JP2014107627A - Image formation device and image formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve reproduction of a target hue and suppression in decrease in saturation by suppressing the amount of toner used for development in printing on a form having large surface unevenness.SOLUTION: There is provided an image formation device which forms an image on a recording medium using a plurality of color materials, the image formation device including acquisition means of acquiring surface roughness precision indicating an index representing roughness of a recording surface of the recording medium, and control means of controlling an increment in the amount of a coloring material, formed on an outermost surface of the recording surface among the plurality of color materials, based upon the amount of the color material on the recording medium whose recording surface has roughness less than roughness that the surface roughness information indicates to an amount larger than increments of other color materials among the plurality of color materials.

Description

  The present invention relates to an image forming process according to the surface shape of a recording medium.

  As an apparatus for forming an image on a recording medium (hereinafter also referred to as “paper” or “paper”), there is an electrophotographic image forming apparatus (hereinafter also referred to as an electrophotographic printer). In an electrophotographic printer, toner developed on a photoreceptor is generally primarily transferred to an intermediate transfer belt (hereinafter also referred to as “intermediate transfer member”), and secondarily transferred from the intermediate transfer member to a recording medium. An image is formed by heating and pressurizing the transferred toner to fix the toner on the recording medium.

  In recent years, various types of paper are used in electrophotographic printers, but it is known that transfer defects may occur depending on the type of paper.

  As a technique for solving the above problems, a technique using a transparent toner in addition to a colored toner for forming a desired image on a recording medium is disclosed. This is a technique for developing in such an order that the transparent toner becomes the uppermost layer on the recording medium (Patent Document 1). That is, this is a technique for preventing the color development of an image from being affected by making a toner layer that cannot be completely transferred in a transfer process a layer made of transparent toner.

  However, in the above configuration, when a sheet with large surface irregularities is used, a transfer failure may occur in the concave portion due to a large potential difference required for transfer. As a technique for solving this problem, a technique using a transparent toner having a lower adhesion and charge amount than a colored toner is disclosed (Patent Document 2).

  Further, as a technique that does not use a transparent toner, in a wet development type electrophotographic image forming apparatus, a liquid developer having a thickness corresponding to the smoothness of paper and the absorbability of the liquid developer is formed on the developer carrier. A technique is disclosed (Patent Document 3). That is, the rougher the surface of the paper or the stronger the adsorption force, the more toner is developed, thereby suppressing transfer defects and forming a uniform toner layer on the paper.

JP 08-106195 A JP 2009-25713 A JP-A-11-212368

  Various factors are cited for the transfer failure, and one of them is a failure due to a so-called air gap between the paper to be transferred and the toner on the intermediate transfer member. FIG. 1 is a conceptual diagram illustrating toner movement from an intermediate transfer member to paper before and after transfer. FIG. 1A shows a state before transfer, and FIG. 1B shows a state after transfer. When the toner on the intermediate transfer body 101 enters the transfer nip, the charged toner is transferred to the paper 102 side. Although not shown, if the paper is smooth, the air gap is almost the same regardless of the location, so that the toner layer is uniformly transferred to the paper. However, in the paper having a large surface unevenness as shown in FIG. 1, the air gap widens in the concave portion of the paper and the transfer electric field weakens, so that the toner is not sufficiently transferred to the concave portion and the residual toner 105 on the intermediate transfer member Become. Further, FIG. 1 shows an example of secondary colors of the yellow toner 103 and the cyan toner 104. However, not only in the case of a multi-color, but also in the primary color, a transfer failure occurs when the amount of developed toner is large. Is likely to occur.

  As described with reference to FIG. 1, when a transfer failure occurs due to surface irregularities on the paper, the toner on the upper layer on the paper is not sufficiently transferred, and the amount of toner on the paper is greater than the amount of toner after development or primary transfer. (Hereinafter also referred to as “loading amount”) is reduced. As a result, the transfer amount of the upper layer toner becomes smaller than the assumed amount, and the image quality problem that the expected color development cannot be obtained due to the unevenness of the paper occurs.

  The above phenomenon will be described with reference to FIG. FIG. 2 is an a * -b * plane in the CIE L * a * b * color space. The graph of FIG. 2 shows the color measurement results of a printed matter printed using a predetermined printer. Point 201 is a plot of the colorimetric values of the printed matter on a * -b * plane when a solid green image composed of 100% cyan and 100% yellow is printed on a sheet on which no transfer failure occurs. is there. The dotted line in the figure represents the target green hue, and at point 201, the target hue is developed. A point 202 is obtained by plotting the colorimetric values of the printed matter on the a * -b * plane when printing is performed on a sheet having large surface irregularities in which transfer failure occurs. Even though a green solid image composed of 100% cyan and 100% yellow is printed, the upper layer yellow on the paper is not sufficiently transferred, resulting in a state as shown in FIG. The hue is shifted to the cyan side, and sufficient saturation is not obtained.

  The two types of paper described above are, for example, plain paper in terms of printer driver and controller settings, but there are a point 201 where no transfer failure occurs and a point 202 where a transfer failure occurs. At point 202, it is assumed that the loading amount on the paper has become 90%, which is smaller than the assumed 100%, due to transfer defects. In order to obtain a target green hue, it is conceivable to record cyan with an amount less than 100%, for example, 90%, and to make the applied amount of cyan and applied amount of yellow on paper as expected. . FIG. 14 is a conceptual diagram showing toner movement from the intermediate transfer body to the paper before and after transfer in the case where recording is performed by reducing the amount of cyan as the lower layer on the paper. 14A shows a state before transfer, and FIG. 14B shows a state after transfer. By reducing the cyan toner 1404 in advance by the amount of residual toner 1405 generated by the upper layer yellow toner 1403 in the intermediate transfer body 1401, the ratio on the paper 1402 can be made uniform.

  By performing this process, a target hue can be obtained, but saturation reduction cannot be suppressed. A point 203 is a colorimetric value of the printed matter obtained by this processing. As shown in the figure, in consideration of the fact that the applied amount of yellow as the upper layer on paper decreases to 90%, the target hue can be obtained by setting the applied amount of cyan as the lower layer on paper to 90%. it can. However, since the above-described countermeasure does not suppress the decrease in saturation, a decrease in the color reproduction range cannot be avoided.

  The present invention has been made in view of the above problems, and controls the amount of toner to be developed (hereinafter, also referred to as “development amount”) when printing on paper with large surface irregularities, thereby achieving the target hue. The purpose is to achieve reproduction and saturation reduction suppression.

  An image forming apparatus according to the present invention is an image forming apparatus that forms an image on a recording medium using a plurality of color materials, and includes surface roughness information indicating an index representing a roughness of a recording surface of the recording medium. Based on the acquisition means for acquiring and the surface roughness information, the recording surface of the color material amount of the color material formed on the outermost surface of the recording surface among the plurality of color materials is the roughness indicated by the surface roughness information. Control means for controlling an increase amount with respect to the color material amount in the case of a recording medium less coarse than the above to an amount larger than the increase amount in the other color materials among the plurality of color materials.

  According to the present invention, when printing on a sheet with large surface irregularities, reproduction of a target hue and suppression of saturation reduction can be realized by controlling the amount of toner to be developed.

FIG. 6 is a schematic diagram illustrating toner movement from an intermediate transfer body to paper before and after transfer. The a * -b * plane in the CIE L * a * b * color space is shown. FIG. 6 is a schematic diagram illustrating toner movement from an intermediate transfer body to paper before and after transfer. 1 is a block diagram illustrating an image processing system configuration in an image forming apparatus according to Embodiment 1. FIG. An example of a table stored in the transfer order storage unit 409 is shown. 1 shows an example of the configuration of a one-drum type electrophotographic recording type image forming apparatus. It is a flowchart which shows the flow of the process which controls development amount. 6 is a graph showing a part of a color separation LUT when the development amount is not corrected. The example of the pulse signal in the PWM process part 405 is shown. It is a graph which shows a part of color separation LUT when correcting the development amount. It is a graph which shows the relationship between a color separation value and PWM. 6 is a block diagram illustrating a configuration of an image processing system in an image forming apparatus according to Embodiment 2. FIG. FIG. 10 is a block diagram illustrating a configuration of an image processing system in an image forming apparatus according to a third embodiment. FIG. 6 is a conceptual diagram illustrating toner movement before and after transfer when recording with a lower toner amount on paper.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Outline of color control method)
In the present embodiment, a description will be given of controlling color development by controlling the developing amount (coloring material amount) when printing on a recording medium (hereinafter also referred to as paper or paper) having a large surface unevenness, for example, plain paper. First, the outline will be described with reference to FIG. Although an example of toner is shown below, the color material is not limited to toner, and may be ink or the like.

  FIG. 3 is a schematic diagram showing toner movement before and after transfer from the intermediate transfer member to paper. FIG. 1 shows an example in which the development amount is 100% cyan and 100% yellow with respect to a solid green image composed of 100% cyan and 100% yellow. FIG. 3 shows a case where the cyan development amount is 100% for a green solid image composed of 100% cyan and 100% yellow, but the development amount of yellow is higher than 100%, for example, 110%. It is an example. 3A shows the state before transfer, and FIG. 3B shows the state after transfer. Yellow toner 303 and cyan toner 304 are present on the intermediate transfer member 301. In FIG. 3A showing the state before transfer, the amount of yellow toner 303 is larger on the intermediate transfer member 301 than in FIG. 1A. Each toner is transferred to the paper 302. In FIG. 3B showing the state after the transfer, the residual toner 305 on the intermediate transfer body is generated without being transferred at the concave portion of the paper, but the amount of cyan toner and the amount of yellow toner on the paper become equal. ing.

  As in the example shown in FIG. 3, the colorimetric value of the printed material when the development amount is controlled is indicated by a point 204 in FIG. 2. It can be seen that the point 204 reproduces the target hue and has higher saturation than the point 203. That is, it is possible to realize the reproduction of the target hue and the suppression of the decrease in saturation by controlling the development amount on a sheet having a large surface unevenness. The reason why the saturation is slightly lower than that of the point 201 is that although the amount of transferred toner is equivalent to that of smooth paper, the amount of toner is non-uniform depending on the location (region) due to surface irregularities.

(Image processing system)
FIG. 4 is a block diagram illustrating a configuration of an image processing system in the image forming apparatus according to the present exemplary embodiment. A central processing unit (CPU) (not shown) controls the entire system, and includes a read-only storage device (ROM) and a storage device (RAM) on which the CPU temporarily reads and writes during calculation processing.

  The image input unit 401 inputs an image to be printed.

  The color conversion processing unit 402 maps an image signal of an input image (for example, input image data of RGB values or CMYK values) to a device-independent color space (for example, CIE L * a * b * or CIE XYZ). To do. In general, since the color reproduction range of the printer is narrower than the color reproduction range of the monitor, a conversion process is performed to perform color compression to a color in a range that can be reproduced by the printer. This conversion processing is performed based on, for example, a lookup table (LUT) in which correspondence between RGB values to L * a * b * values is described. However, the conversion processing is not limited to this, and matrix conversion is also possible. I do not care.

  The color separation processing unit 403 converts the device-independent color space value converted by the color conversion processing unit 402 into a signal value (for example, CMYK value) of each color material color mounted in the image forming apparatus. To do. The conversion method is not limited to one. For example, referring to the color separation LUT 407 in which the correspondence between L * a * b * values and CMYK values is described, conversion into signal values of each color material color is performed. To do.

  The color separation LUT 407 holds a plurality of different color separation LUTs corresponding to the paper roughness information, which indicates an index representing the roughness of the recording surface of the paper acquired by the paper information acquisition unit 408.

  The transfer order storage unit 409 stores order information indicating the order in which the color toners are secondarily transferred by the image forming unit 406, for example, as a table. FIG. 5 shows an example of a table stored in the transfer order storage unit 409. In this example, it is assumed that images are transferred in the order of K, C, M, and Y on the paper, but the order is not limited to this example. If the number of color material colors increases, an order is provided for all color material colors. Further, the order may be provided for only some of the color material colors without providing the order for all the color material colors.

  The quantization processing unit 404 performs quantization processing on the image for each color material color converted by the color separation processing unit 403. For example, when the output of the color separation processing unit 403 is 8-bit (256 gradations) data, the data is converted into 1-bit (2 gradations) data.

  The PWM processing unit 405 performs pulse width modulation processing for controlling the width of the exposure pulse for the quantized image data. The exposure signal data subjected to the pulse width modulation processing by the PWM processing unit 405 is sent to the image forming unit 406.

(Image forming device)
FIG. 6 shows a configuration example of a so-called one-drum type electrophotographic recording type image forming apparatus. The image forming apparatus includes a laser diode 6001, a polygon mirror 6002, a photosensitive drum 6003, an exposure device 6004, a charging device 6005, a developing device 6006, a primary transfer device 6008, and a photosensitive drum cleaner 6012. Further, the image forming apparatus includes an intermediate transfer belt 6007, a registration roller 6014 that conveys a recording medium to a secondary transfer device at an appropriate timing, a secondary transfer device 6009, a recording medium 6010, a fixing device 6011, and an intermediate transfer belt cleaner 6018. In the case of the one-drum type, a plurality of color developing devices share a laser diode, a polygon mirror, a photosensitive drum, an exposure device, a charger, a primary transfer device, and a photosensitive drum cleaner.

  The laser diode 6001 emits laser light in response to the exposure signal data generated by the PWM processing unit 605 described above. The emitted laser light passes through a polygon mirror 6002 and an fθ lens (not shown) and is exposed and scanned onto a photosensitive drum 6003 that is an image carrier rotating in the direction of an arrow. As a result, an electrostatic latent image is formed on the photosensitive drum 6003.

  The photosensitive drum 6003 is uniformly charged by the exposure device 6004 and then uniformly charged by the charger 6005. Thereafter, an electrostatic latent image corresponding to the binary image data is formed on the photosensitive drum 6003 in response to the exposure scanning of the previous laser beam. The electrostatic latent image is developed as a visible image (toner image) with toner supplied from the developing unit 6006.

  The developed toner image is transferred onto the intermediate transfer belt 6007 that is stretched between a plurality of rollers and driven endlessly by the action of the primary transfer unit 6008.

  This operation is repeated while switching the developing units (cyan 6006C, magenta 6006M, yellow 6007Y, black 6006K) of each color used in the developing device 6006, and a toner image composed of a plurality of colors sequentially transferred onto the intermediate transfer belt 6007 is formed. To do.

  On the other hand, the recording medium 6010 is conveyed from the paper feed tray 6013 to the registration roller 6014 and is conveyed to the secondary transfer unit 6009 by the registration roller 6014 at an appropriate timing. The toner images composed of a plurality of colors transferred onto the intermediate transfer belt 6007 by the secondary transfer device 6009 are transferred to the transported recording medium 6010. The recording medium 6010 is conveyed, passes through the fixing device 6011, and fixes the toner image on the recording medium 6010.

  Thereafter, when the duplex printing is not executed, the recording medium 6010 is discharged onto the paper discharge tray 6016 by the paper discharge roller 6015. On the other hand, when double-sided printing is performed, the rear end of the recording medium 6010 is chucked by the paper discharge roller 6015. Next, the recording medium 6010 is guided to the conveyance path 6017 by the reverse rotation of the paper discharge roller 6015 and is conveyed to the registration roller 6014. The toner image is conveyed again to the secondary transfer device 6009 by the registration roller 6014 at an appropriate timing, and after the toner image of the second side image is transferred and fixed, it is discharged to the paper discharge tray 6016.

  Residual toner remaining on the photosensitive drum 6003 is scraped off by the photosensitive drum cleaner 6012 and collected. Further, after the transfer material 6010 is separated, the remaining toner on the intermediate transfer belt 6007 is scraped off by an intermediate transfer belt cleaner 6018 such as a blade.

  In this embodiment, an example of the image forming unit 406 of the one-drum type electrophotographic recording system is shown. However, a tandem type electrophotographic recording system having a mechanism for each developing device of a plurality of colors, Other recording methods may be used.

(Development amount control method)
A method for controlling the development amount will be described. In this embodiment, the color separation processing unit 403 and the PWM processing unit 405 correct the development amount.

  FIG. 7 is a flowchart showing the flow of processing for controlling the development amount.

  In step S701, paper roughness information is acquired. The acquisition method includes a user interface in which roughness information is designated by the user and may be acquired from a user instruction, or a known surface roughness sensor is provided inside the printer to acquire a sensor value. May be. Note that the user instruction may be information on whether or not to take measures against paper roughness. When an instruction not to take measures is acquired, the comparison between the paper roughness information and the threshold value in step S702 below is skipped. Is possible.

  In step S702, it is determined whether the above-described paper roughness is equal to or greater than a preset threshold value.

  If the paper roughness is smaller than the threshold value, the process ends. When the processing ends, the development amount is not corrected. That is, the color separation processing unit 403 selects a preset default color separation LUT, and the PWM processing unit 405 executes a preset default PWM process. FIG. 8 is a graph showing a part of the color separation LUT when the development amount is not corrected. The graph shows the correspondence between the input signal value from cyan to green through yellow and the color separation value. This input signal is, for example, a value of L * a * b * converted by the color conversion processing unit 402. The color separation values (for example, CMYK values) are a cyan toner amount 801 and a yellow toner amount 802. FIG. 9A shows an example of a pulse signal in the PWM processing unit 405 when the development amount is not corrected.

  If the paper roughness is greater than or equal to the threshold, the process proceeds to step S703. In step S703, the transfer order for the paper stored in the transfer order storage unit 409 is acquired.

  In step S704, the development amount is appropriately controlled by the color separation processing unit 403 based on the paper roughness information acquired in step S701 and the transfer order acquired in step S703. Specifically, based on the paper roughness information acquired in S701, a color separation LUT corresponding to the paper roughness information is selected from the plurality of color separation LUTs held by the color separation LUT 407. For example, when the roughness information of the paper indicates that the roughness of the surface shape of the paper is large (in the case of rough paper), it is formed closest to the surface of the intermediate transfer member or on the outermost surface of the recording surface of the paper. It is necessary to increase the development amount of the color material. Therefore, a color separation LUT having a color material value (color separation value) greater than that of other color separation LUTs is selected. At this time, the color material closest to the surface of the intermediate transfer body (color material formed on the outermost surface of the recording surface of the paper) is determined based on the transfer order acquired in S703, and the color material value of the determined color material is determined. Select a color separation LUT that is larger than other color separation LUTs.

  FIG. 10 is a graph showing a part of the color separation LUT that is selected when the paper has a large roughness and the transfer order acquired in step S703 is the order shown in FIG. The amount of cyan toner 1001 is the same as that of paper with a flat surface, and the transfer order to paper is slow (closest to the surface of the intermediate transfer member) Yellow toner 1002 has a color separation value in the green hue, It can be seen that it exceeds 100%, which is the case of flat paper. That is, among the plurality of color materials, the change amount of the development amount of the color material formed on the outermost surface of the paper recording surface with respect to the development amount when the recording surface is flat is an increase amount. In this case, the amount is controlled to be larger than the increase amount in the other color materials among the plurality of color materials. The yellow toner 1003 is a color separation value that controls the amount of yellow toner in the case of paper that is coarser than that of the yellow toner 1002. The rougher the paper, the lower the transfer efficiency, so that the maximum value of the yellow toner after the transfer order is increased. The increase amount of the cyan toner amount 1001 may be relatively smaller than the increase amount of the yellow toner, and may not be zero.

  In addition, if only a certain color material is controlled in a green hue reproduced by mixed colors, gradation with surrounding colors is deteriorated. Therefore, as shown by the yellow toner 1002 and the yellow toner 1003, it is preferable that the color separation value is changed smoothly according to the surrounding hue.

  Generally, the relationship between the color separation value and the amount of toner to be developed is monotonically increasing. This monotonic increase is when the color separation value is up to 100%. That is, it is necessary to increase the development amount when the color separation value is 100% or more in the processing after the quantization processing. This embodiment shows a method of using PWM to develop a larger amount of toner when the color separation value is higher than 100% than when the color separation value is 100%. FIG. 11 is a graph showing the relationship between color separation values and PWM. When the color separation value is 100% or less, a preset PWM (70% in this embodiment) is applied. If the color separation value exceeds 100%, the PWM is increased. An example when the PWM is increased is shown in FIG.

  As described above, compared to the case where the paper roughness is smaller than the threshold value, when the paper roughness is equal to or larger than the threshold value, the area close to the solid of the secondary color which is a color mixture of the primary colors. Since the exposure amount increases, the development amount also increases.

  Further, it is preferable to store a plurality of color separation LUTs in which the color separation value of the secondary solid color part exceeds 100% in the color separation LUT 407 in accordance with the degree of paper roughness. Even if the color separation LUT corresponding to the degree of paper roughness is not held, color separation processing is performed in real time by performing an interpolation operation using the color separation LUT close to the paper roughness information. Also good.

  In the above-described embodiment, the development amount is controlled by determining the roughness of the paper surface. However, the index representing the roughness of the paper surface is the paper type, for example, rough for plain paper and rough for coated paper. The development amount may be controlled by determining that there is no.

  In the above embodiment, the color separation LUT is selected based on the transfer order. However, if the transfer order is fixed, the transfer order information is not necessary. At this time, the color separation LUT to be held, which is a selection target, may be prepared in advance by changing the color material values according to a fixed transfer order.

  In the above-described embodiment, the case of developing amount control using PWM that is pulse width modulation is described as an example. However, control may be performed using so-called PAM that is pulse amplitude modulation. FIG. 9C shows an example in which the exposure amount is increased by PAM. Compared with FIG. 9A, it can be seen that the total exposure amount is increased in both FIG. 9B and FIG. 9C.

  In the above embodiment, the development amount is corrected by exposure. However, the development amount control method is not limited to this, and may be controlled by, for example, a development bias (applied voltage in development).

  In the first embodiment, an example in which the same development amount control processing is performed for all image regions has been shown. However, in this embodiment, the development amount control processing is performed only with a color signal representing a secondary solid color region or a region close thereto. The structure for performing will be described. The description of the same configuration as that of the first embodiment is omitted.

  FIG. 12 is a block diagram illustrating a configuration of an image processing system in the image forming apparatus according to the present exemplary embodiment.

  The image input unit 401 inputs an image to be printed.

  The color area determination unit 1201 divides the image input by the image input unit 401 into areas composed of a single pixel or a plurality of pixels, and determines whether the area is a secondary solid color signal or a color signal close thereto. . When the color region determination unit 1201 determines that the color signal is a secondary solid color signal or a color signal close thereto, the image signal (for example, RGB value or CMYK value) of the input image is sent to the color conversion processing unit 402 and the same processing as in the first embodiment I do. Since the subsequent processing contents are the same, description thereof is omitted.

  If the area determination unit 1201 does not determine that the color signal is a secondary solid color signal or a color signal close thereto, the image signal of the corresponding area of the input image is sent to the basic color conversion processing unit 1202. The basic color conversion processing unit 1202 maps the image signal of the input image into a device-independent color space (for example, CIE L * a * b * or CIE XYZ).

  The basic color separation processing unit 1203 is installed in the image forming apparatus by referring to the basic color separation look-up table (LUT) 1208 for the value of the device-independent color space converted by the color conversion processing unit 1202. It converts into the signal value (for example, CMYK value) of each color material color.

  A basic quantization processing unit 1204 performs a quantization process on each color material color image converted by the color separation processing unit 1203.

  The basic PWM processing unit 1205 performs a pulse width modulation process for controlling the width of the exposure pulse on the quantized image data. Exposure signal data that has been subjected to pulse width modulation processing by the PWM processing unit 1205 is sent to the image forming unit 1206.

  By the above-described processing, the processing is speeded up by dividing each image area and performing the development amount control processing only on the secondary color solid color signal or a color signal close thereto.

  In this embodiment, it is determined whether or not the image to be printed has a lot of color signals that are close to or close to the secondary color, and a process for switching ON / OFF of the development amount control process for each image is performed. The configuration will be described. The description of the same configuration as in the above embodiment is omitted.

  FIG. 13 is a block diagram showing the configuration of the image processing system in this embodiment.

  The image input unit 401 inputs an image to be printed.

  The image determination unit 1301 divides the image input by the image input unit 401 into areas composed of a single pixel or a plurality of pixels, and counts areas of secondary color solid color signals or areas close thereto. If this count value is greater than or equal to a predetermined value, that is, if it is determined that there are many secondary color solid signals or similar color signals, the processing from step 402 onward in the first embodiment is executed on the entire image. If this count value is greater than or equal to a predetermined value, that is, if it is determined that there are many secondary color solid signals or similar color signals, the processing from step 1202 of the second embodiment is executed on the entire image.

  If the image determination unit 1301 determines that the count value is greater than or equal to the predetermined value, that is, if there are many secondary color solid signals or similar color signals, the process proceeds to 1201 in the second embodiment. In other words, the development amount control process is performed only for an image having a lot of secondary color solid color or a color signal close thereto, and the development amount control process is performed only for an area of a secondary solid color or a color signal close thereto.

[Other Examples]
The present invention can also be realized by supplying a storage medium storing software program codes for realizing the functions of the above-described embodiments (for example, the steps shown in the above flowchart) to a system or apparatus. In this case, the functions of the above-described embodiments are realized by the computer (or CPU or MPU) of the system or apparatus reading and executing the program code stored in the storage medium so that the computer can read the program code. Further, the program may be executed by one computer or may be executed in conjunction with a plurality of computers.

  As described above, according to the above embodiment, when printing on a sheet with large surface irregularities, reproduction of a target hue and suppression of saturation reduction can be realized by controlling the amount of toner to be developed.

Claims (17)

An image forming apparatus that forms an image on a recording medium using a plurality of color materials, and obtains surface roughness information indicating an index representing the roughness of the recording surface of the recording medium;
Based on the surface roughness information, a recording medium whose color surface is less rough than the roughness indicated by the surface roughness information of the color material amount of the color material formed on the outermost surface of the recording surface among the plurality of color materials An image forming apparatus comprising: a control unit configured to control an increase amount with respect to the color material amount in the above case to an amount larger than the increase amount in the other color materials of the plurality of color materials. The table that holds the color material values of the color material corresponding to the input image data further includes a holding unit that holds a plurality of tables having different color material values corresponding to the roughness information,
The image forming apparatus according to claim 1, wherein the control unit controls the increase amount by selecting a table corresponding to the roughness information from the plurality of tables. Acquisition means for acquiring information indicating an order of transfer of the color material to the recording medium;
3. The apparatus according to claim 1, further comprising: a determination unit that determines a color material formed on the outermost surface of the recording surface among the plurality of color materials based on the information indicating the transfer order. The image forming apparatus described.   The image forming apparatus according to claim 3, wherein the information indicating the transfer order indicates a transfer order for a part of the plurality of color materials.   The control means performs control so that the amount of the color material after the transfer order in the solid portion of the secondary color is larger than the amount of the color material in the solid portion of the primary color constituted only by the color material. The image forming apparatus according to claim 3.   The control means controls so that a change between the color material amount of a solid portion of a secondary color and a color material amount of a color close to the solid portion of the secondary color becomes smooth. The image forming apparatus according to any one of claims 1 to 5.   The image forming apparatus according to claim 1, wherein the surface roughness information is acquired by a surface roughness sensor.   The image forming apparatus according to claim 1, wherein the surface roughness information is acquired by a user instruction. Further having an exposure means,
The image forming apparatus according to claim 1, wherein the control unit controls the color material amount by pulse width modulation in an exposure unit. Further having an exposure means,
9. The image forming apparatus according to claim 1, wherein the control unit controls the color material amount by pulse amplitude modulation in an exposure unit. Further having developing means,
The image forming apparatus according to claim 1, wherein the control unit controls the color material amount by an applied voltage in the developing unit. A color region determination unit that determines whether or not each of the areas including at least one pixel in the image is a predetermined color region;
The image forming apparatus according to claim 1, wherein the control unit performs the control only on the predetermined color region. Image determining means for determining whether or not a predetermined color region is equal to or greater than a preset value in the image;
13. The image forming apparatus according to claim 1, wherein the control unit performs the control when the predetermined color area is equal to or greater than a preset value in the image. .   The image forming apparatus according to claim 1, wherein the surface roughness information is a type of the recording medium.   The image forming apparatus according to claim 1, wherein the increase amount of the other color materials among the plurality of color materials is zero. An image forming method for forming an image on a recording medium using a plurality of color materials,
An acquisition step of acquiring surface roughness information indicating an index representing the roughness of the recording surface in the recording medium;
Based on the surface roughness information, a recording medium whose color surface is less rough than the roughness indicated by the surface roughness information of the color material amount of the color material formed on the outermost surface of the recording surface among the plurality of color materials And a control step of controlling an increase amount with respect to the color material amount in this case to an amount larger than the increase amount in the other color materials of the plurality of color materials.   A program that causes a computer to function as each unit of the image forming apparatus according to any one of claims 1 to 15.

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