Printing device

Abstract

The present disclosure provides a printing device that improves printing quality in a printing device using a robot. The printing device has a head including a first nozzle row in which a plurality of nozzles that eject a first ink are arranged, and a second nozzle row in which a plurality of nozzles that eject a second ink are arranged, and a robot having an arm portion having a tip end at which the head is supported, a base end, and a plurality of joints, and a base portion connected to the base end, the robot changing a position and a posture of the head with respect to a work, the second ink having a lower brightness than the first ink, and a distance between the second nozzle row and the base end being shorter than a distance between the first nozzle row and the base end.

Description

Technical Field

[0001] This disclosure relates to a printing apparatus. Background Technology

[0002] A printing apparatus using an inkjet method employing a robot such as a multi-jointed robot is known. For example, the apparatus described in Patent Document 1 includes a head that serves as an inkjet head and a robot that holds the head.

[0003] When printing with multiple colors of ink, generally, the printing head is equipped with multiple nozzle rows for each color of ink. Patent Document 1 does not describe the configuration of these multiple nozzle rows when printing with multiple colors of ink. In printing apparatuses that use a robot to move the printing head, when printing with multiple colors of ink, it is desirable to achieve an appropriate configuration of the multiple nozzle rows to obtain good print quality.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2016-215438 Summary of the Invention

[0005] To address the above-mentioned issues, one aspect of the printing apparatus disclosed herein includes: a head comprising a first nozzle array with a plurality of nozzles for ejecting a first ink and a second nozzle array with a plurality of nozzles for ejecting a second ink; a robot having an arm and a base, the arm having a tip, a base end, and a plurality of joints, the base being connected to the base end, the head being supported on the tip, the robot causing the head to change position and orientation relative to a workpiece, the brightness of the second ink being lower than the brightness of the first ink, and the distance between the second nozzle array and the base end being smaller than the distance between the first nozzle array and the base end.

[0006] Another aspect of the printing apparatus disclosed herein includes: a head comprising a first nozzle array of a plurality of nozzles for ejecting a first ink and a second nozzle array of a plurality of nozzles for ejecting a second ink; a robot having an arm and a base, the arm having a tip, a base end, and a plurality of joints, the base being connected to the base end and the head being supported on the tip, the robot causing the head to change position and orientation relative to a workpiece, the second ink having a lower brightness than the first ink, wherein a first timing is set for ejecting the first ink from the first nozzle array to a predetermined position on the workpiece, a second timing is set for ejecting the second ink from the second nozzle array to the predetermined position, and the plurality of joints includes at least one joint whose distance from the predetermined position changes during each of the first and second timings, and the joint farthest from the tip of the at least one joint is designated as the first joint, the distance between the second nozzle array and the first joint during the second timing is less than the distance between the first nozzle array and the first joint during the first timing. Attached Figure Description

[0007] Figure 1 A perspective view showing the outline of the printing apparatus according to the first embodiment.

[0008] Figure 2 This is a block diagram illustrating the electrical structure of the printing apparatus according to the first embodiment.

[0009] Figure 3 This is a perspective view showing the outline structure of the head unit used in the first embodiment.

[0010] Figure 4 This diagram is used to explain the printing operation of the printing apparatus according to the first embodiment.

[0011] Figure 5 A diagram representing the state of the robot at the first timing point.

[0012] Figure 6 This diagram illustrates the distance between the tip and base of the robot's arm during the first timing.

[0013] Figure 7 A diagram representing the state of the robot at the second timing.

[0014] Figure 8 This diagram illustrates the distance between the tip and base of the robot's arm during the second timing.

[0015] Figure 9 This is a diagram used to illustrate the printing operation in the second embodiment.

[0016] Figure 10 This is a block diagram illustrating the electrical structure of the printing apparatus according to the third embodiment.

[0017] Figure 11 This is a perspective view showing the outline structure of the head unit used in the third embodiment.

[0018] Figure 12 This diagram is used to explain the printing operation of the printing apparatus according to the third embodiment.

[0019] Figure 13 This is a perspective view showing the outline structure of the head unit used in the fourth embodiment.

[0020] Figure 14 This is a diagram used to illustrate the movement path of the head in the fourth embodiment. Detailed Implementation

[0021] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. It should be noted that the dimensions and scales of the parts in the drawings may differ appropriately from actual dimensions, and some parts may be shown schematically for ease of understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description.

[0022] For simplicity, the following description uses intersecting X-axis, Y-axis, and Z-axis as appropriate. Furthermore, in the following description, one direction along the X-axis is the X1 direction, and the opposite direction is the X2 direction. Similarly, opposite directions along the Y-axis are the Y1 and Y2 directions. Additionally, opposite directions along the Z-axis are the Z1 and Z2 directions.

[0023] Here, the X, Y, and Z axes correspond to the coordinate axes of a world coordinate system set in the space containing the robot 2 (described later). Typically, the Z-axis is a vertical axis, and the Z2 direction corresponds to the downward direction in the vertical direction. Within this world coordinate system, a base coordinate system is established based on the position of the base 210 of the robot 2 (described later) through calibration. For convenience, the following example illustrates the use of the world coordinate system as the robot coordinate system to control the movements of the robot 2.

[0024] Additionally, the Z-axis does not have to be vertical. Furthermore, while the X, Y, and Z axes are typically orthogonal, this is not a limitation, and there are cases where they are not orthogonal. For example, the X, Y, and Z axes can intersect each other at an angle between 80° and 100°.

[0025] 1. First Implementation Method

[0026] 1-1. Overview of Printing Equipment

[0027] Figure 1 The diagram shows a perspective view of the printing apparatus 1 according to the first embodiment. The printing apparatus 1 is an apparatus that performs printing on the surface of a workpiece W by inkjet printing.

[0028] The workpiece W has a surface WF that becomes the object of printing. Figure 1 In the example shown, the workpiece W is a cuboid, and surface WF is a plane. During printing, the workpiece W is supported as needed, for example by a predetermined mounting platform, robotic arm, or conveyor belt. Furthermore, the shape or size of the workpiece W or surface WF is not limited to... Figure 1 The examples shown are arbitrary. For instance, the surface WF can have curved or buckled portions, and the workpiece W can be a thin sheet material such as paper or cloth. Furthermore, the position or orientation of the workpiece W or the surface WF during printing is not limited to any particular type, as long as printing is feasible. Figure 1 The example shown is arbitrary.

[0029] like Figure 1 As shown, the printing apparatus 1 includes: a robot 2, a head unit 3, a controller 5, a piping unit 10, and a wiring unit 11. These components will now be briefly described in turn.

[0030] Robot 2 is the robot that changes the position and orientation of head unit 3 in the world coordinate system. Figure 1 In the example shown, robot 2 is a so-called six-axis vertical jointed robot.

[0031] like Figure 1 As shown, robot 2 has a base 210 and an arm 220.

[0032] The base 210 is a pedestal that supports the arm 220. Figure 1 In the example shown, the base 210 is fixed to a mounting surface such as a floor surface or a base facing the Z1 direction by means of threaded fastening or the like. However, the mounting surface to which the base 210 is fixed can be a surface facing any direction and is not limited to any particular direction. Figure 1 The examples shown could also be surfaces such as walls, ceilings, or movable trolleys.

[0033] Arm 220 is a six-axis robotic arm having a base end EB mounted on a base 210 and a tip ET that allows for three-dimensional changes in position and orientation relative to the base end EB. Specifically, arm 220 has arms 221, 222, 223, 224, 225, and 226, also referred to as links. These arms are connected together in the order of arms 221, 222, 223, 224, 225, and 226.

[0034] Arm 221 is connected to base 210 via joint 230_1, allowing it to rotate about rotation axis O1. Arm 222 is connected to arm 221 via joint 230_2, allowing it to rotate about rotation axis O2. Arm 223 is connected to arm 222 via joint 230_3, allowing it to rotate about rotation axis O3. Arm 224 is connected to arm 223 via joint 230_4, allowing it to rotate about rotation axis O4. Arm 225 is connected to arm 224 via joint 230_5, allowing it to rotate about rotation axis O5. Arm 226 is connected to arm 225 via joint 230_6, allowing it to rotate about rotation axis O6.

[0035] Joints 230_1 to 230_6 are mechanisms that rotatably connect one of two adjacent components of the base 210 and arms 221 to 226 relative to the other. In the following text, joints 230_1 to 230_6 will sometimes be referred to as "joint 230". Here, the base end EB is one end of the arm 220 whose position in the basic coordinate system does not change even when joint 230 rotates, and the tip ET is the other end of the arm 220 whose position in the basic coordinate system changes due to rotation of joint 230_6. The base end EB can be defined, for example, as the intersection of the boundary between the base 210 and arm 221 and the rotation axis O1. Furthermore, the tip ET can be defined, for example, as the intersection of the end face of arm 226 furthest from arm 225 or the surface extending from that end face and the rotation axis O6.

[0036] Although Figure 1 Although not illustrated, joints 230_1 to 230_6 are each equipped with a drive mechanism that rotates one of the corresponding two components relative to the other. This drive mechanism may include, for example, a motor that generates the driving force for the rotation, a speed reducer that reduces and outputs the driving force, and a rotary encoder that detects the amount of motion, such as the angle of rotation. Furthermore, the assembly of these drive mechanisms for joints 230_1 to 230_6 corresponds to the [described later]... Figure 2 The arm drive mechanism 2a shown is illustrated.

[0037] Rotation axis O1 is a perpendicular axis to a mounting surface (not shown) on which the base 210 is fixed. Rotation axis O2 is a perpendicular axis to rotation axis O1. Rotation axis O3 is a parallel axis to rotation axis O2. Rotation axis O4 is a perpendicular axis to rotation axis O3. Rotation axis O5 is a perpendicular axis to rotation axis O4. Rotation axis O6 is a perpendicular axis to rotation axis O5.

[0038] Furthermore, regarding these rotating axes, the term "perpendicular" includes not only the case where the angle between the two rotating axes is strictly 90°, but also the case where the angle between the two rotating axes deviates from 90° within a range of approximately ±5°. Similarly, the term "parallel" includes not only the case where the two rotating axes are strictly parallel, but also the case where one of the two rotating axes is tilted relative to the other within a range of approximately ±5°.

[0039] On the top end ET of the arm 220 of the robot 2 described above, a head unit 3 is installed as an end effector in a fixed state by means of thread fixing or the like.

[0040] Head unit 3 is an assembly having a head 3a that ejects multiple inks of different brightness toward the workpiece W. In this embodiment, in addition to the head 3a, head unit 3 also includes a pressure regulating valve 3b, an energy emission section 3c, and an optical sensor 3g. Further details regarding head unit 3 will be provided later. Figure 3 Let me explain.

[0041] In this embodiment, a case is illustrated using four inks: a first ink, a second ink, a third ink, and a fourth ink, each with different brightness levels. The brightness of these inks, from highest to lowest, is listed as the first ink, the third ink, the fourth ink, and the second ink. In full-color printing, typically, these four inks are yellow ink, magenta ink, cyan ink, and black ink. In this case, the first ink is yellow ink, the second ink is black ink, and one of the third and fourth inks is magenta ink, while the other is cyan ink. Here, the brightness can, for example, conform to CIE L as specified by the International Commission on Illumination (CIE). * a * b * The color space is defined by its luminance. In this embodiment, CIE L... * a * b *The brightness values ​​for the color space are 83 for yellow ink, 54 for magenta ink, 56 for cyan ink, and 11 for black ink. Furthermore, the brightness values ​​of inks can be obtained, for example, by applying the ink to a medium such as printing paper to create a predetermined color mark, and then measuring the color mark using a colorimeter. Here, the comparison of the brightness values ​​of multiple inks can be performed by creating color marks for each of the multiple inks on the same medium using the same amount of ink, and then comparing the values ​​obtained by measuring the color marks of the multiple inks.

[0042] Such inks are, for example, liquid media in which color materials such as dyes or pigments are dissolved or dispersed in a solvent. While each ink can be any of the following: water-based inks that dissolve color materials such as dyes or pigments in aqueous solvents, curable inks using curable resins such as UV-curable inks, and solvent-based inks that dissolve color materials such as dyes or pigments in organic solvents, curable inks are preferred. Although curable inks are not particularly limited, and can be, for example, any of the following: thermosetting, photocurable, radiation-curable, and electron beam-curable inks, photocurable inks such as UV-curable inks are preferred. Furthermore, inks containing color materials are not limited to yellow inks, magenta inks, blue-green inks, and black inks; for example, white inks, gray inks, light blue-green inks, and light magenta inks can also be used.

[0043] The head unit 3 is connected to a piping section 10 and a wiring section 11. The piping section 10 is a piping assembly that supplies ink from an ink tank (not shown) to the head unit 3. The wiring section 11 is a wiring or wiring assembly that supplies electrical signals for driving the head 3a.

[0044] Controller 5 is a robot controller that controls the drive of robot 2. The following is based on... Figure 2 The electrical structure of the printing apparatus 1 will be described in a manner that includes a detailed description of the controller 5.

[0045] 1-2. Electrical Structure of the Printing Equipment

[0046] Figure 2 Here is a block diagram illustrating the electrical structure of the printing apparatus 1 according to the first embodiment. Figure 2 The diagram shows the electrical structural elements within the structural elements of the printing apparatus 1. For example... Figure 2 As shown, in the printing apparatus 1, in addition to having the aforementioned Figure 1 In addition to the structural elements shown, it also includes a control module 6 that is communicatively connected to the controller 5, and a computer 7 that is communicatively connected to both the controller 5 and the control module 6.

[0047] in addition, Figure 2 The various electrical structural elements shown can be appropriately divided, partially included in other structural elements, or integrally formed with other structural elements. For example, part or all of the function of controller 5 or control module 6 can be implemented by computer 7, or by other external devices such as PC (personal computer) connected to controller 5 via a network such as LAN (Local Area Network) or the Internet.

[0048] The controller 5 has the function of controlling the drive of the robot 2 and generating a signal D3 to synchronize the ink ejection action in the head unit 3 with the action of the robot 2.

[0049] The controller 5 has a storage circuit 5a and a processing circuit 5b.

[0050] The storage circuit 5a stores various programs executed by the processing circuit 5b and various data processed by the processing circuit 5b. The storage circuit 5a may include, for example, a semiconductor memory comprising one or both of the following: volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or PROM (Programmable Read-Only Memory). Alternatively, part or all of the storage circuit 5a may be included in the processing circuit 5b.

[0051] The storage circuit 5a stores path information Da. Path information Da represents the path that the head unit 3 should move along and the orientation of the head unit 3 along that path. Path information Da is generated, for example, using information obtained through direct instruction or online instruction, and CAD (computer-aided design) data representing the shape of the workpiece W. Path information Da is represented, for example, using coordinate values ​​from a base coordinate system or a world coordinate system. The path information Da can be input from the computer 7 into the storage circuit 5a.

[0052] The processing circuit 5b controls the movement of the arm drive mechanism 2a of the robot 2 based on the path information Da, and generates a signal D3. The processing circuit 5b may include, for example, one or more processors such as CPUs (Central Processing Units). Alternatively, the processing circuit 5b may replace the CPU or include programmable logic devices such as FPGAs (Field-Programmable Gate Arrays) in addition to the CPU.

[0053] Here, the arm drive mechanism 2a is an assembly of the drive mechanisms of the aforementioned joints 230_1 to 230_6, and for each joint 230, it has a motor for driving the joint 230 and an encoder for detecting the rotation angle of the joint 230.

[0054] The processing circuit 5b performs inverse kinematics calculations, converting the path information Da into motion quantities such as rotation angles and rotational speeds of each joint 230 of the robot 2. Then, the processing circuit 5b outputs control signals Sk1 based on the outputs D1 of each encoder from the arm drive mechanism 2a, in a manner that makes the actual rotation angles and rotational speeds of each joint 230 the motion quantities based on the aforementioned calculation results of the path information Da. The control signals Sk1 are signals used to control the drive of the motors of the arm drive mechanism 2a. Here, the control signals Sk1 are corrected by the processing circuit 5b as needed, based on the outputs from optical sensors 3g, etc.

[0055] Furthermore, the processing circuit 5b generates a signal D3 based on the output D1 from at least one of the plurality of encoders from the arm drive mechanism 2a. For example, the processing circuit 5b generates a trigger signal, including a timing pulse from the output D1 of one of the plurality of encoders, which is set to a predetermined value, as signal D3.

[0056] The control module 6 is a circuit that controls the ink ejection action in the head unit 3 based on the signal D3 output from the controller 5 and the printing data Img from the computer 7. The control module 6 includes a timing signal generation circuit 6a, a power supply circuit 6b, a control circuit 6c, and a drive signal generation circuit 6d.

[0057] The timing signal generation circuit 6a generates a timing signal PTS based on signal D3. The timing signal generation circuit 6a is, for example, composed of a timer that begins generating the timing signal PTS upon detection of signal D3. The timing signal PTS, for example, includes pulses defined based on output D1.

[0058] The power supply circuit 6b receives power from a commercial power supply not shown in the diagram and generates various predetermined potentials. These potentials are appropriately supplied to the control module 6 and various parts of the head unit 3. For example, the power supply circuit 6b generates a power supply potential VHV and a bias potential VBS. The bias potential VBS is supplied to the head unit 3. Furthermore, the power supply potential VHV is supplied to the drive signal generation circuit 6d.

[0059] The control circuit 6c generates the printing data signal SI, the waveform specification signal dCom, the latch signal LAT, the clock signal CLK, and the conversion signal CNG based on the timing signal PTS. These signals are synchronized with the timing signal PTS. The waveform specification signal dCom is input to the drive signal generation circuit 6d, while the other signals are input to the switching circuit 3e of the head unit 3.

[0060] The printing data signal SI is a digital signal used to specify the operating state of the drive element of the head 3a of the head unit 3. Specifically, the printing data signal SI specifies whether to supply the drive signal Com (described later) to the drive element based on printing data. This specification specifies, for example, whether ink is ejected from the nozzle corresponding to the drive element, or the amount of ink ejected from the nozzle. The waveform specification signal dCom is a digital signal used to specify the waveform of the drive signal Com. The latch signal LAT and the conversion signal CNG are used in conjunction with the printing data signal SI and specify the timing of ink ejection from the nozzle by specifying the driving timing of the drive element. The clock signal CLK is a clock signal that is synchronized with the timing signal PTS and serves as a reference.

[0061] The control circuit 6c described above includes, for example, one or more processors such as CPUs. Alternatively, the control circuit 6c may replace a CPU or include programmable logic devices such as FPGAs in addition to a CPU.

[0062] The drive signal generation circuit 6d is a circuit that generates drive signals Com for driving the various drive elements of the head 3a of the head unit 3. Specifically, the drive signal generation circuit 6d includes, for example, a DA conversion circuit and an amplification circuit. In the drive signal generation circuit 6d, the DA conversion circuit converts the waveform specification signal dCom from the control circuit 6c from a digital signal to an analog signal, and the amplification circuit amplifies the analog signal using the power supply potential VHV from the power supply circuit 6b, thereby generating the drive signal Com. Here, the signal of the waveform actually supplied to the drive element in the waveform contained in the drive signal Com is the drive pulse PD. The drive pulse PD is supplied to the drive element from the drive signal generation circuit 6d via the switching circuit 3e of the head unit 3.

[0063] Here, the switching circuit 3e is a circuit that includes a switching element that switches whether to supply at least a portion of the waveform contained in the drive signal Com as a drive pulse PD based on the printed data signal SI.

[0064] The computer 7 has the function of supplying path information Da and other information to the controller 5, and the function of supplying printing data Img and other information to the control module 6. In addition to these functions, the computer 7 in this embodiment also has the function of controlling the drive of the energy emission unit 3c. The computer 7 is, for example, a desktop or laptop computer with programs that implement these functions installed.

[0065] 1-3. Structure of the head unit

[0066] Figure 3 Here is a perspective view showing the outline structure of the head unit 3 used in the first embodiment. For convenience, the following description will appropriately use the intersecting a-axis, b-axis, and c-axis. Furthermore, in the following description, one direction along the a-axis is the a1 direction, and the direction opposite to the a1 direction is the a2 direction. Similarly, the opposite directions along the b-axis are the b1 direction and the b2 direction. Furthermore, the opposite directions along the c-axis are the c1 direction and the c2 direction.

[0067] Here, the a-axis, b-axis, and c-axis correspond to the coordinate axes of the tool coordinate system set in the head unit 3. The robot 2's movements change its relative position and orientation with respect to the world coordinate system or robot coordinate system. Figure 3 In the example shown, the c-axis is parallel to the aforementioned rotation axis O6. Furthermore, while the a-axis, b-axis, and c-axis are typically orthogonal, this is not a limitation; they can intersect at angles between 80° and 100°. Additionally, the tool coordinate system and the base coordinate system or robot coordinate system are established through calibration. Moreover, the tool coordinate system is set, for example, with the center of the ejection surface FN (described later) as the reference (TCP: tool center point).

[0068] As described above, head unit 3 includes a head 3a, a pressure regulating valve 3b, an energy emission section 3c, and an optical sensor 3g. These components are all... Figure 3 The support is shown as 3f with double-dotted lines. Additionally, although in Figure 3 In the example shown, the head unit 3 has one head 3a and one pressure regulating valve 3b, but this number is not limited to one. Figure 3The example shown can also include more than two. Furthermore, the position of the pressure regulating valve 3b is not limited to the head unit 3; for example, it can be the arm 226, or it can be a position fixed relative to the base 210.

[0069] The support 3f is made of, for example, a metallic material and is a solid rigid body. Figure 3 In the example shown, the support 3f is a flat plate extending in a direction orthogonal to axis a. In this embodiment, a head 3a is mounted on the surface of the support 3f facing direction a1. On the other hand, an energy emission section 3c is mounted on the surface of the support 3f facing direction a2. Here, the optical sensor 3g is mounted on the support 3f via a component not shown. Furthermore, the shape of the support 3f is not limited to... Figure 3 The example shown is arbitrary; for example, it could also be box-shaped, etc.

[0070] The aforementioned support body 3f is mounted on the arm 226. Therefore, the head 3a, pressure regulating valve 3b, energy emission part 3c, and optical sensor 3g are supported on the arm 226 in a unified manner by the support body 3f. Thus, the relative positions of the head 3a, pressure regulating valve 3b, energy emission part 3c, and optical sensor 3g with respect to the arm 226 are fixed. Figure 3 In the example shown, a pressure regulating valve 3b is positioned in the c1 direction relative to the head 3a. An optical sensor 3g is positioned in the a1 direction relative to the head 3a. An energy emission section 3c is positioned in the a2 direction relative to the head 3a.

[0071] The head 3a has an ejection surface FN and a plurality of nozzles N that are open on the ejection surface FN. The ejection surface FN is a nozzle surface with the nozzles N open, for example, it is formed by the surface of a nozzle plate on a plate-shaped member made of a material such as silicon (Si) or metal, in which the nozzles N are provided as through holes.

[0072] exist Figure 3 In the example shown, the normal direction of the ejection surface FN is the c2 direction, and the plurality of nozzles N are divided into a first nozzle column L1, a second nozzle column L2, a third nozzle column L3, and a fourth nozzle column L4. These nozzle columns face the a2 direction and are arranged side by side with intervals between each other in the order of the first nozzle column L1, the third nozzle column L3, the fourth nozzle column L4, and the second nozzle column L2.

[0073] The first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 are each a collection of a plurality of nozzles N arranged in a straight line along the b-axis. In this embodiment, the nozzle density of each nozzle N in each nozzle array along the b-axis is 300 npi (number of nozzles per inch). However, the invention is not limited to this; a lower nozzle density is possible, but from the viewpoint of print quality or efficiency, a nozzle density of 25 npi or higher is preferred. Furthermore, to achieve such a nozzle density, the nozzles N can be staggered in each nozzle array. Here, the first nozzle array L1, the second nozzle array L2, the third nozzle array L3, and the fourth nozzle array L4 eject different types of ink. Specifically, the first nozzle array L1 ejects a first ink. The second nozzle array L2 ejects a second ink. The third nozzle array L3 ejects a third ink. The fourth nozzle array L4 ejects a fourth ink. Since any ink is ejected in the c2 direction under ideal conditions, the c2 direction can also be expressed as the ejection direction.

[0074] Although not illustrated, the head 3a has a piezoelectric element as a driving element and a cavity for collecting ink for each nozzle N. Here, the piezoelectric element causes a change in pressure within the cavity corresponding to the piezoelectric element, thereby ejecting ink from the nozzle corresponding to that cavity. Such a head 3a is obtained, for example, by using an adhesive or the like to bond together multiple substrates, such as silicon substrates, that have been appropriately processed by etching. Alternatively, a heater that heats the ink within the cavity can be used instead of the piezoelectric element as the driving element for ejecting ink from the nozzles. With this structure, the presence or absence of ink ejection, or the amount of ink ejected, can be independently controlled for each nozzle N via the aforementioned control module 6, thus forming an image generated by the ink.

[0075] In the above-described head 3a, ink is supplied from the ink tank via the first supply pipe 10a1, the second supply pipe 10a2, the third supply pipe 10a3, and the fourth supply pipe 10a4. Here, a pressure regulating valve 3b is located between each of the first, second, third, and fourth supply pipes 10a1 and the head 3a. The first supply pipe 10a1 is used to supply the first ink to the head 3a. The second supply pipe 10a2 is used to supply the second ink to the head 3a. The third supply pipe 10a3 is used to supply the third ink to the head 3a. The fourth supply pipe 10a4 is used to supply the fourth ink to the head 3a.

[0076] The pressure regulating valve 3b is a valve mechanism that opens and closes according to the pressure of the ink in the head 3a. Through this opening and closing, even if the positional relationship between the head 3a and the aforementioned ink reservoir (not shown) changes, the pressure of the ink in the head 3a is maintained at a negative pressure within a predetermined range. Therefore, the meniscus of the ink formed in the nozzle N of the head 3a is stabilized. As a result, air bubbles entering the nozzle N or ink overflowing from the nozzle N is prevented. Furthermore, the ink from the pressure regulating valve 3b is appropriately distributed to multiple locations in the head 3a via a branched flow path (not shown). Here, the ink from the ink reservoir (not shown) is transferred at a predetermined pressure to the first supply pipe 10a1, the second supply pipe 10a2, the third supply pipe 10a3, and the fourth supply pipe 10a4 using a pump or head difference, etc. Additionally, although not shown, the pressure regulating valve 3b has an ink flow path and a pressure regulating structure for each type of ink, so that the pressure of each of the four inks can be individually adjusted.

[0077] The energy emitting unit 3c emits energy such as light, heat, electron beams, or radiation to harden or cure the ink on the workpiece W. For example, if the ink has ultraviolet curability, the energy emitting unit 3c is composed of a light-emitting element such as an LED (light emitting diode) that emits ultraviolet light. In addition, the energy emitting unit 3c may also appropriately include optical components such as lenses for adjusting the direction or range of energy emission.

[0078] Here, the energy emitting section 3c includes an emission surface FL that emits the energy, and is arranged such that the emission surface FL faces the c2 direction. Furthermore, as described above, since the energy emitting section 3c is arranged in the a2 direction relative to the head 3a, the distance DL2 between the second nozzle array L2 and the emission surface FL is smaller than the distance DL1 between the first nozzle array L1 and the emission surface FL.

[0079] Alternatively, the energy emission section 3c may not completely harden or cure the ink on the workpiece W. In this case, for example, the ink irradiated by the energy emission section 3c may be completely hardened or cured by the energy from a curing light source that is separately provided on the mounting surface of the base 210 of the robot 2.

[0080] The optical sensor 3g is an optical displacement meter or imaging device, including a light-receiving part FS. The light-receiving part FS is an optical component having a surface facing the c2 direction and used, for example, to guide light into a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor. Here, the distance DS2 between the second nozzle line L2 and the light-receiving part FS is greater than the distance DS1 between the first nozzle line L1 and the light-receiving part FS.

[0081] 1-4. Printing Operation of the Printing Equipment

[0082] Figure 4 This is a diagram used to explain the printing operation of the printing apparatus 1 according to the first embodiment. Figure 4 The example illustrates printing on a predetermined area RP of the surface WF of a workpiece W, which is positioned in the Y2 direction relative to the base 210 of the robot 2 when viewed along the Z-axis. Furthermore, the predetermined area RP is positioned in the X2 direction relative to the base 210 of the robot 2 when viewed along the Y-axis.

[0083] During the printing process, robot 2 causes the head 3a to change its position and orientation while simultaneously ejecting ink from the head 3a. The changes in the position and orientation of the head 3a are implemented based on path information Da. Thus, the head 3a maintains a predetermined orientation relative to the surface WF while moving along the movement path RU. Furthermore, the movement of the head 3a along the movement path RU can be performed multiple times each time different colors of ink are ejected, or all ink ejection can be performed in parallel during a single movement of the head 3a along the movement path RU.

[0084] The movement path RU is the path from position PS to position PE. Position PS is the position relative to the predetermined area RP in the X1 direction when viewed in the Z2 direction. Position PE is the position relative to the predetermined area RP in the X2 direction when viewed in the Z2 direction. During the period from position PS to the predetermined area RP, head 3a accelerates until it reaches a predetermined speed. During the period when head 3a is on the predetermined area RP, head 3a moves at a fixed speed at that predetermined speed. During the period from the predetermined area RP to position PE, head 3a decelerates in a manner that allows it to stop at position PE. Here, the predetermined area RP is the area that crosses from position PR1 to position PR2 along the movement path RU.

[0085] exist Figure 4In the example shown, the movement path RU appears as a straight line when viewed in the Z2 direction. In this embodiment, during the execution of the printing action, the robot 2 moves the head 3a linearly along the movement path RU by manipulating four or more of the six joints 230, including joints 230_2, 230_3, and 230_5. Furthermore, the robot 2 moves the head 3a in a direction away from the base 210. Here, the aforementioned a1 direction is forward of the head 3a in the direction of movement. Therefore, the energy emission section 3c is located rearward relative to the head 3a in the direction of movement. Thus, energy from the energy emission section 3c can be applied to ink that has just been sprayed from the head 3a onto the surface WF. Furthermore, the optical sensor 3g is located forward of the head 3a in the direction of movement.

[0086] Alternatively, the workpiece W can be positioned in the X2 direction relative to the base 210 of the robot 2, with its position aligned with the base 210 along the Y-axis. In this case, the movement path RU is a straight line along the X-axis when viewed in the Z2 direction. Furthermore, in this case, the robot 2 performs the printing action by moving three of the six joints 230. More specifically, during the printing action, the robot 2 sets the rotation axes of joints 230_2, 230_3, and 230_5 to be parallel to the Y-axis and moves these joints 230. Through the movement of these three joints 230, the head 3a can move stably along the movement path RU.

[0087] Furthermore, during the printing process, since the aforementioned a1 direction is forward in the direction of movement of the head 3a, these nozzle rows are arranged from far to near relative to the base 210 in the order of the first nozzle row L1, the third nozzle row L3, the fourth nozzle row L4, and the second nozzle row L2. Therefore, when the first ink, the second ink, the third ink, and the fourth ink are ejected at the same position on the surface WF, the posture of the robot 2 at the timing of each ink ejection is different.

[0088] Here, regarding the timing of the ejection of the first ink, the second ink, the third ink, and the fourth ink at the same position on surface WF, the ejection timing of the first ink is referred to as "first timing", the ejection timing of the second ink is referred to as "second timing", the ejection timing of the third ink is referred to as "third timing", and the ejection timing of the fourth ink is referred to as "fourth timing". The following explanation will use the first timing and the second timing as examples.

[0089] Figure 5 Let represent the state of robot 2 under the first timing. Figure 6This diagram illustrates the distance DA between the tip ET and base EB of the arm 220 of robot 2 during the first timing. Figure 5 as well as Figure 6 The example illustrates a state where the timing for ejecting the first ink from the first nozzle array L1 to position PR2 is set to a first timing. Additionally, in... Figure 5 as well as Figure 6 For ease of explanation, the robot 2 and the head unit 3 are schematically illustrated.

[0090] like Figure 5 as well as Figure 6 As shown, under the first timing, the nozzle rows are arranged from far to near relative to the base 210 in the order of first nozzle row L1, third nozzle row L3, fourth nozzle row L4, and second nozzle row L2. Therefore, the distances between these nozzle rows and the base EB, from largest to smallest, are: DN1 between the first nozzle row L1 and the base EB, DN3 between the third nozzle row L3 and the base EB, DN4 between the fourth nozzle row L4 and the base EB, and DN2 between the second nozzle row L2 and the base EB. Furthermore, in this embodiment, distance DN1 is set as the shortest horizontal distance between the center of the first nozzle row L1 and the center of the base EB. Similarly, distances DN2, DN3, and DN4 are respectively set as the shortest horizontal distances between the center of the corresponding nozzle row and the center of the base EB. However, distances DN1, DN2, DN3, and DN4 can also be set simply as the straight-line distance between the center of each nozzle row and the center of the base EB, regardless of direction.

[0091] Preferably, the arrangement of such nozzle arrays is maintained during the execution of printing operations for a predetermined area RP.

[0092] In this embodiment, as the head 3a moves away from the base 210, the angle θ1 between the extension direction of arm 224 and the extension direction of arm 222 increases with the movement of the head 3a during the printing operation. Conversely, the angle θ2 between the extension direction of arm 222 and the rotation axis O1 decreases with the movement of the head 3a during the printing operation.

[0093] Figure 7 Let be a diagram representing the state of robot 2 under the second timing. Figure 8 This is a diagram illustrating the distance between the tip ET and the base EB of the arm 220 of robot 2 during the second timing. Figure 7 as well as Figure 8 The example illustrates a state where the timing for ejecting the second ink from the second nozzle array L2 to position PR2 is set to the second timing. Additionally, in... Figure 7 as well as Figure 8For ease of explanation, the robot 2 and the head unit 3 are schematically illustrated.

[0094] like Figure 7 as well as Figure 8 As shown, under the second timing, similarly to the first timing, the nozzle rows are arranged from far to near relative to the base 210 in the order of first nozzle row L1, third nozzle row L3, fourth nozzle row L4, and second nozzle row L2. Therefore, the distances between these nozzle rows and the base EB, from largest to smallest, are: DN1 between the first nozzle row L1 and the base EB, DN3 between the third nozzle row L3 and the base EB, DN4 between the fourth nozzle row L4 and the base EB, and DN2 between the second nozzle row L2 and the base EB.

[0095] However, the distance DN1 under the second timing is greater than the distance DN1 under the first timing. The difference between these distances DN1 is proportional to the distances between the first nozzle array L1 and the second nozzle array L2. Similarly, the distance DN2 under the second timing is greater than the distance DN2 under the first timing. The distance DN3 under the second timing is greater than the distance DN3 under the first timing. The distance DN4 under the second timing is greater than the distance DN4 under the first timing.

[0096] Here, the arm 220 under the second timing is in an extended state compared to the arm 220 under the first timing. Therefore, the angle θ1 under the second timing is greater than the angle θ1 under the first timing. Furthermore, the angle θ2 under the second timing is less than the angle θ2 under the first timing.

[0097] As described above, the printing operation performed by the printing apparatus 1 includes a first period in which, while the head 3a scans along a predetermined area RP, the head 3a ejects first ink from the first nozzle array L relative to the predetermined area RP. Furthermore, the printing operation performed by the printing apparatus 1 includes a second period in which, while the head 3a scans along the predetermined area RP, the head 3a ejects second ink from the second nozzle array L2 relative to the predetermined area RP.

[0098] During each of the first and second periods, the distance DN2 between the second nozzle array L2 and the base end EB is less than the distance DN1 between the first nozzle array L1 and the base end EB. Furthermore, among the plurality of joints 230, joints 230_3, 230_4, 230_5, and 230_6 are included as at least one joint 230 whose position changes relative to the predetermined region RP during each of the first and second periods. Here, joint 230_3 is an example of a first joint, and is the joint 230 farthest from the tip ET among the at least one joint 230. Also, during each of the first and second periods, the distance DA2 between the second nozzle array L2 and joint 230_3 is less than the distance DA1 between the first nozzle array L1 and joint 230_3. Furthermore, during each of the first and second periods, joint 230_3 is the joint with the largest amount of rotation among the plurality of joints 230. Additionally, the first and second periods may either overlap or not overlap.

[0099] Here, joints 230_3, 230_4, 230_5, and 230_6 are joints 230 whose distance from the predetermined position PR1 changes in each of the first and second timing periods. Furthermore, joint 230_3 is the joint 230 among joints 230_3, 230_4, 230_5, and 230_6 that is furthest from the tip ET. Here, the rotation axis O3 and rotation axis O2 are parallel to each other. Therefore, joint 230_3, as an example of a first joint, can also be expressed as the joint 230 among joints 230_2, an example of a second joint, which has rotation axes parallel to each other between itself and the base end BE, that is furthest from the tip ET. Furthermore, the distance DA2 between the second nozzle line L2 and joint 230_3 in the second timing period is less than the distance DA1 between the first nozzle line L1 and joint 230_3 in the first timing period. Additionally, as... Figure 5 or Figure 7 As shown, distance DA1 can be set as the distance between the first nozzle array L1 and the rotating shaft O3, and distance DA2 can be set as the distance between the second nozzle array L2 and the rotating shaft O3.

[0100] As described above, the printing apparatus 1 includes a head 3a and a robot 2 that changes the position and orientation of the head 3a relative to the workpiece W. Here, the head 3a includes a first nozzle array L1 with multiple nozzles N for ejecting a first ink and a second nozzle array L2 with multiple nozzles N for ejecting a second ink. The robot 2 has an arm 220 with a tip ET, a base EB, and multiple joints 230; and a base 210 connected to the base EB, on which the head 3a is supported. The brightness of the second ink is lower than that of the first ink.

[0101] Based on this, the distance DN2 between the second nozzle line L2 and the base end EB is less than the distance DN1 between the first nozzle line L1 and the base end EB.

[0102] In the printing apparatus 1 described above, because the brightness of the second ink is lower than that of the first ink, the spraying error of the second ink relative to the workpiece W is more noticeable compared to the spraying error of the first ink relative to the workpiece W. That is, compared to the first ink, the second ink is more likely to cause a decrease in printing quality due to the spraying error relative to the workpiece W. Therefore, in order to improve printing quality, the distance DN2 between the second nozzle array L2 and the base end EB is made smaller than the distance DN1 between the first nozzle array L1 and the base end EB. Furthermore, the relationship between these distances DN1 and DN2 is determined based on a comparison under the same posture or timing of the robot 2.

[0103] To explain more specifically, since joint 230 is a movable part of arm 220 and experiences wobbling due to backlash in the reducer, it is more likely to cause vibration in arm 220 compared to other parts of arm 220. Specifically, joint 230_1 among the multiple joints 230 becomes the joint with the greatest impact as a cause of vibration in arm 220. More specifically, since joint 230_1 is the joint 230 closest to the base end EB among the multiple joints 230, the torque around the rotation axis with the head 3a, located at the tip ET of arm 220, as the mass point is more likely to be larger than that of the other joints 230. Therefore, by making the distance DN2 smaller than the distance DN1, the influence of this torque on the second nozzle line L2 can be suppressed compared to the first nozzle line L1. As a result, the vibration of the second nozzle line L2, which is accompanied by the vibration of the multiple joints 230, is less than the vibration of the first nozzle line L1. Therefore, the spraying error of the second ink relative to the workpiece W can be reduced.

[0104] On the other hand, since the vibration of the first nozzle array L1, which is accompanied by the vibration of multiple joints 230, is greater than that of the second nozzle array L2, the first ink, which is less noticeable in terms of spraying error compared to the second ink, is used in the first nozzle array L1.

[0105] As described above, by improving the spraying accuracy of the second ink (whose spraying error is more noticeable) compared to the first ink (whose spraying error is insignificant), the overall print quality degradation caused by the spraying error of the ink relative to the workpiece W can be reduced. Therefore, compared to a structure where the distance DN2 is greater than the distance DN1, print quality can be improved.

[0106] Furthermore, as mentioned above, the head 3a also includes a third nozzle array L3, in which multiple nozzles N are arranged to eject a third ink. The brightness of the third ink is lower than that of the first ink but higher than that of the second ink. Furthermore, the distance DN3 between the third nozzle array L3 and the base end EB is smaller than the distance DN1 between the first nozzle array L1 and the base end EB, and larger than the distance DN2 between the second nozzle array L2 and the base end EB. Therefore, even when a third ink is used in addition to the first and second inks, the reduction in print quality caused by ink ejection error relative to the workpiece W can be reduced.

[0107] Furthermore, in this embodiment, during the period when the robot 2 causes the head 3a to scan along the predetermined area RP on the workpiece W, including the predetermined position PR2, and simultaneously ejects the first ink from the first nozzle array L1, and during the period when the robot 2 causes the head 3a to scan along the predetermined area RP, and simultaneously ejects the second ink from the second nozzle array L2, the distance DN2 between the second nozzle array L2 and the base end EB is maintained to be less than the distance DN1 between the first nozzle array L1 and the base end EB.

[0108] Here, as described above, the plurality of joints 230 includes at least one joint 230 whose position changes relative to the predetermined region RP during each of the first and second periods. Furthermore, during each of the first and second periods, the distance DA2 between the second nozzle array L2 and joint 230_3 is less than the distance DA1 between the first nozzle array L1 and joint 230_3. Here, joint 230_3 is the joint 230 among the at least one joint 230 that is furthest from the tip ET. That is, joint 230_3 is the joint 230 among the at least one joint 230 where the torque about the rotation axis with the head 3a, which is positioned at the tip ET of the arm portion 220, is most likely to become the greatest. Therefore, the vibration of the head 3a caused by the rotation of joint 230_3 is more likely to increase. Therefore, by making the distance DA2 less than the distance DA1, the influence of this torque on the second nozzle array L2 can be suppressed compared to the first nozzle array L1. Therefore, having a distance DA2 smaller than a distance DA1 is particularly useful in reducing the degradation of print quality caused by ink spraying error relative to the workpiece W. Furthermore, it is preferable to maintain a relationship where the distance DA2 between the second nozzle line L2 and the joint 230_3 is smaller than the distance DA1 between the first nozzle line L1 and the joint 230_3 during the printing operation. However, this relationship does not necessarily need to be maintained outside of the printing operation.

[0109] Furthermore, as mentioned above, since joint 230_3 is the joint with the largest amount of rotation among the multiple joints 230 during both the first and second periods, it is prone to vibration. Therefore, even at this point, making the distance DA2 smaller than the distance DA1 is particularly useful in reducing the reduction in print quality caused by ink spraying error relative to the workpiece W.

[0110] Here, the timing for ejecting the first ink from the first nozzle array L1 to a predetermined position PR1 on the workpiece W is designated as the first timing, and the timing for ejecting the second ink from the second nozzle array L2 to the predetermined position PR1 is designated as the second timing. A plurality of joints 230 include at least one joint 230 whose distance from the predetermined position PR1 changes under each of the first and second timings. The joint 230 furthest from the tip ET among these at least one joint 230 is joint 230_3. Furthermore, the distance DA2 between the second nozzle array L2 and joint 230_3 under the second timing is less than the distance DA1 between the first nozzle array L1 and joint 230_3 under the first timing.

[0111] Furthermore, as described above, the printing apparatus 1 also includes an energy emission section 3c. The energy emission section 3c is supported by a top end ET and includes an emission surface FL that emits energy to cure the first ink and the second ink respectively. Therefore, the period from the time the second ink is ejected from the workpiece W to the time the energy is irradiated onto the second ink can be shorter than the period from the time the first ink is ejected from the workpiece W to the time the energy is irradiated onto the first ink. Here, since the brightness of the second ink is lower than that of the first ink, the bleeding of the second ink onto the workpiece W is more noticeable compared to the first ink. Therefore, shortening the period from the time the second ink is ejected from the workpiece W to the time the energy is irradiated onto the second ink has the effect of improving print quality. Furthermore, since the bleeding of the first ink onto the workpiece W is less noticeable compared to the second ink, even if the period from the time the first ink is ejected from the workpiece W to the time the energy is irradiated onto the first ink is longer, it is less likely to cause a decrease in print quality.

[0112] Furthermore, in this embodiment, the printing apparatus 1 also includes an optical sensor 3g. The optical sensor 3g is supported by a top end ET and includes a light-receiving part FS.

[0113] Based on this, the distance DS2 between the second nozzle array L2 and the light-receiving section FS is greater than the distance DS1 between the first nozzle array L1 and the light-receiving section FS. Therefore, the amount of second ink adhering to the light-receiving section FS can be less than the amount of first ink. Here, since the brightness of the second ink is lower than that of the first ink, the second ink absorbs light directed towards the light-receiving section FS more readily than the first ink. Therefore, reducing the amount of second ink adhering to the light-receiving section FS has the effect of suppressing a decrease in light-receiving efficiency in the light-receiving section FS. Furthermore, since the first ink absorbs light directed towards the light-receiving section FS less readily than the second ink, even if the amount of first ink adhering to the light-receiving section FS increases, a decrease in light-receiving efficiency in the light-receiving section FS is less likely to occur.

[0114] Furthermore, as described above, the printing apparatus 1 also includes a first supply pipe 10a1 and a second supply pipe 10a2. The first supply pipe 10a1 is a pipe for supplying first ink to the first nozzle array L1. The second supply pipe 10a2 is a pipe for supplying second ink to the second nozzle array L2. A portion of each of the first supply pipe 10a1 and the second supply pipe 10a2 is held on the arm 220. Preferably, the length of the second supply pipe 10a2 is shorter than the length of the first supply pipe 10a1. When the deformation of the second supply pipe 10a2 increases with the movement of the robot 2, the flow resistance within the second supply pipe 10a2 changes, which may result in poor ejection of the second ink. Therefore, by making the length of the second supply pipe 10a2 shorter than the length of the first supply pipe 10a1, the deformation of the second supply pipe 10a2 with the movement of the arm 220 can be made less than the deformation of the first supply pipe 10a1. As a result, poor ejection of the second ink can be prevented. Here, as mentioned above, since the distance DN2 is less than the distance DN1, the length of the second supply pipe 10a2 can be shorter than the length of the first supply pipe 10a1 without making the first supply pipe 10a longer than required.

[0115] In this embodiment, as described above, the second ink is the ink with the lowest brightness among the inks ejected from the first 3a. Therefore, the printing quality can be appropriately improved.

[0116] Furthermore, as mentioned above, the second ink is black ink. Generally speaking, black ink is the ink with the lowest brightness among the various colors of ink used in full-color printing. Therefore, by setting black ink as the second ink, the printing quality of full-color printing and the like can be appropriately improved.

[0117] In this embodiment, as described above, the first ink is the ink with the highest brightness among the inks ejected from the first 3a. Therefore, the printing quality can be appropriately improved.

[0118] Furthermore, as mentioned above, the first ink is yellow ink. Generally speaking, among the multiple colors of ink used in full-color printing, yellow ink is the brightest. Therefore, by setting yellow ink as the first ink, the print quality in full-color printing can be appropriately improved. Additionally, in structures using five or more inks, white ink is sometimes used as the brightest ink. In this case, the first ink can also be white ink.

[0119] Furthermore, as described above, in the first 3a, the multiple nozzle rows for ejecting ink include a first nozzle row L1, a second nozzle row L2, a third nozzle row L3, and a fourth nozzle row L4. Here, for the first nozzle row L1 and the second nozzle row L2, the ink ejected from the nozzle row selected from any two of these multiple nozzle rows that is farther from the base end EB has a higher brightness than the ink ejected from the nozzle row that is closer to the base end EB. That is, these multiple nozzle rows are configured such that the greater the distance between them and the base end EB, the higher the brightness of the ink ejected from the nozzle row. Therefore, when using multiple inks, the reduction in print quality caused by ink drop errors relative to the workpiece W can be appropriately reduced.

[0120] 2. Second Implementation Method

[0121] The second embodiment of the present invention will now be described. Elements that function and operate the same as those in the first embodiment as in the embodiments illustrated below will be referred to by the same symbols used in the description of the first embodiment, and detailed descriptions of each will be omitted as appropriate.

[0122] Figure 9 This diagram illustrates the printing operation in the second embodiment. In this embodiment, everything is the same as in the first embodiment except for the predetermined region RP. Although the first embodiment illustrates a method where the distances DN1 to DN4 between each nozzle row and the base EB remain unchanged during the printing operation, this relationship can also vary.

[0123] In this embodiment, the printing area PR is extended in the X1 direction compared to the first embodiment. Here, when viewed along the Z-axis, the predetermined area RP is divided into area RP1 and area RP2 by an imaginary straight line YB that passes through the base end EB and is orthogonal to the scanning direction of the head 3a along the movement path RU.

[0124] exist Figure 9 In the example shown, when viewed along the Z-axis, since the movement path RU is parallel to the X-axis, the straight line YB is parallel to the Y-axis. Region RP1, when viewed along the Z-axis, is located in the X1 direction relative to the straight line YB. Conversely, region RP2, when viewed along the Z-axis, is located in the X2 direction relative to the straight line YB.

[0125] When printing is performed while the head 3a moves along the movement path RU in the X2 direction relative to such a predetermined area RP from position PS to position PE, the ink ejection from the nozzle array begins at position PR1 within area RP1 and stops at position PR2 within area RP2. Here, the arrangement order of the nozzle array along the X-axis is maintained throughout the entire printing period. Therefore, the size relationship of distances DN1 to DN4 changes midway through the printing period.

[0126] More specifically, when the tip ET is located in region RP2, similarly to the first embodiment, the distances between each nozzle row and the base EB satisfy the relationship DN1 > DN2. Conversely, when the tip ET is located in region RP1, the distances between each nozzle row and the base EB satisfy the relationship DN1 < DN2. In this way, at the point when the tip ET crosses the straight line YB, the relationship between distances DN1 to DN4 changes midway through the printing process.

[0127] From the perspective of improving print quality, it is not preferable to perform printing in a state where DN1 < DN2. Therefore, it is preferable that the predetermined area RP does not contain a region RP1 in a DN1 < DN2 relationship. Alternatively, it is preferable that even if the predetermined area RP includes region RP1, the movement of the robot 2 is controlled in a manner that makes the relationship DN1 > DN2.

[0128] However, printing can also be performed in a state where the DN1 < DN2 relationship exists. That is, there are also printing processes that allow for a DN1 < DN2 relationship. Here, when the predetermined area RP includes area RP1, from the viewpoint of balancing print quality and productivity, it is preferable that the length of area RP1 along the movement path RU is shorter than the length of area RP2 along the movement path RU. More preferably, the length of area RP1 along the movement path RU is less than half the length of area RP2 along the movement path RU. In this way, as long as the length of area RP1 along the movement path RU is short enough, even if there are periods when printing is performed in a DN1 < DN2 relationship, printing can still be performed in a DN1 > DN2 relationship, thus achieving a better balance between print quality and productivity.

[0129] 3. Third Implementation Method

[0130] The third embodiment of the present invention will now be described. Elements that function and operate the same as those in the first embodiment as in the embodiments illustrated below will be referred to by the same symbols used in the description of the first embodiment, and detailed descriptions of each will be omitted as appropriate.

[0131] Figure 10 This is a block diagram illustrating the electrical structure of the printing apparatus 1A according to the third embodiment. In the printing apparatus 1A, except that a head unit 3A is provided instead of a head unit 3, everything else is configured in the same manner as the printing apparatus 1 of the first embodiment. The head unit 3A is configured in the same manner as the head unit 3, except that the optical sensor 3g is omitted and the arrangement of the energy emission section 3c is different.

[0132] Figure 11 This is a perspective view showing the outline structure of the head unit 3A used in the third embodiment. Figure 11 As shown, in the head unit 3A, an energy emission section 3c is arranged at a position in the a1 direction relative to the head 3a. Therefore, the distance DL2 between the second nozzle array L2 and the emission surface FL is greater than the distance DL1 between the first nozzle array L1 and the emission surface FL.

[0133] Figure 12 This is a diagram used to explain the printing operation of the printing apparatus 1A according to the third embodiment. Figure 12 In the middle, and the aforementioned Figure 4 Similarly, an example is shown where printing is performed on a predetermined area RP of the surface WF of a workpiece W, which is positioned in the X2 direction relative to the base 210 of the robot 2 when viewed along the Y-axis.

[0134] In this embodiment, the robot 2 moves its head 3a toward the base 210. Here, the direction a2 is forward in the direction of movement of the head 3a. Therefore, similar to the first embodiment, the nozzle rows are arranged from far to near relative to the base 210 in the order of first nozzle row L1, third nozzle row L3, fourth nozzle row L4, and second nozzle row L2.

[0135] Furthermore, the energy emission section 3c is located rearward compared to the head 3a in the direction of movement of the head 3a. Therefore, energy from the energy emission section 3c can be irradiated relative to the ink that has just been sprayed from the head 3a onto the surface WF.

[0136] Even according to the third embodiment described above, print quality can be improved. Although the printing apparatus 1A has an energy emission section 3c in this embodiment, unlike the first embodiment, the distance DL2 between the second nozzle array L2 and the emission surface FL is greater than the distance DL1 between the first nozzle array L1 and the emission surface FL. Therefore, the amount of second ink adhering to the emission surface FL can be reduced compared to the amount of first ink. Here, since the brightness of the second ink is lower than that of the first ink, the second ink is more likely to absorb energy from the emission surface FL than the first ink. Therefore, reducing the amount of second ink adhering to the emission surface FL has the effect of suppressing the decrease in the irradiation efficiency of the energy irradiating each ink from the emission surface FL, or reducing the maintenance frequency such as cleaning of the emission surface FL. In addition, since the first ink is less likely to absorb energy from the emission surface FL compared to the second ink, even if the amount of the first ink adhering to the emission surface FL increases, it is less likely to cause problems such as lower irradiation efficiency of energy irradiating each ink from the emission surface FL or more frequent maintenance such as cleaning of the emission surface FL compared to the case where the second ink is adhering to the emission surface FL.

[0137] Furthermore, the relationship between distances DL1 and DL2 in the first and third embodiments is determined by considering factors such as the ease with which the second ink bleeds. For example, if the second ink bleeds easily, a structure where distance DL2 is smaller than distance DL1 can be used, as in the first embodiment. Conversely, if the second ink does not bleed easily, a structure where distance DL2 is larger than distance DL1 can be used, as in the second embodiment.

[0138] 4. Fourth Implementation Method

[0139] The fourth embodiment of the present invention will now be described. Elements that function and operate the same as those in the first embodiment as in the embodiments illustrated below will be referred to by the same symbols used in the description of the first embodiment, and detailed descriptions of each will be omitted as appropriate.

[0140] Figure 13 This is a perspective view showing the outline structure of the head unit 3B used in the fourth embodiment. In the printing apparatus 1B, except for having two head units B, everything else is configured in the same manner as the printing apparatus 1 of the first embodiment. Figure 13 As shown, in the head unit 3B, one of the two energy emission sections 3c is positioned in the a1 direction relative to the head 3a, and the other energy emission section 3c is positioned in the a2 direction relative to the head 3a.

[0141] Figure 14This diagram illustrates the movement paths RU1 and RU2 of head 3a in the fourth embodiment. Movement path RU1 is the path from position PS1 to position PE1. Robot 2 moves head 3a along movement path RU1 in a direction away from base 210. At this time, direction a1 is forward in the movement direction of head 3a. Movement path RU2 is the path from position PS2 to position PE2. Robot 2 moves head a along movement path RU2 in a direction closer to base 210. At this time, direction a2 is forward in the movement direction of head 3a.

[0142] Although not illustrated here, positions PS1 and PE2 represent the X1-direction positions relative to the predetermined area RP when viewed from the Z2 direction.

[0143] Even according to the fourth embodiment described above, printing quality can be improved. In this embodiment, as described above, two energy emission sections 3c are arranged via the head 3a. Therefore, regardless of whether printing is performed in the direction away from or close to the base 210, energy can be irradiated onto the ink immediately after it has been sprayed onto the workpiece W while maintaining the relationship between the distances DN1 and DN2 as in the first and third embodiments.

[0144] 5. Change the example

[0145] The various methods illustrated above can be modified in a wide variety of ways. The following sections illustrate specific modifications that can be applied to the aforementioned methods. Furthermore, two or more methods chosen from the following examples can be appropriately combined without contradiction.

[0146] 5-1. Modify Example 1

[0147] Although in the aforementioned arrangement, the nozzle rows are configured in the order of first nozzle row L1, third nozzle row L3, fourth nozzle row L4, and second nozzle row L2 relative to the base 210 from far to near, the arrangement is not limited to the aforementioned arrangement, as long as the second nozzle row L2 is positioned closer to the base 210 than the first nozzle row L1. For example, the nozzle rows may also be configured in the order of first nozzle row L1, fourth nozzle row L4, third nozzle row L3, and second nozzle row L2 relative to the base 210 from far to near.

[0148] 5-2. Modify Example 2

[0149] Although the foregoing description illustrates a structure for printing using four types of inks, the present disclosure is not limited to any structure using only the first and second inks. It can also be applied to structures using two, three, or five or more types of inks. Furthermore, the first ink is not limited to yellow ink, as long as it has a higher brightness compared to the second ink. Similarly, the second ink is not limited to black ink, as long as it has a lower brightness compared to the first ink.

[0150] 5-3. Modify Example 3

[0151] Although the structure using the energy emission section 3c is illustrated in the foregoing, the system is not limited to this structure, and the energy emission section 3c may be omitted. In this case, for example, another device that emits light to harden or cure ink on the workpiece may be configured outside the robot 2.

[0152] 5-4. Modify Example 4

[0153] While the foregoing description illustrates a structure using a six-axis vertical multi-axis robot as a movement mechanism, it is not limited to this structure. The movement mechanism can be, for example, a vertical multi-axis robot with axes other than six, or a horizontal multi-axis robot. Furthermore, the robot's arm can have a telescopic mechanism or a linear mechanism, in addition to a rotating part composed of a rotating mechanism. However, from the viewpoint of balancing print quality during printing operations and the degrees of freedom of the robot's movements during non-printing operations, a multi-axis robot with six or more axes is preferred.

[0154] 5-5. Modify Example 5

[0155] While the foregoing examples illustrate structures such as threaded fixing for securing the head relative to the robot, the method is not limited to these structures. For instance, the head can also be secured relative to the robot by using a gripping mechanism such as a handle installed as an end effector of the robot to hold it in place.

[0156] 5-6. Modify Example 6

[0157] The application of the printing apparatus disclosed herein is not limited to printing. For example, the printing apparatus that ejects a solution of color material can be used as a manufacturing apparatus for forming color filters for liquid crystal display devices. Furthermore, the printing apparatus that ejects a solution of conductive material can be used as a manufacturing apparatus for forming wiring or electrodes for wiring substrates. In addition, the printing apparatus can also be used as a jet dispenser for coating liquids such as adhesives onto a medium.

[0158] Symbol Explanation

[0159] 1…Printing apparatus; 1A…Printing apparatus; 1B…Printing apparatus; 2…Robot; 2a…Arm drive mechanism; 3…Head unit; 3A…Head unit; 3B…Head unit; 3a…Head; 3b…Pressure regulating valve; 3c…Energy emission unit; 3e…Switching circuit; 3f…Support body; 3g…Optical sensor; 5…Controller; 5a…Storage circuit; 5b…Processing circuit; 6…Control module; 6a…Timing signal generation circuit; 6b…Power supply circuit; 6c…Control circuit; 6d…Drive signal generation circuit; 7…Computer; 10…Pipeline section; 10a…First supply pipe; 10 a1…First supply tube; 10a2…Second supply tube; 10a3…Third supply tube; 10a4…Fourth supply tube; 11…Wiring section; 210…Base; 220…Arm section; 221…Arm; 222…Arm; 223…Arm; 224…Arm; 225…Arm; 226…Arm; 230…Joint; 230_1…Joint; 230_2…Joint; 230_3…Joint (first joint); 230_4…Joint; 230_5…Joint; 230_6…Joint; CLK…Clock signal; CNG…Conversion signal; Com…Drive signal; D1…Output; D 3…signal; DA…distance; DA1…distance; DA2…distance; DL1…distance; DL2…distance; DN1…distance; DN2…distance; DN3…distance; DN4…distance; DS1…distance; DS2…distance; Da…path information; EB…base end; ET…top end; FL…emission surface; FN…ejection surface; FS…light receiving part; Img…printing data; L1…first nozzle row; L2…second nozzle row; L3…third nozzle row; L4…fourth nozzle row; LAT…latch signal; N…nozzle; O1…rotation axis; O2…rotation axis; O3…rotation… Moving axis; O4…rotating axis; O5…rotating axis; O6…rotating axis; PD…drive pulse; PE…position; PE1…position; PE2…position; PR1…position; PR2…position; PS…position; PS1…position; PS2…position; PTS…timing signal; RP…predetermined area; RU…moving path; RU1…moving path; RU2…moving path; SI…printing data signal; Sk1…control signal; VBS…bias potential; VHV…power supply potential; W…workpiece; WF…surface; dCom…waveform specification signal; θ1…angle; θ2…angle.

Claims

1. A printing apparatus comprising: The head includes a first nozzle array arranged with a plurality of nozzles ejecting a first ink and a second nozzle array arranged with a plurality of nozzles ejecting a second ink. A robot has an arm and a base. The arm has a tip, a base, and multiple joints. The base is connected to the base, and a head is supported on the tip. The robot can change the position and orientation of the head relative to a workpiece. The brightness of the second ink is lower than that of the first ink. When the head is positioned opposite a predetermined area of ​​the workpiece, including a predetermined position from which the first ink is ejected from the first nozzle array, and the first ink is ejected from the first nozzle array to the predetermined position, the distance between the second nozzle array and the base end is less than the distance between the first nozzle array and the base end.

2. The printing apparatus as claimed in claim 1, wherein, The head also includes a third nozzle array comprising a plurality of nozzles arranged to eject a third ink. The brightness of the third ink is lower than that of the first ink but higher than that of the second ink. When the head is positioned opposite the predetermined area and the first ink is ejected from the first nozzle array to the predetermined position, the distance between the third nozzle array and the base end is less than the distance between the first nozzle array and the base end, and greater than the distance between the second nozzle array and the base end.

3. The printing apparatus as claimed in claim 1 or 2, wherein, During the first period when the robot causes the head to scan along the predetermined area while expelling the first ink from the first nozzle array, and during the second period when the robot causes the head to scan along the predetermined area while expelling the second ink from the second nozzle array, the distance between the second nozzle array and the base end is maintained to be less than the distance between the first nozzle array and the base end.

4. The printing apparatus as claimed in claim 3, wherein, The plurality of joints includes at least one joint whose position changes relative to the predetermined region during each of the first and second periods, wherein the joint furthest from the apex among the at least one joints is designated as the first joint. During each of the first and second periods, the distance between the second nozzle array and the first joint is less than the distance between the first nozzle array and the first joint.

5. The printing apparatus as claimed in claim 4, wherein, During each of the first and second periods, the first joint is the joint with the largest amount of rotation among the plurality of joints.

6. The printing apparatus as claimed in claim 1, wherein, It also has an energy emission section supported by the top end and includes an emission surface that emits energy to cure each of the first ink and the second ink. The distance between the second nozzle array and the exit surface is greater than the distance between the first nozzle array and the exit surface.

7. The printing apparatus as claimed in claim 1, wherein, It also has an energy emission section supported by the top end and includes an emission surface that emits energy to cure each of the first ink and the second ink. The distance between the second nozzle array and the exit surface is less than the distance between the first nozzle array and the exit surface.

8. The printing apparatus as claimed in claim 1, wherein, It also includes an optical sensor, which is supported by the top end and includes a light-receiving portion. The distance between the second nozzle array and the light-receiving part is greater than the distance between the first nozzle array and the light-receiving part.

9. The printing device of claim 1, wherein, It also has: A first supply tube is used to supply the first ink to the first nozzle array; A second supply tube is used to supply the second ink to the second nozzle array. A portion of each of the first and second supply tubes is held by the arm. The length of the second supply tube is shorter than the length of the first supply tube.

10. The printing apparatus of claim 1, wherein, The second ink is the ink with the lowest brightness among the inks ejected from the head.

11. The printing apparatus as claimed in claim 1, wherein, The second ink is black ink.

12. The printing apparatus of claim 1, wherein, The first ink is the ink with the highest brightness among the inks ejected from the head.

13. The printing apparatus of claim 1, wherein, The first ink is either yellow or white.

14. The printing apparatus as claimed in claim 1, wherein, The head includes multiple rows of nozzles that eject ink. The plurality of nozzle columns include the first nozzle column and the second nozzle column. The brightness of ink ejected from the nozzle column that is farther from the base end, selected from any two nozzle columns, is higher than the brightness of ink ejected from the nozzle column that is closer to the base end.

15. A printing apparatus comprising: The head includes a first nozzle array arranged with a plurality of nozzles ejecting a first ink and a second nozzle array arranged with a plurality of nozzles ejecting a second ink. A robot has an arm and a base. The arm has a tip, a base, and multiple joints. The base is connected to the base, and a head is supported on the tip. The robot can change the position and orientation of the head relative to a workpiece. The brightness of the second ink is lower than that of the first ink. When the timing for ejecting the first ink from the first nozzle array to a predetermined position on the workpiece is set as a first timing, the timing for ejecting the second ink from the second nozzle array to the predetermined position is set as a second timing, and the plurality of joints includes at least one joint whose distance from the predetermined position changes within each of the first and second timings, and the joint among the at least one joints that is furthest from the tip is set as the first joint, the following conditions are met: The distance between the second nozzle array and the first joint under the second timing is less than the distance between the first nozzle array and the first joint under the first timing.

16. A printing method, which is the printing method of the printing apparatus according to claim 1, wherein the printing apparatus comprises: The head includes a first nozzle array arranged with a plurality of nozzles ejecting a first ink, and a second nozzle array arranged with a plurality of nozzles ejecting a second ink with a lower brightness compared to the first ink; A robot has an arm and a base. The arm has a tip, a base, and multiple joints. The base is connected to the base, and a head is supported on the tip. The robot can change the position and orientation of the head relative to a workpiece. In the printing method, This includes the printing action of the head ejecting the first ink and the second ink while the robot moves the head away from the base. During the printing operation, the distance between the second nozzle array and the base end is less than the distance between the first nozzle array and the base end.

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