Image forming apparatus and image formation method

Abstract

To optimize an application condition and a dry condition of a pretreatment liquid on the basis of a read image obtained by reading an image formed on a medium.SOLUTION: An image forming apparatus includes a pretreatment liquid application part for applying a pretreatment liquid to a sheet-shaped medium, a pretreatment liquid dry part for drying the pretreatment liquid applied to the medium, an image formation part for forming a specific image on the medium obtained by drying the pretreatment liquid, a medium conveyance part for conveying the medium to the pretreatment liquid application part, the pretreatment liquid dry part, and the image formation part in this order and conveying the medium with the image formed downstream, an image read part arranged downstream of the image formation part to acquire the read image obtained by reading the image formed on the medium, and a control part for controlling an application amount and drying of the pretreatment liquid. The control part determines control conditions of the pretreatment liquid application part and the pretreatment liquid dry part in accordance with a determination result based on brightness information in the read image, and controls operations of the pretreatment liquid application part and the pretreatment liquid dry part according to the control conditions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Image forming apparatuses that form images on conveyed media are known, as are pretreatment liquid application devices that apply a pretreatment liquid to the media prior to image formation processing in order to prepare the surface of the media on which the image is to be formed in a state suitable for image formation.

[0003] In order to prevent abnormal images such as "bleeding" that occurs when liquid ink is applied to a medium to form an image, a configuration has been disclosed in which the amount of pretreatment liquid applied and the drying conditions of the pretreatment liquid are controlled based on the printing resolution (see Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] When making a judgment based on print resolution, as in the configuration disclosed in Patent Document 1, the desired image quality may not be obtained if the printing conditions vary depending on the type of medium (paper) and the external environment (temperature and humidity in the environment in which the device is operating).

[0005] An object of the present invention is to optimize the application conditions and drying conditions of a pretreatment liquid based on a read image obtained by reading an image formed on a medium. [Means for solving the problem]

[0006] and a control unit that controls the amount of application of the pretreatment liquid and the drying of the pretreatment liquid, wherein the control unit determines control conditions for the pretreatment liquid application unit and the pretreatment liquid drying unit in accordance with a determination result based on luminance information of the read image, and controls operations of the pretreatment liquid application unit and the pretreatment liquid drying unit in accordance with the control conditions.

[0007] According to the present invention, it is possible to optimize the application conditions and drying conditions of the pretreatment liquid based on the read image obtained by reading an image formed on a medium. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing the overall configuration of an embodiment of an image forming system according to the present invention; [Figure 2] FIG. 4 is a diagram showing an example of a test chart formed in the embodiment. [Figure 3] FIG. 10 is a diagram showing another example of the test chart formed in the embodiment. [Figure 4] 4 is a flowchart illustrating a process for creating the test chart. [Figure 5] 6A and 6B are diagrams showing examples of determination results based on the density determination test chart according to the embodiment. [Figure 6] FIG. 10 is a diagram showing an example of density rank according to the embodiment. [Figure 7] FIG. 4 is a partially enlarged view of a test chart for determining color bleeding according to the present embodiment. [Figure 8] FIG. 8 is a diagram showing an example of luminance information of the test chart for determining color fringing shown in FIG. 7; [Figure 9] FIG. 8 is an explanatory diagram of the color bleeding determination test chart shown in FIG. 7 . [Figure 10] 5A and 5B are diagrams showing examples of color fringing ranks according to the embodiment. [Figure 11] FIG. 4 is a partially enlarged view of a test chart for determining color bleeding according to the present embodiment. [Figure 12] 12 is a diagram showing an example of luminance information of the test chart for determining color fringing shown in FIG. 11. FIG. [Figure 13] 10 is a flowchart illustrating a process for adjusting pretreatment liquid application conditions and drying conditions according to the present embodiment. [Figure 14] 14 is a diagram showing an example of data generated in the adjustment processing illustrated in FIG. 13. [Figure 15] FIG. 10 is a diagram showing the overall configuration of another embodiment of the image forming system according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of a line-type inkjet printer 100 as an embodiment of an image forming apparatus according to the present invention. In this embodiment, the image forming method is exemplified as a so-called inkjet method in which liquid ink is ejected onto paper P as a sheet-like medium to form an image. As will be explained below, this embodiment is premised on the premise that, before forming an image on paper P, a treatment agent is applied in advance to make the image-forming surface of paper P suitable for achieving the purpose of improving image quality, and the image is formed on the treatment agent. Therefore, it does not matter whether the image forming method is a direct method or an indirect method in which secondary transfer is performed via intermediate transfer.

[0010] As shown in FIG. 1, the inkjet printer 100 includes a pretreatment liquid application unit 110 that applies a pretreatment liquid Pr as a treatment agent to paper P. The pretreatment liquid application unit 110 is disposed upstream of the image forming unit 130 and applies a pretreatment liquid to the image forming surface of paper P. The pretreatment liquid application unit 110 has an effect of changing the properties of the image forming surface of paper P to a state suitable for improving image quality. The pretreatment liquid application unit 110 is configured with an inkjet head and applies the pretreatment liquid to paper P by ejecting the pretreatment liquid from the inkjet head. The pretreatment liquid application unit 110 is configured to be able to vary the amount of pretreatment liquid applied by controlling the pattern in which the pretreatment liquid is ejected from the inkjet head (the pattern of the ejection operation).

[0011] The inkjet printer 100 also includes a pretreatment liquid drying unit 120 that dries the pretreatment liquid applied to the paper P. The pretreatment liquid drying unit 120 is disposed downstream of the pretreatment liquid application unit 110 and upstream of the image forming unit 130.

[0012] The inkjet printer 100 also includes an image forming unit 130 that forms an image by ejecting liquid ink onto the paper P from which the pretreatment liquid has dried. The image forming unit 130 is disposed downstream of the pretreatment liquid drying unit 120.

[0013] The image forming unit 130 includes a liquid ejection unit that ejects liquid inks of multiple colors onto the image forming surface of the paper P, onto which the pretreatment liquid has dried and adhered. For example, in the transport direction indicated by arrow C in Fig. 1, liquid inks of each color are ejected onto the paper P at predetermined timings and in predetermined amounts in the order of K (black), C (cyan), M (magenta), and Y (yellow) to form an image.

[0014] There are various types of images formed in the image forming unit 130, but it is also possible to form a "test chart" as a specific image consisting of an array of rectangular images filled with a specific color. The test chart is an image in which adjacent colors of the arranged rectangular images are different but complementary colors, and is used to inspect the quality of the image formed in the image forming unit 130.

[0015] The inkjet printer 100 also includes an ink drying section 140 that dries the liquid ink that has adhered to the paper P in the image forming section 130, thereby fixing the image. The ink drying section 140 is disposed downstream of the image forming section 130.

[0016] The inkjet printer 100 also includes an image reading unit 150 that reads an image formed on the paper P and acquires the read image. The image reading unit 150 is disposed downstream of the ink drying unit 140. The image reading unit 150 optically reads an image formed in the image forming unit 130 and acquires the read image. The image reading unit 150 includes an image sensor and acquires, for example, a test chart formed on the paper P as the read image.

[0017] The inkjet printer 100 also includes a transport unit 160 as a medium transport unit that transports the paper P through the pretreatment liquid application unit 110, the pretreatment liquid drying unit 120, the image forming unit 130, the ink drying unit 140, and the image reading unit 150 in this order.

[0018] The inkjet printer 100 also includes a control unit 170 that controls the operations of the pretreatment liquid application unit 110, the pretreatment liquid drying unit 120, the image forming unit 130, the ink drying unit 140, the image reading unit 150, and the conveying unit 160. The control unit 170 has a configuration similar to that of a so-called information processing device, and is configured by combining a calculation unit such as a CPU with storage devices such as ROM and RAM. The control unit 170 is capable of realizing a functional configuration that can realize the following control processes by executing computer software processes using computer hardware resources.

[0019] The control unit 170 controls the operations of the above-mentioned units and determines the "density" and "color bleeding" states of a specific image included in the read image from the read image acquired by the image reading unit 150. Furthermore, the control unit 170 determines the control conditions for the pretreatment liquid application unit 110 and the pretreatment liquid drying unit 120 according to the determination results from the specific image, and controls the operations of these units.

[0020] If the scanned image is a test chart, the control unit 170 adjusts the amount of pretreatment liquid (application amount) to be applied to the paper P and the drying state of the pretreatment liquid based on the "density" and "color bleeding" of the test chart, so as to obtain a state more suitable for image formation.

[0021] The control unit 170 determines the read image by, for example, calculating the image density value and then determining the color fringing state. For example, the control unit 170 calculates the image density value using a lookup table that associates the luminance values ​​of the pixels that make up the image with the spectral characteristic values. The determination of the fringing state is then made based on the amount of change in luminance values ​​at the color boundary portions included in the specific image that makes up the test chart.

[0022] [Example of test chart] 2 and 3, examples of test charts serving as specific images that serve as the basis for scanned images for adjusting pretreatment application conditions and drying conditions in inkjet printer 100 will be described. Fig. 2 is a diagram that schematically shows an example of a density determination test chart T1. Fig. 3 is a diagram that schematically shows an example of a color bleeding determination test chart T2.

[0023] The inkjet printer 100 uses a density determination test chart T1 and a color bleeding determination test chart T2 to adjust the pretreatment liquid application conditions and drying conditions. More specifically, the density determination test chart T1 and the color bleeding determination test chart T2 are formed on paper P, and the paper P is transported to the image reading unit 150. Then, read images are acquired from each of the density determination test chart T1 and the color bleeding determination test chart T2 and notified to the control unit 170. The control unit 170 determines the image formation state of each read image related to each test chart, and adjusts (changes) the application amount of the pretreatment liquid and the drying process conditions based on the determination result.

[0024] The control unit 170 determines the density of the first read image G1 based on the density determination test chart T1 read by the image reading unit 150. The control unit 170 also determines the degree of color bleeding from the state of color fluctuation at the boundary portion between different colors (color boundary portion) of the second read image G2 based on the color bleeding determination test chart T2 read by the image reading unit 150. In other words, the control unit 170 determines "bleeding (color bleeding)" from the amount of change in luminance of adjacent portions of each rectangular image constituting the second read image G2.

[0025] As shown in FIG. 2, the density determination test chart T1 is composed of a plurality of first scanned images G1. The first scanned images G1 are formed as solid monochrome images. Each of the first scanned images G1 has a different combination of image density (density of the printed image) and the amount (application amount) of pretreatment liquid applied before image formation. In the density determination test chart T1, the first scanned images G1 are arranged in the X-axis direction in FIG. 2 so that the image density is the same but the application amount of pretreatment liquid is different. That is, in FIG. 2, the first scanned images G1 formed by increasing the application amount of pretreatment liquid from "0%, " "25%, " "50%, " "75%, " "100%" are arranged in the X-axis direction.

[0026] Furthermore, in the density determination test chart T1, the first read images G1 are arranged such that the application amounts of pretreatment liquid are the same but the image densities are different in the Y-axis direction in Fig. 2. That is, in Fig. 2, the first read images G1 are arranged so that the density of the printed image decreases in the Y-axis direction, such as "high gradation," "medium gradation," and "low gradation."

[0027] 3, the color bleeding evaluation test chart T2 is composed of a plurality of second read images G2. The second read images G2 are formed by arranging fill images of different colors. Each of the second read images G2 has a different combination of image density (printed image density) of the fill images arranged in complementary colors and the amount (application amount) of pretreatment liquid applied before image formation. The colors that make up the second read images G2 may be a combination of complementary colors, for example, one of which is green and the other is red.

[0028] As shown in Fig. 3, in the color bleeding evaluation test chart T2, as in Fig. 2, the arrangement of the second read images G2 is such that the image density is the same but the application amount of the pretreatment liquid is different in the direction of the X axis in Fig. 3. That is, in Fig. 3 as well, the second read images G2 formed by increasing the application amount of the pretreatment liquid in the direction of the X axis, such as "0%, " "25%, " "50%, " "75%, " "100%, " are arranged.

[0029] Furthermore, in the test chart T2 for evaluating color bleeding, the arrangement of the second read images G2 is such that the application amount of the pretreatment liquid is the same but the image density is different in the Y-axis direction in Fig. 3. That is, in Fig. 3 as well, the second read images G2 formed so that the density of the printed image becomes lighter in the Y-axis direction, such as "high gradation," "medium gradation," and "low gradation."

[0030] The numerical values ​​of the application amounts of the pretreatment liquid indicate the ejection pattern of the pretreatment liquid ejected from the inkjet heads included in the pretreatment liquid application unit 110. Therefore, by changing the ejection pattern of the inkjet heads according to the numerical values ​​of the application amounts of the pretreatment liquid, the pattern in which the pretreatment liquid is applied to the paper P is changed, and it is possible to change the application amount of the pretreatment liquid in the area of ​​the printed image. In other words, by changing the ejection pattern of the inkjet heads, the application amount of the pretreatment liquid is changed for each printed image (patch image) constituting the color bleeding evaluation test chart T2.

[0031] 2 and 3 are gradations that correspond to approximate median values ​​when 100% gradation is taken as the maximum density of a print image that can be formed by the inkjet printer 100. That is, Fig. 2 illustrates a case where 83%, which is the approximate median gradation when 100% gradation is divided into three (100-67%, 66-34%, 33-0%), is taken as "high gradation", 50% as "medium gradation", and 17% as "low gradation".

[0032] As described above, when the control unit 170 adjusts the application conditions and drying conditions of the pretreatment liquid in the inkjet printer 100, it determines the density value of each filled image using a "density determination test chart T1" consisting of an array of rectangular images of a single color (first read image G1). Also, it determines the degree of "color bleeding" based on the state of color fluctuation at the color boundary of each patch image using a "color bleeding determination test chart T2" in which a combination of rectangular images of different colors (second read image G2) is arranged.

[0033] [Processing flow of the test chart creation method according to this embodiment] Next, a test chart creation method, which is one of the image generation methods executed in the inkjet printer 100, will be described with reference to the flowchart in Fig. 4. First, the initial setting of the temperature in the pretreatment liquid drying unit 120 is set to "low" (S401). In addition to "low," parameters that can be set in the pretreatment liquid drying unit 120 include "medium" and "high." Here, the temperature settings "low," "medium," and "high" are relative, and examples are low: 80°C, medium: 100°C, and high: 120°C.

[0034] Next, an image forming process is executed to create the two test charts (the density determination test chart T1 and the color fringing determination test chart T2) illustrated in FIGS. 2 and 3 (S402).

[0035] Subsequently, the two test charts formed in step S402 are conveyed by the conveying unit 160 to the image reading unit 150, where each test chart is read and a read image of each is acquired (S403).

[0036] Subsequently, each read image acquired in step S403 is stored in association with the pretreatment liquid drying temperature setting (S404).

[0037] Next, it is determined whether the pre-treatment drying temperature is set to "high" (S405). If the setting is not "high" (S405: NO), the pre-treatment drying temperature is increased from "low" to "medium" and from "medium" to "high" (S406), and the process proceeds to step S402.

[0038] If the pre-treatment drying temperature is "high" in step S405 (S405: YES), the process ends.

[0039] As described above, two types of test charts are formed for each drying condition (drying temperature setting) of the pretreatment liquid, and the respective read images are obtained and stored. Note that the flowchart in Fig. 4 is an example when the drying condition is defined as the drying temperature, and illustrates the process for forming each test chart and obtaining read images under three temperature conditions: "low," "medium," and "high."

[0040] [Concentration judgment] Next, an example of a determination result based on the density determination test chart T1 according to this embodiment will be described with reference to Fig. 5. Fig. 5 shows an example of the density measurement result for a certain amount of ink adhesion. The image reading unit 150 performs measurements for each amount of ink adhesion (high gradation, medium gradation, low gradation).

[0041] The image reading unit 150 calculates each density of the first read image G1 from the density determination test chart T1. The control unit 170's storage area, for example, an information storage area realized by a nonvolatile memory element such as a ROM (see FIG. 1) included in the control unit 170, is provided with a density range for determining the level of measured density. In the following description, the information storage area realized by a ROM or the like included in the control unit 170 will be simply referred to as the "storage area of ​​the control unit 170." The control unit 170 determines which density range each measured density of the first read image G1 falls within. The relationship between the density rank and the density range used to determine the density rank is as shown in FIG. 6. That is, the density rank can be determined from the density range determination value based on the relationship shown in FIG. 6. The density range shown in FIG. 5 is set to a different value depending on the amount of ink attached to the rectangular image (patch) to be measured.

[0042] Here, the "density range 1," "density range 2," and "density range 3" shown in Fig. 6 will be described in more detail. Each of these density ranges is stored in advance in the memory area of ​​the control unit 170, and is information corresponding to the judgment conditions for judging the level of the measured density. In each density range, the relationship between the target density value (target density D) when forming a rectangular image (patch) and the measured density is, for example, as follows:

[0043] Concentration range 1 corresponds to the range of "±0.1" with respect to the target concentration D. That is, it corresponds to the relationship of "D - 0.1 ≤ measured concentration ≤ D + 0.1".

[0044] Concentration range 2 corresponds to the range of "less than -0.1 to -0.3 or greater than +0.1 to +0.3" with respect to the target concentration D. That is, it corresponds to the relationship of "D - 0.3 ≤ measured concentration < D - 0.1, or, D + 0.3 < measured concentration ≤ D + 0.3".

[0045] Concentration range 3 corresponds to the range of "less than -0.3 to -0.5 or greater than +0.3 to +0.5" with respect to the target concentration D. That is, it corresponds to the relationship of "measured concentration < D - 0.3, or, D + 0.3 < measured concentration".

[0046] That is, using the concentration ranges exemplified above, according to the first reading image G1, the target concentration D used for determination is changed, and the above processing is performed.

[0047] [Color bleeding determination] Next, an example of the determination result based on the color bleeding determination test chart T2 according to the present embodiment will be described using FIG. 7. FIG. 7 is a diagram showing an enlarged view of the second reading image G2 included in the color bleeding determination test chart T2 and an example of the luminance measurement positions. FIG. 8 is an example of luminance information.

[0048] The image reading unit 150 acquires the second reading image G2 exemplified in FIG. 7 and notifies the control unit 170. The control unit 170 sets a plurality of measurement points as exemplified in FIG. 7 for the reading image, and calculates a "bleeding rank" for distinguishing the degree of "color bleeding" based on the luminance information at these measurement points.

[0049] FIG. 8 shows an example of luminance information at a certain measurement point. The image reading unit 150 reads an image by an image sensor and acquires the RGB luminance information of the pixels included in a specific measurement point from the read image.

[0050] FIG. 8 is a graph in which the horizontal axis represents the "measurement coordinates," which are the coordinates of a pixel included in a certain measurement point, and the vertical axis represents the RGB brightness values ​​at each measurement coordinate.

[0051] As shown in Figure 8, the RGB brightness values ​​of each pixel along the measurement points of the second scanned image G2, which is formed by adjacently forming rectangular images of different colors, change significantly within a specific coordinate range. The coordinate areas where this change is significant correlate with the color boundary between different colors. In other words, color bleeding can be determined based on information about areas where the rate of change in brightness value is large. In the case of Figure 8, it can be seen that the bleeding determination process can be performed based on the R data.

[0052] Fig. 9 is an explanatory diagram of the color fringing determination process. Fig. 9 extracts only the R luminance information used in the color fringing determination process from Fig. 8. Fig. 10 is a diagram illustrating the relationship between the color fringing determination value (number of pixels) and the color fringing rank.

[0053] The color fringing judgment process calculates a color fringing judgment value shown in the drawing, and determines the color fringing rank according to the numerical value of the color fringing judgment value.

[0054] Two thresholds for calculating a color fringing judgment value are stored in a memory area of ​​the control unit 170. In a color boundary portion defined by these two thresholds, a width Rj (number of images) of brightness between the first threshold Th1 and the second threshold Th2 becomes the color fringing judgment value. This width Rj corresponds to the width of a brightness change region in an adjacent portion where different colors are adjacent.

[0055] Note that the threshold values ​​shown in Fig. 9 are merely examples and vary depending on the color of the second scanned image G2 and the RGB type used to calculate the color bleeding judgment value. The color bleeding judgment value is the width of the area where inks of adjacent colors are mixed, and the smaller the color bleeding judgment value, the greater the degree of color bleeding. The "color bleeding judgment value" shown in Fig. 9 is calculated for each measurement point shown in Fig. 7, and the "color bleeding rank" is determined based on the largest color bleeding judgment value.

[0056] Fig. 11 is an example of a scanned image in which "color bleeding" occurs at the boundaries of adjacent rectangular regions included in the second scanned image G2. Fig. 12 is an example of bleeding determination values ​​at the measurement points in Fig. 11.

[0057] Fig. 11 illustrates an example of color bleeding occurring in an adjacent region Br of two specific color regions (regions of complementary colors) that constitute the second read image G2. For the second read image G2 in Fig. 11, the luminance value of each pixel is calculated along the measurement points in the color adjacency direction, and Fig. 12 shows an example of a graph illustrating only the R data with the largest change in luminance value (change rate). As shown in Fig. 12, when color bleeding occurs in different color regions, the range Rj of the color bleeding judgment value becomes larger than the color bleeding judgment value when no color bleeding occurs (see Fig. 9).

[0058] [Flowchart for determining pretreatment application conditions] Next, the flow of the pretreatment application condition determination process will be described using the flowchart in Fig. 13. First, the read image acquired in the process described in Fig. 4 with the drying conditions set to a predetermined temperature is called up (S1301). A density rank for the read read image is calculated (S1302). Next, a color bleeding rank for the read read image is calculated (S1303).

[0059] Next, based on the calculated color fringing rank, the pretreatment application amount corresponding to the temperature setting of the scanned image to be processed is determined. The pretreatment application amount is determined by calculating the integrated values ​​of the calculated density rank and color fringing rank for each determination patch, and the condition with the largest integrated value for the rank is determined as the pretreatment application amount. If the integrated values ​​of the density ranks corresponding to multiple pretreatment application amounts are the same, the smaller pretreatment application amount is determined as the pretreatment application amount condition for each temperature setting. After determining the pretreatment application amount for each temperature setting, the total of the integrated values ​​of the pretreatment application amount ranks for each determination patch is calculated, and the total values ​​for each temperature setting are compared to determine the temperature setting. The temperature setting is determined as the setting with the largest total of the integrated values ​​of the ranks of the determined pretreatment amount. Furthermore, if there are multiple temperatures with the same total value, the lower temperature is determined as the determined temperature setting. The control unit 170 adjusts the operation control value of the pretreatment liquid application unit 110 based on the determined pretreatment application amount and temperature setting (S1304).

[0060] If not all the scanned images have been read (S1305: NO), the scanned image to be processed is changed to the image acquired by changing the temperature setting (S1306), and the process returns to step S1301.

[0061] If all scanned images have been read (S1305: YES), the total rank value for each temperature is calculated (S1307), and the pretreatment liquid drying temperature is determined (S1308). The pretreatment liquid drying conditions are determined by calculating the total integrated value of the rank of each ink adhesion amount for each drying temperature, comparing the total integrated value of the rank for each drying temperature, and determining the highest value as the drying temperature.

[0062] 14 shows an example of pretreatment application condition determination data calculated in the pretreatment application condition determination process and stored in the storage area of ​​the control unit 170. As shown in FIG. 14, for each pretreatment drying temperature condition (low temperature, medium temperature, high temperature), a density rank of "high gradation," "medium gradation," or "low gradation" is calculated (S1302), and a color bleeding rank is calculated (S1303), and the pretreatment liquid application amount is determined based on the rank integrated value (S1304). Then, the sum of the rank integrated values ​​of "high gradation," "medium gradation," and "low gradation" is calculated as the total integrated value of the determination condition (S1307). In FIG. 14, the total integrated value of the determination conditions for the low temperature condition is 18, and the total integrated value of the determination conditions for the medium temperature condition and the high temperature condition is the same as 27, so the medium temperature condition, which is the lower temperature, is determined as the pretreatment drying temperature, and further the application amount of the pretreatment liquid is determined as "50%" when the gradation of the printed image is high, "25%" when the gradation of the printed image is medium, and "0%" when the gradation of the printed image is low.

[0063] As described above, the pretreatment application condition determination process according to this embodiment adjusts the application amount of the pretreatment liquid and the drying conditions to optimal conditions using a test chart obtained by sequentially performing a pretreatment liquid application process of applying the pretreatment liquid to a sheet of paper P, a pretreatment liquid drying process of drying the pretreatment liquid applied to the paper P, and an image formation process of forming a specific image on the paper P from which the pretreatment liquid has been dried. At this time, density information and luminance information are calculated from the read image obtained by reading the specific image (test chart) formed on the paper P, and these are evaluated by a predetermined evaluation process. Then, the process conditions in the pretreatment liquid application process and the pretreatment liquid drying process are adjusted according to the evaluation results.

[0064] In the example of FIG. 14, the total value of the medium temperature and the high temperature is equal, so the drying temperature setting is "medium."

[0065] [Modification of the inkjet printer 100] The inkjet printer 100 described in FIG. 1 is of the so-called "direct printing type," but the present invention is not limited to the image formation type, and can also be applied to the so-called "intermediate transfer type" as shown in FIG. 15.

[0066] As shown in Figure 15, the intermediate transfer type inkjet printer 100a has an intermediate transfer belt 161 as an intermediate transfer unit that constitutes a conveying unit 160, and forms an image by forming a color image formed in a head unit 131 of an image forming unit 130 on the intermediate transfer belt 161 and then performing a secondary transfer from the intermediate transfer belt 161 to paper P as a medium.

[0067] When the rotary roller 162 rotates in the rotation direction A1, the intermediate transfer belt 161 moves in the movement direction A2.

[0068] For example, when forming a full-color image, i.e., a four-color image, the head unit 131 is composed of four-color heads. Specifically, the head unit 131 is composed of a yellow head 131Y, a magenta head 131M, a cyan head 131C, and a black head 131K. In the following, the liquid is ink, and an example is taken in which an image is formed when the head unit 131 applies ink to the paper P.

[0069] However, the head unit 131 may include heads other than the yellow head 131Y, the magenta head 131M, the cyan head 131C, and the black head 131K. For example, the head unit 131 may include a head corresponding to a color such as white.

[0070] The head unit 131 forms an image on the image forming surface of the intermediate transfer belt 161. Hereinafter, the image formed on the intermediate transfer belt 161 will be referred to as an "intermediate image."

[0071] The transfer unit 163 is realized by, for example, a transfer roller, etc. The transfer unit 163 also transfers the intermediate image formed on the intermediate transfer belt 161 onto the paper P being transported in the transport direction A3.

[0072] The cleaning unit 164 cleans the intermediate transfer belt 161. For example, the cleaning unit 164 is realized by a roller, a blade, or the like. The cleaning unit 164 brings the roller, the blade, or the like into contact with the intermediate transfer belt 161 to perform cleaning to remove any remnants of the intermediate image remaining on the intermediate transfer belt 161.

[0073] The detection unit 165 is realized by, for example, an optical sensor. However, the detection unit 165 may also be realized by an encoder. The type of sensor for the detection unit 165 is not important as long as it can detect the position of the intermediate transfer belt 161. The sensors that realize the detection unit 165 may be installed at multiple locations or may be of multiple types.

[0074] The inkjet printer 100a includes a pretreatment liquid application unit 110 and a pretreatment liquid drying unit 120 on the upstream side of the head unit 131.

[0075] The inkjet printer 100a according to this embodiment includes an ink drying unit 140 and an image reading unit 150 downstream of the transfer unit 163. The image formed on the paper P is acquired in the image reading unit 150, and the control unit 170 (not shown in FIG. 15) executes the control processing already described.

[0076] In the embodiment of the present invention described above, a color bleeding determination is performed, and the application amount of the pretreatment liquid and the drying temperature are controlled based on the determination result so as to suppress color bleeding, but the control based on the color bleeding determination result is not limited to this. For example, the color bleeding determination result may be applied to the control of the application amount of the liquid ink, the particle size of the liquid ink, etc.

[0077] Furthermore, the embodiment described above is based on an image forming method in which liquid ink is ejected onto paper P, such as the inkjet printer 100. However, the suppression of color bleeding according to the present invention is not limited to the inkjet method, but can also be applied to electrophotography and offset printing. For example, it is possible to adjust the fixing temperature of the toner (image developer) based on the color bleeding assessment result.

[0078] As described above, according to the embodiment of the present invention, it is possible to determine optimal conditions, such as the application conditions of the pretreatment liquid, based on an image that has actually been formed.

[0079] The present invention is not limited to the above-described exemplary embodiments, and various modifications are possible without departing from the technical gist thereof. The present invention covers all technical matters included in the technical concept described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various modifications from the disclosed content. Such modifications are also included in the technical scope described in the claims.

[0080] The control method described above may be realized, for example, by a program. That is, the control method is a method executed by a computer by causing an arithmetic unit, a storage unit, an input unit, an output unit, and a control unit to cooperate with each other based on the program. The program may be written to a storage unit or a storage medium and distributed, or distributed via a telecommunications line, etc.

[0081] For example, aspects of the present invention are as follows. <1> a pretreatment liquid application unit that applies a pretreatment liquid to a sheet-like medium; a pretreatment liquid drying unit that dries the pretreatment liquid applied to the medium; an image forming unit that forms a specific image on a medium on which the pretreatment liquid has been dried; a medium transport unit that transports the medium in the order of the pretreatment liquid application unit, the pretreatment liquid drying unit, and the image forming unit, and transports the medium with the image formed thereon downstream; an image reading unit disposed downstream of the image forming unit and configured to obtain a read image by reading the image formed on the medium; a control unit that controls the application amount of the pretreatment liquid and the drying; Equipped with the control unit determines control conditions for the pretreatment liquid application unit and the pretreatment liquid drying unit in accordance with a determination result based on luminance information of the read image, and controls operations of the pretreatment liquid application unit and the pretreatment liquid drying unit in accordance with the control conditions. The image forming apparatus is characterized by the above. <2> The control unit adjusts the amount of pretreatment liquid to be applied to the medium in accordance with the determination result. The aforementioned <1> 2. The image forming apparatus according to claim 1, wherein: <3> the control unit adjusts drying conditions for the pretreatment liquid applied to the medium in accordance with the determination result. The aforementioned <1> or <2> 2. The image forming apparatus according to claim 1, wherein: <4> The read image is a specific image in which filled-in images filled with different specific colors are arranged adjacent to each other. The aforementioned <1> and above <3> 10. The image forming apparatus according to claim 9, wherein the first and second electrodes are arranged parallel to each other. <5> adjacent colors and densities of the fill image are different; The aforementioned <4> 2. The image forming apparatus according to claim 1, wherein: <6> The specific image is an image in which a plurality of filled-in images with different densities are arranged according to the magnitude of the densities. The aforementioned <4> or the above <5> 2. The image forming method according to claim 1. <7> the control unit determines a degree of color bleeding in adjacent portions where different colors are adjacent to each other in adjacent filled-in images included in the specific image; The aforementioned <4> and above <6> 10. The image forming apparatus according to claim 9, wherein the first and second electrodes are arranged parallel to each other. <8> The control unit determines the degree of color bleeding based on an amount of change in luminance in adjacent portions of different colors among adjacent filled-in images included in the specific image. The aforementioned <7> 2. The image forming apparatus according to claim 1, wherein: <9> the control unit determines the degree of color bleeding based on a width of a luminance change area in an adjacent portion where different colors are adjacent to each other in adjacent filled-in images included in the specific image; The aforementioned <7> 2. The image forming apparatus according to claim 1, wherein: <10> a pretreatment liquid application unit that applies a pretreatment liquid to a sheet-like medium; a pretreatment liquid drying unit that dries the pretreatment liquid applied to the medium; an image forming unit that forms an image on a medium on which the pretreatment liquid has been dried; a medium transport unit that transports the medium in the order of the pretreatment liquid application unit, the pretreatment liquid drying unit, and the image forming unit, and transports the medium with the image formed thereon downstream; an image reading unit disposed downstream of the image forming unit and configured to obtain a read image by reading the image formed on the medium; a control unit that controls operations of the pretreatment liquid application unit and the pretreatment liquid drying unit based on the read image; Equipped with the control unit adjusts the operating conditions of the image forming unit in accordance with the determination result of color bleeding in the read image, and controls the operation of the image forming unit in accordance with the operating conditions. The image forming apparatus is characterized by the above. <11> a pretreatment liquid application step of applying a pretreatment liquid to a sheet-like medium, a pretreatment liquid drying step of drying the pretreatment liquid applied to the medium, and an image forming step of forming an image on the medium from which the pretreatment liquid has been dried, in that order, while the medium is being conveyed; and an image reading step of acquiring a read image by reading the image formed on the medium after the image forming step. adjusting processing conditions in the pretreatment liquid application step and the pretreatment liquid drying step according to the determination results of density information and luminance information of the read image; The image forming method is characterized by the above. [Explanation of symbols]

[0082] 100, 100a: Inkjet printer 110: Pretreatment liquid application section 120: Pre-treatment liquid drying section 130: Image forming unit 131: Head 131C: Cyan head 131K: Blackhead 131M: Magenta head 131Y: Yellow Head 140: Ink drying unit 150: Image reading unit 160: Transport unit 161: Intermediate transfer belt 162: Rotating roller 163: Transcription unit 164: Cleaning section 165:Detection unit 170: Control unit [Prior art documents] [Patent documents]

[0083] [Patent Document 1] Japanese Patent Application Publication No. 2023-248881

Claims

1. a pretreatment liquid application unit that applies a pretreatment liquid to a sheet-like medium; a pretreatment liquid drying unit that dries the pretreatment liquid applied to the medium; an image forming unit that forms a specific image on a medium on which the pretreatment liquid has been dried; a medium transport unit that transports the medium in the order of the pretreatment liquid application unit, the pretreatment liquid drying unit, and the image forming unit, and transports the medium with the image formed thereon downstream; an image reading unit disposed downstream of the image forming unit, for obtaining a read image by reading the specific image formed on the medium; a control unit that controls the application amount of the pretreatment liquid and the drying; Equipped with the control unit determines control conditions for the pretreatment liquid application unit and the pretreatment liquid drying unit in accordance with a determination result based on luminance information of the read image, and controls operations of the pretreatment liquid application unit and the pretreatment liquid drying unit in accordance with the control conditions. An image forming apparatus characterized by:

2. The control unit adjusts the amount of pretreatment liquid to be applied to the medium in accordance with the determination result. The image forming apparatus according to claim 1 .

3. the control unit adjusts drying conditions for the pretreatment liquid applied to the medium in accordance with the determination result.

3. The image forming apparatus according to claim 1.

4. The read image is a specific image in which filled-in images filled with different specific colors are arranged adjacent to each other.

3. The image forming apparatus according to claim 1.

5. adjacent colors and densities of the fill image are different; The image forming apparatus according to claim 4 .

6. The specific image is an image in which a plurality of filled-in images with different densities are arranged according to the magnitude of the densities. The image forming apparatus according to claim 4 .

7. the control unit determines a degree of color bleeding in adjacent portions where different colors are adjacent to each other in adjacent filled-in images included in the specific image; The image forming apparatus according to claim 4 .

8. The control unit determines the degree of color bleeding based on an amount of change in luminance in adjacent portions of adjacent filled-in images included in the specific image where different colors are adjacent to each other. The image forming apparatus according to claim 7 .

9. the control unit determines the degree of color bleeding based on a width of a luminance change area in an adjacent portion where different colors are adjacent to each other in adjacent filled-in images included in the specific image; The image forming apparatus according to claim 7 .

10. a pretreatment liquid application unit that applies a pretreatment liquid to a sheet-like medium; a pretreatment liquid drying unit that dries the pretreatment liquid applied to the medium; an image forming unit that forms a specific image on a medium on which the pretreatment liquid has been dried; a medium transport unit that transports the medium in the order of the pretreatment liquid application unit, the pretreatment liquid drying unit, and the image forming unit, and transports the medium with the image formed thereon downstream; an image reading unit disposed downstream of the image forming unit and configured to obtain a read image by reading the image formed on the medium; a control unit that controls the application amount of the pretreatment liquid and the drying; Equipped with the control unit determines control conditions for the pretreatment liquid application unit and the pretreatment liquid drying unit in accordance with a determination result based on luminance information of the read image, and controls operations of the pretreatment liquid application unit and the pretreatment liquid drying unit in accordance with the control conditions. An image forming apparatus characterized by:

11. a pretreatment liquid application step of applying a pretreatment liquid to a sheet-like medium, a pretreatment liquid drying step of drying the pretreatment liquid applied to the medium, and an image forming step of forming a specific image on the medium from which the pretreatment liquid has been dried, in this order, while the medium is being conveyed; and an image reading step of acquiring a read image by reading the specific image formed on the medium after the image forming step. determining control conditions for the pretreatment liquid application step and the pretreatment liquid drying step according to a determination result based on luminance information of the read image; An image forming method comprising:

Images