Liquid discharge head, liquid discharge device, and liquid discharge apparatus

A liquid discharge head includes a plurality of nozzles from which a liquid is discharged, a plurality of pressure chambers communicating with the plurality of nozzles, respectively, a substrate in which the plurality of pressure chamber is arranged in a predetermined direction, a diaphragm provided on a first side of the substrate opposite a second side of the substrate facing the plurality of nozzles, the diaphragm forming walls of the plurality of pressure chambers, and a plurality of electromechanical transducer elements provided on the diaphragm corresponding to the plurality of pressure chambers, respectively. A groove is formed in the substrate on an end side of the plurality of pressure chambers in the predetermined direction, and the groove includes an opening that opens toward a direction opposite to the diaphragm.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2017-053293, filed on Mar. 17, 2017, in the Japan Patent Office, Japanese Patent Application No. 2017-053323, filed on Mar. 17, 2017, in the Japan Patent Office, Japanese Patent Application No. 2018-023119, filed on Feb. 13, 2018, in the Japan Patent Office, Japanese Patent Application No. 2018-023136, filed on Feb. 13, 2018, in the Japan Patent Office, the entire disclosure of which are hereby incorporated by reference herein.

BACKGROUND

Technical Field

Aspects of the present disclosure relate to a liquid discharge head, a liquid discharge device, and a liquid discharge apparatus.

Related Art

Liquid discharging heads are known that include nozzles to discharge liquid droplets such as ink, pressure chambers communicating with the nozzles, and electromechanical transducer elements such as piezoelectric elements to pressurize liquid inside the pressure chambers. Two types of liquid discharge heads are used: a liquid discharge head using piezoelectric actuators vibrating in a longitudinal vibration mode and the liquid discharge head using piezoelectric actuators vibrating in a flexural vibration mode.

As the liquid discharge head using the piezoelectric actuators vibrating in the flexural vibration mode, for example, a head is known that is manufactured by the following procedure. First, a uniform piezoelectric material layer is formed by a film forming technique over the entire surface of a diaphragm. Then, the piezoelectric material layer is cut into a shape corresponding to pressure chambers by a lithography method to form independent electromechanical transducer elements for the respective pressure chambers.

One of the liquid discharge head including the piezoelectric actuators vibrating in the flexural vibrating mode includes a groove formed on a surface of a channel substrate on a side of a nozzle substrate.

SUMMARY

In an aspect of this disclosure, a liquid discharge head includes a plurality of nozzles from which a liquid is discharged, a plurality of pressure chambers communicating with the plurality of nozzles, respectively, a substrate in which the plurality of pressure chamber is arranged in a predetermined direction, a diaphragm provided on a first side of the substrate opposite a second side of the substrate facing the plurality of nozzles, the diaphragm forming walls of the plurality of pressure chambers, and a plurality of electromechanical transducer elements provided on the diaphragm corresponding to the plurality of pressure chambers, respectively. A groove is formed in the substrate on an end side of the plurality of pressure chambers in the predetermined direction, and the groove includes an opening that opens toward a direction opposite to the diaphragm. The diaphragm at the plurality of pressure chambers is formed to be deflexed toward the plurality of pressure chambers, and the diaphragm at the groove is formed to be deflexed opposite to the opening of the groove. A degree of deflection of the diaphragm at the plurality of pressure chambers is larger than a degree of deflection of the diaphragm at the groove.

In another aspect of this disclosure, a liquid discharge head includes a plurality of nozzles from which a liquid is discharged, a plurality of pressure chambers communicating with the plurality of nozzles, respectively, a substrate in which the plurality of pressure chamber is arranged in a predetermined direction, a diaphragm provided on a first side of the substrate opposite a second side of the substrate facing the plurality of nozzles, the diaphragm forming walls of the plurality of pressure chambers, and a plurality of electromechanical transducer elements provided on the diaphragm corresponding to the plurality of pressure chambers, respectively. A groove is formed in the substrate on an end side of the plurality of pressure chambers in the predetermined direction, and the groove includes an opening that opens toward a direction opposite to the diaphragm. The diaphragm at the groove is formed to be deflexed opposite to the opening of the groove, and a radius of curvature Ra of the diaphragm at the groove is equal to or larger than 5000 μm.

In still another aspect of this disclosure, a liquid discharge apparatus includes a plurality of nozzles from which a liquid is discharged, a plurality of pressure chambers communicating with the plurality of nozzles, respectively, a substrate in which the plurality of pressure chamber is arranged in a predetermined direction, a diaphragm provided on a first side of the substrate opposite a second side of the substrate facing the plurality of nozzles, the diaphragm forming walls of the plurality of pressure chambers, and a plurality of electromechanical transducer elements provided on the diaphragm corresponding to the plurality of pressure chambers, respectively. A groove is formed in the substrate on an end side of the plurality of pressure chambers in the predetermined direction, and the groove includes an opening that opens toward a direction opposite to the diaphragm. The diaphragm at the plurality of pressure chambers is formed to be deflexed toward the plurality of pressure chambers, and the diaphragm at the groove is formed to be deflexed opposite to the opening of the groove.

DETAILED DESCRIPTION

Although the embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the disclosure and all of the components or elements described in the embodiments of this disclosure are not necessarily indispensable. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Hereinafter, embodiments of the present disclosure are described with reference to the attached drawings. A liquid discharge head according to an embodiment of the present disclosure is described with reference toFIGS. 1 through 3.

Configurations of embodiments according to the present disclosure are described below with reference toFIGS. 1 to 24.

First Embodiment

[Configuration of Liquid Discharge Head]

FIG. 1is an enlarged cross-sectional view of a liquid discharge head1according to an embodiment of the present disclosure. Hereinafter, the “liquid discharge head” is simply referred to as “head”. The head1includes a substrate10, a diaphragm20, an electromechanical transducer element30, and an insulating protective film40. Further, the electromechanical transducer element30includes a lower electrode31, an electromechanical transducer film32, and an upper electrode33.

In the head1, the diaphragm20is formed on the substrate10, and a lower electrode31of the electromechanical transducer element30is formed on the diaphragm20. Further, an electromechanical transducer film32is formed in a predetermined region of the lower electrode31, and an upper electrode33is further formed on the electromechanical transducer film32. The insulating protective film40covers the electromechanical transducer element30. The insulating protective film40has an opening40cfor selectively exposing the lower electrode31and the upper electrode33, and a wiring can be drawn from the lower electrode31and the upper electrode33via the opening40c.

A nozzle plate50including a nozzle51from which ink droplets are discharged is joined to the lower portion of the substrate10. The nozzle plate50, the substrate10, and the diaphragm20form a pressure chamber10X communicating with the nozzle51. The pressure chamber10X is also referred to as an ink channel, a pressure liquid chamber, a pressurizing chamber, a discharge chamber, and a liquid chamber, for example. The diaphragm20forms a part of a wall surface of the pressure chamber10X. In other words, the pressure chamber10X is partitioned by the substrate10(constituting the side surfaces), the nozzle plate50(constituting the lower surface), and the diaphragm20(constituting the upper surface). The pressure chamber10X communicates with the nozzle51.

The diaphragm20is provided on a first side of the substrate10opposite a second side of the substrate10facing the plurality of nozzles51. The diaphragm20forms walls of the plurality of pressure chambers10X.

FIG. 2illustrates a method for manufacturing the head1. First, the diaphragm20, the lower electrode31, the electromechanical transducer film32, and the upper electrode33are sequentially laminated on the substrate10as illustrated inFIG. 2. Then, the lower electrode31, the electromechanical transducer film32, and the upper electrode33are etched to have a desired shape. Then, the lower electrode31, the electromechanical transducer film32, and the upper electrode33are covered with the insulating protective film40. Then, the opening40cfor selectively exposing the lower electrode31and the upper electrode33is formed in the insulating protective film40. Then, the pressure chamber10X is formed by etching the substrate10from a lower side of the substrate10. Next, the nozzle plate50including the nozzles51is bonded to the lower surface of the substrate10so that manufacturing of the head1is completed.

FIG. 3is a cross-sectional view of an actual head2. Only one head1is illustrated inFIG. 1. However, the actual head2includes a plurality of heads1arranged in a nozzle array direction indicated by arrow NAD inFIG. 3. A plurality of nozzles51of the heads1is arrayed in a row in the nozzle array direction NAD. The head2has a structure in which a plurality of heads1are arrayed in the nozzle array direction NAD. The head1includes the nozzle51for discharge liquid, the pressure chamber10X communicating with the nozzle51, and a discharge driver to increase a pressure of the liquid in the pressure chamber10X. Here, the discharge driver includes the diaphragm20that forms a part of the wall of the pressure chamber10X and the electromechanical transducer element30including the electromechanical transducer film32.

In the head2, a portion of the head1including the pressure chamber10X, the diaphragm20, and the electromechanical transducer element30for discharging the liquid is referred to as a drive channel3.

Next, a configuration of the head2including a wiring, for example, is described with reference toFIGS. 4A and 4B.FIGS. 4A and 4Billustrate an example of parts such as the wiring of the head2.FIG. 4Ais a cross-sectional view of the head2.FIG. 4Bis a plan view of the head2. Here the insulating protective film40and70are omitted inFIG. 4B.

In an example illustrated inFIGS. 4A and 4B, the insulating protective film40is formed of two layers of insulating protective films40aand40b.A plurality of wirings60is provided on a second layer of the insulating protective film40b,and an insulating protective film70is further provided over the wirings60. The insulating protective film40has a plurality of openings40x.The surface of the lower electrode31or the upper electrode33is exposed in the opening40x.The wiring60includes a wiring connected to the upper electrode33via the opening40x(a portion of a contact hole H inFIG. 4B) and a wiring connected to the lower electrode31via the opening40x.

The insulating protective film70includes a plurality of openings70x,and surfaces of the wirings60are exposed in the openings70x,respectively. Each of the wirings60exposed in the openings70xbecomes the electrode pads61,62, and63. The electrode pad61is a common electrode pad and is connected to the lower electrode31via the wiring60. The lower electrode31is common to each of the electromechanical transducer elements30. The electrode pads62and63are individual electrode pads and are connected to the upper electrodes33via the wirings60, respectively. The upper electrodes33are independent for each electromechanical transducer elements30.

In a process of manufacturing the head2, the diaphragm20deflects (curved) so that the diaphragm20is convex toward the pressure chamber10X side as illustrated inFIG. 5when the pressure chamber10X is manufactured. That is, in a state where no voltage is applied to the electromechanical transducer element30, the diaphragm20deflects (curved) to be convex toward the pressure chamber10X side. Therefore, the diaphragm20is formed in a state in which the diaphragm20deflects in a convex shape toward the pressure chamber10X side. An amount of deflection of the diaphragm20influences a displacement amount of the diaphragm20. Further, when the diaphragm20deflects, residual vibration occurs when the head2discharges ink. Generation of a predetermined waveform is necessary to suppress the residual vibration. However, reducing a frequency of the predetermined waveform is necessary to suppress the residual vibration. Thus, securing discharge performance of the head2at high frequency becomes difficult.

To secure discharge performance at a high frequency, a rigidity of the diaphragm20, electromechanical transducer film32, and the insulating protective film40has to be increased. Thus, it is necessary to use material having high Young's ratio or using material having a large film thickness for the diaphragm20, the electromechanical transducer film32, and the insulating protective film40. In the head2, the diaphragm20is formed from a plurality of layers including materials such as a silicon oxide film (SiO2), a silicon nitride film (SiN), and polysilicon (Poly-Si) in consideration of stress design. Thickness of the diaphragm20is preferably in a range of from 1 μm or greater and 3 μm or less. Further, setting the Young's modulus of the diaphragm20to be equal to 75 GPa or more and 95 GPa or less can secure a discharging performance at a high frequency.

Next, an amount of deflection of the diaphragm20is described below. A definition of the amount of deflection of the diaphragm20is described with reference toFIG. 6. In order to calculate the deflection amount of the diaphragm20, a deflection distribution of the diaphragm20illustrated inFIG. 6Ais acquired from the pressure chamber10X side using a deflection amount meter (CCI 3000, manufactured by Ametec Corporation).

Calculation of a radius of curvature R of the diaphragm20based on the acquired deflection distribution is described below. As illustrated inFIG. 5as an example, a central portion of the diaphragm20has a large deflection, and both ends of the diaphragm have a small deflection. Next, a point C that is a center point of the deflection of the diaphragm20is obtained based on points A and B disposed at both ends of the diaphragm20in the deflection distribution of the diaphragm20illustrated inFIG. 6Aacquired using the deflection amount meter. The deflection amount at each points A and B becomes the smallest in the diaphragm20. Then, a distance X between the center point C and each of the points A and B at both ends of the diaphragm20is obtained. Then, two points D and E at a distance of 0.8X are obtained with reference to the center point C of the deflection. Next, as illustratedFIG. 6B, a point F of intersection between a line DE connecting the point D and the point E and a line perpendicular to the line DE and passing the center point C is obtained. Then, a distance Y between the point F and the point C is obtained. This distance Y can be obtained from a difference between a height at the points D and E and the height at the center point C in the deflection distribution. Further, a distance between a point O and the point F can be calculated by determining the point O of a center of a curvature circle of the deflection. Thus, the radius of curvature R can be calculated using the pythagoran theorem in a right triangle composed of the points O, E, and F.

In the following description, the radius of curvature R is calculated by the above calculation method unless otherwise specified. The method of calculating the radius of curvature R of the diaphragm20is not limited to the method as illustrated inFIGS. 6A and 6B. For example, the center point C in the deflection distribution of the diaphragm20is obtained. Then, the radius of curvature R is calculated based on two or three coordinate points separated from the center point C by a predetermined distance in a direction from the center point C to the points A and B of both ends of the diaphragm20.

[Material for Liquid Discharge Head]

Next, preferred materials for constituting the head2are described below. A silicon single crystal substrate is preferably used as the substrate10, and the substrate10preferably has a thickness of from 100 μm to 600 μm. As plane orientations, three kinds of (100), (110), and (111) are known. However, (100) and (111) are generally used widely in the semiconductor industry. In the head2of the present embodiment, a silicon single crystal substrate mainly having (100) plane orientation is used.

In fabricating the pressure chamber10X, the silicon single crystal substrate is processed by etching. In such a case, an anisotropic etching is typically used as a method of etching. The anisotropic etching utilizes the property in which the etching rate is different between plane orientations of crystal structure.

For example, in the anisotropic etching in which a substrate is immersed in an alkaline solution, such as KOH, the etching rate of a (111) plane is about 1/400 of the etching rate of a (100) plane. Therefore, a structure having an inclination of about 54° can be produced in the plane orientation (100). On the other hand, a deep groove can be formed in the plane orientation (110). Therefore, a single crystal substrate having a plane orientation of (110) may also be used for the head2since an array density can be increased while maintaining more rigidity. However, it should be noted that in this case, a mask material SiO2is also etched.

The width (length in a short direction) of the pressure chamber10X is preferably from 50 μm to 250 μm and more preferably from 60 μm to 150 μm.

The diaphragm20is deformed and displaced by receiving a force generated by the electromechanical transducer film32, and discharges an ink droplet in the pressure chamber10X. Therefore, a material having predetermined strength is preferably used as the diaphragm20. As the materials of the diaphragm20, for example, Si, SiO2, and Si3N4are prepared according to a chemical vapor deposition (CVD) method. A material having a linear expansion coefficient close to the linear expansion coefficient of each of the lower electrode31and the electromechanical transducer film32is preferably selected for the diaphragm20.

As a material of the electromechanical transducer film32, in which PZT is typically used, the diaphragm20may be made of a material having a linear expansion coefficient of from5×10−6to10×10−6[1/K] close to a linear expansion coefficient of8×10−6[1/K]. Furthermore, a material having a linear expansion coefficient of7×10−6to9×10−6[1/K] is more preferable.

Examples of the materials of the diaphragm20include aluminum oxide, zirconium oxide, iridium oxide, ruthenium oxide, tantalum oxide, hafnium oxide, osmium oxide, rhenium oxide, rhodium oxide, palladium oxide, and compounds of the foregoing materials. Using such materials, the diaphragm20can be produced by a sputtering method or a spin coater using a sol-gel method.

The film thickness of the diaphragm20is preferably in a range of from 1 μm to 10 μm, and more preferably in a range of from 2 μm to 5 μm.

Examples of a metal material of the lower electrode31and the upper electrode33include platinum having high heat-resistance and low reactivity. However, platinum may not have a sufficient barrier property against lead. Accordingly, platinum group elements, such as iridium and platinum-rhodium, or alloy films of the platinum group elements may be used for the lower electrode31and the upper electrode33.

When platinum is used as the material for the lower electrode31and the upper electrode33, adhesion of platinum with the diaphragm20(in particular, SiO2) as a base is poor. Therefore, the lower electrode31and the upper electrode33are preferably laminated via an adhesive layer composed of material, for example, Ti, TiO2, Ta, Ta2O5, or Ta3N5. Examples of a method of producing the lower electrode31and the upper electrode33include a sputtering method and a vacuum deposition such as vacuum evaporation. The film thickness of the lower electrode31and the upper electrode33are preferably in a range of from 0.05 μm to 1 μm, and more preferably in a range of from 0.1 μm to 0.5 μm.

Further, an oxide electrode film formed of SrRuO3or LaNiO3as a material may be formed between the above-described metal material and the electromechanical transducer film32in the lower electrode31and the upper electrode33. Note that the oxide electrode film between the lower electrode31and the electromechanical transducer film32also affects an orientation control of the electromechanical transducer film32(PZT film, for example) to be formed on the oxide electrode film. Thus, the materials selected for the oxide electrode film is different depend on the orientation to be prioritized.

For example, a seed layer of LaNiO3, TiO2, PbTiO3is preferably formed on the metal material as the lower electrode31, and then the PZT film is formed on the lower electrode31when a piezoelectric body such as PZT is used as the electromechanical transducer film32and is preferentially oriented to PZT (100) in the head2.

SrRuOx (SRO) film may be used as the oxide electrode film between the upper electrode33and the electromechanical transducer film32. A film thickness of the SRO film is preferably in a range of from 20 nm to 80 nm, and more preferably in a range from 30 nm to 50 nm.

As a material of the electromechanical transducer film32, lead zirconate titanate (PZT) can be preferably used. Note that PZT is a solid solution of lead zirconate (PbZrO3) and lead titanate (PbTiO3) and has different properties according to the ratio of PbZrO3and PbTiO3. For example, a PZT, in which the ratio of PbZrO3and PbTiO3is 53:47, can be used, which is represented by a chemical formula of Pb (Zr0.53, Ti0.47) O3or generally represented as PZT (53/47).

However, when PZT(100) plane has a priority orientation using the PZT as the electromechanical transducer film32, a composition ratio of Zr/Ti represented by Ti/(Zr+Ti) is preferably 0.45 or more and 0.55 or less, and more preferably 0.48 or more and 0.52 or less.

The crystal orientation is expressed by ρ (hkl)=I (hkl)/ΣI (hkl). Here, ρ (hkl) is the degree of orientation of (hkl) plane orientation, I (hkl) is peak intensity of arbitrary orientation, and ΣI (hkl) is the sum of each peak intensity. When a sum of peak intensities obtained by θ-2θ measurement in an X-ray diffraction method is assumed to be 1, an orientation degree in (100) orientation calculated based on a ratio of a peak intensity in each orientation is preferably 0.75 or more, and more preferably 0.85 or more.

The electromechanical transducer film32may be manufactured by a sputtering method or a spin coater using sol-gel method. In such a case, a desired pattern is obtained by, for example, photolithoetching for patterning.

When the PZT used for manufacturing the electromechanical transducer film32is prepared by a sol-gel method, lead acetate, zirconium alkoxide, and titanium alkoxide compounds are used as starting materials. The lead acetate, the zirconium alkoxide, and the titanium alkoxide compounds are dissolved in methoxyethanol functioning as a common solvent, and a uniform solution is obtained. Thus, a PZT precursor solution is prepared. Since a metal alkoxide compound is easily hydrolyzed by atmospheric water, a stabilizer, such as acetylacetone, acetic acid, or diethanolamine may be appropriately added to the PZT precursor solution.

When the PZT film (electromechanical transducer film32) is formed on an entire surface of the lower electrode31, the PZT film is obtained by forming a coating by a solution coating method, such as a spin coating method, and performing each heat treatment of solvent drying, thermal decomposition, and crystallization on the coating. Transformation from the coating to a crystalline film causes volume contraction. Therefore, a concentration of the PZT precursor solution is adjusted to obtain a film thickness of 100 nm or less by one step in order to obtain a crack-free film. The film thickness of the electromechanical transducer film32is preferably in a range of from 1 μm to 3 μm, and more preferably in a range of from 1.5 μm to 2.5 μm.

As the electromechanical transducer film32, an ABO 3 type perovskite type crystalline film other than PZT may be used. As the ABO 3 type perovskite type crystalline film other than PZT, for example, a lead-free complex oxide film such as barium titanate may be used. In such a case, barium alkoxide and titanium alkoxide compounds are used as a starting material and are dissolved in a common solvent, to prepare a barium titanate precursor solution.

These materials are complex oxides represented by the chemical formula ABO3, where A=Pb, Ba, or Sr, B=Ti, Zr, Sn, Ni, Zn, Mg, or Nb as main components. Specific examples of the composite oxides include (Pb1-x, Ba) (Zr, Ti) O3and (Pb1-x, Sr) (Zr, Ti) O3, in which a part of Pb at A site is replaced with Ba or Sr. The substitution is enabled in a bivalent element and an effect of the substitution is to decrease characteristic deterioration by the evaporation of the lead during the heat treatment.

As a material of the insulating protective film40, a dense inorganic material is preferable because it is necessary to select a material that is impermeable to moisture in the atmosphere and prevents damages to the piezoelectric element (electromechanical transducer element30) in a film formation process and etching process.

As the first insulating protective film40, an oxide, nitride, or carbonized film may be used to obtain a high degree of protection performance with a thin film. However, it is necessary to select a material having high adhesion with the electrode material, the piezoelectric material, and the diaphragm material that serve as the base of the insulating protective film40. In addition, it is necessary to select a film forming method that does not damage the piezoelectric element (electromechanical transducer element30). That is, it is not preferable to use a plasma CVD (chemical vapor deposition) method in which a reactive gas is converted into a plasma and deposited on a substrate, or a sputtering method in which a film is formed by causing plasma to collide with a target material and to blow off atoms in the target material. As a preferable film formation method, vapor deposition method, ALD (Atomic Layer Deposition) method can be used. However, the ALD method having a wide choice of materials that can be used is preferable. Examples of preferable material for the insulating protective film40include an oxide film used for ceramic materials, such as A12O3, ZrO2, Y2O3, Ta2O3, and TiO2. In particular, according to the ALD method, a thin film with quite high film density is produced, thus reducing damage to the electromechanical transducer element30during manufacturing process.

The insulating protective film40has a thickness that is large enough to obtain a protection performance of the electromechanical transducer element30and is small enough not to hamper the displacement of the diaphragm20. The film thickness of the insulating protective film40is preferably in the range from 20 nm to 100 nm.

The insulating protective film40may have two layer configuration that includes insulating protective films40aand40bas illustrated inFIG. 4A. In this case, in order to increase the thickness of the second layer of the insulating protective film40b,the second layer insulating protective film40bmay include an opening so that the second layer of the insulating protective film40bdoes not significantly hamper a vibration displacement of the diaphragm20. As the second layer of the insulating protective film40b,any oxide, nitride, and carbide or a composite compound thereof can be used.

For example, SiO2, which is typically used in a semiconductor device, may be used. Any suitable method may be used for forming the film such as the CVD method or sputtering, for example. In particular, considering about coating a step portion of a pattern forming part, such as an electrode forming part, the CVD method capable of isotropically forming a film is preferably used. The film thickness of the second layer of the insulating protective film40bhas to be set to the thickness in which the second layer of the insulating protective film40bis not dielectrically broken down by a voltage applied to the lower electrode31and the wirings60.

That is, the electric field intensity applied to the insulating protective film40has to be set in a range in which the insulating protective film40is not dielectrically broken down. Consideration about a surface properties or pin holes of the base of the second layer of the insulating protective film40b,the film thickness is preferably equal to 200 nm or more, and more preferably 500 nm or more.

The insulating protective film70functions as a passivation layer having a function of a protective layer of the wiring60. As illustrated inFIGS. 4A and 4B, the upper electrode33and the lower electrode31are covered except for the locations of the electrode pads61and62(opening70x). Thus, low cost Al or an alloy material including Al as main ingredient can be used for the material of the upper electrode33and the lower electrode31. As a result, the head2can be manufactured with low cost and high reliability.

As a material of the insulating protective film70, any inorganic material or any organic material can be used. However, a material with low moisture permeability is preferable. Examples of inorganic material include oxide, nitride, and carbide. Examples of organic material include polyimide, acrylic resin, and urethane resin. However, the organic material is not suitable because the thickness of the insulating protective film70has to be increased. Accordingly, the inorganic material is preferably used because the inorganic material can exhibit a function of protecting the wiring in a thin film. In particular, it is preferable to use Si3N4on the Al wiring because using Si3N4on the Al wiring is technologically proved in semiconductor devices.

The film thickness of the insulating protective film70is preferably 200 nm or more, and more preferably 500 nm or more.

Further, the electromechanical transducer element30and the diaphragm20around the electromechanical transducer element30preferably include an opening. This is similar to thinning the individual chamber area of the insulating protective film40. Thus, the head2that can efficiently and reliability discharge liquid is obtained.

The openings are formed by, for example, a photolithography method or dry etching because the electromechanical transducer element30is protected by the insulating protective film40and70. Further, each area of the electrode pads61and62is preferably 50×50 μm2or more, more preferably 100×300 μm2or more.

The material of the wiring60is preferably a metal electrode material composed of any one of an Ag alloy, Cu, Al, Au, Pt, and Ir. As a manufacturing method of the wiring60, a sputtering method or a spin coating method is used. Then, a desired pattern is obtained by photolithography, for example. The film thickness is preferably in a range of from 0.1 μm to 20 μm, and more preferably in a range of from 0.2 μm to 10 μm.

In addition, the contact resistance at the contact hole portion (for example, 10 μm×10 μm) is preferably 10Ω or less for the lower electrode31and 1Ω or less for the upper electrode33, more preferably 5Ω or less for the lower electrode31, and 0.5Ω or less for the upper electrode33.

[Liquid Discharge Head Including Escape Groove]

It is known to provide an escape grooves in the head2on an end side of the head2in the arrangement direction of the pressure chambers10X. The arrangement direction of the pressure chambers10X is parallel to the nozzle array direction (NAD) inFIG. 3. The escape grooves guides the adhesive to prevent the adhesive from flowing into a liquid channel in the head2at the time of joining the substrates for manufacturing the head2. The “escape grooves” are also simply referred to as “grooves”.

It was found that variation in an amount of displacement occurs at the end portion side of the drive channels3by providing the escape grooves on the end side of the head2. Thus, means for suppressing the variation in the amount of displacement of the drive channel3becomes necessary.

FIG. 7is a cross sectional view of the head2that includes the escape grooves11. The head2as illustrated inFIG. 7includes escape grooves11on the end side in the arrangement direction of the pressure chambers10X. The escape grooves11are formed by etching the substrate10from the direction in which the nozzle51is formed, that is similar to a direction from which the pressure chambers10X is formed. The escape grooves11are a through groove penetrating the substrate10in a thickness direction of the substrate10. Portions of the diaphragm20facing the pressure chamber10X and the escape grooves11are exposed. InFIG. 7, four escape grooves11are formed on one end side in the arrangement direction of the pressure chambers10X. The groove11includes an opening that opens toward a direction opposite to the diaphragm20.

However, the number of the escape grooves11is not limited to four but any desired number. Further, inFIG. 7, the escape grooves11are formed at one end side of the head2in the arrangement direction of the pressure chambers10X. However, the escape grooves11are also formed at another end side of the head2. Thus, the another side of the head2has a same configuration with the one side of the head2.

At a position where the escape groove11is formed, the diaphragm20forms a part of the wall of the escape groove11. Further, the electromechanical transducer element30is not formed on the diaphragm20at the position where the escape groove11is formed. Further, the insulating protective film40, a plurality of the wirings60, and the insulating protective film70are formed on the diaphragm20in this order at the position where the escape groove11is formed. The wiring60is a wiring layer for supplying a driving signal and driving power to the electromechanical transducer element30. The wiring60and the insulating protective films40and70constitute a wiring portion72.

The wiring60is formed on a first side of the diaphragm20opposite a second side of the diaphragm20facing the groove11(escape groove).

Then, the nozzle plate50including the nozzles51is bonded to the lower surface of the substrate10with the adhesive80.FIG. 8is a cross sectional view of the head2.FIG. 8illustrates the head2formed by bonding the nozzle plate50to the head2inFIG. 7. The nozzle51is formed at a position corresponding to the pressure chamber10X as illustrated inFIG. 8. Conversely, the nozzle51is not formed at a position corresponding to the escape grooves11.

A degree of deflection including a shape (radius of curvature) of deflection and an amount of deflection of the diaphragm20of the head2including the escape groove11as illustrated inFIG. 7is examined. Then, it is found that a deflection of the diaphragm20on the escape grooves11influences the deflection of the diaphragm20of the pressure chambers10X at each ends of the head2close to the escape grooves11. The electromechanical transducer elements30is formed on the diaphragm20on which the pressure chamber10X is formed.

FIGS. 9A and 9Bare graphs illustrating a relation between a width of the diaphragm20and an amount of displacement of the diaphragm20at each channel at positions of the escape grooves11and positions of the drive channels3.FIG. 9Aillustrates a relation between a width of the diaphragm20and an amount of displacement of the diaphragm20at each channel at positions of the escape grooves11.FIG. 9Billustrates a relation between a width of the diaphragm20and an amount of displacement of the diaphragm20at each channel at positions of the pressure chambers10X (drive channels3). Here, a broken line inFIGS. 9A and 9Bindicates a position of the diaphragm20when the diaphragm20is not deformed. As illustrated inFIG. 9A, the diaphragm20at the position of the escape grooves11is deformed in a direction in which a center portion of the diaphragm20is convex upward (in a direction opposite to the escape groove11) due to a difference in a layer configuration on the diaphragm20. Here, lower side inFIGS. 9A and 9Bis a side toward the nozzles51(nozzle side). Conversely, as illustrated inFIG. 9B, the diaphragm20at the position of the pressure chambers10X (drive channels3) is deformed in a direction in which a center portion of the diaphragm20is convex downward (in a direction toward the pressure chamber10X, or nozzle side). In this manner, the direction of the deflection of the diaphragm20at the positions of the escape grooves11is opposite to the direction of the deflection of the diaphragm20at the positions of the pressure chambers10X (drive channels3). For example, the diaphragm20inFIG. 9A(at escape grooves11) deforms upward and the diaphragm20inFIG. 9B(at pressure chambers10X) deforms downward.

FIG. 10is a cross-sectional view of the head2having the same configuration asFIG. 7except that the escape groove11is formed in the head2ofFIG. 10. For comparison purpose, the degree of deflection of the diaphragm20is examined for the head2having the same configuration as inFIG. 7, except that the escape groove11is not formed in the head2ofFIG. 10.

FIG. 11is a graph illustrating the amount of deflection of the diaphragm20of the head2that includes the escape grooves11as illustrated inFIG. 7and the head2that does not include the escape grooves11as illustrated inFIG. 10. InFIG. 11, the amount of the deflection of the diaphragm20from an end (first channel) of the drive channels3to the twentieth (20th) channel is illustrated. Further, the amount of the deflection of the diaphragm20at the fortieth (40th) channel and the eightieth (80th) channel is illustrated.

According toFIG. 11, the amount of deflection of the diaphragm20at the end side (left end inFIG. 11) of the drive channels3becomes small in the head2that includes the escape grooves11as illustrated inFIG. 7. Further, as illustrated inFIG. 11, there is a difference between the amount of deflection of the diaphragm20of the end side of the drive channels3and the amount of deflection of the diaphragm20of the center side of the drive channels3in the head7as illustrated inFIG. 7.

In the head2as illustrated inFIG. 10, the difference between the amount of deflection of the diaphragm20on the end side of the drive channels3and the amount of deflection of the diaphragm20of the center side of the drive channels3is very small to close to none. The diaphragm20on the end side of the drive channels3is closed to the escape grooves11. The diaphragm20on the center side of the drive channels3is away from the escape grooves11. Thus, the head2illustrated inFIG. 10does not influenced by the difference in the film configuration on the diaphragm20.

According to the above-described examination, it is known that there is difference between the amount of deflection of the diaphragm20of the end side of the drive channels3close to the escape groove11and the amount of deflection of the diaphragm20on the center side of the drive channels3away from the escape grooves11. Thus, formation of the escape grooves11influences the amount of deflection of the diaphragm20between the drive channels3. The amount of deflection of the diaphragm20on the end side of the drive channel3close to the escape grooves11changes by a stress from the diaphragm20at the position of the escape grooves11. Thus, variation in the amount of deflection of the diaphragm20between the drive channels3of the head2influences a discharge performance of the head2.

Conversely, if the layer configuration of the wiring portion72on the diaphragm20at the escape grooves11is made identical to the layer configuration of the diaphragm20at the drive channels3, the influence of the stress from the diaphragm20at the position of the escape grooves11can be reduced. Thus, the variation in the amount of deflection between the drive channels3can be suppressed.

However, when considering the wiring resistance, for example, it is difficult to make all the layer configuration of the diaphragm20at the escape grooves11to be identical to the layer configuration of the diaphragm20at the drive channels3in the arrangement direction of the pressure chamber10X in the head2. Thus, as illustrated inFIG. 7, it is necessary to form the wiring60without forming the electromechanical transducer film32in the structure located outside the end side of the drive channels3in order to lower the wiring resistance.

Thus, the head2(liquid discharge head) according to the present embodiment includes the substrate10(pressure chamber substrate), the diaphragm20, and the electromechanical transducer element30. The pressure chambers10X are arranged in a predetermined direction in the substrate10.

The pressure chambers10X communicates with the nozzles51, respectively, for discharging liquid from the nozzles51. The diaphragm20is provided opposite to the nozzle51side in the substrate10. A part of the diaphragm20constitutes a wall of the pressure chamber10X. The electromechanical transducer elements30are provided on the diaphragm20corresponding to pressure chambers10X, respectively. The escape grooves11are formed in the substrate10on an end side of the head2in the predetermined direction (the arrangement direction of the pressure chambers10X or nozzle array direction (NAD)).

The escape groove11(groove) includes an opening in a surface facing the nozzle51. The escape groove11introduces an excessive adhesive when the substrate (pressure chamber substrate)10is joined with other substrates. The diaphragm20at the pressure chambers10X (drive channels3) is formed to be displaced in a direction toward the pressure chamber10X (downward inFIG. 8) for each of the pressure chambers10X. The diaphragm20at the escape grooves11(grooves) is formed to be displaced in a direction opposite to the opening of the escape grooves11(upward inFIG. 8) for each of the escape grooves11. The amount of deflection of the diaphragm20at each pressure chambers10X is larger than the amount of deflection of the diaphragm20at each escape grooves11(grooves). Here, the description in parentheses indicates reference numerals and application examples in the embodiments.

As illustrated inFIG. 5, the diaphragm20at the pressure chambers10X (drive channels3) is displaced to be convex toward the pressure chamber10X (downward inFIG. 5) in the manufacturing process of the head2. That is, the diaphragm20on the pressure chamber10X deflects (curved) to convex toward the pressure chamber10X (downward inFIG. 5).

On the other hand, as described above, the wiring60and the insulating protective films40and70are formed on the diaphragm20over the escape grooves11. The electromechanical transducer elements30are not formed on the diaphragm20over the escape grooves11. Thus, the diaphragm20on the escape grooves11deflects to be convex in a direction opposite to the escape groove11since the electromechanical transducer element30having a strong tensile stress is not formed on the diaphragm20on the escape grooves11. Thus, the diaphragm20on the escape groove11is deflects (curved) to be convex in a direction opposite to the escape groove11(upward inFIG. 7).

However, difference in the deflection direction of the diaphragm20on the pressure chamber10X and the deflection direction of the diaphragm20on the escape grooves11influences the deflection of the diaphragm20of the pressure chambers10X (drive channels3).

Thus, the head2according to the present disclosure adjusts the degree of deflection (deflection degree) of the diaphragm20on the escape groove11by controlling the layer configuration of the wiring portion72on the diaphragm20at the escape grooves11. As a control of the layer configuration of the wiring portion72, at least one of a thickness and material of the wiring60and a thickness and material of the insulating protective films40and70is adjusted. Thus, the deflection degree of the diaphragm20on the escape grooves11is set to be sufficiently smaller than the deflection degree of the diaphragm20on the drive channels3.

Further, the degree of deflection of the diaphragm20of the pressure chambers10X (drive channels3) is adjusted (increased) by controlling a physical properties of the film to increase the tensile stress of the electromechanical transducer element30The degree of deflection of the diaphragm20of the drive channels3may be made larger than the degree of deflection of the diaphragm20on the escape grooves11.

In this way, the degree of deflection of the diaphragm20on the drive channels3can be made larger than the degree of deflection of the diaphragm20on the escape grooves11by controlling the layer configuration of the wiring portion72on the diaphragm20at the escape grooves11and the layer configuration on the diaphragm20at the drive channels3(pressure chambers10X).

As described above, the head2according to the present disclosure reduces the influence on the diaphragm20of the drive channels3by making the deflection degree of the diaphragm20of the drive channels3to be larger than the deflection degree of the diaphragm20of the escape grooves11. Thus, the head2according to the present disclosure can suppress the influence of the escape grooves11on the deflection of the diaphragm20of the drive channels3(pressure chambers10X) in the end side of the head2that is close to the escape grooves11even when the head2includes the escape grooves11. Thus, the head2can suppress the variation of the amount of deflection of the diaphragm20between drive channels3. The variation is caused by the difference of the deflection direction of the diaphragm20at the escape grooves11and the deflection direction of the diaphragm20at the drive channels3that is opposite to the deflection direction of the diaphragm20at the escape grooves11.

Next, an evaluation method of the degree of deflection (deflection degree) is described below. The degree of deflection can be evaluated, for example, by using the radius of curvature R of the diaphragm20. The radius of curvature R may be, for example, calculated by the calculation method described with reference toFIG. 6.

FIG. 12Ais a cross sectional view of the diaphragm20at the position of the escape groove11illustrating a radius of curvature of the diaphragm20.FIG. 12Bis a cross-sectional view of the diaphragm20at the position of the drive channel3illustrating a radius of curvature of the diaphragm20. The layer configuration on the diaphragm20is omitted inFIGS. 12A and 12Bbecause of simplicity. As illustrated inFIGS. 12A and 12B, a relation of Ra>Rb is satisfied where Ra is a radius of curvature of the diaphragm20at the escape groove11, and Rb is a radius of curvature of the diaphragm20at the drive channel3.

Further, the degree of deflection can be evaluated using the deflection amount of the diaphragm20.FIG. 13Ais a cross sectional view of the diaphragm20at the position of the escape groove11illustrating an amount of deflection of the diaphragm20.FIG. 13Bis a cross-sectional view of the diaphragm20at the drive channel3illustrating an amount of deflection of the diaphragm20.

In this case, as illustrated inFIGS. 13A and 13B, an amount of deflection of the diaphragm20is defined as described below. First, a line perpendicular to a line (broken line inFIGS. 13A and 13B) of a formation position of the diaphragm20when there is no deflection in the diaphragm20is defined. Then, the amount of deflection of the diaphragm20is defined by a distance between a center point C of the deflection of the diaphragm20and the formation position (broken line inFIGS. 13A and 13B) of the diaphragm20when there is no deflection in the diaphragm20. As illustrated inFIGS. 13A and 13B, a relation of a>b is satisfied where “a” is an amount of deflection of the diaphragm20at the escape groove11, and “b” is an amount of deflection of the diaphragm20at the drive channel3.

The examples described-above define a relation between the deflection degree of the diaphragm20at the escape groove11and the deflection degree of the diaphragm20at the drive channels3. However, it is not necessary to define the relation between the amount of deflection of the diaphragm20at the escape groove11and the amount of deflection of the diaphragm20at the drive channel3. For example, the radius of the curvature of the deflection of the diaphragm20at the escape groove11may be sufficiently made large. Thus, the head2can suppress the variation of the deflection amount of the diaphragm20between groups of drive channels3. The variation is caused by the difference of the deflection direction of the diaphragm20at the escape grooves11and the deflection direction of the diaphragm20at the drive channels3that is opposite to the deflection direction of the diaphragm20at the escape grooves11.

The radius of curvature R of the diaphragm20at the escape groove11is preferably 5000 μm or more, and more preferably 7000 μm or more.

Thus, the diaphragm20at the plurality of pressure chambers10X is formed to be deflexed toward the plurality of pressure chambers10X, the diaphragm20at the groove11(escape groove) is formed to be deflexed opposite to the opening of the groove11, and a degree of deflection of the diaphragm20at the plurality of pressure chambers10X is larger than a degree of deflection of the diaphragm20at the groove11.

Each of the degree of deflection of the diaphragm20at the plurality of pressure chambers10X and the degree of deflection of the diaphragm20at the groove11is determined by a radius of curvature R. The radius of curvature Ra of the diaphragm20at the groove11is larger than a radius of curvature Rb of the diaphragm20at the plurality of pressure chambers10X.

The degree of deflection of the diaphragm20is determined by an amount of deflection of the diaphragm20, and an amount of deflection of the diaphragm20at the groove11is smaller than an amount of deflection of the diaphragm20at the plurality of the pressure chambers10X.

Next, a size of the escape grooves11and a forming position of the escape grooves11are described below.FIG. 14Ais a cross-sectional view of the head2in the arrangement direction of the pressure chambers10X (in the nozzle array direction, NAD). The head2inFIG. 14Ais in a state where the nozzle plate50is not joined to the substrate10.FIG. 14Bis a plan view of the head2seen from the nozzle plate50side. The layer configuration of the head2as illustrated inFIGS. 14A and 14Bis the same with the layer configuration of the head2as illustrated inFIG. 7. As illustrated inFIG. 14B, intervals of the escape grooves11satisfy a predetermined relation. Further, a distance Z between the endmost drive channel3(the endmost pressure chamber10X) and the escape groove11satisfies a predetermined relation.

As illustrated inFIG. 14B, the arrangement direction of the pressure chambers10X (a short-side direction of the pressure chamber) is defined as a X-direction, and the direction perpendicular to X-direction (a longitudinal direction of the pressure chamber) is defined as a Y-direction. The following equation (1) is preferably satisfied when it is assumed that the size of the escape groove11in the X-direction is X1, the size of the escape groove11in the Y-direction is Y1, the size of the pressure chamber10X in the X-direction is X2, and the size of the pressure chamber10X in the Y-direction is Y2.
X1≤X2and Y1<Y2(1)

In this way, the influence of stress can be preferably reduced by making the size of the escape groove11to be smaller than the size of the pressure chamber10X. Here, the size of the escape groove11and the pressure chamber10X may be the same in the X-direction (X1=X2).

The size of the escape groove11is preferably 100 μm or less for both of X1and Y1, and more preferably 50 μm.

Further, the arrangement interval of the escape grooves11is preferably 30 μm or more in the X-direction, and is 30 μm or more in the Y-direction, more preferably 100 μm or more.

The distance Z between the endmost drive channel3(the endmost pressure chamber10X) and the escape groove11is preferably 100 μm or more, more preferably 200 μm.

In this way, the head2can reduce the influence of the stress on the endmost drive channel3and reduce variations in discharge performance between the drive channels3by forming the size and the forming position of the escape groove11to satisfy the predetermined relation as described above.

The head2according to the present disclosure can suppress the variation in the deflection degree of the diaphragm20between the drive channels3in a configuration including the escape groove11. Thus, the head2has a good discharge performance.

The head2according to the present disclosure is not limited to the configuration as illustrated inFIGS. 7 and 14. The head2according to the present disclosure is also applied to other various types of the heads having a configuration corresponding to the escape groove for guiding excessive adhesive.

Second Embodiment

The head2according to a second embodiment of the present disclosure is described below. Note that redundant descriptions of the same or similar components and configurations may be omitted below.

As illustrated inFIG. 15, the head2includes dummy channels4that respectively include dummy electromechanical transducer elements34on the end of the pressure chambers10X in the arrangement direction of the electromechanical transducer elements30(drive channels3). The dummy electromechanical transducer element34does not discharge liquid droplets i The dummy channel4discharges air bubbles during filling the liquid to the head2to improve the filling property of the liquid to the head2. In the head2as illustrated inFIGS. 15, and 16A and 16B, a unit composed of a dummy pressure chamber12(seeFIGS. 16A and 16B), the diaphragm20, and the electromechanical transducer element30that do not discharge the liquid are referred to as a dummy channel4.

Thus, the head2in the second embodiment includes the dummy channel4on the end side (outside) of the drive channels3in the arrangement direction of the pressure chambers10X and the escape groove11provided on the end side (outside) of the dummy channel4. An arrayed number of dummy channels4may be at least one per one end portion of the drive channels3. However, the arrayed number of dummy channels4is preferably three or more per one end portion of the drive channels3to improve the filling property of the liquid to the head2.

FIGS. 16A and 16Billustrate still another example of the head2according to a second embodiment.FIG. 16Ais a cross-sectional view of the head2in the arrangement direction of the pressure chambers10X (in the nozzle array direction, NAD). The head2inFIG. 16Ais in a state where the nozzle plate50is not joined to the substrate10.FIG. 16Bis a plan view of the head2seen from the nozzle plate50side.

FIG. 17illustrates an example in which the nozzle plate50is joined to the head2illustrated inFIGS. 16A and 16Bwith the adhesive80. As illustrated inFIG. 17, the nozzle51is formed at a position corresponding to the pressure chambers10X, and the nozzle51is not formed at a position corresponding to the dummy pressure chambers12and the escape grooves11.

Here, the configuration of the dummy pressure chamber12of the dummy channel4and the layer configuration on the diaphragm20of the dummy channel4may be the same as the configuration of the pressure chamber10X and the layer configuration on the diaphragm20of the drive channel3. Thus, the diaphragm20of the dummy channel4also deflects to be convex toward the dummy pressure chamber12at the time of manufacturing the dummy pressure chamber12in the process of manufacturing the head2. Therefore, the diaphragm20is formed in a state to be convex toward the dummy pressure chamber12.

The distance Z between the endmost dummy channel4(the endmost dummy pressure chamber12) and the escape groove11is preferably 30 μm or more, more preferably 100 μm. The size of the escape groove11and the interval between the escape grooves11in the second embodiment as illustrated inFIGS. 16A and 16Bare preferably the same as the size of the escape groove11and the interval between the escape grooves11in the first embodiment as illustrated inFIGS. 14A and 14B.

The direction of deflection of the diaphragm20at the escape groove11is opposite to the direction of deflection of the diaphragm20at the dummy channel4and the drive channel3. This difference in the direction of the deflection affects the deflection of the diaphragm20of the drive channel3.

Conversely, in the second embodiment, the layer configuration on the diaphragm20on the escape groove11or the physical properties of the film of the electromechanical transducer element30is controlled. Thus, the degree of deflection of the diaphragm20at the escape groove11is made smaller than the degree of deflection of the diaphragm20at the drive channel3and the dummy channel4. Therefore, the influence of the stress from the escape groove11on the deflection of the diaphragm20of the drive channel3can be reduced.

According to the head2according to the second embodiment as described-above, it is possible to reduce the influence of the stress from the escape groove11on the endmost drive channel3. Further, it is possible to suppress variations in discharge performance between the drive channels3. Further, the dummy channel4is provided between the drive channel3and the escape groove11in the arrangement direction of the pressure chambers10X. Thus, it is possible to improve the filling property of the liquid to the head2as compared with the configuration without the dummy channel4such as the first embodiment, for example.

Third Embodiment

FIGS. 18A and 18Billustrate still another example of the head2according to a third embodiment.FIG. 18Ais a cross-sectional view of the head2in the arrangement direction of the pressure chambers10X (in the nozzle array direction, NAD). The head2inFIG. 18Ais in a state where the nozzle plate50is not joined to the substrate10.FIG. 18Bis a plan view of the head2seen from the nozzle plate50side.

In the first and second embodiments, the escape grooves11penetrate the substrate10. In the third embodiment, the escape groove11has a shape in which the surface of the substrate10on the nozzle51side is opened, and the escape groove11does not penetrate through the substrate10.

As illustrated inFIG. 18A, a part of the substrate10exists between the diaphragm20and the escape groove11in the head2according to the third embodiment as described above, Thus, the head2in the third embodiment prevents the deflection of the diaphragm20at the escape groove11and reduces the influence of the stress from the escape groove11on the end side of the drive channel3close to the escape groove11. Therefore, the head2of the third embodiment can reduce variations in the discharge performance between the drive channels3.

Fourth Embodiment

FIG. 19is a cross sectional view of the head2according to a fourth embodiment. The nozzle plate50is directly joined (bonded) to the substrate10in the above-described examples. However, a substrate to be joined (bonded) to the nozzle51side of the substrate10is not limited to the nozzle plate50. For example, as illustrated inFIG. 19, a communication channel substrate90is joined (bonded) to the nozzle plate50so that the communication channel substrate90is disposed between the substrate10and the nozzle plate50. The communication channel substrate90is a substrate in which a communicating channel for communicating the pressure chamber10X with the nozzle51is provided.

Fifth Embodiment

The head2(liquid discharge head) according to the fifth embodiment includes the substrate10(pressure chamber substrate), the diaphragm20, and the electromechanical transducer element30. The pressure chambers10X are arranged in a predetermined direction (arrangement direction of the pressure chambers10X) in the substrate10. The pressure chambers10X communicates with the nozzles51, respectively, for discharging liquid from the nozzles51. The diaphragm20is provided opposite to the nozzle51side in the substrate10. A part of the diaphragm20constitutes a wall of the pressure chamber10X.

The electromechanical transducer elements30are provided on the diaphragm20corresponding to pressure chambers10X, respectively. The escape grooves11are formed in the substrate10on an end side of the pressure chambers10X in the predetermined direction (arrangement direction of the pressure chambers10X or nozzle array direction (NAD)).

The escape groove11(groove) includes an opening in a surface facing the nozzle51. The escape groove11guides (introduces) an excessive adhesive when the substrate10(pressure chamber substrate) is joined (bonded) with other substrates. The diaphragm20at the pressure chambers10X (drive channels3) is formed to be displaced in a direction toward the pressure chamber10X (downward inFIG. 8) for each of the pressure chambers10X. The diaphragm20at the escape grooves11(grooves) is formed to be displaced in a direction toward the openings of the escape grooves11(downward inFIG. 8) for each of the escape grooves11. Here, the description in parentheses indicates reference numerals and application examples in the embodiments.

That is, the direction of deflection of the diaphragm20at the escape groove11and the direction of deflection of the diaphragm20at the drive channel3are in the same direction. The degree of deflection of the diaphragm20at the drive channels3is preferably larger than the degree of deflection of the diaphragm20at the escape grooves11. The radius of curvature R of the diaphragm20at the escape groove11is preferably 2000 μm or more, and more preferably 6000 μm or more.

Thus, the head2according to the present disclosure adjusts the degree of deflection (deflection degree) of the diaphragm20on the escape groove11by controlling the layer configuration of the wiring portion72on the diaphragm20at the escape grooves11. As a control of the layer configuration of the wiring portion72, at least one of a thickness and material of the wiring60and a thickness and material of the insulating protective films40and70is adjusted. That is, the direction of deflection of the diaphragm20at the escape groove11is made to be convex toward the opening side of the escape groove11. Thus, the direction of deflection of the diaphragm20at the escape groove and the direction of deflection of the diaphragm20at the drive channel3becomes the same. In other words, as similar to the diaphragm at the drive channels3, a tensile stress is also applied on the diaphragm20at the escape grooves11.

Thus, the degree of deflection of the diaphragm20at the escape grooves11is preferably set to be sufficiently smaller than the deflection degree of the diaphragm20on the drive channels3.

For example, as described above, it is preferable to use a SiN film having a tensile stress for the insulating protective films40and70. At this time, it is possible to adjust the stress state of the diaphragm20at the escape grooves11to be same as the stress state of the diaphragm20at the drive channels3by controlling the film thickness of the SiN film. If the tensile stress of the diaphragm20at the escape groove11is too large, the amount of deflection at the end side of the drive channels3(twenty channels from the end of the pressure chambers10X, for example) becomes large. Thus, the variation in the degree of deflection occurs. Therefore, the tensile stress of the diaphragm20at the escape grooves11has to be appropriately adjusted.

In this way, the direction of deflection of the diaphragm20at the escape groove11and the direction of deflection of the diaphragm20at the drive channel3are formed to be the same by controlling the layer configuration of the wiring portion72on the diaphragm20at the escape grooves11. Further, the degree of deflection of the diaphragm20at the drive channels3can be made larger than the degree of deflection of the diaphragm20at the escape grooves11.

As described above, the head2according to the present disclosure reduces the influence of the deflection of the diaphragm20at the escape grooves11on the diaphragm20at the drive channels3. Thus, the head2can suppress the influence of the escape grooves11on the deflection of the diaphragm20of the end side of the drive channels3that is close to the escape grooves11even when the head2includes the escape grooves11. Thus, the variation in the amount of deflection of the diaphragm20between the drive channels3can be suppressed.

Next, an evaluation method of the degree of deflection (deflection degree) is described below. The degree of deflection can be evaluated, for example, by using the radius of curvature R of the diaphragm20. The radius of curvature R is, for example, calculated by the calculation method described with reference toFIGS. 6A and 6B.

FIG. 20Ais a cross sectional view of the diaphragm20illustrating a radius of curvature R of the diaphragm20at the forming position of the escape grooves11.FIG. 20Bis a cross-sectional view of the diaphragm20at the position of the drive channel3illustrating a radius of curvature of the diaphragm20. The layer configuration on the diaphragm20is omitted inFIGS. 20A and 20Bfor simplicity. As illustrated inFIGS. 20A and 20B, a relation of Ra>Rb is satisfied where Ra is a radius of curvature of the diaphragm20at the escape groove11, and Rb is a radius of curvature of the diaphragm20at the drive channel3.

Further, the degree of deflection can be evaluated using the deflection amount of the diaphragm20.FIG. 21Ais a cross sectional view of the diaphragm20illustrating an amount of deflection of the diaphragm20at the forming position of the escape groove11.FIG. 21Bis a cross-sectional view of the diaphragm20at the drive channel3illustrating an amount of deflection of the diaphragm20.

In this case, as illustrated inFIGS. 21A and 21B, an amount of deflection of the diaphragm20is defined as described below. First, a line perpendicular to a line (broken line inFIGS. 21A and 21B) of a formation position of the diaphragm20when there is no deflection in the diaphragm20is defined. Then, the amount of deflection of the diaphragm20is defined by a distance between a center point C of the deflection of the diaphragm20and the formation position (broken line inFIGS. 21A and 21B) of the diaphragm20when there is no deflection in the diaphragm20. As illustrated inFIGS. 21A and 21B, a relation of a<b is satisfied where “a” is an amount of deflection of the diaphragm20at the escape groove11, and “b” is an amount of deflection of the diaphragm20at the drive channel3.

The examples described above define a relation between the degree of deflection of the diaphragm20at the escape groove11and the degree of deflection of the diaphragm20at the drive channels3. However, it is not necessary to define the relation between the amount of deflection of the diaphragm20at the escape groove11and the amount of deflection of the diaphragm20at the drive channel3. For example, the diaphragm20at the escape groove11is formed to be deflexed in a direction toward the opening of the escape groove11. Further, the radius of the curvature R of the deflection of the diaphragm20at the escape groove11may be sufficiently made large. Thus, the variation in the amount of deflection of the diaphragm20between the drive channels3can be suppressed.

Sixth Embodiment

The head2according to the sixth embodiment has a same configuration with the above-described second embodiment illustrated inFIGS. 16A and 16Bexcept that the direction of deflection of the diaphragm20at the escape grooves11, the direction of deflection of the diaphragm20at the dummy channels4, and the direction of deflection of the diaphragm20at the drive channels3are all made same. Thus, the degree of deflection of the diaphragm20at the escape groove11is made smaller than the degree of deflection of the diaphragm20at the drive channel3and the dummy channel4.

The head2according to the sixth embodiment can suppress the influence of the stress from the escape grooves11by making the direction of deflection of the diaphragm20at the escape grooves11, the direction of deflection of the diaphragm20at the dummy channels4, and the direction of deflection of the diaphragm20at the drive channels3to be the same.

The head2according to the sixth embodiment can suppress the influence of the stress from the escape grooves11by making the degree of deflection of the diaphragm20at the escape grooves11to be smaller than the degree of deflection of the diaphragm20at the dummy channels4and the drive channels3.

FIGS. 22 and 23illustrate an example of a liquid discharge apparatus600according to the present embodiment.FIG. 22is a plan view of a main part of the liquid discharge apparatus600.FIG. 23is a side view of a main part of the liquid discharge apparatus600.

The liquid discharge apparatus600is a serial-type apparatus in which a main scan moving unit493reciprocally moves a carriage403in a main scanning direction indicated by arrow MSD inFIG. 22. The main scan moving unit493includes a guide401, a main scanning motor405, a timing belt408, etc. The guide401is laterally bridged between a left side plate491A and a right side plate491B and supports the carriage403so that the carriage403is movable along the guide401. The main scanning motor405reciprocally moves the carriage403in the main scanning direction MSD via the timing belt408laterally bridged between a drive pulley406and a driven pulley407.

The carriage403mounts a liquid discharge device440in which the head2according to the present embodiment and a head tank441are integrated as a single unit. The head2of the liquid discharge device440discharges color liquids of, for example, yellow (Y), cyan (C), magenta (M), and black (K). The head2includes nozzle arrays51A and51B, each including the plurality of nozzles51arrayed in row in a sub-scanning direction indicated by arrow SSD inFIG. 22. The sub-scanning direction (SSD) is perpendicular to the main scanning direction MSD and along the nozzle array direction NAD. The head404is mounted to the carriage403so that ink droplets are discharged downward.

The liquid stored outside the head2is supplied to the head404via a supply unit494that supplies the liquid from a liquid cartridge450to the head tank441.

The supply unit494includes, e.g., a cartridge holder451as a mount part to mount a liquid cartridge450, a tube456, and a liquid feed unit452including a liquid feed pump. The liquid cartridge450is detachably attached to the cartridge holder451. The liquid is supplied to the head tank441by the liquid feed unit452via the tube456from the liquid cartridge450.

The liquid discharge apparatus600includes a conveyance unit495to convey a sheet410. The conveyance unit495includes a conveyance belt412as a conveyor and a sub-scanning motor416to drive the conveyance belt412.

The conveyance belt412attracts the sheet410and conveys the sheet410at a position facing the head2. The conveyance belt412is in the form of an endless belt. The conveyance belt412is stretched between a conveyance roller413and a tension roller414. The sheet410is attracted to the conveyance belt412by electrostatic force or air aspiration.

The conveyance roller413is rotated by a sub-scanning motor416via a timing belt417and a timing pulley418, so that the conveyance belt412circulates in a sub-scanning direction (SSD) inFIG. 20.

At one side in the main scanning direction (MSD) of the carriage403, a maintenance unit420to recover the head2in good condition is disposed on a lateral side (right-hand side) of the conveyance belt412inFIG. 20.

The maintenance unit420includes, for example, a cap421to cap a nozzle face of the head2and a wiper422to wipe the nozzle face. The nozzle face is a surface of the nozzle plate50in which the nozzles51are formed.

The main scan moving unit493, the supply unit494, the maintenance unit420, and the conveyance unit495are mounted to a housing491that includes the left side plate491A, the right side plate491B, and a rear side plate491C.

In the liquid discharge apparatus600thus configured, a sheet410is conveyed on and attracted to the conveyance belt412and is conveyed in the sub-scanning direction (SSD) by the cyclic rotation of the conveyance belt412.

The head2is driven in response to image signals while the carriage403moves in the main scanning direction (MSD), to discharge liquid to the sheet410stopped, thus forming an image on the sheet410.

As described above, the liquid discharge apparatus600includes the head2according to the present embodiment. Thus, the head2can discharge the liquid without a failure caused by a drive failure of the diaphragm20and have a stable discharge characteristic of the liquid. Therefore, the head2allows stable formation of high quality images.

FIG. 24illustrates another example of the liquid discharge device440including the head2according to the present embodiment.FIG. 24is a plan view of a main part of the liquid discharge device440.

The liquid discharge device440includes the housing491, the main scan moving unit493, the carriage403, and the head2among components of the liquid discharge apparatus600. The left side plate491A, the right side plate491B, and the rear side plate491C constitute the housing491.

Note that, in the liquid discharge device440, at least one of the maintenance unit420and the supply unit494described above may be mounted on, for example, the right side plate491B.

FIG. 25illustrates another example of the liquid discharge device440including the head2according to the present embodiment.FIG. 25is a front view of the liquid discharge device440.

The liquid discharge device440includes the head2to which a channel part444is mounted and a tube456connected to the channel part444.

Further, the channel part444is disposed inside a cover442. Instead of the channel part444, the liquid discharge device440may include the head tank441. A connector443to electrically connect the head2to a power source is disposed above the channel part444.

In the above-described embodiments of the present disclosure, the “liquid discharge apparatus” includes the liquid discharge head or the liquid discharge device, and drives the liquid discharge head to discharge liquid. The liquid discharge apparatus may be, for example, an apparatus capable of discharging liquid to a material to which liquid can adhere and an apparatus to discharge liquid toward gas or into liquid.

The “liquid discharge apparatus” may include devices to feed, convey, and eject the material on which liquid can adhere. The liquid discharge apparatus may further include a pretreatment apparatus to coat a treatment liquid onto the material, and a post-treatment apparatus to coat a treatment liquid onto the material, onto which the liquid has been discharged.

The “liquid discharge apparatus” may be, for example, an image forming apparatus to form an image on a sheet by discharging ink, or a three-dimensional fabricating apparatus to discharge a fabrication liquid to a powder layer in which powder material is formed in layers, so as to form a three-dimensional fabrication object.

In addition, “the liquid discharge apparatus” is not limited to such an apparatus to form and visualize meaningful images, such as letters or figures, with discharged liquid. For example, the liquid discharge apparatus may be an apparatus to form meaningless images, such as meaningless patterns, or fabricate three-dimensional images. The above-described term “material on which liquid can be adhered” represents a material on which liquid is at least temporarily adhered, a material on which liquid is adhered and fixed, or a material into which liquid is adhered to permeate.

Examples of the “material on which liquid can be adhered” include recording media, such as paper sheet, recording paper, recording sheet of paper, film, and cloth, electronic component, such as electronic substrate and piezoelectric element, and media, such as powder layer, organ model, and testing cell. The “material on which liquid can be adhered” includes any material on which liquid is adhered, unless particularly limited.

Examples of the material on which liquid can be adhered include any materials on which liquid can be adhered even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, and ceramic.

Examples of the liquid are, e.g., ink, treatment liquid, DNA sample, resist, pattern material, binder, fabrication liquid, or solution and dispersion liquid including amino acid, protein, or calcium.

“The liquid discharge apparatus” may be an apparatus to relatively move a head and a medium on which liquid can be adhered. However, the liquid discharge apparatus is not limited to such an apparatus. For example, the liquid discharge apparatus may be a serial head apparatus that moves the liquid discharge head or a line head apparatus that does not move the liquid discharge head.

Examples of the “liquid discharge apparatus” further include a treatment liquid coating apparatus to discharge a treatment liquid to a sheet to coat the treatment liquid on the surface of the sheet to reform the sheet surface and an injection granulation apparatus in which a composition liquid including raw materials dispersed in a solution is injected through nozzles to granulate fine particles of the raw materials.

The “liquid discharge device” is an integrated unit including the liquid discharge head and a functional parts or mechanisms, and is an assembly of parts relating to liquid discharge. For example, the “liquid discharge device” may be a combination of the liquid discharge head with at least one of the head tank, the carriage, the supply unit, the maintenance unit, and the main scan moving unit.

Here, examples of the integrated unit include a combination in which the liquid discharge head and a functional part(s) are secured to each other through, e.g., fastening, bonding, or engaging, and a combination in which one of the liquid discharge head and a functional part(s) is movably held by another. The head may be detachably attached to the functional part(s) or unit(s) each other.

The liquid discharge device may be, for example, a liquid discharge device in which the liquid discharge head and the head tank are integrated as a single unit, such as the liquid discharge device440illustrated inFIG. 25. The liquid discharge head and the head tank may be connected each other via, e.g., a tube to integrally form the liquid discharge device. Here, a unit including a filter may further be added to a portion between the head tank and the head of the liquid discharge device.

The liquid discharge device may be an integrated unit in which a liquid discharge head is integrated with a carriage.

The liquid discharge device may be the liquid discharge head movably held by a guide that forms part of a main scan moving unit, so that the liquid discharge head and the main scan moving unit are integrated as a single unit. Like the liquid discharge device440illustrated inFIG. 24, the liquid discharge device may be an integrated unit in which the liquid discharge head, the carriage, and the main scan moving unit are integrally formed as a single unit.

In another example, the cap that forms part of the maintenance unit is secured to the carriage mounting the head so that the head, the carriage, and the maintenance unit are integrated as a single unit to form the liquid discharge device.

Like the liquid discharge device440illustrated inFIG. 25, the liquid discharge device may be an integrated unit in which the tube is connected to the liquid discharge head mounting the head tank or the channel part so that the liquid discharge head and the supply unit are integrally formed.

The main scan moving unit may be a guide only. The supply unit may be a tube(s) only or a mount part (loading unit) only.

In addition, “the liquid discharging head” has no specific limit to the pressure generator used in the liquid discharge head. The pressure generator is not limited to the piezoelectric actuator such as a laminate type piezoelectric element in the above-described embodiments, and may be, for example, a thermal actuator that employs a thermoelectric transducer element, such as a thermal resistor or an electrostatic actuator including a diaphragm and opposed electrodes.

The terms “image formation”, “recording”, “printing”, “image printing”, and “fabricating” used herein may be used synonymously with each other.

The embodiments described above are just preferred embodiments and the present disclosure is not limited thereto. Various modifications can be made without departing from the scope of the present disclosure.

For example, the upper electrode is an individual electrode and the lower electrode is a common electrode in the above-described embodiment. However, the present disclosure is not limited to this configuration. That is, the same effect can be obtained also in a configuration in which the upper electrode is a common electrode and the lower electrode is an individual electrode.

EXAMPLE

Hereinafter, Examples of the present disclosure is described.

Then, a titanium film (film thickness 20 nm) was formed as an adhesion layer on the diaphragm20by a sputtering apparatus at a deposition temperature of 350° C. Then, the adhesion layer is thermally oxidized at 750° C. using RTA (rapid thermal processing). Further, a platinum film (film thickness 160 nm) was formed on the adhesion layer by a sputtering apparatus at a film formation temperature of 400° C. to prepare a lower electrode31.

Then, a solution adjusted so as to have a ratio of Pb:Ti=1:1 as a PbTiO3layer serving as a base layer and a solution adjusted so as to have a ratio of Pb:Zr:Ti=115:49:51 as an electromechanical transducer film32were prepared, and a film was formed by a spin coating method on the lower electrode31.

For synthesis of a precursor coating liquid, lead acetate trihydrate, titanium isopropoxide, and zirconium isopropoxide were used as starting materials. Crystal water of lead acetate was dissolved in methoxyethanol and was then dehydrated. The amount of lead is excessively large for a stoichiometric composition. This is to prevent deterioration of crystallinity caused by so-called lead missing during heat treatment.

The titanium isopropoxide and the zirconium isopropoxide were dissolved in methoxyethanol, an alcohol exchange reaction and an esterification reaction were advanced, a resultant was mixed with a methoxyethanol solution having dissolved the lead acetate, and the PZT precursor solution was synthesized. The concentration of PZT was prepared to be 0.5 mol/l. A PT solution was produced in a similar manner to PZT. First, a PT layer film was formed by spin coating using these solutions. After film formation, the PT layer film was dried at 120° C. Thereafter, a film was formed by spin coating using the PZT solution, was dried at 120° C., and then was subjected to pyrolysis at 400° C.

After the thermal decomposition of the third layer, crystallization heat treatment (temperature 730° C.) is conducted by RTA. At this time, the film thickness of PZT was 240 nm. This step was performed eight times (24 layers) in total to obtain a PZT film thickness of about 2 μm as the electromechanical transducer film32.

Subsequently, a SrRuO3film (film thickness 40 nm) was formed by sputtering as an oxide film of the upper electrode33, and a Pt film (film thickness 125 nm) was formed by sputtering as a metal film. Then, a film was formed by the spin coating method using a photoresist (TSMR8800) manufactured by TOKYO OHKA KOGYO., LTD, a resist pattern was formed by a normal photolithographic method, and a pattern illustrated inFIGS. 4A and 4Bwas manufactured using an ICP etching device (manufactured by SAMCO INC.). Accordingly, the electromechanical transducer element30was produced on the diaphragm20.

Subsequently, an Al2O3film of 50 nm was formed on the electromechanical transducer element30using an ALD (Atomic Layer Deposition) method as the insulating protective film40. As raw materials, TMA (Sigma-Aldrich Corporation) for Al and O3generated by an ozone generator for O were stacked alternately, and film formation was thereby performed.

Then, SiO2was formed to a thickness of 1000 nm by a plasma CVD method as the insulating protective film40b,and then a contact hole H was formed by etching as illustrated inFIG. 4B. Thereafter, a film of Al was formed by sputtering. The film of Al was patterned by etching to form the wiring60. A film of Si3N4was formed on the wiring60by plasma CVD to have a film thickness of 500 nm as the insulating protective film70. Then, an opening70xis formed in the insulating protective film70so that a part of the wiring60is exposed to form the electrode pads61,62, and63as illustrated inFIGS. 4A and 4B. Note that the electrode pad61is a common electrode pad, the electrode pads62and63are individual electrode pads, and the distance between the individual electrode pads is 80 μm.

Thereafter, as illustrated inFIGS. 16A and 16B, the back surface of the substrate10was etched to form the pressure chamber10X (X2: width 60 μm, Y2: length 1000 μm), thereby forming a liquid discharge head2. However, the nozzle plate50including the nozzles51is not joined (bonded) to the lower portion of the substrate10, and the head2is in a semifinished state.

At this time, as illustrated inFIG. 26, the holding substrate15was used to hold the pressure chamber10X. The holding substrate15includes recesses15xon a back surface of the holding substrate15. A number of recesses15xin the holding substrate15corresponds to a number of electromechanical transducer elements30in the head2. Specifically, the holding substrate15was bonded to the substrate10via an adhesive layer before forming the pressure chamber10X in the substrate10so that electromechanical transducer elements30were accommodated in the recesses15x, respectively. Then, the back surface of the substrate10was etched to form the pressure chamber10X.

At this time, one dummy channel4is formed while forming the escape groove11(X1: width 60 μm, Y1: length 60 μm). The number of dummy channels4is counted for the dummy channels4formed on one end side of the pressure chambers10X, and the same applies hereinafter. The interval between the adjacent escape grooves11was 60 μm in both the X-direction and the Y-direction. The distance Z between the escape groove11and the dummy channel4was set to 60 μm.

The head2was produced in the same manner as in the Example 1 except that SiO2was formed to a thickness of 800 nm as the insulating protective film40b,Si3N4was formed to have a thickness of 600 nm by the plasma CVD method, and four dummy channels4were formed.

The escape groove11(X1: width 100 μm, Y1: length 100 μm) was formed while forming four dummy channels4by setting the width of the pressure chamber10X at 100 μm. The interval between the adjacent escape grooves11was 30 μm in both the X-direction and the Y-direction. Further, the distance between the escape groove11and the dummy channel4was set to 30 μm. The head2was produced in the same manner as in Example 1 except the conditions as described above.

As illustrated inFIG. 7, the head2was produced as in the same manner in Example 1 except that the back surface of the substrate10was etched to prepare the pressure chamber10X (no dummy channel was formed), and the distance between the endmost drive channel3and the escape groove11was 100 μm.

As illustrated inFIG. 18, the head2was produced as in the same manner in Example 1 except that the back surface of the substrate10was etched to form the pressure chamber10X and four dummy channels4, and the substrate10at the escape groove11is half-etched to have a non-penetration structure as illustrated inFIG. 18A.

The head2was produced in the same manner as in the Example 1 except that SiO2was formed to a thickness of 1200 nm by the plasma CVD method as the insulating protective film40b,Si3N4was formed to have a thickness of 400 nm by the plasma CVD method, and four dummy channels4were formed.

Comparative Example 1

The head2was produced in the same manner as in the Example 1 except that SiO2was formed to a thickness of 1500 nm by the plasma CVD method as the insulating protective film40b,Si3N4was formed to have a thickness of 100 nm by the plasma CVD method, the pressure chambers10X were formed by etching the back surface of the substrate10, and the escape groove11was not formed.

Comparative Example 2

As illustrated inFIG. 10, the head2was manufactured in the same manner as in Example 1 except that the back surface of the substrate10was etched to prepare the pressure chamber10X, and the escape groove11was not formed.

[Consideration on Examples 1 to 6 and Comparative Examples 1 and 2]

The heads2prepared in Examples 1 to 6 and Comparative Examples 1 and 2 were evaluated for nozzle bonding property and liquid filling property.FIGS. 27A and 27Billustrate an evaluation results and details of each Examples and Comparative Examples.

InFIGS. 27A and 27B, in each Examples 1 to 6, the difference between the maximum value and the minimum value of the curvature radius R (the difference in curvature radius) of the diaphragm20in each groups of the drive channels3from the end of the drive channels (first channel) to twenty channels is 1500 μm or less. Conversely, in Comparative Example 1, the difference in curvature radius is 2500 μm that is larger than 2000 μm.

As can be seen fromFIGS. 27A and 27B, in each Examples 1 to 6, the difference in displacement (Δδ/δ_ave) is within 8% that is a targeted value of a displacement gradient in each groups of the drive channels from the end of the drive channels (first channel) to twenty channels. However, in the Comparative Example 1, the difference in displacement (Δδ/δ_ave) was 13% having a large variation. Note that δ is the displacement characteristic of the electromechanical transducer film32when the evaluation is performed by applying an electric field strength of 150 kv/cm. Δδ is the slope difference of the displacement characteristic δ with respect to the arrangement direction of the electromechanical transducer film32. δ_ave is an average value of the displacement characteristics δ.

The nozzle plate50including the nozzles51is joined (bonded) to the lower part of the substrate10of each of the heads2(semifinished head2) produced in Examples 1 to 6 and Comparative Example 1 to complete the production of the heads2. Then, a discharge evaluation test was performed for each of the heads2.

Specifically, discharge condition was confirmed while applying a voltage from −10 V to −30 V by a simple push waveform using the ink whose viscosity was adjusted to 5 cp. As a result, in Comparative Examples 1 and 2 in which the escape groove11is not formed, a problem was confirmed such as the adhesive entering the pressure chamber10X at the time of joining (bonding) the nozzle plate50to the substrate10(see nozzle bonding property “POOR” inFIG. 25B).

On the other hand, in each of the heads2produced in Examples 1 to 6 in which the escape grooves11were formed, good nozzle bonding property was obtained (see nozzle bonding property “EXCELLENT” inFIG. 25B). In addition, it was confirmed that providing the dummy channels4in Examples 1 to 3, 5, and 6 can improve the filling property of the liquid to the head2and to solve discharge troubles caused by air bubbles, for example. Hereinafter, Examples of a fifth embodiment and a sixth embodiment according to the present disclosure is described.

Then, a titanium film (film thickness 20 nm) was formed as an adhesion layer on the diaphragm20by a sputtering apparatus at a deposition temperature of 350° C. Then, the adhesion layer is thermally oxidized at 750° C. using RTA (rapid thermal processing). Further, a platinum film (film thickness 160 nm) was formed on the adhesion layer by a sputtering apparatus at a film formation temperature of 400° C. to prepare a lower electrode31.

Then, a solution adjusted so as to have a ratio of Pb:Ti=1:1 as a PbTiO3layer serving as a base layer and a solution adjusted so as to have a ratio of Pb:Zr:Ti=115:49:51 as an electromechanical transducer film32were prepared, and a film was formed by a spin coating method on the lower electrode31.

For synthesis of a precursor coating liquid, lead acetate trihydrate, titanium isopropoxide, and zirconium isopropoxide were used as starting materials. Crystal water of lead acetate was dissolved in methoxyethanol and was then dehydrated. The amount of lead is excessively large for a stoichiometric composition. This is to prevent deterioration of crystallinity caused by so-called lead missing during heat treatment.

The titanium isopropoxide and the zirconium isopropoxide were dissolved in methoxyethanol, an alcohol exchange reaction and an esterification reaction were advanced, a resultant was mixed with a methoxyethanol solution having dissolved the lead acetate, and the PZT precursor solution was synthesized. The concentration of PZT was prepared to be 0.5 mol/l. A PT solution was produced in a similar manner to PZT. First, a PT layer film was formed by spin coating using these solutions. After film formation, the PT layer film was dried at 120° C. Thereafter, a film was formed by spin coating using the PZT solution, was dried at 120° C., and then was subjected to pyrolysis at 400° C.

After the thermal decomposition of the third layer, crystallization heat treatment (temperature 730° C.) is conducted by RTA. At this time, the film thickness of PZT was 240 nm. This step was performed eight times (24 layers) in total to obtain a PZT film thickness of about 2 μm as the electromechanical transducer film32.

Subsequently, a SrRuO3film (film thickness 40 nm) was formed by sputtering method as an oxide electrode film constituting the upper electrode33, and a Pt film (film thickness 125 nm) was formed by sputtering as a metal film. Then, a film was formed by the spin coating method using a photoresist (TSMR8800) manufactured by TOKYO OHKA KOGYO., LTD, a resist pattern was formed by a normal photolithographic method, and a pattern illustrated inFIGS. 4A and 4Bwas manufactured using an ICP etching device (manufactured by SAMCO INC.). Accordingly, the electromechanical transducer element30was produced on the diaphragm20.

Subsequently, an Al2O3film of 50 nm was formed using an ALD (Atomic Layer Deposition) method as the insulating protective film40on the electromechanical transducer element30. As raw materials, TMA (Sigma-Aldrich Corporation) for Al and O3generated by an ozone generator for O were stacked alternately, and film formation was thereby performed.

Then, a film of Si3N4was formed to a thickness of 1000 nm by a plasma CVD method as the insulating protective film40b,and then a contact hole H was formed by etching as illustrated inFIG. 4B. Thereafter, a film of Al was formed by sputtering. The film of Al was patterned by etching to form the wiring60. A film of Si3N4was formed on the wiring60by plasma CVD to have a film thickness of 500 nm as the insulating protective film70.

Thereafter, as illustrated inFIGS. 16A and 16B, the back surface of the substrate10was etched to form the pressure chamber10X (X2: width 60 μm, Y2: length 1000 μm), thereby forming the head2. However, the nozzle plate50including the nozzles51is not joined (bonded) to the lower portion of the substrate10, and the head2is in a semifinished state.

At this time, as illustrated inFIG. 26, the holding substrate15was used to hold the pressure chamber10X. The holding substrate15includes recesses15xon a back surface of the holding substrate15. A number of recesses15xin the holding substrate15corresponds to a number of electromechanical transducer elements30in the head2. Specifically, the holding substrate15was bonded to the substrate10via an adhesive layer before forming the pressure chamber10X in the substrate10so that electromechanical transducer elements30were accommodated in the recesses15x, respectively. Then, the back surface of the substrate10was etched to form the pressure chamber10X.

At this time, one dummy channel4is formed while forming the escape groove11(X1: width 60 μm, Y1: length 60 μm). The number of dummy channels4is counted for the dummy channels4formed on one end side of the pressure chambers10X, and the same applies hereinafter. The interval between the adjacent escape grooves11was 60 μm in both the X-direction and the Y-direction. The distance Z between the escape groove11and the dummy channel4was set to 60 μm. The radius of curvature of the groove11was 2300 μm, and the radius of curvature of the end side of the drive channel3was 4500 μm.

The head2was produced in the same manner as in the Example 7 except that Si3N4was formed to a thickness of 700 nm by the plasma CVD method as the insulating protective film40b,Si3N4was formed to have a thickness of 300 nm by the plasma CVD method as the insulating protective film70, and four dummy channels4were formed. The radius of curvature of the escape groove11was 6400 μm, and the radius of curvature of the diaphragm20at the end side of the drive channels3was 4200 μm.

The head2was produced in the same manner as in the Example 7 except that Si3N4was formed to a thickness of 700 nm by the plasma CVD method as the insulating protective film40b,Si3N4was formed to have a thickness of 300 nm by the plasma CVD method as the insulating protective film70, a width of the pressure chambers10X is 100 μm, and four dummy channels4were formed. Further, the escape grooves11(X1: width 100 μm, Y1: length 100 μm) were formed. The interval between the adjacent escape grooves11was 30 μm in both the X-direction and the Y-direction. Further, the distance between the escape groove11and the dummy channel4was set to 30 μm. The head2was produced in the same manner as in Example 7 except the conditions as described above. The radius of curvature of the escape groove11was 6200 μm, and the curvature radius of the end side of the drive channel3was 4250 μm.

As illustrated inFIG. 7, the back surface of the substrate10was etched to prepare a pressure chamber10X (dummy channel not formed), a film of Si3N4was formed to 700 nm as an insulating protective film40bby a plasma CVD method. Further, a film of Si3N4was formed as the insulating protective film70by 300 nm by a plasma CVD method. The head2was manufactured in the same manner as in Example 7 except that the distance between the endmost drive channel3and the escape groove11was set to 100 μm. The radius of curvature of the escape groove11was 6500 μm, and the radius of curvature of the end side of the drive channels3was 4300 μm.

As illustrated inFIG. 18, the head2was produced as in the same manner in Example 7 except that the back surface of the substrate10was etched to form the pressure chambers10X and four dummy channels4, and the substrate10at the escape groove11is half-etched to have a non-penetration structure as illustrated inFIG. 18A. The radius of curvature of the drive channel3at the end was 4400 μm.

Comparative Example 3

The head2was produced in the same manner as in the Example 7 except that Si3N4was formed to a thickness of 1500 nm by the plasma CVD method as the insulating protective film40b,Si3N4was formed to have a thickness of 1000 nm by the plasma CVD method as the insulating protective film70, and the pressure chambers10X and four dummy channels4were formed by etching the back surface of the substrate10. The radius of curvature of the escape groove11was 1200 μm, and the radius of curvature of the end side of the drive channels3was 4600 μm.

Comparative Example 4

As illustrated inFIG. 9, the head2was manufactured in the same manner as in Example 7 except that the back surface of the substrate10was etched to prepare the pressure chamber10X, and the escape grooves11and the dummy channels4were not formed. The radius of curvature of the end side of the drive channel3was 4350 μm.

[Consideration on Examples 7 to 11 and Comparative Examples 3 and 4]

The heads2prepared in Examples 7 to 11 and Comparative Examples 3 and 4 were evaluated for nozzle bonding property and liquid filling property. Evaluation results and details of each Examples and Comparative Examples are illustrated inFIGS. 28A and 28B.

InFIGS. 28A and 28B, in each Examples 7 to 11, the difference between the maximum value and the minimum value of the curvature radius R (the difference in curvature radius) of the diaphragm20in each groups of the drive channels3from the end of the drive channels3(first channel) to twenty channels is 1500 μm or less. Conversely, in Comparative Example 3, the difference in curvature radius is 2500 μm that is larger than 2000 μm. In Comparative Example 3, the radius of curvature of the escape groove11is smaller than the radius of curvature of the drive channel3.

As can be seen fromFIGS. 28A and 28B, in each Examples 7 to 11, the difference in displacement (Δδ/δ_ave) is within 8% that is a targeted value of a displacement gradient in each groups of the drive channels3from the end of the drive channels3(first channel) to twenty channels. However, in the Comparative Example 3, the difference in displacement (Δδ/δ_ave) was 13% having a large variation. Note that δ is the displacement characteristic of the electromechanical transducer film32when the evaluation is performed by applying an electric field strength of 150 kv/cm. Δδ is the slope difference of the displacement characteristic δ with respect to the arrangement direction of the electromechanical transducer film32. δ_ave is an average value of the displacement characteristics δ.

The nozzle plate50including the nozzles51is joined (bonded) to the lower part of the substrate10of each of the heads2(semifinished head2) produced in Examples 7 to 11 and Comparative Example 3 to complete the production of the heads2. Then, a discharge evaluation test was performed for each of the heads2.

Specifically, discharge condition was confirmed while applying a voltage from −10V to −30V by a simple push waveform using the ink whose viscosity was adjusted to 5 cp. As a result, in Comparative Examples 4 in which the escape groove11is not formed, a problem was confirmed such as the adhesive entering the pressure chamber10X at the time of joining (bonding) the nozzle plate50to the substrate10(see nozzle bonding property “POOR” inFIG. 28B).

On the other hand, in each of the heads2produced in Examples 7 to 11 in which the escape grooves11were formed, good nozzle bonding property was obtained (see nozzle bonding property “EXCELLENT” inFIG. 28B). In addition, it was confirmed that providing the dummy channels4in Examples 7 to 9 and 11 can improve the filling property of the liquid to the head2and to solve discharge troubles caused by air bubbles, for example. In Examples 8 and 9 in which the radius of curvature of the groove11was made larger than the radius of curvature of the drive channel3, it was confirmed that the filling property is better than in Example 7 in which the radius of curvature of the groove11is smaller than the radius of curvature of the drive channel3(see filling property “EXCELLENT” inFIG. 28B).