Liquid ejection device and liquid ejection method

Abstract

To suppress deviation of a flight direction of a droplet ejected from a nozzle.SOLUTION: A liquid ejection device comprises: a liquid ejection head having a nozzle for ejecting droplets, a pressure chamber communicating with the nozzle, and a driving element driven to vary a pressure of liquid in the pressure chamber in response to a supplied driving signal; a flight deviation detection unit that detects occurrence of a flight deviation of droplets ejected from the nozzle. The driving signal includes: a second driving signal COM2 being a flight deviation suppression driving signal supplied to the driving element when the flight deviation detection unit detects that the flight deviation of the droplets has occurred; and a first driving signal COM1 being a normal driving signal supplied to the driving element when the flight deviation detection unit does not detect the occurrence of the flight deviation of the droplets.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus having a liquid ejection head that ejects liquid from a nozzle, and a liquid ejection method. [Background technology]

[0002] Conventionally, liquid ejection devices equipped with a liquid ejection head having a nozzle array that ejects a liquid such as ink onto a medium such as cloth or paper have been known. For example, Patent Document 1 discloses a liquid ejection device that performs a maintenance operation to discharge ink from the nozzles at a predetermined timing and wipe the nozzle surface with a wiper in order to maintain good ejection characteristics of ink droplets from the nozzles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-36594 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a liquid ejection head in which a water-repellent film is provided on the ejection surface where the nozzles are provided, there is a risk that the water-repellent film near the nozzle openings will be peeled off when the ejection surface is wiped with a wiper. Since the water repellency of ink droplets differs between the part of the ejection surface where the water-repellent film remains and the part where the film has peeled off, there is a risk that the flight direction of ink droplets ejected from the nozzles will be deflected. [Means for solving the problem]

[0005] An aspect of the present invention that solves the above problem is a liquid ejection device that includes a liquid ejection head having a nozzle that ejects droplets, a pressure chamber that communicates with the nozzle, and a drive element that is driven to vary the pressure of the liquid in the pressure chamber in response to a supplied drive signal, and a flight curvature detection unit that detects the occurrence of flight curvature of droplets ejected from the nozzle, wherein the drive signal includes a flight curvature suppression drive signal that is supplied to the drive element when the flight curvature detection unit detects the occurrence of flight curvature of the droplets, and a normal drive signal that is supplied to the drive element when the flight curvature detection unit does not detect the occurrence of flight curvature of the droplets.

[0006] Another aspect of the present invention that solves the above problem is a liquid ejection method for a liquid ejection device that includes a nozzle that ejects droplets, a pressure chamber that communicates with the nozzle, and a drive element that is driven to vary the pressure of the liquid in the pressure chamber in response to a supplied drive signal, wherein the liquid ejection method detects the occurrence of deflection in the flight of droplets ejected from the nozzle, and if it is detected that deflection in the flight of droplets has occurred, supplies a flight deflection suppression drive signal to the drive element, and if it is detected that deflection in the flight of droplets has not occurred, supplies a normal drive signal to the drive element. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic configuration diagram of a liquid ejecting device according to a first embodiment. [Figure 2] FIG. 1 is an exploded perspective view of a liquid jet head according to a first embodiment. [Figure 3] 1 is a cross-sectional view of a liquid jet head according to a first embodiment. [Figure 4] FIG. 2 is a block diagram showing the electrical configuration of the liquid ejecting device according to the first embodiment. [Figure 5] FIG. 3 is a diagram showing a driving signal according to the first embodiment. [Figure 6] 1 is a cross-sectional view of the vicinity of a nozzle when droplets are ejected according to the first embodiment. [Figure 7] 1 is a cross-sectional view of the vicinity of a nozzle when droplets are ejected according to the first embodiment. [Figure 8]1 is a cross-sectional view of the vicinity of a nozzle when droplets are ejected according to the first embodiment. [Figure 9] 1 is a cross-sectional view of the vicinity of a nozzle when droplets are ejected according to the first embodiment. [Figure 10] 1 is a cross-sectional view of the vicinity of a nozzle when droplets are ejected according to the first embodiment. [Figure 11] FIG. 10 is a diagram showing a driving signal according to the second embodiment. [Figure 12] FIG. 10 is a cross-sectional view of the vicinity of the nozzle when droplets are ejected according to the second embodiment. [Figure 13] FIG. 10 is a cross-sectional view of the vicinity of the nozzle when droplets are ejected according to the second embodiment. [Figure 14] FIG. 10 is a diagram showing a flow for selecting a drive signal according to the second embodiment. [Figure 15] FIG. 10 is a diagram showing a driving signal according to the third embodiment. [Figure 16] FIG. 10 is a cross-sectional view of the vicinity of the nozzle when droplets are ejected according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention will be described in detail below based on embodiments. However, the following description illustrates one aspect of the present invention and can be modified as desired within the scope of the present invention. In each drawing, the same reference numerals indicate the same components, and their description will be omitted as appropriate. In each drawing, X, Y, and Z represent three spatial axes that are orthogonal to each other. In this specification, the directions along these axes are referred to as the X direction, Y direction, and Z direction. In each drawing, the direction indicated by the arrow is the positive (+) direction, and the direction opposite the arrow is the negative (-) direction. In addition, the directions of the three spatial axes, which are not limited to the positive and negative directions, will be described as the X-axis direction, Y-axis direction, and Z-axis direction.

[0009] (Embodiment 1) FIG. 1 is a diagram showing a schematic configuration of a liquid ejecting apparatus 1 according to a first embodiment of the present invention.

[0010] 1, the liquid ejection device 1 is a so-called serial printer that includes multiple liquid ejection heads H that eject ink as a liquid, and prints by transporting a medium S in the X-axis direction while moving the liquid ejection heads H back and forth in the Y-axis direction, ejecting liquid from the liquid ejection heads H toward the medium S in the +Z direction. Note that the medium S can be made of any material, such as cloth, recording paper, or resin film.

[0011] Such a liquid ejecting device 1 includes a liquid ejecting head H, a liquid storage section 2, a control section 3, a transport mechanism 4, a moving mechanism 5, a wiping member 8, and a scanner 9.

[0012] The liquid jet head H jets liquid supplied from a liquid storage unit 2 that stores ink as liquid in the form of droplets in the +Z direction.

[0013] The liquid storage unit 2 individually stores multiple types of liquid with different colors and components to be ejected from the liquid ejection head H. Examples of the liquid storage unit 2 include a cartridge that is detachable from the liquid ejection device 1, a bag-shaped ink pack made of flexible film, and an ink tank that can be refilled with ink. Note that FIG. 1 illustrates one liquid storage unit 2. The liquid storage unit 2 may be a liquid storage unit 2 having separate chambers that individually store multiple types of liquid, or may be multiple liquid storage units 2 that are individually provided according to the multiple types of liquid. The liquid storage unit 2 may also be divided into a main tank and a sub-tank. A configuration may be adopted in which the sub-tank is connected to the liquid ejection head H, and liquid consumed by ejecting droplets from the liquid ejection head H is replenished from the main tank to the sub-tank.

[0014] The control unit 3 comprehensively controls each element of the liquid ejecting device 1, that is, the liquid ejecting head H, the transport mechanism 4, the moving mechanism 5, and the like.

[0015] The transport mechanism 4 transports the medium S in the X-axis direction and has a transport roller 4a. The transport mechanism 4 transports the medium S in the X-axis direction by rotating the transport roller 4a. The transport roller 4a is rotated by driving a transport motor (not shown). The control unit 3 controls the transport of the medium S by controlling the driving of the medium transport motor. Note that the transport mechanism 4 that transports the medium S is not limited to one that includes the transport roller 4a, and may transport the medium S by, for example, a belt or a drum.

[0016] The movement mechanism 5 is a mechanism for reciprocating the liquid ejection head H in the Y-axis direction, and includes a holder 6 and a conveyor belt 7. The holder 6 is a so-called carriage that holds the liquid ejection head H, and is fixed to the conveyor belt 7. The conveyor belt 7 is an endless belt that is installed along the Y-axis direction. The conveyor belt 7 is rotated by driving a conveyor motor (not shown). The control unit 3 controls the driving of the conveyor motor to rotate the conveyor belt 7, and moves the liquid ejection head H back and forth in the Y-axis direction together with the holder 6. Note that the holder 6 may be configured to mount a liquid storage unit 2 together with the liquid ejection head H.

[0017] The liquid jet head H performs a jetting operation to jet the liquid supplied from the liquid storage unit 2 as droplets in the +Z direction under the control of the control unit 3. This jetting operation by the liquid jet head H is performed in parallel with the transport of the medium S by the transport mechanism 4 and the reciprocating movement of the liquid jet head H by the movement mechanism 5, thereby applying the liquid to the medium S, i.e., performing so-called printing.

[0018] The wiping member 8 wipes the ejection surface of the liquid ejection head H and is, for example, a plate-shaped blade made of an elastic material such as rubber, or a porous material such as a woven fabric, a nonwoven fabric, or a sponge. The wiping member 8 moves along the X-axis direction relative to the ejection surface of the liquid ejection head H, thereby wiping the ejection surface along the X-axis direction. The relative movement between the liquid ejection head H and the wiping member 8 in the X-axis direction may be achieved by moving the liquid ejection head H, by moving the wiping member 8, or by moving both the liquid ejection head H and the wiping member 8. Note that the direction of relative movement of the wiping member 8 with respect to the liquid ejection head H is not limited to the X-axis direction, but may also be along the Y-axis direction or inclined with respect to both the X-axis and Y-axis directions. In other words, the direction in which the wiping member 8 moves relative to the liquid ejection head H when performing the wiping operation is not particularly limited. In addition, the wiping member 8 may be configured to wipe the spray surface using a woven or nonwoven fabric wound around a roller, and then wind up the used part of the woven or nonwoven fabric, so that the spray surface is always wiped with a new surface of the woven or nonwoven fabric.

[0019] The scanner 9 is a device that reads an image printed on the medium S and generates image data, and the image data is sent to the control unit 3. As will be described in detail later, the image data generated by the scanner 9 is used by the control unit 3 to detect flight curvature.

[0020] An example of the liquid jet head H will be described using Figures 2 and 3. Figure 2 is an exploded perspective view of the liquid jet head, and Figure 3 is a cross-sectional view of the liquid jet head taken along a line perpendicular to the X-axis direction. Each direction of the liquid jet head will be described based on the X-axis, Y-axis, and Z-axis directions when the liquid jet head is mounted on the liquid jet device 1. Of course, the arrangement of the liquid jet head H in the liquid jet device 1 is not particularly limited.

[0021] The flow path forming substrate 10 constituting the liquid jet head H is made of a silicon single crystal substrate, and a vibration plate 50 is formed on one surface thereof. The vibration plate 50 may be a single layer or a multilayer selected from a silicon dioxide layer and a zirconium oxide layer.

[0022] A plurality of pressure chambers 12 are arranged in parallel along the X-axis direction in the flow path forming substrate 10. A communication section 13 is formed in an area of the flow path forming substrate 10 on the +Y direction side of the pressure chambers 12, and the communication section 13 and each pressure chamber 12 are communicated with each other via an ink supply path 14 and a communication path 15 provided for each pressure chamber 12. The communication section 13 communicates with the manifold section 31 of the protection substrate 30 and constitutes a part of a manifold 100 that serves as a common ink chamber for each pressure chamber 12. The ink supply path 14 is formed with a width narrower than that of the pressure chambers 12, and keeps the flow path resistance of ink flowing from the communication section 13 into the pressure chambers 12 constant.

[0023] A nozzle plate 20 is fixed to the surface of the flow path forming substrate 10 in the +Z direction using an adhesive, a heat-sealing film, or the like. Nozzles 21 are formed in the nozzle plate 20, communicating with the vicinity of the end of each pressure chamber 12 on the opposite side from the ink supply path 14. In this embodiment, the plurality of nozzles 21 are arranged side by side in the X-axis direction so as to be at the same position in the Y-axis direction. A nozzle row 22 is formed from the plurality of nozzles 21 arranged side by side in the X-axis direction. Note that the arrangement of the nozzles 21 is not particularly limited thereto. For example, among the nozzles 21 arranged side by side in the X-axis direction, every other nozzle 21 may be arranged at a position offset in the Y-axis direction, in a so-called staggered arrangement. Of course, the nozzle row 22 may also be formed in multiple rows in the Y-axis direction or in a direction intersecting both the X-axis direction and the Y-axis direction.

[0024] The nozzle plate 20 is made of, for example, glass ceramics, a silicon single crystal substrate, stainless steel, or the like. A water-repellent film 25 is formed on the +Z direction surface of the nozzle plate 20 where the nozzles 21 open. The water-repellent film 25 can be formed of, for example, a fluorine-containing organic compound or a fluorine-containing organic silicon compound. The water-repellent film 25 is formed over the entire +Z direction surface of the nozzle plate 20, and a portion of the water-repellent film 25 is also formed near the openings inside the nozzles 21. The +Z direction surface of the nozzle plate 20, or in this embodiment, the +Z direction surface of the water-repellent film 25, is referred to as the ejection surface 23. Note that the water-repellent film 25 does not need to be provided over the entire +Z direction surface of the nozzle plate 20, and may be provided near the nozzles 21.

[0025] A vibration plate 50 is formed on the surface of the flow channel forming substrate 10 in the -Z direction. Piezoelectric actuators 300 are provided on the vibration plate 50 so as to face each pressure chamber 12. The piezoelectric actuator 300 is formed by laminating a first electrode 60, a piezoelectric layer 70, and a second electrode 80 by film formation and lithography. In this embodiment, the piezoelectric actuator 300 serves as a driving element that generates a pressure change in the ink in the pressure chamber 12. In this embodiment, one piezoelectric actuator 300 is provided for one pressure chamber 12, but this is not a limitation. For example, any number of piezoelectric actuators 300 may be provided for one pressure chamber 12, or one piezoelectric actuator 300 may be provided for any number of pressure generating chambers.

[0026] The piezoelectric actuator 300, also referred to as a piezoelectric element, refers to a portion including a first electrode 60, a piezoelectric layer 70, and a second electrode 80. Typically, one of the electrodes of the piezoelectric actuator 300 is a common electrode, and the other electrode and the piezoelectric layer 70 are patterned for each pressure chamber 12. In this embodiment, the first electrode 60 is the common electrode for the piezoelectric actuator 300, and the second electrode 80 is an individual electrode for the piezoelectric actuator 300. However, this may be reversed for convenience of the drive circuit and wiring. In the above example, the diaphragm 50 and the first electrode 60 function as a diaphragm. However, this is not limiting. For example, the diaphragm 50 may be omitted, and only the first electrode 60 may function as a diaphragm. Furthermore, the piezoelectric actuator 300 itself may essentially function as a diaphragm.

[0027] A lead electrode 90 is connected to the second electrode 80 of each piezoelectric actuator 300 , and a voltage is selectively applied to each piezoelectric actuator 300 via this lead electrode 90 .

[0028] A protective substrate 30 having a manifold portion 31 that constitutes at least a part of the manifold 100 is bonded to the surface of the flow-path forming substrate 10 on the piezoelectric actuator 300 side via an adhesive 35. In this embodiment, the manifold portion 31 penetrates the protective substrate 30 in the Z-axis direction and is formed across the width direction of the pressure chambers 12, and is connected to the communication portion 13 of the flow-path forming substrate 10 to constitute the manifold 100 that serves as a common ink chamber for each pressure chamber 12.

[0029] A piezoelectric actuator holding portion 32 having a space large enough not to impede the movement of the piezoelectric actuator 300 is provided in an area of the protective substrate 30 facing the piezoelectric actuator 300. The piezoelectric actuator holding portion 32 only needs to have a space large enough not to impede the movement of the piezoelectric actuator 300, and the space may or may not be sealed.

[0030] The protective substrate 30 is preferably made of a material having a thermal expansion coefficient substantially identical to that of the flow path forming substrate 10, such as glass or a ceramic material. In this embodiment, the protective substrate 30 is made of a silicon single crystal substrate made of the same material as the flow path forming substrate 10.

[0031] The protective substrate 30 is provided with a through hole 33 that penetrates the protective substrate 30 in the Z-axis direction. The vicinity of the end of the lead electrode 90 drawn out from each piezoelectric actuator 300 is provided so as to be exposed within the through hole 33.

[0032] A drive circuit 120 for driving the piezoelectric actuator 300 is provided on the −Z direction surface of the protection substrate 30. For example, a circuit board or a semiconductor integrated circuit (IC) can be used as this drive circuit 120. The drive circuit 120 and the lead electrode 90 are electrically connected via connection wiring 121 made of a conductive wire such as a bonding wire.

[0033] A compliance substrate 40 made up of a sealing film 41 and a fixing plate 42 is bonded to the surface of the protection substrate 30 in the -Z direction. The sealing film 41 is made of a material that has low rigidity and flexibility, and one side of the manifold section 31 is sealed by this sealing film 41. The fixing plate 42 is made of a relatively hard material. The region of the fixing plate 42 facing the manifold 100 is an opening 43 that is completely removed in the thickness direction, and therefore one side of the manifold 100 is sealed only by the flexible sealing film 41.

[0034] In the liquid jet head H of this embodiment, ink is taken in from the liquid storage section 2 shown in Figure 1 and the interior is filled with ink from the manifold 100 to the nozzles 21. Then, in accordance with a drive signal from the drive circuit 120, a voltage is applied between each of the first electrodes 60 and second electrodes 80 corresponding to the pressure chambers 12, causing the vibration plate 50 and the piezoelectric actuator 300 to flex and deform, thereby increasing the pressure within each pressure chamber 12 and ejecting ink droplets from the nozzles 21.

[0035] 4 is a block diagram showing the electrical configuration of the liquid ejection device 1. The control unit 3 is an element that performs overall control of the liquid ejection device 1. The control unit 3 includes an external interface 211 (hereinafter referred to as the external I / F 211), a RAM 212 that temporarily stores various data, a ROM 213 that stores control programs and the like, a control processing unit 214 that includes a CPU and the like, an oscillation circuit 215 that generates a clock signal (CK), a drive signal generating unit 216 that generates a drive signal to be supplied to the liquid ejection head H, and an internal interface 217 (hereinafter referred to as the internal I / F 217).

[0036] The external I / F 211 is an interface for transmitting and receiving data to and from a host computer (not shown). Examples of data received by the control unit 3 from the host computer via the external I / F 211 include print data composed of character codes, graphic functions, image data, and the like. Examples of data transmitted by the control unit 3 via the external I / F 211 include a busy signal (BUSY) and an acknowledge signal (ACK). The RAM 212 functions as a receive buffer 212A, an intermediate buffer 212B, an output buffer 212C, and a work memory (not shown). The receive buffer 212A temporarily stores print data received by the external I / F 211, the intermediate buffer 212B stores intermediate code data converted by the control processing unit 214, and the output buffer 212C stores dot pattern data. The dot pattern data is composed of recording data (SI) obtained by decoding (translating) gradation data.

[0037] The drive signal generating unit 216 includes a first drive signal generating unit 216A, which is a first drive signal generating means capable of generating a first drive signal COM1, and a second drive signal generating unit 216B, which is a second drive signal generating means capable of generating a second drive signal COM2. The first drive signal corresponds to a normal drive signal, and the second drive signal corresponds to a flight curve suppression drive signal. As will be described in detail later, the first drive signal COM1 is a drive signal used when flight curve is not occurring, and the second drive signal COM2 is a drive signal used when flight curve is occurring. The first drive signal COM1 and the second drive signal COM2 are collectively referred to as drive signals COM.

[0038] The first drive signal COM1 generated by the first drive signal generating section 216A is a signal that has, within one unit period T, a first ejection pulse DP1 that drives the piezoelectric actuator 300 to eject ink droplets from the nozzle 21, and is repeatedly generated for each unit period T. The second drive signal COM2 generated by the second drive signal generating section 216B is a signal that has, within one unit period T, a second ejection pulse DP2 that drives the piezoelectric actuator 300 to eject ink droplets from the nozzle, and is repeatedly generated for each unit period T. The unit period T is the repeating unit of the drive signal COM, and corresponds to one pixel of the image to be printed on the medium S.

[0039] The ROM 213 stores font data, graphic functions, and the like, as well as control programs (control routines) for causing the control processing unit 214 to perform various data processing operations. The control processing unit 214 reads print data from the receive buffer 212A and converts the print data to generate intermediate code data, which it then stores in the intermediate buffer 212B. The control processing unit 214 also analyzes the intermediate code data read from the intermediate buffer 212B and, referring to the font data and graphic functions stored in the ROM 213, develops the intermediate code data into record data. The control processing unit 214 then performs any necessary decoration processing and stores the developed record data in the output buffer 212C. The control program may be read from a recording medium, such as a floppy disk, CD-ROM, DVD-ROM, or USB memory, connected directly via the external I / F 211 or via the host computer. The control program may also be provided in the host computer as a printer driver.

[0040] When ink droplets are ejected based on such recording data, the control processing unit 214 selects either the first drive signal COM1 or the second drive signal COM2 depending on whether or not the nozzle 21 is deflecting.

[0041] First, the detection of flight curvature will be described. The control processing unit 214 of the control unit 3 has a function of detecting flight curvature. Specifically, the control processing unit 214 detects the landing position on the medium S of droplets ejected by supplying the first drive signal COM1, which is a normal drive signal, to the drive element, and if the amount of deviation between the landing position and a reference position is equal to or greater than a threshold, it determines that flight curvature has occurred.

[0042] As described above, a water-repellent film 25 is formed on the ejection surface 23 of the liquid ejection head H, and the wiping action of the wiping member 8 may cause a portion of the water-repellent film 25 near the nozzle to peel off. If droplets are ejected while the water-repellent film 25 near the nozzle 21 is peeled off, deflected flight may occur. Deflected flight refers to a phenomenon in which the direction of droplets ejected from the liquid ejection head H deviates from the reference position of the dot to be formed on the medium S by the droplets, resulting in a deviation of the actual dot position. Note that deflected flight can also occur when an excessive amount of water-repellent film is provided near the nozzle. The reference position of the dot is a design target position, and refers to the position of the dot that should be formed when droplets are ejected from a normal nozzle. A normal nozzle refers to a nozzle in which the water-repellent film is not peeled off near the nozzle or in which an excessive amount of water-repellent film is not formed.

[0043] As an example, flight curvature is detected as follows: A test pattern is printed on the medium S using a liquid ejection head H equipped with nozzles 21 in which flight curvature does not occur, and the printed image is read by the scanner 9 to generate image data. This image data is referred to as reference image data. The reference image data is stored in the ROM 213. Alternatively, the reference image data is stored in a host computer (not shown) or the like, and then stored in the RAM 212 via the external I / F 211.

[0044] Next, the control processing unit 214 executes a flight curve detection process consisting of steps 1 to 5 to detect flight curve. 1. The same test pattern as that used when generating the reference image data is printed on the liquid ejection head H, 2. The image formed on the medium S is read by the scanner 9, 3. The image data (hereinafter referred to as test image data) formed by the scanner 9 is read into the RAM 212 via the internal I / F 217, 4. The deviation of each dot between the test image data and the reference image data is measured by image processing. 5. If the deviation amount exceeds the threshold value, it is determined that the nozzle 21 that ejected that dot is experiencing flight deflection.

[0045] The above-described steps 1 to 5 are implemented as a program executed by the control processing unit 214, and are stored in the ROM 213 or the like, like the control program. There are no particular limitations on the timing of detecting flight curvature, but it is preferable to perform the detection after the wiping member 8 has wiped the ejection surface 23 of the liquid ejection head H. In this embodiment, the positions of the dots in the test image data formed by the scanner 9 correspond to the landing positions, and the positions of the dots in the reference image data correspond to the reference positions. Furthermore, the control processing unit 214 and the program including steps 1 to 5 executed by the control processing unit 214 correspond to a flight curvature detection unit.

[0046] The flight curvature detection process detects whether flight curvature has occurred for each nozzle 21. If flight curvature has occurred for even one of the multiple nozzles 21, the second drive signal COM2 for suppressing flight curvature may be supplied to the piezoelectric actuators 300 of all the nozzles 21, or the second drive signal COM2 may be supplied only to the piezoelectric actuator 300 of the nozzle 21 in which flight curvature has occurred.

[0047] Here, we will explain the case where a second drive signal COM2 that suppresses flight curvature is supplied to the piezoelectric actuator 300 of a nozzle 21 where flight curvature has occurred, and a first drive signal COM1, which is a normal drive signal, is supplied to the piezoelectric actuator 300 of a nozzle 21 where flight curvature has not occurred.

[0048] After the flight curve detection process, the control processing unit 214 generates a selection signal for applying the first drive signal COM1 to the piezoelectric actuator 300 for nozzles 21 that are not experiencing flight curve, and for applying the second drive signal COM2 to the piezoelectric actuator 300 for nozzles 21 that are experiencing flight curve, and stores this signal in the RAM 212. For example, the selection signal may take on two values, "0" or "1." "0" indicates that the normal first drive signal COM1 that does not suppress flight curve is used, and "1" indicates that the second drive signal COM2 that suppresses flight curve is used. The control processing unit 214 generates such a binary selection signal for each nozzle 21.

[0049] Then, when printing is performed after the flight curve detection process, once the control processing unit 214 has obtained recording data equivalent to one line of the liquid ejection head H, it outputs this one line of recording data together with a selection signal to the liquid ejection head H via the internal I / F 217. Furthermore, when one line of recording data is output from the output buffer 212C, the expanded intermediate code data is erased from the intermediate buffer 212B, and expansion processing is performed on the next intermediate code data.

[0050] The liquid jet head H includes a drive circuit 120. The drive circuit 120 is a circuit that selects either the first drive signal COM1 or the second drive signal COM2 and applies it to the piezoelectric actuators 300 based on the recording data (SI) and selection signal (SEL) sent from the control unit 3 via the internal I / F 217. Such selection and application of the drive signal is performed for each of the plurality of piezoelectric actuators 300.

[0051] The print data consists of multiple pixel data to be ejected for each of the multiple dots that make up a line. For example, the pixel data may be binary, with "1" indicating that a dot should be formed and "0" indicating that a dot should not be formed. If the pixel data is "1" and the selection signal is "0," the drive circuit 120 supplies a first drive signal COM1 to the piezoelectric actuator 300, which causes droplets to be ejected from the nozzle 21 corresponding to that pixel data. If the pixel data is "1" and the selection signal is "1," the drive circuit 120 supplies a second drive signal COM2 to the piezoelectric actuator 300, which causes droplets to be ejected from the nozzle corresponding to that pixel data. If the pixel data is "0," the drive circuit 120 does not supply any drive signal to the piezoelectric actuator 300.

[0052] If even one of the nozzles 21 experiences deflection, the control processing unit 214 supplies the drive circuit 120 with the second drive signal COM2 to suppress deflection. The control processing unit 214 then supplies the drive circuit 120 with the print data and a selection signal indicating that the second drive signal COM2 should be used. The drive circuit 120 then selects the second drive signal COM2 based on the selection signal and applies the second drive signal COM2 to each piezoelectric actuator 300 based on the print data. By supplying the second drive signal COM2 to all piezoelectric actuators 300 in this manner, even if some nozzles 21 experience deflection, the deflection can be suppressed. In this case, the second drive signal COM2 that suppresses deflection is also supplied to normal nozzles 21 whose water-repellent coating 25 is not peeled off, allowing droplets to be ejected without deflection.

[0053] In this way, the liquid jet head H ejects ink droplets, which are liquid droplets, from each nozzle 21 at a timing defined by the recording data or the like under the control of the control unit 3. The control unit 3 then controls the transport mechanism 4 to transport the medium S and the movement mechanism 5 to move the liquid jet head H back and forth via the internal I / F 217, in parallel with the ejection operation by the liquid jet head H. Printing is performed on the medium S under such control of the control unit 3.

[0054] 5 is a diagram showing the drive signals. The first drive signal COM1 and the second drive signal COM2 will be described in detail.

[0055] The first drive signal COM1 is repeatedly generated by the first drive signal generating section 216A of the drive signal generating section 216 at each unit period T defined by a clock signal transmitted from the oscillation circuit 215. The unit period T corresponds to one pixel of an image or the like to be printed on the medium S. In this embodiment, a first ejection pulse DP1 is generated at each unit period T.

[0056] The second drive signal COM2 is repeatedly generated by the second drive signal generating section 216B of the drive signal generating section 216 at the same unit period T as the first drive signal COM1. In this embodiment, the second ejection pulse DP2 is generated at the unit period T.

[0057] In this embodiment, the first drive signal COM1 and the second drive signal COM2 are supplied to the second electrode 80, which is an individual electrode, with the first electrode 60, which is a common electrode of the piezoelectric actuator 300, serving as a reference potential. In other words, the voltage applied to the second electrode 80 by the drive signal is expressed as a potential with the reference potential as the reference.

[0058] The first ejection pulse DP1 of the first drive signal COM1 comprises a first expansion waveform element a1 that changes in potential from a reference potential to a first potential so as to expand the volume of the pressure chamber 12 from the reference volume, an expansion maintaining waveform element a2 that maintains the volume of the pressure chamber 12 expanded by the first expansion waveform element a1 for a certain period of time, a first ejection waveform element a3 that changes in potential from a first potential to a second potential so as to contract the volume of the pressure chamber 12 and eject droplets from the nozzle 21, a contraction maintaining waveform element a4 that maintains the volume of the pressure chamber 12 contracted by the first ejection waveform element a3 for a certain period of time, and a vibration damping element a5 that returns the pressure chamber 12 from the contracted state at the second potential to the reference volume at the reference potential and damps residual vibration of the liquid in the pressure chamber 12.

[0059] When the first ejection pulse DP1 is supplied to the piezoelectric actuator 300, the first expansion waveform element a1 causes the piezoelectric actuator 300 to deform in a direction that expands the volume of the pressure chamber 12. This draws the meniscus in the nozzle 21 toward the pressure chamber 12, and ink is supplied to the pressure chamber 12 from the manifold 100 side. The expanded state of the pressure chamber 12 is maintained by the expansion maintaining waveform element a2. After that, the first ejection waveform element a3 is supplied, causing the pressure chamber 12 to rapidly contract from its expanded volume to a contracted volume corresponding to the second potential, pressurizing the ink in the pressure chamber 12 and ejecting an ink droplet from the nozzle 21. The contracted state of the pressure chamber 12 is maintained by the contraction maintaining waveform element a4. During this time, the ink pressure in the pressure chamber 12, which had decreased due to the ejection of the ink droplet, rises again due to its natural vibration. A damping element a5 is supplied in synchronization with this rise, causing the pressure chamber 12 to return to its reference volume and absorbing the pressure fluctuations in the pressure chamber 12.

[0060] The second ejection pulse DP2 of the second drive signal COM2 includes a second expansion waveform element b1 that changes in potential from a reference potential to a third potential between the reference potential and the first potential so as to expand the volume of the pressure chamber, an expansion potential maintaining waveform element b2 that maintains the third potential, a third expansion waveform element b3 that changes in potential from the third potential to a fourth potential so as to further expand the volume of the pressure chamber 12, an expansion maintaining waveform element b4 that maintains the fourth potential, and a second ejection waveform element b5 that changes in potential from the fourth potential to a fifth potential so as to contract the volume of the pressure chamber 12 and eject a droplet from the nozzle 21. The second ejection pulse DP2 further includes a contraction maintaining waveform element b6 that maintains the volume of the pressure chamber 12 contracted by the second ejection waveform element b5 for a certain period of time, and a vibration damping element b7 that returns the pressure chamber 12 from the contracted state at the fifth potential to the reference volume at the reference potential and damps residual vibration of the liquid in the pressure chamber 12.

[0061] The first potential and the fourth potential may be the same or different, and the second potential and the fifth potential may be the same or different.

[0062] Furthermore, although the first ejection pulse DP1 of the first drive signal COM1 and the second ejection pulse DP2 of the second drive signal COM2 have the same unit period, this unit period does not have to be the same. For example, the unit period of the first drive signal COM1 may be shorter than the unit period of the second drive signal COM2. When only the first drive signal COM1 is supplied to all of the piezoelectric actuators 300, the first drive signal COM1 is used as is, and when only the second drive signal COM2 is supplied to all of the piezoelectric actuators 300, the second drive signal COM2 is used as is.

[0063] On the other hand, when selectively supplying the first drive signal COM1 and the second drive signal COM2 to all piezoelectric actuators 300 based on the flight curvature, the shorter unit period is adjusted to match the longer unit period. For example, by providing time between the first ejection pulse DP1 and the next first ejection pulse DP1, the unit period is matched to the unit period of the second ejection pulse DP2. By adjusting the unit period in this manner, when only the first drive signal COM1 is supplied to all piezoelectric actuators 300, the unit period is relatively short compared to when the second drive signal COM2 is also supplied, so printing speed is not reduced. Furthermore, when a mixture of the first drive signal COM1 and the second drive signal COM2 is supplied to all piezoelectric actuators 300, there is no mismatch in the ejection timing between the piezoelectric actuators 300 supplied with the first drive signal COM1 and the piezoelectric actuators 300 supplied with the second drive signal COM2.

[0064] 6 to 10 are cross-sectional views of the vicinity of the nozzle when a droplet is ejected. Using these figures, it will be explained how supplying the second ejection pulse DP2 to the piezoelectric actuator 300 suppresses deflection of the flight of the droplet.

[0065] As shown in FIG. 6, a water-repellent film 25 is formed on the +Z direction surface of the nozzle plate 20, with a portion of the film extending into the nozzle 21. Ideally, the water-repellent film 25 inside the nozzle 21 would be formed to a uniform depth; however, there is a risk that a portion of the water-repellent film 25 may peel off due to the wiping action of the wiping member 8, for example. In the example shown in FIG. 6, the water-repellent film 25 was originally formed to a uniform depth inside the nozzle 21, but a portion on the −Y direction side peeled off, causing the depth of the water-repellent film 25 to vary in the depth direction of the nozzle 21 (Z-axis direction). Because a portion of the water-repellent film 25 has peeled off in this manner, the meniscus M of the ink formed in the nozzle 21 has an asymmetric shape that protrudes toward the +Z direction at the portion where the water-repellent film 25 has peeled off. In other words, an asymmetric shape is when the position of the outer periphery of the meniscus M in the Z direction varies depending on the location, and a symmetric shape is when the position of the outer periphery of the meniscus M in the Z direction is uniform.

[0066] This also applies not only to cases where a portion of the water-repellent film 25 is peeled off, but also to cases where the water-repellent film 25 is excessively formed. That is, it is possible that a portion of the water-repellent film 25 inside the nozzle 21 is formed deeper than the designed depth. In the example of FIG. 6, if a portion of the water-repellent film 25 on the -Y direction side is formed to the designed depth, the water-repellent film 25 on the +Y direction side is formed deeper than the designed depth. That is, a portion of the water-repellent film 25 is excessively formed. Even in such a case, the meniscus M has an asymmetric shape in which the portion of the +Y direction side where the water-repellent film 25 is excessively formed is recessed toward the -Z direction. Hereinafter, a case where a portion of the water-repellent film 25 is peeled off will be described, but the same applies to cases where the water-repellent film 25 is excessively formed.

[0067] A second drive signal COM2 is applied to the piezoelectric actuator 300 corresponding to the nozzle 21 where a portion of the water-repellent film 25 has peeled off. First, as shown in FIG. 7, the second expansion waveform element b1 causes the piezoelectric actuator 300 to deform in a direction that expands the volume of the pressure chamber 12. This deformation causes the ink in the nozzle 21 to be drawn deeper (toward the -Z direction) than the water-repellent film 25 near the opening of the nozzle 21, and ink is supplied to the pressure chamber 12 from the manifold 100 side. The expanded state of the pressure chamber 12 is then maintained by the expansion potential maintaining waveform element b2. The meniscus M, which was asymmetric during period B of the expansion potential maintaining waveform element b2, gradually becomes symmetric.

[0068] Next, as shown in Figure 8, the third expansion waveform element b3 causes the piezoelectric actuator 300 to deform in a direction that expands the volume of the pressure chamber 12, and the meniscus M in the nozzle 21 is pulled further toward the back of the nozzle 21. At this time, the ink meniscus M maintains its symmetrical shape because it is not affected by the water-repellent film 25. The expanded state of the pressure chamber 12 is maintained by the expansion maintaining waveform element b4.

[0069] 9 and 10, the second ejection waveform element b5 is supplied, causing the pressure chamber 12 to rapidly contract from the expanded volume to the contracted volume corresponding to the fifth potential, pressurizing the ink in the pressure chamber 12 and ejecting a droplet D from the nozzle 21. As shown in Figures 7 and 8, the pressure chamber 12 is contracted with the meniscus M in the nozzle 21 symmetrically aligned, and therefore the droplet D is ejected, thereby preventing the droplet D from flying in a curved manner.

[0070] In this way, the second drive signal COM2 includes the second expansion waveform element b1 and the expansion potential maintaining waveform element b2. The shape of the meniscus M can be made symmetrical during the period B of the expansion potential maintaining waveform element b2. Then, ink is ejected by the second ejection waveform element b5 with the shape of the meniscus M made symmetrical within the nozzle 21, so that flight curvature can be suppressed compared to when droplets D are ejected with the meniscus M remaining asymmetric.

[0071] If the pressure chamber 12 were to expand all at once like the first drive signal COM1 without including the expansion potential maintaining waveform element b2, the second expansion waveform element b1, and the third expansion waveform element b3, the meniscus M would remain asymmetric and be pulled in the -Z direction. If a droplet were to be ejected in this state, the shape of the meniscus M and the flow of ink in the nozzle 21 would remain unstable and the first ejection waveform element a3 would be supplied, causing the droplet to traverse its flight.

[0072] After that, although not specifically shown, the contracted state of the pressure chamber 12 is maintained by a contraction maintaining waveform element b6, and the ink pressure in the pressure chamber 12, which had decreased during this time due to the ejection of the ink droplet, rises again due to its natural vibration. A damping element b7 is supplied in time with this rise, and the pressure chamber 12 returns to its reference volume, absorbing the pressure fluctuations in the pressure chamber 12.

[0073] Although there are no particular limitations on the period A of the second expansion waveform element b1, it has been empirically found that a shorter period A results in better retraction in the -Z direction, and specifically it is preferable to set it to one-fourth or less of the natural vibration period. The natural vibration period of the pressure chamber 12 is determined by factors such as the structures of the piezoelectric actuator 300, the diaphragm 50, the pressure chamber 12, the nozzle 21, etc., and the properties of the ink, and refers to the natural vibration period that occurs in the ink within the pressure chamber 12 and the nozzle 21.

[0074] Furthermore, the period B of the expansion potential maintaining waveform element b2 is not particularly limited, but is preferably 0.1 μsec or longer. By setting the period B in this manner, the meniscus M can be more reliably aligned symmetrically, as shown in FIG.

[0075] Furthermore, it is preferable that the period B is 2 μsec or less. By setting the period B of the expansion potential maintaining waveform element b2 in this way, it is possible to prevent the meniscus M, which has been pulled in toward the −Z direction and become symmetrical as shown in Figure 7, from returning toward the +Z direction. It is also possible to prevent the waveform length of the second ejection pulse DP2 from becoming too long.

[0076] As described above, the liquid ejection device 1 of this embodiment is equipped with a piezoelectric actuator 300, which is a drive element driven by a drive signal, and the drive signal includes a second drive signal COM2, which is a flight curvature suppression drive signal that is supplied to the piezoelectric actuator 300 when the flight curvature detection unit detects that flight curvature of the droplets has occurred, and a first drive signal COM1, which is a normal drive signal that is supplied to the piezoelectric actuator 300 when the flight curvature detection unit does not detect the occurrence of flight curvature of the droplets.

[0077] According to this liquid ejection device 1, a normal drive signal is supplied to the piezoelectric actuator 300 corresponding to the nozzle 21 where no deflection of flight has occurred. On the other hand, a deflection suppression drive signal is supplied to the piezoelectric actuator 300 corresponding to the nozzle 21 where deflection of flight has occurred. In this way, a drive signal is selected depending on whether or not the nozzle 21 has deflection of flight, and droplets are ejected, thereby suppressing deflection of flight and reducing deterioration in the quality of the printed image.

[0078] Furthermore, peeling of the water-repellent film 25, which causes deflection of ink droplets, does not occur in the early stages of use after the liquid ejection head H is manufactured, but progresses gradually as wiping operations using the wiping member 8 are performed. The degree of progress varies depending on the frequency and number of wiping operations performed, as well as individual differences between the liquid ejection heads H, and is difficult to accurately estimate during manufacturing. Therefore, it is necessary to estimate the extent to which the water-repellent film 25 will peel off due to the wiping operation to the maximum extent possible, and to use a drive signal from the beginning that will suppress deflection of ink droplets that may occur in that case. In such a case, the unit cycle included in the drive signal is expected to be long, and as the unit cycle becomes longer, the time required for ejection increases, which may result in a decrease in printing speed.

[0079] However, the liquid injection device 1 of this embodiment supplies the first drive signal COM1 to the piezoelectric actuator 300 if no flight curvature is detected, thereby making it possible to avoid using a drive signal with a long unit period to suppress flight curvature from the beginning.

[0080] (Embodiment 2) In this embodiment, a liquid ejection device 1 is described that uses multiple flight curve suppression drive signals, specifically two signals: a first flight curve suppression drive signal and a second flight curve suppression drive signal, and selects one of the multiple flight curve suppression drive signals depending on the degree of flight curve and supplies it to a piezoelectric actuator 300. Note that the same reference numerals are used for the same components as in embodiment 1, and redundant explanations will be omitted.

[0081] The liquid ejecting device 1 of this embodiment uses the same first drive signal COM1 as in embodiment 1 as the normal drive signal, the same second drive signal COM2 as in embodiment 1 as the first flight curve suppression drive signal, and the third drive signal COM3 as the second flight curve suppression drive signal. Although not specifically shown, the drive signal generating unit 216 further includes a third drive signal generating unit that is third drive signal generating means capable of generating the third drive signal COM3.

[0082] 11 shows examples of the second drive signal COM2 and the third drive signal COM3. The third drive signal COM3 generated by the third drive signal generating unit is a signal that has a third ejection pulse DP3 within one unit period T, which drives the piezoelectric actuator 300 to eject ink droplets from the nozzle 21, and is repeatedly generated every unit period T.

[0083] The third ejection pulse DP3 of the third drive signal COM3 includes a fourth expansion waveform element b11 that changes potential from a reference potential to a sixth potential between the reference potential and the fourth potential so as to expand the volume of the pressure chamber, a second expansion potential maintaining waveform element b12 that maintains the sixth potential, a fifth expansion waveform element b13 that changes potential from the sixth potential to the fourth potential so as to further expand the volume of the pressure chamber 12, an expansion maintaining waveform element b14 that maintains the fourth potential, and a third ejection waveform element b15 that changes potential from the fourth potential to the fifth potential so as to contract the volume of the pressure chamber 12 and eject a droplet from the nozzle 21. The third ejection pulse DP3 further includes a contraction maintaining waveform element b16 that maintains the volume of the pressure chamber 12 contracted by the third ejection waveform element b15 for a certain period of time, and a vibration damping element b17 that returns the pressure chamber 12 to the reference volume at the reference potential from the contracted state of the fifth potential and damps residual vibration of the liquid in the pressure chamber 12.

[0084] The third potential of the second ejection pulse DP2 is different from the sixth potential of the third ejection pulse DP3. The third potential is a potential between the reference potential and the sixth potential. In this embodiment, the sixth potential is lower than the third potential. Because the sixth potential of the third ejection pulse DP3 is lower than the third potential, a strong force acts on the meniscus M, pulling it toward the -Z direction, which is the back side of the nozzle 21.

[0085] 12 and 13 show two nozzles 21a and 21b with different degrees of peeling of the water-repellent film 25. For nozzle 21a, a portion of the water-repellent film 25 has peeled off but remains within nozzle 21a. For nozzle 21b, a portion of the water-repellent film 25 has peeled off from within nozzle 21b to the edge of the opening of nozzle 21b. Because more of the water-repellent film 25 has peeled off from nozzle 21b than from nozzle 21a, a portion of the meniscus Mb within nozzle 21b protrudes further in the +Z direction than the meniscus Ma within nozzle 21a. In other words, if the index of meniscus asymmetry is defined as the difference between the position on the outer periphery of the meniscus closest to the +Z direction and the position on the outer periphery of the meniscus closest to the -Z direction, the difference Hb of the meniscus Mb of nozzle 21b is greater than the difference Ha of the meniscus Ma of nozzle 21a.

[0086] The greater the difference in the outer periphery of the meniscus along the Z direction, the stronger the pulling force in the -Z direction of the deflection suppression drive signal applied, thereby more reliably aligning the meniscus symmetrically. For example, as shown in FIG. 12, when the second drive signal COM2 is applied to the piezoelectric actuator 300 corresponding to the nozzle 21a where a relatively small asymmetric meniscus Ma is formed, the second expansion waveform element b1 and the expansion potential sustain waveform element b2 transform the asymmetric meniscus Ma into a symmetric meniscus Na. Also, as shown in FIG. 13, when the third drive signal COM3 is applied to the piezoelectric actuator 300 corresponding to the nozzle 21b where a relatively large asymmetric meniscus Mb is formed, the fourth expansion waveform element b11 and the second expansion potential sustain waveform element b12 transform the asymmetric meniscus Mb into a symmetric meniscus Nb.

[0087] The flow for selecting the first drive signal COM1, the second drive signal COM2, and the third drive signal COM3 described above in accordance with the degree of peeling of the water-repellent film will be described with reference to FIG.

[0088] First, the control processing unit 214 supplies the first drive signal COM1, which is a normal drive signal, to the piezoelectric actuator 300 and prints a test pattern (step S1). Next, the control processing unit 214 detects whether there is any flight curvature (step S2). The detection of flight curvature is performed in the same manner as described in the first embodiment.

[0089] If no deflection of ink flight is detected for any of the multiple nozzles 21 (step S2: No), the first drive signal COM1 is applied to the subsequent printing as an appropriate drive signal to be applied to all piezoelectric actuators 300 (step S8).

[0090] If flight curvature is detected for one or more nozzles 21 out of the multiple nozzles 21 (step S2: Yes), the second drive signal COM2, which is the first flight curvature suppression drive signal, is supplied to the piezoelectric actuator 300, and a test pattern is printed (step S3). Next, the control processing unit 214 detects whether flight curvature is present (step S4).

[0091] If no deflection of the ink jet is detected for any of the multiple nozzles 21 (step S4: No), the second drive signal COM2 used in step S3 is applied to subsequent printing as the appropriate drive signal to be applied to all piezoelectric actuators 300 (step S8).

[0092] If flight curvature is detected for one or more nozzles 21 out of the multiple nozzles 21 (step S4: Yes), the third drive signal COM3, which is a second flight curvature suppression drive signal, is supplied to the piezoelectric actuator 300, and a test pattern is printed (step S5). Next, the control processing unit 214 detects whether flight curvature is present (step S6).

[0093] If no deflection of the ink jet is detected for any of the multiple nozzles 21 (step S6: No), the third drive signal COM3 used in step S5 is applied to the subsequent printing as the appropriate drive signal to be applied to all piezoelectric actuators 300 (step S8).

[0094] If flight curvature is detected for one or more nozzles 21 out of the multiple nozzles 21 (step S6: Yes), maintenance other than supplying a flight curvature suppression drive signal is performed (step S7). Such maintenance may include replacing the liquid ejection head H. Another example is to register the nozzle where flight curvature has occurred as an ejection-prohibited nozzle. Furthermore, the user of the liquid ejection device 1 may be allowed to manually select the drive signal to be used.

[0095] In the above-described flow, if even one nozzle 21 in which flight curvature has occurred is detected, any one of the first drive signal COM1, the second drive signal COM2, and the third drive signal COM3 is supplied to all of the piezoelectric actuators 300. However, this is not a limitation. For example, the above-described flow may be applied to each of multiple nozzles 21. Specifically, flight curvature may be detected for each nozzle 21, and depending on the presence or absence and degree of flight curvature, any one of the first drive signal COM1, the second drive signal COM2, and the third drive signal COM3 may be applied to printing for each nozzle 21 after flight curvature has been detected.

[0096] In the above flow, the second drive signal COM2, which is the first flight curve suppression drive signal with a weaker force that pulls the meniscus toward the -Z direction, which is the back side of the nozzle 21, is used to detect flight curve (steps S3 to S4), and then the third drive signal COM3, which is the second flight curve suppression drive signal with a stronger force that pulls the meniscus toward the -Z direction, is used to detect flight curve (steps S5 to S6).Of course, this order is not limited to this, and the signals may be applied in order from strongest to weakest.

[0097] Furthermore, instead of detecting the presence or absence of flight curve, the degree of flight curve may be detected, and the flight curve suppression drive signal to be applied may be selected based on that degree. For example, the degree of flight curve may be detected by using multiple thresholds for comparing test image data with reference image data. If the degree of flight curve is determined to be true, small, or large, if the distance between the position of a dot in the test image data and the position of a dot in the reference image data is less than a first threshold, flight curve is determined to be absent; if the distance is equal to or greater than the first threshold but less than a second threshold, flight curve is determined to be small; and if the distance is equal to or greater than the second threshold, flight curve is determined to be large.

[0098] Then, if no flight curvature has occurred for any of the nozzles 21, the control processing unit 214 applies the first drive signal COM1 to the piezoelectric actuator 300 for all of the nozzles 21 in the subsequent printing. Furthermore, if even a small flight curvature has occurred for any of the nozzles 21, the control processing unit 214 applies the second drive signal COM2 to the piezoelectric actuator 300 for all of the nozzles 21 in the subsequent printing. Furthermore, if even a large flight curvature has occurred for any of the nozzles 21, the control processing unit 214 applies the third drive signal COM3 to the piezoelectric actuator 300 for all of the nozzles 21 in the subsequent printing. Of course, rather than applying the same signal to all of the nozzles 21, it is also possible to apply one of the first drive signal COM1, the second drive signal COM2, or the third drive signal COM3 to each nozzle 21 individually depending on the degree of flight curvature for that nozzle 21 in the subsequent printing.

[0099] The liquid ejection device 1 according to this embodiment uses a flight curve suppression drive signal that includes a first flight curve suppression drive signal and a second flight curve suppression drive signal. In this manner, multiple flight curve suppression drive signals can be selected depending on the degree of flight curve. This allows an appropriate flight curve suppression drive signal to be applied to the piezoelectric actuator 300 depending on the degree of flight curve of the nozzle 21, thereby more reliably suppressing flight curve. Note that, although this embodiment uses two flight curve suppression drive signals, the first flight curve suppression drive signal and the second flight curve suppression drive signal, there is no particular limitation on the number of flight curve suppression drive signals.

[0100] (Embodiment 3) The liquid ejecting device 1 of this embodiment uses the same first drive signal COM1 as in the first embodiment as the normal drive signal, and uses the fourth drive signal COM4 as the flight curve suppression drive signal. Although not specifically shown, the drive signal generating unit 216 further includes a fourth drive signal generating unit that is fourth drive signal generating means capable of generating the fourth drive signal COM4.

[0101] 15 shows a fourth drive signal COM4, which is an example of a flight curve suppression drive signal. The fourth drive signal COM4 generated by the fourth drive signal generating unit is a signal that has a fourth ejection pulse DP4 within one unit period T, which drives the piezoelectric actuator 300 to eject ink droplets from the nozzle 21, and is repeatedly generated every unit period T.

[0102] The fourth ejection pulse DP4 of the fourth drive signal COM4 includes a contraction waveform element c1 whose potential changes from the reference potential to a seventh potential so as to contract the volume of the pressure chamber 12, a fifth expansion waveform element c3 whose potential changes from the seventh potential to the fourth potential so as to expand the volume of the pressure chamber 12, and a fourth ejection waveform element c5 whose potential changes from the fourth potential to the fifth potential so as to contract the volume of the pressure chamber 12 and eject a droplet from the nozzle 21. Furthermore, the fourth ejection pulse DP4 includes a contraction maintaining waveform element c2 that maintains the volume of the pressure chamber 12 contracted by the contraction waveform element c1 for a certain period of time, an expansion maintaining waveform element c4 that maintains the fourth potential, a contraction maintaining waveform element c6 that maintains the volume of the pressure chamber 12 contracted by the fourth ejection waveform element c5 for a certain period of time, and a vibration damping element c7 that returns the pressure chamber 12 to the reference volume at the reference potential from the contracted state at the fifth potential and damps residual vibration of the liquid in the pressure chamber 12.

[0103] 16 is a cross-sectional view of the vicinity of the nozzle when a droplet is ejected. Using this figure, it will be explained how supplying the fourth ejection pulse DP4 to the piezoelectric actuator 300 prevents the droplet from flying in a curved direction.

[0104] A water-repellent film 25 is formed on the +Z direction surface of the nozzle plate 20, and due to partial peeling or excessive formation of the water-repellent film 25, an asymmetric meniscus M1 is formed with a portion protruding toward the +Z direction.

[0105] A fourth drive signal COM4 is applied to the piezoelectric actuator 300 corresponding to such a nozzle 21. First, the contraction waveform element c1 causes the piezoelectric actuator 300 to deform in a direction that contracts the volume of the pressure chamber 12. Then, the contracted state of the pressure chamber 12 is maintained by the contraction maintaining waveform element c2.

[0106] Next, the fifth expansion waveform element c3 causes the piezoelectric actuator 300 to deform in a direction that expands the volume of the pressure chamber 12, and the expansion maintaining waveform element c4 maintains the expanded state of the pressure chamber 12.

[0107] The contraction waveform element c1 and the contraction maintaining waveform element c2 cause the meniscus M2 to protrude in the +Z direction beyond the opening of the nozzle 21, forcing the entire inner surface of the nozzle 21 to be wetted. When the volume of the pressure chamber 12 expands in this state due to the fifth expansion waveform element c3, the shape of the meniscus M2 is not significantly distorted and it is drawn back into the nozzle 21 while maintaining a substantially symmetrical state. In other words, at the start of the fourth ejection waveform element c5, the meniscus M3 drawn back into the nozzle 21 also maintains its symmetrical shape.

[0108] Next, the fourth ejection waveform element c5 is supplied, causing the pressure chamber 12 to rapidly contract from the expanded volume to a contracted volume corresponding to the fifth potential. As described above, the entire inner surface of the nozzle 21 is forcibly wetted with ink, so similar to the examples of Figures 9 and 10, the pressure chamber 12 is contracted and droplets are ejected with the meniscus M3 inside the nozzle 21 maintained symmetrically, making it possible to prevent the droplets from flying in a curved manner.

[0109] As in the first and second embodiments, when a flight curve is detected in the nozzle 21, the control processing unit 214 applies the fourth drive signal COM4 to the piezoelectric actuator 300 in printing after the flight curve detection process.

[0110] As described above, the liquid ejection device 1 of this embodiment uses the fourth drive signal COM4 as the flight curve suppression drive signal. Even if the wetting is uneven due to a portion of the water-repellent film 25 peeling off or an excess portion being applied to the inner surface of the nozzle 21, applying the fourth drive signal COM4 can forcibly wet the entire inner surface of the nozzle 21 uniformly. As a result, it is possible to eject droplets with a symmetrical meniscus shape regardless of the state of the water-repellent film 25. This makes it possible to suppress flight curves even when droplets are ejected from a nozzle 21 where a portion of the water-repellent film 25 peels off or is excessive, which may cause flight curves, and to suppress deterioration of print quality.

[0111] (Other embodiments) Although one embodiment of the present invention has been described above, the basic configuration of the present invention is not limited to the above.

[0112] In the above-described embodiments, the case where deflection of ink droplets can occur due to the peeling off of a portion of the water-repellent film 25 or the formation of an excessive amount of the water-repellent film 25 has been described, but the cause is not limited to these. For example, even in a case where a foreign object adheres near the opening of the nozzle 21 and the foreign object causes the meniscus to become asymmetric, the deflection of ink droplets can be suppressed by applying the deflection suppression signal.

[0113] Furthermore, the first drive signal COM1 is a signal that includes one first ejection pulse DP1 per unit period T and repeats this unit period T, and the second drive signal COM2 is a signal that includes one second ejection pulse DP2 per unit period T and repeats this unit period T, but the drive signals are not limited to these, and each of the first drive signal COM1 and the second drive signal COM2 may include a plurality of different ejection pulses per unit period T. Such drive signals are used when ejecting droplets of different amounts according to the gradation of pixel data, but as they are well known, detailed explanation will be omitted.

[0114] For example, the first drive signal COM1 is configured to include, in a unit period, multiple ejection pulses that have the same shape as the first ejection pulse DP1 as shown in embodiment 1 but have different first and second potentials. The second drive signal COM2 is configured to include, in a unit period, multiple ejection pulses that have the same shape as the second ejection pulse DP2 as shown in embodiment 1 but have different third, fourth, and fifth potentials.

[0115] If no deflection is detected, ejection pulses selected from among the ejection pulses included in the first drive signal COM1 according to the gradation of the pixel data are applied. On the other hand, if deflection is detected, ejection pulses selected from among the ejection pulses included in the second drive signal COM2 according to the gradation of the pixel data are applied. Even when such drive signals are used, deflection can be suppressed.

[0116] In the above-described embodiment 1, a drive signal is not supplied to nozzles 21 that do not eject droplets, but this is not particularly limited to this, and a drive signal for micro-vibration may be supplied to perform micro-vibration to vibrate the meniscus of nozzle 21 to the extent that droplets are not ejected.

[0117] In the first embodiment described above, the flight deflection detection unit detects flight deflection by printing a test pattern on the medium S, scanning the printed image with a scanner to form test image data, and comparing the test image data with reference image data. However, this is not particularly limited. For example, the presence or absence of flight deflection may be detected by capturing an image of the droplet from when it is ejected from the nozzle 21 until it lands on the medium S and comparing the trajectory of the droplet with a reference trajectory. Alternatively, the flight deflection detection unit may capture an image of the nozzle 21 and use image processing to detect whether a portion of the water-repellent film 25 has peeled off or is excessively formed, or whether a foreign object is present near the nozzle 21, and determine that flight deflection has occurred based on the detection of these factors.

[0118] In the above-described first embodiment, a thin-film piezoelectric actuator is used as the pressure generating means for generating a pressure change in the pressure chamber 12, but the present invention is not limited to this, and other types of piezoelectric actuators can be used, such as thick-film piezoelectric actuators formed by methods such as attaching green sheets, or longitudinal vibration piezoelectric actuators in which piezoelectric material and electrode-forming material are alternately laminated to expand and contract in the axial direction. Furthermore, the pressure generating means can be a so-called electrostatic actuator, which generates static electricity between a vibration plate and an electrode, deforms the vibration plate by electrostatic force, and ejects droplets from the nozzle opening.

[0119] In the first embodiment described above, the liquid ejection device 1 includes the scanner 9, but the present invention is not limited to this configuration. The scanner 9 may be separate from the liquid ejection device 1. In this case, it is sufficient that the test image data and reference image data formed by the scanner 9 can be transmitted to the control unit 3 using removable media or wireless or wired communication means.

[0120] Furthermore, although the control unit 3 included in the liquid ejection device 1 detects flight curvature, the present invention is not limited to this. For example, an external device such as a host computer may store test image data and reference image data, detect flight curvature based on these, and transmit the detection results to the control unit 3 via the external I / F 211. In this case, the external device corresponds to the flight curvature detection unit.

[0121] Furthermore, in the above-described liquid ejection device 1, an example was given in which the liquid ejection head H is mounted on a holder 6 and moves in the Y-axis direction, which is the main scanning direction, but this is not particularly limited to this, and the present invention can also be applied to, for example, a so-called line-type liquid ejection device in which the liquid ejection head H is fixed and printing is performed simply by moving a medium S, such as paper, in the X-axis direction.

[0122] Furthermore, the present invention is broadly intended for liquid jet heads in general, and can be applied to, for example, recording heads such as various ink jet recording heads used in image recording devices such as printers, color material jetting heads used in manufacturing color filters for liquid crystal displays and the like, electrode material jetting heads used in forming electrodes for organic EL displays, FEDs (field emission displays), and the like, and bioorganic material jetting heads used in manufacturing biochips.

[0123] (Addendum) From the above-described exemplary embodiments, the following configurations can be understood, for example.

[0124] A preferred embodiment of a liquid ejection device according to aspect 1 includes a liquid ejection head including a nozzle for ejecting droplets, a pressure chamber communicating with the nozzle, and a drive element driven to vary the pressure of the liquid in the pressure chamber in response to a supplied drive signal; and a flight curvature detection unit that detects the occurrence of flight curvature of droplets ejected from the nozzle. The drive signal includes a flight curvature suppression drive signal that is supplied to the drive element when the flight curvature detection unit detects the occurrence of flight curvature of droplets, and a normal drive signal that is supplied to the drive element when the flight curvature detection unit does not detect the occurrence of flight curvature of droplets. As a result, the normal drive signal is supplied to the drive element corresponding to a nozzle where flight curvature is not occurring. On the other hand, the flight curvature suppression drive signal is supplied to the drive element corresponding to a nozzle where flight curvature has occurred. In this way, a drive signal is selected according to the flight curvature of each nozzle when ejecting droplets, thereby preventing flight curvature.

[0125] In Aspect 2, which is a specific example of Aspect 1, the normal drive signal includes a first expansion waveform element that changes potential from a reference potential to a first potential to expand the volume of the pressure chamber, and a first ejection waveform element that changes potential from the first potential to a second potential to contract the volume of the pressure chamber and eject a droplet from the nozzle, and the flight curvature suppression drive signal includes a second expansion waveform element that changes potential from the reference potential to a third potential between the reference potential and the first potential to expand the volume of the pressure chamber, an expansion potential maintaining waveform element that maintains the third potential, a third expansion waveform element that changes potential from the third potential to a fourth potential to further expand the volume of the pressure chamber, and a second ejection waveform element that changes potential from the fourth potential to a fifth potential to contract the volume of the pressure chamber and eject a droplet from the nozzle. Because the flight curvature suppression drive signal includes the second expansion waveform element and the expansion potential maintaining waveform element, the shape of the meniscus can be made symmetrical during the period of the expansion waveform maintaining element. Furthermore, since the liquid is ejected by the second ejection waveform element in a state where the shape of the meniscus is made symmetrical within the nozzle, it is possible to suppress deflection of the ejected liquid.

[0126] In Aspect 3, which is a specific example of Aspect 2, the period of the second expansion waveform element is equal to or less than one-fourth of the natural vibration period of the pressure chamber. This makes it possible to more reliably draw the meniscus of the liquid in the nozzle toward the back of the nozzle, thereby making the meniscus symmetrical.

[0127] In Aspect 4, which is a specific example of Aspect 2, the period of the expansion maintenance waveform element is 0.1 μsec or more, which makes it possible to more reliably form the meniscus into a symmetrical shape.

[0128] In Aspect 5, which is a specific example of Aspect 1, the normal drive signal includes a first expansion waveform element that changes potential from a reference potential to a first potential to expand the volume of the pressure chamber, and a first ejection waveform element that changes potential from the first potential to a second potential to contract the volume of the pressure chamber and eject a droplet from the nozzle; the flight curve suppression drive signal includes a first flight curve suppression drive signal and a second flight curve suppression signal; and the first flight curve suppression drive signal includes a second expansion waveform element that changes potential from the reference potential to a third potential between the reference potential and the first potential to expand the volume of the pressure chamber, a first expansion potential maintaining element that maintains the third potential, a third expansion waveform element that changes potential from the third potential to a fourth potential to further expand the volume of the pressure chamber, and a fourth ejection waveform element that changes potential from the first potential to a fourth potential to contract the volume of the pressure chamber and eject a droplet from the nozzle. and a second ejection waveform element that changes potential from a fourth potential to a fifth potential so as to eject a droplet from the nozzle, and the second flight curve suppression drive signal includes a fourth expansion waveform element that changes potential from a reference potential to a sixth potential between the reference potential and the first potential so as to expand the volume of the pressure chamber, a second expansion potential maintaining waveform element that maintains the sixth potential, a fifth expansion waveform element that changes potential from the sixth potential to the fourth potential so as to further expand the volume of the pressure chamber, and a third ejection waveform element that changes potential from the fourth potential to the fifth potential so as to contract the volume of the pressure chamber and eject a droplet from the nozzle, and the third potential is different from the third potential and the sixth potential, and when the flight curve detection unit detects that a droplet is being curved, the first flight curve suppression drive signal and the second flight curve suppression drive signal are selected depending on the degree of flight curve. This makes it possible to apply an appropriate flight curve drive signal to the drive element depending on the degree of flight curve of the nozzle, thereby more reliably suppressing flight curve.

[0129] In Aspect 6, which is a specific example of Aspect 1, the normal drive signal includes a first expansion waveform element that changes potential from a reference potential to a first potential to expand the volume of the pressure chamber, and a first ejection waveform element that changes potential from the first potential to a second potential to contract the volume of the pressure chamber and eject a droplet from the nozzle. The flight deflection suppression drive signal includes a contraction waveform element that changes potential from the reference potential to a seventh potential to contract the volume of the pressure chamber, a fifth expansion waveform element that changes potential from the seventh potential to a fourth potential to expand the volume of the pressure chamber, and a fourth ejection waveform element that changes potential from the fourth potential to the fifth potential to contract the volume of the pressure chamber and eject a droplet from the nozzle. This forcibly wets the entire inner surface of the nozzle uniformly, and then draws the liquid toward the back of the nozzle to form a meniscus. As a result, droplets can be ejected with a symmetrically shaped meniscus, thereby suppressing flight deflection.

[0130] In Aspect 7, which is a specific example of Aspect 1, the flight deflection detection unit detects the landing position on the medium of a droplet ejected by supplying the normal drive signal to the drive element, and determines that flight deflection has occurred if the amount of deviation from a reference position is equal to or greater than a threshold. This makes it possible to detect flight deflection based on the landing position on the medium and the reference position. Such detection can be achieved by image processing, making it possible to detect flight deflection in a simple manner.

[0131] A preferred embodiment of the liquid ejection method according to aspect 8 is a liquid ejection method for a liquid ejection device including a nozzle for ejecting droplets, a pressure chamber communicating with the nozzle, and a drive element driven to vary the pressure of the liquid in the pressure chamber in response to a supplied drive signal, the method detecting the occurrence of deflection of droplets ejected from the nozzle, and supplying a deflection suppression drive signal to the drive element when deflection of droplets is detected, and supplying a normal drive signal to the drive element when deflection of droplets is not detected. The normal drive signal is supplied to the drive element corresponding to the nozzle where deflection of droplets is not occurring, and the deflection suppression drive signal is supplied to the drive element corresponding to the nozzle where deflection of droplets is occurring. In this way, the drive signal is selected according to the deflection of each nozzle when ejecting droplets, thereby suppressing deflection of droplets. [Explanation of symbols]

[0132] a1...first expansion waveform element, a2...expansion maintenance waveform element, a3...first ejection waveform element, a4...contraction maintenance waveform element, a5...damping element, b1...second expansion waveform element, b2...expansion potential maintenance waveform element, b3...third expansion waveform element, b4...expansion maintenance waveform element, b5...second ejection waveform element, b6...contraction maintenance waveform element, b7...damping element, b11...fourth expansion waveform element, b12...second expansion potential maintenance waveform element, b13...fifth expansion waveform element, b14...expansion maintenance waveform element, b15...third ejection waveform element, b16...contraction maintenance waveform element, b17...damping element, c1...contraction waveform element, c2...contraction maintenance waveform element, c3...fifth expansion waveform element, c4...expansion maintenance waveform element, c5...third 4 ejection waveform element, c6...contraction maintenance waveform element, c7...damping element, COM1...first drive signal, COM2...second drive signal, COM3...third drive signal, COM4...fourth drive signal, DP1...first ejection pulse, DP2...second ejection pulse, DP3...third ejection pulse, DP4...fourth ejection pulse, H...liquid ejection head, 1...liquid ejection device, 3...controller, 9...scanner, 10...flow path forming substrate, 12...pressure chamber, 20...nozzle plate, 21...nozzle, 21a...nozzle, 21b...nozzle, 22...nozzle array, 23...ejection surface, 25...water-repellent film, 120...drive circuit, 214...control processing unit (flight curvature detection unit), 300...piezoelectric actuator (drive element)

Claims

1. a liquid ejection head including a nozzle for ejecting droplets, a pressure chamber communicating with the nozzle, and a drive element that is driven to vary the pressure of the liquid in the pressure chamber in response to a supplied drive signal; a flight deflection detection unit that detects occurrence of flight deflection of droplets ejected from the nozzle; Equipped with A liquid ejection device characterized in that the drive signal includes a flight curvature suppression drive signal that is supplied to the drive element when a flight curvature detection unit detects that flight curvature of the droplet has occurred, and a normal drive signal that is supplied to the drive element when the flight curvature detection unit does not detect the occurrence of flight curvature of the droplet.

2. the normal drive signal comprises a first expansion waveform element that changes in potential from a reference potential to a first potential so as to expand the volume of the pressure chamber, and a first ejection waveform element that changes in potential from the first potential to a second potential so as to contract the volume of the pressure chamber and eject a droplet from the nozzle, The flight curve suppression drive signal includes a second expansion waveform element that changes in potential from a reference potential to a third potential between the reference potential and the first potential so as to expand the volume of the pressure chamber, an expansion potential maintaining waveform element that maintains the third potential, a third expansion waveform element that changes in potential from the third potential to a fourth potential so as to further expand the volume of the pressure chamber, and a second ejection waveform element that changes in potential from the fourth potential to a fifth potential so as to contract the volume of the pressure chamber and eject a droplet from the nozzle. The liquid ejection apparatus according to claim 1 .

3. The period of the second expansion waveform element is equal to or less than one-fourth of the natural vibration period of the pressure chamber. The liquid ejection apparatus according to claim 2 .

4. The duration of the expansion maintenance waveform element is 0.1 μsec or greater. The liquid ejection apparatus according to claim 1 .

5. the normal drive signal comprises a first expansion waveform element that changes in potential from a reference potential to a first potential so as to expand the volume of the pressure chamber, and a first ejection waveform element that changes in potential from the first potential to a second potential so as to contract the volume of the pressure chamber and eject a droplet from the nozzle, the flight curve suppression drive signal includes a first flight curve suppression drive signal and a second flight curve suppression signal, the first flight curve suppression drive signal comprises a second expansion waveform element that changes in potential from a reference potential to a third potential between the reference potential and the first potential so as to expand the volume of the pressure chamber, a first expansion potential maintenance element that maintains the third potential, a third expansion waveform element that changes in potential from the third potential to a fourth potential so as to further expand the volume of the pressure chamber, and a second ejection waveform element that changes in potential from the fourth potential to a fifth potential so as to contract the volume of the pressure chamber and eject a droplet from the nozzle; the second flight curve suppression drive signal comprises a fourth expansion waveform element that changes in potential from a reference potential to a sixth potential between the reference potential and the first potential so as to expand the volume of the pressure chamber, a second expansion potential maintaining waveform element that maintains the sixth potential, a fifth expansion waveform element that changes in potential from the sixth potential to the fourth potential so as to further expand the volume of the pressure chamber, and a third ejection waveform element that changes in potential from the fourth potential to the fifth potential so as to contract the volume of the pressure chamber and eject a droplet from the nozzle; Unlike the third and sixth potentials, When the flight curve detection unit detects that the flight curve of the droplet is occurring, a first flight curve suppression drive signal or a second flight curve suppression drive signal is selected according to the flight curve. The liquid ejection apparatus according to claim 1 .

6. the normal drive signal comprises a first expansion waveform element that changes in potential from a reference potential to a first potential so as to expand the volume of the pressure chamber, and a first ejection waveform element that changes in potential from the first potential to a second potential so as to contract the volume of the pressure chamber and eject a droplet from the nozzle, The flight curve suppression drive signal includes a contraction waveform element whose potential changes from a reference potential to a seventh potential so as to contract the volume of the pressure chamber, a fifth expansion waveform element whose potential changes from the seventh potential to a fourth potential so as to expand the volume of the pressure chamber, and a fourth ejection waveform element whose potential changes from the fourth potential to a fifth potential so as to contract the volume of the pressure chamber and eject a droplet from the nozzle. The liquid ejection apparatus according to claim 1 .

7. The flight deflection detection unit detects the landing position on the medium of the droplets ejected by supplying the normal drive signal to the drive element, and determines that flight deflection has occurred if the amount of deviation from the reference position is equal to or greater than a threshold value. The liquid ejection apparatus according to claim 1 .

8. A liquid ejection method for a liquid ejection device including a nozzle that ejects droplets, a pressure chamber that communicates with the nozzle, and a drive element that is driven to vary the pressure of the liquid in the pressure chamber in response to a supplied drive signal, comprising: detecting the occurrence of deflection of flight of droplets ejected from the nozzle; When it is detected that the droplet flight curve has occurred, a flight curve suppression drive signal is supplied to the drive element, and when it is detected that the droplet flight curve has not occurred, a normal drive signal is supplied to the drive element. A liquid ejection method comprising:

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