JP4387052B2 - Manufacturing method of liquid crystal display device - Google Patents

Description

【００７６】
負の誘電率異方性を有する前記一般式の液晶化合物を含み、その末端アルキル基の炭素数ｍが偶数である液晶材料を用いると、バルク液晶の比抵抗を高く保つことが可能である。極性基を持たないニュートラル成分も含み前記一般式のｍ数が偶数であるものを含有した液晶は、同様の成分を含みｍ数が奇数であるものを含有した液晶に比して、初期の比抵抗、高温放置後の比抵抗、紫外線（ＵＶ）暴露後の比抵抗の全てにおいて、ｍ数が偶数の液晶の方に良好な結果が得られる。
【００７７】
更に、前記一般式の液晶化合物のうち、ｍ数が２，４のものに限って使用することが望ましい。
一般に、液晶化合物の末端アルキル鎖が長くなると、液晶粘性が大きくなる等、液晶表示装置にとっては好ましくない方向となる。前記一般式の液晶化合物は、混合液晶の温度範囲を低温側にも広くネマチック相を維持する作用もあり、この場合、化合物としてはｍ数が異なる２種類以上を含ませることが良い。従って、液晶粘性の上昇を抑えるために、ｍ数は２，４の化合物を用いることが好適である。
【００７８】
本発明の液晶表示装置及びその製造方法では、少なくとも一方が透明である一対の基板を有し、画像表示領域の周辺部にシール剤の塗布による枠パターンが形成され、前記枠パターン内に誘電率異方性が負の液晶を滴下して前記各基板を貼り合せ、前記シール剤が硬化されてなる垂直配向型の液晶表示装置を対象とし、前記液晶材料は、極性を有しないニュートラル液晶化合物を含み、このニュートラル液晶化合物を含む液晶は、滴下された際に真空放置下で重量比が１％以上減少する高揮発性を有し、非揮発性のニュートラル液晶化合物に比して回転粘性が１５％以上低いものであることを特徴とする。
【００７９】
回転粘性は低粘性材を導入することにより、導入前の状態から液晶粘性を１５％以上小さくすることができ、このときの液晶の揮発性は、重量比率で１％以上の減少（揮発）を示す。このように、液晶材料を低粘度化することにより、液晶表示装置の応答速度を向上させることができる。
【００８０】
この場合、前記液晶材料を、その透明点が７０℃以上であり、その誘電率異方性Δεが−４．０≦Δε＜０を満たし、その屈折率異方性Δｎが０．１０００以上となるようにすることが好適である。これらの条件を満たすことにより、輝度（透過率）・応答速度等の表示特性や量産性を向上させることが可能となる。
【００８１】
更に、これらの液晶表示装置は、その液晶分子の倒れ込む方向が２方向以上となるマルチドメイン構造を有するものとすることが好適である。これにより、視野角特性の向上を図ることが可能となり、液晶モニタ等への適用に都合が良い。
【００８２】
【発明の実施の形態】
以下、本発明を適用した好適な諸実施形態について、図面を参照しながら詳細に説明する。
【００８３】
−液晶表示装置の一般的構成−
図１は、液晶表示装置の一般的な主要構成を示す概略断面図である。
この液晶表示装置は、所定間隔をあけて対向する一対の透明ガラス基板１，２と、これら透明ガラス基板１，２間に狭持される液晶層３とを備えて構成されている。
【００８４】
一方の透明ガラス基板１上には、絶縁層４を介して複数の画素電極１５が形成され、画素電極５を覆うように透明の配向膜６ａが形成されており、他方の透明ガラス基板２上には、カラーフィルター７、共通電極８及び配向膜６ｂが順次積層されている。そして、液晶層３を狭持するように配向膜６ａ，６ｂが突き合わせられてガラス基板１，２が固定され、各基板１，２の外側に偏光子９，１０が設けられる。画素電極５はアクティブマトリクスと共に形成され、図示の例ではアクティブマトリクスのデータバスライン１１が示されている。なお、電極は一方の基板のみに設けられることもある（例えば、ＩＰＳモードの場合）。
【００８５】
ここでは、滴下注入法を用いて液晶層３を形成するに際して、構造上、製造工程上、及び当該製造に用いる液晶滴下装置について諸々の改善を施した例を以下に示す諸実施形態として開示する。
【００８６】
各実施形態で共通に用いられる液晶表示装置の製造方法としては、メインシールの材料として紫外線硬化樹脂又は（紫外線＋熱）硬化樹脂を用い、ＴＦＴ（薄膜トランジスタ）基板となるガラス基板Ａと、ＣＦ（カラーフィルタ）基板となるガラス基板Ｂを用意し、例えばガラス基板Ｂの画像表示領域にディスペンサによりメインシールの枠パターンを形成し、滴下注入法により枠パターン内に液晶を滴下した後、各基板Ａ，Ｂを貼り合せ、メインシールを硬化する。しかる後、貼り合わされた基板Ａ，ＢからＴＦＴ基板＋ＣＦ基板の状態に切り出しを行ない、諸々の後工程を経て液晶表示装置を完成させる。
【００８７】
（第１の実施形態）
図２は、本実施形態において、滴下注入法により液晶注入工程を行なう前の枠パターンの形成されたガラス基板の様子を示す概略平面図である。
本例では、メインシール２１に紫外線樹脂（例えば、スリーボンド社製、製品名３０Ｙ−３６３）を用い、ＣＦ基板となるガラス基板２２側の表示表示領域２３の周辺部にディスペンサで繋ぎパターン及び枠パターンを形成する。重なり部３１の始点３１ａと終点３１ｂは、非実装辺側且つ枠パターン外となる位置に設け、繋ぎパターンは貼り合せ後にそれぞれが隣接するように形成する。
【００８８】
なお、メインシール２１のシール幅は１ｍｍ、コーナ部は線幅が直線部と同等となるように半径１ｍｍとする。枠パターンは貼り合せ後にその内周辺と遮光膜２３との間隙が０．５ｍｍとなるように形成する。
【００８９】
次に、液晶滴下法により、枠パターン内に必要量の液晶を滴下して真空中でガラス基板２２とＴＦＴ基板となるガラス基板とを貼り合せ、大気開放により液晶を注入する。
【００９０】
ガラス基板２２側から紫外線を一括照射した後、熱処理によりシール硬化を行い、これを所定寸法に切断して液晶表示パネルを得る。なお、基板の切断については、ＣＦ基板となるガラス基板２２が切断線３２に沿って、ＴＦＴ基板となるガラス基板が切断線３３に沿って実行される。
【００９１】
ここで、本例の液晶表示装置との比較のため、比較例として図２３で示した液晶表示装置を作製する。
【００９２】
比較例１では、図２３（ａ）に示したようにメインシール１０２により枠パターンを形成する。始点と終点は枠パターン上となる位置に設け、始点と終点で枠パターンが連結される（重なり部１０３が形成される）ように形成する。それ以外は本例と同様にして液晶表示パネルを得る。
【００９３】
比較例２では、図２３（ｂ）に示したようにメインシール１０２に枠パターンを形成する。始点と終点は枠パターン上且つコーナー部となる位置にし、始点と終点で枠パターンが連結される（重なり部１０３が形成される）ように形成する。なお、コーナー部は円弧状には形成しない。それ以外は本例と同様にして液晶表示パネルを得る。
【００９４】
本例では、始点３１ａと終点３１ｂが枠パターン外にあるため、枠パターン上に始点３１ａと終点３１ｂの重なりは形成されず、枠パターン連結部のメインシール２１は遮光膜２３に重ならない。これに対して、比較例１，２では、枠パターン上に始点と終点の重なり部１０３が形成されるため、枠パターン連結部のメインシール１０２は遮光膜１０５と重なる。比較例１，２の枠パターン連結部のシール幅は２．６ｍｍ、メインシール１０２を２重に塗布した時のシール幅は２．０ｍｍである。これは始点と終点ではディスペンサが上下方向に移動するため、直線部よりシール塗布量が多くなるためである。比較例１の枠パターンの連結部では、内周辺側に０．８ｍｍ突出し、内周辺と遮光膜１０５の間隙が０．５ｍｍであることから、メインシール１０２は遮光膜１０５に０．３ｍｍ重なる。従来例２の枠パターン連結部では、突出量は０．８ｍｍと同じであるが、内周辺と遮光膜１０５の間隙が１．４倍に広がるため、メインシール１０２と遮光膜１０５の重なりは小さく、０．１ｍｍであった。内周辺と遮光膜の間隙を更に広げれば、メインシール１０２と遮光膜１０５の重なりを無くすことができるが、画像表示領域に対する外形寸法の割合が拡大するために適切ではない（広額縁化）。
【００９５】
また、始点と終点を枠パターン上で離して形成してもメインシールと遮光離の重なりを無くすことができるが、枠パターン連結部のシール幅が細くなってメインシール１０２に必要な強度を維持出来なくなるため適切ではない。
【００９６】
本例及び比較例１，２の液晶表示パネルを点灯試験に供した。その結果、本例では表示ムラは発生しなかったが、比較例１，２では枠パターン連結部でメインシール１０２の硬化不良により表示ムラが発生した。
【００９７】
以上説明したように、第１の実施形態によれば、シール剤に起因して発生しがちな保持力低下による表示ムラを抑止し、滴下注入法を用いて歩留まり良く簡便に液晶表示装置を製造し、信頼性の高い液晶表示装置を実現することが可能となる。
【００９８】
−変形例−
ここで、第１の実施形態の諸変形例について説明する。
【００９９】
（変形例１）
変形例１では、ＣＦ基板となるガラス基板２２側の画像表示領域の周辺部に、ディスペンサでメインシール４１により図３に示すような２面取りのシールパターン及びメインシール４２により図４に示すような４面取りのシールパターンをそれぞれ形成する。
【０１００】
図３の２面取りでは、始点４３ａと終点４３ｂを基板２２上で連結させて１つの重なり部４３としてシールパターンを連続して形成し、枠パターン結合部でメインシール４１が交差しないようにする。他方、図４の４面取りでは、始点４４ａと終点４４ｂを基板２２上で連結させて１つの重なり部４４としてシールパターンを連続して形成し、枠パターン結合部でメインシール４２が交差するようにする。それ以外は第１の実施形態と同様にして液晶表示パネルを得る。
【０１０１】
図３の２面取りでは、始点４３ａと終点４３ｂが枠パターン外にあり、枠パターン結合部でメインシール４１が交差しないため、枠パターン連結部のメインシール４１は遮光膜２３に重ならない。また、図４の４面取りでは、枠パターン結合部でメインシール４２が交差してシール幅は２．０ｍｍと太くなるが、始点４４ａと終点４４ｂの重なり部４４よりは細く、結合部がコーナー部であることから枠パターン連結部のメインシール４２は遮光膜２３に重ならない。
【０１０２】
図３の２面取り及び図４の４面取りを用いて作製された液晶表示パネルをそれぞれ点灯試験に供した。その結果、双方共に表示むらは発生しなかった。
【０１０３】
（変形例２）
変形例２の主要工程を図５に示す。ここで（ａ）が基板２２ａの概略平面図、（ｂ）が基板２２ａのトランスファシール近傍における概略断面図、（ｃ）がトランスファシールを拡大して示す概略断面図である。
【０１０４】
ここでは、樹脂スペーサ（例えば、積水ファインケミカル社製の商品名ミクロパールＳＰ）の表面にＩＴＯ膜を蒸着により形成し、導電性粒子４５を得る。トランスファシール２４には第１の実施形態で用いた紫外線硬化樹脂を用い、導電性粒子４５を１ｗｔ％混入させる。導電性粒子４５及び透明電極４６による紫外線の減衰率を測定したところ、トランスファシール２４に照射される光量はメインシール２１のそれと比べて１０％少ないことが分かった。
【０１０５】
また、アルミ膜を用いてＴＦＴ基板側のトランスファーシール２４の形成位置に電極となる反射膜４７を形成する。アルミ膜の形成はＴＦＴの成膜工程と一括して行う。紫外線照射は、基板２２側からメインシール２１を紫外線硬化させる光量を一括照射し、その後、トランスファシール２４にライトガイド４８を用いて平行光からなる紫外線を基板鉛直方向からスポット照射した。スポット照射の光量は導電性粒子４５及び透明電極４６による紫外線の減衰分とほぼ同等（変形例２Ａ）及び当該減衰分の２／３（変形例２Ｂ）にした。それ以外は第１の実施形態と同様にして液晶表示パネルを得る。
【０１０６】
ここで、本例の液晶表示装置との比較のため、比較例として図２４で示した液晶表示装置を作製する。
この比較例では、樹脂スペーサの表面にニッケルをコーティングした導電性粒子（例えば、積水ファインケミカル社製の商品名ミクロパールＮＩ）を用い、トランスファシール１０６に１ｗｔ％混入させる。それ以外は第１の実施形態の比較例１と同様にして液晶表示パネルを得る。
【０１０７】
変形例２Ａ，２Ｂ及び比較例による液晶表示パネルをそれぞれ点灯試験に供した。その結果、変形例２Ａ，２Ｂでは表示ムラは発生しなかったが、比較例では、枠パターン連結部（重なり部１０３）とトランスファシール１０６で硬化不良による表示ムラが発生した。変形例２Ｂでは、トランスファシール２４に照射される光量は不足しているが、反射膜４７により紫外線が反射されて不足分が補われるため、硬化不良による表示ムラは発生しない。
【０１０８】
なお、液晶が劣化する光量とシール剤が紫外線硬化する光量に多少のマージンがあれば、トランスファシール２４にスポット照射しなくても、トランスファシール２４下に反射膜を形成し、一括照射の光量を若干増やしてトランスファシール２４を硬化させることも可能である。
【０１０９】
（変形例３）
変形例３では、図６に示すように、シール材の硬化により基板２２ａ，２２ｂを貼り合わせて基板５１とした後、基板５１面を多点支持する構造の搬送アーム出入用スペーサ５３の設けられた基板搬送カセット５２を用いて紫外線照射後の熱処理を行う。
【０１１０】
これに対して、比較例として、図２５に示したような従来の基板端で基板１１０を支持する構造の基板搬送カセット１０８を用いて、紫外線照射後の熱処理を行う。
【０１１１】
それ以外は変形例３及び比較例ともに第１の実施形態と同様にして液晶表示パネルを得る。
【０１１２】
変形例３及び比較例による液晶表示パネルをそれぞれ点灯試験に供した。その結果、変形例３では熱処理中に位置ズレは発生しなかったが、比較例では位置ズレが発生した。変形例３では基板５１面を多点支持するため、基板５１を平行保持することができるが、比較例では基板端のみで支持するため基板１０８の中央で撓みが大きくなり、熱硬化中に位置ズレが発生する。
【０１１３】
（第２の実施形態）
図７は、本実施形態において、滴下注入法により液晶注入工程を行なった後、紫外線照射する際の様子を示す概略斜視図、図８は図７における円C内を拡大してガラス基板の様子を示す概略断面図である。
【０１１４】
本例では、メインシールに紫外線硬化型樹脂（商品名３０Ｙ−３６３／スリーボンド社製／硬化光量はＩ線基準で２５００ｍＪ／ｃｍ²）を用い、滴下注入法により液晶注入した後、ＣＦ基板となるガラス基板６１とＴＦＴ基板となるガラス基板６２とを貼り合わせ、切り出しを行なって液晶表示パネルを作製する。本例は、ガラス基板６１，６２の貼り合せの際に行なう紫外線照射工程を改善するものである。
【０１１５】
ガラス基板６１上の配向膜６３端は当該樹脂の内周辺外側且つ外周辺内側となる領域に形成した。
【０１１６】
また比較のため、図９に示すように、従来例としてＣＦ基板となるガラス基板６１上の配向膜６３端を当該樹脂の内周辺内側に形成し、遮光マスク６４を設けた液晶表示パネルも作製する。
【０１１７】
紫外線照射は光源に高圧水銀灯を用い、図７に示すように、３００ｎｍ未満の短波長をほぼ透過しないカットフィルタ６４と５００ｎｍ以上の長波長をほぼ透過しないカットフィルタ６５を照射光源側に配置して行う。
【０１１８】
図１０に示すように、両フィルタを組合せた場合の透過率は３１３ｎｍ輝線ピークで５０％、３６５ｎｍ輝線ピークで９０％である。紫外線光量は、Ｉ線基準で２７００ｍＪ／ｃｍ²としたが、照射エリアのバラツキを調べたところ、バラツキの最小値部分で２３００ｍＪ／ｃｍ²、最大値部分で３１００ｍＪ／ｃｍ²であった。
【０１１９】
ガラス基板及び配向膜を付加したガラス基板それぞれの透過率を測定したところ、３１３ｎｍ輝線ピークでガラス基板（商品名ＮＡ３５／ＮＨテクノグラス社製／０．７ｍｍ厚）が８４％、配向膜（商品名ＪＡＬＳ−６８４／ＪＳＲ社製／膜厚８０ｎｍ）が７１％であり、配向膜により該波長が１５％程度減衰されることが分かった。
【０１２０】
長・短波長のカットフィルタ６４，６５を用いて液晶（商品名ＭＪ９６１２１３／メルク社製）に紫外線を照射し、液晶の光分解が活性化される紫外線光量のしきい値を保持率低下から求めた。その結果、図１１に示すように、ガラス基板越しに紫外線を照射した場合に３１３ｎｍ輝線ピーク近傍の波長帯（３１０±２０ｎｍ）の積算光量で１０００ｍＪ／ｃｍ²程度、Ｉ線基準で３０００ｍＪ／ｃｍ²程度で保持率低下が大きくなり、これ以下では保持率低下が小さかった。また、同様に短波長のカットフィルタ６４のみを用いて液晶の光分解が活性化される紫外線光量のしきい値を保持率低下から求めたところ、その値はＩ線基準で１０００〜１５００ｍＪ／ｃｍ²程度であり、長・短波長のカットフィルタの半分以下になることが分かった。これは５００ｎｍ以上の長波長が照射されることにより液晶が熱せられ、３００ｎｍ以上３２０ｎｍ未満の波長による液晶の光分解反応が促進されるからである。従って、照射エリアのどの部分においても配向膜を透過する紫外線光量はこの値を越えてしまうため、液晶の光分解は活性化されることが分かった。
【０１２１】
本例では、長・短波長のカットフィルタ６４，６５を適用してメインシールの硬化を行う。他方、従来例では短波長のカットフィルタのみ適用（従来例１）と長・短波長のカットフィルタを適用（従来例２）し、当該樹脂以外を遮光マスクでマスキングをしてメインシールの硬化を行う。このようにして作製した液晶表示パネルを点灯表示検査に供したところ、従来例１ではメインシール近傍の全周において保持率低下による表示ムラが、従来例２では照射エリアの最大値部分に対応したメインシール近傍において保持率低下による表示ムラが発生した。これは紫外線照射による液晶の光分解が原因と考えられる。
【０１２２】
また従来例１，２では、一部のコーナ部で保持率低下が発生した。コーナー部はシール塗布の際にシール幅が太くならないようにＲ（円弧）を付けているが、これにより表示領域と当該樹脂の距離は周辺部より近くなっている。従来例では配向膜を当該該樹脂の内周辺内側に設けているため、該樹脂に僅かでも未硬化成分が残っているとそれが熱処理で液晶中に拡散し、表示領域ぎりぎりまで達してしまう。その結果、一部のコーナ部で保持率低下が発生したと考えられる。
【０１２３】
他方、本例では、従来例１，２で発生した保持率低下による表示ムラは発生しなかった。これはフィルタおよび配向膜により液晶の光分解を抑え、また配向膜により該樹脂の未硬化成分の溶出を抑えたからである。
【０１２４】
以上説明したように、第２の実施形態によれば、シール剤に起因して発生しがちな保持率低下による表示ムラを抑止し、滴下注入法を用いて歩留まり良く簡便に液晶表示装置を製造し、信頼性の高い液晶表示装置を実現することが可能となる。
【０１２５】
−変形例−
ここで、第２の実施形態の変形例について説明する。
【０１２６】
この変形例では、ガラス基板６１上の透明電極端及び配向膜端を当該樹脂の内周辺外側且つ外周辺内側となる領域に形成し、第２の実施形態と同様の手法により液晶表示パネルを作製する。紫外線の照射条件は紫外線光量をＩ線基準で３２００ｍＪ／ｃｍ²とした以外は第２の実施形態と同様とする。照射エリアのバラツキを調べたところ、バラツキの最小値部分で２７００ｍＪ／ｃｍ²、最大値部分で３７００ｍＪ／ｃｍ²であった。
【０１２７】
透明電極及び配向膜を付加したガラス基板の透過率を測定したところ、３１３ｎｍ輝線ピークにおいてガラス基板が８４％、透明電極（ＩＴＯ／膜厚１３００Ａ）および配向膜が４６％であり、透明電極及び配向膜により当該波長が４５％程度減衰されることが分かった。
【０１２８】
従って、照射エリアの最大値部分においても透明電極及び配向膜を透過する紫外線光量は透明電極および配向膜により減衰されるため上記のしきい値を越えず、液晶の光分解は活性化されないことが分かった。
【０１２９】
このようにして作製した液晶表示パネルを点灯表示検査に供したところ、従来例で発生した保持率低下による表示ムラは発生しなかった。また、透明電極及び配向腹端外側の当該樹脂に照射する紫外線光量を増やしたことにより、バラツキの最低値部分でも硬化光量以上照射されるため、第２の実施形態に比べてこの変形例では接着強度が１０％改善した。
【０１３０】
−比較例１，２−
第２の実施形態と同様の手法により液晶表示パネルを作製する。紫外線の照射条件は第２の実施形態と同様とするが、図１２に示すように、紫外線の照射光源は高圧水銀ランプを用い、３２０ｎｍ未満の短波長をほぼ透過しないカットフィルタ６５をガラス基板６１側に配置する。
【０１３１】
当該短波長のカットフィルタ６５を用いて液晶の光分解が活性化される紫外線光量のしきい値を保持率低下から求めたところ、Ｉ線基準で３０００ｍＪ／ｃｍ²照射しても液晶の光分解は活性化されないことが分かった。従って、当該樹脂内周辺外側且つ外周辺内側となる領域に本例の透明電極膜や配向膜のような３００ｎｍ以上３２０ｎｍ未満の波長を減衰するフィルターが無くても液晶の光分解は活性化されないことが分かった。
【０１３２】
このようにして作製した液晶表示パネル（比較例１）を点灯表示検査に供したところ、メインシール近傍の全局において保持率低下による表示ムラが発生した。このパネルを分解してメインシール近傍の液晶をガスクロマトグラフィーで分析したところ、メインシール由来の樹脂成分が検出された。
【０１３３】
また、公知例のように３２０ｎｍ以上の長波長側に吸収帯を持つ光開始剤を用いて紫外線硬化樹脂を作製し、これをメインシールにして同様の比較を行った。このようにして作成した液晶表示パネル（比較例２）を点灯表示検査に供したところ、メインシール近傍の一部で保持卒低下による表示ムラが発生した。このパネルを分解してメインシール近傍の液晶をガスクロマトグラフィーで分析したところ、比較例１より程度は小さいがメインシール由来の樹脂成分が検出された。
【０１３４】
これは３２０ｎｍ以上の長波長側で当該樹脂の硬化を行うと、３００ｎｍ以上３２０ｎｍ未満の波長を用いた場合と比べてエネルギー量が足らない分、当該樹脂の反応率が低下するためであり、光開始剤の吸収帯を３２０ｎｍ以上の長波長側にずらしてもエネルギーの吸収効率が改善するだけで、当該樹脂の反応率は同程度にならないことを示している。
【０１３５】
（第３の実施形態）
図１３は、本実施形態の液晶滴下装置の概略構成図である。
この液晶滴下装置は、所定量の液晶を吐出するディスペンサ７１と、ディスペンサによる液晶の吐出量を測定する測定手段７２とを有して構成される。
【０１３６】
ディスペンサ７１は、ニードル状の吐出部から所定量の液晶を吐出し、ガラス基板に形成された枠パターン内に滴下するものである。
【０１３７】
測定手段７２は、照射光源であるレーザ装置７３と、このレーザ装置７３から照射されたレーザ光を感知する光学センサ７４と、この光学センサ７４の出力を時間に関して記録するデータロガー７５と、このデータロガー７５による記録結果を解析し表示するコンピュータ７６とを有して構成されている。
【０１３８】
この液晶滴下装置では、ディスペンサ７１から吐出した液晶に対してレーザ装置７３からレーザ光を照射し、滴下する液晶を横切ったレーザ光を光学センサ７４で感知した結果をデータロガー７５により記録する。このとき、データロガー７５では、例えば図１４に示すような時間に依存した出力変動を記録する。この出力をコンピュータ７６で時間積分することにより、液晶の吐出量を測定する。コンピュータ７６では、予め作成しておいた光学センサ７４の出力と液晶の重量との相関関係に基き、当該重量を推定する。
【０１３９】
なお、図示の例では１つの光学センサのみを示したが、２つの光学センサを設け、互いにほぼ直交する２方向から液晶の吐出量を測定するようにしたり、更に光学センサを設けて多角的に測定するようにしても好適である。
【０１４０】
更に、ディスペンサ７１を、液晶をシリンジ内のピストンを移動させることにより吐出し、吐出量の制御をピストンのストローク量により調節するものであり、画像処理の結果を基にピストンのストローク量を自動的に変えるように構成しても好適である。
【０１４１】
ディスペンサ７１と光学センサ７４との位置関係としては、図１５に示すように、およそ液晶吐出口から２ｃｍ程度までは液滴が連続して滴下することから、１ｃｍ程度が最も好適であることが分かった。これは、ニードル内の内側と外側の圧力差や気泡の発生により吐出距離が２ｃｍを超える程度に長くなると、はじめ連続に吐出していた液晶が不連続となり測定精度が下がるためである。
【０１４２】
実際にこの液晶滴下装置を用いて吐出量を測定した。このとき、走査の回数は１秒間に１００，０００回とし、滴下する液晶は総量２５０ｍｇで、４８個所に摘下するので１回あたりの滴下量は５．２１ｍｇとなる。この量を吐出するようにディスペンサ７１を設定した。
【０１４３】
滴下後、４８回の光学センサ７４の出力から滴下総量を推定すると、２４５ｍｇであった。そこで、マイクロシリンジを用いて５ｍｇ追加した。
このようにして作製した液晶表示パネルのセル厚のバラツキを測定したところ、約１％以内の変動に収まっていた。本例では、吐出した液晶を走査する回数を非常に多くとることができるので、短時間に吐出を繰り返す機能のディスペンサでも十分に対応できる。
【０１４４】
以上説明したように、第３の実施形態の液晶滴下装置によれば、滴下注入法による液晶の滴下量を精密に測定・制御することを可能とし、滴下部位毎で滴下量を適宜調節してセル厚を均一化させ、歩留まり良く信頼性の高い液晶の滴下注入を行なうことが可能となる。
【０１４５】
−変形例−
ここで、第３の実施形態の諸変形例について説明する。
【０１４６】
（変形例１）
変形例１では、図１６（ａ）に示すように、測定手段７７が、ディスペンサ７１からガラス基板の枠パターン内に滴下した液晶の液滴形状から吐出量を測定するように構成されている。
【０１４７】
測定手段７７は、滴下した液晶を撮像するＣＣＤ７８と、このＣＣＤ７８の出力から、図１６（ｂ）に示すように、液晶７９の斜線部位の面積を算出し、予め作成しておいた当該面積と液晶の重量（体積）との相関関係に基き、当該重量を推定するコンピュータ７６とを有して構成されている。
【０１４８】
なお、図示の例では１つのＣＣＤのみを示したが、測定精度の更なる向上を図るには、複数のＣＣＤを設け、異なる方向から液晶形状を捉えるように構成すれば良い。
【０１４９】
（変形例２）
変形例２では、図１７（ａ）に示すように、測定手段８１が、ディスペンサ７１から吐出した液晶の空中における液滴形状から吐出量を測定するように構成されている。
【０１５０】
測定手段８１は、照射光源であるレーザ装置７３と、このレーザ装置７３から照射されたレーザ光を感知する光学センサ７４と、この光学センサ７４がレーザ光により液晶の通過を認識するタイミングで、滴下した液晶を空中で撮像するＣＣＤ７８と、このＣＣＤ７８の出力から、図１７（ｂ）に示すように、液晶７９の斜線部位の面積を算出し、予め作成しておいた当該面積と液晶の重量（体積）との相関関係に基き、当該重量を推定するコンピュータ７６とを有して構成されている。
【０１５１】
この場合、ＣＣＤ７８により空中で液晶形状を確実に捉えることができるので、ガラス基板の表面形状の影響を受けることなく高精度の測定が可能となる。また、図示の例では１つのＣＣＤのみを示したが、測定精度の更なる向上を図るには、複数のＣＣＤを設け、異なる方向から液晶形状を捉えるように構成しても好適である。
【０１５２】
（変形例３）
変形例３の液晶滴下装置は、図１８（ａ）に示すように、複数の細いガラス管８２を有し、各細管８２から所定量の液晶を吐出する吐出手段である計量滴下治具８３と、この計量滴下治具８３の各細管８２に対応した各受け皿８４を有し、これら受け皿８４で受け取った液晶の液滴の重量をそれぞれ測定する測定手段８５とを備えて構成されており、測定手段８５により重量が測定され吐出量が特定された液晶の液滴を、各受け皿８４を回動させてガラス基板の枠パターン内へ滴下供給するものである。
【０１５３】
各細管８２は、図１８（ｂ）に示すように、液晶の接する内面に撥水性の高いテフロンコートが施されており、不活性ガスの押圧により液晶が押し出されて吐出する構造とされている。ガラス基板に液晶を滴下する際に、各細管８２の中に液晶が残存することが多く、不活性ガスを利用して吐出を助長することが好ましく、各細管８２の内面にテフロンコートをすることにより更に効果的な吐出が可能となる。
【０１５４】
（第４の実施形態）
本実施形態では、液晶滴下法に適用して好適な液晶材料について開示する。
本例の液晶材料は、下記の一般式で表される液晶化合物を含み、その末端アルキル基の炭素数ｍが２以上の偶数とされたものである。
【０１５５】
【化３】

【０１５６】
負の誘電率異方性を有する前記一般式の液晶化合物を含み、その末端アルキル基の炭素数ｍが偶数個である液晶材料を用いると、バルク液晶の比抵抗を高く保つことが可能となる。
【０１５７】
本例では、極性を持たないニュートラル成分を共通母体とし、その中に前記一般式のｍ数が奇数であるものを含有した液晶ａと、前記一般式のｍ数が偶数であるものを含有した液晶ａ’とを用意し、２つの液晶材料について、以下に示す条件によりバルク液晶の比抵抗値を比較した。
【０１５８】
初期の比抵抗、高温放置後の比抵抗、紫外線（ＵＶ）暴露後の比抵抗の全てにおいて、ａ’（ｍ：偶数）を用いた方が良好な結果が得られた。特に、ＵＶ暴露後については、その比抵抗値が１桁ほど高く保てることから、滴下注入プロセスにおけるＵＶシール硬化時において、非常に有利なものとなる。これらの関係を図１９に示す。ここで、液晶ａとして液晶Ａ（ｎ＝１，３）を、液晶ａ’として液晶Ｂ、液晶Ｃをそれぞれ用いた。
【０１５９】
更に、前記一般式の液晶化合物のうち、ｍ数が２，４のものに限って使用することが望ましい。一般に、液晶化合物の末端が長くなると、液晶粘性が大きくなり、応答速度が低下することから、液晶表示装置にとっては好ましくない方向になる。前記一般式の液晶化合物は、混合液晶の温度範囲を低温側にも広くネマチック相を維持する作用もあり、その場合、化合物としては前記ｍ数を２以上とすることが良い。従って、液晶粘性の上昇を抑えるために、前記ｍ数は２，４の化合物を用いることが望ましい。
【０１６０】
液晶材料を低粘度化し、液晶表示装置の応答速度を向上させることも必要である。滴下注入法では、貼り合せる際に真空放置状態が（排気時間を含めて）極めて短い。従来、数時間前後を要していた排気時間を数分に短縮化できる。そのため、従来は真空中において液晶が揮発することから、その揮発性を抑えた液晶化合物により液晶を調整するが必要であったが、滴下注入法では揮発性を有する材料でも量産用に使いこなせるようになった。
【０１６１】
また、液晶粘度を下げる低粘性材を導入すると、液晶粘性を導入前のものに対して１５％以上小さくすることができる（図２１：液晶Ｅ→液晶Ｄ）。その際の液晶の揮発性は、重量比率で１％以上の減少（揮発）を示すことが分かった。
【０１６２】
Ｔ−Ｖ特性を測定したところ、低粘性材の導入前と導入後とでは有意差は見られない。一方、応答特性に関しては、中間調を含めて高速化させることができ、効果があることを確認した。
【０１６３】
また、液晶表示装置の仕様との関係から、液晶材料の透明点は７０℃以上とし、誘電率異方性△εを−４．０≦△ε＜０とし、屈折率異方性△ｎが０．１０００以上である液晶材料を用いると、輝度（透過率）・応答速度などの表示特性や、量産性が向上する意味で良い。
【０１６４】
更に、この液晶表示装置では、液晶分子の倒れこむ方向が２以上であるマルチドメイン構造とすると、視野角特性が優れて液晶モニタなどに都合が良い。
【０１６５】
−実験例−
以下、第４の実施形態による液晶表示装置を作製し、諸々の表示特性を調べた実験例について説明する。
【０１６６】
（実験例１）
ＩＴＯ電極を有する基板を用いて、配向膜として商品名ＪＡＬＳ−６８４（ＪＳＲ社製）をスピナーにより形成し、所定のスペーサ（セル厚：４．０μｍ）を散布し、熱硬化シール材を用いて貼合せ、空セルを作製した。
【０１６７】
これらの空セルに対して、前記ｍ数＝１，３とした液晶Ａと、前記ｍ数＝２，４とした液晶Ｂ，Ｃとを、各々の空セルに注入し、封止して偏光板をクロスニコルで貼合せて、ＶＡセルを作製した。
【０１６８】
図２０に示すように、各セルについて、電圧保持率、イオン密度、及び残留ＤＣ電圧をそれぞれ測定し、その電気特性の違いを調べた。液晶Ａ、液晶Ｂ、液晶Ｃは、以下の表１に示す物性値を有するものである。また、（ａ），（ｂ）が電圧保持率、（ｃ）がイオン密度、（ｄ）が残留ＤＣ電圧を示す。実験の結果、液晶Ａ（ｍ数＝１，３）よりも、液晶Ｂ，Ｃ（ｍ数＝２，４）の方が電気特性が改善され、積成成分による依存性が確認された。
【０１６９】
【表１】

【０１７０】
（実験例２）
前記液晶Ａ，Ｂ，Ｃの比抵抗を測定した。バルク液晶の初期値、ＵＶ暴露後（１００ｍＷ／ｃｍ²、６０秒）、加熱後（１２０℃、６０分）、ＵＶ硬化性樹脂を滴下後（汚染依存性）、の４つの条件に対して調べた。液晶Ｂ，Ｃ（ｍ数＝２，４）は、全ての条件において、液晶Ａ（ｍ数＝１，３）よりも上回る結果が得られ、特にＵＶ暴露後のデータは、その比抵抗値が１桁高い、といった大きな改善効果があることを確認できた。
【０１７１】
（実験例３）
低粘性材料を導入する前の液晶Ｄと、導入した後の液晶Ｅとの違いについて調べた。導入した液晶Ｄは、従来の真空ディップ注入を用いても問題ない液晶である。一方、液晶Ｅについては、低粘性材料を導入したことから、真空放置に対する揮発性がある。
【０１７２】
実験の結果、図２１に示すように、１時間の放置で、液晶Ｅは１％強の重量変化（減少）を示し、液晶Ｄよりも十分に揮発性が高いことを確認した。
【０１７３】
液晶Ｄ，Ｅを用いて、スペーサを変更（セル厚３．５μｍ）する以外は、第３の実施形態と同じ手順によりＶＡセルを作製した。Ｔ−Ｖ特性は同等である。図２２に示すように、応答速度を調べた結果、全ての印加電圧に対して、低粘性材を導入した液晶Ｅは導入無しの液晶Ｄより高速化され、特に低階調側に相当する中間調領域において、その高速化の効果が大きいことが確認できた。
【０１７４】
以上説明したように、第４の実施形態によれば、滴下注入法に最も適した液晶材料を提供することが可能となり、これにより、その液晶粘性を小さく抑え、応答速度、特に中間調の高速化を図り、表示特性の更なる向上を可能とする液晶表示装置を実現する。
【０１７５】
以下、本発明の諸態様を付記としてまとめて記載する。
【０１７６】
（付記１） 一対の基板の一方に設けられる画像表示領域の周辺部にシール剤を塗布して枠パターンを形成し、前記枠パターン内に液晶を滴下して前記各基板を貼り合せ、前記シール剤を硬化することにより液晶表示装置を製造する方法であって、
前記枠パターン外に前記シール剤塗布の始点又は終点の少なくとも一方が位置するように、前記シール剤を塗布することを特徴とする液晶表示装置の製造方法。
【０１７７】
（付記２） 前記始点又は前記終点の少なくとも一方を、前記基板の非実装辺側に位置するように前記シール剤の塗布を行なうことを特徴とする付記１に記載の液晶表示装置の製造方法。
【０１７８】
（付記３） 前記始点又は前記終点の少なくとも一方を前記枠パターンと前記非実装辺を横切るように結び付けることを特徴とする付記２に記載の液晶表示装置の製造方法。
【０１７９】
（付記４） 前記始点と前記終点を前記基板上で一致させ、前記シール剤によるシールパターンを連続して形成することを特徴とする付記１に記載の液晶表示装置の製造方法。
【０１８０】
（付記５） 一対の基板の一方に設けられる画像表示領域の周辺部にシール剤を塗布して枠パターンを形成し、前記枠パターン内に液晶を滴下して前記各基板を貼り合せ、前記シール剤を硬化することにより液晶表示装置を製造する方法であって、
前記一対の基板間を導通させるため、樹脂に導電性粒子を混入してなるトランスファシールに、前記樹脂を硬化するため、平行光からなる紫外線を基板鉛直方向又は斜め方向からスポット照射することを特徴とする液晶表示装置の製造方法。
【０１８１】
（付記６） 一対の基板の一方に設けられる画像表示領域の周辺部にシール剤を塗布して枠パターンを形成し、前記枠パターン内に液晶を滴下して前記各基板を貼り合せ、前記シール剤を硬化することにより液晶表示装置を製造する方法であって、
前記一対の基板間を導通させるため、樹脂に導電性粒子を混入してなるトランスファシールを塗布し、前記樹脂を硬化して前記基板同士を貼り合わせるため、紫外線照射によりこれを硬化した後、
前記紫外線の照射後に、支持筐体により前記基板を平行保持した状態で前記基板を熱処理することを特徴とする液晶表示装置の製造方法。
【０１８２】
（付記７） 一対の基板の一方に設けられた画像表示領域の周辺部にシール剤の塗布による枠パターンが形成され、前記枠パターン内に液晶を滴下して前記各基板を貼り合せ、前記シール剤が硬化されてなる液晶表示装置であって、
透明導電膜を表面にコーティングした粒子を混入してなるトランスファシールにより前記一対の基板間が導通していることを特徴とする液晶表示装置。
【０１８３】
（付記８） 一対の基板の一方に設けられた画像表示領域の周辺部にシール剤の塗布による枠パターンが形成され、前記枠パターン内に液晶を滴下して前記各基板を貼り合せ、前記シール剤が硬化されてなる液晶表示装置であって、
樹脂に導電性粒子を混入してなり、前記一対の基板間を導通させるトランスファシール下の電極として、前記樹脂を硬化するために照射する紫外線を反射する膜が形成されていることを特徴とする液晶表示装置。
【０１８４】
（付記９） 紫外線を反射する膜としてアルミ膜又は銀膜を用い、薄膜トランジスタ側の前記基板に形成することを特徴とする付記８に記載の液晶表示装置の製造方法。
【０１８５】
（付記１０） 一対の基板の一方に設けられる画像表示領域の周辺部にシール剤を塗布して枠パターンを形成し、前記枠パターン内に液晶を滴下して前記各基板を貼り合せ、前記シール剤を硬化することにより液晶表示装置を製造する方法であって、
液晶の配向膜をその端部が前記シール剤の内周辺外側且つ外周辺内側となる領域に形成し、ほぼ３００ｎｍ以上５００ｎｍ未満の波長の光を照射して、前記シール剤の硬化を行うことを特徴とする液晶表示装置の製造方法。
【０１８６】
（付記１１） 少なくともカラーフィルタの形成される前記基板上の前記配向膜の端部を前記シール剤の内周辺外側且つ外周辺内側となる領域に形成し、当該基板側から前記波長の光を照射して、前記シール剤の硬化を行うことを特徴とする付記１０に記載の液晶表示装置の製造方法。
【０１８７】
（付記１２） ほぼ３００ｎｍ以上５００ｎｍ未満の波長の光を照射する手段として、当該波長以外をほぼカットするフィルタを照射光源側に配置することを特徴とする付記１０又は１１に記載の液晶表示装置の製造方法。
【０１８８】
（付記１３） 前記シール剤の硬化光量をＩ線基準でほぼ３０００ｍＪ／ｃｍ²以下とすることを特徴とする付記１０〜１２のいずれか１項に記載の液晶表示装置の製造方法。
【０１８９】
（付記１４） 所定量の液晶を吐出するディスペンサ手段と、
前記ディスペンサ手段による液晶の吐出量を測定する測定手段とを備え、
前記測定手段は、光学センサを有し、前記ディスペンサ手段から吐出した液晶が前記光学センサを通過した際に生じる当該光学センサの信号変動を積分し、液晶の吐出量を測定することを特徴とする液晶滴下装置。
【０１９０】
（付記１５） 前記測定手段は、吐出する液晶とほぼ垂直方向にレーザ光を走査し、吐出した液晶がこのレーザ光を横切ることでレーザ光の出力を変動させて前記光学センサにより検知し、液晶の吐出量を測定することを特徴とする付記１４に記載の液晶滴下装置。
【０１９１】
（付記１６） 前記測定手段は、少なくとも２方向から液晶の吐出量を測定することを特徴とする付記１４又は１５に記載の液晶滴下装置。
【０１９２】
（付記１７） 前記測定手段は、互いにほぼ直交する２方向から液晶の吐出量を測定することを特徴とする付記１６に記載の液晶滴下装置。
【０１９３】
（付記１８） 前記光学センサは、前記ディスペンサ手段の液晶吐出口から２ｃｍ以内の位置に設置されることを特徴とする付記１４〜１７のいずれか１項に記載の液晶滴下装置。
【０１９４】
（付記１９） 所定量の液晶を吐出するディスペンサ手段と、
前記ディスペンサ手段により吐出された液晶の液滴形状を認識し、これに基いて実際の液晶の吐出量を推定する液晶測定手段とを備えたことを特徴とする液晶滴下装置。
【０１９５】
（付記２０） 前記測定手段は、液晶の前記液滴形状を光学的に認識し、当該形状の画像から実際の液晶の吐出量を推定することを特徴とする付記１９に記載の液晶滴下装置。
【０１９６】
（付記２１） 前記ディスペンサ手段の液晶吐出口の近傍に光学センサを設け、吐出した液晶が光学センサを通過した際に発生する当該光学センサの信号をトリガ信号として、液晶の液滴形状の画像から実際の液晶の吐出量を推定することを特徴とする付記２０に記載の液晶滴下装置。
【０１９７】
（付記２２） 前記ディスペンサ手段は、液晶をシリンジ内のピストンを移動させることにより吐出し、吐出量の制御を前記ピストンのストローク量により調節するものであり、画像処理の結果を基に前記ピストンのストローク量を自動的に変えることを特徴とする付記１９〜２１のいずれか１項に記載の液晶滴下装置。
【０１９８】
（付記２３） 複数の細管を有し、前記各細管から所定量の液晶を吐出する吐出手段と、
前記吐出手段の各細管に対応した各受け皿を有し、前記各受け皿で受け取った液晶の液滴の重量をそれぞれ測定する測定手段とを備え、
前記測定手段により重量が測定され吐出量が特定された液晶の液滴を、前記各受け皿から供給することを特徴とする液晶滴下装置。
【０１９９】
（付記２４） 前記測定手段の液晶と接触する部位に、液晶を弾く撥水加工が施されていることを特徴とする付記２３に記載の液晶滴下装置。
【０２００】
（付記２５） 少なくとも一方が透明である一対の基板を有し、画像表示領域の周辺部にシール剤の塗布による枠パターンが形成され、前記枠パターン内に誘電率異方性が負の液晶を滴下して前記各基板を貼り合せ、前記シール剤が硬化されてなる垂直配向型の液晶表示装置であって、
下記の一般式で表される液晶化合物を含み、その末端アルキル基の炭素数ｍが２以上の偶数である液晶材料を用いたことを特徴とする液晶表示装置。
【化４】

【０２０１】
（付記２６） 前記液晶化合物は、その末端アルキル基の炭素数ｍが２又は４であることを特徴とする付記２５に記載の液晶表示装置。
【０２０２】
（付記２７） 少なくとも一方が透明である一対の基板を有し、画像表示領域の周辺部にシール剤の塗布による枠パターンが形成され、前記枠パターン内に誘電率異方性が負の液晶を滴下して前記各基板を貼り合せ、前記シール剤が硬化されてなる垂直配向型の液晶表示装置であって、
前記液晶材料は極性を有しないニュートラル液晶化合物を含み、このニュートラル液晶化合物を含む液晶は、滴下された際に真空放置下で重量比が１％以上減少する高揮発性を有し、非揮発性のニュートラル液晶化合物に比して回転粘性が１５％以上低いものであることを特徴とする液晶表示装置。
【０２０３】
（付記２８） 前記液晶材料は、その透明点が７０℃以上であり、その誘電率異方性Δεが−４．０≦Δε＜０を満たし、その屈折率異方性Δｎが０．１０００以上であることを特徴とする付記２７に記載の液晶表示装置。
【０２０４】
【発明の効果】
本発明によれば、シール剤に起因して発生しがちな保持率低下による表示ムラを抑止し、滴下注入法を用いて歩留まり良く簡便に液晶表示装置を製造し、信頼性の高い液晶表示装置を実現することが可能となる。
【０２０５】
また、滴下注入法による液晶の滴下量を精密に測定・制御することを可能とし、滴下部位毎で滴下量を適宜調節してセル厚を均一化させ、歩留まり良く信頼性の高い液晶の滴下注入を行なう液晶滴下装置を実現することが可能となる。
【０２０６】
更に、滴下注入法に最も適した液晶材料を用いることにより、その液晶粘性を小さく抑え、応答速度、特に中間調の高速化を図り、表示特性の更なる向上を可能とする液晶表示装置を実現することができる。
【図面の簡単な説明】
【図１】 液晶表示装置の一般的な主要構成を示す概略断面図である。
【図２】 第１の実施形態において、滴下注入法により液晶注入工程を行なう前の枠パターンの形成されたガラス基板の様子を示す概略平面図である。
【図３】 第１の実施形態の変形例１の主要構成（２面取り）を示す概略平面図である。
【図４】 第１の実施形態の変形例１の主要構成（４面取り）を示す概略平面図である。
【図５】 第１の実施形態の変形例２の主要工程を示す概略図である。
【図６】 第１の実施形態の変形例３の基板搬送カセットを示す概略斜視図である。
【図７】 第２の実施形態において、滴下注入法により液晶注入工程を行なった後、紫外線照射する際の様子を示す概略斜視図である。
【図８】 図７における円C内を拡大してガラス基板の様子を示す概略断面図である。
【図９】 第２の実施形態の比較例を示す概略断面図である。
【図１０】 透過率の波長依存性を示す特性図である。
【図１１】 液晶の光分解反応を示す特性図である。
【図１２】 第２の実施形態の比較例１，２を示す概略断面図である。
【図１３】 第３の実施形態の液晶滴下装置の概略構成図である。
【図１４】 光学センサの時間に依存した出力変動を示す特性図である。
【図１５】 ディスペンサと光学センサとの位置関係を示す概略構成図である。
【図１６】 第３の実施形態の液晶滴下装置の変形例１を示す概略構成図である。
【図１７】 第３の実施形態の液晶滴下装置の変形例２を示す概略構成図である。
【図１８】 第３の実施形態の液晶滴下装置の変形例３を示す概略構成図である。
【図１９】 第４の実施形態において、液晶材料の初期の比抵抗、高温放置後の比抵抗、紫外線（ＵＶ）暴露後の比抵抗を示す特性図である。
【図２０】 実験例１において、各セルの電圧保持率、イオン密度、及び残留ＤＣ電圧をそれぞれ測定した結果を示す特性図である。
【図２１】 実験例３において、低粘性材料を導入する前の液晶と、導入した後の液晶との揮発性の違いについて調べた結果を示す特性図である。
【図２２】 実験例３において、低粘性材料を導入する前の液晶と、導入した後の液晶との高速化の違いについて調べた結果を示す特性図である。
【図２３】 従来におけるシール剤に関する問題を説明するための概略図である。
【図２４】 比較例におけるシール剤に関する問題を説明するための概略図である。
【図２５】 比較例におけるシール剤に関する問題を説明するための概略図である。
【符号の説明】
１，２，２２ ガラス基板
２１，４１，４２ メインシール
２３ 遮光膜
２４ トランスファシール
３１，４４ 重なり部
３１ａ 始点
３１ｂ 終点
４５ 導電性粒子
４６ 透明電極
４７ 反射膜
５２ 基板搬送用カセット
６４ ３００ｎｍ未満の短波長カットフィルタ
６５ ５００ｎｍ以下の長波長カットフィルタ
７１ ディスペンサ
７２，７７，８５ 測定手段
７３ レーザ装置
７４ 光学センサ
７５ データロガー
７６ コンピュータ
７８ ＣＣＤ
８２ 細いガラス管
８３ 計量滴下治具
８４ 受け皿[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device obtained by dropping a liquid crystal in a frame pattern formed by forming an ultraviolet curable resin or an ultraviolet ray + thermosetting resin on a substrate, bonding the upper and lower substrates, and curing the resin, and a manufacturing method thereof, The present invention also relates to a liquid crystal dropping device for performing the above-described dropping injection method.
[0002]
[Prior art]
Conventionally, when a liquid crystal display panel is manufactured, a method of injecting liquid crystal into a panel from an injection port provided in a sealed cell is used in a liquid crystal injection process. Recently, there is a high demand for a large screen of a liquid crystal display panel, and it is becoming difficult to obtain sufficient display characteristics with this method.
[0003]
Therefore, a frame pattern is formed by applying a sealing agent made of ultraviolet curable resin or (ultraviolet ray + heat) curable resin to the periphery of the image display area of the cell substrate, and liquid crystal is dropped into the frame pattern to drop each substrate. Attention has been focused on the dropping injection method of bonding the two. This dripping injection method significantly reduces the time and simplification of the panel forming process including the liquid crystal injecting process, enables the production of a low-cost and highly reliable liquid crystal display panel, The liquid crystal display panel produced by using this method has the advantages of a very high contrast ratio from the front, excellent visual characteristics, and good black and white responsiveness. It is suitable to apply.
[0004]
[Problems to be solved by the invention]
As described above, the liquid crystal injection by the dropping injection method has an extremely excellent effect on the manufacturing process and the display characteristics of the product, but has various problems to be improved as described below.
[0005]
See FIG.
In the dropping injection method, since the injection port is not required for the cell (substrate 101), the main seal 102 has a closed frame pattern, but when a closed frame pattern is formed using a dispenser, the start and end points of the seal application overlap, In that portion 103, the seal width is increased. A light shielding film 105 is formed in the periphery of the display area, and when the seal width is increased, a part of the sealing agent is shielded from light and a curing failure occurs (FIG. 23A). For this reason, in the prior art, the main seal 102 is sufficiently separated from the light-shielding film so that the sealant is not shielded from light, or the seal coating start point and end point are made into corner portions with a large margin (see Japanese Patent Laid-Open No. 8-240807) ) Has been proposed (FIG. 23B).
[0006]
However, if the main seal 102 is formed sufficiently away from the light-shielding film so that the sealant is not shielded from light, the ratio of the external dimensions to the image display area 104 becomes large. Moreover, if the start point and end point of the seal application are set to the corner portions, the seal agent is certainly less likely to be applied to the light shielding film than the straight portions. However, this is because the distance between the light shielding film and the sealant is about 1.4 times that of the straight line portion. If the bulge of the overlapping portion 103 becomes larger than the distance, the light shielding film is applied to the light shielding film, which also causes poor curing. It will be.
[0025]
As explained above, the drop injection method is a technology that contributes to the efficient production of liquid crystal display panels and the realization of excellent display characteristics, but there are various problems to be improved, and there is a need for future solutions. is there.
[0026]
The present invention has been made in view of the above problems, and provides a method for manufacturing a liquid crystal display device that achieves the following objects.
[0027]
Display unevenness due to a decrease in retention rate that tends to occur due to a sealing agent is suppressed, and a liquid crystal display device is manufactured easily with a high yield using a dropping injection method, thereby realizing a highly reliable liquid crystal display device.
[0030]
[Means for Solving the Problems]
As a result of intensive studies, the inventors have arrived at the following aspects of the invention.
[0031]
In the method for manufacturing a liquid crystal display device according to the present invention, a frame pattern is formed by applying a sealant to a peripheral portion of an image display area provided on one of a pair of substrates, and liquid crystal is dropped into the frame pattern so that each of the liquid crystal display devices is provided. A method of manufacturing a liquid crystal display device by bonding a substrate and curing the sealant, wherein the sealant is applied so that both a start point and an end point of the sealant application are located outside the frame pattern. It is characterized by doing.
Thereby, since the start point and the end point do not overlap on the frame pattern, it is possible to prevent the seal width from increasing on the frame pattern and overlapping the light shielding film.
[0032]
In this case, it is preferable to apply the sealing agent so that at least one of the start point or the end point is located on the non-mounting side of the substrate.
If the point is formed so as to be located outside the frame pattern, a connection pattern that is connected to the frame pattern is required. Since the cutting position of the substrate is different between the upper side and the lower side on the mounting side, if the point is located on the mounting side, the substrates of the cutting part are bonded to each other by the connecting pattern and are difficult to cut. Since the cutting position of the substrate is the same at the upper and lower sides on the non-mounting side, the substrates at the cutting portion are not bonded by the connecting pattern, and the substrate can be easily cut.
[0033]
Furthermore, it is preferable that at least one of the start point or the end point is connected so as to cross the frame pattern and the non-mounting side.
By forming the connection pattern diagonally, it is possible to connect the point and the frame pattern in a form that does not cross the non-mounting side. However, it is difficult to apply the seal in the diagonal direction because it is difficult to control the dispenser means, which is not practical. . If the points and the frame pattern are connected so as to cross the non-mounting side, the connecting pattern can be formed in a straight line, so that the seal application becomes easy.
[0034]
Further, it is preferable that the start point and the end point coincide with each other on the substrate, and a seal pattern by the sealant is continuously formed.
If the seal pattern is continuously formed in the manner of one-stroke writing, the start point and the end point can be eliminated from the frame pattern, and the seal can be easily applied even to a multi-sided substrate.
[0035]
In the liquid crystal display device and the manufacturing method thereof according to the present invention, a frame pattern is formed by applying a sealant to the periphery of an image display area provided on one of a pair of substrates, and the liquid crystal is dropped into the frame pattern to drop the liquid crystal. The substrates are bonded to each other, and the sealant is cured to target a liquid crystal display device, and the pair of substrates are electrically connected by a transfer seal formed by mixing particles coated with a transparent conductive film on the surface. To do.
[0036]
Among transparent conductive films, for example, ITO film has a larger resistance than nickel or gold conventionally used as a conductive film, but is widely used in liquid crystal display panels as a transparent electrode. It doesn't matter. Although UV light is partially absorbed by the ITO film and attenuates, the metal film has the highest transmittance. By mixing this with the transfer seal, the UV light can easily reach the inside of the seal, which facilitates hardening of the transfer seal. It becomes.
[0037]
In the liquid crystal display device and the manufacturing method thereof according to the present invention, a frame pattern is formed by applying a sealant to the periphery of an image display area provided on one of a pair of substrates, and the liquid crystal is dropped into the frame pattern to drop the liquid crystal. In order to conduct the liquid crystal display device by bonding each substrate and curing the sealing agent, the conductive resin is mixed with the resin, and the resin is mixed with the resin under the transfer seal. It is characterized in that a film reflecting ultraviolet rays irradiated to cure the film is formed.
[0038]
As a result, a part of the ultraviolet rays irradiated to the transfer seal can be reused by the reflective film, so that the amount of light for curing the transfer seal can be suppressed to a smaller level than before.
[0039]
In this case, it is preferable that an aluminum film or a silver film is used as the film that reflects the ultraviolet light and is formed on the substrate on the thin film transistor side.
If it is an aluminum film or a silver film, it reflects an ultraviolet ray and is a metal film widely used in the TFT process, so that a reflective film can be formed without increasing the number of processes.
[0040]
In the method for manufacturing a liquid crystal display device according to the present invention, a frame pattern is formed by applying a sealant to the periphery of an image display area provided on one of a pair of substrates, and liquid crystal is dropped into the frame pattern to drop each of the above. In order to cure the resin in a transfer seal formed by mixing conductive particles in a resin in order to connect a pair of substrates and cure the sealant to cure the liquid crystal display device. In addition, it is characterized in that ultraviolet rays made of parallel light are spot-irradiated from the substrate vertical direction or oblique direction.
[0041]
Spot irradiation can irradiate parallel light with high straightness by using a light guide made of quartz fiber or the like.
Since the transfer seal contains conductive particles that absorb or reflect part or all of the ultraviolet rays, the ultraviolet rays that reach the transfer seal are attenuated by the particles. Further, the transfer seal is sandwiched between transparent electrodes, and this also attenuates ultraviolet rays. If the transfer seal is spot-irradiated with ultraviolet rays composed of parallel light from the vertical direction or the oblique direction of the substrate, it is possible to additionally irradiate only the transfer seal with the attenuated ultraviolet rays. In addition, since parallel light can be irradiated, it is possible to minimize deterioration of the liquid crystal due to the wraparound of light.
[0042]
In the method for manufacturing a liquid crystal display device according to the present invention, a frame pattern is formed by applying a sealant to the periphery of an image display area provided on one of a pair of substrates, and liquid crystal is dropped into the frame pattern to drop each of the above. Applying a transfer seal in which conductive particles are mixed into the resin to cure the resin in order to connect the pair of substrates by bonding the substrates and curing the sealing agent. Therefore, after curing this by ultraviolet irradiation, the substrate is heat-treated in a state where the substrate is held in parallel by a supporting housing after the ultraviolet irradiation.
[0043]
Rather than the conventional transfer cassette that supports the substrate at the edge of the substrate, the substrate is held in parallel by a transfer cassette or parallel plate with a structure that holds the substrate in parallel by supporting multiple points on the substrate surface. The occurrence of misalignment at is suppressed.
[0044]
In the method for manufacturing a liquid crystal display device according to the present invention, a frame pattern is formed by applying a sealant to the periphery of an image display area provided on one of a pair of substrates, and liquid crystal is dropped into the frame pattern to drop each of the above. Targeting a liquid crystal display device by laminating a substrate and curing the sealing agent, a liquid crystal alignment film is formed in a region where the end portion is on the inner periphery outside and the outer periphery inner side of the sealing agent, and is approximately 300 nm or more The sealing agent is cured by irradiating light having a wavelength of less than 500 nm.
[0045]
The photolysis of the liquid crystal occurs at a short wavelength of less than about 320 nm, and the curing of the resin requires a wavelength of not less than 300 nm and less than 320 nm. A device to irradiate the wavelength is required. However, it is difficult in reality, and even if the cut filter is used as a mask and alignment is performed for each liquid crystal display panel, the above-described problem occurs, which is not preferable. Therefore, a device is devised to attenuate the wavelength of 300 nm or more and less than 320 nm within a range where the reaction rate of the resin is not lowered so much that the photolysis of the liquid crystal is minimized.
[0046]
The resin reaction rate was measured by irradiating the resin with ultraviolet rays of a curing light amount using edge filters having different transmittances at wavelengths of 300 nm or more and less than 320 nm. As a result, it was found that although there was a slight difference depending on the resin used, the reaction rate hardly decreased if the transmittance at that wavelength was about 30% when seen at the 313 nm emission line peak of the high pressure mercury lamp. This is because the curing light amount is an ultraviolet light amount at which the reaction rate of the resin almost reaches saturation, but the curing reaction of the resin suddenly rises at about 30% of the curing light amount, and the reaction rate does not vary greatly thereafter. .
[0047]
However, when this filter was used to irradiate the liquid crystal with the same amount of ultraviolet light, the photolysis of the liquid crystal was still large, and display failure occurred due to a decrease in the retention rate. Therefore, the liquid crystal was irradiated with the same amount of ultraviolet rays by cutting a long wavelength of 500 nm or longer, which has little influence on the curing of the resin. As a result, the photolysis of the liquid crystal was reduced, and display defects due to a decrease in the retention rate did not occur. This is because the long wavelength of 500 nm or more alone does not cause the photolysis of the liquid crystal, but when combined with the wavelength of 300 nm or more and less than 320 nm, the long wavelength of 500 nm or more becomes a heat source and the photolysis of the liquid crystal is promoted. It is.
[0048]
The reason why the alignment film edge is formed in the inner peripheral outer side and outer peripheral inner side of the resin is that the alignment film absorbs uncured components of the resin and suppresses diffusion into the liquid crystal. In addition, if the alignment film edge is formed flush with the inner periphery of the resin, a gap is generated between the alignment film edge and the resin due to the displacement, and if the alignment film edge is formed outside the outer periphery of the resin, the moisture resistance is increased. This is because the resin and the substrate are bonded to each other through an alignment film having weak properties, and thus the adhesive strength is remarkably lowered under high temperature and high humidity. In addition, since the alignment film attenuates the wavelength of the 313 nm emission line peak by about 15%, it can be used as a filter for relaxing the photolysis of the liquid crystal. Thereby, since the wavelength transmittance of the filter used for the irradiation light source can be increased, the resin on the outer side of the alignment film can be hardened more firmly.
[0049]
Therefore, by combining the above methods, the photodecomposition of the liquid crystal can be minimized without significantly reducing the reaction rate of the resin, so that display defects due to a decrease in the retention rate do not occur.
[0050]
In this case, at least an end portion of the alignment film on the substrate on which the color filter is formed is formed in a region which is an inner peripheral outer side and an outer peripheral inner side of the sealing agent, and the light of the wavelength is irradiated from the substrate side. It is preferable to cure the sealing agent.
[0051]
This color filter serves as a mask for the image display area. If the edge of the alignment film on the substrate is formed in the region and light is irradiated from the substrate side, it is not necessary to mask the region other than the resin region.
[0052]
Further, at least the transparent electrode on the substrate on which the color filter is formed and the alignment film are formed so that each end portion exists in a region which is an inner peripheral outer side and an outer peripheral inner side of the sealing agent, and the substrate side It is preferable to cure the sealing agent by irradiating light of a wavelength.
[0053]
The transparent electrode film attenuates the wavelength of the 313 nm emission line peak by about 35%, and when used in combination with the alignment film, attenuates the wavelength by about 45%. Therefore, the transparent electrode film is used as a filter for relaxing the photolysis of liquid crystal. As a result, the wavelength transmittance of the filter used for the irradiation light source can be further increased, so that the resin on the outer side of the transparent electrode and the alignment film can be hardened more firmly.
[0054]
Further, as a means for irradiating light having a wavelength of approximately 300 nm or more and less than 500 nm, it is preferable to dispose a filter that substantially cuts other than the wavelength on the irradiation light source side.
[0055]
In the above-described known example, a filter that cuts off ultraviolet rays having a specific wavelength or less harmful to the liquid crystal is disposed between the mask and the liquid crystal display panel. When the filter of the present invention is arranged in such an arrangement, the long wavelength cut filter generates heat because it absorbs a long wavelength of 500 nm or more, and the liquid crystal display panel is also heated. If the wavelength of 300 nm or more and less than 320 nm is irradiated while the liquid crystal display panel is heated, the photodecomposition reaction of the liquid crystal is promoted as described above. Therefore, by disposing a long wavelength cut filter on the irradiation light source side, heat transfer to the liquid crystal display panel is prevented. In addition, the short wavelength cut filter often has absorption not only on the short wavelength side but also on the long wavelength side, and is arranged on the irradiation light source side to suppress heat transfer to the liquid crystal display panel.
[0056]
Furthermore, the curing light amount of the sealing agent is approximately 3000 mJ / cm on an I-line basis. ² The following is preferable.
[0057]
The curing light amount of the resin is set based on the integrated light amount in the wavelength band (about 350 nm ± 30 nm) near the 365 nm emission line (I line) peak where the irradiation intensity of the high-pressure mercury lamp is maximized. If the intensity of the I-line peak is 100, the 313 nm emission line peak is about 60 for the high-pressure mercury lamp and about 30 for the metal halide lamp. Since it becomes broad in the vicinity of the peak, there is not much difference between the two lamps in the integrated light quantity of the wavelength of 300 nm or more and less than 320 nm.
[0058]
The liquid crystal was irradiated with light having a wavelength of approximately 300 nm or more and less than 500 nm, and the amount of ultraviolet light that activates the photolysis of the liquid crystal was determined from the decrease in retention rate. The transmittance of the cut filter used is 50% at the 313 nm emission line peak and 90% at the 365 nm emission line peak. As a result, although there is a slight difference depending on the liquid crystal, the integrated light quantity in the wavelength band near the 313 nm emission line peak (about 310 nm ± 20 nm) is 1000 mJ / cm. ² It was about. However, since it is difficult to compare with the curing light amount of the resin, it is 3000 mJ / cm when converted to the ultraviolet ray light amount based on the I-line. ² It will be about. In the present invention, the wavelength of 300 nm or more and less than 320 nm can be attenuated by about 15% by the alignment film, but the guaranteed illuminance variation when ultraviolet rays are irradiated onto a large substrate is usually about ± 15%, Curing light quantity is 3000mJ / cm on I-line basis ² In the above, since the maximum value portion of the dispersion exceeds this value and the liquid crystal is irradiated with ultraviolet rays, the photolysis of the liquid crystal is activated and the retention rate is reduced. To activate the reaction, more than a certain amount of energy is required. If energy exceeding that amount is applied, the reaction proceeds at an accelerated rate. Does not progress as much as the difference.
[0059]
The liquid crystal dropping device of the present invention comprises a dispenser means for discharging a predetermined amount of liquid crystal, and a measuring means for measuring the discharge amount of the liquid crystal by the dispenser means, the measuring means having an optical sensor, and the dispenser means Integrating signal fluctuation of the optical sensor generated when the liquid crystal discharged from the optical sensor passes through the optical sensor, and measuring the discharge amount of the liquid crystal.
[0060]
Since the amount of liquid crystal discharged from the dispenser means is not accurate only by self-control of the dispenser means, the measuring means is provided, and the amount (volume) of the liquid crystal is measured by scanning the optical sensor with the liquid crystal discharged from the dispenser means. taking measurement. In this case, the output of the optical sensor measures the width of the ejected liquid crystal droplets, and if measured continuously, the change over time in the ejection amount is measured, and if the measurement result is integrated, a value corresponding to the total ejection amount is obtained. can get. This value and the actual discharge amount are measured and compared to obtain a correlation in advance, and the actual discharge amount can be estimated in real time based on the correlation. This makes it possible to accurately control the total discharge amount dropped onto a desired site, and to make the cell thickness uniform even when manufacturing a large-screen liquid crystal panel.
[0061]
In this case, as a specific example of the measuring means, laser light is scanned in a direction substantially perpendicular to the liquid crystal to be ejected, and the output of the laser light is changed by the ejected liquid crystal crossing the laser light and detected by the optical sensor. It is preferable to measure the discharge amount of the liquid crystal. As described above, by using the laser as the irradiation light source, the discharge amount of the liquid crystal can be measured more quickly and accurately.
[0062]
Further, it is preferable to measure the discharge amount of the liquid crystal from at least two directions, or to measure the discharge amount from two directions substantially orthogonal to each other, so that the accuracy of the discharge amount measurement can be expected.
[0063]
Further, it is preferable that the optical sensor is installed at a position within 2 cm from the liquid crystal discharge port of the dispenser means.
[0064]
An optical sensor is provided at the liquid crystal discharge port of the needle of the dispenser means, and when the amount of liquid crystal actually dropped is measured, the liquid droplets are continuously dropped up to about 2 cm from the liquid crystal discharge port, and about 1 cm is most suitable. I found out. This is because, when the discharge distance becomes longer than 2 cm due to the pressure difference between the inside and outside of the needle or the generation of bubbles, the liquid crystal that was continuously discharged becomes discontinuous and the measurement accuracy decreases.
[0065]
The liquid crystal dropping device of the present invention includes a dispenser means for discharging a predetermined amount of liquid crystal, a measuring means for recognizing a liquid crystal droplet shape discharged by the dispenser means, and estimating an actual liquid crystal discharge amount from the shape. It is provided with.
[0066]
Since the amount of liquid crystal discharged from the dispenser means is not accurate only by self-control of the dispenser means, the measuring means is provided to recognize the shape of liquid crystal droplets discharged from the dispenser means, and from this shape to the actual liquid crystal The amount of discharge is estimated. In this case, the correlation between the liquid crystal droplet shape and its amount (volume) is obtained in advance, and the actual discharge amount is estimated based on the knowledge. This makes it possible to accurately control the total discharge amount dropped onto a desired site, and to make the cell thickness uniform even when manufacturing a large-screen liquid crystal panel.
[0067]
In this case, as a specific example of the measuring means, the liquid droplet shape of the liquid crystal is optically recognized, and the actual liquid crystal ejection amount is estimated from the image of the shape.
[0068]
In addition, an optical sensor is provided in the vicinity of the liquid crystal discharge port of the dispenser means, and the optical sensor signal generated when the discharged liquid crystal passes through the optical sensor is used as a trigger signal from the image of the liquid crystal droplet shape. It is also preferable to estimate the discharge amount of the liquid crystal.
[0069]
Further, the dispenser means discharges the liquid crystal by moving the piston in the syringe, and the control of the discharge amount is adjusted by the stroke amount of the piston, and the stroke amount of the piston is determined based on the result of image processing. It is also suitable to be configured to change automatically.
[0070]
Thereby, the estimated value of the discharge amount from the dispenser means measured by the measurement means is fed back to the dispenser means, and the liquid crystal discharge amount can be accurately controlled.
[0071]
The liquid crystal dropping device of the present invention has a plurality of thin tubes, has discharge means for discharging a predetermined amount of liquid crystal from each of the thin tubes, and each tray corresponding to each of the thin tubes of the discharge means, and is received by each of the trays. Measuring means for measuring the weight of each liquid crystal droplet, and supplying the liquid crystal droplet whose weight is measured by the measuring means and whose discharge amount is specified from each of the trays.
[0072]
Since the amount of liquid crystal discharged from the discharge means is not accurate only by self-control of the discharge means, the measurement means is provided, and after receiving the liquid droplets discharged from each thin tube with a receiving pan and measuring the weight of the liquid droplets Drops are supplied from the tray. At this time, the amount of liquid crystal remaining in the tray is measured in advance, and the supply amount is controlled based on this knowledge. This makes it possible to accurately control the total discharge amount dropped onto a desired site, and to make the cell thickness uniform even when manufacturing a large-screen liquid crystal panel.
[0073]
In this case, it is preferable that a water repellent process for repelling the liquid crystal is applied to the portion of the measuring means that contacts the liquid crystal.
Thereby, the remaining of the liquid crystal is prevented as much as possible, and the liquid crystal amount can be supplied more accurately.
[0074]
In the liquid crystal display device and the method of manufacturing the same of the present invention, at least one of the pair of substrates is transparent, a frame pattern is formed on the periphery of the image display region by applying a sealant, and the dielectric constant is included in the frame pattern. Dropping a liquid crystal having negative anisotropy and bonding the substrates together, targeting a vertical alignment type liquid crystal display device in which the sealant is cured, including a liquid crystal compound represented by the following general formula: The liquid crystal material whose carbon number m of the terminal alkyl group is 2 or more is used.
[0075]
[Chemical formula 2]

[0076]
When a liquid crystal material containing a liquid crystal compound of the above general formula having negative dielectric anisotropy and having an even number of carbon atoms m in the terminal alkyl group is used, the specific resistance of the bulk liquid crystal can be kept high. A liquid crystal containing a neutral component having no polar group and containing an even number of m in the above general formula has an initial ratio as compared with a liquid crystal containing the same component and containing an odd number of m. In all of the resistance, the specific resistance after being left at high temperature, and the specific resistance after exposure to ultraviolet rays (UV), good results are obtained for the liquid crystal having an even number of m.
[0077]
Furthermore, among the liquid crystal compounds of the above general formula, it is desirable to use only those having an m number of 2,4.
In general, when the terminal alkyl chain of the liquid crystal compound is long, the liquid crystal viscosity is increased. The liquid crystal compound of the above general formula also has an action of maintaining the nematic phase in a wide temperature range of the mixed liquid crystal even on the low temperature side. In this case, it is preferable to include two or more compounds having different m numbers. Therefore, in order to suppress the increase in the viscosity of the liquid crystal, it is preferable to use a compound having m number of 2 or 4.
[0078]
In the liquid crystal display device and the method of manufacturing the same of the present invention, at least one of the pair of substrates is transparent, a frame pattern is formed on the periphery of the image display region by applying a sealant, and the dielectric constant is included in the frame pattern. The liquid crystal material is a neutral liquid crystal compound having no polarity, intended for a vertical alignment type liquid crystal display device in which liquid crystal having negative anisotropy is dropped and the substrates are bonded together and the sealant is cured. The liquid crystal containing this neutral liquid crystal compound has a high volatility in which the weight ratio decreases by 1% or more when left in a vacuum when dropped, and has a rotational viscosity of 15 compared with a non-volatile neutral liquid crystal compound. % Or lower.
[0079]
By introducing a low-viscosity material for rotational viscosity, the viscosity of the liquid crystal can be reduced by 15% or more from the state before the introduction, and the volatility of the liquid crystal at this time is reduced by 1% or more (volatilization) by weight ratio. Show. Thus, the response speed of the liquid crystal display device can be improved by reducing the viscosity of the liquid crystal material.
[0080]
In this case, the liquid crystal material has a clearing point of 70 ° C. or higher, a dielectric anisotropy Δε of −4.0 ≦ Δε <0, and a refractive index anisotropy Δn of 0.1000 or more. It is preferable that By satisfying these conditions, display characteristics such as luminance (transmittance) and response speed and mass productivity can be improved.
[0081]
Further, it is preferable that these liquid crystal display devices have a multi-domain structure in which the liquid crystal molecules fall in two or more directions. This makes it possible to improve viewing angle characteristics, which is convenient for application to a liquid crystal monitor or the like.
[0082]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments to which the present invention is applied will be described in detail with reference to the drawings.
[0083]
-General configuration of liquid crystal display-
FIG. 1 is a schematic cross-sectional view showing a general main configuration of a liquid crystal display device.
The liquid crystal display device includes a pair of transparent glass substrates 1 and 2 facing each other at a predetermined interval, and a liquid crystal layer 3 sandwiched between the transparent glass substrates 1 and 2.
[0084]
A plurality of pixel electrodes 15 are formed on one transparent glass substrate 1 via an insulating layer 4, and a transparent alignment film 6 a is formed so as to cover the pixel electrodes 5. The color filter 7, the common electrode 8, and the alignment film 6b are sequentially stacked. The alignment films 6 a and 6 b are abutted so as to sandwich the liquid crystal layer 3, and the glass substrates 1 and 2 are fixed. Polarizers 9 and 10 are provided outside the substrates 1 and 2. The pixel electrode 5 is formed together with an active matrix, and in the illustrated example, a data bus line 11 of the active matrix is shown. Note that the electrode may be provided only on one of the substrates (for example, in the IPS mode).
[0085]
Here, when the liquid crystal layer 3 is formed by using the dropping injection method, examples in which various improvements are made on the structure, the manufacturing process, and the liquid crystal dropping device used for the manufacturing will be disclosed as embodiments shown below. .
[0086]
As a method of manufacturing a liquid crystal display device commonly used in each embodiment, an ultraviolet curable resin or an (ultraviolet ray + heat) curable resin is used as a main seal material, a glass substrate A serving as a TFT (thin film transistor) substrate, and a CF ( Color filter) A glass substrate B serving as a substrate is prepared. For example, a frame pattern of a main seal is formed by a dispenser on an image display area of the glass substrate B, and a liquid crystal is dropped into the frame pattern by a dropping injection method. , B are bonded together, and the main seal is cured. Thereafter, the bonded substrates A and B are cut into a TFT substrate + CF substrate state, and a liquid crystal display device is completed through various post-processes.
[0087]
(First embodiment)
FIG. 2 is a schematic plan view showing a state of the glass substrate on which the frame pattern is formed before performing the liquid crystal injection process by the dropping injection method in the present embodiment.
In this example, an ultraviolet resin (for example, product name 30Y-363, manufactured by ThreeBond Co., Ltd.) is used for the main seal 21, and a peripheral pattern of the display display area 23 on the glass substrate 22 side serving as a CF substrate is connected by a dispenser and a frame pattern. Form. The start point 31a and the end point 31b of the overlapping portion 31 are provided at positions on the non-mounting side and outside the frame pattern, and the connecting patterns are formed so as to be adjacent to each other after bonding.
[0088]
The main seal 21 has a seal width of 1 mm, and the corner portion has a radius of 1 mm so that the line width is equal to that of the straight portion. The frame pattern is formed so that the gap between the inner periphery and the light shielding film 23 is 0.5 mm after bonding.
[0089]
Next, by a liquid crystal dropping method, a required amount of liquid crystal is dropped into the frame pattern, the glass substrate 22 and the glass substrate to be the TFT substrate are bonded in a vacuum, and the liquid crystal is injected by opening to the atmosphere.
[0090]
After collectively irradiating ultraviolet rays from the glass substrate 22 side, seal hardening is performed by heat treatment, and this is cut into a predetermined dimension to obtain a liquid crystal display panel. In addition, about the cutting | disconnection of a board | substrate, the glass substrate 22 used as CF board | substrate is performed along the cutting line 32, and the glass substrate used as a TFT substrate is performed along the cutting line 33. FIG.
[0091]
Here, for comparison with the liquid crystal display device of this example, the liquid crystal display device shown in FIG. 23 is manufactured as a comparative example.
[0092]
In Comparative Example 1, a frame pattern is formed by the main seal 102 as shown in FIG. The start point and the end point are provided at positions on the frame pattern, and the frame pattern is connected at the start point and the end point (the overlapping portion 103 is formed). Otherwise, a liquid crystal display panel is obtained in the same manner as in this example.
[0093]
In Comparative Example 2, a frame pattern is formed on the main seal 102 as shown in FIG. The start point and the end point are located on the frame pattern and at a corner, and the frame pattern is connected at the start point and the end point (the overlapping portion 103 is formed). The corner portion is not formed in an arc shape. Otherwise, a liquid crystal display panel is obtained in the same manner as in this example.
[0094]
In this example, since the start point 31 a and the end point 31 b are outside the frame pattern, the overlap between the start point 31 a and the end point 31 b is not formed on the frame pattern, and the main seal 21 of the frame pattern connecting portion does not overlap the light shielding film 23. On the other hand, in Comparative Examples 1 and 2, since the overlapping portion 103 of the start point and the end point is formed on the frame pattern, the main seal 102 of the frame pattern connecting portion overlaps the light shielding film 105. The seal width of the frame pattern connecting portions of Comparative Examples 1 and 2 is 2.6 mm, and the seal width when the main seal 102 is applied twice is 2.0 mm. This is because the dispenser moves in the vertical direction at the start point and the end point, so that the amount of seal application is larger than that of the straight line portion. The connecting portion of the frame pattern of Comparative Example 1 protrudes 0.8 mm toward the inner periphery and the gap between the inner periphery and the light shielding film 105 is 0.5 mm. Therefore, the main seal 102 overlaps the light shielding film 105 by 0.3 mm. In the frame pattern connecting portion of Conventional Example 2, the protrusion amount is the same as 0.8 mm, but the gap between the inner periphery and the light shielding film 105 is increased by 1.4 times, so the overlap between the main seal 102 and the light shielding film 105 is small. 0.1 mm. If the gap between the inner periphery and the light-shielding film is further widened, the overlap between the main seal 102 and the light-shielding film 105 can be eliminated, but this is not appropriate because the ratio of the external dimensions to the image display area is increased (widening of the frame).
[0095]
Even if the start point and the end point are formed apart on the frame pattern, the overlap between the main seal and the light shielding can be eliminated, but the seal width of the frame pattern connecting portion is narrowed and the strength required for the main seal 102 is maintained. It is not appropriate because it cannot be done.
[0096]
The liquid crystal display panels of this example and comparative examples 1 and 2 were subjected to a lighting test. As a result, display unevenness did not occur in this example, but in Comparative Examples 1 and 2, display unevenness occurred due to poor curing of the main seal 102 at the frame pattern connecting portion.
[0097]
As described above, according to the first embodiment, display unevenness due to a decrease in holding power that tends to occur due to a sealant is suppressed, and a liquid crystal display device is easily manufactured with a high yield using a dropping injection method. Thus, a highly reliable liquid crystal display device can be realized.
[0098]
-Modification-
Here, various modifications of the first embodiment will be described.
[0099]
(Modification 1)
In the first modification, a two-chamfered seal pattern as shown in FIG. 3 and a main seal 42 as shown in FIG. 4 are provided at the periphery of the image display area on the glass substrate 22 side serving as a CF substrate by a main seal 41 with a dispenser. A four-chamfer seal pattern is formed.
[0100]
In the two chamfering of FIG. 3, the start point 43a and the end point 43b are connected on the substrate 22 to continuously form a seal pattern as one overlapping portion 43 so that the main seal 41 does not intersect at the frame pattern connecting portion. On the other hand, in the four chamfering of FIG. 4, the start point 44 a and the end point 44 b are connected on the substrate 22 to continuously form a seal pattern as one overlapping portion 44, and the main seal 42 intersects at the frame pattern coupling portion. To do. Otherwise, the liquid crystal display panel is obtained in the same manner as in the first embodiment.
[0101]
In the two chamfering of FIG. 3, the start point 43 a and the end point 43 b are outside the frame pattern, and the main seal 41 does not intersect at the frame pattern coupling portion, so the main seal 41 at the frame pattern connecting portion does not overlap the light shielding film 23. 4, the main seal 42 intersects at the frame pattern coupling portion and the seal width becomes as thick as 2.0 mm, but is narrower than the overlapping portion 44 of the start point 44a and the end point 44b, and the coupling portion is a corner portion. Therefore, the main seal 42 at the frame pattern connecting portion does not overlap the light shielding film 23.
[0102]
Each of the liquid crystal display panels manufactured using the two chamfers of FIG. 3 and the four chamfers of FIG. 4 was subjected to a lighting test. As a result, display unevenness did not occur in both cases.
[0103]
(Modification 2)
The main steps of Modification 2 are shown in FIG. Here, (a) is a schematic plan view of the substrate 22a, (b) is a schematic cross-sectional view in the vicinity of the transfer seal of the substrate 22a, and (c) is a schematic cross-sectional view showing the transfer seal in an enlarged manner.
[0104]
Here, an ITO film is formed on the surface of a resin spacer (for example, trade name Micropearl SP manufactured by Sekisui Fine Chemical Co., Ltd.) to obtain conductive particles 45. The transfer seal 24 uses the ultraviolet curable resin used in the first embodiment, and 1 wt% of the conductive particles 45 are mixed therein. When the attenuation rate of ultraviolet rays by the conductive particles 45 and the transparent electrode 46 was measured, it was found that the amount of light applied to the transfer seal 24 was 10% less than that of the main seal 21.
[0105]
Also, a reflective film 47 serving as an electrode is formed at the formation position of the transfer seal 24 on the TFT substrate side using an aluminum film. The aluminum film is formed together with the TFT film forming process. In the ultraviolet irradiation, a light amount for ultraviolet curing the main seal 21 was collectively irradiated from the substrate 22 side, and then, the transfer seal 24 was spot-irradiated with parallel light using a light guide 48 from the vertical direction of the substrate. The amount of spot irradiation was set substantially equal to the amount of attenuation of ultraviolet rays by the conductive particles 45 and the transparent electrode 46 (Modification 2A) and 2/3 of the attenuation (Modification 2B). Otherwise, the liquid crystal display panel is obtained in the same manner as in the first embodiment.
[0106]
Here, for comparison with the liquid crystal display device of this example, the liquid crystal display device shown in FIG. 24 is manufactured as a comparative example.
In this comparative example, conductive particles (for example, trade name Micropearl NI manufactured by Sekisui Fine Chemical Co., Ltd.) whose surface is coated with nickel are used, and 1 wt% is mixed into the transfer seal 106. Otherwise, a liquid crystal display panel is obtained in the same manner as in Comparative Example 1 of the first embodiment.
[0107]
The liquid crystal display panels according to the modified examples 2A and 2B and the comparative example were each subjected to a lighting test. As a result, no display unevenness occurred in the modified examples 2A and 2B, but in the comparative example, display unevenness due to poor curing occurred in the frame pattern connecting portion (overlapping portion 103) and the transfer seal 106. In Modification 2B, the amount of light applied to the transfer seal 24 is insufficient, but the reflection film 47 reflects the ultraviolet rays to compensate for the shortage, so display unevenness due to poor curing does not occur.
[0108]
If there is a slight margin between the amount of light that deteriorates the liquid crystal and the amount of light that cures the ultraviolet ray of the sealant, a reflective film is formed under the transfer seal 24 without spot irradiation on the transfer seal 24 to reduce the amount of light for batch irradiation. It is also possible to harden the transfer seal 24 with a slight increase.
[0109]
(Modification 3)
In the third modification, as shown in FIG. 6, after the substrates 22 a and 22 b are bonded to each other by curing the sealing material to form the substrate 51, a transfer arm entrance / exit spacer 53 having a structure that supports the substrate 51 at multiple points is provided. The substrate transfer cassette 52 is used to perform heat treatment after the ultraviolet irradiation.
[0110]
On the other hand, as a comparative example, heat treatment after ultraviolet irradiation is performed using a substrate transport cassette 108 having a structure in which the substrate 110 is supported by the conventional substrate edge as shown in FIG.
[0111]
Otherwise, the liquid crystal display panel is obtained in the same manner as in the first embodiment in both the modified example 3 and the comparative example.
[0112]
The liquid crystal display panels according to the modified example 3 and the comparative example were each subjected to a lighting test. As a result, in the third modification, no positional deviation occurred during the heat treatment, but in the comparative example, a positional deviation occurred. In Modification 3, the substrate 51 is supported at multiple points, so that the substrate 51 can be held in parallel. However, in the comparative example, since the substrate 51 is supported only at the end of the substrate, the deflection becomes large at the center of the substrate 108, and the position is during thermal curing. Deviation occurs.
[0113]
(Second Embodiment)
FIG. 7 is a schematic perspective view showing the state of ultraviolet irradiation after performing the liquid crystal injection step by the drop injection method in this embodiment, and FIG. 8 is an enlarged view of the circle C in FIG. It is a schematic sectional drawing which shows.
[0114]
In this example, an ultraviolet curable resin (trade name 30Y-363 / manufactured by ThreeBond Co., Ltd./curing light amount is 2500 mJ / cm on an I-line basis in the main seal. ² The glass substrate 61 to be the CF substrate and the glass substrate 62 to be the TFT substrate are bonded together and cut out to produce a liquid crystal display panel. In this example, the ultraviolet irradiation process performed when the glass substrates 61 and 62 are bonded together is improved.
[0115]
The end of the alignment film 63 on the glass substrate 61 was formed in a region that is on the inner peripheral outer side and the outer peripheral inner side of the resin.
[0116]
For comparison, as shown in FIG. 9, a liquid crystal display panel in which an end of an alignment film 63 on a glass substrate 61 serving as a CF substrate is formed inside the inner periphery of the resin and a light shielding mask 64 is provided as a conventional example. To do.
[0117]
For ultraviolet irradiation, a high-pressure mercury lamp is used as a light source, and as shown in FIG. 7, a cut filter 64 that hardly transmits a short wavelength of less than 300 nm and a cut filter 65 that does not substantially transmit a long wavelength of 500 nm or more are arranged on the irradiation light source side. Do.
[0118]
As shown in FIG. 10, the transmittance when both filters are combined is 50% at the 313 nm emission line peak and 90% at the 365 nm emission line peak. The amount of ultraviolet light is 2700 mJ / cm on an I-line basis. ² However, when the variation of the irradiation area was examined, the minimum value portion of the variation was 2300 mJ / cm. ² The maximum value is 3100 mJ / cm ² Met.
[0119]
When the transmittance of each of the glass substrate and the glass substrate to which the alignment film was added was measured, the glass substrate (trade name NA35 / NH Techno Glass Co., Ltd./0.7 mm thickness) was 84% at the 313 nm emission line peak, and the alignment film (trade name) JALS-684 / manufactured by JSR / film thickness of 80 nm) was 71%, and it was found that the wavelength was attenuated by about 15% by the alignment film.
[0120]
The liquid crystal (product name: MJ961213 / Merck) is irradiated with ultraviolet rays using the long and short wavelength cut filters 64, 65, and the threshold value of the amount of ultraviolet light that activates the photolysis of the liquid crystal is obtained from the decrease in retention rate. It was. As a result, as shown in FIG. 11, when the ultraviolet ray is irradiated through the glass substrate, the integrated light quantity in the wavelength band (310 ± 20 nm) near the 313 nm emission line peak is 1000 mJ / cm. ² Degree, 3000 mJ / cm on I-line basis ² The decrease in the retention rate increased with the degree, and the decrease in the retention rate was small below this. Similarly, when the threshold value of the amount of ultraviolet light that activates the photodecomposition of the liquid crystal using only the short-wavelength cut filter 64 is obtained from the decrease in the retention rate, the value is 1000 to 1500 mJ / cm on the I-line basis. ² It was found to be less than half of the long / short wavelength cut filter. This is because the liquid crystal is heated by irradiation with a long wavelength of 500 nm or more, and the photolysis reaction of the liquid crystal with a wavelength of 300 nm or more and less than 320 nm is promoted. Therefore, it was found that the photolysis of the liquid crystal is activated because the amount of ultraviolet light transmitted through the alignment film exceeds this value in any part of the irradiation area.
[0121]
In this example, the main seal is cured by applying the long and short wavelength cut filters 64 and 65. On the other hand, in the conventional example, only the short wavelength cut filter is applied (conventional example 1) and the long / short wavelength cut filter is applied (conventional example 2), and the main seal is cured by masking other than the resin with a light shielding mask. Do. When the thus manufactured liquid crystal display panel was subjected to a lighting display inspection, in the conventional example 1, display unevenness due to a decrease in the retention rate in the entire circumference in the vicinity of the main seal corresponds to the maximum value portion of the irradiation area in the conventional example 2. In the vicinity of the main seal, display unevenness due to a decrease in retention rate occurred. This is considered to be caused by the photolysis of the liquid crystal by ultraviolet irradiation.
[0122]
Further, in the conventional examples 1 and 2, a decrease in retention rate occurred in some corner portions. The corner portion is provided with an R (arc) so that the seal width does not become thicker when the seal is applied, so that the distance between the display area and the resin is closer than the peripheral portion. In the conventional example, since an alignment film is provided on the inner peripheral inner side of the resin, if any uncured component remains in the resin, it diffuses into the liquid crystal by heat treatment and reaches the limit of the display area. As a result, it is considered that a decrease in retention rate occurred in some corner portions.
[0123]
On the other hand, in this example, display unevenness due to a decrease in the retention rate that occurred in the conventional examples 1 and 2 did not occur. This is because the photolysis of the liquid crystal is suppressed by the filter and the alignment film, and the elution of the uncured component of the resin is suppressed by the alignment film.
[0124]
As described above, according to the second embodiment, display unevenness due to a decrease in retention rate that tends to occur due to a sealant is suppressed, and a liquid crystal display device is easily manufactured with a high yield using a drop injection method. Thus, a highly reliable liquid crystal display device can be realized.
[0125]
-Modification-
Here, a modification of the second embodiment will be described.
[0126]
In this modification, the transparent electrode end and the alignment film end on the glass substrate 61 are formed in the inner and outer peripheral regions of the resin, and the liquid crystal display panel is manufactured by the same method as in the second embodiment. To do. The irradiation condition of ultraviolet rays is 3200 mJ / cm with respect to the amount of ultraviolet rays based on the I-line. ² Except for the above, it is the same as in the second embodiment. When the variation of the irradiation area was examined, the minimum value portion of the variation was 2700 mJ / cm. ² , 3700mJ / cm at maximum value ² Met.
[0127]
When the transmittance of the glass substrate to which the transparent electrode and the alignment film were added was measured, the glass substrate was 84%, the transparent electrode (ITO / film thickness 1300A) and the alignment film were 46% at the 313 nm emission line peak, and the transparent electrode and the alignment film were aligned. It was found that the wavelength was attenuated by about 45% by the film.
[0128]
Therefore, even in the maximum value portion of the irradiation area, the amount of ultraviolet light transmitted through the transparent electrode and the alignment film is attenuated by the transparent electrode and the alignment film, so that the above threshold value is not exceeded and the photolysis of the liquid crystal is not activated. I understood.
[0129]
When the thus manufactured liquid crystal display panel was subjected to a lighting display inspection, display unevenness due to a decrease in retention rate that occurred in the conventional example did not occur. Further, since the amount of ultraviolet light irradiated to the transparent electrode and the resin outside the alignment belly end is increased, even the lowest value portion of the variation is irradiated more than the curing light amount. The strength was improved by 10%.
[0130]
-Comparative examples 1 and 2-
A liquid crystal display panel is manufactured by the same method as in the second embodiment. Although the ultraviolet irradiation conditions are the same as those in the second embodiment, as shown in FIG. 12, a high-pressure mercury lamp is used as the ultraviolet irradiation light source, and a cut filter 65 that hardly transmits a short wavelength of less than 320 nm is provided on the glass substrate 61. Place on the side.
[0131]
The threshold value of the amount of ultraviolet light that activates the photolysis of the liquid crystal using the short-wavelength cut filter 65 was determined from the decrease in retention rate, and was 3000 mJ / cm on the basis of I-line. ² It was found that photolysis of the liquid crystal was not activated by irradiation. Therefore, even if there is no filter that attenuates the wavelength of 300 nm or more and less than 320 nm, such as the transparent electrode film or alignment film in this example in the outer peripheral inner side and outer peripheral inner side, the photolysis of the liquid crystal is not activated. I understood.
[0132]
When the liquid crystal display panel thus manufactured (Comparative Example 1) was subjected to a lighting display inspection, display unevenness due to a decrease in retention rate occurred in all stations near the main seal. When the panel was disassembled and the liquid crystal in the vicinity of the main seal was analyzed by gas chromatography, a resin component derived from the main seal was detected.
[0133]
Further, as in a known example, an ultraviolet curable resin was prepared using a photoinitiator having an absorption band on the long wavelength side of 320 nm or longer, and the same comparison was performed using this as a main seal. When the liquid crystal display panel thus prepared (Comparative Example 2) was subjected to a lighting display inspection, display unevenness due to a decrease in retention stroke occurred in a part near the main seal. When the panel was disassembled and the liquid crystal in the vicinity of the main seal was analyzed by gas chromatography, a resin component derived from the main seal was detected to a lesser extent than in Comparative Example 1.
[0134]
This is because when the resin is cured on the long wavelength side of 320 nm or more, the reaction rate of the resin is reduced by the amount of energy compared to the case where a wavelength of 300 nm or more and less than 320 nm is used. It shows that even if the absorption band of the initiator is shifted to the longer wavelength side of 320 nm or more, only the energy absorption efficiency is improved, and the reaction rate of the resin is not comparable.
[0135]
(Third embodiment)
FIG. 13 is a schematic configuration diagram of the liquid crystal dropping device of the present embodiment.
This liquid crystal dropping apparatus includes a dispenser 71 that discharges a predetermined amount of liquid crystal, and a measuring unit 72 that measures the amount of liquid crystal discharged by the dispenser.
[0136]
The dispenser 71 discharges a predetermined amount of liquid crystal from a needle-like discharge portion and drops it into a frame pattern formed on the glass substrate.
[0137]
The measuring means 72 includes a laser device 73 that is an irradiation light source, an optical sensor 74 that senses the laser light emitted from the laser device 73, a data logger 75 that records the output of the optical sensor 74 with respect to time, and the data And a computer 76 for analyzing and displaying the result of recording by the logger 75.
[0138]
In this liquid crystal dropping device, laser light is irradiated from the laser device 73 to the liquid crystal discharged from the dispenser 71, and the result of sensing the laser light crossing the dropped liquid crystal with the optical sensor 74 is recorded by the data logger 75. At this time, the data logger 75 records time-dependent output fluctuations as shown in FIG. 14, for example. The output of the liquid crystal is measured by integrating the output with the computer 76 over time. The computer 76 estimates the weight based on the correlation between the output of the optical sensor 74 and the weight of the liquid crystal prepared in advance.
[0139]
Although only one optical sensor is shown in the illustrated example, two optical sensors are provided to measure the amount of liquid crystal discharged from two directions that are substantially perpendicular to each other, and further provided with an optical sensor in a multifaceted manner. Even if it measures, it is suitable.
[0140]
Furthermore, the dispenser 71 discharges the liquid crystal by moving the piston in the syringe, and the control of the discharge amount is adjusted by the stroke amount of the piston, and the stroke amount of the piston is automatically set based on the result of the image processing. It is also suitable to be configured to change to
[0141]
As shown in FIG. 15, the positional relationship between the dispenser 71 and the optical sensor 74 is that about 1 cm is the most suitable because liquid droplets continuously drop from the liquid crystal discharge port to about 2 cm. It was. This is because, when the discharge distance becomes longer than 2 cm due to the pressure difference between the inside and outside of the needle or the generation of bubbles, the liquid crystal that was continuously discharged becomes discontinuous and the measurement accuracy decreases.
[0142]
The discharge amount was actually measured using this liquid crystal dropping device. At this time, the number of scans is 100,000 times per second, and the total amount of liquid crystal to be dropped is 250 mg. Since the liquid crystal is dropped at 48 locations, the drop amount per time is 5.21 mg. The dispenser 71 was set to discharge this amount.
[0143]
After dropping, the total amount dropped was estimated to be 245 mg from the output of the optical sensor 74 48 times. Therefore, 5 mg was added using a micro syringe.
When the variation in the cell thickness of the liquid crystal display panel thus produced was measured, it was within a fluctuation of about 1%. In this example, since the number of times of scanning the discharged liquid crystal can be very large, even a dispenser having a function of repeating discharge in a short time can sufficiently cope with it.
[0144]
As described above, according to the liquid crystal dropping device of the third embodiment, it is possible to precisely measure and control the liquid crystal dropping amount by the dropping injection method, and appropriately adjust the dropping amount for each dropping portion. It is possible to make the cell thickness uniform and perform highly reliable liquid crystal drop injection with a high yield.
[0145]
-Modification-
Here, various modifications of the third embodiment will be described.
[0146]
(Modification 1)
In Modification 1, as shown in FIG. 16A, the measuring unit 77 is configured to measure the discharge amount from the liquid crystal droplet shape dropped from the dispenser 71 into the frame pattern of the glass substrate.
[0147]
The measuring means 77 calculates the area of the hatched portion of the liquid crystal 79 from the CCD 78 that images the dropped liquid crystal and the output of the CCD 78, as shown in FIG. The computer 76 is configured to estimate the weight based on the correlation with the weight (volume) of the liquid crystal.
[0148]
In the illustrated example, only one CCD is shown. However, in order to further improve the measurement accuracy, a plurality of CCDs may be provided so that the liquid crystal shape can be captured from different directions.
[0149]
(Modification 2)
In the second modification, as shown in FIG. 17A, the measuring unit 81 is configured to measure the discharge amount from the shape of liquid droplets discharged from the dispenser 71 in the air.
[0150]
The measuring means 81 includes a laser device 73 that is an irradiation light source, an optical sensor 74 that senses the laser light emitted from the laser device 73, and a timing at which the optical sensor 74 recognizes the passage of liquid crystal by the laser light. As shown in FIG. 17 (b), the area of the hatched portion of the liquid crystal 79 is calculated from the CCD 78 that images the liquid crystal in the air and the output of the CCD 78, and the area and the weight of the liquid crystal ( And a computer 76 for estimating the weight based on the correlation with the volume.
[0151]
In this case, since the liquid crystal shape can be reliably captured in the air by the CCD 78, high-precision measurement can be performed without being affected by the surface shape of the glass substrate. In the illustrated example, only one CCD is shown. However, in order to further improve the measurement accuracy, it is preferable to provide a plurality of CCDs and capture the liquid crystal shape from different directions.
[0152]
(Modification 3)
As shown in FIG. 18 (a), the liquid crystal dropping device of Modification 3 includes a plurality of thin glass tubes 82, and a metering dropping jig 83 which is a discharge means for discharging a predetermined amount of liquid crystal from each thin tube 82. The measuring and dropping jig 83 includes each receiving tray 84 corresponding to each thin tube 82, and includes measuring means 85 that respectively measure the weight of liquid crystal droplets received by the receiving tray 84. Liquid crystal droplets whose weight is measured by means 85 and whose discharge amount is specified are dropped and supplied into the frame pattern of the glass substrate by rotating each tray 84.
[0153]
As shown in FIG. 18 (b), each thin tube 82 has a structure having a highly water-repellent Teflon coating on the inner surface where the liquid crystal comes into contact, and the liquid crystal is pushed out by an inert gas and discharged. . When the liquid crystal is dropped on the glass substrate, the liquid crystal often remains in each capillary 82, and it is preferable to promote discharge using an inert gas, and the inner surface of each capillary 82 is coated with Teflon. Thus, more effective discharge becomes possible.
[0154]
(Fourth embodiment)
In this embodiment, a liquid crystal material suitable for application to a liquid crystal dropping method is disclosed.
The liquid crystal material of this example includes a liquid crystal compound represented by the following general formula, and the terminal alkyl group has an even number of carbon atoms m of 2 or more.
[0155]
[Chemical 3]

[0156]
When a liquid crystal material containing a liquid crystal compound of the above general formula having a negative dielectric anisotropy and having an even number of carbon atoms m in the terminal alkyl group is used, the specific resistance of the bulk liquid crystal can be kept high. .
[0157]
In this example, a neutral component having no polarity is used as a common matrix, and a liquid crystal a containing an odd number of m in the general formula and an even number of m in the general formula are included. The liquid crystal a ′ was prepared, and the specific resistance values of the bulk liquid crystals were compared for the two liquid crystal materials under the following conditions.
[0158]
In all of the initial specific resistance, the specific resistance after being left at high temperature, and the specific resistance after exposure to ultraviolet rays (UV), better results were obtained when a ′ (m: even number) was used. In particular, after UV exposure, the specific resistance value can be kept high by an order of magnitude, which is very advantageous at the time of UV seal curing in the dropping injection process. These relationships are shown in FIG. Here, liquid crystal A (n = 1, 3) was used as liquid crystal a, and liquid crystal B and liquid crystal C were used as liquid crystal a ′.
[0159]
Furthermore, among the liquid crystal compounds of the above general formula, it is desirable to use only those having an m number of 2,4. In general, when the terminal of the liquid crystal compound becomes longer, the viscosity of the liquid crystal increases and the response speed decreases, which is undesirable for a liquid crystal display device. The liquid crystal compound of the above general formula also has an effect of maintaining the nematic phase in a wide temperature range of the mixed liquid crystal even on the low temperature side. In that case, the m number is preferably 2 or more. Therefore, in order to suppress the increase in the viscosity of the liquid crystal, it is desirable to use a compound having the m number of 2 or 4.
[0160]
It is also necessary to reduce the viscosity of the liquid crystal material and improve the response speed of the liquid crystal display device. In the dropping injection method, the vacuum standing state (including the exhaust time) is extremely short when bonding. Conventionally, the exhaust time which required several hours can be shortened to several minutes. For this reason, liquid crystal has been volatilized in a vacuum in the past, so it has been necessary to adjust the liquid crystal with a liquid crystal compound that suppresses its volatility, but the dripping injection method can also be used for mass production of volatile materials. became.
[0161]
In addition, when a low-viscosity material that lowers the viscosity of the liquid crystal is introduced, the viscosity of the liquid crystal can be reduced by 15% or more with respect to that before introduction (FIG. 21: liquid crystal E → liquid crystal D). It was found that the volatility of the liquid crystal at that time showed a decrease (volatilization) of 1% or more by weight.
[0162]
When the TV characteristics were measured, no significant difference was observed before and after the introduction of the low viscosity material. On the other hand, with regard to response characteristics, it was confirmed that the speed can be increased including halftones, and there is an effect.
[0163]
Also, from the relationship with the specifications of the liquid crystal display device, the clearing point of the liquid crystal material is 70 ° C. or higher, the dielectric anisotropy Δε is −4.0 ≦ Δε <0, and the refractive index anisotropy Δn is When a liquid crystal material of 0.1000 or more is used, it may mean that display characteristics such as luminance (transmittance) and response speed, and mass productivity are improved.
[0164]
Further, in this liquid crystal display device, when a multi-domain structure in which the direction in which the liquid crystal molecules fall is 2 or more, the viewing angle characteristics are excellent and convenient for a liquid crystal monitor or the like.
[0165]
-Experimental example-
An experimental example in which the liquid crystal display device according to the fourth embodiment is manufactured and various display characteristics are examined will be described below.
[0166]
(Experimental example 1)
Using a substrate having an ITO electrode, a brand name JALS-684 (manufactured by JSR) is formed as an alignment film by a spinner, a predetermined spacer (cell thickness: 4.0 μm) is dispersed, and a thermosetting sealant is used. Lamination and empty cells were produced.
[0167]
For these empty cells, the liquid crystal A with the m number = 1, 3 and the liquid crystals B, C with the m number = 2, 4 are injected into each empty cell, sealed, and polarized. The plate was bonded with crossed Nicols to produce a VA cell.
[0168]
As shown in FIG. 20, the voltage holding ratio, the ion density, and the residual DC voltage were measured for each cell, and the difference in electrical characteristics was examined. Liquid crystal A, liquid crystal B, and liquid crystal C have the physical property values shown in Table 1 below. Further, (a) and (b) show the voltage holding ratio, (c) shows the ion density, and (d) shows the residual DC voltage. As a result of the experiment, the electrical characteristics of liquid crystals B and C (m number = 2, 4) were improved compared to liquid crystal A (m number = 1, 3).
[0169]
[Table 1]

[0170]
(Experimental example 2)
The specific resistances of the liquid crystals A, B and C were measured. Initial value of bulk liquid crystal, after UV exposure (100 mW / cm ² , 60 seconds), after heating (120 ° C., 60 minutes), and after dropping the UV curable resin (contamination dependency), the four conditions were examined. The liquid crystals B and C (m number = 2, 4) obtained results higher than the liquid crystal A (m number = 1, 3) under all conditions. Particularly, the data after UV exposure has a specific resistance value. It was confirmed that there was a big improvement effect that it was one digit higher.
[0171]
(Experimental example 3)
The difference between the liquid crystal D before the introduction of the low-viscosity material and the liquid crystal E after the introduction was examined. The introduced liquid crystal D is a liquid crystal that does not have any problem even if the conventional vacuum dip injection is used. On the other hand, the liquid crystal E has volatility against being left in a vacuum because a low-viscosity material is introduced.
[0172]
As a result of the experiment, as shown in FIG. 21, the liquid crystal E showed a change in weight (decrease) of more than 1% when left for 1 hour, and was confirmed to be sufficiently volatile than the liquid crystal D.
[0173]
A VA cell was fabricated by the same procedure as in the third embodiment except that the spacers were changed (cell thickness: 3.5 μm) using the liquid crystals D and E. The TV characteristics are equivalent. As shown in FIG. 22, as a result of examining the response speed, the liquid crystal E in which the low-viscosity material is introduced is faster than the liquid crystal D in which the low-viscosity material is introduced with respect to all applied voltages. It was confirmed that the effect of speeding up was great in the adjustment region.
[0174]
As described above, according to the fourth embodiment, it is possible to provide a liquid crystal material most suitable for the dropping injection method, thereby suppressing the viscosity of the liquid crystal and reducing the response speed, particularly a halftone high speed. And a liquid crystal display device capable of further improving the display characteristics.
[0175]
Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.
[0176]
(Appendix 1) A sealant is applied to the periphery of an image display area provided on one of a pair of substrates to form a frame pattern, and liquid crystal is dropped into the frame pattern to bond the substrates together, and the seal A method of manufacturing a liquid crystal display device by curing an agent,
The manufacturing method of a liquid crystal display device, wherein the sealing agent is applied so that at least one of a start point or an end point of the application of the sealing agent is located outside the frame pattern.
[0177]
(Additional remark 2) The manufacturing method of the liquid crystal display device of Additional remark 1 characterized by performing the application | coating of the said sealing agent so that at least one of the said starting point or the said end point may be located in the non-mounting side side of the said board | substrate.
[0178]
(Additional remark 3) The manufacturing method of the liquid crystal display device of Additional remark 2 characterized by connecting at least one of the said starting point or the said end point so that the said frame pattern and the said non-mounting side may be crossed.
[0179]
(Additional remark 4) The said start point and the said end point are made to correspond on the said board | substrate, and the sealing pattern by the said sealing agent is formed continuously, The manufacturing method of the liquid crystal display device of Additional remark 1 characterized by the above-mentioned.
[0180]
(Supplementary Note 5) A sealant is applied to the periphery of an image display area provided on one of a pair of substrates to form a frame pattern, and liquid crystal is dropped into the frame pattern to bond the substrates together, and the seal A method of manufacturing a liquid crystal display device by curing an agent,
In order to conduct between the pair of substrates, a transfer seal formed by mixing conductive particles in the resin is irradiated with ultraviolet rays made of parallel light from the vertical or oblique direction of the substrate in order to cure the resin. A method for manufacturing a liquid crystal display device.
[0181]
(Supplementary Note 6) A sealant is applied to the periphery of an image display area provided on one of a pair of substrates to form a frame pattern, and a liquid crystal is dropped into the frame pattern to bond the substrates together. A method of manufacturing a liquid crystal display device by curing an agent,
In order to conduct between the pair of substrates, by applying a transfer seal formed by mixing conductive particles in the resin, to cure the resin and bond the substrates together, after curing this by ultraviolet irradiation,
A method of manufacturing a liquid crystal display device, comprising: heat-treating the substrate in a state where the substrate is held in parallel by a support housing after the irradiation of the ultraviolet rays.
[0182]
(Appendix 7) A frame pattern is formed by applying a sealant around the image display area provided on one of the pair of substrates, and a liquid crystal is dropped into the frame pattern to bond the substrates together. A liquid crystal display device obtained by curing the agent,
A liquid crystal display device, wherein the pair of substrates are electrically connected by a transfer seal formed by mixing particles coated with a transparent conductive film on the surface.
[0183]
(Appendix 8) A frame pattern is formed by applying a sealant around the image display area provided on one of the pair of substrates, and a liquid crystal is dropped into the frame pattern to bond the substrates together. A liquid crystal display device obtained by curing the agent,
A film that reflects ultraviolet rays irradiated to cure the resin is formed as an electrode under a transfer seal that is formed by mixing conductive particles in the resin and that conducts between the pair of substrates. Liquid crystal display device.
[0184]
(Additional remark 9) The manufacturing method of the liquid crystal display device of Additional remark 8 characterized by using an aluminum film or a silver film as a film | membrane which reflects an ultraviolet-ray, and forming in the said board | substrate by the side of a thin-film transistor.
[0185]
(Supplementary Note 10) A sealant is applied to the periphery of an image display area provided on one of a pair of substrates to form a frame pattern, and liquid crystal is dropped into the frame pattern to bond the substrates, and the seal A method of manufacturing a liquid crystal display device by curing an agent,
A liquid crystal alignment film is formed in a region where the end portion is the inner periphery outer side and the outer periphery inner side of the sealing agent, and the sealing agent is cured by irradiating light having a wavelength of approximately 300 nm or more and less than 500 nm. A method for manufacturing a liquid crystal display device.
[0186]
(Additional remark 11) At least the edge part of the alignment film on the substrate on which the color filter is formed is formed in a region on the inner peripheral outer side and the outer peripheral inner side of the sealing agent, and the light of the wavelength is irradiated from the substrate side. The method for manufacturing a liquid crystal display device according to appendix 10, wherein the sealing agent is cured.
[0187]
(Supplementary note 12) The liquid crystal display device according to supplementary note 10 or 11, wherein as a means for irradiating light having a wavelength of approximately 300 nm or more and less than 500 nm, a filter that substantially cuts other than the wavelength is disposed on the irradiation light source side. Production method.
[0188]
(Additional remark 13) The hardening light quantity of the said sealing agent is about 3000 mJ / cm on an I-line basis. ² The method for producing a liquid crystal display device according to any one of appendices 10 to 12, characterized in that:
[0189]
(Supplementary note 14) Dispenser means for discharging a predetermined amount of liquid crystal;
Measuring means for measuring the discharge amount of the liquid crystal by the dispenser means,
The measurement means includes an optical sensor, and integrates signal fluctuations of the optical sensor generated when the liquid crystal discharged from the dispenser means passes through the optical sensor, and measures the discharge amount of the liquid crystal. Liquid crystal dropping device.
[0190]
(Supplementary Note 15) The measuring means scans the laser beam in a direction substantially perpendicular to the liquid crystal to be discharged, and the discharged liquid crystal crosses the laser light so that the output of the laser light is changed and detected by the optical sensor. 15. The liquid crystal dropping device according to appendix 14, wherein a discharge amount of the liquid crystal is measured.
[0191]
(Supplementary note 16) The liquid crystal dropping device according to supplementary note 14 or 15, wherein the measurement means measures the discharge amount of the liquid crystal from at least two directions.
[0192]
(Supplementary note 17) The liquid crystal dropping device according to supplementary note 16, wherein the measurement unit measures a discharge amount of liquid crystal from two directions substantially orthogonal to each other.
[0193]
(Additional remark 18) The said optical sensor is installed in the position within 2 cm from the liquid-crystal discharge port of the said dispenser means, The liquid crystal dropping apparatus of any one of Additional remarks 14-17 characterized by the above-mentioned.
[0194]
(Supplementary note 19) Dispenser means for discharging a predetermined amount of liquid crystal;
A liquid crystal dropping device comprising: a liquid crystal measuring means for recognizing a liquid crystal droplet shape ejected by the dispenser means and estimating an actual liquid crystal ejection amount based on the shape.
[0195]
(Supplementary note 20) The liquid crystal dropping device according to supplementary note 19, wherein the measurement unit optically recognizes the droplet shape of the liquid crystal and estimates an actual discharge amount of the liquid crystal from an image of the shape.
[0196]
(Supplementary Note 21) An optical sensor is provided in the vicinity of the liquid crystal discharge port of the dispenser means, and a signal of the optical sensor generated when the discharged liquid crystal passes through the optical sensor is used as a trigger signal from a liquid crystal droplet shape image. Item 20. The liquid crystal dropping device according to appendix 20, wherein an actual discharge amount of liquid crystal is estimated.
[0197]
(Appendix 22) The dispenser means discharges the liquid crystal by moving the piston in the syringe, and adjusts the control of the discharge amount by the stroke amount of the piston. The liquid crystal dropping device according to any one of appendices 19 to 21, wherein the stroke amount is automatically changed.
[0198]
(Supplementary Note 23) Discharge means having a plurality of thin tubes and discharging a predetermined amount of liquid crystal from each of the thin tubes;
Each receiving tray corresponding to each thin tube of the discharge means, and each of the receiving means, and measuring means for measuring the weight of liquid crystal droplets received by each receiving tray,
A liquid crystal dropping apparatus, wherein liquid crystal droplets whose weight is measured by the measuring means and whose discharge amount is specified are supplied from the respective trays.
[0199]
(Supplementary note 24) The liquid crystal dropping device according to supplementary note 23, wherein a portion of the measuring means that comes into contact with the liquid crystal is subjected to a water repellent treatment to repel the liquid crystal.
[0200]
(Supplementary Note 25) A pair of substrates, at least one of which is transparent, has a frame pattern formed by applying a sealant around the periphery of the image display area, and a liquid crystal having a negative dielectric anisotropy is formed in the frame pattern. A liquid crystal display device of a vertical alignment type in which the respective substrates are dropped and bonded, and the sealing agent is cured,
A liquid crystal display device comprising a liquid crystal material containing a liquid crystal compound represented by the following general formula, wherein the terminal alkyl group has an even number of 2 or more carbon atoms.
[Formula 4]

[0201]
(Supplementary note 26) The liquid crystal display device according to supplementary note 25, wherein the liquid crystal compound has 2 or 4 carbon atoms in the terminal alkyl group.
[0202]
(Supplementary Note 27) A pair of substrates, at least one of which is transparent, has a frame pattern formed by applying a sealant around the periphery of the image display region, and a liquid crystal having a negative dielectric anisotropy is formed in the frame pattern. A liquid crystal display device of a vertical alignment type in which the respective substrates are dropped and bonded, and the sealing agent is cured,
The liquid crystal material contains a neutral liquid crystal compound having no polarity, and the liquid crystal containing the neutral liquid crystal compound has a high volatility in which the weight ratio is reduced by 1% or more when left in a vacuum when dropped, and is non-volatile. A liquid crystal display device having a rotational viscosity of 15% or more lower than that of the neutral liquid crystal compound.
[0203]
(Supplementary Note 28) The liquid crystal material has a clearing point of 70 ° C. or higher, a dielectric anisotropy Δε of −4.0 ≦ Δε <0, and a refractive index anisotropy Δn of 0.1000 or more. 28. The liquid crystal display device according to appendix 27, wherein
[0204]
【The invention's effect】
According to the present invention, display unevenness due to a decrease in retention rate that is likely to occur due to a sealing agent is suppressed, and a liquid crystal display device is easily manufactured with a high yield by using a dropping injection method, and a highly reliable liquid crystal display device Can be realized.
[0205]
In addition, it is possible to precisely measure and control the amount of liquid crystal dropped by the drop injection method, and adjust the drop amount appropriately for each dropping site to make the cell thickness uniform, thereby dropping the liquid crystal with high yield and high reliability. It is possible to realize a liquid crystal dropping device that performs the above.
[0206]
In addition, by using the most suitable liquid crystal material for the drop injection method, the liquid crystal display device that realizes further improvement in display characteristics by suppressing the viscosity of the liquid crystal and increasing the response speed, especially halftone, is realized. can do.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a general main configuration of a liquid crystal display device.
FIG. 2 is a schematic plan view showing a state of a glass substrate on which a frame pattern is formed before performing a liquid crystal injection step by a dropping injection method in the first embodiment.
FIG. 3 is a schematic plan view showing a main configuration (two chamfering) of a first modification of the first embodiment.
FIG. 4 is a schematic plan view showing a main configuration (four chamfering) of a first modification of the first embodiment.
FIG. 5 is a schematic diagram showing main steps of Modification 2 of the first embodiment.
FIG. 6 is a schematic perspective view showing a substrate transfer cassette according to Modification 3 of the first embodiment.
FIG. 7 is a schematic perspective view showing a state when an ultraviolet ray is irradiated after performing a liquid crystal injection step by a drop injection method in the second embodiment.
8 is a schematic cross-sectional view showing a state of a glass substrate by enlarging a circle C in FIG.
FIG. 9 is a schematic cross-sectional view showing a comparative example of the second embodiment.
FIG. 10 is a characteristic diagram showing the wavelength dependence of transmittance.
FIG. 11 is a characteristic diagram showing a photolysis reaction of liquid crystal.
FIG. 12 is a schematic cross-sectional view showing comparative examples 1 and 2 of the second embodiment.
FIG. 13 is a schematic configuration diagram of a liquid crystal dropping device of a third embodiment.
FIG. 14 is a characteristic diagram showing an output variation depending on time of the optical sensor.
FIG. 15 is a schematic configuration diagram showing a positional relationship between a dispenser and an optical sensor.
FIG. 16 is a schematic configuration diagram showing a first modification of the liquid crystal dropping device of the third embodiment.
FIG. 17 is a schematic configuration diagram showing a second modification of the liquid crystal dropping device of the third embodiment.
FIG. 18 is a schematic configuration diagram showing a third modification of the liquid crystal dropping device of the third embodiment.
FIG. 19 is a characteristic diagram showing an initial specific resistance of a liquid crystal material, a specific resistance after being left at high temperature, and a specific resistance after exposure to ultraviolet rays (UV) in a fourth embodiment.
20 is a characteristic diagram showing the results of measurement of the voltage holding ratio, ion density, and residual DC voltage of each cell in Experimental Example 1. FIG.
FIG. 21 is a characteristic diagram showing the results of examining the difference in volatility between the liquid crystal before introducing the low-viscosity material and the liquid crystal after introducing in Experimental Example 3.
FIG. 22 is a characteristic diagram showing the results of examining the difference in speeding up between the liquid crystal before introducing the low-viscosity material and the liquid crystal after introducing in Experimental Example 3.
FIG. 23 is a schematic view for explaining a problem with a conventional sealing agent.
FIG. 24 is a schematic view for explaining a problem related to a sealing agent in a comparative example.
FIG. 25 is a schematic view for explaining a problem related to a sealing agent in a comparative example.
[Explanation of symbols]
1,2,22 Glass substrate
21, 41, 42 Main seal
23 Shading film
24 Transfer seal
31, 44 Overlapping part
31a Starting point
31b End point
45 Conductive particles
46 Transparent electrode
47 Reflective film
52 Substrate transport cassette
64 Short wavelength cut filter less than 300nm
65 Long wavelength cut filter of 500nm or less
71 dispenser
72, 77, 85 Measuring means
73 Laser equipment
74 Optical sensor
75 data logger
76 computers
78 CCD
82 Thin glass tube
83 Weighing dripping jig
84 saucer

Claims (4)

A sealant is applied to the periphery of the image display area provided on one of the pair of substrates to form a frame pattern, and liquid crystal is dropped into the frame pattern to bond the substrates, and the sealant is cured. A method of manufacturing a liquid crystal display device,
The manufacturing method of a liquid crystal display device, wherein the sealing agent is applied so that both a starting point and an ending point of the sealing agent application are located outside the frame pattern. 2. The method of manufacturing a liquid crystal display device according to claim 1, wherein the sealant is applied so that both the start point and the end point are located on the non-mounting side of the substrate. 3. The method of manufacturing a liquid crystal display device according to claim 2, wherein both the start point and the end point are connected so as to cross the frame pattern and the non-mounting side. 2. The method of manufacturing a liquid crystal display device according to claim 1, wherein the start point and the end point coincide with each other on the substrate, and a seal pattern by the sealant is continuously formed.

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