Droplet ejection apparatus, method of suppressing liquid aggregation in droplet ejection apparatus, and program

Abstract

To provide a droplet ejection apparatus, a method of suppressing liquid aggregation in a droplet ejection apparatus, and a program capable of suppressing both a reduction in impact accuracy of a first liquid and generation of mist of a second liquid.SOLUTION: An inkjet recording apparatus 1 being a droplet ejection device comprises: a droplet ejection section 4 which ejects droplets from nozzles; and a controller 2 which controls droplet ejection of the droplet ejection section 4. The droplet ejection section 4 includes: an inkjet head 421 being a first head for ejecting an ink being a first liquid; and a treatment liquid head 431 being a second head for ejecting a treatment liquid being a second liquid for aggregation of the first liquid. The controller 2 performs control such that an ejection speed of the second head is slower than the ejection speed of the first head.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a droplet ejection device, a method for suppressing liquid aggregation in a droplet ejection device, and a program. [Background technology]

[0002] Conventionally, a droplet ejection device is known that ejects a first liquid from a nozzle provided on a nozzle surface of a head. Also, a droplet ejection device configured to eject a second liquid that aggregates the first liquid inline from the head is known.

[0003] In such a droplet ejection device, if a mist of one liquid adheres to the nozzle surface of the head that ejects the other liquid, agglomerates are formed on the nozzle surface. In particular, if a mist of the second liquid adheres to the nozzle of the first head that ejects the first liquid, causing ejection failure of the first liquid, this has a greater impact than ejection failure of the second liquid.

[0004] Therefore, for example, Patent Document 1 describes a configuration in which an airflow generating section is provided between a first head and a second head that ejects the second liquid, in order to prevent the mist of the second liquid from adhering to the nozzles of the first head. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-094757 Summary of the Invention [Problem to be solved by the invention]

[0006] The configuration described in Patent Document 1 can prevent mist of the second liquid from adhering to the nozzles of the first head. However, this configuration cannot prevent mist of the second liquid from being generated. Therefore, there remains a risk that mist of the second liquid will adhere to the nozzles of the first head. Furthermore, the configuration described in Patent Document 1 requires an airflow generating unit, which increases the size and cost of the device and reduces the flexibility of head placement.

[0007] To address this issue, the inventors conducted extensive research and discovered that the generation of mist can be suppressed by slowing down the droplet ejection speed to a predetermined speed. However, slowing down the droplet ejection speed increases the impact of air resistance. As a result, another issue arose: the landing accuracy of the first liquid decreases.

[0008] The present invention has been made in view of the above circumstances, and its purpose is to provide a droplet ejection device, a method for suppressing liquid aggregation in a droplet ejection device, and a program therefor, that can suppress both a decrease in landing accuracy of a first liquid and the generation of mist from a second liquid. [Means for solving the problem]

[0009] In order to solve the above problem, the invention described in claim 1 is a droplet ejection device, a droplet ejection unit that ejects droplets from a nozzle; the droplet ejection unit includes a first head that ejects a first liquid and a second head that ejects a second liquid that aggregates the first liquid; The ejection speed of the second head is slower than the ejection speed of the first head.

[0010] The invention described in claim 2 is the droplet ejection device described in claim 1, The ejection speed of the second head is 4.0 m / s or more and is slower than the ejection speed of the first head by 0.5 m / s or more.

[0011] The invention described in claim 3 is the droplet ejection device described in claim 1, The ejection speed of the first head and the second head is 10.0 m / s or less.

[0012] The invention described in claim 4 is the droplet ejection device described in claim 1, The ejection amount of the nozzles of the first head and the nozzles of the second head is 4 pL or more and 30 pL or less.

[0013] The invention described in claim 5 is the droplet ejection device described in claim 1, the first liquid comprises a dispersion; The second liquid contains a flocculating agent that causes the dispersion to flocculate.

[0014] The invention described in claim 6 is the droplet ejection device described in claim 1, The distance between the nozzle surface of the second head, on which the nozzles are provided, and the recording medium is 1 mm or more and 6 mm or less.

[0015] The invention described in claim 7 is the droplet ejection device described in claim 1, The number of satellites of the droplets ejected by the second head is smaller than the number of satellites of the droplets ejected by the first head.

[0016] The invention described in claim 8 is the droplet ejection device described in any one of claims 1 to 7, The liquid droplet ejection device includes a control unit that controls the liquid droplet ejection from the liquid droplet ejection unit.

[0017] The invention described in claim 9 is the droplet ejection device described in claim 8 which relies on claim 7, an acquisition unit that acquires the number of satellites in droplets ejected from the first head and the second head; The control unit controls the voltages applied to the first head and the second head in accordance with the content acquired by the acquisition unit.

[0018] The invention described in claim 10 is the droplet ejection device described in claim 8, The control unit makes the voltage applied to the second head smaller than the voltage applied to the first head.

[0019] An eleventh aspect of the present invention is the droplet ejection device according to the eighth aspect, The control unit applies a voltage to the second head that has a waveform different from that of the voltage applied to the first head.

[0020] The invention described in claim 12 is the droplet ejection device described in claim 8, The control unit makes the viscosity of the second liquid higher than the viscosity of the first liquid.

[0021] The invention described in claim 13 is the droplet ejection device described in claim 12, The control unit makes the temperature of the second liquid lower than the temperature of the first liquid.

[0022] The invention described in claim 14 is the droplet ejection device described in claim 8, The control unit sets the ejection frequency of the second head higher than the ejection frequency of the first head.

[0023] The invention described in claim 15 is the droplet ejection device described in claim 8, the droplet ejection unit includes, as the first head, a plurality of types of inkjet heads that eject ink of each color; Among the plurality of types of inkjet heads, the number of the second heads is more than any one type of inkjet head.

[0024] The invention described in claim 16 is the droplet ejection device described in claim 8, The control unit causes the first head to eject droplets at a timing different from the timing at which the second head ejects droplets.

[0025] The invention described in claim 17 is the droplet ejection device described in claim 16, The control unit determines the ejection timing of the first head and the second head in accordance with the distance between a nozzle face of the droplet ejection unit that ejects liquid and a recording medium.

[0026] The invention described in claim 18 is a droplet ejection unit that ejects droplets from a nozzle; A liquid aggregation suppression method for a droplet ejection device, wherein the droplet ejection unit includes a first head that ejects a first liquid and a second head that ejects a second liquid that causes the first liquid to aggregate, comprising: a control step of controlling droplet ejection from the droplet ejection unit, The control step controls the ejection speed of the second head to be slower than the ejection speed of the first head.

[0027] The invention described in claim 19 is a program, a droplet ejection unit that ejects droplets from a nozzle; a droplet ejection device in which the droplet ejection unit includes a first head that ejects a first liquid and a second head that ejects a second liquid that aggregates the first liquid; a control unit that controls the droplet discharge of the droplet discharge unit; The control unit controls the ejection speed of the second head to be slower than the ejection speed of the first head. [Effects of the Invention]

[0028] According to the present invention, it is possible to suppress both a decrease in landing accuracy of the first liquid and the generation of mist of the second liquid. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a perspective view of a droplet ejection device. [Figure 2] FIG. 2 is a block diagram of a droplet ejection device. [Figure 3] FIG. 2 is a schematic front view of the carriage. [Figure 4]10 is a graph summarizing the relationship between the droplet ejection speed and the amount of mist generated. [Figure 5] 10 is a graph summarizing the relationship between the droplet ejection speed and the amount of landing deviation. [Figure 6] FIG. 1 is a side view of a drop watcher. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, droplet ejection devices according to embodiments of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In the following description, components having the same functions and configurations will be given the same reference numerals, and their description will be omitted.

[0031] [Overall configuration of inkjet recording device] Fig. 1 is a perspective view of an inkjet recording apparatus 1, which is one embodiment of a droplet ejection device of the present invention. Fig. 2 is a block diagram showing the functional configuration of the inkjet recording apparatus 1. The inkjet recording apparatus 1 includes a control unit 2, a transport unit 3, and a droplet ejection unit 4.

[0032] In the following description, the X direction, Y direction, and Z direction are the directions shown in Fig. 1. In the following description, the X direction, Y direction, and Z direction are referred to as the width direction, conveyance direction, and height direction, respectively.

[0033] (Control unit) The control unit 2 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). The control unit 2 controls the overall operation of the inkjet recording apparatus 1.

[0034] The CPU controls each part of the inkjet recording apparatus 1. The RAM is a volatile memory that temporarily stores various pieces of information in a writable and readable manner. The ROM is a non-volatile memory that stores various pieces of information and programs in a readable manner. More specifically, the control unit 2 reads a specified program from the various programs stored in the ROM using the CPU and expands it into the RAM. The control unit 2 then executes various processes in cooperation with the expanded program.

[0035] (Transportation section) 1, the conveying unit 3 includes two conveying rollers 3a and 3b that rotate in the conveying direction around a rotation axis extending in the width direction, and a loop-shaped conveying belt 3c.

[0036] The inner side of the conveyor belt 3c is supported by conveyor rollers 3a and 3b. The recording medium M is placed on the conveyor surface of the conveyor belt 3c. The conveyor rollers 3a and 3b rotate and move in the conveyance direction in response to the operation of the roller conveyance motor. As a result, the conveyor belt 3c conveys the recording medium M in the conveyance direction.

[0037] Furthermore, it is preferable that a predetermined adhesive (adhesive) be applied to the loading surface of the transport belt 3c, which is the outer surface on which the recording medium M is loaded, and which is different from the inner surface that contacts the transport rollers 3a and 3b. When an adhesive is applied to the loading surface, deterioration in image quality due to misalignment of the recording medium M can be suppressed.

[0038] The recording medium M is, for example, a fabric cut to a certain size. The recording medium M is supplied onto the conveyor belt 3c by a medium supply unit (not shown). The recording medium M on which an image is recorded by ink discharge from the droplet discharge unit 4 is discharged to a predetermined discharge unit. Note that the recording medium M is not limited to fabric. The recording medium M may be any medium, such as paper, as long as it is capable of fixing the ink that has landed on it.

[0039] (Droplet discharge part) The droplet ejection unit 4 forms an image by ejecting color inks at appropriate timing based on image data acquired from an external device or the like onto the recording medium M transported by the transport unit 3. The droplet ejection unit 4 includes a carriage 41 on which an ink ejection unit 42 is mounted, the ink ejection unit 42 including a plurality of inkjet heads 421 that eject ink of each color, for example, C (cyan), M (magenta), Y (yellow), and K (black).

[0040] {carriage} 3 is a schematic front view of a cross section of the carriage 41 as viewed from the transport direction. An ink ejection unit 42 and a treatment liquid ejection unit 43 are mounted on the carriage 41. The carriage 41 has, for example, a belt stretched between two pulleys that are rotated by a motor (not shown). The carriage 41 causes the ink ejection unit 42 and the treatment liquid ejection unit 43 to scan in the width direction by the rotation of the motor based on a drive signal output by the control unit 2.

[0041] The inkjet recording device 1 according to this embodiment is a serial head type (multi-pass type) that forms an image by discharging color inks from the ink discharge units 42 onto the recording medium M while scanning the carriage 41 in the width direction. Note that an image may be formed by scanning the carriage 41 once, or may be formed by scanning the carriage 41 multiple times.

[0042] The inkjet recording apparatus 1 according to this embodiment is an in-line type, that is, the droplet ejection unit 4 performs pre-treatment by ejecting treatment liquid from the treatment liquid ejection unit 43 and image formation by ejecting ink from the ink ejection unit 42 consecutively.

[0043] {Ink ejection section} The ink ejection unit 42 includes a plurality of inkjet heads 421 that eject color inks, which are a first liquid. Each inkjet head 421 includes a color ink tank, a flow path, an actuator, and a plurality of nozzles. The actuator is, for example, a piezoelectric element. In order to eject ink from the nozzle, the actuator applies pressure fluctuations to the ink in the nozzle in response to a voltage signal with a predetermined drive waveform applied from the control unit 2.

[0044] 3, a plurality of inkjet heads 421 are mounted in the width direction on the carriage 41. Under the control of the control unit 2, the inkjet heads 421 eject color ink onto the recording medium M by applying pressure fluctuations to color inks supplied from tanks to nozzles via flow paths using actuators.

[0045] The color inks ejected by the ink ejection unit 42 may be pigment inks containing pigment dispersions, resin inks containing resins, or disperse dye inks in which dyes are dispersed.

[0046] {Treatment liquid discharge section} The treatment liquid ejection unit 43 includes a treatment liquid ejection head 431 provided at a first end in the width direction of the carriage 41. The treatment liquid ejection head 431 is provided outside the ink ejection unit 42, and like the inkjet head 421, includes a treatment liquid tank, a flow path, an actuator, a plurality of nozzles, etc. The treatment liquid ejection unit 43 ejects the treatment liquid, which is the second liquid, under the control of the control unit 2.

[0047] In more detail, the treatment liquid ejected by the treatment liquid ejection head 431 is, for example, a transparent pretreatment ink containing an aggregating agent, and is mixed in liquid form with the colored inks ejected by the inkjet head 421. The pretreatment ink contains at least an aggregating agent. In addition to the aggregating agent, the pretreatment ink may contain components such as a solvent, a surfactant, or water. The aggregating agent contained in the pretreatment ink is not particularly limited as long as it generates aggregates when it comes into contact with the colored ink. The aggregating agent contained in the pretreatment ink is, for example, a polyvalent metal salt, an organic acid, an inorganic acid, or a cationic polymer.

[0048] Furthermore, the treatment liquid ejection head 431 ejects the treatment liquid when the carriage 41 scans toward the first end (the right side in FIG. 3) where the treatment liquid ejection unit 43 is provided. According to this configuration, pre-treatment and image formation can be performed simultaneously with a single scan of the carriage 41, thereby improving productivity.

[0049] The treatment liquid ejection head 431 may be provided at both ends in the width direction of the carriage 41. In this configuration, by ejecting the treatment liquid from the treatment liquid ejection head 431 on the front side of the carriage 41 in the scanning direction, image formation processing can be performed on both the outward and return paths of the carriage 41, thereby improving productivity.

[0050] The distance from the nozzles of the treatment liquid ejection head 431 to the recording medium M is preferably 1 mm or more and 6 mm or less. By making the distance from the nozzles of the treatment liquid ejection head 431 to the recording medium M 1 mm or more, it is possible to prevent the nozzles from coming into contact with the recording medium M. Furthermore, by making the distance from the nozzles of the treatment liquid ejection head 431 to the recording medium M 6 mm or less, it is possible to prevent the generation of mist caused by the treatment liquid flying up.

[0051] In the following description, when no particular distinction is made between the inkjet head 421 and the treatment liquid ejection head 431, they will simply be referred to as "heads."

[0052] [Discharge control] In such an inkjet recording apparatus 1, the control unit 2 controls the ejection of droplets by the droplet ejection unit 4. Specifically, the control unit 2 controls the ejection speed of the treatment liquid from the treatment liquid ejection head 431 to be slower than the ejection speed of the ink from the inkjet head 421.

[0053] The head ejection speed can be calculated, for example, by the following procedure. First, the difference Δt between the time when the droplet reaches the recording medium M 500 μm away from the nozzle and the time when the droplet reaches the recording medium M 600 μm away is calculated. Then, the flying distance Δl (=100 μm) is divided by the required time Δt, resulting in the value Δl / Δt, which is the ejection speed. Note that, to improve measurement accuracy, it is preferable to perform this trial 10 times and calculate the average value. The head ejection speed can also be measured using, for example, a jetXpert, a flying droplet observation device manufactured by imageXpert.

[0054] FIG. 4 is a graph summarizing the relationship between the droplet ejection speed and the amount of mist generated. In FIG. 4, the horizontal axis represents the ejection speed, and the vertical axis represents the amount of mist generated. FIG. 5 is a graph summarizing the relationship between the droplet ejection speed and the amount of landing deviation. In FIG. 5, the horizontal axis represents the ejection speed, and the vertical axis represents the amount of landing deviation. As shown in FIG. 4, when the droplet ejection speed is reduced, the amount of mist generated decreases. On the other hand, as shown in FIG. 5, when the droplet ejection speed is reduced, the effect of air resistance increases, and the amount of landing deviation increases.

[0055] Therefore, in the inkjet recording apparatus 1 according to this embodiment, the control unit 2 reduces only the ejection speed of the treatment liquid ejection head 431. This reduces the generation of mist of the treatment liquid, thereby preventing nozzle clogging caused by the mist of the treatment liquid adhering to and coagulating in the nozzles of the inkjet head 421. Furthermore, because the treatment liquid is colorless and transparent as described above, the landing deviation caused by the reduction in the ejection speed of the treatment liquid ejection head 431 does not affect the quality of the image formed. Furthermore, because the ejection speed of the inkjet head 421 remains the same as before, the occurrence of image distortion can also be reduced.

[0056] Specifically, the control unit 2 controls the ejection speed of the treatment liquid ejection head 431 so that it is at least 0.5 m / s slower than the ejection speed of the inkjet head 421. When the ejection speed of the treatment liquid ejection head 431 is at least 0.5 m / s slower than the ejection speed of the ink of the inkjet head 421, a sufficient effect of suppressing the generation of mist of the treatment liquid can be obtained.

[0057] On the other hand, the control unit 2 controls the discharge speed of the treatment liquid discharge head 431 to be 4.0 m / s or more. If the discharge speed of the treatment liquid discharge head 431 is less than 4.0 m / s, the influence of air resistance becomes large, and mist is more likely to be generated.

[0058] The control unit 2 also controls the ejection speed of the inkjet head 421 and the treatment liquid ejection head 431 to be 10.0 m / s or less. This is because if the ejection speed is 10.0 m / s or more, the effect of suppressing landing deviation will not be any greater. Furthermore, if the ejection speed is 10.0 m / s or more, the number of satellites (microdroplets) in the droplets increases. Then, the satellites are affected by air resistance, which increases the number of mists.

[0059] (Discharge speed reduction method) Any known method can be adopted as the method for causing the control unit 2 to reduce the discharge speed of the treatment liquid discharge head 431. For example, the control unit 2 can reduce the discharge speed of the treatment liquid discharge head 431 by making the voltage applied to the actuator of the treatment liquid discharge head 431 smaller than the voltage applied to the actuator of the inkjet head 421.

[0060] Alternatively, the control unit 2 can reduce the ejection speed of the treatment liquid ejection head 431 by differentiating the drive waveform of the voltage signal applied to the actuator of the treatment liquid ejection head 431 from the drive waveform of the voltage signal applied to the actuator of the inkjet head 421.

[0061] Alternatively, the control unit 2 can reduce the ejection speed of the treatment liquid ejection head 431 by controlling the viscosity of the treatment liquid to be higher than the viscosity of the ink. Specifically, the control unit 2 can make the viscosity of the treatment liquid higher than the viscosity of the ink by controlling the temperature of the treatment liquid to be lower than the temperature of the ink. Alternatively, the control unit 2 can make the viscosity of the treatment liquid higher than the viscosity of the ink by differentiating the components of the treatment liquid from the components of the ink.

[0062] The viscosity of the treatment liquid and ink is preferably in the range of 2 cp to 10 cp, inclusive. By keeping the viscosity of the treatment liquid and ink within this range, sufficient ejection stability from the head can be obtained. [Example]

[0063] Next, the results of evaluation of preferred configurations by various tests for examples of the present invention and comparative examples will be described. The present invention will be specifically described below using examples, but the present invention is not limited to these.

[0064] [Test 1. Evaluation of mist dispersion amount] A treatment liquid ejection head 431 that ejects treatment liquid colored with a cationic pigment and a dummy head with paper attached to the nozzle surface were arranged 3 mm apart in the transport direction. The treatment liquid was then ejected continuously for one minute at a predetermined ejection speed toward a piece of fabric 1 mm away from the nozzle surface of the treatment liquid ejection head 431, and the number of microdroplets that adhered to the paper on the nozzle surface of the dummy nozzle was evaluated. The test results were rated as NG (Not Good) if the number of microdroplets that adhered to the paper was 100 or more, and G (Good) if the number was less than 100.

[0065] [Test 2. Impact position deviation evaluation] The treatment liquid ejection head 431, which ejects treatment liquid colored with a cationic pigment, was made to print a fine line pattern at a specified ejection speed onto a cloth 1 mm away from the nozzle surface, and the amount of deviation in the landing position was evaluated. The test results were rated A if the amount of deviation was less than 35 mm and acceptable for ink, B if it was 35 mm or more but less than 75 mm and acceptable for treatment liquid, and C if it was 75 mm or more and unacceptable for treatment liquid.

[0066] The formulations of the processing solutions used in Tests 1 and 2 are as shown in Table I below.

[0067] [Table 1]

[0068] The results of Tests 1 and 2 are shown in Table II.

[0069] [Table 2]

[0070] As shown in Table II, mist generation is suppressed when the ejection speed is in the range of 4.0 to 5.5 m / s. In contrast, print misalignment is suppressed as the ejection speed increases. In the case of the treatment liquid, print misalignment is acceptable if it is B or higher. Therefore, it is preferable that the ejection speed of the treatment liquid is 4.0 to 5.5 m / s.

[0071] [Effects of the first embodiment] As described above, the inkjet recording apparatus 1 according to this embodiment includes a droplet ejection unit 4 that ejects droplets from nozzles, and a control unit 2 that controls the droplet ejection of the droplet ejection unit 4. The droplet ejection unit 4 includes an inkjet head 421 that is a first head that ejects ink, which is a first liquid, and a treatment liquid head 431 that is a second head that ejects treatment liquid, which is a second liquid that aggregates the ink, which is the first liquid. The control unit 2 controls the ejection speed of the treatment liquid head 431, which is the second head, to be slower than the ejection speed of the inkjet head 421, which is the first head.

[0072] This configuration can suppress the generation of mist of the treatment liquid. As a result, it is possible to suppress nozzle clogging caused by the mist of the treatment liquid adhering to the nozzle surface of the inkjet head 421. Furthermore, since the ejection speed of the inkjet head 421 is not reduced, there is no decrease in landing accuracy. As a result, it is possible to suppress the occurrence of image distortion.

[0073] [Other configurations] Although the present invention has been specifically described above based on the embodiments thereof, the present invention is not limited to the above-described embodiments. Of course, the present invention can be modified in various ways within the scope of the invention described in the claims and its equivalents.

[0074] For example, in the above description, the inkjet recording apparatus 1 is provided with a droplet ejection unit 4 in which the first liquid is ink and the second liquid is a treatment liquid, but the present invention is not limited to this. In other words, the various configurations of the present invention can be applied to any droplet ejection device that ejects a first liquid and a second liquid that aggregates the first liquid.

[0075] Furthermore, although the droplet ejection unit 4 of a serial head type in which the ink ejection unit 42 and the treatment liquid ejection unit 43 are mounted on one carriage 41 has been exemplified, the present invention is not limited to this. In other words, the configuration of the present invention can also be applied to an inkjet recording device 1 equipped with a droplet ejection unit 4 of a line head type (one-pass type) in which the ink ejection unit 42 and the treatment liquid ejection unit 43 are arranged consecutively in the transport direction.

[0076] Furthermore, as described above, the number of satellites in droplets ejected by the head significantly contributes to the number of mist particles generated. Therefore, the control unit 2 may control the drive waveform so that the number of satellites in droplets ejected by the treatment liquid ejection head 431 is smaller than the number of satellites in droplets ejected by the inkjet head 421. In this configuration, the control unit 2 functions as an acquisition unit that acquires the number of satellites in droplets ejected from the head.

[0077] Specifically, as shown in FIG. 6, a drop watcher equipped with a trigger camera and lens D1 and a strobe camera D2 is installed below the head of the transport unit 3, facing each other in the width direction. In this configuration, the trigger camera is focused on the droplets, and a strobe is placed at a position facing each head in the XY plane. Then, when the droplets are ejected, the strobe is flashed for a moment between 400 and 600 ns, allowing the satellites of the droplets to be measured during flight. The control unit 2 then acquires the image captured by the drop watcher multiple times for each nozzle, and adjusts the drive waveform based on the average value of the satellites of both droplets.

[0078] More specifically, the control unit 2 counts the number of satellites when the leading droplet of the tenth droplet ejected from the head in ten consecutive ejections is located 500 μm from the nozzle. The control unit 2 then controls the drive waveforms applied to the inkjet head 421 and the treatment liquid ejection head 431 so that the average number of treatment liquid satellites is smaller than the average number of ink satellites. In particular, the control unit 2 preferably controls the drive waveforms so that the number of treatment liquid satellites is half or less of the number of ink satellites.

[0079] Furthermore, if the control unit 2 only reduces the ejection speed of the treatment liquid ejection head 431, the amount of treatment liquid applied will decrease, which may result in an insufficient amount of treatment liquid being applied to the recording medium M. Therefore, the control unit 2 may suppress the reduction in the amount of treatment liquid applied by increasing the ejection frequency of the treatment liquid ejection head 431 more than the ejection frequency of the inkjet head 421. Alternatively, the reduction in the amount of treatment liquid applied may be suppressed by providing a number of treatment liquid ejection head units 431 mounted on the carriage 41 greater than the number of inkjet heads 421 of any one color in the ink ejection unit 42.

[0080] Furthermore, if the control unit 2 only reduces the ejection speed of the treatment liquid ejection head 431, there is a risk that misalignment will occur in the landing positions of the ink and the treatment liquid at the edge of the recording medium M. Therefore, the control unit 2 may align the landing positions by causing the inkjet head 421 and the treatment liquid ejection head 431 to eject droplets at different timings. Note that the ejection timing of the treatment liquid ejection head 431 and the inkjet head 421 can be calculated appropriately from a print gap based on, for example, the thickness of the recording medium M.

[0081] Furthermore, the control unit 2 may control not only the ejection speed of the head but also the amount of droplets ejected. Specifically, the control unit 2 preferably controls the amount of droplets ejected from the nozzles to be in the range of 4 pL to 30 pL. By controlling the amount to be in this range, the droplets are less susceptible to the influence of air resistance, and the generation of mist can be suppressed.

[0082] Furthermore, although the above describes an example of a configuration in which the control unit 2 controls the ejection speeds of the inkjet head 421 and the treatment liquid ejection head 431, the present invention is not limited to this. That is, even if the ejection speeds cannot be controlled (changed) by the control unit 2, the configuration of the present invention is applicable as long as the ejection speed of the treatment liquid ejection head 431 is set in advance to be slower than the ejection speed of the inkjet head 421, for example.

[0083] Although the above describes an example in which a hard disk or a semiconductor nonvolatile memory is used as a computer-readable medium for the program according to the present invention, the present invention is not limited to this example. Other computer-readable media include portable recording media such as CD-ROMs. Furthermore, a carrier wave can also be used as a medium for providing the program data according to the present invention via a communication line. [Explanation of symbols]

[0084] 1. Inkjet recording device (droplet ejection device) 2. Control unit (acquisition unit) 4 Droplet discharge part 421 Inkjet head (first head) 431 Processing liquid ejection head (second head) M Recording medium

Claims

1. a droplet ejection unit that ejects droplets from a nozzle; the droplet ejection unit includes a first head that ejects a first liquid, and a second head that ejects a second liquid that aggregates the first liquid; A droplet ejection device in which the ejection speed of the second head is slower than the ejection speed of the first head.

2. 2. The droplet ejection device according to claim 1, wherein the ejection speed of the second head is 4.0 m / s or more and is slower than the ejection speed of the first head by 0.5 m / s or more.

3. 2. The droplet ejection device according to claim 1, wherein the ejection speed of the first head and the second head is 10.0 m / s or less.

4. 2. The droplet ejection device according to claim 1, wherein the ejection amount of the nozzles of the first head and the nozzles of the second head is 4 pL or more and 30 pL or less.

5. the first liquid comprises a dispersion; 2. The droplet ejection device according to claim 1, wherein the second liquid contains a flocculating agent that causes the dispersion to flocculate.

6. 2. The droplet ejection device according to claim 1, wherein the distance between the nozzle surface of the second head, on which the nozzles are provided, and the recording medium is 1 mm or more and 6 mm or less.

7. 2. The droplet ejection device according to claim 1, wherein the number of satellites of the droplets ejected by the second head is smaller than the number of satellites of the droplets ejected by the first head.

8. The droplet ejection device according to claim 1 , further comprising a control unit that controls the droplet ejection of the droplet ejection unit.

9. an acquisition unit that acquires the number of satellites in droplets ejected from the first head and the second head; The droplet ejection device according to claim 8 , which cites claim 7 , wherein the control unit controls the voltages applied to the first head and the second head in accordance with the content acquired by the acquisition unit.

10. The droplet ejection device according to claim 8 , wherein the control unit applies a voltage to the second head that is lower than a voltage to the first head.

11. The droplet ejection device according to claim 8 , wherein the control unit applies to the second head a voltage having a waveform different from that of the voltage applied to the first head.

12. The droplet ejection device according to claim 8 , wherein the control unit makes the viscosity of the second liquid higher than the viscosity of the first liquid.

13. The droplet ejection device according to claim 12 , wherein the control unit makes the temperature of the second liquid lower than the temperature of the first liquid.

14. The droplet ejection device according to claim 8 , wherein the control unit makes the ejection frequency of the second head higher than the ejection frequency of the first head.

15. the droplet ejection unit includes, as the first head, a plurality of types of inkjet heads that eject ink of each color; The droplet ejection device according to claim 8 , wherein the number of the second heads is greater than any one type of inkjet head among the plurality of types of inkjet heads.

16. The droplet ejection device according to claim 8 , wherein the control unit causes the first head to eject droplets at a timing different from the timing at which the second head ejects droplets.

17. 17. The droplet ejection device according to claim 16, wherein the control unit determines ejection timings of the first head and the second head in accordance with a distance between a nozzle face of the droplet ejection unit that ejects liquid and a recording medium.

18. a droplet ejection unit that ejects droplets from a nozzle; A liquid aggregation suppression method for a droplet ejection device, wherein the droplet ejection unit includes a first head that ejects a first liquid and a second head that ejects a second liquid that causes the first liquid to aggregate, comprising: a control step of controlling droplet ejection from the droplet ejection unit, The control step controls the ejection speed of the second head to be slower than the ejection speed of the first head.

19. a droplet ejection unit that ejects droplets from a nozzle; a droplet ejection device in which the droplet ejection unit includes a first head that ejects a first liquid and a second head that ejects a second liquid that aggregates the first liquid; a control unit that controls the droplet discharge of the droplet discharge unit; The control unit is a program that controls the ejection speed of the second head to be slower than the ejection speed of the first head.

Images