LIQUID DISCHARGE HEAD AND RECORDING DEVICE

A liquid discharge head includes a discharge unit including a nozzle, a pressurizing chamber, and a pressurizer and dummy units including a dummy pressurizing chamber and a dummy pressurizer. The liquid discharge head includes a discharge region where the discharge units is disposed in a row and a dummy region where one or more dummy units are disposed adjacent to the discharge region on an extended line of the row of the discharge units. The discharge region includes a central region located at the center of the row and an end portion region located adjacent to the dummy region at the end portion of the row.

TECHNICAL FIELD

The disclosed embodiments relate to a liquid discharge head and a recording device.

BACKGROUND OF INVENTION

A known printing apparatus is an inkjet printer or an inkjet plotter using an inkjet recording method. A liquid discharge head for discharging a liquid is mounted in such a printing apparatus using an inkjet method.

Such a liquid discharge head introduces, for example, a liquid in a reservoir, into a pressure chamber, applies a drive signal for operating a piezoelectric element, and discharges the liquid in the pressure chamber from a nozzle. In the configuration, a proposed technique disposes a dummy pressure chamber that does not discharge liquid at an end portion of a region of discharging liquid and improves discharge performance.

CITATION LIST

Patent Literature

Patent Document 1: JP 2015-37863 A

Patent Document 2: JP 2018-65391 A

SUMMARY

A liquid discharge head according to an aspect of an embodiment includes a discharge unit and a dummy unit. The discharge unit includes a nozzle configured to discharge a droplet, a pressurizing chamber connected to the nozzle, and a pressurizer supplied with a drive signal and configured to deform the pressurizing chamber. The dummy unit includes a dummy pressurizing chamber and a dummy pressurizer supplied with a drive signal and configured to deform the dummy pressurizing chamber. The liquid discharge head includes a discharge region and a dummy region. The discharge region is a region where a plurality of the discharge units is disposed in one row. The dummy region is a region where one or more of the dummy units are disposed adjacent to the discharge region on an extended line of the row of the discharge units. The discharge region includes a central region located at the center of the row and an end portion region located adjacent to the dummy region at an end of the row. The end portion region is a region where the discharge unit having a size of a dot larger than the discharge unit located in the central region is located. The dot is formed on a recording medium by a droplet discharged by an identical drive signal when the dummy unit is not driven. In the liquid discharge head, a drive signal is supplied to the dummy unit while the drive signal is being supplied to the discharge unit located in the end portion region.

DESCRIPTION OF EMBODIMENTS

Embodiments of a liquid discharge head and a recording device disclosed in the present application will be described in detail below with reference to the accompanying drawings. The present invention is not limited by the following embodiment.

There is still room for improvement in discharge performance in a liquid discharge head in which a dummy pressure chamber that does not discharge liquid is disposed at an end portion of a region where liquid is discharged.

Therefore, provision of a liquid discharge head and a recording device that can improve discharge performance is expected.

Printer Configuration

First, with reference toFIG.1andFIG.2, a description will be given of an overview of a printer1serving as an example of a recording device according to an embodiment.FIG.1is a front view schematically illustrating an overall front of a printer1according to an embodiment.FIG.2is a plan view schematically illustrating an overall plan of a printer1according to an embodiment. The printer1according to the embodiment is, for example, a color inkjet printer.

As illustrated inFIG.1, the printer1includes a paper feed roller2, guide rollers3, an applicator4, a head case5, a plurality of transport rollers6, a plurality of frames7, a plurality of liquid discharge heads8, transport rollers9, a dryer10, transport rollers11, a sensor portion12, and a collection roller13. A transport roller6is an example of a transporter.

The printer1further includes a controller14configured to control each part of the printer1. The controller14controls the operation of the paper feed roller2, the guide rollers3, the applicator4, the head case5, the plurality of transport rollers6, the plurality of frames7, the plurality of liquid discharge heads8, the transport rollers9, the dryer10, the transport rollers11, the sensor portion12, and the collection roller13.

The printer1records an image and a character on a printing sheet P by causing droplets to impact on the printing sheet P. The printing sheet P is an example of a recording medium. The printing sheet P is rolled on the paper feed roller2prior to use. The printer1conveys the printing sheet P from the paper feed roller2to the inside of the head case5via the guide rollers3and the applicator4.

The applicator4uniformly applies a coating agent over the printing sheet P. This can perform surface treatment on the printing sheet P, improving the printing quality of the printer1.

The head case5houses the plurality of transport rollers6, the plurality of frames7, and the plurality of liquid discharge heads8. The inside of the head case5is formed with a space separated from the outside except for a part connected to the outside such as parts where the printing sheet P enters and exits.

As required, the controller14controls at least one of controllable factors of the internal space of the head case5, such as temperature, humidity, and air pressure. The transport rollers6convey the printing sheet P near the liquid discharge heads8inside the head case5.

The frames7are rectangular flat plates and are positioned above and close to the printing sheet P to be conveyed by the transport rollers6. As illustrated inFIG.2, the frames7are positioned having the longitudinal direction orthogonal to the conveyance direction of the printing sheet P. Inside the head case5, the plurality of (e.g., 4) frames7is located at predetermined intervals along the conveyance direction of the printing sheet P.

A liquid, for example, ink, is supplied to the liquid discharge heads8from a liquid tank (not illustrated). The liquid discharge heads8discharge the liquid supplied from the liquid tank.

The controller14controls the liquid discharge head8based on data such as an image and a character to discharge a liquid toward the printing sheet P. The distance between each liquid discharge head8and the printing sheet P is, for example, approximately 0.5 mm to 20 mm.

Each of the liquid discharge heads8is fixed to the frame7. The liquid discharge heads8are positioned having the longitudinal direction orthogonal to the conveyance direction of the printing sheet P.

That is, the printer1according to the embodiment is a so-called line printer in which the liquid discharge heads8are fixed inside the printer1. Note that the printer1according to the embodiment is not limited to a line printer and may also be a so-called serial printer.

The serial printer is a printer employing a method of alternately performing operations of recording while moving the liquid discharge heads8in a manner such as reciprocation in a direction intersecting (e.g., substantially orthogonal to) the conveyance direction of the printing sheet P, and conveying the printing sheet P.

As illustrated inFIG.2, a plurality of (e.g., five) liquid discharge heads8are fixed to one frame7.FIG.2illustrates an example in which three liquid discharge heads8are located on the forward side and two liquid discharge heads8are located on the rear side, in the conveyance direction of the printing sheet P. Further, the liquid discharge heads8are positioned without their centers overlapping in the conveyance direction of the printing sheet.

The plurality of liquid discharge heads8positioned in one frame7form a head group8A. Four head groups8A are positioned along the conveyance direction of the printing sheet P. The liquid discharge heads8belonging to the same head group8A are supplied with ink of the same color. As a result, the printer1can perform printing with four colors of ink using the four head groups8A.

The colors of the ink discharged from the respective head groups8A are, for example, magenta (M), yellow (Y), cyan (C), and black (K). The controller14can print a color image on the printing sheet P by controlling the respective head groups8A to discharge the plurality of colors of ink onto the printing sheet P.

Note that a surface treatment may be performed on the printing sheet P, by discharging a coating agent from the liquid discharge head8onto the printing sheet P.

The number of the liquid discharge heads8included in one head group8A or the number of the head groups8A mounted on the printer1can be appropriately changed according to a printing target and a printing condition. For example, if the color to be printed on the printing sheet P is a single color and the range of the printing can be covered by a single liquid discharge head8, only a single liquid discharge head8may be provided in the printer1.

The printing sheet P printed inside the head case5is conveyed to the outside of the head case5by the transport rollers9and passes through the inside of the dryer10. The dryer10dries the printing sheet P printed. The printing sheet P dried by the dryer10is transported by the transport rollers11and then collected by the collection roller13.

In the printer1, by drying the printing sheet P with the dryer10, it makes it possible to suppress bonding, or rubbing of an undried liquid, between the printing sheets P overlapped with each other and rolled at the collection roller13.

The sensor portion12includes a position sensor, a speed sensor, or a temperature sensor. Based on information from the sensor portion12, the controller14can determine the state of each part of the printer1and control each part of the printer1.

In the printer1described above, the printing sheet P is the printing target (i.e., the recording medium), but the printing target in the printer1is not limited to the printing sheet P, and a roll type fabric or the like may be the printing target.

The printer1may convey the printing sheet P put on a conveyor belt instead of directly conveying it. Using the conveyor belt allows the printer1to use a sheet of paper, a cut cloth, wood, a tile, or the like to be printed.

The printer1may discharge a liquid containing electrically conductive particles from the liquid discharge heads8, to print a wiring pattern or the like of an electronic device. The printer1may make chemicals by causing the liquid discharge head8to discharge a predetermined amount of a liquid chemical agent or a liquid containing a chemical agent toward a reaction vessel or the like.

The printer1may also include a cleaner for cleaning the liquid discharge heads8. The cleaner cleans the liquid discharge head8by, for example, a wiping process or a capping process.

The wiping process is, for example, a process of wiping a surface of a portion from which a liquid is discharged using a flexible wiper, thereby removing the liquid attached to the liquid discharge head8.

The capping process is performed as follows, for example. First, a cap is put to cover a portion to which liquid is discharged, for example, a second surface21b(seeFIG.6) of a channel member21(this is called capping). As a result, a substantially sealed space is formed between the second surface21band the cap.

The discharge of liquid is then repeated in such a hermetically sealed space. This makes it possible to remove a liquid, a foreign matter, or the like clogged in a discharge hole (nozzle)163(seeFIG.6) and having viscosity higher than that in a standard state.

Configuration of Liquid Discharge Head

Next, the configuration of the liquid discharge head8according to an embodiment will be described usingFIG.3.FIG.3is an exploded perspective view illustrating an overall configuration of the liquid discharge head8according to an embodiment.

The liquid discharge head8includes a head body20, a wiring portion30, a housing40, and a pair of heatsinks45. The head body20includes the channel member21, a piezoelectric actuator substrate22(seeFIG.4), and a reservoir23.

In the following description, for convenience, the direction in which the head body20is provided in the liquid discharge head8may be represented as “lower”, and the direction in which the housing40is provided with respect to the head body20may be represented as “upper”.

The channel member21of the head body20has a substantially flat plate shape, and includes a first surface21a(seeFIG.6), which is one main surface, and the second surface21b(seeFIG.6) located at an opposite side to the first surface21a.The first surface21aincludes an opening not illustrated, and liquid is supplied from the reservoir23to the inside of the channel member21through the opening.

The second surface21bhas a plurality of the discharge holes163(seeFIG.6) for discharging liquid onto the printing sheet P. The channel member21internally has a channel through which liquid flows from the first surface21ato the second surface21b.

The piezoelectric actuator substrate22is located on the first surface21aof the channel member21. The piezoelectric actuator substrate22includes a plurality of displacement elements170(seeFIG.6). The piezoelectric actuator substrate22is electrically connected to a flexible substrate31of the wiring portion30.

The reservoir23is located on the piezoelectric actuator substrate22. The reservoir23is provided with openings23aat both end portions in a main scanning direction, which is a direction orthogonal to a sub scanning direction, which is the conveyance direction of the printing sheet P, and parallel to the printing sheet P. The reservoir23includes a channel therein, and is supplied with a liquid from the outside through the opening23a.The reservoir23supplies liquid to the channel member21. The reservoir23stores liquid to be supplied to the channel member21.

The wiring portion30includes the flexible substrate31, a wiring board32, a plurality of driver ICs33, a pressing member34, and an elastic member35. The flexible substrate31transmits, to the head body20, a predetermined signal sent from the outside. As illustrated inFIG.3, the liquid discharge head8according to the embodiment may include two flexible substrates31.

The flexible substrate31has one end portion electrically connected to the piezoelectric actuator substrate22of the head body20. The other end portion of the flexible substrate31is drawn upward in a manner to be inserted through a slit23bof the reservoir23, and is electrically connected to the wiring board32. This enables the piezoelectric actuator substrate22of the head body20and the outside to be electrically connected.

The wiring board32is located above the head body20. The wiring board32distributes signals to the plurality of driver ICs33.

The plurality of driver ICs33is located on a main surface of one of the flexible substrates31. As illustrated inFIG.3, in the liquid discharge head8according to an embodiment, two driver ICs33are provided on each flexible substrate31, but the number of the driver ICs33provided on each flexible substrate31is not limited to two.

The driver IC33drives the piezoelectric actuator substrate22of the head body20based on a drive signal sent from the controller14(seeFIG.1). With this configuration, the driver IC33drives the liquid discharge head8.

The pressing member34has a substantially U shape in cross-sectional view, and presses the driver IC33on the flexible substrate31toward the heatsink45from the inside. As a result, in the embodiment, the heat generated when the driver IC33is driven can be efficiently radiated to the outer heatsink45.

The elastic member35is disposed in a manner to be in contact with an outer wall of a pressing portion not illustrated in the pressing member34. By providing such an elastic member35, it is possible to reduce the likelihood of the pressing member34causing breakage of the flexible substrate31when the pressing member34presses the driver ICs33.

The elastic member35is made of, for example, double-sided foam tape or the like. For example, by using a non-silicon-based thermal conductive sheet as the elastic member35, it is possible to improve the heat radiating properties of the driver IC33. Note that the elastic member35does not necessarily have to be provided.

The housing40is disposed on the head body20in a manner to cover the wiring portion30. This enables the wiring portion30to be sealed with the housing40. The housing40is made of, for example, resin or metal.

The housing40has a box shape elongated in the main scanning direction, and includes a first opening40aand a second opening40bat a pair of side surfaces opposed along the main scanning direction, respectively. The housing40includes a third opening40cat a lower surface, and a fourth opening40dat an upper surface.

One of the heatsinks45is disposed in the first opening40ato close the first opening40a,and the other of the heatsinks45is disposed in the second opening40bto close the second opening40b.

The heatsink45is provided to extend in the main scanning direction, and is made of metal, alloy, or the like having high heat radiating properties. The heatsink45is provided to be in contact with the driver IC33, and radiates heat generated in the driver IC33.

The pair of heatsinks45is fixed to the housing40by screws not illustrated. Therefore, the housing40to which the heatsink45is fixed has a box shape in which the first opening40aand the second opening40bare closed and the third opening40cand the fourth opening40dare opened.

The third opening40cis positioned to oppose the reservoir23. The flexible substrate31and the pressing member34are inserted into the third opening40c.

The fourth opening40dis provided in order to insert a connector (not illustrated) provided on the wiring board32. When a space between the connector and the fourth opening40dis sealed with resin or the like, liquid, dust, or the like is less likely to enter the housing40.

The housing40includes heat insulating portions40e.The heat insulating portions40eare respectively provided in a manner to be adjacent to the first opening40aand the second opening40b,and are provided in a manner to protrude outward from side surfaces of the housing40along the main scanning direction.

The heat insulating portions40eare formed in a manner to extend in the main scanning direction. That is, the heat insulating portions40eare positioned between the heatsinks45and the head body20. By providing the heat insulating portions40ein the housing40as described above, heat generated by the driver IC33is less likely to be transferred to the head body20via the heatsinks45.

Note thatFIG.3illustrates an example of the configuration of the liquid discharge head8, which may further include a member other than the members illustrated inFIG.3.

Configuration of Head Body

Next, the configuration of the head body20according to the embodiment will be described with reference toFIGS.4to7.FIG.4is a plan view illustrating the configuration of a main part of the liquid discharge head according to an embodiment.FIG.5is an enlarged view of a region V illustrated inFIG.4.

As described above, the head body20includes the channel member21and the piezoelectric actuator substrate22. The head body20includes a discharge region24and dummy regions25(25aand25b) adjacent to the discharge region24. A plurality of discharge units26is located in the discharge region24. A plurality of dummy units26ais located in the dummy region25a,and a plurality of dummy units26bis located in the dummy region25b. The dummy unit26aand the dummy unit26bhave the same structure.

As illustrated inFIG.5, a plurality of pressurizing chambers162is arrayed in the discharge region24. In the dummy region25a,a plurality of dummy pressurizing chambers162ais arrayed. The pressurizing chamber162constitutes a part of the discharge unit26(seeFIG.6). The dummy pressurizing chambers162aconstitute a part of the dummy unit26a(seeFIG.7).

FIG.6is a cross-sectional view taken along line VI-VI illustrated inFIG.5. As illustrated inFIG.6, the channel member21has a layered structure layering a plurality of plates. In these plates, a cavity plate21A, a base plate21B, an aperture plate21C, a supply plate21D, manifold plates21E,21F, and21G, a cover plate21H, and a nozzle plate211are positioned in this order from the first surface21aside of the channel member21.

A large number of holes are formed in the plates constituting the channel member21. The thickness of each plate is about10um to300um. This can increase the accuracy of forming the hole. The plates are layered in alignment such that these holes communicate with one another to constitute an individual channel164and a supply manifold161.

In the channel member21, the individual channel164connects between the supply manifold161and the discharge hole163. The supply manifold161is located on the second surface21bside inside the channel member21, and the discharge hole163is located on the second surface21bof the channel member21.

The individual channel164includes the pressurizing chamber162and an individual supply channel165. The pressurizing chamber162is located on the first surface21aof the channel member21, and the individual supply channel165is a channel connecting the supply manifold161and the pressurizing chamber162.

The individual supply channel165includes an aperture166having a narrower width than other parts. Since the aperture166is narrower than the other parts of the individual supply channel165, the channel resistance is high. As described above, when the channel resistance of the aperture166is high, the pressure generated in the pressurizing chamber162hardly escapes to the supply manifold161.

The piezoelectric actuator substrate22includes piezoelectric ceramic layers22A and22B, a common electrode171, an individual electrode172, a connection electrode175, a dummy connection electrode176, and a surface electrode (not illustrated).

In the piezoelectric actuator substrate22, the piezoelectric ceramic layer22B, the common electrode171, the piezoelectric ceramic layer22A, and the individual electrode172are laminated in this order.

The piezoelectric ceramic layers22A and22B each have a thickness of about 20 μm. Both layers of the piezoelectric ceramic layers22A and22B extend across the plurality of pressurizing chambers162. For the piezoelectric ceramic layers22A and22B, a lead zirconate titanate (PZT)-based ceramic material having ferroelectricity can be used.

The common electrode171is formed over substantially the entire surface in the plane direction in a region between the piezoelectric ceramic layer22A and the piezoelectric ceramic layer22B. That is, the common electrode171overlaps all the pressurizing chambers162in the region opposed to the piezoelectric actuator substrate22. The common electrode171has a thickness of about 2 μm. For the common electrode171, a metal material such as an Ag-Pd-based metal material can be used.

The individual electrode172includes an individual electrode body173and an extraction electrode174. The individual electrode body173is located in a region opposed to the pressurizing chamber162on the piezoelectric ceramic layer22B. The individual electrode body173is slightly smaller than the pressurizing chamber162and has a shape substantially similar to that of the pressurizing chamber162.

The extraction electrode174is extracted from the individual electrode body173. The connection electrode175is located at a part at one end of the extraction electrode174, the part extracted to the outside of the region opposed to the pressurizing chamber162. For the individual electrode172, for example, a metal material such as an Au-based metal material can be used.

The connection electrode175is located on the extraction electrode174and has a convex shape with a thickness of about15um. The connection electrode175is electrically joined to an electrode provided on the flexible substrate31(seeFIG.3). For the connection electrode175, for example, silver-palladium containing glass frit can be used.

The dummy connection electrode176is located on the piezoelectric ceramic layer22A so as not to overlap with various electrodes such as the individual electrode172. The dummy connection electrode176connects the piezoelectric actuator substrate22and the flexible substrate31to increase connection strength.

The dummy connection electrode176uniformizes distribution of contact positions between the piezoelectric actuator substrate22and the piezoelectric actuator substrate22, and stabilizes electrical connection. The dummy connection electrode176is preferably formed of a material and by a process equivalent to that of the connection electrode175.

The surface electrode is located on the piezoelectric ceramic layer22A while avoiding the individual electrode172. The surface electrode is connected to the common electrode171via a via hole formed in the piezoelectric ceramic layer22A. Therefore, the surface electrode is grounded and held at the ground potential. The surface electrode is preferably formed of a material and by a process equivalent to that of the individual electrode172.

The plurality of individual electrodes172is electrically connected individually to the controller14(seeFIG.1) each via the flexible substrate31and the wiring in order to individually control the potential. Then, when the individual electrode172and the common electrode171are set to different potentials and an electric field is applied in the polarization direction of the piezoelectric ceramic layer22A, a part applied with the electric field in the piezoelectric ceramic layer22A operates as an active part that is distorted by the piezoelectric effect.

That is, the portions opposed to the pressurizing chamber162in the individual electrode172, the piezoelectric ceramic layer22A, and the common electrode171in the piezoelectric actuator substrate22bconstitute the displacement element170. When the displacement element170undergoes unimorph deformation, the pressurizing chamber162is pressed, and liquid is discharged from the discharge hole163. That is, the displacement element170functions as a pressurizer that deforms the pressurizing chamber162. The discharge hole163is an example of a nozzle penetrating the nozzle plate21I.

FIG.7is a cross-sectional view taken along line VII-VII illustrated inFIG.5. As illustrated inFIG.7, the dummy unit26aincludes the dummy pressurizing chamber162aand a dummy pressurizer (displacement element170a). The dummy unit26ahas the same configuration as that of the discharge unit26except not including the discharge hole163, the individual channel164, the individual supply channel165, and an opening corresponding to the aperture166illustrated inFIG.6.

The piezoelectric actuator substrate22includes the piezoelectric ceramic layers22A and22B, a common electrode171a,an individual electrode172a,a connection electrode175a,a dummy connection electrode176a,and a surface electrode (not illustrated).

In the piezoelectric actuator substrate22, the piezoelectric ceramic layer22B, the common electrode171a,the piezoelectric ceramic layer22A, and the individual electrode172aare laminated in this order. Both layers of the piezoelectric ceramic layers22A and22B extend across the plurality of dummy pressurizing chambers162a.

The common electrode171ais formed over substantially the entire surface in the plane direction in a region between the piezoelectric ceramic layer22A and the piezoelectric ceramic layer22B. That is, the common electrode171aoverlaps all the dummy pressurizing chambers162ain the region opposed to the piezoelectric actuator substrate22. The common electrode171acan be formed in the same manner as the common electrode171.

The individual electrode172aincludes an individual electrode body173aand an extraction electrode174a.The individual electrode body173ais located in a region opposed to the dummy pressurizing chamber162aon the piezoelectric ceramic layer22B. The individual electrode body173ais slightly smaller than the dummy pressurizing chamber162aand has a shape substantially similar to that of the dummy pressurizing chamber162a.

The extraction electrode174ais extracted from the individual electrode body173a. The connection electrode175ais located at a part at one end of the extraction electrode174a, the part extracted to the outside of the region opposed to the dummy pressurizing chamber162a.The same metal material as that of the individual electrode172can be used for the individual electrode172a.

The connection electrode175ais located on the extraction electrode174a.The connection electrode175ais electrically joined to an electrode provided on the flexible substrate31(seeFIG.3). The connection electrode175acan have the material and shape similar to those of the connection electrode175, for example.

The dummy connection electrode176ais located on the piezoelectric ceramic layer22A so as not to overlap with various electrodes such as the individual electrode172a.The dummy connection electrode176aconnects the piezoelectric actuator substrate22and the flexible substrate31to increase connection strength.

The dummy connection electrode176auniformizes distribution of contact positions between the piezoelectric actuator substrate22and the piezoelectric actuator substrate22, and stabilizes electrical connection. The dummy connection electrode176ais preferably formed of a material and by a process equivalent to that of the connection electrode175a.

The surface electrode is located on the piezoelectric ceramic layer22A while avoiding the individual electrode172a.The surface electrode is connected to the common electrode171avia a via hole formed in the piezoelectric ceramic layer22A. Therefore, the surface electrode is grounded and held at the ground potential. The surface electrode is preferably formed of a material and by a process equivalent to that of the individual electrode172a.

The plurality of individual electrodes172ais electrically connected individually to the controller14(seeFIG.1) each via the flexible substrate31and the wiring in order to individually control the potential. Then, when the individual electrode172aand the common electrode171aare set to different potentials and an electric field is applied in the polarization direction of the piezoelectric ceramic layer22A, a part applied with the electric field in the piezoelectric ceramic layer22A operates as an active part that is distorted by the piezoelectric effect.

That is, the portions opposed to the dummy pressurizing chamber162ain the individual electrode172a,the piezoelectric ceramic layer22A, and the common electrode171ain the piezoelectric actuator substrate22constitute the displacement element170a. When the displacement element170aundergoes unimorph deformation, the dummy pressurizing chamber162ais pressed. That is, the displacement element170afunctions as a dummy pressurizer that deforms the dummy pressurizing chamber162a.The dummy units26aand26bhave no discharge hole, and liquid is not discharged to the outside even by pressurizing the dummy pressurizing chamber162a.That is, the dummy region25is a non-printing region where printing is not performed even when the drive signal is supplied. On the other hand, the discharge region24is a printable region where printing is performed in response to a supplied drive signal.

Drive Control of Dummy Unit

FIG.8is an explanatory diagram illustrating an array of a discharge unit and a dummy unit. In the example illustrated inFIG.8, among the plurality of discharge units26and the dummy units26aand26bincluded in the liquid discharge head8, the discharge units26and the dummy units26aand26barranged side by side in a row along the main scanning direction will be described.

As illustrated inFIG.8, the discharge unit26includes a discharge unit261positioned in one end portion region26d1and a discharge unit262positioned in the other end portion region26d2. The dummy units (26aand26b) respectively include the dummy unit26alocated in the dummy region25aadjacent to the discharge unit261and the dummy unit26blocated in the dummy region25badjacent to the discharge unit262.

FIG.9Ais a chart showing an example of a drive signal supplied to the discharge unit. A drive signal50shown inFIG.9Aincludes three pulses. When the drive signal50is supplied to the discharge unit26, time T from the start of the first pulse to the end of the last pulse included in the drive signal50is defined as “while the drive signal50is being supplied.”

Next, drive control of the dummy units26aand26bwill be described.FIG.9Bis an explanatory chart showing a fluctuation of a dot diameter when the dummy unit is not operated.FIG.9Cis an explanatory chart showing a fluctuation of a dot diameter when the dummy unit is operated.

As shown inFIG.9B, the dots of the droplets discharged from the discharge unit26located at both end parts of the discharge region24may be larger than the dots of the droplets discharged from the discharge unit26located at the central part of the discharge region24. Such phenomenon is considered to be caused by crosstalk between the plurality of discharge units26. That is, when the plurality of discharge units26are simultaneously driven, vibrations having different phases are transmitted from the other discharge units26, whereby the discharged droplet amount is reduced as compared with the case of driving one discharge unit26alone, and the dots formed by the discharged droplets are reduced. The other discharge units26are positioned on both sides of the discharge unit26positioned at the center of the row, whereas the other discharge units26are positioned only on one side of the discharge unit26positioned at the end of the row. Therefore, compared with the discharge unit26located at the center of the row, in the discharge unit26located at the end of the row, the influence of the crosstalk becomes small, the discharged droplet amount becomes large, and the dots formed by the discharged droplets become large. Note that this phenomenon is most noticeable in the discharge unit26that is the endmost in the row, but since the vibration propagates beyond the discharge unit26, a similar phenomenon may occur in the second or third discharge unit26from the end. Then, the difference in dot size is recognized as a density difference, and the quality of the printing target (recording medium) is deteriorated. In particular, when a part having a different density exists in a part of a region having a constant density, or when a part having a different density from the surroundings has a certain size or more, the part is easily recognized as a density unevenness.

In the liquid discharge head8according to the embodiment, as illustrated inFIG.8, the drive signal is supplied to the dummy unit26alocated in the dummy region25aadjacent to the discharge unit261while the drive signal is being supplied to the discharge unit261located at one end portion of the discharge region24. The drive signal is supplied to the dummy unit26blocated in the dummy region25badjacent to the discharge unit262while the drive signal is being supplied to the discharge unit262located at the other end portion of the discharge region24. As a result, as shown inFIG.9C, it is possible to reduce the difference between the size of the dots by the droplets discharged from the discharge unit26(261and262) positioned at both end parts of the discharge region24and the size of the other dots. Therefore, according to the liquid discharge head8of the embodiment, it is possible to reduce the density unevenness generated in the recording medium.

FIG.10Ais a chart showing an example of a drive signal supplied to the dummy unit, andFIG.10Bis a chart showing a variation of the drive signal supplied to the dummy unit.

As shown inFIG.10A, a drive signal52may be supplied to the dummy units (26aand26b) at the same timing as a drive signal51(namely, “first drive signal”) supplied to the discharge unit26located at the end portion of the discharge region24. That is, the drive signal52identical to the drive signal51supplied to the discharge unit26located in the end portion region26dmay be supplied to the dummy units (26aand26b) at the same timing as the drive signal51supplied to the discharge unit26located in the end portion region26d. This can enhance the effect of reducing the density unevenness. As shown inFIG.10B, as long as the drive signal52is supplied while the drive signal51is being supplied to the discharge unit26located at the end portion of the discharge region24, the timings at which the drive signals51and52are supplied need not be the same. Note that time T2from the start of the first pulse to the end of the last pulse included in the drive signal52may be the same as or different from time T1from the start of the first pulse to the end of the last pulse included in the drive signal51.

In the example illustrated inFIG.8, one discharge unit26exists in one end portion region of the discharge region24, but the present invention is not limited to this, and a plurality of the discharge units26may exist in one end portion region. The end portion region is a region located at an end of the row of the discharge units26, and is a region where the discharge unit26having the size of the dot larger than the discharge unit26located in the central region is located. The dot is formed on the recording medium by the droplets discharged by the identical drive signal when the dummy unit (26aor26b) located in the adjacent dummy region25(25aor25b) is not driven. When a difference of equal to or greater than 1% of the mean value of the size of the dots formed on the recording medium by the droplets discharged from the discharge unit26located in the central region exists between the two, it can be determined to “be larger compared to the discharge unit26located in the central region”. A region located at the center of the row of the discharge units26, the region where the discharge units26of 20% of the total number of the discharge units26in one row are located, can be defined as a central region.

As described above, the liquid discharge head8of the present embodiment includes the discharge unit26and the dummy units (26aand26b). The discharge unit26includes the nozzle (discharge hole163) for discharging droplets, the pressurizing chamber162connected to the nozzle (discharge hole163), and the pressurizer (displacement element170) that is supplied with a drive signal (namely, “first drive signal”) and deforms the pressurizing chamber162. The dummy units (26aand26b) include the dummy pressurizing chamber162aand the dummy pressurizer (displacement element170a) that is supplied with a drive signal (namely, “second drive signal”) and deforms the dummy pressurizing chamber162a.The liquid discharge head8includes the discharge region24and the dummy region25. The discharge region24is a region where the plurality of discharge units26is disposed in one row. The dummy region25is a region where one or more dummy units (26aand26b) are disposed adjacent to the discharge region24on the extended line of the row of the discharge units26. The discharge region24includes a central region26c(seeFIG.11A) located at the center of the row and the end portion region26dlocated adjacent to the dummy region25at the end portion of the row. The end portion region26dis a region where the discharge unit26having the size of the dot larger than the discharge unit26located in the central region26cis located. The dot is formed on the recording medium by the droplet discharged by the identical drive signal (namely, “first drive signal”) when the dummy units (26aand26b) are not driven. In the liquid discharge head8, a drive signal (namely, “second drive signal”) is supplied to the dummy units (26aand26b) while the drive signal (namely, “first drive signal”) is being supplied to the discharge unit26located in the end portion region26d.With such a configuration, it is possible to reduce generation of density unevenness caused by the difference in size of the dots formed on the recording medium by the droplets discharged from the discharge unit26.

In the liquid discharge head8of the present embodiment, the drive signal (namely, “second drive signal”) is supplied to the dummy units (26aand26b) while the drive signal (namely, “third drive signal”) is being supplied to the discharge units26(261and262) at the position closest to the respective dummy regions25(25aand25b). Such a configuration can reduce the difference between the size of the dot formed on the recording medium by the droplets discharged from the discharge units26(261and262) at the position closest to the dummy region25and the size of another dot, where the size of the dot formed on the recording medium by the droplet discharged by the identical drive signal tends to be the largest.

FIGS.11A to12Care explanatory diagrams illustrating examples of drive control of the dummy unit. In the example illustrated inFIG.11A, a drive signal (A) identical to the drive signal is supplied to dummy units26a1and26a2located in the dummy region25aadjacent to the end portion region26d1while the drive signal (A) is being supplied to the discharge unit261located in the end portion region26d1. A drive signal (B) identical to the drive signal is supplied to dummy units26b1and26b2located in the dummy region25badjacent to the end portion region26d2while the drive signal (B) is being supplied to the discharge unit262located in the end portion region26d2. That is, in the liquid discharge head8illustrated inFIG.11A, the drive signal (A) (namely, “second drive signal”) is supplied to the dummy units26a1and26a2at the closest and second closest positions to the end portion region26d1adjacent to the dummy region25awhile the drive signal (A) (namely, “third drive signal”) is being supplied to the discharge unit261at the position closest to the dummy region25a.The drive signal (B) (namely, “second drive signal”) is supplied to the dummy units26b1and26b2at the closest and second closest positions to the end portion region26d2adjacent to the dummy region25bwhile the drive signal (B) (namely, “third drive signal”) is being supplied to the discharge unit262at the position closest to the dummy region25b.This reduces the difference between the size of the dots due to the droplets discharged from the discharge units261and262having the highest possibility of having the largest dot and the size of other dots. Note that different drive signals may be supplied to the discharge unit261and the dummy units26a1and26a2, and different drive signals may be supplied to the discharge unit262and the dummy units26b1and26b2.

As illustrated inFIGS.11B and11C, the drive signal (A) identical to the drive signal may be supplied to only one of the dummy units26a1and26a2in the dummy region25aadjacent to the end portion region26d1while the drive signal (A) is being supplied to the discharge unit261located in the end portion region26d1located at one end of the discharge region24. The drive signal (B) identical to the drive signal may be supplied to only one of the dummy units26b1and26b2located in the dummy region25badjacent to the end portion region26d2while the drive signal (B) is being supplied to the discharge unit262located in the end portion region26d2located at the other end of the discharge region24.

That is, in the liquid discharge head8illustrated inFIG.11B, the drive signal (A) (namely, “second drive signal”) is supplied to the dummy unit26a2at the position second closest to the end portion region26d1adjacent to the dummy region25awhile the drive signal (A) (namely, “third drive signal”) is being supplied to the discharge unit261at the position closest to the dummy region25a.The drive signal (C) (namely, “second drive signal”) is supplied to the dummy unit26a1at the position closest to the end portion region26d1while a drive signal (C) (namely, “fourth drive signal”) is being supplied to a discharge unit263at the position second closest to the dummy region25a.Similarly, the drive signal (B) (namely, “second drive signal”) is supplied to the dummy unit26b2located second closest to the end portion region26d2adjacent to the dummy region25bwhile the drive signal (B) (namely, “third drive signal”) is being supplied to the discharge unit262located closest to the dummy region25b.The drive signal (D) (namely, “second drive signal”) is supplied to the dummy unit26b1at the position closest to the end portion region26d2while a drive signal (D) (namely, “fourth drive signal”) is being supplied to a discharge unit264at the position second closest to the dummy region25b.In such case, it is possible to reduce the difference between the size of the dots due to the droplets discharged from the discharge units261to264and the size of other dots. In each of the discharge units261and262located on the outermost side, vibrations propagating from both sides can be equalized. Note that different drive signals may be supplied to the discharge unit261and the dummy unit26a2, and different drive signals may be supplied to the discharge unit262and the dummy unit26b2. Different drive signals may be supplied to the discharge unit263and the dummy unit26a1, and different drive signals may be supplied to the discharge unit264and the dummy unit26b1.

In the liquid discharge head8illustrated inFIG.11C, the drive signal (A) is supplied to the dummy unit26a1at the position closest to the end portion region26d1adjacent to the dummy region25awhile the drive signal (A) is being supplied to the discharge unit261at the position closest to the dummy region25a.The drive signal (C) is supplied to the dummy unit26a2at the position second closest to the end portion region26d1while the drive signal (C) is being supplied to the discharge unit263at the position second closest to the dummy region25a.Similarly, the drive signal (B) is supplied to the dummy unit26b1at the position closest to the end portion region26d2adjacent to the dummy region25bwhile the drive signal (B) is being supplied to the discharge unit262located closest to the dummy region25b.The drive signal (D) is supplied to the dummy unit26b2at the position second closest to the end portion region26d2while the drive signal (D) is being supplied to the discharge unit264at the position second closest to the dummy region25b.In such case, it is possible to reduce also the difference between the size of the dots by the droplets discharged from the discharge units263and264and the size of other dots while preferentially reducing the difference between the size of the dots by the droplets discharged from the discharge units261and262and the size of other dots. Therefore, according to the liquid discharge head8of the embodiment, the discharge performance can be improved. Note that different drive signals may be supplied to the discharge unit261and the dummy unit26a1, and different drive signals may be supplied to the discharge unit262and the dummy unit26b1. Different drive signals may be supplied to the discharge unit263and the dummy unit26a2, and different drive signals may be supplied to the discharge unit264and the dummy unit26b2.

FIGS.12A to12Cillustrate a case where the number of the discharge units26positioned in each end portion region26dis3.FIGS.12A and12Billustrate a case where the number of dummy units (26a(26a1to26a3) or26b(26b1to26b3)) located in the respective dummy regions25(25aand25b) is 3.

In the liquid discharge head8illustrated inFIG.12A, the drive signal (A) (namely, “second drive signal”) is supplied to the dummy unit26a3at the position third closest to the end portion region26d1adjacent to the dummy region25awhile the drive signal (A) (namely, “third drive signal”) is being supplied to the discharge unit261at the position closest to the dummy region25a.The drive signal (C) (namely, “second drive signal”) is supplied to the dummy unit26a2at the position second closest to the end portion region26d1while the drive signal (C) (namely, “fourth drive signal”) is being supplied to the discharge unit263at the position second closest to the dummy region25a.The drive signal (E) (namely, “second drive signal”) is supplied to the dummy unit26a1at the position closest to the end portion region26d1while a drive signal (E) (namely, “fifth drive signal”) is being supplied to a discharge unit265at the position third closest to the dummy region25a. Similarly, the drive signal (B) (namely, “second drive signal”) is supplied to the dummy unit26b3located third closest to the end portion region26d2adjacent to the dummy region25bwhile the drive signal (B) (namely, “third drive signal”) is being supplied to the discharge unit262located closest to the dummy region25b.The drive signal (D) (namely, “second drive signal”) is supplied to the dummy unit26b2at the position second closest to the end portion region26d2while the drive signal (D) (namely, “fourth drive signal”) is being supplied to the discharge unit264at the position second closest to the dummy region25b.The drive signal (E) (namely, “second drive signal”) is supplied to the dummy unit26b1at the position closest to the end portion region26d2while the drive signal (E) (namely, “fifth drive signal”) is being supplied to a discharge unit266at the position third closest to the dummy region25b. In such case, it is possible to reduce the difference between the size of the dots due to the droplets discharged from the discharge units261to266and the size of other dots. Note that different drive signals may be supplied to the discharge unit261and the dummy unit26a3, and different drive signals may be supplied to the discharge unit262and the dummy unit26b3. Different drive signals may be supplied to the discharge unit263and the dummy unit26a2, and different drive signals may be supplied to the discharge unit264and the dummy unit26b2. Different drive signals may be supplied to the discharge unit265and the dummy unit26a1, and different drive signals may be supplied to the discharge unit266and the dummy unit26b1.

In the liquid discharge head8illustrated inFIG.12B, the drive signal (A) (namely, “second drive signal”) is supplied to the dummy unit26a1at the position closest to the end portion region26d1adjacent to the dummy region25awhile the drive signal (A) (namely, “third drive signal”) is being supplied to the discharge unit261at the position closest to the dummy region25a.The drive signal (C) (namely, “second drive signal”) is supplied to the dummy unit26a2at the position second closest to the end portion region26d1while the drive signal (C) (namely, “fourth drive signal”) is being supplied to the discharge unit263at the position second closest to the dummy region25a.The drive signal (E) (namely, “second drive signal”) is supplied to the dummy unit26a3at the position third closest to the end portion region26d1while the drive signal (E) (namely, “fifth drive signal”) is being supplied to the discharge unit265at the position third closest to the dummy region25a.Similarly, the drive signal (B) (namely, “second drive signal”) is supplied to the dummy unit26b1at the position closest to the end portion region26d2adjacent to the dummy region25bwhile the drive signal (B) (namely, “third drive signal”) is being supplied to the discharge unit262located closest to the dummy region25b.The drive signal (D) (namely, “second drive signal”) is supplied to the dummy unit26b2at the position second closest to the end portion region26d2while the drive signal (D) (namely, “fourth drive signal”) is being supplied to the discharge unit264at the position second closest to the dummy region25b.The drive signal (E) (namely, “second drive signal”) is supplied to the dummy unit26b3at the position third closest to the end portion region26d2while the drive signal (E) (namely, “fifth drive signal”)is being supplied to the discharge unit266at the position third closest to the dummy region25b.In such case, it is possible to reduce also the difference between the size of the dots by the droplets discharged from the discharge units263to266and the size of other dots while preferentially reducing the difference between the size of the dots by the droplets discharged from the discharge units261and262and the size of other dots. Note that different drive signals may be supplied to the discharge unit261and the dummy unit26a1, and different drive signals may be supplied to the discharge unit262and the dummy unit26b1. Different drive signals may be supplied to the discharge unit263and the dummy unit26a2, and different drive signals may be supplied to the discharge unit264and the dummy unit26b2. Different drive signals may be supplied to the discharge unit265and the dummy unit26a3, and different drive signals may be supplied to the discharge unit266and the dummy unit26b3.

In the liquid discharge head8illustrated inFIG.12C, the drive signal (C) (namely, “second drive signal”) is supplied to the dummy unit26a1at the position closest to the end portion region26d1adjacent to the dummy region25awhile the drive signal (C) (namely, “fourth drive signal”) is being supplied to the discharge unit263at the position second closest to the dummy region25a.The drive signal (E) (namely, “second drive signal”) is supplied to the dummy unit26a2at the position second closest to the end portion region26d1while the drive signal (E) (namely, “fifth drive signal”) is being supplied to the discharge unit265at the position third closest to the dummy region25a.Similarly, the drive signal (D) (namely, “second drive signal”) is supplied to the dummy unit26b1at the position closest to the end portion region26d2adjacent to the dummy region25bwhile the drive signal (D) (namely, “fourth drive signal”) is being supplied to the discharge unit264at the position second closest to the dummy region25b.The drive signal (E) (namely, “second drive signal”) is supplied to the dummy unit26b2at the position second closest to the end portion region26d2while the drive signal (E) (namely, “fifth drive signal”) is being supplied to the discharge unit266at the position third closest to the dummy region25b.In such case, in each of the discharge units261and262located on the outermost side, the vibrations propagating from both sides can be substantially equalized, and therefore the difference between the size of the dots due to the droplets discharged from the discharge units261and262and the size of other dots can be reduced. Note that different drive signals may be supplied to the discharge unit263and the dummy unit26a1, and different drive signals may be supplied to the discharge unit264and the dummy unit26b1. Different drive signals may be supplied to the discharge unit265and the dummy unit26a2, and different drive signals may be supplied to the discharge unit266and the dummy unit26b2.

In each embodiment described above, the number of the dummy units26aand the number of the dummy units26bare the same, but may be different. The drive signal may be supplied to only one of the dummy unit26aand the dummy unit26b.For example, when the printer1includes the plurality of liquid discharge heads8, the drive signal may be supplied only to the dummy unit located in the dummy region25overlapping the discharge region24of another liquid discharge head8in the conveyance direction of the recording medium. In such a case, the power consumption can be reduced by not supplying the drive signal to the dummy unit in the dummy region25located at the end portion of the printing region where the density difference is inconspicuous. When the discharge region24of the liquid discharge head8includes a plurality of rows of the discharge units26, performing the drive control of the dummy units26aand26bdescribed above in at least one row can obtain an effect according to the number of rows of the dummy units26aand26bto be driven. For example, the drive control of the dummy units26aand26bdescribed above may be performed every other row. The largest effect can be obtained by performing the drive control of the dummy units26aand26bdescribed above in all the rows. In the embodiment described above, the discharge units263to266need not be located in the end portion region.

The drive control of the dummy units26aand26bdescribed above is merely an example and may be another aspect. That is, the drive signal is supplied to any one of the dummy units (26aor26b) located in the dummy region25adjacent to the end portion region26dwhile the drive signal is being supplied to any one of the discharge units26located in the end portion region26d,and thus the above-described effect (improvement in discharge performance) can be expected.

Although each embodiment of the present disclosure has been described above, the present disclosure is not limited to the embodiments described above, and various changes can be made without departing from the spirit of the present disclosure. For example, in the above-described embodiment, an example in which the channel member21includes the plurality of layered plates has been described, but the channel member21is not limited to the case of including the plurality of layered plates.

For example, the channel member21may be configured by forming the supply manifold161, the individual channel164, or the like by etching processing.

Further effects and variations can be easily derived by those skilled in the art. Thus, a wide variety of aspects of the present disclosure are not limited to the specific details and representative embodiments represented and described above. Accordingly, various changes are possible without departing from the spirit or scope of the general inventive concepts defined by the appended claims and their equivalents.