JP5893977B2 - Liquid discharge head and recording apparatus using the same - Google Patents

Description

  The present invention relates to a liquid discharge head that discharges droplets 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 for discharging 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 head system that ejects ink as droplets from the ink ejection holes, and a part of the wall 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, and the ink A piezoelectric method for discharging liquid droplets from discharge holes is generally known.

  In addition, in such a liquid discharge head, a serial type that performs recording while moving the liquid discharge head in a direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording medium, and main scanning from the recording medium There is a line type in which recording is performed on a recording medium conveyed in the sub-scanning direction with a liquid discharge head that is long in the direction fixed. The line type has the advantage that high-speed recording is possible because there is no need to move the liquid discharge head as in the serial type.

  As the liquid discharge head, in addition to the liquid discharge head main body including the flow path member having the discharge holes and the piezoelectric actuator that applies pressure so that the liquid can be discharged from the discharge holes, the liquid discharge head main body is stably supplied with the liquid. A device having a reservoir for temporarily storing liquid so as to be supplied is known (for example, see Patent Document 1). In this reservoir, a reservoir channel is provided on one side of a reservoir that is long in one direction.

JP 2005-169839 A

However, in the liquid discharge head according to Patent Document 1, poor weight balance of the liquid ejection head, thereby, after attaching the liquid discharging head in a printer, there is the mounting accuracy is deteriorated. More specifically, in a printer that uses a plurality of liquid ejection heads, when one side is heavy, the liquid ejection head is slightly tilted and printing accuracy may be deteriorated. Further, in the serial printer, when the liquid ejection head is moved, there is a case where a slight deviation occurs in the movement due to the difference in weight between the left and right, and the printing accuracy may be deteriorated.

  Accordingly, an object of the present invention is to provide a liquid discharge head having a good weight balance in the longitudinal direction and a recording apparatus using the same.

The liquid discharge head of the present invention includes a plurality of discharge holes and a plurality of pressurizing chambers connected to the plurality of discharge holes, respectively, and a flow path member that is long in one direction, and is joined to the flow path member. includes a plurality of the pressure to pressurize the plurality of liquids in the pressure chamber, respectively, it is bonded to the flow path member, a reservoir flow path for supplying the liquid to the plurality of pressure chambers And the reservoir is configured by laminating a plurality of reservoir plates each having an opening serving as a reservoir channel. The reservoir channel is externally provided with the reservoir channel. An introduction channel that is supplied from the one end in the one direction to the other end of the reservoir and is connected to the introduction channel, and the one end from the central portion in the one direction of the reservoir. And the filter on the way And a vignetting in which filter passages, the reservoir plate holes serving as the filter flow path of the reservoir passage hole is opened, the air gap on the opposite side of the hole and the one direction It is provided.

  The recording apparatus of the 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 the plurality of pressurizing units. Features.

  According to the present invention, since the difference in mass in the longitudinal direction of the liquid ejection head is reduced, the mounting accuracy and the movement accuracy when moving the liquid ejection head are unlikely to deteriorate.

1 is a schematic configuration diagram of a color inkjet printer that is a recording apparatus including a liquid ejection head according to an embodiment of the present invention. FIG. 2 is a partial longitudinal sectional view of the liquid ejection head of FIG. 1. (A) is a plan view of a flow path member and a piezoelectric actuator constituting the liquid ejection head of FIG. 2, (b) is a plan view of a branch flow path member constituting the liquid ejection head, and (c) These are the top views of the member which comprises the reservoir body which comprises a liquid discharge head, (d) is a longitudinal cross-sectional view in alignment with the XX line of (c), (e) is the present invention. It is a longitudinal cross-sectional view of the same part as (d) of the member which comprises another liquid discharge head. FIG. 4 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. FIG. 4 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. It is a longitudinal cross-sectional view along the VV line of FIG.

  FIG. 1 is a schematic configuration diagram of a color ink jet printer which is a recording apparatus including a liquid discharge head according to an embodiment of the present invention. This color inkjet printer 1 (hereinafter referred to as printer 1) has a liquid ejection head 2. The liquid discharge head 2 is fixed to the printer 1. The liquid discharge head 2 has a long and narrow shape in a direction from the front to the back in FIG. This long direction is sometimes called the longitudinal direction.

  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 printing 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 supply unit 114 includes a paper storage case 115 that can store a plurality of printing papers P, and a paper supply roller 145. The paper feed roller 145 can send out the uppermost print paper P among the print 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 printing paper P. The printing paper P sent out from the paper supply unit 114 is guided by these feed rollers 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 two belt rollers. Thus, the conveyor belt 111 is stretched without slack along two parallel planes each including a common tangent line of the two belt rollers. Of these two planes, the plane closer to the liquid ejection head 2 is a transport surface 127 that transports the printing 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 printing 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 printing paper P is pressed against the transport surface 127 of the transport belt 111 and is fixed on the transport surface 127. The printing 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 printing paper P can be securely fixed to the transport surface 127.

  The liquid discharge head 2 has a head body 2a at the lower end. The lower surface of the head body 2a is a discharge hole surface 4-1, in which a large number of discharge holes for discharging liquid are provided.

  Two color liquid droplets (ink) are ejected from ejection holes provided in one liquid ejection head 2. The ejection holes for ejecting each color of the liquid ejection head 2 are arranged at equal intervals in one direction (a direction parallel to the printing paper P and perpendicular to the conveyance direction of the printing paper P, and the longitudinal direction of the liquid ejection head 2). Therefore, each color can be printed without any gap in one direction. The colors of the liquid discharged from the liquid discharge head 2 are, for example, two colors of magenta (M), yellow (Y), cyan (C), and black (K), respectively. The liquid discharge head 2 is disposed with a slight gap between the discharge hole surface 4-1 on the lower surface of the head body 2 a and the transport surface 127 of the transport belt 111.

  The printing paper P transported by the transport belt 111 passes through the gap between the liquid ejection head 2 and the transport belt 111. At that time, droplets are ejected from the head main body 2 a constituting the liquid ejection head 2 toward the upper surface of the printing 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 printing 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 printing paper P on which the color image is printed is conveyed to the peeling plate 140 by the conveying belt 111. At this time, the printing paper P is peeled from the transport surface 127 by the right end of the peeling plate 140. Then, the printing paper P is sent out to the paper receiving unit 116 by the feed rollers 121a to 122b. In this way, the printed printing 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 that are the most upstream in the transport direction of the printing 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 printing 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 conveyance motor 174, and the like so that the conveyance of the printing paper P and the printing of the image are synchronized based on the detection result sent from the paper surface sensor 133.

  Next, the liquid discharge head 2 of the present invention will be described.

  FIG. 2 is a longitudinal sectional view in a direction along the longitudinal direction of the liquid discharge head 2. However, a part located above the reservoir 40 and a flow path inside the flow path member 4 are partially omitted. 3A is a plan view of the flow path member 4 and the piezoelectric actuator 21 constituting the liquid discharge head 2 of FIG. 2, and FIG. 3B is a plan view of the branch flow path member 51 constituting the liquid discharge head 2. (C) is a plan view of a flow path structure 41a constituting the reservoir body 40 constituting the liquid ejection head 2, and (d) is a longitudinal section along the line XX in (c). It is a top view, (e) is a longitudinal cross-sectional view of the same part as (d) of the flow path structure 241a constituting another liquid discharge head of the present invention.

  FIG. 4 is an enlarged view of a region surrounded by a one-dot chain line in FIG. 2A, and a part of the flow paths is omitted for explanation. FIG. 5 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. 2A, and is a view in which a part of the flow paths different from FIG. 4 and 5, in order to make the drawings easy to understand, the manifold 5, the discharge hole 8, and the pressurizing chamber 10 that are to be drawn by broken lines below the piezoelectric actuator substrate 21 are drawn by solid lines. 6 is a longitudinal sectional view taken along the line VV in FIG.

  The liquid discharge head 2 includes a head body 2a and a reservoir 40. A metal casing 90 may be further attached to the liquid discharge head 2. Also. The head body 2 a includes a flow path member 4 and a piezoelectric actuator substrate 21 in which a displacement element (pressurizing unit) 30 is formed. Further, the reservoir 40 includes a reservoir main body 41 and a branch flow path member 51.

  The flow path member 4 constituting the head body 2a includes a manifold 5 which is a common flow path, a plurality of pressurizing chambers 10 connected to the manifold 5, and a plurality of discharge holes respectively connected to the plurality of pressurizing chambers 10. 8, the pressurizing chamber 10 is opened on the upper surface of the flow path member 4, and the upper surface of the flow path member 4 is a pressurizing chamber surface 4-2. In addition, an opening 5a connected to the manifold 5 is provided on the upper surface of the flow path member 4, and liquid is supplied from the opening 5a.

  A piezoelectric actuator substrate 21 including a displacement element 30 is bonded to the upper surface of the flow path member 4, and each displacement element 30 is provided so as to be positioned on the pressurizing chamber 10. The piezoelectric actuator substrate 21 is connected to a signal transmission unit such as an FPC (Flexible Printed Circuit) for supplying a signal to each displacement element 30.

The reservoir 40 includes a reservoir body 41 in which a reservoir channel 42 is formed and a branch channel 52.
The branched flow path member 51 in which the is formed is joined. The supply hole 42a of the reservoir channel 42 opens to the outside, and the liquid supplied from the outside passes through the supply hole 42a of the reservoir channel 42 and the outflow hole of the branch channel, and the manifold hole of the channel member 4 5 is supplied. Specifically, in order from the outside, the reservoir channel 42 is connected to an introduction channel that extends from one end to the other end in the longitudinal direction of the reservoir 42, and is connected to the center in the longitudinal direction of the reservoir 42. A filter channel provided with a filter 48 in the middle and extending from one end of the reservoir 40 in the longitudinal direction to the other end, and at the center in the longitudinal direction. And a branch channel 52 connected to the common channel at one end and the other end in the longitudinal direction.

  With such a flow path configuration, when liquid is first introduced, the liquid is supplied from the supply hole 42a of the reservoir flow path on the side where the filter flow path is, and a part thereof is directed to the flow path member 4. In addition, the part is taken out from the supply hole 42a of the reservoir channel on the side opposite to the filter channel, thereby suppressing the bubbles that are mixed with the liquid from entering the channel member 4 and improving the efficiency. Can put liquid well. This is because the liquid mainly passes through the filter 48 on the supply flow path 42a side of the reservoir flow path to the branch flow path supply hole 52a in the central portion of the reservoir 40. This is because the liquid flow in the vicinity of the filter 48 in the filter channel above the hole 52a is mainly directed from the bottom to the top (from the filter channel to the introduction channel). At the time of printing, the liquid is supplied from either one, and the other is closed by a printer mechanism (not shown). As a result, the liquid in the reservoir channel 42 is mainly closed from the supply hole 42a of the reservoir channel 42 to which the liquid is supplied to the supply hole 52a of the central branch channel, and is closed. On the other side, the liquid does not flow very much.

On the other hand, with such a configuration, in the liquid ejection head 2, in the longitudinal direction, the gap is increased on the side where the filter flow path is provided, and the liquid discharge head 2 becomes lighter. If the weight balance is poor, after attaching the liquid discharge head 2 in the printer, or the mounting accuracy is deteriorated, the etc. serial printer, when using by moving the liquid discharge head 2, the difference between the left and right motion, etc. May occur. At that time, by providing the mass adjustment space 41a-4 on the opposite side to the filter flow path, it is possible to reduce the left-right difference in mass. The mass adjustment space 41 a-4 is not limited to the configuration of the reservoir channel 42 described above, and the volume of the reservoir channel 42 is small from the center in the longitudinal direction of the reservoir 40 to one end and from the center to the other end. It only has to be provided on the side.

  Further, since the heat transfer between the mass adjusting space 41a-4 and the reservoir channel 42 is low, the portion of the reservoir 42 surrounded by them can be used as the heat conducting portion 41a-3. If the heat conducting portion 41a-3 is provided along the longitudinal direction, the heat is mainly transmitted in the longitudinal direction in the heat conducting portion 41a-3, so that the temperature difference between the left and right sides of the liquid ejection head 2 can be reduced. As a result, even when the viscosity of the liquid or the pressure unit 30 is temperature-dependent, variations in ejection characteristics can be reduced.

More specifically, when viewed from the joining direction in which the reservoir 40 and the flow path member 4 are joined, that is, in a plan view of the flat reservoir 40, the heat conducting portion 41 a-3 and the short side of the reservoir 40 Between the outer walls in the direction, the reservoir channel 42 or the mass adjusting space 41a-4 exists. Gas liquids and the mass adjusting space 41a-4 of the etc. water to meet the reservoir channel 42 as a main component, because of the low thermal conductivity than configured heat conducting portion 41a-3 such as a metal, a reservoir flow path 42 acts as a heat insulating portion that suppresses heat from being transmitted from the heat conducting portion 41a-3 to the outer wall in the short direction and escaping to the outside, and heat is easily transferred in the longitudinal direction.

When the heater is attached to the reservoir 40 and heated to about 40 to 60 ° C., heat is dissipated from both ends in the longitudinal direction, so even if the heater is attached to almost the entire main surface of the reservoir 40, The temperature at both ends of the liquid discharge head 2 tends to be lower than the center temperature. When the heat conducting portion 41a-3 does not exist, for example, a temperature difference of about 2 to 5 ° C. may occur in the longitudinal direction, but the viscosity of the liquid and the displacement characteristics of the displacement element 30 vary to some extent depending on the temperature. Dischargeability may vary due to the difference. By being present in the heat conducting portion 41a-3, depending on other structures, for example, the temperature difference in the longitudinal direction can be about 1 ° C. or less.

  If the heat conduction part 41a-3 is provided in the center part in the short direction, the temperature difference in the short direction can be reduced. Here, providing the heat conducting portion 41a-3 in the center portion in the short direction means that the heat conducting portion 41a-3 is a region having a half width in the short direction at the center in the short direction (that is, It indicates that it overlaps with the region from 1/4 to 3/4 from the edge in the short direction, and the region of 1/4 of the center width (that is, 3/8 to 5/8 from the edge in the short direction). It is preferable that it overlaps with the region up to.

  In the case where a plurality of reservoir channels 42 are provided, as shown in FIG. 3E, the mass difference between the left and right can be further reduced by providing the reservoir channels 42 so as to overlap and cover the plurality of reservoir channels 42.

  The reservoir body 41 is configured by stacking reservoir plates. Specifically, the flow path structure 41a, the flat plates 41b and 41d, and the damper plate 41c are laminated. The flow path structure 41a has a thickness of about 5 to 10 mm, and the three layers of the flat plates 41b and d and the damper plate 41c have a thickness of about 0.5 to 2 mm as a whole.

  Furthermore, although the flow path structure 41a can be formed of metal, resin, or ceramics, it is preferable that the flow path structure 41a is made of resin. The plates 40b and 40d can be made of resin or metal. However, the formation of the resin is preferable because the plate 40b and d can be made inexpensive and there is no difference in expansion coefficient with the reservoir body 40a.

  A part of the inner wall of the reservoir channel 42 is a damper 46 composed of a damper plate 41c made of an elastically deformable material. Since the damper 46 can be deformed in the direction facing the surface opposite to the reservoir channel 42, the damper 46 can be elastically deformed to change the volume of the reservoir channel 42, and the liquid discharge amount can be reduced. The liquid can be stably supplied when it suddenly increases. The material of the damper plate 41c is, for example, resin or metal, and the thickness is about 5 to 30 μm.

  In the present embodiment, two reservoir channels 42 are provided independently along the longitudinal direction. Although details will be described later, it is possible to eject two colors of ink from one liquid ejection head 2.

  The branch channel member 51 is provided with a branch channel 52, and the supply hole 52 a at the center of the branch channel 52 is connected to the reservoir channel 42 in the reservoir body 41. The branch flow path 52 branches in the middle and is connected to the opening 5 a of the manifold 5 in the flow path member 4.

By providing the branch flow path 52 and supplying the liquid to the flow path member 4 from both ends of the manifold 5, it is possible to prevent the liquid from being insufficiently supplied. Further, as compared with the case where the liquid is supplied from one end of the manifold 5, the difference in pressure loss caused when the liquid flows through the manifold 5 can be reduced to about half, so that the variation in the liquid discharge characteristics can be reduced. Further, in order to reduce the difference in pressure loss, it is conceivable to supply near the center of the manifold 5 or from several places along the manifold 5, but in such a structure, the width of the liquid discharge head 2 is considered. And the spread of the arrangement of the discharge holes 8 in the width direction also increases. If this is the case, the influence of the deviation in the angle at which the liquid ejection head 2 is attached to the printer 1 on the printing result is increased, which is not preferable. Even when printing is performed using a plurality of liquid ejection heads 2, the area in which the entire ejection holes 8 of the plurality of liquid ejection heads 2 are arranged increases, so that the relative position accuracy of the plurality of liquid ejection heads 2 is increased. Is not preferable because the influence on the printing result becomes large. Therefore, in order to reduce the difference in pressure loss while reducing the width of the liquid discharge head 2, it is preferable to supply from both ends of the manifold 5. The branch channel 52 may not be provided, and the reservoir channel 42 and the opening 5a of the manifold 5 may be directly connected.

  Further, in order to reduce the pressure loss, the positions of both ends in the longitudinal direction of the branch flow path 52 and the positions of both ends of the manifold 5 when viewed in plan are made the same. It is preferable to connect from both ends to both ends of the manifold 5 with a flow path linearly downward.

  Since the supply hole 52a of the branch flow path 52 is formed in the central portion in the longitudinal direction, the flow length to the manifold 5 connected by a plurality of portions can be made relatively close, so that the liquid supply is stabilized. Can be made.

  A concave portion is provided between both ends of the elongated shape joined to the flow path member 4 of the branch flow path member 51, and the piezoelectric actuator substrate 21 is accommodated. Because of this structure, the piezoelectric actuator substrate 21 has a width of 80% or more of the flow path member 4, a length of 80% or more between the openings 5a of the manifold, and the individual electrodes 25 constituting the displacement element 30 are 4 inches. The very large thing currently formed over can be used. As a result, the number of piezoelectric actuator substrates 21 to be bonded can be reduced, so that the process can be simplified and the variation of the displacement elements 30 between the piezoelectric actuator substrates 21 that occurs when using a plurality of piezoelectric actuator substrates 21 is eliminated. Variations can be reduced.

  The branch channel member 51 is configured by stacking a plurality of rectangular plates 51a to 51c. The branch channel 52 branches to one side and the other in the longitudinal direction directly below the supply hole 52a of the branch channel 52, and goes downward near the end in the longitudinal direction. 4 to the opening 5 a of the manifold 5. The branched flow paths 52 after branching are substantially equal in length to the manifold 5. As a result, temperature fluctuations and pressure fluctuations of the liquid supplied from the outside are transmitted to the plurality of connecting portions with the manifold 5 with a small time difference, so that variations in the discharge characteristics of the liquid droplets in the liquid discharge head 2 can be further reduced. . Note that “substantially equal” here means that the shortest flow path length is 80% or more with respect to the longest flow path length, and more preferably 90% or more. Moreover, it is preferable that the branch flow paths 52 not only have the same length but also have the same cross-sectional area. Here, the cross-sectional areas are substantially equal means that the difference in cross-sectional area of the flow path at the same flow path length from the liquid introduction hole 60b of the branch flow path 52 is 20% or less. Is more preferable.

  The head body 2 a has a flat plate-like flow path member 4 and one piezoelectric actuator substrate 21 including a displacement element 30 on the flow path member 4. The planar shape of the piezoelectric actuator substrate 21 is rectangular, and is arranged on the upper surface of the flow path member 4 so that the long side of the rectangle is along the longitudinal direction of the flow path member 4.

  Four manifolds 5 are 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 openings 5 a of the manifold 5 are formed on the upper surface of the flow path member 4 at both ends thereof. In the present embodiment, four manifolds 5 are provided independently, and each manifold 5 is connected to the branch flow path 52 at the opening 5a.

  The flow path member 4 is formed by two-dimensionally expanding a plurality of pressurizing chambers 10. The pressurizing chamber 10 is a hollow region having a substantially rhombic planar shape with rounded corners. The pressurizing chamber 10 opens to the pressurizing chamber surface 4-2 that is the upper surface of the flow path member 4.

  The pressurizing chamber 10 is connected to one manifold 5 via an individual supply channel 14. Along the one manifold 5, two pressurizing chamber rows 11, which are rows of pressurizing chambers 10 connected to the manifold 5, are provided on each side of the manifold 5, for a total of four rows. Therefore, a total of 16 pressurizing chamber rows 11 are provided. The intervals in the longitudinal direction of the pressurizing chambers 10 in the respective pressurizing chamber rows 11 are the same, and the interval is 37.5 dpi. The pressurization chamber 10 at the end of each pressurization chamber row 11 is a dummy and is not connected to the manifold 5. By this dummy, the structure (rigidity) around the pressurizing chamber 10 that is one inner side from the end is close to the structure (rigidity) of the other pressurizing chamber 10, so that the difference in liquid ejection characteristics can be reduced.

  The pressurizing chambers 10 of each pressurizing chamber row 11 are arranged in a staggered manner so that the corners are located between the adjacent pressure chamber rows 11. A pressurizing chamber group is constituted by the pressurizing chambers 10 connected to one manifold 5, and there are four pressurizing chamber groups. The relative arrangement of the pressurizing chambers 10 in each pressurizing chamber group is the same, and each pressurizing chamber group is arranged slightly shifted in the longitudinal direction. These pressurizing chambers 10 are arranged over almost the entire surface of the upper surface of the flow path member 4 in a region facing the piezoelectric actuator substrate 21, although there are some widened portions such as between the pressurizing chamber groups. . That is, the pressurizing chamber group 9 formed by these pressurizing chambers 10 occupies a region having almost the same size and shape as the piezoelectric actuator substrate 21. Further, the opening of each pressurizing chamber 10 is closed by bonding the piezoelectric actuator substrate 21 to the upper surface of the flow path member 4.

  A descender connected to the discharge hole 8 opened on the discharge surface 4-1 on the lower surface of the flow path member 4 extends from a corner portion of the pressurizing chamber 10 facing the corner portion where the individual supply flow path 14 is connected. Yes. The descender extends in the direction of extending the diagonal line of the pressurizing chamber in plan view. That is, the arrangement of the discharge holes 8 in the longitudinal direction and the arrangement of the pressurizing chamber 10 are the same. In each pressurizing chamber row 11, the pressurizing chambers 10 are arranged at an interval of 37.5 dpi, and the pressurizing chambers 10 connected to one manifold 5 as a whole have an interval of 150 dpi in the longitudinal direction. Further, since the pressurizing chambers 10 connected to the four manifolds 5 are displaced in the longitudinal direction at an interval corresponding to 600 dpi, the liquid pressurizing chambers 10 are formed at an interval of 600 dpi in the longitudinal direction as a whole. ing. As described above, since the arrangement of the discharge holes 8 in the longitudinal direction is the same as that of the liquid pressurizing chamber 10, the distance between the discharge holes 8 in the longitudinal direction is also 600 dpi.

  In other words, when the discharge holes 8 are projected so as to be orthogonal to the virtual straight line parallel to the longitudinal direction of the flow path member 4, each manifold 5 is within the range of R of the virtual straight line shown in FIG. That is, four discharge holes 8 connected to, that is, a total of 16 discharge holes 8 are equally spaced at 600 dpi. Thus, by supplying the same color ink to all the manifolds 5, it is possible to form an image with a resolution of 600 dpi in the longitudinal direction as a whole. In addition, the four discharge holes 8 connected to one manifold 5 are equally spaced at 150 dpi in the range of the imaginary straight line R. As a result, by supplying different colors of ink to the two manifolds 5, it is possible to form two-color images with a resolution of 300 dpi in the longitudinal direction as a whole. In this case, if two liquid ejection heads 2 are used, an image of four colors of 300 dpi can be printed.

Individual electrodes 25 are formed at positions facing the pressurizing chambers 10 on the upper surface of the piezoelectric actuator substrate 21. The individual electrode 25 includes an individual electrode main body 25a that is slightly smaller than the pressurizing chamber 10 and has a shape substantially similar to the pressurizing chamber 10, and an extraction electrode 25b that is extracted from the individual electrode main body 25a. In the same manner as the pressurizing chamber 10, the individual electrode 25 constitutes an individual electrode row and an individual electrode group. A common electrode surface electrode 28 electrically connected to the common electrode 24 is formed on the upper surface of the piezoelectric actuator substrate 21. The common electrode surface electrodes 28 are formed in two rows along the longitudinal direction at the central portion of the piezoelectric actuator substrate 21 in the lateral direction, and are formed in one row along the lateral direction near the end in the longitudinal direction. ing. Although the illustrated common electrode surface electrode 28 is intermittently formed on a straight line, it may be formed continuously on a straight line. Two signal transmission units are arranged and bonded to the piezoelectric actuator substrate 21 from the two long sides of the piezoelectric actuator substrate 21 toward the center. The common electrode surface electrode 28 is connected at the end of the signal transmission unit (the tip and the longitudinal end of the piezoelectric actuator substrate 21), and the common electrode surface electrode 28 and the common electrode connection electrode formed thereon are provided. Since the area is larger than that of the extraction electrode 25b and the connection electrode 26 formed on the extraction electrode 25b, the signal transmission part can be hardly separated from the end.

  Further, the discharge hole 8 is arranged at a position avoiding the area facing the manifold 5 arranged on the lower surface side of the flow path member 4. Further, the discharge hole 8 is disposed in a region facing the piezoelectric actuator substrate 21 on the lower surface side of the flow path member 4. These discharge holes 8 occupy a region having almost the same size and shape as the piezoelectric actuator substrate 21 as a group, and the displacement elements 30 of the corresponding piezoelectric actuator substrate 21 are displaced to displace the discharge holes 8 from the discharge holes 8. Droplets can be ejected.

  The flow path member 4 included in the head main body 2a has a laminated structure in which a plurality of plates are laminated. These plates are a cavity plate 4a, a base plate 4b, an aperture plate 4c, a supply plate 4d, manifold plates 4e to 4g, a cover plate 4h, and a nozzle plate 4i in this order from the upper surface of the flow path member 4. A number of holes are formed in these plates. Since the thickness of each plate is about 10 to 300 μm, the formation accuracy of the holes to be formed can be increased. Each plate is aligned and laminated so that these holes communicate with each other to form the individual flow path 12 and the manifold 5. In the head main body 2a, the pressurizing chamber 10 is on the upper surface of the flow path member 4, the manifold 5 is on the inner lower surface side, the discharge holes 8 are on the lower surface, and the parts constituting the individual flow path 12 are close to each other in different positions. The manifold 5 and the discharge hole 8 are connected via the pressurizing chamber 10.

  The holes formed in each plate will be described. These holes include the following. The first is the pressurizing chamber 10 formed in the cavity plate 4a. Second, there is a communication hole that constitutes an individual supply channel 14 that is connected from one end of the pressurizing chamber 10 to the manifold 5. This communication hole is formed in each plate from the base plate 4b (specifically, the inlet of the pressurizing chamber 10) to the supply plate 4c (specifically, the outlet of the manifold 5). The individual supply flow path 14 includes a squeeze 6 that is formed in the aperture plate 4c and is a portion where the cross-sectional area of the flow path is small.

  Third, there is a communication hole constituting a flow path communicating from the other end of the pressurizing chamber 10 to the discharge hole 8, and this communication hole is referred to as a descender (partial flow path) in the following description. The descender is formed on each plate from the base plate 4b (specifically, the outlet of the pressurizing chamber 10) to the nozzle plate 4i (specifically, the discharge hole 8). Fourthly, communication holes constituting the manifold 5. The communication holes are formed in the manifold plates 4e to 4g.

The first to fourth communication holes are connected to each other to form an individual flow path 12 from the liquid inflow port (outlet of the manifold 5) to the discharge hole 8 from the manifold 5. The liquid supplied to the manifold 5 is discharged from the discharge hole 8 through the following path. First, from the manifold 5, it passes through the individual supply channel 14 and reaches one end of the aperture 6. Next, it proceeds horizontally along the extending direction of the restriction 6 and reaches the other end of the restriction 6. From there, it reaches one end of the pressurizing chamber 10 upward. Furthermore, it progresses horizontally along the extending direction of the pressurizing chamber 10 and reaches the other end of the pressurizing chamber 10. While moving little by little in the horizontal direction from there, it proceeds mainly downward and proceeds to the discharge hole 8 opened in the lower surface.

  Similarly to the channel member 4, the branch channel member 51 is obtained by a rolling method or the like and is processed into a predetermined shape by etching or grinding on the plates 51a to 51c. The thickness of the plates 51a to 51c is, for example, about 0.3 to 3m.

  The piezoelectric actuator substrate 21 has a laminated structure composed of two piezoelectric ceramic layers 21a and 21b. Each of these piezoelectric ceramic layers 21a and 21b has a thickness of about 20 μm. The thickness from the lower surface of the piezoelectric ceramic layer 21a of the piezoelectric actuator substrate 21 to the upper surface of the piezoelectric ceramic layer 21b is about 40 μm. Both of the piezoelectric ceramic layers 21 a and 21 b extend so as to straddle the plurality of pressure chambers 10. The piezoelectric ceramic layers 21a and 21b are made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity.

  The piezoelectric actuator substrate 21 includes a common electrode 24 made of a metal material such as Ag—Pd and an individual electrode 25 made of a metal material such as Au. As described above, the individual electrode 25 includes the individual electrode main body 25a disposed at a position facing the pressurizing chamber 10 on the upper surface of the piezoelectric actuator substrate 21, and the extraction electrode 25b extracted therefrom. A connection electrode 26 is formed at a portion of one end of the extraction electrode 25 b that is extracted outside the region facing the pressurizing chamber 10. The connection electrode 26 is made of, for example, silver-palladium containing glass frit, and has a convex shape with a thickness of about 15 μm. The connection electrode 26 is electrically joined to an electrode provided in the signal transmission unit. Although details will be described later, a drive signal is supplied to the individual electrode 25 from the control unit 100 through the signal transmission unit. The drive signal is supplied in a constant cycle in synchronization with the conveyance speed of the print medium P. The dummy connection electrode 27 connects the piezoelectric actuator substrate 21 and the signal transmission unit to increase the connection strength, uniformize the distribution of the portion connected on the piezoelectric actuator substrate 21, and stabilize the connection when connecting. You can.

  The common electrode 24 is formed over almost the entire surface in the region between the piezoelectric ceramic layer 21a and the piezoelectric ceramic layer 21b. That is, the common electrode 24 extends so as to cover all the pressurizing chambers 10 in the region facing the piezoelectric actuator substrate 21. The thickness of the common electrode 24 is about 2 μm. The common electrode 24 is connected to the common electrode surface electrode 28 formed at a position avoiding the electrode group composed of the individual electrodes 25 on the piezoelectric ceramic layer 21b through a via hole formed in the piezoelectric ceramic layer 21b. Grounded and held at ground potential. The common electrode surface electrode 28 is connected to another electrode on the signal transmission unit in the same manner as the large number of individual electrodes 25.

  As will be described later, when a predetermined drive signal is selectively supplied to the individual electrode 25, pressure is applied to the liquid in the pressurizing chamber 10 corresponding to the individual electrode 25. As a result, droplets are discharged from the corresponding liquid discharge ports 8 through the individual flow paths 12. That is, the portion of the piezoelectric actuator substrate 21 that faces each pressurizing chamber 10 corresponds to the individual displacement element 30 corresponding to each pressurizing chamber 10 and the liquid discharge port 8. That is, in the laminated body composed of two piezoelectric ceramic layers, the displacement element 30 which is a piezoelectric actuator having a unit structure as shown in FIG. Is formed by a diaphragm 21a, a common electrode 24, a piezoelectric ceramic layer 21b, and an individual electrode 25. The piezoelectric actuator substrate 21 includes a plurality of displacement elements 30 serving as pressure parts. In the present embodiment, the amount of liquid ejected from the liquid ejection port 8 by one ejection operation is about 5 to 7 pl (picoliter).

  The large number of individual electrodes 25 are individually electrically connected to the control unit 100 via signal transmission units and wires so that the potentials can be individually controlled. When an electric field is applied to the piezoelectric ceramic layer 21b in the polarization direction by setting the individual electrode 25 to a potential different from that of the common electrode 24, a portion to which the electric field is applied functions as an active portion that is distorted by the piezoelectric effect. In this configuration, when the control unit 100 sets the individual electrode 25 to a predetermined positive or negative potential with respect to the common electrode 24 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 pressurizing chamber 10 (unimorph deformation).

In an actual driving procedure in the present embodiment, the individual electrode 25 is set to a potential higher than the common electrode 24 (hereinafter referred to as a high potential) in advance, and the individual electrode 25 is temporarily set to the same potential as the common electrode 24 every time there is a discharge request. (Hereinafter referred to as a low potential), and then set to a high potential again at a predetermined timing. As a result, the piezoelectric ceramic layers 21a and 21b return to their original shapes at the timing when the individual electrodes 25 become low potential, and the volume of the pressurizing chamber 10 increases compared to the initial state (the state where the potentials of both electrodes are different). To do. At this time, a negative pressure is applied to the pressurizing chamber 10 and the liquid is sucked into the pressurizing chamber 10 from the manifold 5 side. After that, at the timing when the individual electrode 25 is set to a high potential again, the piezoelectric ceramic layers 21a and 21b are deformed so as to protrude toward the pressurizing chamber 10, and the pressure in the pressurizing chamber 10 is reduced due to the volume reduction of the pressurizing chamber 10. The pressure becomes positive and the pressure on the liquid rises, and droplets are discharged. That is, in order to discharge the droplet, a drive signal including a pulse based on a high potential is supplied to the individual electrode 25. The ideal pulse width is AL (Acoustic Length), which is the length of time during which the pressure wave propagates from the orifice 6 to the discharge hole 8. According to this, when the inside of the pressurizing chamber 10 is reversed from the negative pressure state to the positive pressure state, both pressures are combined, and the liquid droplets can be discharged at a stronger pressure.

  In gradation printing, gradation expression is performed by the number of droplets ejected continuously from the ejection holes 8, that is, the droplet amount (volume) adjusted by the number of droplet ejections. For this reason, the number of droplet discharges corresponding to the designated gradation expression is continuously performed from the discharge holes 8 corresponding to the designated 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 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 this case, it is considered that the speed of the liquid droplets ejected later increases, but this is preferable because the landing points of a plurality of liquid droplets are close.

  In the present embodiment, the displacement element 30 using piezoelectric deformation is shown as the pressurizing portion. However, the present invention is not limited to this, and any other device that can pressurize the liquid in the pressurizing chamber 10 may be used. For example, the liquid in the pressurizing chamber 10 may be heated and boiled to generate pressure, or may be one using MEMS (Micro Electro Mechanical Systems).

  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 24 is formed on a part of the green sheet by a printing method or the like. Further, a via hole is formed in a part of the green sheet as necessary, and a via conductor is filled in 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 25 is printed on the fired body surface using an organic gold paste, fired, and then the connection electrode 26 is printed using an Ag paste. And the piezoelectric actuator board | substrate 21 is produced by baking.

  Next, the flow path member 4 is produced by laminating 4a to i obtained by a rolling method or the like via an adhesive layer. Holes to be the manifold 5, the individual supply channel 14, the pressurizing chamber 10, the descender and the like are processed into a predetermined shape by etching in the plates 4 a to i.

  These plates 4a-i are preferably formed of at least one metal selected from the group 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 reservoir 40 comprises a flow channel structure 41a of an injection molded reservoir body that constitutes the reservoir body 41, plates 41b and d having various holes in a metal, and a damper plate 41c, and a laminated adhesive branch flow channel member 51. The plates 51a to 51c having various holes in the metal were laminated and bonded, and the filter 48 was attached.

  The piezoelectric actuator substrate 21 and the flow path member 4 can be laminated and bonded through, for example, an adhesive layer. A well-known adhesive layer can be used as the adhesive layer, but in order not to affect the piezoelectric actuator substrate 21 and the flow path member 4, an epoxy resin or a phenol resin 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 polyphenylene ether resins. By heating to the thermosetting temperature using such an adhesive layer, the piezoelectric actuator substrate 21 and the flow path member 4 can be heat-bonded.

  Subsequently, the liquid discharge head 2 can be manufactured by bonding the reservoir 40 and the flow path member 4. A well-known adhesive layer can be used as the adhesive layer, but in order not to affect the piezoelectric actuator substrate 21 and the flow path member 4, an epoxy resin or a phenol resin 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 polyphenylene ether resins. By heating to the thermosetting temperature using such an adhesive layer, the branch flow path member 51 and the flow path member 4 can be heat-bonded.

DESCRIPTION OF SYMBOLS 1 ... Printer 2 ... Liquid discharge head 2a ... Head main body 4 ... Channel member 4a-i ... (of channel member) 4-1 ... Discharge hole surface 4-2 ... Pressure chamber surface 5 ... Manifold (common flow path)
5a ... Opening 6 ... Squeezing 8 ... Discharge hole 9 ... Discharge hole array 10 ... Pressurizing chamber 11 ... Pressurizing chamber array 12 ... Individual flow path 14 ... Individual Supply flow path 21 ... Piezoelectric actuator substrate 21a ... Piezoelectric ceramic layer (vibrating plate)
21b ... Piezoceramic layer 24 ... Common electrode 25 ... Individual electrode 25a ... Individual electrode body 25b ... Extraction electrode 26 ... Connection electrode 27 ... Dummy connection electrode 28 ... Common Electrode surface electrode 30 ... Displacement element (pressure part)
40 ... Reservoir 41 ... Reservoir body 41a, 241a ... Channel structure 41a-3, 241a-3 ... Heat conduction part 41a-4, 241a-4 ... Mass adjustment space 41b, d ... Plate 41c (reservoir body) ... Damper plate 41c-1
42 ... reservoir channel 42a ... reservoir channel supply hole 44 ... through hole 46 ... damper 48 ... filter 51 ... branch channel member 51a-c ... (branch flow) Plate 52) ... Branch channel 52a ... Branch channel supply hole 52b ... Branch channel outlet hole

Claims (3)

A flow path member that is long in one direction and includes a plurality of discharge holes and a plurality of pressurizing chambers connected to the plurality of discharge holes, respectively.
Is bonded to the flow path member, and a plurality of the pressure to pressurize the plurality of liquids in the pressure chamber, respectively,
A reservoir that is joined to the flow path member and that has a reservoir flow path for supplying the liquid to the plurality of pressurizing chambers and is long in the one direction;
The reservoir is configured by laminating a plurality of reservoir plates having holes serving as reservoir flow paths,
The reservoir channel is
An introduction flow path extending from one end to the other end of the one direction of the reservoir, to which the liquid is supplied from the outside;
A filter channel that is connected to the introduction channel, extends from the central portion in the one direction of the reservoir to the one end, and is provided with a filter in the middle;
With
The liquid ejection head, wherein a gap is provided on a side opposite to the hole in the one direction of the reservoir plate in which a hole serving as the filter channel is opened among holes of the reservoir channel. . The channel member supplies the liquid to the plurality of pressure chamber has a common passage extending to the other end from the one direction of the one end,
Before SL reservoir channel, as well as extending from the one end of the front Symbol reservoir to said other end, said is connected to the filter flow path one direction of the central portion, the one end and the other end in the liquid discharge head according to claim 1, further comprising said Tei Rukoto the branch flow paths are connected to the common flow channel.   The liquid discharge head according to claim 1, a transport unit that transports a recording medium to the liquid discharge head, and a control unit that controls the plurality of pressure units. A recording device.

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