JP2018167576A - Piezoelectric device, liquid injection head, and liquid injection device - Google Patents

Abstract

To provide a piezoelectric device which suppresses deformation of a substrate on the basis of residual stress and can improve adhesion reliability of the substrate, and a liquid injection head and a liquid injection device.SOLUTION: A piezoelectric device comprises: a substrate (16) in which a plurality of spaces (26) is disposed side-by-side by being partitioned by walls (30); and a partition member (17) partitioning a part of the spaces across the adjacent walls on one surface of the substrate. When a width of each wall in a direction in which the spaces are disposed side-by-side is defined as a, a height of each wall from the one surface to the other surface at an opposite side to the one surface is defined as b, a thickness of the partition member is defined as t, and a dimension in a longitudinal direction of a displaceable and movable area in the partition member is defined as L, t×L/(a×b)≤5×10is satisfied.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a piezoelectric device, a liquid ejecting head, and a liquid ejecting apparatus, each including a substrate having a plurality of spaces separated by walls and a partition member that partitions a part of the space on one surface of the substrate. It is about.

  A substrate having a plurality of spaces separated by walls and a partition member that partitions a part of the space on one surface of the substrate, and a portion corresponding to the space in the partition member functions as a movable region. Piezoelectric devices are applied to various devices (liquid ejecting devices, sensors, etc.). For example, in a liquid ejecting apparatus, there is a piezoelectric device in which a liquid is introduced into a space of a substrate, and a flexible partition member (elastic film) that partitions a part of this space is displaced by a piezoelectric element as a drive element. The liquid jet head is incorporated (for example, see Patent Document 1). In such a liquid ejecting head, the partition member is displaced by driving the piezoelectric element to cause a pressure fluctuation in the liquid in the space, and the liquid is ejected from a nozzle communicating with the space by the pressure fluctuation. In addition, for example, the piezoelectric device having the above-described configuration may be employed for a sensor that detects pressure change, vibration, displacement, or the like of the movable region.

JP 2017-013390 A

  By the way, the above-described piezoelectric device is configured by laminating a plurality of materials, and depending on the stress (residual stress) of each material, the substrate may be deformed or distorted in the manufacturing process. Thereby, when trying to join another member to the wall partitioning the space as described above with an adhesive, there is a possibility that the position of the joining surface of the plurality of walls varies and a joining failure may occur. . In addition, in order to suppress such bonding failure, when the thickness of the adhesive is increased in consideration of the variation of the bonding surface, the adhesive may protrude from the bonding region to the space side. When the protruding adhesive adheres to the movable region, the displacement amount when the movable region is displaced may change from the state before the adhesion. As a result, the displacement amount of the movable region may vary from space to space.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a piezoelectric device and a liquid ejecting head capable of improving the adhesion reliability of the substrate by suppressing the deformation of the substrate based on the residual stress. And providing a liquid ejecting apparatus.

The piezoelectric device of the present invention has been proposed in order to achieve the above-mentioned object, and a substrate in which a plurality of spaces are arranged in parallel with a wall,
A partition member that partitions a part of the space across the adjacent walls on one surface of the substrate;
A piezoelectric element formed on the side opposite to the space side of the partition member;
With
The width of the wall in the parallel arrangement direction of the space is a, the height of the wall from the one surface to the other surface opposite to the one surface is b, the thickness of the partition member is t, The dimension in the longitudinal direction of the movable region that can be displaced in the partition member is L,
t × L ⁴ / (a × b ³ ) ≦ 5 × 10 ⁵
It is characterized by satisfying.

  According to this configuration, the strength in the height direction (vertical direction) of the wall is ensured, so that deformation of the substrate is suppressed. Thereby, since the dispersion | variation in the position of the end surface of the wall joined to another member is suppressed, the joining defect at the time of another member joining to the other surface of a board | substrate with an adhesive agent is reduced. Moreover, since the thickness of the adhesive for suppressing poor bonding can be suppressed, it is possible to reduce the protrusion (flow out) of the adhesive from the bonded portion to the space. Thus, adverse effects on the displacement characteristics of the movable region due to the adhesive flowing out to the space side adhering to the movable region are suppressed.

In each of the above configurations, 1.2 × 10 ⁵ ≦ t × L ⁴ / (a × b ³ ) ≦ 1.6 × 10 ⁵
It is more desirable to satisfy.

  According to this configuration, it is possible to achieve both suppression of substrate distortion and the like and suppression of so-called crosstalk that affects driving characteristics when the movable region is driven in an adjacent space.

In the above configuration, t × b ⁴ / (a × L ³ ) ≦ 1.2 × 10 ⁻³
It is further desirable to satisfy.

  According to this configuration, the strength in the direction in which the partitions are arranged in the space (lateral direction) is ensured, so that crosstalk is more reliably suppressed.

  Further, the present invention is suitable for a configuration in which the partition member has a residual stress.

  According to this configuration, the deformation of the substrate due to the residual stress of the partition member can be suppressed.

In the above configuration, the base material of the wall is silicon,
The partition member may be a silicon oxide film formed by thermal oxidation of the base material.

  According to this configuration, as a result of oxygen bonding to silicon as a base material in the thermal oxidation process, the partition member has compressive stress (residual stress). Even in such a configuration, the deformation of the substrate due to the compressive stress of the partition member can be suppressed.

  According to another aspect of the invention, there is provided a liquid jet head including the piezoelectric device having any one of the configurations described above.

  According to the present invention, since the piezoelectric device in which poor bonding is suppressed is provided, the risk of leakage of liquid from a location where adhesion is insufficient is reduced.

  According to another aspect of the invention, a liquid ejecting apparatus includes the liquid ejecting head having the above-described configuration.

  According to the aspect of the invention, since the liquid ejecting head in which the risk of liquid leakage is reduced is provided, the reliability is improved.

It is a perspective view explaining one form of a liquid ejecting device. FIG. 6 is a cross-sectional view illustrating one embodiment of a liquid ejecting head. It is sectional drawing of the space longitudinal direction explaining one form of a piezoelectric device. It is sectional drawing of the space juxtaposition direction explaining one form of a piezoelectric device. It is a top view explaining one form of a board | substrate. It is a schematic diagram explaining the shape and dimension of the wall which divides space, and a division member (movable area | region). It is a figure explaining the malfunction in the manufacturing process of a piezoelectric device. It is a figure explaining the malfunction in the manufacturing process of a piezoelectric device. It is a figure explaining the malfunction in the manufacturing process of a piezoelectric device. It is a graph explaining the relationship between the intensity | strength in the vertical direction of a wall, and the dispersion | variation (partition wall level | step difference) of the front-end surface of a wall. It is a graph which shows the relationship between the intensity | strength in the horizontal direction of a wall, and a crosstalk rate. It is the table | surface shown about the generation | occurrence | production of the partition level | step difference and crosstalk according to the intensity | strength in the vertical direction of a wall, and the intensity | strength in the horizontal direction of a wall. It is a top view of the pressure chamber formation board in a 2nd embodiment. It is an external view which shows an example of the ultrasonic diagnosing device provided with the piezoelectric device (ultrasonic sensor) in 3rd Embodiment. It is a top view of the piezoelectric device in a 3rd embodiment. It is sectional drawing of the piezoelectric device in 3rd Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In the embodiments described below, various limitations are made as preferred specific examples of the present invention. However, the scope of the present invention is not limited to the following description unless otherwise specified. However, the present invention is not limited to these embodiments. In the following, an ink jet recording head (hereinafter referred to as a recording head) that is one form of a liquid ejecting head including the piezoelectric device according to the present invention, and an ink jet type that is one form of a liquid ejecting apparatus equipped with the same. A printer (hereinafter referred to as a printer) will be described as an example.

  The configuration of the printer 1 will be described with reference to FIG. The printer 1 is a device that records an image or the like by ejecting ink from a nozzle 27 (see FIG. 2) of the recording head 3 onto the surface of a recording medium 2 such as recording paper. The printer 1 includes a recording head 3, a carriage 4 to which the recording head 3 is attached, a carriage moving mechanism 5 that moves the carriage 4 in the main scanning direction, a platen roller 6 that transfers the recording medium 2 in the sub-scanning direction, and the like. I have. Ink, which is a kind of liquid, is stored in an ink cartridge 7 as a liquid supply source. When the ink cartridge 7 is detachably attached to the carriage 4, the ink stored in the ink cartridge 7 is supplied to the recording head 3. It is also possible to employ a configuration in which the ink cartridge 7 is disposed on the main body side of the printer 1 and is supplied from the ink cartridge 7 to the recording head 3 through an ink supply tube.

  The carriage moving mechanism 5 includes a timing belt 8. The timing belt 8 is driven by a pulse motor 9 such as a DC motor. Accordingly, when the pulse motor 9 is operated, the carriage 4 is guided by the guide rod 10 installed on the printer 1 and reciprocates in the main scanning direction (width direction of the recording medium 2).

  FIG. 2 is a cross-sectional view showing an example of the configuration of the recording head 3. 3 is a cross-sectional view of the piezoelectric device 13 included in the recording head 3 in the longitudinal direction of the pressure chamber, and FIG. 4 is a cross-sectional view of the piezoelectric device 13 in the juxtaposition direction of the pressure chamber. FIG. 5 is a plan view of the periphery of the upper opening of the pressure chamber 26 in the pressure chamber forming substrate 16. For convenience, the stacking direction of each member will be described as the vertical direction. The recording head 3 in this embodiment includes a piezoelectric device 13 that is an embodiment of the piezoelectric device of the present invention. The piezoelectric device 13 includes a plurality of substrates, specifically, a nozzle plate 14, a communication substrate 15, and a pressure chamber forming substrate 16 (a kind of substrate in the present invention) which are stacked in this order and bonded to each other by an adhesive 21. It is united by joining. Further, on the surface of the piezoelectric device 13 opposite to the communication substrate 15 side of the pressure chamber forming substrate 16, an elastic film 17 (a kind of partition member in the present invention), a piezoelectric element 18 (a kind of driving element), and A protective substrate 19 that protects the piezoelectric element 18 is laminated. The recording head 3 is configured by attaching the piezoelectric device 13 having such a configuration to the case 20.

  The case 20 is a synthetic resin box-like member to which the piezoelectric device 13 is fixed on the bottom surface side. On the lower surface side of the case 20, a housing hollow portion 22 that is recessed in a rectangular parallelepiped shape from the lower surface to the middle of the height direction of the case 20 is formed, and when the piezoelectric device 13 is joined to the lower surface, the piezoelectric device 13. The pressure chamber forming substrate 16, the elastic film 17, the piezoelectric element 18, and the protective substrate 19 are accommodated in the accommodating space 22. Further, an ink introduction path 23 is formed in the case 20. The ink from the ink cartridge 7 side is introduced into the common liquid chamber 24 of the piezoelectric device 13 through the ink introduction path 23.

  The pressure chamber forming substrate 16 in this embodiment is manufactured from a silicon single crystal substrate (corresponding to a base material in the present invention; hereinafter, also simply referred to as a silicon substrate). In the pressure chamber forming substrate 16, a plurality of pressure chamber vacancies that divide the pressure chamber 26 (a kind of space in the present invention) are arranged in parallel separated by a partition wall 30 (a kind of wall in the present invention). Each pressure chamber cavity is formed by performing anisotropic etching from the surface of the pressure chamber forming substrate 16 on the side of the communication substrate 15. In this way, a space serving as a flow path such as a pressure chamber is formed in the silicon substrate by anisotropic etching, so that higher dimensional and shape accuracy can be ensured. An opening (hereinafter referred to as an upper opening) in the pressure chamber vacant portion on one surface of the pressure chamber forming substrate 16 (the surface opposite to the communication substrate 15 side) is sealed with an elastic film 17. Further, a communication substrate 15 (a kind of other member) is joined to the other surface of the pressure chamber forming substrate 16 opposite to the elastic film 17, and the other opening of the pressure chamber cavity is formed by the communication substrate 15. Sealed. Thereby, the pressure chamber 26 is partitioned. That is, the elastic film 17 partitions a part of the pressure chamber 26 across the adjacent partition walls 30.

In the present embodiment, the pressure chamber forming substrate 16 and the elastic film 17 are integrally formed. More specifically, a silicon oxide film (SiO ₂ ) is formed by thermally oxidizing one surface of a silicon substrate that is a base material of the pressure chamber forming substrate 16, and from the other surface of the silicon substrate. An anisotropic etching process is performed up to the silicon oxide film to form a pressure chamber cavity, and the remaining silicon oxide film functions as the elastic film 17. Note that an insulating film made of zirconium dioxide (ZrO ₂ ) (not shown) is laminated on the elastic film 17. And the piezoelectric element 18 is formed in the position corresponding to the pressure chamber 26 on this insulator film (surface on the opposite side to the pressure chamber 26 side of the elastic film 17), respectively. Here, a portion of the elastic film 17 that seals the upper opening of the pressure chamber 26 functions as a part of a movable region that can be displaced by driving the piezoelectric element 18. On the other hand, in the elastic film 17, the area outside the upper opening of the pressure chamber 26, the area where the weight layer 35 described below is formed, and the area outside this area are deformed and deformed by the elastic film 17. It becomes a non-movable area to be inhibited. Details of the movable region will be described later.

  The pressure chamber 26 in the present embodiment is a hollow portion that is long in a direction orthogonal to the direction in which the nozzles 27 are juxtaposed. One end portion of the pressure chamber 26 in the longitudinal direction communicates with the nozzle 27 via the nozzle communication port 28 of the communication substrate 15. The other end of the pressure chamber 26 in the longitudinal direction communicates with the common liquid chamber 24 via the individual communication port 29 of the communication substrate 15. A plurality of the pressure chambers 26 are provided in parallel by being separated by a partition wall 30 along the nozzle row direction corresponding to each nozzle 27.

The piezoelectric element 18 in the present embodiment is a so-called flexural mode piezoelectric element. In the piezoelectric element 18, a lower electrode layer 32 (first electrode layer), a piezoelectric layer 33 that is a kind of dielectric, and an upper electrode layer 34 (second electrode layer) are sequentially stacked on the elastic film 17. Configured. In the present embodiment, the lower electrode layer 32 is patterned independently for each piezoelectric element 18. As shown in FIG. 5, the lower electrode layer 32 in this embodiment extends along the longitudinal direction of the pressure chamber 26 with a width narrower than the width w in the nozzle row direction of the pressure chambers 26 (pressure chamber juxtaposition direction). Exist. Both ends of the lower electrode layer 32 in the extending direction (longitudinal direction) extend from the inside of the upper opening of the pressure chamber 26 to the non-movable region outside the upper opening. On the other hand, the upper electrode layer 34 is continuously formed across the pressure chambers 26 along the pressure chamber juxtaposition direction. Then, the piezoelectric material in which the upper electrode layer 34, the piezoelectric layer 33, and the lower electrode layer 32 overlap with each other when viewed in the stacking direction causes piezoelectric distortion by applying voltage to the electrode layers 32, 34. Active part. That is, the upper electrode layer 34 is a common electrode provided in common to the plurality of piezoelectric elements 18, and the lower electrode layer 32 is an individual electrode provided individually for each piezoelectric element 18. The lower electrode layer 32 and the upper electrode layer 34 may be made of iridium (Ir), platinum (Pt), titanium (Ti), tungsten (W), nickel (Ni), palladium (Pd), gold (Au), etc. Various metals, and alloys thereof, conductive oxides such as LaNiO ₃ , and the like are used.

  The piezoelectric layer 33 in the present embodiment is formed on the elastic film 17 so as to cover the lower electrode layer 32. As the piezoelectric layer 33, a material containing lead (Pb), titanium (Ti) and zirconium (Zr), for example, a ferroelectric piezoelectric material such as lead zirconate titanate (PZT), niobium oxide, What added metal oxides, such as nickel oxide or magnesium oxide, etc. can be used. As shown in FIG. 5, an opening 36 is formed in a portion corresponding to a region between adjacent pressure chambers 26 in the piezoelectric layer 33. The opening 36 is constituted by a recess or a through hole formed by partially removing the piezoelectric layer 33, and extends along the side (opening edge) of the opening of the pressure chamber 26. In short, the opening 36 is a portion that is relatively thinner than the thickness of other portions in the piezoelectric layer 33 or penetrates the piezoelectric layer 33. Both ends of the opening 36 in the longitudinal direction of the pressure chamber have a tapered shape in which the width in the direction in which the pressure chambers are arranged is gradually narrowed.

  A piezoelectric layer 33 thicker than the portion of the opening 36 is provided in a beam shape at the position of the upper opening of the pressure chamber 26 in the region between the adjacent openings 36. The beam-shaped piezoelectric layer 33 is provided in a portion corresponding to the piezoelectric active portion. The width of the piezoelectric layer 33 of the beam-like portion in the pressure chamber juxtaposition direction is slightly narrower than the width w of the pressure chamber 26 in the same direction. By providing the openings 36 on both sides of the beam-like piezoelectric layer 33 in the pressure chamber juxtaposition direction, the piezoelectric layer 33 corresponding to the piezoelectric active portion can be smoothly displaced.

  As shown in FIGS. 3 and 5, a weight layer 35 is stacked on the upper electrode layer 34 of the piezoelectric element 18 in the present embodiment. In the present embodiment, the weight layer 35a and the weight layer 35b are formed at a position corresponding to one end of the pressure chamber 26 and a position corresponding to the other end of the pressure chamber 26, respectively. As the weight layer 35, gold (Au), copper (Cu), aluminum (Al), an alloy thereof, or the like is used. When the weight layer 35 is made of gold (Au) or the like, the adhesion layer made of titanium (Ti), nickel (Ni), chromium (Cr), tungsten (W), or an alloy thereof is used as the upper electrode. It may be provided between the layer 34.

  The weight layers 35 a and 35 b are stacked on the upper electrode layer 34 in the vicinity of one end and the other end in the longitudinal direction of the pressure chamber 26, and are electrically connected to the upper electrode layer 34. The weight layers 35 a and 35 b in the present embodiment are provided at positions slightly outside the upper opening of the pressure chamber 26 in the longitudinal direction of the pressure chamber 26. By providing these weight layers 35a and 35b, when the piezoelectric element 18 is driven, irregular deformation of the piezoelectric element 18 and the elastic film 17 in the vicinity of the edge of the upper opening of the pressure chamber 26 is suppressed. Damage to the piezoelectric element 18 and the elastic film 17 in the portion is suppressed. In the elastic film 17 in the present embodiment, the weight layer 35a on one side is within the range of the width w of the pressure chamber 26 (more precisely, within the range between the openings 36 adjacent in the pressure chamber juxtaposition direction). A region between the weight layer 35b on the other side is a movable region that can be substantially displaced when the piezoelectric element 18 is driven. That is, in the present embodiment, the region between the weight layers 35 a and 35 b on both sides, and the region outside the upper opening of the pressure chamber 26 can move somewhat according to the driving of the piezoelectric element 18. Functions as part of the movable region. Similar to the upper electrode layer 34, both ends of the weight layers 35a and 35b in the nozzle row direction extend to the outside of the region where the group of pressure chambers 26 are formed. Note that the weight layers 35a and 35b may be provided at a position where a part of the weight layers 35a and 35b overlaps with an end portion of the upper opening of the pressure chamber 26 in plan view. Further, the weight layer 35 is not necessarily provided. In this case, a region that is substantially displaced when the piezoelectric element 18 is driven becomes a movable region.

  The communication substrate 15 is a plate material made of a silicon substrate in the same manner as the pressure chamber forming substrate 16. In this communication substrate 15, an empty portion serving as a common liquid chamber 24 (also referred to as a reservoir or a manifold) provided in common to the plurality of pressure chambers 26 of the pressure chamber forming substrate 16 is formed by anisotropic etching. The common liquid chamber 24 is a long space along the direction in which the pressure chambers 26 are arranged side by side. As shown in FIG. 2, the common liquid chamber 24 in the present embodiment includes a first liquid chamber 24 a penetrating in the plate thickness direction of the communication substrate 15, and the communication substrate from the lower surface side to the upper surface side of the communication substrate 15. The second liquid chamber 24b is formed in a state where the thin wall portion is left on the upper surface side until the middle of the plate thickness direction. One end of the second liquid chamber 24b in the longitudinal direction of the pressure chamber (the end far from the nozzle 27) communicates with the first liquid chamber 24a, while the other end in the same direction is the pressure chamber 26 in plan view. It is formed in the position which overlaps. On the other end of the second liquid chamber 24b, that is, on the side opposite to the first liquid chamber 24a side, individual communication ports 29 penetrating the thin wall portion correspond to the pressure chambers 26 of the pressure chamber forming substrate 16, respectively. A plurality are formed. One end of the individual communication port 29 communicates with the second liquid chamber 24 b and the other end of the individual communication port 29 communicates with the pressure chamber 26 of the pressure chamber forming substrate 16.

  The nozzle plate 14 is a plate material in which a plurality of nozzles 27 are arranged in a row. In the present embodiment, a plurality of nozzles 27 are provided at a formation pitch corresponding to the dot formation density to form a nozzle row. The nozzle plate 14 in the present embodiment is made of a silicon substrate, and a cylindrical nozzle 27 is formed on the substrate by dry etching. In the piezoelectric device 13 in this embodiment, an ink flow path is formed from the common liquid chamber 24 to the nozzle 27 through the individual communication port 29, the pressure chamber 26, and the nozzle communication port 28. .

  In the recording head 3 including the piezoelectric device 13 having the above-described configuration, the movable region of the elastic film 17 becomes a nozzle when the piezoelectric active portion bends and deforms according to the change in the voltage of the drive signal applied to the piezoelectric element 18. It is displaced in a direction approaching 27 or in a direction away from the nozzle 27. As a result, pressure fluctuation occurs in the ink in the pressure chamber 26, and ink is ejected from the nozzles 27 using this pressure fluctuation.

  FIG. 6 is a schematic diagram for explaining the shapes and dimensions of the partition wall 30 defining the pressure chamber 26 and the elastic film 17 (movable region). Hereinafter, the width (thickness) of the partition walls 30 in the direction in which the pressure chambers 26 are juxtaposed (in the nozzle row direction in this embodiment) is a, and the height of the partition walls 30 is from the base end on the elastic film 17 side to the communication substrate 15 side. Let b be the length to the tip), and L be the length of the movable region of the elastic film 17 in the longitudinal direction of the pressure chamber 26 (longitudinal direction of the movable region). In recent years, the formation pitch of the nozzles 27 in the recording head 3 has become narrower in response to demands for higher resolution and smaller size, and accordingly, the formation pitch of the pressure chambers 26 has become narrower. Thereby, the width (thickness) a of the partition wall 30 becomes thinner and the width w of the pressure chamber 26 tends to become narrower. Assuming that the longitudinal dimension of the pressure chamber 26 is constant and the width w of the pressure chamber 26 is narrowed, the volume of the pressure chamber 26 is reduced accordingly. In order to maintain the weight (exclusion deposition) of the ink ejected from the nozzles 27 when driven by applying a predetermined voltage to the piezoelectric element 18, the longitudinal dimension of the pressure chamber 26 is made longer. Thus, it is necessary to make the length L of the movable region longer. However, the strength in the height direction of the partition wall 30 is reduced by increasing the length L of the movable region. This may cause the following problems in the manufacturing process of the recording head 3 (piezoelectric device 13).

  7 to 9 are schematic views for explaining problems in the manufacturing process of the recording head 3 (piezoelectric device 13). In addition, in each figure, illustration of other structural members, such as the piezoelectric element 18 formed on the elastic film 17, is abbreviate | omitted. Further, in FIGS. 8 and 9, the distortion of the pressure chamber forming substrate 16 is shown exaggerated from the actual one. For example, in the manufacturing process of the piezoelectric device 13 in the present embodiment, as shown in FIG. 7, one surface of the pressure chamber forming substrate 16 made of a silicon substrate is thermally oxidized to thereby form an elastic film made of a silicon oxide film. 17 is formed. As a result of oxygen bonding to silicon as a base material in this step, the elastic film 17 has compressive stress (a kind of residual stress) because it tends to expand. In this state, as indicated by an arrow in FIG. 8, an empty portion that becomes the pressure chamber 26 is formed from the other surface of the pressure chamber forming substrate 16 by anisotropic etching using an etching solution such as potassium hydroxide (KOH). As a result, the strength of the pressure chamber forming substrate 16 that supports the elastic film 17 is reduced accordingly, whereby the compressive stress of the elastic film 17 is gradually released and the pressure chamber forming substrate 16 is deformed (distorted). Occurs. As shown in FIG. 9, when anisotropic etching is performed until the elastic film 17 that functions as an etching stop is reached, the elastic film 17 is formed in a portion corresponding to the pressure chamber 26 in the pressure chamber forming substrate 16. Therefore, depending on the strength of the partition wall 30 in the height direction (longitudinal direction), the pressure chamber forming substrate 16 is more distorted, and the tip surface of the partition wall 30, that is, other members in the subsequent process, The position of the surface joined to a certain communication substrate 15 varies greatly. In such a state, it is difficult to uniformly apply the adhesive 21 to the front end surface of the partition wall 30 by transfer or the like when bonding to the communication substrate 15, which may cause bonding failure.

  In addition, if the positions of the surfaces to be joined vary, the transfer itself cannot be performed depending on the adhesive as described above (a part that cannot be joined occurs), and even if it can be transferred, in order to prevent ink leakage from the joint part It is necessary to increase the thickness of the adhesive, and if it is joined in this state, the amount of adhesive protruding to the flow path side (pressure chamber 26 side) will vary. In this way, the adhesive that protrudes to the flow path side may change the amount of displacement when the movable region is driven, for example, when the adhesive reaches the elastic film 17 through the partition wall of the pressure chamber 26 by capillary action and hardens. is there. If the amount of the protruding adhesive varies, the amount of the adhesive that rises up to the elastic film 17 also varies. As a result, there is a problem that the displacement amount of the movable region varies in each pressure chamber 26.

In view of the above problems, in the printer 1 according to the present invention, the occurrence of deformation of the pressure chamber forming substrate 16 is suppressed by appropriately setting the above dimensions. More specifically, the following condition (1) is satisfied for the width a of the partition wall 30, the height b of the partition wall 30, the length L of the movable region of the elastic film 17, and the film thickness t of the elastic film 17. Each dimension is set in.
t × L ⁴ / (a × b ³ ) ≦ 5 × 10 ⁵ (1)
In the above condition (1), “t × L ⁴ / (a × b ³ )” indicates the strength in the height direction (longitudinal direction) of the partition wall 30 functioning as a beam having both ends fixed in the pressure chamber forming substrate 16. (Hereinafter, referred to as a longitudinal strength calculation formula as appropriate). In this longitudinal strength calculation formula, since the height b of the partition wall 30 is the third power and the length L of the movable region is the fourth power, the length of the movable region is particularly effective in securing the strength of the partition wall 30 in the vertical direction. It is effective to make L shorter and the height b of the partition wall 30 lower.

  FIG. 10 illustrates the relationship between the vertical strength of the partition wall 30 and the variation in the front end surface of the partition wall 30 (hereinafter referred to as a partition wall step as appropriate) for a plurality of recording heads (piezoelectric devices) having different dimensions and shapes. It is a graph to do. In the figure, the horizontal axis indicates the calculated value of the above-described vertical strength calculation formula representing the vertical strength of the partition wall 30, and the vertical axis indicates the partition wall level difference [nm]. Note that, as shown in FIG. 9, the step of the partition wall is the tip of each partition wall 30 from a virtual plane (a surface having a height indicated by Pv in FIG. 9) passing through both ends of the pressure chamber forming substrate 16 in the pressure chamber juxtaposition direction. It is represented by the difference Δd between the maximum value and the minimum value of the height to the surface (distance in the normal direction of the virtual surface Pv).

As shown in FIG. 10, when the value of the longitudinal strength calculation formula exceeds a certain value, the strength in the longitudinal direction of the partition wall 30 is reduced and the partition wall step is significantly increased. Here, in the case where the adhesive 21 is applied to the front end surface of the partition wall 30 by transfer and the communication substrate 15 is bonded, the thickness of the adhesive 21 is not extremely increased, that is, on the flow channel side such as the pressure chamber 26. In order to suppress the occurrence of bonding failure while suppressing the protrusion of the adhesive 21 to the surface, it is desirable that the partition wall step be 200 [nm] or less. In order for the partition wall step to be 200 [nm] or less, the value of the longitudinal strength needs to be 5 × 10 ⁵ or less. As shown in the figure, when the value of the longitudinal strength exceeds 5 × 10 ⁵ , the partition wall step becomes larger than 200 [nm], thereby increasing the possibility of occurrence of bonding failure.

By setting the dimensions so that the above condition (1) is satisfied, the vertical strength of the partition wall 30 is ensured, so that the deformation of the pressure chamber forming substrate 16 is suppressed. Thereby, since the variation in the position of the front end surface of the partition wall 30 is suppressed, the bonding failure when the communication substrate 15 is bonded to the other surface of the pressure chamber forming substrate 16 by the adhesive 21 is reduced. As a result, the yield of the piezoelectric device 13 is improved and the reliability is also improved. In particular, in the present embodiment, since the elastic film 17 is formed by thermal oxidation of silicon, it has compressive stress (residual stress), and when the pressure chamber 26 is formed by anisotropic etching in this state. Also, the deformation of the pressure chamber forming substrate 16 due to the release of the compressive stress of the elastic film 17 can be suppressed, which is preferable. And since the thickness of the adhesive 21 for suppressing poor bonding can be suppressed, it is possible to reduce the protrusion (flow out) of the adhesive 21 to the flow path such as the pressure chamber 26. As a result, adverse effects on the displacement characteristics of the movable region due to the adhesive 21 flowing out to the flow path side adhering to the movable region of the elastic film 17 are suppressed.
In the recording head 3 employing such a piezoelectric device 13, the risk of ink leakage from a location where the adhesion is insufficient is reduced. In addition, since the variation in the displacement characteristics of the movable region caused by the flow of the adhesive 21 is suppressed, it is possible to suppress the variation in the ejection characteristics of the nozzles 27. Furthermore, in the printer 1 including such a recording head 3, the reliability is improved.

By the way, even when the condition (1) is satisfied, depending on the strength (lateral strength) of the partition walls 30 in the pressure chamber juxtaposition direction, the partition walls 30 are caused by pressure fluctuations generated in the pressure chambers 26 when ink is ejected. Due to the deformation, the ejection characteristics such as the amount of ink ejected from the nozzles 27 and the flying speed fluctuate, that is, the so-called crosstalk that affects the driving characteristics when the movable region is driven in the adjacent space may occur. There is.
From this viewpoint, in the printer 1 according to the present invention, the dimensions are set so as to further satisfy the following condition (2).
t × b ⁴ / (a × L ³ ) ≦ 1.2 × 10 ⁻³ (2)
In the above condition (2), “t × b ⁴ / (a × L ³ )” is the horizontal direction (pressure chamber side-by-side direction) of the partition wall 30 that functions as a beam whose both ends are fixed in the pressure chamber forming substrate 16. This is a formula representing the strength (hereinafter, referred to as a lateral strength calculation formula as appropriate).

FIG. 11 is a graph showing the relationship between the strength in the lateral direction of the partition wall 30 and the crosstalk rate. Here, the crosstalk rate refers to the ink flying speed Vma when ink is ejected simultaneously from a plurality of adjacent nozzles 27 belonging to the same nozzle row (when all are ON), and the ink is individually ejected from one nozzle 27. This is the degree of change in ejection characteristics represented by the ratio to the ink flying speed Vms when ejected (when 1 ON), and is represented by the following equation (CT).
Crosstalk rate = 1−Vms / Vma (CT)
For example, when Vma = 10 [m / s] and Vms = 8 [m / s], the crosstalk rate is 0.2. When the printer 1 records an image or the like on the recording medium 2, particularly when a higher resolution image is recorded, the crosstalk rate is required to be less than 0.15. When the crosstalk ratio exceeds 0.15, the landing position deviation of the ink ejected from the nozzle 27 from the target position in the recording medium 2 becomes remarkable, and the recorded image or the like is visually as in the so-called graininess. This is because the roughness becomes conspicuous.

  Therefore, by setting the dimensions so that the above condition (2) is satisfied, the strength in the lateral direction of the partition wall 30 (the direction in which the pressure chambers are arranged side by side) is secured. Displacement of the partition wall 30 is suppressed when the pressure 18 is driven and a pressure fluctuation occurs in the pressure chamber 26. As a result, the crosstalk is suppressed. That is, fluctuations in ejection characteristics (the amount of ink ejected from the nozzles 27 and the flying speed) are suppressed.

  FIG. 12 is a table showing the partition wall level difference and the occurrence of crosstalk (CT) according to the vertical strength and the horizontal strength. In the figure, the portion surrounded by a thick frame indicates a range in which the longitudinal strength and the lateral strength satisfy the above condition (1) and the condition (2), respectively. In addition, “◯” indicates that there is almost no partition wall level difference, “Δ” indicates that a level difference of 200 nm or less is generated, and “X” indicates a level difference exceeding 200 nm. Indicates that this has occurred. Further, for crosstalk, “◯” indicates that almost no crosstalk has occurred (for example, the crosstalk rate is less than 0.1), and “Δ” indicates that crosstalk has occurred but is within an allowable range. (For example, the crosstalk rate is 0.1 or more and 0.15 or less). The width a of the partition wall 30, the length L of the movable region, and the film thickness t of the elastic film 17 are fixed at such values that the above-described exclusion deposition is a predetermined value, and only the height b of the partition wall 30 is changed. As a result, the values of longitudinal strength and lateral strength are changed.

As shown in FIG. 12, when the condition (1) is satisfied, both the partition wall step and the crosstalk are “Δ” or “◯”, and both the suppression of the partition wall step and the suppression of the crosstalk can be achieved. However, the following condition (3) or condition (4) may be further satisfied so that both of the partition wall step and the crosstalk become “◯”.
1.2 × 10 ⁵ ≦ t × L ⁴ / (a × b ³ ) ≦ 1.6 × 10 ⁵ (3)
5.9 × 10 −4 ≦ t × b ⁴ / (a × L ³ ) ≦ 8.6 × 10 ⁻³ (4)
As a result, it is possible to more effectively achieve both the suppression of the partition wall step and the suppression of crosstalk.

  By the way, the present invention is not limited to the above-described embodiment, and various modifications can be made based on the description of the scope of claims.

  FIG. 13 is a plan view of the pressure chamber forming substrate 40 in the second embodiment of the present invention. In the first embodiment, the configuration in which the periphery of the upper opening of the pressure chamber 26 is surrounded by the structural wall including the partition wall 30 of the pressure chamber forming substrate 16 without interruption is illustrated, but the present invention is not limited to this. In the pressure chamber forming substrate 40 in the present embodiment, a plurality of pressure chambers 41 corresponding to the spaces in the present invention are arranged in parallel separated by a partition wall 42 corresponding to a wall in the present invention, and are common to the pressure chambers 41. The common liquid chamber 44 and an individual communication port 43 for communicating the common liquid chamber 44 with each pressure chamber 41 are formed. For this reason, the upper opening of the pressure chamber 41 is not closed by the structural wall of the pressure chamber forming substrate 40 including the partition wall 42, and is opened at a portion corresponding to the individual communication port 43. Even in such a configuration, the present invention can be applied similarly to the configuration of the first embodiment. That is, the width of the partition wall 42 in the direction in which the pressure chambers 41 are arranged is a, the height of the partition wall 42 is b, and the length of the movable region of the elastic film (partition member) provided on one surface of the pressure chamber forming substrate 40. If L is L and the thickness of the elastic film is t, and the dimensions are set so that the above conditions (1) to (4) are satisfied, the same effects as the configuration of the first embodiment can be obtained. . Other configurations are the same as those in the first embodiment.

  FIG. 14 is a diagram illustrating a configuration of an ultrasonic diagnostic apparatus 51 including an ultrasonic sensor 60 which is a kind of electronic device according to the third embodiment. FIG. 15 is a plan view showing an example of the ultrasonic sensor 60 according to the present embodiment, and FIG. 16 is a cross-sectional view of the main part in the row direction (lateral direction in FIG. 15) of the ultrasonic sensor 60. In each of the above embodiments, the configuration in which ink that is a kind of liquid is ejected from the nozzle by displacing the movable region is exemplified, but the present invention is not limited to this, and the movable sensor is movable like the ultrasonic sensor 60 in the present embodiment. The present invention can also be applied to a sensor that detects vibration (displacement) or the like of a region. For this reason, the space in the present invention is not limited to the one through which the liquid flows.

  An ultrasonic diagnostic apparatus 51 shown in FIG. 14 includes an apparatus terminal 52 and an ultrasonic probe 53. The device terminal 52 and the ultrasonic probe 53 are connected to each other by a cable 54. The device terminal 52 and the ultrasonic probe 53 transmit and receive electrical signals through the cable 54. The ultrasonic probe 53 includes a main body 55 and a probe head 56 that is detachably attached to the main body 55. An ultrasonic sensor 60 is provided on the probe head 56. The ultrasonic sensor 60 transmits a sound wave (ultrasonic wave) from the surface (the surface shown in FIG. 15) toward the measurement target and receives a reflected wave from the measurement target, thereby measuring the distance to the measurement target and the measurement. The shape of the target is detected. The ultrasonic sensor 60 in the present embodiment is configured by forming an element array 62 on a base 61. The element array 62 includes an array of piezoelectric elements 64. The array is formed in a matrix of a plurality of rows and a plurality of columns. As shown in FIG. 16, the piezoelectric element 64 includes an upper electrode 65, a lower electrode 66, and a piezoelectric film 67, and the piezoelectric film 67 is sandwiched between the upper electrode 65 and the lower electrode 66. . In the present embodiment, the upper electrode 65 functions as a common electrode common to the piezoelectric elements 64, and the lower electrode 66 functions as individual electrodes of the piezoelectric elements 64. Note that the functions of the upper electrode 65 and the lower electrode 66 may be interchanged. That is, the lower electrode may be provided in common for the piezoelectric elements 64 of the entire matrix, while the upper electrode may be provided individually for each piezoelectric element 64. In addition, with respect to the arrangement of the element array 62, for example, a configuration in which the positions in the column direction of the piezoelectric elements 64 in adjacent columns are alternate may be employed. In this case, the even-numbered piezoelectric element 64 groups may be arranged so as to be shifted in the column direction by a half of the row pitch with respect to the odd-numbered piezoelectric element 64 groups.

  In the base 61, a first terminal array 68 a and a second terminal array 68 b are formed at one end side and the other end side in the column direction of the piezoelectric elements 64, respectively, at positions away from the element array 62. Each of the terminal arrays 68a and 68b is composed of a pair of common electrode terminals 69 arranged on both sides in the row direction and a plurality of individual electrode terminals 70 arranged between the common electrode terminals 69 on both sides. Yes. The common electrode terminal 69 is electrically connected to the upper electrode 65 of the piezoelectric element 64, and the individual electrode terminal 70 is electrically connected to the lower electrode 66 of the piezoelectric element 64. A flexible wiring board (not shown) having one end connected to a control circuit (not shown) of the ultrasonic diagnostic apparatus 51 is electrically connected to each terminal array 68a, 68b. As described later, the drive signal VDR and the reception signal VR are transmitted and received between the control circuit and the ultrasonic sensor 60 through the flexible wiring board.

As shown in FIG. 16, the base 61 includes a substrate 72 and a flexible film 73 (a kind of partition member in the present invention) stacked on each other. More specifically, the flexible film 73 is formed on one surface of the substrate 72. A plurality of voids 74 (a kind of space in the present invention) are partitioned and formed on the substrate 72 by partition walls 75 (a kind of wall in the present invention) corresponding to the respective piezoelectric elements 64. That is, the voids 74 are arranged in an array with respect to the substrate 72, and the partition walls 75 are arranged between two adjacent voids 74. A portion of the flexible film 73 corresponding to the upper opening of the empty portion 74 functions as the movable region 78. The movable region 78 is a portion of the flexible film 73 that can oscillate (displace) in the thickness direction of the substrate 72 by partitioning a part (ceiling surface) of the empty portion 74. In the present embodiment, the substrate 72 and the flexible film 73 are integrally formed. More specifically, a silicon oxide film (SiO ₂ ) is formed by thermally oxidizing one surface of a silicon substrate which is a base material of the substrate 72, and a silicon oxide film is formed from the other surface of the silicon substrate. Thus, anisotropic etching is performed to form a void 74, and the remaining silicon oxide film functions as the flexible film 73. Note that an insulating film (not shown) is laminated on the flexible film 73. Then, the lower electrode 66, the piezoelectric film 67, and the upper electrode 65 are sequentially laminated on the surface of the movable region 78 (the surface opposite to the surface on the empty portion 74 side), and the piezoelectric element 64 is disposed. .

  A reinforcing plate 76 is bonded to the back surface of the substrate 61 (the surface opposite to the flexible film 73 side) with an adhesive 80. The reinforcing plate 76 closes the empty portion 74 on the back surface of the ultrasonic sensor 60. As the reinforcing plate 76, for example, a silicon substrate can be used.

  In the ultrasonic sensor 60, during a transmission period (vibration period) in which ultrasonic waves are transmitted, the drive signal VDR output from the control circuit is supplied (applied) to the lower electrode 66 of each piezoelectric element 64 via the individual electrode terminal 70. ) Further, during a reception period (vibration period) in which an ultrasonic reflected wave (echo) is received, the reception signal VR from the piezoelectric element 64 is output via the lower electrode 66 and the individual electrode terminal 70. A common voltage VCOM is supplied to the upper electrode 65 of each piezoelectric element 64 via the common electrode terminal 69. This common voltage VCOM is a constant DC voltage. When a difference voltage between the drive signal VDR and the common voltage VCOM is applied to each piezoelectric element 64, an ultrasonic wave having a predetermined frequency is transmitted from the piezoelectric element 64. Then, the ultrasonic waves radiated from all the piezoelectric elements 64 are combined to form an ultrasonic wave radiated from the element array surface of the ultrasonic sensor 60. This ultrasonic wave is transmitted toward the measurement target (for example, inside the human body). In addition, when the reflected wave reflected from the measurement target is input to the piezoelectric element 64 after the ultrasonic wave is transmitted, the piezoelectric element 64 vibrates as a vibration part for detection in response to the electromotive force. Arise. This electromotive force is output to the control circuit as a reception signal VR. In the present embodiment, the piezoelectric element group functioning as a detection vibration unit alternately transmits sound waves and receives reflected waves at different times.

  As in the first embodiment, when deformation or distortion occurs in the substrate 72 during the manufacturing process, the position of the surface to be bonded (the surface where the substrate 72 is bonded to the reinforcing plate 76) varies, resulting in poor bonding or movable There is a possibility that variation in the displacement amount of the region 78 may occur. Therefore, the width of the partition 75 in this embodiment is a, the height of the partition 75 is b, the length of the movable region 78 in the longitudinal direction is L, and the film thickness t of the movable region 78 is the above. If the dimensions are set so that the conditions (1) to (4) are satisfied, the same effects as the configuration of the first embodiment can be obtained. That is, since the deformation of the substrate 72 is suppressed, poor bonding when the reinforcing plate 76 is bonded to the other surface of the substrate 72 by the adhesive 80 is reduced. As a result, the yield of the ultrasonic sensor 60 that is a piezoelectric device is improved, and the reliability is also improved. And since the thickness of the adhesive 80 for suppressing a joint failure can be suppressed, it becomes possible to reduce the protrusion (flow out) of the adhesive 80 to the empty part 74 side. Thus, adverse effects on the displacement characteristics (vibration characteristics) of the movable region 78 due to the adhesive 80 flowing out toward the empty portion 74 being attached to the movable region 78 are suppressed. Furthermore, since the strength of the partition 75 is ensured, displacement of the partition 75 during vibration of the piezoelectric element 64 and the movable region 78 is suppressed. As a result, fluctuations in the vibration characteristics (transmission characteristics / reception characteristics) of the movable region 78 due to so-called adjacent crosstalk are suppressed.

  The residual stress of the partition member is not limited to compressive stress, and the partition member may have tensile stress depending on the film forming method, and the present invention can be applied to such a configuration. Thereby, it becomes possible to suppress the deformation | transformation of the board | substrate resulting from a tensile stress.

  Furthermore, according to the present invention, the present invention can also be applied to a configuration in which a substrate and other members (other base materials) bonded thereto have residual stresses (regardless of compressive stress or tensile stress). Thereby, it is possible to suppress the deformation of the substrate due to the difference in these residual stresses.

  In the first embodiment, the ink jet recording head 3 is described as an example of the liquid ejecting head. However, in the present invention, the space is separated from the wall by bonding a plurality of substrates with an adhesive. The present invention can also be applied to other liquid ejecting heads that employ a configuration in which a plurality of spaces are formed and a part of the space is partitioned by a partition member having a movable region. For example, a color material ejecting head used for manufacturing a color filter such as a liquid crystal display, an electrode material ejecting head used for forming an electrode such as an organic EL (Electro Luminescence) display, FED (surface emitting display), a biochip (biochemical element) The present invention can also be applied to bioorganic matter ejecting heads and the like used in the production of In a color material ejecting head for a display manufacturing apparatus, a solution of each color material of R (Red), G (Green), and B (Blue) is ejected as a kind of liquid. Further, an electrode material ejecting head for an electrode forming apparatus ejects a liquid electrode material as a kind of liquid, and a bioorganic matter ejecting head for a chip manufacturing apparatus ejects a bioorganic solution as a kind of liquid.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Recording medium, 3 ... Recording head, 4 ... Carriage, 5 ... Carriage moving mechanism, 6 ... Platen roller, 7 ... Ink cartridge, 8 ... Timing belt, 9 ... Pulse motor, 10 ... Guide rod, 13 DESCRIPTION OF SYMBOLS ... Piezoelectric device, 14 ... Nozzle plate, 15 ... Communication substrate, 16 ... Pressure chamber forming substrate, 17 ... Elastic film, 18 ... Piezoelectric element, 19 ... Protective substrate, 20 ... Case, 21 ... Adhesive, 22 ... Housing space , 23 ... Ink introduction path, 24 ... Common liquid chamber, 26 ... Pressure chamber, 27 ... Nozzle, 28 ... Nozzle communication port, 29 ... Individual communication port, 30 ... Bulkhead, 32 ... Lower electrode layer, 33 ... Piezoelectric layer, 34 ... upper electrode layer, 35 ... weight layer, 36 ... opening, 40 ... pressure chamber forming substrate, 41 ... pressure chamber, 42 ... partition wall, 43 ... individual communication port, 44 ... common liquid chamber, 51 ... ultrasonic diagnostic device, 52 ... Terminal equipment , 53 ... ultrasonic probe, 54 ... cable, 55 ... main body, 56 ... probe head, 60 ... ultrasonic sensor, 61 ... substrate, 62 ... element array, 64 ... piezoelectric element, 65 ... upper electrode, 66 ... lower electrode , 67 ... Piezoelectric film, 68 ... Terminal array, 69 ... Common electrode terminal, 70 ... Individual electrode terminal, 72 ... Substrate, 73 ... Flexible film, 74 ... Empty part, 75 ... Bulkhead, 76 ... Reinforcing plate, 78 ... Movable region, 80 ... adhesive

Claims (7)

A substrate in which a plurality of spaces are arranged side by side with a wall;
A partition member that partitions a part of the space across the adjacent walls on one surface of the substrate;
A piezoelectric element formed corresponding to each space on the side opposite to the space side of the partition member;
With
The width of the wall in the parallel arrangement direction of the space is a, the height of the wall from the one surface to the other surface opposite to the one surface is b, the thickness of the partition member is t, The dimension in the longitudinal direction of the movable region that can be displaced in the partition member is L,
t × L ⁴ / (a × b ³ ) ≦ 5 × 10 ⁵
A piezoelectric device characterized by satisfying Furthermore, 1.2 × 10 ⁵ ≦ t × L ⁴ / (a × b ³ ) ≦ 1.6 × 10 ⁵
The piezoelectric device according to claim 1, wherein: t × b ⁴ / (a × L ³ ) ≦ 1.2 × 10 ⁻³
The piezoelectric device according to claim 1 or 2, wherein:   The piezoelectric device according to any one of claims 1 to 3, wherein the partition member has a residual stress. The base material of the wall is silicon;
The piezoelectric device according to claim 4, wherein the partition member is a silicon oxide film formed by thermal oxidation of the base material.   A liquid ejecting head comprising the piezoelectric device according to claim 1.   A liquid ejecting apparatus comprising the liquid ejecting head according to claim 6.

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