JP2011025632A - Liquid discharging element, liquid discharging head using the same, and recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid discharging element capable of stably feeding a liquid from a constriction to a liquid pressurizing chamber, a liquid discharging head using the liquid discharging element, and a recording apparatus using the liquid discharging head. <P>SOLUTION: In the liquid discharging element, a hole to be the liquid pressurizing chamber 10 and the constriction 12 connected each other is opened on a surface, and a pressurizing part 50 is laminated on a flow path member 4, equipped with a liquid discharging hole 8 connected to the liquid pressurizing chamber 10 and a liquid feeding flow path 6 connected to the constriction 12, so as to cover the hole. The depth of a part to be the constriction 12 of the hole is shallower than the depth of a part to be the liquid pressurizing chamber 10. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid discharge element used for a liquid discharge head such as an ink jet recording head, a liquid discharge head using the same, and a recording apparatus using the same.

  In recent years, printing apparatuses using inkjet recording methods such as inkjet printers and inkjet plotters are not only printers for general consumers, but also, for example, formation of electronic circuits, manufacture of color filters for liquid crystal displays, manufacture of organic EL displays It is also widely used for industrial applications.

  In such an ink jet printing apparatus, a liquid discharge head including a liquid discharge element for discharging a liquid is mounted as a print head. This type of print head includes a heater as a pressurizing unit in an ink flow path filled with ink, heats and boiles the ink with the heater, pressurizes the ink with bubbles generated in the ink flow path, A thermal system that ejects droplets from the ink ejection holes, and a part of the walls of the ink channel filled with ink is bent and displaced by a displacement element, and the ink in the ink channel is mechanically pressurized to eject ink. A piezoelectric method for discharging liquid droplets from holes is generally known.

  As a piezoelectric liquid discharge element, as shown in FIG. 9, a liquid discharge head 913 includes a manifold 905, a liquid supply channel 906 (including a squeezed inside 912) in order from the manifold 905, and a liquid pressurizing chamber 910. And a flat channel member 904 having an individual channel 932 connected to the liquid discharge hole 908 via the communication path 907, and an actuator having a plurality of displacement elements 950 provided so as to cover the liquid pressurizing chamber 910, respectively. A configuration in which the unit 921 is stacked is known (see, for example, Patent Document 1). In the liquid discharge head 913, by displacing the displacement element 950 of the actuator unit 921 provided so as to cover the liquid pressurization chamber 910, droplets are discharged from the respective liquid discharge holes 908 of the respective liquid pressurization chambers 910, Printing is possible at a resolution of 600 dpi in the main scanning direction.

  The flow path member 904 is formed by laminating metal plates 922 to 931. The piezoelectric actuator 921 includes a piezoelectric ceramic layer 921a, a common electrode 934, a piezoelectric ceramic layer 921b, and individual electrodes 935 in order from the flow path member 904 side. Laminated.

JP 2003-305852 A

  In the liquid ejection element as described in Patent Document 1, the displacement element is driven to reduce the volume of the liquid pressurizing chamber, thereby ejecting liquid droplets from the liquid ejection hole and driving the displacement element to move the liquid. By increasing the volume of the pressurizing chamber, the liquid is supplied from the manifold to the liquid pressurizing chamber. In order to prevent a part of the pressure applied when reducing the volume of the liquid pressurizing chamber from escaping to the manifold through the liquid supply channel, it is desirable that the squeezing inhibits the movement of the liquid. However, if the degree of inhibition is large, there is a problem that the liquid supply from the manifold becomes insufficient even if the volume of the liquid pressurizing chamber is increased.

  Accordingly, an object of the present invention is to provide a liquid discharge element capable of stably supplying a liquid from a squeeze to a liquid pressurizing chamber, a liquid discharge head using the same, and a recording apparatus.

  The liquid discharge element according to the present invention has a liquid discharge hole connected to the liquid pressurization chamber via a liquid channel, and a hole serving as a liquid pressurization chamber connected to each other. A liquid discharge element in which a pressure member is laminated so as to cover the hole on a flow path member provided with a liquid supply flow path connected to the squeezing, and the portion of the hole to be the squeezed The depth is shallower than the depth of the portion serving as the liquid pressurizing chamber.

  Further, a second depth that is shallower than a portion of the hole serving as the liquid pressurizing chamber as the liquid flow path connecting the liquid pressurizing chamber and the liquid discharge hole to the surface of the flow path member. It is preferable that the hole is open and the second pressure member is stacked so as to cover the second hole.

  The liquid discharge head according to the present invention includes a plurality of the liquid discharge elements, the liquid discharge holes of the liquid discharge elements are open on the same surface, and the squeezing of the liquid discharge elements in the flow path member. It is preferable to provide a manifold in which a plurality of are connected.

  The recording apparatus of the present invention includes the liquid discharge head, a transport unit that transports a recording medium to the liquid discharge head, and a control unit that controls driving of the liquid discharge head. And

  According to the liquid ejection element of the present invention, the surface of the liquid ejection chamber connected to the liquid pressurization chamber via the liquid flow path is formed on the surface so as to open as a liquid pressurization chamber connected to each other. A liquid discharge element in which a pressure member is laminated so as to cover the hole on a flow path member including a hole and a liquid supply flow path connected to the squeezing, and serves as the squeezing of the hole When the pressurization unit reduces the volume of the liquid pressurization chamber because the depth of the part is shallower than the depth of the part that becomes the liquid pressurization chamber, Reduces the cross-sectional area in the direction of flow from the liquid supply channel to the liquid pressurizing chamber, so that the pressure applied to the liquid in the liquid pressurizing chamber is less likely to escape via the liquid inside the squeeze, The pressurizing part increases the volume of the liquid pressurizing chamber. The pressurizing unit increases the cross-sectional area of the squeezed liquid in the direction in which the liquid flows from the liquid supply channel to the liquid pressurization chamber. Since the flow of liquid to the pressure chamber becomes smooth, the amount of liquid supply can be increased.

  Further, a second depth that is shallower than a portion of the hole serving as the liquid pressurizing chamber as the liquid flow path connecting the liquid pressurizing chamber and the liquid discharge hole to the surface of the flow path member. When the hole is open and the second pressurizing unit is stacked so as to cover the second hole, the pressurizing unit increases the volume of the liquid pressurizing chamber. The second pressurizing unit can reduce the cross-sectional area of the liquid flow path connecting the liquid pressurizing chamber and the liquid discharge hole in the direction in which the liquid flows from the liquid discharge hole to the liquid pressurization chamber. Since the liquid is less likely to flow from the liquid discharge hole to the liquid pressurizing chamber, the liquid is more easily supplied from the liquid supply channel to the liquid pressurizing chamber through the squeezing.

  The liquid discharge head according to the present invention includes a plurality of the liquid discharge elements, the liquid discharge holes of the liquid discharge elements are open on the same surface, and the squeezing of the liquid discharge elements in the flow path member. By providing a manifold in which a plurality of are connected, it is possible to discharge liquid over a wide area.

  In addition, according to the recording apparatus of the present invention, the recording apparatus includes the liquid discharge head, a transport unit that transports a recording medium to the liquid discharge head, and a control unit that controls driving of the liquid discharge head. Thus, a good image can be recorded.

1 is a schematic configuration diagram illustrating a printer that is an example of a recording apparatus of the present invention. FIG. 2 is a plan view showing a head body that constitutes the liquid ejection head of FIG. 1. FIG. 3 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. FIG. 3 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. (A) is sectional drawing of one liquid discharge element in FIG. 3, (b) is (a) top view. (A) is a top view of the other example of the liquid discharge element of this invention, (b) is (a) top view. It is a top view of the other example of the liquid discharge head of the present invention. (A) It is sectional drawing of the other example of the liquid discharge element of this invention, (b) is a top view, (c) is the other of this invention using the liquid discharge element of (a) and (b). It is a perspective view of the liquid discharge head. (A) is a longitudinal cross-sectional view of the conventional liquid discharge element.

  FIG. 1 is a schematic configuration diagram showing a color ink jet printer which is an example of a recording apparatus of the present invention. This color inkjet printer 1 (hereinafter referred to as printer 1) has four liquid ejection heads 2. These liquid discharge heads 2 are arranged along the conveyance direction of the recording paper P that is a recording medium, and are fixed to the printer 1. The liquid discharge head 2 has an elongated shape in a direction from the front to the back in FIG.

  In the printer 1, a paper feed unit 114, a transport unit 120, and a paper receiver 116 are sequentially provided along the transport path of the recording paper P. In addition, the printer 1 is provided with a control unit 100 for controlling the operation of each unit of the printer 1 such as the liquid discharge head 2 and the paper feeding unit 114.

  The paper feed unit 114 includes a paper storage case 115 that can store a plurality of recording papers P, and a paper supply roller 145. The paper feed roller 145 can send out the uppermost recording paper P among the recording papers P stacked and stored in the paper storage case 115 one by one.

  Between the paper feed unit 114 and the transport unit 120, two pairs of feed rollers 118a and 118b and 119a and 119b are arranged along the transport path of the recording paper P. The recording paper P sent out from the paper supply unit 114 is guided by these feed rollers 118 a, 118 b, 119 a and 119 b and further sent out to the transport unit 120.

  The transport unit 120 includes an endless transport belt 111 and two belt rollers 106 and 107. The conveyor belt 111 is wound around belt rollers 106 and 107. The conveyor belt 111 is adjusted to such a length that it is stretched with a predetermined tension when it is wound around the two belt rollers 106 and 107. Thus, the conveyor belt 111 is stretched without slack along two planes parallel to each other including the common tangent lines of the two belt rollers 106 and 107, respectively. Of these two planes, the plane closer to the liquid ejection head 2 is a transport surface 127 that transports the recording paper P.

  As shown in FIG. 1, a conveyance motor 174 is connected to the belt roller 106. The transport motor 174 can rotate the belt roller 106 in the direction of arrow A. The belt roller 107 can rotate in conjunction with the transport belt 111. Therefore, the conveyance belt 111 moves along the direction of arrow A by driving the conveyance motor 174 and rotating the belt roller 106.

  In the vicinity of the belt roller 107, a nip roller 138 and a nip receiving roller 139 are arranged so as to sandwich the conveyance belt 111. The nip roller 138 is urged downward by a spring (not shown). A nip receiving roller 139 below the nip roller 138 receives the nip roller 138 biased downward via the conveying belt 111. The two nip rollers are rotatably installed and rotate in conjunction with the conveyance belt 111.

  The recording paper P sent out from the paper supply unit 114 to the transport unit 120 is sandwiched between the nip roller 138 and the transport belt 111. As a result, the recording paper P is pressed against the transport surface 127 of the transport belt 111 and is fixed on the transport surface 127. Then, the recording paper P is transported in the direction in which the liquid ejection head 2 is installed according to the rotation of the transport belt 111. The outer peripheral surface 113 of the conveyor belt 111 may be treated with adhesive silicon rubber. Thereby, the recording paper P can be reliably fixed to the transport surface 127.

  The four liquid discharge heads 2 are arranged close to each other along the conveyance direction by the conveyance belt 111. Each liquid discharge head 2 has a head body 13 at the lower end. A large number of liquid ejection holes 8 for ejecting liquid are provided on the lower surface of the head body 13 (see FIG. 3).

  Liquid droplets (ink) of the same color are ejected from the liquid ejection holes 8 provided in one liquid ejection head 2. The liquid discharge holes 8 of each liquid discharge head 2 are arranged at equal intervals in one direction (a direction parallel to the recording paper P and perpendicular to the conveyance direction of the recording paper P and the longitudinal direction of the liquid discharge head 2). Therefore, it is possible to record without a gap in one direction. The colors of the liquid ejected from each liquid ejection head 2 are magenta (M), yellow (Y), cyan (C), and black (K), respectively. Each liquid ejection head 2 is disposed with a slight gap between the lower surface of the head body 13 and the transport surface 127 of the transport belt 111.

  The recording paper P transported by the transport belt 111 passes through a gap between the recording belt P and the transport belt 111 on the lower surface side of the liquid ejection head 2. At that time, droplets are ejected from the head body 13 constituting the liquid ejection head 2 toward the upper surface of the recording paper P. As a result, a color image based on the image data stored by the control unit 100 is formed on the upper surface of the recording paper P.

  A separation plate 140 and two pairs of feed rollers 121a and 121b and 122a and 122b are arranged between the transport unit 120 and the paper receiver 116. The recording paper P on which the color image is recorded is transported from the transport belt 111 to the peeling plate 140. At this time, the recording paper P is peeled from the transport surface 127 by the right end of the peeling plate 140. Then, the recording paper P is sent out to the paper receiving unit 116 by the feed rollers 121a, 121b, 122a and 122b. In this way, the recorded recording paper P is sequentially sent to the paper receiving unit 116 and stacked on the paper receiving unit 116.

  Note that a paper surface sensor 133 is installed between the liquid ejection head 2 and the nip roller 138 on the most upstream side in the conveyance direction of the recording paper P. The paper surface sensor 133 includes a light emitting element and a light receiving element, and can detect the leading end position of the recording paper P on the transport path. The detection result by the paper surface sensor 133 is sent to the control unit 100. The control unit 100 can control the liquid ejection head 2, the transport motor 174, and the like based on the detection result sent from the paper surface sensor 133 so that the transport of the recording paper P and the image recording are synchronized.

  Next, the head main body 13 constituting the liquid discharge head 2 of the present invention will be described. FIG. 2 is a plan view showing the head main body 13 shown in FIG. FIG. 3 is an enlarged view of a region surrounded by a one-dot chain line in FIG. 2, which is a part of the head main body 13, and a flow path from the middle of the descender 7 to the liquid discharge hole 8 is omitted. FIG. 4 is an enlarged perspective view of the same position as in FIG. 3, in which some of the flow paths are omitted so that the position of the liquid discharge holes 8 can be easily understood. In FIGS. 3 and 4, for the sake of easy understanding of the drawings, the fluid pressurizing chamber 10 to be drawn with a broken line below the piezoelectric actuator unit 21 and the hole 15 and the descender 7 to be drawn 12 are drawn with solid lines. Yes. FIG. 5A is a longitudinal sectional view of one liquid ejection element in FIG. 3, and FIG. 5B is a plan view thereof. In FIG. 5B, the adjacent liquid ejection elements are drawn with the flow paths omitted.

  The head main body 13 includes a flat plate-like channel member 4 and a piezoelectric actuator unit 21 that is an actuator unit and is disposed on the channel member 4. The piezoelectric actuator unit 21 has a trapezoidal shape, and is disposed on the upper surface of the flow path member 4 so that a pair of parallel opposing sides of the trapezoidal shape is parallel to the longitudinal direction of the flow path member 4. In addition, two piezoelectric actuator units 21 are arranged along the two virtual straight lines parallel to the longitudinal direction of the flow path member 4, that is, a total of four piezoelectric actuator units 21 are arranged on the flow path member 4 as a whole. Yes. The oblique sides of the piezoelectric actuator units 21 adjacent on the flow path member 4 partially overlap when the short direction of the flow path member 4 is viewed. In the area recorded by driving the piezoelectric actuator unit 21 in the overlapping portion, the liquid droplets discharged by the two piezoelectric actuator units 21 are mixed and landed.

  A manifold 5 that is a part of the liquid flow path is formed inside the flow path member 4. The manifold 5 has an elongated shape extending along the longitudinal direction of the flow path member 4, and an opening 5 b of the manifold 5 is formed on the upper surface of the flow path member 4. A total of ten openings 5 b are formed along each of two straight lines (imaginary lines) parallel to the longitudinal direction of the flow path member 4. The opening 5b is formed at a position that avoids a region where the four piezoelectric actuator units 21 are disposed. The manifold 5 is supplied with liquid from a liquid tank (not shown) through the opening 5b.

  The manifold 5 formed in the flow path member 4 is branched into a plurality of branches (the manifold 5 at the branched portion may be referred to as a sub-manifold 5a). The manifold 5 connected to the opening 5 b extends along the oblique side of the piezoelectric actuator unit 21 and is disposed so as to intersect with the longitudinal direction of the flow path member 4. In a region sandwiched between two piezoelectric actuator units 21, one manifold 5 is shared by adjacent piezoelectric actuator units 21, and the sub-manifold 5 a branches off from both sides of the manifold 5. These sub-manifolds 5 a extend in the longitudinal direction of the head main body 13 adjacent to each other in regions facing the piezoelectric actuator units 21 inside the flow path member 4.

  The flow path member 4 includes a plurality of liquid pressurizing chambers 10 and a plurality of apertures 12, but a plurality of holes 15 are formed. When the flow path member 4 is viewed in plan, the arrangement of the holes 15 in the flow path member 4 includes four liquid pressurizing chamber groups 9 that are formed in a matrix (that is, two-dimensional and regular). It comes to form. The hole 15 is a hollow region having a polygonal planar shape with rounded corners. More specifically, the planar shape of the hole 15 is formed by rounding the corners of the rectangle, the descender 7 is connected near one short side of the rectangle, and the liquid supply channel 6 is connected near the other short side. ing.

  The hole 15 is formed so as to open on the upper surface of the flow path member 4. These holes 15 are arranged over almost the entire area of the upper surface of the flow path member 4 facing the piezoelectric actuator unit 21. Accordingly, each liquid pressurizing chamber group 9 formed by these holes 15 occupies a region having almost the same size and shape as the piezoelectric actuator unit 21. Further, the opening of the hole 15 is closed by adhering the piezoelectric actuator unit 21 to the upper surface of the flow path member 4.

  In this embodiment, as shown in FIG. 3, the manifold 5 branches into six rows of sub-manifolds 5a arranged in parallel with each other in the short direction of the flow path member 4, and is connected to each sub-manifold 5a. The holes 15 constitute a row of holes 15 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the rows are arranged in two rows in parallel with each other in the lateral direction. The rows of the holes 15 connected to the sub-manifold 5a are arranged on each side of the sub-manifold 5a.

  As a whole, the holes 15 connected from the manifold 5 constitute a row of holes 15 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the rows are arranged in 12 rows parallel to each other in the lateral direction. The number of holes 15 included in each row of holes 15 is arranged so as to gradually decrease from the long side toward the short side corresponding to the outer shape of the displacement element 50 that is an actuator.

  Further, the descender 7 which is a liquid flow path connecting the hole 9 and the liquid discharge hole 8 has the same position where the hole 9 and the descender 7 are connected, and the position of the descender 7 is from the hole 9 to the liquid discharge hole 8. They are connected while shifting the position in the plane direction of the flow path member 4. And the descender shape in the row | line | column of one hole 15 is the same. As a result, the rows of the liquid discharge holes 8 connected to the row of the holes 15 are linearly spaced by R. The descenders 7 connected to the rows of the holes 15 are displaced in the planar direction by the liquid connected to the holes 15 belonging to the rows of the holes 15 during the length R of the flow path member 4 in the longitudinal direction. There is one discharge hole 8, and 16 liquid discharge holes 8 connected from the 16 rows of holes 15 are arranged at intervals of R / 16 in the longitudinal direction of the flow path member 4. As a result, it is possible to form an image with a resolution of 600 dpi in the longitudinal direction as a whole. That is, the individual flow paths 32 are connected to each sub-manifold 5a at intervals equivalent to 100 dpi on average.

  Individual electrodes 35 to be described later are formed at positions facing the respective holes 15 on the upper surface of the piezoelectric actuator unit 21. The individual electrode main body, which is a portion overlapping the hole 15 of the individual electrode 35, is slightly smaller than the liquid pressurizing chamber 10 and has a shape substantially similar to the hole 15.

  A large number of liquid discharge holes 8 are formed in the liquid discharge surface on the lower surface of the flow path member 4. These liquid discharge holes 8 are arranged at a position avoiding a region facing the sub-manifold 5 a arranged on the lower surface side of the flow path member 4. Further, these liquid discharge holes 8 are arranged in a region facing the piezoelectric actuator unit 21 on the lower surface side of the flow path member 4. These liquid discharge hole groups occupy an area having almost the same size and shape as the piezoelectric actuator unit 21, and by displacing the displacement element 50 of the corresponding piezoelectric actuator unit 21, a droplet is discharged from the liquid discharge hole 8. Can be discharged. The arrangement of the liquid discharge holes 8 will be described in detail later. The liquid discharge holes 8 in each region are arranged at equal intervals along a plurality of straight lines parallel to the longitudinal direction of the flow path member 4.

  The flow path member 4 constituting the head body 13 has a laminated structure in which a plurality of plates are laminated. These plates are a cavity plate 22, supply plates 23 and 24, manifold plates 25, 26, 27 and 28, a cover plate 29 and a nozzle plate 30 in order from the upper surface of the flow path member 4. A number of holes are formed in these plates. Each plate is aligned and laminated so that these holes communicate with each other to form the individual flow path 32 and the sub-manifold 5a. As shown in FIG. 5A, the head main body 13 has a liquid pressurizing chamber 10 and a hole 15 serving as a squeeze 12 on the upper surface of the flow path member 4, and the sub manifold 5 a on the lower surface side inside. The discharge hole 8 has a configuration in which each part constituting the individual flow path 32 is disposed close to each other at different positions on the lower surface, and the sub manifold 5a and the liquid discharge hole 8 are connected via the liquid pressurizing chamber 10. Have.

  The holes formed in each plate will be described. These holes include the following. First, a liquid pressurizing chamber 10 formed in the cavity plate 22 and a squeeze 12 connected to the liquid pressurizing chamber 10. Second, the liquid supply flow path 6 is a communication hole that forms a flow path connecting one end of the aperture 12 to the sub-manifold 5a. The liquid supply flow path 6 is formed in each plate from the cavity plate 22 (specifically, the inlet of the aperture 12) to the supply plate 24 (specifically, the outlet of the sub-manifold 5a).

  Third, there is a communication hole that constitutes a communication path that communicates from the other end of the liquid pressurizing chamber 10 to the liquid discharge hole 8, and this communication path is a descender (partial flow channel) in the liquid discharge hole 8 and the following description. ) It consists of a part called 7. The descender 7 is formed on each plate from the supply plate 23 (specifically, the outlet of the liquid pressurizing chamber 10) to the cover plate 29 (specifically, the connection end with the liquid discharge hole 8). Fourthly, there is a communication hole constituting the sub-manifold 5a. This communication hole is formed in the manifold plates 25-28.

  Such communication holes are connected to each other to form an individual flow path 32 from the liquid inflow port (the outlet of the submanifold 5a) from the submanifold 5a to the liquid discharge hole 8. The liquid supplied to the sub manifold 5a is discharged from the liquid discharge hole 8 through the following path. First, the sub-manifold 5a passes upward through the liquid supply channel 6 and reaches one end of the aperture 12. Next, it proceeds horizontally along the extending direction of the squeezing 12 and reaches one end of the liquid pressurizing chamber 10. Further, the liquid pressurizing chamber 10 proceeds horizontally along the extending direction of the liquid pressurizing chamber 10 and reaches the other end of the liquid pressurizing chamber 10. From there, while moving little by little in the plane of the descender 7, it proceeds mainly downward and to the liquid discharge hole 8 opened on the lower surface. Since the descender 7 is formed so as to be slightly shifted in the plane direction, the position of the liquid discharge hole 8 in the plane direction with respect to the liquid pressurizing chamber 10 is changed. As a result, the liquid discharge as shown in FIG. An arrangement of holes 8 is obtained. The descender 7a represents a hole opened in the plate 24, the descender 7b represents a hole opened in the plate 23, and the descender 7c represents a hole opened in the plates 24 to 29, all having the same diameter. .

  As shown in FIG. 5A, the piezoelectric actuator unit 21 has a laminated structure including two piezoelectric ceramic layers 21a and 21b. Each of these piezoelectric ceramic layers 21a and 21b has a thickness of about 20 μm. The total thickness of the piezoelectric actuator unit 21 is about 40 μm. Each of the piezoelectric ceramic layers 21a and 21b extends so as to straddle the plurality of liquid pressurizing chambers 10 (see FIG. 3). The piezoelectric ceramic layers 21a and 21b are made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity.

  The piezoelectric actuator unit 21 and the flow path member 4 are bonded through, for example, an adhesive layer. As the adhesive layer, in order not to affect the piezoelectric actuator unit 21 and the flow path member 4, at least one kind selected from the group of epoxy resin, phenol resin, and polyphenylene ether resin having a thermosetting temperature of 100 to 150 ° C. A thermosetting resin adhesive is used. The reason why the thermosetting resin adhesive is used is that the room temperature curing adhesive may not ensure sufficient ink resistance. For this reason, the piezoelectric actuator unit 21 is in a state in which a stress generated by a difference in thermal expansion coefficient between the flow path member 4 and the piezoelectric actuator unit 21 is applied by being cooled from the thermosetting temperature to room temperature. When the stress is large, the piezoelectric actuator unit 21 may be broken, and even if the stress is not so high that the piezoelectric actuator unit 21 is broken, the characteristics of the piezoelectric actuator unit 21 vary depending on the applied stress. Specifically, in a state where compressive stress is applied, the piezoelectric constant is lowered, but the influence of the phenomenon of drive deterioration in which the amount of displacement is reduced when the drive is repeated for a very long time is reduced. Conversely, in a state where tensile stress is applied, the piezoelectric constant increases, but the influence of drive deterioration increases. In any case, the difference in coefficient of thermal expansion between the flow path member 4 and the piezoelectric actuator unit 21 needs to be reduced. It is preferable that a small compressive stress is weakly applied. Therefore, when PZT ceramics are used for the piezoelectric actuator unit 21, it is preferable to use 42 alloy as the material of the flow path member 4.

  The piezoelectric actuator unit 21 includes a common electrode 34 made of a metal material such as Ag—Pd and an individual electrode 35 made of a metal material such as Au. As described above, the individual electrode 35 is disposed at a position facing the liquid pressurizing chamber 10 on the upper surface of the piezoelectric actuator unit 21. More specifically, as shown in FIG. 5B, the individual electrode 35 is drawn out of the liquid pressurizing chamber 10 from the individual electrode main body 35a overlapping the liquid pressurizing chamber 10 and the individual electrode main body 35a. The connection electrode 35a is included. On the connection electrode 35b, for example, gold including glass frit is formed, and a land having a convex shape with a thickness of about 15 μm is formed. The land on the connection electrode 35b is electrically joined to an electrode provided in an FPC (Flexible Printed Circuit) (not shown). Although details will be described later, a drive signal is supplied to the individual electrode 35 from the control unit 100 through the FPC. The drive signal is supplied at a constant period in synchronization with the conveyance speed of the recording paper P.

  The common electrode 34 is formed over almost the entire surface in the area between the piezoelectric ceramic layer 21a and the piezoelectric ceramic layer 21b. That is, the common electrode 34 extends so as to cover all the liquid pressurizing chambers 10 in the region facing the piezoelectric actuator unit 21. The thickness of the common electrode 34 is about 2 μm. The common electrode 34 is grounded in a region not shown, and is held at the ground potential. In the present embodiment, a surface electrode (not shown) different from the individual electrode 35 is formed on the piezoelectric ceramic layer 21b at a position avoiding the electrode group composed of the individual electrodes 35. The surface electrode is electrically connected to the common electrode 34 through a through-hole formed in the piezoelectric ceramic layer 21b, and is connected to another electrode on the FPC in the same manner as many individual electrodes 35. ing.

  As shown in FIG. 5A, the common electrode 34 and the individual electrode 35 are disposed so as to sandwich only the uppermost piezoelectric ceramic layer 21b. A region sandwiched between the individual electrode 35 and the common electrode 34 in the piezoelectric ceramic layer 21b is referred to as an active portion, and the piezoelectric ceramic in that portion is polarized. In the piezoelectric actuator unit 21 of the present embodiment, only the uppermost piezoelectric ceramic layer 21b includes an active portion, and the piezoelectric ceramic 21 layer a does not include an active portion and functions as a diaphragm. The piezoelectric actuator unit 21 has a so-called unimorph type configuration.

  As will be described later, when a predetermined drive signal is selectively supplied to the individual electrode 35, pressure is applied to the liquid in the liquid pressurizing chamber 10 corresponding to the individual electrode 35. As a result, droplets are discharged from the corresponding liquid discharge ports 8 through the individual flow paths 32. That is, the portion of the piezoelectric actuator unit 21 that faces each liquid pressurizing chamber 10 corresponds to an individual displacement element 50 (actuator, pressurizing unit) corresponding to each liquid pressurizing chamber 10 and the liquid discharge port 8. That is, in the laminate composed of the two piezoelectric ceramic layers 21a and 21b, the displacement element 50 having a unit structure as shown in FIG. The piezoelectric actuator unit 21 includes a plurality of displacement elements 50. The piezoelectric actuator unit 21 includes a plurality of displacement elements 50. The piezoelectric actuator unit 21 includes a plurality of displacement elements 50.

  A large number of individual electrodes 35 are individually electrically connected to the actuator control means via contacts and wirings on the FPC so that potentials can be individually controlled.

  In the piezoelectric actuator unit 21 in the present embodiment, when an electric field is applied in the polarization direction to the piezoelectric ceramic layer 21b by setting the individual electrode 35 to a potential different from that of the common electrode 34, the portion to which this electric field is applied is piezoelectric. It works as an active part that is distorted by the effect. At this time, the piezoelectric ceramic layer 21b expands or contracts in the thickness direction, that is, the stacking direction, and tends to contract or extend in the direction perpendicular to the stacking direction, that is, the surface direction, due to the piezoelectric lateral effect. On the other hand, since the remaining piezoelectric ceramic layer 21a is an inactive layer that does not have a region sandwiched between the individual electrode 35 and the common electrode 34, it does not spontaneously deform. In other words, the piezoelectric actuator unit 21 uses the upper piezoelectric ceramic layer 21b (that is, the side away from the liquid pressurizing chamber 10) as a layer including the active portion and the lower side (that is, close to the liquid pressurizing chamber 10). This is a so-called unimorph type configuration in which the piezoelectric ceramic layer 21a on the side) is an inactive layer.

  In this configuration, when the individual electrode 35 is set to a predetermined positive or negative potential with respect to the common electrode 34 by the actuator controller so that the electric field and the polarization are in the same direction, a portion sandwiched between the electrodes of the piezoelectric ceramic layer 21b. (Active part) contracts in the surface direction. On the other hand, the piezoelectric ceramic layer 21a, which is an inactive layer, is not affected by an electric field, so that it does not spontaneously shrink and tries to restrict deformation of the active portion. As a result, there is a difference in strain in the polarization direction between the piezoelectric ceramic layer 21b and the piezoelectric ceramic layer 21a, and the piezoelectric ceramic layer 21b is deformed so as to protrude toward the liquid pressurizing chamber 10 (unimorph deformation). .

  In an actual driving procedure in the present embodiment, the individual electrode 35 is set to a potential higher than the common electrode 34 (hereinafter referred to as a high potential) in advance, and the individual electrode 35 is temporarily set to the same potential as the common electrode 34 every time an ejection request is made ( Hereinafter, this is referred to as a low potential), and then the potential is set again at a predetermined timing. Thereby, the piezoelectric ceramic layers 21a and 21b return to their original shapes at the timing when the individual electrode 35 becomes low potential, and the volume of the liquid pressurizing chamber 10 is compared with the initial state (the state where the potentials of both electrodes are different). To increase. At this time, a negative pressure is applied to the liquid pressurizing chamber 10 and the liquid is sucked into the liquid pressurizing chamber 10 from the manifold 5 side. Thereafter, at the timing when the individual electrode 35 is set to a high potential again, the piezoelectric ceramic layers 21 a and 21 b are deformed so as to protrude toward the liquid pressurizing chamber 10. Becomes a positive pressure, the pressure on the liquid rises, and droplets are ejected. That is, a drive signal including a pulse based on a high potential is supplied to the individual electrode 35 in order to eject a droplet. The ideal pulse width is AL (Acoustic Length), which is the length of time during which the pressure wave propagates from the manifold 5 to the liquid discharge hole 8 in the liquid pressurizing chamber 10. According to this, when the inside of the liquid pressurizing chamber 10 is reversed from the negative pressure state to the positive pressure state, both pressures are combined, and the liquid droplet can be ejected with a stronger pressure.

  In the case of recording with gradation, gradation expression is performed by the number of droplets ejected continuously from the liquid ejection holes 8, that is, the droplet amount (volume) adjusted by the number of droplet ejections. It is. For this reason, the number of droplet discharges corresponding to the specified gradation expression is continuously performed from the liquid discharge hole 8 corresponding to the specified dot region. In general, when liquid ejection is performed continuously, it is preferable that the interval between pulses supplied to eject liquid droplets is AL. As a result, the period of the residual pressure wave of the pressure generated when discharging the previously discharged liquid droplet coincides with the period of the pressure wave of the pressure generated when discharging the liquid droplet discharged later, and these are superimposed. Thus, the pressure for discharging the droplet can be amplified.

  In such a printer 1, by adjusting the cycle of the recording paper P at the conveyance speed and the drive signal, it is possible to record an image having a resolution of 600 dpi in the longitudinal direction and 600 dpi in the conveyance direction. For example, if the drive signal is 20 kHz and the transport speed is 0.85 m / s, the ejected droplets can land on the recording paper P every about 42 μm in the transport direction, and the resolution in the transport direction is 600 dpi. .

  Further, the shape of the liquid flow path, particularly the liquid pressurizing chamber 10 and the squeezing 12 and the behavior of the liquid during discharge will be described in detail. The liquid pressurizing chamber 10 is a portion of the hole 15 that is connected to the liquid discharge hole 8 and covered with the piezoelectric actuator 21 that is a pressurizing unit. The squeezing 12 is a part of the hole 15 that is connected to the liquid supply path 6 and covered with the piezoelectric actuator 21 that is a pressurizing part. In the following description, a direction from the liquid supply path 6 in the hole 9 toward the liquid discharge hole 8 is a length direction, and a direction orthogonal thereto is a width direction.

  The liquid pressurizing chamber has a depth of 10 to 200 μm, a width of 100 to 1000 μm, and a length of about 200 to 2000 μm. The liquid pressurizing chamber 10 is designed in combination with the descender 7 so that the natural vibration period of the liquid inside thereof is suitable for the liquid discharge operation.

  The squeeze 12 has a depth of 0.05 to 1 μm, a width of 100 to 1000 μm, and a length of about 10 to 100 μm. The width of the liquid pressurizing chamber 10 and the width of the squeeze 15 may be different values, but they should be the same width so that the vibration state of the driving unit becomes complicated and unnecessary vibration does not occur. Further, a portion having a width smaller than those widths is not provided between the liquid pressurizing chamber 10 and the squeezing 15 so that the displacement amount of the driving portion of the squeezing 15 portion is increased.

  It is considered that the displacement amount of the driving unit is maximized in the vicinity of the center of gravity of the area of the hole 15, and the amount is, for example, about 0.05 to 0.5 μm. When the liquid pressurizing chamber 10 includes the center of gravity of the hole 15 and occupies 2/3 or more of the area of the hole 15 in plan view, the displacement of the drive unit pressurizes the liquid in the liquid pressurizing chamber 10. Can be used for this. The squeezing 12 changes its cross-sectional area due to the drive of the drive unit, so that the flow path resistance changes, the volume of the liquid pressurizing chamber 10 decreases, and the liquid flows from the liquid pressurizing chamber 10 to the liquid discharge hole 8. When heading, the cross-sectional area of the squeeze 12 becomes small, and the liquid is prevented from going to the liquid supply path 6 through the squeeze 12. Further, when the volume of the liquid pressurizing chamber 10 is increased by driving the driving unit, the cross-sectional area of the throttle 12 is large, and the liquid is supplied from the liquid supply path 6 through the throttle 12. In order to perform such an operation, the depth of the hole 15 in the portion to be the squeezing 12 is 1/10 or less, particularly 1/20, of the depth of the hole 15 in the portion to be the liquid pressurizing chamber 10. Is preferred.

  It is preferable that the maximum displacement amount in the portion of the aperture 12 of the drive unit is 1/3 or more of the depth of the aperture 12 so that the change in the flow path resistance becomes large. Considering that the deformation of the drive unit is a substantially conical shape, the volume change by the drive unit of the squeezing 12 is about 1/9, and the change in flow path resistance is a value that sufficiently contributes to the change in the movement of the liquid. In order to increase the change in the flow path resistance of the squeezing 12, the maximum amount of displacement in the portion of the squeezing 12 of the drive unit is more preferably ½ or more of the depth of the squeezing 12. The maximum amount of displacement in the portion of the squeeze 12 of the drive unit may be equal to or greater than the depth of the squeeze 12, that is, when driven, the squeeze 12 may be contacted. Thereby, the change in the channel resistance of the channel of the squeezing 12 can be increased.

  FIG. 6 is a cross-sectional view of another liquid ejection element of the present invention. The basic configuration of a liquid discharge head using this liquid discharge element is the same as that shown in FIGS. The flow path of the liquid discharge element in FIG. 6 is connected to the liquid discharge hole 208 through the liquid supply flow path 206, the aperture 212, the liquid pressurization chamber 210, and the descender 207 in order from the manifold 205. Similar to the hole 15 described above, the hole 215 includes a portion where the depth of the hole serving as the aperture 212 is shallow and a portion where the depth of the hole serving as the liquid pressurizing chamber 210 is deep. The hole 215 is covered with a piezoelectric actuator 221 that is a pressurizing unit, more specifically, a displacement element 250. In addition, the flow path member 204 has a second hole 225 that is a part of the descender 207 connected to the liquid pressurizing chamber 210 and is shallower than the hole 215 in the portion that becomes the liquid pressurizing chamber 210. . The second hole 225 is a displacement element composed of a piezoelectric actuator 221 as a second pressurizing unit, more specifically, an electrode 237, an electrode 238, a piezoelectric ceramic layer 221a sandwiched between them, and a diaphragm 221b directly below the piezoelectric ceramic layer 221a. Covered with.

  When driving such a liquid discharge element, the squeeze 212 can change its cross-sectional area by the drive unit, similarly to the squeeze 12 of the liquid discharge element described above. At that time, the displacement element 250 and the piezoelectric ceramic layer 221a are reversed in phase to the voltage applied to the piezoelectric ceramic layer 221a, and are composed of the m electrode 237, the electrode 238, the piezoelectric ceramic layer 221a sandwiched between them, and the diaphragm 221b directly below the m electrode 237. When the displacement element to be driven is driven, when the pressurizing unit increases the volume of the liquid pressurizing chamber 210, the second pressurizing unit moves the liquid of the descender 207 from the liquid discharge hole 208 to the liquid pressurizing chamber 210. Since the cross-sectional area in the flowing direction can be reduced, it is difficult for the liquid to flow from the liquid discharge hole 208 to the liquid pressurizing chamber 210, so that the liquid is supplied from the liquid supply channel 206 through the squeezing 212. It becomes easier to be supplied to.

  FIG. 7 is a partial plan view of another liquid discharge head of the present invention. The basic configuration of the liquid discharge head is the same as that shown in FIGS. 1 to 4 except that the arrangement of liquid discharge elements connected to the manifold is different as will be described later.

  The flow path of the liquid discharge element in FIG. 7 is connected to the liquid discharge hole 308 through the liquid supply flow path 306, the aperture 312, the liquid pressurization chamber 310, and the descender 307 in order from the manifold 305. The liquid discharge holes 308 between the two manifolds 305 are arranged on the virtual straight line A at equal intervals. In such an arrangement, 16 rows of liquid discharge holes 308 are formed from 17 manifolds 305. With such an arrangement, the liquid discharge elements can be arranged efficiently, and the liquid discharge holes 308 arranged on the virtual straight line A are connected to different manifolds 305, so that crosstalk via the manifold 305 is suppressed. Therefore, stable ejection can be obtained.

  FIG. 8A is a cross-sectional view of another liquid discharge element of the present invention, FIG. 8B is a plan view thereof, and FIG. 8C is a perspective view of a liquid discharge head using the liquid discharge element. . In the liquid and the main element in FIG. 7, the flow path is connected to the liquid discharge hole 408 through the liquid supply flow path 406, the throttle 412, the liquid pressurizing chamber 410, and the descender 407 in order from the manifold 405. Similar to the hole 15 described above, the hole 415 includes a portion where the depth of the hole serving as the aperture 412 is shallow and a portion where the depth of the hole serving as the liquid pressurizing chamber 410 is deep. The hole 415 is covered with a piezoelectric actuator 421 that is a pressurizing unit, more specifically, a displacement element 450. In addition, the flow path member 404 has a second hole 425 that is a part of the descender 407 connected to the liquid pressurizing chamber 410 and is shallower than the hole 415 of the portion that becomes the liquid pressurizing chamber 410. . The second hole 425 is covered with a displacement element composed of a piezoelectric actuator 421 that is a pressurizing unit, more specifically, an electrode 437, an electrode 438, a piezoelectric ceramic layer 421a sandwiched between them, and a diaphragm 421b directly below the piezoelectric ceramic layer 421a. ing.

  The channel member 404 is formed by laminating plates 422 and 423 similarly to the channel member 4.

  The liquid discharge head 313 in FIG. 8C is formed by connecting individual liquid discharge heads 313a having a plurality of liquid discharge elements shown in FIGS. 8A and 8B arranged in a straight line via a spacer 313b. Yes.

  The liquid discharge head 2 as described above is manufactured as follows, for example.

  A tape composed of a piezoelectric ceramic powder and an organic composition is formed by a general tape forming method such as a roll coater method or a slit coater method, and a plurality of green sheets that become piezoelectric ceramic layers 21a and 21b after firing are produced. . An electrode paste to be the common electrode 34 is formed on a part of the green sheet by a printing method or the like. Further, if necessary, a via hole is formed in a part of the green sheet, and a via conductor is inserted into the via hole.

  Next, each green sheet is laminated to produce a laminate, and pressure adhesion is performed. The laminated body after pressure contact is fired in a high-concentration oxygen atmosphere, and then the individual electrode 55 is printed on the fired body surface using an organic gold paste, fired, and then the connection electrode 36 is printed using an Ag paste. And the piezoelectric actuator unit 21 is produced by baking.

  Next, the flow path member 4 is produced by laminating the plates 22 to 30 via the adhesive layer. The plates 22 to 31 were prepared by a rolling method or the like, and then the holes to be the manifold 5, the liquid supply channel 6, the hole 9 and the descender 7 were processed into a predetermined shape by etching. The portion of the hole 9 that becomes the squeezing 12 was produced by half etching. For example, the thickness of the plate 22 in which the hole 15 is formed is 50 μm, the liquid pressurizing chamber is 700 μm long, 400 μm wide, 50 μm deep, and the aperture 12 is 80 μm long, 400 μm wide, deep. The thickness is 0.1 μm.

  These plates 22 to 31 are preferably formed of at least one metal selected from the group consisting of Fe—Cr, Fe—Ni, and WC—TiC, particularly when ink is used as a liquid. Since it is desired to be made of a material having excellent corrosion resistance against ink, Fe-Cr is more preferable.

  The piezoelectric actuator 21 and the flow path member 4 can be laminated and bonded via an adhesive layer, for example. A well-known adhesive layer can be used as the adhesive layer. However, in order not to affect the piezoelectric actuator 21 and the flow path member 4, an epoxy resin, a phenol resin, or a polyphenylene ether having a thermosetting temperature of 100 to 150 ° C. It is preferable to use at least one thermosetting resin adhesive selected from the group of resins. By heating to the thermosetting temperature using such an adhesive layer, the piezoelectric actuator 21 and the flow path member 4 can be heat-bonded.

  Thereafter, if necessary, an FPC or the like for electrically connecting the piezoelectric actuator 21 and the control unit 100 can be joined to obtain the liquid ejection head 2.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made as long as they are described in the claims.

DESCRIPTION OF SYMBOLS 1 ... Printer 2 ... Liquid discharge head 4 ... Flow path member 5 ... Manifold 5a ... Sub manifold 5b ... Opening 6 ... Liquid supply flow path 7 ... Decender (continuous) aisle)
DESCRIPTION OF SYMBOLS 8 ... Liquid discharge hole 9 ... Liquid pressurization chamber group 10 ... Liquid pressurization chamber 12 ... Squeezing 15 ... Hole 21 ... Piezoelectric actuator unit 21a ... Piezoelectric ceramic layer (vibration) Board)
21b ... Piezoelectric ceramic layer 22-30 ... Plate 32 ... Individual flow path 34 ... Common electrode 35 ... Individual electrode 36 ... Connection electrode 50 ... Displacement element

Claims (4)

  A liquid supply hole connected to the liquid pressurizing chamber connected to the liquid pressurizing chamber through the liquid flow path and the liquid pressurizing chamber connected to the liquid pressurizing chamber through the liquid flow path, and the liquid pressurizing chamber connected to each other. A liquid discharge element in which a pressure member is stacked so as to cover the hole on a flow path member provided with a flow path, and a depth of a portion of the hole serving as the squeezing is the liquid pressure chamber A liquid discharge element characterized by being shallower than the depth of the portion to be.   A second hole having a shallower depth than a portion of the hole serving as the liquid pressurizing chamber as the liquid flow path connecting the liquid pressurizing chamber and the liquid discharge hole is formed on the surface of the flow path member. The liquid ejection element according to claim 1, wherein the second pressure unit is stacked so as to open and cover the second hole.   A plurality of the liquid ejection elements according to claim 1 or 2, wherein the liquid ejection holes of the liquid ejection elements are open on the same surface, and a plurality of the squeezes of the liquid ejection elements are connected in the flow path member. A liquid discharge head comprising a manifold.   A recording apparatus comprising: the liquid discharge head according to claim 3; a transport unit that transports a recording medium to the liquid discharge head; and a control unit that controls driving of the liquid discharge head. .