IMAGE FORMING APPARATUS

FIELD OF THE INVENTION AND RELATED ART

The present invention relates to an image forming apparatus, such as a printer, a copying machine, a facsimile machine, or a multi-function machine, of an electrophotographic type.

An image forming apparatus includes a cassette and a manual feeding tray on which sheets are settable, and forms images on various sheets fed from these cassette and manual feeding tray by transferring toner images onto the sheets. There is a case that as the sheet, a sheet subjected to perforation processing (hereinafter, referred to as a perforated sheet) is used in some cases (Japanese Laid-Open Patent Publication (JP-A) No. 2022-71751). Further, conventionally, in order to generate image data for output at a lower gradation than a gradation of inputted image data, an image forming apparatus capable of selectively executing, as half-tone processing, screen processing and error diffusion processing has been proposed (JP-A No. Hei 9-331450).

However, conventionally, there as a liability that an image defect occurs when the toner image is formed on the perforated sheet.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided an image forming apparatus capable of forming an image on a perforated sheet, comprising: an image forming portion configured to form a toner image on a sheet; an image processing portion configured to perform image processing, on image data acquired, which is at least either one of screen processing and error diffusion processing; and a controller configured to control the image processing portion to form the toner image on the basis of the image data processed by the image processing portion, wherein in a case that the sheet on which the toner image is to be formed is the perforated sheet, the image processing portion performs the error diffusion processing on the image data acquired.

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

FIG. 1 is a schematic view showing an image forming apparatus of an embodiment.

FIG. 2 is a control block diagram showing a control constitution of the image forming apparatus.

FIG. 3 is a schematic view showing an operating portion.

FIG. 4 is a schematic view showing a sheet selection screen.

FIG. 5 is a flowchart showing image forming processing in a first embodiment.

FIG. 6 is a schematic view showing a change/non-change selection screen.

FIG. 7 is a schematic view for illustrating a print ratio.

FIG. 8 is a schematic view showing an image in the case where AM screen processing is performed.

FIG. 9 is a schematic view showing an image in the case where error diffusion processing is performed.

FIG. 10 is a flowchart showing image forming processing in a second embodiment.

FIG. 11 is a schematic view showing a perforation position setting screen.

FIG. 12 is a schematic view showing a change range setting screen.

FIG. 13 is a schematic view showing an image in the case where the error diffusion processing is performed in a perforated region and the AM screen processing is performed in a region other than the perforated region.

DESCRIPTION OF THE EMBODIMENTS
First Embodiment
<Image Forming Apparatus>

An image forming apparatus of the present invention will be described using FIG. 1. An image forming apparatus 100 is an electrophotographic full-color printer of a tandem type. The image forming apparatus 100 includes image forming portions Pa, Pb, Pc, and Pd for forming images of yellow, magenta, cyan, and black, respectively. The image forming apparatus 100 forms the toner image on a sheet S on the basis of image data sent from an original reading device 130 connected to, for example, the image forming apparatus 100 or from an external device 1000 such as a personal computer connected to the image forming apparatus 100. As the sheet S, it is possible to cite sheet materials, such as plain paper, thick paper, roughened paper, uneven paper and coated paper.

The original reading device 130 as an original reading portion is provided at an upper portion of the image forming apparatus 100, and includes an image reading portion 131 for reading an image on the sheet S on which the image has already been formed in advance and an original conveying portion 132 for automatically conveying the sheet S to the image reading portion 131. The image reading portion 131 irradiates the sheet S, conveyed onto a plating glass 133, with light by an irradiation portion 131a and receives, by a light receiving portion 131b, the irradiated light reflected from the sheet S, and is capable of reading the image on the sheet S with a dot density determined in advance.

A conveying process of the sheet S in the image forming apparatus 100 will be described. The sheet S is capable of being set in a cassette 10 in a stacked form. Or, the sheet S is capable of being set on a manual feeding tray 17 in the stacked form. The sheet S set in the cassette 10 or on the manual feeding tray 17 is sent in accordance with an image forming timing by a supplying roller 13. The cassette 10 or the manual feeding tray 17 is provided so as to be openable and closable, and a user may be capable of arbitrarily opening and closing the cassette 10 or the manual feeding tray 17.

The sheet S fed by the supplying roller 13 is conveyed toward a registration roller pair 12 provided along a conveying portion 114. Then, the sheet S is subjected to oblique movement correction or timing correction in the registration roller pair 12, and thereafter, is sent to a secondary transfer nip T2. The secondary transfer nip T2 is a transfer nip portion formed by an inner secondary transfer roller 14 and an outer secondary transfer roller 11 (second transfer portion), and the toner image is transferred onto the sheet S in response to application of a secondary transfer voltage to the outer secondary transfer roller 11 as a transfer portion by a power source 90. Incidentally, only one cassette 10 is shown in FIG. 1, but a plurality of cassettes 10 may be provided. The conveying portion 114 conveys the sheet S from the cassette 10 or the manual feeding tray 17 to the secondary transfer nip T2.

In contrast to the sheet S conveying process until the above-described secondary transfer nip T2, an image forming process of the image sent to the secondary transfer nip T2 at a similar timing will be described. First, although the image forming portions will be described, the respective color image forming portions Pa, Pb, Pc and Pd are constituted substantially similar to each other except that colors of toner used in developing devices 1a, 1b, 1c and 1d are yellow (Y), magenta (M), cyan (C), and black (K), respectively, which are different from each other. Therefore, in the following, as a representative, the image forming portion Pd for black will be described, and other image forming portions Pa, Pb and Pc will be omitted from description.

The image forming portion Pd is principally constituted by the developing device 1d as a developing portion, a charging device 2d as a charging portion, a photosensitive drum 3d as a photosensitive member, a photosensitive drum cleaner 4d, an exposure device 5d as an exposure portion, a primary transfer roller 6d, and the like. A surface of a rotating photosensitive drum 3d is electrically charged uniformly in advance by the charging device 2d, and thereafter, an electrostatic latent image is formed by the exposure device 5d driven on the basis of a signal of image information. Then, the electrostatic latent image formed on the photosensitive drum 3d is developed into a toner image with use of a developer by the developing device 1d. Then, the toner image formed on the photosensitive drum 3d is primary-transferred onto an intermediary transfer belt 80 in response to application of a primary transfer voltage to the primary transfer roller 6d disposed while sandwiching the intermediary transfer belt 80 therebetween. Primary transfer residual toner slightly remaining on the photosensitive drum 3d is collected by the photosensitive drum cleaner 4d.

The intermediary transfer belt 80 (intermediary transfer member) as an image bearing member is stretched by the inner secondary transfer roller 14, and stretching rollers 15 and 16, and is driven in an arrow R2 direction in contact with the photosensitive drums 3a to 3d. The stretching roller 16 also functions as a driving roller for driving the intermediary transfer belt 80. The respective color image forming processes performed in parallel by the image forming portions Pa to Pd are carried out at timings each when an associated toner image is superposedly transferred successively onto an upstream toner image primarily transferred onto the intermediary transfer belt 80. As a result, finally, a full-color toner image is formed on the intermediary transfer belt 80 and is conveyed to the secondary nip T2 while being carried on the intermediary transfer belt 80. Secondary transfer residual toner after passing through the secondary transfer nip T2 is removed from the intermediary transfer belt 80 by a belt cleaner 22.

In the above, by the above-described conveying process and the above-described image forming process, in the secondary transfer nip T2, a timing of the sheet S and a timing of the full-color toner image coincide with each other, so that secondary transfer is carried out. Thereafter, the sheet S is conveyed to a fixing device 50, in which heat and pressure are applied to the sheet S, so that the toner image is fixed on the sheet S. The fixing device 50 nips and conveys the sheet S on which the toner image is formed, and applies heat and pressure to the conveyed sheet S, so that the fixing device 50 fixes the toner image on the sheet S. That is, the toner of the toner image formed on the sheet S is melted and mixed by application of heat and pressure, and is fixed as the full-color image on the sheet S. The sheet S on which the toner image is fixed is discharged onto a discharge tray 95 provided outside an apparatus main assembly of the image forming apparatus 100. Or, in the case where another post-processing device (not shown) such as a finisher is connected to the apparatus main assembly of the image forming apparatus 100, the sheet S on which the toner image is fixed is conveyed to the post-processing device. The finisher apparatus performs, for example, punch processing in which the sheet S is perforated, stapling (processing) in which a plurality of sheets S are bundled and stapled, and the like processing.

In the image forming apparatus 100 of the present invention, as the developer, a two-component developer containing the toner and a carrier is used. The toner contains a binder resin, a colorant, and a parting agent. As the binder resin, a known binder resin can be used. For example, it is possible to use resin materials such as a vinyl copolymer represented by a styrene-(meth) acrylic copolymer, a polyester resin, a hybrid resin obtained by chemically bonding a vinyl copolymer and a polyester to each other, an epoxy resin, a styrene-butadiene copolymer, and the like. As the colorant, it is possible to use known colorants for yellow (Y), magenta (M), cyan (C), and black (K), respectively.

As the parting agent, for example, it is possible to cite aliphatic hydrocarbon waxes such as low-molecular weight polyethylene wax, low-molecular weight olefin copolymer wax, microcrystalline wax, Fischer-Tropsch wax, and paraffin wax; oxides of the aliphatic hydrocarbon waxes such as oxidized polyethylene wax; their block copolymers; waxes principally containing fatty acid esters such as carnauba wax and montanic acid ester wax; ester wax which is synthetic reaction product between higher aliphatic acid, such as behenyl behenate or behenyl stearate, and higher alcohol; fatty acid esters a part or all of which is deoxidized, such as deoxidized carnauba wax; and the like.

As shown in FIG. 1, the image forming apparatus 1 includes a controller 101. A control constitution of the image forming apparatus 100 will be described using FIG. 2 while making reference to FIG. 1. Incidentally, to the controller 101, in addition to devices (portions) illustrated in FIG. 2, various devices such as respective portions constituting the image forming apparatus 100, and driving sources (motors and power sources) for driving these portions are connected. However, these devices are not the main object of the present invention herein, and therefore, will be omitted from illustration and description.

The controller 101 includes a CPU (central processing unit) 102, a ROM (read only memory) 103, and a RAM (random access memory) 104, and controls entirety of the image forming apparatus 100. In the ROM 103, various programs such as an image forming job and the like are stored. The controller 101 is capable of acquiring, for example, various data inputted from an operating portion 110, image data sent from an external device 1000 (see FIG. 1), or image data of an image read by the original reading device 130, or the like (hereinafter, these image data are referred to as inputted image data. These data acquired by the controller 101 are stored in the RAM 104. Incidentally, the RAM 104 is capable of temporarily storing a calculation (computation) processing result or the like with execution of the various programs.

The image forming apparatus 100 includes the operating portion 110 (see FIG. 1) including a display portion 111, and the operating portion 110 is connected to the controller 101. The controller 101 is capable of causing the display portion 111 to display various screens presenting the various programs and various data or the like, and receives input of a start of the various programs and input of the various data, and the like, in response to an operation by a user through the operating portion 110. Although described later, the operating portion 110 as an input portion is capable of causing the value to input a position of burrs formed on a perforated sheet S and a range of a perforated region.

When the controller 101 receives a start instruction of an image forming job, the controller 101 executes image forming processing (program) stored in the ROM 103, and controls the image forming portions Pa to Pd for forming an image on the sheet S. An image processing portion 105 subjects the image data, acquired by the controller 101, to half-tone processing (medium tone processing). Here, the user is capable of setting, as a kind of the half-tone processing, AM screen processing or error diffusion processing.

The image processing portion 105 outputs image data for image output after subjecting the input image data to the half-tone processing (this image data for image output is referred to as output image data). On the basis of the output image data, the controller 101 causes the image forming portions Pa to Pd to form the toner images.

The AM screen processing is processing such that a half-tone is expressed by periodical dot arrangement, and includes, for example, dot screen processing, line screen processing, and the like. The dot screen processing expresses shades (gradations) of color by changing a size of dots which are equidistantly arranged. In the dot screen processing, a shape of each of the dot circles and the dots are equidistantly arranged, so that a periodical dot pattern is generated. In the line screen processing, a periodical dot pattern is generated, but different from the dot screen processing, the shades of color are not expressed by a magnitude of the size of the dots, but are expressed by changing a thickness of lines which are equidistantly arranged. In this embodiment, a direction (screen angle) in which the dots in the AM screen processing is determined in advance for each of the colors. For example, the screen angle for yellow (Y) is taken as 0 degrees, and on the basis of the screen angle for yellow, screen angles for cyan (C), black (K), and magenta (M) are set clockwise to 15 degrees, 45 degrees, and 75 degrees, respectively, and thus are different for each color.

The error diffusion processing is processing such that a dot pattern without periodicity is generated. In the error diffusion processing, on the basis of density information on pixels constituting an image of inputted image data, first, a density of one pixel (this pixel is referred to as a noting pixel) is binarized, and an error (difference) between a density after binarization and a density before the binarization is acquired. Then, a value obtained by multiplying the error by a weighing coefficient (this value is referred to as a diffusion value) is acquired, and the diffusion value is added to each of other pixels falling within a predetermined range from the noting pixel. Next, although either one of these other pixels falling within the predetermined range from the noting pixel is subjected to the binarization (this pixel is referred to as a subsequent noting pixel), a density before the binarization in this case is a density to which the diffusion value is added. Thereafter, in the subsequent noting pixel, an error between a density after the binarization and a density before the binarization is acquired, and the diffusion value is added to each of other pixels falling within a predetermined range from the subsequent noting pixel. Thus, the error of the noting pixel is diffused so as to be added to peripheral pixels, whereby there is no periodicity in error distribution degree, and therefore, in the error diffusion processing, the dot pattern without periodicity is generated.

The operating portion 110 as a selecting portion (input portion) will be described using FIG. 3. As shown in FIG. 3, the operating portion 110 includes a display portion 111 such as a liquid crystal monitor, and hardware keys. The display portion 111 may be a touch panel on which the user is capable of performing a touch operation, and is capable of displaying a screen including, as touch-operable software keys, various buttons and switches. At the display portion 111, a “sheet selection screen” (see FIG. 4) and a “change/non-change selection screen” (see FIG. 6), and the like which are described later are displayed.

As the hardware keys, for example, there are a setting key 1102, a power saving key 1103, a hardware key group 1104, a reset key 1105, a stop key 1106, a start key 1107, and the like. The start key 1107 has a function of instructing starts of, for example, reading printing (copying) of an original image and other operations. In the start key 1107, unshown LEDs of two colors of green and red are incorporated, and the start key 1107 indicates that the start of the operation is enabled during turning-on of the green LED, and indicates that the start of the operation is disabled during turning-on of the red LED. The stop key 1106 has a function of once stopping image formation or the like during operation. The hardware key group 1104 includes, for example, numeric keys, a clear key, an authentication key, and the like.

The power saving key 1103 has a function of shifting an operation in a mode of the image forming apparatus 100 from an operation in a normal mode to an operation in a sleep mode in which the image forming apparatus 100 is on standby in power saving or of returning the operation in the mode of the image forming apparatus 100 from the operation in the sleep mode to the operation in the normal mode. That is, the image forming apparatus 100 shifts in operation mode to the sleep mode when the user presses the power saving key 1103 in the operation in the normal mode, and shifts in operation mode to the normal mode when the user presses the power saving key 1103 in the operation in the sleep mode. The setting key 1102 is used when, for example, a setting of a kind of the sheet S or the like is made. The reset key 1105 is used when, for example, the set kind of the sheet S is canceled.

At the display portion 111 of the operating portion 110, the “sheet selection screen” is displayed. The “sheet selection screen” is displayed at the display portion 111, for example, in the case where the user operates a sheet kind selection button from a “menu screen” (not shown) displayed at the display portion 111 or in the case where the user opens the cassette 10 or the manual feeding tray 17. The “sheet selection screen” will be described using FIG. 4.

As shown in FIG. 4, in the “sheet selection screen”, a dialog box 1201 on which kinds of the sheet S which are stored in advance in the ROM 103 (see FIG. 2) and on which the image is capable of being formed by the image forming apparatus 100 are selectable is displayed. Here, “plain paper”, “thick paper”, and “perforated paper” (perforated sheet) are displayed, but the user is capable of displaying other kinds in which the image is capable of being formed, by scrolling a screen displayed in the dialog box 1201. The user is capable of selecting the kind of the sheet S from a plurality of kinds displayed in the dialog box 1201. The selected kind of the sheet S is determined by operating a determination button 1203.

Next, image forming processing of the image forming apparatus 100 will be described using FIGS. 5 to 9 while making reference to FIG. 2. The image forming processing is started by receiving a start instruction of the image forming job by the controller 101. Incidentally, in the following, the case where before the user starts the image forming job, from the operating portion 110, the AM screen processing has already been set as the half-tone processing will be described as an example.

As shown in FIG. 5, when the controller 101 receives the start instruction of the image forming job, the controller 101 discriminates whether or not the kind of the sheet S is the perforated sheet S (S1). The controller 101 discriminates whether or not the kind of the sheet S is the perforated sheet S, depending on whether or not the kind of the sheet S selected by the user from the above-described “sheet selection screen” (see FIG. 4) is the perforated sheet S. Incidentally, when a constitution in which the image forming job includes sheet information on the sheet S is employed, on the basis of the sheet information of the image forming job, the controller 101 may discriminate whether or not the kind of the sheet S is the perforated sheet S.

In the case where the kind of the sheet S is not the perforated sheet S (No of S1), the controller 101 causes the image processing portion 105 to subject the inputted image data to the AM screen processing set in advance by the user, and causes the image forming portions Pa to Pd to form the image on the basis of output image data (S2). The output image data are used when the photosensitive drums 3a to 3d are exposed to light by the exposure devices 5a to 5d. After the photosensitive drums 3a to 3d are exposed to light on the basis of the output image data by the exposure devices 5a to 5d, the controller 101 causes the developing devices 1a to 1d to develop electrostatic latent images. Thereafter, the toner images formed on the photosensitive drums 3a to 3d are transferred onto the sheet S by way of the intermediary transfer belt 80.

After the image is formed on the sheet S, the controller 101 discriminates whether or not the image forming job is ended (S5). In the case where the images are formed on sheets S in number designated by the user, the controller 101 discriminates that the image forming job is ended (Yes of S5), the controller 101 ends the image forming processing. In the case where the image forming job is not ended (No of S5), the controller 101 causes the processing to return to the processing of the step S1 in order to carry out formation of an image on a subsequent sheet S, and causes the image forming apparatus 100 to repeat the image forming processing until the images are formed on sheets S in a designated number of sheets S.

On the other hand, in the case where the kind of the sheet S is the perforated sheet S (Yes of S1), the controller 101 discriminates whether or not a half-tone processing changing function is effective (S3). Discrimination as to whether or not the half-tone processing changing function is effective is made on the basis of selection by the user using a “change/non-change selection screen” (see FIG. 6) described later.

In the case where the half-tone processing changing function is effective (Yes of S3), for controller 101 changes the half-tone processing from the AM screen processing set in advance by the user to the error diffusion processing (S4). The controller 101 causes the image processing portion 105 to perform the error diffusion processing on the inputted image data and causes the image forming portions Pa to Pd to form an image (S2).

In the case where the half-tone processing changing function is not effective (No of S3), the controller 101 does not change the AM screen processing to the error diffusion processing, and causes the image forming portions Pa to Pd to perform the AM screen processing, set in advance by the user, on the inputted image data, and then causes the image forming portions Pa to Pd to form an image on the basis of output image data (S2).

Next, the above-described “change/non-change selection screen” will be described using FIG. 6. The “change/non-change selection screen” is displayed at the display portion 111 of the operating portion 110 as shown in FIG. 6 in the case where the “perforated paper” is selected as the kind of the sheet S in the “sheet selection screen” (see FIG. 4). In FIG. 6, as the “change/non-change selection screen”, a selection button display portion 1202 is displayed in a pop-up manner.

At the selection button display portion 1202, in order to make execution/non-execution of the half-tone processing changing function (mode) selectable by the user, an “EFF” (effective) button for making the half-tone processing changing function effective and a “NON-EFF” (non-effective) button for making the half-tone processing changing function non-effective are displayed. The user operates either one of the “EFF” button and the “NON-EFF” button at the selection button display portion 1202 and thus is capable of selecting that the half-tone processing changing function is made effective or non-effective. Thereafter, in response to the operation of a “DETERMINE” button 1203 by the user, the half-tone processing changing function is determined to either one of “EFF (execution)” or “NON-EFF (non-execution)”.

The determined kind of the sheet S and the determined execution or non-execution of the half-tone processing changing function are stored in the RAM 104 (see FIG. 2). During execution of the image forming job, the controller 101 makes reference to the kind of the sheet S and the execution or non-execution of the half-tone processing changing function, which are stored in the RAM 104.

As has already be described above, when the toner image is transferred onto the perforated sheet S, an image defect such that unintended electric discharge occurs in the perforated region where the burrs generate and the toner is transferred onto an unintended portion and that a shape and an arrangement of dots forming the image are disordered and thus a color tint of the toner image changes can arise.

Particularly, in the case where the AM screen processing is performed, the image defect due to the burrs of the sheet was liable to occur in the perforated region. On the other hand, the image forming apparatus 100 is capable of suppressing the image defect due to the burrs of the perforated sheet S by changing the half-tone processing on the image formed on the perforated sheet S from the amount screen processing to the error diffusion processing (see S4 of FIG. 5). A table 1 shows a result of evaluation of occurrence or non-occurrence of the image defect in the perforated region due to the burrs of the perforated sheet S in the case where the AM screen processing is performed as the half-tone processing and in the case where the error diffusion processing is performed as the half-tone processing.

TABLE 1

HTP*¹
AM SCREEN
ERROR DIFFUSION

IMAGE DEFECT
OCCURRED
NOT OCCURRED

*¹“HTP” is the half-tone processing.

The occurrence or non-occurrence of the image defect in the table 1 was evaluated in the following manner. The perforated sheet S was subjected to the “AM SCREEN” processing and the “ERROR DIFFUSION” processing which were shown in a row of “HTP*¹” (half-tone processing) in the table 1 so that an image was formed with the K toner so that a print ratio becomes 30%.

The print ratio mentioned in this case is a ratio (area ratio) of an area in which the toner is present in a minute region 201 of an image forming region 200 as shown in FIG. 7 on the basis of the print ratio of “100%” taken when the toner is present in a whole area of the minute region 201 of the image forming region 200.

The user discriminated whether or not the image defect occurred by checking the toner image, by eye observation, formed in each of the case where the AM screen processing is performed and the case where the error diffusion processing is performed.

As shown in the table 1, in the case where the amount screen processing was performed, the image defect due to the burrs of the sheet S occurred. On the other hand, in the case where the error diffusion processing was performed, the image defect due to the burrs of the sheet S did not occur. Here, in FIG. 8, an image in the case where the AM screen processing was performed is shown, and in FIG. 9, an image in the case where the error diffusion processing was performed is shown.

As shown in FIG. 8, in the case where the AM screen processing was performed, the image is formed by arranging dots of the K toner linearly. However, in the perforated region including perforations 260, as regards a part of the dots, a shape thereof changes. Or, disordering such that the dots are not linearly arranged is observed (see minute region 211). At this time, a phenomenon occurred in the image formed in the image forming region 200 is as follows. The perforated region where the burrs generate is a portion where a thickness of the sheet S locally changes or the sheet S is perforated. Then, when the toner image is transferred onto the perforated sheet S in the secondary transfer nip T2 (see FIG. 1), unintended local electric discharge can generate in the perforated region. By this unintended electric discharge, the toner is transferred onto an unintended portion, so that the shape and the arrangement of the dots are disordered. Therefore, the toner image formed in the perforated region seems, compared with the toner image formed in another region, different in color tint, so that this appears as the image defect.

On the other hand, as shown in FIG. 9, in the case where the error diffusion processing is performed, the image is formed in a state in which an arrangement and a size of the dots of the respective colors are different from each other, (see minute region 222). When a random dot arrangement pattern is formed, even in the case where the shape and arrangement of the dots are disordered due to the above-described unintended local electric discharge, the disordering of the shape and the arrangement of the dots does not readily appear as a difference from a peripheral portion. Therefore, even when the toner image formed in the perforated region and the toner image formed in a region other than the perforated region are compared with each other, the color tint is unchanged.

As described above in the image forming apparatus 100 of this embodiment, in the case where the kind of the sheet S is the perforated sheet S, the half-tone processing can be changed from the AM screen processing set in advance by the user to the error diffusion processing. Thus, in the case where the image forming apparatus 100 of this embodiment forms the image on the perforated sheet S, the image forming apparatus 100 is capable of reducing a degree of appearance of the disordering of the local dot shape and arrangement, so that it is possible to suppress the occurrence of the image defect due to the burrs of the sheet S.

Incidentally, in the image forming apparatus 100, the user is made capable of arbitrarily selecting change or non-change of half-tone processing in the “change/non-change selection screen” (see FIG. 6). This is because depending on a use environment, a reference for color design, and the like of the user, a possibility that the output image data by the half-tone processing after the change is not optimized is considered. If so, the change or non-change of the half-tone processing may desirably be selectable independently in each condition. In an unexpected situation including malfunction of the image forming apparatus 100, in the case where the user discriminates that the half-tone processing changing function does not normally operate, it is desirable that the half-tone processing changing function can be set to “non-effective”. Therefore, depending on a use status and a product of individual users, selection that the half-tone processing changing function is made effective or non-effective can be made, so that it is possible to provide a higher-quality product.

Second Embodiment

In the above-described embodiment, irrespective of whether or not the region is the perforated region or the region other than the perforated region, in the whole area of the perforated sheet S, the half-tone processing is made changeable from the AM screen processing to the error diffusion processing, but the present invention is not limited thereto. For example, only for the toner image formed in the perforated region, the half-tone processing may also be made changeable from the AM screen processing to the error diffusion processing toner.

Image forming processing of the image forming apparatus 100 of a second embodiment capable of realizing such a change will be described using FIGS. 10 to 13 while making reference to FIG. 2. The image forming processing is started by receiving a start instruction of the image forming job by the controller 101.

Incidentally, in this embodiment, the case where the user has already set the AM screen processing as the half-tone processing from the operating portion 110 before the image forming job. Further, in the image forming processing shown in FIG. 10, processes similar to those in the image forming processing shown in FIG. 5 will be briefly described or omitted from description.

As shown in FIG. 10, when the controller 101 receives the start instruction of the image forming job, the controller 101 discriminates whether or not the kind of the sheet S is the perforated sheet S (S1). The controller 101 discriminates whether or not the kind of the sheet S is the perforated sheet S, depending on whether or not the kind of the sheet S selected by the user from the above-described “sheet selection screen” (see FIG. 4) is the perforated sheet S. In the case where the kind of the sheet S is not the perforated sheet (No of S11) S, the controller 101 causes the image processing portion 105 to subject the inputted image data to the AM screen processing set in advance by the user, and causes the image forming portions Pa to Pd to form the image on the basis of output image data (S12).

After the image is formed on the sheet S, the controller 101 discriminates whether or not the image forming job is ended (S21). In the case where the images are formed on sheets S in number designated by the user, the controller 101 discriminates that the image forming job is ended (Yes of S21), the controller 101 ends the image forming processing. In the case where the image forming job is not ended (No of S21), the controller 101 causes the processing to return to the processing of the step S11 in order to carry out formation of an image on a subsequent sheet S, and causes the image forming apparatus 100 to repeat the image forming processing until the images are formed on sheets S in a designated number of sheets S.

On the other hand, in the case where the kind of the sheet S is the perforated sheet S (Yes of S11), the controller 101 sets positioned information in a processing region (S13). A setting of the positional information of the perforated region is made on the basis of a coordinate setting by the user with use of a “perforation position setting screen) (see FIG. 11) described later. After the positional information of the perforated region is set, on the basis of the inputted image data and the set positional information, the controller 101 discriminates whether or not the image to be formed in the perforated region is an image of the monochromatic K toner (S14). In the case where the image formed in the perforated region is not the image of the monochromatic K toner (No of S14), the controller 101 causes the image processing portion 105 to perform the AM screen processing, set in advance by the user, on a whole area of the perforated sheet S irrespective of the perforated region or the region other than the perforated region, and causes the image forming portions Pa to Pd to form the image on the basis of the output image data (S12).

In the case where the image formed in the perforated region is present (Yes of S14), the controller 101 discriminates whether or not a half-tone processing changing range is only the perforated region (S15). On the basis of a change range setting by the user with use of a “change range setting screen (see FIG. 12) described later, the controller 101 discriminates whether or not the range in which the half-tone processing is changed is only the perforated region.

In the case where the range in which the half-tone processing is changed is the whole area of the perforated sheet S, not only the perforated region (No of S15), the controller 101 discriminates whether or not the half-tone processing changing function is effective (S16). Discrimination as to whether or not the half-tone processing changing function is effective is made on the basis of selection by the user using a selection button display portion 1202 (see FIG. 12) displayed on a “change range setting screen” described later.

In the case where the half-tone processing changing function is effective (Yes of S16), with respect to the whole area of the perforated sheet S, the controller 101 changes the half-tone processing from the AM screen processing set in advance by the user to the error diffusion processing (S17). The controller 101 causes the image processing portion 105 to perform the error diffusion processing on the inputted image data and causes the image forming portions Pa to Pd to form the image on the basis of the output image data (S12). In the case where the half-tone processing changing function is not effective (No of S16), with respect to the whole area of the perforated sheet S, the controller 101 causes the image processing portion 105 to perform the AM screen processing set in advance by the user on the inputted image data without changing the half-tone processing to the error diffusion processing and causes the image forming portions Pa to Pd to form the image on the basis of the output image data (S12).

On the other hand, in the case where the range in which the half-tone processing is changed is only the perforated region (Yes of S15), the controller 101 sets a range of the perforated region (S18). The setting of the range of the perforated region is made by a user setting using a region width setting box 1209 (see FIG. 12) displayed on the “change range setting screen” described later. Thereafter, the controller 101 discriminates whether or not the half-tone processing changing function is effective (S19).

In the case where the half-tone processing changing function is effective (Yes of S19), for the perforated region, the controller 101 changes the half-tone processing from the AM screen processing set in advance by the user to the error diffusion processing (S20). For the inputted image data on the perforated region, the controller 101 causes the image processing portion 105 to perform the error diffusion processing, and for the inputted image data on a region other than the perforated region, the controller 101 causes the image processing portion 105 to perform the AM screen processing, and then causes the image forming portions Pa to Pd to form the image on the basis of the output image data (S12). On the basis of the position of the perforations, the controller 101 is capable of specifying the inputted image data on the perforated region and the inputted image data on the region other than the perforated region.

In the case where the half-tone processing changing function is not effective (No of S19), irrespective of whether the region is the perforated region or the region other than the perforated region, the controller 101 causes the image processing portion 105 to perform the AM screen processing on the inputted image data for the whole area of the sheet S without changing the half-tone processing to the error diffusion processing and causes the image forming portions Pa to Pd to form the image on the basis of the output image data (S12).

On the display portion 111, a “perforation position setting screen” is displayed (S13 of FIG. 10). The “perforation position setting screen” is displayed at the display portion 111 in the case where for example, the user operates a predetermined setting start button from a “menu screen” (not shown) displayed at the display portion 111. The “perforation position setting screen” will be described using FIG. 11.

As shown in FIG. 11, on the “perforation position setting screen”, a dialog box 1204 from which a perforation position acquiring method for acquiring a coordinate position of the perforations of the perforated sheet S is selectable is shown. In this embodiment, as the perforation position acquiring method, an example in which “SCAN” and “INPUT” which are stored in advance in the ROM 103 is shown. The “SCAN” is a method in which a position of a perforation (burr) of the perforated sheet S is read by the original reading device 130 (see FIG. 1).

In the case where the user selects the “SCAN as the perforation position acquiring method, the user places the perforated sheet S, on which the image is not formed, on the original reading device 130 (see FIG. 1), and then presses down a scan start button 1205. Then, the original reading device 130 reads the position of the perforation (burr) on the perforated sheet S, and the read position (start coordinate and end coordinate) of the perforation is displayed on a position coordinate setting box 1206. In an example shown in FIG. 11, as displayed on a pre-view screen, two perforations are formed on the perforated sheet S, so that a start coordinate and an end coordinate are displayed for each of a “PRFRTN (perforation) 1” and a “PRFRTN 2”. A “DETERMINE” button 1207 is pressed down by the user, so that the start coordinate and the end coordinate of each perforation are stored in the RAM 104 (see FIG. 2). Incidentally, as desired, the user may be capable of changing the start coordinate and the end coordinate of each perforation displayed on the position coordinate setting box 1206 by operating numerical keys of a hardware key groups 1104.

The “INPUT” is a method in which the user directly inputs the start coordinate and the end coordinate of each perforation of the perforated sheet S without reading the perforated sheet S by the original reading device 130. The user selects the “INPUT” on the dialog box 1204, and then operates numerical keys of the hardware key group 1104 after designating an arbitrary input column of the position coordinate setting box 1206, so that the user is capable of inputting the start coordinate and the end coordinate of each perforation of the perforated sheet S. Then, the “DETERMINE” button 1207 is pressed down by the user, so that the start coordinate and the end coordinate of each perforation inputted by the user are stored in the RAM 104 (see FIG. 2). Incidentally, the above-described perforation position acquiring method is an example, and may also be not necessarily be executed in the above-described manner.

Next, the “change range setting screen” (S15 of FIG. 10) will be described using FIG. 12. The “change range setting screen” is displayed at the display portion 111 in the case where, for example, the user operates a half-tone processing change range setting button from a “menu screen” (not shown) displayed at the display portion 111.

As shown in FIG. 12, on the “change range setting screen”, a dialog box 1208 from which a change range in which the half-tone processing is changed is selectable is displayed. In this embodiment, a “WHOLE AREA” in which the whole area of the perforated sheet S is the change range and a “PERFORATION REGION” in which the perforated region of the perforated sheet S is the change range are displayed. The user is capable of setting the change range of the half-tone processing by touching either one of items displayed on the dialog box 1208.

On the “change range setting screen”, a region width setting box 1209 is displayed. The user is capable of setting a width (mm) of the perforated region in the region width setting box 1209 by operating numerical keys of a hardware key groups 1104. For example, the width of the perforated region (perforation region width) is set to “10 mm”. Incidentally, as described above, the toner constituting the perforated region is transferred onto an unintended portion print a shape change of the sheet by being subjected to perforation processing, so that the shape and arrangement of dots are disordered. For that reason, a width of a region to which the screen processing is changed to the error diffusion, i.e., a width of the perforated region may desirably be set to a value larger than a value of a width of a region in which the shape and arrangement of dots are disordered.

Further, on the “change range setting screen”, the above-described selection button display portion 1202 is displayed. The user is capable of selecting that a half-tone processing changing function is made effective or non-effective, by operating either one of an “EFF” button or a “NON-EFF” button of the selection button display portion 1202. Then, the user presses down the “DETERMINE” button 1210, so that a change range of a half-tone processing, the perforation region width, execution or non-execution of the half-tone changing function are stored in the RAM 104 (see FIG. 2).

As has already been described above, when the toner image is transferred onto the perforated sheet S, the image defect such that the unintended electric discharge generates in the perforated region in which the burrs generate and the toner is transferred onto the unintended portion, and thus the shape and the arrangement of the dots forming the image are disordered and the color tint of the toner image changes can arise.

Therefore, in this embodiment, the half-tone processing for the image to be formed in the perforated region in which the burrs generate is changed from the AM screen processing to the error diffusion processing (see S20 of FIG. 10), so that it is possible to suppress the image defect due to the burrs of the sheet.

A table 2 shows a result of evaluation of occurrence or non-occurrence of the image defect due to the burrs of the sheet S in the case where the AM screen processing is performed irrespective of the perforated region or the region other than the perforated region and in the case where the error diffusion processing is performed in the perforated region and the AM screen processing is performed in the region other than the perforated region.

TABLE 2

PR:ED*²

HTP*¹
AM SCREEN
ROTPR:AMS*³

IMAGE DETECT
OCCURRED
NOT OCCURRED

*¹“HTP” is the half-tone processing.

*²“PR:ED” is “perforated region:error diffusion”.

*³“ROTPR:AMS” is “region other than perforated region:AM screen”.

The occurrence or non-occurrence of the image defect in the table 2 was evaluated in the following manner. First, a toner image was formed on the perforated sheet S on the basis of predetermined image information. The predetermined image information in this case is image information using processing indicated in the “HTP*¹” (half-tone processing) row in the table 2 so that a print ratio becomes 30 in the case of the monochromatic K toner. Incidentally, the print ratio mentioned in this case is a ratio (areal ratio) of an area in which the toner is present in a minute region 201 of an image forming region 200 as shown in FIG. 7 on the basis of the print ratio of “100%” taken when the toner is present in a whole area of the minute region 201 of the image forming region 200.

The user discriminated whether or not the image defect occurred by checking the toner image, formed on the basis of each of output image data outputted after being subjected to the half-tone processing, by eye observation.

As shown in table 2, in the case where the AM screen processing was performed irrespective of the perforated region or the region other than the perforated region, the image defect due to the burrs of the sheet S occurred. On the other hand, in the case where the error diffusion processing was performed in the perforated region and the AM screen processing was performed in the region other than the perforated region, the image defect due to the burrs of the sheet S was suppressed.

In FIG. 13, images formed on the basis of the output image data outputted by being subjected to the error diffusion processing in the perforated region and being subjected to the amount screen processing in the region other than the perforated region. A width of a perforated region 265 set on the basis of perforations 260 “10 mm” for example.

As shown in FIG. 13, in the region other than the perforated region 265 subjected to the AM screen processing, dots of the K toner are linearly arranged, whereby the image is formed (see minute region 250). In the region other than the perforated region 265, the unintended electric discharge does not generate, so that the toner is not transferred onto the unintended portion. That is, the shape and the arrangement of the dots forming the image are not disordered, so that the image defect such as a change in color tint of the toner image does not occur.

On the other hand, in the perforated region 265 subjected to the error diffusion processing, dots of the K toner are randomly arranged, whereby the image is formed (see minute region 251). In the perforated region 265, as described above, the unintended local electric discharge generates. However, the half-tone processing on the image forming the perforated region 265 is changed from the AM screen processing to the error diffusion processing, so that even when the shape and the arrangement of the dots are disordered with the unintended electric discharge, it becomes difficult to recognize whether or not the disordering occurred.

Thus, in the case where the kind of the sheet S is the perforated sheet S, for the perforated region, the half-tone processing can be changed from the screen processing set in advance by the user to the error diffusion processing, so that the image formation is carried out on the basis of the output image data outputted after the error diffusion processing is performed. By this, in the case where the image is formed on the perforated sheet S, a degree of appearance of the local disordering of the shape and the arrangement of the dots can be reduced, so that the occurrence of the image defect due to the burrs of the sheet can be suppressed.

Incidentally, in the above-described second embodiment, in the case where the half-tone processing changing function is effective (Yes of S19), the controller 101 causes the image processing portion 105 to perform the error diffusion processing on the inputted image data in the perforated region 265 and to perform the AM screen processing on the inputted image data in the region other than the perforated region, but the present invention is not limited thereto. For example, the controller 101 may also change an object on which the half-tone processing is changed from the AM screen processing to the error diffusion processing is not limited to the inputted image data in the perforated region 265 but may also be the inputted image data on entirety of a single image formed in a range including the perforated region 265.

Other Specific Embodiments

Incidentally, in the above-described first and second embodiments, the case where the controller 101 includes the image processing portion 105 was described as an example, but the present invention is not limited thereto. For example, as shown in FIG. 1, a constitution in which an information processing apparatus 101A is connected to the image forming apparatus 100 so as to be capable of transmitting and receiving data therebetween, and in which the information processing apparatus 101A includes an image processing portion 105A for performing the AM screen processing or the error diffusion processing may be employed. In the case of this constitution, an external device 1000A is connected to the information processing apparatus 101A so as to be capable of transmitting and receiving data therebetween, so that the information processing apparatus 101A receives image data (inputted image data) sent from the external device 1000A. The information processing apparatus 101A causes the image processing portion 105A to subject the inputted image data to the half-tone processing and then sends the image data as the output image data to the image forming apparatus 100. The controller 101 of the image forming apparatus 100 does not subject the output image data, received from the information processing apparatus 101A to half-tone processing and then causes the image forming portions Pa to Pd to form an image on the basis of the outputted image data received from the information processing apparatus 101A. At that time, the controller 101 sends, to the information processing apparatus whenever necessary, for example, the kind of the sheet S, execution or non-execution of the half-tone processing changing function, the change range of the half-tone processing, the width of the perforated region, the position of perforations, and the like, which are inputted by operation of the operating portion 110 by the user. On the basis of these pieces of information, the information processing apparatus 101A is capable of subjecting the perforated sheet S to the half-tone processing on the inputted image data by the image processing portion 105A after switching the AM screen processing to the error diffusion processing as described above.

Incidentally, in the above-described first and second embodiments, the case where before the image forming job is started, the user has already set the AM screen processing as the half-tone processing from the operating portion 110 was described as an example, but the present invention is not limited thereto. The case where the user has already set FM screen processing as the half-tone processing may also be employed. In this case, when the half-tone processing changing function is effective, the half-tone processing is changed from the FM screen processing to the error diffusion processing.

Incidentally, in the above-described first and second embodiments, the image forming apparatus having the constitution in which the toner images of the respective colors are primary-transferred from the photosensitive drums 3a to 3d for the respective colors onto the intermediary transfer belt 80, and then composite toner images of the respective colors are secondary-transferred collectively on the sheet S was described, but the present invention is not limited thereto. For example, the image forming apparatus may also be an image forming apparatus of a direct transfer type in which toner images on photosensitive drums are directly transferred onto a sheet, conveyed to a conveyance belt forming a nip between itself and each of the photosensitive drums, under application of a transfer roller disposed opposed to the associated one of the photosensitive drums while nipping the conveyance belt between the photosensitive drum and the transfer roller. Further, the image forming apparatus may also be an image forming apparatus (monochromatic machine) capable of forming a monochromatic (black) toner image.

OTHER EMBODIMENTS

Embodiments of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.

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.

This application claims the benefit of Japanese Patent Application No. 2023-098588 filed on Jun. 15, 2023, which is hereby incorporated by reference herein in its entirety.

IMAGE FORMING APPARATUS

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