Image forming apparatus and image forming method

Abstract

To provide an image forming apparatus capable of alleviating a tailing phenomenon.SOLUTION: An image forming apparatus includes an acquisition unit configured to acquire image data indicating densities of a plurality of pixels, and a control unit configured to execute a process of printing using a sublimation-type thermal transfer method by two or more scans, wherein the control unit executes, in each scan of the two or more scans, a process of printing, among the plurality of pixels, a pixel having a density in a range satisfying a condition for the each scan.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an image forming apparatus and an image forming method. [Background technology]

[0002] Patent Document 1 discloses a dye-sublimation thermal printer that controls the gradation level by controlling the energization time of the heat-generating resistor elements, and reduces the voltage supplied to the heat-generating resistor elements midway through printing one line. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-192757 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology disclosed in Patent Document 1 reduces the voltage supplied to the heating resistor element midway through printing one line, thereby preventing the occurrence of tailing, which results in blurred image quality due to printing at a temperature different from the ideal temperature. However, with the technology disclosed in Patent Document 1, when printing a region with relatively low pixel density after printing a region with relatively high pixel density and wide, the temperature of the heating resistor element may not drop to the ideal temperature. In this case, with the technology disclosed in Patent Document 1, tailing may occur at the boundary between the region with relatively high pixel density and wide and the region with relatively low pixel density. Therefore, one aspect of the present disclosure aims to provide an image forming apparatus and image forming method that can mitigate the tailing phenomenon. [Means for solving the problem]

[0005] An image forming apparatus according to one embodiment of the present disclosure includes an acquisition unit that acquires image data indicating the density of a plurality of pixels, and a control unit that executes a process of printing using a dye-sublimation thermal transfer method by performing two or more scans, and in each of the two or more scans, the control unit executes a process of printing pixels of the plurality of pixels having a density within a range that satisfies the conditions for each scan.

[0006] An image forming method according to one embodiment of the present disclosure includes a step of acquiring image data indicating the density of a plurality of pixels, and a step of performing a printing process using a dye-sublimation thermal transfer method by performing two or more scans, and in the step of performing the printing process, a process is performed in which, in each of the two or more scans, pixels of the plurality of pixels having a density within a range that satisfies the conditions for each scan are printed. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an example of the structure of an image forming apparatus. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of an ink ribbon. [Figure 3] FIG. 1 is a block diagram showing an example of a configuration of an image forming apparatus. [Figure 4] 5 is a flowchart illustrating an example of an operation of the image forming apparatus according to the first embodiment. [Figure 5A] 10 is a graph showing pixel densities along the printing direction indicated by image data. [Figure 5B] 5B is a diagram showing an example of the temperature of the thermal head when printing is performed in one scan for image data showing the density illustrated in FIG. 5A, and an example of the printed image. FIG. [Figure 5C] 5B is a diagram showing another example of the temperature of the thermal head when printing is performed in one scan for image data showing the density illustrated in FIG. 5A, and an example of the printed image. FIG. [Figure 6A] 5B is a diagram showing an example of the density of a pixel region having a relatively low density in the first scan in the image data showing the density illustrated in FIG. 5A, and an example of a printed image. FIG. [Figure 6B] 5B is a diagram showing an example of the density of a pixel region having a relatively low density in the second scan in the image data showing the density illustrated in FIG. 5A, and an example of a printed image. FIG. [Figure 7] 1 is a graph showing an image and the density of pixels along the printing direction within the image. [Figure 8] 8 is a diagram showing an example of an image in which a first pixel region made up of pixels having a density equal to or lower than the threshold value shown in FIG. 7 is printed, out of the image shown in FIG. [Figure 9] 8 is a diagram showing an example of an image in which a second pixel region made up of pixels having a density exceeding the threshold value shown in FIG. 7 is printed, out of the images shown in FIG. [Figure 10] 10 is a flowchart illustrating an example of an operation of an image forming apparatus according to a third embodiment. [Figure 11] 8 is a graph showing an example of the amount of density change in the printing direction illustrated in the upper diagram of FIG. 7 for the image illustrated in the upper diagram of FIG. 7. [Figure 12] 8 is a graph showing an example of the density change amount of pixels printed in the forward printing direction and the density change amount of pixels printed in the backward printing direction for the image illustrated in the upper diagram of FIG. 7. [Figure 13] FIG. 8 is a diagram showing an example of an image printed by scanning on the outward path, out of the images shown in the upper diagram of FIG. 7. [Figure 14] FIG. 8 is a diagram showing an example of an image printed by a backward scan, out of the images shown in the upper diagram of FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0008] (First embodiment) The first embodiment will be described with reference to Figures 1 to 9. In the drawings, the same or similar elements are given the same reference numerals, and redundant explanations will be omitted.

[0009] 1 is a diagram showing an example of the structure of an image forming apparatus 100. The image forming apparatus 100 includes a thermal head 101 and an ink ribbon .

[0010] The image forming apparatus 100 prints using a dye-sublimation thermal transfer method with two or more scans. The dye-sublimation thermal transfer method is a method in which a heated thermal head 101 is pressed against an ink ribbon 102 to sublimate the ink and adhere it to a printing medium 103.

[0011] The thermal head 101 is configured to include heating resistor elements arranged along the length of one image in the printing direction. The ink ribbon 102 is formed by applying ink of multiple colors. The multiple inks applied to the ink ribbon 102 are color materials that are sublimated by heat.

[0012] The thermal head 101 uses heat generated by the current flowing through the heating resistor elements to sublimate the ink of each color applied to the ink ribbon 102 and transfer it to the printing medium 103. In Figure 1, roll paper is shown as an example of the printing medium 103, but the printing medium 103 may also be sheet paper.

[0013] 2 is a diagram showing an example of the configuration of the ink ribbon 102. The ink ribbon 102 is configured by connecting four surfaces, each corresponding to one image, including a surface coated with an overcoat (OC), a surface coated with a cyan (C) coloring material, a surface coated with a magenta (M) coloring material, and a surface coated with a yellow (Y) coloring material. By applying the overcoat (OC) on top of the image coated with the cyan (C), magenta (M), and yellow (Y) coloring materials, gloss and strength are improved.

[0014] 3 is a block diagram showing an example of the configuration of the image forming apparatus 100. The image forming apparatus 100 includes a storage unit 301, an acquisition unit 302, an image forming unit 303, a conveyance unit 304, an output unit 305, and a control unit 306.

[0015] The storage unit 301 is a recording medium capable of recording various data, programs, etc. The storage unit 301 is configured by, for example, a hard disk drive (HDD), a solid state drive (SSD), a semiconductor memory, etc.

[0016] The acquiring unit 302 acquires image data 311. The image data 311 indicates the density of a plurality of pixels. For example, the acquiring unit 302 acquires the image data 311 by receiving the image data 311 transmitted from a terminal device (not shown) connected to the image forming apparatus 100 via a network.

[0017] The image forming unit 303 prints an image based on the image data 311 onto the printing medium 103. The image forming unit 303 is realized by the thermal head 101, the ink ribbon 102, and the like.

[0018] The transport unit 304 transports the print medium 103 on which an image based on the image data 311 is printed. The transport unit 304 is configured with rollers and the like.

[0019] The output unit 305 outputs the printing medium 103 on which an image based on the image data 311 has been formed from a paper discharge outlet.

[0020] The control unit 306 executes various processes in accordance with the programs stored in the storage unit 301. For example, the control unit 306 is configured by a processor such as a CPU (Central Processing Unit).

[0021] The control unit 306 executes a process of printing using a dye-sublimation thermal transfer method by two or more scans. Specifically, the control unit 306 executes a process of printing pixels having densities within a range that satisfies the conditions for each scan, out of a plurality of pixels having densities indicated by the image data 311, in each of the two or more scans.

[0022] FIG. 4 is a flowchart showing an example of the operation of the image forming apparatus 100 according to this embodiment.

[0023] In step S 401 , the acquisition unit 302 acquires the image data 311 .

[0024] In step S402, the control unit 306 selects a first pixel region made up of pixels with densities equal to or less than a threshold value from among the densities of the plurality of pixels indicated by the image data 311.

[0025] In step S403, the control unit 306 selects a second pixel region made up of pixels with densities exceeding a threshold value from among the densities of the plurality of pixels indicated by the image data 311.

[0026] In step S404, the control unit 306 prints the first pixel region selected in step S402 in the first scan of two or more scans. That is, the condition for the first scan of two or more scans is that the density is equal to or less than a threshold value. For example, the first scan is the first scan. In the first scan, the control unit 306 heats the heating resistor elements of the thermal head 101 according to the density of each pixel included in the first pixel region, thereby adjusting the temperature of the thermal head 101.

[0027] In step S405, the control unit 306 prints the second pixel region selected in step S403 in the second scan of the two or more scans. That is, the condition for the second scan, which is performed after the first scan of the two or more scans, is that the density exceeds the threshold. For example, the second scan is the second scan. In the second scan, the control unit 306 adjusts the temperature of the thermal head 101 to within a temperature range exceeding the threshold, depending on the density of each pixel included in the second pixel region.

[0028] Through the processing of steps S404 and S405, image forming apparatus 100 according to this embodiment generates an image with a density equal to or lower than the threshold value in the first scan, and then generates an image with a density exceeding the threshold value in the second scan. That is, image forming apparatus 100 according to this embodiment prints a pixel area with a relatively low density, and then prints a pixel area with a relatively high density. Note that the condition for the first scan may be a density exceeding the threshold value, and the condition for the second scan may be a density equal to or lower than the threshold value. That is, the condition for one of the first and second scans is a density equal to or lower than the threshold value, and the condition for the other of the first and second scans is a density exceeding the threshold value.

[0029] As described above, the image forming apparatus 100 according to this embodiment can prevent a sudden change in temperature of the thermal head 101. As a result, the image forming apparatus 100 according to this embodiment can prevent bleeding of the printed image caused by the thermal head 101 being unable to adapt to a sudden change in temperature.

[0030] 5A to 5C, a case where an image in which pixel density changes rapidly along the printing direction is printed in a single scan will be described as an example of a comparative example of image forming apparatus 100 according to this embodiment. Fig. 5A is a graph showing pixel density along the printing direction indicated by image data 311. In the graph shown in Fig. 5A, the horizontal axis represents the printing direction and the vertical axis represents pixel density.

[0031] FIG. 5B shows an example of the temperature of the thermal head 101 when printing image data 311 showing the density shown in FIG. 5A in one scan, and an example of the printed image. The upper diagram in FIG. 5B is a graph showing an example of the temperature of the thermal head 101 when printing an image showing the density shown in FIG. 5A in one scan. The upper graph in FIG. 5B has the printing direction on the horizontal axis and the temperature on the vertical axis. The lower diagram in FIG. 5B shows an example of the image printed when the temperature of the thermal head 101 changes as shown in the upper diagram in FIG. 5B.

[0032] As shown in the lower diagram of Figure 5B, when printing an image in which pixel density changes rapidly along the printing direction in a single scan, the temperature change of the thermal head 101 may not be able to keep up with the speed at which the print medium 103 is transported by the transport unit 304, and the image may be printed at a temperature that is different from the ideal temperature. As a result, as shown in the lower diagram of Figure 5B, there is a risk of bleeding at the boundary where the density changes. In other words, there is a risk of a trailing phenomenon occurring, where the image appears blurred when the image is printed at a temperature that is different from the ideal temperature.

[0033] FIG. 5C shows another example of the temperature of the thermal head 101 when printing an image based on image data 311 exhibiting the density shown in FIG. 5A in a single scan, and an example of the printed image. The upper diagram in FIG. 5C is a graph showing an example of the temperature of the thermal head 101 when printing an image exhibiting the density shown in FIG. 5A in a single scan. The upper graph in FIG. 5C has the printing direction on the horizontal axis and the temperature on the vertical axis. The lower diagram in FIG. 5C shows an example of an image printed when the temperature of the thermal head 101 changes as shown in the upper diagram in FIG. 5C.

[0034] As shown in the upper graph of Fig. 5C, when printing an image in which the density of pixels changes suddenly along the printing direction in a single scan, the temperature of the thermal head 101 may drop excessively in order to adapt to the sudden change in density. As a result, as shown in the lower graph of Fig. 5C, the boundary area where the density changes may become white.

[0035] Next, Figures 6A and 6B are figures showing an example of an image in which pixel areas with relatively low density and pixel areas with relatively high density are printed using different scans for the image showing the density illustrated in Figure 5A.

[0036] FIG. 6A shows an example of the density of a pixel region where the density is relatively low in the first scan for the image showing the density example in FIG. 5A, and an example of the printed image. The upper diagram in FIG. 6A is a graph showing an example of the density of the first pixel region. In the upper graph in FIG. 6, the horizontal axis represents the printing direction and the vertical axis represents the density. The lower diagram in FIG. 6A shows an example of the printed image for the pixel region where the density is relatively low. As shown in the upper graph in FIG. 6A, if the density does not change abruptly in one scan, the temperature of the thermal head 101 does not change abruptly, and the pixel region where the density is relatively low is printed. Therefore, the image forming apparatus 100 according to this embodiment can suppress the occurrence of the tailing phenomenon in the first scan, as shown in the lower diagram in FIG. 6A.

[0037] FIG. 6B shows an example of the density of a pixel region where the density is relatively high in the second scan for the image showing the density example in FIG. 5A, and an example of the printed image. The upper diagram in FIG. 6B is a graph showing an example of the density of the second pixel region. In the upper graph in FIG. 6B, the horizontal axis represents the printing direction and the vertical axis represents the density. The lower diagram in FIG. 6B shows an example of the printed image for the pixel region where the density is relatively high. As shown in the upper diagram in FIG. 6B, if the density does not change abruptly in one scan, the pixel region where the density is relatively high is printed without abrupt changes in the temperature of the thermal head 101. Therefore, as shown in the lower diagram in FIG. 6B, the occurrence of the tailing phenomenon in the second scan can be suppressed. Note that, in pixel regions that are not printed, even if the temperature of the thermal head 101 drops excessively, the whitening phenomenon caused by an excessive drop in the temperature of the thermal head 101 does not occur.

[0038] Therefore, as illustrated in Figures 6A and 6B, the image forming apparatus 100 according to this embodiment can mitigate the tailing phenomenon by printing pixel areas with relatively low density and pixel areas with relatively high density using different scans.

[0039] FIG. 7 is a graph showing an image 701 and the densities of pixels along a printing direction 702 in the image 701. The upper diagram in FIG. 7 is a diagram showing an example of the image 701. The image 701 is an image determined by the densities of multiple pixels indicated by image data 311. The lower diagram in FIG. 7 is a graph showing an example of the densities of pixels along the printing direction 702 shown in the upper diagram in FIG. 7. In the graph in the lower part of FIG. 7, the horizontal axis represents the printing direction and the vertical axis represents the density.

[0040] For example, in step S402 illustrated in Fig. 4, the control unit 306 selects a first pixel region made up of pixels with a density equal to or less than a threshold value 703 illustrated in the lower diagram of Fig. 7. Furthermore, in step S403 illustrated in Fig. 4, the control unit 306 selects a second pixel region made up of pixels with a density exceeding the threshold value 703. For example, the threshold value 703 is a predetermined value. Alternatively, the threshold value 703 may be determined according to the densities of multiple pixels represented by the image data 311.

[0041] Fig. 8 is a diagram showing an example of an image in which a first pixel region made up of pixels with a density equal to or less than the threshold value 703 shown in Fig. 7 is printed from the image 701 shown in Fig. 7. In step S404 shown in Fig. 4, the control unit 306 prints the first pixel region selected in step S402 shown in Fig. 4. For example, as shown in Fig. 8, the control unit 306 prints the pixel region made up of pixels with a density equal to or less than the threshold value 703 in the first scan of two or more scans.

[0042] Fig. 9 is a diagram showing an example of an image in which a second pixel region composed of pixels with a density exceeding the threshold value 703 shown in Fig. 7 is printed from the image 701 shown in Fig. 7. In step S405 shown in Fig. 4, the control unit 306 prints the second pixel region selected in step S403 shown in Fig. 4. For example, as shown in Fig. 9, the control unit 306 prints a pixel region composed of pixels with a density equal to or less than the threshold value 703 in the second scan of two or more scans.

[0043] As illustrated in Figures 8 and 9, the image forming apparatus 100 according to this embodiment can mitigate the tailing phenomenon by printing an image through two or more scans, even when pixel density changes suddenly.

[0044] Second Embodiment A second embodiment will be described. In the drawings, the same or similar elements are denoted by the same reference numerals, and redundant explanations will be omitted. Configurations and processes having substantially the same functions as those of other embodiments will be denoted by the same reference numerals, and explanations will be omitted. Differences from other embodiments will be described.

[0045] The control unit 306 according to this embodiment executes a process of printing by scanning back and forth. In the image forming apparatus 100 according to this embodiment, two or more scans include a scan that is an outward path and a scan that is a return path. For example, of the two or more scans, the first scan is an outward path and the second scan is a return path.

[0046] For example, when the control unit 306 executes a printing process by scanning two or more times in the same direction, the control unit 306 must execute the printing process by the first scan and then cause the conveying unit 304 to convey the printing medium 103 so that the position of the printing medium 103 returns to the position where the scanning starts. Then, the control unit 306 executes the printing process by the first scan after the position of the printing medium 103 returns to the position where the scanning starts. On the other hand, the image forming apparatus 100 according to this embodiment executes the printing process by the first scan along the printing direction of the outward path, and then executes the printing process by the second scan along the printing direction of the return path. This allows the image forming apparatus 100 according to this embodiment to reduce the time required for printing compared to when the control unit 306 executes the printing process by scanning two or more times in the same direction.

[0047] (Third embodiment) The third embodiment will be described with reference to Figures 10 to 14. In the drawings, the same or similar elements are denoted by the same reference numerals, and duplicated explanations will be omitted. Configurations and processes having substantially the same functions as those of other embodiments will be denoted by the same reference numerals, and explanations will be omitted, and differences from other embodiments will be described.

[0048] Like the control unit 306 according to the second embodiment, the control unit 306 according to this embodiment executes a process of printing by scanning back and forth. For example, of two or more scans, the first scan is the outbound scan, and the second scan is the return scan. The condition for each scan according to this embodiment is that the density change amount in the scanning direction is within a range that satisfies a criterion. For example, the condition for each scan is that the density change amount in the scanning direction is within a range from a pixel whose density change amount in the scanning direction is greater than 0 to the pixel immediately preceding the pixel whose density change amount in the scanning direction is less than 0.

[0049] FIG. 10 is a flowchart showing an example of the operation of the image forming apparatus 100 according to this embodiment.

[0050] In step S 1001 , the acquisition unit 302 acquires the image data 311 .

[0051] In step S1002, the control unit 306 selects a first pixel area from the densities of multiple pixels indicated by the image data 311 based on the density change amount in the forward printing direction. The forward printing direction is the direction of scanning in the forward pass. The first pixel area is an area composed of pixels whose density change amount in the forward printing direction satisfies a criterion. For example, the first pixel area ranges from a pixel whose density change amount in the forward printing direction is greater than 0 to the pixel immediately preceding the pixel whose density change amount in the forward printing direction is less than 0. In other words, pixels whose density change amount in the forward printing direction is greater than 0 belong to the first pixel area. Furthermore, for an area where consecutive pixels have a density change amount of 0 in the forward printing direction, if the immediately preceding density change amount in the forward printing direction is other than 0 and is greater than 0, the pixel belongs to the first pixel area. In addition, in an area where there are consecutive pixels with a density change amount of 0 in the printing direction of the forward pass, if there is no pixel with a density change amount other than 0 immediately before in the printing direction of the forward pass and the density change amount immediately after in the printing direction of the forward pass is greater than 0, the pixel belongs to the first pixel area.

[0052] In step S1003, the control unit 306 selects a second pixel area from the densities of multiple pixels indicated by the image data 311 based on the density change amount in the backward printing direction. The backward printing direction is the direction of scanning in the backward print. The second pixel area is an area composed of pixels whose density change amount in the backward print direction satisfies a criterion. For example, the second pixel area ranges from a pixel whose density change amount in the backward print direction is greater than 0 to the pixel immediately preceding the pixel whose density change amount in the backward print direction is less than 0. In other words, pixels whose density change amount in the backward print direction is greater than 0 belong to the second pixel area. A pixel whose density change amount in the backward print direction is greater than 0 is a pixel whose density change amount in the forward print direction is less than 0. Furthermore, for an area where consecutive pixels have a density change amount of 0 in the backward print direction, if the immediately preceding density change amount in the backward print direction is other than 0 and is greater than 0, the pixel belongs to the second pixel area.

[0053] In step S1004, the control unit 306 prints the first pixel area selected in step S1002 by scanning along the printing direction on the outward path.

[0054] In step S1005, the control unit 306 prints the second pixel area selected in step S1003 by scanning along the printing direction on the backward path.

[0055] FIG. 11 is a graph showing an example of density change in the printing direction 702 shown in the upper diagram of FIG. 7 for the image 701 shown in the upper diagram of FIG. 7. The diagram shown in the lower diagram of FIG. 11 is a graph showing differential values ​​of pixel density along the printing direction of the forward pass. In the graph shown in the lower diagram of FIG. 11, the horizontal axis represents the printing direction of the forward pass, and the vertical axis represents the density change. Density change amounts 1101 to 1105 represent density change amounts that are greater than 0 in the printing direction of the forward pass. On the other hand, density change amounts 1106 to 1109 represent density change amounts that are less than 0 in the printing direction of the forward pass. In other words, density change amounts 1106 to 1109 represent density change amounts that are greater than 0 in the printing direction of the backward pass.

[0056] Fig. 12 is a graph showing an example of the density change amount of pixels printed in the forward printing direction and the density change amount of pixels printed in the backward printing direction for the image 701 shown in the upper diagram of Fig. 7. In Fig. 12, the horizontal axis represents the printing direction and the vertical axis represents the density change amount. In the graph shown in Fig. 12, the solid line represents the density change amount of pixels printed in the forward printing direction. Furthermore, in the graph shown in Fig. 12, the dotted line represents the density change amount of pixels printed in the backward printing direction.

[0057] A pixel whose density change amount in the forward printing direction is greater than 0 is a pixel printed in the forward printing direction and belongs to the first pixel region. Furthermore, in an area where pixels whose density change amount in the forward printing direction is 0 are consecutive, if the previous non-zero density change amount in the forward printing direction is greater than 0, the pixel is a pixel printed in the forward printing direction and belongs to the first pixel region. In an area where pixels whose density change amount in the forward printing direction is 0 are consecutive, if the previous pixel whose density change amount in the forward printing direction is not non-zero and the next non-zero density change amount in the forward printing direction is greater than 0, the pixel is a pixel printed in the forward printing direction and belongs to the first pixel region. On the other hand, as shown in FIG. 12, a pixel that is not printed in the forward printing direction is a pixel printed in the backward printing direction and belongs to the second pixel region. Therefore, an area where pixels with a density change amount of 0 are consecutive belongs to either the first pixel area or the second pixel area, depending on the density change amount other than 0 immediately before.

[0058] FIG. 13 is a diagram showing an example of an image printed by scanning on the outward path, out of the image 701 shown in the upper diagram of FIG.

[0059] In step S1004 illustrated in Fig. 10, the control unit 306 prints the first pixel area selected in step S1002 illustrated in Fig. 10. That is, the control unit 306 executes processing to print the first pixel area configured from pixels whose density change amount in the printing direction of the forward pass is greater than 0 during the forward scan.

[0060] During the first scan of the two or more scans, the control unit 306 prints a first pixel area ranging from a pixel whose density change amount in the printing direction of the forward pass is greater than 0 to the pixel immediately preceding the pixel whose density change amount in the printing direction of the forward pass is less than 0, as shown in Fig. 13. In other words, it executes processing to print a first pixel area made up of pixels whose density change amount in the printing direction of the forward pass is greater than 0.

[0061] FIG. 14 is a diagram showing an example of an image printed by a backward scan from among the images 701 shown in the upper diagram of FIG.

[0062] In step S1005 illustrated in Fig. 10, the control unit 306 prints the second pixel area selected in step S1003 illustrated in Fig. 10. That is, the control unit 306 executes processing to print the second pixel area in which the amount of density change in the printing direction of the backward scan is greater than 0.

[0063] As described above, the image forming apparatus 100 according to this embodiment prints, in each of two or more scans, the range from a pixel whose density change amount in the scanning direction is greater than 0 to the pixel immediately preceding the pixel whose density change amount in the scanning direction is less than 0. This allows the image forming apparatus 100 according to this embodiment to mitigate the tailing phenomenon even when pixel density changes suddenly.

[0064] The processes executed in the above embodiments are not limited to the processing modes exemplified in the above embodiments. The above-described functional blocks may be realized using either a logic circuit (hardware) formed in an integrated circuit or the like, or software using a CPU. The processes executed in the above embodiments may be executed by multiple computers. For example, some of the processes executed by the control unit 306 may be executed by another computer, or all of the processes may be shared and executed by multiple computers.

[0065] The present disclosure is not limited to the above-described embodiments, and may be replaced with a configuration that is substantially the same as the configuration shown in the above-described embodiments, a configuration that achieves the same effect, or a configuration that can achieve the same purpose. The present disclosure also includes within its technical scope embodiments obtained by appropriately combining the technical means disclosed in different embodiments. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. [Explanation of symbols]

[0066] 100 Image forming apparatus, 101 Thermal head, 102 Ink ribbon, 103 Printing medium, 301 Storage unit, 302 Acquisition unit, 303 Image forming unit, 304 Conveyance unit, 305 Output unit, 306 Control unit, 311 Image data, 701 Image, 702 Printing direction, 703 Threshold value, 1101 to 1109 Density change amount

Claims

1. an acquisition unit that acquires image data indicating the densities of a plurality of pixels; a control unit that executes a process of printing using a dye-sublimation thermal transfer method by scanning two or more times; Equipped with The control unit executes a process of printing pixels of the plurality of pixels having a density range that satisfies a condition for each of the two or more scans. Image forming device.

2. the two or more scans include a first scan and a second scan performed after the first scan; The condition for one of the first scanning and the second scanning is that the density is equal to or less than a threshold, and the condition for the other of the first scanning and the second scanning is that the density is greater than the threshold. The image forming apparatus according to claim 1 .

3. the control unit executes a process of scanning back and forth and printing; The two or more scans include a forward scan and a backward scan.

3. The image forming apparatus according to claim 1.

4. The condition for each scan is that the amount of density change in the scanning direction must be within a range that satisfies a standard. The image forming apparatus according to claim 3 .

5. The condition for each scan is that the range is from a pixel where the density change amount is greater than 0 to a pixel immediately before the pixel where the density change amount is less than 0 along the scanning direction. The image forming apparatus according to claim 4 .

6. the control unit executes, in a forward scan, a process of printing a first pixel area made up of pixels whose density change amount in the forward scan direction is greater than 0, and, in a backward scan, a process of printing a second pixel area made up of pixels whose density change amount in the backward scan direction is greater than 0; The area where pixels with a density change amount of 0 are consecutive is determined to belong to the first pixel area or the second pixel area depending on the density change amount other than 0 immediately before. The image forming apparatus according to claim 5 .

7. acquiring image data indicative of densities of a plurality of pixels; a step of performing a printing process using a dye-sublimation thermal transfer method by scanning two or more times; Equipped with In the step of executing the printing process, a process is executed in which, in each of the two or more scans, pixels of a density range that satisfies a condition for each scan are printed out of the plurality of pixels. Image forming method.

Images