JP2004004741A - Electrophoretic particle dispersion solution, image display medium having the solution and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electrophoretic particle dispersion solution in which the electrophoretic particles are stably dispersed and the response speed of which is increased by speeding up the electrophoresis speed of electrophoretic particles even though low electric field is applied and to provide an image display medium having the solution and an image display device. <P>SOLUTION: In the electrophoretic particle dispersion solution, electrophoretic particles which are constituted of white color particles and/or colored particles having colors other than white color are dispersed in a dispersion medium. The dispersion medium includes non-polar solvent, a sulfonic acid compound that is at least soluble to a non-polar solvent, and a polymer compound that is soluble in the non-polar solvent. The sulfonic acid compound is selected, for example, from alkane sulfonic acid, alkylbenzenesulfonic acid, alkylnaphthalenesulfonic acid and their salts. It is preferred that the alkylbenzenesulfonic acid is a long chain alkylbenzenesulfonic acid such as dodecylbenzenesulfonic acid. <P>COPYRIGHT: (C)2004,JPO

Description

［式中、Ｒ_１　は水素原子又はメチル基であり、Ｒ_１´は水素原子又は炭素数１〜４のアルキル基であり、ｎは自然数であり、そして、ｘは１〜３の整数である。］
【００１９】
請求項７に記載された発明は、請求項１〜６のいずれかに記載された発明において、前記高分子化合物が、非イオン性の極性基を有する高分子化合物であることを特徴とするものである。
【００２０】
請求項８に記載された発明は、請求項７に記載された発明において、前記非イオン性の極性基を有する高分子化合物が、（ａ）２−ヒドロキシエチル（メタ）アクリレート、２，３−ジヒドロキシプロピル（メタ）アクリレート、４−ヒドロキシブチル（メタ）アクリレート、２−ヒドロキシ−３−プロピルメタクリレート、２−クロロエチル（メタ）アクリレート、２，３−ジブロモプロピル（メタ）アクリレート、（メタ）アクリロニトリル、イソブチル−２−シアノアクリレート、２−シアノエチルアクリレート、エチル−２−シアノアクリレート、メタクリルアセトン、テトラヒドロフルフリルメタクリレート、トリフロロエチルメタクリレート、ｐ−ニトロスチレン、ビニルピロリドン、アクリルアミド、メタクリルアミド、Ｎ，Ｎ−ジメチルメタクリルアミド、及び、Ｎ，Ｎ−ジブチルメタクリルアミドから選ばれる極性モノマーの少なくとも１種と、（ｂ）（メタ）アクリル酸のアルキルエステル及び（メタ）アクリル酸のアリールエステルから選ばれるモノマーの少なくとも１種と、の共重合体であることを特徴とするものである。
【００２１】
請求項９に記載された発明は、請求項１〜８のいずれかに記載された発明において、前記分散媒が、これに可溶な非イオン性の極性基を有する化合物を含有していることを特徴とするものである。
【００２２】
請求項１０に記載された発明は、請求項９に記載された発明において、前記非イオン性の極性基を有する化合物が、ヒドロキシル基、エステル基、エーテル基、ケトン基、アルデヒド基、ハロゲン基及びアミド基から選ばれる基を有していることを特徴とするものである。
【００２３】
請求項１１に記載された発明は、請求項１〜１０のいずれかに記載された発明において、前記電気泳動粒子が、その表面に塩基性の極性基を有する電気泳動粒子であることを特徴とするものである。
【００２４】
請求項１２に記載された発明は、請求項１１に記載された発明において、前記塩基性の極性基を有する電気泳動粒子が、塩基性基を有するモノマーを構成成分とする重合体又は共重合体よりなる前記非極性溶媒に不溶なバインダー樹脂中に白色粒子及び／又は白色以外の着色粒子を分散してなる電気泳動粒子であることを特徴とするものである。
【００２５】
請求項１３に記載された発明は、請求項１２に記載された発明において、前記バインダー樹脂が、（ａ）Ｎ−メチルアミノエチル（メタ）アクリレート、Ｎ−エチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジエチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジブチルアミノエチルアクリレート、Ｎ，Ｎ−ジ−ｔｅｒｔ−ブチルアミノエチルアクリレート、Ｎ−フェニルアミノエチルメタクリレート、Ｎ，Ｎ−ジフェニルアミノエチルメタクリレート、アミノスチレン、ジメチルアミノスチレン、Ｎ−メチルアミノエチルスチレン、ジメチルアミノエトキシスチレン、ジフェニルアミノエチルスチレン、Ｎ−フェニルアミノエチルスチレン、２−Ｎ−ピペリジルエチル（メタ）アクリレート、２−ビニルピリジン、４−ビニルピリジン、２　−ビニル−６　−メチルピリジン等の塩基性基を有するモノマーの少なくとも１種と、（ｂ）（メタ）アクリル酸のアルキルエステル及び（メタ）アクリル酸のアリールエステルから選ばれるモノマーの少なくとも１種と、の共重合体で構成されることを特徴とするものである。
【００２６】
請求項１４に記載された発明は、請求項１２に記載された発明において、前記バインダー樹脂が、非イオン性の極性基を有する高分子化合物であることを特徴とするものである。
【００２７】
請求項１５に記載された発明は、請求項１１に記載された発明において、前記塩基性の極性基を有する電気泳動粒子が、塩基性基を有するモノマー又は塩基性基を有するシランカップリング剤で白色粒子及び／又は白色以外の着色粒子の表面を処理してなる電気泳動粒子であることを特徴とするものである。
【００２８】
請求項１６に記載された発明は、請求項１５に記載された発明において、前記塩基性基を有するモノマーが、Ｎ−メチルアミノエチル（メタ）アクリレート、Ｎ−エチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジエチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジブチルアミノエチルアクリレート、Ｎ，Ｎ−ジ−ｔｅｒｔ−ブチルアミノエチルアクリレート、Ｎ−フェニルアミノエチルメタクリレート、Ｎ，Ｎ−ジフェニルアミノエチルメタクリレート、アミノスチレン、ジメチルアミノスチレン、Ｎ−メチルアミノエチルスチレン、ジメチルアミノエトキシスチレン、ジフェニルアミノエチルスチレン、Ｎ−フェニルアミノエチルスチレン、２−Ｎ−ピペリジルエチル（メタ）アクリレート、２−ビニルピリジン、４−ビニルピリジン、及び、２−ビニル−６−メチルピリジンから選ばれ、そして、前記塩基性基を有するシランカップリング剤が、γ−アミノプロピルトリメトキシシラン、γ−アミノプロピルトリエトキシシラン、Ｎ−フェニル−γ−アミノプロピルトリメトキシシラン、Ｎ−β（アミノエチル）γ−アミノプロピルメチルジメトキシシラン、Ｎ−β（アミノエチル）γ−アミノプロピルトリメトキシシラン、及び、Ｎ−β（アミノエチル）γ−アミノプロピルトリエトキシシランから選ばれることを特徴とするものである。
【００２９】
請求項１７に記載された発明は、請求項１〜１６のいずれかに記載された発明において、前記分散媒が、電気泳動粒子と異なる色の染料を溶解してなることを特徴とするものである。
【００３０】
請求項１８に記載された発明は、間隔を設けて配備された少なくとも一方が光透過性である一対の導電層間に、請求項１〜１７のいずれかに記載の電気泳動粒子分散液を含有してなることを特徴とする画像表示媒体である。
【００３１】
請求項１９に記載された発明は、請求項１８に記載の画像表示媒体を有することを特徴とする画像表示装置である。
【００３２】
【発明の実施の形態】
図１は、本発明の一実施の形態を示す表示媒体を模式的に示す断面図である。図２は、本発明の一実施の形態を示す画像表示媒体の動作を原理的に示す説明図であって、（ａ）は、表示媒体の右半分と左半分とに仕切った一対の導電層に外部から電圧を印加する状態を示し、（ｂ）は、電気泳動粒子が外部電界に沿って上方に移動する状態を示し、そして、（ｃ）は、電気泳動粒子が上部導電層に到達した状態を示す。そして、図３は、本発明の一実施の形態を示す画像表示装置の模式図である。
【００３３】
（実施の形態１）
本発明の電気泳動粒子分散液は、白色粒子及び／又は白色以外の着色粒子からなる電気泳動粒子を分散媒中に分散させた分散媒よりなり、その分散媒は、（イ）非極性溶媒、（ロ）該非極性溶媒に少なくとも可溶なスルホン酸化合物、及び、（ハ）該非極性溶媒に可溶な高分子化合物を共に含有している。前記スルホン酸化合物は、好ましくは、前記非極性溶媒の０．０１〜１重量％の割合で含有され、また、前記高分子化合物は、好ましくは、前記非極性溶媒の１〜２０重量％の割合で含有される。また、前記電気泳動粒子は、好ましくは、前記分散媒の１〜２０重量％の割合で含有される。
【００３４】
前記「非極性溶媒」は、例えば、▲１▼ペンタン、ヘキサン、ヘプタン、オクタン、ノナン、デカン、ドデカン等のパラフィン系炭化水素、▲２▼イソヘキサン、イソオクタン、イソドデカン等のイソパラフィン系炭化水素、▲３▼流動パラフィン等のアルキルナフテン系炭化水素、▲４▼ベンゼン、トルエン、キシレン、アルキルベンゼン、ソルベントナフサ等の芳香族炭化水素、及び、▲５▼ジメチルシリコーンオイル、フェニルメチルシリコーンオイル、ジアルキルシリコーンオイル、アルキルフェニルシリコーンオイル、環状ポリジアルキルシロキサン、環状ポリアルキルフェニルシロキサン等のシリコーン系のオイルであるが、本発明の目的に反しないかぎり、これら以外の非極性溶媒であってもかまわない。
【００３５】
前記「スルホン酸化合物」は、９６（ＣＨ_３ＳＯ_３Ｈ）〜５００の分子量範囲であり、例えば、炭素数１〜３０のアルカンスルホン酸、炭素数７〜３０のアルキルベンゼンスルホン酸及び炭素数１１〜３０のアルキルナフタレンスルホン酸並びにそれらの塩から選ばれる化合物であるが、好ましくは、ドデシルベンゼンスルホン酸等の炭素数１０〜３０の長鎖アルキルベンゼンスルホン酸である。これらのスルホン酸化合物は一つ或いは２つ以上を混合して用いても良い。
【００３６】
このような非極性溶媒に少なくとも可溶なスルホン酸化合物が非極性溶媒中に存在していると、次の化学平衡式に示されるように解離する。
【化３】

そして、このような非極性溶媒中に、表面に塩基性基を有する粒子が分散されていると、粒子の表面の塩基性基は、次の化学平衡式に示されるように解離する。
【化４】

このように、非極性溶媒に少なくとも可溶なスルホン酸化合物が電子泳動粒子分散液中に存在していると、スルホン酸化合物より解離して生じたＨ^＋　が電気泳動粒子と反応して、電気泳動粒子の帯電量が大きくなり、そのために、本発明の電気泳動粒子分散液によれば、低電界でも電気泳動粒子の泳動速度を速くして応答速度を速くすることができ、即ち、従来より小さい外部電圧でも良好に応答することができる。
【００３７】
本発明の電気泳動粒子分散液は、非極性溶媒に可溶な高分子化合物を有している。このような「非極性溶媒に可溶な高分子化合物」としては、公知の熱可塑性樹脂、熱硬化性樹脂のうち非極性溶媒に可溶なものが全て使用できるが、非極性溶媒よりも白色粒子及び／又は白色以外の着色粒子からなる電気泳動粒子の表面との引力相互作用が強いものが好ましく、例えば、（メタ）アクリル酸のアルキル又はアリールエステル等の非極性溶媒との親和性が高いモノマーの少なくとも１種を構成要件とする重合体があげられる。組み合わせるモノマーの種類、重合時の配合比を好適に定めることにより、非極性溶媒に可溶な樹脂を作れば良い。このような「非極性溶媒に可溶な高分子化合物」は、白色粒子及び／又は白色以外の着色粒子からなる電気泳動粒子の表面に吸着されるので、その立体効果によって、白色粒子及び／又は白色以外の着色粒子からなる電気泳動粒子を分散媒中に安定して分散させることができる。
【００３８】
また、前記「高分子化合物」は、好ましくは、少なくとも酸性基を有する高分子化合物である。このような「酸性基を有する高分子化合物」は、好ましくは、（メタ）アクリル酸、マレイン酸、無水マレイン酸、イタコン酸、無水イタコン酸、フマル酸、桂皮酸、クロトン酸、ビニル安息香酸、２−メタクリロキシエチルコハク酸、２−メタクリロキシエチルマレイン酸、２−メタクリロキシエチルヘキサヒドロフタル酸、２−メタクリロキシエチルトリメリット酸、ビニルスルホン酸、アリルスルホン酸、スチレンスルホン酸、２−スルホエチルメタクリレート、２−アクリルアミド−２−メチルプロパンスルホン酸、３−クロロアミドホスホキシプロピルメタクリレート、２−メタクリロキシエチルアシッドホスフェート、及び、ヒドロキシスチレンから選ばれる酸性基を有するモノマーの少なくとも１種を重合成分に有する重合体である。
【００３９】
このように、本発明によれば、電気泳動分散粒子に対して、電荷生成と立体効果とによる分散安定性のそれぞれを担う２種の化合物を分散媒に加えると、優れた電気泳動性と分散安定性とを両立させることができることが明らかになった。
【００４０】
このように高分子化合物が少なくとも酸性基を有する高分子化合物であると、その酸性基（例えば−ＣＯＯＨ）より解離して生じたＨ^＋　が前記式（３）に示すように電気泳動粒子と反応して、電気泳動粒子の帯電量が大きくなり、そのために、本発明の電気泳動粒子分散液によれば、低電界でも電気泳動粒子の泳動速度を速くして応答速度を速くすることができる。
【００４１】
また、前記高分子化合物は、好ましくは、下記一般式（１）で示される単量体を重合して得た高分子化合物である。
【化５】

［式中、Ｒ_１　は水素原子又はメチル基であり、Ｒ_１´は水素原子又は炭素数１〜４のアルキル基、好ましくは、メチル基である。好ましい置換基の組み合わせは、Ｒ_１　及びＲ_１´が、メチル基の場合である。ｎは自然数、好ましくは、２〜２００、より好ましくは、５〜１００であり、そして、ｘは１〜３の正数、好ましくは、３である。］
【００４２】
前記式（１）で示される高分子化合物は、非極性溶媒との親和力が特に強いので、非極性溶媒中で電気泳動粒子に吸着し、そのために、特に優れた立体効果に基づく電気泳動粒子の分散安定性を与えることができる。
【００４３】
また、前記高分子化合物は、好ましくは、非イオン性の極性基を有する高分子化合物である。このような「非イオン性の極性基を有する高分子化合物」は、好ましくは、（ａ）２−ヒドロキシエチル（メタ）アクリレート、２，３−ジヒドロキシプロピル（メタ）アクリレート、４−ヒドロキシブチル（メタ）アクリレート、２−ヒドロキシ−３−プロピルメタクリレート、２−クロロエチル（メタ）アクリレート、２，３−ジブロモプロピル（メタ）アクリレート、（メタ）アクリロニトリル、イソブチル−２−シアノアクリレート、２−シアノエチルアクリレート、エチル−２−シアノアクリレート、メタクリルアセトン、テトラヒドロフルフリルメタクリレート、トリフロロエチルメタクリレート、ｐ−ニトロスチレン、ビニルピロリドン、アクリルアミド、メタクリルアミド、Ｎ，Ｎ−ジメチルメタクリルアミド、及び、Ｎ，Ｎ−ジブチルメタクリルアミドから選ばれる極性モノマーの少なくとも１種と、（ｂ）（メタ）アクリル酸のアルキルエステル及び（メタ）アクリル酸のアリールエステルから選ばれるモノマーの少なくとも１種と、の共重合体である。
【００４４】
このように高分子化合物が非イオン性の極性基を有する高分子化合物であると、分散媒が非イオン性の極性基を持つ化合物を含有することとなり、イオン解離に対する溶媒和の働きをするので、イオン解離による電気泳動粒子の帯電量が増加し、そのために、さらに応答速度の速い電気泳動分散液を提供することが可能になる。
【００４５】
前記分散媒は、好ましくは、これに可溶な非イオン性の極性基を有する化合物を含有することができる。このような「非イオン性の極性基を有する化合物」は、ヒドロキシル基、エステル基、エーテル基、ケトン基、アルデヒド基、ハロゲン基及びアミド基から選ばれる基を有している。このように分散媒がこれに可溶な非イオン性の極性基を有する化合物を含有すると、分散媒が非イオン性の極性基を持つ化合物を含有することとなり、イオン解離に対する溶媒和の働きをするので、イオン解離による電気泳動粒子の帯電量が増加し、そのために、さらに応答速度の速い電気泳動分散液を提供することが可能になる。
【００４６】
前記「白色粒子及び／又は白色以外の着色粒子からなる電気泳動粒子」としては、例えば、▲１▼シリカ、チタニア、アルミナ等の金属酸化物、▲２▼カーボンブラック、アニリンブラック、ファーネスブラック、ランプブラック等の黒色の着色剤、▲３▼フタロシアニンブルー、メチレンブルー、ビクトリアブルー、メチルバイオレット、アニリンブルー、ウルトラマリンブルー等のシアン系の着色剤、▲４▼ローダミン６Ｇレーキ、ジメチルキナクリドン、ウォッチングレッド、ローズベンガル、ローダミンＢ、アリザリンレーキ等のマゼンタの着色剤、及び、▲５▼クロムイエロー、ベンジジンイエロー、ハンザイエロー、ナフトールイエロー、モリブデンオレンジ、キノリンイエロー、タートラジン等のイエローの着色剤が用いられる。
【００４７】
これらの電気泳動粒子は、好ましくは、表面に非イオン性の極性基を有する電気泳動粒子とされる。そして、これらの電気泳動粒子の粒径は、好ましくは、０．１〜１０μｍとされる。
【００４８】
このような「塩基性基を有する電気泳動粒子」は、好ましくは、塩基性基を有するモノマーを構成成分とする重合体又は共重合体よりなる非極性溶媒に不溶なバインダー樹脂中に白色粒子及び／又は白色以外の着色粒子を分散してなる電気泳動粒子である。前記「バインダー樹脂」は、好ましくは、（ａ）Ｎ−メチルアミノエチル（メタ）アクリレート、Ｎ−エチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジエチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジブチルアミノエチルアクリレート、Ｎ，Ｎ−ジ−ｔｅｒｔ−ブチルアミノエチルアクリレート、Ｎ−フェニルアミノエチルメタクリレート、Ｎ，Ｎ−ジフェニルアミノエチルメタクリレート、アミノスチレン、ジメチルアミノスチレン、Ｎ−メチルアミノエチルスチレン、ジメチルアミノエトキシスチレン、ジフェニルアミノエチルスチレン、Ｎ−フェニルアミノエチルスチレン、２−Ｎ−ピペリジルエチル（メタ）アクリレート、２−ビニルピリジン、４−ビニルピリジン、２−ビニル−６−メチルピリジン等の塩基性基を有するモノマーの少なくとも１種と、（ｂ）（メタ）アクリル酸のアルキルエステル及び（メタ）アクリル酸のアリールエステルから選ばれるモノマーの少なくとも１種と、の共重合体で構成される。前記非極性溶媒に不溶なバインダー樹脂は、組み合わせるモノマーの種類、重合時の配合比を好適に定めることにより製造される。本発明の電気泳動粒子は、前記各成分を非極性溶媒中に混合分散することにより製造される。この際、分散手段としてボールミル、サンドミル、アトライター等を用いてもよい。なお、混合順序は特に限定されるものではない。このような分散処理により、顔料粒子がバインダー樹脂に吸着或いは支持されてなる電気泳動粒子が得られる。
【００４９】
このように、電気泳動粒子が表面に塩基性基を有する電気泳動粒子であると、電気泳動粒子がバインダー樹脂の塩基性基のイオン性に起因して電荷を生成するので、電気泳動粒子の帯電量が増加し、そのために、さらに応答速度の速い電気泳動分散液を提供することが可能になる。
【００５０】
前記表面に塩基性基を有する電気泳動粒子バインダー樹脂は、好ましくは、非イオン性の極性基を有する高分子化合物である。このような「非イオン性の極性基を有する高分子化合物」は、好ましくは、（ａ）Ｎ−メチルアミノエチル（メタ）アクリレート、Ｎ−エチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジエチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジブチルアミノエチルアクリレート、Ｎ，Ｎ−ジ−ｔｅｒｔ−ブチルアミノエチルアクリレート、Ｎ−フェニルアミノエチルメタクリレート、Ｎ，Ｎ−ジフェニルアミノエチルメタクリレート、アミノスチレン、ジメチルアミノスチレン、Ｎ−メチルアミノエチルスチレン、ジメチルアミノエトキシスチレン、ジフェニルアミノエチルスチレン、Ｎ−フェニルアミノエチルスチレン、２−Ｎ−ピペリジルエチル（メタ）アクリレート、２−ビニルピリジン、４−ビニルピリジン、２−ビニル−６−メチルピリジン等の塩基性基を有するモノマーの少なくとも１種と、（ｂ）（メタ）アクリル酸のアルキルエステル及び（メタ）アクリル酸のアリールエステルから選ばれるモノマーの少なくとも１種と、（ｃ）２−ヒドロキシエチル（メタ）アクリレート、２，３−ジヒドロキシプロピル（メタ）アクリレート、４−ヒドロキシブチル（メタ）アクリレート、２−ヒドロキシ−３−プロピルメタクリレート、２−クロロエチル（メタ）アクリレート、２，３−ジブロモプロピル（メタ）アクリレート、（メタ）アクリロニトリル、イソブチル−２−シアノアクリレート、２−シアノエチルアクリレート、エチル−２−シアノアクリレート、メタクリルアセトン、テトラヒドロフルフリルメタクリレート、トリフロロエチルメタクリレート、ｐ−ニトロスチレン、ビニルピロリドン、アクリルアミド、メタクリルアミド、Ｎ，Ｎ−ジメチルメタクリルアミド、及び、Ｎ，Ｎ−ジブチルメタクリルアミドから選ばれる極性モノマーの少なくとも１種と、の共重合体である。
【００５１】
このように、表面に塩基性基を有する電気泳動粒子のバインダー樹脂が非イオン性の極性基を有する高分子化合物であると、電子泳動粒子表面の塩基性基の局所的な部分に溶媒和となる成分が集中するので、電気泳動粒子の表面に効率よく電荷が生成し、そのために、さらに応答速度の速い電気泳動分散液を提供することが可能になる。
【００５２】
また、前記塩基性基を有する電気泳動粒子は、好ましくは、塩基性基を有するモノマー又は塩基性基を有するシランカップリング剤で白色粒子及び／又は白色以外の着色粒子の表面を処理してなる電気泳動粒子である。このような「塩基性基を有するモノマー」は、好ましくは、Ｎ−メチルアミノエチル（メタ）アクリレート、Ｎ−エチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジメチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジエチルアミノエチル（メタ）アクリレート、Ｎ，Ｎ−ジブチルアミノエチルアクリレート、Ｎ，Ｎ−ジ−ｔｅｒｔ−ブチルアミノエチルアクリレート、Ｎ−フェニルアミノエチルメタクリレート、Ｎ　，Ｎ　−ジフェニルアミノエチルメタクリレート、アミノスチレン、ジメチルアミノスチレン、Ｎ−メチルアミノエチルスチレン、ジメチルアミノエトキシスチレン、ジフェニルアミノエチルスチレン、Ｎ−フェニルアミノエチルスチレン、２−Ｎ−ピペリジルエチル（メタ）アクリレート、２−ビニルピリジン、４−ビニルピリジン、及び、２−ビニル−６−メチルピリジンから選ばれ、そして、前記塩基性基を有するシランカップリング剤が、γ−アミノプロピルトリメトキシシラン、γ−アミノプロピルトリエトキシシラン、Ｎ−フェニル−γ−アミノプロピルトリメトキシシラン、Ｎ−β（アミノエチル）γ−アミノプロピルメチルジメトキシシラン、Ｎ−β（アミノエチル）γ−アミノプロピルトリメトキシシラン、及び、Ｎ−β（アミノエチル）γ−アミノプロピルトリエトキシシランから選ばれる。
【００５３】
このように、塩基性基を有する電気泳動粒子が塩基性基を有するモノマー又は塩基性基を有するシランカップリング剤で白色粒子及び／又は白色以外の着色粒子の表面を処理してなる電気泳動粒子であると、電気泳動粒子と生成した塩基性基を有するモノマーの重合体又は塩基性基を有するシランカップリング剤の界面の局所的な部分に溶媒和となる成分が集中して、効率よく電荷を生成する。したがって、酸塩基解離による電気泳動粒子の帯電量が増加するので、さらに応答速度の速い電気泳動分散液を提供することが可能になる。
【００５４】
前記分散媒は、電気泳動粒子と異なる色の染料を溶解してなるものであってもよい。このような染料は、例えば、上記分散媒に可溶な油溶性染料が挙げられ、Ｃｏｌｏｕｒ　ＩｎｄｅｘにおいてＳｏｌｖｅｎｔ　ｄｙｅに分類される染料が好適に使用される。これらの油溶性染料には、アゾ系、アントラキノン系、フタロシアニン系、トリアリルメタン系の染料がある。これら油性染料は、例えば、スピリットブラック（ＳＢ，ＳＳＢＢ，ＡＢ）、ニグロシンベース（ＳＡ，ＳＡＰ，ＳＡＰＬ，ＥＥ，ＥＥＬ，ＥＸ，ＥＸＢＰ，ＥＢ）、オイルイエロー（１０５，１０７，１２９，３Ｇ，ＧＧＳ）、オイルオレンジ（２０１，ＰＳ，ＰＲ）、ファーストオレンジ、オイルレッド（５Ｂ，ＲＲ，ＯＧ）、オイルスカーレット、オイルピンク３１２、オイルバイオレット＃７３０、マクロレックスブルーＲＲ、スミプラストグリーンＧ、オイルブラウン（ＧＲ，４１６）、スーダンブラックＸ６０、オイルグリーン（５０２，ＢＧ）、オイルブルー（６１３，２Ｎ，ＢＯＳ）、オイルブラック（ＨＢＢ，８６０，ＢＳ）、バリファーストイエロー（１１０１，１１０５，３１０８，４１２０）、バリファーストオレンジ（３２０９，３２１０）、バリファーストレッド（１３０６，１３５５，２３０３，３３０４，３３０６，３３２０）、バリファーストピンク２３１０Ｎ、バリファーストブラウン（２４０２，３４０５）、バリファーストブルー（３４０５，１５０１，１６０３，１６０５，１６０７，２６０６，２６１０）、バリファーストバイオレット（１７０１，１７０２）、バリファーストブラック（１８０２，１８０７，３８０４，３８１０，３８２０，３８３０）が代表的なものとしてあげられるが、本発明の目的に反しない限り、ここに記載された染料以外の油性染料又は油溶性染料であってもかまわない。
【００５５】
このように、分散媒が電気泳動粒子と異なる色の染料を溶解していると、表示コントラストの大きい電気泳動粒子分散液の提供が可能となる。
【００５６】
（実施の形態２）
図１に示すように、本発明の画像表示媒体１０は、間隔を設けて配備された少なくとも一方が光透過性である一対の導電層１，２の間に、請求項１〜１７のいずれかに記載の電気泳動粒子分散液を含有している。
前記導電層としては、Ａｌ，Ａｇ，Ｎｉ，Ｃｕ等の金属やＩＴＯ，ＳｎＯ_２　，ＺｎＯ，Ａｌ等の透明導電体をスパッタリング法、真空蒸着法、ＣＶＤ法、塗布法等で薄膜状に形成したもの、或いは、導電剤を溶媒あるいは合成樹脂バインダーに混合して塗布したものが用いられる。このような導電剤には、ポリメチルベンジルトリメチルクロライド、ポリアリルポリメチルアンモニウムクロライド等のカチオン性高分子電解質、ポリスチレンスルホン酸塩、ポリアクリル酸塩等のアニオン性高分子電解質や電子伝導性の酸化亜鉛、酸化スズ、酸化インジウム微粉末等が用いられる。導電層１，２は、自体が自己保持機能を有する程度に厚い場合もあるし、図示しない自己保持機能を有する基体上に導電層が設けられている場合もあり、いずれの場合も好適に使用できる。また、導電層１，２は、異方導電性を示す層であってもよいし、厚さ方向に導電性部分が貫通したパターン状ないしマルチドット状のセグメントを有する層であってもよい。いずれにおいても、導電層１，２の一部に電源電極をコンタクトすれば導電層１，２の間に電界を生じさせることが可能となるので、白色又は白色以外の着色粒子３は確実に移動できる。表示を行なうには、導電層１，２間の電圧印加手段を用意すればよいので、簡便である。着色剤が使用できる量は、好ましくは、バインダー樹脂１０重量部に対して着色剤０．１重量部〜３００重量部、より好ましくは、バインダー樹脂１０重量部に対して着色剤１重量部〜１００重量部である。図１において、４は分散媒であり、５は分散媒に可溶な高分子化合物である。本発明においては、高分子化合物５は、白色又は白色以外の着色粒子３の表面に吸着された状態となる。
【００５７】
本発明の画像表示媒体によれば、図２（ａ）に示すように、画像表示媒体の右半分と左半分とは仕切られた導電層１，２に外部から適当な手段で電圧を印加すると、図２（ｂ）に示すように、電荷を持つ白色又は白色以外の着色粒子３は、分散媒４の中を外部電界に沿って上方、即ち、基板２の方向に移動しはじめ、そして、図２（ｃ）に示すように、電荷を持つ白色又は白色以外の着色粒子３は、静電気力によって基板２に付着し移動を完結する。図２（ｃ）の状態を画像表示媒体の上方、即ち、導電層２の外側から眺めると、その左半分では、電荷を持つ白色又は白色以外の着色粒子３の色が見られ、右半分は、分散媒４に添加した染料の色が見られる。以上が、本発明の画像表示媒体による画像表示の基本動作原理であるが、この表示様式は可逆であるので、繰り返し使用することができる。
【００５８】
（実施の形態３）
本発明の画像表示装置は、請求項１８に記載の画像表示媒体を有している。
図３に示されるように、本発明の画像表示装置２０は、画像表示媒体１０を備え、そして、図示しない駆動回路、演算回路、内部メモリ、電源等を備えている。表示媒体における電極は、ドットマトリックスを形成し、指定のドットをＯＮ表示することにより、全体として画像を表示する。図３において、１１は、筺体であり、また、１２は、情報入力手段である。
【００５９】
【実施例】
本発明を参考例及び実施例によりさらに詳細に説明する。ただし、本発明は、下記の実施例に限定されるものではない。なお、以下の参考例、実施例及び比較例で用いる部は、全て重量部である。
【００６０】
（参考例１）
（高分子化合物の合成例）
撹拌機、温度計及び還流冷却器を備えた反応容器に、アイソパーＨ（エクソンケミカル社）３００部を採り、これを８５℃に加熱した。この中にラウリルメタクリレート４０重量部及び重合開始剤であるベンゾイルパーオキサイド１部よりなる溶液を１時間に亘って滴下した。次いで、同温度で５時間撹拌を続け、反応を終了した。得られた樹脂溶液から溶媒のアイソパーＨをエバポレーターで蒸発させて、アイソパーＨに可溶な粘稠な高分子化合物を得た。
【００６１】
（参考例２）
（高分子化合物の合成例）
撹拌機、温度計及び還流冷却器を備えた反応容器に、アイソパーＨ（エクソンケミカル社）３００部を採り、これを８５℃に加熱した。この中にラウリルメタクリレート３６重量部、メタクリル酸４重量部及び重合開始剤であるベンゾイルパーオキサイド１部よりなる溶液を１時間に亘って滴下した。次いで、同温度で５時間撹拌を続け、反応を終了した。得られた樹脂溶液から溶媒のアイソパーＨをエバポレーターで蒸発させて、アイソパーＨに可溶な粘稠な高分子化合物を得た。
【００６２】
（参考例３）
（高分子化合物の合成例）
参考例１で用いた反応容器に、シリコーンオイル（東レ・ダウコーニング・シリコーン社ＳＨ−２００；１ｃｓ）３００部を採り、これを８０℃に加熱した。この中に、前記一般式（１）で示される高分子化合物においてＲ_１　＝ＣＨ_３　、ｘ＝３及びｎ＝１０であるもの３９重量部、メタクリル酸１重量部、並びに、重合開始剤であるアゾビスイソブチロニトリル３部よりなる溶液を１時間に亘って滴下した。次いで、同温度で５時間撹拌を続け、反応を終了した。得られた樹脂溶液から溶媒のシリコーンオイルをエバポレーターで蒸発させて、シリコーンオイルに可溶な粘稠な高分子化合物を得た。
【００６３】
（参考例４）
（高分子化合物の合成例）
参考例１で用いた反応容器に、シリコーンオイル（東レ・ダウコーニング・シリコーン社ＳＨ−２００；１ｃｓ）３００部を採り、これを８０℃に加熱した。この中に、前記一般式（１）で示される高分子化合物においてＲ_１　＝ＣＨ_３　、ｘ＝３、及び、ｎ＝１０であるもの３７重量部、メタクリル酸１重量部、ビニルピロリドン２部、並びに、重合開始剤であるアゾビスイソブチロニトリル３部よりなる溶液を１時間に亘って滴下した。次いで、同温度で５時間撹拌を続け、反応を終了した。得られた樹脂溶液から溶媒のシリコーンオイルをエバポレーターで蒸発させて、シリコーンオイルに可溶な粘稠な高分子化合物を得た。
【００６４】
（参考例５）
（分散粒子の作製例）
参考例１で用いた反応容器に、シリコーンオイル（東レ・ダウコーニング・シリコーン社ＳＨ−２００；１ｃｓ）５００部を採り、８５℃に加熱した。この中に、前記一般式（１）で示される高分子化合物においてＲ_１　＝ＣＨ_３　、ｘ＝３、及び、ｎ＝１０であるもの４重量部、ジメチルアミノエチルメタクリレート４重量部、メチルメタクリレート４０重量部、Ｎ−アクリロイルモルホリン２部、並びに、重合開始剤であるアゾビスイソブチロニトリル３部よりなる溶液を１時間に亘って滴下した。次いで同温度で５時間撹拌を続け、反応を終了した。シリコーンオイルを蒸発させて目的の固体のバインダー樹脂を得た。
次いで、シリコーンオイル（東レ・ダウコーニング・シリコーン社ＳＨ−２００；１ｃｓ）１００部に、上記バインダー樹脂８部、ルチル型の酸化チタン２部を加え、ボールミルで２４時間分散処理をした。終了後シリコーンオイルを蒸発させて目的の樹脂分散粒子を得た。
【００６５】
（参考例６）
（分散粒子の作製例）
水：エタノール＝１：１の混合溶媒４０００部に３−アミノプロピルトリメトキシシラン３部とトリメチルエトキシシラン１部を溶解した溶液にルチル型の酸化チタン４００部を加え室温で１昼夜攪拌した。反応終了後、粒子を回収しエタノールで洗浄したものを乾燥して目的とする粒子を得た。
【００６６】
（実施例１）
イソパラフィン（アイソパーＨ）１００重量部に、酸化チタン粒子５重量部、ドデシルベンゼンスルホン酸０．１重量部、参考例１で得た高分子化合物１０重量部、及び、染料（バイエル　マクロレックスブルーＲＲ）０．１重量部を加え、これらを１時間超音波分散処理をして電気泳動粒子分散液を得た。そして、２枚のＩＴＯ電極付基板間に１ｃｍ□の開口を設けた１００μｍ厚のポリエステルフィルムを挟んで空間を形成し、この空間に前記電気泳動粒子分散液を封入した。
【００６７】
（実施例２）
イソパラフィン（アイソパーＨ）１００重量部に参考例５で得た樹脂分散粒子５重量部、ドデシルベンゼンスルホン酸０．１重量部、参考例１で得た高分子化合物１０重量部、及び、染料（バイエル　マクロレックスブルーＲＲ）０．１重量部を加え、これらを１時間超音波分散処理をして電気泳動粒子分散液を得た。そして、２枚のＩＴＯ電極付基板間に１ｃｍ□の開口を設けた１００μｍ厚のポリエステルフィルムを挟んで空間を形成し、この空間に前記電気泳動粒子分散液を封入した。
【００６８】
（実施例３）
イソパラフィン（アイソパーＨ）１００重量部に参考例６で得た粒子５重量部、ドデシルベンゼンスルホン酸０．１重量部、参考例２で得た高分子化合物１０重量部、及び、染料（バイエル　マクロレックスブルーＲＲ）０．１重量部を加え、これらを１時間超音波分散処理をして電気泳動粒子分散液を得た。そして、２枚のＩＴＯ電極付基板間に１ｃｍ□の開口を設けた１００μｍ厚のポリエステルフィルムを挟んで空間を形成し、この空間に前記電気泳動粒子分散液を封入した。
【００６９】
（実施例４）
イソパラフィン（アイソパーＨ）１００重量部に、参考例６で得た粒子５重量部、ドデシルベンゼンスルホン酸０．１重量部、参考例２で得た高分子化合物１０重量部、染料（バイエル　マクロレックスブルーＲＲ）０．１重量部、及び、Ｎ，Ｎ−ジエチルプロピオンアミド（非イオン性極性化合物）１重量部を加え、これらを１時間超音波分散処理をして電気泳動粒子分散液を得た。そして、２枚のＩＴＯ電極付基板間に１ｃｍ□の開口を設けた１００μｍ厚のポリエステルフィルムを挟んで空間を形成し、この空間に前記電気泳動粒子分散液を封入した。
【００７０】
（実施例５）
メチルフェニルシリコーンオイル（ＳＨ５５６）１００重量部に、参考例６で得た粒子５重量部、ドデシルベンゼンスルホン酸０．１重量部、参考例３で得た高分子化合物１０重量部、及び、染料（バイエル　マクロレックスブルーＲＲ）０．１重量部を加え、これらを１時間超音波分散処理をして電気泳動粒子分散液を得た。そして、２枚のＩＴＯ電極付基板間に１ｃｍ□の開口を設けた１００μｍ厚のポリエステルフィルムを挟んで空間を形成し、この空間に前記電気泳動粒子分散液を封入した。
【００７１】
（実施例６）
メチルフェニルシリコーンオイル（ＳＨ５５６）１００重量部に、参考例６で得た粒子５重量部、ドデシルベンゼンスルホン酸０．１重量部、参考例４で得た高分子化合物１０重量部、及び、染料（バイエル　マクロレックスブルーＲＲ）０．１重量部を加え、これらを１時間超音波分散処理をして電気泳動粒子分散液を得た。そして、２枚のＩＴＯ電極付基板間に１ｃｍ□の開口を設けた１００μｍ厚のポリエステルフィルムを挟んで空間を形成し、この空間に前記電気泳動粒子分散液を封入した。
【００７２】
（実施例７）
メチルフェニルシリコーンオイル（ＳＨ５５６）１００重量部に、参考例５で得た樹脂分散粒子５重量部、ドデシルベンゼンスルホン酸０．１重量部、参考例３で得た高分子化合物１０重量部、及び、染料（バイエル　マクロレックスブルーＲＲ）０．１重量部を加え、これらを１時間超音波分散処理をして電気泳動粒子分散液を得た。そして、２枚のＩＴＯ電極付基板間に１ｃｍ□の開口を設けた１００μｍ厚のポリエステルフィルムを挟んで空間を形成し、この空間に前記電気泳動粒子分散液を封入した。
【００７３】
（比較例１）
メチルフェニルシリコーンオイル（ＳＨ５５６）１００重量部に、酸化チタン粒子５重量部、ドデシルベンゼンスルホン酸０．１重量部、及び、染料（バイエル　マクロレックスブルーＲＲ）０．１重量部を加え、これらを１時間超音波分散処理をして電気泳動粒子分散液を得た。そして、２枚のＩＴＯ電極付基板間に１ｃｍ□の開口を設けた１００μｍ厚のポリエステルフィルムを挟んで空間を形成し、この空間に前記電気泳動粒子分散液を封入した。
【００７４】
（比較例２）
イソパラフィン（アイソパーＨ）１００重量部に、酸化チタン粒子５重量部、、参考例２で得た高分子化合物１０重量部、及び、染料（バイエル　マクロレックスブルーＲＲ）０．１重量部を加え、これらを１時間超音波分散処理をして電気泳動粒子分散液を得た。そして、２枚のＩＴＯ電極付基板間に１ｃｍ□の開口を設けた１００μｍ厚のポリエステルフィルムを挟んで空間を形成し、この空間に前記電気泳動粒子分散液を封入した。
【００７５】
以上、実施例及び比較例で得られた画像表示媒体の上部ＩＴＯ電極に−１００Ｖを印加して、封入された電子泳動粒子の動きを見た後、上部電極に＋１００Ｖを印加して、封入された電子泳動粒子の動きを見ることにより、実施例及び比較例で得られた画像表示媒体の評価を行った。同様に、このような極性の切り替えを１００回程度行なって実施例及び比較例で得られた画像表示媒体の評価を行った。また、これらの画像表示媒体について電圧を解除した後の状態も観察した。そして、実施例及び比較例で得られた画像表示媒体について、同様の表示動作を±５０Ｖで行って、実施例及び比較例で得られた画像表示媒体の評価を行った。
【００７６】
評価は、次の基準で行った。
ａ：分散粒子は速やかに移動した。この極性の切り替えを１００回程度行なったが、安定して繰り返すことができた。また、電圧を取り去っても電着した状態を保持していた。
ｂ：応答速度はやや遅いが、電圧極性の切り替えを１００回程度行ったところ、安定して動作を繰り返すことができた。また、電圧を取り去っても電着した状態を保持していた。
ｃ：はじめの数回は速やかに移動するが、繰り返しは１０回程度しかできなかった。
ｄ：応答速度が遅く、繰り返しも１０回程度しかできなかった。
ｅ：応答しなかった。
【００７７】
評価結果は、次の表１に示される。
【００７８】
【表１】

【００７９】
【発明の効果】
（１）請求項１〜３に記載された発明によれば、非極性溶媒に少なくとも可溶なスルホン酸化合物が電子泳動粒子分散液中に存在しているので、スルホン酸化合物より解離して生じたＨ^＋　が電気泳動粒子と反応して、電気泳動粒子の帯電量が大きくなり、そのために、低電界でも電気泳動粒子の泳動速度を速くして応答速度を速くすることができる。しかも、請求項１に記載された発明によれば、非極性溶媒に可溶な高分子化合物が電子泳動粒子分散液中に存在しているので、高分子化合物が白色粒子及び／又は白色以外の着色粒子からなる電気泳動粒子の表面に吸着され、その立体効果によって、白色粒子及び／又は白色以外の着色粒子からなる電気泳動粒子を分散媒中に安定して分散させることができる。
【００８０】
（２）請求項４，５に記載された発明によれば、高分子化合物が少なくとも酸性基を有する高分子化合物であるので、その酸性基（例えば−ＣＯＯＨ）より解離して生じたＨ^＋　が電気泳動粒子と反応して、電気泳動粒子の帯電量が大きくなり、そのために、低電界でも電気泳動粒子の泳動速度を速くして応答速度を速くすることができる。
【００８１】
（３）請求項６に記載された発明によれば、高分子化合物が前記式（１）で示される単量体を重合して得た、非極性溶媒との親和力が特に強い、高分子化合物であるので、この高分子化合物が非極性溶媒中で電気泳動粒子に吸着し、そのために、特に優れた立体効果に基づく電気泳動粒子の分散安定性を与えることができる。
【００８２】
（４）請求項７，８に記載された発明によれば、高分子化合物が非イオン性の極性基を有する高分子化合物であるので、分散媒が非イオン性の極性基を持つ化合物を含有することとなり、よって、イオン解離に対する溶媒和の働きをすることとなって、イオン解離による電気泳動粒子の帯電量が増加し、そのために、さらに応答速度の速い電気泳動分散液を提供することが可能になる。
【００８３】
（５）請求項９，１０に記載された発明によれば、前記分散媒がこれに可溶な非イオン性の極性基を有する化合物を含有しているので、分散媒が非イオン性の極性基を持つ化合物を含有することとなり、よって、イオン解離に対する溶媒和の働きをすることとなって、イオン解離による電気泳動粒子の帯電量が増加し、そのために、さらに応答速度の速い電気泳動分散液を提供することが可能になる。
【００８４】
（６）請求項１１に記載された発明によれば、電気泳動粒子がその表面に塩基性基を有する電気泳動粒子とされるので、電子泳動粒子とこれに吸着した高分子化合物との界面の局所的な部分に溶媒和となる成分が集中するので、電気泳動粒子の表面に効率よく電荷生成し、そのために、さらに応答速度の速い電気泳動分散液を提供することが可能になる。
【００８５】
（７）請求項１２，１３に記載された発明によれば、塩基性基を有する電気泳動粒子が、塩基性基を有するモノマーを構成成分とする重合体又は共重合体よりなる非極性溶媒に不溶なバインダー樹脂中に白色粒子及び／又は白色以外の着色粒子を分散してなる電気泳動粒子であるので、電気泳動粒子がバインダー樹脂の塩基性基のイオン性に起因して電荷を生成してその電気泳動粒子の帯電量が増加し、そのために、さらに応答速度の速い電気泳動分散液を提供することが可能になる。
【００８６】
（８）請求項１４に記載された発明によれば、表面に塩基性基を有する電気泳動粒子のバインダー樹脂が非イオン性の極性基を有する高分子化合物であるので、電子泳動粒子表面の塩基性基の局所的な部分に溶媒和となる成分が集中して、その表面に効率よく電荷が生成し、そのために、さらに応答速度の速い電気泳動分散液を提供することが可能になる。
【００８７】
（９）請求項１５，１６に記載された発明によれば、塩基性基を有する電気泳動粒子が、塩基性基を有するモノマー又は塩基性基を有するシランカップリング剤で白色粒子及び／又は白色以外の着色粒子の表面を処理してなる電気泳動粒子であるので、電気泳動粒子と生成した塩基性基を有するモノマーの重合体又は塩基性基を有するシランカップリング剤の界面の局所的な部分に溶媒和となる成分が集中して効率よく電荷を生成する。したがって、酸塩基解離による電気泳動粒子の帯電量が増加するので、さらに応答速度の速い電気泳動分散液を提供することが可能になる。
【００８８】
（１０）請求項１７に記載された発明によれば、分散媒が電気泳動粒子と異なる色の染料を溶解しているので、表示コントラストの大きい電気泳動粒子分散液の提供が可能となる。
【００８９】
（１１）請求項１８，１９に記載された発明によれば、請求項１〜１７に記載の電気泳動粒子分散液を有しているので、従来よりも小さい外部電圧で良好に応答する画像表示媒体及び画像表示装置を提供することができる。
【図面の簡単な説明】
【図１】
本発明の一実施の形態を示す表示媒体を模式的に示す断面図である。
【図２】
本発明の一実施の形態を示す画像表示媒体の動作を原理的に示す説明図であって、（ａ）は、表示媒体の右半分と左半分とに仕切った一対の導電層に外部から電圧を印加する状態を示し、（ｂ）は、電気泳動粒子が外部電界に沿って上方に移動する状態を示し、そして、（ｃ）は、電気泳動粒子が上部導電層に到達した状態を示す。
【図３】
本発明の一実施の形態を示す画像表示装置の模式図である。
【符号の説明】
１，２　導電層
３　白色又は白色以外の着色粒子
４　分散媒
５　高分子化合物
１０　画像表示媒体
１１　筺体
１２　情報入力手段
２０　画像表示装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electrophoretic particle dispersion liquid capable of reversibly changing a visible state by moving white particles and / or colored particles charged by the action of an electric field in a dispersion medium, and an image display medium having the same. And an image display device.
[0002]
[Prior art]
Conventionally, display devices such as a cathode ray tube (CRT) and a liquid crystal display have been used as image display devices for displaying images such as characters, still images, and moving images. These display devices can display digital data instantaneously and can be rewritten. However, (1) it is difficult to carry around because it is installed and used on a desktop or the like; (2) There have been problems such as eye fatigue when working on this for a long time, and (3) display cannot be performed when the power is turned off.
[0003]
On the other hand, when digital information such as characters and still images is distributed as a paper medium such as a document or stored as a paper medium such as a document, the information is recorded on a paper medium by a printer. Paper media on which such information is recorded are widely used as hard copies. Hard copy has the following features: 1) characters are easier to read than displays, 2) eyes are less tiring, 3) they can be read in a free position, and 4) they are lightweight and portable. have. However, after the hard copy is used, it is discarded or recycled, but this requires a lot of labor and cost, and there is a problem in terms of resource saving.
[0004]
Therefore, the need for a rewritable paper-like display medium that has the advantages of both display and hard copy has increased, and polymer dispersed liquid crystal devices, bistable cholesteric liquid crystal devices, electrochromic devices, and electrophoretic devices And other display media have been proposed. These display media are attracting attention as being reflective and capable of bright display and having memory properties. Among them, a display medium using an electrophoretic element (hereinafter, referred to as “electrophoretic display medium”) is excellent in terms of display quality, power consumption during a display operation, and the like. And Japanese Patent No. 26124472.
[0005]
In such an electrophoretic display medium, for example, a colored dispersion medium is sealed between a set of transparent electrodes, and a plurality of electrons having a color different from the color are contained in the colored dispersion medium. Moving particles are dispersed. Electron moving particles are charged in the surface of the dispersion medium in a dispersion medium, so if a voltage opposite to the charge of the electron moving particles is applied to one of a pair of transparent electrodes, the electrophoretic particles Is deposited on one of the transparent electrodes and the color of the migrating particles is observed.If a voltage is applied in the same direction as the charge of the migrating particles, the color of the dispersion medium is observed because the electrophoretic particles move to the opposite side. Is done. Information is displayed on the electrophoretic display medium based on such a principle.
[0006]
The stability of the electrophoretic particles in the dispersion medium is generally obtained by an electrostatic effect or a steric effect (also called an adsorption layer effect). Regarding the electrostatic effect, the DLVO theory has been established, and in this theory, the spread of the electric double layer and the interface potential (so-called ζ potential) are important factors. The formation of these requires the presence of ions. On the other hand, as for the steric effect, a thing equivalent to the DLVO theory has not been established yet, but the following research is known in a non-aqueous solvent system (mainly a petroleum solvent). That is, F. A. Waite, J .; Oil Col. Chem. Assoc. , 54, 342 (1971) relates to a basic method for producing a stable non-aqueous solvent-based dispersion, in which particles dispersed in a solvent (insoluble in a solvent) are used. This is to produce a block or graft copolymer containing a compatible component and a component soluble in the solvent. As a method utilizing this method, Japanese Patent Publication No. 40-7047 discloses a stable polymethyl methacrylate (PMMA) dispersion obtained by radical polymerization of methyl methacrylate (MMA) in the presence of a degraded rubber in a hydrocarbon solvent. The method of obtaining is described. In this method, it is not considered that the degraded rubber is adsorbed on the PMMA particles, and from the fact that the PMMA particles are dispersion-stabilized, it is considered that MMA is graft-polymerized on the degraded rubber. In addition, in the graft polymer, the insoluble portion is agglomerated on the particle surface, and the dissolved portion has a steric effect, so that it is considered that the dispersion stability of the particle is maintained. .
[0007]
However, the stability of the particles in the particle dispersion obtained by dispersing the particles in a non-aqueous solvent system was not sufficient, so that an electrodeposition paint composed of such a particle dispersion, an electrophotographic liquid developer, The life of a display medium for a display is limited. Therefore, the present inventors have proposed an electrophoretic particle dispersion in which electrophoretic particles charged with ions are stably dispersed in a non-polar solvent such as a non-polar aprotic solvent, that is, a petroleum-based solvent. Japanese Patent Application No. 2001-162750, Japanese Patent Application No. 2001-71966, and Japanese Patent Application No. 2002-17754).
[0008]
In proposing the electrophoretic particle dispersion, the present inventors have proposed a) an organic substance having an acidic group but not having a basic group, b) an organic substance having a basic group but having no acidic group, and , C) any one of the components (a) and (b) including three components of an organic substance having a nonionic polar component that is compatible with the petroleum-based solvent and is a copolymer with the component of (c). May be present. >> When various experiments were conducted on the non-polar solvent-based dispersion, it was found that the components a) and b) caused acid-base ion dissociation in the solvent. Then, at that time, it was recognized that ion-dipole interaction, that is, solvation was present. Further, the present inventors have found that when the three components a), b) and c) are present in the solvent, non-ionic dissociation between the acid and the base via solvation of the polar group in the component c) causes non-dissociation. It has been found that ions can stably exist even in a polar solvent. Further, as described above, the present inventors have made solid particles such as pigments and metal oxides coexist in a system containing the three components a), b) and c). ) Or b) the acid group or the basic group of the component is fixed by chemical bonding, adsorption or the like, and ion dissociation occurs at the interface between the surface of the solid particle and the solvent via the solvation of the component c). Has been found to be uniformly charged to a positive or negative polarity, and that the solid particles are dispersed more stably than before by the synergistic action of the electrostatic effect and the steric effect.
[0009]
[Problems to be solved by the invention]
However, in the petroleum solvent proposed by the present inventors, that is, the electrophoretic particle dispersion liquid in which the electrophoretic particles charged with ions in a nonpolar solvent such as a nonpolar aprotic solvent are stably dispersed is not necessarily. However, since the electrophoretic particles do not have a sufficient charge amount to improve the electrophoretic speed, a problem that the electrophoretic particles must be electrophoresed at a high electric field by applying a high electric field to the electrophoretic particles. was there.
[0010]
The present invention aims to solve such a problem.
That is, the present invention provides an electrophoretic particle dispersion liquid capable of stably dispersing the electrophoretic particles in a dispersion medium, increasing the migration speed of the electrophoresis particles even in a low electric field, and increasing the response speed. It is an object to provide an image display medium and an image display device having the same.
[0011]
[Means for Solving the Problems]
The inventor of the present invention has disclosed an electrophoretic particle dispersion in which electrophoretic particles composed of white particles and / or colored particles other than white are dispersed in a dispersion medium, wherein (a) a non-polar solvent, (b) When a sulfonic acid compound at least soluble in the non-polar solvent and a polymer compound (c) soluble in the non-polar solvent are contained together, the electrophoretic particles are stably dispersed due to the steric effect of the polymer compound. At the same time, the inventors have found that the electrophoretic particles are sufficiently charged due to the ionicity of the sulfonic acid compound, and that the electrophoretic particles have a high electrophoretic speed even in a low electric field, thereby completing the present invention.
[0012]
In order to achieve the above object, the invention according to claim 1 is an electrophoretic particle dispersion in which electrophoretic particles composed of white particles and / or colored particles other than white are dispersed in a dispersion medium. Wherein the medium contains (a) a non-polar solvent, (b) a sulfonic acid compound at least soluble in the non-polar solvent, and (c) a polymer compound soluble in the non-polar solvent. This is an electrophoretic particle dispersion.
[0013]
The invention described in claim 2 is characterized in that, in the invention described in claim 1, the sulfonic acid compound is selected from alkanesulfonic acid, alkylbenzenesulfonic acid, alkylnaphthalenesulfonic acid, and salts thereof. Things.
[0014]
According to a third aspect of the present invention, in the second aspect, the alkylbenzenesulfonic acid is a long-chain alkylbenzenesulfonic acid such as dodecylbenzenesulfonic acid.
[0015]
The invention described in claim 4 is the invention according to any one of claims 1 to 3, wherein the polymer compound is a polymer compound having at least an acidic group.
[0016]
The invention described in claim 5 is the invention according to claim 4, wherein the polymer compound having an acidic group is (meth) acrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, Fumaric acid, cinnamic acid, crotonic acid, vinyl benzoic acid, 2-methacryloxyethyl succinic acid, 2-methacryloxyethyl maleic acid, 2-methacryloxyethyl hexahydrophthalic acid, 2-methacryloxyethyl trimellitic acid, vinyl sulfone Selected from acid, allylsulfonic acid, styrenesulfonic acid, 2-sulfoethylmethacrylate, 2-acrylamido-2-methylpropanesulfonic acid, 3-chloroamidophosphoxypropylmethacrylate, 2-methacryloxyethylacid phosphate, and hydroxystyrene Monomer having acidic group It is characterized in that a polymer having at least one the polymerization component.
[0017]
The invention described in claim 6 is the invention according to any one of claims 1 to 5, wherein the polymer compound is obtained by polymerizing a monomer represented by the following general formula (1). It is a molecular compound.
[0018]
Embedded image

[Wherein, R ₁ Is a hydrogen atom or a methyl group; ₁ 'Is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, n is a natural number, and x is an integer of 1 to 3. ]
[0019]
The invention described in claim 7 is the invention described in any one of claims 1 to 6, wherein the polymer compound is a polymer compound having a nonionic polar group. It is.
[0020]
In the invention described in claim 8, in the invention described in claim 7, the polymer compound having a nonionic polar group is (a) 2-hydroxyethyl (meth) acrylate, 2,3- Dihydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxy-3-propyl methacrylate, 2-chloroethyl (meth) acrylate, 2,3-dibromopropyl (meth) acrylate, (meth) acrylonitrile, isobutyl -2-cyanoacrylate, 2-cyanoethylacrylate, ethyl-2-cyanoacrylate, methacrylacetone, tetrahydrofurfuryl methacrylate, trifluoroethyl methacrylate, p-nitrostyrene, vinylpyrrolidone, acrylamide, methacrylamide, N, (B) at least one polar monomer selected from dimethyl methacrylamide and N, N-dibutyl methacrylamide, and (b) a monomer selected from alkyl esters of (meth) acrylic acid and aryl esters of (meth) acrylic acid. It is a copolymer of at least one kind.
[0021]
According to a ninth aspect of the present invention, in the invention according to any one of the first to eighth aspects, the dispersion medium contains a compound having a nonionic polar group soluble in the dispersion medium. It is characterized by the following.
[0022]
According to a tenth aspect of the present invention, in the invention according to the ninth aspect, the compound having a nonionic polar group includes a hydroxyl group, an ester group, an ether group, a ketone group, an aldehyde group, a halogen group and It has a group selected from an amide group.
[0023]
The invention described in claim 11 is the invention according to any one of claims 1 to 10, wherein the electrophoretic particles are electrophoretic particles having a basic polar group on a surface thereof. Is what you do.
[0024]
According to a twelfth aspect of the present invention, in the first aspect, the electrophoretic particles having a basic polar group are a polymer or a copolymer containing a monomer having a basic group as a component. And electrophoretic particles obtained by dispersing white particles and / or colored particles other than white in a binder resin insoluble in the nonpolar solvent.
[0025]
The invention according to claim 13 is the invention according to claim 12, wherein the binder resin is (a) N-methylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl acrylate, N, N-di-tert-butylaminoethyl acrylate, N-phenylaminoethyl methacrylate, N, N-diphenylaminoethyl methacrylate, aminostyrene, dimethylaminostyrene, N-methylaminoethylstyrene, dimethylaminoethoxystyrene, diphenylaminoethylstyrene, N-phenylaminoethylstyrene, 2-N-piperidylethyl (meth) At least one kind of monomer having a basic group such as acrylate, 2-vinylpyridine, 4-vinylpyridine, or 2-vinyl-6-methylpyridine, and (b) an alkyl ester of (meth) acrylic acid and (meth) acrylic acid It is characterized by comprising a copolymer of at least one monomer selected from aryl esters of acids.
[0026]
According to a fourteenth aspect, in the twelfth aspect, the binder resin is a polymer compound having a nonionic polar group.
[0027]
The invention according to claim 15 is the invention according to claim 11, wherein the electrophoretic particles having a basic polar group are a monomer having a basic group or a silane coupling agent having a basic group. It is an electrophoretic particle obtained by treating the surface of white particles and / or colored particles other than white.
[0028]
The invention according to claim 16 is the invention according to claim 15, wherein the monomer having a basic group is N-methylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl acrylate, N, N-di-tert-butylaminoethyl acrylate, N-phenylaminoethyl methacrylate , N, N-diphenylaminoethyl methacrylate, aminostyrene, dimethylaminostyrene, N-methylaminoethylstyrene, dimethylaminoethoxystyrene, diphenylaminoethylstyrene, N-phenylaminoethylstyrene, 2-N-piperidylethyl (methyl ) Is selected from acrylate, 2-vinylpyridine, 4-vinylpyridine and 2-vinyl-6-methylpyridine, and the silane coupling agent having a basic group is γ-aminopropyltrimethoxysilane, γ -Aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, and , N-β (aminoethyl) γ-aminopropyl triethoxysilane.
[0029]
The invention described in claim 17 is characterized in that, in the invention described in any one of claims 1 to 16, the dispersion medium is obtained by dissolving a dye having a different color from the electrophoretic particles. is there.
[0030]
The invention according to claim 18 includes the electrophoretic particle dispersion liquid according to any one of claims 1 to 17, between at least one of a pair of conductive layers that are arranged at intervals and is light-transmissive. An image display medium characterized by the following.
[0031]
According to a nineteenth aspect of the present invention, there is provided an image display apparatus including the image display medium according to the eighteenth aspect.
[0032]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a cross-sectional view schematically showing a display medium according to an embodiment of the present invention. 2A and 2B are explanatory diagrams showing the operation of an image display medium according to an embodiment of the present invention in principle. FIG. 2A shows a pair of conductive layers partitioned into a right half and a left half of the display medium. Shows a state in which a voltage is externally applied, (b) shows a state in which the electrophoretic particles move upward along an external electric field, and (c) shows a state in which the electrophoretic particles reach the upper conductive layer. Indicates the status. FIG. 3 is a schematic diagram of an image display device according to an embodiment of the present invention.
[0033]
(Embodiment 1)
The electrophoretic particle dispersion liquid of the present invention is composed of a dispersion medium in which electrophoretic particles composed of white particles and / or colored particles other than white are dispersed in a dispersion medium, and the dispersion medium includes (a) a nonpolar solvent, (B) a sulfonic acid compound that is at least soluble in the nonpolar solvent, and (c) a polymer compound that is soluble in the nonpolar solvent. The sulfonic acid compound is preferably contained in a proportion of 0.01 to 1% by weight of the nonpolar solvent, and the polymer compound is preferably contained in a proportion of 1 to 20% by weight of the nonpolar solvent. It is contained in. Further, the electrophoretic particles are preferably contained at a ratio of 1 to 20% by weight of the dispersion medium.
[0034]
Examples of the "non-polar solvent" include: (1) paraffinic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane and dodecane; (2) isoparaffinic hydrocarbons such as isohexane, isooctane and isododecane; ▼ Alkyl naphthenic hydrocarbons such as liquid paraffin, ４4 ▼ Aromatic hydrocarbons such as benzene, toluene, xylene, alkylbenzene, solvent naphtha, and ５5 ▼ Dimethyl silicone oil, phenylmethyl silicone oil, dialkyl silicone oil, alkyl Silicone oils such as phenylsilicone oil, cyclic polydialkylsiloxane, and cyclic polyalkylphenylsiloxane, but other non-polar solvents may be used as long as the object of the present invention is not contravened.
[0035]
The “sulfonic acid compound” is 96 (CH ₃ SO ₃ H) a molecular weight range of from 500 to 500, for example, a compound selected from alkanesulfonic acid having 1 to 30 carbon atoms, alkylbenzenesulfonic acid having 7 to 30 carbon atoms, alkylnaphthalenesulfonic acid having 11 to 30 carbon atoms, and salts thereof. However, preferred is a long-chain alkylbenzenesulfonic acid having 10 to 30 carbon atoms such as dodecylbenzenesulfonic acid. These sulfonic acid compounds may be used alone or in combination of two or more.
[0036]
When a sulfonic acid compound at least soluble in such a nonpolar solvent is present in the nonpolar solvent, it dissociates as shown in the following chemical equilibrium equation.
Embedded image

When particles having a basic group on the surface are dispersed in such a nonpolar solvent, the basic group on the surface of the particles dissociates as shown in the following chemical equilibrium equation.
Embedded image

As described above, when the sulfonic acid compound at least soluble in the nonpolar solvent is present in the electrophoretic particle dispersion, H generated by dissociation from the sulfonic acid compound is generated. ⁺ Reacts with the electrophoretic particles to increase the charge amount of the electrophoretic particles, and therefore, according to the electrophoretic particle dispersion of the present invention, the electrophoretic particles have a high electrophoretic speed even at a low electric field, thereby increasing the response speed. It can be faster, that is, it can respond well even with an external voltage smaller than before.
[0037]
The electrophoretic particle dispersion of the present invention has a polymer compound soluble in a non-polar solvent. As such a “polymer compound soluble in a non-polar solvent”, any of known thermoplastic resins and thermosetting resins that are soluble in a non-polar solvent can be used, but are more white than the non-polar solvent. It is preferable that the particles have strong attractive interaction with the surface of the electrophoretic particles composed of particles and / or colored particles other than white. For example, the particles have high affinity with nonpolar solvents such as alkyl or aryl esters of (meth) acrylic acid. Examples of the polymer include at least one kind of monomer as a constituent requirement. A resin soluble in a non-polar solvent may be prepared by suitably determining the types of monomers to be combined and the mixing ratio during polymerization. Such a “polymer compound soluble in a non-polar solvent” is adsorbed on the surface of electrophoretic particles composed of white particles and / or colored particles other than white, so that white particles and / or Electrophoretic particles composed of colored particles other than white can be stably dispersed in a dispersion medium.
[0038]
Further, the “polymer compound” is preferably a polymer compound having at least an acidic group. Such a "polymer compound having an acidic group" is preferably (meth) acrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, cinnamic acid, crotonic acid, vinylbenzoic acid, 2-methacryloxyethyl succinic acid, 2-methacryloxyethyl maleic acid, 2-methacryloxyethyl hexahydrophthalic acid, 2-methacryloxyethyl trimellitic acid, vinylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, 2-sulfo Ethyl methacrylate, 2-acrylamido-2-methylpropanesulfonic acid, 3-chloroamidophosphoxypropyl methacrylate, 2-methacryloxyethyl acid phosphate, and at least one monomer having an acidic group selected from hydroxystyrene as a polymerization component Polymer having A.
[0039]
As described above, according to the present invention, when two types of compounds, each of which is responsible for dispersion stability due to charge generation and steric effect, are added to the dispersion medium, the electrophoretic dispersion particles exhibit excellent electrophoretic properties and dispersion. It has become clear that stability can be achieved at the same time.
[0040]
As described above, when the polymer compound is a polymer compound having at least an acidic group, H generated by dissociation from the acidic group (for example, -COOH) is generated. ⁺ Reacts with the electrophoretic particles as shown in the above formula (3) to increase the charge amount of the electrophoretic particles. Therefore, according to the electrophoretic particle dispersion of the present invention, the electrophoretic particles The response speed can be increased by increasing the migration speed.
[0041]
Further, the polymer compound is preferably a polymer compound obtained by polymerizing a monomer represented by the following general formula (1).
Embedded image

[Wherein, R ₁ Is a hydrogen atom or a methyl group; ₁ 'Is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, preferably a methyl group. A preferred combination of substituents is R ₁ And R ₁ 'Is a methyl group. n is a natural number, preferably 2 to 200, more preferably 5 to 100, and x is a positive number of 1 to 3, preferably 3. ]
[0042]
Since the polymer compound represented by the formula (1) has a particularly strong affinity for a non-polar solvent, it is adsorbed to the electrophoretic particles in the non-polar solvent, and therefore, the electrophoretic particles based on a particularly excellent steric effect are formed. Dispersion stability can be provided.
[0043]
Further, the polymer compound is preferably a polymer compound having a nonionic polar group. Such a “polymer compound having a nonionic polar group” is preferably (a) 2-hydroxyethyl (meth) acrylate, 2,3-dihydroxypropyl (meth) acrylate, or 4-hydroxybutyl (meth). ) Acrylate, 2-hydroxy-3-propyl methacrylate, 2-chloroethyl (meth) acrylate, 2,3-dibromopropyl (meth) acrylate, (meth) acrylonitrile, isobutyl-2-cyanoacrylate, 2-cyanoethylacrylate, ethyl- 2-cyanoacrylate, methacrylacetone, tetrahydrofurfuryl methacrylate, trifluoroethyl methacrylate, p-nitrostyrene, vinylpyrrolidone, acrylamide, methacrylamide, N, N-dimethylmethacrylamide, and N, A copolymer of at least one polar monomer selected from dibutyl methacrylamide and at least one monomer selected from (b) an alkyl ester of (meth) acrylic acid and an aryl ester of (meth) acrylic acid; is there.
[0044]
When the polymer compound is a polymer compound having a nonionic polar group, the dispersion medium contains a compound having a nonionic polar group, and acts as a solvate for ion dissociation. In addition, the amount of charge of the electrophoretic particles due to ion dissociation increases, which makes it possible to provide an electrophoretic dispersion having a higher response speed.
[0045]
The dispersion medium may preferably contain a compound having a nonionic polar group soluble in the dispersion medium. Such a “compound having a nonionic polar group” has a group selected from a hydroxyl group, an ester group, an ether group, a ketone group, an aldehyde group, a halogen group, and an amide group. When the dispersion medium contains a compound having a nonionic polar group which is soluble in the dispersion medium, the dispersion medium contains a compound having a nonionic polar group. Therefore, the charge amount of the electrophoretic particles due to ion dissociation increases, and therefore, it is possible to provide an electrophoretic dispersion having a higher response speed.
[0046]
Examples of the “electrophoretic particles composed of white particles and / or colored particles other than white” include: (1) metal oxides such as silica, titania, and alumina; (2) carbon black, aniline black, furnace black, and lamps. Black colorants such as black; (3) cyan colorants such as phthalocyanine blue, methylene blue, Victoria blue, methyl violet, aniline blue, and ultramarine blue; (4) rhodamine 6G lake, dimethylquinacridone, watching red, and rose Magenta colorants such as Bengal, Rhodamine B and Alizarin Lake, and (5) yellow colorants such as chrome yellow, benzidine yellow, Hanza yellow, naphthol yellow, molybdenum orange, quinoline yellow and tartrazine are used. .
[0047]
These electrophoretic particles are preferably electrophoretic particles having a nonionic polar group on the surface. And, the particle size of these electrophoretic particles is preferably 0.1 to 10 μm.
[0048]
Such `` electrophoretic particles having a basic group '' are preferably white particles in a binder resin insoluble in a non-polar solvent consisting of a polymer or copolymer having a monomer having a basic group as a component. And / or electrophoretic particles in which colored particles other than white are dispersed. The “binder resin” is preferably (a) N-methylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylamino. Ethyl (meth) acrylate, N, N-dibutylaminoethyl acrylate, N, N-di-tert-butylaminoethyl acrylate, N-phenylaminoethyl methacrylate, N, N-diphenylaminoethyl methacrylate, aminostyrene, dimethylaminostyrene , N-methylaminoethylstyrene, dimethylaminoethoxystyrene, diphenylaminoethylstyrene, N-phenylaminoethylstyrene, 2-N-piperidylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridyl And (b) at least one monomer selected from alkyl esters of (meth) acrylic acid and aryl esters of (meth) acrylic acid, and (b) at least one monomer having a basic group such as 2-vinyl-6-methylpyridine. It is composed of a seed and a copolymer of The binder resin insoluble in the nonpolar solvent is produced by suitably determining the type of the monomer to be combined and the mixing ratio at the time of polymerization. The electrophoretic particles of the present invention are produced by mixing and dispersing the above components in a non-polar solvent. At this time, a ball mill, a sand mill, an attritor, or the like may be used as the dispersing means. The mixing order is not particularly limited. By such a dispersion treatment, electrophoretic particles in which the pigment particles are adsorbed or supported by the binder resin are obtained.
[0049]
As described above, when the electrophoretic particles are electrophoretic particles having a basic group on the surface, the electrophoretic particles generate electric charge due to the ionicity of the basic group of the binder resin. The amount is increased, which makes it possible to provide an electrophoretic dispersion having a higher response speed.
[0050]
The electrophoretic particle binder resin having a basic group on the surface is preferably a polymer compound having a nonionic polar group. Such a “polymer compound having a nonionic polar group” is preferably (a) N-methylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N, N-dimethylamino. Ethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl acrylate, N, N-di-tert-butylaminoethyl acrylate, N-phenylaminoethyl methacrylate, N, N- Diphenylaminoethyl methacrylate, aminostyrene, dimethylaminostyrene, N-methylaminoethylstyrene, dimethylaminoethoxystyrene, diphenylaminoethylstyrene, N-phenylaminoethylstyrene, 2-N-piperidylethyl (meth) acrylate, 2-bi (B) alkyl (meth) acrylic acid ester and (meth) acrylic acid aryl ester from at least one monomer having a basic group such as pyridine, 4-vinylpyridine, or 2-vinyl-6-methylpyridine. (C) 2-hydroxyethyl (meth) acrylate, 2,3-dihydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxy-3-propyl methacrylate, 2-chloroethyl (meth) acrylate, 2,3-dibromopropyl (meth) acrylate, (meth) acrylonitrile, isobutyl-2-cyanoacrylate, 2-cyanoethylacrylate, ethyl-2-cyanoacrylate, methacrylacetone, tetrahydrofurfurfury With at least one polar monomer selected from methacrylate, trifluoroethyl methacrylate, p-nitrostyrene, vinylpyrrolidone, acrylamide, methacrylamide, N, N-dimethylmethacrylamide, and N, N-dibutylmethacrylamide It is a polymer.
[0051]
As described above, when the binder resin of the electrophoretic particles having a basic group on the surface is a polymer compound having a nonionic polar group, solvation occurs at a local portion of the basic group on the electrophoretic particle surface. Since such components are concentrated, electric charges are efficiently generated on the surface of the electrophoretic particles, so that it is possible to provide an electrophoretic dispersion having a higher response speed.
[0052]
Further, the electrophoretic particles having a basic group are preferably obtained by treating the surfaces of white particles and / or colored particles other than white with a monomer having a basic group or a silane coupling agent having a basic group. Electrophoretic particles. Such a “monomer having a basic group” is preferably N-methylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl acrylate, N, N-di-tert-butylaminoethyl acrylate, N-phenylaminoethyl methacrylate, N, N-diphenylaminoethyl methacrylate, aminostyrene, Dimethylaminostyrene, N-methylaminoethylstyrene, dimethylaminoethoxystyrene, diphenylaminoethylstyrene, N-phenylaminoethylstyrene, 2-N-piperidylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine N-pyridine and 2-vinyl-6-methylpyridine, and the silane coupling agent having a basic group is γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl- γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, and N-β (aminoethyl) γ-amino Selected from propyltriethoxysilane.
[0053]
Thus, electrophoretic particles obtained by treating the surfaces of white particles and / or colored particles other than white with a monomer having a basic group or a silane coupling agent having a basic group. In this case, the components that are solvated are concentrated on the local portion of the interface between the electrophoretic particles and the polymer of the monomer having a basic group or the silane coupling agent having a basic group, and the charge is efficiently charged. Generate Therefore, the charge amount of the electrophoretic particles due to the acid-base dissociation increases, so that it is possible to provide an electrophoretic dispersion having a higher response speed.
[0054]
The dispersion medium may be one obtained by dissolving a dye having a different color from the electrophoretic particles. Such dyes include, for example, oil-soluble dyes soluble in the dispersion medium, and dyes classified as Solvent dye in Color Index are preferably used. These oil-soluble dyes include azo dyes, anthraquinone dyes, phthalocyanine dyes, and triallylmethane dyes. These oil-based dyes include, for example, spirit black (SB, SSBB, AB), nigrosine base (SA, SAP, SAPL, EE, EEL, EX, EXBP, EB), oil yellow (105, 107, 129, 3G, GGS). , Oil Orange (201, PS, PR), Fast Orange, Oil Red (5B, RR, OG), Oil Scarlet, Oil Pink 312, Oil Violet # 730, Macrolex Blue RR, Sumiplast Green G, Oil Brown (GR , 416), Sudan Black X60, Oil Green (502, BG), Oil Blue (613, 2N, BOS), Oil Black (HBB, 860, BS), Bali First Yellow (1101, 1105, 3108, 4120), Bali First ole (3209, 3210), Balifast Red (1306, 1355, 2303, 3304, 3306, 3320), Balifast Pink 2310N, Balifast Brown (2402, 3405), Balifast Blue (3405, 1501, 1603, 1605) 1607, 2606, 2610), Balifast Violet (1701, 1702) and Balifast Black (1802, 1807, 3804, 3810, 3820, 3830) as typical examples, provided that they do not violate the object of the present invention. Oily dyes or oil-soluble dyes other than the dyes described here may be used.
[0055]
As described above, when the dispersion medium dissolves a dye having a color different from that of the electrophoretic particles, it is possible to provide an electrophoretic particle dispersion having high display contrast.
[0056]
(Embodiment 2)
As shown in FIG. 1, the image display medium 10 of the present invention is provided between a pair of conductive layers 1 and 2 at least one of which is provided with an interval and is light transmissive. Described above.
Examples of the conductive layer include metals such as Al, Ag, Ni, and Cu, and ITO and SnO. ₂ , ZnO, Al or other transparent conductor formed into a thin film by sputtering, vacuum evaporation, CVD, coating, or the like, or a conductor obtained by mixing a conductive agent with a solvent or a synthetic resin binder and applying it Can be Such conductive agents include cationic polymer electrolytes such as polymethylbenzyltrimethyl chloride and polyallylpolymethylammonium chloride, anionic polymer electrolytes such as polystyrene sulfonate and polyacrylate, and electron conductive oxides. Zinc, tin oxide, indium oxide fine powder and the like are used. The conductive layers 1 and 2 may be thick enough to have a self-holding function, or may be provided with a conductive layer on a substrate having a self-holding function (not shown). it can. Further, the conductive layers 1 and 2 may be layers exhibiting anisotropic conductivity, or may be layers having a pattern or multi-dot segment in which a conductive portion penetrates in a thickness direction. In any case, if a power supply electrode is brought into contact with a part of the conductive layers 1 and 2, an electric field can be generated between the conductive layers 1 and 2, so that the white or non-white colored particles 3 move without fail. it can. In order to perform display, a voltage applying means between the conductive layers 1 and 2 may be provided, which is simple. The amount of the colorant that can be used is preferably 0.1 to 300 parts by weight of the colorant with respect to 10 parts by weight of the binder resin, and more preferably 1 to 100 parts by weight of the colorant with respect to 10 parts by weight of the binder resin. Parts by weight. In FIG. 1, 4 is a dispersion medium, and 5 is a polymer compound soluble in the dispersion medium. In the present invention, the polymer compound 5 is in a state of being adsorbed on the surface of the white or non-white colored particles 3.
[0057]
According to the image display medium of the present invention, as shown in FIG. 2A, the right half and the left half of the image display medium are separated from each other by applying a voltage to the conductive layers 1 and 2 from outside by appropriate means. As shown in FIG. 2B, the charged white or non-white colored particles 3 begin to move upward in the dispersion medium 4 along the external electric field, that is, in the direction of the substrate 2, and As shown in FIG. 2C, the charged white or non-white colored particles 3 adhere to the substrate 2 by electrostatic force and complete the movement. When the state of FIG. 2C is viewed from above the image display medium, that is, from the outside of the conductive layer 2, the left half shows the color of the charged white or non-white colored particles 3, and the right half shows the color. The color of the dye added to the dispersion medium 4 can be seen. The above is the basic operation principle of image display by the image display medium of the present invention. Since this display mode is reversible, it can be used repeatedly.
[0058]
(Embodiment 3)
An image display device according to the present invention has the image display medium according to claim 18.
As shown in FIG. 3, the image display device 20 of the present invention includes the image display medium 10, and includes a drive circuit, an arithmetic circuit, an internal memory, a power supply, and the like (not shown). The electrodes on the display medium form a dot matrix and display an image as a whole by turning on designated dots. In FIG. 3, reference numeral 11 denotes a housing, and reference numeral 12 denotes information input means.
[0059]
【Example】
The present invention will be described in more detail by reference examples and examples. However, the present invention is not limited to the following examples. All parts used in the following Reference Examples, Examples and Comparative Examples are parts by weight.
[0060]
(Reference Example 1)
(Synthesis example of polymer compound)
300 parts of Isopar H (Exxon Chemical Co.) was placed in a reaction vessel equipped with a stirrer, thermometer and reflux condenser, and heated to 85 ° C. A solution comprising 40 parts by weight of lauryl methacrylate and 1 part of benzoyl peroxide as a polymerization initiator was added dropwise thereto over 1 hour. Next, stirring was continued at the same temperature for 5 hours to complete the reaction. The solvent Isopar H was evaporated from the obtained resin solution by an evaporator to obtain a viscous polymer compound soluble in Isopar H.
[0061]
(Reference Example 2)
(Synthesis example of polymer compound)
300 parts of Isopar H (Exxon Chemical Co.) was placed in a reaction vessel equipped with a stirrer, thermometer and reflux condenser, and heated to 85 ° C. A solution consisting of 36 parts by weight of lauryl methacrylate, 4 parts by weight of methacrylic acid and 1 part of benzoyl peroxide as a polymerization initiator was added dropwise thereto over 1 hour. Next, stirring was continued at the same temperature for 5 hours to complete the reaction. The solvent Isopar H was evaporated from the obtained resin solution by an evaporator to obtain a viscous polymer compound soluble in Isopar H.
[0062]
(Reference Example 3)
(Synthesis example of polymer compound)
The reaction vessel used in Reference Example 1 was charged with 300 parts of silicone oil (SH-200; 1cs, Dow Corning Silicone Co., Ltd.) and heated to 80 ° C. Among them, in the polymer compound represented by the general formula (1), R ₁ = CH ₃ , X = 3 and n = 10, a solution consisting of 39 parts by weight, 1 part by weight of methacrylic acid, and 3 parts of azobisisobutyronitrile as a polymerization initiator was added dropwise over 1 hour. Next, stirring was continued at the same temperature for 5 hours to complete the reaction. The silicone oil as a solvent was evaporated from the obtained resin solution by an evaporator to obtain a viscous polymer compound soluble in the silicone oil.
[0063]
(Reference Example 4)
(Synthesis example of polymer compound)
The reaction vessel used in Reference Example 1 was charged with 300 parts of silicone oil (SH-200; 1cs, Dow Corning Silicone Co., Ltd.) and heated to 80 ° C. Among them, in the polymer compound represented by the general formula (1), R ₁ = CH ₃ , X = 3, and n = 10, a solution consisting of 37 parts by weight, 1 part by weight of methacrylic acid, 2 parts of vinylpyrrolidone, and 3 parts of azobisisobutyronitrile as a polymerization initiator in one hour. It was dripped over. Next, stirring was continued at the same temperature for 5 hours to complete the reaction. The silicone oil as a solvent was evaporated from the obtained resin solution by an evaporator to obtain a viscous polymer compound soluble in the silicone oil.
[0064]
(Reference Example 5)
(Example of preparing dispersed particles)
The reaction vessel used in Reference Example 1 was charged with 500 parts of silicone oil (SH-200; 1 cs, Dow Corning Silicone Co., Ltd.) and heated to 85 ° C. Among them, in the polymer compound represented by the general formula (1), R ₁ = CH ₃ , X = 3 and n = 10, 4 parts by weight, dimethylaminoethyl methacrylate 4 parts by weight, methyl methacrylate 40 parts by weight, N-acryloylmorpholine 2 parts, and azobisisobutyro which is a polymerization initiator A solution consisting of 3 parts of nitrile was added dropwise over 1 hour. Then, stirring was continued at the same temperature for 5 hours to complete the reaction. The desired solid binder resin was obtained by evaporating the silicone oil.
Next, 8 parts of the above binder resin and 2 parts of rutile-type titanium oxide were added to 100 parts of silicone oil (SH-200; 1 cs, Dow Corning Silicone Co., Ltd.), and the mixture was dispersed for 24 hours by a ball mill. After completion, the silicone oil was evaporated to obtain the target resin dispersed particles.
[0065]
(Reference Example 6)
(Example of preparing dispersed particles)
400 parts of rutile-type titanium oxide was added to a solution of 3 parts of 3-aminopropyltrimethoxysilane and 1 part of trimethylethoxysilane in 4000 parts of a mixed solvent of water: ethanol = 1: 1, and the mixture was stirred at room temperature for 24 hours. After the completion of the reaction, the particles were recovered, washed with ethanol, and dried to obtain target particles.
[0066]
(Example 1)
100 parts by weight of isoparaffin (Isopar H), 5 parts by weight of titanium oxide particles, 0.1 part by weight of dodecylbenzenesulfonic acid, 10 parts by weight of the polymer compound obtained in Reference Example 1, and a dye (Bayer Macrolex Blue RR) 0.1 parts by weight were added, and these were subjected to ultrasonic dispersion treatment for 1 hour to obtain an electrophoretic particle dispersion. Then, a space was formed by sandwiching a 100 μm-thick polyester film having an opening of 1 cm square between two substrates with ITO electrodes, and the electrophoretic particle dispersion was sealed in this space.
[0067]
(Example 2)
100 parts by weight of isoparaffin (Isopar H), 5 parts by weight of the resin dispersed particles obtained in Reference Example 5, 0.1 part by weight of dodecylbenzenesulfonic acid, 10 parts by weight of the polymer compound obtained in Reference Example 1, and a dye (Bayer 0.1 parts by weight of Macrolex Blue RR) were added thereto, and these were subjected to ultrasonic dispersion treatment for 1 hour to obtain an electrophoretic particle dispersion. Then, a space was formed by sandwiching a 100 μm-thick polyester film having an opening of 1 cm square between two substrates with ITO electrodes, and the electrophoretic particle dispersion was sealed in this space.
[0068]
(Example 3)
100 parts by weight of isoparaffin (Isopar H), 5 parts by weight of the particles obtained in Reference Example 6, 0.1 part by weight of dodecylbenzenesulfonic acid, 10 parts by weight of the polymer compound obtained in Reference Example 2, and a dye (Bayer Macrolex) Blue RR) was added thereto and subjected to an ultrasonic dispersion treatment for 1 hour to obtain an electrophoretic particle dispersion. Then, a space was formed by sandwiching a 100 μm-thick polyester film having an opening of 1 cm square between two substrates with ITO electrodes, and the electrophoretic particle dispersion was sealed in this space.
[0069]
(Example 4)
100 parts by weight of isoparaffin (Isopar H), 5 parts by weight of particles obtained in Reference Example 6, 0.1 part by weight of dodecylbenzenesulfonic acid, 10 parts by weight of polymer compound obtained in Reference Example 2, dye (Bayer Macrolex Blue) (RR) 0.1 part by weight and N, N-diethylpropionamide (nonionic polar compound) 1 part by weight were added and subjected to ultrasonic dispersion treatment for 1 hour to obtain an electrophoretic particle dispersion. Then, a space was formed by sandwiching a 100 μm-thick polyester film having an opening of 1 cm square between two substrates with ITO electrodes, and the electrophoretic particle dispersion was sealed in this space.
[0070]
(Example 5)
100 parts by weight of methylphenyl silicone oil (SH556), 5 parts by weight of the particles obtained in Reference Example 6, 0.1 part by weight of dodecylbenzenesulfonic acid, 10 parts by weight of the polymer compound obtained in Reference Example 3, and a dye ( 0.1 parts by weight of Bayer Macrolex Blue RR) was added thereto, and these were subjected to ultrasonic dispersion treatment for 1 hour to obtain an electrophoretic particle dispersion. Then, a space was formed by sandwiching a 100 μm-thick polyester film having an opening of 1 cm square between two substrates with ITO electrodes, and the electrophoretic particle dispersion was sealed in this space.
[0071]
(Example 6)
100 parts by weight of methylphenyl silicone oil (SH556), 5 parts by weight of the particles obtained in Reference Example 6, 0.1 part by weight of dodecylbenzenesulfonic acid, 10 parts by weight of the polymer compound obtained in Reference Example 4, and a dye ( 0.1 parts by weight of Bayer Macrolex Blue RR) was added thereto, and these were subjected to ultrasonic dispersion treatment for 1 hour to obtain an electrophoretic particle dispersion. Then, a space was formed by sandwiching a 100 μm-thick polyester film having an opening of 1 cm square between two substrates with ITO electrodes, and the electrophoretic particle dispersion was sealed in this space.
[0072]
(Example 7)
100 parts by weight of methylphenyl silicone oil (SH556), 5 parts by weight of the resin dispersed particles obtained in Reference Example 5, 0.1 part by weight of dodecylbenzenesulfonic acid, 10 parts by weight of the polymer compound obtained in Reference Example 3, and 0.1 parts by weight of a dye (Bayer Macrolex Blue RR) was added, and these were subjected to ultrasonic dispersion treatment for 1 hour to obtain an electrophoretic particle dispersion. Then, a space was formed by sandwiching a 100 μm-thick polyester film having an opening of 1 cm square between two substrates with ITO electrodes, and the electrophoretic particle dispersion was sealed in this space.
[0073]
(Comparative Example 1)
To 100 parts by weight of methylphenyl silicone oil (SH556), 5 parts by weight of titanium oxide particles, 0.1 part by weight of dodecylbenzenesulfonic acid, and 0.1 part by weight of a dye (Bayer Macrolex Blue RR) were added. An ultrasonic dispersion treatment was performed for a time to obtain an electrophoretic particle dispersion. Then, a space was formed by sandwiching a 100 μm-thick polyester film having an opening of 1 cm square between two substrates with ITO electrodes, and the electrophoretic particle dispersion was sealed in this space.
[0074]
(Comparative Example 2)
To 100 parts by weight of isoparaffin (Isopar H), 5 parts by weight of titanium oxide particles, 10 parts by weight of the polymer compound obtained in Reference Example 2, and 0.1 part by weight of a dye (Bayer Macrolex Blue RR) were added. Was subjected to an ultrasonic dispersion treatment for 1 hour to obtain an electrophoretic particle dispersion. Then, a space was formed by sandwiching a 100 μm-thick polyester film having an opening of 1 cm square between two substrates with ITO electrodes, and the electrophoretic particle dispersion was sealed in this space.
[0075]
As described above, after applying -100 V to the upper ITO electrode of the image display medium obtained in the example and the comparative example, and observing the movement of the encapsulated electrophoretic particles, applying +100 V to the upper electrode to encapsulate the encapsulated electrophoretic particles. By observing the movement of the electrophoretic particles, the image display media obtained in Examples and Comparative Examples were evaluated. Similarly, the switching of the polarity was performed about 100 times, and the image display media obtained in Examples and Comparative Examples were evaluated. The state after the voltage was released for these image display media was also observed. The same display operation was performed at ± 50 V on the image display media obtained in the example and the comparative example, and the image display media obtained in the example and the comparative example were evaluated.
[0076]
The evaluation was performed according to the following criteria.
a: The dispersed particles moved quickly. This polarity switching was performed about 100 times, but could be repeated stably. Further, the electrodeposited state was maintained even when the voltage was removed.
b: Although the response speed was rather slow, the operation could be stably repeated when the voltage polarity was switched about 100 times. Further, the electrodeposited state was maintained even when the voltage was removed.
c: The first several times moved quickly, but the repetition was only about 10 times.
d: The response speed was slow, and the repetition was performed only about 10 times.
e: No response.
[0077]
The evaluation results are shown in Table 1 below.
[0078]
[Table 1]

[0079]
【The invention's effect】
(1) According to the invention described in claims 1 to 3, since the sulfonic acid compound at least soluble in the non-polar solvent is present in the electrophoretic particle dispersion, the sulfonic acid compound is dissociated from the sulfonic acid compound. H ⁺ Reacts with the electrophoretic particles to increase the charge amount of the electrophoretic particles. Therefore, even in a low electric field, the migration speed of the electrophoretic particles can be increased to increase the response speed. In addition, according to the first aspect of the present invention, since the polymer compound soluble in the non-polar solvent is present in the electrophoretic particle dispersion, the polymer compound is not white particles and / or other than white. The particles are adsorbed on the surface of the electrophoretic particles composed of colored particles, and the steric effect allows the electrophoretic particles composed of white particles and / or colored particles other than white to be stably dispersed in the dispersion medium.
[0080]
(2) According to the invention described in claims 4 and 5, since the polymer compound is a polymer compound having at least an acidic group, H formed by dissociation from the acidic group (for example, -COOH). ⁺ Reacts with the electrophoretic particles to increase the charge amount of the electrophoretic particles. Therefore, even in a low electric field, the migration speed of the electrophoretic particles can be increased to increase the response speed.
[0081]
(3) According to the invention as set forth in claim 6, the polymer compound obtained by polymerizing the monomer represented by the formula (1) has a particularly strong affinity for a non-polar solvent. Therefore, the polymer compound is adsorbed on the electrophoretic particles in the non-polar solvent, and therefore, the dispersion stability of the electrophoretic particles based on a particularly excellent steric effect can be provided.
[0082]
(4) According to the invention described in claims 7 and 8, since the polymer compound is a polymer compound having a nonionic polar group, the dispersion medium contains a compound having a nonionic polar group. Therefore, it acts as a solvation for ion dissociation, increasing the charge amount of the electrophoretic particles due to ion dissociation, and therefore, it is possible to provide an electrophoretic dispersion having a higher response speed. Will be possible.
[0083]
(5) According to the ninth and tenth aspects of the present invention, since the dispersion medium contains a compound having a nonionic polar group soluble in the dispersion medium, the dispersion medium has a nonionic polar group. The compound contains a compound having a group, and thus acts as a solvate for ion dissociation, thereby increasing the charge amount of the electrophoretic particles due to ion dissociation, and therefore, the electrophoretic dispersion having a faster response speed A liquid can be provided.
[0084]
(6) According to the eleventh aspect of the present invention, since the electrophoretic particles are electrophoretic particles having a basic group on the surface, the interface between the electrophoretic particles and the polymer compound adsorbed thereon is Since the components to be solvated are concentrated at the local portion, electric charges are efficiently generated on the surface of the electrophoretic particles, and therefore, it is possible to provide an electrophoretic dispersion having a higher response speed.
[0085]
(7) According to the invention as set forth in claims 12 and 13, the electrophoretic particles having a basic group are converted into a non-polar solvent comprising a polymer or a copolymer containing a monomer having a basic group as a constituent. Since the electrophoretic particles are obtained by dispersing white particles and / or colored particles other than white in an insoluble binder resin, the electrophoretic particles generate electric charge due to the ionicity of the basic group of the binder resin. The amount of charge of the electrophoretic particles increases, and therefore, it is possible to provide an electrophoretic dispersion having a higher response speed.
[0086]
(8) According to the invention described in claim 14, since the binder resin of the electrophoretic particles having a basic group on the surface is a polymer compound having a nonionic polar group, the base on the surface of the electrophoretic particles is The components to be solvated are concentrated on the local portion of the functional group, and electric charges are efficiently generated on the surface thereof. Therefore, it is possible to provide an electrophoretic dispersion having a higher response speed.
[0087]
(9) According to the invention described in claims 15 and 16, the electrophoretic particles having a basic group are converted to white particles and / or white particles by using a monomer having a basic group or a silane coupling agent having a basic group. Since the electrophoretic particles are obtained by treating the surface of colored particles other than the above, a local portion of the interface between the electrophoretic particles and the generated polymer of a monomer having a basic group or the silane coupling agent having a basic group The components that form a solvate are concentrated in this region to efficiently generate charges. Therefore, the charge amount of the electrophoretic particles due to the acid-base dissociation increases, so that it is possible to provide an electrophoretic dispersion having a higher response speed.
[0088]
(10) According to the invention described in claim 17, since the dispersion medium dissolves a dye having a different color from the electrophoretic particles, it is possible to provide an electrophoretic particle dispersion having a high display contrast.
[0089]
(11) According to the invention described in (18), (19), since the electrophoretic particle dispersion liquid according to any one of (1) to (17) is provided, an image display that responds favorably with an external voltage smaller than that of the related art. A medium and an image display device can be provided.
[Brief description of the drawings]
FIG.
1 is a cross-sectional view schematically illustrating a display medium according to an embodiment of the present invention.
FIG. 2
FIGS. 3A and 3B are explanatory views showing the principle of the operation of the image display medium according to the embodiment of the present invention, and FIG. 3A is a diagram in which a voltage is externally applied to a pair of conductive layers partitioned into a right half and a left half of the display medium. (B) shows a state where the electrophoretic particles move upward along the external electric field, and (c) shows a state where the electrophoretic particles reach the upper conductive layer.
FIG. 3
1 is a schematic diagram of an image display device according to an embodiment of the present invention.
[Explanation of symbols]
1,2 conductive layer
3 white or colored particles other than white
4 Dispersion medium
5 High molecular compounds
10 Image display media
11 Housing
12 Information input means
20 Image display device

Claims (19)

In an electrophoretic particle dispersion obtained by dispersing electrophoretic particles composed of white particles and / or colored particles other than white in a dispersion medium, the dispersion medium may contain at least (a) a nonpolar solvent and (b) at least An electrophoretic particle dispersion comprising a soluble sulfonic acid compound and (c) a polymer compound soluble in the nonpolar solvent. The electrophoretic particle dispersion according to claim 1, wherein the sulfonic acid compound is selected from alkanesulfonic acid, alkylbenzenesulfonic acid, alkylnaphthalenesulfonic acid, and salts thereof. The electrophoretic particle dispersion according to claim 2, wherein the alkylbenzenesulfonic acid is a long-chain alkylbenzenesulfonic acid such as dodecylbenzenesulfonic acid. The electrophoretic particle dispersion according to any one of claims 1 to 3, wherein the polymer compound is a polymer compound having at least an acidic group. The polymer compound having an acidic group is (meth) acrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, cinnamic acid, crotonic acid, vinylbenzoic acid, 2-methacryloxyethyl succinic acid 2-methacryloxyethyl maleic acid, 2-methacryloxyethyl hexahydrophthalic acid, 2-methacryloxyethyl trimellitic acid, vinylsulfonic acid, allylsulfonic acid, styrenesulfonic acid, 2-sulfoethylmethacrylate, 2-acrylamide- A polymer having at least one monomer having an acidic group selected from 2-methylpropanesulfonic acid, 3-chloroamidophosphoxypropyl methacrylate, 2-methacryloxyethyl acid phosphate, and hydroxystyrene as a polymerization component. Characterized by Electrophoretic particle dispersion liquid according to Motomeko 4. The electrophoretic particle dispersion according to any one of claims 1 to 5, wherein the polymer compound is a polymer compound obtained by polymerizing a monomer represented by the following general formula (1). .

Wherein R ₁ is a hydrogen atom or a methyl group, R ₁ ′ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, n is a natural number, and x is an integer of 1 to 3 . ] The electrophoretic particle dispersion according to any one of claims 1 to 6, wherein the polymer compound is a polymer compound having a nonionic polar group. The polymer compound having a nonionic polar group is (a) 2-hydroxyethyl (meth) acrylate, 2,3-dihydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, or 2-hydroxy- 3-propyl methacrylate, 2-chloroethyl (meth) acrylate, 2,3-dibromopropyl (meth) acrylate, (meth) acrylonitrile, isobutyl-2-cyanoacrylate, 2-cyanoethylacrylate, ethyl-2-cyanoacrylate, methacrylacetone , Tetrahydrofurfuryl methacrylate, trifluoroethyl methacrylate, p-nitrostyrene, vinylpyrrolidone, acrylamide, methacrylamide, N, N-dimethylmethacrylamide, and N, N-dibutylmethacryl It is a copolymer of at least one kind of polar monomer selected from amide and (b) at least one kind of monomer selected from alkyl esters of (meth) acrylic acid and aryl esters of (meth) acrylic acid. The electrophoretic particle dispersion according to claim 7, characterized in that: The electrophoretic particle dispersion according to any one of claims 1 to 8, wherein the dispersion medium contains a compound having a nonionic polar group soluble in the dispersion medium. 10. The method according to claim 9, wherein the compound having a nonionic polar group has a group selected from a hydroxyl group, an ester group, an ether group, a ketone group, an aldehyde group, a halogen group and an amide group. The electrophoretic particle dispersion according to the above. The electrophoretic particle dispersion according to any one of claims 1 to 10, wherein the electrophoretic particles are electrophoretic particles having a basic polar group on a surface thereof. The electrophoretic particles having a basic polar group are white particles and / or other than white in a binder resin insoluble in the non-polar solvent made of a polymer or a copolymer having a monomer having a basic group as a constituent component. The electrophoretic particle dispersion according to claim 11, which is an electrophoretic particle obtained by dispersing colored particles of (1). The binder resin is (a) N-methylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate N, N-dibutylaminoethyl acrylate, N, N-di-tert-butylaminoethyl acrylate, N-phenylaminoethyl methacrylate, N, N-diphenylaminoethyl methacrylate, aminostyrene, dimethylaminostyrene, N-methylamino Ethylstyrene, dimethylaminoethoxystyrene, diphenylaminoethylstyrene, N-phenylaminoethylstyrene, 2-N-piperidylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, 2 -vinyl At least one kind of a monomer having a basic group such as 6 -methylpyridine and (b) at least one kind of a monomer selected from an alkyl ester of (meth) acrylic acid and an aryl ester of (meth) acrylic acid The electrophoretic particle dispersion according to claim 12, which is composed of a polymer. The electrophoretic particle dispersion according to claim 12, wherein the binder resin is a polymer compound having a nonionic polar group. Electrophoretic particles having the above-mentioned electrophoretic particles having a basic polar group, wherein the surfaces of white particles and / or non-white colored particles are treated with a monomer having a basic group or a silane coupling agent having a basic group. The electrophoretic particle dispersion according to claim 11, wherein The monomer having a basic group is N-methylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) Acrylate, N, N-dibutylaminoethyl acrylate, N, N-di-tert-butylaminoethyl acrylate, N-phenylaminoethyl methacrylate, N, N -diphenylaminoethyl methacrylate, aminostyrene, dimethylaminostyrene, N-methyl Aminoethylstyrene, dimethylaminoethoxystyrene, diphenylaminoethylstyrene, N-phenylaminoethylstyrene, 2-N-piperidylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, and A silane coupling agent selected from 2-vinyl-6-methylpyridine and having the basic group is γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyl Trimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, and N-β (aminoethyl) γ-aminopropyltriethoxysilane The electrophoretic particle dispersion according to claim 15, which is selected from the group consisting of: 17. The electrophoretic particle dispersion according to claim 1, wherein the dispersion medium is formed by dissolving a dye having a different color from the electrophoretic particles. An image display medium comprising the electrophoretic particle dispersion liquid according to any one of claims 1 to 17, between a pair of conductive layers at least one of which is provided with an interval and is light-transmissive. . An image display device comprising the image display medium according to claim 18.

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