JP2018094860A - Liquid discharge head and manufacturing method of liquid discharge head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge head capable of securing rigidity even if a thickness of a discharge port plate is thinned.SOLUTION: A liquid discharge head includes: a diaphragm 11; and a pressure chamber 16 surrounded by a discharge port plate 13. The liquid discharge head discharges liquid in the pressure chamber from a discharge port 14 of the discharge port plate using deflection of the diaphragm caused by a piezoelectric body formed on the diaphragm. Both of an internal angle θin a contact section between an inner wall 17 in a short-side direction of the pressure chamber and the diaphragm and an internal angle θin a contact section between the inner wall 17 and the discharge port plate are obtuse angles. A width Win the short-side direction of the pressure chamber on the diaphragm side and a width Win the short-side direction of the pressure chamber on the discharge port plate side satisfy W>W.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid discharge head that discharges droplets using a piezoelectric element and a method for manufacturing the same.

A liquid discharge head that performs recording by discharging droplets of ink or the like onto a recording medium includes a liquid discharge head in which a large number of liquid discharge units are two-dimensionally arranged in order to perform higher-definition recording at a high speed. Yes.
Each liquid discharge section includes a liquid chamber communicating with the discharge port, and a pressure generating unit that is provided to face the discharge port and applies a discharge pressure to the liquid in the liquid chamber. A device using a piezoelectric element as a pressure generating means is known. In particular, a bend type piezoelectric actuator having a structure in which a piezoelectric element including a thin film piezoelectric body and a diaphragm are bonded together is preferably used. Bend-type piezoelectric actuators (also referred to simply as actuators) are bent because the piezoelectric body tends to contract in the surface direction by applying a voltage between the electrodes formed on both sides of the thin film piezoelectric body, while the diaphragm does not contract. Deformation occurs. A liquid discharge head according to this method is configured to bend and deform a wall surface of a liquid chamber (hereinafter referred to as a pressure chamber) that generates a pressure facing a discharge port by an actuator, and to discharge the liquid by increasing or decreasing the volume of the pressure chamber. . Such a liquid discharge head is widely used because it is relatively easy to arrange actuators with high density and accuracy using a semiconductor process. The discharge port plate in which the discharge ports are formed is desired to have rigidity in order to receive liquid pressure during liquid discharge. On the other hand, in order to improve the discharge accuracy, the processing accuracy of the discharge port is required.

  Patent Document 1 discloses a liquid discharge head (inkjet head) having a structure in which two members are bonded to each other to form a discharge port plate. As for the structure of the discharge port plate, one is a plate-like member having a circular hole, and the other is a polymer resin film-like member having a hole having a smaller diameter than the circular hole.

Further, each ejection unit of the liquid ejection head has a time during which it does not eject liquid such as ink during operation. In addition, there are discharge ports that do not discharge liquid for a long time even during continuous recording, depending on the size of the recording medium, such as the white background and margin of the recording medium, and the drawing pattern to be printed. Therefore, a discharge failure may occur due to evaporation and thickening of a part of the liquid component inside the discharge port while the liquid is not discharged.
As one of countermeasures, a method has been proposed in which a circulation tank is provided so that liquid is always circulated in the flow path in the head connected to the ejection port regardless of whether or not ejection is performed. This suppresses the thickening of the liquid by diffusing a part of the liquid thickened inside the discharge port by evaporation into the circulating liquid.

JP-A-3-239555

  The liquid discharge head described in Patent Document 1 has an effect of imparting rigidity to the discharge port plate because one plate-like member of the discharge port plate is a rigid member. However, since the discharge port plate has a structure in which two members are bonded together, the structure is complicated. Furthermore, when applied to the liquid circulation in the liquid flow path, the discharge port plate has a bonded structure of two members, so that the discharge port becomes deeper. There is a possibility that the diffusion of the liquid into the circulating liquid becomes insufficient. Therefore, it is desired to reduce the thickness of the discharge port plate, but there is a problem that it is difficult to ensure the rigidity of the discharge port plate if the thickness is reduced.

  Accordingly, an object of the present invention is to provide a liquid discharge head capable of improving the rigidity of the discharge port plate.

According to one aspect of the present invention, the diaphragm has a pressure chamber surrounded by the diaphragm and the discharge port plate, and the diaphragm is bent by the piezoelectric body formed on the surface of the diaphragm facing the pressure chamber. A liquid discharge head that discharges the liquid in the pressure chamber from the discharge port of the discharge port plate, the inner wall at the contact portion between the inner wall in the short direction of the pressure chamber and the diaphragm, and the The internal angle formed by the short direction is an obtuse angle, the internal angle formed by the inner wall and the short direction at the contact portion between the short direction inner wall of the pressure chamber and the discharge port plate is an obtuse angle, and the vibration width W _d of the lateral direction of the pressure chamber plate _side, when the width W _s of the transverse direction of the pressure chamber of the discharge port plate side, the liquid ejection head and satisfies the following formula (1) Will be provided:
W _d > W _s (1).

Further, according to another aspect of the present invention, the vibration by the piezoelectric body having a vibration plate and a pressure chamber surrounded by the discharge port plate and formed on a surface of the vibration plate facing the pressure chamber. A liquid discharge head that discharges the liquid in the pressure chamber from the discharge port of the discharge port plate by utilizing the bending of a plate, and the pressure chamber is formed as a through hole in a substrate constituting a side wall of the pressure chamber. The width in the short direction of the pressure chamber on the diaphragm side is W _d , the width in the short direction of the pressure chamber on the discharge port plate side is W _s, and the thickness of the substrate is T _w , Provided is a liquid discharge head characterized by satisfying the following formulas (1) and (2), where θ is an external angle formed between a short side direction and a side wall surface of the pressure chamber:
W _d > W _s (1)
_{T w ≧ (1/2) · (} W d -W s) · tanθ ··· (2).

According to still another aspect of the present invention, the diaphragm includes a diaphragm and a pressure chamber surrounded by a discharge port plate, and the diaphragm is formed by a piezoelectric body formed on a surface of the diaphragm facing the pressure chamber. Manufacturing a liquid discharge head that discharges the liquid in the pressure chamber from the discharge port of the discharge port plate by using the deflection of the discharge chamber, wherein the pressure chamber has the diaphragm on the first surface and the discharge port plate. Formed on a substrate having a second surface opposite to the first surface, the substrate having a rectangular cross-section in the plane direction, and having a short side on the first surface side of the through-hole direction of the opening width W _d, wherein when the second short-side direction of the opening width of the side and W _s, the liquid having a step of forming the through hole in the substrate such that W _d> W _s A method for manufacturing a discharge head is provided.

  According to the present invention, it is possible to provide a liquid discharge head capable of improving the rigidity of the discharge port plate.

FIG. 3 is a schematic cross-sectional view showing a main part of a liquid ejection head according to an embodiment of the present invention. It is a schematic diagram which shows the whole liquid discharge head which concerns on the example of 1 embodiment of this invention, (a) is the BB cross section of (b), (b) is the AA cross section of (a), (c). Shows the CC cross section of (b). It is process drawing which shows the manufacturing method of the liquid discharge head which concerns on the example of 1 embodiment of this invention. It is a schematic diagram which shows the liquid discharge head which concerns on the other embodiment of this invention. FIG. 3 is a schematic diagram illustrating a part of a liquid discharge head according to an embodiment of the present invention. FIG. 10 is a process diagram illustrating another example of the manufacturing method of the liquid ejection head according to the embodiment of the present invention.

  About the liquid discharge head concerning this invention, and its manufacturing method, a preferable embodiment example is given using a figure and the structure of this invention, an effect | action, and an effect are demonstrated.

[Embodiment 1]
FIG. 1 is a diagram showing a configuration of a main part of a liquid discharge head according to an embodiment of the present invention, and a schematic view of the vicinity of the discharge port of a discharge port plate in the short direction of a pressure chamber 16 of the liquid discharge head 10. FIG. The pressure chamber 16 is a through hole formed in the substrate 15, and the diaphragm 11 formed on one surface (first surface) of the substrate 15 and the discharge formed on the other surface (second surface). It is configured to be surrounded by the outlet plate 13. The diaphragm 11 has a piezoelectric element 12 on the surface facing the pressure chamber 16, and the diaphragm 11 is bent by expansion and contraction in the surface direction of the piezoelectric body of the piezoelectric element 12, whereby the discharge pressure is applied to the liquid in the pressure chamber 16. Is granted. The discharge port plate 13 is provided with a discharge port 14, and the liquid in the pressure chamber 16 is discharged as droplets from the discharge port 14 by the discharge pressure. In FIG. 1, two pressure chambers 16 are arranged for simplification, but a predetermined number of pressure chambers are arranged in the short direction illustrated in the direction of the discharge port arrangement of the liquid discharge head. The arrangement of the pressure chamber 16 can be variously designed depending on the resolution, the shape of the pressure chamber, and the like. For example, when 150 npi (nozzle per inch) nozzles (discharge ports) are arranged per row, the pressure chambers 16 are arranged such that the pitch of the discharge ports 14 is 169 μm.

  FIG. 2 is a diagram illustrating the overall configuration of the liquid ejection head according to the present embodiment, and FIG. 2A is a schematic cross-sectional view of the pressure chamber 16 in the short direction, similar to FIG. FIG. 2B shows the AA cross section of FIG. 2A, and the BB cross section of FIG. 2B corresponds to FIG. FIG. 2C is a schematic cross-sectional view of the pressure chamber 16 in the longitudinal direction, and corresponds to the CC cross section of FIG. Here, assuming that FIG. 2B is the XY direction, FIG. 2A shows the XZ direction and FIG. 2C shows the YZ direction. As shown in FIG. 2B, the pressure chamber 16 has a rectangular shape having a short side and a long side in a two-dimensional manner (XY direction). The short direction of the pressure chamber 16 means a direction parallel to the rectangular short side (X direction).

  In FIG. 2, in addition to the configuration shown in FIG. 1, a substrate 22 is bonded to the diaphragm 11 side via an adhesive layer 21. Between the vibration plate 11 and the substrate 22, there is a space partitioned for each pressure chamber, and the bending of the vibration plate 11 by the piezoelectric element 12 is allowed. 2C, the substrate 22 is provided with a supply path 23 that communicates with the pressure chamber 16 and supplies the liquid to the pressure chamber 16, and a recovery path 24 that recovers the liquid from the pressure chamber 16. ing. The liquid circulation path from the supply path 23 to the recovery path 24 suppresses the thickening of the liquid at the discharge port 14. The supply path 23 and the recovery path 24 communicate with a common liquid chamber (circulation tank) (not shown), and liquids from a plurality of pressure chambers (also referred to as individual liquid chambers) are averaged in the common liquid chamber. The same liquid is circulated in the individual liquid chambers. The recovery path 24 is not essential and is not formed in the case of a liquid discharge head that does not circulate liquid. The discharge port 14 is formed substantially at the center in the longitudinal direction (Y direction) of the pressure chamber 16 so as to be the farthest from the supply path 23 and the recovery path 24. When the recovery path 24 is not provided, it can be provided at the end opposite to the supply path 23 in the longitudinal direction of the pressure chamber 16.

The cross-sectional shape of the pressure chamber 16 in the short direction is such that the inner angle θ _d formed by the inner wall 17 and the short direction at the contact portion between the inner wall 17 and the diaphragm 11 is an obtuse angle, and the inner wall 17 in the short direction of the pressure chamber 16. The inner angle θ _n formed by the inner wall 17 at the contact portion between the discharge port plate 13 and the short direction is an obtuse angle. Therefore, the cross-sectional shape of the pressure chamber 16 in the short direction is, for example, a hexagon as shown in FIG. 1 or an octagon. In FIG. 1, the inner wall 17 in the cross section in the short direction of the pressure chamber 16 is a substantially straight line combination, but may have a curve in part. For this reason, it becomes possible to enlarge a cross-sectional area compared with the case where the cross-sectional shape of the transversal direction of the pressure chamber 16 is a rectangle, for example, and can reduce the flow-path resistance of a circulating liquid. Further, if the cross-sectional shape in the short direction of the pressure chamber 16 is a shape in which all of the inner angles do not have an acute angle or a right angle portion, the occurrence of bubble accumulation in the pressure chamber 16 is suppressed and the discharge is stabilized. Can be made.

The cross-sectional shape of the pressure chamber 16 in the short direction is the width of the pressure chamber 16 on the diaphragm 11 side in the short direction W _d , and the width of the pressure chamber 16 on the discharge port plate 13 side in the short direction is W _s. In this case, the configuration satisfies W _d > W _s . For this reason, the beam width in the short direction of the discharge port plate 13 facing the pressure chamber 16, that is, W _s , can be made narrower than when the cross-sectional shape of the pressure chamber in the short direction is rectangular. Note that the wall surface of the pressure chamber 16 having a cross-sectional shape in the longitudinal direction can have the same shape as the wall surface of the pressure chamber 16 having a cross-sectional shape in the short direction. For this reason, the beam width in the longitudinal direction of the discharge port plate 13 of the pressure chamber 16 is wider than the beam width in the lateral direction. However, since it is the beam width in the short direction that is the dominant factor that determines the rigidity that the discharge port plate 13 needs reinforcement, the rigidity of the discharge port plate 13 can be improved by narrowing the beam width in the short direction. Can do.

The lower limit of W _s, as is apparent from FIG. 2 (b), a diameter of the discharge opening (diameter). In addition, since the upper limit of W _d is naturally limited by the pitch of the discharge ports, the upper limit of W _s is also restricted thereby. Practically, W _s may be set within a width that can ensure sufficient rigidity according to the material and thickness of the discharge port plate.

Next, each member will be described.
The diaphragm 11 is made of, for example, silicon nitride (SiN), and can have a thickness of, for example, about 500 nm to 2000 nm. As a film forming method, for example, a low pressure chemical vapor deposition (LPCVD) can be used to obtain a low stress and high density film more suitable for a diaphragm. Silicon oxide (SiO ₂ ) can be used as another material for the diaphragm 11. In this case, the film forming method is preferably PE (plasma enhanced) CVD. Single crystal silicon (Si) can also be used as the diaphragm 11. The diaphragm 11 may be a film made of a plurality of materials instead of a single film. For example, a two-layer structure in which the first layer is SiN and the second layer is SiO ₂ may be used. The selection of the material of the diaphragm 11 may be determined based on consistency with other processes such as internal stress, adhesion, and etching selectivity.

  For the piezoelectric element 12, a piezoelectric material that is doped with PZT (lead zirconate titanate) or Nb or the like is used. The thickness of the piezoelectric body can be set to, for example, 500 nm to 3000 nm. As a method for forming a piezoelectric body, for example, by using a sputtering method, a piezoelectric body suitable for a liquid discharge head having high crystallinity and high withstand voltage can be obtained. The piezoelectric element 12 has a laminated structure in which a piezoelectric body is sandwiched between a lower electrode and an upper electrode. Pt or the like can be used for the lower electrode, and the film formation method is, for example, a sputtering method, and the thickness can be about 50 to 150 nm. For the upper electrode, Pt, IrO, RuO, TiW, or the like can be used. The film formation method is preferably a sputtering method, and the thickness can be about 50 to 150 nm. In addition, an adhesion layer may be inserted between the respective layers in order to improve adhesion to the diaphragm 11, adhesion between the piezoelectric body and the lower electrode, and adhesion between the piezoelectric body and the upper electrode. The adhesion layer is made of Ti or the like, for example, and can be used by forming a film with a thickness of about 1 to 5 nm. The adhesion layer on the surface on which the piezoelectric body is formed may function as a layer for controlling the crystal orientation of the piezoelectric body. In addition to the adhesion layer, a layer for controlling the crystal orientation of the piezoelectric body may be provided. Note that the upper electrode, the piezoelectric body, the lower electrode, and each of the other layers are patterned by photolithography to have a predetermined shape (for example, a rectangular shape as a planar shape).

  The discharge port plate 13 can be made of various known materials. The discharge port plate can be selected from various resin materials and inorganic materials, and it is preferable to use a photosensitive resin material capable of forming the discharge port with high positional accuracy by photolithography. From the viewpoint of diffusing a part of the liquid thickened inside the discharge port due to evaporation into the liquid circulating in the pressure chamber, the thickness of the discharge port plate is appropriately optimized according to the size of the discharge port. Set to The discharge port plate 13 is preferably formed to a thickness equal to or less than the radius of the discharge port within a range in which the rigidity can be ensured. For example, the discharge port plate 13 is made of a photosensitive dry film and has a thickness of, for example, 10 μm. The discharge port plate 13 may be a Si single crystal.

  Any substrate 15 can be used as long as the substrate 15 constituting the wall of the pressure chamber 16 can form the pressure chamber according to the present embodiment and has resistance to the liquid in the pressure chamber. For example, any of inorganic materials such as a Si substrate and organic materials such as a photosensitive dry film can be used. Moreover, the structure which bonded two base material in which the through-hole was formed may be sufficient.

(Production Example 1)
Next, a method for manufacturing a liquid ejection head according to this embodiment will be described. In the following description, a case will be described in which a Si substrate, particularly a Si substrate having a (100) plane orientation, is used as the substrate 15.
FIG. 3 is a schematic diagram illustrating an example of a method for manufacturing the liquid ejection head 100 according to the present embodiment. FIGS. 3A to 3I are cross-sectional views of the pressure chamber in each process in the short direction. Show.

First, as shown in FIG. 3A, a sacrificial layer 31 is formed on one surface of the Si substrate 15A by using photolithography and etching. The sacrificial layer 31 defines a wall surface on the diaphragm side of the pressure chamber, and is usually formed in a rectangular pattern having a short side and a long side. The plane orientation of this Si substrate 15A is (100). At this time, the sacrificial layer 31 is aligned and arranged so that the short side of the rectangular pattern is parallel to the <110> axis. The long side of the rectangular pattern of the sacrificial layer 31 may be aligned and arranged so as to be parallel to the <110> axis. The film thickness of the sacrificial layer 31 can be in the range of 500 nm to 2000 nm, for example. Since the sacrificial layer 31 is removed in a later sacrificial layer removing step, it is preferable that the sacrificial layer 31 has a high etching selectivity with respect to surrounding members and has a high etching rate. Examples of combinations of such sacrificial layers, surrounding members, and etchants are as follows. As a first example, there is a combination in which a sacrificial layer is a silicon oxide film (SiO ₂ ), a surrounding member (vibrating plate) is SiN, and an etchant is HF. If the same material as the sacrificial layer is used as another member, this member may be protected in advance. As a second example, there is a combination in which the sacrificial layer is polycrystalline Si, the surrounding members are SiN, and the etchant is a KOH solution. As a third example, there is a combination in which the sacrificial layer is Al, the surrounding members are SiN, and the etchant is Al wet etchant. Other combinations may be used as long as the etching selectivity can be secured. In this example, as the sacrificial layer 31, for example, a silicon oxide film is formed using a thermal oxidation method. Note that the silicon oxide film of the sacrificial layer 31 may be formed by using PECVD in addition to the thermal oxidation method, or by appropriately selecting other methods. The pattern shape of the sacrificial layer 31 is preferably formed in a shape that is inclined so that the side surface extends toward the diaphragm 11. By forming the sacrificial layer 31 in this way, all the internal angles of the pressure chamber formed by removing the sacrificial layer can be made obtuse.

Next, as illustrated in FIG. 3B, the vibration plate 11 is formed on the Si substrate 15 </ b> A including the sacrificial layer 31. The diaphragm 11 is made of, for example, SiN, and can have a thickness of, for example, about 500 nm to 2000 nm. For example, LPCVD, PECVD, or the like can be used as the film forming method. In the case of SiN, the use of LPCVD provides a low stress and high density film more suitable for a diaphragm. Note that PECVD is preferably used when it is desired to lower the film formation temperature due to restrictions on the manufacturing process before and after. As the other film, SiO ₂ can be used, and PECVD is preferable as the film forming method.

  Next, as shown in FIG. 3C, the piezoelectric element 12 is formed on the vibration plate 11. The piezoelectric element 12 is formed by stacking the above-described layers on the entire surface of the substrate, and then patterning into each element shape by photolithography. In the photolithography process, the pattern of the piezoelectric element 12 has a similar shape to the sacrificial layer 31, and the plane center of the piezoelectric element 12 matches the plane center of the sacrificial layer 31. Either wet etching or dry etching can be used for etching, but the use of dry etching causes less process damage to the piezoelectric element 12 and the side etching amount. Further, for etching each layer of the piezoelectric element 12, a layer patterned on the top may be used as a hard mask.

  As shown in FIG. 3D, the Si substrate 15A is thinned and processed into a substrate 15 that can form a pressure chamber 16 having a desired height. At this time, it is possible to perform bonding using the adhesive layer 21 between the substrate 22 and the substrate 15 serving as a constituent member of the liquid discharge head on the support substrate of the substrate 15 and thinning of the Si substrate 15A. The Si substrate 15A can be thinned by, for example, grinding with a grinder and CMP (chemical mechanical polishing). Here, the Si substrate 15A is thinned to, for example, 60 μm, which is the height of the pressure chamber 16, but the present invention is not limited to this. The substrate 15 can be obtained by a method using an SOI (silicon on insulator) substrate instead of thinning the thick Si substrate 15A. In this case, for example, an SOI substrate having a (100) Si layer having the same thickness as the desired height of the pressure chamber 16 as a device layer is prepared. Next, the same steps as in FIGS. 3A to 3C are performed on the device layer. Next, the structure of FIG. 3D can also be obtained by bonding using the adhesive layer 21 to the substrate 22 and removing the handle layer and the BOx (burried oxide) layer of the SOI substrate.

Next, as shown in FIG. 3E, a protective film 32 is formed on the surface of the substrate 15 opposite to the surface on which the diaphragm 11 is formed, and then a groove pattern is formed in the protective film 32. The groove pattern is formed so that the central axis in the longitudinal direction of the pattern of the sacrificial layer 31 coincides with the central axis in the longitudinal direction of the groove pattern. The material of the protective film 32 is, for example, SiO ₂ . For example, PECVD may be used as the film forming method, or another film forming method may be used. The film thickness of the protective film 32 can be in the range of 1000 nm to 2000 nm, for example. This protective film 32 serves as an etching mask when forming a pressure chamber in a later process. When an SOI substrate is used as described above, the BOx layer may be left as the protective film 32 after the handle layer is removed. Next, a resist film 33 is formed on the protective film 32, and a groove pattern 34 is formed by photolithography. The groove pattern 34 is formed inside the groove pattern of the protective film 32 so that the resist film 33 covers the protective film 32 entirely. Further, the sacrificial layer 31 is formed so that the central axis in the longitudinal direction of the pattern of the sacrificial layer 31 coincides with the central axis in the longitudinal direction of the groove pattern 34.

Next, in FIG. 3F, substrate perforations 35 are formed in the substrate 15 by, for example, silicon DRIE (deep reactive ion etching) using the groove pattern 34 of the resist film 33 as an etching mask. At this time, by using the sacrificial layer 31 as an etching stop layer, it is possible to prevent etching damage to the diaphragm 11 during silicon DRIE. Here, the depth of the substrate perforation 35 may be changed according to the material of the sacrificial layer 31 described in the sacrificial layer forming step of FIG. For example, when the sacrificial layer 31 is SiO ₂ or Al, the Si substrate 15 is not etched by the etchant of the sacrificial layer 31, so that the substrate perforations 35 need to reach the sacrificial layer 31. On the other hand, when the sacrificial layer 31 is polycrystalline Si, the substrate perforation 35 may be deep enough to penetrate even if it does not reach the sacrificial layer 31. This is because an etchant when the sacrificial layer 31 is polycrystalline Si, for example, Si in the portion of the substrate perforation 35 not penetrating through the substrate is etched by the KOH solution to reach the polycrystalline Si of the sacrificial layer 31 and be removed. Because it can.

Next, as shown in FIG. 3G, the sacrificial layer 31 is removed by introducing an etchant of the sacrificial layer 31 into the substrate perforations 35. An etchant is selected according to the material of the sacrificial layer 31 described in the sacrificial layer forming step of FIG. In FIG. 3A, since SiO ₂ is used as the sacrificial layer 31, Vapor-HF is used as the etchant. Vapor-HF can efficiently etch the sacrificial layer 31 through the narrow substrate perforations 35. At this time, since the protective film 32 using SiO ₂ is protected by the resist film 33, only the sacrificial layer 31 can be selectively removed. A space 36 is formed after the sacrificial layer 31 is removed. Thereafter, the resist film 33 is removed. The removal of the resist film 33 is performed by, for example, ashing using oxygen plasma. In the case where the sacrificial layer 31 is made of a material having an etching selection ratio with respect to the protective film 32 such as Al or polycrystalline Si, the resist film 33 is removed after the substrate perforation 35 is formed and before the sacrificial layer 31 is removed. May be.

  Next, as shown in FIG. 3H, crystal anisotropic etching is performed using, for example, a KOH solution as an etchant using the substrate 15 as the vibration plate 11 and the protective film 32 as an etching mask. Etching is performed by introducing an etchant into the space 36 formed by removing the substrate perforations 35 and the sacrificial layer 31. The groove pattern of the protective film 32 was formed such that the central axis in the longitudinal direction of the pattern of the sacrificial layer 31 coincided with the central axis in the longitudinal direction of the groove pattern. Therefore, the etching of the substrate 15 made of (100) Si proceeds so that the {111} plane becomes a wall surface by crystal anisotropic etching. Further, since the width in the short direction of the space 36 is wider than the width in the short direction of the groove pattern of the protective film 32, the space 36 is etched extensively on the diaphragm 11 side. The cross section in the short direction of the pressure chamber 16 formed by this etching has a substantially hexagonal cross section.

That is, according to the manufacturing method of this embodiment, the shape of the pressure chamber 16 can be defined with high accuracy by the thickness of the substrate 15, the etching mask, and the crystal plane of the substrate 15. The etchant is not limited to a KOH solution, and a chemical solution capable of crystal anisotropic etching, such as a TMAH (tetramethylammonium hydroxide) solution, may be used. Further, the wall surface shape in the longitudinal direction of the pressure chamber 16 can have a shape in which the {111} surface is the wall surface, similarly to the wall surface shape in the short direction. When etching is performed after the substrates 22 are bonded together, the etchant wraps around so that the substrate 22 is not etched. For example, etching can be performed using an etching jig (not shown) having a structure in which the substrate 22 is protected and the etchant contacts only the substrate 15. Further, a protective film (not shown) may be formed on the substrate 22.
Next, the protective film 32 on the substrate 15 is removed. When the protective film 32 of SiO ₂ is, for example, it can be used an HF solution and BHF (buffered hydrogen fluoride) solution and Vapor-HF. In the step of removing the protective film 32, since the material other than the protective film 32 has a high etching selectivity with respect to these etchants, the protective film 32 can be selectively removed. In the case where there is a portion exposed to the etchant in a portion made of the same material as that of the protective film 32, a protective film may be formed in advance from a different material on the portion to be protected.

Next, as shown in FIG. 3 (i), a discharge port having a discharge port 14 on the surface facing the diaphragm 11 across the pressure chamber 16, that is, on the lower side where the width in the short direction of the pressure chamber 16 is narrow. An outlet plate 13 is formed. Here, the discharge port plate 13 can be formed using, for example, a photosensitive dry film. The discharge port 14 is formed by aligning a photomask (not shown) having a pattern of the discharge port 14 with the opening position of the pressure chamber 16 after the photosensitive dry film is pasted, and exposing the pattern of the discharge port 14. -It can be formed with high accuracy by developing. Alternatively, the discharge port plate 13 may be formed by forming the discharge port 14 in advance, aligning it with the opening position of the pressure chamber 16, and attaching the discharge port plate 13 to the substrate 15 by a tenting method. The ejection port 14 can be formed by using, for example, laser processing in addition to exposure / development, or by other methods. The thickness of the discharge port plate 13 is, for example, 10 μm, and the radius of the discharge port 14 is, for example, 10 μm. Note that the present invention is not limited to these materials and dimensions.
In this embodiment, as shown in Production Example 1, the sacrificial layer 31 is formed on the vibration plate 11 side, and a through hole that becomes the pressure chamber 16 is formed in the (100) Si substrate 15 from the space 36 from which the sacrificial layer 31 is removed. doing. For this reason, the diaphragm 11 has an inner wall surface separated from an extension line of one surface (first surface) of the (100) Si substrate in the pressure chamber 16. However, the inner wall surface in the pressure chamber of the diaphragm can be on an extension line of the substrate.

[Embodiment 2]
FIG. 4A is a schematic cross-sectional view for explaining the present embodiment, and shows one pressure chamber 46A for simplification of the drawing. Here, the width in the short direction of the pressure chamber 46A on the diaphragm 41 side is W _d , the width in the short direction of the pressure chamber 46A on the discharge port plate 43 side is W _s, and the thickness of the substrate 45 is T _w. And θ represents the outer angle formed by the discharge port plate 43 and the side wall surface 47A of the pressure chamber 46A. Since θ is an acute angle, the internal angle of the pressure chamber 46A on the discharge port plate side is an obtuse angle. At this time, the pressure chamber 46A of the liquid ejection head is configured to satisfy the following two expressions.

W _d > W _s (1),
_{T w = (1/2) · (} W d -W s) · tanθ ··· (2-1).

When a (100) Si substrate is used as the substrate 45, the side wall surface 47A is a {111} plane, so θ is defined to be about 55 degrees. The thickness _{T w} of the substrate 45, for example, when a 60 [mu] _m, W d -W _s is approximately a 170 [mu] m. The present invention is not limited to this and may have other values. The cross-sectional shape in the short direction of the pressure chamber 46 </ b> A is a substantially trapezoid surrounded by the side wall surface 47 </ b> A formed on the substrate 45, the vibration plate 41, and the discharge port plate 43.

On the other hand, as described in the first embodiment, when the cross-sectional shape of the pressure chamber in the short direction is a hexagon or the like in which the inner angles are all obtuse, the flow resistance of the circulating liquid can be reduced. Also in this embodiment, as shown in FIG. 4B, a hexagonal pressure chamber 46B in which the inner angles are all obtuse can be formed. In this case, the width W _{d in} the short direction on the diaphragm 41 side is as shown in FIG. It becomes narrower than the case of (a). Therefore, the width W _s of the width W _d of the vibration plate side of the thickness T _w and the pressure chamber 46B of the substrate 45 discharge port plate side is configured to satisfy the following two equations.

W _d > W _s (1),
_{T w> (1/2) · (} W d -W s) · tanθ ··· (2-2).

As described above, the liquid discharge head according to the present embodiment has a configuration in which the cross-sectional shape of the pressure chamber in the short direction satisfies the following expressions (1) and (2). Here, W _d is the width in the short direction of the pressure chamber on the diaphragm side, W _s is the width in the short direction of the pressure chamber on the discharge port plate side, and T _w is the thickness of the substrate constituting the wall surface of the pressure chamber. , Θ represents the external angle formed by the nozzle hole plate and the side wall surface of the pressure chamber.

W _d > W _s (1),
_{T w ≧ (1/2) · (} W d -W s) · tanθ ··· (2).

  As described above, the rigidity of the discharge port plate 43 can be improved by narrowing the beam width in the short direction of the pressure chamber 46 on the discharge port plate 43 side. In the present embodiment, the inner wall surface of the diaphragm in the pressure chamber is formed on an extension of the first surface of the substrate. However, as shown in the first embodiment, the inner wall surface of the diaphragm is the first surface of the substrate. It can also be applied to a configuration away from the extension line of the surface.

[Embodiment 3]
In this embodiment, the relationship between the thickness of the discharge port plate and the beam width around the discharge port will be described. In the region where the discharge port is not formed, the beam width W _s of the discharge port plate facing the pressure chamber is supported by the substrate at both ends, so that it is possible to ensure rigidity even with a somewhat wide beam width. On the other hand, in the vicinity of the discharge port, since it is divided by the discharge port, it is in a cantilever state and the rigidity is low. That is, ensuring the rigidity becomes difficult when the beam width W _b of the cantilever increases.
On the other hand, when the liquid in the pressure chamber is circulated in order to suppress the thickening of the liquid at the discharge port, it is necessary to reduce the depth of the discharge port in order to diffuse the liquid inside the discharge port into the circulating liquid. Become. That is, the thickness of the discharge port plate that defines the depth of the discharge port is reduced. However, if the thickness of the discharge port plate is extremely reduced, sufficient rigidity of the region where the discharge port is not formed cannot be obtained. Therefore, in the present invention, the thickness T _n of the discharge port plate is preferably in the range of 4 μm to 20 μm.

  FIG. 5 is a schematic cross-sectional view of the pressure chamber in the short direction, showing the main part of the liquid ejection head for explaining the configuration according to this embodiment. In the figure, for simplification, only the periphery of the discharge port of one pressure chamber is shown. Other configurations are the configurations described in the first or second embodiment, and the members and the like are not described because the materials described in the first embodiment can be used.

As shown in FIG. 5, the beam width W _s of the discharge port plate 53 is expressed by the following equation (3A) from the radius r of the discharge port 54 and the beam width W _{b of the} cantilever beam.
W _s = 2 (W _b + r) (3A)
Here, it is important for securing the rigidity that the beam width W _b is not more than three times the thickness T _n of the discharge port plate 53. Further, the size (diameter) of the discharge port 54 is more than twice the thickness T _n of the discharge port plate 53 in consideration of diffusion of the liquid in the discharge port 54 into the circulating liquid, that is, the radius of the discharge port 54. r is the following formula (4)
r ≧ T _n (4)
It becomes. Substituting W _b = 3T _n and r = T _n into the above equation (3A),
W _s = 2 (4T _n ) = 8T _n (3B)
It becomes. That is, if the following formula (3C) is satisfied, it is considered that rigidity can be obtained.
W _s ≦ 8T _n (3C)
However, in actuality, when the alignment margin for forming the discharge port is estimated to be about 5 μm on one side, the beam width W _s satisfies the following formula (3) in _order to satisfy W _b ≦ 3T _n when T _n is 4 μm, which is the minimum value. It is preferable to satisfy.
W _s ≦ (5.5T _n +10) (3)

Here, the thickness T _n of the discharge port plate 53 is 4 μm, the discharge port radius r is 4 μm, and the width W _{s in} the short direction of the pressure chamber 56 is 32 μm or less from the above equation (3). In this case, the beam width W _{b in} the short direction of the discharge port plate 53 is 12 μm or less which is not more than three times the thickness T _n with respect to the thickness T _n = 4 μm of the discharge port plate 53. Rigidity can be ensured. As another dimension example, the thickness T _n of the discharge port plate 53 is 20 μm, the radius r of the discharge port 54 is 20 μm, and the width W _{s in} the short direction of the pressure chamber 56 is 120 μm or less from the above equation (3). It is. In this case, the beam width _{W b} of the thickness _T n = 20 [mu] m, becomes less 40μm to be less than twice the _{T n,} it is possible to ensure the rigidity of the discharge port plate 53.

As described above, in this embodiment, the thickness of the discharge port plate is T _n (μm), the radius of the discharge port is r (μm), and the width W in the short direction of the pressure chamber on the discharge port plate side. _{When s} (μm), the following formulas (3) to (5) are satisfied.

W _s ≦ (5.5 T _n +10 μm) (3),
r ≧ T _n (4),
4 μm ≦ T _n ≦ 20 μm (5).

Therefore, it is possible to narrow the beam width W _b is a dominant factor determining the stiffness required reinforcement in the peripheral discharge openings 54 of the discharge port plate 53, a thin and even rigid the thickness of the discharge port plate 53 It becomes possible to secure. Furthermore, even if the liquid is circulated, the liquid inside the discharge port 54 is sufficiently diffused into the circulating liquid, so that it is possible to suppress the occurrence of discharge failure due to thickening of the liquid inside the discharge port 54 and to stabilize the discharge. As described in the first embodiment, the lower limit value of the width W _s is 2r that is the hole diameter of the discharge port, and in that case, W _b = 0. In addition, the present embodiment example can be applied to both configurations of the first and second embodiment examples.

[Embodiment example of manufacturing method]
Embodiments of the method for manufacturing a liquid discharge head according to the present invention will be described below. In the liquid discharge head according to the present invention, the pressure chamber is a cross-section in the surface direction of the substrate formed on the substrate having the vibration plate on the first surface and the discharge port plate on the second surface facing the first surface. Is constituted by a rectangular through hole. And the manufacturing method of the liquid discharge head which concerns on any embodiment of this invention is common also including the manufacturing method (manufacturing example 1) shown in embodiment 1 by the following points. That is, when the said first surface side of the lateral direction of the opening width W _d, the second short side direction of the opening width of the side W _s of the through hole, and W _d> W _s A step of forming the through hole in the substrate. In the following description, description of members common to Production Example 1 is omitted.

(Production Example 2)
FIG. 6 is a process diagram showing a method of manufacturing a liquid ejection head according to an embodiment of the present invention, and shows a cross section in the short direction of the pressure chamber 616. FIG. 6A shows a step of preparing a substrate (hereinafter referred to as a pressure generating substrate) 625 for generating pressure. A pressure chamber space (cavity) 626 for storing the piezoelectric element 612 on the vibration plate 611 is formed in the pressure generating substrate 625. That is, a pressure generating substrate can be formed by bonding the vibration plate 611 on which the piezoelectric element 612 is formed to the substrate 625 on which the cavity 626 is formed.

Next, FIG. 6B is a step of preparing a substrate 615 in which a through hole to be a pressure chamber 616 is formed. The substrate 615 is made of, for example, a (100) Si substrate, and is formed so that the lateral direction of the pressure chamber 616 is parallel to the <110> axis. The cross section in the short direction of the pressure chamber 616 has a {111} plane as a side wall by crystal anisotropic etching. In addition, the cross-sectional shape of the pressure chamber 616 in the short-side direction satisfies W _d > W _s . W _d is the width in the short direction of the pressure chamber 616 on the diaphragm 611 side (first surface) to be bonded in the subsequent process, and W _s is the discharge port plate 613 side (first surface) formed in the subsequent process. The width in the short direction of the pressure chamber 616 on the second surface is shown. The cross-sectional shape of the pressure chamber 616 in the short direction is formed, for example, in a substantially hexagonal shape where the inner angles are all obtuse. The longitudinal cross section of the pressure chamber 616 has the same {111} plane as the lateral cross section. The substrate 615 is not limited to a (100) Si substrate, and may be a resin substrate having photosensitivity, and the cross-sectional shape of the pressure chamber 616 in the short direction is approximately 6 as long as W _d > W _s is satisfied. It is not limited to a square. In this manufacturing example, a structure can be formed in which the inner wall surface of the pressure chamber 616 of the diaphragm 611 is an extension of the first surface of the substrate 615.

  FIG. 6C shows a step of bonding the pressure generating substrate 625 to the first surface of the substrate 615. In this step, using the alignment mark (not shown) formed on both substrates, the longitudinal center axis and the center of the piezoelectric element 612 of the pressure generating substrate 625 are the center axis in the longitudinal direction of the upper surface of the pressure chamber 616. Substrate bonding is performed by aligning with the center. The substrate bonding step may be performed using surface activated bonding in which the substrate bonding surface is bonded after surface activation treatment with, for example, plasma, or may be performed using an adhesive.

Next, in FIG. 6D, the discharge port plate 613 having the discharge ports 614 is formed on the second surface of the substrate 615. As in the case of Production Example 1, the discharge port uses a photosensitive dry film as the discharge port plate material. After the photosensitive dry film is bonded to the second surface of the substrate 615, the discharge port 614 is formed by photolithography. be able to. Alternatively, the discharge port plate 613 in which the discharge ports 614 are formed in advance may be bonded.
Further, after the discharge port plate 613 having the discharge ports 614 is formed on the second surface of the substrate 615, the pressure generating substrate 625 may be bonded to the first surface of the substrate 615.

  The liquid discharge head according to the present invention can be mounted on an apparatus such as a printer, a copying machine, a facsimile having a communication system, a word processor having a printer unit, or an industrial recording apparatus combined with various processing apparatuses. By using an apparatus equipped with this liquid discharge head, it is possible to perform recording on various recording media such as paper, thread, fiber, leather, metal, plastic, glass, wood, and ceramic. Further, it can be applied as a head for ejecting a liquid for biochip manufacturing or electronic circuit printing. Among these, the liquid discharge head according to the present invention is suitable as an ink jet head using water-based ink or the like.

10: Liquid discharge head 11: Vibration plate 12: Piezoelectric element 13: Discharge port plate 14: Discharge port 15: Substrate having a pressure chamber 16: Pressure chamber 17: Pressure chamber wall

Claims (12)

A liquid having a pressure chamber surrounded by a vibration plate and a discharge port plate, and utilizing the bending of the vibration plate by a piezoelectric body formed on a surface of the vibration plate facing the pressure chamber. A liquid discharge head for discharging from the discharge port of the discharge port plate,
The inner angle formed by the inner wall and the short direction at the contact portion between the inner wall in the short direction of the pressure chamber and the diaphragm is an obtuse angle,
The internal angle formed by the inner wall and the short direction at the contact portion between the inner wall in the short direction of the pressure chamber and the discharge port plate is an obtuse angle,
A liquid that satisfies the following formula (1), where W _{d is} the width in the short direction of the pressure chamber on the diaphragm side, and W _s is the width in the short direction of the pressure chamber on the discharge port plate side. Discharge head:
W _d > W _s (1). A liquid having a pressure chamber surrounded by a vibration plate and a discharge port plate, and utilizing the bending of the vibration plate by a piezoelectric body formed on a surface of the vibration plate facing the pressure chamber. A liquid discharge head for discharging from the discharge port of the discharge port plate,
The pressure chamber is formed as a through hole in a substrate constituting a side wall of the pressure chamber,
The width in the short direction of the pressure chamber on the diaphragm side is W _d , the width in the short direction of the pressure chamber on the discharge port plate side is W _s , and the thickness of the substrate is T _w , A liquid discharge head satisfying the following formulas (1) and (2), where θ is an external angle formed by the side wall surface of the pressure chamber:
W _d > W _s (1),
_{T w ≧ (1/2) · (} W d -W s) · tanθ ··· (2). When the thickness of the discharge port plate is T _n (μm), the discharge port radius is r (μm), and the width of the pressure chamber on the discharge port plate side in the short direction is W _s (μm), The liquid discharge head according to claim 1, wherein (3) to (5) are satisfied.
W _s ≦ (5.5 T _n +10 μm) (3),
r ≧ T _n (4),
4 μm ≦ T _n ≦ 20 μm (5).   The pressure chamber is a through hole formed in a (100) Si substrate and having a {111} plane as a wall surface, and the longitudinal direction and the short direction of the pressure chamber are parallel to the <110> axis of the Si substrate. The liquid discharge head according to claim 1, wherein the liquid discharge head is a liquid discharge head.   The diaphragm is formed continuously on one surface of the (100) Si substrate, and has an inner wall surface separated from an extension line of one surface of the (100) Si substrate in the pressure chamber. The liquid ejection head according to claim 4, wherein the liquid ejection head is a liquid ejection head.   6. The liquid discharge head according to claim 1, further comprising a supply path for supplying a liquid into the pressure chamber and a recovery path for recovering the liquid from the pressure chamber. A liquid having a pressure chamber surrounded by a vibration plate and a discharge port plate, and utilizing the bending of the vibration plate by a piezoelectric body formed on a surface of the vibration plate facing the pressure chamber. A liquid discharge head manufacturing method for discharging the discharge port from the discharge port of the discharge port plate,
The pressure chamber is formed in a substrate having the vibration plate on the first surface and the discharge port plate on the second surface facing the first surface, and the substrate has a rectangular cross section in the surface direction. A hole,
Said through-hole, the first direction of the short side of the opening width of the side W _d, the second lateral direction of the opening width of the side when the W _s, so as to be W _d> W _s A method of manufacturing a liquid discharge head, further comprising the step of forming the through hole in the substrate. The substrate is a Si substrate having a plane orientation on a (100) plane,
Forming a sacrificial layer having a short side and a long side on the first surface of the Si substrate, the sacrificial layer being parallel to the <110> axis of the Si substrate;
Forming a diaphragm on the Si substrate including the sacrificial layer;
Forming a piezoelectric element including a piezoelectric body on a surface of the diaphragm facing the first surface of the Si substrate;
A protective film is formed on the second surface of the Si substrate opposite to the first surface, and has a central axis that coincides with the central axis in the longitudinal direction of the sacrificial layer, Forming a groove pattern in the protective film having a short direction narrower than the width;
Forming a substrate perforation from the second surface toward the sacrificial layer inside the groove pattern of the protective film;
Removing the sacrificial layer from the substrate perforations to form a space in the first surface of the Si substrate;
The substrate is perforated and an etchant is introduced into the space, and the through-hole having a {111} plane in the lateral direction is formed in the Si substrate by crystal anisotropic etching using the diaphragm and the protective film as a mask. Process,
Forming a discharge port plate on the second surface of the Si substrate;
The method of manufacturing a liquid discharge head according to claim 7, comprising: Providing a space for storing the piezoelectric element on a substrate different from the substrate in which the through-hole is formed, and bonding the diaphragm on which the piezoelectric element is formed to prepare a pressure generating substrate;
Bonding the diaphragm side of the pressure generating substrate to the first surface of the substrate in which the through hole is formed;
Forming a discharge port plate on the second surface of the substrate in which the through hole is formed;
The method of manufacturing a liquid discharge head according to claim 7, comprising:   10. The liquid ejection head according to claim 9, wherein the substrate in which the through hole is formed is a Si substrate having a plane orientation in a (100) plane, and a side wall surface of the through hole is a {111} plane. Manufacturing method.   The step of forming the discharge port plate includes a step of attaching a photosensitive discharge port plate material to the second surface of the substrate in which the through hole is formed, and forming a discharge port in the discharge port plate material by photolithography. The method of manufacturing a liquid ejection head according to claim 8, further comprising:   11. The step of forming the discharge port plate includes a step of bonding a discharge port plate having a discharge port to the second surface of the substrate on which the through hole is formed. Manufacture of the liquid discharge head of item 1.

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