JP2004339008A - Sheet material for forming piezoelectric element - Google Patents
Sheet material for forming piezoelectric element Download PDFInfo
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- JP2004339008A JP2004339008A JP2003138321A JP2003138321A JP2004339008A JP 2004339008 A JP2004339008 A JP 2004339008A JP 2003138321 A JP2003138321 A JP 2003138321A JP 2003138321 A JP2003138321 A JP 2003138321A JP 2004339008 A JP2004339008 A JP 2004339008A
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- PXXNTAGJWPJAGM-UHFFFAOYSA-N vertaline Natural products C1C2C=3C=C(OC)C(OC)=CC=3OC(C=C3)=CC=C3CCC(=O)OC1CC1N2CCCC1 PXXNTAGJWPJAGM-UHFFFAOYSA-N 0.000 description 4
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
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- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 2
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- 229910052785 arsenic Inorganic materials 0.000 description 1
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 1
- 239000013039 cover film Substances 0.000 description 1
- NKZSPGSOXYXWQA-UHFFFAOYSA-N dioxido(oxo)titanium;lead(2+) Chemical compound [Pb+2].[O-][Ti]([O-])=O NKZSPGSOXYXWQA-UHFFFAOYSA-N 0.000 description 1
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 1
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Landscapes
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は圧電素子形成用シートに関し、更に詳しくは無機物質と熱可塑性樹脂からなり厚みが２〜１０００μｍである自立性多孔質の圧電素子形成用シート材料に関する。また圧電素子の製造に関して、該圧電素子形成用シート材料を用いる製造方法に関する。
【０００２】
【従来の技術】
エレクトロニクス機器分野において、微小な圧電素子を高密度に配置できるマイクロ化が求められており、なかでも圧電素子をマイクロ化し、薄膜化して、しかもより大きな屈曲性を持つものが望まれている。
【０００３】
従来この様な圧電素子層は、スクリーン印刷法あるいはグリーンシート法により形成されている。（特許文献１．２）しかしながらいずれの方法も、金属電極に沿った凹凸が残存する現象（ピローイング）が生じ平坦面を得ることが難しい。また十分な絶縁耐圧が得られないため圧電体層を薄くすることが極めて難しい。
【０００４】
【特許文献１】
特開平５−２５４９４６号公報 ２頁
【０００５】
【特許文献２】
特開平９−３３１０８７号公報 ２頁
【０００６】
【発明が解決しようとする課題】
本発明の主な目的は、圧電素子形成用シート材料を提供することにある、より詳細には薄膜の圧電素子形成用シート材料を提供することにある。
【０００７】
本発明の他の目的は、圧電体層を得るのに適した圧電素子形成用シート材料の製造方法を提供することにある。
【０００８】
本発明の他の目的は、該圧電素子形成用シート材料を用いた圧電素子の製造方法を提供することにある。
【０００９】
【課題を解決するための手段】
本発明者らは鋭意検討の結果、無機物質を分散した自立性多孔質シートを用いることにより上記目的を達成することを見出し、本発明に至った。
【００１０】
すなわち本発明は次のとおりのものである。
１． 無機物質と熱可塑性樹脂からなり厚みが２〜１０００μｍである自立性多孔質シート材料であって、無機物質と該熱可塑性樹脂の合計量に基づいた容量百分率で無機物質を３０容量％、該熱可塑性樹脂を１〜７０容量％含有することを特徴とする圧電素子形成用シート材料。
２． 熱可塑性樹脂が実質的にポリオレフィン樹脂である上記に記載の圧電素子形成用シート材料。
３． 熱可塑性樹脂が実質的に少なくとも５ｄｌ／ｇの固有粘度を有するポリエチレンからなる上記に記載の圧電素子形成用シート材料。
４． 気孔率が５０〜９５％である上記に記載の圧電素子形成用シート材料。
５． 無機物質が焼結可能なセラミックス成分であることを特徴とする上記に記載の圧電素子形成用シート材料。
６． 無機物質と該熱可塑性樹脂の合計量に基づいた容量百分率で無機物質を４５容量％以上含有することを特徴とする上記に記載の圧電素子形成用シート材料。
７． 厚みが２〜５００μｍである上記に記載の圧電素子形成用シート材料。
８． 無機物質と熱可塑性樹脂からなり、厚みが２〜１０００μｍ以下であり、該無機物質と該熱可塑性樹脂の合計量に基づいた容量百分率で無機物質を３０容量％以上、該熱可塑性樹脂を１〜７０容量％含有する自立性多孔質の圧電素子形成用シート材料を製造する方法であって、実質的に溶剤、無機物質及び熱可塑性樹脂からなる熱可逆的ゲル化溶液を用いてゲル化製膜し、ついで延伸することによりシート状に形成したことを特徴とする圧電素子形成用シート材料の製造方法。
９． 上記に記載の圧電素子形成用シート材料を、空気中で仮焼して熱可塑性樹脂を除去した後、磁器容器内で焼成する工程を有する圧電素子の製造方法。
【００１１】
【発明の実施の形態】
以下、本発明を詳細に説明する。
本発明のシート材料は実質的に無機物質と熱可塑性樹脂とからなる。ここで現在用いられているシート材料の製法について説明する。
【００１２】
本発明のシートは無機物質を最大で９９％含有することが可能であるため、高密度でピンホールの少ない圧電体層を形成することができ、絶縁耐圧が著しく向上する。その結果圧電体層の薄層化が可能であり、圧電素子のマイクロ化に有利である。
【００１３】
無機物質の含有率は、無機物質と該熱可塑性樹脂の合計量に基づいた重量百分率で３０容量％以上、好ましくは４５容量％以上、さらに好ましくは６０〜９５容量％、より好ましくは８０〜９５容量％である。９９容量％より無機物質の含有率が多い場合は、機械的強度に問題が生じる場合がある。逆に無機物質が少ない場合は、無機物質の密度が低いため焼成後の無機膜の密度が低下し、絶縁耐圧の低下等を生じる。
【００１４】
また本発明のシート材料は無機物質とその結着剤としての熱可塑性樹脂以外には基本的には溶剤、可塑剤成分を含有しない。従って高温により脱バインダさせ、さらに焼結するときに溶剤の気化による気泡生成等の問題が少ない。
【００１５】
本発明のシート材料は自立性の多孔シートである事を特徴としている。現行用いられているグリーンシートはそれ自体に基本的に自立性がないためベースフィルム、カバーフィルムに挟まれた形で供給されている。その結果使用時にこれらのフィルムを除去する必要があり廃棄物処理の観点から好ましくない。またグリーンシート自体タック性を有す自己保持性のないシートでありハンドリングも困難である。
【００１６】
一方本発明のシート材料は自立性を有するため、ベースフィルムのような不要な廃棄物を用いる必要もなく、引張強度に優れハンドリングの面でもきわめて優れている。
【００１７】
本発明のシートの熱可塑性樹脂成分は実質的にポリオレフィン樹脂が好ましい。ここで実質的というのはポリオレフィン樹脂中に安定剤、可塑剤等、少量の改質成分を含んでも問題ないということである。ポリオレフィン樹脂としてはポリエチレン樹脂、ポリプロピレン樹脂等が例示できる。更には該熱可塑性樹脂は実質的に少なくとも５ｄｌ／ｇの固有粘度を有するポリエチレン樹脂である。固有粘度が５ｄｌ／ｇ未満の場合、シートとしての強度が不十分となり自立性等が失われる可能性がある。このような条件を満たすポリエチレン樹脂としては超高分子量ポリエチレン（ＵＨＭＷＰＥ）や高密度ポリエチレン（ＨＤＰＥ）が例示できる。またこれらのブレンド物、あるいはこれらの高分子ポリマーと低分子ポリマーのブレンド体であっても、ブレンド体の固有粘度が５ｄｌ／ｇ以上であれば差し支えない。
【００１８】
本発明の圧電素子形成用シート材料の厚みとしては、２〜１０００μｍ以下である。なお本発明のような多孔質シートの場合、測定の方法により大きく厚みが異なる。本願発明での厚みは光学顕微鏡、レーザー顕微鏡あるいはＳＥＭ等の観察により非接触で測定した厚みである。１０００μｍより厚い場合は、電子部品のマイクロ化の流れと相反することになる。好ましくは２０μｍ以上５００μｍ以下である。２０μｍより薄い場合、無機圧電体を保持できない可能性がある。本発明における多孔質シートを用いて圧電体層を作成する場合、熱プレスにより該多孔質シートの空孔をほぼ実質的につぶす工程を有する。従って実際に作成される圧電体層は該多孔質シートの見掛けの厚みよりもはるかに薄いものとなり、薄層化が容易である。またこの際この空孔が電極の凹凸を吸収するため、表面の平坦化を行うことができる。これらの点が従来のグリーンシート法や印刷法により得られたものとは大きく異なる。
【００１９】
本発明のシート材料は上記のように多孔質であることを特徴としている。現行の印刷法やグリーンシート法ではガラス基板に形成された金属電極の凹凸を平坦化することができず、圧電体層表面もその影響で凹凸化することを回避することは困難であった。しかし本発明のシート材料を用いた場合、該シート材料を基板に熱圧着する際該多孔質シートが電子部品の凹凸を吸収し、圧電体層焼成後表面が平坦化される。
【００２０】
本発明のシート材料を構成する自立性多孔質シートの多孔性としては、気孔率として３０〜９５％が好適である。ここで気孔率は下記式
気孔率＝（ρ０−ρ）／ρ０ Ｘ １００（％）
で定義される。ここでρ０は気孔がない場合の理論密度、ρは気孔を含有した多孔質シートの実測の密度である。
【００２１】
本発明の圧電素子形成用シート材料に用いる無機物質としては、焼結可能なセラミックス成分であることが好ましい。焼結可能なセラミックス成分としては例えば、チタン酸鉛、ジルコン酸チタン酸鉛、酸化ジルコニウム、酸化アルミニウム、酸化マグネシウム、ムライト、窒化アルミニウム、窒化珪素、ガラス等が挙げられる。安定化された酸化ジルコニウムは、振動部が薄くても機械強度が高いこと、靱性が高いこと、導電膜と化学反応性が小さいこと等のため、特に好ましい。
【００２２】
本発明の圧電素子形成用シート材料の製造方法としては、特に制限はないが、実質的にゲル化製膜及び得られたゲル化シートを延伸することにより製造することができる。例えば、無機の圧電体粉末をミリング装置等を用いて適当なゲル化溶媒中に分散させた後、結着剤としての熱可塑性樹脂と適当な上記ゲル化溶媒の残りを加えて、該熱可塑性樹脂と該溶媒を加熱溶解させることによりゾル化させる。このようにして得られたゾル化組成物をゲル化温度以上の温度にてテープ状に付形し、該シート状物をゲル化点以下に急冷することによりゲル化シートを作成する。このゲル化シートを、熱可塑性樹脂のガラス転移点以上の温度で１軸あるいは２軸に延伸し、その後熱固定することにより製造することができる。かかる溶媒としては、例えばポリエチレンを熱可塑性樹脂として用いる場合、通常デカリン、ヘキサン、パラフィン等が挙げられる。これらは２種類以上組み合わせて用いてもよい。
【００２３】
本発明によれば、得られた圧電素子形成用シート材料を、空気中で仮焼して熱可塑性樹脂を除去した後、磁器容器内で焼成する工程により圧電素子を製造することができる。
【００２４】
圧電素子の構成としては例えば、半導体基板と、半導体基板上に設けられた下地導電体層と、下地導電体層上に設けられた圧電膜と、圧電膜上に設けられた導電性電極パターンとからなるものが挙げられる。圧電素子の製法としては、基板上に反応層を形成させるための薄膜を形成し、この薄膜上に下部電極材料及び圧電体材料を積層し、高温で熱処理して前記薄膜と基板及び下部電極材料を反応させて反応層を形成し、基板と下部電極を接合する方法が挙げられる。
【００２５】
このような従来公知である種々の圧電素子の製法に本発明の圧電素子形成用シート材料を用いることにより、良好な特性でありかつ薄膜である圧電素子を得ることができる。
【００２６】
本発明の圧電素子形成用シート材料を用いて圧電素子を得る場合は、金属電極に沿った凹凸が残存する現象（ピローイング）が解消され、平坦面を得ることが可能となる。また薄膜の圧電素子であっても、十分な絶縁耐圧が得られる。
【００２７】
本発明によって作成された圧電素子は、圧電式アクチュエーター、スピーカー用振動子、高周波フィルター、発振子、発音体マイク、着火用素子などに使用可能である。
【００２８】
【発明の効果】
本発明によれば、無機物質と熱可塑性樹脂からなり厚みが２〜１０００μｍである自立性多孔質シート材料を用いることにより、圧電素子の圧電体層をより高密度かつ平坦に充填することができる。その結果、圧電体層をより高絶縁耐圧化、薄層化することができる。これにより良好な特性の薄膜圧電素子が提供でき、小型・軽量の電子装置を提供することができる。
【００２９】
【実施例】
次に本発明を以下の実施例につき詳細に説明するが、本発明は以下の実施例に制限されるものではない。記載の量を以下に記載の方法で測定した。
【００３０】
延伸シートの厚さは、走査型電子顕微鏡ｏｒレーザー顕微鏡で測定した。
シートの密度は、概知容量のフィルム片の重量を測定することにより決定した。気孔率は、測定した密度ρと空孔の無い無機物含有シートの理論密度ρ０の密度から以下のように決定した。
気孔率＝（ρ０−ρ）／ρ０ Ｘ １００（％）
引張強さは、試料の横断全面をベースとしてＡＳＴＭ標準規格Ｄ８８２に基づいて測定した。
【００３１】
［実施例１］
デカリン５６重量部に、パラフィン油（Ｓｈｅｌｌ製 Ｏｎｄｉｎａ Ｏｉｌ６８）３４重量部及び１５ｄｌ／ｇの極限粘度数（デカリン中１３５℃で測定）を有する超高分子量ポリエチレン（三井化学株式会社製 ハイゼックスミリオン２４０Ｍ）１０重量部を加え、チタン酸ジルコン酸鉛（ＰＺＴ）９０重量部を分散させた。該分散体を２軸混練押し出し機を用いて１８０℃で溶解させてゾル化し、該ゾル化物をフラットフィルム押出ダイを介して１５０℃で押出した。ついで、該押出品を水浴を通過させて冷却しゲル化させた。このようにして成形されたシートを８０℃で１時間乾燥させることにより、デカリンを除去した。このシートの厚みは７００μｍであった。
【００３２】
このパラフィンがシート中に残留したパラフィン油含有シートを、延伸中の温度を１１０から１２５℃でＭＤ方向に２倍、ＴＤ方向に７倍に二軸延伸し、その後１４０℃で１分間熱固定処理を行った。シートの延伸後、パラフィン油をフィルムからヘキサンを用いて抽出し、８０℃で１時間乾燥した。得られたこのシートは多孔質であり、下記表１に記載の特性を有していた。
【００３３】
得られた多孔質シートの厚みは液体窒素を用いて冷凍割断したシート断面をレザーテック株式会社製 リアルタイム走査型レーザー顕微鏡１ＬＭ２１Ｄにて測定した。
【００３４】
また密度ρ０は重量と上記方法で求めた厚み、面積を用いて計算した。理論密度ρはρ＝５．０ｇ／ｃｍ３であった。
【００３５】
作製したシートを、厚さ２ｍｍのジルコニア基板に１５５℃にて圧力１０ＭＰａで３分間熱圧着し、３℃／分の昇温速度で６００℃まで昇温し、６００℃にて１０分保持した後、冷却した。得られた圧電体膜の特性を表１に示す。
【００３６】
【表１】
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piezoelectric element forming sheet, and more particularly, to a self-supporting porous piezoelectric element forming sheet material made of an inorganic substance and a thermoplastic resin and having a thickness of 2 to 1000 μm. In addition, the present invention relates to a method of manufacturing a piezoelectric element using the piezoelectric element forming sheet material.
[0002]
[Prior art]
In the field of electronic devices, there is a demand for microfabrication in which minute piezoelectric elements can be arranged at a high density. In particular, microfabricated piezoelectric elements that are made thinner and that have greater flexibility are desired.
[0003]
Conventionally, such a piezoelectric element layer is formed by a screen printing method or a green sheet method. However, in any of the methods, a phenomenon (pillowing) that unevenness remains along the metal electrode occurs, and it is difficult to obtain a flat surface. Further, it is extremely difficult to make the piezoelectric layer thin because a sufficient withstand voltage cannot be obtained.
[0004]
[Patent Document 1]
JP-A-5-254946, page 2 [0005]
[Patent Document 2]
JP-A-9-331087, page 2
[Problems to be solved by the invention]
A main object of the present invention is to provide a sheet material for forming a piezoelectric element, and more specifically, to provide a thin-film sheet material for forming a piezoelectric element.
[0007]
Another object of the present invention is to provide a method for producing a piezoelectric element forming sheet material suitable for obtaining a piezoelectric layer.
[0008]
Another object of the present invention is to provide a method for manufacturing a piezoelectric element using the sheet material for forming a piezoelectric element.
[0009]
[Means for Solving the Problems]
Means for Solving the Problems As a result of intensive studies, the present inventors have found that the above object is achieved by using a self-supporting porous sheet in which an inorganic substance is dispersed, and have accomplished the present invention.
[0010]
That is, the present invention is as follows.
1. A self-supporting porous sheet material comprising an inorganic substance and a thermoplastic resin and having a thickness of 2 to 1000 μm, wherein 30% by volume of the inorganic substance is expressed as a volume percentage based on the total amount of the inorganic substance and the thermoplastic resin. A sheet material for forming a piezoelectric element, comprising 1 to 70% by volume of a plastic resin.
2. The sheet material for forming a piezoelectric element according to the above, wherein the thermoplastic resin is substantially a polyolefin resin.
3. The piezoelectric element forming sheet material as described above, wherein the thermoplastic resin is substantially made of polyethylene having an intrinsic viscosity of at least 5 dl / g.
4. The sheet material for forming a piezoelectric element according to the above, wherein the porosity is 50 to 95%.
5. The above-mentioned sheet material for forming a piezoelectric element, wherein the inorganic substance is a ceramic component capable of being sintered.
6. The sheet material for forming a piezoelectric element according to the above, wherein the material contains 45% by volume or more of the inorganic material in a volume percentage based on the total amount of the inorganic material and the thermoplastic resin.
7. The sheet material for forming a piezoelectric element according to the above, which has a thickness of 2 to 500 µm.
8. It is composed of an inorganic substance and a thermoplastic resin, has a thickness of 2 to 1000 μm or less, and contains 30% by volume or more of the inorganic substance in a volume percentage based on the total amount of the inorganic substance and the thermoplastic resin, and 1 to 100% of the thermoplastic resin. A method for producing a self-supporting porous piezoelectric element-forming sheet material containing 70% by volume, comprising gelling using a thermoreversible gelling solution substantially consisting of a solvent, an inorganic substance and a thermoplastic resin. A method for producing a sheet material for forming a piezoelectric element, wherein the sheet material is formed by stretching.
9. A method for producing a piezoelectric element, comprising a step of calcining the above-described sheet material for forming a piezoelectric element in air to remove a thermoplastic resin, and then firing in a porcelain container.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The sheet material of the present invention substantially comprises an inorganic substance and a thermoplastic resin. Here, the manufacturing method of the sheet material currently used will be described.
[0012]
Since the sheet of the present invention can contain up to 99% of an inorganic substance, a piezoelectric layer having high density and few pinholes can be formed, and the withstand voltage can be significantly improved. As a result, the thickness of the piezoelectric layer can be reduced, which is advantageous for miniaturization of the piezoelectric element.
[0013]
The content of the inorganic substance is 30% by volume or more, preferably 45% by volume or more, more preferably 60 to 95% by volume, more preferably 80 to 95% by weight based on the total amount of the inorganic substance and the thermoplastic resin. % By volume. When the content of the inorganic substance is more than 99% by volume, a problem may occur in mechanical strength. Conversely, when the amount of the inorganic substance is small, the density of the inorganic film after firing is reduced due to the low density of the inorganic substance, which causes a decrease in the withstand voltage.
[0014]
Further, the sheet material of the present invention basically does not contain a solvent and a plasticizer component other than the inorganic substance and the thermoplastic resin as its binder. Therefore, there are few problems such as generation of bubbles due to evaporation of the solvent when the binder is removed at a high temperature and further sintered.
[0015]
The sheet material of the present invention is characterized in that it is a self-supporting porous sheet. Currently used green sheets are not supplied by themselves because they are basically not self-supporting, so they are sandwiched between a base film and a cover film. As a result, it is necessary to remove these films at the time of use, which is not preferable from the viewpoint of waste disposal. Further, the green sheet itself is a sheet having tackiness and having no self-holding property, and is difficult to handle.
[0016]
On the other hand, since the sheet material of the present invention is self-supporting, there is no need to use unnecessary waste such as a base film, and the sheet material is excellent in tensile strength and extremely excellent in handling.
[0017]
Preferably, the thermoplastic resin component of the sheet of the present invention is substantially a polyolefin resin. Here, "substantially" means that there is no problem even if a small amount of a modifying component such as a stabilizer or a plasticizer is contained in the polyolefin resin. Examples of the polyolefin resin include a polyethylene resin and a polypropylene resin. Further, the thermoplastic resin is a polyethylene resin having an intrinsic viscosity of substantially at least 5 dl / g. When the intrinsic viscosity is less than 5 dl / g, the strength as a sheet becomes insufficient, and the self-sustainability and the like may be lost. Ultra-high molecular weight polyethylene (UHMWPE) and high-density polyethylene (HDPE) can be exemplified as polyethylene resins satisfying such conditions. Even if these blends or a blend of these high-molecular polymers and low-molecular polymers are used, the blend may have an intrinsic viscosity of 5 dl / g or more.
[0018]
The thickness of the piezoelectric element forming sheet material of the present invention is 2 to 1000 μm or less. In the case of a porous sheet as in the present invention, the thickness varies greatly depending on the method of measurement. The thickness in the present invention is a thickness measured in a non-contact manner by observation with an optical microscope, a laser microscope, an SEM, or the like. If the thickness is more than 1000 μm, it will be contrary to the flow of micronization of electronic components. Preferably it is 20 μm or more and 500 μm or less. If the thickness is less than 20 μm, there is a possibility that the inorganic piezoelectric body cannot be held. When a piezoelectric layer is formed using the porous sheet according to the present invention, the method includes a step of substantially substantially crushing the pores of the porous sheet by hot pressing. Therefore, the piezoelectric layer actually formed is much thinner than the apparent thickness of the porous sheet, and it is easy to reduce the thickness. At this time, the holes absorb the irregularities of the electrode, so that the surface can be flattened. These points are significantly different from those obtained by the conventional green sheet method or printing method.
[0019]
The sheet material of the present invention is characterized by being porous as described above. The current printing method and the green sheet method cannot flatten the unevenness of the metal electrode formed on the glass substrate, and it has been difficult to avoid the unevenness of the surface of the piezoelectric layer due to the influence. However, when the sheet material of the present invention is used, when the sheet material is thermocompression-bonded to a substrate, the porous sheet absorbs the unevenness of the electronic component, and the surface is flattened after firing the piezoelectric layer.
[0020]
The porosity of the self-supporting porous sheet constituting the sheet material of the present invention is preferably 30 to 95% as a porosity. Here, the porosity is expressed by the following formula: porosity = (ρ0−ρ) / ρ0 × 100 (%)
Is defined by Here, ρ0 is the theoretical density when there are no pores, and ρ is the actually measured density of the porous sheet containing pores.
[0021]
The inorganic substance used for the piezoelectric element forming sheet material of the present invention is preferably a sinterable ceramic component. Examples of the sinterable ceramic component include lead titanate, lead zirconate titanate, zirconium oxide, aluminum oxide, magnesium oxide, mullite, aluminum nitride, silicon nitride, and glass. Stabilized zirconium oxide is particularly preferred because of its high mechanical strength, high toughness, and low chemical reactivity with the conductive film even when the vibrating portion is thin.
[0022]
The method for producing the sheet material for forming a piezoelectric element of the present invention is not particularly limited, but it can be produced by substantially forming a gelled film and stretching the obtained gelled sheet. For example, after dispersing an inorganic piezoelectric powder in an appropriate gelling solvent using a milling device or the like, adding a thermoplastic resin as a binder and the remainder of the appropriate gelling solvent, the thermoplastic resin is added. The resin and the solvent are dissolved by heating to form a sol. The sol composition thus obtained is shaped into a tape at a temperature equal to or higher than the gelation temperature, and the sheet is rapidly cooled to a gel point or lower to prepare a gel sheet. The gelled sheet can be manufactured by stretching uniaxially or biaxially at a temperature equal to or higher than the glass transition point of the thermoplastic resin and then heat-setting. As the solvent, for example, when polyethylene is used as the thermoplastic resin, usually, decalin, hexane, paraffin and the like can be mentioned. These may be used in combination of two or more.
[0023]
According to the present invention, a piezoelectric element can be manufactured by calcining the obtained sheet material for forming a piezoelectric element in air to remove the thermoplastic resin, and then firing the sheet in a porcelain container.
[0024]
As the configuration of the piezoelectric element, for example, a semiconductor substrate, a base conductor layer provided on the semiconductor substrate, a piezoelectric film provided on the base conductor layer, and a conductive electrode pattern provided on the piezoelectric film And those consisting of As a method of manufacturing a piezoelectric element, a thin film for forming a reaction layer is formed on a substrate, a lower electrode material and a piezoelectric material are laminated on the thin film, and heat treatment is performed at a high temperature, and the thin film and the substrate and the lower electrode material are heated. Are reacted to form a reaction layer, and the substrate and the lower electrode are joined.
[0025]
By using the sheet material for forming a piezoelectric element of the present invention in such a conventionally known method of manufacturing various piezoelectric elements, a piezoelectric element having good characteristics and a thin film can be obtained.
[0026]
When a piezoelectric element is obtained using the piezoelectric element forming sheet material of the present invention, a phenomenon (pillowing) in which irregularities remain along metal electrodes is eliminated, and a flat surface can be obtained. Further, even with a thin film piezoelectric element, a sufficient withstand voltage can be obtained.
[0027]
The piezoelectric element produced by the present invention can be used for a piezoelectric actuator, a vibrator for a speaker, a high-frequency filter, an oscillator, a sounding microphone, an ignition element, and the like.
[0028]
【The invention's effect】
According to the present invention, by using a self-supporting porous sheet material made of an inorganic substance and a thermoplastic resin and having a thickness of 2 to 1000 μm, the piezoelectric layer of the piezoelectric element can be more densely and flatly filled. . As a result, the piezoelectric layer can have a higher dielectric strength and a lower thickness. As a result, a thin film piezoelectric element having good characteristics can be provided, and a small and lightweight electronic device can be provided.
[0029]
【Example】
Next, the present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples. The stated amounts were measured by the methods described below.
[0030]
The thickness of the stretched sheet was measured with a scanning electron microscope or a laser microscope.
Sheet density was determined by measuring the weight of a piece of film of known capacity. The porosity was determined as follows from the measured density ρ and the density of the theoretical density ρ0 of the inorganic substance-containing sheet having no pores.
Porosity = (ρ0−ρ) / ρ0 × 100 (%)
Tensile strength was measured according to ASTM Standard D882 based on the entire cross section of the sample.
[0031]
[Example 1]
Ultra high molecular weight polyethylene (Hizex Million 240M, manufactured by Mitsui Chemicals, Inc.) having 56 parts by weight of decalin, 34 parts by weight of paraffin oil (Ondina Oil 68 manufactured by Shell) and an intrinsic viscosity of 15 dl / g (measured at 135 ° C. in decalin) 10 By weight, 90 parts by weight of lead zirconate titanate (PZT) was dispersed. The dispersion was melted at 180 ° C. using a twin-screw extruder to form a sol, and the sol was extruded at 150 ° C. through a flat film extrusion die. The extrudate was then cooled by passing through a water bath to gel. The thus formed sheet was dried at 80 ° C. for 1 hour to remove decalin. The thickness of this sheet was 700 μm.
[0032]
The paraffin oil-containing sheet with the paraffin remaining in the sheet is biaxially stretched at a temperature during stretching of 110 to 125 ° C. twice in the MD direction and seven times in the TD direction, and then heat-set at 140 ° C. for 1 minute. Was done. After stretching the sheet, paraffin oil was extracted from the film using hexane and dried at 80 ° C. for 1 hour. The obtained sheet was porous and had the properties shown in Table 1 below.
[0033]
The thickness of the obtained porous sheet was measured with a real-time scanning laser microscope 1LM21D manufactured by Leathertech Co., Ltd. on a section of the sheet frozen and cut using liquid nitrogen.
[0034]
The density ρ0 was calculated using the weight and the thickness and area obtained by the above method. The theoretical density ρ was 5.0 g / cm 3 .
[0035]
The prepared sheet is thermocompression-bonded to a zirconia substrate having a thickness of 2 mm at 155 ° C. at a pressure of 10 MPa for 3 minutes, heated to 600 ° C. at a rate of 3 ° C./min, and held at 600 ° C. for 10 minutes. And cooled. Table 1 shows the characteristics of the obtained piezoelectric film.
[0036]
[Table 1]
Claims (9)
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| JP2003138321A JP2004339008A (en) | 2003-05-16 | 2003-05-16 | Sheet material for forming piezoelectric element |
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04500835A (en) * | 1989-07-20 | 1992-02-13 | デーエスエム・ナムローゼ・フェンノートシャップ | Thin inorganic molded body containing organic binder and method for producing the same |
| JP2003045737A (en) * | 2001-07-31 | 2003-02-14 | Tdk Corp | Method of manufacturing laminated component, and sheet for manufacturing the laminated component |
-
2003
- 2003-05-16 JP JP2003138321A patent/JP2004339008A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04500835A (en) * | 1989-07-20 | 1992-02-13 | デーエスエム・ナムローゼ・フェンノートシャップ | Thin inorganic molded body containing organic binder and method for producing the same |
| JP2003045737A (en) * | 2001-07-31 | 2003-02-14 | Tdk Corp | Method of manufacturing laminated component, and sheet for manufacturing the laminated component |
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