JP4274350B2 - Mold manufacturing method - Google Patents

Description

で表される領域において駆動することが好ましい。
ただし、γ：液体の表面張力、ε_０：真空の誘電率、ｒ：ノズル半径、ｈ：ノズル−基板間距離、ｋ：ノズル形状に依存する比例定数（1.5<k<8.5）とする。
（５）上記各請求項の構成、上記（１）、（２）、（３）又は（４）の構成において、印加する任意波形電圧が1000V以下であることが好ましい。
（６）上記各請求項の構成、上記（１）、（２）、（３）、（４）又は（５）の構成において、印加する任意波形電圧が500V以下であることが好ましい。
基材を導電性または絶縁性の基材ホルダーに裁置ことが好ましい。
（７）上記各請求項の構成、上記（１）〜（６）いずれかの構成において、ノズルと基板との距離が500[μm]以下とすることが、ノズル径を微細にした場合でも高い着弾精度を得ることができるので好ましい。
（８）上記各請求項の構成、上記（１）〜（７）いずれかの構成において、ノズル内の溶液に圧力を印加するように構成することが好ましい。
（９）上記各請求項の構成、上記（１）〜（８）いずれかの構成において、単一パルスによって吐出する場合、
【数２】

により決まる時定数τ以上のパルス幅Δｔを印加する構成としても良い。ただし、ε：流体の誘電率、σ：導電率とする。
【００３１】
【発明の実施の形態】
以下、本発明の実施形態について図面を参照しながら説明する。以下の本実施形態では、まず、本発明に係る液体吐出装置についての説明を行い、その後に液体吐出装置を用いた金型の製造方法についての説明を行う。
【００３２】
なお、以下の各実施形態で説明する液体吐出装置のノズル径（内部直径）は、30[μm]以下であることが好ましく、さらに好ましくは20[μm]未満、さらに好ましくは8[μm]以下、さらに好ましくは4[μm]以下とすることが好ましい。また、ノズル径は、0.2[μm]より大きいことが好ましい。
【００３３】
［液体吐出装置］
（液体吐出装置の全体構成）
以下、液体吐出装置について図１及び図２に基づいて説明する。図１は後述するノズル２１に沿った液体吐出装置２０の断面図であり、図２は液体の吐出動作と液体に印加される電圧との関係を示す説明図であって、特に図２（Ａ）は吐出を行わない状態であり、図２（Ｂ）は吐出状態を示す。
【００３４】
図１に示す通り、液体吐出装置２０は、帯電可能な液体の液滴をその先端部から吐出する超微細径のノズル２１と、ノズル２１の先端部に対向する対向面を有すると共にその対向面で液滴の着弾を受ける基材９９を支持する対向電極２３と、ノズル２１内の流路２２に液体を供給する液体供給手段（図示略）と、ノズル２１内の液体に吐出電圧を印加する吐出電圧印加手段２５と、基材９９に着弾した液滴に光を照射する光照射手段（図示略）と、対向電極２３及び基材９９を支持した状態で基材９９の位置決め、位置調整等を行うＸＹステージ３１と、を備えている。
なお、上記ノズル２１と液体供給手段の一部の構成と吐出電圧印加手段２５の一部の構成はノズルプレート２６により一体的に形成されている。
【００３５】
（ノズル）
上記ノズル２１は、後述するノズルプレート２６の下面層２６ｃと共に一体的に形成されており、当該ノズルプレート２６の平板面上から垂直に立設されている。さらに、ノズル２１にはその先端部からその中心線に沿って貫通するノズル内流路２２が形成されている。
【００３６】
ノズル２１についてさらに詳説する。ノズル２１は、前述の通り、超微細径で形成されている。具体的な各部の寸法の一例を挙げると、ノズル内の流路２２の内部直径は1[μm]、ノズル２１の先端部における外部直径は2[μm]、ノズル２１の根元の直径は5[μm]、ノズル２１の高さは100[μm]に設定されており、その形状は限りなく円錐形に近い円錐台形に形成されている。また、ノズル２１はその全体がノズルプレート２６の下面層２６ｃと共に絶縁性の樹脂材により形成されている。
【００３７】
なお、ノズルの各寸法は上記一例に限定されるものではない。特にノズル内径については、後述する電界集中の効果により液滴の吐出を可能とする吐出電圧が1000[Ｖ]未満を実現する範囲であって、例えば、ノズル直径70[μm]以下であり、より望ましくは、直径20[μm]以下であって、現行のノズル形成技術により液体を通す貫通穴を形成することが実現可能な範囲である直径をその下限値とする。
【００３８】
また、図１の液体吐出装置２０には、一つのノズル２１のみを図示したが、実際の液体吐出装置２０には、複数のノズル２１がＸ軸方向（左右方向）及びＹ軸方向（前後方向）に沿ってマトリクス状に設けられている。
【００３９】
（液体供給手段）
液体供給手段は、ノズルプレート２６の内部であってノズル２１の根元となる位置に設けられると共にノズル内流路２２に連通する液室２４と、図示しない外部の液体タンクから液室２４に液体を導く液体供給路２７と、液室２４への液体の供給圧力を付与する図示しない供給ポンプとを備えている。
上記供給ポンプは、ノズル２１の先端部まで液体を供給し、当該先端部からこぼれ出さない範囲の供給圧力を維持して液体の供給を行う（図２（Ａ）参照）。
【００４０】
（吐出電圧印加手段）
吐出電圧印加手段２５は、ノズルプレート２６の内部であって液室２４とノズル内流路２２との境界位置に設けられた吐出電圧印加用の吐出電極２８と、この吐出電極２８に常時直流のバイアス電圧を印加するバイアス電源３０と、吐出電極２８にバイアス電圧に重畳して吐出に要する電位とするパルス電圧を印加する吐出電圧電源２９と、を備えている。
【００４１】
上記吐出電極２８は、液室２４内部において液体に直接接触し、液体を帯電させると共に吐出電圧を印加する。
バイアス電源３０によるバイアス電圧は、液体の吐出が行われない範囲で常時電圧印加を行うことにより、吐出時に印加すべき電圧の幅を予め低減し、これによる吐出時の反応性の向上を図っている。
【００４２】
吐出電圧電源２９は、液体の吐出を行う際にのみパルス電圧をバイアス電圧に重畳させて印加する。このときの重畳電圧Ｖは次式の条件を満たすようにパルス電圧の値が設定されている。
【数３】

但し、γ：液体の表面張力、ε₀：真空の誘電率、ｒ：ノズル半径、ｋ：ノズル形状に依存する比例定数（1.5<k<8.5）とする。
一例を挙げると、バイアス電圧はDC300[V]で印加され、パルス電圧は100[V]で印される。従って、吐出の際の重畳電圧は400[V]となる。
【００４３】
（ノズルプレート）
ノズルプレート２６は、図１において最も上層に位置する上面層２６ａと、その下に位置する液体の供給路を形成する流路層２６ｂと、この流路層２６ｂのさらに下に形成される下面層２６ｃとを備え、流路層２６ｂと下面層２６ｃとの間には前述した吐出電極２８が介挿されている。
【００４４】
上記上面層２６ａは、シリコン基板或いは絶縁性の高い樹脂又はセラミックにより形成され、その下に溶解可能な樹脂層を形成すると共に供給路２７及び液室２４のパターンに従う部分のみを残して除去し、除去された部分に絶縁樹脂層を形成する。この絶縁樹脂層が流路層２６ｂとなる。そして、この絶縁樹脂層の下面に導電素材（例えばNiP）のメッキにより吐出電極２８を形成し、さらにその下から絶縁性のレジスト樹脂層を形成する。このレジスト樹脂層が下面層２６ｃとなるので、この樹脂層はノズル２１の高さを考慮した厚みで形成される。そして、この絶縁性のレジスト樹脂層を電子ビーム法やフェムト秒レーザにより露光し、ノズル形状を形成する。ノズル内流路２２もレーザ加工により形成される。そして、供給路２７及び液室２４のパターンに従う溶解可能な樹脂層を除去し、これら供給路２７及び液室２４が開通してノズルプレートが完成する。
【００４５】
（対向電極）
対向電極２３は、ノズル２１に垂直な対向面を備えており、かかる対向面に沿うように基材９９の支持を行う。ノズル２１の先端部から対向電極２３の対向面までの距離は、一例としては100[μm]に設定される。
また、この対向電極２３は接地されているため、常時接地電位を維持している。従って、パルス電圧の印加時には、ノズル２１の先端部と対向面との間に生じる電界による静電力により吐出された液滴が対向電極２３側に誘導される。
【００４６】
なお、液体吐出装置２０は、ノズル２１の超微細化による当該ノズル２１の先端部での電界集中により電界強度を高めることで液滴の吐出を行うことから、対向電極２３による誘導がなくとも液滴の吐出を行うことは可能ではあるが、ノズル２１と対向電極２３との間での静電力による誘導が行われた方が望ましい。また、帯電した液滴の電荷を対向電極２３の接地により逃がすことも可能である。
【００４７】
（光照射手段）
光照射手段は、上記の通り、基材９９に着弾した液滴に光を照射するものであって、図示しないが、基材９９に着弾した液滴に光を照射できる位置（例えば、ノズル２１近傍）に設けられている。ここでいう「光」とは、広義の光であって、紫外線，電子線，Ｘ線，可視光線、赤外線等を含むものである。しかし、光源のコスト等を考慮すると紫外線を照射する光照射手段を適用することが好ましい。
なお、紫外線を照射する「光源」としては、低圧水銀ランプ、紫外線レーザー、キセノンフラッシュランプ、捕虫灯、ブラックライト、殺菌灯、冷陰極管、ＬＥＤ（Light Emitting Diode）、ＬＥＤ高圧水銀ランプ、メタルハライドランプ、エキシマーランプ、無電極紫外線ランプ等が適用可能であり、これら以外の光源を適用してもよい。
【００４８】
（ＸＹステージ）
ＸＹステージ３１は、Ｘ軸方向（左右方向）に移動可能なＸステージとＹ軸方向（前後方向）に移動可能なＹステージとを積み重ねた載物台である。ＸＹステージ３１の上には、真空吸引機能を有するホルダ（図示略）が装着されている。このＸＹステージ３１は、ホルダにより基材９９を真空吸引して固定し、更に各ステージにより基材９９をＸ軸方向及び／又はＹ軸軸方向に微小移動させる。
【００４９】
（液体）
本実施形態に用いられる液体は、液体供給手段から供給路２７を通り液室２４に供給され、その後、ノズル２１の先端部から超微細な液滴として対向電極２３側に吐出されて基材９９に着弾する。この液体は、具体的に、光の被照射により硬化する光硬化型樹脂であり、特に照射される光の照度によって半硬化状態と完全硬化状態とに移行自在な性質を備えている。
【００５０】
なお、ここでいう「光硬化型樹脂」とは、紫外線硬化型接着剤、フォトレジスト剤をいう。紫外線硬化型接着剤に含まれる紫外線硬化型モノマー、オリゴマーの成分は、エポキシアクリルレート、ウレタンアクリルレート、ポリブタジエンアクリルレート、ポリエステルアクリルレート等が適用可能であり、その反応形態は、ラジカル重合である。また、フォトレジスト剤にはポジ型及びネガ型があり、一般的な化学構造及び化学反応を化学式１及び２に示す。
【００５１】
【化１】
ネガ型フォトレジスト

【化２】
ポジ型フォトレジスト

【００５２】
（基材）
基材９９としては、シリコン、二酸化ケイ素等の半導体材料、ガリウム砒素、アルミガリウム砒素、インジウムガリウム砒素等の量子素子材料、アルミ、ステンレス等の構造材料、タングステン、チタン、タングステンカーバイド、ボロンナイトライド、四窒化チタン、セラミックス等の難削材料又は高硬度材料、プラスチック、ポリイミド、ガラス、石英ガラス、光学ガラス、ルビー、サファイア、フッ化マグネシウム、ジンクセレン、ジンクテルル等の光学材料等が適用可能である。
【００５３】
（液体吐出装置による微小液滴の吐出動作）
図１及び図２により液体吐出装置２０の動作説明を行う。
液体供給手段の供給ポンプによりノズル内流路２２には液体が供給された状態にあり、かかる状態でバイアス電源３０により吐出電極２８を介してバイアス電圧が液体に印加されている。かかる状態で、液体は帯電すると共に、ノズル２１の先端部において液体による凹状に窪んだメニスカスが形成される（図２（Ａ）参照）。
そして、吐出電圧電源２９によりパルス電圧が印加されると、ノズル２１の先端部では集中された電界の電界強度による静電力により液体がノズル２１の先端側に誘導され、外部に突出した凸状メニスカスが形成されると共に、かかる凸状メニスカスの頂点に電界が集中し、ついには液体の表面張力に抗して液体が対向電極２３側に吐出される（図２（Ｂ）参照）。
【００５４】
（液体吐出装置を用いる金型の製造方法）
図１〜図４（特に図３及び図４）により液体吐出装置２０を用いる金型の製造方法の説明を行う。図３及び図４は、液体吐出装置を用いる金型の製造方法を説明するための図面であり、特に図３は、基材９９上に所定のドットパターンを形成する工程を説明するための図面であり、図４は、基材９９上に形成されたドットパターンから金型を製造する工程を説明するための図面である。
【００５５】
まず、所定の基材９９をＸＹステージ３１のホルダにセットし、ホルダにより基材９９の裏面を真空吸引して基材９９をＸＹステージ３１に固定する。
その後、複数のノズル２１のうちの所定のノズル２１から基材９９に液滴を吐出し、基材９９に直径約０．１〜約３０μｍのドット状の液滴からなる所定のドットを形成する（図３（ａ）参照）。その後、基材９９に着弾した各液滴に対して光照射手段から光を照射し、各液滴を半硬化させる（図３（ｂ）参照）。その後、ＸＹステージ３１のＸステージ及びＹステージの少なくとも一方のステージを移動させることで、基材９９の位置決め及び位置調整を行う。その後、基材９９上において半硬化した状態の各液滴の隙間に、更に所定のノズル２１から基材９９に液滴を吐出して更なるドットを基材９９に形成し（図３（ｃ）参照）、これら各液滴に対して光照射手段から光を照射して各液滴を半硬化させる（図３（ｄ）参照）。
【００５６】
その後、このような基材９９の移動、ドットの形成及び光の照射の各動作を繰り返すことで、基材９９の所定領域に所望のドットパターンを形成し（図３（ｅ）参照）、光の照射を受けていない各液滴に対して光照射手段から光を照射して全ての液滴を半硬化させる（図３（ｆ）参照）。その後、基材９９上において半硬化した状態の全ての液滴に対し更に光照射手段から光を照射して、これら全ての液滴を完全に硬化させる（図３（ｇ）参照）。
【００５７】
なお、各液滴を半硬化させるために一次的に照射する光としては、長波長の光を適用し、各液滴を完全に硬化させるために二次的に照射する光としては、一次的に照射される光よりも短波長の光を適用するのが好ましい。この場合において、一次的な長波長の光の照射では、各液滴の表層を硬化させて基材９９上での各液滴の広がりを抑えられ、二次的な短波長の光の照射では、照射線が届き難い基材９９近傍の各液滴の内部を硬化させて各液滴と基材９９との密着性を高めることができる。
【００５８】
その後、基材９９の各面のうちの所定のドットパターンが形成された面に対して、スパッタリングにより金（Ａｕ）を成膜し、母型４０が完成する（図４（ａ）参照）。その後、母型４０に対して電鋳加工処理を行う。詳しくは、スルファミン酸ニッケル等の電解液中に母型４０を入れ、母型４０を陰極とすることで母型４０にニッケル（Ｎｉ）を電気化学的に析出させる（図４（ｂ）参照）。その後、ニッケルが所定の肉厚になった時点でニッケルの析出部分を母型４０から剥離し、金の成膜面を有するとともに母型４０と鏡像関係を有する金型５０が製造される（図４（ｃ）参照）。
【００５９】
（まとめ）
以上のような液体吐出装置２０では、微小径のノズル２１により液滴の吐出を行うので、ノズル内流路２２内で帯電した状態の液滴により電界が集中され、電界強度が高められる。このため、電界の集中化が行われない構造のノズルでは吐出に要する電圧が高くなり過ぎて事実上吐出不可能とされていた微細径でのノズルによる液体の吐出を低電圧で行うことを可能としている。
【００６０】
そして、微細径であるがために、ノズルコンダクタンスの低さによりその単位時間あたりの吐出流量を低減する制御を容易に行うことができると共に、パルス幅を狭めることなく十分に小さな液滴（直径約０．１〜約３０μｍのドット状の液滴）による液体の吐出を実現している。
【００６１】
さらに、吐出される各液滴は帯電されているので、微小の液滴であっても蒸気圧が低減され、蒸発を抑制することから液滴の質量の損失を低減し、飛翔の安定化を図り、液滴の着弾精度の低下を防止している。
【００６２】
そして、液体吐出装置２０を用いる金型５０の製造方法では、母型４０を形成する工程において、従来のようにエネルギービームを基材９９に照射しながら基材９９に凹凸パターンを形成するのではなく、基材９９に対して直接的に液体を着弾させて凹凸パターンを形成している。従って、従来よりも安価な装置（つまり液体吐出装置２０）を用いてこの母型４０の形成工程にかかる加工時間を短縮することができ、ひいては安価な装置で金型５０の製造にかかる加工時間を短縮できる。
【００６３】
なお、この金型５０は、導光板、光スイッチ、光トランシーバ、光合分波器、光アッテネータ、光カプラ等の光学素子を製造する際に好適に用いることができるものである。
【００６４】
また、ノズル２１にエレクトロウェッティング効果を得るために、ノズル２１の外周に電極を設けるか、また或いは、ノズル内流路２２の内面に電極を設け、その上から絶縁膜で被覆してもよい。そして、この電極に電圧を印加することで、吐出電極２８により電圧が印加されている液体に対して、エレクトロウェッティング効果によりノズル内流路２２の内面のぬれ性を高めることができ、ノズル内流路２２への液体の供給を円滑に行うことができ、良好に吐出を行うと共に、吐出の応答性の向上を図ることが可能となる。
【００６５】
また、吐出電圧印加手段２５ではバイアス電圧を常時印加すると共にパルス電圧をトリガーとして液滴の吐出を行っているが、吐出に要する振幅で常時交流又は連続する矩形波を印加すると共にその周波数の高低を切り替えることで吐出を行う構成としてもよい。液滴の吐出を行うためには液体の帯電が必須であり、液体の帯電する速度を上回る周波数で吐出電圧を印加していても吐出が行われず、液体の帯電が十分に図れる周波数に替えると吐出が行われる。従って、吐出を行わないときには吐出可能な周波数より大きな周波数で吐出電圧を印加し、吐出を行う場合にのみ吐出可能な周波数帯域まで周波数を低減させる制御を行うことで、液体の吐出を制御することが可能となる。かかる場合、液体に印加される電位自体に変化はないので、より時間応答性を向上させると共に、これにより液滴の着弾精度を向上させることが可能となる。
【００６６】
さらに、上記実施形態では、ノズル２１から液体を液滴として吐出し複数のドットからなる所定のドットパターンを基材９９上に形成する例を示したが、液滴によるドットに加えて又は液滴によるドットに代えて、ノズル２１から液体を連続的に吐出するとともに基材９９をＸＹステージ３１の移動により移動させて、直線状、屈曲状、湾曲状若しくはこれらを組み合わせた形状の幅約０．１〜約３０μｍの突条パターンを基材９９上に形成してもよい。この場合に、液滴によるドット同士、連続的に繋がる液体による突条同士又は液滴によるドットと連続的に繋がる液体による突条とを、互いに積層させるようにして所望の高さを有する凹凸パターンを基材９９上に形成してもよい。
【００６７】
詳しくは、例えば、図５（ａ）、（ｂ）に示すように、略同様の大きさ（滴量）を有する液滴によるドットを順次積層して、略三角錐状の凹凸パターンを基材９９上に形成してもよい。また、図５（ｃ）、（ｄ）に示すように、略同様の大きさ（滴量）を有する液滴によるドットを順次積層して、略円柱状の凹凸パターンを基材９９上に形成してもよい。また、図５（ｅ）、（ｆ）に示すように、互いに異なる大きさ（滴量）を有する液滴によるドットを順次積層して、略円柱状の凹凸パターンを基材９９上に形成してもよい。また、図５（ｇ）に示すように、略同様の大きさ（滴量）を有する液滴によるドットを順次積層して、略三角柱状のドットの集合体を横に寝かせたしたような凹凸パターンを基材９９上に形成してもよい。また、図５（ｈ）に示すように、連続的に繋がる液体による突条を順次積層させるようにして、略三角柱状の突条の集合体を横に寝かせたような凹凸パターンを基材９９上に形成してもよい。また、図５（ｉ）に示すように、連続的に繋がる液体による湾曲した突条を基材９９上に積層させるようにして、所望の凹凸パターンを形成してもよい。勿論、液滴によるドット同士、連続的に繋がる液体による突条同士又は液滴によるドットと連続的に繋がる液体による突条とを互いに組み合わせて、図５に示す以外の種々の凹凸パターンを基材９９上に形成してもよい。
【００６８】
また、上記の通りに基材９９上に液滴を積層する場合に、基材９９上に着弾した液滴に光照射手段より光を照射せずに次の新しい液滴を積層させてもよいし、基材９９上に着弾した液滴に光照射手段より光を照射して液滴を半硬化させてから次の新しい液滴を積層させてもよいし、基材９９上に着弾した液滴に光照射手段より光を照射して液滴を完全に硬化させてから次の新しい液滴を積層させてもよい。
【００６９】
さらに、上記実施形態では、ノズル２１から吐出される液体として光硬化型樹脂を適用した例を示したが、ノズル２１から吐出される液体として、加熱により硬化する熱硬化型樹脂を適用してもよい。この場合、光照射手段に代えて、基材９９に着弾した各液滴を加熱するための加熱手段（例えば、加熱ヒータ）を、液体吐出装置２０に設ける必要がある。また、光照射手段及び加熱手段の両手段を液体吐出装置２０に設けるとともに、光硬化型樹脂及び熱硬化型樹脂の各液体樹脂を別々にノズル２１から吐出し、互いに異なる液体樹脂により基材９９上に所定の凹凸パターンを形成してもよい。
【００７０】
さらに、上記した実施形態では、液体吐出部と基材９９との間に電位を印加し静電力によりノズル２１から液滴を引き出して基材９９に付着させる電解制御方式の液体吐出装置２０を示したが、これに代えて、超音波振動により、常時、液体を液滴状にノズルから加圧噴射させ、噴射した液滴を帯電させ、電場により偏向させることで連続的に記録する連続方式の液体吐出装置を適用してもよい。また、さらには、電解制御方式の液体吐出装置２０に代えて、ピエゾ素子の変形を利用し液体を適時に吐出させる電気機械変換方式、熱による気泡の発生を利用し液体を適時に吐出させる電気熱変換方式等を含むドロップオンデマンド方式の液体吐出装置を適用してもよい。
【００７１】
（印加電圧低下および微少液滴量の安定吐出実現の方策）
本発明では、静電吸引型インクジェット方式において果たすノズルの役割を再考察し、
【数４】

即ち、
【数５】

或いは
【数６】

という従来吐出不可能として試みられていなかった領域において、マクスウェル力などを利用することで、微細液滴を形成することができる。
このような駆動電圧低下および微少量吐出実現の方策のための吐出条件等を近似的に表す式を導出したので以下に述べる。
以下の説明は、上記各本発明の実施形態で説明した液体吐出装置に適用可能である。
いま、半径ｒのノズルに導電性溶液を注入し、基材としての無限平板導体からｈの高さに垂直に位置させたと仮定する。この様子を図６に示す。このとき、ノズル先端部に誘起される電荷は、ノズル先端の半球部に集中すると仮定し、以下の式で近似的に表される。
【数７】

ここで、Ｑ：ノズル先端部に誘起される電荷、ε₀：真空の誘電率、ε：基板の誘電率、h：ノズル−基板間距離、ｒ：ノズル内径の半径、Ｖ：ノズルに印加する電圧である。α：ノズル形状などに依存する比例定数で、1〜1.5程度の値を取り、特にr<<hのときほぼ1程度となる。
【００７２】
また、基材としての基板が導体基板の場合、基板内の対称位置に反対の符号を持つ鏡像電荷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反対符号の映像電荷Ｑ’が誘導される。
ところで、ノズル先端部に於ける電界強度E_loc.は、先端部の曲率半径をRと仮定すると、
【数８】

で与えられる。ここでｋ：比例定数で、ノズル形状などにより異なるが、1.5〜8.5程度の値をとり、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) 198-210）。今簡単のため、ｒ＝Ｒとする。これは、ノズル先端部に表面張力で導電性溶液がノズル径ｒと同じ半径を持つ半球形状に盛り上がっている状態に相当する。
ノズル先端の液体に働く圧力のバランスを考える。まず、静電的な圧力は、ノズル先端部の液面積をSとすると、
【数９】

（８）、（９）、（１０）式よりα＝１とおいて、
【数１０】

と表される。
【００７３】
一方、ノズル先端部に於ける液体の表面張力をPsとすると、
【数１１】

ここで、γ：表面張力、である。
静電的な力により流体の吐出が起こる条件は、静電的な力が表面張力を上回る条件なので、
【数１２】

となる。十分に小さいノズル径ｒをもちいることで、静電的な圧力が、表面張力を上回らせる事が可能である。
この関係式より、Ｖとｒの関係を求めると、
【数１３】

が吐出の最低電圧を与える。すなわち、式（７）および式（１４）より、
【数１４】

が、本発明の動作電圧となる。
【００７４】
ある半径ｒのノズルに対し、吐出限界電圧Ｖｃの依存性を前述した図７に示す。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、吐出開始電圧は、ノズル径の減少に伴い低下する事が明らかになった。つまり、ノズル径が２０μｍ未満であることにより、電界を集中させることができ、微細液滴を安定に吐出でき、かつ吐出開始電圧を低減できる。図７より、ノズル径が８μｍ以下であることにより、さらに電界を集中させることができ、微細液滴をさらに安定に吐出でき、かつさらに吐出開始電圧を低減できることがわかる。また、さらにノズル径は、４μｍ以下であることが好ましい。
従来の電界に対する考え方、すなわちノズルに印加する電圧と対向電極間の距離によって定義される電界のみを考慮した場合では、微小ノズルになるに従い、吐出に必要な電圧は増加する。一方、局所電界強度に注目すれば、微細ノズル化により吐出電圧の低下が可能となる。
【００７５】
静電吸引による吐出は、ノズル端部における流体の帯電が基本である。帯電の速度は誘電緩和によって決まる時定数程度と考えられる。
【数１５】

ここで、ε：流体の比誘電率、σ：流体の導電率である。流体の比誘電率を10、導電率を10^-6 S/m を仮定すると、τ＝1.854×10^-5secとなる。あるいは、臨界周波数をfcとすると、
【数１６】

となる。このfcよりも早い周波数の電界の変化に対しては、応答できず吐出は不可能になると考えられる。上記の例について見積もると、周波数としては10 kHz程度となる。このとき、ノズル半径2μｍ、電圧500V弱の場合、Gは10^-13m³/sと見積もることができるが、上記の例の液体の場合、10kHzでの吐出が可能なので、1周期での最小吐出量は10fl（フェムトリットル、1fl：10^-15 l）程度を達成できる。
【００７６】
なお、各上記本実施の形態においては、図６に示したようにノズル先端部に於ける電界の集中効果と、対向基板に誘起される鏡像力の作用を特徴とする。このため、先行技術のように基板または基板支持体を導電性にしたり、これら基板または基板支持体に電圧を印加する必要はない。すなわち、基板として絶縁性のガラス基板、ポリイミドなどのプラスチック基板、セラミックス基板、半導体基板などを用いることが可能である。
また、上記各実施形態において電極への印加電圧はプラス、マイナスのどちらでも良い。
さらに、ノズルと基材との距離は、500[μm]以下に保つことにより、溶液の吐出を容易にすることができる。また、図示しないが、ノズル位置検出によるフィードバック制御を行い、ノズルを基材に対し一定に保つようにする。
また、基材を、導電性または絶縁性の基材ホルダーに裁置して保持するようにしても良い。
【００７７】
図８は、本発明の他の基本例の一例としての液体吐出装置の側面断面図を示したものである。ノズル１の側面部には電極１５が設けられており、ノズル内溶液３との間に制御された電圧が引加される。この電極１５の目的は、Electrowetting 効果を制御するための電極である。十分な電場がノズルを構成する絶縁体にかかる場合この電極がなくともElectrowetting効果は起こると期待される。しかし、本基本例では、より積極的にこの電極を用いて制御することで、吐出制御の役割も果たすようにしたものである。ノズル１を絶縁体で構成し、その厚さが1μm、ノズル内径が2μm、印加電圧が300Ｖの場合、約30気圧のElectrowetting効果になる。この圧力は、吐出のためには、不十分であるが溶液のノズル先端部への供給の点からは意味があり、この制御電極により吐出の制御が可能と考えられる。
【００７８】
前述した図８は、本発明における吐出開始電圧のノズル径依存性を示したものである。液体吐出装置として、図１に示すものを用いた。微細ノズルになるに従い吐出開始電圧が低下し、従来より低電圧で吐出可能なことが明らかになった。
【００７９】
上記各実施形態において、溶液吐出の条件は、ノズル基板間距離(L)、印加電圧の振幅（V）、印加電圧振動数（f）のそれぞれの関数になり、それぞれにある一定の条件を満たすことが吐出条件として必要になる。逆にどれか一つの条件を満たさない場合他のパラメーターを変更する必要がある。
【００８０】
この様子を図９を用いて説明する。
まず吐出のためには、それ以上の電界でないと吐出しないというある一定の臨界電界Ecが存在する。この臨界電界は、ノズル径、溶液の表面張力、粘性などによって変わってくる値で、Ec以下での吐出は困難である。臨界電界Ec以上すなわち吐出可能電界強度において、ノズル基板間距離(L)と印加電圧の振幅(V)の間には、おおむね比例の関係が生じ、ノズル間距離を縮めた場合、臨界印加電圧Ｖを小さくする事が出来る。
逆に、ノズル基板間距離Ｌを極端に離し、印加電圧Ｖを大きくした場合、仮に同じ電界強度を保ったとしても、コロナ放電による作用などによって、流体液滴の破裂すなわちバーストが生じてしまう。そのため良好な吐出特性を得るためには、ノズル基板間距離は100μｍ程度以下に抑えることが吐出特性並びに、着弾精度の両面から望ましい。
【００８１】
【発明の効果】
請求項１に記載の発明によれば、母型形成工程において、従来のようにエネルギービームを基材に照射しながら基材に凹凸パターンを形成するのではなく、基材に対して直接的に液体を着弾させて凹凸パターンを形成している。従って、例えば、インクジェット方式による装置を用いて基材に直接的に液体を着弾させて凹凸パターンを形成すれば、従来よりも安価な装置を用いてこの母型形成工程にかかる加工時間を短縮することができ、ひいては安価な装置を用いて金型の製造にかかる加工時間を短縮できる。
【図面の簡単な説明】
【図１】液体吐出装置の断面図である。
【図２】液体の吐出動作と液体に印加される電圧との関係を示す説明図であって、図２（Ａ）は吐出を行わない状態であり、図２（Ｂ）は吐出状態を示す。
【図３】基材上に所定のドットパターンを形成する工程を説明するための図面である。
【図４】基材上に形成されたドットパターンから金型を製造する工程を説明するための図面である。
【図５】基材上に形成された種々の凹凸パターンを示す図面であって、図５（ａ）は複数のドットを積み重ねた状態を側面から見た側面図であり、図５（ｂ）は図５（ａ）の平面図であり、図５（ｃ）は複数のドットを積み重ねた状態を側面から見た側面図であり、図５（ｄ）は図５（ｃ）の平面図であり、図５（ｅ）は互いに大きさの異なる複数のドットを積み重ねた状態を側面から見た側面図であり、図５（ｆ）は図５（ｅ）の平面図であり、図５（ｇ）は複数のドットを積み重ねた状態を示す斜視図であり、図５（ｈ）は突条を積み重ねた状態を示す斜視図であり、図５（ｉ）は湾曲状の突条を示す斜視図である。
【図６】ノズルの電界強度の計算を説明するために示したものである。
【図７】ノズルのノズル径とメニスカス部で吐出する液滴が飛翔を開始する吐出開始電圧、該初期吐出液滴のレイリー限界での電圧値及び吐出開始電圧とレイリー限界電圧値の比との関係を示す線図である。
【図８】液体吐出装置の側面断面図を示したものである。
【図９】液体吐出装置における距離−電圧の関係による吐出条件を説明した図である。
【符号の説明】
２０ 液体吐出装置
２１ ノズル
２２ 流路
２３ 対向電極
２４ 液室
２５ 吐出電圧印加手段
２６ ノズルプレート
２７ 液体供給路
２８ 吐出電極
２９ 吐出電圧電源
３０ バイアス電源
３１ ＸＹステージ
４０ 母型
５０ 金型
９９ 基材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a mold having a fine concavo-convex pattern and a liquid discharge apparatus used in this method.
[0002]
[Prior art]
In recent years, liquid crystal display devices are widely used as display means for displaying images, moving pictures, and the like from small display screens such as cellular phones to large display screens such as television monitors and personal computer monitors. In a liquid crystal display device, since the liquid crystal itself does not emit light, in general, a backlight such as a fluorescent tube and a light guide plate molded from acrylic resin are installed on the back of the liquid crystal display device to guide light from the backlight. The liquid crystal display device is illuminated from the back side by being incident on the light plate and causing the entire light emitting surface of the light guide plate to emit light.
[0003]
By the way, in the backlight type liquid crystal display device, in order to efficiently emit the light of the backlight from the light emitting surface, it is common to form a fine uneven pattern on the back side of the light guide plate. In addition to the optical plate, the substrate that propagates light over the entire optical elements such as optical switches, optical transceivers, optical multiplexers / demultiplexers, optical attenuators, optical couplers, etc. has a fine uneven pattern for efficiently transmitting light. Is formed.
[0004]
In order to manufacture a substrate having a fine concavo-convex pattern, for example, the workpiece is first irradiated with an energy beam such as an ion beam or a laser through a mask having a predetermined transmission hole. A fine concave / convex pattern is directly formed at a position, and then, a mold having a mirror image relationship with the workpiece is produced by electroforming, etc. By utilizing this, it is possible to mass-produce a substrate on which a minute uneven pattern similar to that of a mother die is indirectly formed (for example, see Patent Document 1).
[0005]
Moreover, when forming a fine uneven | corrugated pattern directly in a to-be-processed object, it is also considered to form a concavo-convex pattern by discharging a droplet to a to-be-processed object by the conventional inkjet system. In this ink jet recording method, a piezoelectric method in which ink droplets are ejected by deforming an ink flow path by vibration of a piezoelectric element, a heating element is provided in the ink flow path, and the heating element is heated to generate bubbles. There is a thermal method that discharges ink droplets according to pressure changes in the ink flow path due to air bubbles, and an electrostatic suction method that charges ink in the ink flow paths and discharges ink droplets by the electrostatic suction force of the ink. Are known.
[0006]
[Patent Document 1]
JP-A-8-264511
[Patent Document 2]
JP-A-8-238774
[Patent Document 3]
JP 2000-127410 A
[0007]
[Problems to be solved by the invention]
However, in the mold manufacturing method as described above, in the step of forming the mother die, an uneven pattern must be formed on the workpiece while irradiating the workpiece with an energy beam. Long time. In addition, a microfabrication apparatus used in such a mold manufacturing method (specifically, used in a matrix forming process) requires an expensive member such as an energy beam source, and thus becomes a very expensive apparatus.
[0008]
In addition, when the inkjet method is applied, there are the following problems.
(1) Stability of microdroplet formation
Since the nozzle diameter is large, the shape of the droplet discharged from the nozzle is not stable.
(2) Insufficient landing accuracy of micro droplets
The kinetic energy imparted to the droplet ejected from the nozzle decreases in proportion to the third power of the droplet radius. For this reason, micro droplets cannot secure sufficient kinetic energy to withstand air resistance, and are not expected to land accurately due to disturbance due to air convection. Furthermore, as the droplet becomes finer, the effect of surface tension increases, so the vapor pressure of the droplet increases and the amount of evaporation increases. For this reason, fine droplets cause a significant loss of mass during flight, and it is difficult to maintain the shape of the droplets upon landing.
As described above, miniaturization and high accuracy of droplets are conflicting issues, and it has been difficult to realize both simultaneously.
[0009]
(3) High applied voltage
According to the principle of the conventional electrostatic attraction method, the meniscus bulge is generated by concentrating charges at the center of the meniscus. The radius of curvature of the raised tailor cone tip is determined by the amount of charge concentration, and when the electrostatic force due to the concentrated charge amount and the electric field strength exceeds the surface tension of the meniscus at that time, droplet separation starts.
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 at the meniscus portion.
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, the surface tension of the ink is considered to be constant, and a method of reducing the droplet size by increasing the electric field strength has been adopted.
Therefore, in the ink jet devices disclosed in Patent Documents 2 and 3 described above, as a discharge principle, both form a strong electric field strength field in a meniscus area that is much wider than the projected area of the discharged droplet. Since electric charges are concentrated at the center of the meniscus and ejection is performed by an electrostatic force composed of the concentrated electric charges and the electric field strength formed, it is necessary to apply a very high voltage close to 2000 [V], and drive control is possible. In addition to being difficult, there was also a problem in terms of safety in operating the ink jet apparatus.
(4) Discharge response
In the ink jet devices disclosed in Patent Documents 2 and 3 described above, as a discharge principle, both of the meniscus are formed by forming a field having a strong electric field strength in a meniscus region having an area far larger than the projected area of the discharged droplet. Charge is concentrated at the center, and discharge is performed by electrostatic force consisting of the concentrated charge and the formed electric field strength, so the charge movement time for moving the charge to the center of the meniscus part affects the discharge response. This has been a problem in improving the printing speed.
[0010]
The subject of this invention is a manufacturing method of the metal mold | die for manufacturing various elements (including optical elements, such as a light-guide plate) which have fine unevenness | corrugation, Comprising: It manufactures a metal mold | die using an inexpensive apparatus. Provided is a mold manufacturing method capable of reducing processing time. Another object of the present invention is to provide a liquid discharge apparatus used in this mold manufacturing method (particularly, used in a mother mold forming process).
[0011]
[Means for Solving the Problems]
The invention described in claim 1
In the manufacturing method of a mold having a fine uneven pattern,
A nozzle having a receiving surface for receiving the discharge of the charged liquid and having a receiving end opposed to the base, and a nozzle having a nozzle diameter for discharging the liquid from the leading end of greater than 0.2 μm and less than 4 μm, and the nozzle A liquid supply device that includes a liquid supply unit that supplies the liquid therein, and a discharge voltage application unit that applies a discharge voltage to the liquid in the nozzle. The Above A desired uneven pattern is formed by landing on a substrate and forming dots having a diameter of about 0.1 to about 30 μm, protrusions having a width of about 0.1 to about 30 μm, or a combination of these on the substrate. A matrix forming process for forming the matrix;
A mold manufacturing process for manufacturing a mold having a mirror image relationship with the mother mold by electrochemically depositing a predetermined metal on the mother mold by an electroforming process after the mother mold forming step;
It is characterized by providing.
[0012]
In the first aspect of the present invention, in the matrix forming step, the liquid is directly applied to the base material instead of forming an uneven pattern on the base material while irradiating the base material with an energy beam as in the prior art. An uneven pattern is formed by landing. Therefore, for example, if a concave / convex pattern is formed by directly applying a liquid to a substrate using an ink jet type apparatus, the processing time required for this matrix forming process can be shortened using an inexpensive apparatus. As a result, the processing time required to manufacture the mold can be shortened by using an inexpensive apparatus.
[0013]
Here, as in the invention described in claim 2 or 3, the liquid may be a photocurable resin that is cured by irradiation with light, or may be a thermosetting resin that is cured by heating. Good.
[0015]
Claim 1 In the configuration described in (1), the nozzle or the substrate is arranged so that the receiving surface of the liquid droplet faces the tip of the nozzle. The placement operation for realizing the mutual positional relationship may be performed by either movement of the nozzle or movement of the base material.
Then, the liquid is supplied into the nozzle by the liquid supply means. The liquid in the nozzle is required to be charged for discharging. The charging of the liquid may be performed by applying a voltage within a range where the liquid is not discharged by a discharge voltage applying unit that applies a discharge voltage, or an electrode dedicated for charging may be provided.
[0016]
Claim 1 The configuration described in (1) is characterized in that the electric field strength is increased by concentrating the electric field at the tip of the nozzle by making the nozzle have an ultrafine diameter that is not conventional. The diameter reduction of the nozzle will be described in detail later. In such a case, it is possible to discharge liquid droplets without a counter electrode facing the tip of the nozzle. For example, when a substrate is arranged facing the nozzle tip in the absence of a counter electrode, and the substrate is a conductor, the nozzle tip is symmetrical with respect to the receiving surface of the substrate. When the substrate is an insulator, a reverse polarity image charge is induced at a symmetrical position determined by the dielectric constant of the substrate with respect to the receiving surface of the substrate. . Then, the droplets fly by electrostatic force between the charge induced at the nozzle tip and the mirror image charge or the image charge.
[0017]
However, although the configuration of the present invention can eliminate the need for the counter electrode, the counter electrode may be used in combination. By using the counter electrode together, it is possible to use the electrostatic force due to the electric field between the nozzle and the counter electrode for the induction of the flying electrode, and if the counter electrode is grounded, the charge of the charged droplet can be reduced. Since it can escape through the counter electrode and the effect of reducing the accumulation of electric charge can be obtained, it can be said that the combined use is desirable.
[0018]
Claim 1 As the cited invention that cites the invention described in Claim 1 And having the same configuration as the invention described in the above, the discharge voltage is constant, and the operating frequency is
f = σ / 2πε
A configuration may be adopted in which frequency control means is provided that performs operation control for switching between discharge and stop by switching between a value larger than and smaller than the boundary value f represented by Where σ is the electrical conductivity of the liquid and ε is the relative dielectric constant of the liquid.
[0019]
In the above configuration, Claim 1 The operation similar to that of the invention described in the above is performed, and a discharge voltage having a potential at which droplets can be discharged is continuously applied to the liquid in the nozzle. Take control. That is, the boundary value f = σ / 2πε is a critical frequency determined according to the charging speed based on the conductivity and relative permittivity of the liquid, and when the discharge voltage is applied at a frequency higher than this, for example, the potential Even if is within the appropriate range, no droplet is ejected. Accordingly, the discharge voltage having a dischargeable potential is continuously applied to the liquid in the nozzle, and when the discharge is not performed, the frequency is maintained in a state higher than the boundary value f. By switching to a state smaller than the boundary value f, droplets can be discharged.
[0020]
In addition, when controlling the on / off state of droplet discharge by switching the frequency of the discharge voltage, when switching on / off the droplet discharge by turning on / off the application of the discharge voltage, or when switching on / off the droplet discharge by changing the potential of the discharge voltage. Is also excellent in time responsiveness, and it is possible to improve the responsiveness during re-ejection.
[0021]
Claim 1 As the cited invention that cites the invention described in Claim 1 And at least the inner surface of the flow path of the nozzle is insulated, and the flow supply electrode is provided outside the insulated portion around the liquid in the flow path. , May be adopted.
[0022]
In the above configuration, “providing the flow supply electrode outside the insulated portion” means that the entire nozzle is formed of an insulating material even when the flow supply electrode is provided inside the nozzle via an insulating film. This also includes the case where a fluid supply electrode is provided outside the nozzle.
[0023]
Generally, when a voltage is applied to each electrode by providing a potential difference between the electrode that insulates the inner surface of the pipe line and an electrode that is provided via the insulating portion and an electrode that applies a voltage to the liquid inside the pipe line Thus, the effect of the so-called electrowetting phenomenon that the wettability of the liquid with respect to the inner surface of the insulated conduit is improved can be obtained.
In the configuration of the above invention, the electrowetting is achieved by providing a potential difference between the applied voltage by the flow supply electrode provided outside the portion where the inner surface of the nozzle is insulated and the applied voltage by the discharge voltage applying means. The wettability in the nozzle can be improved due to the effect, and the liquid can be smoothly supplied into the nozzle by the electrowetting effect.
[0027]
In the present invention, “nozzle diameter” refers to the internal diameter of the tip of the nozzle.
By setting the nozzle diameter to less than 20 [μm], the electric field strength distribution becomes narrow. As a result, the electric field can be concentrated. As a result, the formed droplets can be made minute and the shape can be stabilized, and the total applied voltage can be reduced. In addition, immediately after the droplet is ejected from the nozzle, the droplet is accelerated by an electrostatic force acting between the electric field and the electric charge. However, when the droplet is separated from the nozzle, the electric field rapidly decreases, and thereafter, the droplet is decelerated due to air resistance. However, a droplet that is a minute droplet and has a concentrated electric field is accelerated by mirror image force as it approaches the counter electrode. By balancing the deceleration by the air resistance and the acceleration by the mirror image force, it is possible to stably fly the fine droplets and improve the landing accuracy.
[0028]
The internal diameter of the nozzle is preferably 8 [μm] or less. By making the internal diameter of the nozzle 8 [μm] or less, it becomes possible to further concentrate the electric field, and further miniaturization of droplets and fluctuations in the distance of the counter electrode during flight affect the electric field strength distribution. Since it can be reduced, it is possible to reduce the influence of the position accuracy of the counter electrode, the characteristics of the base material, the thickness on the droplet shape, and the impact accuracy.
[0029]
Furthermore, by setting the internal diameter of the nozzle to 4 [μm] or less, it is possible to achieve a remarkable electric field concentration, to increase the maximum electric field strength, The initial discharge speed of the droplet can be increased. Thereby, by improving the flight stability, it is possible to further improve the landing accuracy and improve the ejection response.
[0030]
The inner diameter of the nozzle is preferably larger than 0.2 [μm]. By making the inner diameter of the nozzle larger than 0.2 [μm], the charging efficiency of the droplets can be improved, and thus the droplet discharge stability can be improved.
Furthermore, the above claims and Claim 1 In the configuration of the cited invention that cites the invention described in
(1) Preferably, the nozzle is formed of an electrical insulating material, and an electrode is inserted into the nozzle or plated.
(2) In the configuration of each of the above claims or the configuration of (1), it is preferable that the nozzle is formed of an electrical insulating material, the electrode is inserted or plated in the nozzle, and the electrode is provided outside the nozzle.
According to (1) and (2), in addition to the effects of the above claims, the discharge force can be improved, so that the liquid can be discharged at a low voltage even if the nozzle diameter is further reduced.
(3) In the configuration of each of the above claims and the configuration of (1) or (2), the base material is preferably formed of a conductive material or an insulating material.
(4) In the configuration of each of the above claims and the configuration of (1), (2) or (3), the voltage V applied to the nozzle is
[Expression 1]

Represented by region It is preferable to drive.
Where γ: surface tension of the liquid, ε ₀ : Dielectric constant of vacuum, r: nozzle radius, h: distance between nozzle and substrate, k: proportional constant depending on nozzle shape (1.5 <k <8.5).
(5) In the configurations of the above claims and the configurations of (1), (2), (3), or (4), it is preferable that an arbitrary waveform voltage to be applied is 1000 V or less.
(6) In the configurations of the above claims and the configurations of (1), (2), (3), (4), or (5), it is preferable that the arbitrary waveform voltage to be applied is 500 V or less.
It is preferable to place the substrate on a conductive or insulating substrate holder.
(7) In the configuration of each of the above claims and the configuration of any of (1) to (6) above, the distance between the nozzle and the substrate is 500 [μm] or less, even when the nozzle diameter is made fine. Since landing accuracy can be obtained, it is preferable.
(8) In the configuration of each of the above claims and the configuration of any one of (1) to (7), it is preferable that the pressure is applied to the solution in the nozzle.
(9) In the configuration of each of the above claims and the configuration of any of the above (1) to (8), when discharging by a single pulse,
[Expression 2]

A configuration may be adopted in which a pulse width Δt having a time constant τ or more determined by is applied. Where ε is the dielectric constant of the fluid and σ is the conductivity.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiment, a liquid ejection apparatus according to the present invention will be described first, and then a mold manufacturing method using the liquid ejection apparatus will be described.
[0032]
In addition, the nozzle diameter (internal diameter) of the liquid ejection device described in the following embodiments is preferably 30 [μm] or less, more preferably less than 20 [μm], and still more preferably 8 [μm] or less. More preferably, it is preferably 4 [μm] or less. The nozzle diameter is preferably larger than 0.2 [μm].
[0033]
[Liquid ejection device]
(Overall configuration of liquid ejection device)
Hereinafter, the liquid ejection apparatus will be described with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view of a liquid ejection device 20 along a nozzle 21 to be described later, and FIG. 2 is an explanatory diagram showing a relationship between a liquid ejection operation and a voltage applied to the liquid, and particularly FIG. ) Is a state where no discharge is performed, and FIG. 2B shows a discharge state.
[0034]
As shown in FIG. 1, the liquid ejection device 20 includes an ultrafine nozzle 21 that ejects a droplet of a chargeable liquid from its tip, a facing surface that faces the tip of the nozzle 21, and the facing surface. The liquid supply means (not shown) for supplying a liquid to the flow path 22 in the nozzle 21, and the discharge voltage is applied to the liquid in the nozzle 21. The discharge voltage application means 25, the light irradiation means (not shown) for irradiating the droplets landed on the base material 99, and the positioning and position adjustment of the base material 99 while supporting the counter electrode 23 and the base material 99 And an XY stage 31 for performing the above.
A part of the nozzle 21 and the liquid supply means and a part of the discharge voltage applying means 25 are integrally formed by a nozzle plate 26.
[0035]
(nozzle)
The nozzle 21 is integrally formed with a lower surface layer 26c of the nozzle plate 26 described later, and is erected vertically from the flat plate surface of the nozzle plate 26. Further, the nozzle 21 is formed with an in-nozzle flow path 22 penetrating from the tip portion along the center line.
[0036]
The nozzle 21 will be further described in detail. As described above, the nozzle 21 is formed with an ultrafine diameter. As an example of specific dimensions of each part, the internal diameter of the flow path 22 in the nozzle is 1 [μm], the external diameter at the tip of the nozzle 21 is 2 [μm], and the diameter of the base of the nozzle 21 is 5 [μm]. [mu] m] and the height of the nozzle 21 is set to 100 [[mu] m], and the shape thereof is formed in a truncated cone shape that is close to a conical shape. The entire nozzle 21 is formed of an insulating resin material together with the lower surface layer 26 c of the nozzle plate 26.
[0037]
In addition, each dimension of a nozzle is not limited to the said example. In particular, the nozzle inner diameter is a range in which the discharge voltage enabling the discharge of droplets by the effect of electric field concentration described below is less than 1000 [V], for example, the nozzle diameter is 70 [μm] or less. Desirably, the diameter is 20 [μm] or less, and the diameter within the range in which it is feasible to form a through-hole through which a liquid passes by the current nozzle forming technique is set as the lower limit.
[0038]
Further, although only one nozzle 21 is illustrated in the liquid ejection device 20 in FIG. 1, a plurality of nozzles 21 are provided in the actual liquid ejection device 20 in the X-axis direction (left-right direction) and the Y-axis direction (front-rear direction). ) In a matrix.
[0039]
(Liquid supply means)
The liquid supply means is provided inside the nozzle plate 26 at a position that is the root of the nozzle 21 and supplies liquid to the liquid chamber 24 from an external liquid tank (not shown) that communicates with the flow path 22 in the nozzle. A liquid supply path 27 for guiding the liquid and a supply pump (not shown) for applying a liquid supply pressure to the liquid chamber 24 are provided.
The supply pump supplies the liquid to the tip of the nozzle 21 and supplies the liquid while maintaining the supply pressure in a range that does not spill from the tip (see FIG. 2A).
[0040]
(Discharge voltage application means)
The discharge voltage applying means 25 includes a discharge electrode 28 for applying a discharge voltage provided in a boundary position between the liquid chamber 24 and the flow path 22 in the nozzle inside the nozzle plate 26, and a constant direct current is supplied to the discharge electrode 28. A bias power source 30 that applies a bias voltage and an ejection voltage power source 29 that applies a pulse voltage that is superimposed on the bias voltage and that is a potential required for ejection to the ejection electrode 28 are provided.
[0041]
The discharge electrode 28 is in direct contact with the liquid inside the liquid chamber 24 to charge the liquid and apply a discharge voltage.
The bias voltage from the bias power source 30 is applied in a constant manner within a range where no liquid is discharged, thereby reducing in advance the width of the voltage to be applied during discharge, thereby improving the reactivity during discharge. Yes.
[0042]
The ejection voltage power supply 29 applies the pulse voltage superimposed on the bias voltage only when ejecting the liquid. At this time, the value of the pulse voltage is set so that the superimposed voltage V satisfies the following equation.
[Equation 3]

Where γ: surface tension of the liquid, ε ₀ : Dielectric constant of vacuum, r: Nozzle radius, k: Proportional constant depending on nozzle shape (1.5 <k <8.5).
As an example, the bias voltage is applied at DC 300 [V] and the pulse voltage is marked at 100 [V]. Therefore, the superimposed voltage at the time of ejection is 400 [V].
[0043]
(Nozzle plate)
The nozzle plate 26 includes an upper surface layer 26a positioned at the uppermost layer in FIG. 1, a flow path layer 26b that forms a liquid supply path positioned below the upper surface layer 26a, and a lower surface layer formed further below the flow path layer 26b. 26c, and the discharge electrode 28 described above is interposed between the flow path layer 26b and the lower surface layer 26c.
[0044]
The upper surface layer 26a is formed of a silicon substrate or a highly insulating resin or ceramic, and forms a resin layer that can be dissolved under the upper layer 26a, and removes only the portion that follows the pattern of the supply path 27 and the liquid chamber 24, and is removed. An insulating resin layer is formed on the removed portion. This insulating resin layer becomes the flow path layer 26b. Then, the discharge electrode 28 is formed on the lower surface of the insulating resin layer by plating with a conductive material (for example, NiP), and an insulating resist resin layer is further formed thereunder. Since the resist resin layer becomes the lower surface layer 26 c, the resin layer is formed with a thickness in consideration of the height of the nozzle 21. Then, this insulating resist resin layer is exposed by an electron beam method or a femtosecond laser to form a nozzle shape. The nozzle internal flow path 22 is also formed by laser processing. Then, the dissolvable resin layer according to the pattern of the supply path 27 and the liquid chamber 24 is removed, and the supply path 27 and the liquid chamber 24 are opened to complete the nozzle plate.
[0045]
(Counter electrode)
The counter electrode 23 has a counter surface perpendicular to the nozzle 21 and supports the base material 99 along the counter surface. As an example, the distance from the tip of the nozzle 21 to the opposing surface of the opposing electrode 23 is set to 100 [μm].
Since the counter electrode 23 is grounded, the ground potential is always maintained. Accordingly, when a pulse voltage is applied, a liquid droplet ejected by an electrostatic force generated by an electric field generated between the tip portion of the nozzle 21 and the opposing surface is guided to the opposing electrode 23 side.
[0046]
The liquid discharge device 20 discharges liquid droplets by increasing the electric field strength by concentrating the electric field at the tip of the nozzle 21 due to the ultra-miniaturization of the nozzle 21, so that the liquid discharge device 20 does not induce by the counter electrode 23. Although it is possible to discharge droplets, it is desirable that induction by electrostatic force is performed between the nozzle 21 and the counter electrode 23. In addition, the charge of the charged droplet can be released by grounding the counter electrode 23.
[0047]
(Light irradiation means)
As described above, the light irradiating means irradiates light onto the liquid droplets that have landed on the base material 99, and although not shown in the drawing, the light can be irradiated onto the liquid droplets that have landed on the base material 99 (for example, the nozzle 21. In the vicinity). Here, “light” is light in a broad sense, and includes ultraviolet rays, electron beams, X-rays, visible rays, infrared rays, and the like. However, in consideration of the cost of the light source and the like, it is preferable to apply a light irradiation means for irradiating ultraviolet rays.
The “light source” for irradiating ultraviolet rays includes low-pressure mercury lamp, ultraviolet laser, xenon flash lamp, insect trap, black light, germicidal lamp, cold cathode tube, LED (Light Emitting Diode), LED high-pressure mercury lamp, metal halide lamp. Excimer lamps, electrodeless ultraviolet lamps, and the like are applicable, and light sources other than these may be applied.
[0048]
(XY stage)
The XY stage 31 is a mounting table in which an X stage movable in the X-axis direction (left-right direction) and a Y stage movable in the Y-axis direction (front-back direction) are stacked. A holder (not shown) having a vacuum suction function is mounted on the XY stage 31. The XY stage 31 fixes the substrate 99 by vacuum suction with a holder, and further moves the substrate 99 minutely in the X-axis direction and / or the Y-axis direction by each stage.
[0049]
(liquid)
The liquid used in this embodiment is supplied from the liquid supply means to the liquid chamber 24 through the supply path 27, and then discharged from the tip of the nozzle 21 to the counter electrode 23 side as an ultrafine droplet to be supplied to the base material 99. To land on. Specifically, this liquid is a photo-curing resin that cures when irradiated with light, and has a property that can be shifted between a semi-cured state and a fully cured state depending on the illuminance of the irradiated light.
[0050]
Here, the “photo-curable resin” means an ultraviolet curable adhesive or a photoresist agent. Epoxy acrylate, urethane acrylate, polybutadiene acrylate, polyester acrylate, and the like can be applied to the components of the ultraviolet curable monomer and oligomer contained in the ultraviolet curable adhesive, and the reaction form is radical polymerization. Photoresist agents include positive and negative types, and general chemical structures and chemical reactions are shown in Chemical Formulas 1 and 2.
[0051]
[Chemical 1]
Negative photoresist

[Chemical formula 2]
Positive photoresist

[0052]
(Base material)
As the base material 99, semiconductor materials such as silicon and silicon dioxide, quantum element materials such as gallium arsenide, aluminum gallium arsenide, and indium gallium arsenide, structural materials such as aluminum and stainless steel, tungsten, titanium, tungsten carbide, boron nitride, Difficult-to-cut materials or high hardness materials such as titanium tetranitride and ceramics, optical materials such as plastic, polyimide, glass, quartz glass, optical glass, ruby, sapphire, magnesium fluoride, zinc selenium, and zinc tellurium are applicable.
[0053]
(Discharge operation of micro droplets by liquid discharge device)
The operation of the liquid ejection device 20 will be described with reference to FIGS.
The liquid is supplied to the nozzle flow path 22 by the supply pump of the liquid supply means, and in this state, a bias voltage is applied to the liquid via the discharge electrode 28 by the bias power source 30. In this state, the liquid is charged, and a meniscus that is recessed in the liquid is formed at the tip of the nozzle 21 (see FIG. 2A).
Then, when a pulse voltage is applied by the discharge voltage power supply 29, the liquid is guided to the tip side of the nozzle 21 by the electrostatic force due to the electric field strength of the concentrated electric field at the tip portion of the nozzle 21, and the convex meniscus protruding outside. Is formed, and the electric field is concentrated at the apex of the convex meniscus, and finally the liquid is discharged to the counter electrode 23 against the surface tension of the liquid (see FIG. 2B).
[0054]
(Manufacturing method of mold using liquid ejection device)
A method for manufacturing a mold using the liquid ejection device 20 will be described with reference to FIGS. 1 to 4 (particularly FIGS. 3 and 4). 3 and 4 are drawings for explaining a mold manufacturing method using a liquid ejection device, and in particular, FIG. 3 is a drawing for explaining a process of forming a predetermined dot pattern on a base material 99. FIG. FIG. 4 is a diagram for explaining a process of manufacturing a mold from a dot pattern formed on the base material 99.
[0055]
First, a predetermined base material 99 is set in a holder of the XY stage 31, and the back surface of the base material 99 is vacuumed by the holder to fix the base material 99 to the XY stage 31.
Thereafter, droplets are ejected from the predetermined nozzle 21 of the plurality of nozzles 21 to the base material 99 to form predetermined dots composed of dot-shaped droplets having a diameter of about 0.1 to about 30 μm on the base material 99. (See FIG. 3 (a)). Thereafter, each droplet that has landed on the substrate 99 is irradiated with light from the light irradiating means, so that each droplet is semi-cured (see FIG. 3B). After that, the base material 99 is positioned and adjusted by moving at least one of the X stage and the Y stage of the XY stage 31. Thereafter, droplets are further ejected from the predetermined nozzle 21 to the substrate 99 in the gaps between the semi-cured droplets on the substrate 99 to form further dots on the substrate 99 (FIG. 3C )), Each of the droplets is irradiated with light from the light irradiating means to semi-cure each droplet (see FIG. 3D).
[0056]
Thereafter, the movement of the base material 99, the formation of dots, and the light irradiation are repeated to form a desired dot pattern in a predetermined region of the base material 99 (see FIG. 3 (e)). All the droplets are semi-cured by irradiating light from the light irradiation means to each droplet that has not been irradiated (see FIG. 3F). Thereafter, all the droplets in a semi-cured state on the substrate 99 are further irradiated with light from the light irradiation means to completely cure all these droplets (see FIG. 3G).
[0057]
In addition, as light that is primarily irradiated to semi-cure each droplet, light having a long wavelength is applied, and light that is secondarily irradiated to completely cure each droplet is primary. It is preferable to apply light having a shorter wavelength than the light applied to the light. In this case, the primary long-wavelength light irradiation cures the surface layer of each droplet to suppress the spread of each droplet on the substrate 99, and the secondary short-wavelength light irradiation The inside of each droplet in the vicinity of the base material 99 that is difficult to reach the irradiation line can be cured to improve the adhesion between each droplet and the base material 99.
[0058]
Thereafter, gold (Au) is deposited on the surface of each surface of the substrate 99 on which a predetermined dot pattern is formed, thereby completing the mother die 40 (see FIG. 4A). Thereafter, an electroforming process is performed on the mother die 40. Specifically, the mother die 40 is placed in an electrolytic solution such as nickel sulfamate, and nickel (Ni) is electrochemically deposited on the mother die 40 by using the mother die 40 as a cathode (see FIG. 4B). . Thereafter, when nickel reaches a predetermined thickness, the nickel deposit is peeled off from the mother die 40, and a die 50 having a gold film-forming surface and having a mirror image relationship with the mother die 40 is manufactured (FIG. 4 (c)).
[0059]
(Summary)
In the liquid ejection apparatus 20 as described above, since the droplets are ejected by the nozzle 21 having a small diameter, the electric field is concentrated by the charged droplets in the nozzle flow path 22 and the electric field strength is increased. For this reason, it is possible to discharge liquid at a low voltage using a nozzle with a fine diameter, which was impossible to discharge in a nozzle with a structure that does not concentrate the electric field. It is said.
[0060]
And since it has a fine diameter, it is possible to easily perform control to reduce the discharge flow rate per unit time due to the low nozzle conductance, and sufficiently small droplets (diameter of about diameter) without narrowing the pulse width. Liquid ejection by 0.1 to about 30 μm dot-like droplets) is realized.
[0061]
In addition, since each ejected droplet is charged, the vapor pressure is reduced even for very small droplets, which suppresses evaporation, reducing the loss of droplet mass and stabilizing flight. As a result, a drop in droplet landing accuracy is prevented.
[0062]
In the method of manufacturing the mold 50 using the liquid ejection device 20, in the step of forming the mother die 40, the concave / convex pattern is formed on the base material 99 while irradiating the base material 99 with the energy beam as in the prior art. Instead, the liquid is landed directly on the base material 99 to form an uneven pattern. Therefore, it is possible to reduce the processing time required for the formation process of the master die 40 by using an inexpensive apparatus (that is, the liquid ejection apparatus 20), and as a result, the processing time required for manufacturing the mold 50 with an inexpensive apparatus. Can be shortened.
[0063]
The mold 50 can be suitably used when manufacturing optical elements such as a light guide plate, an optical switch, an optical transceiver, an optical multiplexer / demultiplexer, an optical attenuator, and an optical coupler.
[0064]
Further, in order to obtain an electrowetting effect on the nozzle 21, an electrode may be provided on the outer periphery of the nozzle 21, or an electrode may be provided on the inner surface of the nozzle internal flow path 22 and covered with an insulating film from above. . By applying a voltage to this electrode, the wettability of the inner surface of the nozzle internal flow path 22 can be increased by the electrowetting effect for the liquid to which the voltage is applied by the discharge electrode 28, and the inside of the nozzle can be increased. It is possible to smoothly supply the liquid to the flow path 22, to discharge well, and to improve the responsiveness of discharge.
[0065]
In addition, the discharge voltage application means 25 always applies a bias voltage and discharges a droplet by using a pulse voltage as a trigger. However, the discharge voltage application means 25 always applies an alternating current or a continuous rectangular wave with the amplitude required for the discharge and increases and decreases its frequency. It is good also as a structure which discharges by switching. In order to discharge liquid droplets, it is essential to charge the liquid, and even if a discharge voltage is applied at a frequency that exceeds the speed at which the liquid is charged, discharge is not performed. Discharging is performed. Therefore, when discharging is not performed, a discharge voltage is applied at a frequency higher than the frequency at which ejection can be performed, and control is performed to reduce the frequency to a frequency band where ejection can be performed only when ejection is performed, thereby controlling liquid ejection. Is possible. In such a case, since there is no change in the potential applied to the liquid, it is possible to further improve the time response and thereby improve the landing accuracy of the droplet.
[0066]
Furthermore, in the above-described embodiment, an example in which the liquid is discharged from the nozzle 21 as a droplet and a predetermined dot pattern composed of a plurality of dots is formed on the substrate 99 has been described. Instead of the dots by the above, the liquid is continuously discharged from the nozzle 21 and the substrate 99 is moved by the movement of the XY stage 31 so that the width of the linear shape, the bent shape, the curved shape or a combination thereof is about 0. A protrusion pattern of 1 to about 30 μm may be formed on the substrate 99. In this case, an uneven pattern having a desired height by laminating dots by droplets, ridges by continuously connected liquid, or ridges by liquid continuously connected by dots by droplets. May be formed on the substrate 99.
[0067]
Specifically, for example, as shown in FIGS. 5A and 5B, dots of droplets having substantially the same size (droplet amount) are sequentially stacked to form a substantially triangular pyramid uneven pattern as a base material. 99 may be formed. Also, as shown in FIGS. 5C and 5D, dots of droplets having substantially the same size (droplet amount) are sequentially stacked to form a substantially cylindrical uneven pattern on the substrate 99. May be. Further, as shown in FIGS. 5 (e) and 5 (f), dots of droplets having different sizes (droplet amounts) are sequentially stacked to form a substantially cylindrical uneven pattern on the substrate 99. May be. Further, as shown in FIG. 5 (g), irregularities that are formed by sequentially laminating dots of droplets having substantially the same size (droplet amount) and laying a collection of substantially triangular prism-like dots horizontally. A pattern may be formed on the substrate 99. Further, as shown in FIG. 5 (h), the protrusions and protrusions made of the continuously connected liquid are sequentially stacked, and the uneven pattern such that the aggregate of the substantially triangular prism-shaped protrusions is laid sideways is formed on the substrate 99. It may be formed on top. Further, as shown in FIG. 5 (i), a desired concavo-convex pattern may be formed by laminating curved ridges made of continuously connected liquids on a substrate 99. Needless to say, various uneven patterns other than those shown in FIG. 5 are formed by combining dots formed by droplets, protrusions formed by continuously connected liquids, or protrusions formed by liquid continuously connected by droplets. 99 may be formed.
[0068]
Further, when droplets are stacked on the substrate 99 as described above, the next new droplet may be stacked without irradiating the droplets landed on the substrate 99 with light from the light irradiation means. Then, the droplet landed on the substrate 99 may be irradiated with light from the light irradiating means so that the droplet is semi-cured and then the next new droplet may be laminated, or the liquid landed on the substrate 99 The droplet may be irradiated with light from the light irradiation means to completely cure the droplet, and then the next new droplet may be stacked.
[0069]
Further, in the above-described embodiment, an example in which a photocurable resin is applied as the liquid discharged from the nozzle 21 is shown, but a thermosetting resin that is cured by heating may be applied as the liquid discharged from the nozzle 21. Good. In this case, it is necessary to provide the liquid ejection device 20 with a heating means (for example, a heater) for heating each droplet landed on the substrate 99 instead of the light irradiation means. Further, both the light irradiating means and the heating means are provided in the liquid discharge device 20, and each liquid resin of the photocurable resin and the thermosetting resin is separately discharged from the nozzle 21, and the base material 99 is made of different liquid resins. A predetermined uneven pattern may be formed thereon.
[0070]
Furthermore, in the above-described embodiment, the electrolysis control type liquid ejection apparatus 20 is shown in which a potential is applied between the liquid ejection section and the base material 99 and droplets are drawn from the nozzles 21 by electrostatic force to adhere to the base material 99. However, instead of this, continuous recording is performed by ultrasonically oscillating the liquid under pressure from the nozzle in the form of droplets, charging the ejected droplets, and deflecting them with an electric field. A liquid discharge apparatus may be applied. Further, in place of the electrolysis control type liquid ejection device 20, an electromechanical conversion system in which liquid is ejected in a timely manner by utilizing deformation of a piezoelectric element, and electricity in which liquid is ejected in a timely manner by using generation of bubbles due to heat. A drop-on-demand liquid ejection device including a heat conversion method may be applied.
[0071]
(Measures to reduce the applied voltage and realize stable ejection of small droplets)
In the present invention, the role of the nozzle played in the electrostatic suction type ink jet system is reconsidered,
[Expression 4]

That is,
[Equation 5]

Or
[Formula 6]

In a region that has not been attempted as impossible in the past, it is possible to form fine droplets by utilizing Maxwell force or the like.
Formulas that approximate the discharge conditions and the like for measures for realizing such a drive voltage drop and a small amount of discharge are derived and will be described below.
The following description is applicable to the liquid ejection apparatus described in the above embodiments of the present invention.
Now, it is assumed that a conductive solution is injected into a nozzle having a radius r and is positioned perpendicular to the height of h from an infinite plate conductor as a base material. This is shown in FIG. At this time, it is assumed that the charge induced in the nozzle tip is concentrated in the hemisphere at the nozzle tip, and is approximately expressed by the following equation.
[Expression 7]

Where Q: charge induced at the nozzle tip, ε ₀ : Dielectric constant of vacuum, ε: Dielectric constant of substrate, h: Distance between nozzle and substrate, r: Radius of nozzle inner diameter, V: Voltage applied to nozzle. α: A proportional constant that depends on the nozzle shape, etc., and takes a value of about 1 to 1.5, especially r < It is about 1 when <h.
[0072]
Further, when the substrate as the base material is a conductor substrate, it is considered that a mirror image charge Q ′ having an opposite sign is induced at a symmetrical position in the substrate. When the substrate is an insulator, a video charge Q ′ having an opposite sign is similarly induced at a symmetrical position determined by the dielectric constant.
By the way, the electric field strength E at the nozzle tip _loc. Assuming that the radius of curvature of the tip is R,
[Equation 8]

Given in. Here, k: proportional constant, which varies depending on the nozzle shape and the like, 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) 198-210). For simplicity, let r = R. This corresponds to a state in which the conductive solution swells in a hemispherical shape having the same radius as the nozzle diameter r due to surface tension at the nozzle tip.
Consider the balance of pressure acting on the liquid at the nozzle tip. First, the electrostatic pressure is S, where the liquid area at the nozzle tip is S.
[Equation 9]

From the formulas (8), (9) and (10), α = 1 is set.
[Expression 10]

It is expressed.
[0073]
On the other hand, if the surface tension of the liquid at the nozzle tip is Ps,
[Expression 11]

Here, γ: surface tension.
The conditions under which fluid discharge occurs due to electrostatic force is a condition where the electrostatic force exceeds the surface tension.
[Expression 12]

It becomes. By using a sufficiently small nozzle diameter r, the electrostatic pressure can exceed the surface tension.
From this relational expression, when the relationship between V and r is obtained,
[Formula 13]

Gives the lowest discharge voltage. That is, from Equation (7) and Equation (14),
[Expression 14]

Is the operating voltage of the present invention.
[0074]
The dependency of the discharge limit voltage Vc on a nozzle having a certain radius r is shown in FIG. From this figure, it is clear that the discharge start voltage decreases as the nozzle diameter decreases, considering the effect of electric field concentration by the fine nozzles. That is, when the nozzle diameter is less than 20 μm, the electric field can be concentrated, fine droplets can be stably discharged, and the discharge start voltage can be reduced. From FIG. 7, it can be seen that when the nozzle diameter is 8 μm or less, the electric field can be further concentrated, fine droplets can be discharged more stably, and the discharge start voltage can be further reduced. Further, the nozzle diameter is preferably 4 μm or less.
In the conventional way of thinking about the electric field, that is, considering only the electric field defined by the voltage applied to the nozzle and the distance between the counter electrodes, the voltage required for ejection increases as the nozzle becomes smaller. On the other hand, if attention is paid to the local electric field strength, the discharge voltage can be reduced by making the nozzle fine.
[0075]
Discharging by electrostatic suction is based on charging of fluid at the nozzle end. The charging speed is considered to be about a time constant determined by dielectric relaxation.
[Expression 15]

Here, ε is the relative dielectric constant of the fluid, and σ is the conductivity of the fluid. The relative dielectric constant of the fluid is 10, the conductivity is 10 ^-6 Assuming S / m, τ = 1.854 × 10 ^-Five sec. Or, if the critical frequency is fc,
[Expression 16]

It becomes. It is considered that the ejection cannot be performed because it cannot respond to the change in the electric field having a frequency faster than fc. Estimating the above example, the frequency is about 10 kHz. At this time, if the nozzle radius is 2μm and the voltage is less than 500V, G is 10 ^-13 m ^Three / s can be estimated, but in the case of the liquid in the above example, discharge at 10 kHz is possible, so the minimum discharge amount in one cycle is 10 fl (femtoliter, 1 fl: 10 ^-15 l) Degree can be achieved.
[0076]
Each of the present embodiments is characterized by the effect of electric field concentration at the nozzle tip as shown in FIG. 6 and the effect of image force induced on the counter substrate. For this reason, it is not necessary to make the substrate or the substrate support conductive as in the prior art or to apply a voltage to these substrates or substrate support. That is, an insulating glass substrate, a plastic substrate such as polyimide, a ceramic substrate, a semiconductor substrate, or the like can be used as the substrate.
In each of the above embodiments, the voltage applied to the electrode may be either positive or negative.
Furthermore, the discharge of the solution can be facilitated by keeping the distance between the nozzle and the substrate at 500 [μm] or less. Although not shown, feedback control based on nozzle position detection is performed to keep the nozzle constant with respect to the substrate.
Further, the base material may be placed and held on a conductive or insulating base material holder.
[0077]
FIG. 8 is a side sectional view of a liquid ejection apparatus as an example of another basic example of the present invention. An electrode 15 is provided on the side surface of the nozzle 1, and a controlled voltage is applied to the nozzle solution 3. The purpose of the electrode 15 is an electrode for controlling the electrowetting effect. If a sufficient electric field is applied to the insulator constituting the nozzle, the Electrowetting effect is expected to occur even without this electrode. However, in this basic example, the role of discharge control is also fulfilled by controlling more positively using this electrode. When the nozzle 1 is made of an insulator, its thickness is 1 μm, the nozzle inner diameter is 2 μm, and the applied voltage is 300 V, an electrowetting effect of about 30 atmospheres is obtained. This pressure is insufficient for discharge, but is meaningful from the viewpoint of supplying the solution to the nozzle tip, and it is considered that discharge can be controlled by this control electrode.
[0078]
FIG. 8 described above shows the nozzle diameter dependence of the discharge start voltage in the present invention. As the liquid ejection device, the one shown in FIG. 1 was used. It became clear that the discharge start voltage decreased as the nozzle became finer, and discharge was possible at a lower voltage than before.
[0079]
In each of the above embodiments, the solution discharge conditions are functions of the nozzle substrate distance (L), the applied voltage amplitude (V), and the applied voltage frequency (f), and satisfy certain conditions for each. This is necessary as a discharge condition. Conversely, if any one of the conditions is not met, the other parameters must be changed.
[0080]
This will be described with reference to FIG.
First, for discharge, there is a certain critical electric field Ec that does not discharge unless the electric field is higher than that. This critical electric field varies depending on the nozzle diameter, the surface tension of the solution, the viscosity, and the like, and it is difficult to discharge below Ec. Above the critical electric field Ec, that is, at the dischargeable electric field strength, there is a roughly proportional relationship between the nozzle substrate distance (L) and the amplitude of the applied voltage (V). When the distance between the nozzles is reduced, the critical applied voltage V Can be reduced.
Conversely, when the distance L between the nozzle substrates is extremely increased and the applied voltage V is increased, even if the same electric field strength is maintained, the fluid droplets burst or burst due to the action of corona discharge or the like. Therefore, in order to obtain good ejection characteristics, it is desirable from the viewpoints of ejection characteristics and landing accuracy that the distance between the nozzle substrates is suppressed to about 100 μm or less.
[0081]
【The invention's effect】
According to the first aspect of the present invention, in the matrix forming step, the concave / convex pattern is not directly formed on the base material while irradiating the base material with an energy beam as in the prior art. An uneven pattern is formed by landing a liquid. Therefore, for example, if a concave / convex pattern is formed by directly applying a liquid to a substrate using an ink jet type apparatus, the processing time required for this matrix forming process can be shortened using an inexpensive apparatus. As a result, the processing time required to manufacture the mold can be shortened by using an inexpensive apparatus.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a liquid ejection device.
FIGS. 2A and 2B are explanatory diagrams showing a relationship between a liquid discharge operation and a voltage applied to the liquid, in which FIG. 2A shows a state where no discharge is performed, and FIG. 2B shows a discharge state; .
FIG. 3 is a drawing for explaining a process of forming a predetermined dot pattern on a substrate.
FIG. 4 is a drawing for explaining a process of manufacturing a mold from a dot pattern formed on a substrate.
FIG. 5 is a drawing showing various uneven patterns formed on a substrate, and FIG. 5 (a) is a side view showing a state in which a plurality of dots are stacked from the side, and FIG. 5 (b) FIG. 5A is a plan view of FIG. 5A, FIG. 5C is a side view of a state where a plurality of dots are stacked, and FIG. 5D is a plan view of FIG. 5C. FIG. 5 (e) is a side view of a state in which a plurality of dots having different sizes are stacked from the side, and FIG. 5 (f) is a plan view of FIG. 5 (e). FIG. 5G is a perspective view showing a state in which a plurality of dots are stacked, FIG. 5H is a perspective view showing a state in which ridges are stacked, and FIG. 5I is a perspective view showing curved ridges. FIG.
FIG. 6 is a graph for explaining the calculation of the electric field strength of the nozzle.
FIG. 7 shows a relationship between a nozzle diameter of a nozzle, a discharge start voltage at which a droplet discharged from a meniscus starts to fly, a voltage value at the Rayleigh limit of the initial discharge droplet, and a ratio between the discharge start voltage and the Rayleigh limit voltage value. It is a diagram which shows a relationship.
FIG. 8 is a side sectional view of the liquid ejection device.
FIG. 9 is a diagram illustrating ejection conditions based on a distance-voltage relationship in the liquid ejection apparatus.
[Explanation of symbols]
20 Liquid discharge device
21 nozzles
22 Flow path
23 Counter electrode
24 liquid chamber
25 Discharge voltage application means
26 Nozzle plate
27 Liquid supply path
28 Discharge electrode
29 Discharge voltage power supply
30 Bias power supply
31 XY stage
40 mother mold
50 mold
99 Base material

Claims (3)

In the manufacturing method of a mold having a fine uneven pattern,
A nozzle having a receiving surface for receiving the discharge of the charged liquid and having a tip portion opposed to the base, and a nozzle diameter for discharging the liquid from the tip portion being larger than 0.2 μm and not larger than 4 μm, and the nozzle using a liquid supply means for supplying the liquid, a liquid discharge apparatus and a discharge voltage application means for applying a discharge voltage to the liquid in the nozzle within and landed the liquid to the substrate, the diameter Forming a matrix having a desired concavo-convex pattern by forming dots of about 0.1 to about 30 [mu] m, protrusions of about 0.1 to about 30 [mu] m in width, or concavo-convex combinations thereof on a substrate Process,
A mold manufacturing process for manufacturing a mold having a mirror image relationship with the mother mold by electrochemically depositing a predetermined metal on the mother mold by an electroforming process after the mother mold forming step;
A method of manufacturing a mold, comprising: In the manufacturing method of the metal mold according to claim 1,
The method for producing a mold, wherein the liquid is a photocurable resin that is cured by light irradiation. In the manufacturing method of the metal mold according to claim 1,
The method for producing a mold, wherein the liquid is a thermosetting resin that is cured by heating.

Images