Image forming apparatus

Abstract

The present disclosure relates to an image forming apparatus having a normal image forming mode and a wide color gamut image forming mode in which the developer amount per unit area of a developer image of at least a color different from a prescribed color among a plurality of colors is increased compared to the normal image forming mode. Image data is generated such that in the normal image forming mode, an image portion formed in the prescribed color of an image formed on a recording material is formed solely by the developer image of the prescribed color, but in the wide color gamut image forming mode, the image portion formed in the prescribed color of the image formed on the recording material is formed by superimposing a developer image of a color different from the prescribed color on the developer image of the prescribed color, or by replacing the developer image of the prescribed color with a developer image of a different color.

Description

[0001] This application is a divisional application of the invention patent application with application number 201910377666.1, application date May 8, 2019, and invention name “Image Forming Device”. Technical Field

[0002] The present invention relates to a color image forming device using an electronic photographic system, which fixes an unfixed colorant image of object image information formed on a recording material (transfer material, printing paper) and carried thereby into a fixed image by using an intermediate transfer system or a direct transfer system in an image forming processing part. Background Art

[0003] Among color image forming apparatuses employing an electrophotographic system, some have a wide color gamut image forming mode (hereinafter, referred to as a wide color gamut mode) that expands the color reproduction range (Japanese Patent Application Publication No. 2017-173465). For example, the color reproduction range is expanded by increasing the peripheral speed of a developing roller, which serves as a developer carrier, relative to the peripheral speed of a photosensitive drum, which serves as an image carrier, to increase the amount of toner per unit area on the photosensitive drum.

[0004] According to Japanese Patent Application Publication No. 2017-173465, by forming an image with a developer amount corresponding to a normal image forming mode (hereinafter referred to as normal mode) in the boundary portion between an area to be given a wide color gamut and an area not requiring a wide color gamut, both suppression of developer splashing and a wide color gamut can be achieved.

[0005] However, applying the wide color gamut mode to all colors (black (hereinafter, Bk), magenta (hereinafter, M), cyan (hereinafter, C), and yellow (hereinafter, Y)) does not always suit the needs of users. For example, since Bk is mainly used in characters, when there is a level difference in the developer amount in the outline portion as described in Japanese Patent Application Publication No. 2017-173465, the outline portion may first become blurred in the character portion composed of thin lines, and the readability of the characters will decrease. In addition, since the consumption of Bk is greater than that of other colors, undesirable situations from the point of view of color material consumption are also expected. Users who want to give a wide color gamut only to specific colors, such as in the case of printing a cheap base price in dark red in the retail industry, may encounter a similar situation. Specifically, it is undesirable to shorten the life of a color that uses a large amount of M and Y but less use C and Bk for reproduction and does not require a wide color gamut by rotating the developing portion more than usual.

[0006] Based on the above, although it is conceivable to set image forming conditions (operating conditions of the image forming apparatus) in which the wide color gamut mode is not applied to all colors, this situation is not without problems. When the wide color gamut mode is applied, in order to effectively transfer a larger amount of developer than under normal conditions to the recording material, a transfer setting higher than normal must be configured. In this case, for colors to which the wide color gamut mode is not applied, since the electric field intensity is higher than necessary, resulting in charge reversal and deterioration of transfer efficiency (increase in the retransfer rate (the ratio of toner that was initially transferred but then returned to the drum)), the concentration decreases compared to during the normal mode. Therefore, a problem arises that the color difference between the colors to be given the wide color gamut and the colors of the normal color gamut becomes more apparent than when all colors are printed in the normal mode, and therefore, the image quality decreases. Summary of the Invention

[0007] An image forming apparatus according to the present invention is an image forming apparatus having an image forming portion capable of forming an image on a recording material by using developer images of a plurality of colors including a first color and a second color, the image forming apparatus including:

[0008] a data generator that generates first image data for forming a developer image of a first color and second image data for forming a developer image of a second color, wherein:

[0009] The image forming part includes:

[0010] a first image bearing member corresponding to a first color;

[0011] a second image bearing member corresponding to a second color;

[0012] a first light emitting unit that irradiates the first image bearing member with light and forms an electrostatic latent image based on first image data;

[0013] a second light emitting unit that irradiates the second image bearing member with light and forms an electrostatic latent image based on second image data;

[0014] a first developing member that supplies a developer to the electrostatic latent image formed on the first image bearing member; and

[0015] a second developing member that supplies a developer to the electrostatic latent image formed on the second image bearing member;

[0016] wherein, in the wide color gamut mode, the image forming portion operates to increase the developer supply capacity for the second image bearing member beyond the developer supply capacity for the first image bearing member relative to the normal mode,

[0017] wherein, in the wide color gamut mode, the data generator generates image data of a second color corresponding to an image portion indicated by the first image data, or generates image data of a plurality of colors constituting the second color corresponding to the image portion, and

[0018] The image forming apparatus further includes a unit for forming a developer image of a plurality of colors by superimposing the first image data and the second image data generated by the data generator.

[0019] Furthermore, in order to achieve the above-mentioned object, an image forming apparatus according to the present invention is an image forming apparatus including an image forming portion capable of forming an image on a recording material by using developer images of a plurality of colors including a first color and a second color, wherein

[0020] The image forming part includes:

[0021] a first image bearing member corresponding to a first color;

[0022] a second image bearing member corresponding to a second color;

[0023] a first light emitting unit that irradiates the first image bearing member with light and forms an electrostatic latent image;

[0024] a second light emitting unit that irradiates the second image bearing member with light and forms an electrostatic latent image;

[0025] a first developing member that supplies a developer to the electrostatic latent image formed on the first image bearing member; and

[0026] a second developing member that supplies a developer to the electrostatic latent image formed on the second image bearing member;

[0027] In the wide color gamut mode, the image forming portion operates to increase the developer supply capacity for the second image bearing member beyond the developer supply capacity for the first image bearing member, and

[0028] The average particle size of the developer of the first color is smaller than the average particle size of the developer of the second color.

[0029] Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment;

[0031] Figure 2 is a block diagram showing a printer control portion of the image forming apparatus according to the first embodiment;

[0032] Figure 3 is a primary transfer characteristic curve of the image forming apparatus according to the first embodiment;

[0033] Figure 4 is a graph representing the ratio of current required for secondary transfer of a single color to that of multiple colors according to the first embodiment;

[0034] Figure 5 is an explanatory diagram of a problem that becomes visible on an image when a wide color gamut mode limited to specified colors is applied;

[0035] Figure 6 shows experimental results indicating the color reproduction range when the average toner particle size is changed;

[0036] Figure 7 is a schematic diagram of a drive connection configuration according to a first embodiment;

[0037] Figure 8 is a flow chart of a control flow according to the first embodiment;

[0038] Figure 9 is a schematic diagram of a bias voltage application configuration according to the first embodiment; and

[0039] Figure 10 is a schematic diagram of a drive connection configuration according to a second embodiment. DETAILED DESCRIPTION

[0040] Hereinafter, embodiments (examples) of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, or relative arrangements of the components described in the embodiments may be appropriately changed depending on the configuration of the device to which the present invention is applied or various conditions. Therefore, the dimensions, materials, shapes, or relative arrangements of the components described in the embodiments are not intended to limit the scope of the present invention to the following embodiments.

[0041] First embodiment

[0042] Examples of image forming apparatuses to which the present invention is applicable include copiers, laser beam printers (LBPs), printers, facsimile machines, microfilm reader-printers, and recording devices employing an electrophotographic system image forming process. These image forming apparatuses fix an unfixed toner image of an object image information formed on a recording material (transfer material, printing paper, photosensitive paper, glossy paper, OHT, dielectric coated paper, etc.) in an image forming process section using an intermediate transfer system or a direct transfer system and carried by the recording material to a fixed image.

[0043] The image forming apparatus according to this embodiment has two image forming modes: a normal image forming mode for generating a normal image density as a first image forming operation, and a wide color gamut image forming mode for reproducing a wide color gamut image as a second image forming operation. The first image forming operation and the second image forming operation are controlled so as to be executable by a control unit. In the wide color gamut image forming mode, the peripheral speed ratio between the photosensitive drum as an image bearing member and the developing roller as a developer bearing member (or, in other words, the ratio of the peripheral speed of the developing roller to the peripheral speed of the photosensitive drum) is changed compared to the normal image forming mode. Therefore, each image forming mode differs from each other in terms of the peripheral speed ratio between the photosensitive drum and the developing roller.

[0044] (1) Configuration of Image Forming Apparatus

[0045] Figure 1 1 is a schematic cross-sectional view of an image forming apparatus 100 according to a first embodiment of the present invention. Image forming apparatus 100 according to this embodiment is a full-color laser printer employing an inline system and an intermediate transfer system. Image forming apparatus 100 is capable of forming a full-color image on a recording material based on image information.

[0046] As a plurality of image forming parts, the image forming apparatus 100 includes first, second, third, and fourth image forming parts SY, SM, SC, and SK for forming images of yellow (Y), magenta (M), cyan (C), and black (Bk), respectively. In this case, each image forming part (or image forming station) is composed of a process cartridge 40 and a primary transfer roller 22 arranged on the opposite side via an intermediate transfer belt 21 as an intermediate transfer member. In addition, the scanner unit 13 described later is also a component constituting the image forming part. The process cartridge 40 is composed of: a drum unit including a photosensitive drum 11, a cleaning blade 16, and a developer container 42; and a developing unit 44 ( Figure 7 ). Except for the difference in the color of the image formed, the configuration and operation of the first to fourth image forming sections are basically the same. Therefore, unless it is necessary to distinguish the image forming sections from each other, the suffixes Y, M, C, and K or Bk added to the reference numerals in each figure to represent which element will generate which color will be omitted, and the image forming sections will be described together.

[0047] It should be noted that the photosensitive drums 11Y, 11M, and 11C in this embodiment correspond to the second image bearing member according to the present invention, and the photosensitive drum 11K in this embodiment corresponds to the first image bearing member according to the present invention. Furthermore, the developing units 44Y, 44M, and 44C in this embodiment correspond to the second developing unit (developing member) according to the present invention, and the developing unit 44K in this embodiment corresponds to the first developing unit (developing member) according to the present invention. Furthermore, the developing rollers 14Y, 14M, and 14C in this embodiment correspond to the second developer bearing member according to the present invention, and the developing roller 14K in this embodiment corresponds to the first developer bearing member according to the present invention.

[0048] Furthermore, the Y-LD, M-LD, and C-LD, which irradiate light based on image data (second image data) for forming Y, M, and C electrostatic latent images on the photosensitive drums 11Y, 11M, and 11C, correspond to the second light-emitting unit according to the present invention. Furthermore, the K-LD, which irradiates light based on image data (first image data) for forming K electrostatic latent images on the photosensitive drum 11K in the scanner unit 13, corresponds to the first light-emitting unit according to the present invention. It should be noted that the Y-LD through the K-LD are laser diode units that are provided to correspond to the process cartridges 40Y to 40K, respectively, and irradiate laser beams, and are components of the scanner unit 13. However, the use of laser diodes is not restrictive, and an LED array provided for each of the process cartridges 40Y to 40K may be used instead.

[0049] The photosensitive drum 11 is driven by a driving unit ( Figure 7 )exist Figure 1 The charging roller 12, the scanner unit 13, the developing roller 14 and the cleaning blade 16 are arranged in sequence around the photosensitive drum 11 along its rotation direction. Furthermore, the intermediate transfer unit 15 is arranged for primary transfer of the toner image, which is the developer image on the photosensitive drum 11, to the intermediate transfer belt 21, which is an image bearing member opposed to the photosensitive drum 11 and serves as an endless belt. In addition, the secondary transfer portion 24 for secondary transfer of the toner image on the intermediate transfer belt 21 to the recording material P is arranged on the downstream side (in the conveying direction) with respect to the primary transfer portion in which the intermediate transfer unit 15 and the photosensitive drum 11 are in contact with each other. Figure 1 The intermediate transfer belt 21 is along the Figure 1The primary transfer rollers 22 for transferring the toner image on the photosensitive drum 11 onto the intermediate transfer belt 21 are arranged parallel to each other on the inner side of the intermediate transfer belt 21. A charge having a positive polarity is applied from the primary transfer rollers 22 to the intermediate transfer belt 21, and the toner image having a negative polarity on the photosensitive drum 11 is primarily transferred onto the intermediate transfer belt 21. In addition, the secondary transfer roller 25 is arranged at a position opposite to the drive roller 23 of the intermediate transfer unit 15. A charge having a positive polarity is applied from the secondary transfer roller 25 to the recording material P that has been conveyed to the secondary transfer portion, and the primarily transferred toner image having a negative polarity on the intermediate transfer belt 21 is secondarily transferred. Thus, the toner image formed on the photosensitive drum 11 is transferred onto the recording material P. A cleaning device 26 for removing unnecessary toner remaining on the intermediate transfer belt 21 after the secondary transfer is arranged at a position opposing the tension roller 29 of the intermediate transfer unit 15. Subsequently, the removed residual toner passes through a waste toner conveying path (not shown) to be collected in a waste toner recovery container.

[0050] The feed roller 18 feeds the recording material P in the uppermost portion of the feed cassette 17 toward the resist roller pair 19. In addition, the resist roller pair 19 feeds the recording material P to the secondary transfer portion 24 in synchronization with the image writing start position on the intermediate transfer belt 21.

[0051] The fixing unit 20, which serves as a fixing unit, fixes the toner images of multiple colors that have been transferred to the recording material P. The fixing unit 20 is composed of a fixing roller 1, which is a cylindrical rotating member serving as a heat-generating member on the image forming surface side, and a pressure roller 7, which is a pressure member serving as a pressure unit opposed to the fixing roller 1. A pressure spring (not shown) causes the recording material P to be sandwiched between the fixing roller 1 and the pressure roller 7 and pressurized with a specified pressure. As the fixing roller 1 is driven to rotate, the image forming surface side is heated and conveyed, the non-image forming surface side is pressed by the pressure roller 7, and the toner image is melted to fix the toner image to the recording material P.

[0052] A discharge portion is constructed downstream of the fixing unit 20 in the recording material conveying direction, a conveying roller pair 27 is provided in the discharge portion, and a discharge roller pair 28 is provided further downstream in the transfer material conveying direction to discharge the recording material P to the outside of the apparatus body.

[0053] (2) Description of image forming operation

[0054] Figure 23 is a block diagram showing a printer control section 300 provided in the image forming apparatus according to the present embodiment. The printer controller 301 communicates with the host computer 311 and receives image data, expands the received image data into information that can be printed by the printer, and exchanges signals and performs serial communication with the engine control section 302. The engine control section 302 exchanges signals with the printer controller 301 and also controls the image forming section described previously via serial communication. In other words, various operations including image forming operations in the image forming apparatus 100 are controlled by the engine control section 302. As operations during image formation, the engine control section 302 performs operations in accordance with the received image formation timing. Figure 1 The photosensitive drum 11 is driven clockwise and the scanner unit 13 is driven. During this process, the outer peripheral surface of the photosensitive drum 11 undergoes a primary charging process by the charging roller 12, which serves as a charging unit. Subsequently, the scanner unit 13, which serves as an exposure unit, forms an electrostatic latent image on the outer peripheral surface of the photosensitive drum 11. The developing roller 14, which serves as a developing unit, transfers toner, which serves as a developer, to the low-potential portion of the electrostatic latent image, forming a toner image of each color on the outer peripheral surface of the photosensitive drum 11. The formed toner image is transferred to the intermediate transfer belt 21 in an overlapping manner by the primary transfer roller 22 while synchronizing the image positions. At this point, once the toner images of all colors have been primarily transferred, an unfixed full-color toner image is formed on the intermediate transfer belt 21. The transfer residual toner remaining on each photosensitive drum 11 after the primary transfer is removed by the cleaning blade 16 and stored in a storage area within the cleaning device.

[0055] Subsequently, the leading end of the full-color toner image on the intermediate transfer belt 21 is rotationally conveyed to a point where the intermediate transfer belt 21 and the secondary transfer roller 25 face each other. At this timing, the resist roller pair 19 begins to rotate and feeds the recording material P to the secondary transfer portion so that the image formation start position of the recording material P matches the leading end of the toner image on the intermediate transfer belt 21. Furthermore, due to the secondary transfer bias applied to the secondary transfer roller 25, the full-color toner image on the intermediate transfer belt 21 is transferred while the recording material P is conveyed. Untransferred toner remaining on the intermediate transfer belt 21 is removed by the cleaning device 26 and sent to and stored in a waste toner box (not shown).

[0056] Subsequently, the recording material P to which the full-color toner image has been transferred is conveyed from the secondary transfer portion to the fixing unit 20. After the toner image is thermally fixed to the recording material P in the fixing unit 20, the recording material P is discharged from the discharge portion to the outside of the apparatus main body by the conveying roller pair 27 and the discharge roller pair 28 in a state in which the image-formed surface faces downward.

[0057] like Figure 7As shown, in this embodiment, the configuration of the drive unit that drives the shaft of the photosensitive drum 11, the developing roller 14, the stirring member 37, and the supply roller 34 is different from one process cartridge 40 to another. Figure 7 is a schematic diagram showing a drive connection configuration according to a first embodiment of the present invention.

[0058] The process cartridges for yellow (Y), magenta (M), and cyan (C) are configured as follows. Specifically, Figure 7 As shown, the drive unit for rotationally driving the photosensitive drums 11Y, 11M, and 11C and the drive unit for rotationally driving the developing rollers 14Y, 14M, and 14C are configured with different drive sources. The drive unit for rotationally driving the photosensitive drums 11Y, 11M, and 11C comprises a drive motor 51 as a first drive source and a gear train that transmits the rotational drive force of the drive motor 51. On the other hand, the drive unit for rotationally driving the developing rollers 14Y, 14M, and 14C comprises a drive motor 52 as a second drive source and a gear train that transmits the rotational drive force of the drive motor 52. It should be noted that the drive motor 52 also constitutes a drive unit that rotationally drives the rotating shaft of the stirring members 37Y, 37M, and 37C in conjunction with another gear train. Furthermore, the drive motor 52 also constitutes a drive unit that rotationally drives the supply rollers 34Y, 34M, and 34C in conjunction with another gear train.

[0059] In the process cartridge 40K for black (K), the drive unit for rotationally driving the photosensitive drum 11K, the drive unit for rotationally driving the developing roller 14K, and the drive unit for rotationally driving the supply roller 34K are constituted by a single shared drive motor 53 as a third drive source. Furthermore, the drive motor 53 constitutes a drive unit for rotationally driving the rotating shaft of the stirring member 37K in conjunction with another gear train, and further constitutes a drive unit for rotationally driving the drive roller 23 that circulates the intermediate transfer belt 21 in conjunction with another gear train. The various drive motors and gear trains described above correspond to drive units capable of individually and variably rotationally driving the image bearing member, developer bearing member, supply member, and conveying member according to the present invention, and are controlled by the engine control section 302 serving as a control section.

[0060] Conventionally, the photosensitive drum and the developing roller are driven by the same drive source (drive motor) via a gear train. Therefore, the peripheral speed ratio between the photosensitive drum and the developing roller is uniquely determined by the transmission ratio in a fixed manner. On the contrary, in the present embodiment, since the YMC box is configured so that the photosensitive drum and the developing roller are driven by different drive sources, the peripheral speed ratio between the photosensitive drum and the developing roller can be made variable.

[0061] (3) Normal image forming mode and wide color gamut image forming mode

[0062] The image forming apparatus according to this embodiment is configured so that the photosensitive drum 11 and the developing roller 14 of each color can be driven at separate rotation speeds by the drive unit configured as described above. With this configuration, the image forming apparatus according to this embodiment has two image forming modes, namely, a normal image forming mode (image forming mode 1) that produces a normal image density, and a wide color gamut image forming mode (image forming mode 2) that can reproduce a wide color gamut image by changing the peripheral speed ratio between the photosensitive drum 11 and the developing roller 14. Each image forming mode is a condition in which the rotation speed ratio (peripheral speed ratio) between the photosensitive drum 11 and the developing roller 14 is different, and each speed is as listed in Table 1. For a specified color, the peripheral speed ratio in the wide color gamut mode is set higher than in the normal mode, and the rotation operation of the photosensitive drum 11 and the developing roller 14 when set to the high peripheral speed ratio corresponds to an operation for increasing the developer supply capacity.

[0063] In addition, you can refer to the following Figure 9 The various bias application configurations described variably set the development contrast such as shown in (B) in Table 1 for each mode and each color. The operation for making the development contrast variable also corresponds to the operation for increasing the developer supply capacity.

[0064] (Table 1)

[0065] (A)

[0066]

[0067] (B)

[0068]

[0069] As shown in (A) in Table 1, in the wide color gamut image forming mode (specified color), the peripheral speed ratio is set higher to increase the amount of toner supplied per unit time from the developing roller 14 to the photosensitive drum 11 compared to the normal image forming mode. The ratio between the modes of the peripheral speed ratio is set so that the wide color gamut image forming mode is 1.59 times that of the normal image forming mode (=230% / 145%). It should be noted that the method for changing the peripheral speed ratio is not limited to the method described above. For example, a configuration can be adopted in which the peripheral speed ratio is changed by increasing the linear speed of the developing roller 14 while maintaining the linear speed of the photosensitive drum 11 constant.

[0070] In addition, as a setting for developing all the colorants supplied from the developing roller 14 on the photosensitive drum, the development contrast (the absolute value of the difference between the development bias and the bright part potential) in the wide color gamut mode (specified color) is higher than that in the normal mode. In other words, the normal image forming mode is a mode in which the charging bias V is set to -1100V, Vd is set to -500V, V1 is set to -100V, and the development bias is set to -300. The wide color gamut image forming mode is a high-definition printing mode in which the charging bias V is set to -1600V, Vd is set to -800V, V1 is set to -100V, and the development bias is set to -600V. And, depending on the bias application configuration, there is a case where the development contrast in the wide color gamut mode (non-specified color) can be set to the same development contrast as that of the specified color. In this case, the development contrast setting of the non-specified color is not limited to (B) in Table 1. In the wide color gamut image forming mode, since the potential difference (absolute value) between the dark portion potential Vd and the light portion potential V1 is large, the reproducibility of thin lines can be improved. As described above, in this embodiment, a plurality of modes in which the potential difference of the electrostatic latent image (in other words, the potential difference between the light portion potential and the dark portion potential) is different from each other can be set as the image forming mode.

[0071] Figure 9 Schematic diagram showing various bias application configurations in the image forming apparatus according to this embodiment. Figure 9 As shown, in each image forming section, a charging bias is applied to the charging roller 12 from a charging bias applying section 612 including a high-voltage power supply, and a developing bias is applied to the developing roller 14 from a developing bias applying section 614 including a high-voltage power supply. Furthermore, in each image forming section, a primary transfer bias is applied to the primary transfer roller 22, which serves as a primary transfer member, from a common primary transfer bias applying section 61, which serves as a first applying unit including a high-voltage power supply. Alternatively, a configuration may be employed in which a separate primary transfer bias applying section is provided for each image forming section. Furthermore, a secondary transfer bias is applied to the secondary transfer roller 25, which serves as a secondary transfer member, from a secondary transfer bias applying section 62, which serves as a second applying unit including a high-voltage power supply. Alternatively, a configuration may be adopted in which each primary transfer bias applying portion is eliminated and primary transfer is performed in each primary transfer portion by applying a primary transfer bias to each primary transfer portion via the intermediate transfer belt 21 due to bias application by the secondary transfer bias applying portion 62. Various bias applying configurations are controlled by the engine control portion 302.

[0072] (Table 2)

[0073] Target transfer current (μA) Primary transfer part Secondary transfer part Normal mode 10 30 Wide color gamut mode 8.5 14

[0074] Table 2 compiles the transfer conditions for each mode. When viewed in conjunction with Table 1, it is shown that in the wide color gamut mode, although the processing speed of the intermediate transfer belt 21 and the recording material P is 1 / 3 relative to the normal mode, the target transfer current is set to be equal to or higher than a certain speed ratio. This is because the intermediate transfer belt 21 and the colorant image carried by the photosensitive drum 11, which are longer than in the normal mode, are transferred at each transfer portion. A more detailed description will be given with reference to the following equation 1. Equation 1 is an equation representing the amount of transfer current It required to transfer a colorant image having a width W and a certain charge per unit area at a prescribed processing speed PS. According to this equation, since the total charge amount Q increases with the toner amount that increases in the wide color gamut mode, even if the processing speed is reduced to 1 / 3, it can be described that a transfer current equal to or greater than 1 / 3 of the transfer current in the normal mode is required.

[0075] It=Q / M×M / S×PS×W=Q / S×PS×W…(Equation 1)

[0076] here,

[0077] It: Required transfer current

[0078] Q / M: The amount of charge per unit weight of the developer (so-called triboelectricity)

[0079] M / S: Developer weight per unit area

[0080] PS: Processing speed

[0081] W: Image width

[0082] Q / S: Toner charge per unit area

[0083] So far, the difference between the normal mode and the wide color gamut mode has been described.

[0084] (4) Wide color gamut image formation mode limited to specified colors

[0085] The following describes a wide color gamut mode limited to designated colors. As described above in the background art, applying the wide color gamut mode to all colors does not always suit user needs. For example, Bk toner is typically used primarily for reproducing characters. Although the wide color gamut mode is effective in generating color depth (L* reduction), since the consumption of Bk is greater than that of other colors, undesirable situations may occur from the perspective of color material consumption. For the reasons described above, the image forming apparatus according to this embodiment includes a wide color gamut image forming mode limited to designated colors, wherein Bk is excluded from the image forming conditions of the wide color gamut mode even during the wide color gamut mode, and only the other designated colors of Y, M, and C as the second color are subjected to the wide color gamut mode. More specifically, for Bk, which is a non-designated color in the wide color gamut mode as the first color, the peripheral speed ratio of the developing roller 14 relative to the photosensitive drum 11 is the same as in the normal mode, as shown in Table 1(A) described above. Due to this setting, the number of rotations of the developing roller can be suppressed compared to the designated color, and unnecessary acceleration of life consumption can be prevented.

[0086] As an operation method limited to the wide color gamut mode of a designated color, for example, a method of providing a switch for enabling / disabling its function on a printer driver (not shown) that sends an operation instruction from the host computer 311 to the printer controller 301 may be adopted.

[0087] (5) Problems when using a wide color gamut mode limited to specific colors

[0088] (5-1) Basic characteristics of the transfer process

[0089] Before describing the problem in specific terms, the basic characteristics of the transfer process will be described. First, a weak dip and a strong dip will be described. The weak dip and the strong dip refer to portions outside the transfer effective area in the transfer characteristic curve, and are both transfer failures indicating a decrease in transfer efficiency. A decrease in transfer efficiency in an insufficiently charged area is referred to as a weak dip, and a decrease in transfer efficiency in an excessively charged area is referred to as a strong dip. In addition, retransfer refers to a phenomenon in which the toner transferred onto the intermediate transfer belt 21 at the upstream image forming unit in the primary transfer portion returns to the photosensitive drum 11 at the downstream image forming unit and causes a decrease in the amount of toner on the intermediate transfer belt 21.

[0090] Figure 3 The primary transfer characteristic curve of the image forming apparatus according to the present embodiment is shown. The abscissa represents the applied bias voltage, the ordinate represents the transfer efficiency or the retransfer rate, the solid line represents the transfer efficiency characteristic, and the dotted line represents the retransfer characteristic. Figure 3In the embodiment of the present invention, the transfer efficiency rises until the applied bias voltage is 200 (V), saturates between 200 and 600 (V), and decreases from 600 (V). A transfer failure that occurs at 200 (V) or less is called a weak drop, and a transfer failure that occurs at 600 (V) or more is called a strong drop. In addition, a rise in the retransfer rate that occurs at 300 (V) or more is called retransfer. Generally, the applied bias voltage is set in a transfer margin region that can obtain a stable density by taking into account the balance between weak drop, strong drop, and retransfer.

[0091] (5-2) Weak descent mechanism

[0092] This is a state in which the toner on the photosensitive drum 11 moves to the intermediate transfer belt 21 and at the same time there is no sufficient charge for supplying the carried charge of the toner to the intermediate transfer belt 21. As a result, the toner ends up remaining on the photosensitive drum 11.

[0093] (5-3) Strong descent / retransfer generation mechanism

[0094] As the applied bias increases, the transfer current eventually exceeds the amount required for toner transfer. This excess current flows as an electrical discharge between the photoreceptor drum 11 and the intermediate transfer belt 21, changing the toner's triboelectric charge (Q / M). The triboelectric charge of the toner that has entered the physical nip formed by the photoreceptor drum 11 and the intermediate transfer belt 21 drops to zero due to the discharge within the physical nip. The force acting on the toner, no longer subject to electrostatic forces, is reduced to a mere non-electrostatic adhesion force, and approximately half of the toner remains attached to the photoreceptor drum 11. This state is known as strong dip. The untransferred toner immediately reverses to positive through electrical discharge upon exiting the physical nip. Therefore, due to the strong dip, the triboelectric charge of most of the toner remaining on the photoreceptor drum is observed to be in a positive-reversed state. Because the change in triboelectric charge in the nip depends on the amount of discharge between the photoreceptor drum 11 and the intermediate transfer belt 21, the strong dip weakens as the applied bias and latent image contrast (the difference between the potential of the exposed portion and the potential of the dark portion) increase.

[0095] Retransfer can be described in a similar manner to strong drop. When toner is transferred multiple times onto the intermediate transfer belt 21 during the primary transfer process, the monochrome image on the intermediate transfer belt 21, which has already been transferred at the upstream image forming unit, passes through the transfer nip of the downstream image forming unit. Because the surface of the photosensitive drum opposite the monochrome image portion at this point has a dark portion potential, the transfer contrast in this portion exceeds the transfer contrast that is optimal for primary transfer. Therefore, in the monochrome image portion, discharge occurs within the nip between the photosensitive drum and the intermediate transfer belt. This is the mechanism of retransfer. As a result, the triboelectric charge of the secondary and higher color toners on the intermediate transfer belt after multiple transfers is less than the triboelectric charge of the monochrome toner.

[0096] (5-4) Problems when using a wide color gamut mode limited to specific colors

[0097] Table 3 represents the results of the secondary transfer target current It at each processing speed calculated according to (Equation 1) based on the measurement results of the weight and charge amount of the developer on the recording material P in the normal mode and the wide color gamut mode in the image forming apparatus according to the present embodiment (assuming an image width W of 297 mm). As can be seen from the table, compared with the normal mode, the M / S of monochrome (specified color) and multicolor (specified color) in the wide color gamut mode increases (the value of multicolor in this case is the value of the maximum colorant amount after multiple transfers). In addition, as described above, the toner triboelectricity of the secondary and higher colors after multiple transfers is less than that of the monochrome, and results consistent with the basic characteristics of the aforementioned transfer process are obtained. The toner triboelectricity Q / M was measured by using an E-spart analyzer EST-G (a charge amount / particle size distribution measuring instrument manufactured by HOSOKAWA MICRON CORPORATION).

[0098] (Table 3)

[0099]

[0100]

[0101] Figure 4 The representation is a result of compiling the ratio of the current required for secondary transfer of monochrome to multicolor (It ratio) by using the results shown in Table 3. The It ratio is an indicator indicating how much the required current value that is optimal for transferring monochrome deviates from the required current value that is optimal for transferring multicolor. The closer the value is to 1, the closer the required current values for multicolor and monochrome are to each other, which means that an overcurrent is less likely to flow in excess of the amount required for transfer of the single-color toner, and a state in which a transfer margin exists occurs. When the value is small, the monochrome becomes a strong drop / retransfer area where an overcurrent flows under the current required for transferring multicolor, the concentration on the recording material decreases, and the transfer margin decreases (see Figure 3 ).

[0102] like Figure 4 As shown in FIG. 1 , the It ratio of the non-specified color (in this embodiment, Bk) in the wide color gamut mode is smaller than the It ratio in the normal mode. In other words, for the color (in this embodiment, Bk) to which the wide color gamut mode is not applied, since a higher-than-necessary electric field intensity is imparted to the transfer portion, the charge of the developer is reversed and the transfer efficiency deteriorates, resulting in a lower density than during the normal mode.

[0103] Figure 5This is a simplified diagram used to explain the problem that becomes visible on images when a wide color gamut mode limited to designated colors is applied. In the wide color gamut mode limited to designated colors on the right side of the figure, although the multicolor (designated colors) that are designated colors of the wide color gamut mode have a wide color gamut, the density of the single colors (non-designated colors) that are not designated for the wide color gamut becomes lower than in normal mode. As a result, colors including the designated colors are highly rendered, while colors composed only of colors other than the designated colors have low color rendering, and in some cases, color differences between colors in a single image become more noticeable than when printing in the normal mode shown on the left side of the figure.

[0104] (6) Method of Reducing Color Difference and Image Quality Difference Between Designated Colors and Non-designated Colors in a Wide Color Gamut (Description of Advantageous Effects of the Present Embodiment)

[0105] Hereinafter, the advantageous effects of the present embodiment will be described. According to the calculation formula (Equation 1) for the required transfer current value described above, when the processing speed and the image width are the same, the required transfer current value depends only on Q / S (the amount of charge per unit area). Therefore, approximating the Q / S of the non-designated color to the Q / S of the designated color results in an improved transfer margin. In view of this, the image forming apparatus according to the present embodiment approximates (increases) the Q / S of the non-designated color to the Q / S of the designated color by transferring another color multiple times to the monochrome non-designated color within a range where the color difference is equal to or less than a specified value or replacing the monochrome non-designated color with another color in order to solve the problem.

[0106] In addition to forming an image solely using the Bk toner, a black image portion (an area represented by black in the image on the recording material) can be formed in an image formed on a recording material by superimposing (mixing) toners of three colors, Y, M, and C, other than Bk, in a specified ratio. A UCR (Under Cover Removal) process is known that utilizes this property to replace the black and / or gray portions of an image formed using the three colors Y, M, and C with Bk. In this embodiment, a black image portion, which is formed solely using the Bk toner in normal mode, is formed in wide color gamut mode by (i) superimposing the three colors Y, M, and C on Bk, or (ii) using only the three colors Y, M, and C without using Bk. Specifically, (i) image data for the Y, M, and C colors, which are the second colors, is added to the image data for the Y, M, and C colors as the second image data. The image data for the Y, M, and C colors as the second colors corresponds to the black image portion, which is the image portion indicated by the image data for Bk as the first image data. Alternatively, (ii) at least a portion of the image data of Bk as the first image data is replaced by image data of multiple colors constituting Y, M and C as the second color, and the image data of multiple colors constituting Y, M and C as the second color corresponds to a black image portion as the image portion indicated by the image data of Bk.

[0107] Figure 8 A specific control flow is shown below: First, the printer controller 301 receives print job data from the host computer 311 (S101).

[0108] Based on the data of the received print job, the printer controller 301 makes a determination according to, for example, a print command from the user or the contents of the image data, and selects a wide color gamut mode limited to a designated color ( S102 ).

[0109] In step S103, the printer controller 301 processes the received image data. The printer controller 301 performs processing to add image data to the image data for Y, M, C, and Bk, respectively, in the four received color-separated image data. More specifically, the printer controller 301 generates an image portion identical to or similar to the black image portion indicated by Bk from each item of image data for Y, M, and C, and adds this portion to the image data (image signal) for each color. The printer controller 301 generates the image data for each color so that each item of image data for Y, M, and C is formed on a recording medium at a predetermined toner ratio (S103).

[0110] While the ratios at which the Y, M, and C toners are superimposed on the black image portion in this embodiment are set to Y: 15%, M: 30%, and C: 30%, these ratios are not restrictive. For example, Y, M, and C can all be set to 30%, or only a portion of the Y, M, and C colors can be used (not all colors need to be superimposed). Alternatively, the printer controller 301 can generate four items of color-separated image data for Y, M, C, and Bk, converted so that the black image portion is formed using only the three toners of Y, M, and C without using Bk (S103). In short, any ratio can be appropriately adopted as long as it maintains the color difference between the non-designated color (Bk) and the designated color monochrome image below a specified amount when applying normal mode, or in other words, within a specified allowable range. As a data generation unit (generator), the printer controller 301 transmits the image data generated as described above to the engine control unit 302 (S104). Based on the received image data, the engine control unit 302 controls the image forming units and forms an image.

[0111] It should be noted that the "%" for Y, M, C, and Bk in the foregoing description and in Tables 4 and 6 given below indicates the ratio of the corresponding color in 256 levels (grayscale values 0 to 255). For example, "30%" for C means that the grayscale value of C is "76."

[0112] (Table 4)

[0113]

[0114]

[0115]

[0116] Table 4 shows the results of a comparative experiment performed by using the image forming apparatus according to the present embodiment and the comparative example with respect to the density of the designated color single color and the non-designated color multiple colors in the wide color gamut mode and the color difference between the two colors. 2 ) was used as a recording material, and the chromaticity and density were measured by using Spectrolino (Backing Black) manufactured by X-Rite, Incorporated.

[0117] Table 4 reveals the following.

[0118] As a difference between the non-specified color (Bk) and the normal mode, in the comparative conventional example using Bk 100% even in the wide color gamut mode limited to the specified color, the density is lower than Bk 100% in the normal mode. This is because the transfer efficiency is reduced.

[0119] On the other hand, according to this embodiment, adding C 30%, M 30%, and Y 15% to Bk 100% enables the color difference from the normal mode Bk 100% to be set to 1.4, which is equal to or less than the color difference ΔE*0.8 to 1.6, which is the AA grade tolerance (JIS Z8721). In addition, it was confirmed that similar results (equal to or less than the color difference ΔE*0.8 to 1.6) were obtained when C 30%, M 30%, and Y 30% or when only part of Y, M, and C were used as additional colors.

[0120] Meanwhile, taking multi-colors (green and red) created with designated colors (C, M, and Y) as an example, the chromaticity C* of each multi-color is greater than that of the normal mode, and a wide color gamut is achieved.

[0121] Now, note that in the process of S103 explained above, a table for converting RGB data in wide color gamut mode into CMYK data can be prepared in advance, and this table can be used when the RGB data is input from outside the device to the printer controller 301. In addition, a conversion table for normal mode can also be prepared in advance. These two tables can be stored in the memory of the printer controller 301. Therefore, the printer controller 301 switches the table to be used according to the image formation mode selected in the print job.

[0122] In the table for wide color gamut mode, when an image whose RGB values are recognized as gray or black is input to the printer controller 301, the ratio of CMY values in the gray or black image can be greater than the ratio of K values in the gray or black image. Furthermore, the ratio of the ratio of CMY values to the ratio of K values in the table for wide color gamut mode can be higher than that in the table for normal mode. Therefore, the table for wide color gamut mode outputs converted image data in which the ratio of the ratio of CMY values to the ratio of K values is increased more than in normal image formation mode. After outputting the image data converted from the table, the printer controller 301 performs the same processing as in S104.

[0123] As described above, according to this embodiment, in an image forming apparatus having printing conditions in which designated colors using a wide color gamut mode coexist with non-designated colors not using the wide color gamut mode, image quality differences and color differences between the designated colors using a wide color gamut and the non-designated colors can be reduced. Furthermore, an image forming apparatus can be provided that exhibits the original color gamut magnification effect while preventing unnecessary acceleration of the lifespan of the non-designated colors.

[0124] Second embodiment

[0125] In a second embodiment of the present invention, a device will be described that reduces the color difference and image quality difference between the designated colors and non-designated colors of a wide color gamut by means different from those of the first embodiment. Specifically, in the second embodiment, for non-designated colors in a wide color gamut mode limited to designated colors, a toner having an average particle size smaller than that of the designated color is used to increase the monochrome density when carrying the same toner amount (M / S). Reducing the average toner particle size is also advantageous because fine images such as fine lines and fine characters can be formed with high image quality. This is particularly effective for Bk. It should be noted that even during the wide color gamut mode, the image forming apparatus according to the second embodiment excludes C and Bk from the image forming conditions of the wide color gamut mode, and the wide color gamut image is limited to the other colors Y and M as designated colors. In other words, a main body configuration is pre-adopted in which the circumferential speed ratio of the developing roller relative to the photosensitive drum cannot be changed with respect to C and Bk. Although Y, M, and C are the wide color gamut mode designated colors (second colors) and Bk is the wide color gamut mode non-designated color (first color) in the first embodiment, in the second embodiment, Y and M are the wide color gamut mode designated colors (second colors) and Bk and C are the wide color gamut mode non-designated colors (first colors). In other words, in this embodiment, the wide color gamut mode non-designated colors (first colors) are composed of a plurality of colors.

[0126] Figure 10 is a schematic diagram illustrating a drive connection configuration according to a second embodiment of the present invention. As shown in the figure, in the second embodiment, the drive unit configured to form a C toner image, the drive unit configured to form a Bk toner image, and the drive unit for the intermediate transfer belt 21 are composed of a single shared drive motor 53. The device configuration other than the above is similar to that of the first embodiment, and a repeated description thereof will be omitted.

[0127] (Table 5)

[0128]

[0129] Table 5 shows the average particle size of the toner of each color stored in each developer container 42Y, 42M, 42C, or 42K in the full-color image forming apparatus according to this embodiment. As can be seen from the table, the average particle size of the toners of C and Bk, which are the non-designated colors in the wide color gamut mode, is smaller than the average particle size of the toners of Y and M, which are the designated colors in the wide color gamut mode. By using small-particle-sized toners for the non-designated colors in this manner, it is expected that the use of small-particle-sized toners will result in an expanded color gamut and increased clarity.

[0130] Figure 6The color reproduction range when the average toner particle size is changed is shown. Although the difference in color reproduction range caused by the difference in toner particle size is small at M / S = 0.6 mg / cm, since the toner hides the base, the difference in color reproduction range caused by the difference in toner particle size is small at M / S = 0.6 mg / cm 2 Although the color gamut is not clear in the region where the toner amount is small, the results obtained indicate that the smaller the toner particle size, the greater the color gamut is enlarged. In other words, it indicates that the smaller the M / S value, the greater the change in the a-axis value in the L*a*b* color system (CIE) due to the difference in the average toner particle size. In particular, Figure 6 The portion (A) surrounded by the dotted line has a M / S of 0.2 mg / cm 2 It should be noted that the L axis in the L*a*b* color system (CIE) is perpendicular to the Figure 6 The M / S of a single color (non-specified color) in the wide color gamut mode according to this embodiment is 0.45 mg / cm shown in Table 3 of the first embodiment. 2 , and, produces a color gamut enlargement effect due to the reduction in toner particle size.

[0131] Table 6 shows the results of a comparative experiment performed on the density of a designated color single color and non-designated color multiple colors in a wide color gamut mode and the color difference between the two colors by using the image forming apparatus according to the present embodiment and a comparative example. 2 ) was used as a recording material, and chromaticity and density were measured using Spectrolino (Backing Black) manufactured by X-Rite, Incorporated.

[0132] (Table 6)

[0133]

[0134]

[0135]

[0136] Table 6 reveals the following.

[0137] As a difference between the non-designated color (C) and the normal mode, in the comparative conventional example using the same average toner particle size of 7.5 μm as other colors even in the wide color gamut mode limited to the designated color, the density is lower than the normal mode.

[0138] On the other hand, the reduction in toner particle size (6.5 μm) according to the present embodiment enables the color difference of the normal mode to be set to 1.1, which is equal to or smaller than the color difference E*0.8 to 1.6 as the Class AA tolerance (JIS Z8721).

[0139] Meanwhile, taking multicolor (red) created with designated colors (M and Y) as an example, the chromaticity C* of the multicolor is greater than that of the normal mode, and a wide color gamut is achieved.

[0140] In other words, it was found that using a small particle size toner results in a wider color gamut (≈higher density) and smaller color difference from multicolor (specified color) even when M / S is the same.

[0141] It should be noted that the average particle size and particle size distribution of the toner can be measured by various methods including using a Coulter Counter TA-II or a Coulter Multisizer (both manufactured by Beckman Coulter, Inc.). For example, the measurement can be performed by using a Coulter Multisizer (manufactured by Beckman Coulter, Inc.). An interface for outputting number distribution and volume distribution (manufactured by Nikkaki Bios Co., Ltd.) and a PC9801 personal computer (manufactured by NEC Corporation) are connected to the Coulter Multisizer. As the electrolyte, first-grade sodium chloride can be used, and a formulation of a 1% NaCL aqueous solution can be used. As the Coulter Multisizer, for example, an ISOTON R-II (manufactured by Coulter-Scientific Japan Co., Ltd.) can be used.

[0142] As a measurement method, 0.1 to 5 ml of a surfactant (favorably, an alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the above-mentioned aqueous electrolyte solution, and 2 to 20 mg of the measurement sample is added thereto. The electrolyte solution in which the sample is suspended is subjected to a dispersion process for approximately 1 to 3 minutes using an ultrasonic disperser, and the number of toner particles equal to or larger than 2 μm in the sample is measured using a Coulter Multisizer using an aperture of 100 μm. Thus, the number distribution is calculated and the number average particle size (D) is obtained.

[0143] As described above, according to this embodiment, in an image forming apparatus having printing conditions in which designated colors using a wide color gamut mode coexist with non-designated colors not using the wide color gamut mode, the color difference and image quality difference between the designated colors using the wide color gamut and the non-designated colors can be reduced. Furthermore, an image forming apparatus can be provided that prevents unnecessary acceleration of the lifespan of the non-designated colors while achieving the original color gamut magnification effect.

[0144] Third embodiment

[0145] In the first embodiment, a mode in which image data items for Y, M, and C are added, respectively, corresponding to the image portion indicated by the Bk image data, or a mode in which image data for Y, M, or C is added alternatively has been described. Furthermore, in the second embodiment, a case has been described in which toner having an average particle size smaller than that of the designated colors is used for non-designated colors (Bk and C (cyan)) to increase the monochrome density while carrying the same toner amount (M / S). However, the first and second embodiments are not limited to modes in which the embodiments are implemented independently. The first and second embodiments may be implemented together.

[0146] Specifically, the average particle size of the toner of the non-designated color (Bk) according to the first embodiment can be set to be smaller than that of the designated color disclosed in the second embodiment. It has been confirmed that by setting the average particle size of the toner of the non-designated color smaller than that of the first embodiment, an image with higher definition relative to the non-designated color can be obtained.

[0147] While the operation for changing the peripheral speed ratio of the developing roller relative to the photosensitive drum has been described as an operation for increasing the developer supply capacity of the image forming portion, the present invention is not limited to this configuration. For example, when the image forming apparatus is configured so that a sufficient amount of toner is supplied to the developing sleeve in a so-called two-component developing system, the output of the primary transfer bias for each color may be sufficient.

[0148] As described above, according to the present disclosure, when a designated color to which a wide color gamut mode is applied and a non-designated color to which the wide color gamut mode is not applied are provided, a color difference and an image quality difference between the designated color and the non-designated color can be reduced.

[0149] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An image forming apparatus, characterized in that: An image forming apparatus having an image forming portion capable of forming an image on a recording material using developer images of a plurality of colors including a first color and a second color, comprising: a data generator that generates first image data for forming a developer image of a first color and second image data for forming a developer image of a second color, and A unit for forming a developer image of multiple colors by superimposing first image data and second image data generated by a data generator, wherein The image forming part comprises: a first image bearing member corresponding to a first color; a second image bearing member corresponding to a second color; a first light emitting unit that irradiates the surface of the first image bearing member with light and forms an electrostatic latent image based on first image data; a second light emitting unit that irradiates the surface of the second image bearing member with light and forms an electrostatic latent image based on second image data; a first developing member that supplies a developer to the electrostatic latent image formed on the first image bearing member; and a second developing member that supplies a developer to the electrostatic latent image formed on the second image bearing member; wherein the image forming portion operates in a normal mode and a wide color gamut mode, and a developer supply capability from the second developing member to the second image bearing member is increased in the wide color gamut mode as compared to the normal mode, When operating in the wide color gamut mode, the data generator generates image data of a second color corresponding to an image portion indicated by the first image data, or generates image data of a plurality of colors constituting the second color corresponding to the image portion, and The peripheral speed ratio between the second image bearing member and the second developing member, which are respectively rotationally driven, in the wide color gamut mode is greater than that in the normal mode.

2. The image forming apparatus according to claim 1, wherein The data generator generates image data of the second color or image data of the multiple colors so that the color difference between (i) a case where the image portion indicated by the first image data is formed solely based on the first image data in a normal mode in which the image forming portion operates without increasing the developer supply capacity and (ii) a case where the image portion indicated by the first image data is formed in a wide color gamut mode by adding image data of the second color corresponding to the image portion indicated by the first image data to the second image data or generating image data of multiple colors constituting the second color corresponding to the image portion is equal to or less than a specified amount.

3. The image forming apparatus according to claim 1, wherein The amount of charge per unit area (Q / S) in the image portion indicated by the first image data of the developer image formed on the recording material is greater in (ii) the case where the image portion is formed in the wide color gamut mode by adding image data of the second color corresponding to the image portion indicated by the first image data to the second image data or generating image data of a plurality of colors constituting the second color corresponding to the image portion, compared to (i) the case where the image portion is formed solely based on the first image data in the normal mode in which the image forming portion operates without increasing the developer supply capacity.

4. The image forming apparatus according to claim 1, wherein The average particle size of the developer of the first color is smaller than the average particle size of the developer of the second color.

5. The image forming apparatus according to claim 1 , further comprising: an intermediate transfer member to which a plurality of developer images respectively formed on a plurality of image bearing members including a first image bearing member and a second image bearing member are transferred in a superimposed manner, and the transferred developer images composed of a plurality of colors are transferred to a recording material; a first driving source that supplies a driving force for driving the second image bearing member; a second driving source for supplying a driving force for driving the second developer carrying member; and The third driving source supplies a driving force for driving the intermediate transfer member.

6. The image forming apparatus according to claim 5, further comprising: an applying unit that applies a primary transfer bias to a plurality of primary transfer portions in which developer images are transferred from a plurality of image bearing members to an intermediate transfer member, respectively, wherein The applying unit applies the primary transfer bias so that a ratio of a magnitude of a current flowing through the primary transfer portion to a process speed that is a speed of image formation is larger in the wide color gamut mode than in the normal mode.

7. The image forming apparatus according to claim 6, wherein: When It represents the amount of current flowing through the primary transfer portion, Q / S represents the charge amount of the developer per unit area in the developer image to be transferred to the intermediate transfer member, PS represents the process speed, and W represents the width of the developer image to be transferred to the intermediate transfer member, It satisfies It=Q / S×PS×W.

8. The image forming apparatus according to claim 1, wherein The development contrast in the wide color gamut mode, which represents the magnitude of the absolute value of the difference between the development bias applied to the developer carrying component that carries the developer supplied to the second image carrying component in the second developing component and the bright portion potential in the electrostatic latent image formed on the second image carrying component by the second light emitting unit, is greater than that in the normal mode.

9. The image forming apparatus according to claim 1, wherein The absolute value of the difference between the dark and light potentials in the electrostatic latent image formed on the second image bearing member by the second light emitting unit in the wide color gamut mode is greater than that in the normal mode.

10. The image forming apparatus according to claim 1, wherein The first color is either black or black and cyan.

11. The image forming apparatus according to claim 1, wherein the peripheral speed of the first image bearing member and the peripheral speed of the second image bearing member in the wide color gamut mode are lower than the peripheral speed of the first image bearing member and the peripheral speed of the second image bearing member in the normal mode, wherein the peripheral speed of the first developing component and the peripheral speed of the second developing component in the wide color gamut mode are lower than the peripheral speed of the first developing component and the peripheral speed of the second developing component in the normal mode, and Wherein, in the wide color gamut mode, the peripheral speed of the first developing component is lower than the peripheral speed of the second developing component.

Images