Image formation device, method for colorimetry, and colorimetry program

Abstract

To provide an image formation device that can improve colorimetry accuracy of a colorimetry chart that is formed of photocurable ink, and to provide a method for colorimetry and a colorimetry program.SOLUTION: An image formation device includes an image formation unit 20, a colorimetry unit 40, and a control unit 50. The image formation unit 20 forms an image on a medium 60 with a photocurable ink. The colorimetry unit 40 performs colorimetry of a colorimetry chart 61 that is formed by the image formation unit 20. The control unit 50 controls such that the colorimetry unit 40 performs colorimetry of the colorimetry chart 61 after the lapse of a color change time from light irradiation to the colorimetry chart 61.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, a color measurement method, and a color measurement program. [Background technology]

[0002] Conventionally, image forming apparatuses equipped with a color measurement device for color calibration, etc. have been known. For example, the image forming apparatus disclosed in Patent Document 1 fixes an image for measurement, cools it, and then measures the color. Cooling is considered to be an effective means of avoiding the effects of thermochromism. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-85122 Summary of the Invention [Problem to be solved by the invention]

[0004] Images formed on media using photocurable inks undergo color change even when not exposed to high temperatures. This color change is caused by the reaction of the photopolymerization initiator. This color change requires time to stabilize, but conventionally, color measurement was performed before stabilization. Therefore, even when color measurement and color adjustment were performed using a color measurement chart, it was not possible to achieve advanced color adjustment.

[0005] The present invention has been made to solve the above-mentioned problems, and its object is to provide an image forming apparatus, a color measurement method, and a color measurement program that can improve the color measurement accuracy of a color measurement chart formed with photocurable ink. [Means for solving the problem]

[0006] An image forming apparatus according to one aspect of the present invention includes an image forming unit that forms an image on a medium using photocurable ink, a color measurement unit that measures the color of a color measurement chart formed by the image forming unit, and a control unit that causes the color measurement unit to measure the color of the color measurement chart after a color change time has elapsed since the color measurement chart was irradiated with light. [Effects of the Invention]

[0007] According to the present invention, it is possible to improve the color measurement accuracy of a color measurement chart formed from photocurable ink. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 1 is a front view of a medium on which a color measurement chart according to a first embodiment of the present invention is formed. [Figure 3] 10 is a graph illustrating a color change in a photocurable ink after being irradiated with light. [Figure 4] 4 is a flowchart showing the flow of a color measurement method in the image forming apparatus according to the first embodiment of the present invention. [Figure 5] FIG. 10 is a front view of a medium on which a color measurement chart according to a second embodiment of the present invention is formed. [Figure 6] 10 is a flowchart showing the flow of a color measurement method in an image forming apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] Fig. 1 is a schematic diagram showing the configuration of an inkjet image forming apparatus according to an embodiment, Fig. 2 is a front view of a medium 60 on which a color measurement chart has been formed by the image forming apparatus. The image forming apparatus 1 includes a paper feed section 10, an image forming section 20, a discharge section 30, a color measurement unit 40, and a control section 50.

[0010] The paper feed unit 10 has a paper feed tray 11 and a medium supply unit 12. The paper feed tray 11 stores media 60. The medium supply unit 12 transports and supplies the media 60 from the paper feed tray 11 to the image forming unit 20. The medium supply unit 12 has a looped belt supported by two rollers on the inside. The medium supply unit 12 transports the medium 60 from the paper feed tray 11 to the image forming unit 20 by rotating the rollers with the medium 60 placed on the belt.

[0011] The image forming unit 20 forms an image on the medium 60 using photocurable ink. The photocurable ink used is ink containing a photopolymerization initiator. The photocurable ink undergoes a color change due to the curing reaction of the photopolymerization initiator. This color change stabilizes over time. Furthermore, the image forming unit 20 forms an image of the color measurement chart on the medium 60 at the timing of performing color measurement. The color measurement chart 61 has a large number of patches 62 to be measured. The color measurement chart 61 may have patches 62 for all colors included in the image data. The color measurement chart 61 of this embodiment has a large number of rectangular patches 62 arranged vertically and horizontally in a matrix.

[0012] Returning to FIG. 1, the image forming section 20 includes a transport drum 21, a delivery unit 22, a heating section 23, a head unit 24, a fixing section 25, an imaging section 26, and a delivery section . The transport drum 21 is formed in a cylindrical shape. The outer peripheral surface of the transport drum 21 serves as a transport surface on which the medium 60 is placed. The transport drum 21 holds the medium 60 on the transport surface and rotates in the direction of the arrow in Figure 1. As a result, the transport drum 21 transports the medium 60 along the transport surface.

[0013] The transfer unit 22 includes a swing arm 221 and a transfer drum 222. The transfer unit 22 is disposed between the medium supply unit 12 of the paper feed unit 10 and the transport drum 21. The transfer unit 22 holds and picks up the medium 60 transported from the medium supply unit 12 with the swing arm 221, and transfers it to the transport drum 21 via the transfer drum 222.

[0014] The heating unit 23 is disposed between the delivery drum 222 and the head unit 24. The medium 60 held by the transport drum 21 is heated to a predetermined temperature range. The heating unit 23 includes, for example, an infrared heater.

[0015] The head unit 24 includes a plurality of inkjet heads that eject photocurable ink. The head unit 24 forms an image by ejecting photocurable ink onto the medium 60 based on image data at appropriate timing according to the rotation of the transport drum 21. The head unit 24 is disposed with its ink ejection surface facing the transport drum 21 at a predetermined distance.

[0016] The image forming apparatus 1 of this embodiment includes a plurality of head units 24 corresponding to four colors of ink: yellow (Y), magenta (M), cyan (C), and black (K). The plurality of head units 24 are arranged in the order of Y, M, C, and K from the upstream side in the transport direction of the medium 60.

[0017] The fixing unit 25 has a light-emitting unit arranged across the width direction (height direction of the cylindrical shape) of the transport drum 21. The fixing unit 25 irradiates the medium 60 placed on the transport drum 21 with energy rays such as ultraviolet rays, thereby curing and fixing the photo-curable ink on the medium 60.

[0018] The imaging unit 26 is located downstream of the head unit 24 and the fixing unit 25 in the conveyance direction on the conveyance path, and captures an image of the surface of the medium 60, outputting the image as read data to the control unit 50. The imaging unit 26 has multiple line sensors. The line sensors may be, for example, CMOS sensors.

[0019] The delivery unit 28 is a discharge path for the medium 60 on which an image has been formed. The delivery unit 28 is provided between the image forming unit 20 and the discharge unit 30. The delivery unit 28 has a belt loop 282 and a transfer drum 281. The belt loop 282 has a ring-shaped belt supported by two rollers. The transfer drum 281 has a cylindrical shape and transfers the medium 60 from the transport drum 21 to the belt loop 282. The delivery unit 28 transports the medium 60 that has been transferred from the transport drum 21 onto the belt loop 282 by the transfer drum 281, and discharges the medium 60 to the discharge unit 30.

[0020] The delivery unit 28 of this embodiment includes a switching unit 283 downstream of the delivery drum 281. The switching unit 283 switches the destination of the medium 60 sent from the image forming unit 20. The switching unit 283 selectively switches the destination of the medium 60 between the discharge unit 30, the first sampling tray 32, and the colorimetry unit 40. During normal image formation, the destination of the switching unit 283 is the discharge unit 30. In this case, the switching unit 283 sends the medium 60 to the belt loop 282.

[0021] Furthermore, the switching unit 283 can take out some of the media 60 and discharge them to the first sampling tray 32, separate from the media 60 discharged to the discharge unit 30. In other words, the switching unit 283 can switch the destination to send the media 60 to the belt loop 284 that is continuous with the first sampling tray 32. When performing colorimetry of the colorimetry chart 61, the switching section 283 sends the medium 60 on which the colorimetry chart 61 is formed to the colorimetry unit .

[0022] The discharge unit 30 is disposed downstream of the image forming unit 20, specifically downstream of the belt loop 282. The discharge unit 30 has a paper output tray 31 on which the medium 60 conveyed by the belt loop 282 is placed.

[0023] The color measurement unit 40 measures the color of a color measurement chart 61 formed on a medium 60 by the image forming unit 20. The color measurement unit 40 includes a color measurement transport unit 41, an environmental temperature detection unit 42, a medium heating unit 43, a color measurement unit 44, and a second sampling tray 45. The colorimetry transport section 41 transports the medium 60 sent out from the switching section 283 to the colorimetry position of the colorimetry unit 40. The colorimetry transport section 41 has an introduction section 46 and a standby section 47 between it and the colorimetry section 44. The introduction section 46 transports the medium 60 from the switching section 283 to the standby section 47. The standby section 47 causes the introduced medium 60 to wait upstream of the colorimetry section 44. The introduction section 46 and the standby section 47 each have independent rollers and belts and can be driven separately.

[0024] The environmental temperature detection unit 42 detects the environmental temperature of the colorimetric unit 40. In this embodiment, the cover 48 covers almost the entire unit, including the colorimetric transport unit 41 and the colorimetric unit 44. The environmental temperature detection unit 42 detects the temperature of the internal space of the cover 48 in which the medium 60 is placed, and transmits the temperature to the control unit 50.

[0025] The medium heating unit 43 heats the medium 60 on which the color measurement chart 61 is formed. The medium heating unit 43 may be, for example, a hot air supply unit that blows hot air onto the medium 60. The medium heating unit 43 may also be an IR heater that irradiates the medium 60 with infrared rays. Furthermore, the medium heating unit 43 may be a belt heating unit that heats a belt that carries and transports the medium 60. The medium heating unit 43 can heat the medium to a temperature higher than the ambient temperature. However, the medium heating unit 43 must heat the medium within a temperature range that does not cause discoloration of the photocurable ink or the medium 60. The heating temperature of the medium heating unit 43 can be measured as the surface temperature of the medium 60.

[0026] The colorimetric unit 44 measures the color of each patch 62 on the colorimetric chart 61. In this embodiment, the colorimetric unit 44 is capable of measuring the color of all patches 62 on the colorimetric chart 61. The colorimetric values ​​of each patch 62 are acquired as values ​​quantified in the Lab color space, for example. The color measurement values ​​fluctuate due to color changes caused by the photopolymerization initiator in the photocurable ink. In this embodiment, each patch 62 on the color measurement chart 61 is irradiated with light by the fixing unit 25 of the image forming unit 20, and as a result, the patch 62 turns yellow over time.

[0027] 3 is a graph showing an example of color change in photocurable ink after light irradiation. The horizontal axis represents the time elapsed after light irradiation in the fixing unit 25, and the vertical axis represents the degree of yellowing detected by the amount of change in colorimetric value. In Figure 3, solid line A shows the change when medium 60 is heated by medium heating unit 43, and dotted line B shows the change when medium 60 is not heated by medium heating unit 43. Both solid line A and dotted line B are results obtained when the same photocurable ink is used. Note that the vertical dashed dotted lines in Figure 3 indicate the elapsed time at which each colorimetric value is considered to have stabilized.

[0028] As is clear from Figure 3, the time elapsed until the colorimetric values ​​stabilize varies depending on the type of photocurable ink and the temperature of the medium. In the case of the change without heating shown by dotted line B in Figure 3, the time elapsed until the colorimetric values ​​stabilize depends on the formulation of the photocurable ink, but it takes about 10 minutes. On the other hand, in the case of the change with heating shown by solid line A, it is clear that although the time until stabilization can be shortened, a certain amount of time or more is still required until stabilization.

[0029] Therefore, the color measurement section 44 of the color measurement unit 40 of this embodiment acquires stable color measurement values ​​for each patch of the color measurement chart 61 after the color change has stabilized under the control of the control section 50 described below. The colorimetric values ​​of each patch on the colorimetric chart 61 are transferred to the control unit 50 and used for color correction in the image forming unit 20, etc.

[0030] 1 , the second sampling tray 45 is a portion where the medium 60 on which the colorimetry chart 61 is formed is discharged after colorimetry, and is disposed downstream of the colorimetry unit 44. The medium 60 that has been measured by the colorimetry unit 44 is conveyed to the second sampling tray 45 by the colorimetry conveying unit 41.

[0031] The operation of the color measurement unit 40 is controlled by a control unit 50, which will be described later. The color measurement unit 40 of this embodiment is configured to be operable even when the image forming unit 20 is stopped. For example, even if various errors occur in the image forming unit 20 and operation stops, the color measurement unit 40 continues to measure the color of the medium 60 that has already been introduced.

[0032] The control unit 50 includes a central processing unit (CPU), read only memory (ROM), and random access memory (RAM), which are computer hardware resources. The CPU reads out a predetermined program from the ROM, loads it into the RAM, and controls the overall operation of each part of the image forming apparatus 1 in accordance with the loaded program. That is, the control unit 50 of this embodiment controls the operations of the paper feed unit 10, the image forming unit 20, the discharge unit 30, and the color measurement unit 40. The computer-readable recording medium storing the program is not limited to a ROM, and may be a portable recording medium such as a hard disk drive (HDD), a CD-ROM, or a DVD disk. The ROM and portable recording medium are used as examples of a computer-readable non-transitory storage medium that stores the program executed by the control unit 50.

[0033] In controlling the operation of the color measurement unit 40, the control unit 50 causes the color measurement unit 40 to measure the color of the color measurement chart 61 after the color change time has elapsed since the color measurement chart 61 was irradiated with light. The control unit 50 controls the operation of the color measurement unit 40 in accordance with a color measurement program.

[0034] The color measurement program will be described later, but this color measurement program includes a step of making the color measurement unit 40 wait for the medium 60 in accordance with the color change time from the light irradiation. The control unit 50 can preset a standby time corresponding to the color change time. The control unit 50 also causes the colorimetric unit 40 to stop transport by the colorimetric transport unit 41 during the preset standby time.

[0035] The control unit 50 can change the waiting time depending on the type of photocurable ink. The type of photocurable ink may be distinguished, for example, by the type and amount of photopolymerization initiator contained in the photocurable ink. The control unit 50 stores in advance in a storage unit (not shown) a table showing the correlation between the type of photo-curable ink and the standby time from light irradiation. When the image forming apparatus 1 is operating, the operator inputs information that identifies the type of ink into the input unit, and the control unit 50 can appropriately set the standby time for the color measurement chart 61 in the color measurement unit 40.

[0036] Furthermore, the control unit 50 can change the standby time depending on the ambient temperature of the color measurement unit 40. Furthermore, when the medium 60 is heated by the medium heating unit 43, the standby time can be changed depending on the heating temperature of the medium heating unit 43. When the ambient temperature or the heating temperature by the medium heating unit 43 is high, the control unit 50 can shorten the standby time because the curing reaction is promoted.

[0037] The control unit 50 also stores in advance in a storage unit (not shown) a table showing the correlation between the ambient temperature and the standby time from light irradiation, and a table showing the correlation between the heating temperature of the medium heating unit 43 and the standby time from light irradiation. The control unit 50 can appropriately set the standby time for the color measurement chart 61 by transmitting and acquiring information on the ambient temperature and heating temperature. The color measurement program causes the color measurement chart 61 to wait, and then causes the color measurement unit 40 to measure the color of the color measurement chart 61 and obtain the color measurement values ​​of the color measurement chart 61 .

[0038] Next, a method for measuring the color of the color measurement chart 61 in the color measurement unit 40 will be described. FIG. 4 is a flowchart showing the flow of the color measurement method in which the color measurement program is executed. First, the control unit 50 acquires the type of photocurable ink when performing color measurement of the color measurement chart 61 in the color measurement unit 40 (S1). The type of photocurable ink includes the type and amount of photopolymerization initiator. The type of photocurable ink may be input by the operator into the input unit. Next, the control unit 50 acquires the environmental temperature from information transmitted from the environmental temperature detection unit 42 (S2). Then, the control unit 50 sets the standby time based on the type of photo-curable ink, the environmental temperature, and the heating temperature (S3).

[0039] Meanwhile, the image forming unit 20 prints by forming a color measurement chart 61 on the medium 60 before or after normal image formation, or during image formation (S4). Then, the control unit 50 starts measuring the standby time from the light irradiation of the fixing unit 25 of the image forming unit 20. Next, the control unit 50 moves the medium 60 of the colorimetry chart 61 from the image forming unit 20 to the standby unit 47 of the colorimetry unit 40 via the switching unit 283 and the introduction unit 46. Then, the control unit 50 stops the medium 60 at the standby position of the standby unit 47 and makes it wait (S5).

[0040] In the standby unit 47, the control unit 50 turns on the medium heating unit 43 to heat the standby position to a preset heating temperature, thereby heating the medium 60 of the color measurement chart 61 (S6). The control unit 50 maintains this state until the preset standby time is reached (S7). Then, after the standby time has elapsed, the control unit 50 turns off the medium heating unit 43 to end heating of the standby position (S8).

[0041] Then, the control unit 50 moves the medium 60 of the colorimetry chart 61 to the colorimetry unit 44 using the colorimetry transport unit 41. The colorimetry unit 44 measures the color of each patch of the colorimetry chart 61 and transmits the colorimetry value of each patch to the control unit 50 (S9). The colorimetry value of each patch of the colorimetry chart 61 is used for color correction of the image forming unit 20, etc. Thereafter, the colorimetry transport unit 41 moves the medium 60 with the colorimetry chart 61 onto the second sampling tray 45 and discharges it (S10). This completes the colorimetry of the medium 60 with the colorimetry chart formed thereon.

[0042] According to the image forming apparatus 1 of the present embodiment as described above, the control unit 50 causes the color measurement unit 40 to perform color measurement after the color change time has elapsed since the light irradiation of the color measurement chart 61. Therefore, the color measurement unit 40 can obtain the color measurement values ​​of the color measurement chart 61 after the color change of the color measurement chart 61 has stabilized. As a result, the color measurement accuracy of the color measurement chart 61 is improved.

[0043] The photocurable ink of this embodiment contains a photopolymerization initiator. The color measurement unit 40 measures the color after the color change time has elapsed. Therefore, even when using photocurable ink containing a photopolymerization initiator, the color measurement unit 40 can prevent a decrease in the accuracy of the color measurement values ​​due to color changes such as yellowing of the color measurement chart 61 caused by the photopolymerization initiator.

[0044] In this image forming apparatus 1, the control unit 50 causes the color measurement chart 61 to wait in accordance with the passage of time for color change, and then causes the color measurement unit 40 to measure the color of the color measurement chart 61. Therefore, the color measurement unit 40 can easily obtain the color measurement values ​​of the color measurement chart 61 after the color change of the color measurement chart 61 has stabilized.

[0045] In this embodiment, the colorimetric unit 40 has a colorimetric transport unit 41 that transports the colorimetric chart 61 to the colorimetric position. The control unit 50 also controls the colorimetric transport unit 41 to stop transporting the colorimetric chart 61 in accordance with a preset color change time. Therefore, the colorimetric transport unit 41 can stop the colorimetric chart 61 before color measurement and wait. This makes it easier for the colorimetric unit 40 to ensure a wait time corresponding to the color change time.

[0046] The control unit 50 of this embodiment can set a standby time corresponding to the color change time. The standby time can be changed depending on the type of photocurable ink. This allows the control unit 50 to appropriately adjust the standby time in accordance with the color change time of various photocurable inks, thereby allowing the color measurement unit 40 to appropriately measure the colors, making it easier for the control unit 50 to ensure color measurement accuracy.

[0047] Furthermore, the control unit 50 can change the standby time depending on the environmental temperature of the color measurement unit 40 . This allows the control unit 50 to appropriately adjust the standby time in accordance with the color change time of the photo-curable ink at the ambient temperature, thereby allowing the color measurement unit 40 to appropriately perform color measurement. Therefore, the control unit 50 can easily shorten the color measurement time of the color measurement chart 61 while ensuring color measurement accuracy.

[0048] Moreover, the color measurement unit 40 includes a medium heating section 43 that heats the medium 60 of the color measurement chart 61. Furthermore, the control section 50 can change the standby time by changing the heating temperature of the medium heating section 43. Therefore, the medium heating unit 43 can accelerate the photocuring reaction by the heating temperature, thereby shortening the color change time. The control unit 50 can then appropriately adjust the standby time according to the color change time at the heating temperature, allowing the color measurement unit 40 to appropriately measure the color. Furthermore, the control unit 50 can shorten the color measurement time of the color measurement chart 61 while ensuring color measurement accuracy.

[0049] The control unit 50 of this embodiment can operate the color measurement unit 40 while the image forming unit 20 is stopped. Therefore, even if the image forming unit 20 stops due to various errors, the color measurement of the color measurement chart 61 can be continued. Therefore, the color measurement unit 40 can efficiently measure the color of the color measurement chart 61.

[0050] The image forming apparatus 1 of this embodiment includes a discharge section 30 downstream of the image forming section 20 for discharging the image-formed medium 60. In the delivery section 28, which is a discharge path between the image forming section 20 and the discharge section 30, a first sampling tray 32 and a second sampling tray 45 are provided, each branching off from the discharge path. The first sampling tray 32 is for discharging a portion of the medium 60 that is discharged to the discharge section 30. The second sampling tray 45 is for discharging the medium 60 on which the color measurement chart 61 is formed after color measurement.

[0051] In this way, the control unit 50 can separate and discharge the media 60 that are not to be discharged to the discharge unit 30 from the media 60 that are to be discharged to the discharge unit 30. Furthermore, among the media 60 that are not to be discharged to the discharge unit 30, the control unit 50 can separate and discharge the media 60 on which the colorimetry chart 61 is formed and the other media 60 to separate sampling trays 32, 45. Therefore, the control unit 50 can easily process the media 60 after image formation.

[0052] [Modification of the first embodiment] In the image forming apparatus and color measurement method of the first embodiment, the control unit 50 stops the medium 60 at the standby position of the standby unit 47, thereby causing the medium 60 to wait, but this is not limited to this. The control unit 50 may set the time from light irradiation by the fixing unit 25 of the image forming unit 20 until color measurement to be a preset standby time.

[0053] For example, the control unit 50 may adjust the conveying speed of the colorimetry conveying unit 41 so as to decrease it in accordance with a preset color change time. The conveying speed can also be set by an operator inputting it into the input unit. This allows the colorimetry unit 40 to adjust the time it takes to be transported to the transport position before colorimetry. Therefore, the colorimetry unit 40 can make the medium 60 of the colorimetry chart 61 before colorimetry wait in the colorimetry transport section 41 without stopping it midway through transport. Even with this method, the control section 50 can ensure a wait time corresponding to the color change time before colorimetry, thereby improving colorimetry accuracy.

[0054] [Another Modification of the First Embodiment] In the first embodiment, an example was described in which the control unit 50 sets the standby time based on information about the ambient temperature and the heating temperature, but this is not particularly limited. For example, the control unit 50 may set the standby time based only on the type of ink, without relying on this information. Furthermore, the control unit 50 may set the standby time based on the type of ink and information about either the ambient temperature or the heating temperature.

[0055] [Second embodiment] Next, a second embodiment of the present invention will be described. Fig. 5 is a front view of a color measurement chart 61 used in the color measurement method of the second embodiment. Fig. 6 is a flowchart showing the flow of the color measurement method executed by the color measurement program in the second embodiment. In the second embodiment, the configuration of the medium 60 on which the color measurement chart 61 is formed and the color measurement unit 40 differ from those in the first embodiment. Also, in the second embodiment, the color measurement method differs from that in the first embodiment. The rest is the same as in the first embodiment.

[0056] As shown in FIG. 5 , the medium 60 formed in the second embodiment has a color measurement chart 61 and a color change detection patch 62b. The color measurement chart 61 is the same chart as in the first embodiment, and is measured in the color measurement unit 44, with the color measurement results being used for color correction and the like in the image forming unit 20. The color change detection patch 62b is a patch 62 provided in a separate area from the color measurement chart 61. The medium 60 of this embodiment has one color change detection patch 62b adjacent to the color measurement chart 61. The color measurement chart 61 and the color change detection patch 62b are formed simultaneously in the image forming unit 20.

[0057] The image forming apparatus 1 of the second embodiment can also be described with reference to the schematic diagram showing the overall configuration shown in FIG. The color measurement unit 40 of the second embodiment has a device configuration that can repeatedly measure the color of some of the same patches 62 on the medium 60 of the color measurement chart 61. Specifically, the color measurement unit 40 of the second embodiment differs from the measurement unit 40 of the first embodiment in that it has a device configuration that allows repeated color measurement of the color change detection patch 62b.

[0058] As in the first embodiment, the color measurement unit 40 has a chart color measurement head 44a in the color measurement section 44 that measures the color of the color measurement chart 61. In addition, the color measurement unit 40 of the second embodiment has a color change detection color measurement head 44b in the standby section 47 that can repeatedly measure the color of the color change detection patch 62b. The chart color measurement head 44a is installed in the color measurement unit 44. The chart color measurement head 44a is installed so as to be movable relative to the color measurement chart 61 in order to measure the color of a large number of patches 62 on the color measurement chart 61.

[0059] The color measurement head for color change detection 44b is fixedly installed at a specific position in the standby section 47. When the medium 60 stops in the standby section 47, the specific position where the color measurement head for color change detection 44b is installed is a position facing the color change detection patch 62b. When the medium moves without stopping in the standby section 47, the specific position where the color measurement head for color change detection 44b is installed is a position facing the movement path of the color change detection patch 62b.

[0060] The control unit 50 of the second embodiment controls the operation of the color measurement unit 40 in accordance with a color measurement program. The color measurement program, which will be described later, includes a step of causing the color measurement unit 40 to repeatedly measure the color of the color change detection patches 62b and determining the passage of time for the color change based on changes in the detected color measurement values. The control unit 50 determines that the time for the color change has passed since the light irradiation when the change in the color measurement values ​​of the color change detection patches 62b falls within a predetermined range. After this determination, the control unit 50 causes the color measurement transport unit 41 to move the medium 60 to the color measurement unit 44 to acquire the color measurement values ​​of the color measurement chart 61.

[0061] Hereinafter, a method for measuring the color of the color measurement chart 61 using the color measurement unit 40 of the second embodiment will be described. As shown in FIG. 6, to measure the color of the color measurement chart 61 in the color measurement unit 40, the image forming section 20 first forms and prints the color measurement chart 61 and color change detection patches 62b on the medium 60 (S21). The control unit 50 moves the medium 60, on which the color measurement chart 61 and the color change detection patches 62b are formed, from the image forming unit 20 to the standby unit 47 of the color measurement unit 40 via the switching unit 283 and the introduction unit 46. In the standby unit 47, the medium 60 waits in a stopped state.

[0062] The control unit 50 causes the color measurement head 44b for detecting a color change to measure the color of the patch 62b for detecting a color change on the medium 60 in the standby unit 47 (S22). The control unit 50 stores the color measurement values ​​at this time in a storage unit (not shown). Then, the control unit 50 determines whether the color change is stable by comparing the measured colorimetric value with the previous colorimetric value (S23). The first time, there is no previous colorimetric value, and the control unit 50 compares the measured colorimetric value with the default value, so the control unit 50 always determines that the color change is not stable.

[0063] When it is determined that the color change is not stable, the control unit 50 counts a predetermined time. This predetermined time in the timer count (S24) may be significantly shorter than the standby time in the first embodiment. Thereafter, the control unit 50 again causes the color measurement head 44b for detecting color change to measure the color of the patch 62b for detecting color change (S22), and compares the color measurement value with the previous color measurement value to determine whether the color change is stable (S23).

[0064] The control unit 50 repeats the steps of measuring the color change detection patch 62b (S22), comparing it with the previous color measurement value (S23), and counting a predetermined time on the timer (S24).The control unit 50 then acquires the change between the measured color measurement value and the previous color measurement value stored in the memory unit each time. Then, the control unit 50 determines that the color change has stabilized when the change between the colorimetric value measured and the previous colorimetric value falls within a predetermined range (S23).

[0065] After stabilization, the control unit 50 controls the colorimetry transport unit 41 to move the medium 60 to the colorimetry unit 44. The colorimetry unit 44 measures the color of each patch 62 on the colorimetry chart 61 and transmits the colorimetry value of each patch 62 to the control unit 50 (S25). The colorimetry value of each patch 62 on the colorimetry chart 61 is used for color correction of the image forming unit 20, etc. Thereafter, the control unit 50 moves the medium 60 with the color measurement chart 61 by the color measurement transport unit 41 to the second sampling tray 45 and ejects it (S26). This allows the control unit 50 to complete the color measurement of the medium 60 on which the color measurement chart 61 and the color change detection patches 62b are formed.

[0066] The image forming apparatus 1, color measurement method, and color measurement program of the second embodiment described above can also obtain the same effects as those of the first embodiment by using the same configuration. Moreover, in the second embodiment, the color measurement unit 40 can repeatedly measure the color of the same color change detection patch 62b on the medium 60 on which the color measurement chart 61 is formed. The control unit 50 then causes the color measurement unit 40 to repeat the color measurement, and determines whether a color change time has elapsed based on a change in the color measurement value of the same color change detection patch 62b. Therefore, the control unit 50 can reliably determine that the color change has stabilized, and the color measurement accuracy of the color measurement chart 61 can be reliably improved.

[0067] Furthermore, the control unit 50 of the second embodiment acquires the colorimetric values ​​of the colorimetric chart 61 after the change in the colorimetric values ​​of the same color change detection patch 62b has reached a predetermined range. Therefore, the control unit 50 can easily cause the color measurement unit 40 to obtain the color measurement values ​​of the color measurement chart 61 after the color change of the color measurement chart 61 has stabilized.

[0068] Furthermore, the colorimetry unit 40 of the second embodiment has a chart colorimetry head 44a and a color change detection colorimetry head 44b that repeatedly measures the color of the same color change detection patch 62b. Therefore, the control unit 50 can prevent the chart colorimetry head 44a of the colorimetry unit 40 from being used too frequently to detect the stability of color changes. This allows the control unit 50 to prevent a portion of the chart colorimetry head 44a from deteriorating or losing accuracy, and maintain high colorimetry accuracy.

[0069] Furthermore, the medium 60 of the second embodiment has a color measurement chart 61 and a color change detection patch 62b provided in a region separate from the color measurement chart 61. In this way, the color measurement unit 40 can be equipped with a color change detection color measurement head 44b dedicated to measuring the color of the color change detection patch 62b. Moreover, the color measurement unit 40 can fix the color change detection color measurement head 44b without having to move it to a specific position on the color measurement unit 40. This eliminates the need for a mechanism to move the color change detection color measurement head 44b, allowing for a simplified device configuration of the color measurement unit 40.

[0070] [Modification of the second embodiment] In the second embodiment described above, the medium 60 had the color measurement chart 61 and the color change detection patch 62b. Also, the color change detection color measurement head 44b was provided in the standby section 47 to measure the color of the color change detection patch 62b. However, the second embodiment is not limited to this as long as it is within the scope of the present invention.

[0071] For example, the medium 60 may not have the color change detection patches 62b, but may have the color measurement chart 61 as in the first embodiment. In this case, the control unit 50 can cause the color change detection color measurement head 44b in the standby unit 47 to repeatedly measure the color of some of the same patches 62 in the color measurement chart. Then, after the change in the color measurement value of the same patch 62 reaches a predetermined range, the control unit 50 can move the medium 60 to the color measurement unit 44 and cause it to measure the color of the color measurement chart 61.

[0072] Furthermore, standby section 47 of colorimetry unit 40 does not have to have color change detection colorimetry head 44b. In that case, if medium 60 having colorimetry chart 61 and color change detection patches 62b is used, colorimetry section 44 may have chart colorimetry head 44a and color change detection colorimetry head 44b. In this way, the color measurement unit 40 does not need to have the standby section 47, and therefore the device configuration can be simplified.

[0073] Furthermore, if the medium 60 does not have a patch 62b for detecting color changes but has a color measurement chart 61, the control unit 50 may cause the chart color measurement head 44a of the color measurement unit 44 to repeatedly measure the color of some of the same patches 62 in the color measurement chart. In this way, in the second embodiment, even if the color measurement unit 40 repeatedly performs color measurement to detect the stability of color change, it is possible to prevent the device configuration from becoming complicated.

[0074] In the second embodiment and its modified example, the colorimetry transport unit 41 moves the medium 60 in one direction from the standby unit 47 to the colorimetry unit 44. However, the colorimetry transport unit 41 may be capable of moving the medium 60 in both directions between the standby unit 47 and the colorimetry unit 44. In this case, the control unit 50 can return the medium 60 from the colorimetry unit 44 to the standby unit 47 and wait there after measuring the color of the color change detection patches 62b. The control unit 50 can measure the color of the color change detection patches 62b by repeatedly moving the medium 60 back and forth between the colorimetry unit 44 and the standby unit 47 until the color change of the color change detection patches 62b measured by the colorimetry unit 44 stabilizes. In this case, the standby section 47 may be large enough to allow multiple media 60 to be on standby.

[0075] It should be noted that the first and second embodiments described above can be modified in other respects as well, as long as the modifications do not depart from the gist of the invention as defined in the claims of the present invention. For example, in each of the above embodiments, the control unit 50 controls the operation of the entire apparatus as well as the color measurement unit 40. However, the control unit of the color measurement unit 40 may be configured separately from the control units of other parts such as the image forming unit 20. The colorimetry of the colorimetry chart 61 in each of the above embodiments can also be combined. For example, first, as in the first embodiment, the control unit 50 puts the colorimetry chart 61 into standby for a preset color change time. Then, as in the second embodiment, the control unit 50 can repeatedly measure the colorimetry of the same color change detection patch 62b, and after determining that the color change has reliably stabilized, measure the colorimetry chart 61. In this case, in the flow of the colorimetry method shown in FIGS. 4 and 6, the control unit 50 sets a standby time (S1 to S3), puts the colorimetry chart 61 into standby (S4 to S8), determines whether the color of the color change detection patch 62b has stabilized (S22 to S24), and measures the colorimetry chart 61. In this way, even if the control unit 50 sets an inappropriate standby time or sets the standby time simply without regard to various conditions, it is possible to reliably measure the color after the color has stabilized. [Explanation of symbols]

[0076] 1...image forming apparatus, 20...image forming section, 21...conveyor drum, 23...heating section, 24...head unit, 25...fixing section (light irradiation section), 28...delivery section (discharge path), 32...first sampling tray, 40...colorimetry unit, 41...colorimetry transport section, 42...ambient temperature detection section, 43...media heating section, 44...colorimetry section, 44a...chart colorimetry head, 44b...color change detection colorimetry head, 45...second sampling tray, 47...standby section, 50...control section, 60...medium, 61...colorimetry chart, 62...patch, 62b...color change detection patch

Claims

1. an image forming unit that forms an image on a medium using photocurable ink; a color measurement unit that performs color measurement of a color measurement chart formed on the medium by the image forming unit; a control unit that causes the color measurement unit to measure the color of the color measurement chart after a color change time has elapsed since the light irradiation of the color measurement chart; An image forming apparatus comprising:

2. The image forming apparatus according to claim 1 , wherein the control unit causes the color measurement chart to wait in accordance with the lapse of the color change time, and then causes the color measurement of the color measurement chart to be performed.

3. the color measurement unit has a color measurement transport section that transports the color measurement chart to a color measurement position, The image forming apparatus according to claim 2 , wherein the control unit causes the colorimetry transport unit to stop transport in accordance with the preset color change time.

4. the color measurement unit has a color measurement transport section that transports the color measurement chart to a color measurement position, The image forming apparatus according to claim 2 , wherein the control unit adjusts the transport speed of the colorimetry transport unit in accordance with the preset color change time.

5. the control unit is capable of setting a standby time corresponding to the color change time, The image forming apparatus according to claim 2 , wherein the waiting time is variable depending on the type of the photocurable ink.

6. the control unit is capable of setting a standby time corresponding to the color change time, The image forming apparatus according to claim 2 , wherein the standby time is variable depending on an environmental temperature of the color measurement unit.

7. the color measurement unit includes a medium heating section that heats the medium of the color measurement chart, the control unit is capable of setting a standby time corresponding to the color change time, 3. The image forming apparatus according to claim 2, wherein the standby time is variable depending on the heating temperature of the medium heating unit.

8. The medium heating unit is a hot air supply heating unit that supplies hot air to the medium, an IR heater that irradiates the medium with infrared rays, or a belt heating unit that places and transports the medium. The image forming apparatus according to claim 7 .

9. the color measurement unit is capable of repeatedly measuring the color of the same patch of at least a portion of the medium; 9. The image forming apparatus according to claim 1, wherein the control unit causes the color measurement unit to repeatedly measure the color of the same patch, and determines whether the color change time has elapsed based on a change in the color measurement value of the same patch.

10. The image forming apparatus according to claim 9 , wherein the control unit acquires the colorimetric values ​​of the colorimetric chart after a change in the colorimetric values ​​of the same patch has reached a predetermined range.

11. The color measurement unit a chart color measurement head that measures the color of the color measurement chart; The image forming apparatus according to claim 9 , further comprising: a color measurement head for detecting color change capable of repeatedly measuring the color of the same patch.

12. the color measurement unit has a chart color measurement section that measures the color of the color measurement chart, The image forming apparatus according to claim 9 , wherein the chart colorimetric measurement unit is capable of repeatedly measuring the color of the same patch.

13. 12. The image forming apparatus according to claim 11, wherein the medium is provided with the color measurement chart and a color change detection patch provided in an area separate from the color measurement chart.

14. The image forming apparatus according to claim 1 , wherein the control unit is capable of operating the color measurement unit while the image forming unit is out of operation.

15. a discharge section downstream of the image forming section for discharging the medium on which the image has been formed, The discharge path between the image forming unit and the discharge unit includes: a first sampling tray for discharging a portion of the medium discharged to the discharge section; and a second sampling tray for discharging the medium on which the color measurement chart is formed after color measurement, the second sampling tray being branched off from the discharge path.

16. The image forming apparatus according to claim 1 , wherein the photocurable ink contains a photopolymerization initiator.

17. A color measurement method for measuring the color of a color measurement chart formed on a medium using photocurable ink, comprising: Irradiating the color measurement chart with light; The medium is allowed to stand by for a predetermined waiting time corresponding to a color change time from the light irradiation; the color measurement chart is measured after the waiting time has elapsed.

18. A color measurement method for measuring the color of a color measurement chart formed on a medium using photocurable ink, comprising: Irradiating the color measurement chart with light, by repeatedly measuring the color of at least a portion of the same patch on the color measurement chart, a change in the color measurement value of the same patch is obtained; a color measurement method, wherein the color of the color measurement chart is measured after the change in the color measurement value reaches a predetermined range.

19. a step of making the medium wait for a predetermined waiting time corresponding to a color change time from light irradiation in a color measurement unit that performs color measurement on a color measurement chart formed on the medium using light-curable ink; a procedure of causing the color measurement unit to measure the color of the color measurement chart after the waiting time has elapsed, thereby acquiring color measurement values ​​of the color measurement chart; A color measurement program to be executed by a computer.

20. a step of causing a color measurement unit that performs color measurement on a color measurement chart formed on a medium using photocurable ink to repeatedly measure the color of at least a portion of the same patch on the color measurement chart, and detecting a change in the color measurement value of the same patch; a procedure for acquiring the colorimetric values ​​of the colorimetric chart by causing the colorimetric unit to measure the colorimetric chart after the change in the colorimetric values ​​of the same patch has reached a predetermined range; A color measurement program to be executed by a computer.

Images