JP6900182B2 - Liquid discharge head and manufacturing method of liquid discharge head - Google Patents

Description

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

The liquid discharge head that discharges droplets of ink or the like onto the object to be recorded for recording is provided with a liquid discharge head in which a large number of liquid discharge parts are arranged two-dimensionally in order to perform higher-definition recording at a high speed. There is.
Each liquid discharge unit has a liquid chamber communicating with the discharge port and a pressure generating means provided facing the discharge port to apply a discharge pressure to the liquid in the liquid chamber. A piezoelectric element is known as a pressure generating means. 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 to each other is preferably used. In the bend type piezoelectric actuator (also simply called an actuator), the piezoelectric body tries to contract in the plane direction by applying a voltage between the electrodes formed on both sides of the thin film piezoelectric body, while the vibrating plate does not shrink and is bent. Deformation occurs. The liquid discharge head according to this method bends and deforms the wall surface of the liquid chamber (hereinafter referred to as the pressure chamber) that generates pressure facing the discharge port by an actuator, and increases or decreases the volume of the pressure chamber to discharge the liquid. .. Such a liquid discharge head is widely used because it is relatively easy to arrange actuators at high density and with high accuracy using a semiconductor process. It is desired that the discharge port plate on which the discharge port is formed has 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 together to form a discharge port plate. The structure of the discharge port plate is a plate-shaped member having a circular hole on one side and a polymer resin film-like member having a hole having a diameter smaller than that of the circular hole on the other side.

Further, each discharge portion of the liquid discharge head has a time during operation in which a liquid such as ink is not discharged. Further, there is a discharge port that does not discharge the liquid for a long time even during continuous recording, depending on the size of the recorded body, the white background of the recorded body, the margins, etc., and the drawing pattern to be printed. Therefore, there is a possibility that a discharge failure may occur due to a part of the liquid component inside the discharge port evaporating and thickening while the liquid is not discharged.
As one of the countermeasures, a method has been proposed in which a circulation tank is provided and the liquid is always circulated in the flow path in the head connected to the discharge port regardless of the presence or absence of discharge. This is to suppress the thickening of the liquid by diffusing a part of the liquid thickened inside the discharge port to the circulating liquid by evaporation.

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-shaped 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. Further, when applied to liquid circulation in a liquid flow path, the discharge port plate has a structure in which two members are bonded together, so that the discharge port becomes deep, and even if liquid circulation is performed, the liquid inside the discharge port is used. May be insufficiently diffused into the circulating liquid. Therefore, it is desired to reduce the thickness of the discharge port plate, but there is a problem that it is difficult to secure the rigidity of the discharge port plate if the thickness is reduced.

Therefore, 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 said by a piezoelectric element having a diaphragm and a pressure chamber surrounded by a discharge port plate and including a piezoelectric body formed on a surface of the diaphragm facing the pressure chamber. A liquid discharge head that discharges liquid in the pressure chamber from the discharge port of the discharge port plate by utilizing the deflection of the diaphragm, and at a contact portion between the inner wall of the pressure chamber in the lateral direction and the vibration plate. The inner angle formed by the inner wall and the lateral direction is an blunt angle, and the inner angle formed by the inner wall and the lateral direction at the contact portion between the inner wall in the lateral direction of the pressure chamber and the discharge port plate is an blunt angle. There, the transverse direction of width of the pressure chamber of the diaphragm-side when the W _d, the width W _s of the transverse direction of the pressure chamber of the discharge port plate side, meets the following formula (1):
W _d > W _s ... (1) ,
The thickness T _n of the discharge port plate _([mu] m), the radius of the discharge port r (μm), the lateral direction of the width of the pressure chamber of the discharge port plate side when the W _{s (μm),} the following formula A liquid discharge head characterized by satisfying (3) to (5) is provided:
W _s ≤ (5.5T _n + 10 μm) ・ ・ ・ (3),
r ≧ T _n ... (4),
4 μm ≤ T _n ≤ 20 μm ... (5).

Further, according to another aspect of the present invention, the vibration due to a piezoelectric body having a vibrating plate and a pressure chamber surrounded by a discharge port plate and formed on a surface of the vibrating plate facing the pressure chamber. A liquid discharge head that discharges a liquid in the pressure chamber from the discharge port of the discharge port plate by utilizing the bending of the plate, and the pressure chamber is formed as a through hole in a substrate forming a side wall of the pressure chamber. The width of the pressure chamber on the vibrating plate side in the lateral direction is W _d , the width of the pressure chamber on the discharge port plate side in the lateral direction is W _s, and the thickness of the substrate is T _w. when the angle of the formed exterior angle side wall surface in the transverse direction as the pressure chamber and theta, meets the following formula (1) and (2):
W _d > W _s ... (1)
T _w ≧ (1/2) ・ (W _d −W _s ) ・ tan θ ・ ・ ・ (2) ,
The thickness T _n of the discharge port plate _([mu] m), the radius of the discharge port r (μm), the lateral direction of the width of the pressure chamber of the discharge port plate side when the W _{s (μm),} the following formula A liquid discharge head characterized by satisfying (3) to (5) is provided:
W _s ≤ (5.5T _n + 10 μm) ・ ・ ・ (3),
r ≧ T _n ... (4),
4 μm ≤ T _n ≤ 20 μm ... (5).

According to still another aspect of the present invention, the diaphragm made of a piezoelectric material having a diaphragm and a pressure chamber surrounded by a discharge port plate and formed on a surface of the diaphragm facing the pressure chamber. In the manufacture of a liquid discharge head that discharges the liquid in the pressure chamber from the discharge port of the discharge port plate by utilizing the deflection of the pressure chamber, the pressure chamber has the diaphragm on the first surface and the discharge port plate. Is a through hole having a rectangular cross section in the plane direction of the substrate formed on a substrate having a second surface facing the first surface, and the short side of the through hole on the first surface side. when the direction of the opening width W _d, the second lateral direction of the opening width of the side and W _s, have a step of forming the through hole in the substrate such that W _d> W _s ,
The substrate is a Si substrate having a plane orientation on the (100) plane, and has a rectangular pattern having a short side and a long side on the first surface of the Si substrate, and has a <110> axis of the Si substrate. A step of forming a sacrificial layer in which the short sides are parallel to each other, a step of forming a vibrating plate on the Si substrate including the sacrificial layer, and a first surface of the Si substrate of the vibrating plate. A step of forming a piezoelectric element containing a piezoelectric body on a surface facing the surface of the Si substrate, and forming a protective film on the second surface of the Si substrate facing the first surface to form a protective film at the center in the longitudinal direction of the sacrificial layer. From the step of forming a groove pattern on the protective film having a central axis that coincides with the axis and having a lateral direction narrower than the lateral width of the sacrificial layer, and from the second surface, the protective film A step of forming a substrate perforation toward the sacrificial layer inside the groove pattern, a step of removing the sacrificial layer from the substrate perforation to form a space on the first surface of the Si substrate, and the substrate perforation and A step of introducing an etchant into the space and forming the through hole having a side wall in the lateral direction formed of a {111} surface on the Si substrate by crystal anisotropic etching using the vibrating plate and the protective film as a mask, and the above. Provided is a method for manufacturing a liquid discharge head, which comprises a step of forming a discharge port plate on a second surface of a Si substrate.

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

It is a schematic cross-sectional view which shows the main part of the liquid discharge head which concerns on one Embodiment of this invention. It is a schematic diagram which shows the whole of the liquid discharge head which concerns on one 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 a process drawing which shows the manufacturing method of the liquid discharge head which concerns on one Embodiment of this invention. It is a schematic diagram which shows the liquid discharge head which concerns on other embodiment of this invention. It is a schematic diagram which shows a part of the liquid discharge head which concerns on one Embodiment of this invention. It is a process drawing which shows the example of another manufacturing method of the liquid discharge head which concerns on one Embodiment of this invention.

Regarding the liquid discharge head and the manufacturing method thereof according to the present invention, the configuration, operation and effect of the present invention will be described with reference to preferred embodiments.

[Example 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, which is a schematic view of the vicinity of a discharge port of a discharge port plate in the lateral direction of the pressure chamber 16 of the liquid discharge head 10. It is a cross-sectional view. 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 plate formed on the other surface (second surface). It is surrounded by an outlet plate 13. The diaphragm 11 has a piezoelectric element 12 on a surface facing the pressure chamber 16, and the diaphragm 11 bends due to expansion and contraction of the piezoelectric element 12 in the surface direction, so that the discharge pressure is applied to the liquid in the pressure chamber 16. Is given. 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 side by side for simplification, but a predetermined number of pressure chambers are arranged in the short direction shown in the discharge port arrangement direction 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 the nozzles (discharge ports) of 150 npi (nozzle per inch) are arranged per row, the pressure chamber 16 is arranged so that the pitch of the discharge ports 14 is 169 μm.

FIG. 2 is a diagram showing the overall configuration of the liquid discharge head according to the present embodiment, and FIG. 2A is a schematic cross-sectional view of the pressure chamber 16 in the lateral direction as in FIG. 2 (b) shows the AA cross section of FIG. 2 (a), and the BB cross section of FIG. 2 (b) corresponds to FIG. 2 (a). FIG. 2C is a schematic cross-sectional view of the pressure chamber 16 in the longitudinal direction, and corresponds to the cross section CC of FIG. 2B. Here, assuming that FIG. 2 (b) is the XY direction, FIG. 2 (a) shows the XY direction and FIG. 2 (c) shows the YY direction. As shown in FIG. 2B, the pressure chamber 16 has a rectangular shape having a short side and a long side in two dimensions (XY directions). The lateral direction of the pressure chamber 16 means a direction parallel to the short side (X direction) of this rectangular shape.

In FIG. 2, in addition to the configuration shown in FIG. 1, the substrate 22 is bonded to the diaphragm 11 side via the adhesive layer 21. A space is provided between the diaphragm 11 and the substrate 22 for each pressure chamber, and the diaphragm 11 is allowed to bend due to the piezoelectric element 12. Further, as shown in FIG. 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 the liquids from a plurality of pressure chambers (also referred to as individual liquid chambers) are averaged in the common liquid chamber to form a plurality of liquid chambers. Liquids in the same state are 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 the liquid. The discharge port 14 is formed substantially in the center of the pressure chamber 16 in the longitudinal direction (Y direction) so as to be located 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 of the pressure chamber 16 opposite to the supply path 23 in the longitudinal direction.

_{The cross-sectional shape of the pressure chamber 16 in the lateral direction is such that the internal angle θ d} formed by the inner wall 17 and the lateral direction at the contact portion between the inner wall 17 and the vibrating plate 11 is an obtuse angle, and the inner wall 17 in the lateral direction of the pressure chamber 17 _{The internal angle θ n} formed by the inner wall 17 and the lateral direction at the contact portion between the surface and the discharge port plate 13 is an obtuse angle. Therefore, the cross-sectional shape of the pressure chamber 16 in the lateral direction may be, for example, a hexagon as shown in FIG. 1 or an octagon. In FIG. 1, the inner wall 17 in the cross section of the pressure chamber 16 in the lateral direction is a combination of substantially straight lines, but a part having a curved line may be used. Therefore, it is possible to increase the cross-sectional area of the pressure chamber 16 as compared with the case where the cross-sectional shape of the pressure chamber 16 in the lateral direction is, for example, rectangular, and it is possible to reduce the flow path resistance of the circulating liquid. Further, if the cross-sectional shape of the pressure chamber 16 in the lateral direction is such that all the internal angles do not have acute angles or right-angled portions, the generation of foam accumulation in the pressure chamber 16 is suppressed and the discharge is stabilized. Can be made to.

As for the cross-sectional shape of the pressure chamber 16 in the lateral direction, the width of the pressure chamber 16 on the diaphragm 11 side in the lateral direction is W _d , and the width of the pressure chamber 16 on the discharge port plate 13 side in the lateral direction is W _s. Then, the configuration satisfies _{W d} > W _s. Therefore, the lateral direction of the beam width of the discharge port plate 13 facing the pressure chamber 16, i.e. W _s may be the lateral direction of the cross-sectional shape of the pressure chamber is narrower than the case of a rectangular. The wall surface having a cross-sectional shape in the longitudinal direction of the pressure chamber 16 can have the same shape as the wall surface having a cross-sectional shape in the lateral direction of the pressure chamber 16. Therefore, 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 lateral direction that is a controlling factor that determines the rigidity of the discharge port plate 13, it is necessary to improve the rigidity of the discharge port plate 13 by narrowing the beam width in the lateral direction. Can be done.

As _{is clear from FIG. 2B, the lower limit of W s} is the hole diameter (diameter) of the discharge port. Further, since _{the upper limit of W d} is naturally limited by the pitch of the discharge port, _{the upper limit of W s} is also restricted accordingly. _{Practically, W s} may be set within a width that can secure 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 its thickness can be, for example, about 500 nm to 2000 nm. By using, for example, LPCVD (low pressure chemical vapor deposition) as a film forming method, a film having low stress and high density and more suitable for a diaphragm can be obtained. _{Silicon oxide (SiO 2} ) can be used as another material for the diaphragm 11. In this case, PE (plasma enhanced) CVD is preferable as the film forming method. In addition, single crystal silicon (Si) can also be used as the diaphragm 11. Further, the diaphragm 11 may use a film made of a plurality of materials instead of a single film. For example, a two-layer structure may be formed in which the first layer is SiN and the second layer is SiO _2. The selection of the material of the diaphragm 11 may be judged from the consistency with other processes such as internal stress, adhesion, and etching selection ratio.

As the piezoelectric element 12, a piezoelectric body doped with PZT (lead zirconate titanate), Nb, or the like is used. The thickness of the piezoelectric material can be, for example, 500 nm to 3000 nm. As a method for forming a piezoelectric material, for example, by using a sputtering method, it is possible to obtain a piezoelectric material suitable for a liquid discharge head having high crystallinity and high dielectric strength. 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 forming method thereof is, for example, a sputtering method, and the thickness can be about 50 to 150 nm. Pt, IrO, RuO, TiW and the like can be used for the upper electrode, and the film forming method thereof is preferably a sputtering method, and the thickness can be about 50 to 150 nm. Further, in order to improve the adhesion to the diaphragm 11, the adhesion between the piezoelectric body and the lower electrode, and the adhesion between the piezoelectric body and the upper electrode, an adhesion layer may be inserted between the layers. The adhesion layer is, for example, Ti or the like, and can be used by forming a film having a film thickness of about 1 to 5 nm. The adhesion layer on the surface on which the piezoelectric material is formed may function as a layer for controlling the crystal orientation of the piezoelectric material. Further, a layer for controlling the crystal orientation of the piezoelectric material may be provided separately from the adhesion layer. The upper electrode, the piezoelectric body, the lower electrode, and each of the other layers are patterned by photolithography to form a predetermined shape (for example, a rectangle 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 a discharge port with high positional accuracy by photolithography. The thickness of the discharge port plate should be appropriately optimized according to the size of the discharge port from the viewpoint of diffusing a part of the liquid thickened inside the discharge port by evaporation to the liquid circulating in the pressure chamber. Is set to. The discharge port plate 13 is preferably formed to have 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 that constitutes the wall portion of the pressure chamber 16 can be used as long as it can form the pressure chamber shape according to the present embodiment and has resistance to the liquid in the pressure chamber. For example, any of an inorganic material such as a Si substrate and an organic material such as a photosensitive dry film can be used. Further, the structure may be such that two base materials having through holes are bonded together.

(Manufacturing Example 1)
Next, a method of manufacturing the liquid discharge head according to the present embodiment will be described. In the following description, a case where a Si substrate, particularly a Si substrate having a plane orientation of (100) is used as the substrate 15, will be described.
FIG. 3 is a schematic view showing an example of a method for manufacturing the liquid discharge head 100 according to the present embodiment, and FIGS. 3 (a) to 3 (i) show cross sections of the pressure chamber in each step in the lateral direction. Shown.

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 the wall surface of the pressure chamber on the diaphragm side, and is usually formed in a rectangular pattern having a short side and a long side. The plane orientation of the Si substrate 15A is (100). At this time, the short sides of the rectangular pattern of the sacrificial layer 31 are aligned and arranged so as to be 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, for example, in the range of 500 nm or more and 2000 nm. 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 the surrounding members and a high etching rate. The combinations of such sacrificial layers, surrounding members, and etchants are as follows. As a first example, there is a combination in which the sacrificial layer is a silicon oxide film (SiO ₂ ), the surrounding member (diaphragm) is SiN, and the etchant is HF. When 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. In addition, another combination may be used as long as the etching selectivity can be ensured. In this example, as the sacrificial layer 31, for example, a silicon oxide film is formed by using a thermal oxidation method. In addition to the thermal oxidation method, PECVD may be used to form the silicon oxide film of the sacrificial layer 31, and other methods may be appropriately selected and used. Further, the pattern shape of the sacrificial layer 31 is preferably formed so that the side surface is inclined so as to spread 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 obtuse.

Next, as shown in FIG. 3B, the diaphragm 11 is formed on the Si substrate 15A including the sacrificial layer 31. The diaphragm 11 is made of, for example, SiN, and its thickness can be, for example, about 500 nm to 2000 nm. As the film forming method, for example, LPCVD, PECVD and the like can be used. In the case of SiN, LPCVD can obtain a film with low stress and high density, which is more suitable for a diaphragm. When it is desired to lower the film formation temperature due to the restrictions of the manufacturing process before and after, it is preferable to use PECVD. _{SiO 2} can be used as the other film, and PECVD is preferable as the film forming method.

Next, as shown in FIG. 3C, the piezoelectric element 12 is formed on the diaphragm 11. The piezoelectric element 12 is patterned into each element shape by photolithography after the above-mentioned lamination of each layer is formed on the entire surface of the substrate. In the photolithography step, the pattern of the piezoelectric element 12 is formed so as to have a similar shape to the sacrificial layer 31, and the plane center of the piezoelectric element 12 is aligned with the plane center of the sacrificial layer 31. Both wet etching and dry etching can be used for etching, but using dry etching causes less process damage to the piezoelectric element 12 and can reduce the amount of side etching. Further, for etching each layer of the piezoelectric element 12, the layer patterned on the upper portion may be used as a hard mask.

As shown in FIG. 3D, the Si substrate 15A is thinned and processed into a substrate 15 capable of forming a pressure chamber 16 having a desired height. At this time, the support substrate of the substrate 15 can be bonded using the adhesive layer 21 between the substrate 22 and the substrate 15 which are the constituent members of the liquid discharge head, and the Si substrate 15A can be thinned. The thinning of the Si substrate 15A can be performed by, for example, polishing 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 shown in FIG. 3 (d) can also be obtained by bonding the substrate 22 with the adhesive layer 21 and removing the handle layer and the BOX (burried oxide) layer of the SOI substrate.

Next, as shown in FIG. 3 (e), 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 on the protective film 32. This groove pattern is formed so that the central axis in the longitudinal direction of the pattern of the sacrificial layer 31 and the central axis in the longitudinal direction of the groove pattern coincide with each other. The material of the protective film 32 is, for example, SiO ₂ . As the film forming method, for example, PECVD may be used, or another film forming method may be used. The film thickness of the protective film 32 can be, for example, in the range of 1000 nm to 2000 nm. The protective film 32 serves as an etching mask when forming a pressure chamber in a later step. When the SOI substrate is used as described above, the protective film 32 may be used by leaving the BOX layer after removing the handle layer. Next, the resist film 33 is formed on the protective film 32, and the 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 entire protective film 32. Further, the sacrificial layer 31 is formed so that the central axis in the longitudinal direction of the pattern and the central axis in the longitudinal direction of the groove pattern 34 coincide with each other.

Next, in FIG. 3 (f), the substrate perforation 35 is 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. 4A. For example, when the sacrificial layer 31 is SiO ₂ or Al, the substrate perforation 35 needs to reach the sacrificial layer 31 because the Si substrate 15 is not etched by the etchant of the sacrificial layer 31. On the other hand, when the sacrificial layer 31 is polycrystalline Si, the substrate perforation 35 may have a depth before penetrating the sacrificial layer 31 even if it does not reach the sacrificial layer 31. The reason for this is that when the sacrificial layer 31 is polycrystalline Si, the Si of the non-penetrating portion of the substrate perforation 35 is etched by an etchant, for example, a KOH solution, to reach the polycrystalline Si of the sacrificial layer 31 and be removed. Because it can be done.

Next, as shown in FIG. 3 (g), an etchant of the sacrificial layer 31 is introduced into the substrate perforation 35 to remove the sacrificial layer 31. The etchant is selected according to the material of the sacrificial layer 31 described in the sacrificial layer forming step of FIG. 3 (a). In FIG. 3A, since SiO ₂ was used as the sacrificial layer 31, Vapor-HF was 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. After removal of the sacrificial layer 31, space 36 is formed. After that, the resist film 33 is removed. The resist film 33 is removed by, for example, ashing using oxygen plasma. When the sacrificial layer 31 is a material such as Al or polycrystalline Si that has an etching selectivity with that of the protective film 32, the resist film 33 is removed after the substrate perforation 35 is formed and before the sacrificial layer 31 is removed. You can stay.

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

That is, according to the manufacturing method of the present 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 the KOH solution, and a chemical solution capable of crystalline anisotropic etching, for example, a TMAH (tetramethylammonium hydroxide) solution may be used. Further, the wall surface shape of the pressure chamber 16 in the longitudinal direction can have a shape in which the {111} surface is the wall surface, which is the same as the wall surface shape in the lateral direction. When etching is performed after the substrates 22 are bonded together, the etchant is prevented from wrapping around and etching the substrate 22. 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 of the substrate 15 is removed. When the protective film 32 is SiO ₂ , for example, an HF solution, a BHF (buffered hydrogen fluoride) solution, or Vapor-HF can be used. In the step of removing the protective film 32, the protective film 32 can be selectively removed because the materials other than the protective film 32 have a high etching selectivity with respect to these etchants. If there is a portion made of the same material as the protective film 32 that is exposed to the etchant, a protective film may be formed in advance on the portion to be protected with another material.

Next, as shown in FIG. 3 (i), the discharge port 14 has a discharge port 14 on the surface facing the diaphragm 11 with the pressure chamber 16 interposed therebetween, that is, on the lower side of the pressure chamber 16 having a narrow width in the lateral direction. The outlet plate 13 is formed. Here, the discharge port plate 13 can be formed by using, for example, a photosensitive dry film. To form the discharge port 14, after the photosensitive dry film is attached, a photomask (not shown) having the pattern of the discharge port 14 is aligned with the opening position of the pressure chamber 16 to expose the pattern of the discharge port 14. -It can be formed with high precision by developing. Further, the discharge port plate 13 may be formed by forming the discharge port 14 in advance, aligning the discharge port 14 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 discharge port 14 can be formed by, for example, laser processing, in addition to exposure and development, or may be formed 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. The present invention is not limited to these materials and dimensions.
In this embodiment, as shown in Production Example 1, a sacrificial layer 31 is formed on the diaphragm 11 side, and a through hole serving as a pressure chamber 16 is formed in the (100) Si substrate 15 from the space 36 from which the sacrificial layer 31 is removed. doing. Therefore, the diaphragm 11 has an inner wall surface in the pressure chamber 16 which is separated from the extension line of one surface (first surface) of the (100) Si substrate. However, the inner wall surface of the diaphragm in the pressure chamber may be an extension of the substrate.

[Example 2]
FIG. 4A is a schematic cross-sectional view for explaining an example of the present embodiment, and shows one pressure chamber 46A for simplification of the drawings. Here, the width of the pressure chamber 46A on the diaphragm 41 side in the lateral direction is W _d , the width of the pressure chamber 46A on the discharge port plate 43 side in the lateral direction is W _s, and the thickness of the substrate 45 is T _w. Let θ be the outer angle formed by the discharge port plate 43 and the side wall surface 47A of the pressure chamber 46A. θ is an acute angle, so that 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 discharge head has a configuration that satisfies the following two equations.

W _d > W _s ... (1),
T _w = (1/2) · (W _d −W _s ) · tan θ ··· (2-1).

When a (100) Si substrate is used as the substrate 45, the side wall surface 47A is a {111} surface, so θ is defined as about 55 degrees. Assuming that the thickness T _w of the substrate 45 is, for example, 60 μm, W _d− W _s is approximately 170 μm. The present invention is not limited to this, and other values may be used. The cross-sectional shape of the pressure chamber 46A in the lateral direction is a substantially trapezoidal shape surrounded by the side wall surface 47A formed on the substrate 45, the diaphragm 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 lateral direction is a hexagon having all obtuse internal angles, the flow path resistance of the circulating liquid can be reduced. As shown in FIG. 4 (b) In the present embodiment, can be a pressure chamber 46B of the hexagonal internal angles are all obtuse, in which case, the width W _d of the short side direction of the diaphragm 41 side 4 It is narrower than in the case of (a). Therefore, the thickness T _{w of the substrate 45, the width W d of the} pressure chamber 46B on the diaphragm side, _{and the width W s} on the discharge port plate side satisfy the following two equations.

W _d > W _s ... (1),
T _w > (1/2) ・ (W _d −W _s ) ・ tan θ ・ ・ ・ (2-2).

As described above, the liquid discharge head of the present embodiment has a configuration in which the cross-sectional shape of the pressure chamber in the lateral direction satisfies the following equations (1) and (2). Here, W _d is the width of the pressure chamber on the vibrating plate side in the lateral direction, W _s is the width of the pressure chamber on the discharge port plate side in the lateral direction, and T _w is the thickness of the substrate constituting the wall surface of the pressure chamber. , Θ represent the angles of the outer angles formed by the nozzle hole plate and the side wall surface of the pressure chamber, respectively.

W _d > W _s ... (1),
T _w ≧ (1/2) ・ (W _d −W _s ) ・ tan θ ・ ・ ・ (2).

In this way, by narrowing the beam width of the pressure chamber 46 on the discharge port plate 43 side in the lateral direction, the rigidity of the discharge port plate 43 can be improved. In the present embodiment, the inner wall surface of the pressure chamber of the diaphragm is formed on an extension of the first surface of the substrate, but 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 configurations that are separated from the extension of the surface of.

[Example 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 does not form a discharge port area, the beam width W _s of the discharge port plate facing the pressure chamber, since both ends are supported by the substrate, it is possible to secure the rigidity to some extent wider 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, when the beam width W _{b of the} cantilever becomes large, it becomes difficult to secure the rigidity.
On the other hand, in order to suppress the thickening of the liquid at the discharge port, when circulating the liquid in the pressure chamber, it is necessary to make the depth of the discharge port shallow 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 made extremely thin, the rigidity of the region where the discharge port is not formed cannot be sufficiently obtained. Therefore, in the present invention, it is preferable that the thickness T _n of the discharge port plate is 20μm or less in the range of 4 [mu] m.

FIG. 5 shows a main part of the liquid discharge head for explaining the configuration according to the present embodiment, and is a schematic cross-sectional view of the pressure chamber in the lateral direction. In the figure, for simplification, only the vicinity of the discharge port of one pressure chamber is shown. Other configurations are the configurations described in the first or second embodiment, and the materials described in the first embodiment can be used for the members and the like, and thus the description thereof will be omitted.

As shown in FIG. 5, the beam width W _s of the discharge port plate 53 is represented by the following equation (3A) from the radius r of the discharge port 54 and the beam width W _{b of the cantilever.}
W _s = 2 (W _b + r) ・ ・ ・ (3A)
Here, it is important that the beam width W _b is 3 times or less of the thickness Tn of the discharge port plate 53 in _{order to secure the rigidity.} The size of the discharge port 54 (diameter), considering the diffusion of the circulating liquid of the liquid in the discharge port 54, more than twice the thickness T _n of the discharge port plate 53, i.e., the radius of the discharge port 54 r is the following equation (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, it is considered that rigidity can be obtained for the time being if the following equation (3C) is satisfied.
W _s ≤ 8T _n ... (3C)
However, when actually expected alignment margin of the discharge port forming about one 5 [mu] m, to T _n satisfies W _b ≦ 3T _n at 4μm minima, the beam width W _s following equation (3) It is preferable to be satisfied.
W _s ≤ (5.5T _n + 10) ・ ・ ・ (3)

Here, 4 [mu] m thickness _{T n} of the discharge port plate 53, and 4 [mu] m discharge ports radius r, the width _{W s} of the transverse direction of the pressure chamber 56 is equal to or less than 32μm from the above equation (3). In this case, the beam width W _{b in} the lateral direction of the discharge port plate 53 is 12 μm or less, which is 3 times or less of 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 example of dimensions, 20 [mu] m thickness _{T n} of the discharge port plate 53, the radius r of the discharge ports 54 and 20 [mu] m, the width _{W s} of the short direction above formula of the pressure chamber 56 (3) from 120μm or less Is. In this case, the _{beam width W b is 40 μm or less, which is twice or less of T n} , with _{respect to the thickness T n} = 20 μm, and the rigidity of the discharge port plate 53 can be ensured.

As described above, in the present 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 of the pressure chamber on the discharge port plate side in the lateral direction. _{When s} (μm) is used, the following equations (3) to (5) are satisfied.

W _s ≤ (5.5T _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. Further, 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 the thickening of the liquid inside the discharge port 54 and stabilize the discharge. As described in the first embodiment, the lower limit of the width W _s is 2r, which is the hole diameter of the discharge port, and in that case, W _b = 0. Further, the present embodiment can be applied to any of the configurations of the first and second embodiments.

[Example of Manufacturing Method]
An example of an embodiment of the method for manufacturing a liquid discharge head according to the present invention is shown below. In the liquid discharge head according to the present invention, the pressure chamber is formed on a substrate having a diaphragm on the first surface and a discharge port plate on the second surface facing the first surface, and has a cross section in the surface direction of the substrate. Is composed of a rectangular through hole. The method for manufacturing the liquid discharge head according to any of the embodiments of the present invention is common to the manufacturing method (manufacturing example 1) shown in the first embodiment in the following points. That is, when the opening width of the through hole in the lateral side on the first surface side is W _d and the opening width in the lateral direction on the second surface side is W _s , W _d > W _s. As described above, the substrate has a step of forming the through hole. In the following description, the description of the members common to Production Example 1 will be omitted.

(Manufacturing Example 2)
FIG. 6 is a process diagram showing a method of manufacturing a liquid discharge head according to an embodiment of the present invention, and shows a cross section of the pressure chamber 616 in the lateral direction. FIG. 6A is a step of preparing a substrate for generating pressure (hereinafter referred to as a pressure generating substrate) 625. The pressure generating substrate 625 is formed with a pressure chamber space (cavity) 626 for accommodating the piezoelectric element 612 on the diaphragm 611. That is, the pressure generating substrate can be formed by attaching the diaphragm 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 on which a through hole serving as 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 of the pressure chamber 616 in the lateral direction has a {111} plane as a side wall due to crystal anisotropic etching. Further, the cross-sectional shape of the pressure chamber 616 in the lateral direction is configured to satisfy _{W d} > W _s. W _d is the width of the pressure chamber 616 on the diaphragm 611 side (first surface) to be bonded in a later process in the lateral direction, and W _s is the width of the discharge port plate 613 side (first surface) formed in a later process. The width of the pressure chamber 616 of the second side) in the lateral direction is shown. The cross-sectional shape of the pressure chamber 616 in the lateral direction is, for example, formed into a substantially hexagon whose internal angles are all obtuse angles. The cross section of the pressure chamber 616 in the longitudinal direction has the same {111} plane as the cross section in the lateral direction as the side wall. The substrate 615 is not limited to the (100) Si substrate, and may be a photosensitive resin substrate, and the cross-sectional shape of the pressure chamber 616 in the lateral direction is approximately 6 as long as it has a configuration satisfying _{W d} > W _s. It is not limited to a square shape. In this production 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 is a step of attaching the pressure generating substrate 625 to the first surface of the substrate 615. In this step, using the alignment marks (not shown) formed on both substrates, the central axis in the longitudinal direction of the piezoelectric element 612 of the pressure generating substrate 625 and the center are the central axes in the longitudinal direction of the upper surface of the pressure chamber 616. The boards are bonded by aligning them so that they match the center. The substrate bonding step may be performed by using surface-activated bonding in which the substrate bonding surface is surface-activated by, for example, plasma or the like, and then bonded, or bonding may be performed using an adhesive.

Next, FIG. 6D forms a discharge port plate 613 having a discharge port 614 on the second surface of the substrate 615. As in Production Example 1, a photosensitive dry film is used as the discharge port plate material for the discharge port, and after the photosensitive dry film is attached to the second surface of the substrate 615, the discharge port 614 is formed by a photolithography method. be able to. Further, the discharge port plate 613 having the discharge port 614 formed in advance may be attached.
Further, after forming the discharge port plate 613 having the discharge port 614 on the second surface of the substrate 615, the pressure generating substrate 625 may be attached to the first surface of the substrate 615.

The liquid discharge head according to the present invention can be mounted on a device such as a printer, a copying machine, a facsimile having a communication system, a word processor having a printer unit, and an industrial recording device complexly combined with various processing devices. Then, by using the device equipped with this liquid discharge head, recording can be performed on various recorded objects such as paper, thread, fiber, leather, metal, plastic, glass, wood, and ceramic. It can also be applied as a head for discharging liquids for biochip manufacturing and electronic circuit printing. Among them, the liquid ejection head according to the present invention is suitable as an inkjet head or the like using water-based ink or the like.

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

Claims (8)

The diaphragm has a pressure chamber surrounded by a diaphragm and a discharge port plate, and the deflection of the diaphragm by a piezoelectric element including a piezoelectric body formed on a surface of the diaphragm facing the pressure chamber is utilized. A liquid discharge head that discharges the liquid in the pressure chamber from the discharge port of the discharge port plate.
The inner angle formed by the inner wall in the lateral direction and the inner wall in the lateral direction at the contact portion between the inner wall in the lateral direction of the pressure chamber and the diaphragm is an obtuse angle.
The inner angle formed by the inner wall in the lateral direction and the inner wall in the lateral direction at the contact portion between the inner wall in the lateral direction of the pressure chamber and the discharge port plate is an obtuse angle.
The width W _d of the lateral direction of the pressure chamber of the _{diaphragm-side,} when the width W _s of the transverse direction of the pressure chamber of the discharge port plate side, meets the following formula (1):
W _d > W _s ... (1) ,
The thickness T _n of the discharge port plate _([mu] m), the radius of the discharge port r (μm), the lateral direction of the width of the pressure chamber of the discharge port plate side when the W _{s (μm),} the following formula Liquid discharge head characterized by satisfying (3) to (5):
W _s ≤ (5.5T _n + 10 μm) ・ ・ ・ (3),
r ≧ T _n ... (4),
4 μm ≤ T _n ≤ 20 μm ... (5). The diaphragm has a pressure chamber surrounded by a diaphragm and a discharge port plate, and the deflection of the diaphragm by a piezoelectric element including a piezoelectric body formed on a surface of the diaphragm facing the pressure chamber is utilized. A liquid discharge head that discharges the liquid in the pressure chamber from the discharge port of the discharge port plate.
The pressure chamber is formed as a through hole in a substrate forming a side wall of the pressure chamber.
The width of the pressure chamber on the vibrating plate side in the lateral direction is W _d , the width of the pressure chamber on the discharge port plate side in the lateral direction is W _s , and the thickness of the substrate is T _w. when the angle of the formed exterior angle side wall surface of the pressure chamber and theta, meets the following formula (1) and (2):
W _d > W _s ... (1),
T _w ≧ (1/2) ・ (W _d −W _s ) ・ tan θ ・ ・ ・ (2) ,
The thickness T _n of the discharge port plate _([mu] m), the radius of the discharge port r (μm), the lateral direction of the width of the pressure chamber of the discharge port plate side when the W _{s (μm),} the following formula Liquid discharge head characterized by satisfying (3) to (5):
W _s ≤ (5.5T _n + 10 μm) ・ ・ ・ (3),
r ≧ T _n ... (4),
4 μm ≤ T _n ≤ 20 μm ... (5). The pressure chamber is a through hole having a {111} surface formed on the (100) Si substrate as a wall surface, and the longitudinal direction and the lateral direction of the pressure chamber are parallel to the <110> axis of the Si substrate. The liquid discharge head according to claim 1 or 2. The diaphragm is continuously formed 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 discharge head according to claim 3. The liquid discharge head according to any one of claims 1 to 4 , further comprising a supply path for supplying the liquid into the pressure chamber and a recovery path for recovering the liquid from the pressure chamber. The diaphragm has a pressure chamber surrounded by a diaphragm and a discharge port plate, and the deflection of the diaphragm by a piezoelectric element including a piezoelectric body formed on a surface of the diaphragm facing the pressure chamber is utilized. A method for manufacturing a liquid discharge head that discharges a liquid in a pressure chamber from a discharge port of the discharge port plate.
The pressure chamber is formed on a substrate having the diaphragm on the first surface and the discharge port plate on the second surface facing the first surface, and the cross section of the substrate in the surface direction is rectangular. It ’s a hole,
When the opening width of the through hole in the lateral direction on the first surface side is W _d and the opening width in the lateral direction on the second surface side is W _s , W _d > W _s. the step of forming the through hole in the substrate possess a,
The substrate is a Si substrate having a plane orientation on the (100) plane.
A step of forming a sacrificial layer having a rectangular pattern having a short side and a long side on the first surface of the Si substrate and having the short side parallel to the <110> axis of the Si substrate.
A step of forming a diaphragm on the Si substrate including the sacrificial layer, and
A step of forming a piezoelectric element containing a piezoelectric body on a surface of the diaphragm facing the first surface of the Si substrate, and
A protective film is formed on the second surface of the Si substrate facing the first surface, has a central axis that coincides with the central axis in the longitudinal direction of the sacrificial layer, and has a central axis in the lateral direction of the sacrificial layer. A step of forming a groove pattern having a lateral direction narrower than the width on the protective film, and
A step of forming a substrate perforation from the second surface toward the sacrificial layer inside the groove pattern of the protective film, and
A step of removing the sacrificial layer from the perforation of the substrate to form a space on the first surface of the Si substrate.
An etchant is introduced into the substrate perforation and the space, and the through hole having a side wall in the lateral direction composed of a {111} plane is formed on the Si substrate by crystal anisotropic etching using the diaphragm and the protective film as a mask. Process and
A method for manufacturing a liquid discharge head, which comprises a step of forming a discharge port plate on the second surface of the Si substrate. The steps of forming the discharge port plate include a step of attaching a photosensitive discharge port plate material to the second surface of the substrate on which the through hole is formed, and a step of forming a discharge port on the discharge port plate material by photolithography. The method for manufacturing a liquid discharge head according to claim 6 , further comprising a step of making a liquid discharge head. The step according to claim 6 or 7 , wherein the step of forming the discharge port plate includes a step of attaching a discharge port plate having a discharge port to the second surface of the substrate on which the through hole is formed. Manufacture of liquid discharge heads.

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