JP3892423B2 - Nozzle plate and manufacturing method thereof - Google Patents

Description

【０１２３】
ここで、Ｑ：ノズル先端部に誘起される電荷（Ｃ）、ε_０：真空の誘電率（Ｆ／ｍ）、ｄ：ノズルの直径（ｍ）、Ｖ_０：ノズルに印加する総電圧である。また、αは、ノズル形状などに依存する比例定数であり、１〜１．５程度の値を取るが、特にｄ＜＜ｈ（ｈ：ノズル（正確にはノズル孔）−基板間距離（ｍ））の時はほぼ１となる。
【０１２４】
また、基板として導電基板を用いた場合、ノズルと対向して基板内の対称位置に、上記電荷Ｑと反対の極性を持つ鏡像電荷Ｑ’が誘導されると考えられる。基板が絶縁体の場合は、誘電率によって定まる対称位置に同様に電荷Ｑと逆極性の映像電荷Ｑ’が誘導される。
【０１２５】
ノズル先端部における集中電界強度Ｅ_ｌｏｃは、先端部の曲率半径をＲと仮定すると、
【０１２６】
【数２】

【０１２７】
で与えられる。ここで、ｋは、ノズル形状などに依存する比例定数であり、１．５〜８．５程度の値を取るが、多くの場合５程度と考えられる（P.J. Birdseye and D.A. Smith, Surface Science, 23(1970), p.198-210）。また、ここでは、流体吐出モデルを簡単にするため、Ｒ＝ｄ／２と仮定する。これは、ノズル先端部において表面張力によって流体がノズル径ｄと同じ曲率径を持つ半球形状に盛り上がっている状態に相当する。
【０１２８】
ノズル先端部の流体に働く圧力のバランスを考える。まず、静電的な圧力Ｐ_ｅは、ノズル先端部の液面積をＳとすると、
【０１２９】
【数３】

【０１３０】
となる。（８）〜（１０）式より、圧力Ｐ_ｅは、α＝１とおいて、
【０１３１】
【数４】

【０１３２】
と表される。
【０１３３】
一方、ノズル先端部における流体の表面張力による圧力Ｐ_ｓとすると、
【０１３４】
【数５】

【０１３５】
となる。ここで、γ：表面張力である。静電的な力により吐出が起こる条件は、静電的な力が表面張力を上回ることなので、静電的な圧力Ｐ_ｅと表面張力による圧力Ｐ_ｓとの関係は、
【０１３６】
【数６】

【０１３７】
となる。
【０１３８】
図２に、ある直径ｄのノズルを与えた時の、表面張力による圧力Ｐ_ｓと静電的な圧力Ｐ_ｅとの関係を示す。流体の表面張力としては、流体が水（γ＝７２ｍＮ／ｍ）の場合を仮定している。ノズルに印加する電圧を７００Ｖとした場合、ノズル直径ｄが２５μｍにおいて静電的な圧力Ｐ_ｅが表面張力による圧力Ｐ_ｓを上回ることが示唆される。このことより、Ｖ_０とｄとの関係を求めると、
【０１３９】
【数７】

【０１４０】
が吐出の最低電圧を与える。
【０１４１】
また、その時の吐出圧力ΔＰは、
【０１４２】
【数８】

【０１４３】
より、
【０１４４】
【数９】

【０１４５】
となる。
【０１４６】
ある直径ｄのノズルに対し、局所的な電界強度によって吐出条件を満たす場合の吐出圧力ΔＰの依存性を図３に、また、吐出臨界電圧（すなわち吐出の生じる最低電圧）Ｖｃの依存性を図４に示す。
【０１４７】
図３から、局所的な電界強度によって吐出条件を満たす場合（Ｖ_０＝７００Ｖ，γ＝７２ｍＮ／ｍと仮定した場合）のノズル径の上限が２５μｍであることが分かる。
【０１４８】
図４の計算では、流体として水（γ＝７２ｍＮ／ｍ）及び有機溶剤（γ＝２０ｍＮ／ｍ）を想定し、ｋ＝５の条件を仮定した。この図より、微細ノズルによる電界の集中効果を考慮すると、吐出臨界電圧Ｖｃはノズル径の減少に伴い低下することが明らかであり、流体が水の場合においてノズル径が２５μｍの場合、吐出臨界電圧Ｖｃは７００Ｖ程度であることが分かる。
【０１４９】
従来の吐出モデルにおける電界の考え方、すなわちノズルに印加する電圧Ｖ_０とノズル−対向電極間距離ｈとによって定義される電界のみを考慮した場合では、ノズル径が微小になるに従い、吐出に必要な駆動電圧は増加する。
【０１５０】
これに対し、本願発明者らが提案する新たな吐出モデルのように、局所電界強度に注目すれば、微細ノズル化により吐出における駆動電圧の低下が可能となる。このような駆動電圧の低下は、装置の小型化およびノズルの高密度化において極めて有利となる。もちろん、駆動電圧を低下させることで、コストメリットの高い低電圧駆動ドライバの使用をも可能にする。
【０１５１】
さらに、上記吐出モデルでは、吐出に必要な電界強度は、局所的な集中電界強度に依存することになるため、対向電極の存在が必須とならない。すなわち、従来の吐出モデルでは、ノズル−基板間に電界を印加するため、絶縁体の基板に対してはノズルと反対側に対向電極を配置するか、あるいは基板を導電性とする必要があった。そして、対向電極を配置する場合、すなわち基板が絶縁体の場合では、使用できる基板の厚さに限界があった。
【０１５２】
これに対し、本発明の吐出モデルでは、対向電極を要さずに絶縁性基板などに対しても印字を行うことが可能となり、装置構成の自由度が増す。また、厚い絶縁体に対しても印字を行うことが可能となる。
【０１５３】
また、図５に、基板との間に働く鏡像力の大きさと基板からの距離ｈとの相関を示す。図より明らかなように、この鏡像力は基板とノズル間の距離が近くなるほどに顕著になり、特にｈが２０μｍ以下で顕著である。
【０１５４】
次に、吐出流量の精密制御について考えて見る。円筒状の流路における流量Ｑは、粘性流の場合、以下のハーゲン・ポアズイユの式によって表される。いま、円筒形のノズルを仮定し、このノズルを流れる流体の流量Ｑは、次式で表される。
【０１５５】
【数１０】

【０１５６】
ここで、η：流体の粘性係数（Ｐａ・ｓ）、Ｌ：流路すなわちノズルの長さ（ｍ）、ｄ：流路すなわちノズル孔の直径（ｍ）、△Ｐ：圧力差（Ｐａ）である。上式より、流量Ｑは、流路の半径の４乗に比例するため、流量を制限するためには、微細なノズルの採用が効果的である。この（１７）式に、（１６）式で求めた吐出圧力△Ｐを代入し、次式を得る。
【０１５７】
【数１１】

【０１５８】
この式は、直径ｄ、長さＬのノズルに電圧Ｖを引加した際に、ノズルから流出する流体の流出量を表している。この様子を、図６に示す。計算にはＬ＝１０ｍｍ、η＝１（ｍＰａ・ｓ）、γ＝７２（ｍＮ／ｍ）の値を用いた。いま、ノズルの直径を先行技術の最小値５０μｍと仮定する。電圧Ｖを徐々に印加していくと、電圧Ｖ＝１０００Ｖで吐出が開始する。この電圧は、図４でも述べた吐出開始電圧に相当する。そのときのノズルからの流量がＹ軸に示されている。吐出開始電圧Ｖｃ直上で流量は急速に立ち上がっている。
【０１５９】
このモデル計算上では、電圧をＶｃより少し上で精密に制御することで微小流量が得られそうに思えるが、片対数で示される図からも予想されるように実際上それは不可能で、特に１０^−１０ｍ^３／ｓ以下、微小量の実現は困難である。また、ある径のノズルを採用した場合には、式（１４）で与えられたように、最小駆動電圧が決まってしまう。このため、先行技術のように、直径５０μｍ以上のノズルを用いる限り、１０^−１０ｍ^３／ｓ以下の微小吐出量や、１０００Ｖ以下の駆動電圧にすることは困難である。
【０１６０】
図から分かるように、直径２５μｍのノズルの場合７００Ｖ以下の駆動電圧で充分であり、直径１０μｍのノズルの場合５００Ｖ以下でも制御可能である。また、直径１μｍのノズルの場合３００Ｖ以下でも良いことが分かる。
【０１６１】
以上のように、本実施の形態に係る静電吸引型流体吐出装置では、局所電界強度に着目して新たに提案された吐出モデルに基づいているため、ノズル径０．０１μｍ〜２５μｍの微細ノズルとすることが可能であり、かつ、１０００Ｖ以下の駆動電圧にて吐出流体の吐出制御を行うことができる。尚、上記モデルに基づいて考察を行った結果、直径２５μｍ以下のノズルの場合は７００Ｖ以下の駆動電圧で、直径１０μｍ以下のノズルの場合は５００Ｖ以下の駆動電圧で、直径１μｍ以下のノズルの場合は３００Ｖ以下の駆動電圧で吐出制御が可能である。
【０１６２】
本実施の形態に係る静電吸引型流体吐出装置では、上述したように、ノズル径および駆動電圧を共に小さくすることが可能であるが、この場合、従来の静電吸引型流体吐出装置に比べ、以下のような傾向が顕著になる。
【０１６３】
すなわち、上述のような静電吸引型流体吐出装置の場合、その吐出特性は、基本的に、流体吐出ヘッド内部における駆動電極からノズル先端までの吐出流体流路内の電気抵抗値に依存して決定するものであり、その電気抵抗値が低い程、吐出応答性が向上する。つまり、吐出流体流路内の電気抵抗値を下げることで、駆動周波数を向上することができ、さらには、より高抵抗な吐出流体材料の吐出が可能となり、吐出流体材料の選択の幅を広げることができる。
【０１６４】
上記電気抵抗値を低くするためには、駆動電極−ノズル先端部間の距離の短縮が効果的である。
【０１６５】
［参考形態］
本発明の参考形態について、図７〜図１２を用いて説明すれば以下の通りである。
【０１６６】
（ノズルプレート）
図７（ａ）は、本参考形態のノズルプレート８の一部の斜視図であり、図７（ｂ）は、図７（ａ）のＡ−Ａ’線断面図である。ノズルプレート８には２個以上の流体吐出孔９が形成されており、図７（ａ）においては２個の流体吐出孔９が示されている。また、図７（ｃ）はノズルプレート８の一部を流体供給側から観察した斜視図である。
【０１６７】
図７（ａ）〜（ｃ）に示すように、ノズルプレート８は、第１のノズル層１、第２のノズル層２、第１の電極層２５、第２の電極層２６、及びノズル孔（ノズル孔部）１１を備えている。
【０１６８】
第１のノズル層１の流体吐出側の面は、ノズルプレート８の流体吐出面８ａをなしており撥液層４が形成され、その反対側となる流体供給側には、第２のノズル層２が配されている。ここで、第１のノズル層は例えば１から８μｍ厚と非常に薄く形成されており、層の厚い第２のノズル層２においてノズルプレート８としての強度・剛性を確保するようになっている。ここでは、強度・剛性を確保するための第２のノズル層２を１層としているが、２層以上であってもよい。
【０１６９】
ノズル孔１１は第１のノズル層１を貫通する第１のノズル孔１１ａと、第２のノズル層２を貫通する第２のノズル孔１１ｂとから構成されている。ここで、第１のノズル孔１１ａの壁面はノズルプレート８の流体吐出面８ａに垂直な略円筒形状であり、撥液層４が形成されている流体吐出面８ａの略円形の開口部が流体吐出孔９となる。一方、第２のノズル孔１１ｂは、円筒形状の第１のノズル孔１１ａとの連通する側の開口部から裾広がりに拡開するテーパー形状（円錐台形状）であり、第２のノズル層２を通って、第１のノズル層１とは反対側の流体供給面８ｂにて開口している。この第２のノズル層２の表面でもある流体供給面８ｂに形成された第２のノズル孔１１ｂの略円形の開口部が流体供給孔１２となる。
【０１７０】
第１のノズル孔１１ａの内壁の略全面、および第１のノズル孔１１ａと第２のノズル孔１１ｂとが連通する連通孔１１ｘ周辺には、第１の電極層２５が形成されている。この第１の電極層２５は、上記したノズル孔１１ａの内壁略全面に形成されてなる円筒部２５ａと、第１のノズル孔１１ａと第２のノズル孔１１ｂとが連通する連通孔１１ｘ周辺において連通孔１１ｘを略中心とする円環形状をなす延設部２５ｂとからなる。このうちの延設部２５ｂが、円錐台形状の第２のノズル孔１１ｂの上底１１ｙを形成している。つまり、第１のノズル孔１１ａと第２のノズル孔１１ｂの連通孔１１ｘ（略円形）の口径をＤ１とすると、Ｄ１は第２のノズル孔１１ｂの上底（流体吐出側の開口部）１１ｙの口径Ｄ２よりも小さい。そして、口径Ｄ２よりも円環形状をなす第１の電極層２５の延設部２５ｂの外径Ｄ３が大きい。
【０１７１】
また、第２のノズル孔１１ｂ内壁には、上記第１の電極層２５と電気的に接続された第２の電極層２６が形成されている。この第２の電極層２６の一部は、ノズルプレート８の流体供給面８ｂにも配設されており、その一部は図７（ｃ）に示すように引き出し配線２６ａをなし、吐出信号電圧印加手段（図示せず）に接続されている。
【０１７２】
なお、図７（ａ）（ｃ）においては、図面を簡素化するために、ノズル孔１１の構成する第１のノズル孔１１ａ及び第２のノズル孔１１ｂの各内壁に形成されている第１の電極層２５及び第２の電極層２６は省略している。
【０１７３】
以下、各部のサイズや材質の具体例を説明するが、本発明がその具体例に限定されるものではない。
【０１７４】
第１のノズル層１には厚さが約１μｍのポリイミド膜が用いられ、第２のノズル層２には厚さが約２０μｍのポリイミド膜が用いられている。第１の電極層２５は厚さが０．５μｍであって、Ｔｉを主成分とする金属材料からなり、そのうちの円筒部２５ａは、第１のノズル孔１１ａの内壁における流体吐出側端部まで形成されている。一方、延設部２５ｂは外径Ｄ３は約２０μｍである。第１のノズル層１と第２のノズル層２との界面に形成される電極層等は界面全体に形成されていると、ノズルプレート全体の応力にて反りを生じさせる原因となるが、このような延設部２５ｂとしてノズル孔１１ごとに部分的に設けた構成では、このような応力による反りを低減することができる。
【０１７５】
一方、第２の電極層２６は、厚さが０．５μｍであって、同じくＴｉを主成分とする金属からなる。そして、第２の電極層２６における第１の電極層２５との接続部分２６ｂは、図８に示すように、第１の電極層２５の延設部２５ｂと面で接触しており、高い接続信頼性を確保している。
【０１７６】
第１のノズル孔１１ａにおける流体吐出孔９となる開口部の口径は約３μｍであり、これに厚さが０．５μｍの第１の電極層２５が形成されるので、流体吐出孔９の実際の径（直径）は約２μｍとなる。また、第２のノズル孔１１ｂの上底１１ｙの口径Ｄ２は１０μｍであり、流体供給孔１２となる開口部の口径は３０μｍである。
【０１７７】
本構成のノズルプレート８においては、超微量流体の吐出を可能とし、微細ドットを形成するためには、流体吐出孔９をφ１０μｍ以下にすることが望ましく、さらに好ましくはφ８μｍ以下が好適である。このようなノズル孔径（直径）とすることで、広範囲に必要であった電場の形成を狭くすることができ、電荷の移動に必要な電圧、すなわち流体を静電吸引させるのに必要な帯電量を該流体に付与するために必要な電圧を大幅に低減させることが可能となる。これによれば、従来のように２０００Ｖといった高電圧を必要としないので、流体ジェット装置を使用する際の安全性の向上を図ることができる。
【０１７８】
特に、φ８μｍ以下とすることで、電界強度分布が該流体吐出孔の吐出面近傍に効果的に集中すると共に、対向電極からノズルの流体突出孔までの距離の変動が電界強度分布に影響することがなくなる。これにより、対向電極の位置精度、記録媒体の材料特性のバラツキや厚さバラツキの影響を受けずにより安定した流体の吐出を行うことができる。
【０１７９】
また、上記のように、電界強度分布を流体吐出孔９の吐出面近傍に集中できることにより、狭い領域に強い電場を形成することが可能となり、この結果、吐出可能な流体量を超微量にすることが可能となる。これにより、流体をインクとした場合に印字画像を高解像度にすることが可能となる。
【０１８０】
また、第１のノズル層１上の撥液層４は、厚さが約０．０５μｍのフッ素重合もしくはシリコン系の高分子膜により形成されている。上記撥液層４は、後述するように流体吐出孔９内に回り込んだ余分な領域を、ドライエッチによって除去する。
【０１８１】
本参考形態によれば、着弾精度に大きな影響を与えるノズルプレート８の流体吐出孔９の形状が、上記１μｍのポリイミド膜の加工精度で決定されるので、流体吐出孔９の加工精度が非常に高く、これに伴って非常に高い着弾精度を確保することができる。
【０１８２】
また、流体吐出孔９の加工精度を高めるためには、ノズルプレート８の流体吐出面に露出している第１のノズル層１の膜厚を減少すれば、さらに高い加工精度を得ることができる。このとき、第１のノズル層１の膜厚を減少することによって、第１のノズル層１の剛性が低下し、流体吐出孔９の構造的な信頼性が減少するが、第１のノズル層１に接して第２のノズル層２を配置することによって、第１のノズル層１が補強され、第１のノズル層１の構造的信頼性を低下することなく流体吐出孔９の形状精度を向上することができる。すなわち、微細な流体吐出孔９を有するノズルプレート８を作成する場合、このような構成が望ましい。
【０１８３】
また、第１の電極層２５はノズル孔１１の形成位置ごとに局所的に設けられているため、隣接するノズル孔１１に配設された第１の電極層２５と電気的に絶縁されている。したがって、個々のチャンネルに独立して吐出信号を印加することができ、クロストークが少なく、これによって描画画像の解像度を向上させることができる。
【０１８４】
また、第２のノズル孔１１ｂがテーパー形状であるため、第２のノズル孔１１ｂ内部において、流体の乱流が発生しにくくなり、流体の吐出安定性を向上させることができとともに、ノズル孔１１ｂの内壁と流体供給面８ｂとのエッジが甘くなるので、流体供給面８ｂにまで延設された第２の電極層２６の断線を効果的に抑制することができる。また、ノズルプレート８の流体吐出面８ａに形成された撥液層４によって、流体が流体吐出孔９近傍に付着することを防止することができる。
【０１８５】
なお、第１の電極層２５に用いられる材料はＴｉを主成分とする金属材料に限定されない。第２のノズル層２のエッチング加工および後述する犠牲層５および流体吐出孔９内に回り込んだ撥液層４のエッチングの際、当該エッチングに対して高い耐性を有する材料、すなわち、エッチングガス（酸素を含有するプラズマ、フッ素を含有するプラズマ等）、または、エッチャント（硝酸、水酸化カリウム水溶液等）に対する耐性の高い材料であればよい。具体的には、Ｔｉ、Ａｌ、Ｃｕ、Ｃｏ、Ｆｅ、Ｎｉ、Ａｕ、Ｐｔ、Ｔａ、Ｗ、Ｎｂ等を主成分とする金属材料が挙げられ、上記エッチングガスあるいはエッチャントとの組み合わせで選択することができる。
【０１８６】
同様に、第２の電極層２６に用いられる材料もＴｉを主成分とする金属材料に限定されない。後述する犠牲層５および流体吐出孔９内に回り込んだ撥液層４のエッチングの際、当該エッチングに対して高い耐性を有する材料、すなわち、エッチングガス（酸素を含有するプラズマ、フッ素を含有するプラズマ等）、または、エッチャント（硝酸、水酸化カリウム水溶液等）に対する耐性の高い材料であればよい。具体的には、Ｔｉ、Ａｌ、Ｃｕ、Ｃｏ、Ｆｅ、Ｎｉ、Ａｕ、Ｐｔ、Ｔａ、Ｗ、Ｎｂ等を主成分とする金属材料が挙げられ、上記エッチングガスあるいはエッチャントとの組み合わせで選択することができる。
【０１８７】
また、第１のノズル層１に用いられる材料はポリイミドに限定されない。ポリイミド以外の高分子有機材料であっても良いし、ＳｉＯ_２、Ｓｉ_３Ｎ_４といったＳｉ化合物材料、あるいはＳｉであっても良い。
【０１８８】
第２のノズル層２に用いられる材料もポリイミドに限定されない。第１のノズル層１と同様に、ポリイミド以外の高分子有機材料であっても良いし、ＳｉＯ_２、Ｓｉ_３Ｎ_４といったＳｉ化合物材料、あるいはＳｉであっても良い。
【０１８９】
また、本参考形態では、第２のノズル孔１１ｂは、第１のノズル孔１１ａとの連通部分にて狭まった円錐台形状（テーパー形状）であるがこれに限定されない。例えば、図９に示すノズルプレート８’のように、第２のノズル孔１１ｂ’の内壁がノズルプレート８’の流体吐出面８ａや流体供給面８ｂと垂直の、いわゆるストレート形状（円筒形状）に形成することもできる。
【０１９０】
この場合、第２のノズル孔１１ｂ’の流体供給孔１２’を、図７（ａ）〜（ｃ）に示した第２のノズル孔１１ｂが円錐台形状の構成の流体供給孔１２よりも小さくすることができ、ノズルの集積度をさらに高めることができる。また、図７（ｂ）に示すように、ノズルプレート８の場合、その製造上の都合で、第２の電極層２６は第２のノズル孔１１ｂ内壁の片側面のみに形成されていたが、図９に示すように、第２のノズル孔１１ｂ内壁の面全体に形成してもよい。
【０１９１】
本参考形態のような構成のノズルプレート８（８’）とすることで、以下の(１)〜(５)の作用を奏する。
(１)流体吐出孔９が、口径８μｍ以下の微細なノズルプレート８（８’）であっても、ノズル孔１１先端まで吐出信号電圧を印加することのできる構造的に安定した電極を形成することができる。
(２)第２のノズル層２の流体供給側で、第２の電極層２６を隣接チャンネル間が電気的に短絡しないように分離することで、容易に個々のチャンネルに独立して吐出信号を印加することが可能となり、クロストークが少なく、これによって描画画像の解像度を向上させることができる。
(３)ノズルプレート８（８’）の剛性は第２のノズル層２で維持できるため、ノズルプレート８（８’）全体の剛性が高くなり、取り扱いが容易になる。
(４)膜厚の厚い第２のノズル層２に加工された第２のノズル孔１１ｂの加工精度がたとえ悪くとも、第２のノズル孔１１ｂの加工時には第１の電極層２５の延設部２５ｂでエッチングが止まるため、流体の吐出量を制御する流体吐出孔９に影響を及ぼすことがない。
(５)第１の電極層２５は、第１のノズル孔１１ａと連通する第２のノズル孔１１ｂに形成された第２の電極層２６と電気的に接続されているので、第２の電極層２６を介してノズルプレート８の流体供給側より駆動信号を供給することが可能となり、第１の電極層２５に駆動信号を供給するための引き出し配線２６ｂから発生する電界によって、記録媒体が電気的な損傷を受けるようなことがない。
【０１９２】
（ノズルプレートの製造方法）
次に、本参考形態にかかるノズルプレート８の一製造方法を説明する。図１０（ａ）〜（ｉ）はノズルプレート８の製造工程を説明する図である。
【０１９３】
まず、Ｓｉやガラスなどからなる任意の厚さの一時保持のための基板６に、犠牲層５を、Ｎｉを用いた湿式鍍金（めっき）によって形成する。さらに犠牲層５上にスピンコートによってポリイミド樹脂を塗布し、３５０℃で２時間焼成し第１のノズル層１を形成する。ここで犠牲層５の厚さを１０μｍとし、第１のノズル層の厚さを１μｍとした。
【０１９４】
次に、上記第１のノズル層１上にフォトレジストにて第１のノズル孔１１ａの開口パターンを形成し、酸素を主成分とするガスを用いたドライエッチングによって、第１のノズル孔１１ａを加工する（図１０（ａ）参照）。
【０１９５】
本エッチング手法ではポリイミド樹脂などの有機物を高速に、精度良く加工することができるとともに、犠牲層５であるＮｉとのエッチング選択性が高い（Ｎｉはほとんどエッチングされない）。したがって、上記加工によって犠牲層５が大きな損傷を受けることがなく、犠牲層５表面の平坦性が維持されるので、犠牲層５表面に形成されることになるノズルプレート８の流体吐出面の平坦性が劣化することがない。また、本加工は非常に高い精度で行うため、異方性の高いエッチング条件を用いている。また、上記のように第１のノズル層１は１μｍと極めて薄いので、超微量の流体を吐出するための第１のノズル孔１１ａを高精度に加工することができる。
【０１９６】
次に、第１のノズル孔１１ａを加工した第１のノズル層１上にＴｉを主成分とする金属材料からなる第１の電極層２５をスパッタ法にて形成する。さらに、上記第１の電極層２５に、ノズル孔開口部に対応する形状のレジストパターン２７を形成する（図１０（ｂ）参照）。ここで、上記第１の電極層２５は第１のノズル孔１１ａの内壁に形成する必要があるため、第１の電極層２５のステップカバレッジ性を高めるために、３０ｍＴｏｒｒのＡｒガス圧条件下で、第１のノズル層１上の膜厚が０．５μｍとなるように成膜した。
【０１９７】
次に、Ａｒを主成分とするガスを用いたプラズマによるドライエッチで、第１の電極層２５を、第１のノズル層１上に直径約２０μｍの上記した延設部２５ｂとなる略円形形状が残るように加工し、レジストを除去する（図１０（ｃ）参照）。この加工工程では、上記第１のノズル孔１１ａの内壁に形成された第１の電極層２５（円筒部２５ａ）の損傷を抑制しつつ、第１のノズル孔１１ａの底となる犠牲層５上に形成された第１の電極層２５を除去するため、異方性の高いエッチング条件を採用した。
【０１９８】
なお、上記第１の電極層１上に部分的に残す上記延設部２５ｂは、ここでは略円形形状としたが、加工工程上では略円形形状である必要はなく、後述するように、第２のノズル孔１１ｂの上底１１ｙが、第１のノズル層１上に第１のノズル孔１１ａより延設して形成された延設部２５ｂ内に配置される形状であれば良い。
【０１９９】
但し、本ノズルプレートは静電吸引型流体吐出装置に応用されるノズルプレート８であり、第１の電極層２５を介してノズル先端部に吐出信号を印加するため、第１の電極層２５においては、ノズル先端部だけでなく、第１のノズル層１上の形状の端部にも電界が集中する。このため、上記第１のノズル層１上の延設部２５ｂ端部に集中する電界を均一化するために、延設部２５ｂの形状としては等方性の高い円形に近い形状に加工することが望ましい。
【０２００】
次に、第２のノズル層２を上記第１のノズル層１および第１の電極層２５上に、２０μｍの厚さで形成する（図１０（ｄ）参照）。第２のノズル層２は、第１のノズル層１と同様に塗布型ポリイミド樹脂をスピンコート法にて塗布し、３５０℃で２時間焼成し２０μｍの厚さとした。ここで、第１のノズル孔１１ａもポリイミド樹脂にて埋められることになる。第２のノズル層２は高精度に加工された膜厚の薄い第１のノズル層１を補強する目的で形成され、ノズルプレート８全体の剛性を高める効果がある。
【０２０１】
次に、上記第２のノズル層２上にフォトリソグラフィによってレジストパターン２８を形成し、酸素を主成分とするガスを用いたドライエッチングを行い、第２のノズル層２に円錐台形状の第２のノズル孔１１ｂを形成する（図１０（ｅ）参照）。なお、上記ドライエッチングは第１のノズル層１上に形成された第１の電極層２５の延設部２５ａで止めることができる。すなわち、Ｔｉを主成分とする金属材料で形成される第１のノズル層１は、酸素を主成分とするガスを用いたドライエッチングによって、ほとんどエッチングされないので、第１の電極層２５が露出した部位では、ドライエッチングがそれ以上進行せず、先の工程で第１のノズル孔１１ａを埋めた第２のノズル層２を容易に除去することができる。また、上記第２のノズル孔１１ｂの加工は、第１のノズル層１との接合部において、第２のノズル孔１１ｂの上底１１ｙが、第１の電極層２５の延設部２５ｂ内に配置されるようにパターニングされる。
【０２０２】
第２のノズル孔１１ｂのテーパー形状の加工に際しては、上記エッチングにおいて、レジストパターン２８のエッチレートと第２のノズル層２のポリイミド樹脂のエッチレートを概ね等しくし、該レジストパターン２８を１５０℃で６０分ポストベークすることによってレジストパターン２８をテーパー形状とし、エッチングによってこの形状を第２のノズル層２に転写する手法を用いた。
【０２０３】
すなわち、図１１（ａ）に示すように、エッチレートが第２のノズル層２を構成するポリイミド樹脂と概ね等しく、テーパー壁面２８Ａを有するレジストパターン２８を形成し、第２のノズル層２のエッチングと同じスピードでレジストパターン２８をエッチングし、レジストパターン２８のエッジを広げる。このとき、図１１（ｂ）に示すように、第２のノズル層２も同時にエッチングされることになり、結果的に第２のノズル層２には、図１１（ｃ）に示すように、レジストパターン２８に形成したテーパーを有する壁面２８Ａと同じ形状を有する第２のノズル孔１１ｂが形成される。また、この場合、レジストパターン２８と第２のノズル層２のエッチレートとが概ね等しいことから、レジストパターン２８の厚さは第２のノズル層２の厚さより厚く形成することが望ましい。なお、図１１では、第１のノズル層１に形成されている第１のノズル孔１１ａ部分の記載は省略している。
【０２０４】
次に、上記第２のノズル層２上に、Ｔｉを主成分とする金属材料からなる第２の電極層２６を成膜する。ここでは、イオンビームスパッタ法を用いて、０．２ｍＴｏｒｒのＡｒガス圧下で、Ａｒ原子によるＴｉ粒子の散乱を抑制しながら、矢印Ｋの方向からＴｉ粒子が飛来するように基板を傾斜し、第２のノズル層２内壁面の片側のみに形成され、かつ第２の電極層２６の一部が第１の電極層２５と電気的に短絡するように成膜した（図１０（ｆ）参照）。膜厚は０．５μｍである。
【０２０５】
このように、斜め方向からＴｉ粒子を入射しながら第２の電極層２６を形成することによって、第１のノズル孔１１ａ内に第２の電極層２６が付着するのを防止することができ、これによって、第１のノズル孔１１ａの形状変化や閉塞することを防止することができる。
【０２０６】
次に、上記第２の電極層２６上に、第２のノズル孔１１ｂと第２のノズル層２上に形成された第２の電極層２６の一部を覆うように、フォトレジストパターン２９を形成する（図１０（ｇ）参照）。このフォトレジストパターン２９は第２のノズル孔１１ｂと第２のノズル層２上に形成された第２の電極層２６の一部を覆うように形成されていればよいが、本実施例においては、第２のノズル層２上に形成された第２の電極層２６が略５０μｍ径の円形形状に加工できる形状とした。ここで、フォトレジストパターン２９は、第２のノズル孔１１ｂを埋めるように形成されるため、第２のノズル孔１１ｂの最も深い領域では、レジスト層の厚さが非常に厚くなる。このため、フォトレジストパターン２９は、露光されない部分がパターンとして残る、ポジ型のフォトレジストを使用することが望ましい。
【０２０７】
また、このとき上記フォトレジストパターン２９を用いて、第２のノズル層２上に第２の電極層２６を用いて引き出し配線２６ａを形成することが望ましい。この場合、別工程で引き出し配線２６ａを作成する必要がないので、工程を簡略化することができる。また、上記のように引き出し配線２６ａをノズルプレート８を介して、記録媒体の反対側に配置することができるので、記録媒体から十分な距離を離すことができ、当該引き出し配線パターンから発生する電界によって、記録媒体に致命的な電気的損傷を与えることがない。
【０２０８】
次に、上記フォトレジストパターン２９をもとに、Ａｒガスを主成分とするプラズマを用いたドライエッチングによって第２の電極層２６を加工し、フォトレジストパターン２９を除去する（図１０（ｈ）参照）。この加工工程では、第２の電極層２６を所望の形状に加工する必要があるので、高い異方性を有するエッチング条件にてエッチングを行った。また、フォトレジストパターン２９の除去はレジスト剥離液を用いて行った。
【０２０９】
次に、上記フォトレジストパターン２９を除去した後、硝酸と水が主成分である水溶液に浸漬して犠牲層５のみをエッチングすることで、ノズルプレート８を基板６から取り外す（図１０（ｉ））。先に述べたように、第１のノズル層１、第２のノズル層２を形成するポリイミド樹脂や、ストッパ層３あるいは吐出孔層１４を形成するＴｉは、上記犠牲層５のエッチング液によってほとんどエッチングされることがないので、犠牲層５のエッチングによって、形状の変化や構造的信頼性の低下を招来することがない。
【０２１０】
次に、犠牲層５が除去された第１のノズル層１の表面に撥液層４を形成する（図１０（ｉ））。ここでは、塗布の容易さを考慮する趣旨でフッ素重合体を用い、これをスタンプなどの方法により第１のノズル層１の表面に塗布し、高分子膜にて厚さ０．０５μｍの撥液層４を形成した。なお、第１のノズル孔１１ａ内に回り込んだ撥液層４については、撥液層４形成後に、酸素を含有するプラズマを用い、第２のノズル孔１１ｂ側からドライエッチングすることで、これを除去した。これにより、ノズルプレート８のダメージを最小限にすることができる。
【０２１１】
以上のように、本実施の形態によれば、加工工程中にフォトリソグラフィとドライエッチングを実施することによって、超微量の流体を吐出する静電吸引型流体吐出装置のノズルプレート８に、チャンネルごとに離間された第１及び第２の電極層２５・２６をノズル孔１１内に精度良く形成することができる。これによって、個々のチャンネルに独立して吐出信号を印加することができるので、クロストークが少なく、これによって描画画像の解像度を向上させることができる。
【０２１２】
また、第１のノズル層１を薄く形成することができるので、第１のノズル孔１１ａ内壁に形成する第１の電極層２５を成膜時のガス圧を制御することにより流体吐出孔９近傍にまで安定して成膜することができる。これによって、電極からノズル先端の電気抵抗Ｒが安定し、チャンネル間の吐出特性が安定する。
【０２１３】
なお、本実施の形態では、犠牲層５としてＮｉ、第１のノズル層１および第２のノズル層２としてとしてポリイミド樹脂、第１及び第２の電極層２５・２６としてＴｉを用いたが、この組み合わせに限定されない。
【０２１４】
犠牲層５には、Ｎｉのほかに、第１のノズル層１、第２のノズル層２、第１の電極層２５、第２の電極層２６に用いる材料との組み合わせによって、Ａｌ、Ｃｕ、などの硝酸、あるいはＫＯＨ水溶液に可溶な材料、またはポリイミドのような酸素プラズマによってエッチングできる材料を用いることができる。また、犠牲層５の形成方法についても鍍金以外に蒸着法、スパッタ法、塗布法などを材料に応じて用いることができる。
【０２１５】
第１のノズル層１、第２のノズル層２、第２の電極層２６には、犠牲層５のエッチングによるダメージが軽微な材料を用いることができる。また、第１の電極層２５には、犠牲層５のエッチングおよび第２のノズル孔１１ｂのエッチングに対して耐性の高い材料を用いることができる。
【０２１６】
ここで、図１２に、使用材料（犠牲層、第１のノズル層、第１の電極層、第２のノズル層、第２の電極層）および加工方法（第１のノズル孔、第１の電極層、第２のノズル孔、第２の電極層、犠牲層除去）について好ましい組み合わせの例を示す。
【０２１７】
図１２に示すように、第１のノズル層１、第２のノズル層２はポリイミド樹脂のような高分子有機材料に限定されず、ＳｉまたはＳｉＯ_２などの無機シリコン化合物を選択することができる。ただし、ＳｉＯ_２やＳｉをドライエッチングするためには、Ｆを含有する反応ガスを使用する必要があり、このエッチングに対して本参考形態で用いたＴｉは耐性が低いため、Ａｕ、Ｐｔなどのエッチング耐性を有する材料を第１の電極層２５あるいは第２の電極層２６として利用することが望ましい。
【０２１８】
また、第１の電極層２５または第２の電極層２６にも、Ｔｉ以外に、図１２に示す組み合わせに応じて、同表に記載の材料を使用することができる。
【０２１９】
なお、第１の電極層２５の材料であるＴｉはＣＦ_４と酸素の混合ガスを用いたプラズマでも比較的速いエッチング速度でエッチングすることができる。しかし、Ｔｉの下に形成された第１のノズル層１（ポリイミド）が、上記ガスのプラズマによってＴｉよりも高速にエッチングされ、大きなダメージを受ける。したがって、本参考形態では第１の電極層２５および第２の電極層２６のパターニングにはＡｒイオンによるドライエッチング法を採用している。
【０２２０】
このように、第１の電極層２５あるいは第２の電極層２６のエッチレートと第１のノズル層１あるいは第２のノズル層２のエッチレートとの差が少ないＡｒイオンによるドライエッチング法を採用することで、第１のノズル層１あるいは第２のノズル層２のダメージを最小限に抑えつつ第１の電極層２５あるいは第２の電極層２６をパターニングすることができる。
【０２２１】
また、本実施の形態では、犠牲層５をエッチングによって完全に除去したが、犠牲層５を完全に除去する必要はなく、犠牲層５のうち第１のノズル層１と接している部分のみをエッチングによって除去すれば、ノズルプレート８を基板６から取り外すことができる。
【０２２２】
また、撥液層４としては、フッ素重合体に限定されず、シリコン系の高分子膜、ＤＬＣ（ダイヤモンドライクカーボン）などを用いることもできる。
【０２２３】
以上の加工工程を用いることによって、上記した(１)〜(５)の作用を奏するノズルプレート８を製造することができる。
【０２２４】
〔実施の形態〕
本発明の実施の形態について、図１３〜図１６を用いて説明すれば以下の通りである。なお、説明の便宜上、上記参考形態の図面に示した部材と同一の機能を有する部材については、同一の符号を付しその説明を省略する。
【０２２５】
（ノズルプレート）
図１３（ａ）は、本実施の形態のノズルプレート８０の一部の斜視図であり、図１３（ｂ）は、図１３（ａ）のＢ−Ｂ’線断面図である。ノズルプレート８０には２個以上の流体吐出孔９が形成されており、図１３（ａ）においては２個の流体吐出孔９が示されている。また、図１３（ｃ）はノズルプレート８０の一部を流体供給側から観察した斜視図である。
【０２２６】
図１３（ａ）〜（ｃ）に示すように、ノズルプレート８０は、第１のノズル層１０に形成された第１のノズル孔１１ｃが第２のノズル孔１１ｂと同様にテーパー形状であると共に、ノズルプレート８０の流体吐出面８０ａには、第１のノズル孔１１ｃにおける流体吐出側の開口部を塞ぐように、表面電極層８１が形成されており、該表面電極層８１に形成された貫通孔８１ａが流体吐出孔９となっている。そして、上記表面電極層８１は、第１のノズル孔１１ｃの内壁に成膜された第１の電極層２５と電気的に接続されており、第１の電極層２５及び第２の電極層２６を介して、ノズルプレート８０の流体供給側より駆動信号を印加可能となっている。ここでも、第２のノズル層２０を１層としているが、２層以上であってもよい。
【０２２７】
なお、図１３（ａ）（ｃ）においても、図面を簡素化するために、ノズル孔１１の構成する第１のノズル孔１１ｃ及び第２のノズル孔１１ｂの各内壁に形成されている第１の電極層２５及び第２の電極層２６は省略している。
【０２２８】
以下、各部のサイズや材質の具体例を説明するが、本発明がその具体例に限定されるものではない。
【０２２９】
表面電極層８１は、Ｐｔを主成分とする金属材料が用いられ、ノズルプレート８０全体の応力を低減するために、５μｍ径の略円形形状に形成されている。また表面電極層８１の厚さは０．５μｍである。
【０２３０】
第１のノズル層１０は、本実施の形態ではＳｉＯ_２を主成分とする無機材料からなり厚さが２μｍに形成されている。第２のノズル層２０は、ポリイミド樹脂を主成分とする有機材料からなり、２０μmの膜厚に形成されている。第１の電極層２５および第２の電極層２６には、Ｔｉを主成分とする金属材料が用いられ、０．５μｍの膜厚に形成されている。
【０２３１】
表面電極層８１に形成された貫通孔８１ａである流体吐出孔９の口径は２μｍとなっており、第１のノズル孔１１ｃとの連通部まで膜面に対して垂直に加工されている。ここで、流体吐出孔９の口径は、参考形態と同様の理由からΦ１０μｍ以下、さらに好ましくはΦ８μｍ以下であることが望ましい。
【０２３２】
また、第１のノズル孔１１ｃは流体吐出孔９との連通部、つまり流体吐出側開口部が４μｍの口径に加工されており、第２のノズル孔１１ｂとの連通部まで、裾広がりに拡開するテーパー形状（円錐台形状）に加工されている。
【０２３３】
また、第２のノズル孔１１ｂは、第１のノズル孔１１ｃとの連通部、つまり流体吐出側開口部において２０μｍの口径に加工されており、裾広がりに拡開するテーパー形状（円錐台形状）であり、第２のノズル層２０を通って、ノズルプレート８０の流体供給面８０ｂにて開口している。
【０２３４】
なお、円錐台形状の第１のノズル孔１１ｃの上底１１ｃｙは、流体吐出孔９を略中心とする円環形状であり、表面電極層８１の一部が当該上底１１ｃｙを成して露出している。したがって、流体吐出孔９と第１のノズル孔１１ｃとの連通孔１１ｃｘ（略円形）の口径は、第１のノズル孔１１ｃの上底１１ｃｙの外口径（上記連通孔１１ｃｘにおける第１のノズル孔１１ｃの外形）より小さい。
【０２３５】
さらに、円錐台形状の第２のノズル孔１１ｂの上底１１ｂｙは、第１のノズル孔１１ｃを略中心とする円環形状であり、第１の電極層の一部が当該上底１１ｂｙを成して露出している。したがって、第１のノズル孔１１ｃと第２のノズル孔１１ｂの連通孔１１ｂｘ（略円形）の口径は、第２のノズル孔１１ｂの上底１１ｂｙの外口径（上記連通孔１１ｂｘにおける第２のノズル孔１１ｂの外形）より小さい。
【０２３６】
また、第１のノズル孔１１ｃの内壁の少なくとも一部に加えて、第１のノズル孔１１ｃと第２のノズル孔１１ｂが連通する周辺部には延設部２５ｂとなる第１の電極層２５が形成されている。ここで、第１のノズル層１０を構成するＳｉＯ_２は、後述する第２のノズル孔１１ｂ加工による酸素を含有するプラズマによるドライエッチに高い耐性を示すため、第１の電極層２５の該延設部２５ｂが形成されておらず第１のノズル層１０あるいは第１のノズル孔１１ｃが第２のノズル孔１１ｂのエッチングにさらされた場合でも、ほとんどエッチングされることなく、第１のノズル孔１１ｃの形状が変形することはない。
【０２３７】
これに対して、第１のノズル層１０に第２のノズル孔１１ｂ加工におけるエッチングに対して耐性の低い材料を用いた場合（たとえば参考形態の場合ように、第１のノズル層１０と第２のノズル層２０が同様の材料）は、第１の電極層２５は第１のノズル孔１１ｃの内壁すべてを被覆するように形成することが望ましい。すなわち、第１の電極層２５は第２のノズル孔１１ｂの加工工程において、第１のノズル孔１１ｃあるいは第１のノズル層１０を当該エッチングから保護する保護層として機能する。
【０２３８】
また、第２のノズル孔１１ｂ内壁には、上記第１の電極層２５と電気的に接続された第２の電極層２６が形成されている。また、第２の電極層２６の一部は、ノズルプレート８０の流体供給面８０ｂを成す第２のノズル層２０の流体供給側表面にも配設されており、図１３（ｃ）に示すように、該表面に形成された第２の電極層２６を加工した、配線パターン２６ａによって、図示しない駆動信号電圧印加手段に接続されている。撥液層４は、厚さが０．０５μｍのフッ素重合体を有する高分子材料から形成されている。
【０２３９】
また、表面電極層８１は第１のノズル孔１１ｃのエッチング手段に対して高い耐性を有しているため、上記第１のノズル孔１１ｃａのエッチングによって流体吐出孔９形状が変形することがない。また着弾精度に大きな影響を与えるノズルプレートの流体吐出孔９の形状が、表面電極層８１となる上記０．５μｍのＴｉ膜の加工精度で決定されるので、流体吐出孔９の加工精度が非常に高く、これに伴って非常に高い着弾精度を確保することができる。
【０２４０】
ところで、流体吐出孔９の加工精度を高めるためには、表面電極層８１の膜厚を減少すれば、さらに高い加工精度を得ることができるが、表面電極層８１の膜厚を減少することによって、表面電極層８１の剛性が低下し、流体吐出孔９の構造的な信頼性が減少する。
【０２４１】
しかしながら、このように、表面電極層８１に接して第１のノズル層１０を配置することによって、表面電極層８１が補強され、表面電極層８１の構造的信頼性を低下することなく流体吐出孔９の形状精度を向上することができる。
【０２４２】
また、第１の電極層２５は第２のノズル孔１１ｂのエッチング手段に対して、高い耐性を有しているので、第２のノズル孔１１ｂの加工によって第１のノズル孔１１ｃの形状が大幅に変形することがないとともに、第２のノズル孔１１ｂの加工のオーバーエッチによって、第１のノズル層１０が完全に除去されることがない。
【０２４３】
なお、表面電極層８１に用いる材料はＰｔを主成分とする金属材料に限定されない。第１のノズル孔１１ｃのエッチングおよび第２のノズル孔１１ｂのエッチングおよび後述する犠牲層５０のエッチング並びに流体吐出孔９内に回り込んだ撥液層４のエッチングの際、当該エッチングに対して高い耐性を有する材料、すなわち、フッ素を含有するプラズマ、酸素を含有するプラズマ、硝酸、水酸化カリウム水溶液等に耐性の高い材料であればよく、犠牲層エッチング、第１のノズル孔加工、第２のノズル孔加工の手法との組み合わせによって使用することができる。具体的には、Ａｌ、Ｃｕ、Ｃｏ、Ｆｅ、Ｎｉ、Ａｕ、Ｐｔ、等を主成分とする金属材料が挙げられ、上記エッチングガスあるいはエッチャントとの組み合わせで選択することができる。
【０２４４】
その他、第１のノズル層１０、第１のノズル層２、第１の電極層２５、第２の電極層２６等の材料も何ら上記に限定されるものではなく、材料と製造方法との好適な組み合わせについて後述する。
【０２４５】
また、本実施の形態では、第２のノズル孔１１ｂは、第１のノズル孔１１ｃとの連通部１１ｂｘが狭まった円錐台形状（テーパー形状）であるがこれに限定されない。例えば、図１４に示す変形例のノズルプレート８０’のように、第２のノズル孔１１ｂの側壁がストッパ層３と垂直の、いわゆるストレート形状（円筒形状）に形成することもできる。この場合、第２のノズル孔１１ｂの流体供給孔１２をより小さくすることができ、ノズルの集積度をさらに高めることができる。また、図１４に示すように、第２の電極層２６は第２のノズル孔１１ｂの内壁面全体に形成してもよく、この場合第２の電極層２６の電気伝導にかかる信頼性が向上する。
【０２４６】
また、ここでは、１つのノズル孔１１に対応する１個の表面電極層８１に対して貫通孔８１ａを１個形成したが、複数個の貫通孔を１個の表面電極層８１に形成して１つのノズル孔１１に対する流体吐出孔９が複数ある構成としても良い。
【０２４７】
また、第１のノズル孔１１ｃを、実施の形態のノズルプレート８の場合のように、側壁がノズルプレート表面に対して垂直の、いわゆるストレート形状（円筒形状）に形成することもできる。この場合、第１のノズル孔の加工精度が向上するため、表面電極層８１の形状を小さくすることができ、表面電極層８１によって発生する応力を低減することができる。
【０２４８】
本実施の形態のような構成のノズルプレート８０（８０’）とすることで、以下のような作用を、前述した(１)〜(５)に加えて奏する。
(６)第１のノズル孔１１ｃがテーパー形状に形成されているため、第１のノズル孔１１ｃ内に形成する第１の電極層２５のカバレッジがよく、導電性にかかる信頼性が向上する。
(７)薄膜の表面電極層８１に形成した貫通孔８１ａが孔流体吐出孔９となるため、加工精度が非常に高いとともに、第１の電極層２５を形成することによる流体吐出孔９の形状変化がないので、吐出信頼性が向上する。
【０２４９】
（ノズルプレートの製造方法）
次に、本実施の形態にかかるノズルプレート８０の一製造方法を説明する。図１５（ａ）〜（ｇ）はノズルプレート８０の製造工程を説明する図である。
【０２５０】
まず、基板６に、犠牲層５０を、参考形態と同様に形成する（図１５（ａ））。ここでは、犠牲層５０の厚さは１０μｍとする。さらに、上記犠牲層５０上に厚さ０．５μｍのＰｔ膜を蒸着などの方法で成膜し、フォトリソグラフィを用いて表面電極層８１をノズル孔１１形成部分に部分的に形成されるように外形形状と、流体吐出孔９となる貫通孔８１の形状のレジストパターンを形成する。しかる後に、ドライエッチング法を用いて上記表面電極層８１の外形形状と流体吐出孔９を同時に加工する。
【０２５１】
Ｐｔ膜は化学的に比較的不活性な材料であるため、ここでは上記ドライエッチングはＡｒを用いたスパッタエッチングを用い、物理的な加工が支配的な方法によって加工した。また、本加工は非常に高い精度で行うため、異方性の高いエッチング条件を用いている。ここで、上記表面電極層８１の形状は５μｍ径の略円形形状に加工されている。また、上記表面電極層８１内部に配設される流体吐出孔９は２μm径の略円形形状に形成されている。
【０２５２】
次に、上記犠牲層５０及び表面電極層８１上にＳｉＯ_２膜からなる第１のノズル層１０をＰ−ＣＶＤ法によって成膜する。本Ｐ−ＣＶＤ法によると、成膜するＳｉＯ_２膜が有する応力を成膜に用いるガスの組成、ガス圧、プラズマを発生するためのＲＦパワーによって制御することができるとともに、段差部のつき周りが良好であるため、上記表面電極層８１の段差部においてクラックなどが発生することがなく、膜としての構造的な信頼性が高い。このため、ノズルプレート全体の構造的な信頼性が高くなる（図１５（ａ）参照）。
【０２５３】
次に、上記第１のノズル層１０上にフォトリソグラフィによってレジストパターンを作成し、フッ素ガスと酸素ガスを含有する反応性イオンエッチング（ＲＩＥ）によって加工し、加工後、レジストをレジスト剥離液によって除去する。（図１５（ｂ）参照）。本エッチング方法では、プラズマによって活性化されたフッ素が選択的にＳｉ原子と反応するため、ＳｉＯ_２のエッチング速度が非常に高い。これに対して、上述したようにＰｔは化学的に安定な材料であるため、前記活性化されたフッ素とはほとんど反応しない。このためＰｔのエッチング速度が遅く、これによって、本エッチングは前記表面電極層８１と第１のノズル層１０の界面で精度よく止めることができる。
【０２５４】
また、本加工工程では、フッ素ガスと酸素ガスを含有するプラズマを用いることで、ＳｉＯ_２とフォトレジストのエッチング速度を同程度に設定し、参考形態の第２のノズル層２０を加工する工程で用いた、レジストの形状を反映する手法を用いてＳｉＯ_２を加工し、第１のノズル孔１１ｃをテーパー形状に加工した。ここで、第１のノズル孔１１ｃの表面電極層８１との接合部に置ける形状を４μｍ径の略円形形状とし、第２のノズル層２０との界面における開口径は６μｍとした。また、第１のノズル孔１１ｃの形状は、流体吐出孔９よりも大きく、第１のノズル孔１１ｃのパターン内に流体吐出孔９が配設されるように加工する。
【０２５５】
また、上記第１のノズル孔１１ｃは表面電極層８１に接合していればよいので、テーパー形状だけでなく、ノズル面に対して垂直な、いわゆるストレート形状でも良い。
【０２５６】
次に、イオンビームスパッタによって、矢印Ｋ１方向から（第１のノズル層１０表面に対して１８°）Ｔｉを成膜し、上記表面電極層８１と第１のノズル孔１１ｃの一部、および第１のノズル層１０上に、厚さ０．５μｍの第１の電極層２５を形成する。このとき、上記表面電極層８１に形成した流体吐出孔９の内部に、上記Ｔｉ膜が成膜されないよう、第１のノズル孔１１ｃの形状、第１のノズル層１０の厚さを考慮し、Ｔｉ粒子の入射方向を決定することが望ましい。また、ここでは基板を固定して第１の電極層２５を形成したが、上記入射角度を設定した後、ノズル面の法線方向を中心にして基板を回転させることで、第１のノズル孔１１ｃ側壁全面に第１の電極層２５を形成することができる。このようにして形成した第１のノズル孔側壁全面に付着する第１の電極層２５は、後述する第２のノズル孔加工の際の第１のノズル孔１１ｃの保護層として機能させることができる。
【０２５７】
次に、ドライエッチング法を用いて上記第１の電極層２５の第１のノズル層１０上の外形形状を加工する。本加工においては、参考形態において第２の電極層２６を加工する際に実施した加工方法を用いて行った。すなわち、ポジ型のフォトレジストで所望のパターンを形成した後、Ａｒガスを主成分とするプラズマを用いたドライエッチングによって加工を行った。ここでは、第１のノズル層１０と第２のノズル層２０の界面に配設される第１の電極層２５の形状を１６μｍ径の略円形形状とした(図１５（ｃ）参照)。
【０２５８】
次に、上記第１のノズル層１０の上に塗布型のポリイミド樹脂を厚さ２０μｍで成膜し、第２のノズル層２０を形成する（図１５（ｄ）参照）。ここで、上記塗布型ポリイミド樹脂は第１のノズル層１０上にスピンコートによって塗布し、３５０℃で２時間焼成した。ここで、流体吐出孔９および第１のノズル孔１１ｃもポリイミド樹脂にて埋められることになる。
【０２５９】
次に、上記第２のノズル層２０上にフォトリソグラフィによってレジストパターン７０を形成し、酸素を主成分とするガスを用いたドライエッチングを行い、第２のノズル層２０にテーパー形状（円錐台形状）の第２のノズル孔１１ｂを形成した（図１５（ｅ）参照）。
【０２６０】
なお、上記ドライエッチングは第１のノズル層１０あるいは第１の電極層２５あるいは表面電極層８１で止めることができる。すなわち、第１のノズル孔１１ｃを除いて第１のノズル層１０または第１の電極層２５が露出した部位では、ドライエッチングがそれ以上進行しない。また同様に、表面電極層８１の上記流体吐出孔９を除いて表面電極層８１が露出した部位では、ドライエッチングがそれ以上進行しない。すなわち、第２のノズル孔１１ｂの加工プロセスにおいて、先の工程でポリイミド樹脂にて埋められた、第１のノズル孔１１ｃおよび流体吐出孔９が、ポリイミド樹脂が除去されることによって再現され、流体吐出孔９は表面電極層８１に形成されたパターンによって決定される形状に存在する第２のノズル層２０材料が除去され、先の工程でポリイミド樹脂によって埋められた形状が再現される。
【０２６１】
次に、上記レジストパターン７０をレジスト剥離液を用いて除去し、上記第２のノズル層２０上に、Ｔｉを主成分とする金属材料からなる第２の電極層２６を成膜する。ここでは、イオンビームスパッタ法を用いて、０．２ｍＴｏｒｒのＡｒガス圧下で、Ａｒ原子によるＴｉ粒子の散乱を抑制しながら、矢印Ｋ２の方向からＴｉ粒子が飛来するように基板を傾斜し、第２のノズル層２０内壁面の片側のみに形成され、第２の電極層２６の一部が第１の電極層２５と電気的に短絡するように成膜した（図１５（ｆ）参照）。膜厚は０．５μｍである。このように、斜め方向からＴｉ粒子を入射しながら第２の電極層２６を形成することによって、流体吐出孔９内に第２の電極層２６が付着するのを防止することができ、これによって、流体吐出孔９の形状変化や閉塞することを防止することができる。
【０２６２】
次に、上記第２の電極層２６を加工するが、この工程は参考形態と同様であるので省略する。第２のノズル層上に形成された第２の電極層２６の形状は略７０μｍ径の円形形状とした。
【０２６３】
次に、硝酸と水が主成分である水溶液に浸漬し犠牲層５０のみをエッチングすることで、ノズルプレート８０を基板６からとりはずす（図１５（ｇ））。先に述べたように、第１のノズル層１０を形成するＳｉＯ_２、第２のノズル層２０を形成するポリイミド樹脂や表面電極層８１を形成するＰｔおよび、第１の電極層２５、第２の電極層２６を形成するＴｉは、上記犠牲層５０のエッチング液によってほとんどエッチングされることがないので、犠牲層５０のエッチングによって、形状の変化や構造的信頼性の低下を招来することがない。
【０２６４】
次に、第１のノズル層１０の表面に撥液層４を形成する（図１５（ｇ））。ここでは、塗布の容易さを考慮する趣旨でフッ素重合体を用い、これをスタンプなどの方法により第１のノズル層１０の表面に塗布し、高分子膜にて撥液層４を形成した。なお、第１のノズル孔１１ｃ内に回り込んだ撥液層については、撥液層形成後に、酸素を含有するプラズマを用い、第２のノズル孔１１ｂ側からドライエッチングすることで、これを除去した。これにより、ノズルプレート８０のダメージを最小限にすることができる。
【０２６５】
本実施の形態では、上記回り込みを酸素を含有するプラズマを用いたドライエッチでエッチング除去する。しかし、本実の形態においては、上述したように流体吐出面に酸素を含有するプラズマを用いたドライエッチに対して高い耐性を有する表面電極層８１が存在しており、この表面電極層８１が流体吐出孔９の形状を決定しているため、上記ドライエッチによって流体吐出孔９の形状が変化することがない。このため非常に高精度のノズル孔を形成することができる。
【０２６６】
具体的には、本実施の形態の工程を用いて作成した２００個の流体吐出孔９を有するノズルプレート８０の各流体吐出孔９の形状を評価したところ、ばらつきは±０．１５μmと非常に高精度に加工できた。また、ノズルプレート８０の反りも１０μm以下と非常に平坦であった。
【０２６７】
なお、本実施の形態では、犠牲層５０にＮｉ、表面電極層８１にＰｔ、第１のノズル層１０にＳｉＯ_２、第２のノズル層２０にポリイミド樹脂、第１の電極層２５にＴｉ、第２の電極層２６にＴｉを用いたが、この組み合わせに限定されない。
【０２６８】
犠牲層５０には、Ｎｉのほかに、表面電極層８１、第１のノズル層１０、第２のノズル層２０、に用いる材料との組み合わせによって、Ａｌ、Ｃｕ、などの硝酸、あるいはＫＯＨ水溶液に可溶な材料を用いることができる。また、犠牲層５０の形成方法についても鍍金以外に蒸着法、スパッタ法、塗布法などを材料に応じて用いることができる。
【０２６９】
第２のノズル層２０および第２の電極層２６には、犠牲層５０のエッチングによるダメージが軽微な材料を用いることができる。ただし、後述する第１のノズル層あるいは表面電極層８１とのエッチングの選択性を考慮したとき、酸素を含有するプラズマを用いたエッチングが可能な有機樹脂が望ましい。さらに、分子鎖同士が架橋反応している分子構造を有する有機樹脂を用いると、第２のノズル層２０の耐熱性、耐環境性が高く、ノズルプレートの信頼性を向上することができる。
【０２７０】
また、第１のノズル層１０および第１の電極層２５には、犠牲層５０のエッチングおよび第２のノズル孔１１ｂのエッチングに対して耐性の高い材料を用いることができる。さらに、表面電極層８１には、犠牲層５０のエッチングおよび第２のノズル孔１１ｂのエッチングおよび第１のノズル孔１１ｃのエッチングに対して耐性の高い材料を用いることができる。
【０２７１】
ここで、図１６に、使用材料（犠牲層、表面電極層、第１のノズル層、第２のノズル層、第１の電極層、第１の電極層の形成領域、第２の電極層）および加工方法（流体吐出孔、第１のノズル孔、第２のノズル孔、犠牲層除去）について好ましい組み合わせの例を示す。
【０２７２】
図１６に示すように、第１のノズル層１０あるいは第２のノズル層２０はポリイミドなどの有機樹脂やＳｉＯ_２のようなＳｉ化合物といった無機材料の組み合わせで、ノズル層を構成することができる。ただし、たとえばＳｉＯ_２/ＳｉＯ_２の組み合わせや、ポリイミド/ポリイミドといった組み合わせのように、第２のノズル孔加工の際に第１のノズル層１０が損傷を受けるような組み合わせの場合、第１の電極層２５を第１のノズル孔１１ｃの内壁全面に形成し、第１のノズル孔１１ｃを保護する必要がある。
【０２７３】
また、本実施の形態では、犠牲層５０をエッチングによって完全に除去したが、犠牲層５０を完全に除去する必要はなく、犠牲層５０のうち第１のノズル層１０と接している部分のみをエッチングによって除去すれば、ノズルプレート８０を基板６から取り外すことができる。
【０２７４】
また、撥液層４としては、フッ素重合体に限定されず、シリコン系の高分子膜、ＤＬＣ（ダイヤモンドライクカーボン）などを用いることもできる。
【０２７５】
以上の加工工程を用いることによって、上記した(１)〜(７)の作用を奏するノズルプレート８０を製造することができる。
【０２７６】
また、上述したすべての実施の形態を通して、撥液層４を形成しない構成を採用することができる。撥液層４を表面電極層８１、あるいは第１のノズル層１上に形成しないことによって、流体吐出孔９の形状精度がさらに向上する。
【０２７７】
また、上述したすべての実施の形態を通して、表面電極層８１、第１の電極層２５、第２の電極層２６、上述した材料を主成分とする金属膜を有する、複数の薄膜から構成されるいわゆる積層膜であっても良い。
【０２７８】
また、上述した各実施の形態では、基板６上に犠牲層５・５０を形成し、該犠牲層５・５０をエッチングすることによって、ノズルプレート８・８０を製造する方法について説明したが、これ以外に、例えばＮｉ板などのように、犠牲層５・５０のエッチングと同様の手法でエッチングすることのできる材料からなる基板上に、直接第１のノズル層１・１０を形成することもできる。
【０２７９】
最後に、本発明は上述した各実施の形態に限定されるものではなく、請求項に示した範囲で種々の変更が可能であり、異なる実施の形態にそれぞれ開示された技術的手段を適宜組み合わせて得られる実施形態についても本発明の技術的範囲に含まれる。
【０２８０】
【発明の効果】
本発明のノズルプレートは、以上のように、第１のノズル孔を有し、流体吐出側に配される薄層の第１のノズル層と、該第１のノズル層の流体供給側に積層され、上記第１のノズル層よりも厚層で、かつ上記第１のノズル孔と連通すると共に第１のノズル孔とでノズル孔部を構成する第２のノズル孔を有する第２のノズル層を少なくとも一層備え、該第１のノズル孔の内壁に成膜された第１の電極層と、第２のノズル孔の内壁に成膜された第２の電極層とが電気的に接続されていることを特徴としている。
【０２８１】
上記構成により、第１のノズル層に形成される第１のノズル孔は、孔径を例えば１０μｍ以下といった超微細に形成することができると共に、このような超微細な第１のノズル孔内壁に第１の電極層を層厚方向に安定して成膜することが可能となり、流体吐出面の第１のノズル孔の開口部を流体吐出孔とした場合、この流体吐出孔近傍にまで第１の電極を成膜することができる。その結果、ノズル内部の電気抵抗Ｒを従来に比べ飛躍的に低減することができ、流体の吐出周波数を向上が図れ、記録媒体に対する高速描画が可能となる。
【０２８２】
しかも、このように形成された第１の電極層は、第１のノズル孔と連通する第２のノズル孔に形成された第２の電極層と電気的に接続されているので、第２の電極層を介してノズルプレートの流体供給側より駆動信号を供給することが可能となる。したがって、第１の電極層に駆動信号を供給するための引き出し配線が媒体に近接することがなく、引き出し配線から発生する電界によって、記録媒体が電気的な損傷を受けるようなこともない。
【０２８３】
また、本発明のノズルプレートでは、さらに、上記第１のノズル孔の流体吐出側に、第１のノズル孔の流体吐出側開口部を塞ぐように、第１のノズル孔の流体吐出側開口部よりも小さい径の貫通孔を有する円板状の表面電極層が配され、該貫通孔と第１のノズル孔とが連通すると共に、上記表面電極層が第１の電極層と電気的に接続されていることを特徴としている。
【０２８４】
上記構成によれば、ノズルプレートの流体吐出面に備えられた表面電極層の貫通孔が流体吐出孔となるので、吐出流体の着弾精度に大きな影響を与える流体吐出孔を表面電極層のエッチングで加工することができる。これによって、内壁に第１の電極層が成膜されている第１のノズル孔の流体吐出側開口部を流体吐出孔とした構成よりもさらに、流体吐出孔の形状精度が飛躍的に安定し、これにともない着弾精度のさらなる安定化が可能となる。
【０２８５】
本発明のノズルプレートの製造方法は、以上のように、基板上に犠牲層を形成する工程と、上記犠牲層上に第１のノズル層を形成する工程と、上記第１のノズル層に複数の第１のノズル孔を形成する工程と、上記第１のノズル層上に各第１のノズル孔の内壁面を含めて第１の電極層を形成する工程と、各第１のノズル孔内壁と各第１のノズル孔周囲部とに残るように上記第１の電極層を加工する工程と、上記第１のノズル層上に、残留する各第１の電極層部分も含めて第２のノズル層を形成する工程と、上記第２のノズル層に複数の第２のノズル孔を、各第２のノズル孔の流体吐出側の開口部が上記第１のノズル層上に残留する各第１の電極層部分に収まるように形成する工程と、上記第２のノズル層上に各第２のノズル孔の内壁面を含めて第２の電極層を形成する工程と、隣接する第２のノズル孔間で電気的に分離されるように第２の電極層を加工する工程とを備えることを特徴としている。
【０２８６】
これによれば、剛性の高い基板上に、犠牲層を介して第１のノズル層、第１の電極層、第２のノズル層、第２の電極層を順次積層する。このため、フォトリソグラフィ技術を利用してレジストパターンを形成後、ドライエッチングによって所望の形状に加工できるため、第１のノズル孔、第２のノズル孔、第１の電極層、第２の電極層を非常に高い形状精度で形成することができる。
【０２８７】
また、ノズルプレートの流体吐出面が、工程の最終段階まで犠牲層によって保護されているため、ノズルプレート製造工程において流体吐出孔が損傷をうけて流体吐出孔が変形するといった危険がない。このため、ノズルプレートの製造歩留まりが向上する。
【０２８８】
また、本発明のノズルプレートの製造方法では、さらに、基板上に犠牲層を形成する工程と犠牲層上に第１のノズル層を形成する工程との間に、上記犠牲層上に表面電極層を形成し、該表面電極層をノズル孔部形成部位に対応して分離すると共に各分離部に貫通孔を形成する工程とを有し、犠牲層上の第１のノズル層を形成する工程では、分離された表面電極層上も含めて第１のノズル層を形成することを特徴とすることもできる。
【０２８９】
本構成のノズルプレートの製造方法は、犠牲層上に形成した表面電極層に貫通孔として流体吐出孔を加工することができるので、第１のノズル孔内に形成された第１の電極層の不均一性（たとえば膜厚分布）によって、流体吐出孔の形状が変形することがなく、さらに高精度の流体吐出孔を有するノズルプレートを製造することができる。
【図面の簡単な説明】
【図１】 本発明の基本となる吐出モデルにおいて、ノズルの電界強度の計算を説明するための図である。
【図２】 表面張力圧力および静電的圧力のノズル径依存性のモデル計算結果を示すグラフである。
【図３】 吐出圧力のノズル径依存性のモデル計算結果を示すグラフである。
【図４】 吐出限界電圧のノズル径依存性のモデル計算結果を示すグラフである。
【図５】 荷電液滴と基板の間に働く鏡像力とノズル−基板間距離の相関を示したグラフである。
【図６】 ノズルから流出する流量と印加電圧との相関関係のモデル計算結果を示したグラフである。
【図７】 （ａ）（ｃ）は、本発明の参考形態にかかるノズルプレートを示す斜視図であり、（ｂ）は、（ａ）のＡ−Ａ’線断面図である。
【図８】 上記ノズルプレートにおける第１の電極層と第２の電極層との接続部分を示す説明図である。
【図９】 本参考形態にかかるノズルプレートの変形例を示すもので、図７（ｃ）に相当する断面図である。
【図１０】 （ａ）〜（ｉ）は、本参考形態の上記ノズルプレートの製造方法を断面の構成により示す説明図である。
【図１１】 （ａ）〜（ｃ）は、図１０（ｅ）に示す工程を、ノズルプレートの断面の構成により詳細に示す説明図である。
【図１２】 本参考形態にかかるノズルプレートを製造する場合に、各層の使用材料と加工方法との好ましい組み合わせを示す説明図である。
【図１３】 （ａ）（ｃ）は、本発明の実施の形態にかかるノズルプレートを示す斜視図であり、（ｂ）は、（ａ）のＢ−Ｂ’線断面図である。
【図１４】 本発明の実施の形態にかかるノズルプレートの変形例を示すもので、図１３（ｃ）に相当する断面図である。
【図１５】 （ａ）〜（ｇ）は、本発明の実施の形態の上記ノズルプレートの製造方法を断面の構成により示す説明図である。
【図１６】 本発明の実施の形態にかかるノズルプレートを製造する場合に、各層の使用材料と加工方法との好ましい組み合わせを示す説明図である。
【図１７】 従来の静電吸引型インクジェット装置の概略構成断面図である。
【図１８】 （ａ）〜（ｃ）は、図１７に示すインクジェット装置におけるインクのメニスカスの挙動を説明する図である。
【図１９】 従来の他の静電吸引型インクジェット装置の概略構成図である。
【図２０】 図１９に示すインクジェット装置のノズル部分の概略断面斜視図である。
【図２１】 図１９に示すインクジェット装置のインク吐出原理を説明する図である。
【図２２】 図１９に示すインクジェット装置のノズル部分での電圧印加時における微粒子の状態を説明する図である。
【図２３】 図１９に示すインクジェット装置のノズル部分における微粒子体形成の原理を説明する図である。
【図２４】 （ａ）〜（ｃ）は、図１９に示すインクジェット装置におけるインクのメニスカスの挙動を説明する図である。
【図２５】 （ａ）は、静電吸引型流体吐出装置における概略構成図であり、（ｂ）はその等価回路である。
【図２６】 静電吸引型インクジェット装置に用いられる従来のノズルプレートの側面断面図である。
【図２７】 従来の静電吸引型インクジェット装置の記録ヘッド部分の構成を示す断面図である。
【図２８】 図２８の静電吸引型インクジェット装置の記録ヘッド部分におけるインク吐出孔を示す部分拡大断面平面図である。
【符号の説明】
１ 第１のノズル層
２ 第２のノズル層
４ 撥液膜
５ 犠牲層
８ ノズルプレート
９ 流体吐出孔
１０ 第１のノズル層
１１ ノズル孔（ノズル孔部）
１１ａ 第１のノズル孔
１１ｃ 第１のノズル孔
１１ｂ 第２のノズル孔
２０ 第２のノズル層
２５ 第１の電極層
２５ｂ 延設部（延設された第１の電極層部分）
２６ 第２の電極層
５０ 犠牲層
８０ ノズルプレート
８１ 表面電極層[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a nozzle plate used in a fluid ejection head that ejects fluid such as ink, and more particularly, an electrostatic suction type fluid ejection device that ejects fluid onto an object by electrostatically attracting the fluid by charging the fluid. Nozzle plate used for
[0002]
[Prior art]
  In general, there are various types of fluid jet methods for ejecting fluid such as ink onto an object (recording medium). Here, an ink jet method using ink as a fluid will be described.
[0003]
  As on-demand type ink jet methods, piezoelectric methods utilizing piezoelectric phenomena, thermal methods utilizing ink film boiling phenomenon, electrostatic suction methods utilizing electrostatic phenomena, etc. have been developed. There is an increasing demand for ink jet systems. In order to realize high-resolution inkjet recording, it is indispensable to make the discharged ink droplets minute.
[0004]
  Here, the behavior until the ink droplet ejected from the nozzle lands on the recording medium is as follows:
      ρink ・ (4/3 ・ π ・ d^Three) ・ Dv / dt
      =-Cd ・ (1/2 ・ ρair ・ v²) ・ (Π ・ d²/ 4) (1)
Can be represented by the equation of motion (Equation (1)).
[0005]
  Where ρink is the ink volume density, v is the droplet velocity, Cd is the drag coefficient, ρair is the air density, d is the ink droplet radius, and Cd is
      Cd = 24 / Re ・ (1 + 3/16 ・ Re^0.62) (2)
(2) expressed by
[0006]
  The Re is the Reynolds number, and η is the viscosity of the air,
      Re = 2 · d · ρink · v / η (3)
(3) expressed by
[0007]
  The influence of the droplet radius on the kinetic energy of the ink droplet on the left side of the equation (1) is larger than the influence of the droplet radius on the viscous resistance of air. For this reason, in the case of the same speed, the smaller the droplet, the faster the droplet speed decelerates, and the recording medium at a predetermined distance cannot be reached, or even if it reaches, the landing accuracy will be poor.
[0008]
  In order to prevent this, it is necessary to increase the initial discharge speed of the droplets, that is, to increase the discharge energy per unit volume.
[0009]
  However, the conventional piezo-type and thermal-type inkjet heads have the following problems when the discharge droplets are miniaturized, that is, when the discharge energy per unit volume of the discharge droplets is increased. In other words, it was particularly difficult to make the diameter of the droplet (hereinafter referred to as the droplet diameter) 10 μm or less.
[0010]
  Problem 1: The ejection energy of a piezo ink jet head is related to the amount of displacement and generated pressure of a driving piezoelectric element. The displacement amount of this piezoelectric element is closely related to the ink discharge amount, that is, the ink droplet size. In order to reduce the droplet size, it is necessary to reduce the displacement amount, and the discharge energy per unit volume of the discharge droplet It is difficult to improve.
[0011]
  Problem 2: Since the thermal ink jet head uses the ink film boiling phenomenon, the pressure at the time of bubble formation has a physical limit, and the ejection energy is almost determined by the area of the heating element. The area of the heating element is substantially proportional to the volume of the generated bubble, that is, the ink discharge amount. For this reason, if the ink droplet size is reduced, the generated bubble volume is reduced and the ejection energy is reduced. Therefore, it is difficult to improve the ejection energy per unit volume of the ink ejection droplet.
[0012]
  Problem 3: In both the piezo method and the thermal method, the driving amount of the driving (heating) element is closely related to the discharge amount, so that it is very difficult to suppress the variation particularly when discharging a very small droplet size.
[0013]
  Therefore, as a method for solving the above-described problems, a method for ejecting micro droplets by an electrostatic suction method has been developed.
[0014]
  In the electrostatic suction method, the equation of motion of the ink droplets ejected from the nozzle is expressed by the following equation (4).
[0015]
      ρink ・ (4/3 ・ π ・ d^Three) ・ Dv / dt
     = q ・ E- Cd ・ (1/2 ・ ρair ・ v²) ・ (Π ・ d²/ 4) (4)
  Here, q is the charge amount of the droplet, and E is the ambient electric field strength.
[0016]
  From the above formula (4), in the electrostatic attraction method, the discharged droplets receive electrostatic force during the flight separately from the discharge energy, so that the discharge energy per unit volume can be reduced, Application to discharge becomes possible.
[0017]
  As such an electrostatic suction type ink jet device (hereinafter referred to as an electrostatic suction type ink jet device), for example, Patent Document 1 discloses an ink jet device in which an electrode for applying a voltage is provided inside a nozzle. . Patent Document 2 discloses an ink jet apparatus that uses a nozzle as a slit and is provided with a needle electrode protruding from the nozzle to eject ink containing fine particles.
[0018]
  The ink jet device disclosed in Patent Document 1 will be described below with reference to FIG. FIG. 17 is a schematic cross-sectional view of the ink jet apparatus.
[0019]
  In the figure, 101 is an ink ejection chamber, 102 is ink, 103 is an ink chamber, 104 is a nozzle hole, 105 is an ink tank, 106 is an ink supply path, 107 is a rotating roller, 108 is a recording medium, 110 is a control element unit, Reference numeral 111 denotes a process control unit.
[0020]
  Further, reference numeral 114 denotes an electrostatic field applying electrode portion disposed on the ink chamber 103 side of the ink ejecting chamber 101, 115 denotes a counter electrode portion that is a metal drum installed on the rotating roller 107, and 116 denotes a number of the counter electrode portion 115. This is a bias power supply unit for applying a negative voltage of 1000V. 117 is a high-voltage power supply unit that supplies a high voltage of several hundred volts to the electrostatic field applying electrode unit 114, and 118 is a grounding unit.
[0021]
  Here, between the electrostatic field applying electrode part 114 and the counter electrode part 115, the bias power supply part 116 having a negative voltage of several thousand volts applied to the counter electrode part 115 and the high voltage power supply part 117 having a voltage of several hundred volts are used. A superposed electric field is formed by superimposing the high voltage, and ejection of the ink 102 from the nozzle hole 104 is controlled by the superposed electric field.
[0022]
  Reference numeral 119 denotes a convex meniscus formed in the nozzle hole 104 by a bias voltage of several thousand volts applied to the counter electrode portion 115.
[0023]
  The operation of the electrostatic suction ink jet apparatus configured as described above will be described below.
[0024]
  First, the ink 102 is transferred to the nozzle hole 104 that discharges the ink 102 through the ink supply path 106 by capillary action. At this time, a counter electrode portion 115 on which the recording medium 108 is mounted is disposed so as to face the nozzle hole 104.
[0025]
  A convex ink meniscus 119 is formed in the ink 102 that has reached the nozzle hole 104 by a bias voltage of several thousand volts applied to the counter electrode portion 115. By applying a signal voltage from the high voltage power supply unit 117 of several hundred volts to the electrostatic field applying electrode unit 114 disposed in the ink chamber 103, the voltage from the bias power supply unit 116 applied to the counter electrode unit 115 is obtained. The ink 102 is superposed and the ink 102 is ejected onto the recording medium 108 by the superposed electric field to form a print image.
[0026]
  The behavior of the meniscus until the droplets fly in the ink jet apparatus disclosed in Patent Document 1 will be described below with reference to FIGS. 18 (a) to 18 (c).
[0027]
  Before the drive voltage is applied, as shown in FIG. 18A, a state in which a raised meniscus 119a is formed on the ink surface due to the balance between the electrostatic force due to the bias voltage applied to the ink and the surface tension of the ink. It has become.
[0028]
  When a driving voltage is applied in the above state, as shown in FIG. 18B, the meniscus 119b starts to move toward the center of the liquid surface rise, and the center of the liquid surface rise is caused. A raised meniscus 119b is formed.
[0029]
  Thereafter, when the drive voltage is continuously applied, as shown in FIG. 18 (c), the charge generated on the liquid surface is further concentrated at the center to form a meniscus 119c called a tailor cone. Droplets are separated and ejected when the electrostatic force due to the amount of charge concentrated on the top of the cone exceeds the surface tension of the ink.
[0030]
  Next, the ink jet apparatus disclosed in Patent Document 2 will be described below with reference to FIG. FIG. 19 is a schematic configuration diagram of an ink jet apparatus.
[0031]
  Inside the holding member of the ink jet apparatus, as shown in the figure, a line type recording head 211 formed of a low dielectric material (acrylic resin, ceramics, etc.) as an ink jet head, and an ink discharge hole of the recording head 211 are provided. A counter electrode 210 made of a metal or a high dielectric material arranged so as to face each other, an ink tank 212 for storing ink in which charged pigment particles are dispersed in a non-conductive ink medium, an ink tank 212 and a recording head 211 An ink circulation system (pumps 214a and 214b, pipes 215a and 215b) that circulates ink between them and a pulse that applies a pulse voltage to each ejection electrode 211a to draw an ink droplet that forms one pixel of a recorded image. Voltage generator 213, a drive circuit for controlling pulse voltage generator 213 according to image data (illustrated 1), a recording medium transport mechanism (not shown) for passing the recording medium 230 through a gap provided between the recording head 211 and the counter electrode 210, a controller (not shown) for controlling the entire apparatus, and the like are accommodated. ing.
[0032]
  The ink circulation system includes two pipes 215a and 215b that connect between the recording head 211 and the ink tank 212, and two pumps 214a and 214b that are driven by the controller.
[0033]
  The ink circulation system is divided into an ink supply system for supplying ink to the recording head 211 and an ink recovery system for recovering ink from the recording head 211.
[0034]
  In the ink supply system, ink is sucked up from the ink tank 212 by the pump 214a, and is pumped to the ink supply unit of the recording head 211 via the pipe 215a. On the other hand, in the ink recovery system, ink is sucked by the pump 215b from the ink recovery portion of the recording head 211, and is forcibly recovered to the ink tank 212 via the pipe 215b.
[0035]
  Further, as shown in FIG. 20, the recording head 211 has an ink supply part 220a for expanding the ink fed from the pipe 215a of the ink supply system to the line width, and an ink flow for guiding the ink from the ink supply part 220a into a mountain shape. Slit ink having an appropriate width (about 0.2 mm) that opens the top of the ink collecting portion 220b and the ink channel 221 to the counter electrode 210 side, the path 221, the ink channel 221 and the pipe 215b of the ink collecting system. The ejection holes 222, a plurality of ejection electrodes 211a arranged in the ink ejection holes 222 at a predetermined pitch (about 0.2 mm), and made of a low dielectric material (for example, ceramic) disposed on both sides and the upper surface of each ejection electrode 211a (Made) partition wall 223 is provided.
[0036]
  Each of the discharge electrodes 211a is made of a metal such as copper or nickel, and a low dielectric film (for example, a polyimide film) for preventing pigment adhesion having good wettability is formed on the surface thereof. The tip of each ejection electrode 211a is formed in a triangular pyramid shape, and each of the ejection electrodes 211a protrudes from the ink ejection hole 222 toward the counter electrode 210 by an appropriate length (70 μm to 80 μm).
[0037]
  When the above-described driving circuit (not shown) gives a control signal to the pulse voltage generator 213 for a time corresponding to the gradation data included in the image data in accordance with the control of the controller, the pulse voltage generator 213 A high voltage signal obtained by placing a pulse top pulse Vp corresponding to the type of the control signal on the bias voltage Vb is superimposed on the bias voltage Vb and output.
[0038]
  Then, when the image data is transferred, the controller drives the two pumps 214a and 214b of the ink circulation system. As a result, the ink is pumped from the ink supply unit 220a and the ink recovery unit 220b becomes negative pressure, so that the ink flowing through the ink flow path 221 crawls up through the gaps of the partition walls 223 by capillary action. It spreads wet to the tip of 211a. At this time, since a negative pressure is applied to the ink liquid surface near the tip of each discharge electrode 211a, an ink meniscus is formed at the tip of each discharge electrode 211a.
[0039]
  Further, the recording medium transport mechanism is controlled by the controller, so that the recording medium 230 is sent in a predetermined direction indicated by an arrow in the figure, and the drive circuit is controlled so that the recording medium 230 is disposed between the ejection electrode 211a and the above. The high voltage signal is applied.
[0040]
  The behavior of the meniscus until the droplets fly in the ink jet apparatus disclosed in Patent Document 2 will be described below with reference to FIGS.
[0041]
  As shown in FIG. 21, when the pulse voltage from the pulse voltage generator 213 is applied to the ejection electrode 211a in the recording head 211, an electric field is generated from the ejection electrode 211a side toward the counter electrode 210 side. Here, since the discharge electrode 211a having a sharp tip is used, the strongest electric field is generated in the vicinity of the tip.
[0042]
  When such an electric field is generated, as shown in FIG. 22, each charged pigment particle 201a in the ink solvent moves toward the ink surface by a force fE (FIG. 21) exerted from this electric field. Thereby, the pigment concentration near the ink surface is concentrated.
[0043]
  When the pigment concentration is concentrated in this way, as shown in FIG. 23, a plurality of charged pigment particles 201a starts to agglomerate near the surface of the ink and are placed on the opposite side of the electrode. When the pigment aggregate 201 starts to grow in a spherical shape near the ink liquid surface, the electrostatic repulsion force fcon from the pigment aggregate 201 starts to act on each charged pigment particle 201a. That is, the resultant force ftotal of the electrostatic repulsion force fcon from the pigment aggregate 201 and the force fE from the electric field E caused by the pulse voltage acts on each charged pigment particle 201a.
[0044]
  Therefore, within the range in which the electrostatic repulsion between the charged pigment particles does not exceed the cohesive force of each other, the charged pigment particles 201a (the tip of the discharge electrode 211a and the pigment aggregates) acted by the resultant force ftotal directed to the pigment aggregate 201. If the force fE exerted from the electric field on the charged pigment particle 201a) on the straight line connecting the center of 201 exceeds the electrostatic repulsion force fcon from the pigment aggregate 201 (fE ≧ fcon), the charged pigment particle 201a is a pigment. Grows into aggregates 201.
[0045]
  A pigment aggregate 201 formed from n charged pigment particles 201a receives an electrostatic repulsion force FE from an electric field E caused by a pulse voltage, and receives a restraining force Fesc from an ink solvent. When the electrostatic repulsive force FE and the restraining force Fesc are balanced, the pigment aggregate 201 is stabilized in a state of slightly protruding from the ink liquid surface.
[0046]
  Further, when the pigment aggregate 201 grows and the electrostatic repulsive force FE exceeds the restraining force Fesc, as shown in FIGS. 24 (a) to 24 (c), the pigment aggregate 201 is separated from the ink liquid level 200a. Escape.
[0047]
  By the way, according to the principle of the conventional electrostatic attraction method, the electric charges are concentrated at the center of the meniscus to generate the bulge of the meniscus. The radius of curvature of the tip of the raised tailor cone is determined by the amount of charge concentration, and when the electrostatic force due to the concentrated charge amount and electric field strength then surpasses the meniscus surface tension, the separation of the droplets begins.
[0048]
  Since the maximum charge amount of the meniscus is determined by the physical property value of the ink and the radius of curvature of the meniscus, the minimum droplet size is determined by the physical property value of the ink (particularly the surface tension) and the electric field strength formed in the meniscus portion.
[0049]
  In general, the surface tension of a liquid tends to be lower when it contains a solvent than a pure solvent, and since various inks are included in actual ink, increasing the surface tension is not possible. difficult. For this reason, it is considered that the surface tension of the ink is constant and the droplet size is reduced by increasing the electric field strength.
[0050]
[Patent Document 1]
          JP-A-8-238774 (published September 17, 1996)
[0051]
[Patent Document 2]
          JP 2000-127410 A (published May 9, 2000)
[0052]
[Patent Document 3]
          JP 58-31757 A (published February 24, 1983)
[0053]
[Patent Document 4]
          Japanese Patent Laid-Open No. 10-175305 (published June 30, 1998)
[0054]
[Patent Document 5]
          Japanese Patent Laid-Open No. 11-42784 (published February 16, 1999)
[0055]
[Problems to be solved by the invention]
  However, as described above, in the conventional electrostatic attraction method, a method of reducing the droplet size by increasing the electric field strength is used. However, in the ink jet devices disclosed in Patent Documents 1 and 2 above, In both cases, as a discharge principle, by forming a field with a strong electric field strength in a meniscus region having an area far larger than the projected area of the discharged droplet, the charge is concentrated at the center of the meniscus and formed with the concentrated charge. In order to perform ejection by an electrostatic force having a certain electric field strength, it is necessary to apply a very high voltage close to 2000V. As a result, drive control is difficult, and there are also problems in terms of safety in operating the ink jet apparatus.
[0056]
  As a result of intensive studies in view of such problems, the inventors of the present application have found that a discharge phenomenon occurs in a discharge model different from the conventional fluid discharge model below a certain nozzle diameter, and a portion where ink is discharged (discharge start) It was found that the electric field strength can be increased without applying a high voltage by reducing the width or the diameter of the portion.
[0057]
  Here, with reference to FIGS. 25A and 25B, basic characteristics of electrostatic suction type microfluidic discharge, in particular, surface potential due to charges accumulated in the meniscus at the nozzle tip will be considered.
[0058]
  First, as shown in FIG. 25A, a simple configuration of the electrostatic suction type fluid ejection device is modeled. In the simple model, the drive electrode 251 is installed inside the nozzle 250 having a sharp point, and the discharge material 252 is filled in the entire nozzle. A substrate 254 is disposed to face the nozzle tip surface, and is grounded by the back electrode 255.
[0059]
  In the case of such a simple configuration model, when the electric charge flowing out from the power supply 256 passes through the fluid 252 that is a discharge material inside the nozzle 250 and faces the substrate 254 on the meniscus 257 having capacitance at the tip of the nozzle. Because of this, the power supply voltage V as shown in FIG.₀And a series circuit of an electric resistance R inside the nozzle and a capacitance C between the meniscus 257 and the substrate 254.
[0060]
  V₀The RC series circuit can be expressed as follows using the accumulated charge Q (t) on the meniscus 257.
[0061]
      R dQ (t) / dt + Q (t) / C = V₀  (5)
Solving the differential equation (5), the accumulated charge Q (t) on the meniscus surface and the meniscus surface potential V (t) can be expressed as follows.
[0062]
      Q (t) = C V₀[1-exp (-t / RC)] (6)
      V (t) = V₀[1-exp (-t / RC)] (7)
  As described above, the accumulated charge Q (t) and meniscus surface potential V (t) on the meniscus surface at a certain time t depend on the electric resistance R inside the nozzle 250 and the capacitance C between the meniscus 257 and the substrate 254. You can see that That is, in the electrostatic suction type fluid discharge device having such a configuration, by reducing the electric resistance R inside the nozzle 250, electric charges are easily accumulated on the surface of the meniscus 257, and the time required for discharging the fluid 252 is reduced. It can be shortened. That is, the discharge frequency can be improved and high-speed drawing can be performed.
[0063]
  As a specific measure for reducing the electrical resistance R inside the nozzle 250, it is desirable to make the drive electrode 251 as close to the tip of the nozzle 250 as possible.
[0064]
  Patent Document 4 discloses a technique for forming an electrode inside a nozzle hole of an electrostatic suction type inkjet nozzle. FIG. 26 is a cross-sectional view showing a nozzle plate manufacturing process in Patent Document 4. The configuration and configuration of Patent Document 4 will be described with reference to FIG.
[0065]
  In the figure, reference numeral 301 denotes a nozzle plate. A plurality of ink reservoir recesses A are formed in the nozzle plate 301 in advance, and conductive plating is applied to the surface of the nozzle plate 301 where the ink reservoir recesses A are not formed. The non-fixed resist layer 302 303 is coated. Then, after the nozzle hole B penetrating the nozzle plate 301 and the resist layer 302 is formed so as to communicate with each ink reservoir recess A, a conductive plating 303 is applied to the inner periphery of the nozzle. Here, since the material to which the conductive plating 303 is not fixed is selected for the resist layer 302, the conductive plating 303 is fixed only to the inside of the nozzle plate 301 and the surface of the nozzle plate 301 where the resist layer 302 is not formed. Will be. Thus, in Patent Document 4, the electrode layer (conductive plating 303) is formed inside the nozzle hole.
[0066]
  Further, Patent Document 5 discloses a configuration in which electrodes are formed on a recording medium facing surface of a nozzle plate of an electrostatic suction type ink jet head. FIG. 27 is an explanatory diagram showing the configuration of the ink-jet head according to Patent Document 5. Patent Document 5 will be described with reference to FIG.
[0067]
  The ink-jet head has a control electrode 401 formed on the surface of the insulation control substrate 411 and a control electrode 402 formed on the back surface thereof. The control electrode 401 or 402 penetrates from the ink tank 430 so that ink can pass through. Ink ejection holes 413 are formed. An ink guide 412 having a protrusion is disposed in the ink discharge hole 413, and an electric field due to a voltage applied to the control electrodes 401 and 402 is concentrated on the tip of the ink guide 412, and the ink droplet 414 is caused by this electric field. It flies to the recording medium 421 installed through the counter electrode 420.
[0068]
  However, the methods disclosed in Patent Documents 4 and 5 have the following problems and cannot be applied to an electrostatic suction type fluid discharge device in which the width or diameter of the portion where ink is discharged is reduced. .
[0069]
  First, according to the configuration of Patent Document 4, according to this, since the conductive plating 303 is formed in a region other than the medium facing surface of the nozzle plate 301, each ink reservoir recess A and nozzle hole B are formed. The formed conductive plating 303 is electrically short-circuited with each other. For this reason, such a nozzle plate 301 cannot eject only one specific channel, and in order to improve the resolution of a drawn image, it is necessary to electrically separate adjacent channels.
[0070]
  For example, the following methods (1) and (2) can be considered.
(1) After forming the conductive plating 303, the ink inflow surface side where the ink reservoir recesses A ... of the nozzle plate 301 are formed is processed, and the conductive plating 303 is divided into channels.
(2) Before forming the conductive plating 303, a resist layer similar to the ejection surface is formed on the ink inflow surface side of the nozzle plate 301 to create a region where the conductive plating 303 is not attached.
[0071]
  However, in the method of (1) dividing after forming the conductive plating layer 303, if machining is used for the dividing process, dust such as cutting waste enters the nozzle hole B, nozzle clogging occurs, and heat such as laser is generated. In the cutting process using the heat, stress due to heat remains and the nozzle plate 301 is deformed by the stress.
[0072]
  Further, it is conceivable to perform a cutting process by etching. However, when etching is used, it is necessary to form a resist pattern on the conductive plating 303 formed on the ink inflow surface side of the nozzle plate. As described above, in the case of a nozzle plate applied to an electrostatic suction type fluid ejecting apparatus in which the width or diameter of the portion where ink is ejected is reduced, the nozzle plate has a nozzle hole of 10 μm or less. In order to improve accuracy, it is desirable to use a nozzle plate base material of about 50 μm. However, since such a thin nozzle plate has low rigidity, when creating a resist pattern, it is easily deformed in handling the nozzle plate, and a pattern with high accuracy cannot be formed.
[0073]
  This also applies to the method (2) described above. Since the nozzle plate itself is thin, the nozzle plate is similarly deformed even before the conductive plating 303 is formed, and a resist pattern can be formed with high accuracy. Therefore, good channel separation cannot be performed.
[0074]
  Furthermore, the technique of Patent Document 4 has a problem that when the nozzle hole diameter is as small as 10 μm or less, the plating solution is not sufficiently supplied, and it is extremely difficult to stably form conductive plating inside the nozzle hole. In this case, it is the nozzle tip that has the shortest supply of plating solution. As described above, it is desirable that the electrode be as close as possible to the tip of the nozzle, and this makes it impossible to stably form the electrode at the most important nozzle tip.
[0075]
  That is, the smaller the nozzle diameter, the smaller the amount of fluid that can be discharged and the better the drawing resolution, but the formation of the electrode becomes unstable. For this reason, the electrical resistance R inside the nozzle at the nozzle tip changes for each channel, whereby the response frequency changes for each channel, and it becomes difficult to uniformly control the appropriate amount of discharge liquid between channels. That is, the print quality of the drawn image is significantly reduced.
[0076]
  On the other hand, since the insulation control substrate 411 corresponding to the nozzle plate disclosed in Patent Document 5 has the control electrode 401 formed on the surface facing the recording medium 421, the position of the electrode with respect to the meniscus is set with very high accuracy. can do. For this reason, there is no problem as in the configuration of Patent Document 4, ejection stability between channels is high, and electrical separation from adjacent channels is sufficient.
[0077]
  However, as shown in FIG. 28, in the configuration of Patent Document 5, a lead-out wiring 405 for applying a voltage from the voltage applying means to the control electrode 401 is simultaneously formed on the surface of the insulation control substrate 411 facing the recording medium 421. In this case, however, an electric field is also generated from the lead-out wiring 405. In particular, a concentrated electric field is likely to be generated from the bent portion 405a of the lead-out wiring 405, and there is a high risk that the electronic component will be damaged by the electric field, for example, when drawing on the electric component.
[0078]
  The present invention has been made in view of the above problems, and is a nozzle plate that can be suitably used for an electrostatic suction type fluid discharge device that discharges an extremely small amount of fluid, and is stable in the vicinity of the nozzle tip. An electrode can be formed, and it is easy to electrically separate a plurality of nozzle holes, and a drive signal can be applied to the electrode formed in the nozzle hole from the fluid supply side of the nozzle plate. It aims at providing the nozzle plate which can be performed, and its manufacturing method.
[0079]
[Means for Solving the Problems]
  In order to solve the above problems, a nozzle plate of the present invention is provided in an electrostatic suction type fluid discharge device that discharges a fluid charged by voltage application from a fluid discharge hole at the tip of a nozzle by electrostatic suction. In the nozzle plate having the hole, the first nozzle hole is provided, and is laminated on the fluid supply side of the first nozzle layer. At least one second nozzle layer having a second nozzle hole that is thicker than one nozzle layer, communicates with the first nozzle hole, and forms a nozzle hole portion with the first nozzle hole is provided. The first electrode layer formed on the inner wall of the first nozzle hole and the second electrode layer formed on the inner wall of the second nozzle hole are electrically connected. It is said.
[0080]
  According to the above configuration, the nozzle plate has a configuration in which at least one thick second nozzle layer is laminated on the thin first nozzle layer, so that the strength and rigidity of the nozzle plate itself is reduced to the second. The nozzle layer can be secured, and the thickness of the first nozzle layer can be sufficiently reduced. By reducing the layer thickness, the first nozzle hole formed in the first nozzle layer can be formed very finely with a hole diameter of, for example, 10 μm or less, and such an ultrafine first nozzle is formed. The first electrode layer can be stably formed in the layer thickness direction on the inner wall of the hole. When the opening of the first nozzle hole on the fluid discharge surface is a fluid discharge hole, the first electrode layer is formed in the vicinity of the fluid discharge hole. The first electrode can be formed up to. As a result, the electrical resistance R inside the nozzle can be drastically reduced as compared with the conventional case, the fluid discharge frequency can be improved, and high-speed drawing on the recording medium becomes possible.
[0081]
  Moreover, since the first electrode layer formed in this way is electrically connected to the second electrode layer formed in the second nozzle hole communicating with the first nozzle hole, the second electrode layer A drive signal can be supplied from the fluid supply side of the nozzle plate via the electrode layer. Accordingly, the lead-out wiring for supplying the drive signal to the first electrode layer does not come close to the medium, and the recording medium is not electrically damaged by the electric field generated from the lead-out wiring.Yes.
[0082]
  In the nozzle plate of the present invention, the fluid discharge side opening of the first nozzle hole is further closed on the fluid discharge side of the first nozzle hole.Smaller diameter than the fluid discharge side opening of the first nozzle holeWith a through holeDisk-shapedA surface electrode layer is disposed, the through hole and the first nozzle hole communicate with each other, and the surface electrode layer is electrically connected to the first electrode layer.
[0083]
  According to the above configuration, since the through hole of the surface electrode layer provided on the fluid discharge surface of the nozzle plate becomes the fluid discharge hole, the fluid discharge hole that greatly affects the landing accuracy of the discharged fluid can be formed by etching the surface electrode layer. Can be processed. As a result, the shape accuracy of the fluid discharge hole is dramatically stabilized more than the configuration in which the fluid discharge side opening of the first nozzle hole in which the first electrode layer is formed on the inner wall is a fluid discharge hole. As a result, the landing accuracy can be further stabilized.Become.
[0084]
  Main departureIn order to solve the above problems, a bright nozzle plate manufacturing method includes a step of forming a sacrificial layer on a substrate, a step of forming a first nozzle layer on the sacrificial layer, and the first nozzle layer. Forming a plurality of first nozzle holes on the first nozzle layer, forming a first electrode layer on the first nozzle layer including an inner wall surface of each first nozzle hole, and each first nozzle A step of processing the first electrode layer so as to remain on the inner wall of the hole and each peripheral portion of the first nozzle hole, and a first electrode layer portion remaining on the first nozzle layer, including the remaining first electrode layer portions; A step of forming the second nozzle layer, a plurality of second nozzle holes in the second nozzle layer, and a fluid discharge side opening of each second nozzle hole remaining on the first nozzle layer. A step of forming the first electrode layer so as to fit in each first electrode layer portion, and an inner wall surface of each second nozzle hole on the second nozzle layer Forming a second electrode layer including, it is characterized by comprising a step of processing the second electrode layer to be electrically separated between adjacent second nozzle hole.
[0085]
  According to this, the first nozzle layer, the first electrode layer, the second nozzle layer, and the second electrode layer are sequentially laminated on the highly rigid substrate via the sacrificial layer. For this reason, after forming a resist pattern using photolithography technology, it can be processed into a desired shape by dry etching, so that the first nozzle hole, the second nozzle hole, the first electrode layer, the second electrode layer Can be formed with very high shape accuracy.
[0086]
  Further, since the fluid discharge surface of the nozzle plate is protected by the sacrificial layer until the final stage of the process, there is no risk that the fluid discharge hole is damaged and the fluid discharge hole is deformed in the nozzle plate manufacturing process. For this reason, the manufacturing yield of the nozzle plate is improved.
[0087]
  In the nozzle plate manufacturing method of the present invention, the surface electrode layer is further formed on the sacrificial layer between the step of forming the sacrificial layer on the substrate and the step of forming the first nozzle layer on the sacrificial layer. And forming the first nozzle layer on the sacrificial layer by separating the surface electrode layer corresponding to the nozzle hole portion forming portion and forming a through hole in each separation portion. The first nozzle layer may be formed including the separated surface electrode layer.
[0088]
  In the manufacturing method of the nozzle plate of this configuration, since the fluid discharge hole can be processed as a through hole in the surface electrode layer formed on the sacrificial layer, the first electrode layer formed in the first nozzle hole can be processed. Due to non-uniformity (for example, film thickness distribution), the shape of the fluid discharge hole is not deformed, and a nozzle plate having a highly accurate fluid discharge hole can be manufactured.
[0089]
  The nozzle plate manufacturing method of the present invention may be further characterized in that, in the step of forming the second electrode layer, the film forming particles are incident on the nozzle plate surface obliquely.
[0090]
  The nozzle plate manufacturing method of the present invention may be further characterized in that, in the step of forming the first electrode layer, the film-forming particles are incident obliquely with respect to the nozzle plate surface.
[0091]
  The electrode layers (first and second) formed by obliquely entering the film-forming particles have good adhesion to the side walls of the nozzle holes. Furthermore, since the electrode layer is not formed in the region that is shaded with respect to the sputtering target or the vapor deposition source, for example, the inside of the first nozzle hole when forming the second electrode layer or the first electrode layer is formed. A region where the electrode layer is not desired to be formed, such as the inside of the through hole formed in the surface electrode layer, can be formed as the shadow portion. Accordingly, the region where the electrode layer is formed and the region where the electrode layer is not formed can be easily set, and the adhesion of the electrode layer inside the nozzle hole where the electrode layer is formed can be improved.
[0092]
  Further, in the method for manufacturing a nozzle plate of the present invention, etching is used in the step of forming the second nozzle hole, and the etching of the first electrode layer is more than resistant to etching of the second nozzle layer. It is also possible to select a condition that is highly resistant to.
[0093]
  According to this, since the etching for forming the second nozzle hole can be accurately stopped at the first electrode layer, the first nozzle hole and the first nozzle layer are processed by the second nozzle hole processing. A nozzle plate with high shape accuracy can be manufactured without being damaged by overetching.
[0094]
  In the method for manufacturing a nozzle plate of the present invention, etching is used in the step of forming the first nozzle hole and the step of forming the second nozzle hole, and etching of the first and second nozzle layers is performed. It is also possible to select a condition in which the resistance to etching of the surface electrode layer is higher than the resistance to resistance.
[0095]
  According to this, the surface electrode layer is not damaged by over-etching when forming the first nozzle hole or over-etching when forming the second nozzle hole. For this reason, the fluid discharge hole formed of the through hole of the surface electrode layer is not deformed by overetching and the landing accuracy is not deteriorated, and a nozzle plate having high landing accuracy can be manufactured stably.
[0096]
  Further, in the method for manufacturing a nozzle plate of the present invention, the step of electrically separating the second electrode layer may be performed using dry etching.
[0097]
  According to this, since the separation processing of the second electrode layer is performed by dry etching, the shape accuracy of the processing is high, and the electrode layer material in the region to be processed is removed in the gas phase. There is no risk that dust accompanying the intrusion into the first and second nozzle holes and closes the nozzle holes. For this reason, a nozzle plate with high discharge reliability can be manufactured stably.
[0098]
  In the nozzle plate of the present invention, the first electrode layer is further extended on the first nozzle layer from the first nozzle hole at the interface between the first nozzle layer and the second nozzle layer. The second electrode layer may be electrically connected to the first electrode layer at a portion extending on the first nozzle layer.
[0099]
According to the above configuration, the first electrode layer extends from the first nozzle hole on the first nozzle layer at the interface between the first nozzle layer and the second nozzle layer, and the second electrode layer is Since this extended portion is electrically connected to the first electrode layer, the connection between the first electrode layer and the second electrode layer is made not on the cross section of each electrode layer but on the surface of the electrode layer. ing. Therefore, although it is the structure which connects different electrode layers, the electrical connection reliability of electrode layers is high, and the danger that a drive signal cannot be favorably applied to a 1st electrode layer by disconnection etc. is large. As a result, the ejection reliability can be improved.
[0100]
In the nozzle plate of the present invention, the first electrode layer may be formed on the entire inner wall of the first nozzle hole.
[0101]
In the above configuration, since the first electrode layer is formed on the entire inner wall of the first nozzle hole, a uniform electric field can be applied to the fluid in the fluid discharge hole. For example, in the case where there are a plurality of fluid discharge holes on the fluid discharge surface of the nozzle plate, the landing accuracy decreases if the formation position of the tailor cone differs for each fluid discharge hole. The formation position of can be stabilized and the landing accuracy can be improved.
[0102]
In the nozzle plate of the present invention, the first electrode layer further extends on the first nozzle layer from the first nozzle hole at the interface between the first nozzle layer and the second nozzle layer. The opening of the second nozzle hole on the side communicating with the first nozzle hole is located in a first electrode layer portion extending on the first nozzle layer. You can also.
[0103]
According to the above configuration, the first electrode layer in the second nozzle hole is formed in the portion where the first electrode layer extends on the first nozzle layer at the interface between the first nozzle layer and the second nozzle layer. Since the opening on the side communicating with the nozzle hole of the second nozzle hole is disposed, the extended portion of the first electrode layer functions as an etching stopper portion when the second nozzle hole is etched, and the second nozzle The first nozzle hole or the first nozzle layer is damaged and changed by etching when forming the hole. There is nothing to shape.
[0104]
As described above, if the first nozzle layer outside the extended portion of the first electrode layer is etched, the first electrode layer is separated and removed from the nozzle plate. Thus, the nozzle plate can be manufactured.
[0105]
  In the nozzle plate of the present invention, the first nozzle hole and / or the second nozzle hole may be characterized in that the opening on the fluid supply side is formed larger than the fluid discharge side. .
[0106]
  According to the above configuration, since the first nozzle hole and / or the second nozzle hole is formed with a taper that widens the fluid supply side, the inner wall surface of the nozzle hole and the first nozzle layer Alternatively, the angle formed with each surface of the second nozzle layer becomes an obtuse angle. Accordingly, when the first or second electrode layer is formed from the inner wall surface of the first nozzle hole or the second nozzle hole to the surface of each nozzle layer, the electrode layer is disconnected due to an angle formed by the inner wall surface and the nozzle layer surface. Therefore, it is possible to form an electrode layer with low risk of conduction and high electrical reliability. Further, when supplying the discharge liquid to the nozzle tip, there is little risk of turbulent flow in the nozzle, and the discharge liquid can be supplied stably.
[0107]
Further, in the nozzle plate of the present invention, the second electrode layer in the second nozzle layer that is closest to the fluid supply side is between the adjacent nozzle holes on the fluid supply side of the second nozzle layer. It can also be characterized by being electrically separated.
[0108]
According to the above configuration, in the nozzle plate having a plurality of nozzle holes, the second electrode layer of the second nozzle layer that is closest to the fluid supply side is adjacent to the fluid supply side of the second nozzle layer. Since the nozzle holes are electrically separated from each other, a plurality of nozzle holes can be driven independently, and high-resolution drawing can be performed.
[0109]
  In the nozzle plate of the present invention, the second electrode layer of the second nozzle layer that is closest to the fluid supply side is also formed on the fluid supply side surface of the second nozzle layer, It is also possible to form a lead-out wiring by patterning.
[0110]
According to the above configuration, the second electrode layer of the second nozzle layer that is closest to the fluid supply side is used as the lead wiring on the fluid discharge side surface of the second nozzle layer. At the same time, the second electrode layer can be electrically separated between adjacent nozzle holes. Therefore, the separation process and the formation process of the lead wiring become one process, and the process can be simplified. Further, since the second electrode layer formed on the inner wall of the second nozzle hole and the lead-out wiring are formed by processing the same electrode layer, the connection reliability between the second electrode layer and the lead-out wiring is improved. Very expensive.
[0111]
Further, in the nozzle plate of the present invention, the diameter of the opening on the fluid discharge side of the first nozzle hole or the diameter of the through hole formed in the surface electrode layer is 8 μm or less. You can also.
[0112]
The applicants of the present application set the discharge hole diameter of the nozzle to be a fine diameter of 0.01 to 25 μm, so that a local electric field is generated in accordance with a new discharge model proposed by the inventors of the present application. It has been found and announced earlier that the drive voltage can be reduced. Such a decrease in driving voltage is extremely advantageous in downsizing the apparatus and increasing the density of the nozzles. Of course, by reducing the drive voltage, it is possible to use a low-voltage drive driver with high cost merit, and to improve the safety in use.
[0113]
Further, in the above discharge model, the electric field strength necessary for the discharge depends on the local concentrated electric field strength, so that the presence of the counter electrode is not essential. That is, it is possible to perform printing on an insulating substrate or the like without requiring a counter electrode, increasing the degree of freedom of the apparatus configuration, and printing can be performed on a thick insulator. .
[0114]
In particular, as described above, by setting the diameter of the fluid discharge hole of the nozzle to φ8 μm or less as described above, the electric field strength distribution is effectively concentrated near the discharge surface of the fluid discharge hole, and the counter electrode Variation in the distance from the fluid discharge hole to the fluid discharge hole does not affect the electric field strength distribution, so that stable fluid discharge can be achieved without being affected by variations in the position accuracy of the counter electrode, material characteristics of the recording medium, and thickness variations. It can be carried out.
[0115]
In addition, by effectively concentrating the electric field strength distribution in the vicinity of the discharge surface of the fluid discharge hole, it is possible to stably form a strong electric field in a narrow area and reliably discharge an extremely small amount of fluid, and to print images with high resolution. It becomes possible to.
[0116]
DETAILED DESCRIPTION OF THE INVENTION
  Embodiments of the present invention will be described below.
[0117]
  [Prerequisite configuration]
  First, an electrostatic suction type fluid discharge device that is a premise of the present invention to which a nozzle plate according to the present invention is applied will be described with reference to FIGS.
[0118]
  The electrostatic suction type fluid discharge device which is the premise of the present invention has a nozzle diameter of 0.01 μm to 25 μm and enables fluid discharge control with a drive voltage of 1000 V or less.
[0119]
  Here, in the conventional fluid ejection model, a decrease in the nozzle diameter leads to an increase in the driving voltage. Therefore, unless the nozzle diameter is 50 to 70 μm or less, other measures such as applying a back pressure to the ejected ink are performed. It was considered impossible to eject ink at a driving voltage of 1000 V or less. However, as a result of intensive studies, the present inventors have found that a discharge phenomenon occurs in a discharge model different from a conventional fluid discharge model below a certain nozzle diameter. The present invention has been made based on new knowledge in this fluid ejection model.
[0120]
  First, the fluid ejection model discovered by the present inventors will be described.
[0121]
  It is assumed that a conductive fluid is injected into a nozzle having a diameter d (in the following description, refers to the inner diameter of the nozzle unless otherwise specified), and is positioned perpendicular to the height h from the infinite plate conductor. This is shown in FIG. At this time, it is assumed that the charge Q induced in the nozzle tip (nozzle hole) is concentrated in the hemisphere formed by the fluid at the nozzle tip, and is approximately expressed by the following equation.
[0122]
[Expression 1]

[0123]
  Where Q: charge (C) induced at the nozzle tip, ε₀: Dielectric constant of vacuum (F / m), d: nozzle diameter (m), V₀: Total voltage applied to the nozzle. Α is a proportionality constant depending on the nozzle shape and takes a value of about 1 to 1.5. Particularly, d << h (h: distance between nozzle (more precisely, nozzle hole) and substrate (m )) Is almost 1.
[0124]
  Further, when a conductive substrate is used as the substrate, it is considered that a mirror image charge Q ′ having a polarity opposite to the charge Q is induced at a symmetrical position in the substrate facing the nozzle. When the substrate is an insulator, a video charge Q 'having a polarity opposite to that of the charge Q is similarly induced at a symmetrical position determined by the dielectric constant.
[0125]
  Concentrated electric field strength E at the nozzle tip_locAssuming that the radius of curvature of the tip is R,
[0126]
[Expression 2]

[0127]
Given in. Here, k is a proportionality constant depending on the nozzle shape and the like, and takes a value of about 1.5 to 8.5, and is considered to be about 5 in many cases (PJ Birdseye and DA Smith, Surface Science, 23 (1970), p.198-210). Also, here, R = d / 2 is assumed to simplify the fluid ejection model. This corresponds to a state in which the fluid rises in a hemispherical shape having the same curvature diameter as the nozzle diameter d due to surface tension at the nozzle tip.
[0128]
  Consider the balance of pressure acting on the fluid at the nozzle tip. First, the electrostatic pressure P_eIf the liquid area at the nozzle tip is S,
[0129]
[Equation 3]

[0130]
It becomes. From the equations (8) to (10), the pressure P_eWhere α = 1
[0131]
[Expression 4]

[0132]
It is expressed.
[0133]
  On the other hand, the pressure P due to the surface tension of the fluid at the nozzle tip_sThen,
[0134]
[Equation 5]

[0135]
It becomes. Where γ is the surface tension. The condition under which discharge is caused by an electrostatic force is that the electrostatic force exceeds the surface tension._eAnd pressure P due to surface tension_sThe relationship with
[0136]
[Formula 6]

[0137]
It becomes.
[0138]
  FIG. 2 shows the pressure P due to surface tension when a nozzle having a certain diameter d is given._sAnd electrostatic pressure P_eShows the relationship. As the surface tension of the fluid, it is assumed that the fluid is water (γ = 72 mN / m). When the voltage applied to the nozzle is 700 V, the electrostatic pressure P is obtained when the nozzle diameter d is 25 μm._ePressure P due to surface tension_sIt is suggested to exceed. From this, V₀And the relationship between d and d
[0139]
[Expression 7]

[0140]
Gives the lowest discharge voltage.
[0141]
  The discharge pressure ΔP at that time is
[0142]
[Equation 8]

[0143]
Than,
[0144]
[Equation 9]

[0145]
It becomes.
[0146]
  FIG. 3 shows the dependency of the discharge pressure ΔP when the discharge condition is satisfied by the local electric field strength for a nozzle of a certain diameter d, and the dependency of the discharge critical voltage (that is, the lowest voltage at which discharge occurs) Vc. 4 shows.
[0147]
  From FIG. 3, when the discharge condition is satisfied by the local electric field strength (V₀= 700 V, assuming that γ = 72 mN / m), it can be seen that the upper limit of the nozzle diameter is 25 μm.
[0148]
  In the calculation of FIG. 4, water (γ = 72 mN / m) and an organic solvent (γ = 20 mN / m) are assumed as fluids, and a condition of k = 5 is assumed. From this figure, it is clear that the discharge critical voltage Vc decreases as the nozzle diameter decreases in consideration of the concentration effect of the electric field due to the fine nozzle. When the fluid is water and the nozzle diameter is 25 μm, the discharge critical voltage is It can be seen that Vc is about 700V.
[0149]
  The concept of the electric field in the conventional discharge model, that is, the voltage V applied to the nozzle₀When only the electric field defined by the nozzle-counter electrode distance h is considered, the drive voltage required for ejection increases as the nozzle diameter becomes smaller.
[0150]
  On the other hand, if attention is paid to the local electric field strength as in the new ejection model proposed by the inventors of the present application, the drive voltage in ejection can be reduced by making the nozzle finer. Such a decrease in driving voltage is extremely advantageous in downsizing the apparatus and increasing the density of the nozzles. Of course, by reducing the driving voltage, it is possible to use a low-voltage driving driver with high cost merit.
[0151]
  Further, in the above discharge model, the electric field strength necessary for the discharge depends on the local concentrated electric field strength, so that the presence of the counter electrode is not essential. That is, in the conventional discharge model, since an electric field is applied between the nozzle and the substrate, it is necessary to dispose a counter electrode on the side opposite to the nozzle with respect to the insulating substrate, or to make the substrate conductive. . When the counter electrode is arranged, that is, when the substrate is an insulator, there is a limit to the thickness of the substrate that can be used.
[0152]
  On the other hand, in the ejection model of the present invention, it is possible to perform printing on an insulating substrate or the like without requiring a counter electrode, and the degree of freedom of the apparatus configuration is increased. Further, it is possible to perform printing on a thick insulator.
[0153]
  FIG. 5 shows the correlation between the magnitude of the mirror image force acting on the substrate and the distance h from the substrate. As is apparent from the figure, this image force becomes more prominent as the distance between the substrate and the nozzle becomes closer, and particularly when h is 20 μm or less.
[0154]
  Next, consider precise control of the discharge flow rate. The flow rate Q in the cylindrical channel is expressed by the following Hagen-Poiseuille equation in the case of a viscous flow. Now, assuming a cylindrical nozzle, the flow rate Q of the fluid flowing through this nozzle is expressed by the following equation.
[0155]
[Expression 10]

[0156]
  Where η: fluid viscosity coefficient (Pa · s), L: flow path or nozzle length (m), d: flow path or nozzle hole diameter (m), ΔP: pressure difference (Pa) is there. From the above equation, since the flow rate Q is proportional to the fourth power of the radius of the flow path, it is effective to employ a fine nozzle to limit the flow rate. By substituting the discharge pressure ΔP obtained by the equation (16) into the equation (17), the following equation is obtained.
[0157]
## EQU11 ##

[0158]
  This expression represents the outflow amount of the fluid flowing out from the nozzle when the voltage V is applied to the nozzle having the diameter d and the length L. This is shown in FIG. For the calculation, values of L = 10 mm, η = 1 (mPa · s), and γ = 72 (mN / m) were used. Now, the nozzle diameter is assumed to be 50 μm, which is the minimum value of the prior art. When the voltage V is gradually applied, ejection starts at the voltage V = 1000V. This voltage corresponds to the discharge start voltage described in FIG. The flow rate from the nozzle at that time is shown on the Y axis. The flow rate rises rapidly just above the discharge start voltage Vc.
[0159]
  In this model calculation, it seems that a minute flow rate is likely to be obtained by precisely controlling the voltage slightly above Vc, but this is actually impossible as expected from the semi-logarithmic diagram. 10^-10m³/ S or less, it is difficult to realize a minute amount. Further, when a nozzle having a certain diameter is employed, the minimum drive voltage is determined as given by the equation (14). Therefore, as long as a nozzle having a diameter of 50 μm or more is used as in the prior art, 10^-10m³It is difficult to achieve a minute discharge amount of / s or less or a drive voltage of 1000 V or less.
[0160]
  As can be seen from the figure, a drive voltage of 700 V or less is sufficient for a nozzle with a diameter of 25 μm, and control is possible even with a nozzle of 10 μm in diameter of 500 V or less. Further, it can be seen that the nozzle of 1 μm in diameter may be 300 V or less.
[0161]
  As described above, the electrostatic suction type fluid ejection device according to the present embodiment is based on the newly proposed ejection model with a focus on the local electric field strength, and therefore, a fine nozzle having a nozzle diameter of 0.01 μm to 25 μm. In addition, the discharge control of the discharge fluid can be performed with a drive voltage of 1000 V or less. As a result of consideration based on the above model, a nozzle having a diameter of 25 μm or less has a driving voltage of 700 V or less, a nozzle having a diameter of 10 μm or less, a driving voltage of 500 V or less, and a nozzle having a diameter of 1 μm or less. Can be controlled with a driving voltage of 300 V or less.
[0162]
  In the electrostatic suction type fluid ejection device according to the present embodiment, as described above, both the nozzle diameter and the drive voltage can be reduced, but in this case, compared with the conventional electrostatic suction type fluid ejection device. The following tendencies become remarkable.
[0163]
  That is, in the case of the electrostatic suction type fluid ejection device as described above, the ejection characteristics basically depend on the electrical resistance value in the ejection fluid flow path from the drive electrode to the nozzle tip in the fluid ejection head. The discharge response is improved as the electric resistance value is lower. In other words, the drive frequency can be improved by lowering the electrical resistance value in the discharge fluid flow path, and moreover, discharge of the discharge fluid material with higher resistance becomes possible, and the range of selection of the discharge fluid material is expanded. be able to.
[0164]
  In order to reduce the electrical resistance value, it is effective to shorten the distance between the drive electrode and the nozzle tip.
[0165]
  [Reference form]
  Of the present inventionreferenceThe form will be described below with reference to FIGS.
[0166]
  (Nozzle plate)
  FIG. 7 (a) shows the bookreferenceFIG. 7B is a sectional view taken along line A-A ′ of FIG. 7A. Two or more fluid discharge holes 9 are formed in the nozzle plate 8, and two fluid discharge holes 9 are shown in FIG. FIG. 7C is a perspective view of a part of the nozzle plate 8 observed from the fluid supply side.
[0167]
  As shown in FIGS. 7A to 7C, the nozzle plate 8 includes a first nozzle layer 1, a second nozzle layer 2, a first electrode layer 25, a second electrode layer 26, and nozzle holes. (Nozzle hole) 11 is provided.
[0168]
  The fluid ejection side surface of the first nozzle layer 1 forms the fluid ejection surface 8a of the nozzle plate 8, and the liquid repellent layer 4 is formed. The fluid supply side, which is the opposite side, has a second nozzle layer. 2 is arranged. Here, the first nozzle layer is formed to be very thin, for example, 1 to 8 μm thick, and the strength and rigidity as the nozzle plate 8 are secured in the thick second nozzle layer 2. Here, the second nozzle layer 2 for ensuring strength and rigidity is one layer, but it may be two or more layers.
[0169]
  The nozzle hole 11 includes a first nozzle hole 11 a that penetrates the first nozzle layer 1 and a second nozzle hole 11 b that penetrates the second nozzle layer 2. Here, the wall surface of the first nozzle hole 11a has a substantially cylindrical shape perpendicular to the fluid discharge surface 8a of the nozzle plate 8, and the substantially circular opening of the fluid discharge surface 8a on which the liquid repellent layer 4 is formed is a fluid. It becomes the discharge hole 9. On the other hand, the second nozzle hole 11b has a tapered shape (conical frustum shape) that widens from the opening on the side communicating with the cylindrical first nozzle hole 11a, and the second nozzle layer 2 It passes through and opens at the fluid supply surface 8b on the opposite side to the first nozzle layer 1. The substantially circular opening of the second nozzle hole 11 b formed in the fluid supply surface 8 b which is also the surface of the second nozzle layer 2 becomes the fluid supply hole 12.
[0170]
  A first electrode layer 25 is formed on substantially the entire inner wall of the first nozzle hole 11a and on the periphery of the communication hole 11x where the first nozzle hole 11a communicates with the second nozzle hole 11b. The first electrode layer 25 is formed in the periphery of the communication hole 11x where the first nozzle hole 11a and the second nozzle hole 11b communicate with the cylindrical portion 25a formed on substantially the entire inner wall of the nozzle hole 11a. It consists of the extended part 25b which makes | forms the annular shape centering on the communicating hole 11x. Of these, the extending portion 25b forms the upper base 11y of the second nozzle hole 11b having a truncated cone shape. That is, when the diameter of the communication hole 11x (substantially circular) between the first nozzle hole 11a and the second nozzle hole 11b is D1, D1 is the upper bottom (opening portion on the fluid discharge side) 11y of the second nozzle hole 11b. Smaller than the diameter D2. And the outer diameter D3 of the extension part 25b of the 1st electrode layer 25 which makes the annular | circular shape is larger than the aperture diameter D2.
[0171]
  A second electrode layer 26 electrically connected to the first electrode layer 25 is formed on the inner wall of the second nozzle hole 11b. A part of the second electrode layer 26 is also disposed on the fluid supply surface 8b of the nozzle plate 8, and a part of the second electrode layer 26 forms an extraction wiring 26a as shown in FIG. It is connected to application means (not shown).
[0172]
  In FIGS. 7A and 7C, in order to simplify the drawing, the first nozzle holes 11a and the first nozzle holes 11b formed in the nozzle holes 11 are formed on the inner walls of the first nozzle holes 11a. The electrode layer 25 and the second electrode layer 26 are omitted.
[0173]
  Specific examples of the size and material of each part will be described below, but the present invention is not limited to the specific examples.
[0174]
  A polyimide film having a thickness of about 1 μm is used for the first nozzle layer 1, and a polyimide film having a thickness of about 20 μm is used for the second nozzle layer 2. The first electrode layer 25 has a thickness of 0.5 μm and is made of a metal material mainly composed of Ti, and the cylindrical portion 25a of the first electrode layer 25 extends to the fluid discharge side end of the inner wall of the first nozzle hole 11a. Is formed. On the other hand, the extending portion 25b has an outer diameter D3 of about 20 μm. If the electrode layer or the like formed at the interface between the first nozzle layer 1 and the second nozzle layer 2 is formed over the entire interface, it causes warping due to the stress of the entire nozzle plate. In the configuration in which the extended portion 25b is partially provided for each nozzle hole 11, warping due to such stress can be reduced.
[0175]
  On the other hand, the second electrode layer 26 has a thickness of 0.5 μm and is made of a metal having Ti as a main component. And the connection part 26b with the 1st electrode layer 25 in the 2nd electrode layer 26 is in contact with the extension part 25b of the 1st electrode layer 25 on the surface, as shown in FIG. Reliability is ensured.
[0176]
  The aperture of the first nozzle hole 11a serving as the fluid discharge hole 9 has a diameter of about 3 μm, and the first electrode layer 25 having a thickness of 0.5 μm is formed thereon. The diameter (diameter) is about 2 μm. In addition, the diameter D2 of the upper bottom 11y of the second nozzle hole 11b is 10 μm, and the diameter of the opening serving as the fluid supply hole 12 is 30 μm.
[0177]
  In the nozzle plate 8 of this configuration, it is desirable to make the fluid discharge hole 9 φ10 μm or less, more preferably φ8 μm or less, in order to enable discharge of ultra-trace fluid and form fine dots. By setting the nozzle hole diameter (diameter) in this way, it is possible to narrow the formation of the electric field, which was necessary over a wide range, and the voltage necessary for charge transfer, that is, the amount of charge necessary for electrostatically attracting the fluid It is possible to greatly reduce the voltage required for applying the pressure to the fluid. According to this, since the high voltage of 2000V is not required unlike the past, the safety | security at the time of using a fluid jet apparatus can be aimed at.
[0178]
  In particular, by setting the diameter to 8 μm or less, the electric field strength distribution is effectively concentrated in the vicinity of the discharge surface of the fluid discharge hole, and the variation in the distance from the counter electrode to the fluid projection hole of the nozzle affects the electric field strength distribution. Disappears. Accordingly, it is possible to discharge the fluid more stably without being affected by the positional accuracy of the counter electrode, the variation in the material characteristics of the recording medium, and the variation in the thickness.
[0179]
  Further, as described above, the electric field strength distribution can be concentrated in the vicinity of the discharge surface of the fluid discharge hole 9, so that a strong electric field can be formed in a narrow region. As a result, the amount of fluid that can be discharged is made extremely small. It becomes possible. As a result, when the fluid is ink, the print image can be made high resolution.
[0180]
  The liquid repellent layer 4 on the first nozzle layer 1 is formed of a fluorine polymerized or silicon polymer film having a thickness of about 0.05 μm. As will be described later, the liquid repellent layer 4 removes an extra region that has entered the fluid discharge hole 9 by dry etching.
[0181]
  BookreferenceAccording to the form, since the shape of the fluid discharge hole 9 of the nozzle plate 8 that greatly affects the landing accuracy is determined by the processing accuracy of the polyimide film of 1 μm, the processing accuracy of the fluid discharge hole 9 is very high, Accordingly, very high landing accuracy can be ensured.
[0182]
  Further, in order to increase the processing accuracy of the fluid discharge hole 9, if the film thickness of the first nozzle layer 1 exposed on the fluid discharge surface of the nozzle plate 8 is decreased, higher processing accuracy can be obtained. . At this time, by reducing the film thickness of the first nozzle layer 1, the rigidity of the first nozzle layer 1 is lowered and the structural reliability of the fluid discharge hole 9 is reduced. By disposing the second nozzle layer 2 in contact with the first nozzle layer 1, the first nozzle layer 1 is reinforced, and the shape accuracy of the fluid discharge hole 9 is improved without deteriorating the structural reliability of the first nozzle layer 1. Can be improved. That is, such a configuration is desirable when the nozzle plate 8 having the fine fluid discharge holes 9 is formed.
[0183]
  Further, since the first electrode layer 25 is locally provided at each nozzle hole 11 formation position, the first electrode layer 25 is electrically insulated from the first electrode layer 25 disposed in the adjacent nozzle hole 11. . Therefore, an ejection signal can be applied independently to each channel, and there is little crosstalk, thereby improving the resolution of the drawn image.
[0184]
  Further, since the second nozzle hole 11b has a tapered shape, the fluid turbulence is less likely to occur inside the second nozzle hole 11b, the fluid discharge stability can be improved, and the nozzle hole 11b. Since the edge between the inner wall and the fluid supply surface 8b becomes sweet, disconnection of the second electrode layer 26 extending to the fluid supply surface 8b can be effectively suppressed. Further, the liquid repellent layer 4 formed on the fluid discharge surface 8 a of the nozzle plate 8 can prevent the fluid from adhering to the vicinity of the fluid discharge hole 9.
[0185]
  Note that the material used for the first electrode layer 25 is not limited to a metal material mainly containing Ti. In etching of the second nozzle layer 2 and etching of the liquid repellent layer 4 that has entered the sacrificial layer 5 and the fluid discharge hole 9 described later, a material having high resistance to the etching, that is, an etching gas ( Any material can be used as long as it has high resistance to oxygen-containing plasma, fluorine-containing plasma, or the like, or an etchant (such as nitric acid or a potassium hydroxide aqueous solution). Specific examples include metal materials mainly composed of Ti, Al, Cu, Co, Fe, Ni, Au, Pt, Ta, W, Nb, etc., which should be selected in combination with the above etching gas or etchant. Can do.
[0186]
  Similarly, the material used for the second electrode layer 26 is not limited to a metal material mainly containing Ti. When etching the sacrificial layer 5 and the liquid repellent layer 4 that has entered the fluid discharge hole 9 to be described later, a material having high resistance to the etching, that is, an etching gas (plasma containing oxygen, fluorine is contained). Plasma or the like) or an etchant (such as nitric acid or potassium hydroxide aqueous solution) may be used. Specific examples include metal materials mainly composed of Ti, Al, Cu, Co, Fe, Ni, Au, Pt, Ta, W, Nb, etc., which should be selected in combination with the above etching gas or etchant. Can do.
[0187]
  The material used for the first nozzle layer 1 is not limited to polyimide. Polymer organic materials other than polyimide may be used, and SiO₂, Si₃N₄Such a Si compound material or Si may be used.
[0188]
  The material used for the second nozzle layer 2 is not limited to polyimide. Similar to the first nozzle layer 1, a polymer organic material other than polyimide may be used, or SiO₂, Si₃N₄Such a Si compound material or Si may be used.
[0189]
  Also bookreferenceIn the embodiment, the second nozzle hole 11b has a truncated cone shape (tapered shape) narrowed at a communicating portion with the first nozzle hole 11a, but is not limited thereto. For example, as in the nozzle plate 8 ′ shown in FIG. 9, the inner wall of the second nozzle hole 11b ′ has a so-called straight shape (cylindrical shape) perpendicular to the fluid discharge surface 8a and the fluid supply surface 8b of the nozzle plate 8 ′. It can also be formed.
[0190]
  In this case, the fluid supply hole 12 ′ of the second nozzle hole 11 b ′ is smaller than the fluid supply hole 12 in which the second nozzle hole 11 b shown in FIGS. The degree of nozzle integration can be further increased. Further, as shown in FIG. 7B, in the case of the nozzle plate 8, the second electrode layer 26 was formed only on one side surface of the inner wall of the second nozzle hole 11b for the convenience of manufacturing. As shown in FIG. 9, you may form in the whole surface of the 2nd nozzle hole 11b inner wall.
[0191]
  BookreferenceBy using the nozzle plate 8 (8 ') having the configuration as described above, the following effects (1) to (5) are obtained.
(1) Even if the fluid discharge hole 9 is a fine nozzle plate 8 (8 ′) having a diameter of 8 μm or less, a structurally stable electrode capable of applying a discharge signal voltage to the tip of the nozzle hole 11 is formed. be able to.
(2) On the fluid supply side of the second nozzle layer 2, the second electrode layer 26 is separated so that adjacent channels are not electrically short-circuited. This can be applied, and crosstalk is reduced, thereby improving the resolution of the drawn image.
(3) Since the rigidity of the nozzle plate 8 (8 ') can be maintained by the second nozzle layer 2, the rigidity of the entire nozzle plate 8 (8') is increased and the handling becomes easy.
(4) Even if the processing accuracy of the second nozzle hole 11b processed into the thick second nozzle layer 2 is bad, the extended portion of the first electrode layer 25 is processed when the second nozzle hole 11b is processed. Since the etching stops at 25b, the fluid discharge hole 9 that controls the discharge amount of the fluid is not affected.
(5) Since the first electrode layer 25 is electrically connected to the second electrode layer 26 formed in the second nozzle hole 11b communicating with the first nozzle hole 11a, the second electrode The drive signal can be supplied from the fluid supply side of the nozzle plate 8 through the layer 26, and the recording medium is electrically supplied by the electric field generated from the lead-out wiring 26b for supplying the drive signal to the first electrode layer 25. There will be no physical damage.
[0192]
  (Nozzle plate manufacturing method)
  Then bookreferenceA method for manufacturing the nozzle plate 8 according to the embodiment will be described. 10A to 10I are diagrams for explaining the manufacturing process of the nozzle plate 8.
[0193]
  First, the sacrificial layer 5 is formed by wet plating (plating) using Ni on a substrate 6 made of Si or glass for temporary holding of an arbitrary thickness. Further, a polyimide resin is applied on the sacrificial layer 5 by spin coating, and baked at 350 ° C. for 2 hours to form the first nozzle layer 1. Here, the thickness of the sacrificial layer 5 was 10 μm, and the thickness of the first nozzle layer was 1 μm.
[0194]
  Next, an opening pattern of the first nozzle holes 11a is formed on the first nozzle layer 1 with a photoresist, and the first nozzle holes 11a are formed by dry etching using a gas containing oxygen as a main component. Process (Figure10(See (a)).
[0195]
  In this etching method, an organic substance such as polyimide resin can be processed at high speed and with high accuracy, and the etching selectivity with Ni as the sacrificial layer 5 is high (Ni is hardly etched). Therefore, the sacrificial layer 5 is not significantly damaged by the above processing, and the flatness of the surface of the sacrificial layer 5 is maintained. Therefore, the fluid discharge surface of the nozzle plate 8 to be formed on the surface of the sacrificial layer 5 is flat. The property does not deteriorate. Further, since this processing is performed with very high accuracy, highly anisotropic etching conditions are used. In addition, as described above, the first nozzle layer 1 is as extremely thin as 1 μm, so that the first nozzle hole 11a for discharging an extremely small amount of fluid can be processed with high accuracy.
[0196]
  Next, a first electrode layer 25 made of a metal material containing Ti as a main component is formed on the first nozzle layer 1 in which the first nozzle hole 11a is processed by a sputtering method. Further, a resist pattern 27 having a shape corresponding to the nozzle hole opening is formed on the first electrode layer 25 (see FIG.10(See (b)). Here, since it is necessary to form the first electrode layer 25 on the inner wall of the first nozzle hole 11a, in order to improve the step coverage of the first electrode layer 25, under an Ar gas pressure condition of 30 mTorr. The film was formed such that the film thickness on the first nozzle layer 1 was 0.5 μm.
[0197]
  Next, the first electrode layer 25 is formed into a substantially circular shape that becomes the above-described extended portion 25b having a diameter of about 20 μm on the first nozzle layer 1 by dry etching using plasma using a gas containing Ar as a main component. And remove the resist (Figure10(See (c)). In this processing step, the first electrode layer 25 (cylindrical portion 25a) formed on the inner wall of the first nozzle hole 11a is prevented from being damaged, and the sacrificial layer 5 serving as the bottom of the first nozzle hole 11a is suppressed. In order to remove the first electrode layer 25 formed in (1), highly anisotropic etching conditions were employed.
[0198]
  Note that the extended portion 25b partially left on the first electrode layer 1 has a substantially circular shape here, but does not have to be a substantially circular shape in the processing step. The upper bottom 11y of the second nozzle hole 11b may have a shape that is disposed in the extended portion 25b formed by extending from the first nozzle hole 11a on the first nozzle layer 1.
[0199]
  However, this nozzle plate is a nozzle plate 8 applied to an electrostatic suction type fluid discharge device, and applies a discharge signal to the nozzle tip via the first electrode layer 25. The electric field concentrates not only at the nozzle tip but also at the end of the shape on the first nozzle layer 1. For this reason, in order to make uniform the electric field concentrated on the end of the extended portion 25b on the first nozzle layer 1, the shape of the extended portion 25b is processed into a shape close to a highly isotropic circle. Is desirable.
[0200]
  Next, the second nozzle layer 2 is formed to a thickness of 20 μm on the first nozzle layer 1 and the first electrode layer 25 (see FIG.10(See (d)). As with the first nozzle layer 1, the second nozzle layer 2 was coated with a coating type polyimide resin by a spin coating method, and baked at 350 ° C. for 2 hours to a thickness of 20 μm. Here, the first nozzle hole 11a is also filled with the polyimide resin. The second nozzle layer 2 is formed for the purpose of reinforcing the thin first nozzle layer 1 processed with high accuracy, and has an effect of increasing the rigidity of the entire nozzle plate 8.
[0201]
  Next, a resist pattern 28 is formed on the second nozzle layer 2 by photolithography, and dry etching using a gas containing oxygen as a main component is performed, so that a second truncated cone shape is formed on the second nozzle layer 2. Nozzle hole 11b is formed (see FIG.10(See (e)). The dry etching can be stopped at the extended portion 25 a of the first electrode layer 25 formed on the first nozzle layer 1. That is, the first nozzle layer 1 formed of a metal material mainly containing Ti is hardly etched by dry etching using a gas mainly containing oxygen, so that the first electrode layer 25 is exposed. At the portion, the dry etching does not proceed any further, and the second nozzle layer 2 filling the first nozzle hole 11a in the previous step can be easily removed. Further, the processing of the second nozzle hole 11 b is performed such that the upper bottom 11 y of the second nozzle hole 11 b is in the extended portion 25 b of the first electrode layer 25 at the joint portion with the first nozzle layer 1. Patterned to be placed.
[0202]
  When processing the tapered shape of the second nozzle hole 11b, in the above etching, the etching rate of the resist pattern 28 and the etching rate of the polyimide resin of the second nozzle layer 2 are made substantially equal, and the resist pattern 28 is formed at 150 ° C. The resist pattern 28 was tapered by post-baking for 60 minutes, and a method of transferring this shape to the second nozzle layer 2 by etching was used.
[0203]
  That is, as shown in FIG. 11A, a resist pattern 28 having an etching rate substantially equal to that of the polyimide resin constituting the second nozzle layer 2 and having a tapered wall surface 28A is formed, and etching of the second nozzle layer 2 is performed. The resist pattern 28 is etched at the same speed as in step 1, and the edges of the resist pattern 28 are widened. At this time, as shown in FIG. 11B, the second nozzle layer 2 is also etched at the same time. As a result, as shown in FIG. A second nozzle hole 11b having the same shape as the tapered wall surface 28A formed in the resist pattern 28 is formed. In this case, since the resist pattern 28 and the second nozzle layer 2 have substantially the same etching rate, the resist pattern 28 is desirably formed thicker than the second nozzle layer 2. In FIG. 11, the description of the first nozzle hole 11a portion formed in the first nozzle layer 1 is omitted.
[0204]
  Next, a second electrode layer 26 made of a metal material containing Ti as a main component is formed on the second nozzle layer 2. Here, an ion beam sputtering method is used to tilt the substrate so that Ti particles fly from the direction of arrow K while suppressing the scattering of Ti particles by Ar atoms under Ar gas pressure of 0.2 mTorr. 2 is formed only on one side of the inner wall surface of the nozzle layer 2 and a part of the second electrode layer 26 is electrically short-circuited with the first electrode layer 25 (see FIG. 10F). . The film thickness is 0.5 μm.
[0205]
  Thus, by forming the second electrode layer 26 while entering Ti particles from an oblique direction, it is possible to prevent the second electrode layer 26 from adhering to the first nozzle hole 11a, As a result, it is possible to prevent the first nozzle hole 11a from being changed in shape or blocked.
[0206]
  Next, a photoresist pattern 29 is formed on the second electrode layer 26 so as to cover the second nozzle hole 11b and a part of the second electrode layer 26 formed on the second nozzle layer 2. It forms (refer FIG.10 (g)). The photoresist pattern 29 may be formed so as to cover a part of the second nozzle hole 11b and the second electrode layer 26 formed on the second nozzle layer 2, but in this embodiment, The second electrode layer 26 formed on the second nozzle layer 2 has a shape that can be processed into a circular shape having a diameter of about 50 μm. Here, since the photoresist pattern 29 is formed so as to fill the second nozzle hole 11b, the thickness of the resist layer becomes very thick in the deepest region of the second nozzle hole 11b. For this reason, it is desirable to use a positive type photoresist in which a portion that is not exposed remains as a pattern.
[0207]
  At this time, it is desirable to form the lead-out wiring 26 a using the second electrode layer 26 on the second nozzle layer 2 using the photoresist pattern 29. In this case, since it is not necessary to create the lead-out wiring 26a in a separate process, the process can be simplified. Further, since the lead-out wiring 26a can be arranged on the opposite side of the recording medium via the nozzle plate 8 as described above, a sufficient distance can be separated from the recording medium, and an electric field generated from the lead-out wiring pattern can be obtained. Therefore, fatal electrical damage is not caused to the recording medium.
[0208]
  Next, based on the photoresist pattern 29, the second electrode layer 26 is processed by dry etching using plasma mainly containing Ar gas to remove the photoresist pattern 29 (FIG. 10H). reference). In this processing step, since it is necessary to process the second electrode layer 26 into a desired shape, etching was performed under etching conditions having high anisotropy. The photoresist pattern 29 was removed using a resist stripping solution.
[0209]
  Next, after removing the photoresist pattern 29, the nozzle plate 8 is removed from the substrate 6 by immersing it in an aqueous solution mainly composed of nitric acid and water to etch only the sacrificial layer 5 (FIG. 10 (i)). ). As described above, the polyimide resin that forms the first nozzle layer 1 and the second nozzle layer 2 and the Ti that forms the stopper layer 3 or the discharge hole layer 14 are hardly affected by the etching solution for the sacrificial layer 5. Since etching is not performed, the etching of the sacrificial layer 5 does not cause a change in shape or a decrease in structural reliability.
[0210]
  Next, the liquid repellent layer 4 is formed on the surface of the first nozzle layer 1 from which the sacrificial layer 5 has been removed (FIG. 10 (i)). Here, a fluoropolymer is used for the purpose of considering the ease of application, and this is applied to the surface of the first nozzle layer 1 by a method such as stamping, and a liquid repellent having a thickness of 0.05 μm using a polymer film. Layer 4 was formed. Note that the liquid repellent layer 4 that has entered the first nozzle hole 11a is dry-etched from the second nozzle hole 11b side using plasma containing oxygen after the liquid repellent layer 4 is formed. Was removed. Thereby, damage to the nozzle plate 8 can be minimized.
[0211]
  As described above, according to the present embodiment, by performing photolithography and dry etching during the processing step, the nozzle plate 8 of the electrostatic suction type fluid discharge device that discharges an extremely small amount of fluid is provided for each channel. The first and second electrode layers 25 and 26 separated from each other can be formed in the nozzle hole 11 with high accuracy. As a result, an ejection signal can be applied independently to each channel, so that there is little crosstalk, thereby improving the resolution of the drawn image.
[0212]
  Further, since the first nozzle layer 1 can be formed thin, the vicinity of the fluid discharge hole 9 can be obtained by controlling the gas pressure during the film formation of the first electrode layer 25 formed on the inner wall of the first nozzle hole 11a. It is possible to form a film stably. As a result, the electrical resistance R from the electrode to the nozzle tip is stabilized, and the ejection characteristics between the channels are stabilized.
[0213]
  In the present embodiment, Ni is used as the sacrificial layer 5, polyimide resin is used as the first nozzle layer 1 and the second nozzle layer 2, and Ti is used as the first and second electrode layers 25 and 26. It is not limited to this combination.
[0214]
  In addition to Ni, the sacrificial layer 5 includes Al, Cu, and a combination of materials used for the first nozzle layer 1, the second nozzle layer 2, the first electrode layer 25, and the second electrode layer 26. A material soluble in nitric acid such as nitric acid or an aqueous solution of KOH, or a material that can be etched by oxygen plasma such as polyimide can be used. In addition to the plating, the sacrificial layer 5 can be formed by using a vapor deposition method, a sputtering method, a coating method, or the like depending on the material.
[0215]
  For the first nozzle layer 1, the second nozzle layer 2, and the second electrode layer 26, a material that is slightly damaged by etching of the sacrificial layer 5 can be used. For the first electrode layer 25, a material having high resistance to the etching of the sacrificial layer 5 and the etching of the second nozzle hole 11b can be used.
[0216]
  Here, FIG. 12 shows materials used (sacrificial layer, first nozzle layer, first electrode layer, second nozzle layer, second electrode layer) and processing method (first nozzle hole, first electrode layer). An example of a preferable combination of the electrode layer, the second nozzle hole, the second electrode layer, and the sacrifice layer removal) will be described.
[0217]
  As shown in FIG. 12, the first nozzle layer 1 and the second nozzle layer 2 are not limited to a polymer organic material such as polyimide resin, but may be Si or SiO.₂An inorganic silicon compound such as can be selected. However, SiO₂In order to dry-etch silicon and Si, it is necessary to use a reaction gas containing F. Since Ti used in this embodiment has low resistance to this etching, it has etching resistance such as Au and Pt. It is desirable to use the material as the first electrode layer 25 or the second electrode layer 26.
[0218]
  In addition to Ti, the materials described in the same table can be used for the first electrode layer 25 or the second electrode layer 26 according to the combination shown in FIG.
[0219]
  Note that Ti, which is the material of the first electrode layer 25, is CF.₄Even plasma using a mixed gas of oxygen and oxygen can be etched at a relatively high etching rate. However, the first nozzle layer 1 (polyimide) formed under Ti is etched at a higher speed than Ti due to the plasma of the gas, and is greatly damaged. Therefore, in the present embodiment, the dry etching method using Ar ions is employed for patterning the first electrode layer 25 and the second electrode layer 26.
[0220]
  As described above, the dry etching method using Ar ions is used, which has a small difference between the etching rate of the first electrode layer 25 or the second electrode layer 26 and the etching rate of the first nozzle layer 1 or the second nozzle layer 2. As a result, the first electrode layer 25 or the second electrode layer 26 can be patterned while minimizing damage to the first nozzle layer 1 or the second nozzle layer 2.
[0221]
  In this embodiment, the sacrificial layer 5 is completely removed by etching. However, it is not necessary to completely remove the sacrificial layer 5, and only the portion of the sacrificial layer 5 that is in contact with the first nozzle layer 1 is used. If removed by etching, the nozzle plate 8 can be removed from the substrate 6.
[0222]
  The liquid repellent layer 4 is not limited to a fluoropolymer, and a silicon-based polymer film, DLC (diamond-like carbon), or the like can also be used.
[0223]
  By using the above processing steps, it is possible to manufacture the nozzle plate 8 having the above-described effects (1) to (5).
[0224]
  Embodiment
  Main departureEnlightenmentThe following will describe the embodiment with reference to FIGS. 13 to 16. For convenience of explanation,Reference form aboveThe members having the same functions as those shown in the drawings are denoted by the same reference numerals and the description thereof is omitted.
[0225]
  (Nozzle plate)
  FIG. 13A is a perspective view of a part of the nozzle plate 80 of the present embodiment, and FIG. 13B is a cross-sectional view taken along line B-B ′ of FIG. Two or more fluid ejection holes 9 are formed in the nozzle plate 80. In FIG. 13A, two fluid ejection holes 9 are shown. FIG. 13C is a perspective view of a part of the nozzle plate 80 observed from the fluid supply side.
[0226]
  As shown in FIGS. 13A to 13C, in the nozzle plate 80, the first nozzle holes 11c formed in the first nozzle layer 10 are tapered like the second nozzle holes 11b. A surface electrode layer 81 is formed on the fluid discharge surface 80a of the nozzle plate 80 so as to close the opening on the fluid discharge side of the first nozzle hole 11c, and the through-hole formed in the surface electrode layer 81 is formed. The hole 81 a is the fluid discharge hole 9. The surface electrode layer 81 is electrically connected to the first electrode layer 25 formed on the inner wall of the first nozzle hole 11c, and the first electrode layer 25 and the second electrode layer 26 are connected. A drive signal can be applied from the fluid supply side of the nozzle plate 80 via the. Here, the second nozzle layer 20 is one layer, but may be two or more layers.
[0227]
  In FIGS. 13A and 13C, the first nozzle holes 11c and the second nozzle holes 11b formed in the nozzle holes 11 are formed on the inner walls of the first nozzle holes 11 in order to simplify the drawings. The electrode layer 25 and the second electrode layer 26 are omitted.
[0228]
  Specific examples of the size and material of each part will be described below, but the present invention is not limited to the specific examples.
[0229]
  The surface electrode layer 81 is made of a metal material containing Pt as a main component, and is formed in a substantially circular shape with a diameter of 5 μm in order to reduce the stress of the entire nozzle plate 80. The thickness of the surface electrode layer 81 is 0.5 μm.
[0230]
  The first nozzle layer 10 is made of SiO in the present embodiment.₂The thickness is 2 μm. The second nozzle layer 20 is made of an organic material whose main component is polyimide resin and is formed to a thickness of 20 μm. The first electrode layer 25 and the second electrode layer 26 are made of a metal material mainly composed of Ti and have a thickness of 0.5 μm.
[0231]
  The diameter of the fluid discharge hole 9 which is the through hole 81a formed in the surface electrode layer 81 is 2 μm, and is processed perpendicularly to the film surface up to the communication portion with the first nozzle hole 11c. Here, the diameter of the fluid discharge hole 9 isReference formFor the same reason as above, it is desirable that the diameter is 10 μm or less, more preferably 8 μm or less.
[0232]
  The first nozzle hole 11c has a communicating portion with the fluid discharge hole 9, that is, the fluid discharge side opening is processed to have a diameter of 4 μm, and extends to the communicating portion with the second nozzle hole 11b. It is processed into a tapered shape (conical shape) that opens.
[0233]
  Further, the second nozzle hole 11b is processed to have a diameter of 20 μm at the communicating portion with the first nozzle hole 11c, that is, the fluid discharge side opening, and has a tapered shape (conical truncated cone shape) that widens to spread out. And is opened at the fluid supply surface 80 b of the nozzle plate 80 through the second nozzle layer 20.
[0234]
  Note that the upper base 11cy of the first nozzle hole 11c having a truncated cone shape has an annular shape with the fluid discharge hole 9 as the center, and a part of the surface electrode layer 81 forms the upper base 11cy and is exposed. is doing. Therefore, the diameter of the communication hole 11cx (substantially circular) between the fluid discharge hole 9 and the first nozzle hole 11c is equal to the outer diameter of the upper bottom 11cy of the first nozzle hole 11c (the first nozzle hole in the communication hole 11cx). 11c)).
[0235]
  Further, the upper base 11by of the second nozzle hole 11b having a truncated cone shape has an annular shape with the first nozzle hole 11c as a center, and a part of the first electrode layer forms the upper base 11by. And exposed. Therefore, the diameter of the communication hole 11bx (substantially circular) of the first nozzle hole 11c and the second nozzle hole 11b is the same as the outer diameter of the upper bottom 11by of the second nozzle hole 11b (the second nozzle in the communication hole 11bx). It is smaller than the outer shape of the hole 11b.
[0236]
  Further, in addition to at least a part of the inner wall of the first nozzle hole 11c, the first electrode layer 25 serving as an extending portion 25b is formed in the peripheral portion where the first nozzle hole 11c and the second nozzle hole 11b communicate with each other. Is formed. Here, the SiO constituting the first nozzle layer 10₂Shows high resistance to dry etching by oxygen-containing plasma due to processing of the second nozzle hole 11b described later, so that the extended portion 25b of the first electrode layer 25 is not formed and the first nozzle layer Even when 10 or the first nozzle hole 11c is exposed to the etching of the second nozzle hole 11b, the shape of the first nozzle hole 11c is not deformed without being almost etched.
[0237]
  On the other hand, when the material with low tolerance with respect to the etching in the 2nd nozzle hole 11b process is used for the 1st nozzle layer 10 (for example,Reference formAs in the case of (1), the first nozzle layer 10 and the second nozzle layer 20 are made of the same material), and the first electrode layer 25 may be formed so as to cover the entire inner wall of the first nozzle hole 11c. desirable. That is, the first electrode layer 25 functions as a protective layer that protects the first nozzle hole 11c or the first nozzle layer 10 from the etching in the processing step of the second nozzle hole 11b.
[0238]
  A second electrode layer 26 electrically connected to the first electrode layer 25 is formed on the inner wall of the second nozzle hole 11b. A part of the second electrode layer 26 is also disposed on the fluid supply side surface of the second nozzle layer 20 forming the fluid supply surface 80b of the nozzle plate 80, as shown in FIG. Further, the second electrode layer 26 formed on the surface is connected to drive signal voltage applying means (not shown) by a wiring pattern 26a. The liquid repellent layer 4 is formed from a polymer material having a fluoropolymer having a thickness of 0.05 μm.
[0239]
  Further, since the surface electrode layer 81 has a high resistance to the etching means of the first nozzle hole 11c, the shape of the fluid discharge hole 9 is not deformed by the etching of the first nozzle hole 11ca. Further, since the shape of the fluid discharge hole 9 of the nozzle plate, which has a great influence on the landing accuracy, is determined by the processing accuracy of the 0.5 μm Ti film serving as the surface electrode layer 81, the processing accuracy of the fluid discharge hole 9 is extremely high. Accordingly, it is possible to ensure a very high landing accuracy.
[0240]
  By the way, in order to increase the processing accuracy of the fluid discharge hole 9, if the film thickness of the surface electrode layer 81 is decreased, higher processing accuracy can be obtained. However, by reducing the film thickness of the surface electrode layer 81, The rigidity of the surface electrode layer 81 is lowered, and the structural reliability of the fluid discharge hole 9 is reduced.
[0241]
  However, by disposing the first nozzle layer 10 in contact with the surface electrode layer 81 in this way, the surface electrode layer 81 is reinforced, and the fluid discharge hole is not degraded without lowering the structural reliability of the surface electrode layer 81. The shape accuracy of 9 can be improved.
[0242]
  In addition, since the first electrode layer 25 has high resistance to the etching means for the second nozzle hole 11b, the shape of the first nozzle hole 11c is greatly increased by processing the second nozzle hole 11b. In addition, the first nozzle layer 10 is not completely removed by over-etching the second nozzle hole 11b.
[0243]
  The material used for the surface electrode layer 81 is not limited to a metal material containing Pt as a main component. When etching the first nozzle hole 11c, etching the second nozzle hole 11b, etching a sacrificial layer 50, which will be described later, and etching the liquid repellent layer 4 that has entered the fluid discharge hole 9, the etching is high. A material having resistance, that is, a material having high resistance to fluorine-containing plasma, oxygen-containing plasma, nitric acid, potassium hydroxide aqueous solution, etc. may be used. Sacrificial layer etching, first nozzle hole processing, second It can be used in combination with a nozzle hole processing method. Specifically, a metal material mainly composed of Al, Cu, Co, Fe, Ni, Au, Pt, or the like can be used, and can be selected by a combination with the etching gas or the etchant.
[0244]
  In addition, the materials of the first nozzle layer 10, the first nozzle layer 2, the first electrode layer 25, the second electrode layer 26, and the like are not limited to the above, and the material and the manufacturing method are suitable. This combination will be described later.
[0245]
  In the present embodiment, the second nozzle hole 11b has a truncated cone shape (tapered shape) in which the communication portion 11bx with the first nozzle hole 11c is narrowed, but is not limited thereto. For example, like the modified nozzle plate 80 ′ shown in FIG. 14, the side wall of the second nozzle hole 11 b can be formed in a so-called straight shape (cylindrical shape) perpendicular to the stopper layer 3. In this case, the fluid supply hole 12 of the second nozzle hole 11b can be made smaller, and the degree of nozzle integration can be further increased. Further, as shown in FIG. 14, the second electrode layer 26 may be formed on the entire inner wall surface of the second nozzle hole 11b. In this case, the reliability of the second electrode layer 26 in terms of electrical conduction is improved. To do.
[0246]
  Here, one through hole 81a is formed for one surface electrode layer 81 corresponding to one nozzle hole 11, but a plurality of through holes are formed in one surface electrode layer 81. A plurality of fluid discharge holes 9 for one nozzle hole 11 may be provided.
[0247]
  Further, as in the case of the nozzle plate 8 of the embodiment, the first nozzle hole 11c can be formed in a so-called straight shape (cylindrical shape) whose side wall is perpendicular to the nozzle plate surface. In this case, since the processing accuracy of the first nozzle hole is improved, the shape of the surface electrode layer 81 can be reduced, and the stress generated by the surface electrode layer 81 can be reduced.
[0248]
  By using the nozzle plate 80 (80 ') having the configuration as in the present embodiment, the following operation is achieved in addition to the above-described (1) to (5).
(6) Since the first nozzle hole 11c is formed in a tapered shape, the coverage of the first electrode layer 25 formed in the first nozzle hole 11c is good, and the reliability related to conductivity is improved.
(7) Since the through-hole 81a formed in the surface electrode layer 81 of the thin film becomes the hole fluid discharge hole 9, the processing accuracy is very high, and the shape of the fluid discharge hole 9 by forming the first electrode layer 25 Since there is no change, ejection reliability is improved.
[0249]
  (Nozzle plate manufacturing method)
  Next, a manufacturing method of the nozzle plate 80 according to the present embodiment will be described. FIGS. 15A to 15G are views for explaining a manufacturing process of the nozzle plate 80.
[0250]
  First, the sacrificial layer 50 is formed on the substrate 6.Reference form andIt forms similarly (FIG. 15A). Here, the thickness of the sacrificial layer 50 is 10 μm. Further, a Pt film having a thickness of 0.5 μm is formed on the sacrificial layer 50 by a method such as vapor deposition, and the surface electrode layer 81 is partially formed in the nozzle hole 11 formation portion using photolithography. A resist pattern having an outer shape and a shape of the through hole 81 to be the fluid discharge hole 9 is formed. Thereafter, the outer shape of the surface electrode layer 81 and the fluid discharge hole 9 are simultaneously processed using a dry etching method.
[0251]
  Since the Pt film is a chemically relatively inert material, here, the dry etching is performed by a method in which physical processing is dominant, using sputter etching using Ar. Further, since this processing is performed with very high accuracy, highly anisotropic etching conditions are used. Here, the shape of the surface electrode layer 81 is processed into a substantially circular shape with a diameter of 5 μm. The fluid discharge hole 9 disposed in the surface electrode layer 81 is formed in a substantially circular shape with a diameter of 2 μm.
[0252]
  Next, SiO on the sacrificial layer 50 and the surface electrode layer 81.₂A first nozzle layer 10 made of a film is formed by a P-CVD method. According to the present P-CVD method, the deposited SiO₂The stress of the film can be controlled by the composition of the gas used for film formation, the gas pressure, and the RF power for generating plasma, and the surrounding area of the step portion is good. No cracks or the like occur in the part, and the structural reliability as a film is high. This increases the structural reliability of the entire nozzle plate (see FIG. 15A).
[0253]
  Next, a resist pattern is formed on the first nozzle layer 10 by photolithography and processed by reactive ion etching (RIE) containing fluorine gas and oxygen gas. After the processing, the resist is removed by a resist stripping solution. To do. (See FIG. 15 (b)). In this etching method, since fluorine activated by plasma selectively reacts with Si atoms, SiO 2₂The etching rate of is very high. On the other hand, since Pt is a chemically stable material as described above, it hardly reacts with the activated fluorine. For this reason, the etching rate of Pt is slow, and this etching can be accurately stopped at the interface between the surface electrode layer 81 and the first nozzle layer 10.
[0254]
  Further, in this processing step, by using plasma containing fluorine gas and oxygen gas, SiO 2 is used.₂And the photoresist etching rate are set to the same level,Reference formSiO 2 using a method that reflects the shape of the resist used in the process of processing the second nozzle layer 20 of₂The first nozzle hole 11c was processed into a tapered shape. Here, the shape of the first nozzle hole 11c that can be placed at the junction with the surface electrode layer 81 was a substantially circular shape with a diameter of 4 μm, and the opening diameter at the interface with the second nozzle layer 20 was 6 μm. Further, the shape of the first nozzle hole 11c is larger than that of the fluid discharge hole 9, and the first nozzle hole 11c is processed so that the fluid discharge hole 9 is disposed in the pattern of the first nozzle hole 11c.
[0255]
  Further, since the first nozzle hole 11c only needs to be bonded to the surface electrode layer 81, not only a tapered shape but also a so-called straight shape perpendicular to the nozzle surface may be used.
[0256]
  Next, Ti is formed by ion beam sputtering from the direction of arrow K1 (18 ° with respect to the surface of the first nozzle layer 10), and the surface electrode layer 81, a part of the first nozzle hole 11c, and the first A first electrode layer 25 having a thickness of 0.5 μm is formed on one nozzle layer 10. At this time, considering the shape of the first nozzle hole 11c and the thickness of the first nozzle layer 10 so that the Ti film is not formed inside the fluid discharge hole 9 formed in the surface electrode layer 81, It is desirable to determine the direction of incidence of Ti particles. Here, the substrate is fixed and the first electrode layer 25 is formed. However, after the incident angle is set, the first nozzle hole is formed by rotating the substrate around the normal direction of the nozzle surface. The first electrode layer 25 can be formed on the entire surface of the 11c side wall. The first electrode layer 25 deposited on the entire side wall of the first nozzle hole formed in this way can function as a protective layer for the first nozzle hole 11c when processing the second nozzle hole described later. .
[0257]
  Next, the outer shape of the first electrode layer 25 on the first nozzle layer 10 is processed using a dry etching method. In this processing,Reference formThe processing method performed when processing the second electrode layer 26 was performed. That is, after forming a desired pattern with a positive photoresist, processing was performed by dry etching using plasma mainly containing Ar gas. Here, the shape of the first electrode layer 25 disposed at the interface between the first nozzle layer 10 and the second nozzle layer 20 is a substantially circular shape having a diameter of 16 μm (see FIG. 15C).
[0258]
  Next, a coating type polyimide resin is formed on the first nozzle layer 10 to a thickness of 20 μm to form the second nozzle layer 20 (see FIG. 15D). Here, the coating-type polyimide resin was applied on the first nozzle layer 10 by spin coating and baked at 350 ° C. for 2 hours. Here, the fluid discharge hole 9 and the first nozzle hole 11c are also filled with the polyimide resin.
[0259]
  Next, a resist pattern 70 is formed on the second nozzle layer 20 by photolithography, dry etching using a gas containing oxygen as a main component is performed, and the second nozzle layer 20 is tapered (conical truncated cone shape). ) Second nozzle hole 11b (see FIG. 15E).
[0260]
  The dry etching can be stopped by the first nozzle layer 10, the first electrode layer 25, or the surface electrode layer 81. That is, dry etching does not proceed any further in the portion where the first nozzle layer 10 or the first electrode layer 25 is exposed except for the first nozzle hole 11c. Similarly, dry etching does not proceed any further in the portion of the surface electrode layer 81 where the surface electrode layer 81 is exposed except for the fluid discharge hole 9. That is, in the processing process of the second nozzle hole 11b, the first nozzle hole 11c and the fluid discharge hole 9 filled with the polyimide resin in the previous step are reproduced by removing the polyimide resin, The second nozzle layer 20 material present in the shape determined by the pattern formed in the surface electrode layer 81 is removed from the discharge hole 9, and the shape filled with the polyimide resin in the previous step is reproduced.
[0261]
  Next, the resist pattern 70 is removed using a resist stripping solution, and the second electrode layer 26 made of a metal material mainly composed of Ti is formed on the second nozzle layer 20. Here, using the ion beam sputtering method, the substrate is tilted so that Ti particles come from the direction of the arrow K2 while suppressing the scattering of Ti particles by Ar atoms under Ar gas pressure of 0.2 mTorr. The second electrode layer 26 was formed only on one side of the inner wall surface of the nozzle layer 20, and a part of the second electrode layer 26 was formed so as to be electrically short-circuited with the first electrode layer 25 (see FIG. 15 (f)). The film thickness is 0.5 μm. Thus, by forming the second electrode layer 26 while the Ti particles are incident from an oblique direction, it is possible to prevent the second electrode layer 26 from adhering in the fluid discharge hole 9, thereby , It is possible to prevent the fluid discharge hole 9 from being changed in shape or blocked.
[0262]
  Next, the second electrode layer 26 is processed.Reference formSince it is the same as that, it abbreviate | omits. The shape of the second electrode layer 26 formed on the second nozzle layer was a circular shape having a diameter of about 70 μm.
[0263]
  Next, the nozzle plate 80 is removed from the substrate 6 by immersing in an aqueous solution containing nitric acid and water as main components and etching only the sacrificial layer 50 (FIG. 15G). As described above, the SiO that forms the first nozzle layer 10₂The polyimide resin that forms the second nozzle layer 20, the Pt that forms the surface electrode layer 81, and the Ti that forms the first electrode layer 25 and the second electrode layer 26 depend on the etching solution for the sacrificial layer 50. Since it is hardly etched, the etching of the sacrificial layer 50 does not cause a change in shape or a decrease in structural reliability.
[0264]
  Next, the liquid repellent layer 4 is formed on the surface of the first nozzle layer 10 (FIG. 15G). Here, a fluoropolymer was used for the purpose of considering the ease of application, and this was applied to the surface of the first nozzle layer 10 by a method such as stamping to form the liquid repellent layer 4 with a polymer film. In addition, the liquid repellent layer that has entered the first nozzle hole 11c is removed by dry etching from the second nozzle hole 11b side using plasma containing oxygen after the liquid repellent layer is formed. did. Thereby, damage to the nozzle plate 80 can be minimized.
[0265]
  In this embodiment mode, the wraparound is removed by dry etching using plasma containing oxygen. However, in the present embodiment, as described above, the surface electrode layer 81 having high resistance to dry etching using plasma containing oxygen is present on the fluid discharge surface. Since the shape of the fluid discharge hole 9 is determined, the shape of the fluid discharge hole 9 is not changed by the dry etching. For this reason, a very highly accurate nozzle hole can be formed.
[0266]
  Specifically, when the shape of each fluid discharge hole 9 of the nozzle plate 80 having 200 fluid discharge holes 9 created by using the process of the present embodiment was evaluated, the variation was very large as ± 0.15 μm. We were able to process with high accuracy. Further, the warpage of the nozzle plate 80 was very flat at 10 μm or less.
[0267]
  In the present embodiment, the sacrificial layer 50 is Ni, the surface electrode layer 81 is Pt, and the first nozzle layer 10 is SiO.₂Although the polyimide resin is used for the second nozzle layer 20, Ti is used for the first electrode layer 25, and Ti is used for the second electrode layer 26, the present invention is not limited to this combination.
[0268]
  In addition to Ni, the sacrificial layer 50 may be made of nitric acid such as Al or Cu, or KOH aqueous solution depending on the combination with the materials used for the surface electrode layer 81, the first nozzle layer 10 and the second nozzle layer 20. Soluble materials can be used. As a method for forming the sacrificial layer 50, a vapor deposition method, a sputtering method, a coating method, or the like can be used in addition to the plating depending on the material.
[0269]
  For the second nozzle layer 20 and the second electrode layer 26, a material that is slightly damaged by etching of the sacrificial layer 50 can be used. However, considering the etching selectivity with the first nozzle layer or the surface electrode layer 81 described later, an organic resin that can be etched using plasma containing oxygen is desirable. Furthermore, when an organic resin having a molecular structure in which molecular chains are cross-linked, the second nozzle layer 20 has high heat resistance and environmental resistance, and the reliability of the nozzle plate can be improved.
[0270]
  For the first nozzle layer 10 and the first electrode layer 25, a material having high resistance to the etching of the sacrificial layer 50 and the etching of the second nozzle hole 11b can be used. Furthermore, the surface electrode layer 81 can be made of a material having high resistance to the etching of the sacrificial layer 50, the etching of the second nozzle hole 11b, and the etching of the first nozzle hole 11c.
[0271]
  Here, FIG. 16 shows materials used (sacrificial layer, surface electrode layer, first nozzle layer, second nozzle layer, first electrode layer, first electrode layer formation region, second electrode layer). Examples of preferable combinations for the processing methods (fluid ejection holes, first nozzle holes, second nozzle holes, sacrificial layer removal) will be described.
[0272]
  As shown in FIG. 16, the first nozzle layer 10 or the second nozzle layer 20 is made of organic resin such as polyimide or SiO 2.₂The nozzle layer can be composed of a combination of inorganic materials such as Si compounds. However, for example, SiO₂/ SiO₂In the case where the first nozzle layer 10 is damaged when the second nozzle hole is processed, such as a combination of polyimide and polyimide / polyimide, the first electrode layer 25 is used as the first nozzle hole. It is necessary to protect the first nozzle hole 11c by forming it on the entire inner wall of 11c.
[0273]
  In this embodiment, the sacrificial layer 50 is completely removed by etching. However, it is not necessary to completely remove the sacrificial layer 50, and only the portion of the sacrificial layer 50 that is in contact with the first nozzle layer 10 is used. If removed by etching, the nozzle plate 80 can be removed from the substrate 6.
[0274]
  The liquid repellent layer 4 is not limited to a fluoropolymer, and a silicon-based polymer film, DLC (diamond-like carbon), or the like can also be used.
[0275]
  By using the above processing steps, it is possible to manufacture the nozzle plate 80 having the effects (1) to (7) described above.
[0276]
  Moreover, the structure which does not form the liquid repellent layer 4 can be employ | adopted through all the embodiment mentioned above. By not forming the liquid repellent layer 4 on the surface electrode layer 81 or the first nozzle layer 1, the shape accuracy of the fluid discharge hole 9 is further improved.
[0277]
  In addition, through all the above-described embodiments, the surface electrode layer 81, the first electrode layer 25, the second electrode layer 26, and a plurality of thin films having a metal film containing the above-described material as a main component. A so-called laminated film may be used.
[0278]
  In each of the above-described embodiments, the method of manufacturing the nozzle plates 8 and 80 by forming the sacrificial layers 5 and 50 on the substrate 6 and etching the sacrificial layers 5 and 50 has been described. In addition, the first nozzle layers 1 and 10 can be directly formed on a substrate made of a material that can be etched by the same method as the etching of the sacrificial layers 5 and 50, such as a Ni plate. .
[0279]
  Finally, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and technical means disclosed in different embodiments are appropriately combined. Embodiments obtained in this manner are also included in the technical scope of the present invention.
[0280]
【The invention's effect】
  As described above, the nozzle plate of the present invention has the first nozzle hole and is laminated on the fluid supply side of the first nozzle layer and the thin first nozzle layer disposed on the fluid discharge side. A second nozzle layer that is thicker than the first nozzle layer and has a second nozzle hole that communicates with the first nozzle hole and forms a nozzle hole portion with the first nozzle hole. The first electrode layer formed on the inner wall of the first nozzle hole and the second electrode layer formed on the inner wall of the second nozzle hole are electrically connected to each other. It is characterized by being.
[0281]
  With the above-described configuration, the first nozzle hole formed in the first nozzle layer can be formed with a very fine hole diameter of, for example, 10 μm or less, and the first nozzle hole inside the first nozzle hole has a first diameter. 1 electrode layer can be stably formed in the layer thickness direction, and when the opening of the first nozzle hole on the fluid discharge surface is a fluid discharge hole, the first electrode layer is located near the fluid discharge hole. An electrode can be deposited. As a result, the electrical resistance R inside the nozzle can be drastically reduced as compared with the conventional case, the fluid discharge frequency can be improved, and high-speed drawing on the recording medium becomes possible.
[0282]
  Moreover, since the first electrode layer formed in this way is electrically connected to the second electrode layer formed in the second nozzle hole communicating with the first nozzle hole, the second electrode layer A drive signal can be supplied from the fluid supply side of the nozzle plate via the electrode layer. Therefore, the lead-out wiring for supplying the drive signal to the first electrode layer does not approach the medium, and the recording medium is not electrically damaged by the electric field generated from the lead-out wiring.
[0283]
  In the nozzle plate of the present invention, the fluid discharge side opening of the first nozzle hole is further closed on the fluid discharge side of the first nozzle hole.Smaller diameter than the fluid discharge side opening of the first nozzle holeWith a through holeDisk-shapedA surface electrode layer is disposed, the through hole and the first nozzle hole communicate with each other, and the surface electrode layer is electrically connected to the first electrode layer.
[0284]
  According to the above configuration, since the through hole of the surface electrode layer provided on the fluid discharge surface of the nozzle plate becomes the fluid discharge hole, the fluid discharge hole that greatly affects the landing accuracy of the discharged fluid can be formed by etching the surface electrode layer. Can be processed. As a result, the shape accuracy of the fluid discharge hole is dramatically stabilized more than the configuration in which the fluid discharge side opening of the first nozzle hole in which the first electrode layer is formed on the inner wall is a fluid discharge hole. As a result, the landing accuracy can be further stabilized.
[0285]
  As described above, the method for manufacturing a nozzle plate of the present invention includes a step of forming a sacrificial layer on a substrate, a step of forming a first nozzle layer on the sacrificial layer, and a plurality of the first nozzle layer. Forming the first nozzle hole, forming the first electrode layer including the inner wall surface of each first nozzle hole on the first nozzle layer, and the inner wall of each first nozzle hole And the step of processing the first electrode layer so as to remain around each of the first nozzle holes, and the second electrode layer portion including the remaining first electrode layer portions on the first nozzle layer. A step of forming a nozzle layer, a plurality of second nozzle holes in the second nozzle layer, and a fluid discharge side opening of each second nozzle hole remaining on the first nozzle layer. Including a step of forming the electrode layer portion so as to fit in one electrode layer portion, and an inner wall surface of each second nozzle hole on the second nozzle layer. Forming a second electrode layer, it is characterized by comprising a step of processing the second electrode layer to be electrically separated between adjacent second nozzle hole.
[0286]
  According to this, the first nozzle layer, the first electrode layer, the second nozzle layer, and the second electrode layer are sequentially laminated on the highly rigid substrate via the sacrificial layer. For this reason, after forming a resist pattern using photolithography technology, it can be processed into a desired shape by dry etching, so that the first nozzle hole, the second nozzle hole, the first electrode layer, the second electrode layer Can be formed with very high shape accuracy.
[0287]
  Further, since the fluid discharge surface of the nozzle plate is protected by the sacrificial layer until the final stage of the process, there is no risk that the fluid discharge hole is damaged and the fluid discharge hole is deformed in the nozzle plate manufacturing process. For this reason, the manufacturing yield of the nozzle plate is improved.
[0288]
  In the nozzle plate manufacturing method of the present invention, the surface electrode layer is further formed on the sacrificial layer between the step of forming the sacrificial layer on the substrate and the step of forming the first nozzle layer on the sacrificial layer. And forming the first nozzle layer on the sacrificial layer by separating the surface electrode layer corresponding to the nozzle hole portion forming portion and forming a through hole in each separation portion. The first nozzle layer may be formed including the separated surface electrode layer.
[0289]
  In the manufacturing method of the nozzle plate of this configuration, since the fluid discharge hole can be processed as a through hole in the surface electrode layer formed on the sacrificial layer, the first electrode layer formed in the first nozzle hole can be processed. Due to non-uniformity (for example, film thickness distribution), the shape of the fluid discharge hole is not deformed, and a nozzle plate having a highly accurate fluid discharge hole can be manufactured.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining calculation of electric field strength of a nozzle in a discharge model as a basis of the present invention.
FIG. 2 is a graph showing model calculation results of nozzle diameter dependence of surface tension pressure and electrostatic pressure.
FIG. 3 is a graph showing a model calculation result of nozzle diameter dependence of discharge pressure.
FIG. 4 is a graph showing a model calculation result of nozzle diameter dependence of discharge limit voltage.
FIG. 5 is a graph showing a correlation between a mirror image force acting between a charged droplet and a substrate and a nozzle-substrate distance.
FIG. 6 is a graph showing a model calculation result of a correlation between a flow rate flowing out from a nozzle and an applied voltage.
FIGS. 7 (a) and 7 (c) show the present invention.referenceIt is a perspective view which shows the nozzle plate concerning a form, (b) is the sectional view on the A-A 'line of (a).
FIG. 8 is an explanatory diagram showing a connection portion between the first electrode layer and the second electrode layer in the nozzle plate.
[Figure 9] BookreferenceThe modification of the nozzle plate concerning a form is shown, and it is sectional drawing equivalent to FIG.7 (c).
FIG. 10 (a) to (i) are booksreferenceIt is explanatory drawing which shows the manufacturing method of the said nozzle plate of a form with the structure of a cross section.
FIGS. 11A to 11C are explanatory views showing the process shown in FIG. 10E in detail by the cross-sectional configuration of the nozzle plate.
FIG. 12referenceWhen manufacturing the nozzle plate concerning a form, it is explanatory drawing which shows the preferable combination of the use material and processing method of each layer.
FIGS. 13A and 13C are views of the present invention.ImplementationIt is a perspective view which shows the nozzle plate concerning a form, (b) is the B-B 'sectional view taken on the line of (a).
FIG. 14The present inventionFIG. 14 is a cross-sectional view illustrating a modification of the nozzle plate according to the embodiment and corresponding to FIG.
FIG. 15 (a) to (g)The present inventionIt is explanatory drawing which shows the manufacturing method of the said nozzle plate of embodiment of a cross-sectional structure.
FIG. 16The present inventionWhen manufacturing the nozzle plate concerning embodiment of this, it is explanatory drawing which shows the preferable combination of the use material and processing method of each layer.
FIG. 17 is a schematic cross-sectional view of a conventional electrostatic attraction type inkjet device.
18A to 18C are diagrams for explaining the behavior of the ink meniscus in the ink jet apparatus shown in FIG.
FIG. 19 is a schematic configuration diagram of another conventional electrostatic attraction type inkjet device.
20 is a schematic cross-sectional perspective view of a nozzle portion of the ink jet apparatus shown in FIG.
FIG. 21 is a diagram illustrating an ink discharge principle of the ink jet apparatus shown in FIG.
22 is a diagram illustrating the state of fine particles when a voltage is applied at the nozzle portion of the ink jet apparatus shown in FIG.
FIG. 23 is a diagram illustrating the principle of fine particle formation in the nozzle portion of the ink jet apparatus shown in FIG.
24A to 24C are diagrams for explaining the behavior of the ink meniscus in the ink jet apparatus shown in FIG.
FIG. 25A is a schematic configuration diagram of an electrostatic suction type fluid discharge device, and FIG. 25B is an equivalent circuit thereof.
FIG. 26 is a side sectional view of a conventional nozzle plate used in an electrostatic suction type ink jet device.
FIG. 27 is a cross-sectional view illustrating a configuration of a recording head portion of a conventional electrostatic attraction type inkjet device.
28 is a partially enlarged cross-sectional plan view showing ink ejection holes in a recording head portion of the electrostatic suction type ink jet apparatus of FIG.
[Explanation of symbols]
  1 First nozzle layer
  2 Second nozzle layer
  4 Liquid repellent film
  5 Sacrificial layer
  8 Nozzle plate
  9 Fluid discharge hole
10 First nozzle layer
11 Nozzle hole (nozzle hole)
11a First nozzle hole
11c 1st nozzle hole
11b Second nozzle hole
20 Second nozzle layer
25 First electrode layer
25b Extension part (extended first electrode layer part)
26 Second electrode layer
50 Sacrificial layer
80 nozzle plate
81 Surface electrode layer

Claims (8)

In a nozzle plate having a plurality of nozzle holes, which is provided in an electrostatic suction type fluid discharge device that discharges a fluid charged by voltage application from a fluid discharge hole at a nozzle tip by electrostatic suction.
A thin first nozzle layer having a first nozzle hole and disposed on the fluid ejection side;
It is laminated on the fluid supply side of the first nozzle layer, is thicker than the first nozzle layer, communicates with the first nozzle hole, and constitutes a nozzle hole portion with the first nozzle hole. Comprising at least one second nozzle layer having a second nozzle hole;
The first electrode layer formed on the inner wall of the first nozzle hole and the second electrode layer formed on the inner wall of the second nozzle hole are electrically connected,
A disk having a through-hole having a smaller diameter than the fluid discharge side opening of the first nozzle hole on the fluid discharge side of the first nozzle hole so as to close the fluid discharge side opening of the first nozzle hole A nozzle plate comprising: a surface electrode layer having a shape , wherein the through hole and the first nozzle hole communicate with each other, and the surface electrode layer is electrically connected to the first electrode layer. Forming a sacrificial layer on the substrate;
Forming a first nozzle layer on the sacrificial layer;
Forming a plurality of first nozzle holes in the first nozzle layer;
Forming a first electrode layer on the first nozzle layer including the inner wall surface of each first nozzle hole;
Processing the first electrode layer so as to remain on the inner wall of each first nozzle hole and the periphery of each first nozzle hole;
Forming a second nozzle layer on the first nozzle layer, including each remaining first electrode layer portion;
A plurality of second nozzle holes are formed in the second nozzle layer so that an opening on the fluid discharge side of each second nozzle hole is accommodated in each first electrode layer portion remaining on the first nozzle layer. Forming the step,
Forming a second electrode layer on the second nozzle layer including the inner wall surface of each second nozzle hole;
And a step of processing the second electrode layer so as to be electrically separated between adjacent second nozzle holes. Between the step of forming the sacrificial layer on the substrate and the step of forming the first nozzle layer on the sacrificial layer, a surface electrode layer is formed on the sacrificial layer, and the surface electrode layer is formed into a nozzle hole portion forming portion. And a step of forming a through hole in each separation part,
3. The method for manufacturing a nozzle plate according to claim 2, wherein in the step of forming the first nozzle layer on the sacrificial layer, the first nozzle layer is formed including the separated surface electrode layer.   4. The method for manufacturing a nozzle plate according to claim 2, wherein in the step of forming the second electrode layer, film forming particles are incident on the nozzle plate surface obliquely.   4. The method for manufacturing a nozzle plate according to claim 3, wherein in the step of forming the first electrode layer, the film-forming particles are incident on the nozzle plate surface obliquely.   In the step of forming the second nozzle hole, etching is used, and a condition having higher resistance to etching of the first electrode layer than resistance to etching of the second nozzle layer is selected. A method for manufacturing a nozzle plate according to claim 2 or 3.   In the step of forming the first nozzle hole and the step of forming the second nozzle hole, etching is used, and the resistance to the etching of the surface electrode layer is more than the resistance to the etching of the first and second nozzle layers. The method for manufacturing a nozzle plate according to claim 3, wherein a condition having high resistance is selected.   4. The method for manufacturing a nozzle plate according to claim 2, wherein the step of electrically separating the second electrode layer is performed using dry etching.

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