JP2004323761A - Adhesive agent composition for optical part of water-dispersion type, and optical part with adhesive agent layer - Google Patents

Adhesive agent composition for optical part of water-dispersion type, and optical part with adhesive agent layer Download PDF

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JP2004323761A
JP2004323761A JP2003123168A JP2003123168A JP2004323761A JP 2004323761 A JP2004323761 A JP 2004323761A JP 2003123168 A JP2003123168 A JP 2003123168A JP 2003123168 A JP2003123168 A JP 2003123168A JP 2004323761 A JP2004323761 A JP 2004323761A
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water
component
weight
optical member
parts
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JP4603771B2 (en
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Yutaka Moroishi
裕 諸石
Fumiko Nakano
史子 中野
Kohei Yano
浩平 矢野
Tetsuo Inoue
徹雄 井上
Yoshihide Kawaguchi
佳秀 川口
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Nitto Denko Corp
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Nitto Denko Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition, which is used as an adhesive agent for optical parts without including an organic solvent in consideration of environmental conservation and safety and satisfies durability, peelability and stress relaxation characteristics required for optical purposes. <P>SOLUTION: The preparation process of an adhesive composition of a dispersed aqueous type for optical parts comprises the steps of: polymerizing 100-1,500 pts.wt. of monomers containing an alkyl (meth)acrylate as a major component of an acrylate component based on 100 pts.wt. of a urethane component in an aqueous dispersion of the urethane component without sustantially containing an emulsifier to form a polymer containing 30-80 wt.% of a solvent-insoluble portion comprising the urethane component and the acrylic component; and incorporating 100pts.wt. of the above prepared polymer with 0.01-1 pt.wt. of a silane coupling agent. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、液晶セルなどのフラットディスプレイパネルに粘着剤層を介して貼り付けた光学部材を、貼り付けミスなどで再剥離する際に、上記のパネルを損傷することなく再剥離でき、また接着状態の耐久性にすぐれる水分散型光学部材用粘着剤組成物と、これを用いた粘着剤層付き光学部材に関する。
【０００２】
【従来の技術】
液晶表示装置に用いる光学部材、たとえば、偏光板や位相差板などは、液晶セルに粘着剤を用いて貼り付けられる。このような光学材料は、熱や多湿条件下では伸縮が大きく、それに伴う浮きや剥がれが生じやすくなり、粘着剤にはこれに対応できる耐久性が要求される。
【０００３】
また、貼り付け時のミスでゴミをかみ込んだり、位置ズレを起こした場合は、光学部材を剥離して液晶セルが再利用されるが、その際に剥離時に液晶セルのギャップを変化させたり、破断させるような接着状態にならずに容易に剥離できることが必要とされる。粘着剤の耐久性を重視して、単に接着状態を上げる手法では、このような再剥離性に劣ることになる。
【０００４】
さらに、粘着剤には、熱や多湿条件下における偏光板などの寸歩変化に起因する応力を均一に綬和できる特性、つまり応力緩和特性を備えていることが望まれる。この応力緩和特性に劣るものは、偏光板などに残留応力が残存して、色むらや白ヌケなどの悪影響がでるような場合もある。
【０００５】
光学部材に用いられる粘着剤には、従来より、各種材料が提案されているが、近年、環境衛生や安全性などの点より、粘着剤の製造にあたり、有機溶剤を使用しない方向への転換が進みつつある。このような粘着剤としては、エマルジョン型、ホットメルト型、放射線硬化型などが知られている。
【０００６】
しかし、エマルジョン型は耐水性の欠如という問題があり、ホットメルト型は耐熱性の欠如という問題がある。このため、光学部材を貼り付けた状態で高温多湿の条件下に置くと、光学部材の伸縮が大きく、それに伴う浮きや剥がれが生じたり、界面から水分が入り込んで白濁するなど、耐久性の問題が発生する。放射線硬化型は、耐久性は満足しても、応力を均一に緩和できず、偏光板に残留応力が残存して色むらや白ヌケなどの悪影響がみられる場合がある。
【０００７】
たとえば、光学部材用として、光学用シートと離型性シートとの間にノンソルべントタイプの高粘度樹脂を挟み込んで熱や放射線で硬化させる方法（特許文献１参照）、アクリル系モノマーに光重合開始剤と架橋剤と重量平均分子量１０万以上の高分子量アクリル系ポリマーを配合し（特許文献２参照）、またこれにさらに重量平均分子量５万以下の低分子量アクリル系ポリマーを配合し（特許文献３参照）、これらの光学部材用粘着剤を紫外線の照射により光重合させたのち、加熱乾燥して残存モノマーを減少する方法などが提案されている。
【０００８】
これらの方法に用いられる粘着剤は、いずれも、水おび有機溶剤を含有しない放射線硬化型の粘着剤に属するものである。このうち、特許文献１では未硬化の残存モノマーが多くなり、これに起因した光学部材の浮きや剥がれの問題をさけられず、また特許文献２では残存モノマーを加熱乾燥にて減少させているため、光学部材の浮きや剥がれは少ないが、応力緩和特性には課題があり、さらに特許文献３では粘着剤中に低分子量アクリル系ポリマーを配合することで、応力緩和特性が多少緩和されるものの、まだ十分なレベルではない。
【０００９】
また、光学部材用として、シラン系単量体を共重合成分として使用したエマルジョン型のアクリル系粘着剤が開示されているが（特許文献４参照）、安定したエマルジョン重合（乳化重合）を行うために乳化剤の使用を不可欠としており、この乳化剤が粘着剤中に残ることにより、高温多湿の条件下に置くと、水分を吸収して凝集力が低下したり、接着界面に水分を導入して接着性が大きく低下し、浮きや剥がれ、白濁などの耐久性の問題を生じやすい。
【００１０】
エマルジョン型の粘着剤における上記耐湿性や耐水性の問題を改善するため、反応性乳化剤を用いてポリマー中に乳化剤を取り込む試み、具体的には、反応性乳化剤の種類や重合方法を改良する試みがなされている。しかし、反応性乳化剤が水相で重合したり、未反応状態で残存し、ポリマー中に完全に取り込むことができず、耐湿性や耐水性を大きく改良できないのが現状である。
【００１１】
【特許文献１】
特開平９−５９５７７号公報（第２〜４頁）
【特許文献２】
特開２００２−２４１７０７号公報（第２〜５頁）
【特許文献３】
特開２００２−２４１７０８号公報（第２〜５頁）
【特許文献４】
特開２００２−３０９２１２号公報（第２〜６頁）
【００１２】
【発明が解決しようとする課題】
このように、現状では、光学部材用の粘着剤、とくに環境や安全性に配慮した有機溶剤を使用しない粘着剤として、光学用途としての耐久性、再剥離性および応力緩和特性をすべて満足するものは見い出されていない。
【００１３】
本発明は、このような事情に照らし、上記の三特性をすべて満足する光学部材用粘着剤組成物を提供することを目的とする。より詳しくは、光学部材を液晶セルなどに貼り付けたのち、各種の工程を経るなどの長時間を経過したり、高温に保存されても、液晶セルなどから容易に再剥離できる、とくに大型の液晶セルなどであっても再剥離が容易であり、液晶セルなどに損傷や汚染を与えることなく再利用できるとともに、接着した状態では耐久性にすぐれて剥がれや浮きを生じることがなく、また光学部材の寸法変化に起因する応力の緩和性にもすぐれた光学部材用粘着剤組成物を提供することを目的とする。
【００１４】
【課題を解決するための手段】
本件出願人は、先に、骨格中に中和されたカルボキシル基を有するウレタン成分を用いてアクリル系モノマーを水媒体中で重合処理することにより、ウレタン成分とアクリル成分とからなるポリマーが実質的に乳化剤を使用することなく水に安定に分散された、耐湿性や耐水性の良好な水分散型粘着剤組成物を得ることに成功している（特開２０００−１５４３６６号公報）。
本発明者らは、この先行発明の水分散型粘着剤組成物について、これを光学部材用として応用することについて検討した結果、光学用途に望まれる再剥離性と応力緩和性にはなお改良が必要であることがわかった。
【００１５】
そこで、本発明者らは、上記の再剥離性と応力緩和性を改良するため、さらに検討を続けた結果、実質的に乳化剤を含まないウレタン成分の水分散体、とくに骨格中に中和されたカルボキシル基を有するウレタン成分を水に分散させてなる水分散体に対し、アクリル系モノマーを加えて重合処理するにあたり、ウレタン成分とアクリル成分の使用比率やこれら両成分からなるポリマーの溶剤不溶分を規制し、さらにこのポリマーに特定量のシランカップリング剤を配合したとき、耐湿性や耐水性にすぐれて良好な耐久性を示すとともに、液晶セルなどヘの接着力の経時的な増大がなく再剥離性が容易であり、かつ応力綴和性にもすぐれて、光学部材用としてすぐれた性能を発揮する水分散型粘着剤組成物が得られることを見い出し、本発明を完成するに至ったものである。
【００１６】
すなわち、本発明は、ウレタン成分とアクリル成分とからなるポリマーが実質的に乳化剤を使用することなく水に分散されてなり、上記のポリマーは、ウレタン成分１００重量部あたり、アクリル成分が１００〜１，５００重量部であり、かつ溶剤不溶分が３０〜８０重量％であり、このポリマー１００重量部に対し、シランカップリング剤０．０１〜１重量部を含むことを特徴とする水分散型光学部材用粘着剤組成物に係るものである。
とくに、本発明は、ウレタン成分が、数平均分子量が１，０００〜４，０００、水酸基が０．０００５〜０．００３当量／ｇのポリオールとカルボキシル基含有ポリオールとポリイソシアネートとから誘導されたポリマーである、その中でも、カルボキシル基含有ポリオールが、数平均分子量が３，０００〜２０，０００、カルボキシル基が０．０００７〜０．００３当量／ｇ、水酸基が０．００００５〜０．０００７当量／ｇのアクリルポリオールであり、このアクリルポリオールがポリオール全体の２０〜８０重量％を占める上記構成の水分散型光学部材用粘着剤組成物を提供できるものである。
さらに、本発明は、アクリル成分が、（メタ）アクリル酸アルキルエステルを主モノマーとしたガラス転移温度が２５０Ｋ以下のポリマーである上記構成の水分散型光学部材用粘着剤組成物を提供できるものである。
【００１７】
また、本発明は、光学部材の片面または両面に、上記各構成の水分散型光学部材用粘着剤組成物からなる粘着剤層を設けたことを特徴とする粘着剤層付き光学部材を提供できるものである。さらに、本発明は、ディスプレイ表示板に上記構成の粘着剤層付き光学部材を、その粘着剤層を介して貼り合わせたことを特徴とする画像表示装置を提供できるものである。
【００１８】
また、本発明は、実質的に乳化剤を含まないウレタン成分の水分散体中で、上記ウレタン成分１００重量部あたり、アクリル成分として（メタ）アクリル酸アルキルエステルを主成分としたモノマー１００〜１，５００重量部を、重合反応させることにより、上記のウレタン成分とアクリル成分とからなる溶剤不溶分が３０〜８０重量％のポリマーを生成し、このポリマー１００重量部に対し、シランカップリング剤０．０１〜１重量部を配合することを特徴とする水分散型光学部材用粘着剤組成物の製造方法に係るものである。
とくに、本発明は、実質的に乳化剤を含まないウレタン成分の水分散体が、
（ａ）数平均分子量が１，０００〜４，０００、水酸基が０．０００５〜０．００３当量／ｇのポリオールとカルボキシル基含有ポリオールに、水酸基の全量に対し、１．５〜４倍当量のポリイソシアネートを反応させて得たウレタンプレポリマーを、これにアクリル成分としてのモノマーを加える前または後に、そのカルボキシル基を中和して水に分散させた水分散体であるか、
（ｂ）上記プレポリマーをさらに鎖延長した水分散体であり、
上記（ａ）のウレタンプレポリマーの水分散体では、これにアクリル成分として加えたモノマーを重合する前または後あるいは同時に上記プレポリマーを鎖延長する上記構成の水分散型光学部材用粘着剤組成物の製造方法、中でも、上記のカルボキシル基含有ポリオールが、数平均分子量が３，０００〜２０，０００、カルボキシル基が０．０００７〜０．００３当量／ｇ、水酸基が０．００００５〜０．０００７当量／ｇのアクリルポリオールであり、このアクリルポリオールがポリオール全体の２０〜８０重量％を占める上記構成の水分散型光学部材用粘着剤組成物の製造方法を提供できるものである。
また、本発明は、アクリル成分として加えるモノマーが、ガラス転移温度が２５０Ｋ以下のポリマーを付与するものである上記構成の水分散型光学部材用粘着剤組成物の製造方法を提供できるものである。
【００１９】
【発明の実施の形態】
本発明におけるウレタン成分は、ポリオールとポリイソシアネートとの反応物であり、その骨格にカルボキシル基を有するものである。このようなウレタン成分は、ポリオール（カルボキシル基を含まない通常のポリオール）とカルボキシル基含有ポリオールとの混合物にポリイソシアネートを反応させることにより、合成することができるが、市販品を入手して使用してもよい。
【００２０】
ポリオール（カルボキシル基を含まない通常のポリオール）は、１分子中に水酸基を２個またはそれ以上有するもので、ポリエーテルポリオールやポリエステルポリオールなどが用いられる。これらのポリオールとしては、数平均分子量が１，０００〜４，０００で、水酸基が０．０００５〜０．００３当量／ｇであるものが好ましく用いられる。分子量が小さすぎるとウレタンのハードセグメントが多くなり、弾性率が高く応力緩和時間が大きくなり、接着性に劣る現象が生じ、また分子量が大きすぎると水への分散性に劣りやすくなる。
【００２１】
ポリエーテルポリオールとしては、たとえば、エチレングリコール、ジエチレングリコール、プロピレングリコール、ブチレングリコール、ヘキサメチレングリコールなどの２価アルコール、トリメチロールプロパン、グリセリン、ペンタエリスリトールなどの３価アルコールなどの低分子ポリオールに、エチレンオキサイド、プロピレンオキサイド、テトラヒドロフランなどを付加重合させてなるポリエーテルが用いられる。
ポリエステルポリールとしては、上記の２価アルコール、ジプロピレングリコール、１，４−ブタンジオール、１，６−ヘキサンジオール、ネオペンチルグリコールなどのアルコールと、アジピン酸、アゼライン酸、セバチン酸などの２塩基酸との重縮合物からなるポリエステルが用いられる。
【００２２】
カルボキシル基含有ポリオールとしては，ジメチロールプロピオン酸、ジメチロールブタン酸などの低級ポリオールを使用してもよいし、数平均分子量が３，０００〜２０，０００、カルボキシル基が０．０００７〜０．００３当量／ｇ、水酸基が０．００００５〜０．０００７当量／ｇのアクリルポリオールを使用してもよい。とくに好ましくは、後者のアクリルポリオールを使用し、このアクリルポリオールを、ポリオール全体の（つまり、前記したポリエーテルポリオールやポリエステルポリオールなどの通常のポリオールとの合計量中）２０〜８０重量％を占める割合で使用するのがよい。
なお、アクリルポリオールは、ウレタン成分の原料のひとつとして用いられるものであり、後述するアクリル成分には含まれない。
【００２３】
アクリルポリオールは、通常、（メタ）アクリル酸アルキルエステルと、カルボキシル基を有する単量体と、水酸基を有する単量体および／または水酸基を有する連鎖移動剤とを、２，２−アゾビスイソブロニトリルなどのアゾ系化合物やベンゾイルパーオキサイドなどの過酸化物を重合開始剤として、通常の重合反応を行わせることにより、得ることができる。
重合反応は、ポリエーテルポリオールやポリエステルポリオールなどのカルボキシル基を含まない通常のポリオールの存在下で行うと、重合反応が穏やかになり、またアクリルポリオールの一部が通常のポリオールにグラフトして、通常のポリオールとの相溶性が良好になるため、望ましい。
その際、通常のポリオールがポリオール全体の８０〜２０重量％、換言すればアクリルポリオールがポリオール全体の２０〜８０重量％となるようにする。通常のポリオールが２０重量％未満となると、ウレタン成分の水分散性に劣り、また８０重量％を超えると、水分散体の安定性が悪くなる。
【００２４】
上記の（メタ）アクリル酸アルキルエステルには、たとえば、（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸プロピル、（メタ）アクリル酸ブチル、（メタ）アクリル酸ペンチル、（メタ〉アクリル酸ヘキシル、（メタ）アクリル酸２−エチルヘキシル、（メタ）アクリル酸オクチル、（メタ）アクリル酸イソオクチル、（メタ）アクリル酸ノニル、（メタ〉アクリル酸イソノニルなどが用いられる。
また、カルボキシル基を有する単量体には、アクリル酸、メタクリル酸、マレイン酸、イタコン酸などが用いられる。水酸基を有する単量体には、２−ヒドロキシエチルアクリレート、２−ヒドロキシメタクリレート、ヒドロキシブチルアクリレートなどが用いられる。水酸基を有する連鎖移動剤には、２−メルカプトエタノール、１−メルカプト−２−プロパノール、３−メルカプト−１−プロパノール、ｐ−メルカプトフェノールなどが用いられる。
【００２５】
上記の重合反応において、水酸基を有する連鎖移動剤の量を調整するなどしてアクリルポリオールの数平均分子量を３，０００〜２０，０００の範囲に設定する。分子量が小さすぎると弾性率が高くなりすぎて、接着性能が低下する場合があり、また分子量が大きすぎると水への分散性に劣りやすい。
また、カルボキシル基を有する単量体の使用量を調整することにより、アクリルポリオールのカルボキシル基を０．０００７〜０．００３当量／ｇの範囲に設定する。アクリルポリオールのカルボキシル基の量が少なすぎると、水への分散性に劣り、多すぎても水を吸収するだけで分散しない。
さらに、水酸基を有する単量体や水酸基を有する連鎖移動剤の使用量を調整することにより、アクリルポリオールの水酸基を０．００００５〜０．０００７当量／ｇの範囲に設定する。水酸基を有する単量体ではポリオール分子内の任意の位置に、水酸基を有する連鎖移動剤では分子末端に、水酸基を導入できる。水酸基はポリイソシアネートとの反応に関与するため、水酸基の量が少なすぎると、未反応のアクリルポリオールが多く残存して相分離し、粘着剤の物性が安定しないおそれがあり、また多すぎると粘着剤自体が硬くなりやすい。
【００２６】
ポリイソシアネートには、芳香族、脂肪族、脂環族のポリイソシアネートが用いられる。ポリオール（カルボキシル基を含まない通常のポリオール）とアクリルポリオールなどのカルボキシル基含有ポリオールとの混合物に対する速やかな反応および水との反応の抑制の観点から、イソホロンジイソシアネート、シクロヘキサン−１，４−ジイソシアネート、４，４−ジシクロヘキシルメタンジイソシアネートなどの脂環族ジイソシアネート、ヘキサメチレンジイソシアネートなどの脂肪族ジイソシアネートが、とくに好ましく用いられる。
これらポリイソシアネートのイソシアネート基と水酸基とを反応させるため、触媒として、ジブチルすずジラウレート、オクトエ酸すず、１，４−ジアザビシクロ（２，２，２）オクタンなどを用いるのが望ましい。
【００２７】
本発明におけるアクリル成分は、（メタ）アクリル酸アルキルエステルを主モノマーとしたガラス転移温度が２５０Ｋ以下のポリマーである。ガラス転移温度が２５０Ｋより高いものでは接着性に劣り、好ましくない。このようなポリマーは、（メタ）アクリル酸アルキルエステルを主モノマーとし、これに必要により改質用モノマーを加えた、ガラス転移温度が２５０Ｋ以下のポリマーを付与するモノマーを重合させることにより、得ることができる。
【００２８】
上記の主モノマーには、（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸プロピル、（メタ）アクリル酸ブチル、（メタ）アクリル酸ペンチル、（メタ）アクル酸ヘキシル、（メタ）アクリル酸２−エチルヘキシル、（メタ）アクリル酸オクチル、（メタ）アクリル酸イソオクチル、（メタ）アクリル酸ノニル、（メタ）アクリル酸イソノニルなどがある。
また、上記の改質用モノマーには、（メタ）アクリロニトリル、酢酸ビニル、プロピオン酸ビニル、（メタ）アクリルアミド、マレイン酸のモノまたはジエステル、スチレンまたはその誘導体、Ｎ−メチロール（メタ）アクリルアミド、グリシジル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノプロピル（メタ）アクリルアミド、２−ヒドロキシプロピル（メタ）アクリレート、オリゴエステル（メタ）アクリレート、ε−カプロラクトン（メタ）アクリレートなどがある。
【００２９】
本発明において、上記のアクリル成分は、水分散体中のウレタン成分１００重量部あたり、１００〜１，５００重量部となる割合、とくに好ましくは１５０〜１，２００重量部となる割合で用いられる。アクリル成分が１００重量部未満となると、初期弾性率、応力緩和時間ともに大きくなり、耐久性や応力緩和特性が低下し、１，５００重量部より多くなると、水分散性に劣りやすい。
【００３０】
また、本発明において、上記のアクリル成分と前記のウレタン成分とからなるポリマーは、溶剤不溶分が３０〜８０重量％の範囲にあることが必要で、とくに好ましくは３５〜７５重量％の範囲にあるのがよい。上記ポリマーの溶剤不溶分は、後述するように、ウレタン成分の架椅度やアクリル成分の分子量や架橋度を調整することにより、容易に設定することができる。溶剤不溶分が３０重量％未満では、再剥離時に粘着剤の凝集破壊を起こしてパネルを汚染したり、耐久性が低下し、また８０重量％を超えると、接着性が低下する。
【００３１】
本発明の水分散型光学部材用粘着剤組成物は、上記のウレタン成分とアクリル成分とからなるポリマーが実質的に乳化剤を使用することなく水に分散されているとともに、この水分散体中に、さらに、上記のポリマー１００重量部に対し、シランカップリング剤０．０１〜１重量部、好ましくは０．０２〜０．６重量部を含むことを特徴としたものである。シランカップリング剤の含有量が０．０１重量部未満となると、耐久性が低下しやすく、また１重量部を超えると、液晶セルなどへの接着力が増大しすぎる傾向がみられる。
【００３２】
シランカップリング剤としては、３−グリシドキシプロピルトリメトキシシラン、３−グリシドキシプロピルメチルジエトキシシラン、２−（３、４−エポキシシクロヘキシル）エチルトリメトキシシランなどのエポキシ基含有シランカップリング剤、３−アミノプロピルトリメトキシシラン、Ｎ−２（アミノエチル）３−アミノプロピルメチルジメトキシシラン、３−トリエトキシシリル−Ｎ−（１，３−ジメチル−ブチリデン）プロピルアミンなどのアミノ基含有シランカップリング剤、３−アクリロキシプロピルトリメトキシシラン、３−メタクリロキシプロピルトリエトキシシランなどの（メタ）アクリル基含有シランカップリング剤、３−イソシアネートプロピルトリエトキシシランなどのイソシアネート基含有シランカップング剤などが挙げられる。
【００３３】
本発明の水分散型光学部材用粘着剤組成物は、実質的に乳化剤を含まないウレタン成分の水分散体中で、上記ウレタン成分１００重量部あたり、アクリル成分として、（メタ）アクリル酸アルキルエステルを主成分とした、ガラス転移温度が２５０Ｋ以下のポリマーを付与するモノマー１００〜１，５００重量部を、重合反応させることにより、上記のウレタン成分とアクリル成分とからなる溶剤不溶分が３０〜８０重量％のポリマーを生成し、これに前記した特定割合のシランカップリング剤を配合することにより、製造することができる。
【００３４】
なお、上記した実質的に乳化剤を含まないウレタン成分の水分散体において、「実質的に乳化剤を含まない」の意味は、ウレタン成分を合成する段階で乳化剤を積極的に使用しないことを意味する。したがって、たとえば、ウレタン成分の合成原料成分中からごく微量の乳化剤が混入してくることがあっても、これが最終的に得られる粘着剤組成物の耐湿性や耐水性に影響を与えないときは、かかる乳化剤の混入までをも排除するものではない。
【００３５】
このような実質的に乳化剤を含まないウレタン成分の水分散体には、イ）市販品としてあらかじめ調製された、乳化剤を使用していないウレタン水分散体か、ロ）下記の（ａ）または（ｂ）の方法により調製された水分散体が用いられる。このうち、とくに下記の水分散体が好ましく用いられる。
（ａ）数平均分子量が１，０００〜４，０００、水酸基が０．０００５〜０．００３当量／ｇのポリオール（つまり、前記した通常のポリオール）とカルボキシル基含有ポリオールとの混合物に、ポリイソシアネートを反応させて得たウレタンプレポリマーを、これにアクリル成分としての前記したモノマーを加える前または後に、そのカルボキシル基を中和して水に分散させた水分散体
（ｂ）上記プレポリマーをさらに鎖延長した水分散体
【００３６】
なお、上記（ａ）のウレタンプレポリマーの水分散体にあっては、最終的に、これにアクリル成分として加えたモノマーを重合する前または後あるいは同時に上記プレポリマーを鎖延長して高分子量化する。
また、カルボキシル基含有ポリオールには、好ましくは前記した数平均分子量が３，０００〜２０，０００、カルボキシル基が０．０００７〜０．００３当量／ｇ、水酸基が０．００００５〜０．０００７当量／ｇのアクリルポリオールが用いられる。とくにこのアクリルポリオールが、ポリオール全体の２０〜８０重量％を占める割合となるようにするのが望ましい。
【００３７】
上記（ａ）の方法において、ウレタンプレポリマーを生成するためのポリイソシアネートは、水酸基の全量に対し、１．５〜４倍当量となる割合、つまり当量比（ＮＣＯ／ＯＨ比）が１．５〜４となる割合、とくに好ましくは２〜３となる割合で用いられる。上記の当量比が１．５未満となると、水分散体の分散安定性が悪くなり、また４を超えると、初期弾性率、応力緩和時間ともに大きくなり、耐久性や応力緩和特性が低下しやすい。
また、このようにウレタンプレポリマーを生成したのち、このプレポリマーのカルボキシル基を中和するには、アルカリとしてトリエチルアミンやアンモニアなどが用いられる。中和後、水に分散させる際は、上記のプレポリマーに水を加えてもよいし、逆に水に上記のプレポリマーを加えてもよい。この際、当然ではあるが、均一になるように撹拌するのが望ましい。
【００３８】
上記（ａ），（ｂ）の方法において、ウレタンプレポリマーの鎖延長は、ポリアミンを用いて、残存するイソシアネート基同士を結合させて高分子量化すればよい。ポリアミンの使用量は、ポリイソシアネートの量を勘案して、遊離のイソシアネート基を反応させるに必要な当量が選択される。これとは別に、加熱によりイソシアネート基の水による自己縮合反応を利用してもよい。
【００３９】
このようなウレタン成分の水分散体中で、水分散体の調製段階で加えられた、あるいはその後に加えられたアクリル成分〔（メタ）アクリル酸アルキルエステルを主成分としたモノマー〕を重合反応させる。
この重合反応には、重合開始剤として、一般の乳化重合で用いられる過硫酸アンモニウムなどの過酸化物や水溶性のアゾ化合物が用いられる。水中にイオン生成物を発生させないアゾ化合物がとくに好ましい。油溶性の重合開始剤を用いる場合は、あらかじめ単量体に混合して用いてもよい。
【００４０】
このようにして、ウレタン成分とアクリル成分とからなるポリマーが実質的に乳化剤を使用することなく水に分散された水分散体が得られる。その際、上記のポリマーは、ポリマー全体の溶剤不溶分が３０〜８０重量％、好ましくは３５〜７５重量％となるようにする。この設定は、ウレタン成分の架椅度やアクリル成分の分子量や架橋度を調整することで、容易に行える。
具体的には、ウレタン成分を得る際に、３官能以上の多官能ポリオールの量、アクリルポリオール合成段階での水酸基含有モノマーの量、ポリイソシアネートの量などを調節して、ウレタン成分の架椅度を調整する方法、アクリル成分の重合時に多官能モノマーを少量用いたり、重合開始剤や重合温度などを調節して、アクリル成分の分子量や架橋度を調整する方法などがある。
【００４１】
本発明においては、上記特定の溶剤不溶分とされたポリマーが実質的に乳化剤を使用することなく水に分散された水分散体に、前記特定量のシランカップリング剤を配合して、水分散型光学部材用粘着剤組成物とする。
この水分散型光学部材用粘着剤組成物は、そのままでも、接着性と凝集力にすぐれているが、凝集力をさらに上げるために架橋剤を配合してもよい。ただし、架橋剤を配合して架橋処理したのちでも、その溶剤不溶分が３０〜８０重量％の範囲となるように、調整される。また、紫外線吸収剤、老化防止剤、軟化剤、染料、顔料、充填剤などの各種の添加剤を配合してもよい。
【００４２】
本発明においては、光学部材の片面または両面に、上記の水分散型光学部材用粘着剤組成物粘着剤からなる粘着剤層を設けて、粘着剤層付き光学部材とする。粘着剤層の厚さは２〜５００μｍ、好ましくは５〜１００μｍとするのがよい。この粘着剤層付き光学部材を、その粘着剤層を介して、ディスプレイ表示板に貼り合わせることにより、液晶ディスプレイ、エレクトロルミネッセンスディスプレイ、プラズマディスプレイなどの各種の画像表示装置とする。
【００４３】
光学部材の片面または両面に粘着剤層を設けるには、光学部材上に直接上記の水分散型光学部材用粘着剤組成物を塗布し乾燥し、必要により架橋処理を施してもよいし、剥離処理したシート上に上記の水分散型光学部材用粘着剤組成物を塗布し乾燥し、必要により架橋処理を施したのち、これを光学部材上に貼り合わせ転写してもよい。水分散型光学部材用粘着剤組成物の塗布には、リバースコーターやグラビアコーターなどのロールコーター、カーテンコーター、リップコーター、ダイコーターなどの任意の塗布方法を使用できる。粘着剤層の表面は、実用に供されるまでの間、剥離処理したシートで保護される
【００４４】
光学部材には、偏光板や位相差板、偏光板と位相差板を積層した楕円偏光板、さらには反射型偏光板やそれを用いた前記楕円偏光板など、液晶ディスプレイなどの各種の画像表示装置に用いられるものをいずれも使用でき、その種類はとくに限定されない。楕円偏光板などの積層タイプの光学部材では、その積層に際し本発明の水分散型光学部材用粘着剤組成物を使用してもよいし、これ以外の各種の粘着剤や接着剤などを任意に使用することかできる。
【００４５】
偏光板には、ポリビニルアルコール系フィルムや部分ホルマール化ポリビニルアルコール系フィルム、エチレン−酢酸ビニル共重合体のケン化物などの親水性高分子フィルムに、ヨウ素および／または二色性染料を吸収させて延伸したフィルム、さらにはこのフィルムにトリアセチルセルロースフィルム、ポリカーボネートフィルムなどの保護フィルムを積層したフィルム、さらには保護フィルムや廷伸処理フィルムに微細凹凸を施したもの、蒸着処理したもの、保護粘着フィルムを積層したもの、各種の表面処理を施したものなどがある。
【００４６】
位相差板には、ポリカーボネートやポリメチルメタクリレート、ポリオレフインなどのフィルムを延伸処理した複屈折性フィルムや液晶ポリマーの配向フィルムなどがある。位相差板は、２種以上の位相差層を積層して位相差などの光学特性を制御したものとして形成することもできる。
これらの位相差板や前記の偏光板、保護フィルムや各種表面処理において、紫外線吸収剤や老化防止剤などによる処理も適宜行うことができる。
【００４７】
【実施例】
以下に、本発明の実施例を記載して、より具体的に説明する。なお、以下において、部とあるのは重量部を意味する。また、ウレタン成分とアクリル成分とからなるポリマーの溶剤不溶分は、下記のように測定した。
【００４８】
＜溶剤不溶分の測定＞
水分散体から乾燥した所定量のポリマー（初期重量：Ｗ１）を採取し、これを酢酸エチル溶液に浸漬して、室温で１週間放置したのち、不溶分を取り出し、その乾燥重量（Ｗ２）を測定した。この両測定値（Ｗ１，Ｗ２）から、溶剤不溶分（重量％）＝（Ｗ２／Ｗ１）×１００、を求めた。
【００４９】
さらに、ポリオールなどの数平均分子量は、ゲルパーミエーションクロマトグラフィー（ＧＰＣ）により、下記の条件で測定したものである。
装置：東ソー製の「ＨＬＣ−８１２０ＧＰＣ」
展開液：テトラヒドロフラン
流速：０．８ｍｌ／分
カラム温度：４０℃
標準試料：ポリスチレン
カラム：３本連結カラム
【００５０】
実施例１
数平均分子量３，０００のポリプロピレングリコール（水酸基０．０００６７当量／ｇ）５０部の存在下で、アクリル酸ブチル４５部、アクリル酸５部、連鎖移動剤として２−メルカプトエタノール１部、重合開始剤として２，２−アゾビスイソブチロニトリル０．０５部を用いて、窒素気流下で、５０℃で６時間重合反応を行った。このようにして得られた粘調液体の分子量を、ＧＰＣ（ゲルパーミエーションクロマトグラフィー）で測定したところ、ポリプロピレングリコールに由来する数平均分子量３，０００のピークと、アクリルポリオールに由来する数平均分子量７，５００のピークが認められ、カルボキシル基が０．００１４当量／ｇ、水酸基が０．０００２５当量／ｇである数平均分子量７，５００のアクリルポリオールが得られたことがわかった。
【００５１】
このポリプロピレングリコールとアクリルポリオールとからなる混合粘調液体を１００℃に加熱して減圧処理し、残存する水分を除去した。これに、イソホロンジイソシアネート１０．３部（全水酸基に対して、２．０倍当量）を加えて、ジブチルチンジラウレート０．０１部を加え、６５℃にして３時間反応させて、水酸基をイソシアネート化し、ウレタンプレポリマーを得た。
つぎに、トリエチルアミン７部（カルボキシル基に対して等当量）を加えて、カルボキシル基を中和したのち、撹拌しながら水１５０部を加えて、このウレタンプレポリマーを水に分散させた。さらに、エチレンジアミン１．５部（残存するイソシアネート基に対して等当量）を水１３．５部で希釈した溶液を加えて、６５℃で３時間反応させて、骨格中に中和されたカルボキシル基を有するウレタン成分が水に安定に分散された水分散体を得た。
【００５２】
ついで、このウレタン成分の水分散体（固形分４２．２重量％）５０部に、水１５８部を加え、均一に攪拌したのち、アクリル酸ブチル８０部、メタクリル酸メチル４．４部を加え、窒素気流下で１時間攪拌して、上記単量体を水分散しているウレタン粒子に吸収させた。５０℃に昇温して、２、２−アゾビス〔２−（２−イミダゾリンー２イル）〕プロパン０．０５部を加えて、重合反応を開始した。５０℃に４時間保持したのち、７０℃に昇温して、さらに３時間保持して、重合反応を続け、その後、冷却した。
このようにして、ウレタン成分とアクリル成分とからなるポリマーが水に安定に分散された水分散体を得た。上記ポリマーは、ウレタン成分１００部あたり、アクリル成分が４００部であり、溶剤不溶分が４１．２重量％であった。
つぎに、この水分散体に、その固形分（ポリマー）１００部に対して、シランカップリング剤として３−グリシドキシプロピルメチルトリエトキシシランを、０．１部配合して、水分散型光学部材用粘着剤組成物とした。
【００５３】
ついで、シリコーン剥離処理した厚さが３８μｍのポリエチレンテレフタレートフィルムの上に、上記の水分散型光学部材用粘着剤組成物を、乾燥後の厚さが２５μｍとなるように塗布し、１１０℃で５分間乾燥し、架橋処理して、粘着剤層を形成した。この粘着剤層を偏光フイルムに転写し、５０℃で２４時間エージング処理して、粘着剤層付き光学部材を作製した。
なお、上記の偏光フイルムは、厚さが８０μｍのポリビニルアルコールフィルムを４０℃のヨウ素水溶液中で５倍に延伸したのち、５０℃で４分間乾燥させて偏光子を得、この偏光子の両側にトリアセチルセルロースフィルムをポリビニルアルコール系接着剤を用いて接着したものである。
【００５４】
実施例２
数平均分子量４，０００のポリプロピレングリコール５０部に、Ｎ−メチルピロリドン１０部に溶解したジメチロールプロピオン酸４部を加え、１００℃に加熱脱気して、水分を取り除いた。これに、４，４′−ジシクロヘキシルメタンジイソシアネート１２部（全水酸基に対して、１．７倍当量）を加えて、ジブチルすずジラウレート０．０１部を加え、６５℃で３時間反応させて、水酸基をイソシアネート化し、ウレタンプレポリマーを得た。
つぎに、トリエチルアミン１．５部を加えて、よく攪拌し、カルボキシル基を中和した。別途、フラスコに１．５時間窒素置換した蒸留水７００部を用意しておき、この蒸留水に上記中和したウレタンプレポリマーを、滴下ロートを用いて滴下した。滴下完了後、エチレンジアミン０．５部を蒸留水で３倍に希釈して加え、ウレタン成分が水に安定に分散された水分散体を得た。
【００５５】
つぎに、このウレタン成分の水分散体に、アクリル酸ブチル３００部、アクリル酸エチル３０部、トリエチレングリコールジアクリレート０．１部を加えて、全体を均一に攪拌して、モノマーをウレタン成分に吸収させ、さらに、２，２−アゾビス（２−アミジノプロパン）二塩酸塩０．０５部を加え、５０℃に加熱して、５時間反応を行った。
このようにして、ウレタン成分とアクリル成分とからなるポリマーが水に安定に分散された水分散体を得た。上記ポリマーは、ウレタン成分１００部あたり、アクリル成分が４９０部であり、溶剤不溶分が６８．７重量％であった。
つぎに、この水分散体に、その固形分（ポリマー）１００部に対して、シランカップリング剤として３−グリシドキシプロピルメチルトリエトキシシランを、０．１部配合して、水分散型光学部材用粘着剤組成物とした。
この水分散型光学部材用粘着剤組成物を使用した以外は、実施例１と同様にして、粘着剤層付き光学部材を作製した。
【００５６】
実施例３
数平均分子量３，０００のポリテトラメチレングリコール（水酸基：０．０００６７当量／ｇ）５０部の存在下で、アクリル酸ブチル２５部、アクリル酸エチル２０部、アクリル酸４．５部、アクリル酸２−ヒドロキシエチル０．５部、連鎖移動剤として２−メルカプトエタノール１部、重合開始剤として２，２−アゾビスイソブチロニトリル０．０５部を用いて、窒素気流下で、５０℃で６時間、重合反応を行った。このようにして得られた粘調液体は、数平均分子量３，０００のポリテトラメチレングリコールと、数平均分子量が７，４００、カルボキシル基が０．００１２当量／ｇ、水酸基が０．０００３３当量／ｇのアクリルポリオールとの混合物からなるものであった。
【００５７】
このような混合物からなる粘調液体を１００℃に加熱して減圧処理し、残存する水分を除去した。これに、４，４−ジシクロヘキシルメタンジイソシアネート１９．８部（全水酸基に対して、３倍当量）を加えて、ジブチルチンジラウレート０．０１部を加え、６５℃にして３時間反応させて、水酸基をイソシアネート化し、ウレタンプレポリマーを得た。
つぎに、トリエチルアミン６．３部（カルボキシル基に対して等当量）を加えて、カルボキシル基を中和したのち、撹拌しながら水１５０部を加えて、このウレタンプレポリマーを水に分散させた。さらに、エチレンジアミン１．９部（残存するイソシアネート基に対して等当量）を水１７．１部で希釈した溶液を加えて、６５℃で３時間反応させて、骨格中に中和されたカルボキシル基を有するウレタン成分が水に安定に分散された水分散体を得た。
【００５８】
ついで、このウレタン成分の水分散体（固形分４３．２重量％）５０部に、水７０部を加え、均一に攪拌したのち、アクリル酸ブチル４０部、メタクリル酸メチル３部を加え、窒素気流下で１時間攪拌して、上記単量体を水分散しているウレタン粒子に吸収させた。５０℃に昇温して、２、２−アゾビス〔２−（２−イミダゾリンー２イル）〕プロパン０．０２部を加えて、重合反応を開始した。５０℃に４時間保持したのち、７０℃に昇温して、さらに３時間保持して、重合反応を続け、その後、冷却した。
このようにして、ウレタン成分とアクリル成分とからなるポリマーが水に安定に分散された水分散体を得た。上記ポリマーは、ウレタン成分１００部あたり、アクリル成分が２００部であり、溶剤不溶分が５４．３重量％であった。
つぎに、この水分散体に、その固形分（ポリマー）１００部に対して、シランカップリング剤として３−グリシドキシプロピルメチルトリエトキシシランを、０．１部配合して、水分散型光学部材用粘着剤組成物とした。
この水分散型光学部材用粘着剤組成物を使用した以外は、実施例１と同様にして、粘着剤層付き光学部材を作製した。
【００５９】
実施例４
実施例３で得たウレタン成分の水分散体（固形分４３．２重量％）２０部に、水１７０部を加え、均一に攪拌したのち、アクリル酸ブチル１００部、メタクリル酸メチル１２部、トリメチロールプロパントリアクリレート０．０３部を加えて、窒素気流下で１時間攪拌し、上記単量体を水分散しているウレタン粒子に吸収させた。５０℃に昇温して、２、２−アゾビス〔２−（２−イミダゾリンー２イル）〕プロパン０．１部を加え、重合反応を開始した。５０℃に４時間保持したのち、７０℃に昇温して、さらに３時間保持して、重合反応を続け、その後、冷却した。
このようにして、ウレタン成分とアクリル成分とからなるポリマーが水に安定に分散された水分散体を得た。上記ポリマーは、ウレタン成分１００部あたり、アクリル成分が１，３００部であり、溶剤不溶分が５０．２重量％であった。
つぎに、この水分散体に、その固形分（ポリマー）１００部に対して、シランカップリング剤として３−グリシドキシプロピルメチルトリエトキシシランを、０．１部配合して、水分散型光学部材用粘着剤組成物とした。
この水分散型光学部材用粘着剤組成物を使用した以外は、実施例１と同様にして、粘着剤層付き光学部材を作製した。
【００６０】
実施例５
ウレタン成分の水分散液として、乳化剤を含まないポリウレタンディスパージョン（三井武田ケミカル社製の「タケラックＷ−６０６０」）を用い、このディスパージョン５０部（固形分３０．０重量％）に水１２２部を加え、均一に攪拌したのち、アクリル酸ブチル８０部、メタクリル酸メチル１０部を加えて、窒素気流下で、１時間撹拌し、上記単量体を水分散しているウレタン粒子に吸収させた。５０℃に昇温して、２，２−アゾビス〔２−（２−イミダゾリンー２イル）〕プロパン０．１部加えて、重合反応を開始した。５０℃に４時間保持したのち、７０℃に昇温して、さらに３時間保持して、重合反応を続け、その後、冷却した。
【００６１】
このようにして、ウレタン成分とアクリル成分とからなるポリマーが水に安定に分散された水分散体を得た。上記ポリマーは、ウレタン成分１００部あたり、アクリル成分が６００部であり、溶剤不溶分が４８．２重量％であった。
つぎに、この水分散体に、その固形分（ポリマー）１００部に対して、シランカップリング剤として３−グリシドキシプロピルメチルトリエトキシシランを、０．１部配合して、水分散型光学部材用粘着剤組成物とした。
この水分散型光学部材用粘着剤組成物を使用した以外は、実施例１と同様にして、粘着剤層付き光学部材を作製した。
【００６２】
比較例１
実施例１で得たウレタン成分の水分散体（固形分４２．２重量％）５０部に、水１８部を加え、均一に撹拌したのち、アクリル酸ブチル１０部を加えて、実施例１と同様に重合反応を行い、ウレタン成分とアクリル成分とからなるポリマーが水に分散された水分散体を得た。上記ポリマーは、ウレタン成分１００部あたり、アクリル成分が５０部であり、溶剤不溶分が６６．７重量％であった。
この水分散体に、実施例１と同様のシランカップリング剤を同量配合して、水分散型光学部材用粘着剤組成物とした。
また、この水分散型光学部材用粘着剤組成物を使用した以外は、実施例１と同様にして、粘着剤層付き光学部材を作製した。
【００６３】
比較例２
実施例１で得たウレタン成分の水分散体（固形分４２．２重量％）５０部に、水６３６部を加え、均一に撹拌したのち、アクリル酸ブチル４２２部（ウレタン成分１００部あたり、２，０００部に相当する）を加え、実施例１と同様に重合反応させたが、重合途中で凝集し、安定な水分散体が得られなかった。
このため、この水分散体に対し実施例１と同様のシランカップリング剤を配合して水分散型光学部材用粘着剤組成物を調製することも、またこれより粘着剤層付き光学部材を作製することもできなかった。
【００６４】
比較例３
ウレタン成分の水分散体にアクリル成分を加えて重合反応させる際に、トリメチロールプロパントリアクリレート０．０３部を加えなかった以外は、実施例４と同様に重合反応を行い、ウレタン成分とアクリル成分とからなるポリマーが水に分散された水分散体を得た。この水分散体は、上記ポリマーの溶剤不溶分が２５．５重量％であった。
この水分散体に、実施例１と同様のシランカップリング剤を同量配合して、水分散型光学部材用粘着剤組成物とした。
また、この水分散型光学部材用粘着剤組成物を使用した以外は、実施例１と同様にして、粘着剤層付き光学部材を作製した。
【００６５】
比較例４
ウレタン成分の水分散体にアクリル成分を加えて重合反応させる際に、トリメチロールプロパントリアクリレートの量を０．０３部から０．１部に変更した以外は、実施例４と同様に重合反応を行い、ウレタン成分とアクリル成分とからなるポリマーが水に分散された水分散体を得た。この水分散体は、上記ポリマーの溶剤不溶分が８６．５重量％であった。
この水分散体に、実施例１と同様のシランカップリング剤を同量配合して、水分散型光学部材用粘着剤組成物とした。
また、この水分散型光学部材用粘着剤組成物を使用した以外は、実施例１と同様にして、粘着剤層付き光学部材を作製した。
【００６６】
比較例５
アクリル酸ブチル９０部、アクリル酸２−エチルヘキシル７部、アクリル酸３部を、乳化剤としてポリオキシエチレンラウリル硫酸ナトリウム３部を用いて、水１２２部に乳化させ、重合開始剤として２，２−アゾビス（２−アミジノプロパン）二塩酸塩０．０５部を用いて、５０℃で３時間重合反応を行い、さらに、６５℃で２時間反応を続け、乳化剤を含むアクリル系水分散体を得た。
この水分散体に、実施例１と同様のシランカップリング剤を同量配合して、水分散型光学部材用粘着剤組成物とした。
また、この水分散型光学部材用粘着剤組成物を使用した以外は、実施例１と同様にして、粘着剤層付き光学部材を作製した。
【００６７】
比較例６
実施例２で得たウレタン成分とアクリル成分とからなるポリマーが水に安定に分散された水分散体に、シランカップリング剤を配合しないで、上記の水分散体そのものを水分散型光学部材用粘着剤組成物とした。
また、この水分散型光学部材用粘着剤組成物を使用した以外は、実施例１と同様にして、粘着剤層付き光学部材を作製した。
【００６８】
上記の実施例１〜５および比較例１，３〜６の各粘着剤層付き光学部材について、下記の方法により、接着力試験、耐久性試験および色むら試験を行った。これらの結果は、表１に示されるとおりであった。
【００６９】
＜接着力試験＞
幅２５ｍｍに裁断した粘着剤層付き光学部材を、その粘着剤層を介して、無アルカリガラス板に、２Ｋｇのロール１往復で貼り付け、５０℃、０．５Ｍｐａのオートクレーブで３０分処理したのち、２３℃，５０％の条件下に３時間放置後、剥離角度９０°、剥離速度３００ｍｍ／分で剥離接着力を測定した。これを初期接着力とした。
また、上記のオートクレーブでの処理後、７０℃の条件下に４８時間放置後、２３℃，５０％の条件下に３時間放置後、剥離角度９０°、剥離速度３００ｍｍ／分で剥離接着力を測定した。これを７０℃処理接着力とした。
再剥離性としては、上記の初期接着力とともに、７０℃処理接着力（つまり、加熱処理後の接着力）が増大しないことが望まれる。
【００７０】
＜耐久性試験＞
１２インチサイズとした粘着剤層付き光学部材を、その粘着剤層を介して、厚さが０．５ｍｍの無アルカリガラス板に貼り付け、５０℃，０．５Ｍｐａのオートクレーブで３０分処理したのち、６０℃，９０％ＲＨの雰囲気下に５００時間投入した。この耐久性試験で、光学部材の剥がれや浮きがなければ○、光学部材の剥がれや浮きがあれば×、と評価した。
【００７１】
＜色むら試験＞
１２インチサイズとした粘着剤層付き光学部材を、その粘着剤層を介して、厚さが０．５ｍｍの無アルカリガラス板の両面に偏光板の吸収軸が直行するように貼り付け、５０℃，０．５Ｍｐａのオートクレーブで３０分処理したのち、９０℃の雰囲気で５００時間投入した。このときの色むらや白ヌケなどの発生状態を目視観察し、色むらなどがなければ○、色むらなどがあれば×、と評価した。
【００７２】

Figure 2004323761
【００７３】
上記の表１の結果から明らかなように、実施例１〜５の各粘着剤層付き光学部材は、初期接着力と７０℃処理接着力の差が小さく、液晶セルに貼り付けた際の接着力の増加が少なく、どのような処理条件に置かれても、糊残りや液晶セルの破壊がなく、光学部材を再剥離して液晶セルを再利用でき、しかも長期の過酷試験や液晶表示状態への悪影響もなく、すべて満足する特性を有している。これに対し、比較例１，２〜６の各粘着剤層付き光学部材では、上記特性のバランスをうまく取れないものであることがわかる。
【００７４】
【発明の効果】
以上のように、本発明の水分散型光学部材用粘着剤組成物は、乳化剤を使用しないで水分散化させたポリマーで、そのウレタン成分とアクリル成分との比率および溶剤不溶分を制御した粘着剤組成物であり、かつこれに特定量のシランカップリング剤を含ませたものであり、光学部材を液晶セルに貼り付けたのちに高温高湿状態で保存されても、剥がれや発泡が発生しない高耐久性を発現し、光学部材の寸法変化に超因する応力を均一に緩和でき、偏光板に残留応力が残存して色むらや白ヌケなどの悪影響を抑制できるとともに、光学部材を剥がして液晶セルを再利用する場合でも接着力の増大がみられず、液晶セルに悪影響を与えることなく容易に再剥離できる。また、本発明の水分散型光学部材用粘着剤組成物では、製造工程で有機溶剤を用いないため、環境面でもすぐれている。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides an optical member that is adhered to a flat display panel such as a liquid crystal cell via an adhesive layer, and when the optical member is removed again due to a bonding mistake or the like, it can be removed again without damaging the panel, The present invention relates to a water-dispersed pressure-sensitive adhesive composition for an optical member having excellent durability in a state, and an optical member having a pressure-sensitive adhesive layer using the same.
[0002]
[Prior art]
An optical member used for the liquid crystal display device, for example, a polarizing plate or a retardation plate is attached to the liquid crystal cell using an adhesive. Such an optical material has a large expansion and contraction under heat and high humidity conditions, so that the optical material is likely to be lifted or peeled off, and the adhesive is required to have durability that can cope with this.
[0003]
In addition, in the event that dust is trapped or misaligned due to a mistake during pasting, the optical member is peeled off and the liquid crystal cell is reused. In addition, it is necessary that the film can be easily peeled off without being in an adhesive state such that it is broken. A method of simply increasing the adhesion state with emphasis on the durability of the pressure-sensitive adhesive results in poor removability.
[0004]
Further, it is desired that the pressure-sensitive adhesive has a property capable of uniformly reducing a stress caused by a step change of a polarizing plate or the like under heat or high humidity conditions, that is, a stress relaxation property. Those having poor stress relaxation characteristics may have a residual stress remaining on a polarizing plate or the like, resulting in adverse effects such as color unevenness or white spots.
[0005]
Various materials have been proposed for adhesives used in optical members.However, in recent years, there has been a shift to using organic solvents in the production of adhesives from the viewpoint of environmental health and safety. It is going on. As such an adhesive, an emulsion type, a hot melt type, a radiation curing type and the like are known.
[0006]
However, the emulsion type has a problem of lack of water resistance, and the hot melt type has a problem of lack of heat resistance. For this reason, if the optical member is attached and placed under high-temperature and high-humidity conditions, the optical member expands and contracts greatly, causing floating and peeling, and moisture entering from the interface and becoming cloudy, resulting in durability problems. Occurs. In the radiation-curing type, even if the durability is satisfied, the stress cannot be uniformly relieved, and residual stress remains in the polarizing plate, so that adverse effects such as uneven color and white spots may be observed.
[0007]
For example, for an optical member, a method in which a non-solvent type high-viscosity resin is sandwiched between an optical sheet and a release sheet and cured by heat or radiation (see Patent Document 1), photopolymerization of an acrylic monomer is started. A high molecular weight acrylic polymer having a weight average molecular weight of 100,000 or more (see Patent Document 2), and a low molecular weight acrylic polymer having a weight average molecular weight of 50,000 or less (see Patent Document 3). In addition, there has been proposed a method of reducing the residual monomer by photo-polymerizing the pressure-sensitive adhesive for an optical member by irradiating ultraviolet rays, followed by heating and drying.
[0008]
The pressure-sensitive adhesive used in these methods belongs to a radiation-curable pressure-sensitive adhesive containing no water and no organic solvent. Among them, in Patent Document 1, the uncured residual monomer increases, and the problem of floating and peeling of the optical member caused by this cannot be avoided. In Patent Document 2, the residual monomer is reduced by heating and drying. Although the floating and peeling of the optical member are small, there is a problem in the stress relaxation property. Further, in Patent Document 3, although the stress relaxation property is somewhat relaxed by blending a low molecular weight acrylic polymer in the adhesive, Not enough yet.
[0009]
Further, an emulsion-type acrylic pressure-sensitive adhesive using a silane-based monomer as a copolymer component for an optical member is disclosed (see Patent Document 4), but it is required to perform stable emulsion polymerization (emulsion polymerization). The use of an emulsifier is indispensable, and this emulsifier will remain in the adhesive, and when placed in hot and humid conditions, absorbs moisture and reduces cohesive strength, or introduces moisture into the adhesive interface to bond. Properties are greatly reduced, and durability problems such as floating, peeling, and clouding are likely to occur.
[0010]
Attempts to incorporate reactive emulsifiers into polymers using reactive emulsifiers, specifically to improve the types and polymerization methods of reactive emulsifiers, in order to improve the moisture and water resistance problems of emulsion-type adhesives Has been made. However, at present, the reactive emulsifier is polymerized in the aqueous phase or remains in an unreacted state, cannot be completely taken into the polymer, and cannot greatly improve moisture resistance and water resistance.
[0011]
[Patent Document 1]
JP-A-9-59577 (pages 2 to 4)
[Patent Document 2]
JP-A-2002-241707 (pages 2 to 5)
[Patent Document 3]
JP-A-2002-241708 (pages 2 to 5)
[Patent Document 4]
JP-A-2002-309212 (pages 2 to 6)
[0012]
[Problems to be solved by the invention]
Thus, at present, adhesives for optical components, especially those that do not use organic solvents in consideration of the environment and safety, satisfy all of the durability, removability and stress relaxation properties for optical applications. Has not been found.
[0013]
In view of such circumstances, an object of the present invention is to provide a pressure-sensitive adhesive composition for an optical member that satisfies all the above three characteristics. More specifically, after the optical member is attached to a liquid crystal cell, etc., even after a long time, such as going through various processes, or being stored at a high temperature, it can be easily peeled off from the liquid crystal cell, etc. Even a liquid crystal cell can be easily peeled off and reused without damaging or contaminating the liquid crystal cell, etc., and when bonded, it has excellent durability and does not peel off or float. An object of the present invention is to provide a pressure-sensitive adhesive composition for an optical member that is excellent in relieving stress caused by a dimensional change of the member.
[0014]
[Means for Solving the Problems]
The applicant of the present application has previously conducted a polymerization treatment of an acrylic monomer in an aqueous medium using a urethane component having a carboxyl group neutralized in the skeleton, whereby a polymer consisting of a urethane component and an acrylic component is substantially formed. A water-dispersible PSA composition having good moisture resistance and water resistance, which is stably dispersed in water without using an emulsifier, has been successfully obtained (Japanese Patent Application Laid-Open No. 2000-154366).
The present inventors have studied the application of the water-dispersed pressure-sensitive adhesive composition of the prior invention for optical members, and as a result, the removability and stress relaxation properties desired for optical applications have still been improved. Turned out necessary.
[0015]
Therefore, the present inventors have further studied to improve the removability and the stress relaxation as described above, and as a result, a water dispersion of a urethane component substantially containing no emulsifier, especially neutralized in the skeleton. When an acrylic monomer is added to an aqueous dispersion obtained by dispersing a urethane component having a carboxyl group in water to carry out polymerization treatment, the ratio of the urethane component to the acrylic component used and the solvent insoluble content of the polymer composed of these two components In addition, when a specific amount of silane coupling agent is blended with this polymer, it shows excellent durability with excellent moisture resistance and water resistance, and there is no increase with time in the adhesive strength to liquid crystal cells etc. It has been found that a water-dispersible pressure-sensitive adhesive composition that is easily removable and has excellent stress binding properties and exhibits excellent performance for optical members can be obtained. It is those that led to the formation.
[0016]
That is, in the present invention, a polymer comprising a urethane component and an acrylic component is dispersed in water substantially without using an emulsifier, and the above polymer has an acrylic component of 100 to 1 per 100 parts by weight of the urethane component. , 500 parts by weight, a solvent-insoluble content of 30 to 80% by weight, and 0.01 to 1 part by weight of a silane coupling agent with respect to 100 parts by weight of the polymer. The present invention relates to a pressure-sensitive adhesive composition for a member.
In particular, the present invention relates to a polymer in which a urethane component is derived from a polyol having a number average molecular weight of 1,000 to 4,000, a hydroxyl group of 0.0005 to 0.003 equivalent / g, a carboxyl group-containing polyol, and a polyisocyanate. Among them, the carboxyl group-containing polyol has a number average molecular weight of 3,000 to 20,000, a carboxyl group of 0.0007 to 0.003 equivalent / g, and a hydroxyl group of 0.00005 to 0.0007 equivalent / g. Which can provide the water-dispersed pressure-sensitive adhesive composition for an optical member having the above-mentioned structure in which the acrylic polyol accounts for 20 to 80% by weight of the whole polyol.
Furthermore, the present invention can provide a water-dispersed optical member-use pressure-sensitive adhesive composition having the above constitution, wherein the acrylic component is a polymer having a glass transition temperature of 250 K or less using an alkyl (meth) acrylate as a main monomer. is there.
[0017]
In addition, the present invention can provide an optical member with an adhesive layer, characterized in that an adhesive layer comprising the above-described pressure-sensitive adhesive composition for an aqueous dispersion type optical member is provided on one or both surfaces of the optical member. Things. Further, the present invention can provide an image display device characterized in that the optical member with the pressure-sensitive adhesive layer having the above-mentioned configuration is adhered to the display panel via the pressure-sensitive adhesive layer.
[0018]
In addition, the present invention relates to an aqueous dispersion of a urethane component substantially not containing an emulsifier, wherein 100 parts by weight of the urethane component and 100 to 1, a monomer containing an alkyl (meth) acrylate as a main component as an acrylic component. By polymerizing 500 parts by weight of the polymer, a polymer comprising the urethane component and the acrylic component and having a solvent insoluble content of 30 to 80% by weight is produced. The present invention relates to a method for producing a pressure-sensitive adhesive composition for a water-dispersed optical member, which is characterized in that it is added in an amount of from 0.01 to 1 part by weight.
In particular, the present invention is an aqueous dispersion of a urethane component substantially free of an emulsifier,
(A) The polyol having a number average molecular weight of 1,000 to 4,000 and a hydroxyl group of 0.0005 to 0.003 equivalent / g and a carboxyl group-containing polyol has 1.5 to 4 equivalents of the total amount of the hydroxyl group. A urethane prepolymer obtained by reacting a polyisocyanate, before or after adding a monomer as an acrylic component to the urethane prepolymer, is an aqueous dispersion in which carboxyl groups are neutralized and dispersed in water,
(B) an aqueous dispersion obtained by further extending the chain of the prepolymer,
In the aqueous dispersion of the urethane prepolymer of the above (a), the pressure-sensitive adhesive composition for a water-dispersed optical member having the above-mentioned constitution, in which the prepolymer is chain-extended before, after or simultaneously with the polymerization of the monomer added as an acrylic component. Wherein the carboxyl group-containing polyol has a number average molecular weight of 3,000 to 20,000, a carboxyl group of 0.0007 to 0.003 equivalent / g, and a hydroxyl group of 0.00005 to 0.0007 equivalent. / G of acrylic polyol, wherein the acrylic polyol accounts for 20 to 80% by weight of the whole polyol, and can provide a method for producing the water-dispersed pressure-sensitive adhesive composition for an optical member having the above structure.
Further, the present invention can provide a method for producing a pressure-sensitive adhesive composition for a water-dispersed optical member having the above constitution, wherein the monomer added as an acrylic component gives a polymer having a glass transition temperature of 250 K or less.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
The urethane component in the present invention is a reaction product of a polyol and a polyisocyanate, and has a carboxyl group in its skeleton. Such a urethane component can be synthesized by reacting a mixture of a polyol (an ordinary polyol containing no carboxyl group) and a carboxyl group-containing polyol with a polyisocyanate. You may.
[0020]
Polyols (ordinary polyols containing no carboxyl group) have two or more hydroxyl groups in one molecule, and include polyether polyols and polyester polyols. As these polyols, those having a number average molecular weight of 1,000 to 4,000 and a hydroxyl group of 0.0005 to 0.003 equivalent / g are preferably used. If the molecular weight is too small, the number of urethane hard segments increases, the modulus of elasticity increases, the stress relaxation time increases, and a phenomenon of poor adhesion occurs. If the molecular weight is too large, the dispersibility in water tends to deteriorate.
[0021]
Examples of polyether polyols include low molecular weight polyols such as dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, and hexamethylene glycol; trihydric alcohols such as trimethylolpropane, glycerin and pentaerythritol; A polyether obtained by addition polymerization of propylene oxide, tetrahydrofuran or the like is used.
Examples of the polyester polyol include alcohols such as the above-mentioned dihydric alcohols, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol, and dibasic acids such as adipic acid, azelaic acid, and sebacic acid. A polyester composed of a polycondensate with an acid is used.
[0022]
As the carboxyl group-containing polyol, lower polyols such as dimethylolpropionic acid and dimethylolbutanoic acid may be used, and the number average molecular weight is 3,000 to 20,000, and the carboxyl group is 0.0007 to 0.003. An acrylic polyol having an equivalent / g and a hydroxyl group of 0.00005 to 0.0007 equivalent / g may be used. Particularly preferably, the latter acrylic polyol is used, and this acrylic polyol accounts for 20 to 80% by weight of the entire polyol (that is, in the total amount of the above-mentioned ordinary polyols such as polyether polyol and polyester polyol). Good to use in.
In addition, the acrylic polyol is used as one of the raw materials of the urethane component, and is not included in the acrylic component described later.
[0023]
The acrylic polyol is usually prepared by combining (meth) acrylic acid alkyl ester, a monomer having a carboxyl group, a monomer having a hydroxyl group and / or a chain transfer agent having a hydroxyl group with 2,2-azobisisobronitrile. It can be obtained by performing a usual polymerization reaction using an azo compound such as benzoyl peroxide or a peroxide such as benzoyl peroxide as a polymerization initiator.
When the polymerization reaction is carried out in the presence of a normal polyol containing no carboxyl group such as a polyether polyol or a polyester polyol, the polymerization reaction becomes mild, and a part of the acrylic polyol is grafted to the normal polyol, which is usually used. Is preferred because of its good compatibility with polyols.
At that time, the content of the normal polyol is set to 80 to 20% by weight of the whole polyol, in other words, the content of the acrylic polyol is set to 20 to 80% by weight of the whole polyol. When the amount of the ordinary polyol is less than 20% by weight, the water dispersibility of the urethane component is poor, and when it exceeds 80% by weight, the stability of the aqueous dispersion is deteriorated.
[0024]
The alkyl (meth) acrylate includes, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, ( Metha> hexyl acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, and the like are used.
Further, as the monomer having a carboxyl group, acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like are used. Examples of the monomer having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxymethacrylate, and hydroxybutyl acrylate. Examples of the chain transfer agent having a hydroxyl group include 2-mercaptoethanol, 1-mercapto-2-propanol, 3-mercapto-1-propanol, and p-mercaptophenol.
[0025]
In the above polymerization reaction, the number average molecular weight of the acrylic polyol is set in the range of 3,000 to 20,000 by adjusting the amount of the chain transfer agent having a hydroxyl group. If the molecular weight is too small, the modulus of elasticity becomes too high, and the adhesive performance may decrease. If the molecular weight is too large, the dispersibility in water tends to be poor.
Further, by adjusting the amount of the monomer having a carboxyl group, the carboxyl group of the acrylic polyol is set in the range of 0.0007 to 0.003 equivalent / g. If the amount of the carboxyl group of the acrylic polyol is too small, the dispersibility in water will be poor, and if it is too large, it will only absorb water and will not disperse.
Further, the hydroxyl group of the acrylic polyol is set in the range of 0.00005 to 0.0007 equivalent / g by adjusting the amount of the monomer having a hydroxyl group or the chain transfer agent having a hydroxyl group. A hydroxyl group can be introduced at an arbitrary position in a polyol molecule in a monomer having a hydroxyl group, and a hydroxyl group can be introduced into a molecular terminal in a chain transfer agent having a hydroxyl group. Since the hydroxyl group participates in the reaction with the polyisocyanate, if the amount of the hydroxyl group is too small, a large amount of unreacted acrylic polyol remains and phase separation occurs, and the physical properties of the pressure-sensitive adhesive may not be stabilized. The agent itself tends to be hard.
[0026]
As the polyisocyanate, an aromatic, aliphatic, or alicyclic polyisocyanate is used. Isophorone diisocyanate, cyclohexane-1,4-diisocyanate, and isophorone diisocyanate from the viewpoint of prompt reaction to a mixture of a polyol (an ordinary polyol containing no carboxyl group) and a carboxyl group-containing polyol such as an acrylic polyol and suppression of a reaction with water. Alicyclic diisocyanates such as 4,4-dicyclohexylmethane diisocyanate and aliphatic diisocyanates such as hexamethylene diisocyanate are particularly preferably used.
In order to react the isocyanate group and the hydroxyl group of these polyisocyanates, it is preferable to use dibutyltin dilaurate, tin octoate, 1,4-diazabicyclo (2,2,2) octane or the like as a catalyst.
[0027]
The acrylic component in the present invention is a polymer having a glass transition temperature of 250 K or less, which is mainly composed of an alkyl (meth) acrylate. If the glass transition temperature is higher than 250K, the adhesiveness is poor, which is not preferable. Such a polymer is obtained by polymerizing a monomer which gives a polymer having a glass transition temperature of 250 K or lower, which contains an alkyl (meth) acrylate as a main monomer and, if necessary, a modifying monomer. Can be.
[0028]
The main monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, ( 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, and the like.
Further, the above-mentioned modifying monomers include (meth) acrylonitrile, vinyl acetate, vinyl propionate, (meth) acrylamide, mono or diester of maleic acid, styrene or a derivative thereof, N-methylol (meth) acrylamide, glycidyl ( (Meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, 2-hydroxypropyl (meth) acrylate, oligoester (meth) acrylate, ε-caprolactone (meth) Acrylate and the like.
[0029]
In the present invention, the acrylic component is used in a proportion of 100 to 1,500 parts by weight, particularly preferably 150 to 1,200 parts by weight, per 100 parts by weight of the urethane component in the aqueous dispersion. When the acrylic component is less than 100 parts by weight, both the initial elastic modulus and the stress relaxation time are increased, and the durability and the stress relaxation characteristics are reduced. When the acrylic component is more than 1,500 parts by weight, the water dispersibility tends to be poor.
[0030]
In the present invention, the polymer comprising the acrylic component and the urethane component needs to have a solvent-insoluble content in the range of 30 to 80% by weight, particularly preferably in the range of 35 to 75% by weight. There should be. The solvent-insoluble content of the polymer can be easily set by adjusting the degree of crosslinking of the urethane component, the molecular weight of the acrylic component, and the degree of crosslinking, as described later. When the solvent-insoluble content is less than 30% by weight, cohesive failure of the pressure-sensitive adhesive occurs at the time of re-peeling, thereby contaminating the panel or lowering the durability. When it exceeds 80% by weight, the adhesiveness decreases.
[0031]
The water-dispersed pressure-sensitive adhesive composition for an optical member of the present invention is such that the polymer comprising the urethane component and the acrylic component is dispersed in water substantially without using an emulsifier, and in this aqueous dispersion. Further, the composition is characterized by containing 0.01 to 1 part by weight, preferably 0.02 to 0.6 part by weight, of the silane coupling agent with respect to 100 parts by weight of the polymer. When the content of the silane coupling agent is less than 0.01 part by weight, the durability tends to decrease, and when it exceeds 1 part by weight, the adhesive strength to a liquid crystal cell or the like tends to be excessively increased.
[0032]
Examples of the silane coupling agent include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. Group-containing silanes such as 3-aminopropyltrimethoxysilane, N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine Coupling agent, (meth) acryl group-containing silane coupling agent such as 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, isocyanate group-containing silane coupling such as 3-isocyanatopropyltriethoxysilane And the like.
[0033]
The pressure-sensitive adhesive composition for a water-dispersed optical member of the present invention comprises, in an aqueous dispersion of a urethane component substantially not containing an emulsifier, an alkyl component (meth) acrylate per 100 parts by weight of the urethane component as an acrylic component. By subjecting 100 to 1,500 parts by weight of a monomer which gives a polymer having a glass transition temperature of 250 K or less, which is mainly composed of, to a polymerization reaction, the solvent-insoluble content of the urethane component and the acrylic component is 30 to 80. The polymer can be produced by producing a polymer in a weight% and blending the silane coupling agent in the above-described specific ratio with the polymer.
[0034]
In the aqueous dispersion of the urethane component substantially containing no emulsifier, the meaning of "substantially free of emulsifier" means that the emulsifier is not actively used in the stage of synthesizing the urethane component. . Therefore, for example, even if a very small amount of an emulsifier may be mixed in from the raw material components of the urethane component, when this does not affect the moisture resistance and water resistance of the finally obtained pressure-sensitive adhesive composition, However, even mixing of such an emulsifier is not excluded.
[0035]
Examples of such an aqueous dispersion of a urethane component substantially not containing an emulsifier include: a) an aqueous dispersion of a urethane containing no emulsifier prepared in advance as a commercial product, or b) the following (a) or ( The aqueous dispersion prepared by the method of b) is used. Among them, the following aqueous dispersions are particularly preferably used.
(A) Polyisocyanate is added to a mixture of a polyol having a number average molecular weight of 1,000 to 4,000 and a hydroxyl group of 0.0005 to 0.003 equivalent / g (that is, the ordinary polyol described above) and a carboxyl group-containing polyol. A water dispersion in which the carboxyl group is neutralized and dispersed in water before or after adding the above-mentioned monomer as an acrylic component to the urethane prepolymer obtained by reacting
(B) an aqueous dispersion obtained by further extending the chain of the above prepolymer
[0036]
In the aqueous dispersion of the urethane prepolymer (a), the prepolymer is finally chain-extended before or after or simultaneously with the polymerization of the monomer added as an acrylic component to increase the molecular weight. I do.
The carboxyl group-containing polyol preferably has a number average molecular weight of 3,000 to 20,000, a carboxyl group of 0.0007 to 0.003 equivalent / g, and a hydroxyl group of 0.00005 to 0.0007 equivalent / g. g of acrylic polyol is used. In particular, it is desirable that this acrylic polyol be in a proportion occupying 20 to 80% by weight of the whole polyol.
[0037]
In the above method (a), the polyisocyanate for producing the urethane prepolymer has a ratio of 1.5 to 4 equivalents to the total amount of hydroxyl groups, that is, an equivalent ratio (NCO / OH ratio) of 1.5. It is used at a ratio of ４4, particularly preferably at a ratio of 2-3. When the equivalent ratio is less than 1.5, the dispersion stability of the aqueous dispersion becomes poor, and when it exceeds 4, both the initial elastic modulus and the stress relaxation time increase, and the durability and the stress relaxation characteristics are liable to decrease. .
After the urethane prepolymer is thus produced, triethylamine or ammonia is used as an alkali to neutralize the carboxyl groups of the prepolymer. When dispersing in water after neutralization, water may be added to the above prepolymer, or conversely, the above prepolymer may be added to water. At this time, of course, it is desirable to stir so as to be uniform.
[0038]
In the above methods (a) and (b), the chain extension of the urethane prepolymer may be achieved by using a polyamine to bond the remaining isocyanate groups together to increase the molecular weight. The amount of the polyamine to be used is selected in consideration of the amount of the polyisocyanate and an equivalent necessary for reacting free isocyanate groups. Alternatively, a self-condensation reaction of an isocyanate group with water by heating may be used.
[0039]
In such an aqueous dispersion of the urethane component, an acrylic component (a monomer having alkyl (meth) acrylate as a main component) added during or after the preparation of the aqueous dispersion is polymerized. .
In this polymerization reaction, a peroxide such as ammonium persulfate or a water-soluble azo compound used in general emulsion polymerization is used as a polymerization initiator. Azo compounds that do not generate ion products in water are particularly preferred. When an oil-soluble polymerization initiator is used, it may be used by mixing it with a monomer in advance.
[0040]
In this way, an aqueous dispersion in which the polymer comprising the urethane component and the acrylic component is dispersed in water substantially without using an emulsifier is obtained. At that time, the above-mentioned polymer is adjusted so that the solvent-insoluble content of the whole polymer is 30 to 80% by weight, preferably 35 to 75% by weight. This setting can be easily performed by adjusting the degree of the urethane component and the molecular weight and the degree of crosslinking of the acrylic component.
Specifically, when the urethane component is obtained, the amount of the trifunctional or higher polyfunctional polyol, the amount of the hydroxyl group-containing monomer in the acrylic polyol synthesis stage, the amount of the polyisocyanate, and the like are adjusted to adjust the degree of the urethane component. And a method of adjusting the molecular weight and the degree of crosslinking of the acrylic component by using a small amount of a polyfunctional monomer during the polymerization of the acrylic component, or adjusting the polymerization initiator and the polymerization temperature.
[0041]
In the present invention, the above-mentioned specific amount of the silane coupling agent is blended with an aqueous dispersion in which the specific solvent-insoluble polymer is dispersed in water substantially without using an emulsifier, and the aqueous dispersion is dispersed in water. It is a pressure-sensitive adhesive composition for a mold optical member.
This water-dispersed pressure-sensitive adhesive composition for an optical member has excellent adhesiveness and cohesive strength as it is, but a crosslinking agent may be blended in order to further increase the cohesive strength. However, even after the crosslinking treatment is carried out by adding a crosslinking agent, the content is adjusted so that the solvent-insoluble content is in the range of 30 to 80% by weight. Further, various additives such as an ultraviolet absorber, an antioxidant, a softener, a dye, a pigment, and a filler may be added.
[0042]
In the present invention, an optical member having the above-mentioned pressure-sensitive adhesive composition for a water-dispersible optical member is provided on one or both surfaces of the optical member to obtain an optical member with a pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer is 2 to 500 μm, preferably 5 to 100 μm. By bonding this optical member with an adhesive layer to a display panel via the adhesive layer, various image display devices such as a liquid crystal display, an electroluminescence display, and a plasma display are obtained.
[0043]
To provide a pressure-sensitive adhesive layer on one or both sides of the optical member, the water-dispersible optical member pressure-sensitive adhesive composition may be applied directly on the optical member and dried, and may be subjected to a crosslinking treatment if necessary. The above-mentioned pressure-sensitive adhesive composition for an aqueous dispersion type optical member may be applied to the treated sheet, dried, subjected to a crosslinking treatment if necessary, and then bonded and transferred onto the optical member. For applying the pressure-sensitive adhesive composition for an aqueous dispersion type optical member, any coating method such as a roll coater such as a reverse coater or a gravure coater, a curtain coater, a lip coater, or a die coater can be used. The surface of the pressure-sensitive adhesive layer is protected by a release-treated sheet until it is practically used.
[0044]
Optical members include a polarizing plate, a retardation plate, an elliptically polarizing plate obtained by laminating a polarizing plate and a retardation plate, and a reflection type polarizing plate or the elliptically polarizing plate using the same, and various image displays such as a liquid crystal display. Any one used for the device can be used, and the type is not particularly limited. In an optical member of a laminated type such as an elliptically polarizing plate, the adhesive composition for a water-dispersed optical member of the present invention may be used for lamination, or any other adhesive or adhesive may be used. Can be used.
[0045]
The polarizer is stretched by absorbing iodine and / or a dichroic dye into a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or a saponified ethylene-vinyl acetate copolymer. Film, furthermore, a film obtained by laminating a protective film such as a triacetyl cellulose film or a polycarbonate film on this film, furthermore, a film obtained by subjecting a protective film or a stretched film to fine irregularities, a film subjected to a vapor deposition treatment, a protective adhesive film. Laminated ones, those subjected to various surface treatments, and the like are available.
[0046]
Examples of the retardation plate include a birefringent film obtained by stretching a film of polycarbonate, polymethyl methacrylate, polyolefin, or the like, and an oriented film of a liquid crystal polymer. The retardation plate may be formed by laminating two or more kinds of retardation layers and controlling optical characteristics such as retardation.
In these retardation plates, the above-mentioned polarizing plates, protective films and various surface treatments, treatment with an ultraviolet absorber, an antioxidant, or the like can be appropriately performed.
[0047]
【Example】
Hereinafter, examples of the present invention will be described in more detail. In the following, “parts” means “parts by weight”. The solvent-insoluble content of the polymer composed of the urethane component and the acrylic component was measured as described below.
[0048]
<Measurement of solvent-insoluble content>
A predetermined amount of dried polymer (initial weight: W1) was collected from the aqueous dispersion, immersed in an ethyl acetate solution, allowed to stand at room temperature for one week, and then the insoluble matter was taken out, and its dry weight (W2) was determined. It was measured. From these two measured values (W1, W2), the solvent insoluble content (% by weight) = (W2 / W1) × 100 was determined.
[0049]
Further, the number average molecular weight of a polyol or the like is measured by gel permeation chromatography (GPC) under the following conditions.
Equipment: Tosoh “HLC-8120GPC”
Developing solution: tetrahydrofuran
Flow rate: 0.8 ml / min
Column temperature: 40 ° C
Standard sample: polystyrene
Column: 3 connected columns
[0050]
Example 1
In the presence of 50 parts of polypropylene glycol having a number average molecular weight of 3,000 (hydroxyl group 0.00067 equivalent / g), 45 parts of butyl acrylate, 5 parts of acrylic acid, 1 part of 2-mercaptoethanol as a chain transfer agent, and a polymerization initiator The polymerization reaction was carried out at 50 ° C. for 6 hours under nitrogen stream using 0.05 parts of 2,2-azobisisobutyronitrile. When the molecular weight of the viscous liquid thus obtained was measured by GPC (gel permeation chromatography), the number average molecular weight peak derived from polypropylene glycol of 3,000 and the number average molecular weight derived from acrylic polyol were determined. A peak of 7,500 was observed, and it was found that an acrylic polyol having a number average molecular weight of 7,500 in which a carboxyl group was 0.0014 equivalent / g and a hydroxyl group was 0.00025 equivalent / g was obtained.
[0051]
The mixed viscous liquid comprising the polypropylene glycol and the acrylic polyol was heated to 100 ° C. and subjected to a reduced pressure treatment to remove the remaining water. To this was added 10.3 parts of isophorone diisocyanate (2.0 equivalents based on all hydroxyl groups), 0.01 parts of dibutyltin dilaurate was added, and the mixture was reacted at 65 ° C. for 3 hours to convert the hydroxyl groups into isocyanates. To obtain a urethane prepolymer.
Next, 7 parts of triethylamine (equivalent to carboxyl group) was added to neutralize the carboxyl group, and then 150 parts of water was added with stirring to disperse the urethane prepolymer in water. Further, a solution prepared by diluting 1.5 parts of ethylenediamine (equivalent to the remaining isocyanate groups) with 13.5 parts of water was added, and the mixture was reacted at 65 ° C. for 3 hours. An aqueous dispersion in which a urethane component having the formula (1) was stably dispersed in water was obtained.
[0052]
Then, 158 parts of water was added to 50 parts of this urethane component aqueous dispersion (solid content: 42.2% by weight), and after uniform stirring, 80 parts of butyl acrylate and 4.4 parts of methyl methacrylate were added. The mixture was stirred for 1 hour under a nitrogen stream to absorb the above monomers into urethane particles dispersed in water. The temperature was raised to 50 ° C., and 0.05 parts of 2,2-azobis [2- (2-imidazolin-2-yl)] propane was added to initiate a polymerization reaction. After maintaining the temperature at 50 ° C. for 4 hours, the temperature was raised to 70 ° C., and further maintained for 3 hours to continue the polymerization reaction, followed by cooling.
Thus, an aqueous dispersion in which the polymer comprising the urethane component and the acrylic component was stably dispersed in water was obtained. The polymer had an acrylic component of 400 parts and a solvent-insoluble content of 41.2% by weight per 100 parts of a urethane component.
Next, 0.1 part of 3-glycidoxypropylmethyltriethoxysilane as a silane coupling agent was added to 100 parts of the solid content (polymer) of the aqueous dispersion, and the mixture was mixed with an aqueous dispersion type optical polymer. A pressure-sensitive adhesive composition for a member was obtained.
[0053]
Next, the above-mentioned pressure-sensitive adhesive composition for an aqueous dispersion-type optical member was applied on a silicone-peeled polyethylene terephthalate film having a thickness of 38 μm so that the thickness after drying was 25 μm. After drying for minutes, a cross-linking treatment was performed to form an adhesive layer. This pressure-sensitive adhesive layer was transferred to a polarizing film and subjected to aging treatment at 50 ° C. for 24 hours to produce an optical member with a pressure-sensitive adhesive layer.
The above polarizing film is obtained by stretching a polyvinyl alcohol film having a thickness of 80 μm 5 times in an aqueous solution of iodine at 40 ° C., and then drying the film at 50 ° C. for 4 minutes to obtain a polarizer. A triacetyl cellulose film is bonded using a polyvinyl alcohol-based adhesive.
[0054]
Example 2
To 50 parts of polypropylene glycol having a number average molecular weight of 4,000, 4 parts of dimethylolpropionic acid dissolved in 10 parts of N-methylpyrrolidone was added, and the mixture was heated and degassed at 100 ° C. to remove water. To this, 12 parts of 4,4'-dicyclohexylmethane diisocyanate (1.7 equivalents to the total hydroxyl groups) was added, 0.01 part of dibutyltin dilaurate was added, and the mixture was reacted at 65 ° C. for 3 hours to give hydroxyl groups. Was converted to isocyanate to obtain a urethane prepolymer.
Next, 1.5 parts of triethylamine was added, and the mixture was stirred well to neutralize the carboxyl group. Separately, 700 parts of distilled water purged with nitrogen for 1.5 hours was prepared in a flask, and the neutralized urethane prepolymer was dropped into the distilled water using a dropping funnel. After completion of the dropwise addition, 0.5 part of ethylenediamine was diluted three times with distilled water and added to obtain an aqueous dispersion in which a urethane component was stably dispersed in water.
[0055]
Next, 300 parts of butyl acrylate, 30 parts of ethyl acrylate, and 0.1 part of triethylene glycol diacrylate were added to the aqueous dispersion of the urethane component, and the whole was uniformly stirred to convert the monomer into the urethane component. After absorption, 0.05 parts of 2,2-azobis (2-amidinopropane) dihydrochloride was added, and the mixture was heated to 50 ° C. and reacted for 5 hours.
Thus, an aqueous dispersion in which the polymer comprising the urethane component and the acrylic component was stably dispersed in water was obtained. The above polymer had an acrylic component of 490 parts and a solvent-insoluble content of 68.7% by weight per 100 parts of the urethane component.
Next, 0.1 part of 3-glycidoxypropylmethyltriethoxysilane as a silane coupling agent was added to 100 parts of the solid content (polymer) of the aqueous dispersion, and the mixture was mixed with an aqueous dispersion type optical polymer. A pressure-sensitive adhesive composition for a member was obtained.
An optical member with an adhesive layer was produced in the same manner as in Example 1, except that this water-dispersed pressure-sensitive adhesive composition for optical members was used.
[0056]
Example 3
In the presence of 50 parts of polytetramethylene glycol having a number average molecular weight of 3,000 (hydroxyl group: 0.0067 equivalent / g), 25 parts of butyl acrylate, 20 parts of ethyl acrylate, 4.5 parts of acrylic acid, and 2 parts of acrylic acid 0.5 parts of hydroxyethyl, 1 part of 2-mercaptoethanol as a chain transfer agent, and 0.05 parts of 2,2-azobisisobutyronitrile as a polymerization initiator, at 50 ° C. under nitrogen stream at 6 ° C. The polymerization reaction was performed for a time. The viscous liquid thus obtained was a polytetramethylene glycol having a number average molecular weight of 3,000, a number average molecular weight of 7,400, a carboxyl group of 0.0012 equivalent / g, and a hydroxyl group of 0.00033 equivalent / g. g of acrylic polyol.
[0057]
The viscous liquid composed of such a mixture was heated to 100 ° C. and subjected to a reduced pressure treatment to remove residual moisture. To this, 19.8 parts of 4,4-dicyclohexylmethane diisocyanate (3 equivalents based on all hydroxyl groups) was added, and 0.01 part of dibutyltin dilaurate was added. Was converted to isocyanate to obtain a urethane prepolymer.
Next, 6.3 parts of triethylamine (equivalent to carboxyl group) was added to neutralize the carboxyl group, and then 150 parts of water was added with stirring to disperse the urethane prepolymer in water. Further, a solution prepared by diluting 1.9 parts of ethylenediamine (equivalent to the remaining isocyanate groups) with 17.1 parts of water was added thereto, and reacted at 65 ° C. for 3 hours to obtain carboxyl groups neutralized in the skeleton. An aqueous dispersion in which a urethane component having the formula (1) was stably dispersed in water was obtained.
[0058]
Then, 70 parts of water was added to 50 parts of this aqueous dispersion of the urethane component (solid content: 43.2% by weight), and the mixture was stirred uniformly. Then, 40 parts of butyl acrylate and 3 parts of methyl methacrylate were added, and a nitrogen stream was added. The mixture was stirred under the condition for 1 hour, and the above monomers were absorbed in urethane particles dispersed in water. The temperature was raised to 50 ° C., and 0.02 parts of 2,2-azobis [2- (2-imidazolin-2-yl)] propane was added to initiate a polymerization reaction. After maintaining the temperature at 50 ° C. for 4 hours, the temperature was raised to 70 ° C., and further maintained for 3 hours to continue the polymerization reaction, followed by cooling.
Thus, an aqueous dispersion in which the polymer comprising the urethane component and the acrylic component was stably dispersed in water was obtained. The polymer had an acrylic component of 200 parts and a solvent-insoluble content of 54.3% by weight per 100 parts of a urethane component.
Next, 0.1 part of 3-glycidoxypropylmethyltriethoxysilane as a silane coupling agent was added to 100 parts of the solid content (polymer) of the aqueous dispersion, and the mixture was mixed with an aqueous dispersion type optical polymer. A pressure-sensitive adhesive composition for a member was obtained.
An optical member with an adhesive layer was produced in the same manner as in Example 1, except that this water-dispersed pressure-sensitive adhesive composition for optical members was used.
[0059]
Example 4
170 parts of water was added to 20 parts of the urethane component aqueous dispersion (solid content: 43.2% by weight) obtained in Example 3, and the mixture was stirred uniformly. Then, 100 parts of butyl acrylate, 12 parts of methyl methacrylate, and 0.03 parts of methylolpropane triacrylate was added, and the mixture was stirred for 1 hour under a nitrogen stream to absorb the above monomers into urethane particles dispersed in water. The temperature was raised to 50 ° C., and 0.1 part of 2,2-azobis [2- (2-imidazolin-2-yl)] propane was added to initiate a polymerization reaction. After maintaining the temperature at 50 ° C. for 4 hours, the temperature was raised to 70 ° C., and further maintained for 3 hours to continue the polymerization reaction, followed by cooling.
Thus, an aqueous dispersion in which the polymer comprising the urethane component and the acrylic component was stably dispersed in water was obtained. In the polymer, the acrylic component was 1,300 parts and the solvent-insoluble content was 50.2% by weight per 100 parts of the urethane component.
Next, 0.1 part of 3-glycidoxypropylmethyltriethoxysilane as a silane coupling agent was added to 100 parts of the solid content (polymer) of the aqueous dispersion, and the mixture was mixed with an aqueous dispersion type optical polymer. A pressure-sensitive adhesive composition for a member was obtained.
An optical member with an adhesive layer was produced in the same manner as in Example 1, except that this water-dispersed pressure-sensitive adhesive composition for optical members was used.
[0060]
Example 5
As an aqueous dispersion of the urethane component, a polyurethane dispersion containing no emulsifier ("Takelac W-6060" manufactured by Mitsui Takeda Chemical Co., Ltd.) was used, and 50 parts of this dispersion (solid content: 30.0% by weight) was added to 122 parts of water. Was added, and the mixture was stirred uniformly. Then, 80 parts of butyl acrylate and 10 parts of methyl methacrylate were added, and the mixture was stirred for 1 hour under a nitrogen stream to absorb the monomers into urethane particles dispersed in water. . The temperature was raised to 50 ° C., and 0.1 part of 2,2-azobis [2- (2-imidazolin-2-yl)] propane was added to initiate a polymerization reaction. After maintaining the temperature at 50 ° C. for 4 hours, the temperature was raised to 70 ° C., and further maintained for 3 hours to continue the polymerization reaction, followed by cooling.
[0061]
Thus, an aqueous dispersion in which the polymer comprising the urethane component and the acrylic component was stably dispersed in water was obtained. The polymer had an acrylic component of 600 parts and a solvent-insoluble content of 48.2% by weight per 100 parts of the urethane component.
Next, 0.1 part of 3-glycidoxypropylmethyltriethoxysilane as a silane coupling agent was added to 100 parts of the solid content (polymer) of the aqueous dispersion, and the mixture was mixed with an aqueous dispersion type optical polymer. A pressure-sensitive adhesive composition for a member was obtained.
An optical member with an adhesive layer was produced in the same manner as in Example 1, except that this water-dispersed pressure-sensitive adhesive composition for optical members was used.
[0062]
Comparative Example 1
18 parts of water was added to 50 parts of the urethane component aqueous dispersion (solid content: 42.2% by weight) obtained in Example 1, and after stirring uniformly, 10 parts of butyl acrylate was added. Similarly, a polymerization reaction was carried out to obtain an aqueous dispersion in which a polymer comprising a urethane component and an acrylic component was dispersed in water. The polymer had an acrylic component of 50 parts and a solvent-insoluble content of 66.7% by weight per 100 parts of the urethane component.
The same amount of the same silane coupling agent as in Example 1 was added to this aqueous dispersion to obtain a water-dispersed pressure-sensitive adhesive composition for an optical member.
Further, an optical member with an adhesive layer was produced in the same manner as in Example 1 except that this water-dispersed adhesive composition for optical members was used.
[0063]
Comparative Example 2
To 50 parts of the urethane component aqueous dispersion (solid content: 42.2% by weight) obtained in Example 1, 636 parts of water was added, and the mixture was uniformly stirred. Then, 422 parts of butyl acrylate (2 parts per 100 parts of the urethane component) was added. (Equivalent to 2,000 parts), and the polymerization reaction was carried out in the same manner as in Example 1. However, aggregation occurred during the polymerization, and a stable aqueous dispersion was not obtained.
For this reason, the same silane coupling agent as in Example 1 is blended with this aqueous dispersion to prepare a water-dispersed pressure-sensitive adhesive composition for an optical member, and from this, an optical member with a pressure-sensitive adhesive layer is produced. I couldn't do it.
[0064]
Comparative Example 3
A polymerization reaction was carried out in the same manner as in Example 4, except that 0.03 part of trimethylolpropane triacrylate was not added when the acrylic component was added to the aqueous dispersion of the urethane component to cause a polymerization reaction. An aqueous dispersion in which a polymer consisting of the following was dispersed in water was obtained. This aqueous dispersion had a solvent insoluble content of the polymer of 25.5% by weight.
The same amount of the same silane coupling agent as in Example 1 was added to this aqueous dispersion to obtain a water-dispersed pressure-sensitive adhesive composition for an optical member.
Further, an optical member with an adhesive layer was produced in the same manner as in Example 1 except that this water-dispersed adhesive composition for optical members was used.
[0065]
Comparative Example 4
The polymerization reaction was carried out in the same manner as in Example 4 except that the amount of trimethylolpropane triacrylate was changed from 0.03 part to 0.1 part when the acrylic component was added to the aqueous dispersion of the urethane component to cause a polymerization reaction. As a result, an aqueous dispersion in which a polymer composed of a urethane component and an acrylic component was dispersed in water was obtained. This aqueous dispersion had a solvent-insoluble content of the above polymer of 86.5% by weight.
The same amount of the same silane coupling agent as in Example 1 was added to this aqueous dispersion to obtain a water-dispersed pressure-sensitive adhesive composition for an optical member.
Further, an optical member with an adhesive layer was produced in the same manner as in Example 1 except that this water-dispersed adhesive composition for optical members was used.
[0066]
Comparative Example 5
90 parts of butyl acrylate, 7 parts of 2-ethylhexyl acrylate, and 3 parts of acrylic acid are emulsified in 122 parts of water using 3 parts of sodium polyoxyethylene lauryl sulfate as an emulsifier, and 2,2-azobis is used as a polymerization initiator. Using 0.05 parts of (2-amidinopropane) dihydrochloride, a polymerization reaction was carried out at 50 ° C. for 3 hours, and further the reaction was continued at 65 ° C. for 2 hours to obtain an acrylic aqueous dispersion containing an emulsifier.
The same amount of the same silane coupling agent as in Example 1 was added to this aqueous dispersion to obtain a water-dispersed pressure-sensitive adhesive composition for an optical member.
Further, an optical member with an adhesive layer was produced in the same manner as in Example 1 except that this water-dispersed adhesive composition for optical members was used.
[0067]
Comparative Example 6
A water dispersion in which the polymer comprising the urethane component and the acrylic component obtained in Example 2 was stably dispersed in water was not mixed with a silane coupling agent, and the above water dispersion itself was used for a water dispersion type optical member. An adhesive composition was obtained.
Further, an optical member with an adhesive layer was produced in the same manner as in Example 1 except that this water-dispersed adhesive composition for optical members was used.
[0068]
For the optical members with pressure-sensitive adhesive layers of Examples 1 to 5 and Comparative Examples 1 and 3 to 6, an adhesion test, a durability test, and a color unevenness test were performed by the following methods. These results were as shown in Table 1.
[0069]
<Adhesion test>
The optical member with the pressure-sensitive adhesive layer cut to a width of 25 mm was adhered to a non-alkali glass plate with one reciprocation of a 2 kg roll via the pressure-sensitive adhesive layer, and treated at 50 ° C. and in a 0.5 Mpa autoclave for 30 minutes. After leaving for 3 hours under the conditions of 23 ° C. and 50%, the peel adhesion was measured at a peel angle of 90 ° and a peel speed of 300 mm / min. This was defined as the initial adhesive strength.
After the treatment in the autoclave described above, after leaving for 48 hours under the condition of 70 ° C., after leaving for 3 hours under the condition of 23 ° C. and 50%, the peeling adhesive force was measured at a peeling angle of 90 ° and a peeling speed of 300 mm / min. It was measured. This was defined as the adhesion at 70 ° C.
As the removability, it is desired that the 70 ° C. treatment adhesion (that is, the adhesion after the heat treatment) does not increase together with the initial adhesion described above.
[0070]
<Durability test>
An optical member having a 12-inch size adhesive layer with an adhesive layer was attached to a non-alkali glass plate having a thickness of 0.5 mm via the adhesive layer, and treated with an autoclave at 50 ° C. and 0.5 MPa for 30 minutes. , 60 ° C., 90% RH for 500 hours. In this durability test, it was evaluated as ○ if the optical member did not peel or float, and evaluated as × if the optical member peeled or floated.
[0071]
<Color shading test>
An optical member with a pressure-sensitive adhesive layer having a size of 12 inches was stuck on both sides of a non-alkali glass plate having a thickness of 0.5 mm through the pressure-sensitive adhesive layer so that the absorption axis of the polarizing plate was perpendicular to the optical member. , 0.5 Mpa in an autoclave for 30 minutes, and then charged in an atmosphere at 90 ° C. for 500 hours. At this time, the state of occurrence of color unevenness and white spots was visually observed, and evaluation was evaluated as ○ if there was no color unevenness, and x if there was color unevenness.
[0072]
Figure 2004323761
[0073]
As is clear from the results in Table 1 above, the optical members with pressure-sensitive adhesive layers of Examples 1 to 5 have a small difference between the initial adhesive strength and the adhesive strength at 70 ° C. No increase in force, no residue of adhesive and no destruction of the liquid crystal cell under any processing conditions, the optical member can be re-peeled and the liquid crystal cell can be reused, and long-term severe tests and liquid crystal display conditions All have satisfactory characteristics without any adverse effect on On the other hand, it can be seen that the optical members with the pressure-sensitive adhesive layers of Comparative Examples 1, 2 to 6 cannot well balance the above characteristics.
[0074]
【The invention's effect】
As described above, the pressure-sensitive adhesive composition for a water-dispersed optical member of the present invention is a polymer that is water-dispersed without using an emulsifier, and has a controlled urethane component-acryl component ratio and solvent-insoluble content. The composition contains a specific amount of a silane coupling agent and causes peeling and foaming even when the optical member is attached to a liquid crystal cell and stored in a high-temperature and high-humidity state. High durability, and can uniformly alleviate the stress caused by the dimensional change of the optical member, the residual stress remains on the polarizing plate, the adverse effects such as color unevenness and white spots can be suppressed, and the optical member is peeled off. Even when the liquid crystal cell is reused, no increase in the adhesive force is observed, and the liquid crystal cell can be easily removed again without adversely affecting the liquid crystal cell. The water-dispersed pressure-sensitive adhesive composition for an optical member of the present invention does not use an organic solvent in the production process, and is therefore environmentally friendly.

Claims (10)

ウレタン成分とアクリル成分とからなるポリマーが実質的に乳化剤を使用することなく水に分散されてなり、上記のポリマーは、ウレタン成分１００重量部あたり、アクリル成分が１００〜１，５００重量部であり、かつ溶剤不溶分が３０〜８０重量％であり、このポリマー１００重量部に対し、シランカップリング剤０．０１〜１重量部を含むことを特徴とする水分散型光学部材用粘着剤組成物。A polymer composed of a urethane component and an acrylic component is dispersed in water substantially without using an emulsifier, and the above polymer has an acrylic component of 100 to 1,500 parts by weight per 100 parts by weight of the urethane component. And a solvent-insoluble content of 30 to 80% by weight, and 0.01 to 1 part by weight of a silane coupling agent based on 100 parts by weight of the polymer. . ウレタン成分は、数平均分子量が１，０００〜４，０００、水酸基が０．０００５〜０．００３当量／ｇのポリオールとカルボキシル基含有ポリオールとポリイソシアネートとから誘導されたポリマーである請求項１に記載の水分散型光学部材用粘着剤組成物。The urethane component is a polymer derived from a polyol having a number average molecular weight of 1,000 to 4,000 and a hydroxyl group of 0.0005 to 0.003 equivalent / g, a carboxyl group-containing polyol, and a polyisocyanate. The pressure-sensitive adhesive composition for an aqueous member according to the above. カルボキシル基含有ポリオールは、数平均分子量が３，０００〜２０，０００、カルボキシル基が０．０００７〜０．００３当量／ｇ、水酸基が０．００００５〜０．０００７当量／ｇのアクリルポリオールであり、このアクリルポリオールがポリオール全体の２０〜８０重量％を占める請求項２に記載の水分散型光学部材用粘着剤組成物。The carboxyl group-containing polyol is an acrylic polyol having a number average molecular weight of 3,000 to 20,000, a carboxyl group of 0.0007 to 0.003 equivalent / g, and a hydroxyl group of 0.00005 to 0.0007 equivalent / g, The water-dispersed pressure-sensitive adhesive composition for an optical member according to claim 2, wherein the acrylic polyol accounts for 20 to 80% by weight of the entire polyol. アクリル成分は、（メタ）アクリル酸アルキルエステルを主モノマーとしたガラス転移温度が２５０Ｋ以下のポリマーである請求項１〜３のいずれかに記載の水分散型光学部材用粘着剤組成物。The pressure-sensitive adhesive composition for a water-dispersed optical member according to any one of claims 1 to 3, wherein the acrylic component is a polymer having a glass transition temperature of 250K or less, which contains an alkyl (meth) acrylate as a main monomer. 実質的に乳化剤を含まないウレタン成分の水分散体中で、上記ウレタン成分１００重量部あたり、アクリル成分として（メタ）アクリル酸アルキルエステルを主成分としたモノマー１００〜１，５００重量部を、重合反応させることにより、上記のウレタン成分とアクリル成分とからなる溶剤不溶分が３０〜８０重量％のポリマーを生成し、このポリマー１００重量部に対し、シランカップリング剤０．０１〜１重量部を配合することを特徴とする水分散型光学部材用粘着剤組成物の製造方法。In an aqueous dispersion of a urethane component substantially containing no emulsifier, 100 to 1,500 parts by weight of a monomer mainly composed of an alkyl (meth) acrylate as an acrylic component is polymerized per 100 parts by weight of the urethane component. The reaction produces a polymer having a solvent insoluble content of 30 to 80% by weight composed of the urethane component and the acrylic component, and 0.01 to 1 part by weight of a silane coupling agent is added to 100 parts by weight of the polymer. A method for producing a water-dispersed pressure-sensitive adhesive composition for an optical member, which is blended. 実質的に乳化剤を含まないウレタン成分の水分散体は、
（ａ）数平均分子量が１，０００〜４，０００、水酸基が０．０００５〜０．００３当量／ｇのポリオールとカルボキシル基含有ポリオールに、水酸基の全量に対し、１．５〜４倍当量のポリイソシアネートを反応させて得たウレタンプレポリマーを、これにアクリル成分としてのモノマーを加える前または後に、そのカルボキシル基を中和して水に分散させた水分散体であるか、
（ｂ）上記プレポリマーをさらに鎖延長した水分散体であり、
上記（ａ）のウレタンプレポリマーの水分散体では、これにアクリル成分として加えたモノマーを重合する前または後あるいは同時に上記プレポリマーを鎖延長する請求項５の記載の水分散型光学部材用粘着剤組成物の製造方法。An aqueous dispersion of a urethane component substantially containing no emulsifier,
(A) The polyol having a number average molecular weight of 1,000 to 4,000 and a hydroxyl group of 0.0005 to 0.003 equivalent / g and a carboxyl group-containing polyol has 1.5 to 4 equivalents of the total amount of the hydroxyl group. A urethane prepolymer obtained by reacting a polyisocyanate, before or after adding a monomer as an acrylic component to the urethane prepolymer, is an aqueous dispersion in which carboxyl groups are neutralized and dispersed in water,
(B) an aqueous dispersion obtained by further extending the chain of the prepolymer,
6. The pressure-sensitive adhesive for a water-dispersed optical member according to claim 5, wherein in the aqueous dispersion of the urethane prepolymer of (a), the prepolymer is chain-extended before or after or simultaneously with polymerization of a monomer added as an acrylic component. For producing an agent composition. カルボキシル基含有ポリオールは、数平均分子量が３，０００〜２０，０００、カルボキシル基が０．０００７〜０．００３当量／ｇ、水酸基が０．００００５〜０．０００７当量／ｇのアクリルポリオールであり、このアクリルポリオールがポリオール全体の２０〜８０重量％を占める請求項６に記載の水分散型光学部材用粘着剤組成物の製造方法。The carboxyl group-containing polyol is an acrylic polyol having a number average molecular weight of 3,000 to 20,000, a carboxyl group of 0.0007 to 0.003 equivalent / g, and a hydroxyl group of 0.00005 to 0.0007 equivalent / g, The method according to claim 6, wherein the acrylic polyol accounts for 20 to 80% by weight of the entire polyol. アクリル成分として加えるモノマーは、ガラス転移温度が２５０Ｋ以下のポリマーを付与するものである請求項５〜７のいずれかに記載の水分散型光学部材用粘着剤組成物の製造方法。The method for producing a water-dispersed optical member pressure-sensitive adhesive composition according to any one of claims 5 to 7, wherein the monomer added as the acrylic component gives a polymer having a glass transition temperature of 250K or less. 光学部材の片面または両面に請求項１〜４のいずれかに記載の水分散型光学部材用粘着剤組成物からなる粘着剤層を設けたことを特徴とする粘着剤層付き光学部材。An optical member with a pressure-sensitive adhesive layer, comprising a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition for a water-dispersed optical member according to claim 1, on one or both surfaces of the optical member. ディスプレイ表示板に請求項９に記載の粘着剤層付き光学部材を、その粘着剤層を介して貼り合わせたことを特徴とする画像表示装置。An image display device, wherein the optical member with an adhesive layer according to claim 9 is attached to a display panel via the adhesive layer.
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