JP3792550B2 - Optical print head - Google Patents

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【００４９】
上記表１に示すように、ＩＴＯからなる行電極２の屈折率は２．００である。また、行電極２に隣接するガラスからなる基板１０の屈折率は１．４５であり、アクリル樹脂からなる保護膜１１の屈折率は１．４である。このように、基板１０・保護膜１１と比較すると高屈折率である行電極２は、行電極２よりも低屈折率である基板１０・保護膜１１に挟まれている。
【００５０】
従って、図３に示した電子輸送・発光層１２ｃからの発光光は、まず、行電極２内を透過する。そして、基板１０あるいは保護膜１１との境界面へと到達する。ここで、基板１０・保護膜１１は行電極２よりも低屈折率であるため、行電極２から、行電極２と基板１０または保護膜１１との境界面に入射した光のうち、臨界角を超えて入射した光は全反射して再び行電極２内を透過することとなる。例えば、行電極２がＩＴＯからなり、基板１０がガラスからなる場合、行電極２と基板１０との境界面において、行電極２内で光が全反射する臨界角は４６°である。
【００５１】
こうして、行電極２と基板１０あるいは保護膜１１との境界面において全反射を繰り返しながら、電子輸送・発光層１２ｃからの発光光は行電極２内を導波され端面１ａまで到達する。このとき、端面１ａに到達した光のうち、端面１ａに臨界角より小さい角度で入射した光は、行電極２から外部（ＥＬ素子１から外部）へ、即ち、光分岐部８の方へむけて放出される。
【００５２】
また、電子輸送・発光層１２ｃから反射板４方向へ行電極２内を導波される発光光は、反射板４において反射されるため、端面１ａに導かれることとなる。即ち、対向端面１ｂに反射板４を配することにより、端面１ａから放出される光量を大きくすることができ、光の取り出し効率の向上を図ることができる。
【００５３】
なお、図５（ａ）にＥＬ素子１のある発光箇所に対する印加電圧と輝度との関係を、図５（ｂ）にＥＬ素子１の上記発光箇所に対する印加電圧と電流との関係を示す。
【００５４】
以上のように、被露光体９に光を照射して露光する光プリントヘッド１０１は、１つの発光領域に対応して、基板１０上に、有機ＥＬ層１２と、透光性を有し、かつ、基板１０よりも光の屈折率の大きい材料からなり、有機ＥＬ層１２に電圧を印加する行電極２と、互いに独立した複数の電極により構成され、かつ、有機ＥＬ層１２を挟んで行電極２に対向して配されて行電極２とともに有機ＥＬ層１２に電圧を印加する列電極３…と、行電極２を覆うように配され、かつ、行電極２よりも光の屈折率の小さい材料からなる保護膜１１とを有するＥＬ素子１を備え、列電極３…における複数の電極を選択駆動することにより有機ＥＬ層１２で発生した光は、行電極２を透過し、発光素子１の端面１ａから放出される。
【００５５】
次に、図１の光分岐部８について、図６ないし図８を用いて説明する。
【００５６】
図６に、光分岐部８の構成を示す。光分岐部（光分岐手段）８は、複数の分岐導波路部２０…を備えている。各分岐導波路部２０は、ＥＬ素子１の端面１ａにおける光放出箇所である行電極２の端部と結合されている。分岐導波路部２０は、行電極２の上記端部と結合された光入力用導波路（導波路）８１をＥＬ素子１の各光放出箇所に対応して備え、光入力用導波路８１は、光スイッチ８２によって光出力用導波路８５と、光スイッチ８３によって光出力用導波路８６とに接続されている。光スイッチ８２・８３は、内部に液体ベンゼンが充填されており、加熱されると気体ベンゼンとなって内部の屈折率が変化するようになっている。この加熱を行うために膜厚０．１５μｍのＨｆＢ2 からなるヒータ８９（後述）が設けられている。さらに、このヒータ８９に給電を行うために設けられた電極８８（後述）のコモン側の引き出し電極８４（図６）が設けられている。また、気体ベンゼンの膨張分は図示しない別に設けられたチャンバーに退避するようになっている。
【００５７】
光入力用導波路８１、光出力用導波路８５・８６は紫外線硬化樹脂からなり、その屈折率は液体ベンゼンよりも小さく、気体ベンゼンよりも大きい。ＥＬ素子１の光放出箇所から光入力用導波路８１へ入力された光は、光スイッチ８２・８３がヒータ８４のＯＦＦによって内部が液体ベンゼンの状態であるときに光透過を行うことにより、それぞれ光出力用導波路８５・８６へ光を導波する。逆に、光スイッチ８２・８３がヒータ８４のＯＮによって加熱されて内部が気体ベンゼンの状態であるときに光遮断を行うことにより、光出力用導波路８５・８６へは光が導波されない。また、光スイッチ８２・８３はそれぞれ光透過と光遮断とを独立して切り換え可能であり、光入力用導波路８１は分岐点でその先の導波路が選択される。従って、図７（ａ）に示すように光スイッチ８２・８３の内部が両方とも液体ベンゼンであるときには光入力用導波路８１の光は光出力用導波路８５・８６に分岐して導波される。また、図７（ｂ）に示すように光スイッチ８２の内部が液体ベンゼンで、光スイッチ８３の内部が気体ベンゼンであるときには光入力用導波路８１の光は光出力用導波路８５にのみ導波されて光出力用導波路８６へは導波されない。
【００５８】
このように１つの光入力用導波路８１が２つの光出力用導波路８５・８６に光スイッチ８２・８３によって接続されることにより、１つの導波路が２つに分岐される。また、同図に示すように、上記の光出力用導波路８５・８６はそれぞれ次の分岐点に対しては光入力用導波路となり、光スイッチ８２・８３と同じ光スイッチによってそれぞれさらに２つの光出力用導波路（光入力用導波路８１、光出力用導波路８５・８６と同じ）と接続されて分岐する。同図の場合は、各分岐導波路部２０で２段に分岐されることにより４つの分岐経路が形成されている例であり、ｎ段に分岐すれば２_n 個の分岐経路が形成されることになる。分岐経路の数は各分岐導波路部２０の末端の光出力用導波路の終端、すなわち各分岐導波路部２０から図１の被露光体９へ光照射を行うことのできる照射口の数でもある。従って、図６の場合には、光分岐部８の照射口の総数はＥＬ素子１の光放出箇所の数の４倍となり、また、各分岐導波路部２０に２_n 個の分岐経路がある場合には、光分岐部８の照射口の総数はＥＬ素子１の光放出箇所の数の２_n 倍となる。
【００５９】
本実施の形態にかかる光プリントヘッド１０１では、行電極２…が駆動回路７…によって順次選択されて時系列的に駆動される構成であるので、各行電極２の１回の選択期間中に、各分岐導波路部２０の分岐経路を１つずつ光透過状態とするとともにその他の分岐経路をいずれかの光スイッチで光遮断状態として、光透過状態の分岐経路でＥＬ素子１から入力される光を導波し、各照射口から順に被露光体９への光照射を行うことができる。分岐経路を１つずつ光透過状態とするのに、光プリントヘッド１０１では各分岐点の２つの光スイッチの一方で光透過させ、他方で光遮断する。この場合、被露光体９の各露光対象箇所に対する光照射時の光強度が、対応するＥＬ素子１の光放出箇所から放出される光の強度とほぼ等しくなるので、被露光体９が感光体であるような場合に目的の露光像を適切に得ることができる。
【００６０】
なお、光スイッチ８２・８３としては、上記の熱屈折率変化素子の他に、マイクロマシンなどとして構成される、平行移動マイクロミラー、回動マイクロミラー、ＰＬＺＴなどを用いた光スイッチ、熱毛管スイッチなどでもよい。また、一般に、１つの光入力用導波路と複数の光出力用導波路とが、該複数の光出力用導波路のそれぞれに対応して設けられた光スイッチで接続されていてもよい。
【００６１】
次に、図６の１つの分岐導波路部２０についてのＢ−Ｂ矢視断面図、Ｃ−Ｃ矢視断面図、Ｄ−Ｄ矢視断面図を、図８（ａ）・（ｂ）・（ｃ）に示す。
【００６２】
図８（ａ）は前記ＥＬ素子１の断面図であり、基板１０の上面に行電極２が形成され、その上を覆うように保護膜１１が形成されている。行電極２の屈折率は基板１０、保護膜１１の屈折率よりも大きい。図８（ｂ）においては、基板１０の上面に光入力用導波路８１が形成され、その上を覆うように保護膜８７が形成されている。保護膜８７は紫外線硬化樹脂からなり、屈折率が光入力用導波路８１よりも小さい。また、光入力用導波路８１の屈折率は基板１０の屈折率よりも大きい。図８（ｃ）においては、基板１０の上面に、光スイッチ８２・８３のそれぞれに対して設けられるヒータ８９・８９用の電極８８・８８が形成されている。電極８８・８８はアルミニウムからなる。ヒータ８９・８９は電極８８・８８の上面に形成されており、電極８８・８８の上面に光スイッチ８２・８３が形成されている。そして、これら全ての上を覆うように保護膜８７が形成されている。保護膜８７の屈折率は、光スイッチ８２・８３内部の液体ベンゼンの屈折率よりも小さい。
【００６３】
このように、光分岐部８は、ＥＬ素子１と同一の基板１０上に形成されている。なお、図８（ｂ）・（ｃ）においては、膜厚１μｍ程度のＳｉＯ2 からなる絶縁層や、膜厚０．５μｍ程度の窒化珪素からなる保護層の図示を省略してある。
【００６４】
ここで、光が入射する各境界に対して、前述の図４で定義される屈折率ｎ１およびｎ２と、臨界角θ１あるいはθ２との関係を表２に示す。なお、同表において、屈折率ｎ２の物質から臨界角θ２以下で光が透過する方の物質の屈折率をｎ３で表す。
【００６５】
【表２】

【００６６】
なお、屈折率導波の原理はＥＬ素子１の説明箇所で述べたものと同じ一般的なものであるので、ここでは省略する。同表に示すように、光分岐部８において光入力用導波路８１から内部が気体ベンゼンであるときの光スイッチ８２・８３への光の入射角が４２．５度以上となると、光は光入力用導波路８１と光スイッチ８２・８３との境界面で全反射する。従って、光スイッチ８２・８３のいずれか一方が光透過を行い、他方が光遮断を行う場合に、光入力用導波路８１から光遮断を行う光スイッチへ入射しようとする光の大部分が、光入力用導波路８１とこの光スイッチとの境界面に臨界角である４２．５度以上で入射して全反射し、他方の光スイッチ内へ入射するように、光入力用導波路８１と光スイッチ８２・８３の境界面がなす角度が設定されている。また、この角度は、光スイッチ８２・８３内の物質の屈折率によっても変化する。光透過を行う光スイッチ内には、光入力用導波路から直接入射する光と、光遮断を行う他方の光スイッチで全反射された光とが加わって入射される。
【００６７】
以上の構成の光分岐部８を用いることにより、光プリントヘッド１０１は、ＥＬ素子の所定の各光放出箇所である行電極２の端面１ａ上にある終端から放出される光を、分岐経路を順次光透過状態として、上記の光放出箇所ごとに被露光体９の異なる領域へ光照射を行い、被露光体９に所定解像度で露光を行う。
【００６８】
光放出箇所ごとに対応する被露光体９の領域における各露光対象点での露光および非露光は、光スイッチによって各分岐点で光入力用導波路から光出力用導波路のそれぞれへの光透過あるいは光遮断を行って、分岐経路で光を選択的に導波することにより決定する。従って、被露光体９上の露光像をＥＬ素子１の光放出箇所の数よりも多い露光対象点で形成することができるので、ＥＬ素子１の光放出箇所の数で制限されていた露光解像度を越える高い露光解像度を容易に得ることができる。
【００６９】
また、ＥＬ素子１の各光放出箇所の駆動回路を、露光解像度分だけ設ける場合に比べて少なくすることができる。さらに、ＥＬ素子１の各光放出箇所の面積を、光放出箇所の数を露光解像度分だけ設ける場合に比べて大きくすることができるので、各光放出箇所から放出される光エネルギーを十分に確保することができる。さらに、光分岐部８の末端の光出力用導波路から、光分岐部８により得た光を被露光体９に照射するので、被露光体９への照射光の指向性が向上する。
【００７０】
また、光分岐部８では、各分岐点で２つの光スイッチによって１つの光入力用導波路が２つの光出力用導波路に接続されているので、分岐の場合分けが少なくて制御が容易である。特に、本実施の形態のように、各分岐点で２つの光スイッチの一方で光透過させ、他方で光遮断する場合には、２つの光スイッチの光透過および光遮断を２値で制御することができ、制御が容易になる。またこの場合に、光入力用導波路と光遮断を行う光スイッチとの境界面に入射する光入力用導波路からの光の大部分を全反射させて、光透過を行う光スイッチ内に入射させ、光入力用導波路から光透過を行う光スイッチ内に直接入射する光に加えるので、光透過と光遮断とで明確な光量の差が得られ、被露光体９への露光と非露光とのコントラストが大きくなり、良好な露光像を得ることができる。
【００７１】
また、光分岐部８に設けた光スイッチは、加えられる熱による液体状態と気体状態との間の状態変化によって光入力用導波路から複数の光出力用導波路のそれぞれへの光透過および光遮断が制御されるので、反射ミラーを移動させる方式などの光スイッチを用いた場合に見られる装置の振動や、露光像劣化、騒音を防止することができるとともに、反射ミラー方式などよりも光透過と光遮断とを高速に切り換えることができる。また、サーマルヘッドと同様のリソグラフィー技術で光スイッチを製造することができるとともにＰＬＺＴを用いた場合のような長い光路長が不要であるので、微細化が容易であり、高い露光解像度を実現することができる。
【００７２】
また、上記光スイッチは、ベンゼンのように液体状態と気体状態とが切り換わる材料が光入力用導波路と複数の光出力用導波路のそれぞれとの接続部に設けられたものである。液体状態と気体状態との間の屈折率変化は大きく、光スイッチはこの屈折率変化によって、光透過と光遮断とを明確に切り換えることができるので、被露光体９への露光と非露光とのコントラストが大きくなり、良好な露光像を得ることができる。また、特に応答性に優れた光スイッチングを行うことができる。
【００７３】
また、光プリントヘッド１０１では、発光素子としてＥＬ素子１を用いているので、ＥＬ素子１の駆動電極である行電極２…などで光分岐部８に入力する光の導波路を兼ねる構造が可能となり、全体の構成を簡略化することができる。なお、発光素子としてはＬＥＤアレイでも、光放出箇所が１つのＥＬ素子やＬＥＤでもレーザーダイオードでも構わない。ただし、ＥＬ素子１を用いることにより、ＬＥＤアレイ、ＬＥＤ、レーザダイオードなどを用いるときに行われるチップ化やアセンブリが不要である。すなわち、ＥＬ素子１では、光分岐部８に光を入力するための光導波路を素子とは別に作製する必要がなく、また、基板１０のようなガラス基板へのチップのはりつけや、導通をとるためのワイヤボンディングなどが不要であり、量産向きである。
【００７４】
また、光放出箇所ごとに対応してＥＬ素子１に設けられた各発光領域が、行電極２…および列電極３…という駆動電極によって発光駆動されて、発光領域の各発光箇所での発光光がＥＬ素子１の端面１ａに設けられた光放出箇所のそれぞれに、行電極２によって端面１ａと略垂直方向に導波される。ここで、駆動電極は選択的に駆動されるようになっており、発光領域の発光箇所が選択単位ごとに変化する。従って、ＥＬ素子１の使用時期に応じて、選択する駆動電極を順次切り換えるようにすれば、発光領域の発光箇所も順次切り換わるので、ある駆動電極に対応して発光する発光箇所が寿命になっても、異なる発光箇所を続けて使用することができ、ＥＬ素子１全体としての寿命を延ばすことができる。
【００７５】
また、選択単位ごとの駆動電極を組み合わせて選択することにより、各発光領域において異なる発光箇所を同時に発光させることができるので、光放出箇所から放出される光の強度を変えることができ、被露光体９への露光量を段階的に切り換えることができる。さらに、発光領域は端面１ａと略垂直な導波方向に沿って設けられるので、同じ光放出箇所に対して発光領域を導波方向に沿って対向端面１ｂ側に任意に大きくすることができ、光放出箇所の大きさに制限されずに光放出箇所から放出される光の強度を大きくすることができる。
【００７６】
また、同一の基板１０上にＥＬ素子１と光分岐部８とが形成されていることにより、光プリントヘッド１０１は簡素な構成となるので、各部の高い組み立て精度を確保することができる。従って、特に、被露光体９の露光領域が大きくなるような大きな光プリントヘッド１０１を容易に得ることができる。
【００７７】
ここで、ＥＬ素子１の製造工程の一例について、図９を用いて説明する。
【００７８】
まず、基板１０上にフォトレジスト６１をスピンコートを用いて、厚さ２μｍに形成する（図９（ａ））。そして、Ａｌ膜６６を蒸着法を用いて厚さ１５０ｎｍに成膜する。その後、ＬｉＦ膜６５、Ａｌｑ３膜６４、ａ−ＮＰＤ膜６３およびＣｕＰｃ膜６２を、分子線蒸着法により、この順に成膜する（図９（ｂ））。なお、このときの膜厚は、ＬｉＦ膜６５が０．５ｎｍ、Ａｌｑ３膜６４が６０ｎｍ、ａ−ＮＰＤ膜６３が４０ｎｍ、ＣｕＰｃ膜６２が３０ｎｍとする。次に、レジスト６１を除去する。これにより、所望の形状にパターニングされた列電極３と、正孔注入層１２ａ、正孔輸送層１２ｂ、電子輸送・発光層１２ｃおよび電子注入層１２ｄからなる有機ＥＬ層１２とが形成される。
【００７９】
続いて、基板１０上全面を覆うように、ＩＴＯ膜を厚さ２０００ｎｍに成膜し、所望の形状にパターニングして、行電極２…を形成する（図９（ｃ））。そして、基板１０上全面を覆うように、保護膜１１を成膜し、また、対向端面１ｂには、該対向端面１ｂを覆うようにＡｌ膜を成膜し、反射板４を形成する（図９（ｄ））。その後、必要に応じて、光センサなどを配置する。
【００８０】
ここで、図９（ｅ）は、図９（ｄ）のＥ−Ｅ線矢視断面図である。即ち、ある列電極３に沿った断面図である。
【００８１】
このようにして、ＥＬ素子１は形成される。これにより列電極３を１つの画素内に複数有するとしても、簡単な工程で所望の形状にパターニングすることができるため、量産性に優れた光プリントヘッドを提供することができる。
【００８２】
また、図１に示す光プリントヘッド１０１におけるＥＬ素子１では、各々の列電極３の幅は均一としているが、図１０に示すＥＬ素子１’のように、列電極３ａ・３ｂ・３ｃ・３ｄのように、各々の列電極３の幅を変えてもかまわない。ここでは、列電極３ａが最も幅が小さく、列電極３ｂ・３ｃ・３ｄの順に幅が大きくなっている。それ以外はＥＬ素子１と同様の構成である。駆動回路６・7 の図示は省略してある。
【００８３】
このような構成をとることにより、各発光領域において、対応する行電極２と列電極３ａ・３ｂ・３ｃ・３ｄのうちの１つの列電極３とを組み合わせる選択単位ごとに、発光箇所の発光強度が変化する、即ち、光放出箇所から放出される光の強度が変化する。これにより、各々の列電極３において簡単に重み付けをすることができる。従って、行電極２との間に印加する電圧が各々の列電極３に対応して異なることとなり、有機ＥＬ層１２の電子輸送・発光層１２ｃでの発光強度に重み付けをすることができる。このため、これら列電極３ａ・３ｂ・３ｃ・３ｄを複数組み合わせて選択し、駆動することにより、発生する光の階調を変えることができる。この結果、各発光領域において駆動電極の選択単位ごとに発光する発光箇所の数が少なくても、すなわち少ないビット数でも、被露光体９への露光量をきめ細かく段階的に切り換えて、細かい階調制御、８ビットでは２５６階調制御を行うことができる。
【００８４】
また、図１０に示すように、列電極３ａ・３ｂ・３ｃ・３ｄは、ＥＬ素子１の端面１ａと同様に光放出箇所が設けられた端面１ａ’から遠ざかるにつれ、幅が小さくなるように配されていることが好ましい。即ち、端面１ａ’から遠ざかるにつれ、重みが小さくなるように重み付けされていることが好ましい。
【００８５】
一般に、光が発生する位置から放出される位置までの距離が長い程、光の減衰量は大きくなる。従って、例えば発光させる発光箇所の電極が、光放出箇所から遠い位置に配されている場合、光の減衰量は大きくなる。このため、光放出箇所において所望の光量を得るためには、該光量を発光箇所で得る場合に必要な電極と比較すると、電極を大きめに製造する必要がある。
【００８６】
しかしながら、光放出箇所が設けられている端面１ａ’から遠ざかるにつれ、重みが小さくなるように重み付けされていることにより、例えば、光放出箇所から遠い位置に配されているため、減衰量を考慮して列電極３（例えば列電極３ａ）を大きめに製造する必要があったとしても、重みが小さければ、光放出箇所において所望の光量を発光箇所で得る場合と比較した場合、製造する列電極３の大きさの差が小さくてすむ。
【００８７】
即ち、重みの大きい、即ち、幅の大きな列電極３（例えば列電極３ｄ）を光放出箇所（端面１ａ’）に近い位置に、また、重みの小さい、即ち、幅の小さな列電極３（例えば列電極３ａ）を光放出箇所から遠い位置（対向端面１ｂ側）に配することにより、各発光領域で発光箇所のそれぞれの発光強度差を良好に反映したまま光放出箇所から放出される光の強度の重み付けを行うことができる。光放出箇所において所望の重み付けで光が放出されるための、列電極３の制御（例えば、製造上の制御）を容易にすることができる。
【００８８】
【発明の効果】
本発明の光プリントヘッドは、以上のように、上記光放出箇所のそれぞれに対応して設けられ上記光放出箇所から光が入力される各導波路が、１つの光入力用導波路と複数の光出力用導波路のそれぞれとが上記光出力用導波路ごとに設けられた光透過と光遮断とを切り換え可能な光スイッチで接続されている各分岐点で分岐されることにより、複数の分岐経路が形成されており、上記各光放出箇所から放出される光を、複数の上記分岐経路で選択的に導波して上記被露光体へ照射することにより、上記被露光体上での露光解像度を上記所定解像度とする光分岐手段を備えている構成である。
【００８９】
それゆえ、被露光体上の露光像を発光素子の光放出箇所の数よりも多い露光対象点で形成することができるので、発光素子の光放出箇所の数で制限されていた露光解像度を越える高い露光解像度を容易に得ることができるという効果を奏する。
【００９０】
また、発光素子の各光放出箇所の駆動回路を、露光解像度分だけ設ける場合に比べて少なくすることができるという効果を奏する。さらに、発光素子の各光放出箇所の面積を、光放出箇所の数を露光解像度分だけ設ける場合に比べて大きくすることができるので、各光放出箇所から放出される光エネルギーを十分に確保することができるという効果を奏する。さらに、光分岐手段の末端に導波路を設けて、光分岐手段により得た光を該導波路から被露光体に照射するようにすれば、被露光体への照射光の指向性が向上するという効果を奏する。
【００９１】
さらに本発明の光プリントヘッドは、以上のように、上記光分岐手段において、上記各分岐点で上記光スイッチによって上記光入力用導波路が２つの上記光出力用導波路に接続されている構成である。
【００９２】
それゆえ、分岐の場合分けが少なくて制御が容易であるという効果を奏する。特に、各分岐点で２つの光スイッチの一方で光透過させ、他方で光遮断する場合には、上記２つの光スイッチの光透過および光遮断を２値で制御することができ、制御が非常に容易になるという効果を奏する。また、各光出力用導波路を次の分岐点での光入力用導波路とするように分岐を縦列にｎ段行えば、発光素子の１つの光放出箇所に対して被露光体への光照射箇所を２_n 個得ることができるという効果を奏する。
【００９３】
さらに本発明の光プリントヘッドは、以上のように、上記光分岐手段は、上記各分岐点でいずれか一方の上記光スイッチで上記光透過を行い、他方の上記光スイッチで上記光遮断を行う場合に、上記光入力用導波路と上記光遮断を行う上記光スイッチとの境界面に入射する上記光入力用導波路からの光の大部分を全反射させて、上記光透過を行う上記光スイッチ内に入射させる構成である。
【００９４】
それゆえ、光透過と光遮断とで明確な光量の差が得られるので、被露光体への露光と非露光とのコントラストが大きくなり、良好な露光像を得ることができるという効果を奏する。
【００９５】
さらに本発明の光プリントヘッドは、以上のように、上記光スイッチは、加えられる熱による状態変化によって、上記光入力用導波路から複数の上記光出力用導波路のそれぞれへの上記光透過および上記光遮断が制御される構成である。
【００９６】
それゆえ、装置の振動や、露光像劣化、騒音を防止することができるとともに、光透過と光遮断とを高速に切り換えることができるという効果を奏する。また、サーマルヘッドと同様のリソグラフィー技術で光スイッチを製造することができるとともに長い光路長が不要であるので、微細化が容易であり、高い露光解像度を実現することができるという効果を奏する。
【００９７】
さらに本発明の光プリントヘッドは、以上のように、上記光スイッチは、液体状態と気体状態とが切り換わる材料が上記光入力用導波路と複数の上記光出力用導波路のそれぞれとの接続部に設けられたものであり、上記液体状態と上記気体状態との間の屈折率変化によって、上記接続部の上記光透過および上記光遮断とが制御される構成である。
【００９８】
それゆえ、液体状態と気体状態との間の大きな屈折率変化によって、光透過と光遮断とを明確に切り換えることができるので、被露光体への露光と非露光とのコントラストが大きくなり、良好な露光像を得ることができるという効果を奏する。また、特に応答性に優れた光スイッチングを行うことができるという効果を奏する。
【００９９】
さらに本発明の光プリントヘッドは、以上のように、上記発光素子はエレクトロルミネッセンス素子である構成である。
【０１００】
それゆえ、発光素子の駆動電極などで光分岐手段に入力する光の導波路を兼ねる構造が可能となり、全体の構成を簡略化することができるという効果を奏する。
【０１０１】
さらに本発明の光プリントヘッドは、以上のように、上記エレクトロルミネッセンス素子は、上記各光放出箇所が設けられるとともに上記エレクトロルミネッセンス素子の各層の積層面と垂直な端面と、上記光放出箇所ごとに対応して複数の発光箇所のそれぞれでの発光光が上記光放出箇所まで上記端面と略垂直な導波方向で導波されるように上記導波方向に沿って設けられた発光領域と、上記発光領域の上記発光箇所の発光を駆動するとともに選択的に駆動されると選択単位ごとに上記発光箇所が変化するように設けられた駆動電極とを備えている構成である。
【０１０２】
それゆえ、エレクトロルミネッセンス素子の使用時期に応じて、選択する駆動電極を順次切り換えるようにすれば、発光領域の発光箇所も順次切り換わるので、ある駆動電極に対応して発光する発光箇所が寿命になっても、異なる発光箇所を続けて使用することができ、発光素子全体としての寿命を延ばすことができるという効果を奏する。
【０１０３】
また、選択単位ごとの駆動電極を組み合わせて選択することにより、各発光領域において異なる発光箇所を同時に発光させることができるので、光放出箇所から放出される光の強度を変えることができ、被露光体への露光量を段階的に切り換えることができるという効果を奏する。さらに、発光領域は端面と略垂直な導波方向に沿って設けられるので、同じ光放出箇所に対して発光領域を導波方向に沿って上記端面と反対側に任意に大きくすることができ、光放出箇所の大きさに制限されずに光放出箇所から放出される光の強度を大きくすることができるという効果を奏する。
【０１０４】
さらに本発明の光プリントヘッドは、以上のように、上記発光領域において、
上記駆動電極の選択単位ごとに上記発光箇所の発光強度が変化する構成である。
【０１０５】
それゆえ、光放出箇所から放出される光の強度に重み付けがなされることとなるので、選択する駆動電極を複数通りに組み合わせることにより、発光領域において駆動電極の選択単位ごとに発光する発光箇所の数が少なくても、被露光体への露光量をきめ細かく段階的に切り換えることができるという効果を奏する。
【０１０６】
さらに本発明の光プリントヘッドは、以上のように、上記発光領域において、上記駆動電極の選択単位ごとに発光する上記発光箇所が上記端面に近いほど発光強度が大きい構成である。
【０１０７】
それゆえ、発光箇所のそれぞれの発光強度差を良好に反映したまま光放出箇所から放出される光の強度の重み付けを行うことができ、重み付けの制御が容易になるという効果を奏する。
【０１０８】
さらに本発明の光プリントヘッドは、以上のように、上記エレクトロルミネッセンス素子と上記光分岐手段とが同一の基板上に形成されている構成である。
【０１０９】
それゆえ、簡素な構成となるので、各部の高い組み立て精度を確保することができ、特に、被露光体の露光領域が大きくなるような大きな光プリントヘッドを容易に得ることができるという効果を奏する。
【図面の簡単な説明】
【図１】 本発明の一実施の形態に係る光プリントヘッドの構成を示すブロック図である。
【図２】 図１の光プリントヘッドのＥＬ素子におけるＡ−Ａ線矢視断面図である。
【図３】 図１の光プリントヘッドのＥＬ素子における発光を説明する断面図である。
【図４】 図１の光プリントヘッドのＥＬ素子における発光光の導波を説明する説明図である。
【図５】 （ａ）および（ｂ）は、図１の光プリントヘッドのＥＬ素子の特性を示すグラフである。
【図６】 図１の光プリントヘッドの光分岐部の構成を示す平面図である。
【図７】 （ａ）および（ｂ）は、図６の光分岐部における光スイッチの動作を説明する平面図である。
【図８】 （ａ）は図６の光分岐部におけるＢ−Ｂ線矢視断面図、（ｂ）は図６の光分岐部におけるＣ−Ｃ線矢視断面図、（ｃ）は図６の光分岐部におけるＤ−Ｄ線矢視断面図である。
【図９】 （ａ）ないし（ｄ）は、図１の光プリントヘッドのＥＬ素子の製造工程を説明する断面図、（ｅ）は（ｄ）のＥ−Ｅ線矢視断面図である。
【図１０】 図１の光プリントヘッドのＥＬ素子の他の構成を示す平面図である。
【符号の説明】
１ ＥＬ素子（発光素子、エレクトロルミネッセンス素子）
１’ ＥＬ素子（発光素子、エレクトロルミネッセンス素子）
１ａ 端面
１ａ’ 端面
８ 光分岐部（光分岐手段）
９ 被露光体
１０ 基板
８１ 光入力用導波路（導波路）
８２ 光スイッチ
８３ 光スイッチ
８５ 光出力用導波路
８６ 光出力用導波路
１０１ 光プリントヘッド[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical print head that exposes an object to be exposed with a predetermined resolution using a light emitting element, and more particularly to an optical print head used for exposure in an electrophotographic image forming apparatus such as a copying machine, a printer, or a facsimile. It is about.
[0002]
[Prior art]
In general, an electrophotographic image forming apparatus (electrophotographic apparatus) such as a copying machine, a printer, or a facsimile has an exposure apparatus such as an LSU (laser beam scanner unit), a photosensitive drum, and a developing apparatus. Here, the exposure apparatus forms an electrostatic latent image on the surface of the photosensitive drum by irradiating the rotating photosensitive drum with laser light. The developing device develops (visualizes) the electrostatic latent image by supplying toner to the photosensitive drum. Further, the surface of the photosensitive drum is uniformly charged to a predetermined potential by a charging member such as a charging roller.
[0003]
In the image forming apparatus, first, the surface of the photosensitive drum uniformly charged to a predetermined potential is exposed by laser light from the exposure apparatus. As a result, an electrostatic latent image corresponding to image data (image signal) input from the outside is formed on the surface of the photosensitive drum. Then, toner is adhered to the electrostatic latent image on the photosensitive drum by the developing roller in the developing device, and the electrostatic latent image is developed to form a toner image (visible image).
[0004]
Thus, the exposure apparatus needs to irradiate the photosensitive drum with light in order to form an electrostatic latent image on the surface of the photosensitive drum. For this reason, an optical print head equipped with a light emitting element is required. Provided.
[0005]
The optical print head includes a light emitting element provided with a laser diode provided on the LSU as described above and scanning the photosensitive drum one line at a time through the polygon mirror, or in the line direction to the photosensitive drum. And the like having an LED array that collectively performs the exposure. Recently, as such a light-emitting element, an electroluminescence (hereinafter referred to as EL) element has attracted attention. Optical print heads that utilize the edge emission of EL elements have already been commercialized. The LED array and the EL element have a plurality of light emitting portions, and the photosensitive drum is exposed at a predetermined resolution by irradiating light to different areas of the photosensitive drum for each light emitting portion.
[0006]
In addition to the light emitting element for exposure in the image forming apparatus, the EL element is also used as a light emitting element such as a backlight in a display element of an OA device such as a word processor or a personal computer. An EL element using an organic EL layer that can be made simple has attracted attention. The organic EL display element, which is a display element using the organic EL layer, is a very promising technology as a flat panel display, but at the same time has problems such as a short lifetime.
[0007]
Therefore, as an organic EL display element for extending the life, for example, Japanese Patent Application Laid-Open No. 10-233285 describes a planar light emitting element using comb electrodes. In this flat light emitting device, a pair of electrodes is formed on a substrate with an organic EL layer interposed therebetween. One of the electrodes is a comb electrode and is an independent electrode arranged so as not to overlap each other. The other electrode is a full surface electrode.
[0008]
In the planar light emitting element, light generated in the organic EL layer is extracted from a plane parallel to the substrate (becomes surface emitting). In addition, by having a comb electrode, that is, a plurality of independent electrodes, the electrode can be switched every time the organic EL cannot be used. That is, the lifetime of the planar light emitting element can be extended as a whole by sequentially scanning the plurality of independent electrodes. Further, when the electrodes are switched, a surface that does not emit light is generated, and the light emission location fluctuates. In order to cope with this, light is scattered using a scattering plate.
[0009]
[Problems to be solved by the invention]
However, in a conventional optical print head equipped with a light emitting element such as an LED array or an EL element for exposing the object to be exposed at a predetermined resolution by irradiating light to different areas of the object to be exposed for each light emission location However, the exposure resolution is limited by the number of light emitting portions built into the light emitting element, and there is a problem that a higher resolution cannot be easily obtained. In particular, with respect to EL elements, a technique for maintaining uniform light emission over the entire surface in accordance with a long life in a surface-emitting structure as disclosed in the above publication is disclosed, but many can be driven independently. It was not possible to obtain a high light emission resolution by providing a light emitting portion.
[0010]
The present invention has been made in view of the above-described conventional problems, and an object thereof is to expose an object to be exposed at a predetermined resolution by irradiating light to different areas of the object to be exposed at each light emission location. It is an object of the present invention to provide an optical print head that can easily obtain a high exposure resolution exceeding the exposure resolution that is limited by the number of light emitting portions of the light emitting element, while including the light emitting element.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problems, an optical print head according to the present invention includes a light emitting element, and an object to be exposed is different for each light emitting portion using light emitted from each predetermined light emitting portion of the light emitting element. In the optical print head that exposes the object to be exposed at a predetermined resolution by irradiating the region with light, each waveguide provided corresponding to each of the light emission locations and receiving light from the light emission locations is provided. Each branch in which one optical input waveguide and each of a plurality of optical output waveguides are connected by an optical switch provided for each of the optical output waveguides that can switch between light transmission and light blocking. A plurality of branch paths are formed by branching at a point, and light emitted from each of the light emission locations is selectively guided through the plurality of branch paths to irradiate the object to be exposed. By the above exposure The exposure resolution of the above is characterized in that it comprises a light branching means to the predetermined resolution.
[0012]
According to the above invention, the light splitting means selectively guides the light emitted from each light emitting portion of the light emitting element through the branch path and irradiates the object to be exposed. Exposure is performed with the exposure resolution set to a predetermined resolution. In the optical branching means, one optical input waveguide and each of a plurality of optical output waveguides are connected by optical switches provided for each optical output waveguide and capable of switching between light transmission and light blocking. ing. In the exposure and non-exposure at each exposure target point in the region of the object to be exposed corresponding to each light emission location, light is input from the light emission location to the waveguide provided corresponding to each light emission location. Determined by selectively guiding light through the branch path by transmitting or blocking light from one optical input waveguide to each of a plurality of optical output waveguides at each branch point by an optical switch. To do. Accordingly, an exposure image on the object to be exposed can be formed with more exposure target points than the number of light emitting portions of the light emitting element, and thus the exposure resolution that is limited by the number of light emitting portions of the light emitting element is high. The exposure resolution can be easily obtained.
[0013]
In addition, it is possible to reduce the number of drive circuits for each light emission portion of the light emitting element as compared with the case of providing the exposure resolution. Furthermore, since the area of each light emitting portion of the light emitting element can be increased as compared with the case where the number of light emitting portions is provided by the exposure resolution, sufficient light energy emitted from each light emitting portion is ensured. be able to. Furthermore, if a waveguide is provided at the end of the light branching means and the object to be exposed is irradiated with the light obtained by the light branching means, the directivity of the irradiated light to the object to be exposed is improved. .
[0014]
Furthermore, in order to solve the above problems, the optical print head of the present invention is configured such that, in the optical branching means, the optical input waveguide is connected to the two optical output waveguides by the optical switch at each branch point. It is characterized by having.
[0015]
According to the above invention, since one optical input waveguide is connected to two optical output waveguides by two optical switches at each branch point, there are few cases of branching and control is easy. . In particular, when light is transmitted through one of the two optical switches at each branching point and light is blocked at the other, the light transmission and light blocking of the two optical switches can be controlled with two values, and the control is very To be easier. Further, if n stages of branches are arranged in a column so that each light output waveguide becomes a light input waveguide at the next branch point, light to the object to be exposed can be emitted to one light emitting portion of the light emitting element. 2 irradiated points _n Can be obtained.
[0016]
Furthermore, in the optical print head of the present invention, in order to solve the above problems, the optical branching means transmits the light with one of the optical switches at each branch point, and the optical switch with the other optical switch. When blocking, the light input from the optical input waveguide that is incident on the interface between the optical input waveguide and the optical switch that performs the optical blocking is totally reflected to transmit the light. It is made to enter in the said optical switch to perform.
[0017]
According to the above invention, at each branch point, when one of the optical switches transmits light and the other optical switch blocks light, the optical input waveguide and the optical switch that blocks light are Most of the light from the optical input waveguide incident on the boundary surface is totally reflected, is incident in the optical switch that transmits light, and directly enters the optical switch that transmits light from the optical input waveguide. Add to light. Accordingly, a clear difference in light quantity can be obtained between light transmission and light blocking, so that the contrast between exposure to the object to be exposed and non-exposure is increased, and a good exposure image can be obtained.
[0018]
Furthermore, in order to solve the above-described problems, the optical printhead according to the present invention is configured so that the optical switch is configured to change the optical input waveguide from the optical input waveguide to each of the plurality of optical output waveguides by a change in state caused by applied heat. The light transmission and the light blocking are controlled.
[0019]
According to the above invention, since the optical switch controls light transmission and light blocking from the light input waveguide to each of the plurality of light output waveguides by a change in state due to applied heat, vibration of the device, Exposure image deterioration and noise can be prevented, and light transmission and light blocking can be switched at high speed. In addition, the optical switch can be manufactured by the same lithography technique as that of the thermal head, and a long optical path length is unnecessary, so that miniaturization is easy and high exposure resolution can be realized.
[0020]
Furthermore, in order to solve the above-described problems, the optical print head according to the present invention is configured so that the optical switch is made of a material for switching between a liquid state and a gas state, each of the optical input waveguide and the plurality of optical output waveguides. The light transmission and the light blocking of the connection part are controlled by a change in refractive index between the liquid state and the gas state.
[0021]
According to the above invention, the refractive index change between the liquid state and the gas state is large, and the optical switch can clearly switch between light transmission and light blocking by this refractive index change. The contrast between exposure and non-exposure is increased, and a good exposure image can be obtained. In addition, optical switching with particularly excellent responsiveness can be performed.
[0022]
Furthermore, in order to solve the above problems, the optical print head of the present invention is characterized in that the light emitting element is an electroluminescence element.
[0023]
According to the above invention, since the light-emitting element is an electroluminescence element, a structure that also serves as a waveguide of light input to the light branching means by the drive electrode of the light-emitting element can be realized, and the entire configuration can be simplified. it can.
[0024]
Furthermore, in order to solve the above-described problems, the optical print head according to the present invention includes the electroluminescence element, wherein each of the light emission portions is provided, and an end surface perpendicular to the laminated surface of each layer of the electroluminescence element, and the light emission. A light emitting region provided along the waveguide direction so that light emitted from each of a plurality of light emitting locations is guided in a waveguide direction substantially perpendicular to the end face to the light emitting location corresponding to each location. And a drive electrode provided to drive the light emission at the light emission location in the light emission region and to change the light emission location for each selected unit when driven selectively.
[0025]
According to the above invention, each light emitting region provided in the electroluminescent element corresponding to each light emission location is driven to emit light by the drive electrode, and the emitted light at each light emitting location of the light emitting region is emitted from the electroluminescent device. The light is guided in a direction substantially perpendicular to the end face at each of the light emission locations provided on the end face perpendicular to the laminated surface of each layer. Here, the drive electrode is selectively driven, and the light emission location of the light emission region changes for each selected unit. Therefore, if the drive electrodes to be selected are sequentially switched according to the use period of the electroluminescent element, the light emission locations in the light emitting region are also sequentially switched, so that the light emission locations that emit light corresponding to a certain drive electrode have a lifetime. However, different light emission locations can be used continuously, and the lifetime of the entire light emitting element can be extended.
[0026]
In addition, by selecting a combination of drive electrodes for each selection unit, different light emission locations can be simultaneously emitted in each light emission region, so that the intensity of light emitted from the light emission location can be changed, and exposure is performed. The exposure amount to the body can be switched stepwise. Furthermore, since the light emitting region is provided along the waveguide direction substantially perpendicular to the end surface, the light emitting region can be arbitrarily enlarged on the opposite side of the end surface along the waveguide direction with respect to the same light emission location, The intensity of light emitted from the light emission location can be increased without being limited by the size of the light emission location.
[0027]
Furthermore, in order to solve the above-described problems, the optical print head of the present invention is characterized in that the light emission intensity of the light emission portion changes in the light emission region for each selected unit of the drive electrode.
[0028]
According to the invention described above, in the light emitting region, the light emission intensity at the light emission location changes for each selected unit of the drive electrode, that is, the intensity of light emitted from the light emission location changes. For this purpose, for example, the area of the drive electrode that determines the size of the light emitting portion is changed for each selected unit. Since the intensity of light emitted from the light emission location is weighted, the number of light emission locations that emit light for each selected unit of the drive electrode in the light emission region is reduced by combining a plurality of drive electrodes to be selected. However, it is possible to switch the exposure amount to the object to be exposed in a fine stepwise manner.
[0029]
Furthermore, in order to solve the above-mentioned problems, the optical print head of the present invention is characterized in that the light emission intensity increases as the light emitting portion emitting light for each selected unit of the drive electrode is closer to the end face in the light emitting region. .
[0030]
According to the above invention, in the light emitting region, the light emission intensity is increased as the light emitting portion emitting light for each selected unit when the drive electrode is selectively driven is closer to the end face. Since light from a light emitting location far from the light emitting location is attenuated and guided to the light emitting location, the above configuration allows the light emitting location to reflect the difference in light emission intensity of each light emitting location. The intensity of emitted light can be weighted, and the weighting can be easily controlled.
[0031]
Furthermore, the optical print head of the present invention is characterized in that the electroluminescence element and the light branching means are formed on the same substrate in order to solve the above-mentioned problems.
[0032]
According to the above invention, since the electroluminescence element and the light branching unit are formed on the same substrate, the structure becomes simple, so that high assembling accuracy of each part can be ensured. It is possible to easily obtain a large optical print head having a large exposure area.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment embodying the optical print head of the present invention will be described as follows with reference to FIGS.
[0034]
FIG. 1 shows a configuration of an optical print head 101 according to the present embodiment. The optical print head 101 is provided in an exposure apparatus of an electrophotographic image forming apparatus (electrophotographic apparatus) such as a copying machine, a printer, and a facsimile, and includes an EL element 1, driving circuits 6... Part 8 is provided.
[0035]
The EL element (light emitting element) 1 includes line-like row electrodes 2... And column electrodes 3. The row electrodes 2... And the column electrodes 3 are opposed to each other across the light emission locations, and a plurality of light emission locations are provided perpendicular to each other so as to be arranged in a matrix. A plurality of light emitting portions under one row electrode 2 form one light emitting region. The light emitted from each light emitting region is guided by the row electrode 2 to one end face 1a perpendicular to the laminated surface of each layer of the EL element 1, and the waveguide termination on the end face 1a corresponding to each row electrode 2 emits light. It becomes a place. Further, the EL element 1 includes a reflecting plate 4 and an optical sensor 5. The reflection plate 4 is provided on the opposing end surface 1b facing the end surface 1a of the EL element 1, and reflects the emitted light of the light emitting region guided to the opposing end surface 1b side to the end surface 1a side with a predetermined reflectance. To do. Further, the optical sensor 5 is provided in contact with the outside of the reflecting plate 4 and detects the amount of light emitted from the light emitting region that has passed through the reflecting plate 4.
[0036]
By providing the optical sensor 5, the light emission level of the EL element 1 can be detected. Therefore, for example, by controlling the voltage applied to the row electrode 2 and the column electrode 3 based on the detection result of the optical sensor 5, stable light emission can be performed. In addition, by detecting the light emission level, the degree of decrease in the light emission level, that is, the lifetime can be detected. Thereby, the column electrode 3 to be driven can be switched at an appropriate timing, and as a result, the life of the entire EL element 1 can be extended.
[0037]
Further, each of the drive circuits 6 is connected to one of the column electrodes 3 to drive each column electrode 3 independently. Each of the drive circuits 7 is connected to one of the row electrodes 2 to drive each row electrode 2 independently. Light emitting portions sandwiched between the column electrodes 3... And the row electrodes 2... Selectively driven by the drive circuits 6. Further, the light branching portion 8 is provided adjacent to the end face 1a of the EL element 1, branches the light emitted from each light emitting portion on the end face 1a, and irradiates the object 9 such as a photoconductor. It is like that. The optical branching unit 8 will be described in detail later.
[0038]
Next, the EL element 1 will be described in detail with reference to FIG. 2, which is a cross-sectional view taken along line AA in FIG. 1. The cross-sectional view of FIG. 2 shows a cross section of one light emitting region. As shown in the figure, the EL element 1 includes an organic EL layer 12 and a protective film 11 on a substrate 10 in addition to the row electrodes 2 and the column electrodes 3. In addition, the reflecting plate 4 covers the entire facing end surface 1 b including the end surface of the substrate 10, and the optical sensor 5 is in contact with the entire reflecting plate 4.
[0039]
The substrate 10 is a support substrate made of glass, for example. The column electrodes 3 are made of aluminum and are arranged on the upper surface of the substrate 10 in parallel with each other. Each of the organic EL layers 12 is provided on one column electrode 3, and is composed of a hole injection layer 12a, a hole transport layer 12b, an electron transport / light emitting layer 12c, and an electron injection layer 12d in this order from the top. ing. The hole injection layer 12a is made of CuPc, the hole transport layer 12b is made of a-NPD, the electron transport / light emitting layer 12c is made of Alq3, and the electron injection layer 12d is made of LiF. The row electrodes 2 are transparent electrodes made of ITO (Indium-Tin-Oxide) and are provided on the substrate 10 and the column electrodes 3. The row electrodes 2... Extend in a direction substantially perpendicular to the end face 1 a, and the column electrodes 3... Extend in a direction perpendicular to the row electrodes 2. The protective film 11 is made of an ultraviolet curable acrylic resin, and is provided so as to cover the row electrodes 2, the column electrodes 3, and the organic EL layer 12.
[0040]
The configuration of the organic EL layer 12 is not particularly limited to the above-described configuration, and may be formed of a single thin film or a plurality of thin films as long as it includes at least a light emitting layer. It doesn't matter.
[0041]
Hereinafter, light emission in the organic EL layer 12 and light emission from the EL element 1 will be described.
[0042]
First, the principle of light emission in the organic EL layer 12 will be described with reference to FIG.
[0043]
When a DC voltage is applied to the organic EL layer 12 by the drive circuits 6 and 7 using the row electrode 2 as an anode and the column electrode 3 as a cathode, holes are transported from the hole injection layer 12a through the hole transport layer 12b. It is injected into the light emitting layer 12c. On the other hand, electrons are injected from the electron injection layer 12d into the electron transport / light emitting layer 12c. When electrons and holes are injected into the electron transport / light emitting layer 12c, the electron transport / light emitting layer 12c emits light by recombination of the holes and electrons. Therefore, when a voltage is applied, the electron transport / light emitting layer 12c is in a light emitting state, and emits light in all directions as shown in FIG.
[0044]
The material of the light emitting layer (here, electron transport / light emitting layer 12c) in the organic EL layer 12 is not particularly limited as long as it is an organic compound that can be used as a light emitting material. Moreover, as long as the row electrode 2 and the column electrode 3 can be utilized as an electrode for causing the organic EL layer 12 to emit light, these materials are not particularly limited. However, when light passes through the row electrode 2, the row electrode 2 is made of a light-transmitting material.
[0045]
Next, emission of light from the EL element 1 will be described with reference to FIGS. 3 and 4.
[0046]
Usually, as shown in FIG. 4, when the low refractive index body 51 having a refractive index n1 and the high refractive index body 52 having a refractive index n2 are arranged so as to contact each other, the light in the high refractive index body 52 is When the light is incident on the surface where the high refractive index body 52 and the low refractive index body 51 are in contact with each other, total reflection is performed depending on the incident angle. Here, the refractive indexes n1 and n2 satisfy n1 <n2. For example, the incident angle of light from the high refractive index body 52 to the low refractive index body 51 is θ1, and the incident angle from the high refractive index body 52 to the outside (air layer) is θ2. At this time, when the incident angles θ 1 and θ 2 exceed the critical angle, the light is totally reflected and is not emitted from the high refractive index body 52. That is, the light continues to pass through the high refractive index body 52.
[0047]
Here, the refractive index of the member (material) constituting the EL element 1 is shown in Table 1 together with the material, dimensions, manufacturing method, and the like.
[0048]
[Table 1]

[0049]
As shown in Table 1 above, the refractive index of the row electrode 2 made of ITO is 2.00. The refractive index of the substrate 10 made of glass adjacent to the row electrode 2 is 1.45, and the refractive index of the protective film 11 made of acrylic resin is 1.4. As described above, the row electrode 2 having a higher refractive index than the substrate 10 and the protective film 11 is sandwiched between the substrate 10 and the protective film 11 having a lower refractive index than the row electrode 2.
[0050]
Therefore, the emitted light from the electron transport / light emitting layer 12 c shown in FIG. 3 first passes through the row electrode 2. Then, it reaches the boundary surface with the substrate 10 or the protective film 11. Here, since the substrate 10 and the protective film 11 have a lower refractive index than that of the row electrode 2, the critical angle of the light incident on the boundary surface between the row electrode 2 and the substrate 10 or the protective film 11 from the row electrode 2. The light incident beyond the point is totally reflected and transmitted through the row electrode 2 again. For example, when the row electrode 2 is made of ITO and the substrate 10 is made of glass, the critical angle at which light is totally reflected in the row electrode 2 is 46 ° at the boundary surface between the row electrode 2 and the substrate 10.
[0051]
Thus, while repeating total reflection at the boundary surface between the row electrode 2 and the substrate 10 or the protective film 11, the emitted light from the electron transport / light emitting layer 12c is guided through the row electrode 2 and reaches the end surface 1a. At this time, of the light reaching the end face 1a, light incident on the end face 1a at an angle smaller than the critical angle is directed from the row electrode 2 to the outside (from the EL element 1 to the outside), that is, toward the light branching section 8. Released.
[0052]
Further, the emitted light guided through the row electrode 2 from the electron transport / light emitting layer 12c in the direction of the reflecting plate 4 is reflected by the reflecting plate 4 and thus guided to the end face 1a. That is, by disposing the reflecting plate 4 on the opposing end surface 1b, the amount of light emitted from the end surface 1a can be increased, and the light extraction efficiency can be improved.
[0053]
FIG. 5A shows the relationship between the applied voltage and the luminance with respect to a light emitting portion of the EL element 1, and FIG. 5B shows the relationship between the applied voltage and the current with respect to the light emitting portion of the EL element 1.
[0054]
As described above, the optical print head 101 that exposes the object to be exposed 9 by irradiating light has a light-transmitting property with the organic EL layer 12 on the substrate 10 corresponding to one light emitting region. The row electrode 2 is made of a material having a higher refractive index of light than the substrate 10 and applies a voltage to the organic EL layer 12 and a plurality of independent electrodes, and the row is sandwiched between the organic EL layers 12. A column electrode 3... Which is arranged to face the electrode 2 and applies a voltage to the organic EL layer 12 together with the row electrode 2, and is arranged so as to cover the row electrode 2 and has a light refractive index higher than that of the row electrode 2. The light emitted from the organic EL layer 12 by selectively driving a plurality of electrodes in the column electrodes 3... Is transmitted through the row electrode 2, and the light-emitting element 1. From the end face 1a.
[0055]
Next, the optical branching unit 8 in FIG. 1 will be described with reference to FIGS.
[0056]
FIG. 6 shows the configuration of the optical branching unit 8. The light branching section (light branching means) 8 includes a plurality of branching waveguide sections 20. Each branching waveguide portion 20 is coupled to the end portion of the row electrode 2 which is a light emission location on the end face 1 a of the EL element 1. The branching waveguide unit 20 includes optical input waveguides (waveguides) 81 coupled to the end portions of the row electrodes 2 corresponding to the respective light emission locations of the EL element 1. The optical switch 82 is connected to the optical output waveguide 85, and the optical switch 83 is connected to the optical output waveguide 86. The optical switches 82 and 83 are filled with liquid benzene. When heated, the optical switches 82 and 83 become gaseous benzene and the internal refractive index changes. In order to perform this heating, a heater 89 (described later) made of HfB2 having a thickness of 0.15 .mu.m is provided. Further, an extraction electrode 84 (FIG. 6) on the common side of an electrode 88 (described later) provided for supplying power to the heater 89 is provided. Further, the expansion of the gaseous benzene is retreated in a separate chamber (not shown).
[0057]
The optical input waveguide 81 and the optical output waveguides 85 and 86 are made of ultraviolet curable resin, and the refractive index thereof is smaller than that of liquid benzene and larger than that of gaseous benzene. The light input to the light input waveguide 81 from the light emitting portion of the EL element 1 is transmitted through the optical switches 82 and 83 when the interior is in a liquid benzene state due to the heater 84 being turned off. Light is guided to the optical output waveguides 85 and 86. Conversely, when the optical switches 82 and 83 are heated by turning on the heater 84 and the inside is in a gaseous benzene state, light is blocked, so that no light is guided to the light output waveguides 85 and 86. The optical switches 82 and 83 can switch between light transmission and light blocking independently, and the light input waveguide 81 is selected at the branch point. Accordingly, as shown in FIG. 7A, when both of the optical switches 82 and 83 are liquid benzene, the light in the light input waveguide 81 is branched and guided to the light output waveguides 85 and 86. The Further, as shown in FIG. 7B, when the inside of the optical switch 82 is liquid benzene and the inside of the optical switch 83 is gaseous benzene, the light in the light input waveguide 81 is guided only to the light output waveguide 85. The wave is not guided to the light output waveguide 86.
[0058]
In this way, one optical input waveguide 81 is connected to the two optical output waveguides 85 and 86 by the optical switches 82 and 83, so that one waveguide is branched into two. Further, as shown in the figure, the optical output waveguides 85 and 86 are optical input waveguides for the next branch points, respectively, and two more optical switches are used by the same optical switch as the optical switches 82 and 83, respectively. The optical output waveguide (same as the optical input waveguide 81 and the optical output waveguides 85 and 86) is connected to branch. In the case of the figure, each branching waveguide section 20 is branched into two stages to form four branch paths. _n Branch paths will be formed. The number of branch paths is the end of the optical output waveguide at the end of each branch waveguide section 20, that is, the number of irradiation ports that can irradiate light from each branch waveguide section 20 to the object 9 in FIG. 1. is there. Therefore, in the case of FIG. 6, the total number of irradiation ports of the light branching portion 8 is four times the number of light emitting portions of the EL element 1, and 2 in each branching waveguide portion 20. _n When there are multiple branch paths, the total number of irradiation ports of the light branching unit 8 is 2 which is the number of light emitting portions of the EL element 1. _n Doubled.
[0059]
In the optical print head 101 according to the present embodiment, the row electrodes 2 are sequentially selected by the drive circuit 7 and are driven in time series. Therefore, during one selection period of each row electrode 2, The light that is input from the EL element 1 through the branch path in the light transmission state, with one branch path of each branch waveguide unit 20 set in a light transmission state one by one and the other branch path in a light blocking state by one of the optical switches. Can be irradiated in order from each irradiation port. The optical print head 101 transmits light through one of the two optical switches at each branch point and blocks light at the other to make the light transmission state of each branch path one by one. In this case, since the light intensity at the time of light irradiation to each exposure target portion of the object to be exposed 9 is substantially equal to the intensity of light emitted from the light emitting portion of the corresponding EL element 1, the object to be exposed 9 is the photosensitive member. In such a case, a desired exposure image can be appropriately obtained.
[0060]
As the optical switches 82 and 83, in addition to the above-described thermal refractive index changing elements, optical switches using a translational micromirror, a rotating micromirror, PLZT, etc. configured as a micromachine, a thermocapillary switch, etc. But you can. In general, one optical input waveguide and a plurality of optical output waveguides may be connected by an optical switch provided corresponding to each of the plurality of optical output waveguides.
[0061]
Next, a cross-sectional view taken along a line BB, a cross-sectional view taken along a line C-C, and a cross-sectional view taken along a line D-D for one branching waveguide portion 20 in FIG. Shown in (c).
[0062]
FIG. 8A is a cross-sectional view of the EL element 1, in which the row electrode 2 is formed on the upper surface of the substrate 10, and the protective film 11 is formed so as to cover the row electrode. The refractive index of the row electrode 2 is larger than the refractive indexes of the substrate 10 and the protective film 11. In FIG. 8B, a light input waveguide 81 is formed on the upper surface of the substrate 10, and a protective film 87 is formed so as to cover the waveguide. The protective film 87 is made of an ultraviolet curable resin and has a refractive index smaller than that of the light input waveguide 81. The refractive index of the light input waveguide 81 is larger than the refractive index of the substrate 10. In FIG. 8C, electrodes 88 and 88 for heaters 89 and 89 provided for the optical switches 82 and 83, respectively, are formed on the upper surface of the substrate 10. The electrodes 88 and 88 are made of aluminum. The heaters 89 and 89 are formed on the upper surfaces of the electrodes 88 and 88, and optical switches 82 and 83 are formed on the upper surfaces of the electrodes 88 and 88. A protective film 87 is formed so as to cover all of these. The refractive index of the protective film 87 is smaller than the refractive index of liquid benzene inside the optical switches 82 and 83.
[0063]
As described above, the light branching portion 8 is formed on the same substrate 10 as the EL element 1. 8B and 8C, an insulating layer made of SiO2 having a thickness of about 1 .mu.m and a protective layer made of silicon nitride having a thickness of about 0.5 .mu.m are omitted.
[0064]
Here, Table 2 shows the relationship between the refractive indexes n1 and n2 defined in FIG. 4 and the critical angle θ1 or θ2 for each boundary where light enters. In the table, n3 represents the refractive index of a substance that transmits light at a critical angle θ2 or less from a substance having a refractive index n2.
[0065]
[Table 2]

[0066]
Note that the principle of refractive index guiding is the same as that described in the explanation of the EL element 1, and is omitted here. As shown in the table, when the incident angle of light from the optical input waveguide 81 to the optical switches 82 and 83 when the inside is gaseous benzene in the optical branching section 8 is 42.5 degrees or more, the light is light Total reflection occurs at the interface between the input waveguide 81 and the optical switches 82 and 83. Therefore, when one of the optical switches 82 and 83 transmits light and the other performs light blocking, most of the light entering the optical switch that performs light blocking from the light input waveguide 81 is The optical input waveguide 81 and the optical input waveguide 81 are incident on the boundary surface between the optical input waveguide 81 and the optical switch at a critical angle of 42.5 degrees or more and totally reflected, and enter the other optical switch. An angle formed by the boundary surface between the optical switches 82 and 83 is set. This angle also changes depending on the refractive index of the substance in the optical switches 82 and 83. Into the optical switch that performs light transmission, light that is directly incident from the optical input waveguide and light that is totally reflected by the other optical switch that performs light blocking are added and incident.
[0067]
By using the light branching section 8 having the above-described configuration, the optical print head 101 allows light emitted from the terminal on the end surface 1a of the row electrode 2 which is each predetermined light emitting portion of the EL element to pass through the branch path. As a sequential light transmission state, light is irradiated to a different area of the object to be exposed 9 for each of the light emission positions, and the object 9 is exposed with a predetermined resolution.
[0068]
Exposure and non-exposure at each exposure target point in the region of the object 9 corresponding to each light emission location are performed by transmitting light from the light input waveguide to the light output waveguide at each branch point by an optical switch. Alternatively, it is determined by blocking light and selectively guiding light through a branch path. Therefore, the exposure image on the object to be exposed 9 can be formed with more exposure target points than the number of light emitting portions of the EL element 1, so that the exposure resolution limited by the number of light emitting portions of the EL element 1 is achieved. High exposure resolution exceeding 1 can be easily obtained.
[0069]
In addition, it is possible to reduce the number of drive circuits for each light emission location of the EL element 1 as compared with the case where the exposure resolution is provided. Furthermore, since the area of each light emitting portion of the EL element 1 can be increased as compared with the case where the number of light emitting portions is provided by the exposure resolution, sufficient light energy emitted from each light emitting portion is ensured. can do. Further, since the light to be exposed 9 is irradiated from the light output waveguide at the end of the light branching portion 8 to the object to be exposed 9, the directivity of the irradiation light to the object to be exposed 9 is improved.
[0070]
Further, in the optical branching section 8, since one optical input waveguide is connected to two optical output waveguides by two optical switches at each branching point, there are few cases of branching and control is easy. is there. In particular, when light is transmitted through one of the two optical switches at each branch point and light is blocked at the other as in the present embodiment, the light transmission and light blocking of the two optical switches are controlled by binary values. Can be controlled easily. Also, in this case, most of the light from the optical input waveguide that is incident on the boundary surface between the optical input waveguide and the optical switch that cuts off the light is totally reflected to enter the optical switch that transmits light. In addition, since it is added to the light that directly enters the optical switch that transmits light from the optical input waveguide, a clear difference in light amount is obtained between light transmission and light blocking, and exposure to the object 9 to be exposed and non-exposure are performed. And a high exposure image can be obtained.
[0071]
The optical switch provided in the optical branching unit 8 transmits and transmits light from the optical input waveguide to each of the multiple optical output waveguides by a change in state between a liquid state and a gas state due to applied heat. Since the blocking is controlled, the vibration of the device, exposure image deterioration, and noise that can be seen when using an optical switch such as a method that moves the reflecting mirror can be prevented, and light transmission is better than with the reflecting mirror method. And light blocking can be switched at high speed. In addition, an optical switch can be manufactured by the same lithography technology as that of a thermal head, and a long optical path length as in the case of using PLZT is unnecessary, so that miniaturization is easy and high exposure resolution is realized. Can do.
[0072]
In the optical switch, a material that switches between a liquid state and a gas state, such as benzene, is provided at a connection portion between the light input waveguide and the plurality of light output waveguides. The refractive index change between the liquid state and the gas state is large, and the optical switch can clearly switch between light transmission and light blocking by this refractive index change. The contrast of the image becomes large, and a good exposure image can be obtained. In addition, optical switching with particularly excellent responsiveness can be performed.
[0073]
In addition, since the optical print head 101 uses the EL element 1 as a light emitting element, a structure that also serves as a waveguide for the light input to the optical branching portion 8 by the row electrodes 2... That are the drive electrodes of the EL element 1 is possible. Thus, the overall configuration can be simplified. The light emitting element may be an LED array, an EL element having a single light emission location, an LED, or a laser diode. However, the use of the EL element 1 eliminates the need for chip formation and assembly performed when using an LED array, LED, laser diode, or the like. That is, in the EL element 1, it is not necessary to prepare an optical waveguide for inputting light to the light branching unit 8 separately from the element, and the chip is attached to a glass substrate such as the substrate 10 and is made conductive. Wire bonding and the like are unnecessary and suitable for mass production.
[0074]
Further, each light emitting region provided in the EL element 1 corresponding to each light emission location is driven to emit light by driving electrodes such as row electrodes 2... And column electrodes 3. Is guided in a direction substantially perpendicular to the end face 1 a by the row electrode 2 to each of the light emission locations provided on the end face 1 a of the EL element 1. Here, the drive electrode is selectively driven, and the light emission location of the light emission region changes for each selected unit. Accordingly, if the drive electrodes to be selected are sequentially switched in accordance with the use period of the EL element 1, the light emission locations in the light emitting region are also sequentially switched, so that the light emission locations that emit light corresponding to a certain drive electrode have a lifetime. However, different light emission locations can be used continuously, and the lifetime of the entire EL element 1 can be extended.
[0075]
In addition, by selecting a combination of drive electrodes for each selection unit, different light emission locations can be simultaneously emitted in each light emission region, so that the intensity of light emitted from the light emission location can be changed, and exposure is performed. The exposure amount to the body 9 can be switched stepwise. Furthermore, since the light emitting region is provided along the waveguide direction substantially perpendicular to the end surface 1a, the light emitting region can be arbitrarily enlarged toward the opposite end surface 1b along the waveguide direction with respect to the same light emission location, The intensity of light emitted from the light emission location can be increased without being limited by the size of the light emission location.
[0076]
In addition, since the EL element 1 and the light branching portion 8 are formed on the same substrate 10, the optical print head 101 has a simple configuration, and thus high assembly accuracy of each portion can be ensured. Therefore, in particular, it is possible to easily obtain a large optical print head 101 that increases the exposure area of the object 9 to be exposed.
[0077]
Here, an example of the manufacturing process of the EL element 1 will be described with reference to FIG.
[0078]
First, a photoresist 61 is formed on the substrate 10 to a thickness of 2 μm by spin coating (FIG. 9A). Then, an Al film 66 is formed to a thickness of 150 nm using a vapor deposition method. Thereafter, the LiF film 65, the Alq3 film 64, the a-NPD film 63, and the CuPc film 62 are formed in this order by molecular beam evaporation (FIG. 9B). The film thicknesses at this time are 0.5 nm for the LiF film 65, 60 nm for the Alq3 film 64, 40 nm for the a-NPD film 63, and 30 nm for the CuPc film 62. Next, the resist 61 is removed. Thereby, the column electrode 3 patterned in a desired shape and the organic EL layer 12 including the hole injection layer 12a, the hole transport layer 12b, the electron transport / light emitting layer 12c, and the electron injection layer 12d are formed.
[0079]
Subsequently, an ITO film is formed to a thickness of 2000 nm so as to cover the entire surface of the substrate 10, and is patterned into a desired shape to form row electrodes 2 (FIG. 9C). Then, a protective film 11 is formed so as to cover the entire surface of the substrate 10, and an Al film is formed on the opposing end face 1b so as to cover the opposing end face 1b, thereby forming the reflector 4 (FIG. 9 (d)). Then, an optical sensor etc. are arrange | positioned as needed.
[0080]
Here, FIG. 9E is a cross-sectional view taken along the line E-E in FIG. That is, it is a cross-sectional view along a certain column electrode 3.
[0081]
In this way, the EL element 1 is formed. Accordingly, even if a plurality of column electrodes 3 are provided in one pixel, patterning into a desired shape can be performed with a simple process, and thus an optical print head excellent in mass productivity can be provided.
[0082]
Further, in the EL element 1 in the optical print head 101 shown in FIG. 1, the width of each column electrode 3 is uniform, but like the EL element 1 ′ shown in FIG. 10, the column electrodes 3a, 3b, 3c, and 3d. As described above, the width of each column electrode 3 may be changed. Here, the column electrode 3a has the smallest width and the column electrodes 3b, 3c, and 3d have a width that increases in order. Other than that, the configuration is the same as that of the EL element 1. The drive circuits 6 and 7 are not shown.
[0083]
By adopting such a configuration, in each light emitting region, the light emission intensity of the light emitting portion is selected for each selected unit that combines the corresponding row electrode 2 and one column electrode 3 of the column electrodes 3a, 3b, 3c, and 3d. Changes, that is, the intensity of light emitted from the light emission location changes. Thereby, each column electrode 3 can be weighted easily. Accordingly, the voltage applied to the row electrode 2 differs depending on each column electrode 3, and the light emission intensity in the electron transport / light emitting layer 12 c of the organic EL layer 12 can be weighted. For this reason, the gradation of the generated light can be changed by selecting and driving a plurality of these column electrodes 3a, 3b, 3c and 3d in combination. As a result, even if the number of light emitting portions that emit light for each selected unit of the drive electrode in each light emitting region is small, that is, even if the number of bits is small, the exposure amount to the object to be exposed 9 can be switched in a fine stepwise manner. Control, 256 gradation control can be performed with 8 bits.
[0084]
Further, as shown in FIG. 10, the column electrodes 3a, 3b, 3c, and 3d are arranged so that the width decreases as they move away from the end surface 1a ′ provided with the light emission portions, similarly to the end surface 1a of the EL element 1. It is preferable that That is, it is preferable that the weighting is performed so that the weight decreases as the distance from the end surface 1a ′ increases.
[0085]
In general, the longer the distance from the position where light is emitted to the position where it is emitted, the greater the amount of light attenuation. Therefore, for example, when the electrode of the light emitting portion that emits light is arranged at a position far from the light emitting portion, the amount of light attenuation increases. For this reason, in order to obtain a desired amount of light at the light emission location, it is necessary to manufacture the electrode larger than the electrode necessary for obtaining the light amount at the light emission location.
[0086]
However, as the distance from the end surface 1a ′ where the light emitting portion is provided is increased, the weight is reduced so that, for example, the light emitting portion is disposed at a position far from the light emitting portion. Even if it is necessary to manufacture the column electrode 3 (for example, the column electrode 3a) larger, if the weight is small, the column electrode 3 to be manufactured is compared with the case where a desired amount of light is obtained at the light emission location at the light emission location. The difference in size between the two is small.
[0087]
That is, a column electrode 3 having a large weight, that is, a column having a large width (for example, the column electrode 3d) is positioned close to the light emitting portion (end surface 1a ′), and a column electrode 3 having a small weight, that is, a column having a small width (for example, By disposing the column electrode 3a) at a position far from the light emission location (on the opposite end face 1b side), the light emitted from the light emission location can be well reflected in each light emission region while reflecting the difference in emission intensity of each light emission location. Intensity weighting can be performed. Control of the column electrode 3 (for example, control in manufacturing) for facilitating light emission with a desired weight at the light emission location can be facilitated.
[0088]
【The invention's effect】
As described above, the optical print head according to the present invention is provided corresponding to each of the light emission locations, and each of the waveguides to which light is input from the light emission location includes one optical input waveguide and a plurality of waveguides. Each of the light output waveguides is branched at each branch point connected by an optical switch that can switch between light transmission and light blocking provided for each of the light output waveguides, thereby allowing a plurality of branches. A path is formed, and light emitted from each of the light emission locations is selectively guided through the plurality of branch paths and irradiated to the object to be exposed, whereby exposure on the object to be exposed is performed. The optical branching means is provided with the resolution set to the predetermined resolution.
[0089]
Therefore, since an exposure image on the object to be exposed can be formed with more exposure target points than the number of light emitting portions of the light emitting element, the exposure resolution limited by the number of light emitting portions of the light emitting element is exceeded. There is an effect that a high exposure resolution can be easily obtained.
[0090]
In addition, there is an effect that it is possible to reduce the number of drive circuits for each light emission location of the light emitting element as compared with the case of providing the exposure resolution. Furthermore, since the area of each light emitting portion of the light emitting element can be increased as compared with the case where the number of light emitting portions is provided by the exposure resolution, sufficient light energy emitted from each light emitting portion is ensured. There is an effect that can be. Furthermore, if a waveguide is provided at the end of the light branching means and the object to be exposed is irradiated with the light obtained by the light branching means, the directivity of the irradiated light to the object to be exposed is improved. There is an effect.
[0091]
Further, as described above, the optical print head of the present invention has a configuration in which the optical input waveguide is connected to the two optical output waveguides by the optical switch at each branch point in the optical branching unit. It is.
[0092]
Therefore, there is an effect that control is easy because there are few cases of branching. In particular, when light is transmitted through one of the two optical switches at each branching point and light is blocked at the other, the light transmission and light blocking of the two optical switches can be controlled with two values, and the control is very There is an effect that it becomes easy. Further, if n stages of branches are arranged in a column so that each light output waveguide becomes a light input waveguide at the next branch point, light to the object to be exposed can be emitted to one light emitting portion of the light emitting element. 2 irradiated points _n There is an effect that it can be obtained individually.
[0093]
Furthermore, in the optical print head of the present invention, as described above, the light branching means performs the light transmission with one of the optical switches at each branch point, and performs the light blocking with the other optical switch. In this case, the light that transmits the light by totally reflecting most of the light from the light input waveguide that is incident on the boundary surface between the light input waveguide and the optical switch that cuts off the light. It is the structure which injects in a switch.
[0094]
Therefore, a clear difference in light quantity can be obtained between light transmission and light blocking, so that the contrast between exposure to the object to be exposed and non-exposure is increased, and an excellent exposure image can be obtained.
[0095]
Furthermore, as described above, in the optical print head of the present invention, the optical switch is configured to transmit the light from the optical input waveguide to each of the plurality of optical output waveguides and to change the state due to applied heat. The light blocking is controlled.
[0096]
Therefore, vibration of the apparatus, exposure image deterioration, and noise can be prevented, and light transmission and light blocking can be switched at high speed. In addition, since an optical switch can be manufactured by the same lithography technique as that of the thermal head and a long optical path length is not required, miniaturization is easy and high exposure resolution can be realized.
[0097]
Furthermore, in the optical print head of the present invention, as described above, in the optical switch, the material for switching between the liquid state and the gas state is a connection between the optical input waveguide and each of the plurality of optical output waveguides. The light transmission and the light blocking of the connection part are controlled by a change in refractive index between the liquid state and the gas state.
[0098]
Therefore, a large change in the refractive index between the liquid state and the gas state can clearly switch between light transmission and light blocking, so that the contrast between exposure to the exposed object and non-exposure is increased, which is good The effect that a sufficient exposure image can be obtained is produced. In addition, there is an effect that optical switching with excellent responsiveness can be performed.
[0099]
Furthermore, the optical print head of the present invention has a configuration in which the light-emitting element is an electroluminescence element as described above.
[0100]
Therefore, a structure that also serves as a waveguide for the light that is input to the light branching means by the drive electrode of the light emitting element or the like is possible, and the entire configuration can be simplified.
[0101]
Furthermore, in the optical print head of the present invention, as described above, each of the electroluminescence elements is provided with each of the light emission locations, and an end surface perpendicular to the laminated surface of each layer of the electroluminescence elements, and for each of the light emission locations. Correspondingly, a light emitting region provided along the waveguide direction so that the emitted light at each of the plurality of light emitting locations is guided to the light emitting location in a waveguide direction substantially perpendicular to the end face; and The light emitting area is configured to include a drive electrode that drives the light emission of the light emission area and that is selectively driven to change the light emission area for each selected unit.
[0102]
Therefore, if the drive electrodes to be selected are sequentially switched according to the use period of the electroluminescence element, the light emission locations in the light emitting region are also sequentially switched, so that the light emission locations that emit light corresponding to a certain drive electrode have a lifetime. Even if it becomes, it can use a different light emission location continuously, and there exists an effect that the lifetime as the whole light emitting element can be extended.
[0103]
In addition, by selecting a combination of drive electrodes for each selection unit, different light emission locations can be simultaneously emitted in each light emission region, so that the intensity of light emitted from the light emission location can be changed, and exposure is performed. There is an effect that the exposure amount to the body can be switched stepwise. Furthermore, since the light emitting region is provided along the waveguide direction substantially perpendicular to the end surface, the light emitting region can be arbitrarily enlarged on the opposite side of the end surface along the waveguide direction with respect to the same light emission location, There is an effect that the intensity of light emitted from the light emission location can be increased without being limited by the size of the light emission location.
[0104]
Furthermore, the optical print head of the present invention, as described above, in the light emitting region,
In this configuration, the light emission intensity of the light emission portion changes for each selection unit of the drive electrode.
[0105]
Therefore, since the intensity of the light emitted from the light emission location is weighted, the combination of the drive electrodes to be selected in combination allows a light emission location that emits light for each selected unit of the drive electrode in the light emission region. Even if the number is small, there is an effect that the exposure amount to the object to be exposed can be finely switched in a stepwise manner.
[0106]
Further, as described above, the optical print head of the present invention has a configuration in which the light emission intensity increases as the light emission portion that emits light for each selected unit of the drive electrode is closer to the end face in the light emission region.
[0107]
Therefore, weighting of the intensity of light emitted from the light emitting portion can be performed while favorably reflecting the difference in light emission intensity at each light emitting portion, and the effect of facilitating control of weighting is achieved.
[0108]
Furthermore, the optical print head of the present invention has a configuration in which the electroluminescence element and the light branching unit are formed on the same substrate as described above.
[0109]
Therefore, since the structure is simple, it is possible to ensure high assembly accuracy of each part, and in particular, it is possible to easily obtain a large optical print head that increases the exposure area of the object to be exposed. .
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an optical print head according to an embodiment of the present invention.
2 is a cross-sectional view taken along line AA in the EL element of the optical print head of FIG. 1. FIG.
3 is a cross-sectional view illustrating light emission in an EL element of the optical print head of FIG. 1. FIG.
4 is an explanatory diagram for explaining the waveguide of emitted light in the EL element of the optical print head of FIG. 1. FIG.
5A and 5B are graphs showing characteristics of EL elements of the optical print head of FIG.
6 is a plan view showing a configuration of an optical branching portion of the optical print head of FIG. 1. FIG.
7A and 7B are plan views for explaining the operation of the optical switch in the optical branching section of FIG. 6;
8A is a cross-sectional view taken along the line B-B in the light branching portion of FIG. 6, FIG. 8B is a cross-sectional view taken along the line C-C in the light branching portion of FIG. 6, and FIG. It is DD sectional view taken on the line in the optical branching part.
9A to 9D are cross-sectional views for explaining a manufacturing process of the EL element of the optical print head of FIG. 1, and FIG. 9E is a cross-sectional view taken along line EE in FIG.
10 is a plan view showing another configuration of the EL element of the optical print head of FIG. 1; FIG.
[Explanation of symbols]
1 EL element (light emitting element, electroluminescence element)
1 'EL element (light emitting element, electroluminescence element)
1a End face
1a 'end face
8 Optical branching unit (optical branching means)
9 Object to be exposed
10 Substrate
81 Waveguide for optical input (waveguide)
82 Optical switch
83 Optical switch
85 Optical output waveguide
86 Optical output waveguide
101 Optical print head

Claims (8)

A light emitting element is provided, and light emitted from each predetermined light emitting portion of the light emitting element is irradiated to a different region of the object to be exposed at each light emitting portion at a predetermined resolution. In the optical print head that performs exposure,
Each of the waveguides provided corresponding to each of the light emitting locations and receiving light from the light emitting locations is composed of one light input waveguide and each of a plurality of light output waveguides. A plurality of branch paths are formed by branching at each branch point connected by an optical switch capable of switching between light transmission and light blocking provided for each waveguide. A light branching unit that selectively guides the emitted light through the plurality of branch paths and irradiates the object to be exposed with the exposure resolution on the object to be exposed; together we are,
In the optical branching means, the optical input waveguide is connected to the two optical output waveguides by the optical switch at each branch point,
The optical branching means performs the light transmission with one of the optical switches at each branch point, and blocks the light input waveguide and the light when performing the light blocking with the other optical switch. An optical print head, wherein light from the optical input waveguide incident on a boundary surface with the optical switch to be reflected is reflected and incident into the optical switch that transmits the light. The optical switch is characterized in that the light transmission and the light blocking from the light input waveguide to each of the plurality of light output waveguides are controlled by a state change caused by applied heat. The optical print head according to 1. In the optical switch, a material capable of switching between a liquid state and a gas state is provided at a connection portion between the optical input waveguide and each of the plurality of optical output waveguides. The optical print head according to claim 1, wherein the light transmission and the light blocking of the connection portion are controlled by a change in refractive index between the gas state and the gas state. 4. The optical print head according to claim 1, wherein the light emitting element is an electroluminescence element. The electroluminescence element is provided with the light emission points, and has an end surface perpendicular to the laminated surface of the layers of the electroluminescence element, and light emitted from each of the plurality of light emission points corresponding to the light emission points. A light emitting region provided along the waveguide direction so as to be guided in a waveguide direction substantially perpendicular to the end face to the light emitting location, and driving and selectively emitting light at the light emitting location of the light emitting region The optical print head according to claim 4, further comprising: a drive electrode provided so that the light emission location changes for each selected unit when driven. 6. The optical print head according to claim 5, wherein in the light emitting region, the light emission intensity of the light emitting portion changes for each selection unit of the drive electrode. 7. The optical print head according to claim 6, wherein in the light emitting region, the light emission intensity increases as the light emitting portion that emits light for each selected unit of the drive electrode is closer to the end face. 8. The optical print head according to claim 4, wherein the electroluminescence element and the light branching unit are formed on the same substrate.

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