JP2007281049A - Laminated element, piezoelectric element, and ink-jet recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively relax stress applied to a piezoelectric film during and/or after film formation in a piezoelectric element. <P>SOLUTION: In the piezoelectric element 1; a lower electrode 30, the piezoelectric film 40, and an upper electrode 50 are laminated successively on a substrate 10. Further, a columnar structure film 20 made of a number of columnar bodies 21 extended in a non-parallel direction to the substrate surface of the substrate 10 is provided between the substrate 10 and the piezoelectric film 40. The columnar structure film 20 can function as a stress relaxation layer for relaxing stress applied to the piezoelectric film 40 during and/or after film formation. The lower electrode 30 may be formed in a columnar structure film structure instead of providing the columnar structure film 20 separately from the electrode. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laminated element provided with a stress relaxation layer, a piezoelectric element used for an ink jet recording head, and the like, and an ink jet recording head.

  A piezoelectric element having a piezoelectric film having a piezoelectric property that expands and contracts as the electric field application intensity increases and decreases, and an electrode that applies an electric field to the piezoelectric film is used as an actuator mounted on an ink jet recording head. Yes. As a piezoelectric material, perovskite complex oxides such as lead zirconate titanate (PZT) are known.

  In a piezoelectric element, if the difference in thermal expansion coefficient between the substrate material and the piezoelectric film material is large, stress is applied to the piezoelectric film in the process of film formation or annealing after film formation, and micro cracks are generated in the piezoelectric film. Or the piezoelectric film may peel off from the substrate. Further, even if cracks and peeling do not occur, the adhesion between the substrate and the piezoelectric film may be lowered. If the adhesion between the substrate and the piezoelectric film is low, cracks and peeling may occur after long-term driving in applications such as an ink jet recording head, which is not preferable.

  The above problem is likely to occur when a relatively thick piezoelectric film is formed by an aerosol deposition method or the like. This is presumably because a thick piezoelectric film cannot flexibly follow the stress applied to the piezoelectric film.

In order to solve such a problem, Patent Document 1 discloses that a stress relaxation layer made of a material having a smaller Young's modulus than a piezoelectric film material or a piezoelectric film material has a different thermal expansion coefficient between the substrate and the piezoelectric film. It has been proposed to provide a stress relaxation layer made of a material.
Patent Document 2 proposes to provide a stress relaxation layer made of a porous or amorphous metal oxide film between a substrate and a piezoelectric film.
JP 2004-128492 A JP 11-204849 A

  In the stress relaxation layer described in Patent Document 1, it is necessary to design the composition of the stress relaxation layer according to the characteristics such as the composition of the piezoelectric film and the thermal expansion coefficient of the piezoelectric film material. Can't respond flexibly to changes.

  Patent Document 2 does not describe in detail a stress relaxation layer made of a porous or amorphous metal oxide film. In paragraph 0022 of Patent Document 2, it is described that the stress relaxation layer is “a porous or amorphous film that cancels or absorbs stress generated in a dense film”, and materials such as MgO are exemplified. Degree. Patent Document 2 does not describe the stress relaxation mechanism or the like of the stress relaxation layer, and it is not clear what kind of stress relaxation layer can be used to effectively obtain the stress relaxation effect.

The present invention has been made in view of the above circumstances, and can effectively relieve stress applied to the piezoelectric film during film formation and / or after film formation, and can be flexibly adapted to design changes such as the composition of the piezoelectric film. It is an object of the present invention to provide a piezoelectric element that can cope with the above.
Another object of the present invention is to provide an ink jet recording head and an ink jet recording apparatus provided with the piezoelectric element.

  In addition to the piezoelectric element, the present invention can effectively relieve stress applied to a film whose stress is to be relieved, and can flexibly cope with a design change such as a composition of a film to be relieved of stress. An object of the present invention is to provide a simple laminated element.

In the multilayer element of the present invention, a columnar structure film composed of a number of columnar bodies extending in a non-parallel direction to the substrate surface of the substrate and a non-columnar structure film are sequentially stacked on the substrate.
The columnar structure film is a stress relaxation layer that relieves stress applied to the non-columnar structure film during and / or after film formation.

  In the multilayer element of the present invention, another layer may be interposed between the columnar structure film that is a stress relaxation layer and the non-columnar structure film that is a stress relaxation target.

The multilayer element of the present invention is effective when the difference between the thermal expansion coefficient of the constituent material of the substrate and the thermal expansion coefficient of the constituent material of the non-columnar structure film is 4.0 × 10 ⁻⁶ / ° C. or more. .

In this specification, the “thermal expansion coefficient of the constituent material of the substrate” means a general thermal expansion coefficient measured for a bulk body made of the constituent material of the substrate. Similarly, “the thermal expansion coefficient of the constituent material of the non-columnar structure film” means a general thermal expansion coefficient measured for a bulk body made of the constituent material of the non-columnar structure film. Since it is difficult to accurately measure the thermal expansion coefficient of the thin film itself, the laminated element of the present invention defines the difference in thermal expansion coefficient between the substrate and the non-columnar structure film by the thermal expansion coefficient of the bulk material. is there.
When the temperature T is changed under the condition that the pressure p is constant (Δp = 0), the volume V of the bulk body changes. The volume change ΔV when the temperature is increased by a small amount ΔT is proportional to ΔV / V (where V is the original volume), and the thermal expansion coefficient α of a bulk body made of a certain material is generally expressed by the following equation: It is represented by
Under the condition of Δp = 0, α = (ΔV / V) / ΔT

The first piezoelectric element of the present invention is a piezoelectric in which a lower electrode, a piezoelectric film, and an upper electrode are sequentially laminated on a substrate, and an electric field is applied to the piezoelectric film by the lower electrode and the upper electrode. In the element
A columnar structure film comprising a plurality of columnar bodies extending in a non-parallel direction with respect to the substrate surface of the substrate is provided between the substrate and the piezoelectric film.

The second piezoelectric element of the present invention is a piezoelectric device in which a lower electrode, a piezoelectric film, and an upper electrode are sequentially stacked on a substrate, and an electric field is applied to the piezoelectric film by the lower electrode and the upper electrode. In the element
The lower electrode is a columnar structure film composed of a number of columnar bodies extending in a non-parallel direction with respect to the substrate surface of the substrate.

  In the first and second piezoelectric elements of the present invention, the columnar structure film can function as a stress relaxation layer that relieves stress applied to the piezoelectric film during and / or after film formation.

It is preferable that the average column diameter of the many columnar bodies forming the columnar structure film is 20 to 200 nm.
In this specification, “the average column diameter of a large number of columnar bodies” is obtained by taking a cross-sectional photograph with a scanning electron microscope (SEM) to determine the diameters of arbitrary 10 columnar bodies and calculating the average value of these. Shall.

In the columnar structure film, it is preferable that pores extending in substantially the same direction as the columnar bodies are formed between the plurality of columnar bodies.
It is preferable that the multiple columnar bodies forming the columnar structure film extend in an oblique direction with respect to the substrate surface.

The composition of the piezoelectric film is not particularly limited, and examples thereof include those composed mainly of one or more perovskite oxides represented by the following general formula.
General formula ABO ₃
(In the formula, A: an element at the A site, at least one element selected from the group consisting of Pb, Ba, Nb, La, Li, Sr, Bi, Na, and K;
B: B site element, at least one element selected from the group consisting of Cd, Fe, Ti, Ta, Mg, Mo, Ni, Nb, Zr, Zn, W, and Yb,
O: oxygen atom)
In the present specification, the “main component” is defined as a component having a content of 90% by mass or more.
The piezoelectric film preferably contains 95% by mass or more, and particularly preferably contains 99% by mass or more of one or more perovskite oxides represented by the above general formula.

  The ink jet recording head of the present invention is an ink having the first or second piezoelectric element of the present invention, an ink chamber in which ink is stored, and an ink discharge port through which the ink is discharged from the ink chamber to the outside. And a storage / discharge member.

  An ink jet recording apparatus of the present invention includes the above ink jet recording head of the present invention.

  In the multilayer element of the present invention, as the stress relaxation layer, a columnar structure film composed of a large number of columnar bodies extending in a non-parallel direction to the substrate surface is provided, and a non-columnar structure film that is a stress relaxation target is provided thereon. Yes.

In such a configuration, the stress applied to the non-columnar structure film that is the target of stress relaxation can be effectively relieved during and / or after the film formation due to the presence of the stress relaxation layer made of the columnar structure film. Since this effect can be obtained regardless of the characteristics such as the composition of the non-columnar structure film that is the subject of stress relaxation and the thermal expansion coefficient of the film material, according to the design change such as the composition of the non-columnar structure film that is the subject of stress relaxation, There is no need to design the composition of the stress relaxation layer. Therefore, in the element structure of the present invention, it is possible to flexibly cope with design changes such as the composition of the non-columnar structure film that is the subject of stress relaxation.
The laminated element of the present invention can be preferably applied to a piezoelectric element or the like.

  The piezoelectric element of the present invention is configured such that a columnar structure film composed of a number of columnar bodies extending in a non-parallel direction with respect to the substrate surface is provided between the substrate and the piezoelectric film. In such a configuration, the columnar structure film can function as a stress relaxation layer. According to the present invention, it is possible to effectively relieve stress applied to a piezoelectric film during film formation and / or after film formation, and to flexibly cope with design changes such as the composition of the piezoelectric film. An element can be provided.

“First Embodiment of Piezoelectric Element, Inkjet Recording Head”
A first embodiment of a piezoelectric element (laminated element) according to the present invention and the structure of an ink jet recording head having the same will be described with reference to FIG. FIG. 1A is a cross-sectional view of an essential part of an ink jet recording head (a cross-sectional view in the thickness direction of a piezoelectric element), and FIG. 1B is a partially enlarged cross-sectional view. In order to facilitate visual recognition, the scale of the constituent elements is appropriately changed from the actual one.

  The piezoelectric element (laminated element) 1 according to the present embodiment includes a columnar structure film 20 (a columnar structure 21 shown in FIG. 1) including a large number of columnar bodies 21 extending in a non-parallel direction with respect to the substrate surface of the substrate 10. (B) is formed, and a lower electrode 30, a piezoelectric film (non-columnar structure film that is a stress relaxation target) 40, and an upper electrode 50 are sequentially stacked thereon. The piezoelectric film 40 is made of an inorganic compound having piezoelectricity, and an electric field is applied in the thickness direction by the lower electrode 30 and the upper electrode 50.

The substrate 10 is not particularly limited, and examples thereof include silicon, glass, stainless steel (SUS), yttrium stabilized zirconia (YSZ), alumina, sapphire, and silicon carbide. As the substrate 10, a laminated substrate such as an SOI substrate in which a SiO ₂ oxide film is formed on the surface of a silicon substrate may be used.

  A columnar structure film 20 is formed on substantially the entire surface of the substrate 10. In this embodiment, the columnar structure film 20 is a film formed by oblique vapor deposition, and a large number of columnar bodies 21 forming the columnar structure film 20 extend in an oblique direction with respect to the substrate surface of the substrate 10. . In the columnar structure film 20, a large number of holes 22 extending in substantially the same direction as the columnar bodies 21 are formed between the numerous columnar bodies 21. The shape of the hole 22 is not particularly limited, and examples thereof include a prismatic shape such as a triangular prism shape, a cylindrical shape, and an elliptical column shape. In the figure, the columnar body 21 and the holes 22 are schematically shown.

The material of the columnar structure film 20 is not particularly limited, and any material that can obtain the film structure can be used. The material of the columnar structure film 20 includes oxides, nitrides or oxynitrides of metals such as Ti, Zr, Ta, La, Ni, Al, Ir, Ru, and Pt, or complex oxides or complex nitrides thereof. Thing etc. are mentioned.
The columnar structure film 20 may or may not have crystallinity.

  In the present embodiment, the columnar structure film 20 having the above film structure causes stress applied to the piezoelectric film 40 during and / or after film formation due to a difference in thermal expansion coefficient between the substrate material and the piezoelectric film material. It can function as a stress relaxation layer that relaxes.

  In the columnar structure film 20, the bonding force between the many columnar bodies 21 forming the columnar structure film 20 is relatively weak, and when a partial stress is applied, the plurality of columnar bodies 21 in the part slide on each other, It is thought to absorb and relax the stress. Even though the bonding force between the multiple columnar bodies 21 is relatively weak, the multiple columnar bodies 21 forming the columnar structure film 20 are bonded with a certain amount of bonding force as a whole, so that the stress is low. Even if this is applied, the overall film structure of the columnar structure film 20 itself is maintained.

  In particular, when air holes 22 extending in substantially the same direction as the columnar bodies 21 are formed between the many columnar bodies 21, the movement between the columnar bodies 21 occurs more smoothly, and the stress relaxation effect is more effectively achieved. To express. Further, when a large number of columnar bodies 21 forming the columnar structure film 20 are grown in an oblique direction with respect to the substrate surface of the substrate 10, pores extending in the substantially same direction as the columnar bodies 21 are formed between the numerous columnar bodies 21. 22 is easily formed, and the stress relaxation effect is effectively exhibited.

  As described above, a large number of columnar bodies 21 that form the columnar structure film 20 grow in an oblique direction with respect to the substrate surface of the substrate 10, and extend between the many columnar bodies 21 in substantially the same direction as the columnar bodies 21. It is particularly preferable that the holes 22 be formed. However, if the columnar structure film 20 has a film structure including a large number of columnar bodies 21 extending in a non-parallel direction with respect to the substrate surface of the substrate 10, the stress relaxation effect is achieved. Is obtained. Therefore, the multiple columnar bodies 21 forming the columnar structure film 20 may be grown in a direction perpendicular to the substrate surface of the substrate 10. The holes 22 may not be provided.

  The average column diameter of the many columnar bodies 21 forming the columnar structure film 20 is not particularly limited and is preferably 20 to 200 nm. When the average column diameter of the columnar body 21 is too small, the film structure of the columnar structure film 20 is not different from that of the continuous film, and the stress relaxation effect is not sufficiently exhibited. There is a risk of cracks occurring in the columnar structure film 20 itself.

  The growth direction of the columnar body 21 is not particularly limited, and is preferably an angle direction of 0 ° or more and less than 90 ° from the normal direction of the substrate surface of the substrate 10, and particularly preferably an angle direction of 5 ° or more and 45 ° or less. preferable.

  The average diameter of the pores 22 is not particularly limited, and if it is too large, the surface unevenness of the columnar structure film 20 becomes large.

  The thickness of the columnar structure film 20 is not particularly limited, and if it is too small, the stress relaxation effect due to the columnar structure film 20 is not sufficiently exhibited, and if it is excessively large, the surface unevenness of the columnar structure film 20 becomes large or cracks occur in the columnar structure film 20 itself. Since it may occur, it is preferably 0.1 to 5.0 μm.

  A lower electrode 30 is formed on substantially the entire surface of the substrate 10 on which the columnar structure film 20 is formed, and line-shaped convex portions 41 extending from the front side to the back side in the figure are arranged in stripes on the lower electrode 30. A piezoelectric film 40 having a pattern is formed, and an upper electrode 50 is formed on each convex portion 41. The thickness of the lower electrode 30 and the upper electrode 50 is not particularly limited and is, for example, about 200 nm. In the present embodiment, the lower electrode 30, the piezoelectric film 40, and the upper electrode 50 are non-columnar structure films.

The main component of the lower electrode 30 is not particularly limited, and examples thereof include metals or metal oxides such as Pt, Ir, IrO ₂ , RuO ₂ , LaNiO ₃ , and SrRuO ₃ , and combinations thereof.

  The main component of the upper electrode 50 is not particularly limited, and examples thereof include materials exemplified for the lower electrode 30, electrode materials generally used in semiconductor processes such as Al, Ta, Cr, and Cu, and combinations thereof.

  The pattern of the piezoelectric film 40 is not limited to that shown in the figure, and is designed as appropriate. The piezoelectric film 40 may be a continuous film. However, the piezoelectric film 40 is not a continuous film, but formed by a pattern composed of a plurality of protrusions 41 separated from each other, so that the expansion and contraction of the individual protrusions 41 occurs smoothly, so that a larger displacement amount is obtained. preferable.

  The piezoelectric film 40 is formed by a known method such as a vapor phase method such as a sputtering method, an MOCVD method, or a pulse laser deposition method, a chemical solution deposition method (CSD) such as a sol-gel method or an organometallic decomposition method, or an aerosol deposition method. A film can be formed by a thin film forming method. The piezoelectric film 40 is annealed as necessary after film formation.

The composition of the piezoelectric film 40 is not particularly limited, and examples thereof include those containing as a main component one or more perovskite oxides represented by the following general formula.
General formula ABO ₃
(In the formula, A: an element at the A site, at least one element selected from the group consisting of Pb, Ba, Nb, La, Li, Sr, Bi, Na, and K;
B: B site element, at least one element selected from the group consisting of Cd, Fe, Ti, Ta, Mg, Mo, Ni, Nb, Zr, Zn, W, and Yb,
O: oxygen atom)

Examples of the perovskite oxide represented by the above general formula, lead zirconate titanate (PZT (e.g. _{Pb (Zr 0.52 Ti 0.48) O} 3), PNN-PZT ( general formula Pb (Ni, Nb) O ₃ -PbZrO ₃ 3-component lead zirconate titanate represented by -PbTiO _3), and the like. both the illustrated perovskite oxide, a ferroelectric having a spontaneous polarization characteristics at the time free from electric field application is there.

  The piezoelectric film 40 preferably contains 90% by mass or more of one or more perovskite oxides represented by the above general formula, more preferably 95% by mass or more, and 99% by mass or more. It is particularly preferred.

  The film thickness of the piezoelectric film 40 is not particularly limited and is usually 1 μm or more.

  In the section of “Background Art”, in the conventional piezoelectric element, when the difference in thermal expansion coefficient between the substrate material and the piezoelectric film material is large, stress is applied to the piezoelectric film in a process such as film formation or annealing after film formation, It has been stated that there is a possibility that minute cracks are generated in the piezoelectric film, the piezoelectric film is peeled off from the substrate, or the adhesion between the substrate and the piezoelectric film is lowered. In addition, it has been described that these problems are likely to occur when a relatively thick piezoelectric film is formed by an aerosol deposition method or the like.

  In the present embodiment, since the columnar structure film 20 functions as a stress relaxation layer, even when a relatively thick piezoelectric film 40 is formed by an aerosol deposition method or the like, the columnar structure film 20 is being formed and / or formed. The stress applied to the piezoelectric film 40 after film formation can be relaxed, and the generation of minute cracks in the piezoelectric film 40 can be suppressed.

  That is, this embodiment is effective when the piezoelectric film 40 is relatively thick. Specifically, this embodiment is effective when the thickness of the piezoelectric film 40 is relatively thick at 2.0 to 30.0 μm. In addition, this embodiment is effective when the film is formed by an aerosol deposition method or the like in which the piezoelectric film 40 is relatively thick.

The present inventor has found that the above-described conventional problem occurs remarkably when the difference in thermal expansion coefficient between the substrate material and the piezoelectric film material is 4.0 × 10 ⁻⁶ / ° C. or more. . In this embodiment, even when the thermal expansion coefficient difference between the substrate material and the piezoelectric film material is large, the columnar structure film 20 can relieve stress applied to the piezoelectric film 40 during and / or after film formation. Generation of cracks and peeling of the piezoelectric film 40 from the substrate 10 can be suppressed. In the present embodiment, since a decrease in adhesion between the substrate 10 and the piezoelectric film 40 can be suppressed, the occurrence of cracks and peeling after long-term driving can also be suppressed. Therefore, the piezoelectric element 1 of the present embodiment has excellent long-term reliability.

That is, in this embodiment, when the difference in thermal expansion coefficient between the substrate material and the piezoelectric film material is large, specifically, the difference in thermal expansion coefficient between the substrate material and the piezoelectric film material is 4.0 × 10 ⁻⁶ / ° C. or more. In this case, it is effective.

For example, the thermal expansion coefficient of Si is 4.0 × 10 ⁻⁶ / ° C., the thermal expansion coefficient of PZT is 7.0 to 9.0 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of PNN-PZT is 10. 0 × 10 ⁻⁶ / ° C. Therefore, this embodiment is effective when a Si substrate is used as the substrate 10 and the piezoelectric film 40 made of a PNN-PZT film is formed.

  The ink jet recording head 2 generally includes an ink chamber 71 in which ink is stored and an ink from which ink is ejected to the outside via the vibration plate 60 on the lower surface of the substrate 10 of the piezoelectric element 1 having the above-described configuration. An ink nozzle (ink storage and discharge member) 70 having a discharge port 72 is attached. A plurality of ink chambers 71 are provided corresponding to the number and pattern of the convex portions 41 of the piezoelectric film 40.

  In the ink jet recording head 2, the electric field strength applied to the convex portion 41 of the piezoelectric element 1 is increased / decreased for each convex portion 41 to expand / contract, thereby controlling the ejection of ink from the ink chamber 71 and the ejection amount. Is called.

  In the ink jet recording head 2, a part of the substrate 10 may be processed into the vibration plate 60 and the ink nozzle 70 instead of attaching the vibration plate 60 and the ink nozzle 70 which are members independent of the substrate 10. For example, when the substrate 10 is made of a laminated substrate such as an SOI substrate, the substrate 10 is etched from the lower surface side to form the ink chamber 71, and the vibration plate 60 and the ink nozzle 70 are formed by processing the substrate itself. Can do.

  The piezoelectric element 1 and the ink jet recording head 2 of the present embodiment are configured as described above.

  In the piezoelectric element (laminated element) 1 according to this embodiment, a columnar structure film 20 including a large number of columnar bodies 21 extending in a non-parallel direction to the substrate surface of the substrate 10 is provided as a stress relaxation layer, and stress relaxation is performed thereon. A target piezoelectric film (non-columnar structure film) 40 is provided.

  In such a configuration, the stress applied to the piezoelectric film 40 can be effectively relaxed during and / or after the film formation due to the presence of the stress relaxation layer made of the columnar structure film 20. Since this effect can be obtained regardless of characteristics such as the composition of the piezoelectric film 40 and the thermal expansion coefficient of the film material, the composition of the columnar structure film 20 that is a stress relaxation layer, etc. There is no need to design. Therefore, the element structure of the present embodiment can flexibly cope with design changes such as the composition of the piezoelectric film 40.

  Further, in the present embodiment, the bonding force between the many columnar bodies 21 forming the columnar structure film 20 is relatively weak, and when a partial stress is applied, the plurality of columnar bodies 21 in the portion slide on each other. The presence of the columnar structure film 20 is expected to cause the piezoelectric film 40 to expand and contract more smoothly when an electric field is applied to the piezoelectric film 40, and to exhibit piezoelectricity more effectively.

“Second Embodiment of Piezoelectric Element”
With reference to FIG. 2, a second embodiment of a piezoelectric element (laminated element) according to the present invention and the structure of an ink jet recording head including the same will be described. FIG. 2A is a main part sectional view corresponding to FIG. 1A of the first embodiment, and FIG. 2B is a partial enlarged sectional view. About the same component as 1st Embodiment, the same referential mark is attached | subjected and description is abbreviate | omitted.

  The piezoelectric element (laminated element) 3 of the present embodiment is an element in which a lower electrode 31, a piezoelectric film (non-columnar structure film) 40, and an upper electrode 50 are sequentially laminated on a substrate 10 as in the first embodiment. is there. The ink jet recording head 4 of this embodiment is one in which an ink storing and discharging member 70 is attached to the piezoelectric element 3.

  The piezoelectric element 3 of the present embodiment does not have the columnar structure film 20, and the lower electrode 31 includes a plurality of columnar bodies 32 extending in a non-parallel direction with respect to the substrate surface of the substrate 10. 2 (b)).

  The lower electrode 31 has a film structure similar to that of the columnar structure film 20 of the first embodiment. That is, the lower electrode 31 is a film formed by oblique vapor deposition, and a large number of columnar bodies 32 forming the lower electrode 31 extend in an oblique direction with respect to the substrate surface of the substrate 10. In addition, in the lower electrode 32, a large number of holes 33 extending in substantially the same direction as the columnar body 32 are formed between the numerous columnar bodies 32. The shape of the air holes 33 is not particularly limited, and examples thereof include a prismatic shape such as a triangular prism shape, a cylindrical shape, and an elliptical column shape. In the figure, the columnar body 32 and the holes 33 are schematically shown.

  In the present embodiment, the lower electrode 31 can function as a stress relaxation layer that relieves stress applied to the piezoelectric film 40 during and / or after film formation. Similar to the columnar structure film 20 of the first embodiment, the coupling force between the many columnar bodies 32 forming the lower electrode 31 is relatively weak, and when a partial stress is applied, a plurality of columnar bodies 32 in the portion are formed. It is thought that it slides on each other and absorbs and relaxes stress.

  Also in this embodiment, a large number of columnar bodies 32 that form the lower electrode 31 grow in an oblique direction with respect to the substrate surface of the substrate 10, and extend in a substantially same direction as the columnar bodies 32 between the numerous columnar bodies 32. It is particularly preferable that the holes 33 are formed. However, if the lower electrode 31 has a film structure composed of a large number of columnar bodies 32 extending in a non-parallel direction with respect to the substrate surface of the substrate 10, a stress relaxation effect is obtained. can get. Therefore, the many columnar bodies 32 forming the lower electrode 31 may be grown in a direction perpendicular to the substrate surface of the substrate 10. The holes 33 may not be provided.

  The preferable range of the average column diameter of the many columnar bodies 32 forming the lower electrode 31, the growth direction of the columnar bodies 32, the average diameter of the holes 33, and the thickness of the lower electrode 31 is the columnar structure film 20 of the first embodiment. It is the same.

The constituent material of the lower electrode 31 is not particularly limited, and examples thereof include metals or metal oxides such as Pt, Ir, IrO ₂ , RuO ₂ , LaNiO ₃ , and SrRuO ₃ , and combinations thereof.

The piezoelectric element 3 and the ink jet recording head 4 of the present embodiment are configured as described above.
Even if the lower electrode 31 is formed of a columnar structure film functioning as a stress relaxation layer as in the present embodiment, the same effect as in the first embodiment can be obtained. In such a configuration, it is not necessary to separately form an electrode and a columnar structure film that functions as a stress relaxation layer, so that the process becomes simpler than in the first embodiment.

  Also in the present embodiment, the coupling force between a large number of columnar bodies 32 forming the lower electrode 31 made of a columnar structure film is relatively weak, and when a partial stress is applied, the plurality of columnar bodies 32 in that portion slide against each other. Therefore, due to the presence of the lower electrode 31 made of a columnar structure film, it is expected that the piezoelectric film 40 expands and contracts more smoothly when an electric field is applied to the piezoelectric film 40 and the piezoelectricity is expressed more effectively. .

"Laminated elements"
Although the piezoelectric element has been described as an embodiment according to the present invention, the present invention is not limited to the piezoelectric element, and any laminated element including a columnar structure film that functions as a stress relaxation layer is novel and included in the present invention.

That is, in the multilayer element of the present invention, a columnar structure film composed of a number of columnar bodies extending in a non-parallel direction to the substrate surface of the substrate and a non-columnar structure film are sequentially stacked on the substrate.
The columnar structure film is a stress relaxation layer that relieves stress applied to the non-columnar structure film during and / or after film formation.

The multilayer element of the present invention is effective when the difference in thermal expansion coefficient between the constituent material of the substrate and the non-columnar structure film that is the subject of stress relaxation is 4.0 × 10 ⁻⁶ / ° C. or more.

  In the multilayer element of the present invention, the stress applied to the non-columnar structure film that is the target of stress relaxation can be effectively relieved during and / or after the film formation due to the presence of the stress relaxation layer made of the columnar structure film. Since this effect can be obtained regardless of the characteristics such as the composition of the non-columnar structure film that is the subject of stress relaxation and the thermal expansion coefficient of the film material, according to the design change such as the composition of the non-columnar structure film that is the subject of stress relaxation, There is no need to design the composition of the stress relaxation layer. Therefore, in the element structure of the present invention, it is possible to flexibly cope with design changes such as the composition of the non-columnar structure film that is the subject of stress relaxation.

"Inkjet recording device"
With reference to FIG. 3 and FIG. 4, a configuration example of an ink jet recording apparatus including the ink jet recording head 2 of the above embodiment will be described. 3 is an overall view of the apparatus, and FIG. 4 is a partial top view.

  The illustrated ink jet recording apparatus 100 includes a printing unit 102 having a plurality of ink jet recording heads (hereinafter simply referred to as “heads”) 2K, 2C, 2M, and 2Y provided for each ink color, and each head 2K, An ink storage / loading unit 114 that stores ink to be supplied to 2C, 2M, and 2Y, a paper feeding unit 118 that supplies recording paper 116, a decurling unit 120 that removes curling of the recording paper 116, and a printing unit An adsorption belt conveyance unit 122 that conveys the recording paper 116 while maintaining the flatness of the recording paper 116, and a print detection unit that reads a printing result by the printing unit 102. 124 and a paper discharge unit 126 that discharges printed recording paper (printed matter) to the outside.

  The heads 2K, 2C, 2M, and 2Y that form the printing unit 102 are the ink jet recording heads 2 of the above-described embodiment.

  In the decurling unit 120, heat is applied to the recording paper 116 by the heating drum 130 in the direction opposite to the curl direction, and the decurling process is performed.

  In the apparatus using roll paper, as shown in FIG. 3, a cutter 128 is provided at the subsequent stage of the decurling unit 120, and the roll paper is cut into a desired size by this cutter. The cutter 128 includes a fixed blade 128A having a length equal to or larger than the conveyance path width of the recording paper 116, and a round blade 128B that moves along the fixed blade 128A. The fixed blade 128A is provided on the back side of the print. The round blade 128B is arranged on the print surface side with the conveyance path interposed therebetween. In an apparatus using cut paper, the cutter 128 is unnecessary.

  The decurled and cut recording paper 116 is sent to the suction belt conveyance unit 122. The suction belt conveyance unit 122 has a structure in which an endless belt 133 is wound between rollers 131 and 132, and at least portions facing the nozzle surface of the printing unit 102 and the sensor surface of the printing detection unit 124 are horizontal ( Flat surface).

  The belt 133 has a width that is wider than the width of the recording paper 116, and a plurality of suction holes (not shown) are formed on the belt surface. An adsorption chamber 134 is provided at a position facing the nozzle surface of the printing unit 102 and the sensor surface of the print detection unit 124 inside the belt 133 that is stretched between the rollers 131 and 132. The recording paper 116 on the belt 133 is sucked and held by suctioning at 135 to make a negative pressure.

  When the power of a motor (not shown) is transmitted to at least one of the rollers 131 and 132 around which the belt 133 is wound, the belt 133 is driven in the clockwise direction in FIG. 3 and is held on the belt 133. The recording paper 116 is conveyed from left to right in FIG.

  Since ink adheres to the belt 133 when a borderless print or the like is printed, the belt cleaning unit 136 is provided at a predetermined position outside the belt 133 (an appropriate position other than the print region).

  A heating fan 140 is provided on the upstream side of the printing unit 102 on the paper conveyance path formed by the suction belt conveyance unit 122. The heating fan 140 heats the recording paper 116 by blowing heated air onto the recording paper 116 before printing. Heating the recording paper 116 immediately before printing makes it easier for the ink to dry after landing.

  The printing unit 102 is a so-called full-line head in which line-type heads having a length corresponding to the maximum paper width are arranged in a direction (main scanning direction) perpendicular to the paper feed direction (see FIG. 4). Each of the print heads 2K, 2C, 2M, and 2Y is a line-type head in which a plurality of ink discharge ports (nozzles) are arranged over a length that exceeds at least one side of the maximum size recording paper 116 targeted by the ink jet recording apparatus 100. It is configured.

  Heads 2K, 2C, 2M, and 2Y corresponding to the respective color inks are arranged in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side along the feeding direction of the recording paper 116. ing. A color image is recorded on the recording paper 116 by ejecting the color inks from the heads 2K, 2C, 2M, and 2Y while conveying the recording paper 116, respectively.

  The print detection unit 124 includes a line sensor that images the droplet ejection result of the print unit 102 and detects ejection defects such as nozzle clogging from the droplet ejection image read by the line sensor.

  A post-drying unit 142 including a heating fan or the like for drying the printed image surface is provided at the subsequent stage of the print detection unit 124. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

  A heating / pressurizing unit 144 is provided downstream of the post-drying unit 142 in order to control the glossiness of the image surface. The heating / pressurizing unit 144 presses the image surface with a pressure roller 145 having a predetermined surface irregularity shape while heating the image surface, and transfers the irregular shape to the image surface.

  The printed matter obtained in this manner is outputted from the paper output unit 126. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. In the ink jet recording apparatus 100, there is provided sorting means (not shown) for switching the paper discharge path in order to select the print product of the main image and the print product of the test print and send them to the discharge units 126A and 126B. It has been.

  When the main image and the test print are simultaneously printed on a large sheet of paper, the cutter 148 may be provided to separate the test print portion.

  The ink jet recording apparatus 100 is configured as described above.

(Design changes)
The present invention is not limited to the above-described embodiment, and can be appropriately changed in design without departing from the spirit of the present invention.

  Examples and comparative examples according to the present invention will be described.

Example 1
Zr was obliquely deposited on a 100 μm thick strip-like Si substrate using a sputtering apparatus to form a 300 nm thick Zr film. The film formation conditions are as follows: the substrate temperature is room temperature, the tilt angle with respect to the substrate deposition source (= the angle between the normal direction of the substrate surface and the deposition source direction viewed from the substrate) is 40 °, and the distance between the substrate and the deposition source is The deposition atmosphere was 100 Pa, the Ar atmosphere was 0.9 Pa, and the input power was 150 W.

  On the Zr film, Pt was vapor-deposited using the same apparatus to form a 400 nm thick Pt film. The film formation conditions were as follows: the substrate temperature was room temperature, the distance between the substrate and the evaporation source was 100 mm, the film formation atmosphere was an Ar atmosphere of 0.9 Pa, and the input power was 150 W.

  As described above, the multilayer element of the present invention in which the Zr film and the Pt film were sequentially laminated on the Si substrate was obtained. When the cross section of the obtained element was observed with a scanning electron microscope (SEM), the Zr film was a columnar structure film composed of a number of columnar bodies extending obliquely with respect to the substrate surface. The average column diameter of the columnar body was about 60 nm, and the growth direction of the columnar body was an angular direction of about 20 ° from the normal direction of the substrate. The vacancies between the many columnar bodies were not clearly observed by SEM observation. The Pt film was a dense non-columnar structure film without vacancies or the like.

(Comparative Example 1)
For the Zr film, a comparative multilayer element in which a Zr film and a Pt film were sequentially laminated on a Si substrate was obtained in the same manner as in Example 1 except that front deposition was performed. When SEM observation was performed in the same manner as in Example 1, the Zr film was a dense non-columnar structure film having no voids.

<Evaluation of Example 1 and Comparative Example 1>
Each of the laminated elements obtained in Example 1 and Comparative Example 1 was annealed at 500 ° C. for 10 minutes in an air atmosphere. Before and after annealing, a strip-shaped Si substrate was fixed at one end, and the amount of strain was measured. The internal stress of the thin film (= Zr / Pt laminated film) formed on the Si substrate was calculated from the measured strain amount.
The internal stress was calculated based on “Thin Film Optical Handbook”, Kodansha, Masao Manashita, Masaji Yoshida, p214-215. FIG. 5 is an explanatory diagram of the internal stress measurement method described in this document. This document describes that the internal stress applied to the thin film is expressed by the following formula when the strip-shaped substrate is distorted by the thin film formation.
σ = Et ² δ / {3 (1-v) dl ² }
(Where l is the length of the substrate, t is the thickness of the substrate, d is the thickness of the thin film, E is the Young's modulus of the substrate, and v is the Poisson's ratio of the substrate.)

<Result>
The results are shown in Table 1. In the table, the strain direction is “downward” when the Si substrate is distorted toward the thin film formed on the Si substrate (see FIG. 5), and “when the Si substrate is distorted in the opposite direction”. "Upward". When the strain direction is “downward”, the internal stress applied to the thin film formed on the Si substrate is a compressive stress, and when the strain direction is “upward”, the internal stress applied to the thin film formed on the Si substrate. The stress is a tensile stress.

  In both Example 1 and Comparative Example 1, the strain direction before annealing is downward, the internal stress applied to the thin film formed on the Si substrate is compressive stress, and the strain direction is reversed by annealing. The internal stress applied to the thin film formed on the Si substrate was a tensile stress. However, in Example 1 in which the Zr film is a columnar structure film, the strain amount is remarkably smaller than that in Comparative Example 1 before and after annealing, and the internal stress applied to the thin film formed on the Si substrate is remarkably large. It was small. From this result, it was shown that the columnar structure film has a high stress relaxation function.

(Example 2)
On the Si substrate, TiO ₂ was obliquely deposited using an EB deposition apparatus to form a TiO ₂ film having a thickness of 200 nm. The film forming conditions are as follows: the substrate temperature is room temperature, the angle of inclination with respect to the substrate deposition source (= the angle between the normal direction of the substrate surface and the direction of the deposition source viewed from the substrate is 40 °, and the distance between the substrate and the deposition source is 100 mm. The film forming atmosphere was an Ar atmosphere of 0.9 Pa, and the input power was 150 W.

On the TiO ₂ film, Pt was vapor-deposited using a sputtering apparatus to form a Pt lower electrode having a thickness of 100 nm. The film formation conditions were as follows: the substrate temperature was room temperature, the distance between the substrate and the evaporation source was 100 mm, the film formation atmosphere was an Ar atmosphere of 0.9 Pa, and the input power was 150 W.

A PZT piezoelectric film (Pb (Zr _0.52 Ti _0.48 ) O ₃ ) having a thickness of 10.0 μm is formed on the Pt lower electrode by an aerosol deposition method at a film forming temperature of 600 ° C. After the film was baked at 800 ° C. for 3 hours.

  Finally, a Pt upper electrode having a thickness of 100 nm was formed on the PZT film under the same conditions as the lower electrode to obtain the piezoelectric element of the present invention.

When the cross section of the obtained element was observed by SEM, the TiO ₂ film was a columnar structure film composed of a number of columnar bodies extending in an oblique direction with respect to the substrate surface. The average column diameter of the columnar body was about 100 nm, and the growth direction of the columnar body was an angular direction of about 20 ° from the normal direction of the substrate. Slight vacancies were observed between the many columnar bodies, and the average diameter was estimated to be 10 nm or less. All of the Pt lower electrode, the PZT film, and the Pt upper electrode were dense non-columnar structure films having no voids. When observed with an optical microscope, there were no cracks or the like in the device.

(Comparative Example 2)
A comparative piezoelectric element was obtained in the same manner as in Example 2 except that the conditions for forming the TiO ₂ film were changed. In Comparative Example 2, a TiO ₂ film having a thickness of 200 nm was formed on the Si substrate by front-depositing TiO ₂ using a sputtering apparatus at a substrate temperature of 600 ° C. The distance between the substrate and the evaporation source and the film formation atmosphere were the same as in Example 2. Was carried out in the same manner as in SEM observation as in Example 2, TiO ₂ film was air without holes or the like dense isotropic polycrystalline film (the non-columnar structure film). The obtained piezoelectric element had cracks that could be seen with the naked eye.

From a comparison between Example 2 and Comparative Example 2, the TiO ₂ film of the columnar structure film functions well as a stress relaxation layer, and cracks are also generated when a relatively thick PZT piezoelectric film is formed by the aerosol deposition method. It became clear that it can be suppressed.

(Example 3)
After forming a 10 nm thick Ti adhesion layer on the Si substrate, Pt was obliquely deposited to form a 100 nm thick Pt lower electrode. Next, a PZT piezoelectric film (Pb (Zr _0.52 Ti _0.48 ) O ₃ ) having a thickness of 10.0 μm is formed on the Pt lower electrode by an aerosol deposition method at a film forming temperature of 600 ° C. After film formation, baking was performed at 800 ° C. for 3 hours. Finally, a Pt upper electrode having a thickness of 100 nm was formed on the PZT film under the same conditions as the upper electrode of Example 2 to obtain the piezoelectric element of the present invention.

  When SEM observation was performed in the same manner as in Example 2, the Pt lower electrode was a columnar structure film composed of a number of columnar bodies extending in an oblique direction with respect to the substrate surface. The average column diameter of the columnar body was about 150 nm, and the growth direction of the columnar body was an angular direction of about 15 ° from the normal direction of the substrate. Slight vacancies were observed between the many columnar bodies, and the average diameter was estimated to be 10 nm or less. The PZT film and the Pt upper electrode were dense non-columnar structure films having no voids. When observed with an optical microscope, there were no cracks or the like in the device.

  The laminated element of the present invention can be preferably applied to a piezoelectric element used for an ink jet recording head, a ferroelectric memory (FRAM), a pressure sensor, and the like.

(A) is principal part sectional drawing which shows 1st Embodiment of the piezoelectric element (laminated element) based on this invention, and the structure of an inkjet recording head provided with this, (b) is a partial expanded sectional view. (A) is principal part sectional drawing which shows 2nd Embodiment of the piezoelectric element (laminated | stacked element) which concerns on this invention, and the structure of an inkjet recording head provided with this, (b) is a partial expanded sectional view. 1 is a diagram illustrating a configuration example of an ink jet recording apparatus including the ink jet recording head of FIG. Partial top view of the ink jet recording apparatus of FIG. The figure for demonstrating the evaluation method of Example 1 and Comparative Example 1

Explanation of symbols

1, 3 Piezoelectric element
2, 4 Inkjet recording head 10 Substrate 20 Columnar structure film (stress relaxation layer)
DESCRIPTION OF SYMBOLS 21 Columnar body 22 Hole 30 Lower electrode 31 Lower electrode which consists of columnar structure film (stress relaxation layer) 32 Columnar body 33 Hole 40 Piezoelectric film (non-columnar structure film)
50 Upper electrode 70 Ink nozzle (ink storage and discharge member)
71 Ink chamber 72 Ink discharge port 100 Inkjet recording apparatus

Claims (15)

A columnar structure film composed of a number of columnar bodies extending in a non-parallel direction to the substrate surface of the substrate and a non-columnar structure film are sequentially stacked on the substrate,
The multilayer element, wherein the columnar structure film is a stress relaxation layer that relieves stress applied to the non-columnar structure film during and / or after film formation. 2. The difference between the thermal expansion coefficient of the constituent material of the substrate and the thermal expansion coefficient of the constituent material of the non-columnar structure film is 4.0 × 10 ⁻⁶ / ° C. or more. Laminated element. In a piezoelectric element in which a lower electrode, a piezoelectric film, and an upper electrode are sequentially stacked on a substrate, and an electric field is applied to the piezoelectric film by the lower electrode and the upper electrode.
A piezoelectric element comprising a columnar structure film comprising a plurality of columnar bodies extending in a non-parallel direction with respect to a substrate surface of the substrate between the substrate and the piezoelectric film. In a piezoelectric element in which a lower electrode, a piezoelectric film, and an upper electrode are sequentially stacked on a substrate, and an electric field is applied to the piezoelectric film by the lower electrode and the upper electrode.
The piezoelectric element, wherein the lower electrode is a columnar structure film including a plurality of columnar bodies extending in a non-parallel direction with respect to the substrate surface of the substrate.   5. The piezoelectric element according to claim 3, wherein the columnar structure film is a stress relaxation layer that relaxes stress applied to the piezoelectric film during and / or after film formation.   The piezoelectric element according to claim 3, wherein an average column diameter of the plurality of columnar bodies forming the columnar structure film is 20 to 200 nm.   The piezoelectric element according to any one of claims 3 to 6, wherein in the columnar structure film, holes extending in substantially the same direction as the columnar bodies are formed between the plurality of columnar bodies. .   The piezoelectric element according to claim 3, wherein the plurality of columnar bodies forming the columnar structure film extend in an oblique direction with respect to the substrate surface.   The piezoelectric element according to claim 8, wherein the columnar structure film is formed by oblique vapor deposition.   The piezoelectric element according to claim 3, wherein the columnar structure film has a thickness of 0.1 to 5.0 μm.   The piezoelectric element according to claim 3, wherein the piezoelectric film has a thickness of 2.0 to 30.0 μm.   The piezoelectric element according to claim 3, wherein the piezoelectric film is formed by an aerosol deposition method. The piezoelectric element according to any one of claims 3 to 12, wherein the piezoelectric film is mainly composed of one or more perovskite oxides represented by the following general formula.
General formula ABO ₃
(In the formula, A: an element at the A site, at least one element selected from the group consisting of Pb, Ba, Nb, La, Li, Sr, Bi, Na, and K;
B: B site element, at least one element selected from the group consisting of Cd, Fe, Ti, Ta, Mg, Mo, Ni, Nb, Zr, Zn, W, and Yb,
O: oxygen atom) The piezoelectric element according to any one of claims 3 to 13,
An ink jet recording head, comprising: an ink chamber in which ink is stored; and an ink storage and discharge member having an ink discharge port through which the ink is discharged from the ink chamber to the outside.   An ink jet recording apparatus comprising the ink jet recording head according to claim 14.

Images