Liquid discharge method

Abstract

To provide a liquid discharge method that can improve a quality of a coated film formed using discharge liquid.SOLUTION: The liquid discharge method, which discharges active energy ray curable liquid and irradiates the discharged liquid with active energy ray to cure the liquid, includes the steps of: forming a first coated film on a recording medium by discharging the liquid; forming a second coated film on a substrate, by discharging the liquid; evaluating the second coated film; and changing at least either of an irradiation condition for the active energy ray and a liquid discharge condition, on the basis of an evaluated result in the step of evaluating the second coated film.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a liquid ejection method. [Background technology]

[0002] Conventionally, image forming devices equipped with inkjet heads that eject ultraviolet-curable ink have been known (see, for example, Patent Documents 1 and 2). Such image forming devices include an ultraviolet irradiator that irradiates ultraviolet light to the ink ejected onto a recording medium to cure the ink, a carriage that carries the inkjet head and the ultraviolet irradiator, a carriage drive mechanism that moves the carriage in the main scanning direction, and a control unit that controls the operation of the ultraviolet irradiator. Summary of the Invention [Problem to be solved by the invention]

[0003] In a liquid ejection method using a liquid ejection device equipped with an irradiation unit for irradiating active energy rays such as ultraviolet rays, a decrease in output of the light source due to deterioration of the light source of the irradiation unit may cause poor curing of the liquid. In conventional technology, when the output of the light source decreases, the properties of the coating film formed by the ejected liquid may change.

[0004] An object of the present invention is to improve the quality of a coating film formed from a discharged liquid in a liquid discharge method for discharging an active energy ray-curable liquid. [Means for solving the problem]

[0005] A liquid ejection method according to one embodiment of the present invention is a liquid ejection method that ejects an active energy ray-curable liquid and irradiates the ejected liquid with active energy rays to cure the liquid, and includes the steps of ejecting the liquid to form a first coating film on the recording medium, ejecting the liquid to form a second coating film on a substrate, evaluating the second coating film, and changing at least one of the irradiation conditions of the active energy rays and the liquid ejection conditions based on the evaluation results in the step of evaluating the second coating film. Effect of the Invention

[0006] According to the present invention, in the liquid ejection method for ejecting an active energy ray-curable liquid, it is possible to improve the quality of a coating film formed from the ejected liquid. [Brief description of the drawings]

[0007] [Figure 1] 1 is a perspective view showing an image forming apparatus which performs an image forming method according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a plan view showing a carriage according to the first embodiment of the present invention. [Diagram 3] FIG. 2 is a plan view showing an image forming area, an evaluation image forming area, and a light quantity measuring device installation area according to the first embodiment of the present invention. [Figure 4] 1 is a block diagram showing a control device of an image forming apparatus according to a first embodiment of the present invention. [Diagram 5] 1 is a functional block diagram of an image forming apparatus according to a first embodiment of the present invention. [Figure 6] 4 is a flowchart showing the procedure of an image forming method according to the first embodiment of the present invention. [Figure 7] FIG. 11 is a plan view showing an image forming area, an evaluation image forming area, and a light quantity measuring device installation area according to a second embodiment of the present invention. [Figure 8] 13 is a plan view showing an image forming area, an evaluation image forming area, and a light quantity measuring device installation area according to a modified example. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an image forming method according to an embodiment of the present disclosure will be described with reference to the drawings. In each drawing, arrows indicating the X-axis direction, the Y-axis direction, and the Z-axis direction may be described as three orthogonal directions. The X-axis direction may be the scanning direction. The Y-axis direction may be the sub-scanning direction. The Z-axis direction may be the up-down direction. The X-axis direction, the Y-axis direction, and the Z-axis direction may be other directions. The X-axis direction includes the direction indicated by the arrow and the opposite direction. The Y-axis direction includes the direction indicated by the arrow and the opposite direction. The Z-axis direction includes the direction indicated by the arrow and the opposite direction.

[0009] In the examples shown in this specification, ink is an example of a liquid, and an image forming apparatus that forms an image on a recording medium with ink ejected by a liquid ejection method is described as an example of a liquid ejection method. Also, ultraviolet rays are described as an example of active energy rays, a printing image is described as an example of a first coating film, and an evaluation image is described as an example of a second coating film. Also, an image formation area is described as an example of a first area, and an evaluation image formation area is described as an example of a second area.

[0010] <Configuration of Image Forming Apparatus> Before describing the image forming method according to the first embodiment of the present invention, an image forming apparatus 100 that performs the image forming method according to the first embodiment of the present invention will be described with reference to Figures 1 to 5. Figure 1 is a perspective view showing the image forming apparatus 100 that performs the image forming method according to the first embodiment of the present invention. Figure 2 is a plan view showing a carriage 18 according to the first embodiment of the present invention.

[0011] [Ink and recording medium 20] The image forming apparatus 100 can eject ultraviolet-curable ink onto the recording medium 20 to form an image on the recording medium 20. The recording medium 20 may be, for example, a non-permeable recording medium. The recording medium 20 may be a sheet-shaped plastic material. Examples of the plastic material include polypropylene and polyethylene.

[0012] When forming an image using ultraviolet curable ink, the material of the recording medium is not limited, compared to when normal water-based ink is used. When ultraviolet curable ink is used, there is an advantage that there is a wider selection of recording media available, compared to when water-based ink is used. In this embodiment, a case where ink is ejected onto a recording medium 20 made of a plastic material will be described. Note that the image forming apparatus 100 may form an image by ejecting ultraviolet curable ink onto a recording medium 20 made of a material other than a plastic material.

[0013] [Stage 10] The image forming apparatus 100 includes a stage 10 on which a recording medium 20 is placed. The stage 10 may include a transport mechanism that transports the recording medium 20 in the Y-axis direction. The transport mechanism can transport the recording medium 20 in the Y-axis direction, which is the sub-scanning direction. The stage 10 is also called a flat bed. The stage 10 includes a flat bed surface 12, which is a flat surface on which the recording medium 20 is placed.

[0014] [Recording head 14] As shown in FIG. 2, the image forming apparatus 100 includes a plurality of recording heads 14. The image forming apparatus 100 includes a head unit 15 having a plurality of recording heads 14. The recording head 14 is an image forming section that ejects ultraviolet curable ink. Note that the "ultraviolet curable ink" may be simply referred to as "ink." The recording head 14 includes a flow path, a pressure chamber, and a nozzle. The recording head 14 includes a flow path forming substrate, a pressure chamber substrate, a vibration plate, and a nozzle plate. In the recording head 14, the flow path forming substrate, the pressure chamber substrate, the vibration plate, and the nozzle plate are laminated. An opening and a groove are formed in the flow path forming substrate, the pressure chamber substrate, and the nozzle plate.

[0015] An ink tank that stores ink is connected to the flow path of the recording head 14. Ink supplied from the ink tank to the flow path of the recording head 14 flows through the flow path and is supplied to the pressure chamber. The diaphragm includes a piezoelectric film. When the diaphragm expands and contracts, the volume of the pressure chamber changes, and the pressure of the ink inside the pressure chamber changes.

[0016] The recording head 14 has a circuit board on which a drive circuit for driving the diaphragm is mounted. The circuit board supplies a drive signal to the diaphragm, causing the diaphragm to expand and contract.

[0017] A plurality of nozzles are formed in the nozzle plate. The nozzles are through holes that penetrate the nozzle plate in the plate thickness direction. The nozzles communicate with the pressure chambers. Ink inside the pressure chambers passes through the nozzles and is ejected to the outside of the recording head 14. The nozzles are arranged facing downward. Ink ejected from the nozzles travels downward.

[0018] The multiple nozzles are aligned, for example, in the Y-axis direction. The multiple nozzles aligned in the Y-axis direction are called a nozzle row. The recording head 14 may have multiple nozzle rows arranged at predetermined intervals in the X-axis direction. The ink ejected from the nozzles adheres to the recording medium 20 to form an image on the recording medium 20.

[0019] [Ultraviolet irradiation device 16] The image forming apparatus 100 includes an ultraviolet irradiation device 16. The ultraviolet irradiation device 16 includes a UV lamp as a light source. The ultraviolet irradiation device 16 irradiates ultraviolet rays onto the recording medium 20 on the stage 10. The ultraviolet curable ink on the recording medium 20 is cured by being irradiated with ultraviolet rays. The ultraviolet irradiation devices 16 are disposed on both sides of the head unit 15 in the X-axis direction. The multiple ultraviolet irradiation devices 16 are disposed at a distance from each other in the X-axis direction.

[0020] The light source of the ultraviolet irradiation device 16 outputs an emission spectrum including ultraviolet regions such as UV-A, UV-B, and UV-C. Examples of the light source of the ultraviolet irradiation device 16 include a high-pressure mercury lamp, a metal halide lamp, an electrodeless UV lamp, a UV laser, a xenon lamp, an LED lamp, and a germicidal lamp.

[0021] LED lamps can narrow down the emission wavelength to a certain narrow wavelength range. LED lamps have good luminous efficiency at the peak wavelength. LED lamps can emit ultraviolet light with high illuminance. LED lamps have relatively low power consumption and long life. For example, a typical arc lamp has a peak illuminance of several W / cm at 365 nm. 2 In contrast, the peak illuminance of 395nm LED lamps and 405nm LED lamps is several tens of W / cm 2 , which is several times the peak illuminance of a typical arc lamp.

[0022] The light source used in these ultraviolet irradiation devices 16 may be selected according to the photopolymerization initiator in the ink composition. The light source of the ultraviolet irradiation device 16 may be matched as an emission peak wavelength according to the absorption characteristics of the photopolymerization initiator. For example, if the photopolymerization initiator reaction peak wavelength in the ink composition is 365 nm, it is appropriate to select a lamp with a strong wavelength region of 300 to 450 nm, specifically a metal halide lamp, and if the photopolymerization initiator reaction peak wavelength in the ink composition is 240 nm, it is appropriate to select a high-pressure mercury lamp, etc. As described above, while a normal arc lamp shows an emission spectrum in a wide wavelength range, an LED lamp, as described above, is characterized by showing a narrow emission spectrum around each central wavelength.

[0023] In addition to forming images using two or more types of ultraviolet lamps with different emission wavelengths and ink containing a polymerization initiator that reacts to the emission wavelength of each lamp, it is possible to secure a desired image quality partially by controlling the irradiation conditions. The irradiation conditions include the emission wavelength, leveling time, illuminance intensity, etc.

[0024] [Carriage 18] The image forming apparatus 100 includes a carriage 18 that carries a recording head 14 and an ultraviolet irradiation device 16. The carriage 18 is scanned in the X-axis direction along a gantry 30. The gantry 30 extends in the X-axis direction. The carriage 18 is supported by the gantry 30 and disposed above the stage 10.

[0025] [Maintenance Unit 32] The image forming apparatus 100 includes a maintenance unit 32. The maintenance unit 32 has a flushing area 34, a wiping unit 36, and a cap unit 38. The maintenance unit 32 is disposed below the carriage 18 in the Z-axis direction. The maintenance unit 32 is disposed at a position adjacent to the stage 10 in the X-axis direction. The maintenance unit 32 is disposed at a position overlapping with the stage 10 in the Y-axis direction.

[0026] The carriage 18 moves in the X-axis direction and is disposed above the maintenance unit 32. The carriage 18 can move above the maintenance unit 32 in the X-axis direction.

[0027] The flushing area 34, the wipe unit 36, and the cap unit 38 are arranged side by side in the X-axis direction. The flushing area 34 is arranged in a position closer to the stage 10 in the X-axis direction than the wipe unit 36 ​​and the cap unit 38. The wipe unit 36 ​​is arranged between the flushing area 34 and the cap unit 38 in the X-axis direction. The cap unit 38 is arranged in a position farther from the stage 10 in the X-axis direction than the flushing area 34 and the wipe unit 36.

[0028] The flushing area 34 is an ink discharge section where ink that does not contribute to image formation is ejected. The recording head 14 can adjust the viscosity of the ink in the recording head 14 by discharging ink into the flushing area 34. The wiping unit 36 ​​includes a brush portion that comes into contact with the nozzle surface of the recording head 14. The nozzle surface is the bottom surface of the nozzle plate, and faces downward. When the carriage 18 moves in the X-axis direction, the wiping unit 36 ​​comes into contact with the nozzle surface, and ink adhering to the nozzle surface is removed.

[0029] The cap unit 38 includes a cap that covers the nozzle surface. The cap unit 38 covers the nozzle surface from below. By covering the nozzle surface with the cap unit 38, evaporation of ink in the nozzles is suppressed.

[0030] [Light amount management] Next, a description will be given of light amount management in the image forming apparatus 100. Light amount management is management related to the amount of ultraviolet light irradiated from the ultraviolet irradiation device 16. Parameters in light amount management include peak illuminance (mW / cm 2 ) and the amount of light per unit area (mJ / cm 2 ) etc.

[0031] Note that the way that the landing ink droplets spread may differ depending on the type of recording medium 20. Therefore, the adhesion of the ink to the recording medium 20 and the glossiness of the surface of the ink that has landed on the recording medium 20 may vary depending on the type of recording medium 20. In addition to managing the amount of light, managing the state of the actual image is necessary to improve image quality and maintain coating quality.

[0032] In the image forming apparatus 100, a light amount measuring device (illuminance meter) 28 is installed on the irradiation surface onto which ultraviolet light is irradiated. Furthermore, in the image forming apparatus 100, an actual image (solid print) can be formed. The actual image is an image after irradiation with ultraviolet light. In the image forming apparatus 100, the light amount measuring device 28 can be installed according to the image, so that the peak illuminance, the accumulated light amount, and the actual image state can be grasped. In the image forming apparatus 100, the optimal irradiation conditions can be maintained while grasping the peak illuminance, the accumulated light amount, and the actual image state.

[0033] [Light measurement device 28] The image forming apparatus 100 includes a light amount measuring device 28, which is an illuminance meter that measures ultraviolet light. The light amount measuring device 28 includes a light receiving element. The light amount measuring device 28 can measure the ultraviolet light irradiated from the ultraviolet irradiation device 16. The light amount measuring device 28 is disposed on the stage 10.

[0034] [Light measurement device installation area 26] FIG. 3 is a plan view showing the image forming area, the evaluation image forming area, and the light amount meter installation area according to the first embodiment. A light amount meter installation area 26 is formed on the flat bed surface 12 of the stage 10. A light amount meter 28 is arranged in the light amount meter installation area 26. A mark indicating the range of the light amount meter installation area 26 may be attached to the flat bed surface 12. A user can arrange the light amount meter 28 in the light amount meter installation area 26. A user may change the position of the light amount meter 28 arranged in the light amount meter installation area 26. A plurality of light amount meters 28 may be arranged in the light amount meter installation area 26.

[0035] The light amount meter installation area 26 may be formed continuously in the Y-axis direction. The light amount meter installation area 26 may be arranged at an end of the flat bed surface 12 in the X-axis direction. The light amount meter installation area 26 is formed at an end closer to the maintenance unit 32 in the X-axis direction. The carriage 18 can move in the X-axis direction above the light amount meter installation area 26. The light amount meter installation area 26 is arranged outside the recording medium 20 in a plan view.

[0036] The light quantity measuring device installation area 26 may be formed over the entire length of the image forming area 22 described later.

[0037] [Image formation area 22] An image forming area 22 is set on the flat bed surface 12 of the stage 10. The image forming area 22 is an area where printing is possible. In FIG. 3, the carriage 18 is indicated by a two-dot chain line. The image forming area 22 may be set based on, for example, a print origin 21. For example, in a plan view, the print origin 21 may be a position that is a corner of the image forming area 22. The carriage 18 is movable above the image forming area 22. In a plan view, the image forming area 22 is set inside a recording medium 20 on the stage 10. The recording head 14 can land ink in the image forming area 22. The ultraviolet ray irradiation device 16 is in the image forming area 22 and can irradiate ultraviolet rays to the ink that has landed on the recording medium 20.

[0038] [Evaluation image forming area 24] An evaluation image formation area 24 is formed on the flat bed surface 12 of the stage 10. The evaluation image formation area 24 is set at a position different from the image formation area 22 and the light amount meter installation area 26 in a plan view. The evaluation image formation area 24 is an area in which an image is formed for checking the state of an actual image. The evaluation image formation area 24 is formed between the image formation area 22 and the light amount meter installation area 26 in the X-axis direction. The evaluation image formation area 24 may have the same length as the image formation area 22 in the Y-axis direction. The evaluation image formation area 24 may have the same length as the light amount meter installation area 26 in the Y-axis direction.

[0039] The carriage 18 is capable of moving above the evaluation image forming region 24. The recording head 14 is capable of forming an evaluation image by depositing ink in the evaluation image forming region 24. The ultraviolet ray irradiation device 16 is capable of irradiating the ink that has landed in the evaluation image forming region 24 with ultraviolet rays.

[0040] [Control device 200] Next, the control device 200 of the image forming apparatus 100 will be described with reference to Fig. 4. Fig. 4 is a block diagram showing the control device 200 of the image forming apparatus 100 according to the first embodiment. The control device 200 has a control unit 210.

[0041] A printer driver 110 is connected to the control unit 210. The printer driver 110 generates print data. The printer driver 110 may generate the print data in a host device such as an information processing terminal such as a PC (Personal Computer), an image reading device such as an image scanner, or an imaging device such as a digital camera. The printer driver 110 generates dot pattern data for outputting an image in the image forming apparatus 100.

[0042] [Control unit 210] The control unit 210 includes a CPU (Center Processing Unit) 201, a ROM (Read Only Memory) 202, a RAM (Random Access Memory) 203, and a NVRAM (Random Access Memory) 204.

[0043] The CPU 201 is a calculation unit and controls the overall operation of the image forming apparatus 100. The CPU 201 controls the transport operation of the recording medium 20 and the movement operation of the recording head 14. The ROM 202 is a read-only non-volatile storage medium. The ROM 202 stores programs such as firmware. The RAM 203 is a volatile storage medium that can read and write information at high speed. The RAM 203 is used as a working area when the CPU 201 processes information.

[0044] The NVRAM 204 is a non-volatile storage medium that can read and write information, and stores an OS (Operating System), various control programs, application programs, and the like.

[0045] A software control unit is configured by reading out a program stored in the storage unit into the RAM 203, and the CPU 201 performing calculations according to the program loaded into the RAM 203. The storage unit includes a ROM 202 and a NVRAM 204. The storage unit may include a storage medium such as an optical disk.

[0046] A combination of hardware and software control units constitutes a functional block that realizes the functions of the image forming apparatus 100. A CPU 201 and a RAM 203 function as various control units as shown in Fig. 5. The various control units will be described later.

[0047] The control unit 210 includes a head control unit 212, an ultraviolet irradiation control unit 214, and a transport mechanism control unit 216. The CPU 201 may configure the head control unit 212, the ultraviolet irradiation control unit 214, and the transport mechanism control unit 216 by loading a processing program recorded in the ROM 202 into the RAM 203 and executing the processing program.

[0048] The head control unit 212 generates a drive waveform for driving the recording head 14. The head control unit 212 outputs drive data for selectively driving a pressure generating unit of the recording head 14 and various associated data to the head driver 17. The pressure generating unit includes, for example, a piezoelectric element.

[0049] The ultraviolet irradiation control unit 214 generates a drive signal for driving the ultraviolet irradiation device 16. The ultraviolet irradiation control unit 214 can control the output of ultraviolet light irradiated from the ultraviolet irradiation device 16, for example, by outputting a drive signal to the ultraviolet irradiation device 16.

[0050] The transport mechanism control unit 216 generates a drive signal for driving the carriage transport mechanism 40. The carriage transport mechanism 40 includes a motor for transporting the carriage 18. The transport mechanism control unit 216 can output a drive signal to the motor of the carriage transport mechanism 40 to control the operation of the motor. The transport mechanism control unit 216 can control the carriage transport mechanism 40 to move the carriage 18. The carriage transport mechanism 40 includes a motor for moving the carriage 18 in the X-axis direction, and a motor for moving the gantry 30 in the Y-axis direction.

[0051] The head control unit 212 , the ultraviolet irradiation control unit 214 , and the transport mechanism control unit 216 can control the operation of the image forming apparatus 100 based on the operating conditions of the ultraviolet irradiation device 16 and the carriage transport mechanism 40 .

[0052] [Operation Panel 13] The image forming apparatus 100 includes an operation panel 13. The operation panel 13 is connected to a control unit 210. The operation panel 13 is an input unit that allows a user to operate and input information. The operation panel 13 may be, for example, a liquid crystal panel. The user can change the settings of printing conditions by operating the operation panel 13. The user can also change the settings of the irradiation conditions of ultraviolet light by the ultraviolet light irradiation device 16 by operating the operation panel 13. The user can input evaluation results of an evaluation image, which will be described later, and the like. Information input via the operation panel 13 is transmitted to the control unit 210. The operation panel 13 is provided near the stage 10, as shown in FIG. 1.

[0053] [Function configuration] Next, the functional configuration of the image forming apparatus 100 will be described with reference to Fig. 5. Fig. 5 is a functional block diagram of the image forming apparatus 100 according to the first embodiment. The CPU 201 shown in Fig. 4 executes a program stored in a storage unit such as the ROM 202 to realize the functions of the system control unit 252, memory control unit 254, communication control unit 256, ejection control unit 258, carriage control unit 260, measurement unit 262, evaluation unit 264, light source output adjustment unit 266, and printing condition setting unit 268 shown in Fig. 5. Note that external devices and sensors connected to the control unit 210 may execute some of these functions.

[0054] The system control unit 252 controls the overall operation of the image forming apparatus 100. The memory control unit 254 controls the operation of memories such as the ROM 202, the RAM 203, and the NVRAM 204. The communication control unit 256 controls communication with external devices connected to the control unit 210. The ejection control unit 258 controls the ejection of liquid by the recording head 14.

[0055] The carriage control unit 260 controls the movement of the carriage 18 in the carriage transport mechanism 40. The carriage control unit 260 can move the carriage 18 so that the ultraviolet irradiator 16 passes above the light quantity measuring device 28. The carriage control unit 260 can move the carriage 18 so that the recording head 14 passes above the image forming area 22 and the evaluation image forming area 24.

[0056] The measuring unit 262 calculates the peak illuminance (mW / cm ), which is the light intensity per unit area, based on the detection result by the light quantity measuring device 28. 2 ) and the amount of light per unit area (mJ / cm 2 Based on the detection result by the light quantity meter 28, the measurement unit 262 measures the peak illuminance (mW / cm 2 ) and the amount of light per unit area (mJ / cm 2 ) may be calculated.

[0057] The evaluation unit 264 receives an evaluation result of the evaluation image formed in the evaluation image forming area 24. The evaluation of the evaluation image is performed, for example, by a user. The evaluation unit 264 may link the evaluation result of the evaluation image with the ultraviolet ray irradiation conditions when the evaluation image was formed.

[0058] The light source output adjustment unit 266 adjusts the output of ultraviolet light irradiated from the ultraviolet irradiation device 16. The light source output adjustment unit 266 may change the output of ultraviolet light irradiated from the ultraviolet irradiation device 16 in response to an input operation by the user. The light source output adjustment unit 266 may change the output of ultraviolet light in response to the evaluation result of the evaluation image. The light source output adjustment unit 266 may change the output of ultraviolet light in response to the measurement result by the light quantity meter 28. The light source output adjustment unit 266 may change the output of ultraviolet light in response to the evaluation result of the evaluation image and the measurement result by the light quantity meter 28.

[0059] The light source output adjustment unit 266 may determine whether or not the ink that has landed on the recording medium 20 can be cured by the ultraviolet light irradiated from the ultraviolet light irradiation device 16 based on the measurement result by the light quantity measuring device 28. The light source output adjustment unit 266 may adjust the output of the ultraviolet light irradiated from the ultraviolet light irradiation device 16 based on this determination result. The light source output adjustment unit 266 may determine whether or not the ink can be cured based on a determination threshold. The light source output adjustment unit 266 can increase the output of the ultraviolet light when the amount of light of the ultraviolet light is equal to the determination threshold. For example, the ROM 202 stores a determination threshold for determining whether or not the ink can be cured.

[0060] For example, when the output of ultraviolet light is equal to or less than the determination threshold, the light source output adjustment unit 266 may determine that the ink cannot be cured even if the output of ultraviolet light in the ultraviolet irradiation device 16 is increased. When it is determined that the ink cannot be cured even if the output of ultraviolet light is increased, the printing condition setting unit 268 may change the settings of the printing conditions. The printing condition setting unit 268 may change the settings of the printing conditions so as to reduce the movement speed of the carriage 18.

[0061] The printing condition setting unit 268 can change the settings of the printing conditions in the image forming apparatus 100. The printing condition setting unit 268 may change the settings of the printing conditions in response to an input operation by a user. The printing condition setting unit 268 may change the settings of the printing conditions in response to an evaluation result of the evaluation image. The printing condition setting unit 268 may change the settings of the printing conditions in response to a measurement result by the light quantity meter 28. The printing condition setting unit 268 may change the settings of the printing conditions in response to the evaluation result of the evaluation image and the measurement result by the light quantity meter 28.

[0062] [Image forming method according to the first embodiment] Next, an image forming method according to the first embodiment will be described with reference to Fig. 6. The image forming method can be implemented using the image forming apparatus 100 described above. Fig. 6 is a flow chart showing the procedure of the image forming method according to the first embodiment. The image forming method is a method in which ultraviolet-curable ink is ejected, and the ejected ink is irradiated with ultraviolet light to cure the ink and form an image.

[0063] The image forming method includes a step of forming an image to be printed (step S11), a step of forming an image for evaluation (step S12), a step of measuring the amount of ultraviolet light (step S13), a step of evaluating the image for evaluation (step S14), a step of saving the evaluation results and the measurement results (step S15), a step of adjusting the output of the light source (step S16), and a step of adjusting the movement speed of the carriage 18 (step S17).

[0064] In the process of forming an image to be printed (step S11), ink is ejected from the nozzles to form an image to be printed in an image forming area 22 of the recording medium 20. In the process of forming an image to be printed, the carriage 18 is scanned in the X-axis direction, ink is ejected from the nozzles of the recording head 14, and ultraviolet rays are irradiated onto the ink that has landed on the recording medium 20. In the image forming apparatus 100, ultraviolet rays are irradiated from an ultraviolet irradiation device 16 located behind the recording head 14 in the transport direction while the carriage 18 is transported in the X-axis direction. After being irradiated with this ultraviolet light, the ink is cured.

[0065] In the step of forming an evaluation image (step S12), ink is ejected from the nozzles to form an evaluation image in an evaluation image forming region 24 of the substrate 23. In the step of forming an evaluation image, the carriage 18 is scanned in the X-axis direction, ink is ejected from the nozzles of the recording head 14, and ultraviolet rays are irradiated onto the ink that has landed on the substrate 23. In the image forming apparatus 100, ultraviolet rays are irradiated from an ultraviolet irradiation device 16 located behind the recording head 14 in the transport direction while the carriage 18 is transported in the X-axis direction. After being irradiated with this ultraviolet light, the ink is cured.

[0066] The evaluation image may be, for example, a solid print. A solid print is a state in which the surface of the evaluation image forming area 24 of the base material 23 is completely covered with ink.

[0067] The irradiation of ultraviolet light in the process of forming the image for printing and the process of forming the image for evaluation is performed within the same scanning operation immediately after the ink lands on the recording medium 20 .

[0068] In the image forming method, the step of forming an image for printing (step S11) may be performed after the step of forming an image for evaluation (step S12), or the step of forming an image for printing (step S11) and the step of forming an image for evaluation (step S12) may be performed simultaneously. In the image forming method, the step of forming an image for printing (step S11) and the step of forming an image for evaluation (step S12) may be performed consecutively. "Consecutively" here may mean, for example, within the same scanning operation. "Within the same scanning operation" may mean within an operation in which the carriage 18 is transported from one end to the other in the X-axis direction.

[0069] In the step of measuring the amount of ultraviolet light (step S13), the peak illuminance and the integrated amount of light of the ultraviolet light are measured. In the step of measuring the amount of ultraviolet light, the amount of light is measured using a light amount meter 28 arranged in a light amount meter installation area 26. The light amount meter 28 measures the amount of ultraviolet light irradiated from the ultraviolet irradiation device 16.

[0070] The measurement unit 262 calculates the amount of light per unit area (mJ / cm 2 ) based on the measurement result by the light amount meter 28. 2 The measuring unit 262 calculates the integrated light amount by integrating the peak illuminance (mW / cm 2 ), which is the light intensity per unit area, based on the measurement result by the light amount meter 28. 2 ) is calculated.

[0071] In the step of evaluating the evaluation image (step S14), for example, a user evaluates the evaluation image. Evaluation items for the evaluation image include adhesion between the substrate 23 and the coating film, and gloss of the coating film. The coating film here refers to the coating film after the ink attached to the substrate 23 is irradiated with ultraviolet light and cured.

[0072] A user can check the gloss of the coating film by visually inspecting the coating film formed on the substrate 23. A user can check the adhesion of the coating film by making a cut in the coating film formed on the substrate 23, attaching tape to the surface of the coating film, and peeling off the tape. If a large amount of the coating film peels off, it may be evaluated that the adhesion of the coating film is low and that the irradiation of ultraviolet rays is insufficient.

[0073] In the step of saving the evaluation results and the measurement results (step S15), the evaluation results in step S14 and the measurement results in step S13 are saved in a memory unit of the control unit 210. The memory unit of the control unit 210 may be, for example, the RAM 203. The user can input the evaluation results of the evaluation image to the control unit 210 by operating the operation panel 13. The light quantity meter 28 can input the measurement results to the control unit 210.

[0074] In the step of adjusting the output of the light source (step S16), the control unit 210 adjusts the output of ultraviolet light from the ultraviolet irradiation device 16 based on the evaluation results and measurement results stored in the storage unit. When the amount of ultraviolet light is decreasing, the light source output adjustment unit 266 adjusts the output of ultraviolet light so as to increase the output of ultraviolet light.

[0075] In the process of adjusting the moving speed of the carriage 18 (step S17), the control unit 210 adjusts the moving speed of the carriage 18 based on the evaluation results and measurement results stored in the storage unit. The control unit 210 can reduce the moving speed of the carriage 18 when the amount of ultraviolet light is reduced.

[0076] [Functions and Effects of the Image Forming Method According to the First Embodiment of the Present Invention] The image forming method according to the first embodiment of the present invention is an image forming method for ejecting ultraviolet-curable ink, irradiating the ejected ink with ultraviolet light to cure the ink, and forming an image, and includes the steps of ejecting ink onto a recording medium 20, irradiating the ink on the recording medium 20 with ultraviolet light, and forming an image to be printed on the recording medium 20, a step which is performed simultaneously or successively with the step of forming the image to be printed, ejecting ink onto a substrate 23, irradiating the ink on the substrate 23 with ultraviolet light, and forming an image for evaluation on the substrate 23, a step of evaluating the image for evaluation, and a step of changing at least one of the ultraviolet light irradiation conditions and the printing conditions based on the evaluation results from the step of evaluating the image for evaluation.

[0077] According to this image forming method, by grasping the actual coating film characteristics after irradiation with ultraviolet rays, at least one of the ultraviolet irradiation conditions and the printing conditions can be changed to form an image on the recording medium 20. Therefore, by grasping the deterioration of the ultraviolet irradiation device 16 and changing the conditions for irradiating ultraviolet rays, it is possible to improve the quality of the coating film after the ink is ejected and irradiated with ultraviolet rays.

[0078] In the image forming method, based on the evaluation results from the step of evaluating the evaluation image, only the ultraviolet irradiation conditions may be changed, only the printing conditions may be changed, or both the irradiation conditions and the printing conditions may be changed. Examples of changes in the ultraviolet irradiation conditions include changes in the output (power) of the ultraviolet rays. Examples of changes in the ultraviolet irradiation conditions include changes in the irradiation time per unit area. Also, examples of changes in the printing conditions include changes in the printing speed (the conveying speed of the carriage 18). In the image forming method, by changing the conditions so as to increase the output of the ultraviolet rays without decreasing the printing speed, it is possible to improve the quality of the coating film and suppress a decrease in productivity in image formation.

[0079] The image forming method further includes a step of measuring the amount of ultraviolet light irradiated. In such an image forming method, the conditions for irradiating ultraviolet light can be changed based on the measured amount of ultraviolet light.

[0080] In addition, in the image forming method, in the process of forming an image to be printed, ink is ejected into an image forming area (printing area) 22 on a recording medium 20 while moving a carriage 18 carrying a recording head 14 that ejects ink, thereby forming an image to be printed; in the process of forming an image for evaluation, ink is ejected into an image forming area for evaluation (evaluation area) 24 while moving the carriage 18, thereby forming an image for evaluation; and in the process of measuring the amount of ultraviolet light, the amount of ultraviolet light irradiated into a light quantity meter installation area (measurement area) 26 is measured while moving the carriage 18 carrying an ultraviolet irradiation device (light source) 16 that irradiates ultraviolet light, and the evaluation image forming area 24 and the light quantity meter installation area 26 are present within the scanning range of the carriage 18 when viewed in a plane.

[0081] According to this image forming method, since the evaluation image forming area 24 is present within the scanning range of the carriage 18, the state of ink curing can be evaluated using an evaluation image irradiated with ultraviolet light at an appropriate position.

[0082] In the image forming method, the step of measuring the amount of ultraviolet light includes a step of calculating an integrated amount of light, which is an integrated value of the amount of light for each scan of the carriage 18. This allows the deterioration of the ultraviolet irradiating device 16 to be detected using the calculated integrated amount of light. Furthermore, by calculating the integrated amount of light for each scan, it is possible to detect the amount of light required to improve the quality of the image actually formed on the recording medium 20 and the quality of the coating film. In the image forming method, feedback control may be performed using the amount of light required to improve the quality of the image as a judgment threshold. In the image forming method, feedback control may be performed using the amount of light required to improve the quality of the coating film as a judgment threshold. When the amount of light detected by the light amount meter 28 is equal to or less than the judgment threshold, feedback control may be performed to increase the output by the ultraviolet irradiating device 16.

[0083] In the image forming method, the step of measuring the amount of ultraviolet light includes a step of calculating the peak irradiance of the ultraviolet light. This makes it possible to detect deterioration of the ultraviolet light irradiation device 16 using the calculated peak irradiance.

[0084] In the image forming method, the step of changing the conditions can change the ultraviolet irradiation conditions based on both the evaluation result from the step of evaluating the evaluation image and the measurement result from the step of measuring the amount of ultraviolet light. This makes it possible to accurately detect deterioration of the ultraviolet irradiation device 16 and appropriately change the ultraviolet irradiation conditions. For example, when a decrease in the amount of ultraviolet light is detected, the ultraviolet irradiation conditions can be changed so as to increase the output by the ultraviolet irradiation device 16.

[0085] In the image forming method, the step of changing the conditions can change the print speed based on both the evaluation result from the step of evaluating the evaluation image and the measurement result from the step of measuring the amount of ultraviolet light. This allows the deterioration of the ultraviolet light irradiation device 16 to be detected with high accuracy, and the print speed of the ultraviolet light can be appropriately changed. For example, when a decrease in the amount of ultraviolet light is detected, the print speed can be changed so as to increase the amount of ultraviolet light per unit area by decreasing the carriage transport speed.

[0086] Furthermore, in the image forming method, the evaluation image forming area 24 and the light amount meter installation area 26 are formed outside the image forming area 22 of the recording medium 20. This allows an image to be formed within the image forming area 22, and deterioration of the ultraviolet irradiating device 16 can be detected based on the evaluation results of the evaluation image outside the image forming area 22 and the measurement results by the light amount meter 28 arranged outside the image forming area 22. Since the evaluation image forming area 24 and the light amount meter installation area 26 are arranged outside the image forming area 22, an image can be formed in the entire image forming area 22.

[0087] The step of forming the image for printing and the step of forming the image for evaluation also include a step of moving the carriage 18 in the sub-scanning direction. In the image forming method, the image for printing and the image for evaluation can be formed while moving the carriage 18, and ultraviolet light can be irradiated while moving the carriage 18.

[0088] <Image forming method according to the second embodiment> Next, an image forming method according to a second embodiment will be described. Fig. 7 is a plan view showing the image forming area 22, the evaluation image forming area 24B, and the light quantity meter installation area 26 according to the second embodiment. The image forming method according to the second embodiment differs from the image forming method according to the first embodiment in that the evaluation image forming area 24B is formed so as to overlap with the image forming area 22. In the description of the image forming method according to the second embodiment, the same description as that of the image forming method according to the first embodiment will be omitted.

[0089] 7, in the image forming method according to the second embodiment, the evaluation image forming area 24B is formed so as to overlap with the image forming area 22. The substrate 23 is disposed so as to overlap with the recording medium 20. The evaluation image forming area 24B is formed on the substrate 23 disposed in the image forming area 22. The evaluation image is formed in the evaluation image forming area 24B formed so as to overlap with the image forming area 22.

[0090] In the image forming method, the evaluation image forming area 24B may be formed so as to overlap the image forming area 22 in its entirety, or only a portion of the evaluation image forming area 24B may be formed so as to overlap the image forming area 22.

[0091] [Functions and Effects of the Image Forming Method According to the Second Embodiment] The image forming method according to the second embodiment has the same effect as the image forming method according to the first embodiment. In the image forming method according to the second embodiment, the evaluation image forming area (evaluation area) 24B is formed in the image forming area (printing area) 22, and the light quantity meter installation area (measurement area) 26 is formed outside the image forming area 22.

[0092] In such an image forming method, it is possible to avoid an increase in size of the stage 10 on which the recording medium 20 and the base material 23 are arranged. In the image forming method, the evaluation image forming region 24B may be formed over the entire length of the recording medium 20 in the Y-axis direction, or the evaluation image forming region 24B may be formed in a part of the recording medium 20. In the image forming method, a light quantity meter installation region 26 may be formed in the image forming region 22, and a light quantity meter 28 may be arranged in the light quantity meter installation region 26.

[0093] [First Modification] Fig. 8 is a plan view showing an image forming area, an evaluation image forming area, and a light amount meter installation area according to a modified example. Next, the image forming area 22, the evaluation image forming area 24C, and the light amount meter installation area 26C according to a first modified example will be described with reference to Fig. 8(a). Fig. 8(a) is a plan view showing the image forming area 22, the evaluation image forming area 24C, and the light amount meter installation area 26C according to the first modified example. In the description of the image forming method according to the modified example, the same description as in the above embodiment will be omitted.

[0094] As shown in Fig. 8(a), the evaluation image forming area 24C and the light amount meter installation area 26C may be arranged adjacent to each other in the Y-axis direction. The light amount meter installation area 26C is arranged closer to one end 10a of the stage 10 in the Y-axis direction, and the evaluation image forming area 24C is arranged farther from the end 10a than the light amount meter installation area 26C. The evaluation image forming area 24C and the light amount meter installation area 26C are present within the scanning range of the carriage 18 in a plan view. In the Y-axis direction, the length of the light amount meter installation area 26C is shorter than the length of the evaluation image forming area 24C.

[0095] [Second modified example] Next, the image forming area 22, the evaluation image forming area 24D, and the light quantity measuring device installation area 26D according to the second modified example will be described with reference to Fig. 8(b). Fig. 8(b) is a plan view showing the image forming area 22, the evaluation image forming area 24D, and the light quantity measuring device installation area 26D according to the second modified example.

[0096] As shown in Fig. 8(b), the evaluation image forming area 24D and the light amount meter installation area 26D may be arranged adjacent to each other in the Y-axis direction. The evaluation image forming area 24D is arranged closer to one end 10a of the stage 10 in the Y-axis direction, and the light amount meter installation area 26D is arranged farther from the end 10a than the evaluation image forming area 24D. The evaluation image forming area 24D and the light amount meter installation area 26D are present within the scanning range of the carriage 18 in a plan view. In the Y-axis direction, the length of the light amount meter installation area 26D is shorter than the length of the evaluation image forming area 24D.

[0097] [Third Modification] Next, the image forming area 22, the evaluation image forming area 24E, and the light quantity measuring device installation area 26E according to the third modified example will be described with reference to Fig. 8(c). Fig. 8(c) is a plan view showing the image forming area 22, the evaluation image forming area 24E, and the light quantity measuring device installation area 26E according to the third modified example.

[0098] 8(c), the evaluation image forming area 24E and the light amount meter installation area 26E are disposed adjacent to each other in the X-axis direction. The light amount meter installation area 26E is disposed at a position away from one end 10a of the stage 10 in the Y-axis direction. The evaluation image forming area 24E and the light amount meter installation area 26E are present within the scanning range of the carriage 18 in a plan view. In the Y-axis direction, the length of the light amount meter installation area 26E is shorter than the length of the evaluation image forming area 24E.

[0099] [Fourth Variation] Next, the image forming area 22, the evaluation image forming area 24F, and the light quantity measuring device installation area 26F according to the fourth modified example will be described with reference to Fig. 8(d). Fig. 8(d) is a plan view showing the image forming area 22, the evaluation image forming area 24F, and the light quantity measuring device installation area 26F according to the fourth modified example.

[0100] 8(d), the evaluation image forming area 24F and the light amount meter installation area 26F are disposed adjacent to each other in the X-axis direction. The light amount meter installation area 26F is disposed at a position away from one end 10a of the stage 10 in the Y-axis direction. The evaluation image forming area 24F and the light amount meter installation area 26F are present within the scanning range of the carriage 18 in a plan view. In the Y-axis direction, the length of the light amount meter installation area 26F is shorter than the length of the evaluation image forming area 24F.

[0101] In the X-axis direction, the evaluation image forming area 24F is disposed between the image forming area 22 and the light quantity meter installation area 26F. In the X-axis direction, the evaluation image forming area 24F is disposed at a position closer to the image forming area 22 than the light quantity meter installation area 26F.

[0102] Incidentally, the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from or changing the technical concept of the present invention.

[0103] In the image forming method, the irradiation conditions of ultraviolet light on the recording medium 20 may be changed by changing the distance between the recording medium 20 and the ultraviolet light irradiation device 16 in the Z-axis direction. For example, when the amount of ultraviolet light is low, the distance between the recording medium 20 and the ultraviolet light irradiation device 16 in the Z-axis direction may be shortened. Furthermore, the image forming apparatus 100 may be provided with a mechanism capable of changing the position of the ultraviolet light irradiation device 16 in the Z-axis direction.

[0104] The image forming method may be performed by an image forming apparatus 100 equipped with a carriage 18, or may be performed by an image forming apparatus not equipped with a carriage 18. For example, the image forming method may be performed using a line head type image forming apparatus in which a plurality of recording heads 14 are arranged side by side in the main scanning direction. The image forming apparatus that performs the image forming method may also be equipped with a medium transport mechanism capable of transporting the recording medium 20 in the Y-axis direction. In this case, the printing conditions may be changed so that the transport speed of the recording medium is slowed down to increase the amount of ultraviolet light irradiated per unit area.

[0105] The image forming apparatus 100 may be an MFP (Multifunction Peripheral) having a copy function, a facsimile function, a print function, a scanner function, etc. Alternatively, the image forming apparatus 100 may have a double-sided printing function. The image forming apparatus 100 may form an image by an electrophotographic method.

[0106] Each function executed by the control device 200 of the embodiment described above can be realized by one or more processing circuits. Here, the term "processing circuit" in this specification includes a processor programmed to execute each function by software, such as a CPU implemented by an electronic circuit, and devices such as an ASIC (Application Specific Integrated Circuit), a DSP (digital signal processor), an FPGA (field programmable gate array), and a conventional circuit module designed to execute each function described above.

[0107] Furthermore, the liquid ejection method is not limited to an image forming method in which an image is formed by ejecting ink. The liquid ejection method may eject a liquid other than ink. For example, the liquid ejection method may be applied to a case in which a liquid such as an ultraviolet curable resin is ejected and cured by irradiating the ejected liquid with ultraviolet light.

[0108] One aspect of the present invention may be as follows.

[0109] <1> A liquid ejection method for ejecting an active energy ray-curable liquid and curing the liquid by irradiating the ejected liquid with active energy rays, comprising the steps of: ejecting the liquid to form a first coating film on a recording medium; discharging the liquid to form a second coating film on a substrate; evaluating the second coating; and changing at least one of the active energy ray irradiation conditions and the liquid ejection conditions based on the evaluation results in the step of evaluating the second coating film. <2> The method further comprises a step of measuring the amount of irradiated active energy rays. <1> The liquid ejection method according to claim 1 . <3> In the step of forming the first coating film, the liquid is discharged onto a first region on the recording medium while moving a carriage carrying a discharge head that discharges the liquid, thereby forming the first coating film; In the step of forming the second coating film, the liquid is ejected onto a second region while moving the carriage to form the second coating film; In the step of measuring the amount of active energy rays, the amount of ultraviolet light irradiated to a measurement area is measured while moving the carriage on which a light source for irradiating active energy rays is mounted, The second area and the measurement area are present within a scanning range of the carriage in a plan view. <2> The liquid ejection method according to claim 1 . <4> The step of measuring the amount of light of the active energy rays includes a step of calculating an integrated amount of light, which is an integrated value of the amount of light for each scan of the carriage. <2> or <3> The liquid ejection method according to claim 1 . <5> The step of measuring the amount of active energy rays includes a step of calculating a peak illuminance of the active energy rays. <2> or <3> The liquid ejection method according to claim 1 . <6> the step of changing the conditions changes the irradiation conditions of the active energy rays based on both the evaluation results from the step of evaluating the second coating film and the measurement results from the step of measuring the amount of the active energy rays. <2> ~ <5> 13. A liquid ejection method according to claim 12, wherein <7> the step of changing the conditions changes the printing speed based on both the evaluation result in the step of evaluating the second coating film and the measurement result in the step of measuring the amount of light of the active energy ray, <2> ~ <6> 13. A liquid ejection method according to claim 12, wherein <8> The second region and the measurement region are formed outside the first region. <2> ~ <7> 13. A liquid ejection method according to claim 12, wherein <9> the second region is formed within the first region; The measurement region is formed outside the first region. <2> ~ <8> 13. A liquid ejection method according to claim 12, wherein <10> The step of forming the first coating film and the step of forming the second coating film include a step of moving the carriage in a sub-scanning direction. <2> ~ <9> 13. A liquid ejection method according to claim 12, wherein [Explanation of symbols]

[0110] 100 Image forming device 14 Recording head 16 Ultraviolet irradiation device 18 Carriage 20 Recording media 22 Image forming area (first area) 23 Base material 24 Evaluation image forming area (second area) 26 Light intensity meter installation area 28 Light measuring device XX axis direction (main scanning direction) YY axis direction (sub-scanning direction) ZZ axis direction [Prior art documents] [Patent documents]

[0111] [Patent Document 1] JP 2020-185738 A [Patent Document 2] Patent No. 6801277

Claims

1. A liquid ejection method for ejecting an active energy ray-curable liquid and curing the liquid by irradiating the ejected liquid with active energy rays, comprising the steps of: ejecting the liquid to form a first coating film on a recording medium; discharging the liquid to form a second coating film on a substrate; evaluating the second coating; changing at least one of the active energy ray irradiation conditions and the liquid ejection conditions based on the evaluation results in the step of evaluating the second coating film.

2. The liquid ejection method according to claim 1 , further comprising the step of measuring the amount of light of the irradiated active energy rays.

3. In the step of forming the first coating film, the liquid is discharged onto a first region on the recording medium while moving a carriage carrying a discharge head that discharges the liquid, thereby forming the first coating film; In the step of forming the second coating film, the liquid is ejected onto a second region while moving the carriage to form the second coating film; In the step of measuring the amount of light of the active energy rays, the amount of light of the active energy rays irradiated to a measurement region is measured while moving the carriage having a light source mounted thereon for irradiating the active energy rays, The liquid ejection method according to claim 2 , wherein the second region and the measurement region are present within a scanning range of the carriage in a plan view.

4. The liquid ejection method according to claim 3 , wherein the step of measuring the amount of light of the active energy rays includes a step of calculating an integrated amount of light, which is a value obtained by integrating the amount of light for each scan of the carriage.

5. The liquid ejection method according to claim 3 , wherein the step of measuring the amount of light of the active energy rays includes the step of calculating a peak illuminance of the active energy rays.

6. The liquid ejection method according to claim 3 , wherein the step of changing the conditions changes the irradiation conditions of the active energy rays based on both the evaluation results from the step of evaluating the second coating film and the measurement results from the step of measuring the amount of light of the active energy rays.

7. The liquid ejection method according to claim 3 , wherein the step of changing the conditions changes the printing speed based on both the evaluation results from the step of evaluating the second coating film and the measurement results from the step of measuring the amount of light of the active energy rays.

8. The liquid ejection method according to claim 3 , wherein the second area and the measurement area are formed outside the first area.

9. The second region is formed within the first region, The liquid ejection method according to claim 3 , wherein the measurement region is formed outside the first region.

10. The liquid ejection method according to claim 3 , wherein the step of forming the first coating film and the step of forming the second coating film include a step of moving the carriage in a sub-scanning direction.

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