personal computer (PC) 5. The printing unit 1B is also provided with a UI (User Interface) 23, which is configured with a touch panel or the like and notifies the user of information and receives information input from the user.

[0010] Image forming section 20, as an example of an image forming means, is provided with six image forming units 30T, 30P, 30Y, 30M, 30C, and 30K (hereinafter, sometimes simply referred to as "image forming units 30") arranged in parallel at regular intervals. Each image forming unit 30 includes a photosensitive drum 31 on which an electrostatic latent image is formed while rotating in the direction of arrow A, a charging roll 32 which charges the surface of the photosensitive drum 31, a developing device 33 which develops the electrostatic latent image formed on the photosensitive drum 31, and a drum cleaner 34 which removes toner and the like from the surface of the photosensitive drum 31.

[0011] The image forming section 20 is also provided with a laser exposure device 26 that exposes the photoconductor drum 31 of each image forming unit 30 to laser light. The exposure of the photoconductor drum 31 by the laser exposure device 26 is not limited to using laser light. For example, a light source such as an LED (Light Emitting Diode) may be provided for each image forming unit 30, and the photoconductor drum 31 may be exposed using light emitted from the light source.

[0012] Each image forming unit 30 is configured similarly, except for the toner contained in the developer 33. The image forming units 30Y, 30M, 30C, and 30K form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Further, the image forming units 30T and 30P form toner images using toner corresponding to a corporate color, foaming toner for Braille, fluorescent color toner, toner for improving gloss, etc. In other words, the image forming units 30T and 30P form toner images using toner of a special color.

[0013] The image forming section 20 is also provided with an intermediate transfer belt 41 onto which the toner images of each color formed on the photosensitive drums 31 of the image forming units 30 are transferred. The image forming section 20 is also provided with a primary transfer roll 42 that transfers the respective color toner images of the respective image forming units 30 onto the intermediate transfer belt 41 at a primary transfer portion T1. The image forming unit 20 is also provided with a secondary transfer roll 40 that transfers the toner image transferred onto the intermediate transfer belt 41 onto the paper P at a secondary transfer portion T2. Furthermore, the image forming section 20 is provided with a belt cleaner 45 that removes toner and the like from the surface of the intermediate transfer belt 41, and a fixing device 80 that fixes the secondarily transferred image onto the paper P.

[0014] The image forming unit 20 performs an image forming operation based on a control signal from the control unit 21 . Specifically, in the image forming unit 20, first, image processing is performed on the image data input from the image reading device 4 or the PC 5 by the image processing unit 22, and the image data after image processing is supplied to the laser exposure device 26. Then, for example, in a magenta (M) image forming unit 30M, the surface of the photosensitive drum 31 is charged by the charging roll 32, and then the laser exposure device 26 irradiates the photosensitive drum 31 with laser light modulated by image data obtained from the image processing unit 22.

[0015] As a result, an electrostatic latent image is formed on the photoconductor drum 31 . The formed electrostatic latent image is developed by the developing unit 33, and a magenta toner image is formed on the photosensitive drum 31. Similarly, yellow, cyan and black toner images are formed in the image forming units 30Y, 30C and 30K, and special color toner images are formed in the image forming units 30T and 30P.

[0016] The respective color toner images formed in each image forming unit 30 are electrostatically transferred sequentially by a primary transfer roll 42 onto an intermediate transfer belt 41 rotating in the direction of arrow C in Figure 1, and superimposed toner images are formed on the intermediate transfer belt 41. The superimposed toner image formed on the intermediate transfer belt 41 is transported to a secondary transfer portion T2 constituted by a secondary transfer roll 40 and a backup roll 49 as the intermediate transfer belt 41 moves.

[0017] On the other hand, the paper P is taken out from the first paper storage unit 11 by, for example, the delivery roll 15, and then transported to the position of the registration roll 74 via the transport path. When the superimposed toner image is transported to the secondary transfer portion T2, a sheet of paper P is supplied from the registration roll 74 to the secondary transfer portion T2 in accordance with the transport timing. Then, in the secondary transfer portion T2, the superimposed toner images are electrostatically transferred onto the paper P all at once by the action of a transfer electric field formed between the secondary transfer roll 40 and the backup roll 49.

[0018] Thereafter, the paper P onto which the superimposed toner images have been electrostatically transferred is transported to a fixing device 80. In the fixing device 80, pressure and heat are applied to the paper P on which the unfixed toner image has been formed, and the toner image is fixed to the paper P. Then, the sheet P on which the fixing process has been performed passes through a curl correction section 81 provided in the sheet discharge unit 1C, and is then conveyed to a sheet stacking section (not shown).

[0019] 2 is a diagram showing an example of the hardware configuration of the control unit 21 of the image forming apparatus 1. The control unit 21 provided in the image forming apparatus 1 is realized by a computer. The control unit 21 includes an arithmetic processing unit 21a that executes digital arithmetic processing according to a program, and a secondary storage unit 21g that stores information. The secondary storage unit 21g is realized by an existing information storage device such as an HDD (Hard Disk Drive), a semiconductor memory, or a magnetic tape.

[0020] The arithmetic processing unit 21a is provided with a CPU 21b as an example of a processor. The arithmetic processing unit 21a is also provided with a RAM 21c used as a working memory for the CPU 21b, and a ROM 21d in which programs executed by the CPU 21b are stored. The arithmetic processing unit 21a is also provided with a non-volatile memory 21e that is rewritable and can retain data even if the power supply is interrupted, and an interface unit 21f that controls each unit, such as a communication unit, connected to the arithmetic processing unit 21a.

[0021] The non-volatile memory 21e is composed of, for example, a battery-backed SRAM, a flash memory, etc. The secondary storage unit 21g stores files and the like, as well as programs executed by the arithmetic processing unit 21a. In this embodiment, the arithmetic processing unit 21a reads programs stored in the ROM 21d or the secondary storage unit 21g, thereby executing each process.

[0022] The program executed by the CPU 21b may be provided to the image forming apparatus 1 in a state where it is stored in a computer-readable recording medium such as a magnetic recording medium (such as a magnetic tape or a magnetic disk), an optical recording medium (such as an optical disk), a magneto-optical recording medium, or a semiconductor memory. The program executed by the CPU 21b may also be provided to the image forming apparatus 1 using a communication means such as the Internet.

[0023] In this specification, the term "processor" refers to a processor in a broad sense, including general-purpose processors (e.g., CPU: Central Processing Unit, etc.) and dedicated processors (e.g., GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.). In addition, the operations of the processor may not only be performed by one processor, but may be performed by multiple processors in physically separate locations working together. The order of the operations of the processor is not limited to the order described in this embodiment, and may be changed.

[0024] FIG. 3 is a schematic diagram for explaining image formation in the image forming apparatus 1. The image forming units 30A and 30B shown in FIG. 3 are any of the six image forming units 30T, 30P, 30Y, 30M, 30C, and 30K (see FIG. 1) that the image forming apparatus 1 includes. That is, as described above, the six image forming units 30T, 30P, 30Y, 30M, 30C, and 30K have a common basic configuration, but for convenience of explanation, the reference numerals indicate which of the image forming units 30A and 30B each image forming unit belongs to. More specifically, the reference numerals for the configuration of the image forming unit 30A are followed by "A," and the reference numerals for the configuration of the image forming unit 30B are followed by "B." Also, in FIG. 3, the configurations described in FIG. 1 may be omitted from illustration and explanation.

[0025] 3 is any one of image forming units 30Y, 30M, 30C, and 30K, and image forming unit 30B is any one of image forming units 30T and 30P. That is, image forming unit 30A forms an image with developers of YMCK colors, and image forming unit 30B forms an image with developers of special colors, but is not limited to this. Here, the image forming unit 30A is an example of a first image forming section, and the image forming unit 30B is an example of a second image forming section. The photoconductor drum 31A of the image forming unit 30A is an example of a first image carrier, and the photoconductor drum 31B of the image forming unit 30B is an example of a second image carrier. The YMCK color developers are an example of developers used in the first image forming section, and the special color developer is an example of developers used in the second image forming section.

[0026] 3, the image forming unit 30A includes a charging roll 32A, a developing device 33A, and a drum cleaner 34A arranged around a photoconductor drum 31A that rotates in the direction of arrow A. The photoconductor drum 31A charged by the charging roll 32A is exposed by a laser exposure device 26 to form an electrostatic latent image. The toner image on the photoconductor drum 31A developed by the developing device 33A is transferred to the intermediate transfer belt 41 by a primary transfer roll 42A.

[0027] The image forming unit 30B also includes a charging roll 32B, a developing device 33B, and a drum cleaner 34B arranged around the photoconductor drum 31B that rotates in the direction of the arrow A. The photoconductor drum 31B charged by the charging roll 32B is exposed by the laser exposure device 26 to form an electrostatic latent image. The toner image on the photoconductor drum 31B developed by the developing device 33B is transferred to the intermediate transfer belt 41 by the primary transfer roll 42B.

[0028] The power supply device 143 includes a DC power supply 144 and an AC power supply 145. Under the control of the CPU 21b (see also FIG. 2), the power supply device 143 applies a superimposed voltage of a DC voltage and an AC voltage to each of the charging rolls 32A and 32B, and also applies necessary voltages to the developing devices 33A and 33B and the primary transfer rolls 42A and 42B. The power supply device 143 also applies necessary voltages to the secondary transfer roll 40 (see FIG. 1). It should be noted that cleaning rolls are disposed in contact with and facing the charging rolls 32A and 32B.

[0029] More specifically, as shown in FIG. 3, the CPU 21b includes a charging condition control unit 124 that sets the charging conditions for the charging roll 32A and the charging conditions for the charging roll 32B. The charging condition control unit 124 includes a developer information acquisition unit 125 , a frequency setting unit 126 , an amplitude setting unit 127 , a screen angle setting unit 128 , and a screen line number setting unit 129 .

[0030] The developer information acquisition unit 125 acquires developer information, which is information indicating the developers used in the image forming units 30A and 30B, based on a print instruction including image data transmitted from the image reading device 4 or the PC 5 (see FIG. 1).

[0031] For example, the developer information acquisition unit 125 acquires, as developer information, information indicating whether a special color developer other than YMCK is used in addition to the basic color developers YMCK. Furthermore, when a special color developer is used, the developer information acquisition unit 125 acquires, as developer information, information on the type of developer. Furthermore, when a special color developer is used, the developer information acquisition unit 125 acquires, as developer information, information indicating a relationship between the special color and any of the YMCK colors, for example, whether the colors are similar. Furthermore, the developer information acquisition unit 125 acquires, as developer information, information indicating whether there is a difference in shade between the YMCK colors and the special color.

[0032] The developer information acquired by the developer information acquisition unit 125 is not limited to information indicating the developer used in the image forming units 30A and 30B. That is, the developer information may include only one of information indicating the developer used in the image forming unit 30A and information indicating the developer used in the image forming unit 30B. For example, the developer information may include information indicating the developer used in the image forming unit 30B, but not information indicating the developer used in the image forming unit 30A.

[0033] A frequency setting unit 126, an amplitude setting unit 127, a screen angle setting unit 128, and a screen ruling setting unit 129 set the charging conditions of the charging rolls 32A and 32B based on the developer information acquired by the developer information acquisition unit 125. The charging conditions referred to here include the frequency and amplitude of the superimposed voltage during charging, as well as the conditions regarding the screen angle and screen ruling.

[0034] Specifically, the frequency setting unit 126 sets the frequency when applied to the charging roll 32A and the frequency when applied to the charging roll 32B. The amplitude setting unit 127 sets the amplitude when applied to the charging roll 32A and the amplitude when applied to the charging roll 32B. The screen angle setting unit 128 sets the screen angle of the charging roll 32A and the screen angle of the charging roll 32B. The screen ruling setting unit 129 sets the screen ruling of the charging roll 32A and the screen ruling of the charging roll 32B.

[0035] In the present embodiment, the charging conditions for each of the image forming units 30A and 30B are set based on the developer information, but the present invention is not limited to this. For example, it is conceivable that the image forming unit 30A adopts charging conditions that are determined in advance regardless of the developer information, whereas the image forming unit 30B adopts charging conditions that are determined based on the developer information. It is also possible to select one of the predetermined charging conditions for one or both of the image forming units 30A and 30B based on the developer information. In other words, the charging conditions are switched depending on the developer to be used.

[0036] FIG. 4 is a flowchart showing a processing procedure including the setting of the charging conditions. In the example shown in FIG. 4, when a print instruction including image data transmitted from the image reading device 4 or the PC 5 (see FIG. 1) is received (step 101), it is determined whether the print instruction is to use a special color developer (step 102).

[0037] If the print instruction is to use a special color developer (Yes in step 102), developer information acquisition unit 125 (see FIG. 3) acquires developer information in the print instruction (step 103).

[0038] Based on the acquired developer information, the frequency setting unit 126 and the amplitude setting unit 127 (see FIG. 3) set the frequency and the amplitude (step 104), and the screen angle setting unit 128 and the screen line number setting unit 129 (see FIG. 3) set the screen angle and the screen line number (step 105). Then, charging is performed in the image forming units 30A and 30B according to the charging conditions set as frequency, amplitude, screen angle and screen ruling, and printing is performed (step 106).

[0039] On the other hand, if the printing instruction does not involve the use of a special color developer (No in step 102), the screen angle setting unit 128 and the screen line number setting unit 129 (see Figure 3) set the screen angle and screen line number (step 105), and charging is performed in the image forming unit 30A according to the screen angle and screen line number set as the charging conditions, and printing is performed (step 106).

[0040] Here, an example of setting charging conditions when performing spot color printing (Yes in step 102) will be described. Note that the image forming unit 30A (see FIG. 3) forms an image using YMCK color developers, and the image forming unit 30B (see the same figure) forms an image using a spot color developer.

[0041] (Example 1) The frequencies as the charging conditions of the image forming units 30A and 30B are different from each other. That is, the frequency of the image forming unit 30A is higher than the frequency of the image forming unit 30B, or the frequency of the image forming unit 30B is higher than the frequency of the image forming unit 30A. By increasing the frequency, the selection range of the charging conditions including the screen, such as a 1200 dpi binary screen, is expanded. Here, the charging conditions of the image forming unit 30A are an example of a first charging condition, and the frequency is an example of a first frequency. The charging conditions of the image forming unit 30B are an example of a second charging condition, and the frequency is an example of a second frequency.

[0042] In the case of setting example 1, it is possible to set the frequencies of the image forming units 30A and 30B so that one is an integer multiple of the other. This makes it easy to create a screen with a high line ruling. The integer multiple here can be, for example, 2x or 3x.

[0043] (Example 2) The frequency of image forming unit 30B is preferably an integer multiple of the frequency of image forming unit 30A. In the case of setting example 2, when the developer of image forming unit 30B is a color with a low friction rate such as gold or silver, it is possible to set the frequency of image forming unit 30B higher than the frequency of image forming unit 30A. This promotes wear of photoconductor drum 31B and suppresses the occurrence of deletion, i.e., blank areas in the image. To explain further, it is conceivable to set the frequency of image forming unit 30B higher than the frequency of image forming unit 30A and, alternatively, to set the amplitude of image forming unit 30B higher than the amplitude of image forming unit 30A. The case where the developer of the image forming unit 30B has a low friction rate is one example of a predetermined condition.

[0044] (Example 3) It is possible to set the screen ruling as a charging condition of the image forming unit 30B to be larger than the screen ruling as a charging condition of the image forming unit 30A. Setting example 3 can be adopted together with the above-mentioned setting example 1. This promotes wear of the photoconductor drum 31B and suppresses dilation.

[0045] (Example 4) It is also possible to adopt a setting in which the frequency of image forming unit 30B is an integer multiple of the frequency of image forming unit 30A, and the screen angle of image forming unit 30A is the same as that of image forming unit 30B, thereby suppressing image interference, i.e., moire.

[0046] In the case of setting example 4, it is preferable that the developer of the image forming unit 30A and the developer of the image forming unit 30B are of similar colors. Similar colors here refer to colors that are adjacent or close to each other on the color wheel, for example, the developer of the image forming unit 30B is a light color of YMCK. Also, for example, the developer of the image forming unit 30B is fluorescent pink for the M color. This further suppresses moire.

[0047] In the case of setting example 4, it is preferable that the developer of the image forming unit 30B is lighter in color than the developer of the image forming unit 30A. For example, the developer of the image forming unit 30A is a dark color of YMCK, and the developer of the image forming unit 30B is a light color, such as pink.

[0048] (Example 5) In the above-described setting example 4, when the developer of image forming unit 30B is lighter in color than the developer of image forming unit 30A, or when the developer of image forming unit 30B is lighter in color than the developer of image forming unit 30A, it is preferable that the screen ruling of image forming unit 30B is larger than the screen ruling of image forming unit 30A. For example, it is considered to double the screen ruling.

[0049] (Example 6) The above-mentioned setting example 4 can be adopted when the developer of the image forming unit 30A is a developer of a frequently used color among YMCK colors. The frequently used color here is, for example, K color. More specifically, it is possible to set the screen angle of the special color such as pink of the developer of the image forming unit 30B to the same angle as that of K color, and to set the frequency of the image forming unit 30A to a lower frequency than that of the image forming unit 30B. This suppresses wear of the photoconductor drum 31A, which is frequently used in the image forming unit 30A.

[0050] To explain further, in such a case, it is conceivable to make the screen ruling of the image forming unit 30A the same as that of the image forming unit 30B. In other words, the setting is made such that the spot color such as pink, which is the developer of the image forming unit 30B, is set to the same ruling as any of the YMCK colors.

[0051] Next, various screens according to charging conditions will be specifically described. <First embodiment> FIG. 5 is a diagram for explaining image formation according to the first embodiment, where (a) shows charging conditions and (b) shows an image 91 developed by image formation. The first embodiment shows a case where an image is formed by overlapping a dark color of YMCK and a light spot color. That is, there is a difference in the shade between the developer of the image forming unit 30A and the developer of the image forming unit 30B, even though they are similar colors. As an example, the image forming unit 30A is M color, and the image forming unit 30B is fluorescent pink spot color.

[0052] In this example, an image is formed under the charging conditions shown in FIG. The frequency of the image forming unit 30B is higher than that of the image forming unit 30A and is an integer multiple. Also, the screen angle when the image forming unit 30A is M color is the same as the screen angle of the image forming unit 30B. Furthermore, the screen ruling of the image forming unit 30B is twice that when the image forming unit 30A is M color. In the first embodiment, the frequency of fluorescent pink as a spot color is set to an integer multiple of the YMCK colors, and the light spot color is imaged with the same screen angle as the dark M color, which is a similar color to the spot color, and with twice the screen ruling.

[0053] Under such charging conditions, when an image is created by overlapping similar colors with different shading, the image 91 shown in Fig. 5(b) is obtained. The image 91 includes magenta dots 91a and fluorescent pink dots 91b.

[0054] Here, the principle of the first embodiment will be explained. The higher the screen ruling, the shallower the latent image and the more unstable the dots, so it is common to create darker dots at a lower ruling to improve graininess. Also, the higher the charging frequency, the finer the charging unevenness or ripples in the paper feed direction become, making it easier to create high rulings. On the other hand, as the spatial frequency increases, the number of AC discharges increases, which increases wear, so the charging frequency of basic colors such as YMCK is set to a lower value. In this way, by imaging the special color (fluorescent pink) at the same angle as the M color but with twice the screen ruling, the occurrence of moire is suppressed even when the special color is superimposed on human skin.

[0055] <Second embodiment> FIG. 6 is a diagram for explaining image formation according to the second embodiment, where (a) shows charging conditions and (b) shows an image 92 developed by image formation. 6 shows a second embodiment in which large particle size particles of a special color such as gold are overlapped to form an image, that is, the developer of the image forming unit 30B is a gold or silver developer having a low friction rate.

[0056] In this example, an image is formed under the charging conditions shown in FIG. The frequency of the image forming unit 30B is twice as high as that of the image forming unit 30A, and the screen ruling of the image forming unit 30B is higher than that of the image forming unit 30A. In the second embodiment, when an image is formed by overlapping special colors such as gold and silver having a low friction rate, the special colors are imaged under charging conditions in which the screen ruling and charging frequency are higher than those of the YMCK colors. It is to be noted that in addition to or instead of increasing the frequency of the particular color, it is also conceivable to increase the amplitude of the particular color.

[0057] Under such charging conditions, when an image is created by overlapping special colors such as gold and silver, which have low friction rates, an image 92 as shown in FIG. 6(b) is obtained. Here, the principle of the second embodiment will be explained. Gold and silver toner contains aluminum pieces, so the toner particle size is large, and it is difficult to aggregate in toner pools, so the general issue is that the wear rate is low. In addition, since gold and silver toner is used for stamp-like imaging that is 100% or 0% without using halftones, it can form latent images without problems even with high line counts such as 1200 dpi, and it is charged at a high frequency to increase the wear rate and prevent dilation. In this way, although the developer has a low wear rate for the special color, the wear rate increases by increasing the charging frequency, and this is compatible with suppressing degradation in image quality.

[0058] <Third embodiment> FIG. 7 is a diagram for explaining image formation according to the third embodiment, where (a) shows charging conditions and (b) shows an image 93 developed by image formation. The third embodiment shows a case where an image is created by overlapping a dark YMCK color, for example, M, and a similar but light spot color, for example, pink. In this case, an image is formed under the charging conditions shown in FIG. The frequency of the image forming unit 30B is higher than that of the image forming unit 30A and is twice as high. The screen angle of the image forming unit 30A is the same as that of the image forming unit 30B. The screen ruling of the image forming unit 30B is twice as high as that of the image forming unit 30A. In the third embodiment, when pink or other spot colors are overlaid on the same line and angle as any one of YMCK, an image is formed under charging conditions in which the frequency and number of lines of any one of YMCK are reduced to 1 / 2.

[0059] Under these charging conditions, when a spot color is overlaid with any of YMCK to create an image, an image 93 as shown in Fig. 7(b) is obtained. Image 93 includes dots 93a of any of YMCK and pink dots 93b. The principles of the third embodiment are the same as those of the first embodiment, and therefore a description thereof will be omitted. For example, if the most frequently used color among the YMCK colors is K, and pink is used on the same line and at the same angle as K, moire is likely to occur in the mid-tones in the K (black) plate. Therefore, by lowering the frequency and number of lines, the gradation is reduced, suppressing moire and reducing the wear rate of K in particular.

[0060] <Additional Notes> (((1))) a first image forming unit that charges a first image carrier and then deposits a developer onto the first image carrier to form an image on the first image carrier; a second image forming unit that charges a second image carrier and then deposits a developer onto the second image carrier to form an image on the second image carrier; a processor that sets a first charging condition including a first frequency in the first image forming unit and a second charging condition that is a charging condition in the second image forming unit and includes a second frequency different from the first frequency, based on information about at least one of the developer used in the first image forming unit and the developer used in the second image forming unit; An image forming apparatus comprising: (((2))) one of the first frequency and the second frequency is an integer multiple of the other; 4. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. (((3))) The second frequency is higher than the first frequency. The image forming apparatus according to (((2))) is characterized in that (((4))) the second frequency is set high when the developer of the second image forming unit satisfies a predetermined condition; The image forming apparatus according to (((3))) is characterized in that (((5))) the amplitude of the second frequency is set to be large when the developer of the second image forming unit satisfies a predetermined condition; The image forming apparatus according to (((3))) is characterized in that (((6))) The screen ruling included in the second charging condition is greater than the screen ruling included in the first charging condition. 4. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises: (((7))) the second frequency is an integer multiple of the first frequency, The screen angle included in the first charging condition and the screen angle included in the second charging condition are the same. 4. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction. (((8))) the developer of the first image forming unit and the developer of the second image forming unit are of similar colors; The image forming apparatus according to (((7))) is characterized in that (((9))) the developer of the second image forming unit is lighter in color than the developer of the first image forming unit; The image forming apparatus according to (((8))) is characterized in that (((10))) The screen ruling included in the second charging condition is greater than the screen ruling included in the first charging condition. 4. The image forming apparatus according to claim 3, wherein the image forming apparatus comprises: (((11))) The developer of the first image forming unit is a developer of a frequently used color among YMCK colors. The image forming apparatus according to (((7))) is characterized in that (((12))) the developer of the first image forming unit is any one of YMCK colors; The developer of the second image forming unit is a color other than YMCK. 3. The image forming apparatus according to claim 1, wherein the image forming apparatus comprises: (((13))) a first image forming unit that charges a first image carrier and then deposits a developer onto the first image carrier to form an image on the first image carrier; a second image forming unit that charges a second image carrier and then deposits a developer onto the second image carrier to form an image on the second image carrier; Equipped with Based on information on at least one of the developer used in the first image forming unit and the developer used in the second image forming unit, charging is performed under a first charging condition including a first frequency in the first image forming unit, and charging is performed under a second charging condition which is a charging condition in the second image forming unit and includes a second frequency different from the first frequency. Image forming device. (((14))) a processor included in an image forming apparatus including a first image forming unit that charges a first image carrier and then causes a developer to adhere to the first image carrier to form an image on the first image carrier, and a second image forming unit that charges a second image carrier and then causes a developer to adhere to the second image carrier to form an image on the second image carrier, a function of acquiring information about at least one of a developer used in the first image forming unit and a developer used in the second image forming unit; A function of setting a first charging condition including a first frequency in the first image forming unit and a second charging condition which is a charging condition in the second image forming unit and includes a second frequency different from the first frequency; A program to achieve this.

[0061] According to the invention of (((1))), the range of options for the charging conditions can be expanded compared to the case where image interference is suppressed by changing the screen angle or screen ruling as the charging conditions. According to the invention (((2))), a screen with a high ruling can be produced more easily than in a case where one of the first frequency and the second frequency is not an integer multiple of the other. According to the invention (((3))), the second frequency is higher than the first frequency, so that a screen with a high ruling can be produced more easily than in a case where the second frequency is not provided. According to the invention (((4))), the second frequency can be set high when the developer in the second image forming unit satisfies predetermined conditions, thereby making it possible to suppress the occurrence of blank areas in the image, compared to a case in which the second frequency is not provided. According to the invention (((5))), the amplitude of the second frequency can be set to a large value when the developer in the second image forming unit satisfies predetermined conditions, thereby making it possible to suppress the occurrence of blank areas in the image, compared to a case in which the configuration is not provided. According to the invention (((6))), the occurrence of blank areas in an image can be suppressed compared to a case where the screen ruling included in the second charging condition is greater than the screen ruling included in the first charging condition. According to the invention (((7))), the second frequency is an integer multiple of the first frequency, and screen interference can be prevented more effectively than in the case where the screen angle included in the first charging condition and the screen angle included in the second charging condition are not the same. According to the invention (((8))), the developer in the first image forming unit and the developer in the second image forming unit can prevent screen interference compared to a case in which they are not configured to be similar colors. According to the invention (((9))), the developer in the second image forming unit is lighter in color than the developer in the first image forming unit, and screen interference can be prevented more effectively than in the case where the developer is not lighter in color than the developer in the first image forming unit. According to the invention (((10))), the screen ruling included in the second charging condition is greater than the screen ruling included in the first charging condition, making it possible to prevent screen interference more effectively than in the case where such a configuration is not provided. According to the invention (((11))), the developer of the first image forming unit is a developer of a color that is used more frequently among the YMCK colors, which makes it possible to prevent screen interference more effectively than in the case where the developer is not provided with a configuration in which the developer is a color that is used more frequently among the YMCK colors. According to the invention (((12))), the range of options for charging conditions can be expanded compared to a case in which the developer of the first image forming unit is one of the colors YMCK and the developer of the second image forming unit is a color other than YMCK. According to the invention of (((13))), the range of options for the charging conditions can be expanded compared to when image interference is suppressed by changing the screen angle or screen ruling as the charging conditions. According to the invention of (((14))), the range of options for the charging conditions can be expanded compared to when image interference is suppressed by changing the screen angle or screen ruling as the charging conditions. [Explanation of symbols]

[0062] 1... image forming apparatus, 21b... CPU, 30A, 30B... image forming units, 31A, 31B... photoconductor drums

Claims

1. a first image forming unit that charges a first image carrier and then deposits a developer onto the first image carrier to form an image on the first image carrier; a second image forming unit that charges a second image carrier and then deposits a developer onto the second image carrier to form an image on the second image carrier; a processor that sets a first charging condition including a first frequency in the first image forming unit and a second charging condition that is a charging condition in the second image forming unit and includes a second frequency different from the first frequency, based on information about at least one of a developer used in the first image forming unit and a developer used in the second image forming unit; An image forming apparatus comprising:

2. one of the first frequency and the second frequency is an integer multiple of the other; 2. The image forming apparatus according to claim 1,

3. The second frequency is higher than the first frequency.

3. The image forming apparatus according to claim 2,

4. the second frequency is set high when the developer of the second image forming unit satisfies a predetermined condition; 4. The image forming apparatus according to claim 3.

5. the amplitude of the second frequency is set to be large when the developer of the second image forming unit satisfies a predetermined condition; 4. The image forming apparatus according to claim 3.

6. the screen ruling included in the second charging condition is greater than the screen ruling included in the first charging condition; 2. The image forming apparatus according to claim 1,

7. the second frequency is an integer multiple of the first frequency, a screen angle included in the first charging condition and a screen angle included in the second charging condition are the same.

2. The image forming apparatus according to claim 1,

8. the developer of the first image forming unit and the developer of the second image forming unit are of the same color; 8. The image forming apparatus according to claim 7,

9. the developer of the second image forming unit is lighter in color than the developer of the first image forming unit; 9. The image forming apparatus according to claim 8,

10. the screen ruling included in the second charging condition is greater than the screen ruling included in the first charging condition; 10. The image forming apparatus according to claim 8, wherein the first and second electrodes are arranged in a first direction.

11. the developer of the first image forming unit is a developer of a color that is used frequently among YMCK colors; 8. The image forming apparatus according to claim 7,

12. the developer of the first image forming unit is any one of YMCK colors; the developer of the second image forming unit is a color other than YMCK; 2. The image forming apparatus according to claim 1,

13. a first image forming unit that charges a first image carrier and then deposits a developer onto the first image carrier to form an image on the first image carrier; a second image forming unit that charges a second image carrier and then deposits a developer onto the second image carrier to form an image on the second image carrier; Equipped with Based on information on at least one of the developer used in the first image forming unit and the developer used in the second image forming unit, charging is performed under a first charging condition including a first frequency in the first image forming unit, and charging is performed under a second charging condition which is a charging condition in the second image forming unit and includes a second frequency different from the first frequency. Image forming device.

14. a processor included in an image forming apparatus including a first image forming unit that charges a first image carrier and then causes a developer to adhere to the first image carrier to form an image on the first image carrier, and a second image forming unit that charges a second image carrier and then causes a developer to adhere to the second image carrier to form an image on the second image carrier, a function of acquiring information about at least one of a developer used in the first image forming unit and a developer used in the second image forming unit; a function of setting a first charging condition including a first frequency in the first image forming unit, and a second charging condition which is a charging condition in the second image forming unit and includes a second frequency different from the first frequency; A program to achieve this.

Images