JP4849518B2 - Image forming apparatus, method, program, and recording medium - Google Patents

Description

  The present invention relates to an image forming apparatus, a method, a program, and a recording medium for forming an image using toner such as a digital color copying machine and a color laser printer.

  Various techniques for making the gloss of an output image uniform by using transparent toner in addition to CMYK color toner have been proposed for electrophotographic printers.

  Patent Document 1 determines the amount of transparent toner from the total amount of CMYK toner for each unit area. The larger the total amount of CMYK toner, the smaller the amount of transparent toner, thereby making the pile height of the toner substantially constant and the output image Make the gloss almost constant.

  Patent Document 2 determines the amount of transparent toner in accordance with the degree of roughness of the surface of the recording paper. In the case of recording paper having a large degree of surface roughness, the amount of transparent toner is increased, and the degree of surface roughness. In the case of recording paper having a small size, by reducing the amount of transparent toner, an image with uniform gloss can be obtained without toner offset to the fixing roll. Further, by using the transparent toner, not only the gloss uniformity is improved, but also the color reproduction region and the graininess are improved.

  In Patent Document 3, a transparent toner is first developed and then a color toner (CMYK toner) is developed, and a superimposed toner image is collectively transferred onto a recording paper, so that a part of the transparent toner layer is not transferred onto the recording paper. In this case, the color toner layer is completely transferred, so that an image excellent in color reproduction can be formed. Furthermore, in current electrophotographic printers, toner is heated and pressurized at the time of fixing, so that the toner that forms halftone dots used to express shading is crushed and deformed, which is one of the causes of the deterioration of graininess. Become. This has a greater effect on the color toner dots located in the uppermost layer. However, by providing the transparent toner as the uppermost layer, the color toner can be prevented from being crushed when it is fixed on the dots, and the graininess is improved.

Japanese Patent Laid-Open No. 10-55089 Japanese Patent No. 3518257 JP-A-8-106195

  In the electrophotographic printer, when the total toner amount increases, a transfer defect or a fixing defect occurs. Therefore, the total toner amount is limited in pixel units (or small area units). The limit of the total toner amount (total amount regulation value) is generally about 200% to 250%, and if this value is exceeded, the amount of CMY toner is reduced by the total amount regulation processing, so that the total toner amount is within the total amount regulation value. Fit. Since the total amount of toner increases in the high density portion of the image, this total amount restriction process is likely to be applied. However, reducing the amount of CMY toners by the total amount restriction process is a color reproduction of an image formed as shown in FIG. The area will be narrowed.

  When transparent toner is used, the total amount of toner increases accordingly, so that the total amount regulation value is more likely to be exceeded in the high density portion of the image, and the total amount regulation process is likely to be performed. For this reason, an image excellent in color reproduction should be able to be formed by using a transparent toner, but as a result, only an image having a narrow color reproduction range can be obtained.

The present invention has been made in view of the above problems,
An object of the present invention is to provide an image forming apparatus, a method, a program, and a recording medium that form an image with excellent color reproduction range and graininess using a transparent toner.

In an image forming apparatus for forming an image using a color toner containing a colorant and a transparent toner not containing a colorant, the present invention provides an image formation mode (hereinafter referred to as a first mode) using the transparent toner, and a transparent toner. In the first mode , the black generation / under color removal (BG /) is performed in the middle and high density portions of the image in the first mode, compared to the second mode. The main feature is to increase the amount of UCR) and to reduce the total amount of color toners including colorants.

According to the present invention , in the image forming mode using transparent toner, the total amount of color toner is reduced by increasing the amount of black generation / under color removal (BG / UCR) compared to the image forming mode not using transparent toner. can be reduced, it can be difficult to apply to the total amount control even when using the transparent toner, it is possible to form an image having good color gamut.

According to the present invention , in the image forming mode using transparent toner, the total amount of color toner can be reduced by reducing the amount of light toner used, and the total amount regulation can be made difficult.

According to the present invention , the image quality can be improved by using the transparent toner only for the area where the transparent toner needs to be used.

According to the present invention , the color reproduction by transfer / fixing is performed by attaching the transparent toner to the entire surface of the image or only where the toner dots containing the colorant exist so that the transparent toner becomes the uppermost surface of the toner layer on the paper. Deterioration of area and graininess can be suppressed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Example 1:
FIG. 1 is a schematic diagram of an image forming apparatus according to Embodiment 1 of the present invention. A basic image forming operation will be described with reference to FIG. The recording sheets 1 are separated and called one by one by the sheet feeding roller 2 and are conveyed to the conveying roller pair 3. Further, the transport roller pair 3 transports the recording paper 1 and transports it to the registration roller pair 4. The registration roller pair 4 has a configuration in which the rotation and stop of the roller can be freely controlled by a registration clutch (not shown), and the recording paper 1 is once stopped by the registration roller pair 4 in order to wait for a series of image forming processes to be described later.

  A portion surrounded by a dotted line 36 is a black image forming station. A charging charger 12, an exposure beam 13, a developing device 14, a cleaning blade 15, and a primary transfer charger 16 are disposed around the photoconductor 11, and perform a series of image forming operations. The surface of the photoconductor 11 uniformly charged by the charging charger 12 is irradiated with an exposure beam 13 from a writing unit (not shown) to form a latent image on the photoconductor. The developing device 14 develops black toner on the latent image and visualizes it as a toner image. Further, the toner image is transferred to the intermediate transfer belt 40 by the primary transfer charger 16. The toner remaining on the photoreceptor 11 is scraped off by the cleaning blade 15. Further, it is charged again by the charging charger 12, and thereafter the above-described image forming operation is repeated.

  Portions surrounded by dotted lines 37, 38, 39 are image forming stations for cyan plate, magenta plate, and yellow plate, respectively, and transfer the toner image of each plate to the intermediate transfer belt 40 by the same operation as the black plate. Further, a portion surrounded by a dotted line 35 is an image forming station for a transparent toner plate, and its operation is the same as that of other color plates.

  After all the toner images of the plates are transferred to the transfer belt 40, the recording paper 1 that has been temporarily stopped by the registration roller pair 4 is re-conveyed in accordance with the timing, and the toner is transferred onto the recording paper by the secondary transfer charger 41. Transfer the image. Next, the toner is conveyed to the fixing device 43, and the unfixed toner is fixed on the recording paper by heat and pressure, and is output. The toner remaining on the intermediate transfer belt 40 is scraped off by bringing the intermediate transfer cleaner 42 into contact with the belt, and the intermediate transfer belt 40 is cleaned.

  Since the transparent toner is located on the lowermost layer (transfer belt side) on the transfer belt 40, when transferring the toner image onto the recording paper 1, the color plate toner other than the transparent toner hardly remains on the transfer belt 40. . Therefore, an image with a good color reproduction range can be formed. Further, when fixing is performed by the fixing device 43, since the transparent toner is on the uppermost layer on the recording paper 1, there is a possibility that the dots of the color plate other than the transparent toner are crushed and deformed when pressure is applied. The deterioration of graininess can be suppressed.

  FIG. 4 is a block diagram of image processing according to the first embodiment. The image processing unit 402 is executed in the image forming apparatus of FIG. 1 or on a PC.

  When the user instructs printing from an application of the PC 401, a printer command expressed in PDL (Printer Descript Language) is output via the printer driver. The printer command is composed of drawing commands for three types of objects: character / graphic / image. Further, the user can instruct whether or not to use transparent toner from the print setting screen of the printer driver on the PC 401, and the instruction information (mode information) is also output.

  The command interpreting means 403 interprets the drawing command for each received object, and the developing means 404 develops an image as RGB data on a drawing memory (not shown). Also, object information (information regarding whether it belongs to character / graphic / image) and mode information indicating whether or not to use transparent toner are output.

  The color correction unit 405 converts RGB data into CMYBk data. The color correction means 405 also receives object information and mode information. Details of the processing of the color correction means will be described later.

The total amount regulating means 406 regulates the total amount with respect to the CMYBk data by the following equation (1).
if ((C + M + Y + Bk)> total amount regulation value)
C ′ = C × (total amount regulation value × 255 / 100−Bk) / (C + M + Y)
M ′ = M × (total amount regulation value × 255 / 100−Bk) / (C + M + Y)
Y ′ = Y × (total amount regulation value × 255 / 100−Bk) / (C + M + Y) Formula (1)
However, the CMYKBk data takes values from 0 (white) to 255 (black). C ′, M ′, and Y ′ are values after the total amount regulation, and Bk is not changed by the total quantity regulation.

  The total amount regulation value is, for example, a value of 250%. However, when using transparent toner, it is necessary to lower the total amount regulation value by the amount of the transparent toner. For example, when the transparent toner is formed with a layer thickness of 100%, the total amount regulation value is 150%.

  The halftone processing unit 407 performs halftone processing such as dither processing and error diffusion processing on each of the CMYBk data, and sends dot ON / OFF information of each pixel of each color to the printer 409.

  The transparent plate data generation unit 408 outputs dot ON / OFF information for each pixel of the transparent plate so that, when the mode information is a mode using transparent toner, a dot of transparent toner is output to the area of the photographic object. Is sent to the printer 409.

Hereinafter, processing of the color correction unit 405 will be described. FIG. 6 is a block diagram of the color correction means. The RGB data input to the color correction unit 405 is converted into printer-dependent CMY data by the masking unit 601 by the following masking operation (formula (2)).
C0 = c11 × R + c12 × G + c13 × B + c14
M0 = c21 × R + c22 × G + c23 × B + c24
Y0 = c31 * R + c32 * G + c33 * B + c34 Formula (2)
However, c11 to c34 are predetermined color correction coefficients.

Next, the black generation means 602 generates Bk data. The Bk signal is expressed by the following equation (3) using the black generation parameter α and the black start point Thr1.
When Min (C0, M0, Y0)> Thr1, Bk = α × (Min (C0, M0, Y0) −Thr1)
When Min (C0, M0, Y0) ≦ Thr1, Bk = 0 Formula (3)
The black generation amount can be controlled by the black generation parameter α and the black start point Thr1. FIG. 8 shows the amount of the Bk signal generated with respect to the amount of Min (C0, M0, Y0). FIG. 8 (a) shows that ink begins to be drawn from Min (C0, M0, Y0) = 30. In such a setting, the black generation amount is large, and (b) is a setting in which the black generation amount is small so that the ink starts to be applied from Min (C0, M0, Y0) = 128. Specifically, (a) is Thr1 = 30 and α = 1.13, and (b) is Thr1 = 128 and α = 2.0.

  The black generation means 602 receives mode information (1 bit) and object information (2 bits), and the black generation amount is controlled (switched) as shown in FIG. 9 by these two pieces of information (3 bits). . In a mode that uses transparent toner in a photographic object, the black generation amount is large (set to switch to FIG. 8A), and in a mode that does not use transparent toner, the black generation amount is small (set to switch to FIG. 8B). ) In addition, in the character object and the graphic object, the black generation amount is increased (the setting is switched to FIG. 8A).

Further, the UCR (under color removal) means 603 generates a CMY signal obtained by subtracting the black component from the C0M0Y0 signal and the Bk signal generated by the black generation means 602 by the following calculation formula (4).
C = C0−β × Bk
M = M0−β × Bk
Y = Y0−β × Bk Formula (4)
The UCR amount can be controlled by the UCR parameter β, and the larger the β, the larger the UCR amount.

  The UCR means 603 receives mode information, and the UCR amount is controlled by this information. In the mode using the transparent toner, the UCR amount is increased (for example, β = 1.0), and in the mode not using the transparent toner, the UCR amount is decreased (for example, β = 0.5).

  FIG. 10 schematically shows the total amount of CMYBk toner, where (a) is a mode in which transparent toner is used, and (b) is a mode in which transparent toner is not used. In the mode using the transparent toner, the black generation amount and the UCR amount are large, so that the total amount of CMYBk toner is reduced in the middle and high density portions as compared with the mode not using the transparent toner. In the mode using the transparent toner, the total amount regulation value is reduced by the amount of toner of the transparent toner. Therefore, the total amount regulation value is prevented from being exceeded by reducing the total toner amount of CMYBk.

  (C) is a mode in which transparent toner is used, and is the total amount of toner when the amount of toner is further added by the amount of transparent toner (the amount of transparent toner added to (a)). It can be seen that even if the total toner amount is increased by the amount of the transparent toner, the maximum value of the total toner amount is suppressed to (b) or less when the transparent toner is not used.

  With the configuration of this embodiment, it is possible to prevent the color reproduction range from being lowered due to the total amount regulation process while improving the graininess using the transparent toner. Note that the color correction unit 405 may use a color conversion method called a direct mapping method. This is because a grid point is provided in a color solid in the RGB space, and conversion from RGB to CMYBk on the grid point is provided as a lookup table (LUT), and interpolation processing is performed from a plurality of grid points in the vicinity of input RGB data. Directly calculates CMYBk. The same effect can be obtained by switching the direct mapping type LUT according to the object information and the mode information.

Example 2:
Example 2 is an example in the case of using two types of light and dark toners for black. FIG. 2 is a schematic diagram of an image forming apparatus according to Embodiment 2 of the present invention. 1 except that an image forming station 50 for light black (Lk) is added. By adding light black toner, the graininess can be improved compared to the case of using only normal black toner, but in addition to that, the use of transparent toner can further improve the graininess. it can.

  FIG. 5 is a block diagram of image processing according to the second embodiment. The image processing unit 502 is executed in the image forming apparatus of FIG. 2 or on a PC. The PC 501, the command interpretation unit 503, and the expansion unit 504 are the same as those in the first embodiment.

  The color correction unit 505 converts RGB data into CMYBkLk data. The color correction means 505 also receives object information and mode information. Details of the processing of the color correction means will be described later.

The total amount regulating unit 506 performs total amount regulation on the CMYBkLk data by the following equation (5).
if ((C + M + Y + Bk + Lk)> total amount regulation value)
C ′ = C × (total amount regulation value × 255 / 100−Bk−Lk) / (C + M + Y)
M ′ = M × (total amount regulation value × 255 / 100−Bk−Lk) / (C + M + Y)
Y ′ = Y × (total amount regulation value × 255 / 100−Bk−Lk) / (C + M + Y) Equation (5)
However, the CMYKBkLk data takes values from 0 (white) to 255 (black).
C ′, M ′, and Y ′ are values after the total amount regulation, and Bk and Lk are not changed by the total quantity regulation. The total amount regulation value is, for example, a value of 250%. However, when using transparent toner, it is necessary to lower the total amount regulation value by the amount of the transparent toner. For example, when the transparent toner is formed with a layer thickness of 100%, the total amount regulation value is 150%.

  A halftone processing unit 507 performs halftone processing such as dither processing and error diffusion processing on each of CMYBkLk data, and sends dot ON / OFF information of each pixel of each color to the printer 509. The transparent plane data generation unit 508 is the same as that in the first embodiment.

  Hereinafter, processing of the color correction unit 505 will be described. FIG. 7 is a block diagram of the color correction unit of the second embodiment. The RGB data input to the color correction unit 505 is converted into printer-dependent CMY data by the masking unit 701 by the masking operation of Expression (2) as in the first embodiment.

Next, the black generating means 702 generates K0 data by the following equation (6).
K0 = Min (C0, M0, Y0) Equation (6)

The UCR (under color removal) means 703 generates a CMY signal obtained by subtracting the black component from the C0M0Y0 signal and the K0 signal generated by the black generation means 702 by the following calculation formula (7).
C = C0-K0
M = M0-K0
Y = Y0-K0 Formula (7)

  Further, the light / dark separation unit 704 separates the K0 signal generated by the black generation unit 702 into light / dark black signals Bk and Lk. This separation process is performed using a separation table as shown in FIG. FIG. 11A is a separation table in which the amount of Lk used is suppressed in the middle / high density portion, and FIG. 11B is a separation table using a large amount of Lk. Mode information and object information are input to the density separation means 704, and the separation table is switched as shown in FIG. In a photographic object, the amount of Lk used is small in the mode using transparent toner (set in FIG. 11A), and the amount of Lk used is large in the mode not using transparent toner (set in FIG. 11B). To do. In addition, for character objects and graphic objects, the amount of Lk used is reduced (set in FIG. 11A).

FIG. 13 schematically shows the total amount of BkLk toner, where (a) is a mode in which transparent toner is used, and (b) is a mode in which transparent toner is not used. In the mode using the transparent toner, the amount of Lk used in the medium / high density portion is small, so the total amount of BkLk toner is small in the medium / high density portion compared to the mode not using the transparent toner. In the mode using the transparent toner, the total amount regulation value is reduced by the amount of the toner of the transparent toner, so that the total amount regulation value is prevented from being exceeded by reducing the total toner amount of BkLk.
(C) is a mode in which transparent toner is used, and is the total amount of toner when the amount of toner is further added by the amount of transparent toner (the amount of transparent toner added to (a)). It can be seen that even if the total toner amount is increased by the amount of the transparent toner, the maximum value of the total toner amount is suppressed to be equal to (b) when the transparent toner is not used.

  With the configuration of this embodiment, it is possible to prevent the color reproduction range from being lowered due to the total amount regulation process while improving the graininess using the transparent toner. Also in this embodiment, the direct correction method can be used for the color correction 505 to directly convert from RGB to CMYBkLk. If the LUT at this time is switched according to the object information and mode information, the same effect can be obtained. Can be obtained. In the case where dark and light toners are used for colors other than black, the same effect can be obtained by similarly controlling the amount of dark and light toner used.

  The present invention supplies a storage medium recording software program codes for realizing the functions of the above-described embodiments to a system or apparatus, and a program stored in the storage medium by a computer (CPU or MPU) of the system or apparatus. This is also achieved by reading and executing the code. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiment.

  As a storage medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an OS (operating system) operating on the computer based on the instruction of the program code. A case where part or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included.

  Further, after the program code read from the storage medium is written into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer, the function expansion is performed based on the instruction of the program code. This includes a case where the CPU or the like provided in the board or the function expansion unit performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

1 shows a configuration of an image forming apparatus according to Embodiment 1 of the present invention. 2 shows a configuration of an image forming apparatus according to Embodiment 2 of the present invention. It is a figure explaining that the color reproduction range of an image becomes narrow by total amount regulation processing. 1 shows a configuration of image processing means of Embodiment 1. The structure of the image processing means of Example 2 is shown. 1 illustrates a configuration of a color correction unit according to a first exemplary embodiment. The structure of the color correction means of Example 2 is shown. The black generation amount corresponding to the use / non-use mode of the transparent toner is shown. The relationship between object information, mode information, and black generation amount is shown. The total toner amount of CMYBk is shown. A separation table for separating the K signal into Bk and Lk is shown. The relationship between object information, mode information, and a separation table is shown. The total toner amount of BkLk is shown.

Explanation of symbols

401 PC
402 Image processing means 403 Command interpretation means 404 Development means 405 Color correction means 406 Total amount restriction means 407 Halftone processing means 408 Transparent plate data generation means 409 Printer

Claims (14)

In an image forming apparatus for forming an image using a color toner containing a colorant and a transparent toner not containing a colorant, an image formation mode using the transparent toner (hereinafter referred to as a first mode) and an image not using the transparent toner In the first mode , the black generation / under color removal (BG / UCR) amount is higher in the middle and high density portions of the image than in the second mode. An image forming apparatus characterized by increasing the total amount of color toner including a colorant.   2. The color toner including the colorant, wherein at least one color is a dark and light toner, and the amount of light toner used in the first mode is smaller than that in the second mode. Image forming apparatus. 3. The image forming apparatus according to claim 2, wherein the amount of the light toner used is reduced in a middle / high density portion of the image. 3. The image forming apparatus according to claim 1, wherein in the first mode, transparent toner is used only for a specific image object. 5. The image forming apparatus according to claim 4 , wherein the specific image object is a photographic object.   An image is formed by adhering the transparent toner only on a whole surface of an image or a portion where a toner dot including a colorant exists so that the transparent toner is positioned on an uppermost surface of a toner layer on a recording medium (paper). The image forming apparatus according to claim 1. In an image forming method of forming an image using a color toner containing a colorant and a transparent toner not containing a colorant, an image formation mode using the transparent toner (hereinafter referred to as a first mode) and an image not using the transparent toner In the first mode , the black generation / under color removal (BG / UCR) amount is higher in the middle and high density portions of the image than in the second mode. An image forming method characterized by increasing the total amount of color toner including a colorant. Of the color toners containing the colorant, at least one color is dark and light toners, wherein in the first mode, according to claim 7, wherein reducing the amount of light toner than the second mode Image forming method. 9. The image forming method according to claim 8, wherein the amount of the light toner used is reduced in a middle / high density portion of the image. 9. The image forming method according to claim 7, wherein transparent toner is used only for a specific image object in the first mode. 11. The image forming method according to claim 10 , wherein the specific image object is a photographic object. An image is formed by adhering the transparent toner only on a whole surface of an image or a portion where a toner dot including a colorant exists so that the transparent toner is positioned on an uppermost surface of a toner layer on a recording medium (paper). The image forming method according to claim 7 . A program for causing a computer to realize the image forming method according to any one of claims 7 to 12 . A computer-readable recording medium on which a program for causing a computer to realize the image forming method according to any one of claims 7 to 12 is recorded.

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