Liquid discharge device and liquid discharge method

Abstract

To reduce an influence of sub-droplets.SOLUTION: A liquid discharge device includes: a head for discharging liquid onto an object; and a moving mechanism for moving the object and the head relative to each other. The head discharges the liquid to make the liquid land on the object. Further, in the liquid discharge device, when a first direction denotes a direction in which the head moves relative to the object according to the moving mechanism, a second direction denotes a direction orthogonal to the first direction, and a rear end region denotes a region of an end on a downstream side of the first direction of a discharge region where the liquid is discharged on the object, a length in the second direction of the liquid landed in the rear end region is shorter than a length in the second direction of the liquid landed in a region excluding the rear end region in the discharge region.SELECTED DRAWING: Figure 12

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Liquid ejection devices that eject liquid from a head and apply it to a target object are known.

[0003] For example, Patent Document 1 discloses an inkjet printing device that changes the resolution of the upstream edge of an image to be printed to a lower resolution than the set resolution in order to reduce the effect of sub-droplets. Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the device of Patent Document 1, there is room for improvement in the influence of sub-droplets at the downstream end.

[0005] The present invention aims to reduce the effects of sub-droplets. [Means for solving the problem]

[0006] A liquid ejection device according to one aspect of the present invention includes a head that ejects liquid onto a target object and a movement mechanism that moves the target object and the head relative to each other, wherein the head ejects the liquid to cause the liquid to land on the target object; when a first direction is defined as the direction in which the head moves relative to the target object by the movement mechanism and a second direction is defined as a direction perpendicular to the first direction, and when a rear end region is defined as an end region downstream of the first direction of an ejection region from which the liquid is ejected on the target, the length in the second direction of the liquid that has landed in the rear end region is shorter than the length in the second direction of the liquid that has landed in regions of the ejection region other than the rear end region. [Effects of the Invention]

[0007] According to the present invention, the influence of sub-droplets can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing the overall configuration of a liquid ejection device according to a first embodiment of the present invention. [Figure 2] 1 is a perspective view showing the configuration of a head included in a liquid ejection device according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view of the head taken along plane S1 in FIG. 2. [Figure 4] 2 is a diagram showing the configuration of a supply unit included in the liquid ejection device according to the first embodiment of the present invention. FIG. [Figure 5] 1 is a block diagram showing a configuration of a liquid ejection device according to a first embodiment of the present invention. [Figure 6] 2 is a block diagram showing the functional configuration of a controller included in the liquid ejection device according to the first embodiment of the present invention. FIG. [Figure 7] 3 is a diagram showing an example of a relative movement path of a head provided in the liquid ejection device according to the first embodiment of the present invention with respect to a target object. FIG. [Figure 8] 3A to 3C are diagrams showing a first example of the state of droplets ejected from the liquid ejection device according to the first embodiment of the present invention. [Figure 9] 9 is a diagram showing dots formed by the droplets of FIG. 8. FIG. [Figure 10] 5A and 5B are diagrams showing a second example of the state of droplets ejected from the liquid ejection device according to the first embodiment of the present invention. [Figure 11] 11A and 11B are diagrams showing dots formed by the droplets of FIG. 10. [Figure 12] 5A and 5B are diagrams showing a first example of dots after landing on a target object in the liquid ejection device according to the first embodiment of the present invention. [Figure 13] 10A and 10B are diagrams showing a second example of dots after landing on a target object in the liquid ejection device according to the first embodiment of the present invention. [Figure 14] 10A and 10B are diagrams showing a third example of dots after landing on a target object in the liquid ejection device according to the first embodiment of the present invention. [Figure 15] FIG. 10 is a diagram showing dots after landing on a target according to a comparative example. [Figure 16] FIG. 4 is a diagram showing a first example of the moving speed of the head in the liquid ejection device according to the first embodiment of the present invention. [Figure 17] FIG. 10 is a diagram showing a second example of the moving speed of the head in the liquid ejection device according to the first embodiment of the present invention. [Figure 18] 5 is a diagram showing a first example of the relationship between the discharge cycle and the thickness of a coating film in the liquid discharge device according to the first embodiment of the present invention. FIG. [Figure 19] FIG. 10 is a diagram showing a second example of the relationship between the discharge cycle and the thickness of the coating film in the liquid discharge device according to the first embodiment of the present invention. [Figure 20] FIG. 10 is a diagram showing a third example of the relationship between the discharge cycle and the thickness of the coating film in the liquid discharge device according to the first embodiment of the present invention. [Figure 21] FIG. 10 is a diagram showing a driving voltage of a head in a liquid ejection device according to a comparative example. [Figure 22] FIG. 4 is a diagram showing a first example of a driving voltage for a head in the liquid ejection device according to the first embodiment of the present invention. [Figure 23] FIG. 10 is a diagram showing a second example of the driving voltage of the head in the liquid ejection device according to the first embodiment of the present invention. [Figure 24] FIG. 10 is a diagram showing a third example of the driving voltage of the head in the liquid ejection device according to the first embodiment of the present invention. [Figure 25] FIG. 10 is a diagram showing a fourth example of the driving voltage of the head in the liquid ejection device according to the first embodiment of the present invention. [Figure 26] FIG. 10 is a diagram showing a fifth example of the driving voltage of the head in the liquid ejection device according to the first embodiment of the present invention. [Figure 27] 5 is a flowchart showing a dot data setting process performed by the liquid ejection device according to the first embodiment of the present invention. [Figure 28] 10 is a flowchart showing a process for determining sub-droplet countermeasure details performed by the liquid ejection device according to the first embodiment of the present invention. [Figure 29]3A and 3B are diagrams illustrating the reciprocating relative movement of the head in the liquid ejection device according to the first embodiment of the present invention. [Figure 30] FIG. 1 is a first diagram illustrating a discharge operation during reciprocal relative movement of a head in a liquid discharge device according to a first embodiment of the present invention. [Figure 31] FIG. 2 is a second diagram showing the discharge operation during the reciprocating relative movement of the head in the liquid discharge device according to the first embodiment of the present invention. [Figure 32] FIG. 3 is a third diagram showing a discharge operation during reciprocating relative movement of the head in the liquid discharge device according to the first embodiment of the present invention. [Figure 33] FIG. 4 is a fourth diagram showing the discharge operation of the reciprocating relative movement of the head in the liquid discharge device according to the first embodiment of the present invention. [Figure 34] 3A and 3B are diagrams showing a first example of ejection regions in the liquid ejection device according to the first embodiment of the present invention. [Figure 35] 5A and 5B are diagrams showing a second example of ejection regions in the liquid ejection device according to the first embodiment of the present invention. [Figure 36] 10A and 10B are diagrams showing a third example of ejection regions in the liquid ejection device according to the first embodiment of the present invention. [Figure 37] FIG. 4 is a diagram showing a configuration of a liquid ejection apparatus according to a second embodiment of the present invention. [Figure 38] FIG. 10 is a diagram showing the configuration of a liquid ejection device according to a third embodiment of the present invention. [Figure 39] 39 is a cross-sectional view taken along line XXXIX-XXXIX in FIG. 38. DETAILED DESCRIPTION OF THE INVENTION

[0009] A liquid ejection device and a liquid ejection method according to an embodiment of the present invention will be described in detail with reference to the drawings. However, the following embodiments are merely illustrative of a liquid ejection device and a liquid ejection method for embodying the technical concept of the embodiment of the present invention, and are not limited thereto. Furthermore, unless otherwise specified, the dimensions, materials, shapes, and relative positions of components described in the embodiments are merely illustrative examples and are not intended to limit the scope of the present invention. Note that the size, positional relationship, etc. of components shown in each drawing may be exaggerated for clarity. Furthermore, in the following description, the same names and symbols indicate components that are the same or of the same quality, and detailed description will be omitted as appropriate.

[0010] [First embodiment] <Configuration example of liquid ejection device 100> (Overall composition) Fig. 1 is a diagram showing an example of the overall configuration of a liquid ejection device 100 according to a first embodiment of the present invention. The liquid ejection device 100 has a liquid ejection unit 10 and a movement mechanism 13 that moves a target object 200 and a head 11 relative to each other in a first direction. In the example shown in Fig. 1, the liquid ejection device 100 also has a control unit 20 that controls the liquid ejection unit 10.

[0011] The liquid discharge device 100 includes four liquid discharge units 10 (10-1, 10-2, 10-3, 10-4). The four liquid discharge units 10 (10-1, 10-2, 10-3, 10-4) are arranged around a target object 200 placed at a coating position. Each of the four liquid discharge units 10 (10-1, 10-2, 10-3, 10-4) includes a head 11 that discharges liquid onto the target object 200, and a movement mechanism 13. In the example shown in FIG. 1, the liquid discharge unit 10 also includes a detection unit 12.

[0012] The object 200 is, for example, the body of a vehicle. Vehicles include cars, trucks, etc. In the example shown herein, the object 200 is a vehicle.

[0013] The heads 11 (11-1, 11-2, 11-3, 11-4) include a plurality of nozzles that eject liquid, and are attached to the tip of the movement mechanism 13. The movement mechanism 13 moves the heads 11 relative to the object 200. In the example shown in FIG. 1 , the movement mechanism 13 moves the heads 11 relatively along the surface of the object 200. The heads 11 are moved relatively by the movement mechanism 13, and paint the object 200 by applying liquid ejected from the nozzles to the object 200.

[0014] The detector 12 (12-1, 12-2, 12-3, 12-4) is attached to the tip of the moving mechanism 13. The detector 12 outputs feature point information related to the three-dimensional positions of three or more feature points on the object 200. The detector 12 includes a 3D camera such as a stereo camera, or a 3D sensor other than a stereo camera, a laser displacement meter, or the like. In the example shown in FIG. 1, the detector 12 includes a stereo camera, which measures the position and tilt in the X and Y directions, detects the painting start position, and detects the size of the object to be painted. The stereo camera has multiple cameras and acquires a range image of the object 200 by triangulation based on the parallax between the images captured by each of the multiple cameras. The stereo camera also outputs the range image to the control unit 20 as feature point information. The detector 12 may also include a laser displacement meter, which may measure the Z direction, detect the roof height of the object 200, and detect the curvature of the object 200.

[0015] The movement mechanism 13 (13-1, 13-2, 13-3, 13-4) has links and joints. The movement mechanism 13 changes the relative position and relative inclination between the head 11 and the target 200 by rotating or displacing the links and joints, and positions the nozzle surface of the head 11 facing the target 200.

[0016] The control unit 20 drives the moving mechanism 13 holding the four heads 11 based on the shape data of the predetermined object 200 and feature point information regarding the three-dimensional positions of three or more feature points output from each of the four detection units 12.

[0017] 1, the liquid ejection device 100 may have a supply unit and a maintenance unit. The supply unit can supply liquid to be ejected onto the target object 200 to each of the four heads 11. The maintenance unit removes thickened liquid or foreign matter adhering to the nozzle surface of the head 11 or thickened liquid or foreign matter present inside the head 11. The liquid ejection device 100 can use the maintenance unit to reduce ejection abnormalities such as non-ejection, deflected ejection, and ejection speed fluctuations in the head 11, and maintain the ejection state of the head 11 in a normal state.

[0018] In the liquid discharge device 100, after the object 200 is transported to the coating position, the moving mechanism 13 moves the head 11 relative to the stopped object 200 to coat it. After coating, the object 200 is transported out of the coating position, and the next object 200 is transported to the coating position.

[0019] (Head 11) The configuration of the head 11 provided in the liquid ejection device 100 will be described with reference to Figures 2 and 3. Figure 2 is a diagram showing an example of the configuration of the head 11 according to the first embodiment. Figure 3 is a cross-sectional view of the head 11 according to the first embodiment taken along plane S1 in Figure 2. In Figures 2 and 3, the head 11 has a supply port 111, a recovery port 112, and an ejection module 340.

[0020] The supply port 111 supplies pressurized liquid from the outside to the discharge module 340. The recovery port 112 discharges liquid that has not been discharged to the outside when a nozzle 311, which will be described later, is opened.

[0021] The ejection module 340 includes a housing 110 , a nozzle plate 321 having nozzles 311 , a liquid flow path 322 , a valve body 310 , and a piezoelectric element 324 .

[0022] Nozzle plate 321 is joined to housing 110, and ejects liquid supplied from supply port 111 from nozzle 311. Flow path 322 is a flow path common to multiple (eight in FIG. 3) ejection modules 340 provided in housing 110.

[0023] The valve element 310 shown in Fig. 3 is a needle-shaped valve element. The valve element 310 is driven by a piezoelectric element 324 and moves back and forth in the direction of discharging liquid within the housing 110, thereby opening and closing the nozzle 311. The head 11 shown in Fig. 3 supplies pressurized liquid from the supply port 111 through the flow path 322 with the valve of the recovery port 112 closed. When the valve element 310 is in a position that closes the nozzle 311, the nozzle 311 does not discharge liquid. On the other hand, when the piezoelectric element 324 is driven to raise the valve element 310, the nozzle 311 is opened and liquid is discharged from the nozzle 311.

[0024] (Supply section 14) 4 is a diagram showing an example of the configuration of the supply unit 14 provided in the liquid ejection device 100. The supply unit 14 includes liquid tanks 330 (330-1, 330-2, 330-3, 330-4) as sealed containers that contain the liquid 325 to be ejected from the head 11. The liquid tanks 330 and the inlets (supply ports 111) of the head 11 are connected via tubes 333 so that the liquid can flow through them.

[0025] The liquid tank 330 is connected to the compressor 230 via a pipe 331 including an air regulator 332, and the compressor 230 supplies pressurized air. As a result, pressurized liquid 325 is supplied to the inlet of the head 11, and the liquid ejection device 100 ejects the liquid 325 from the nozzle of the head 11. Note that instead of providing a liquid tank 330 for each head 11, it is also possible to supply liquid to all heads 11 from one liquid tank 330.

[0026] (Control unit 20) 5 is a block diagram showing an example of the configuration of the liquid ejection device 100. The liquid ejection device 100 has a controller 901, a head control device 902, a movement mechanism control device 904, an input device 905, movement mechanisms 13-1 and 13-2, and a PC (Personal Computer) 903.

[0027] The controller 901 includes a CPU (Central Processing Unit) 9001, a ROM (Read Only Memory) 9002, a RAM (Random Access Memory) 9003, and an I / F (Interface) 9004. The controller 901, the head control device 902, and the movement mechanism control device 904 constitute a control unit 20. The head 11 and the detection unit 12 constitute a head unit 103. Note that the movement mechanisms 13-1 and 13-2 are two of the four movement mechanisms 13 shown in FIG. 1.

[0028] The PC 903 has a painting route generation unit 9031 and a painting data generation unit 9032. The painting route generation unit 9031 and the painting data generation unit 9032 shown in Fig. 5 are functional components of the PC 903. The functions of the painting route generation unit 9031 and the painting data generation unit 9032 are realized by a CPU included in the PC 903 executing processes defined by a program stored in a storage unit such as a ROM.

[0029] The painting route generation unit 9031 acquires position data from the detection unit 12 provided in the movement mechanism 13 and generates a painting route, which is a path along which the head 11 is moved by the movement mechanism 13 .

[0030] The paint data generation unit 9032 generates paint dot data from the paint route generated by the paint route generation unit 9031. The paint data generation unit 9032 also has a discharge frequency generation unit 9033, a movement speed generation unit 9034, and a RIP (Raster Image Processor) 9035. In the paint data generation unit 9032, the discharge frequency generation unit 9033 generates a discharge frequency for the head 11 according to the generated dot data, the movement speed generation unit 9034 generates a movement speed for the head 11 by the movement mechanism 13, and also generates drive conditions for the head 11, which are used as paint data.

[0031] The RIP unit 9035 performs image processing according to the color profile or user settings. The RIP unit 9035 has a rendering unit 9036. The rendering unit 9036 breaks down the paint data to be applied to the object 200 into image data. The liquid ejection device 100 performs painting by moving the head 11 in both the main scanning direction and the sub-scanning direction perpendicular to the main scanning direction. The image data is the paint data used in painting for each movement in the main scanning direction.

[0032] The PC 903 is connected to an input device 905 that is used to set image data and coordinate data for painting the object 200, select a painting mode, set the painting range (painting start position, painting end position), and give painting instructions, etc. The input device 905 is composed of a keyboard, mouse, touch panel, etc., and accepts input from the user.

[0033] The controller 901 is connected to a PC 903. The CPU 9001 is a computing device that reads programs or data stored in a ROM 9002 or the like onto a RAM 9003 and executes processing to realize each function of the painting robot 1000. The controller 901 may further include a hard disk drive (HDD), a solid state drive (SSD), or the like.

[0034] The CPU 9001 controls the overall operation of the liquid ejection device 100 using image data or commands received from the PC 903. The ROM 9002 is a non-volatile memory that can retain programs or data even when the power is turned off. The RAM 9003 is a volatile memory used as a work area for the CPU 9001. The I / F 9004 is an interface for inputting and outputting characters, numbers, various instructions, etc., to and from various external devices. The I / F 9004 is an interface that allows communication between the controller 901 and external devices such as the PC 903.

[0035] The movement mechanism 13 includes a head unit 103, an encoder sensor 109, and a drive unit 72. The head 11 ejects liquid in response to a drive signal from a head control device 902. The detection unit 12 transmits the detection result of the target object 200 to a PC 903.

[0036] The encoder sensor 109 optically detects each slit of the encoder provided in, for example, the first joint 104, the second joint 105, and the third joint 106. Then, the encoder sensor 109 detects the positions of the moving mechanisms 13-1 and 13-2 from the amount of rotation of these mechanisms, and obtains three-dimensional position information of the head unit 103.

[0037] The drive unit 72 moves the head unit 103 held by the moving mechanism 13 to a desired position in response to a drive signal from the moving mechanism control device 904. Note that the head control device 902 and the moving mechanism control device 904 are common to the moving mechanisms 13-1 and 13-2, but the moving mechanisms 13-1 and 13-2 may each be equipped with the head control device 902 and the moving mechanism control device 904. Also, the RIP unit 9035 and the rendering unit 9036 may be provided in the controller 901 instead of in the PC 903.

[0038] The head control device 902 receives a discharge period signal from the controller 901 and controls the liquid discharge operation of the head 11 based on the discharge period signal. The movement mechanism control device 904 receives a synchronization control signal from the controller 901 and controls the driving of the drive unit 72 based on the synchronization control signal. By controlling the driving of this drive unit 72, the movement mechanism 13 and head unit 103 move to desired positions.

[0039] (Functional configuration of controller 901) 6 is a block diagram showing an example of the functional configuration of a controller 901 included in the liquid ejection device 100 according to the first embodiment of the present invention. The controller 901 includes a system control unit 9011, a data storage unit 9012, a memory control unit 9013, an ejection period signal generation unit 9014, and a period control unit 9015.

[0040] The system control unit 9011 controls the overall operation of the liquid ejection device 100 using image data and commands received from the PC 903. The data storage unit 9012 stores painting data and the like received from the computer 300. The memory control unit 9013 controls the data storage unit 9012. The ejection period signal generation unit 9014 generates a liquid ejection period signal from the output signal of the encoder sensor 109 and information indicating the resolution of the image data received from the PC 903. The period control unit 9015 coordinates the movements of the moving mechanisms 13-1 and 13-2 with the liquid ejection operation of the heads 11-1 and 11-2 based on the image data, painting instructions, and the like received from the PC 903.

[0041] <Relative movement path of head 11 with respect to object 200> FIG. 7 is a diagram showing an example of a relative movement path of the head 11 provided in the liquid ejection device 100 according to the first embodiment of the present invention with respect to the target object 200. In FIG.

[0042] 7, the object 200 is an automobile, and the coating area 211 (211-1, 211-2, 211-3, 211-4) is the roof of the automobile. The coating area 211 is the area where each of the four movement mechanisms 13 shown in FIG. 1 moves the head 11 relative to the object 200 to paint. The coating area 211 and the relative movement path T10 (T1-1, T1-2, T1-3, T1-4) are different for each of the four heads 11.

[0043] The coating range 211-1 is a range in which coating is performed by moving the head 11-1 by the movement mechanism 13-1 relative to the object 200. The relative movement path T1-1 is a path along which the head 11-1 moves relative to the object 200.

[0044] The coating range 211-2 is a range in which coating is performed by moving the head 11-2 by the movement mechanism 13-2 relative to the object 200. The relative movement path T1-2 is a path along which the head 11-2 moves relative to the object 200.

[0045] The coating range 211-3 is a range in which coating is performed by moving the head 11-3 by the movement mechanism 13-3 relative to the object 200. The relative movement path T1-3 is a path along which the head 11-3 moves relative to the object 200.

[0046] The coating range 211-4 is a range in which coating is performed by moving the head 11-4 by the movement mechanism 13-4 relative to the object 200. The relative movement path T1-4 is a path along which the head 11-4 moves relative to the object 200.

[0047] As described above, the liquid discharger 100 can discharge liquid and perform painting by moving the four heads 11 relative to the roof of the car as the target object 200 using the four movement mechanisms 13.

[0048] Here, we will explain the ejected liquid when the head is ejecting the liquid while moving in the main scanning direction. "Intermittently ejecting liquid" refers to periodically repeating a state in which the liquid is ejected and a state in which the liquid is not ejected while the head is moving in the main scanning direction. A specific example of intermittently ejecting liquid is ejecting droplets. On the other hand, "continuously ejecting liquid" refers to continuing to eject liquid while the head is moving in the main scanning direction. In other words, "continuously ejecting liquid" means ejecting liquid without interruption (or in a continuous manner) in the main scanning direction of the head while the head is moving in the main scanning direction. In the following explanation, intermittently ejected liquid may be referred to as "droplets" and continuously ejected liquid may be referred to as "liquid threads."

[0049] When a liquid ejection device ejects droplets, the droplets that land on the object to be coated spread out in a circular shape on the object to form dots. The formed dots overlap with surrounding dots to fill in the gaps between them and form the coated surface. Because the formed dots are circular, the edges of the coated surface become wavy along the shape of the dots.

[0050] On the other hand, when a liquid ejection device ejects liquid threads, the liquid threads that land on the object to be coated do not form dots but form lines along the main scanning direction of the liquid ejection device, which means that the edge shape of the coated surface in the sub-scanning direction becomes smoother along the main scanning direction.

[0051] <Operation of the liquid ejection device 100> (Reducing the effects of side drops) First, we will explain the effect of reducing the influence of sub-droplets by the liquid ejection device 100. Note that, although the following explanation will be given using droplets as an example, the basic concept is the same for liquid strings.

[0052] The head 11 ejects liquid as droplets, which are liquid particles, by opening and closing the valve body 310. By ejecting the liquid, the head 11 causes the liquid to land on the target 200. By causing the liquid to land on the target 200, the head 11 forms dots on the target 200. The head 11 can also control the volume of the droplets by controlling the time from when the valve body 310 is opened until when it is closed. The longer the time from when the valve body 310 is opened until it is closed, the larger the volume of the droplets. The larger the volume of the droplets, the larger the diameter of the approximately circular dots formed on the target 200.

[0053] A droplet ejected from the head 11 may have a trailing portion called a ligament behind it in the direction of flight, depending on the viscosity or surface tension of the liquid. When a ligament separates from the droplet during flight, the surface tension of the liquid may cause the ligament to break down into small droplets, which may then be generated behind the droplet. In this specification, the main portion of the droplet other than the ligament is referred to as a main droplet, and the small droplets formed by the ligament that has separated from the main droplet are referred to as sub-droplets. Sub-droplets have a smaller volume than the main droplet. Sub-droplets can also be referred to as satellite droplets because they are located at a distance from the main droplet. The main droplet forms a dot by impacting the target 200. The sub-droplets form satellite dots by impacting the target 200.

[0054] The relationship between the state of droplets ejected from the head 11 and the dots formed by those droplets will be described with reference to FIGS. 8 to 11. FIG. 8 is a diagram showing a first example of the state of droplets ejected from the liquid ejection device 100 according to the first embodiment of the present invention. FIG. 9 is a diagram showing dots and satellite dots formed by the droplets shown in FIG. 8. FIG. 10 is a diagram showing a second example of the state of droplets ejected from the liquid ejection device 100 according to the first embodiment of the present invention. FIG. 11 is a diagram showing dots and satellite dots formed by the droplets shown in FIG. 10. FIGS. 8 and 10 show the state of droplets as viewed from a direction substantially perpendicular to the ejection direction C of the liquid from the head 11. FIGS. 9 and 11 show dots and satellite dots formed on the target 200 by the impact of droplets as viewed from a direction normal to the target 200.

[0055] In the first example shown in Fig. 8, droplet 80a includes a main droplet 81a and ligaments 82a formed behind the main droplet 81a. Droplet 80a' in Fig. 8 shows the state of droplet 80a after some time has passed. In droplet 80a', ligaments 82a separate from the main droplet 81a, and the separated ligaments 82a break down into particles in response to the surface tension of the liquid, generating multiple sub-droplets 83a.

[0056] 9, a dot 91a is formed from a main droplet 81a, and satellite dots 92a are formed from multiple sub-droplets 83a. Length L1 represents the distance from the end position of the dot 91a on the satellite dot 92a side to the end position of the satellite dot 92a on the dot 91a side in a first direction A along the direction in which the head 11 moves. Note that, in the embodiment of the present invention, the first direction A refers to the direction (main scanning direction) in which the head 11 moves relative to the target 200 by the movement mechanism 13 when forming dots in a discharge area where liquid is discharged onto the target 200.

[0057] In the second example shown in Fig. 10, droplet 80b includes a main droplet 81b and ligaments 82b formed behind the main droplet 81b. Droplet 80b' in Fig. 10 shows the state of droplet 80b after some time has passed. In droplet 80b', ligaments 82b separate from the main droplet 81b, and the separated ligaments 82b break down into particles in response to the surface tension of the liquid, generating multiple sub-droplets 83b.

[0058] 11, a dot 91b is formed from a main droplet 81b, and satellite dots 92b are formed from multiple sub-droplets 83b. Length L2 represents the distance in first direction A from the end position of dot 91b on the satellite dot 92b side to the end position of satellite dot 92b on the dot 91b side.

[0059] The droplet 80a shown in FIG. 8 has a larger droplet volume and amount than the droplet 80b shown in FIG. 10. Due to the larger droplet volume, the length of the ligaments 82a is longer than the length of the ligaments 82b in the ejection direction C. Due to the longer ligaments 82a, the number of sub-droplets 83a generated from the ligaments 82a increases, and the total length of the multiple sub-droplets 83a aligned in the ejection direction C is longer than the total length of the multiple sub-droplets 83b aligned in the ejection direction C. Due to the longer total length of the multiple sub-droplets 83a aligned in the ejection direction C, the area of ​​the satellite dot 92a shown in FIG. 9 is larger than the area of ​​the satellite dot 92b shown in FIG. 11 on the target object 200. Furthermore, the length L1 of the satellite dots 92a aligned in the first direction A is longer than the length L2 of the satellite dots 92b.

[0060] For example, if the satellite dots become larger or the length of the satellite dots aligned in the first direction A becomes longer, unnecessary liquid may adhere to the target object 200, causing the target object 200 to become dirty.

[0061] Here, with reference to FIGS. 12 to 15, dots formed on a target object 200 by the liquid ejection apparatus 100 according to the first embodiment of the present invention will be described. FIG. 12 is a diagram illustrating a first example of dots 91 after landing on the target object 200 by the liquid ejection apparatus 100 according to the first embodiment of the present invention. FIG. 13 is a diagram illustrating a second example of dots 91 after landing on the target object 200 by the liquid ejection apparatus 100 according to the first embodiment of the present invention. FIG. 14 is a diagram illustrating a third example of dots 91 after landing on the target object 200 by the liquid ejection apparatus 100 according to the first embodiment of the present invention. FIG. 15 is a diagram illustrating dots 91 after landing on the target object 200 according to a comparative example. Note that in FIGS. 12 to 14, the dot 91 is written alongside the reference numerals of the dots 911 and 912 to indicate that the dots 91 include the dots 911 and 912. In FIG. 15, the dot 91 is written alongside the reference numerals of the dots 911 and 912X to indicate that the dots 91 include the dots 911 and 912X. Furthermore, the front end region of the discharge region 120 described below refers to the end region on the upstream side of the first direction A, and the rear end region refers to the end region on the downstream side of the first direction A. Furthermore, the direction perpendicular to the first direction A is referred to as the second direction.

[0062] 12 to 14, the diameter dc of dots 912 in the rear end region 121 in the first direction A of the discharge region 120 where liquid is discharged onto the target 200 is smaller than the diameter d of dots 911 in regions other than the rear end region in the discharge region 120. As a result, the length in the second direction of the liquid that has landed in the rear end region is shorter than the length in the second direction of the liquid that has landed in regions other than the rear end region in the discharge region.

[0063] For example, the liquid ejection device 100 reduces the amount of droplets 80 ejected from the head 11 in the rear end region 121 of the ejection region 120 compared to the amount of droplets 80 in the regions of the ejection region 120 other than the rear end region 121. As a result, the diameter dc of the dots 912 in the rear end region 121 becomes smaller than the diameter d of the dots 911 in the regions other than the rear end region 121. Reducing the amount of droplets 80 shortens the length of the ligaments. This allows the liquid ejection device 100 to reduce the effects of sub-droplets. Furthermore, by reducing the effects of sub-droplets, the liquid ejection device 100 can reduce satellite dots and suppress contamination of the target object 200 due to unnecessary liquid adhering to the target object 200. Note that the effect of reducing the effects of sub-droplets is achieved in all of the first to third examples.

[0064] The range of the rear end region 121 in the first direction A is a range on the upstream side in the direction in which the head 11 moves, from the rear end of the ejection region 120 by a length corresponding to or greater than the diameter d of the dot 911. Furthermore, it is preferable that the diameter dc of the dot 912 is 90% or less of the diameter d of the dot 911.

[0065] 15, the amount of droplets 80 ejected from the head 11 in the rear end region 121X of the ejection region 120 is not less than the amount of droplets 80 in the regions other than the rear end region 121X of the ejection region 120. Therefore, compared to the satellite dots 92 in the first example shown in FIG. 12, the second example shown in FIG. 13, and the third example shown in FIG. 14, the satellite dots 92X in the comparative example are greater in number and larger in size.

[0066] (Reducing variations in paint film thickness) Next, the effect of the liquid ejection device 100 in reducing variations in thickness of the coating film will be described.

[0067] For example, if the amount of droplets 80 in the rear end region 121 is made smaller than the amount of droplets 80 in regions other than the rear end region 121, the thickness of the paint film in the rear end region 121 will be thinner than the thickness of the paint film in regions other than the rear end region 121, which may result in variations in the thickness of the paint film.

[0068] 12, the center-to-center distance pc between dots 912 adjacent in the first direction A in the rear end region 121 is shorter than the center-to-center distance p between dots 911 adjacent in the first direction A in the discharge region 120 in a region other than the rear end region 121. This makes it possible to make the amount of droplets 80 in the rear end region 121 the same as the amount of droplets 80 in the region other than the rear end region 121. As a result, the thickness of the coating film in the rear end region 121 can be made the same as the thickness of the coating film in the region other than the rear end region 121, thereby reducing variation in the thickness of the coating film.

[0069] 13, the center-to-center distance pc between adjacent dots 912 in the first direction A is even shorter in the rear end region 121 of the discharge region 120 than in the first example shown in Fig. 12. In the second example as well, the amount of droplets 80 in the rear end region 121 can be made equal to the amount of droplets 80 in regions other than the rear end region 121.

[0070] 14 , in the rear end region 121, as the dots 912 move in the direction indicated by the arrow in the first direction A, the diameter dc of the dots 912 gradually decreases, and the center-to-center distance between adjacent dots 912 in the first direction A also decreases. In the second example, too, the amount of droplets 80 in the rear end region 121 can be made equal to the amount of droplets 80 in regions other than the rear end region 121.

[0071] Furthermore, in the liquid ejection device 100, in order to reduce variations in thickness of the coating film, the relative movement speed of the head 11 in the rear end region 121 may be slower than the relative movement speed of the head 11 in regions of the ejection region 120 other than the rear end region 121. FIG. 16 is a diagram showing a first example of the movement speed of the head 11 in the liquid ejection device 100 according to the first embodiment of the present invention. FIG. 17 is a diagram showing a second example of the movement speed of the head 11 in the liquid ejection device 100 according to the first embodiment of the present invention. Note that the liquid ejection device 100 can control the movement speed of the head 11 by controlling the number of rotations of the gears in the movement mechanism 13, for example.

[0072] 16, a first period T1 is a period during which the head 11 ejects liquid onto a region of the ejection region 120 other than the rear end region 121. A second period T2 is a period during which the head 11 ejects liquid onto the rear end region 121 of the ejection region 120. The movement speed of the head 11 in the first direction A during the second period T2 is slower than the movement speed of the head 11 in the first direction A during the first period T1. Because the movement speed of the head 11 is slow, the amount of droplets 80 in the rear end region 121 is greater than when the movement speed of the head 11 is fast. This makes it possible to make the amount of droplets 80 in the rear end region 121 the same as the amount of droplets 80 in the region other than the rear end region 121. As a result, the thickness of the coating film in the rear end region 121 can be made the same as the thickness of the coating film in the region other than the rear end region 121, thereby reducing variation in the thickness of the coating film.

[0073] 17, the movement speed of the head 11 in the first direction A during the second period T2 gradually slows as the head 11 moves. Even when the movement speed of the head 11 gradually slows, the amount of droplets 80 in the rear end region 121 is greater than when the movement speed of the head 11 is fast. This makes it possible to make the amount of droplets 80 in the rear end region 121 the same as the amount of droplets 80 in regions other than the rear end region 121. As a result, the thickness of the coating film in the rear end region 121 can be made the same as the thickness of the coating film in regions other than the rear end region 121, thereby reducing variation in the thickness of the coating film.

[0074] Next, the relationship between the discharge cycle and the thickness of the coating film in the liquid ejection device 100 according to the first embodiment of the present invention will be described with reference to Figures 18 to 20. Figure 18 is a diagram showing a first example of the relationship between the discharge cycle and the thickness of the coating film in the liquid ejection device 100 according to the first embodiment of the present invention. Figure 19 is a diagram showing a second example of the relationship between the discharge cycle and the thickness of the coating film in the liquid ejection device 100 according to the first embodiment of the present invention. Figure 20 is a diagram showing a third example of the relationship between the discharge cycle and the thickness of the coating film in the liquid ejection device 100 according to the first embodiment of the present invention.

[0075] 18 to 20 show the discharge cycle q1 of the droplets 80 and the thickness t1 of the coating film 180 in the first period T1, and the discharge cycle q2 of the droplets 80 and the thickness t2 of the coating film 180 in the second period T2. The coating film 180 refers to a film applied onto the target object 200.

[0076] 18, the amount of droplets 80 in the second period T2 is smaller than the amount of droplets 80 in the first period T1. Furthermore, the discharge cycle q2 in the second period T2 is the same as the discharge cycle q1 in the first period T1. As a result, in the first example, the thickness t2 of the coating film 180 in the period T2 is thinner than the thickness t1 of the coating film 180 in the first period T1.

[0077] In the second example shown in FIG. 19 , the amount of droplets 80 in the second period T2 is smaller than the amount of droplets 80 in the first period T1. Furthermore, the discharge cycle q2 in the second period T2 is shorter than the discharge cycle q1 in the first period T1. By shortening the discharge cycle q2, the amount of droplets discharged onto the target object 200 can be increased. As a result, in the second example, the thickness t2 of the coating film 180 in the second period T2 is approximately the same as the thickness t1 of the coating film 180 in the first period T1. Assume that the discharge cycle q2 in the second period T2 is the same as the discharge cycle q1 in the first period T1. In this case, the thickness t2 of the coating film 180 in the period T2 is thinner than the thickness t1 of the coating film 180 in the first period T1. In this case, the thickness variation of the coating film 180 becomes large. On the other hand, in the second example, the thickness t2 of the coating film 180 in the second period T2 can be made approximately equal to the thickness t1 of the coating film 180 in the first period T1, thereby reducing the thickness variation of the coating film 180.

[0078] In the third example shown in FIG. 20 , the amount of droplets 80 in the second period T2 is smaller than the amount of droplets 80 in the first period T1, and gradually decreases as the head 11 moves in the first direction A. Furthermore, the discharge cycle q2 in the second period T2 is shorter than the discharge cycle q1 in the first period T1, and gradually decreases as the head 11 moves in the first direction A. By shortening the discharge cycle q2, the amount of droplets discharged onto the target object 200 can be increased. As a result, in the third example, the thickness t2 of the coating film 180 in the second period T2 is approximately the same as the thickness t1 of the coating film 180 in the first period T1. As a result, in the third example, the thickness variation of the coating film 180 can be reduced.

[0079] Next, with reference to FIGS. 21 to 26, the drive voltage of the head 11 in the liquid ejection device 100 according to the first embodiment of the present invention will be described. FIG. 21 is a diagram showing a first example of the drive voltage of the head 11 in the liquid ejection device 100 according to the comparative example. FIG. 22 is a diagram showing a first example of the drive voltage of the head 11 in the liquid ejection device 100 according to the first embodiment of the present invention. FIG. 23 is a diagram showing a second example of the drive voltage of the head 11 in the liquid ejection device 100 according to the first embodiment of the present invention. FIG. 24 is a diagram showing a third example of the drive voltage of the head 11 in the liquid ejection device 100 according to the first embodiment of the present invention. FIG. 25 is a diagram showing a fourth example of the drive voltage of the head 11 in the liquid ejection device 100 according to the first embodiment of the present invention. FIG. 26 is a diagram showing a fifth example of the drive voltage of the head 11 in the liquid ejection device 100 according to the first embodiment of the present invention.

[0080] In the comparative example shown in FIG. 21, the liquid ejection device 100 applies a drive voltage V1 to the head 11 during an open period Δ1 at a cycle q1. The nozzle 311 opens as the valve element 310 moves by an amount corresponding to the drive voltage V1, and an amount of liquid corresponding to the amount of movement of the valve element 310 and the open period Δ1 is ejected from the nozzle 311. In this case, the amount of liquid droplets is not less than that in the region other than the rear end region of the ejection region, so the satellite dots are more numerous and larger than in the first to fifth examples described below. Therefore, in the embodiment of the present invention, the following configurations are used as shown in FIGS. 22 to 26.

[0081] 22, the liquid ejection device 100 applies a driving voltage V1 to the head 11 during an open period Δ1 with a cycle q1 in a first period T1, and applies a driving voltage V2 to the head 11 during an open period Δ2 with a cycle q2 in a second period T2, which is different from the comparative example shown in FIG. 21. Because the open period Δ2 is shorter than the open period Δ1, the amount of liquid ejected during the second period T2 is less than the amount of liquid ejected during the first period T1. By controlling the ejection of the first example shown in FIG. 22, droplets corresponding to the droplets 80 shown in FIG. 18 are obtained.

[0082] The second example shown in Fig. 23 differs from the first example shown in Fig. 22 in that the period q2 is shorter than the period q1. By the ejection control of the second example shown in Fig. 23, droplets corresponding to the droplets 80 shown in Fig. 19 are obtained.

[0083] The third example shown in Fig. 24 differs from the second example shown in Fig. 23 in that the period q2 gradually becomes shorter as the head 11 moves. By the ejection control of the third example shown in Fig. 24, droplets corresponding to the droplets 80 shown in Fig. 20 are obtained.

[0084] The fourth example shown in Fig. 25 differs from the comparative example shown in Fig. 21 in that the drive voltage V2 is lower than the drive voltage V1. By the ejection control of the fourth example shown in Fig. 25, droplets corresponding to the droplets 80 shown in Fig. 18 are obtained.

[0085] The fifth example shown in Fig. 26 differs from the comparative example shown in Fig. 21 in that the open period Δ1 is the same as the first period T1 and the open period Δ2 is the same as the second period T2. In the ejection control of the fourth example shown in Fig. 25, a continuous liquid string is ejected instead of droplets.

[0086] The liquid ejection device 100 can drive the head 11 with any of the drive voltages from the first example shown in Fig. 22 to the fifth example shown in Fig. 26. Note that ejection control by the liquid ejection device 100 is not limited to controlling the movement amount and opening time of the valve element 310 by applying a voltage to the head 11. For example, ejection control by the liquid ejection device 100 may also be controlling the movement amount and opening time of the valve element 310 by driving the valve element 310 with air.

[0087] Here, in the discharge control of the head 11, the amount of movement of the valve element 310 changes depending on the length of the open period of the nozzle 311, and this changes the sound generated by the movement of the valve element 310. Therefore, if the amount of droplets 80 discharged from the head 11 in the rear end region 121 is made smaller than the amount of droplets 80 in regions other than the rear end region 121, the sound generated by the movement of the valve element 310 in the rear end region 121 will be different from the sound generated by the movement of the valve element 310 in regions other than the rear end region 121. Therefore, from one perspective, it is possible to determine from the sound generated by the movement of the valve element 310 that the amount of droplets 80 discharged from the head 11 in the rear end region 121 is smaller than the amount of droplets 80 in regions other than the rear end region 121.

[0088] <Operation of the liquid ejection device 100> (Dot data setting process) First, the dot data setting process performed by the liquid ejection device 100 according to the first embodiment of the present invention will be described with reference to Fig. 27. Fig. 27 is a flowchart showing an example of the dot data setting process performed by the liquid ejection device 100 according to the first embodiment of the present invention. Each time the liquid ejection device 100 applies paint to the target object 200, the liquid ejection device 100 performs the process shown in Fig. 27 before starting painting.

[0089] First, in step S11, the liquid ejection device 100 reads the painting route stored in a memory unit such as a ROM provided in the PC 903 by the painting route generation unit 9031 of the PC 903 in order to know the movement of the head 11 according to the shape of the target object 200.

[0090] Subsequently, in step S12, the liquid discharger 100 identifies the rear end region 121 for each discharge region 120 in the coating route read in step S11.

[0091] Subsequently, in step S13, the liquid ejection device 100 determines whether or not the rear end region 121 of each of the ejection regions 120 identified in step S12 overlaps with another ejection region 120.

[0092] In step S13, if it is determined that the trailing edge regions 121 for each discharge region 120 do not all overlap (step S13, NO), the liquid discharger 100 proceeds to step S15. In this case, the dot data remains unchanged from its initial state. On the other hand, for the trailing edge regions 121 that are determined to overlap in step S13 (step S13, YES), in step S14, the sub-droplet countermeasure details, which will be described below, are determined with reference to Figure 28. The dot data is changed depending on the sub-droplet countermeasure details.

[0093] Subsequently, in step S15, the liquid ejection device 100 reflects the dot data in the painting route read in step S11.

[0094] In this way, the liquid ejection device 100 can perform the dot data setting process.

[0095] (Decision process for sub-droplet countermeasures) Next, with reference to Figure 28, a process for determining sub-droplet countermeasure details by the liquid ejection device 100 according to the first embodiment of the present invention will be described. Sub-droplet countermeasure details refer to the details of various measures taken to reduce the effects of sub-droplets. Figure 28 is a flowchart showing an example of a process for determining sub-droplet countermeasure details by the liquid ejection device 100 according to the first embodiment of the present invention. The liquid ejection device 100 starts the process of Figure 28 when performing step S14 of Figure 27. It should be noted that the liquid ejection device 100 performs the process of each step in Figure 28 in the rear end region 121 of each of the multiple ejection regions 120.

[0096] First, in step S21, the liquid ejection device 100 determines the range of the rear end region 121 for which sub-droplet countermeasures will be taken. Specifically, the liquid ejection device 100 determines the range of the rear end region 121 for which sub-droplet countermeasures will be taken, as defined by how many times the diameter d of the dot 911 it is from the rearmost end of the ejection region 120 toward the upstream side in the direction in which the head 11 moves. In the following processing, the determined multiple of the diameter d of the dot 911 is referred to as n.

[0097] Next, in step S22, the liquid ejection apparatus 100 determines how many dots to increase the n dots for executing the sub-droplet countermeasure by. If the determined increased number of dots is m, then the relationship n≦m is satisfied.

[0098] Subsequently, in step S23, the liquid ejection device 100 determines the amount of the liquid droplet 80 in the trailing end region 121, which is defined by the drive voltage V2 and the open period Δ2.

[0099] Next, in step S24, the liquid ejection device 100 determines the movement speed of the head 11 in the rear end region 121.

[0100] Next, in step S25, the liquid ejection device 100 determines the ejection cycle q2 in the rear end region 121 in accordance with the movement speed determined in step S25. Note that the ejection cycle q2 may or may not be constant, but is set so that q1≧q2.

[0101] Next, in step S26, the liquid ejection device 100 determines the drive voltage to use to control ejection by the head 11, for example, which of the first to fifth examples shown in Figures 22 to 26, depending on the amount of droplets 80 in the rear end region 121 determined in step S23.

[0102] In this way, the liquid ejection apparatus 100 can perform the process of determining the sub-droplet countermeasure content.

[0103] (Discharge Operation of Liquid Discharger 100 During Reciprocating Relative Movement) Next, with reference to Figs. 29 to 33, the ejection operation during reciprocating relative movement of the liquid ejector 100 according to the first embodiment of the present invention will be described. Fig. 29 is a diagram showing an example of reciprocating relative movement of the head 11 in the liquid ejector 100 according to the first embodiment of the present invention. Fig. 30 is a first diagram showing the ejection operation during reciprocating relative movement of the liquid ejector 100 according to the first embodiment of the present invention. Fig. 31 is a second diagram showing the ejection operation during reciprocating relative movement of the liquid ejector 100 according to the first embodiment of the present invention. Fig. 32 is a third diagram showing the ejection operation during reciprocating relative movement of the liquid ejector 100 according to the first embodiment of the present invention. Fig. 33 is a fourth diagram showing the ejection operation during reciprocating relative movement of the liquid ejector 100 according to the first embodiment of the present invention.

[0104] Each of Figures 29 to 33 shows the head 11 being moved relatively over the object 200 as viewed from above. The outgoing direction A1 is one direction in the first direction A. The returning direction A2 is the opposite direction to the outgoing direction A1 in the first direction A. In Figures 29 to 33, the outgoing direction A1 and the first direction A are written together to indicate that the outgoing direction A1 is a direction in the first direction A. Furthermore, the returning direction A2 is written together to indicate that the returning direction A2 is a direction in the first direction A.

[0105] In Figure 29, the head 11 moves relatively in the forward direction A1 to paint the area of ​​the "first line." After painting the "first line" is completed, the head 11 moves relatively in a second direction B perpendicular to the first direction A to start a new line. After the new line is completed, the head 11 moves relatively in the backward direction A2 to paint the area of ​​the "second line." After painting the "second line" is completed, the head 11 moves relatively in the second direction B to start a new line. After the new line is completed, the head 11 moves relatively in the forward direction A1 to paint the area of ​​the "third line." The liquid ejection device 100 can perform an ejection operation by moving the head 11 relatively in this way.

[0106] FIG. 30 is an enlarged view of operation (1) in FIG. 29. FIG. 31 is an enlarged view of operation (2) in FIG. 29. As shown in FIG. 31(A), the head 11 moves along the second direction B while maintaining its orientation. At this time, as shown in FIG. 31(B), in operation (2), the head 11 may, for example, mirror-invert its orientation around an axis along the second direction B as the axis of rotation. FIG. 32 is an enlarged view of operation (3) in FIG. 29. FIG. 33 is an enlarged view of operation (4) in FIG. 29. In the example shown in FIGS. 30 to 33, the head 11 has five nozzles 311, and droplets are ejected from each of the five nozzles 311.

[0107] Here, for example, if the diameter dc of the dots 912 in the rear end region 121 is made smaller than the diameter d of the dots 911 in regions other than the rear end region 121, the width of the rear end region 121 in direction B will be narrowed. This may result in areas where no droplets are applied, i.e., paint gaps, occurring between the area painted in the "first line" and the area painted in the "second line." The occurrence of paint gaps reduces the quality of painting by the liquid ejection device 100.

[0108] In the liquid ejection device 100, the movement mechanism 13 shown in FIG. 1 moves the target object 200 and the head 11 back and forth relative to each other in the forward direction A1 and the backward direction A2. As shown in FIG. 30, the diameter dc of the dots 912 in the rear end region 121 in the forward direction A1 is smaller than the diameter d of the dots 911 in the region of the ejection region 120 other than the rear end region 121. In other words, the length in the second direction of the liquid that has landed in the rear end region in the forward direction is shorter than the length in the second direction of the liquid that has landed in the region of the ejection region 120 other than the rear end region 122 in the forward direction. Also, as shown in FIG. 32, the diameter de of the dots 913 in the front end region 122 at the upstream end of the ejection region 120 in the backward direction A2 is larger than the diameter d of the dots 911 in the region of the ejection region 120 other than the front end region 122. That is, the length in the second direction of the liquid that lands in the upstream end region in the return direction of the discharge region where the liquid is discharged on the target is longer than the length in the second direction of the liquid that lands in regions other than the upstream end region of the discharge region in the return direction. Note that, for convenience, the front end region 122 at the upstream end in the return direction A2 will be referred to as the "front end region 122." As shown in FIGS. 32 and 33, the position of the rear end region 121 is aligned with the position of the front end region 122 in the first direction A.

[0109] The rear end region 121 is a region downstream of the discharge region 120 in the forward direction A1 or a region downstream of the discharge region 120 in the backward direction A2. The front end region 122 is a region upstream of the discharge region 120 in the forward direction A1 or a region upstream of the discharge region 120 in the backward direction A2. From another perspective, "the position of the rear end region 121 is aligned with the position of the front end region 122 in the first direction A" means that the rear end region 121 is included within the front end region 122 in the first direction A. Note that the position where the rear end region 121 and the front end region 122 are aligned in the first direction A is not limited to the turning position from the forward direction A1 to the backward direction A2 on the reciprocating movement path and the turning position from the backward direction A2 to the forward direction A1 on the reciprocating movement path. The position where the rear end region 121 and the front end region 122 are aligned in the first direction A may be a position other than the turning position on the reciprocating movement path.

[0110] The diameter de of the dots 913 in the front end region 122 of the discharge region 120 in the backward direction A2 is larger than the diameter d of the dots 911 in the discharge region 120 in the region other than the front end region 122. This increases the width of the front end region 122 in the second direction B. Furthermore, because the front end region 122 and the rear end region 121 are aligned in the first direction A, the front end region 122 can cover the region that was not painted in the rear end region 121. As a result, paint voids can be reduced. Reducing paint voids can prevent a decrease in the quality of painting by the liquid discharge device 100.

[0111] 32, the end dots 914 partially overlap with the dots in the rear end region 121. In the example shown in FIGS. 32 and 33, among the multiple dots 913 aligned in the second direction B in the front end region 122, the diameter de of the end dot 914 located at the end in the second direction B on the side where the rear end region 121 is located is larger than the diameter df of the dots 915 other than the end dot 914. This reduces the amount of droplets required to form the dots 915 other than the end dot 914, thereby saving the amount of droplets compared to when the diameters of all the multiple dots 913 are increased. However, in the liquid ejection device 100, the diameter de of all the multiple dots 913 aligned in the second direction B in the front end region 122 may be larger than the diameter d of the dot 911.

[0112] 33, the center-to-center distance pe between dots 913 adjacent in the first direction A in the front end region 122 is longer than the center-to-center distance p between dots 911 adjacent in the first direction in the region other than the front end region 122 in the discharge region 120. This reduces the difference in thickness of the paint film between the front end region 122 and the region other than the front end region 122, which occurs because the amount of droplets forming the dots 913 is greater than the amount of droplets forming the dots 911. As a result, it is possible to reduce variations in the thickness of the paint film.

[0113] (Discharge area 120) Next, the discharge region 120 of the liquid discharger 100 will be described with reference to Figures 34 to 36. Figure 34 is a diagram showing a first example of the discharge region 120 in the liquid discharger 100 according to the first embodiment of the present invention. Figure 35 is a diagram showing a second example of the discharge region 120 in the liquid discharger 100 according to the first embodiment of the present invention. Figure 36 is a diagram showing a third example of the discharge region 120 in the liquid discharger 100 according to the first embodiment of the present invention.

[0114] 34, the liquid discharge device 100 paints the target object 200 by discharging liquid onto the discharge area 120 by moving one head 11 back and forth relative to the target object 200. The rear end of the discharge area 120 in the direction of the reciprocating relative movement is a rear end area 121.

[0115] In each of the second example shown in Fig. 35 and the third example shown in Fig. 36, the liquid ejection device 100 paints the object 200 by moving the first head 11a back and forth relative to the object 200 and ejecting liquid onto the first region 120a. The rear end of the first region 120a in the direction of the reciprocating relative movement is the rear end region 121a. The liquid ejection device 100 paints the object 200 by moving the second head 11b back and forth relative to the object 200 and ejecting liquid onto the second region 120b. The rear end of the second region 120b in the direction of the reciprocating relative movement is the rear end region 121b.

[0116] In the second example shown in Figure 35, the first head 11a paints a first region 120a by moving back and forth relative to the first head 11. The second head 11b paints a second region 120b by moving back and forth relative to the second head 11.

[0117] In the third example shown in Figure 36, the first head 11a moves relatively in the predetermined direction A3 to paint the first region 120a. The second head 11b moves relatively in a direction A4 opposite to the predetermined direction A3 to paint the second region 120b. At least a portion of the rear end region 121a of the first region 120a in the predetermined direction A3 overlaps with the second region 120b. By overlapping at least a portion of the rear end region 121a of the first region 120a in the predetermined direction A3 with the second region 120b, it is possible to reduce contamination of the target object 200 by sub-droplets while maintaining the movement speed of the first head 11a and the amount of droplets ejected by the first head 11a at approximately constant levels.

[0118] [Second embodiment] Next, a liquid ejection device according to a second embodiment will be described. Note that the same names and symbols as those in the previously described embodiments indicate the same or similar components or configurations, and detailed descriptions will be omitted as appropriate. This also applies to the following embodiments.

[0119] A liquid ejection device according to the second embodiment will be described with reference to Fig. 37. Fig. 37 is a diagram showing an example of the configuration of a liquid ejection device 100 according to the second embodiment of the present invention. The liquid ejection device 100 differs from the first embodiment in that the head 11 is fixed and the target object 200 is moved to paint.

[0120] 37, a liquid ejection device 100 holds an object 200 with a movement mechanism 13 and moves it to the vicinity of a fixed head 11. The movement mechanism 13 then moves the object 200 relative to the liquid ejection position of the head 11 to coat it. The liquid ejection device 100 is preferably applied when the object 200 is light or small enough to be movable by the movement mechanism 13 or the like. Note that the liquid ejection method using the liquid ejection device 100 according to the second embodiment of the present invention can employ the same method as in the first embodiment.

[0121] [Third embodiment] A liquid ejection device according to the third embodiment will be described with reference to Fig. 38 and Fig. 39. Fig. 38 is a diagram showing an example of the configuration of a liquid ejection device 100 according to the third embodiment of the present invention. Fig. 39 is a cross-sectional view taken along line XXXIX-XXXIX in Fig. 38.

[0122] The liquid ejection device 100 includes a head 11, a first guide unit 800 that moves the head 11 in a first direction A of the head 11, a fixed guide unit 810 that unitizes the head 11 and the first guide unit 800, and a second guide unit 820 that moves the head 11 in a second direction B that intersects with the first direction A. The liquid ejection device 100 differs from the first embodiment in that the head 11 is provided on a member other than the movement mechanism 13.

[0123] As shown in Figures 38 and 39, the head 11 of the liquid ejection device 100 is provided on a first guide section 800 and is provided so as to be movable in a first direction A. The head 11 and the first guide section 800 are unitized by a fixed guide section 810 and are provided so as to be movable in a second direction B along a second guide section 820. This enables the head 11 to scan in two dimensions along the first guide section 800 and the second guide section 820, and to apply liquid to the target object 200. Note that the liquid ejection method using the liquid ejection device 100 according to the third embodiment of the present invention can employ the same method as in the first embodiment.

[0124] Although the embodiments have been described above, the present invention is not limited to the above-described embodiments, and various modifications and improvements are possible within the scope of the present invention.

[0125] In the embodiment, the liquid ejected from the head 11 may be a solution, suspension, emulsion, or the like containing a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a functionalizing material such as a polymerizable compound, a resin, or a surfactant, a biocompatible material such as DNA, amino acids, proteins, or calcium, an edible material such as a natural colorant, etc. These can be used, for example, in inkjet inks, coating materials, surface treatment solutions, liquids for forming components of electronic elements or light-emitting elements, liquids for forming electronic circuit resist patterns, and material liquids for 3D modeling.

[0126] Each function of the embodiments can be realized by one or more processing circuits. Here, the term "processing circuit" in this specification includes a processor programmed to perform each function by software, such as a processor implemented by an electronic circuit, as well as devices such as an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), and conventional circuit modules designed to perform each function described above.

[0127] The present invention is also applicable to painting processes performed for purposes other than applying color and design to vehicle bodies such as automobiles. For example, the painting process for an automobile body includes a primer coat, which aims to ensure adhesion and rust resistance of the paint film to the vehicle body substrate; a middle coat, which aims to ensure impact resistance and durability; and a top coat, which applies color and design. The painting apparatus of the present invention may be used for the primer coat or middle coat in addition to the top coat. Furthermore, if a protective layer, such as a clear coat, is applied after the top coat process for the purposes of gloss and paint film protection, the painting apparatus of the present invention may be used in the protective layer application process. Furthermore, if a peelable protective layer is applied to protect the painted surface after the automobile is shipped or in the factory, the painting apparatus of the present invention can also be used to apply the protective layer. The peelable protective layer may be any material that adheres to the painted surface of the vehicle body and chemically or physically protects the painted area from dust, metal powder, oil, salt, acid, ultraviolet light, etc., and is preferably formed from a material primarily composed of an acrylic copolymer, for example.

[0128] The present invention is also applicable to droplet ejection devices that eject droplets for purposes other than painting, such as marking devices that eject droplets onto an object to mark a specific location.

[0129] For example, aspects of the present invention are as follows. <1> A liquid ejection device having a head that ejects liquid onto a target object and a movement mechanism that moves the target object and the head relative to each other, wherein the head ejects the liquid to cause the liquid to land on the target object, wherein when a direction in which the head moves relative to the target object by the movement mechanism is defined as a first direction and a direction perpendicular to the first direction is defined as a second direction, and when an end region downstream of the first direction of an ejection region from which the liquid is ejected on the target is defined as a rear end region, the length in the second direction of the liquid that has landed in the rear end region is shorter than the length in the second direction of the liquid that has landed in regions of the ejection region other than the rear end region. <2> the relative movement speed of the head in the rear end region is slower than the relative movement speed of the head in the ejection region other than the rear end region; <1> 2. The liquid ejection apparatus according to claim 1, wherein the liquid ejection apparatus is a liquid ejection apparatus. <3> When the first direction is defined as an outgoing direction and a direction opposite to the outgoing direction is defined as a returning direction, the movement mechanism moves the target and the head back and forth relative to each other in the outgoing direction and the returning direction, and the length in the second direction of the liquid that has landed in the rear end region in the outgoing direction is shorter than the length in the second direction of the liquid that has landed in a region of the ejection region in the outgoing direction other than the rear end region, the length in the second direction of the upstream end region in the returning direction of the ejection region from which the liquid is ejected on the target is longer than the length in the second direction of a region of the ejection region in the returning direction other than the upstream end region, and the position of the rear end region in the outgoing direction is aligned in the first direction with the position of the upstream end region in the returning direction. <1> or the above <2> 2. The liquid ejection apparatus according to claim 1, wherein the liquid ejection apparatus is a liquid ejection apparatus. <4> the head ejects the liquid to cause the liquid to land on the target, thereby forming dots; <1> From the above <3> The liquid ejection device according to any one of the above items. <5> a center-to-center distance between the dots adjacent to each other in the first direction in the rear end region is shorter than a center-to-center distance between the dots adjacent to each other in the first direction in a region other than the rear end region in the ejection region; <4> 2. The liquid ejection apparatus according to claim 1, wherein the liquid ejection apparatus is a liquid ejection apparatus. <6> In the upstream end region, among the plurality of dots aligned in the second direction, the diameter of an end dot located at an end on the side where the rear end region is located in the second direction is larger than the diameter of the dots other than the end dot. <4> or the above <5> 2. The liquid ejection apparatus according to claim 1, wherein the liquid ejection apparatus is a liquid ejection apparatus. <7> a center-to-center distance between the dots adjacent to each other in the first direction in the upstream end region is longer than a center-to-center distance between the dots adjacent to each other in the first direction in a region other than the upstream end region of the ejection region; <4> From the above <6> The liquid ejection device according to any one of the above items. <8> a plurality of heads including a first head and a second head, wherein the first head moves in a predetermined direction in the first direction to form a first region on the object, and the second head moves in a direction opposite to the predetermined direction in the first direction to form a second region on the object, and at least a part of a rear end region of the first region in the predetermined direction overlaps with the second region; <1> From the above <7> The liquid ejection device according to any one of the above items. <9> A liquid ejection method using a liquid ejection device, wherein the liquid ejection device ejects liquid onto a target object using a head, and moves the target object and the head relatively in a first direction using a movement mechanism, and the head ejects the liquid to cause the liquid to land on the target object, and when the direction in which the head moves relatively to the target object using the movement mechanism is defined as the first direction and a direction perpendicular to the first direction is defined as a second direction, and when the end region downstream in the first direction of the ejection region from which the liquid is ejected on the target is defined as a rear end region, the length in the second direction of the liquid that has landed in the rear end region is shorter than the length in the second direction of the liquid that has landed in regions of the ejection region other than the rear end region. [Explanation of symbols]

[0130] 11 heads 11-1, 11-2, 11-3, 11-4 Head 11a First Head 11b 2nd head 12, 12-1, 12-2, 12-3, 12-4 Detector 13, 13-1, 13-2, 13-3, 13-4 Movement mechanism 14 Supply section 20 Control Unit 72 Drive unit 80 droplets 81a, 81b main drop 82a, 82b Ligament 83a, 83b sub-droplet 91, 91a, 91b dots 92, 92a, 92b Satellite Dots 911, 912, 913, 915 dots 914 End Dot 120 Discharge area 120a 1st area 120b 2nd area 121 Posterior area 122 Anterior end area 180 Paint film 800 First guide section 810 Fixed guide part 820 Second guide part 901 Controller 9001 CPU 9002 ROM 9003 RAM 9004 Interface 9011 System Control Unit 9012 Data storage unit 9013 Memory control unit 9014 Discharge cycle signal generation section 9015 Cycle control section 902 Head control device 903 PC 9031 Painting route generation unit 9032 Painting data generation unit 9033 Discharge frequency generator 9034 Movement speed generator 9035 RIP section 9036 Rendering Department 904 Mobile mechanism control device 905 Input Device 100 Liquid dispensing device 103 Head Unit 109 Encoder Sensor 110 Case 111 Supply Port 112 Collection Port 113 Connector 200 objects 201 Roof 211, 211-1, 211-2, 211-3, 211-4 Paint range 230 Compressor 310 Valve body 311 Nozzle 321 Nozzle plate 322 Channel 324 Piezoelectric element 325 liquid 330 Liquid Tank 331 Pipe 332 Air regulator 333 Tube 340 Dispensing Module A 1st direction A1 Outbound A2 Return direction A3 Specified direction A4 opposite direction B Second direction C Discharge direction d, dc, de, df diameter p, pc, pe center distance L1, L2 length q1, q2 period t1, t2 thickness T1 First period T2 Second period T10, T1-1, T1-2, T1-3, T1-4 Relative movement path information Δ1, Δ2 open period V1, V2 drive voltage [Prior art documents] [Patent documents]

[0131] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-024599

Claims

1. a head that ejects liquid onto an object; a movement mechanism that moves the object and the head relative to each other, the head ejects the liquid to cause the liquid to land on the target; a direction in which the head is moved relative to the object by the moving mechanism is defined as a first direction; When a direction perpendicular to the first direction is defined as a second direction, When a region at an end portion on the downstream side in the first direction of the ejection region from which the liquid is ejected on the target is defined as a rear end region, a length in the second direction of the liquid that has landed in the rear end region being shorter than a length in the second direction of the liquid that has landed in an area of ​​the ejection region other than the rear end region;

2. The liquid ejection device according to claim 1 , wherein the relative movement speed of the head in the rear end region is slower than the relative movement speed of the head in a region other than the rear end region in the ejection region.

3. The first direction is a forward direction, When the direction opposite to the forward direction is defined as the backward direction, the moving mechanism moves the object and the head relative to each other in a reciprocating manner in the forward direction and the backward direction; a length in the second direction of the liquid that has landed in the rear end region in the forward direction is shorter than a length in the second direction of the liquid that has landed in a region of the ejection region in the forward direction other than the rear end region, a length in the second direction of an upstream end region in the return direction of the ejection region from which the liquid is ejected on the target is longer than a length in the second direction of an area other than the upstream end region of the ejection region in the return direction; The liquid ejection device according to claim 1 , wherein the position of the rear end region in the forward direction is aligned in the first direction with the position of the upstream end region in the backward direction.

4. The liquid ejection device according to claim 1 , wherein the head ejects the liquid to cause the liquid to land on the target, thereby forming dots.

5. The liquid ejection device according to claim 4 , wherein the center-to-center distance between adjacent dots in the first direction in the rear end region is shorter than the center-to-center distance between adjacent dots in the first direction in a region of the ejection region other than the rear end region.

6. A liquid ejection device as described in claim 4, wherein, in the upstream end region, of the multiple dots arranged in the second direction, the diameter of the end dot located at the end on the side where the rear end region in the second direction is located is larger than the diameter of the dots other than the end dot.

7. 5. A liquid ejection device as described in claim 4, wherein the center-to-center distance between adjacent dots in the first direction in the upstream end region is longer than the center-to-center distance between adjacent dots in the first direction in regions other than the upstream end region of the ejection region.

8. a plurality of heads including a first head and a second head; the first head moves in a predetermined direction in the first direction to form a first area on the object; the second head moves in a direction opposite to the predetermined direction in the first direction to form a second area on the object; The liquid ejection device according to claim 1 , wherein at least a portion of a rear end region of the first region in the predetermined direction overlaps with the second region.

9. A liquid ejection method using a liquid ejection device, The liquid ejection device The head ejects liquid onto the target object. a moving mechanism that moves the object and the head relative to each other in a first direction; the head ejects the liquid to cause the liquid to land on the target; a direction in which the head is moved relative to the object by the moving mechanism is defined as a first direction; When a direction perpendicular to the first direction is defined as a second direction, When a region at an end portion on the downstream side in the first direction of the ejection region from which the liquid is ejected on the target is defined as a rear end region, A liquid ejection method, wherein the length in the second direction of the liquid that has landed in the rear end region is shorter than the length in the second direction of the liquid that has landed in a region of the ejection region other than the rear end region.

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