JP2004315670A - Ink composition, ink set, method of forming image, recorded image, and ink head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a high-quality recorded image which is sharply outlined and has high image density and high definition by an inkjet system while preventing the occurrence of feathering (whisker-like blurring of an ink), color mixing with an ink different in color, and the like. <P>SOLUTION: The high-quality recorded image can be obtained by using an ink composition containing a pigment, preferably with a water-soluble organic solvent, a nonionic surface active agent, a fixing agent, and the balance of water to make printing on a recording medium holding a silicon-containing polyvinylpyrrolidone on the surface and/or in the inside. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４５】
〔式中、ｅおよびｆはそれぞれ、０≦ｅ＋ｆ≦３０の関係を満たす０〜３０の整数を示す。〕
で表されるアセチレングリコール・エチレンオキシド付加物、一般式
【００４６】
【化２】

【００４７】
〔式中、ｋは１１〜１３の整数を示す。ｌは３〜３０の整数を示す。〕
で表される化合物、一般式
【００４８】
【化３】

【００４９】
〔式中、ｈおよびｉはそれぞれ０〜１１の整数を示す。ｊは３〜５０の整数を示す。〕
で表される化合物、一般式
【００５０】
【化４】

【００５１】
〔式中、ａは５〜９の整数を示す。ｂは２．５〜５の正数を示す。ｚおよびｗはそれぞれ、９≦ｚ＋ｗ≦１１の関係を満たす０〜１１の整数を示す。〕
で表される化合物、一般式
ＨＯ（ＣＨ_２ＣＨ_２Ｏ）_ｐ（ＣＨ_２ＣＨ_２ＣＨ_２Ｏ）_ｑ（ＣＨ_２ＣＨ_２Ｏ）_ｒＨ （５）
〔式中、ｐは０〜１８の整数を示す。ｑは２〜１５の整数を示す。ｒは０〜１８の整数を示す。〕
で表される化合物などのエチレンオキシド含有非イオン性界面活性剤が好ましい。本発明では、市販のエチレンオキシド含有非イオン性界面活性剤を使用することもでき、たとえば、サーフィノール（商品名、エアプロダクツ社製）、ソフタノール（商品名、（株）日本触媒製）などが挙げられる。非イオン性界面活性剤は１種を単独で使用できまたは２種以上を併用できる。
【００５２】
非イオン性界面活性剤の含有量は特に制限されることはないけれども、通常本発明インク組成物全量の０．００１〜５重量％、好ましくは０．００１〜３重量％の範囲から選択される。
【００５３】
本発明のインク組成物は、その好ましい特性を損なわない範囲で、記録媒体への定着性を向上させるために、定着剤を含んでいてもよい。定着剤としては公知のものを使用でき、たとえば、アラビアゴムなどの天然ゴム類、サボニンなどのグルコシド類、リグニンスルホン酸塩、セラックなどの天然高分子化合物、アクリル酸樹脂およびその塩、メタクリル酸樹脂およびその塩、スチレン−アクリル酸共重合体およびその塩、ビニルナフタレン−アクリル酸共重合体およびその塩、スチレン−マレイン酸−アクリル酸アルキルエステル共重合体およびその塩、ビニルナフタレン−マレイン酸共重合体およびその塩、スチレン−メタクリル酸−アクリル酸アルキルエステル共重合体およびその塩、β−ナフタレンスルホン酸ホルマリン縮合物のナトリウム塩およびリン酸塩などの陰イオン性高分子化合物、ポリエステル樹脂、ポリビニルアルコール、ポリビニルピロリドン等の非イオン性高分子化合物、アクリロニトリル、酢酸ビニル、アクリルアミド、塩化ビニル、塩化ビニリデン、エチレン、ヒドロキシエチルアクリレート、グリシジルメタクリレートなどの重合性不飽和二重結合を有するモノマー化合物の２種またはそれ以上からなる共重合体などが挙げられる。本発明では、市販の樹脂エマルジョンを定着剤として使用することもできる。市販の樹脂エマルジョンとしては、たとえば、バイロナール（商品名、東洋紡績（株）製、ポリエステル樹脂エマルジョン）などが挙げられる。定着剤は１種を単独で使用できまたは２種以上を併用できる。
【００５４】
本発明のインク組成物は、その好ましい特性を損なわない範囲で、防カビ剤、ｐＨ調整剤、キレート化剤、防錆剤、紫外線吸収剤などの、インクジェット用インク組成物の一般的な添加剤を含んでいてもよい。防カビ剤としては、たとえば、デヒドロ酢酸ナトリウム、安息香酸ナトリウム、ソルビタン酸ナトリウム、２−ピリジンチオール−１−オキシドナトリウム、ペンタクロロフェノールナトリウムなどが挙げられる。ｐＨ調整剤としては、たとえば、ジエタノールアミン、トリエタノールアミンなどのアミン、水酸化リチウム、水酸化カリウム、水酸化ナトリウムなどのアルカリ金属水酸化物、水酸化アンモニウム、第４級アンモニウム水酸化物、第４級ホスホニウム水酸化物、炭酸リチウム、炭酸ナトリウム、炭酸カリウムなどのアルカリ金属炭酸塩、硝酸ナトリウム、硝酸カリウムなどのアルカリ金属硝酸塩などが挙げられる。キレート化剤としては、たとえば、エチレンジアミン四酢酸ナトリウム、ニトリロ三酢酸ナトリウム、ヒドロキシエチルエチレンジアミン三酢酸ナトリウム、ジエチレントリアミン五酢酸ナトリウム、ウラミル二酢酸ナトリウムなどが挙げられる。防錆剤としては、たとえば、酸性亜硫酸塩、チオ硫酸ナトリウム、チオジグリコール酸アンモン、ジイソプロピルアンモニウムニトライト、四硝酸ペンタエリスリトール、ジシクロヘキシルアンモニウムニトライトなどが挙げられる。紫外線吸収剤としては、たとえば、ベンゾトリアゾール化合物、ベンゾフェノン化合物、シアノアクリレート化合物などが挙げられる。添加剤は１種を単独で使用できまたは２種以上を併用できる。
【００５５】
さらに本発明のインク組成物は、必要に応じて、溶解助剤、酸化防止剤、消泡剤、粘度調整剤、目詰まり防止剤などを含んでいてもよい。
【００５６】
本発明のインク組成物は、たとえば、顔料および必要に応じて、水溶性有機溶剤、非イオン性界面活性剤、定着剤、その他の添加剤のそれぞれ適量を用い、さらに水を用いて全量を１００重量％に調整し、各成分を水に分散または溶解させることによって製造できる。
【００５７】
ここで使用される水としては特に制限されず、水道水、純水、イオン交換水、活性炭処理水などを使用できる。これらの中でも、インク組成物の吐出安定性、記録媒体に対する浸透性および乾燥性、保存安定性などを考慮すると、電気伝導率（２５℃）が２５０μＳ／ｃｍ以下の水が好ましく、１μＳ／ｃｍ以下のものが特に好ましい。電気伝導率は、水の純度を示す指標、換言すれば、水に含まれる不純物の量を示す指標である。不純物とは、水に一般的に含まれる微量成分であり、たとえば、無機塩その他のミネラル分などが挙げられる。
【００５８】
分散は、一般的な分散機を用いて行われる。該分散機としては、たとえば、ディスパ、サンドミル、ホモジナイザ、ボールミル、ビーズミル、ペイントシェーカ、超音波分散機などが挙げられる。混合は、攪拌用の羽根を備えている攪拌機、高速の分散機、乳化機などによって行われる。
【００５９】
分散および／または混合ののち、固液分離手段を施してもよい。固液分離手段としては、ろ過、遠心分離などが挙げられる。たとえば、ろ過は、各成分を水媒体に混合または分散させた後に、ろ過を行ってもよい。ろ過は、たとえば、孔径０．８μｍ以下のフィルター、孔径０．４５μｍ以下のフィルターなどを用い、常圧下または減圧下に行われる。
【００６０】
このようにして得られる本発明インク組成物の好ましい形態としては、
（ａ）顔料が、ピグメントブルー１５：３およびピグメントブルー１５：４、ピグメントブルー１５：６から選ばれる１種または２種以上のシアン顔料を含むシアン色系インク組成物、
（ｂ）顔料が、ピグメントレッド１２２、ピグメントレッド２０９およびピグメントヴァイオレット１９から選ばれる１種または２種以上のマゼンタ顔料を含むマゼンタ色系インク組成物、
（ｃ）顔料が、ピグメントイエロー７４、ピグメントイエロー１２８、ピグメントイエロー１３８、ピグメントイエロー１５０およびピグメントイエロー１８０から選ばれる１種または２種以上のイエロー顔料を含むイエロー色系インク組成物、
（ｄ）顔料が、カーボンブラックであるブラック顔料を含むインク組成物、
（ｅ）前記（ａ）、（ｂ）、（ｃ）および（ｄ）のインク組成物から選ばれる２種以上からなるインクセット、
などを挙げることができる。これらの中でも、（ａ）、（ｂ）および（ｃ）のインク組成物からなるインクセットは、色のバランスなどから、特に好ましい。
【００６１】
本発明のインク組成物は、インクジェット方式に用いる場合は、その表面および／または内部にシリコン含有ポリビニルピロリドンが保持された記録媒体に適用されるけれども、インクジェット方式以外の水性インクとして使用することもできる。インクジェット方式以外の水性インクの用途としては、たとえば、グラビアインクなどの印刷インク、水性塗料、化粧品、筆記具用インク、トナー、液体現像剤、電子写真用材料などが挙げられる。
【００６２】
本発明のインク組成物を適用する記録媒体は、その表面および／または内部に、シリコン含有ポリビルピロリドンが保持されている。
【００６３】
このような記録媒体は、たとえば、基材の表面および／または内部にシリコン含有ポリビニルピロリドンを含みかつ残部が水である処理液を塗布および／または含浸させることによって、製造することができる。
【００６４】
ここで基材としては、インクジェット方式に利用されている各種の記録媒体を使用でき、たとえば、普通紙、コート紙、光沢紙、はがき、プラスチックシート、プラスチックフィルムなどが挙げられる。その中でも、たとえば、普通紙、コート紙、光沢紙などのパルプ原料を含む一般的な紙系記録媒体が好ましく、そのステキヒトサイズ度が２０度以下である紙系記録媒体が特に好ましい。
【００６５】
処理液に含まれるシリコン含有ポリビニルピロリドンは、ポリビニルピロリドンとシリコンとの混合物であり、通常は、ポリビニルピロリドンからなるマトリックス中にシリコンが分散した混合物である。
【００６６】
シリコンとしては公知のオルガノポリシロキサンが使用でき、その中でもポリメチルシロキサンなどのポリアルキルシロキサンが好ましい。
【００６７】
シリコン含有ポリビニルピロリドンにおける、シリコンとポリビニルピロリドンとの割合は特に制限されないけれども、通常はポリビニルピロリドン１００重量部に対して、シリコンを５〜３０重量部、好ましくは５〜１５重量部使用すればよい。
【００６８】
シリコン含有ポリビニルピロリドンは、たとえば、米国特許第５０７３２９６号明細書、米国特許第５０８４２０８号明細書などの公知文献に記載の方法に従って製造できる。
【００６９】
本発明では、市販のシリコン含有ポリビニルピロリドンを使用することもできる。その具体例としては、たとえば、ＰＶＰ／Ｓｉ−１０（商品名、ＩＳＰ社製）などが挙げられる。ＰＶＰ／Ｓｉ−１０は、ポリメチルシロキサンからなるコアおよびポリビニルピロリドンからなるシェルを有するコアシェル構造を呈するシリコン含有ポリビニルピロリドンである。
【００７０】
シリコン含有ポリビニルピロリドンは１種を単独で使用できまたは２種以上を併用できる。
【００７１】
シリコン含有ポリビニルピロリドンの含有量は特に制限されず、塗布または含浸する基材の材質、表面物性およびインク吸収特性、他成分の有無、他成分を含む場合の種類と含有量、得られる記録媒体に適用するインク組成物の特性などの各種条件に応じて広い範囲から適宜選択できるけれども、通常は処理液全量の０．１〜１０重量％、好ましくは０．１〜５重量％である。０．１重量％未満では、シリコン含有ポリビニルピロリドンの効果が充分に発揮されない可能性がある。一方１０重量％を大幅に超えると、粘度の上昇が大きくなるおそれがある。
【００７２】
処理液は、シリコン含有ポリビニルピロリドンのほかに、多価アルコールを含んでいてもよい。多価アルコールを含むことによって、たとえば、処理液の基材に対する浸透性および処理液を基材に塗布または含浸する際の作業性（塗工安定性）を向上させ、シリコン含有ポリビニルピロリドンを基材表面および内部に均一に分散させることができる。多価アルコールとしては、たとえば、グリセリン、１，２，６−ヘキサントリオール、１，２−ヘキサンジオールなどが挙げられる。多価アルコールは１種を単独で使用できまたは２種以上を併用できる。
【００７３】
さらに処理液は、非イオン性界面活性剤を含んでいてもよい。非イオン性界面活性剤を含むことによって、たとえば、処理液の基材に対する浸透性および作業性をさらに向上させることができる。非イオン性界面活性剤としては、前述の非イオン性界面活性剤を使用できる。非イオン性界面活性剤は、１種を単独で使用できまたは２種以上を併用できる。
【００７４】
処理液は、たとえば、シリコン含有ポリビニルピロリドンおよび必要に応じて多価アルコール、非イオン性界面活性剤のそれぞれ適量を用い、さらに水を用いて全量を１００重量％に調整し、これらの成分を公知の方法に従って混合することによって製造できる。混合には、たとえば、前述の分散機および混合機を使用できる。
【００７５】
処理液を基材表面に塗布するに際しては、液状成分を固形物の表面に塗布するための公知の方法を採用できる。該方法の具体例としては、たとえば、ハケ塗り、ロールコーター法、ブレードコーター法、エアナイフコーター法、バーコーター法、サイズプレス法、スプレーコート法、グラビアコーター法、カーテンコーター法などが挙げられる。基材表面に塗布される処理液の成分は、基材表面に拡がって保持され、および／または、基材内部に浸透して保持される。基材に対する処理液の塗布量は特に制限されず、有効成分であるシリコン含有ポリビニルピロリドンの含有量、基材の材質および特性（表面物性、インク吸収特性など）、得られる記録媒体に適用されるインク組成物の特性などの各種条件に応じて広い範囲から適宜選択できるけれども、通常は０．１〜３０ｇ／ｍ^２、好ましくは０．５〜２０ｇ／ｍ^２である。
【００７６】
または、処理液に基材を浸漬してもよい。浸漬量は、前記の塗布量と同様でよい。
【００７７】
処理液を塗布または含浸された基材の乾燥は、通常は、５〜４０℃の温度下に行われ、３分以下程度で終了する。
【００７８】
このようにして得られる記録媒体に、本発明のインク組成物を用いて記録画像を形成する。
【００７９】
〔画像形成方法および記録画像〕
本発明の画像形成方法は、インクジェット方式によって、インク組成物の液滴を記録媒体上に吐出して記録画像を形成する方法であり、記録媒体には、その表面および／または内部にシリコン含有ポリビニルピロリドンを保持する記録媒体を使用し、インク組成物には、本発明のインク組成物またはインクセットを使用する。
【００８０】
インクジェット方式としては特に制限されず、公知の方法を採用できる。たとえば、圧電素子を用いる方式、インクに圧力をかけてインクの液滴を吐出する方式、膜沸騰現象を利用して気泡を発生させ、インクを吐出する方式などが挙げられる。これらの中でも、圧電素子を用いる方式、膜沸騰現象を利用する方式などが好ましい。
【００８１】
この画像形成方法によって、高画質品位を有する記録画像を得ることができる。
【００８２】
〔インクヘッド〕
図１は、本発明インクヘッド１の構成を簡略化して示す分解斜視図であり、図２は、図１に示すインクヘッド１を構成するヘッドプレート１０の構成の一部を拡大して示す図である。なお、図１では、図２に示す駆動電極１３は図示せず省略する。
【００８３】
インクヘッド１は、圧電材料からなる平板状の底壁部１１および底壁部１１から予め定める間隔をあけて垂直に立ち上がるように形成される複数の隔壁部１２とを有するヘッドプレート１０と、隔壁部１２の上面に接して設けられる天板２０と、複数の吐出口３１を備え底壁部１１の一方の端部１１ａに設けられるノズルプレート３０と、底壁部１１の他方の端部１１ｂに設けられる図示しない背面板と、天板２０の上面に接して設けられる開口部５１を有するインクタンク５０とを含んで構成される。複数の隔壁部１２は、底壁部１１上で一端部から他端部に向かって垂直に延びて互いに平行に配置されており、複数の隔壁部１２と底壁部１１と天板２０とノズルプレート３０と図示しない背面板とによって複数のインク室４０が形成されている。天板２０には、各インク室４０に連通するインク供給路２１と、インク供給路２１とインクタンク５０の開口部５１とを連結するインク供給管２２とが形成される。インクタンク５０には本発明のインク組成物６０が貯留されており、このインク組成物６０はインク供給路２１内を流過して各インク室４０に供給される。
【００８４】
また図２に示すように、ヘッドプレート１０の底壁部１１および複数の隔壁部１２のインク室４０に臨む表面には、複数の隔壁部１２に電圧を印加する駆動電極１３が設けられる。また複数の隔壁部１２をなす圧電材料は、矢符７０の方向に分極しており、複数の隔壁部１２は圧電素子として機能する。
【００８５】
インクヘッド１は、圧電素子である複数の隔壁部１２に印加される電圧に応じて、吐出口３１からインク組成物６０の液滴を吐出させることのできるピエゾ方式のインクヘッドである。
【００８６】
インクヘッド１において、インク室４０からインク組成物６０を吐出させる動作を、図３を参照しながら説明する。図３は、図１に示すインクヘッド１をインク室４０の延長方向から見た断面図である。ここでは、インク室４０ｂからインク組成物６０を吐出させる動作について説明する。
【００８７】
インク室４０ｂを構成する隔壁部１２ａ，１２ｂに電圧が印加されていないとき、すなわちインク室４０ｂの駆動電極１３ｂとインク室４０ｂに隣接するインク室４０ａの駆動電極１３ａとの間、およびインク室４０ｂの駆動電極１３ｂとインク室４０ｂに隣接するインク室４０ｃの駆動電極１３ｃとの間に電位差が生じていないとき、インク室４０ｂには、毛管作用によってインクタンク５０から供給されるインク組成物６０が充填されている。同様に、インク室４０ａおよび４０ｃもインク組成物６０で充填されている。
【００８８】
駆動電極１３ａ，１３ｃに電圧が印加されると、駆動電極１３ｂと駆動電極１３ａとの間、および駆動電極１３ｂと駆動電極１３ｃとの間に電位差が生じ、インク室４０ｂを構成する隔壁部１２ａ，１２ｂに電圧が印加される。この電圧印加は、隔壁部１２ａ，１２ｂにそれぞれ矢符７１，７２の方向の電界を発生させ、この電界の作用によって、インク室４０ｂの隔壁部１２ａ，１２ｂにひずみが生じ、インク室４０ｂ側に凸になるように変形する。これによって、圧力波が発生し、インク室４０ｂ内のインク組成物６０に大きな圧力がかかり、インク組成物６０の液滴が吐出口３１から吐出する。
【００８９】
駆動電極１３ａ，１３ｃへの電圧の印加を止めると、隔壁部１２ａ，１２ｂの形状が元に戻ってインク室４０ｂの体積が元に戻り、復元された体積分のインク組成物６０がインク供給路２１を介してインクタンク５０から供給され、インク室４０ｂは、インク組成物６０が充填された初期の状態に戻る。
【００９０】
インクヘッド１では、インクタンク５０は本発明のインク組成物６０を貯留し、このインク組成物６０がインク室４０に供給されて吐出口３１から液滴として吐出するので、安定して吐出口３１からインク組成物６０の液滴を吐出させることができる。
【００９１】
インクヘッド１を備えるピエゾ方式のインクジェット記録装置において、本発明のインク組成物を用いて記録を行うと、インクヘッド内のインク供給系への濡れ性が向上し、インクの供給がスムーズに行われるため、信頼性の高いピエゾ方式のインクジェット記録装置が実現できる。
【００９２】
本実施の形態では、インク室４０を構成する隔壁部１２を圧電材料で形成し、圧電素子として機能させるけれども、これに限定されることなく、インク室を構成する隔壁を圧電材料以外の材料で形成し、隔壁の内方または外方に圧電素子を設けてもよい。
【００９３】
図４は、本発明の実施形態であるインクヘッド２の構成を簡略化して示す分解斜視図であり、図５は、図４に示すインクヘッド２の構成の一部を示す平面図である。なお、図５では、図４に示す天板２０およびインクタンク５０は図示せず省略する。インクヘッド２は、インクヘッド１と類似し、対応する部分については同一の参照符号を付して説明を省略する。
【００９４】
インクヘッド２は、ヘッドプレート１００が、基板１０１と、基板１０１上で予め定める間隔をあけ、一端部から他端部へ向かって垂直に延びて互いに平行に配置される複数の隔壁１０２と、基板１０１のインク室４０に臨む表面上に設けられる発熱体であるヒータ１０３と、ヒータ１０３に電圧を印加する駆動電極１０４および１０５とを含んで構成されることを特徴とする。
【００９５】
インクヘッド２は、発熱体であるヒータ１０３に印加される電圧に応じて、吐出口３１からインク組成物６０の液滴を吐出させることのできるサーマルインクジェット方式のインクヘッドである。
【００９６】
インクヘッド２において、インク室４０からインク組成物６０を吐出させる際の動作について説明する。図６は、インク室４０からインク組成物６０の液滴６１が吐出する状態を示す図である。図６では、図５に示すインクヘッド２の切断面線Ｉ−Ｉにおける断面構成を示す。
【００９７】
ヒータ１０３に電圧が印加されていないとき、前述のインクヘッド１において隔壁部１２に電圧が印加されていないときと同様に、インク室４０はインク組成物６０が充填されている。
【００９８】
駆動電極１０４，１０５によってヒータ１０３に電圧が印加されると、ヒータ１０３が発熱し、インク室４０内に充填されているインク組成物６０が加熱されて、気泡６２が発生する。これによって、圧力波が発生し、インク室４０内に充填されているインク組成物６０に大きな圧力がかかり、インク組成物６０の液滴６１が吐出口３１から吐出される。
【００９９】
ヒータ１０３への電圧の印加を止めると、インク室４０内のインク組成物６０が冷却されて気泡６２が消滅し、消滅した気泡の体積分のインク組成物６０がインク供給路２１を介してインクタンク５０から供給され、インク室４０は、インク組成物６０が充填された初期の状態に戻る。
【０１００】
インクヘッド２では、前述のインクヘッド１と同様に、インクタンク５０は本発明インク組成物６０を貯留し、このインク組成物６０がインク室４０に供給されて吐出口３１から液滴６１として吐出するので、安定して吐出口３１からインク組成物６０の液滴６１を吐出させることができる。
【０１０１】
本実施の形態によるインクヘッドを備えるサーマルインクジェット方式のインクジェット記録装置において、本発明のインク組成物を用いて記録を行うと、ヘッド内のインク供給系への濡れ性が向上し、インクの供給がスムーズに行われるため、信頼性の高いサーマル方式のインクジェット記録装置が実現できる。
【０１０２】
［実施例］
以下に参考例、実施例、比較例および試験例を挙げ、本発明を具体的に説明する。なお、以下において「％」とあるのは、特に断らないかぎり「重量％」を意味する。
【０１０３】
参考例１（記録媒体の製造）
表１に示す割合（％）で各成分を混合し、これに水を加えて全量を１００％とした。この混合物を２５℃で１時間攪拌し、処理液を調製した。得られた処理液を、転写方式のゴムローラを用いて、ＰＰＣ用紙（商品名：ＳＦ４ＡＭ３、シャープ（株）製）に塗布し、シリコン含有ポリビニルピロリドンを保持した記録媒体Ｎｏ．１〜５を製造した。塗布量は８ｇ／ｍ^２であった。
【０１０４】
なお、表１における樹脂成分および界面活性剤は、具体的には、次のとおりである。
【０１０５】
〔樹脂成分〕
ＰＶＰ／Ｓｉ−１０：商品名、ＩＳＰ社製、ポリメチルシロキサンを内包するポリビニルピロリドンの２０％水溶液
【０１０６】
〔界面活性剤〕
エチレンオキシド含有化合物１Ａ：一般式（１）において、ｅ＋ｆ＝１０である化合物、商品名サーフィノール４６５、日信化学（株）製
エチレンオキシド含有化合物１Ｂ：一般式（１）において、ｅ＋ｆ＝３．５である化合物、商品名サーフィノール４４０、日信化学（株）製
エチレンオキシド含有化合物４Ａ：一般式（１）において、ｗ＋ｚ＝１１、ａ＝９、ｂ＝５である化合物、商品名ソフタノールＥＰ９０５０、（株）日本触媒製
【０１０７】
【表１】

【０１０８】
実施例１〜５および比較例１〜３（インク組成物の調製）
表２に示す割合（％）で各成分を混合し、これに水を加えて全量を１００％とした。この混合物を２５℃で１時間攪拌した後、１．２μｍのメンブランフィルタを用いて加圧濾過し、次いで脱気処理し、本発明および比較例のインク組成物を調製した。
【０１０９】
なお、表２において、商品名で記載されている界面活性剤および定着剤は、具体的には次のとおりである。
【０１１０】
［定着剤］
バイロナールＭＤ１４００：ポリエステルエマルジョン、東洋紡績（株）製
【０１１１】
［界面活性剤］
サーフィノール２５０２、サーフィノール４６５：いずれもエチレンオキシドを含有するアセチレン系非イオン性界面活性剤、エアプロダクツ社製
【０１１２】
試験例１
実施例１〜６および比較例１〜５で得られたインク組成物について、次の評価試験を行った。結果を表２に示す。
【０１１３】
［高速印刷性］
インクジェットプリンタ（商品名：ＡＪ２０００、シャープ（株）製）のインクヘッドを本発明のインクヘッドに交換したプリンタを用い、印刷濃度５％、１０ＰＰＭ（１０枚／分）で連続的に印刷を行い、良好な画質品位を有する記録画像を印字できる枚数を調べた。印刷枚数が２００枚を超えるものを「○」、１５０〜２００枚であるものを「△」、１５０枚未満のものを「×」と評価した。
【０１１４】
［乾燥性］
印刷終了直後、印刷面に印刷紙と同じ紙を１５秒間押し当て、印刷が転写しないものを「○」、転写するものを「×」と評価した。
【０１１５】
［にじみ性］
ＰＰＣ用紙（商品名：ＳＦ４ＡＭ３、シャープ（株）製）に特定のパターンを印刷して１日間放置後、該パターンのライン幅を測定し、にじみがない場合のライン幅を１００とし、それに対する相対値として評価を行った。１５０未満のものを「○」、１５０〜２５０のものを「△」および２５０を超えるものを「×」と評価した。
【０１１６】
［起泡性］
インク組成物を２０秒間振とうして５分間静置した後、泡高さを測定し、１０ｍｍ以下のものを「○」および１０ｍｍを超えるものを「×」と評価した。泡高さが大きいほど、起泡性が高い。起泡性の高いインク組成物は、吐出ノズル内で泡を発生し、該ノズルが泡をかみ込むので、吐出される液滴量が変化しやすい。起泡性の高いインク組成物は、吐出安定性が低く、高速印刷には使用できない。
【０１１７】
【表２】

【０１１８】
表２から、本発明のインク組成物が、インクジェット方式のプリンタによって充分に印字可能なインクであることがわかる。
【０１１９】
試験例２
実施例１、３、４、６および比較例４のインク組成物を用い、試験例１と同じインクジェットプリンタにて、参考例１の記録媒体Ｎｏ．１〜５に記録画像（ベタ画像または試験用パターン）を印刷した。得られた記録画像について、次の評価試験を行った。結果を表３に示す。
【０１２０】
［印字濃度］
ベタ画像の印字濃度（画像濃度）を、測色計（商品名：Ｘ−Ｒｉｔｅ９３８、マクベス社製）によって測定した。処理液を塗布していないＰＰＣ用紙（ＳＦ４ＡＭ３）の印字濃度に比べ、濃度が上昇しているものを「○」、変化しないものを「△」および下がったものを「×」と評価した。
【０１２１】
［フェザリング］
試験用パターンのライン幅を測定し、処理液を塗布していないＰＰＣ用紙（ＳＦ４ＡＭ３）に形成された試験用パターンのライン幅を１００とし、それに対する相対値として評価を行った。１００未満のものを「○」、１００〜１２０のものを「△」および１２０以上ものを「×」と評価した。
【０１２２】
【表３】

【０１２３】
表３から、インクジェット方式によって、シリコン含有ポリビニルピロリドンを保持した記録媒体に、特定の顔料、水溶性有機溶剤、界面活性剤および定着剤を含み、残部が水である本発明のインク組成物からなる記録画像を形成すると、フェザリングが著しく防止され、印字濃度の高い記録画像が得られることが明らかである。
【０１２４】
試験例３
実施例１〜５のインク組成物および比較例１〜３のインク組成物から、表４に示す組み合わせでシアンインク、マゼンタインクおよびイエローインクを選択し、試験例１と同じインクジェットプリンタにて、参考例１の記録媒体Ｎｏ．１に印字率１：１：１でスリーカラーブラックを印刷した。
【０１２５】
一方、実施例６のインク組成物を用い、上記と同様にして、ブラック単色を記録媒体Ｎｏ．１に印刷した。
【０１２６】
スリーカラーブラックおよびブラック単色の印字を測色計（Ｘ−Ｒｉｔｅ９３８）にかけ、ａ^＊およびｂ^＊を測定した。スリーカラーブラックのａ^＊をＡ２、ｂ^＊をＢ２、ブラック単色のａ^＊をＡ１、ｂ^＊をＢ１としたとき、下記式で表される値（Δａ^＊ｂ^＊）が２０以下のものを「○」および２０より大きいものを「×」と評価した。結果を表２に示す。
Δａ^＊ｂ^＊＝｛（Ａ１−Ａ２）^２＋（Ｂ１−Ｂ２）^２｝^１／２
【０１２７】
【表４】

【０１２８】
表４から、実施例１〜５から選ばれる３種のインク組成物を重ね合わせて得られるＮｏ．イ〜ニの黒色画像は、比較例１〜３の３種類のインク組成物を重ね合わせて得られるＮｏ．ホの黒色画像に比べ、高い画像濃度を有する黒色画像であることが判る。すなわち、本発明の４種のインクセットは、比較例のインクセットに比べ、黒色再現性が良好であり、カラーバランスに優れることが判る。
【０１２９】
以上のように、Ｃ．Ｉ．ピグメントブルー１５：３および１５：４のうちの少なくとも一方の顔料を含有するシアンのインク組成物と、Ｃ．Ｉ．ピグメントレッド１２２、２０９およびＣ．Ｉ．ピグメントヴァイオレット１９からなる群から選ばれる少なくとも１つの顔料を含有するマゼンタのインク組成物と、Ｃ．Ｉ．ピグメントイエロー７４、１３８、１５０および１８０からなる群から選ばれる少なくとも１つの顔料を含有するイエローのインク組成物とを組合せることによって、カラーバランスに優れるインクセットを得られることが判る。
【０１３０】
【発明の効果】
本発明によれば、インクジェット方式によって、シリコン含有ポリビニルピロリドンを表面および／または内部に保持した記録媒体に、顔料、好ましくは自己分散顔料を含む水性インクによる画像を形成することによって、顔料がシリコン含有ポリビニルピロリドンと反応して固定化され、顔料がインク中の水などの液状成分とともに記録媒体の表面を必要以上に拡散することが防止されるので、にじみ（特にフェザリング）、混色、ベタ部分の濃淡などを発生させることなく、輪郭が明瞭で、画像濃度および鮮明性が高く、高画質品位の記録画像を形成でき、しかも高速印刷を行っても、前記と同様の高画質品位の記録画像を形成できるインク組成物が提供される。
【０１３１】
本発明によれば、水溶性有機溶剤、その中でも特定のものをインク組成物に添加することによって、吐出ノズル内でのインク組成物の泡立ちおよび乾燥が防止され、吐出安定性がさらに向上するので、高速印刷を容易に行うことができる。また、インク組成物に、記録媒体に対する適度な浸透性を付与することができる。
【０１３２】
本発明に従えば、非イオン性界面活性剤、その中でも特定のものをインク組成物に添加することによって、吐出ノズル内での泡立ちおよび乾燥が一層起こり難く、安定的にインクジェット記録を行うことができるインク組成物が得られる。
【０１３３】
本発明によれば、特定のシアン顔料を含むシアン系インク組成物、特定のマゼンタ顔料を含むマゼンタ系インク組成物、特定のイエロー顔料を含むイエロー系インク組成物および特定のブラック顔料を含むブラック系インク組成物、ならびに前記４種の各色系インク組成物から選ばれる２種以上からなるインクセットが得られる。前記４種の各色系インク組成物を用い、シリコン含有ポリビニルピロリドンを表面および／または内部に保持させた記録媒体に画像を形成すると、鮮明で濃度の高いシアン色、マゼンタ色、イエロー色または黒色の記録画像が得られる。また前記インクセットを用いると、各色画像がそれぞれ鮮明でかつ画像濃度が高く、しかもカラーバランスが極めて良好な記録画像が得られる。
【０１３４】
本発明によれば、インクジェット方式によって、シリコン含有ポリビニルピロリドンを表面および／または内部に保持した記録媒体に、前述のいずれかのインク組成物を用いて画像を形成することによって、前述したような非常に高画質品位の記録画像を得ることができる。
【０１３５】
本発明によれば、本発明のインク組成物を連続してかつ安定的に吐出することができ、高速印刷を容易に行うことができる、ピエゾ式またはバブル式のインクジェット方式用インクヘッドが提供される。
【図面の簡単な説明】
【図１】本発明のインクヘッドの構成を簡略化して示す分解斜視図である。
【図２】図１に示すインクヘッドを構成するヘッドプレートの構成の一部を拡大して示す図である。
【図３】図１に示すインクヘッドをインク室の延長方向から見た断面図である。
【図４】本発明のインクヘッドの構成を簡略化して示す分解斜視図である。
【図５】図４に示すインクヘッドの構成の一部を示す平面図である。
【図６】インク室からインク組成物の液滴が吐出する様子を示す図であり、図５に示すインクヘッドの切断面線Ｉ−Ｉにおける断面構成を示す。
【符号の説明】
１，２ インクヘッド
１０，１００ ヘッドプレート
１１ 底壁部
１１ａ 一方の端部
１１ｂ 他方の端部
１２，１２ａ，１２ｂ 隔壁部
１３，１３ａ，１３ｂ，１３ｃ，１０４，１０５ 駆動電極
２０ 天板
２１ インク供給路
３０ ノズルプレート
３１ 吐出口
４０，４０ａ，４０ｂ，４０ｃ インク室
５０ インクタンク
５１ 開口部
６０ インク組成物
６１ 液滴
６２ 気泡
７０，７１，７２ 矢符
１０１ 基板
１０２ 隔壁
１０３ ヒータ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink composition, an ink set, an image forming method, a recorded image, and an ink head.
[0002]
[Prior art]
The ink jet method employed in output devices such as personal computers, copiers, and facsimile machines is a printing method in which fine droplets of an ink composition are discharged from a discharge nozzle onto a recording medium, and an image is recorded on the recording medium. A very useful printing method with a number of desirable features such as excellent quietness, easy density and colorization, high-speed printing, and inexpensive printing of relatively high-quality recorded images. It is. Well-known methods for discharging microdroplets include a method using a piezoelectric element and a method using bubbles generated by a film boiling phenomenon.
[0003]
In the ink jet system, in order to obtain a recorded image without printing unevenness, it is necessary to continuously and stably eject a substantially constant amount of fine droplets of the ink composition. For this purpose, foaming in the discharge nozzle, drying, clogging and the like are relatively unlikely to occur, and a low-viscosity ink composition excellent in discharge stability, specifically, an aqueous solution containing a dye or pigment and containing water as a main medium. Ink is used. On the other hand, as the recording medium, papers that can easily record an image with water-based ink, particularly plain paper (PPC paper) are used. However, since the water-based ink has low drying properties despite its high permeability to papers, bleeding is likely to occur when it is attached to papers. In addition, there are various types of plain paper having different ink absorption characteristics depending on surface characteristics such as surface shape and surface roughness, and sizing agents contained therein. To prevent the occurrence of bleeding, it is necessary to select an appropriate ink for each plain paper, but such selection is practically impossible. Therefore, in the ink jet method, the dye or pigment contained in the aqueous ink is diffused together with the liquid component such as water in the ink to the inside of the plain paper or to the margin on the surface to cause bleeding, and the whiskers in the outline portion of the recorded image are generated. The blurring (feathering), color mixture in which inks of different colors are mixed, and the like are likely to occur. As a result, the solid portion becomes non-uniform, the outline portion of the recorded image becomes unclear, and the image density, sharpness, and image quality deteriorate. In view of such a problem, various studies have been made from both sides of the recording medium and the ink composition.
[0004]
First, regarding improvement of a recording medium, for example, a coated paper in which a coating layer made of inorganic particles such as diatomaceous earth is provided on the surface of plain paper has been proposed (for example, see Patent Document 1). However, even with such coated paper, feathering cannot be sufficiently prevented. Further, since the dye has an anionic group, a recording medium in which a compound having a cationic group on the surface and / or inside is present has been proposed. Examples of the compound having a cationic group include polycationic polymer electrolytes such as polyvinylpyridinium halide, polyethyleneimine and polyamine (for example, see Patent Document 2), and cationic groups such as vinylpyrrolidone and amine groups and quaternary ammonium groups. (For example, see Patent Document 3). Even if these recording media are used, the occurrence of feathering cannot be prevented, and the image density of the recorded image is not sufficient. Further, when the coloring material of the ink composition is a pigment, the effect is further reduced.
[0005]
On the other hand, in order to prevent bleeding from the surface of the ink composition and improve the image quality of a recorded image, a water-soluble organic solvent, a surfactant and the like are appropriately selected and added to the ink composition. . For example, an ink composition containing a water-soluble dye, a water-soluble organic solvent such as diethylene glycol, a nonionic surfactant such as an acetylene glycol-ethylene oxide adduct, and water has been proposed (for example, see Patent Document 4). However, this ink composition does not have sufficiently satisfactory performance, particularly in terms of ejection stability during high-speed printing, drying property for a recording medium, prevention of occurrence of feathering in a recorded image, definition of a recorded image, and the like. .
[0006]
Further, an ink composition containing a recording medium under heating containing a dye or pigment, a water-soluble organic solvent such as glycerin, thiodiglycol, and urea, a nonionic surfactant such as acetylene glycol / ethylene oxide adduct, and water. There has been proposed an ink jet recording method for discharging ink (see, for example, Patent Document 5). However, in the ink jet system, printing is sometimes performed on hundreds of sheets, and sometimes on thousands of sheets per day. In such a case, the power consumption for heating the recording medium becomes too large. Not a target. Furthermore, when high-speed printing is performed, unevenness in the way of heat transmission occurs, which in turn causes unevenness in the recorded image, deteriorating the image quality.
[0007]
Further, there has been proposed an ink composition containing a water-soluble dye, a polyhydric alcohol such as ethylene glycol, and a surfactant having a surface tension at a micelle concentration of 20 to 50 dyne / cm in water, with the balance being water. (For example, see Patent Document 6). According to Patent Document 6, by adding a surfactant having specific properties, the surface tension of the ink composition is reduced, and the permeability of the ink to a recording medium is increased. However, since this ink composition permeates too much into a recording medium, it is unavoidable that feathering occurs, image density and sharpness are reduced, and image quality of recorded images becomes insufficient.
[0008]
As described above, in order to obtain a high-quality printed image in the inkjet method, it is necessary to appropriately combine the ink absorption characteristics of the recording medium, the permeability of the ink composition on the recording medium, the drying property, and the like. Is a major issue.
[0009]
[Patent Document 1]
JP-A-1-216881
[Patent Document 2]
JP-A-56-89992
[Patent Document 3]
JP-A-4-288283
[Patent Document 4]
JP-A-56-5871
[Patent Document 5]
JP-A-11-129460
[Patent Document 6]
JP-A-55-29546
[0010]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a clear image, high image density and sharpness, and high-quality image recording without causing bleeding (especially feathering), mixing of different color inks (color mixing), and shading of a solid portion. An object of the present invention is to provide an ink composition and an image forming method capable of forming an image and maintaining high quality of a recorded image even when high-speed printing is performed.
[0011]
Another object of the present invention is to provide a recorded image of high quality.
Another object of the present invention is to provide an ink head that can continuously and stably discharge the above-described ink composition, and that can form a high-quality recorded image.
[0012]
[Means for Solving the Problems]
The present invention relates to an aqueous ink for forming a recorded image on a recording medium holding polyvinylpyrrolidone containing silicon on the surface and / or inside thereof, wherein the aqueous ink contains a pigment as a coloring material, and the balance is water. Characteristic ink composition.
[0013]
According to the present invention, an image is formed by a water-based ink containing a pigment on a recording medium having polyvinylpyrrolidone containing silicon (hereinafter referred to as “polyvinylpyrrolidone containing silicon”) held on its surface and / or inside by an inkjet method. As a result, the pigment reacts with the silicon-containing polyvinylpyrrolidone and is fixed, and the pigment is prevented from unnecessarily diffusing on the surface of the recording medium together with a liquid component such as water in the ink. ), Clear outlines, high image density and sharpness, high-quality recorded images can be formed without causing color mixing, solid portion shading, etc. An ink composition capable of forming a high-quality recorded image is provided.
[0014]
Further, the ink composition of the present invention is characterized in that the above-mentioned pigment is a self-dispersed pigment in which a hydrophilic group is introduced on the surface of the pigment.
[0015]
According to the present invention, by using a self-dispersed pigment as the pigment, the image quality of the obtained recorded image is further improved, and the storage stability of the ink composition itself is improved. Aggregation and sedimentation of the pigment which causes clogging is further reduced. In addition, the permeability and drying property of the ink composition to the recording medium are improved.
[0016]
Further, the ink composition of the present invention is characterized by further containing a water-soluble organic solvent.
[0017]
Further, the ink composition of the present invention is characterized in that the water-soluble organic solvent is a glycol ether and / or a polyhydric alcohol.
[0018]
Further, the ink composition of the present invention is characterized in that the above-mentioned water-soluble organic solvent is a water-soluble organic solvent having a saturated vapor pressure at 20 ° C. of 6.6665 Pa (0.05 mmHg, 20 ° C.) or less.
[0019]
According to the present invention, by adding a water-soluble organic solvent, among them, a specific one to the ink composition, foaming and drying of the ink composition in the discharge nozzle are prevented, and the discharge stability is further improved. , High-speed printing can be easily performed. Further, the ink composition can be imparted with appropriate permeability to a recording medium.
[0020]
Further, the ink composition of the present invention is characterized in that the ink composition further contains a nonionic surfactant.
[0021]
Further, the ink composition of the present invention is characterized in that the above-mentioned nonionic surfactant is a compound having an acetylene group.
[0022]
According to the present invention, by adding a specific nonionic surfactant to the ink composition, foaming and drying in the discharge nozzle are more unlikely to occur, and stable inkjet recording can be performed. The resulting ink composition is obtained.
[0023]
Further, the ink composition of the present invention is a cyan-based ink composition in which the above-mentioned pigment contains one or more cyan pigments selected from Pigment Blue 15: 3, Pigment Blue 15: 4 and Pigment Blue 15: 6. There is a feature.
[0024]
Further, the ink composition of the present invention is characterized in that the above-mentioned pigment is a magenta ink composition containing one or more kinds of magenta pigments selected from Pigment Red 122, Pigment Red 209 and Pigment Violet 19. .
[0025]
In addition, the ink composition of the present invention is a yellow ink composition in which the above-mentioned pigment contains one or more yellow pigments selected from Pigment Yellow 74, Pigment Yellow 128, Pigment Yellow 138, Pigment Yellow 150 and Pigment Yellow 180. It is characterized by being a thing.
[0026]
Further, the ink composition of the present invention is characterized in that the pigment is a black ink composition containing carbon black.
[0027]
The present invention provides an ink set comprising two or more selected from the above-mentioned cyan ink composition, the above-mentioned magenta ink composition, the above-mentioned yellow ink composition and the above-mentioned black ink composition. It is.
[0028]
According to the present invention, a cyan ink composition containing a specific cyan pigment, a magenta ink composition containing a specific magenta pigment, a yellow ink composition containing a specific yellow pigment, and a black ink containing a specific black pigment An ink composition and an ink set composed of two or more types selected from the above four types of color ink compositions are obtained. When an image is formed on a recording medium in which silicon-containing polyvinylpyrrolidone is held on the surface and / or inside using each of the four types of color ink compositions, a clear, high-density cyan, magenta, yellow, or black color is obtained. A recorded image is obtained. When the ink set is used, a recorded image in which each color image is clear, has a high image density, and has a very good color balance can be obtained.
[0029]
The present invention is a method for forming an image on a recording medium by discharging droplets of an ink composition onto a recording medium having polyvinyl pyrrolidone containing silicon on its surface and / or inside by an ink jet method. An image forming method, wherein the ink composition is any one of the above ink compositions or the above ink set.
[0030]
The present invention provides a recorded image formed on a recording medium by the above-described image forming method.
[0031]
According to the present invention, an image is formed on a recording medium having silicon-containing polyvinylpyrrolidone on its surface and / or inside by using an ink-jet method by using any one of the above-described ink compositions. Thus, a high-quality recorded image can be obtained.
[0032]
The present invention provides an ink tank for storing any of the above ink compositions or the above ink set,
An ink chamber having an ejection port for ejecting droplets of the ink composition or the ink set, and an ink chamber to which the ink composition or the ink set is supplied from the ink tank;
A piezoelectric element that generates strain in response to an applied voltage,
A piezoelectric element provided in at least a part of the ink chamber and applying pressure to the ink composition or the ink set contained in the ink chamber,
An electrode provided for applying a voltage to the piezoelectric element.
[0033]
The present invention provides an ink tank for storing any of the above ink compositions or the above ink set,
An ink chamber to which the ink composition or the ink set is supplied from the ink tank, wherein the ink chamber has an ejection port for ejecting droplets of the ink composition or the ink set, and the ink chamber is provided in at least a part of the ink chamber; A heating element that applies pressure to the ink composition or the ink set by heating the ink composition or the ink set contained in the ink chamber to generate air bubbles;
An electrode provided for applying a voltage to the heating element.
[0034]
According to the present invention, there is provided a piezo-type or bubble-type ink-jet ink head which can continuously and stably discharge the ink composition of the present invention and can easily perform high-speed printing. You.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
(Ink composition)
The ink composition of the present invention is an ink for forming an image on a recording medium that holds silicon-containing polyvinylpyrrolidone on the surface and / or inside by an inkjet method.
[0036]
The ink composition of the present invention is an aqueous ink containing a pigment as a coloring material and the balance being water.
[0037]
As the pigment, known inorganic pigments and organic pigments can be used. Examples of the inorganic pigment include carbon black, titanium oxide, iron oxide, and the like manufactured by a known method such as a contact method, a furnace method, and a thermal method. Among them, carbon black is preferred. When a specific example of the organic pigment is represented by a color index number (CI), for example, Pigment Blue 1, 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17, Cyan pigments such as 22, 21, 22, 60, 64, and pigment red 1, 2, 3, 5, 10, 16, 23, 30, 31, 48: 1, 48: 2, 49: 1, 52, 53: Magenta pigments such as 1, 57: 1, 58: 4, 63, 122, 209, and Pigment Bio Red 19; Pigment Yellow 3, 12, 13, 14, 15, 23, 55, 74, 83, 93, 95, 97 , 128, 138, 150, 154, 167, 180, 193 and the like. Among them, those highly safe for the human body are preferable, and cyan pigments such as Pigment Blue 15: 3, 15: 4, and 15: 6; magenta pigments such as Pigment Red 122, 209, and Pigment Violet 19; Particularly preferred are yellow pigments such as 128, 138, 150 and 180. One type of pigment can be used alone, or two or more types of pigments of the same color or different colors can be used in combination.
[0038]
In the present invention, it is preferable to use a self-dispersed pigment obtained by introducing a hydrophilic group such as a carboxyl group or a sulfonic acid group on the surface of the pigment. Since the self-dispersible pigment has dispersibility in water, its use can further improve the ejection stability of the ink composition, the permeability to a recording medium, the drying property, and the like. Known methods can be used to introduce a hydrophilic group such as a carboxyl group or a sulfonic acid group into the pigment surface, and examples thereof include an acid, a coupling agent treatment, a polymer graft treatment, a plasma treatment, an oxidation / reduction treatment, and a capsule. And the like.
[0039]
Although the content of the pigment is not limited, it is selected from the range of 0.1 to 10% by weight, preferably 0.1 to 8% by weight of the total amount of the ink composition of the present invention. If the amount is less than 0.1% by weight, the image density becomes extremely low, so that it is difficult to express a color. On the other hand, if it exceeds 10% by weight, the viscosity increases, and an ink composition having an appropriate viscosity range as an ink cannot be obtained.
[0040]
The ink composition of the present invention may contain a water-soluble organic solvent in order to further improve its ejection stability, permeability to a recording medium, and the like. Known water-soluble organic solvents can be used, for example, amides such as dimethylformamide and dimethylacetamide, polyethylene glycol, polypropylene glycol, ethylene glycol, diethylene glycol, thiodiglycol, propylene glycol, triethylene glycol, 1,5 Glycols such as pentanediol, 1,4-butanediol, 1,2-hexanediol, and 1,3-propanediol; trihydric or higher polyhydric alcohols such as glycerin and 1,2,6-hexanetriol; Ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monobutyl ether, Polyhydric alcohol ethers such as propylene glycol monoethyl ether, tetraethylene glycol monomethyl ether and ethylene glycol monophenyl ether; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; nitrogen such as 2-pyrrolidone, N-methylpyrrolidone and ε-caprolactam Heterocyclic compounds, oxygen-containing heterocyclic compounds such as γ-butyrolactone, and polyfunctional compounds such as dimethylaminoethanol, diethylaminoethanol, triethanolamine, and morpholine.
[0041]
Among these water-soluble organic solvents, glycol ethers, polyhydric alcohols, and the like are preferable in consideration of the degree of improvement in ejection stability, permeability to a recording medium, and the like, and among them, the vapor pressure at 20 ° C. Those having a pressure of 6.6665 Pa (0.05 mmHg) or less, for example, polyhydric alcohols such as glycerin, 1,2-hexanediol, and 1,5-pentanediol are particularly preferable.
[0042]
One type of water-soluble organic solvent can be used alone, or two or more types can be used in combination.
Although the content of the water-soluble organic solvent is not particularly limited, in consideration of further preventing the occurrence of bleeding and further improving the drying property with respect to the recording medium, the content of the ink composition of the present invention is usually the total amount. It is 10 to 70% by weight, preferably 10 to 50% by weight. However, when trying to obtain the ink composition of the present invention containing a larger amount of the aqueous medium than the water-soluble organic solvent, the content of the water-soluble organic solvent, in consideration of prevention of bleeding, drying properties for the recording medium, and the like. It is 10 to 40% by weight, preferably 10 to 30% by weight of the total amount of the ink composition of the present invention.
[0043]
The ink composition of the present invention may further contain a nonionic surfactant. Known nonionic surfactants can be used, and among them, for example, the general formula
[0044]
Embedded image

[0045]
[Wherein, e and f each represent an integer of 0 to 30 that satisfies the relationship of 0 ≦ e + f ≦ 30. ]
Acetylene glycol / ethylene oxide adduct represented by the general formula
[0046]
Embedded image

[0047]
[In the formula, k represents an integer of 11 to 13. l shows the integer of 3-30. ]
A compound represented by the general formula
[0048]
Embedded image

[0049]
[Wherein, h and i each represent an integer of 0-11. j represents an integer of 3 to 50. ]
A compound represented by the general formula
[0050]
Embedded image

[0051]
Wherein a represents an integer of 5 to 9. b represents a positive number of 2.5 to 5. z and w each represent an integer of 0 to 11 that satisfies the relationship of 9 ≦ z + w ≦ 11. ]
A compound represented by the general formula
HO (CH₂CH₂O)_p(CH₂CH₂CH₂O)_q(CH₂CH₂O)_rH (5)
[In the formula, p represents an integer of 0 to 18. q shows the integer of 2-15. r shows the integer of 0-18. ]
Preferred are ethylene oxide-containing nonionic surfactants such as the compounds represented by In the present invention, commercially available nonionic surfactants containing ethylene oxide can also be used, and examples thereof include Surfynol (trade name, manufactured by Air Products), Sophanol (trade name, manufactured by Nippon Shokubai Co., Ltd.) and the like. Can be One type of nonionic surfactant can be used alone, or two or more types can be used in combination.
[0052]
The content of the nonionic surfactant is not particularly limited, but is usually selected from the range of 0.001 to 5% by weight, preferably 0.001 to 3% by weight of the total amount of the ink composition of the present invention. .
[0053]
The ink composition of the present invention may contain a fixing agent in order to improve the fixability to a recording medium as long as the preferable properties are not impaired. Known fixing agents can be used, for example, natural rubbers such as gum arabic, glucosides such as savonin, lignin sulfonates, natural polymer compounds such as shellac, acrylic acid resins and salts thereof, methacrylic acid resins And a salt thereof, a styrene-acrylic acid copolymer and a salt thereof, a vinyl naphthalene-acrylic acid copolymer and a salt thereof, a styrene-maleic acid-alkyl acrylate copolymer and a salt thereof, and a vinyl naphthalene-maleic acid copolymer And its salts, styrene-methacrylic acid-alkyl acrylate copolymers and their salts, anionic polymer compounds such as sodium salts and phosphates of β-naphthalenesulfonic acid formalin condensate, polyester resins, polyvinyl alcohol Non-a, such as polyvinylpyrrolidone Copolymers composed of two or more monomeric compounds having a polymerizable unsaturated double bond such as an ionic polymer compound, acrylonitrile, vinyl acetate, acrylamide, vinyl chloride, vinylidene chloride, ethylene, hydroxyethyl acrylate, and glycidyl methacrylate. Coalescence and the like. In the present invention, a commercially available resin emulsion can also be used as a fixing agent. Examples of commercially available resin emulsions include Vironal (trade name, manufactured by Toyobo Co., Ltd., polyester resin emulsion). As the fixing agent, one type can be used alone, or two or more types can be used in combination.
[0054]
The ink composition of the present invention is a general additive of an inkjet ink composition such as a fungicide, a pH adjuster, a chelating agent, a rust inhibitor, and an ultraviolet absorber as long as the preferable properties are not impaired. May be included. Examples of the fungicide include sodium dehydroacetate, sodium benzoate, sodium sorbitanate, sodium 2-pyridinethiol-1-oxide, sodium pentachlorophenol, and the like. Examples of the pH adjuster include amines such as diethanolamine and triethanolamine, alkali metal hydroxides such as lithium hydroxide, potassium hydroxide and sodium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, and quaternary ammonium hydroxide. Alkali metal carbonates such as graded phosphonium hydroxide, lithium carbonate, sodium carbonate and potassium carbonate; and alkali metal nitrates such as sodium nitrate and potassium nitrate. Examples of the chelating agent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uramildiacetate. Examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and the like. Examples of the ultraviolet absorber include a benzotriazole compound, a benzophenone compound, a cyanoacrylate compound, and the like. One type of additive may be used alone, or two or more types may be used in combination.
[0055]
Further, the ink composition of the present invention may contain a solubilizing agent, an antioxidant, an antifoaming agent, a viscosity adjusting agent, an anti-clogging agent, and the like, if necessary.
[0056]
The ink composition of the present invention is prepared, for example, by using appropriate amounts of a pigment and, if necessary, a water-soluble organic solvent, a nonionic surfactant, a fixing agent, and other additives. It can be manufactured by adjusting the weight% and dispersing or dissolving each component in water.
[0057]
The water used here is not particularly limited, and tap water, pure water, ion-exchanged water, activated carbon treated water and the like can be used. Among these, water having an electric conductivity (25 ° C.) of 250 μS / cm or less is preferable in consideration of the ejection stability of the ink composition, permeability and drying property to a recording medium, storage stability, and the like, and 1 μS / cm or less. Are particularly preferred. The electric conductivity is an index indicating the purity of water, in other words, an index indicating the amount of impurities contained in water. The impurities are trace components generally contained in water, and include, for example, inorganic salts and other mineral components.
[0058]
Dispersion is performed using a general disperser. Examples of the disperser include a disperser, a sand mill, a homogenizer, a ball mill, a bead mill, a paint shaker, and an ultrasonic disperser. Mixing is performed by a stirrer having a stirring blade, a high-speed disperser, an emulsifier, or the like.
[0059]
After dispersion and / or mixing, a solid-liquid separation means may be provided. Examples of the solid-liquid separation means include filtration and centrifugation. For example, the filtration may be performed after each component is mixed or dispersed in an aqueous medium. The filtration is performed under normal pressure or reduced pressure using, for example, a filter having a pore size of 0.8 μm or less, a filter having a pore size of 0.45 μm or less, or the like.
[0060]
Preferred forms of the ink composition of the present invention thus obtained include:
(A) a cyan ink composition in which the pigment contains one or more cyan pigments selected from Pigment Blue 15: 3, Pigment Blue 15: 4, and Pigment Blue 15: 6;
(B) a magenta ink composition in which the pigment contains one or more magenta pigments selected from Pigment Red 122, Pigment Red 209 and Pigment Violet 19;
(C) a yellow ink composition in which the pigment contains one or more yellow pigments selected from Pigment Yellow 74, Pigment Yellow 128, Pigment Yellow 138, Pigment Yellow 150 and Pigment Yellow 180;
(D) an ink composition containing a black pigment, wherein the pigment is carbon black;
(E) an ink set comprising at least two ink compositions selected from the ink compositions of (a), (b), (c) and (d);
And the like. Among these, an ink set composed of the ink compositions (a), (b) and (c) is particularly preferable from the viewpoint of color balance and the like.
[0061]
When the ink composition of the present invention is used in an ink jet system, it is applied to a recording medium in which silicon-containing polyvinylpyrrolidone is held on the surface and / or inside, but can also be used as an aqueous ink other than the ink jet system. . Examples of uses of aqueous inks other than the ink jet method include printing inks such as gravure inks, aqueous paints, cosmetics, inks for writing implements, toners, liquid developers, and materials for electrophotography.
[0062]
The recording medium to which the ink composition of the present invention is applied has silicon-containing polypyrrolidone on its surface and / or inside.
[0063]
Such a recording medium can be produced, for example, by applying and / or impregnating a treatment liquid containing silicon-containing polyvinylpyrrolidone on the surface and / or inside of the substrate and the balance being water.
[0064]
Here, as the substrate, various recording media used in the ink jet system can be used, and examples thereof include plain paper, coated paper, glossy paper, postcards, plastic sheets, and plastic films. Among them, for example, a general paper-based recording medium containing a pulp material such as plain paper, coated paper, glossy paper, or the like is preferable, and a paper-based recording medium having a Steckigt size of 20 degrees or less is particularly preferable.
[0065]
The silicon-containing polyvinylpyrrolidone contained in the treatment liquid is a mixture of polyvinylpyrrolidone and silicon, and is usually a mixture in which silicon is dispersed in a matrix made of polyvinylpyrrolidone.
[0066]
As the silicon, known organopolysiloxanes can be used, and among them, polyalkylsiloxanes such as polymethylsiloxane are preferable.
[0067]
The proportion of silicon and polyvinylpyrrolidone in the silicon-containing polyvinylpyrrolidone is not particularly limited, but usually 5 to 30 parts by weight, preferably 5 to 15 parts by weight of silicon is used per 100 parts by weight of polyvinylpyrrolidone.
[0068]
Silicon-containing polyvinylpyrrolidone can be produced according to a method described in a known document such as, for example, US Pat. No. 5,073,296 and US Pat. No. 5,084,208.
[0069]
In the present invention, commercially available silicon-containing polyvinylpyrrolidone can also be used. Specific examples thereof include, for example, PVP / Si-10 (trade name, manufactured by ISP). PVP / Si-10 is a silicon-containing polyvinylpyrrolidone having a core-shell structure having a core made of polymethylsiloxane and a shell made of polyvinylpyrrolidone.
[0070]
Silicon-containing polyvinylpyrrolidone can be used alone or in combination of two or more.
[0071]
The content of the silicon-containing polyvinylpyrrolidone is not particularly limited, and the material of the substrate to be coated or impregnated, the surface physical properties and ink absorption properties, the presence or absence of other components, the type and content when other components are included, and the obtained recording medium Although it can be appropriately selected from a wide range according to various conditions such as the characteristics of the ink composition to be applied, it is usually 0.1 to 10% by weight, preferably 0.1 to 5% by weight of the total amount of the treatment liquid. If it is less than 0.1% by weight, the effect of the polyvinyl pyrrolidone containing silicon may not be sufficiently exerted. On the other hand, if it exceeds 10% by weight, the increase in viscosity may be large.
[0072]
The treatment liquid may contain a polyhydric alcohol in addition to the silicon-containing polyvinylpyrrolidone. By containing a polyhydric alcohol, for example, the permeability of the treatment liquid to the base material and the workability (coating stability) when applying or impregnating the treatment liquid onto the base material are improved, and the silicon-containing polyvinylpyrrolidone is used as the base material. It can be uniformly dispersed on the surface and inside. Examples of the polyhydric alcohol include glycerin, 1,2,6-hexanetriol, and 1,2-hexanediol. The polyhydric alcohols can be used each alone or two or more of them can be used in combination.
[0073]
Further, the treatment liquid may contain a nonionic surfactant. By including a nonionic surfactant, for example, the permeability and workability of the treatment liquid to the substrate can be further improved. As the nonionic surfactant, the aforementioned nonionic surfactant can be used. As the nonionic surfactant, one type can be used alone, or two or more types can be used in combination.
[0074]
For the treatment liquid, for example, an appropriate amount of each of silicon-containing polyvinylpyrrolidone and, if necessary, a polyhydric alcohol and a nonionic surfactant is used, and the total amount is adjusted to 100% by weight with water. Can be produced by mixing according to the method described above. For the mixing, for example, the aforementioned disperser and mixer can be used.
[0075]
When applying the treatment liquid to the surface of the substrate, a known method for applying the liquid component to the surface of the solid can be employed. Specific examples of the method include a brush coating method, a roll coater method, a blade coater method, an air knife coater method, a bar coater method, a size press method, a spray coat method, a gravure coater method, and a curtain coater method. The components of the treatment liquid applied to the surface of the substrate are spread and held on the surface of the substrate and / or permeate and held inside the substrate. The application amount of the treatment liquid to the substrate is not particularly limited, and is applied to the content of the silicon-containing polyvinylpyrrolidone as an active ingredient, the material and characteristics of the substrate (surface properties, ink absorption characteristics, and the like), and the obtained recording medium. Although it can be appropriately selected from a wide range according to various conditions such as characteristics of the ink composition, it is usually 0.1 to 30 g / m 2.², Preferably 0.5 to 20 g / m²It is.
[0076]
Alternatively, the substrate may be immersed in the treatment liquid. The immersion amount may be the same as the above-mentioned application amount.
[0077]
The drying of the substrate coated or impregnated with the treatment liquid is usually performed at a temperature of 5 to 40 ° C., and is completed in about 3 minutes or less.
[0078]
A recording image is formed on the recording medium thus obtained using the ink composition of the present invention.
[0079]
(Image forming method and recorded image)
The image forming method of the present invention is a method of forming a recorded image by discharging droplets of an ink composition onto a recording medium by an ink jet method. The recording medium has a silicon-containing polyvinyl on its surface and / or inside. A recording medium holding pyrrolidone is used, and the ink composition or the ink set of the present invention is used for the ink composition.
[0080]
The inkjet method is not particularly limited, and a known method can be employed. Examples of the method include a method using a piezoelectric element, a method in which ink is ejected by applying pressure to ink, and a method in which bubbles are generated by using a film boiling phenomenon to eject ink. Among these, a method using a piezoelectric element and a method using a film boiling phenomenon are preferable.
[0081]
With this image forming method, a recorded image having high image quality can be obtained.
[0082]
[Ink head]
FIG. 1 is an exploded perspective view showing a simplified configuration of the ink head 1 of the present invention, and FIG. 2 is an enlarged view showing a part of the configuration of a head plate 10 constituting the ink head 1 shown in FIG. It is. 1, the drive electrode 13 shown in FIG. 2 is not shown and is omitted.
[0083]
The ink head 1 includes a head plate 10 having a flat bottom wall 11 made of a piezoelectric material and a plurality of partition walls 12 formed so as to stand upright at predetermined intervals from the bottom wall 11. The top plate 20 provided in contact with the upper surface of the portion 12, the nozzle plate 30 provided with a plurality of discharge ports 31 and provided at one end 11a of the bottom wall portion 11, and the other end portion 11b of the bottom wall portion 11 It is configured to include a rear plate (not shown) provided and an ink tank 50 having an opening 51 provided in contact with the upper surface of the top plate 20. The plurality of partition walls 12 extend vertically from one end to the other end on the bottom wall 11 and are arranged in parallel with each other. The plurality of partition walls 12, the bottom wall 11, the top plate 20, and the nozzle A plurality of ink chambers 40 are formed by the plate 30 and a back plate (not shown). An ink supply path 21 communicating with each ink chamber 40 and an ink supply pipe 22 connecting the ink supply path 21 and the opening 51 of the ink tank 50 are formed in the top plate 20. The ink composition 60 of the present invention is stored in the ink tank 50, and the ink composition 60 flows through the ink supply path 21 and is supplied to each ink chamber 40.
[0084]
As shown in FIG. 2, a drive electrode 13 for applying a voltage to the plurality of partition walls 12 is provided on the bottom wall 11 of the head plate 10 and the surface of the plurality of partition walls 12 facing the ink chamber 40. Further, the piezoelectric material forming the plurality of partition portions 12 is polarized in the direction of arrow 70, and the plurality of partition portions 12 function as piezoelectric elements.
[0085]
The ink head 1 is a piezo-type ink head that can discharge droplets of the ink composition 60 from the discharge ports 31 according to the voltage applied to the plurality of partition walls 12 that are piezoelectric elements.
[0086]
The operation of discharging the ink composition 60 from the ink chamber 40 in the ink head 1 will be described with reference to FIG. FIG. 3 is a cross-sectional view of the ink head 1 shown in FIG. Here, the operation of discharging the ink composition 60 from the ink chamber 40b will be described.
[0087]
When no voltage is applied to the partition portions 12a, 12b constituting the ink chamber 40b, that is, between the drive electrode 13b of the ink chamber 40b and the drive electrode 13a of the ink chamber 40a adjacent to the ink chamber 40b, and between the ink chamber 40b When no potential difference occurs between the drive electrode 13b of the ink chamber 40b and the drive electrode 13c of the ink chamber 40c adjacent to the ink chamber 40b, the ink composition 60 supplied from the ink tank 50 by the capillary action is supplied to the ink chamber 40b. Is filled. Similarly, the ink chambers 40 a and 40 c are also filled with the ink composition 60.
[0088]
When a voltage is applied to the drive electrodes 13a and 13c, a potential difference is generated between the drive electrode 13b and the drive electrode 13a and between the drive electrode 13b and the drive electrode 13c, so that the partition walls 12a and 13c forming the ink chamber 40b are formed. A voltage is applied to 12b. This voltage application generates an electric field in the directions of arrows 71 and 72 on the partition portions 12a and 12b, respectively, and the action of the electric field causes distortion in the partition portions 12a and 12b of the ink chamber 40b, so that the ink chamber 40b is moved toward the ink chamber 40b. Deform to be convex. As a result, a pressure wave is generated, a large pressure is applied to the ink composition 60 in the ink chamber 40b, and droplets of the ink composition 60 are ejected from the ejection port 31.
[0089]
When the application of the voltage to the drive electrodes 13a and 13c is stopped, the shape of the partition walls 12a and 12b returns to the original shape, and the volume of the ink chamber 40b returns to the original volume. The ink chamber 40 b is supplied from the ink tank 50 via the ink tank 21, and returns to the initial state where the ink composition 60 is filled.
[0090]
In the ink head 1, the ink tank 50 stores the ink composition 60 of the present invention, and the ink composition 60 is supplied to the ink chamber 40 and ejected from the ejection port 31 as droplets. , A droplet of the ink composition 60 can be ejected.
[0091]
When recording is performed using the ink composition of the present invention in a piezo-type inkjet recording apparatus including the ink head 1, the wettability to the ink supply system in the ink head is improved, and the ink supply is performed smoothly. Therefore, a highly reliable piezo-type inkjet recording apparatus can be realized.
[0092]
In the present embodiment, the partition 12 forming the ink chamber 40 is formed of a piezoelectric material and functions as a piezoelectric element. However, without being limited to this, the partition forming the ink chamber is formed of a material other than the piezoelectric material. The piezoelectric element may be formed inside or outside the partition.
[0093]
FIG. 4 is an exploded perspective view showing a simplified configuration of the ink head 2 according to the embodiment of the present invention, and FIG. 5 is a plan view showing a part of the configuration of the ink head 2 shown in FIG. In FIG. 5, the top plate 20 and the ink tank 50 shown in FIG. 4 are not shown and are omitted. The ink head 2 is similar to the ink head 1, and corresponding portions are denoted by the same reference numerals and description thereof is omitted.
[0094]
The ink head 2 includes a head plate 100, a substrate 101, a plurality of partition walls 102 that extend vertically from one end to the other end at predetermined intervals on the substrate 101, and are arranged in parallel with each other. It is characterized by comprising a heater 103 which is a heating element provided on the surface of the 101 facing the ink chamber 40, and drive electrodes 104 and 105 for applying a voltage to the heater 103.
[0095]
The ink head 2 is a thermal inkjet type ink head that can discharge droplets of the ink composition 60 from the discharge port 31 in accordance with a voltage applied to the heater 103 as a heating element.
[0096]
The operation of discharging the ink composition 60 from the ink chamber 40 in the ink head 2 will be described. FIG. 6 is a diagram illustrating a state in which droplets 61 of the ink composition 60 are ejected from the ink chamber 40. FIG. 6 shows a cross-sectional configuration of the ink head 2 shown in FIG. 5 taken along section line II.
[0097]
When no voltage is applied to the heater 103, the ink chamber 40 is filled with the ink composition 60 in the same manner as when no voltage is applied to the partition 12 in the ink head 1 described above.
[0098]
When a voltage is applied to the heater 103 by the drive electrodes 104 and 105, the heater 103 generates heat, and the ink composition 60 filled in the ink chamber 40 is heated to generate bubbles 62. As a result, a pressure wave is generated, a large pressure is applied to the ink composition 60 filled in the ink chamber 40, and the droplet 61 of the ink composition 60 is discharged from the discharge port 31.
[0099]
When the application of the voltage to the heater 103 is stopped, the ink composition 60 in the ink chamber 40 is cooled, the bubbles 62 disappear, and the ink composition 60 corresponding to the volume of the disappeared bubbles is supplied through the ink supply path 21. The ink is supplied from the tank 50, and the ink chamber 40 returns to the initial state where the ink composition 60 is filled.
[0100]
In the ink head 2, similarly to the above-described ink head 1, the ink tank 50 stores the ink composition 60 of the present invention, and the ink composition 60 is supplied to the ink chamber 40 and discharged from the discharge port 31 as a droplet 61. Accordingly, the droplets 61 of the ink composition 60 can be stably ejected from the ejection ports 31.
[0101]
In the thermal inkjet type inkjet recording apparatus including the ink head according to the present embodiment, when recording is performed using the ink composition of the present invention, wettability to an ink supply system in the head is improved, and ink supply is improved. Since the printing is performed smoothly, a highly reliable thermal inkjet recording apparatus can be realized.
[0102]
[Example]
Hereinafter, the present invention will be specifically described with reference to Reference Examples, Examples, Comparative Examples, and Test Examples. In the following, “%” means “% by weight” unless otherwise specified.
[0103]
Reference Example 1 (production of recording medium)
Each component was mixed at the ratio (%) shown in Table 1, and water was added thereto to make the total amount 100%. This mixture was stirred at 25 ° C. for 1 hour to prepare a treatment liquid. The obtained treatment liquid was applied to PPC paper (trade name: SF4AM3, manufactured by Sharp Corporation) using a transfer-type rubber roller, and the recording medium No. 1 holding silicon-containing polyvinylpyrrolidone was used. 1 to 5 were produced. 8g / m²Met.
[0104]
In addition, the resin component and surfactant in Table 1 are specifically as follows.
[0105]
(Resin component)
PVP / Si-10: trade name, manufactured by ISP, 20% aqueous solution of polyvinylpyrrolidone containing polymethylsiloxane
[0106]
(Surfactant)
Ethylene oxide-containing compound 1A: a compound having e + f = 10 in the general formula (1), trade name Surfynol 465, manufactured by Nissin Chemical Co., Ltd.
Ethylene oxide-containing compound 1B: a compound having e + f = 3.5 in the general formula (1), trade name Surfynol 440, manufactured by Nissin Chemical Co., Ltd.
Ethylene oxide-containing compound 4A: a compound of the general formula (1) in which w + z = 11, a = 9, b = 5, trade name SOFTANOL EP9050, manufactured by Nippon Shokubai Co., Ltd.
[0107]
[Table 1]

[0108]
Examples 1 to 5 and Comparative Examples 1 to 3 (Preparation of Ink Composition)
Each component was mixed at the ratio (%) shown in Table 2, and water was added thereto to make the total amount 100%. The mixture was stirred at 25 ° C. for 1 hour, filtered under pressure using a 1.2 μm membrane filter, and then degassed to prepare ink compositions of the present invention and comparative examples.
[0109]
In Table 2, the surfactants and fixing agents described by trade names are specifically as follows.
[0110]
[Fixing agent]
Vylonal MD1400: polyester emulsion, manufactured by Toyobo Co., Ltd.
[0111]
[Surfactant]
Surfynol 2502, Surfynol 465: both acetylene-based nonionic surfactants containing ethylene oxide, manufactured by Air Products
[0112]
Test example 1
The following evaluation tests were performed on the ink compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 5. Table 2 shows the results.
[0113]
[High-speed printability]
Using a printer in which the ink head of an inkjet printer (trade name: AJ2000, manufactured by Sharp Corporation) is replaced with the ink head of the present invention, printing is continuously performed at a print density of 5% and 10 PPM (10 sheets / min). The number of sheets on which a recorded image having good image quality can be printed was examined. When the number of printed sheets exceeded 200, the result was evaluated as “○”, when the number of printed sheets was 150 to 200, the result was evaluated as “△”, and when the number was less than 150, the result was evaluated as “x”.
[0114]
[Dryability]
Immediately after printing was completed, the same paper as the printing paper was pressed against the printing surface for 15 seconds, and those that did not transfer the printing were evaluated as “O”, and those that transferred were evaluated as “X”.
[0115]
[Smearability]
After printing a specific pattern on PPC paper (trade name: SF4AM3, manufactured by Sharp Corporation) and leaving it for one day, measure the line width of the pattern. The evaluation was performed as a value. Those with less than 150 were evaluated as “「 ”, those with 150 to 250 as“ Δ ”, and those with more than 250 as“ x ”.
[0116]
[Foaming property]
After the ink composition was shaken for 20 seconds and allowed to stand for 5 minutes, the bubble height was measured, and those having a height of 10 mm or less were evaluated as "O" and those exceeding 10 mm were evaluated as "X". The higher the foam height, the higher the foamability. The ink composition having a high foaming property generates bubbles in the discharge nozzle, and the nozzle bites the bubbles, so that the amount of discharged droplets is likely to change. An ink composition having a high foaming property has low ejection stability and cannot be used for high-speed printing.
[0117]
[Table 2]

[0118]
Table 2 shows that the ink composition of the present invention is an ink that can be sufficiently printed by an ink jet printer.
[0119]
Test example 2
Using the ink compositions of Examples 1, 3, 4, 6 and Comparative Example 4, the same ink jet printer as in Test Example 1 was used to record the recording medium No. of Reference Example 1. Recording images (solid images or test patterns) were printed on Nos. 1 to 5. The following evaluation test was performed on the obtained recorded image. Table 3 shows the results.
[0120]
[Print density]
The print density (image density) of the solid image was measured by a colorimeter (trade name: X-Rite938, manufactured by Macbeth). Compared with the print density of the PPC paper (SF4AM3) to which the processing liquid was not applied, the print density was evaluated as “○”, the print density was evaluated as “△”, and the print density was evaluated as “X” when the print density was lowered.
[0121]
[Feathering]
The line width of the test pattern was measured, and the line width of the test pattern formed on PPC paper (SF4AM3) to which the processing liquid was not applied was set to 100, and evaluation was made as a relative value to the line width. Those with less than 100 were evaluated as “「 ”, those with 100 to 120 were evaluated as“ Δ ”, and those with 120 or more were evaluated as“ x ”.
[0122]
[Table 3]

[0123]
From Table 3, the recording medium holding the silicon-containing polyvinylpyrrolidone by the ink jet method contains the specific pigment, the water-soluble organic solvent, the surfactant, and the fixing agent, and the balance is water. It is clear that when a recorded image is formed, feathering is significantly prevented, and a recorded image with high print density can be obtained.
[0124]
Test example 3
From the ink compositions of Examples 1 to 5 and the ink compositions of Comparative Examples 1 to 3, a cyan ink, a magenta ink and a yellow ink were selected in combinations shown in Table 4, and the same ink jet printer as in Test Example 1 was used. The recording medium No. of Example 1 was used. 1 was printed with three-color black at a printing ratio of 1: 1: 1.
[0125]
On the other hand, using the ink composition of Example 6, the recording medium No. 1 was printed.
[0126]
Three color black and black single color printing are applied to a colorimeter (X-Rite 938), and a^*And b^*Was measured. Three color black a^*To A2, b^*Is B2, black monochromatic a^*To A1, b^*Is B1, the value represented by the following equation (Δa^*b^*) Was 20 or less as “○”, and those larger than 20 were evaluated as “x”. Table 2 shows the results.
Δa^*b^*= ｛(A1-A2)²+ (B1-B2)²｝^1/2
[0127]
[Table 4]

[0128]
From Table 4, No. 3 obtained by superposing three types of ink compositions selected from Examples 1 to 5 was obtained. The black images of Nos. 1 to 2 were obtained by superposing the three types of ink compositions of Comparative Examples 1 to 3 on each other. It can be seen that the black image has a higher image density than the black image of E. That is, it can be seen that the four ink sets of the present invention have better black reproducibility and better color balance than the ink set of the comparative example.
[0129]
As described above, C.I. I. A cyan ink composition containing at least one pigment selected from the group consisting of C.I. Pigment Blue 15: 3 and 15: 4; I. Pigment Red 122, 209 and C.I. I. Pigment Violet 19, a magenta ink composition containing at least one pigment selected from the group consisting of C.I. I. It can be seen that an ink set having an excellent color balance can be obtained by combining with a yellow ink composition containing at least one pigment selected from the group consisting of CI Pigment Yellow 74, 138, 150 and 180.
[0130]
【The invention's effect】
According to the present invention, a pigment, preferably an aqueous ink containing a self-dispersed pigment, is used to form an image on a recording medium holding silicon-containing polyvinylpyrrolidone on the surface and / or inside by an inkjet method, whereby the pigment containing silicon is contained. It is fixed by reacting with polyvinylpyrrolidone, and prevents the pigment from being unnecessarily diffused on the surface of the recording medium together with liquid components such as water in the ink, so that bleeding (especially feathering), color mixing, Without generating shading, etc., the outline is clear, the image density and sharpness are high, a high quality image can be formed, and even if high speed printing is performed, the same high quality image as described above can be formed. An ink composition that can be formed is provided.
[0131]
According to the present invention, by adding a water-soluble organic solvent, among them, a specific one to the ink composition, foaming and drying of the ink composition in the discharge nozzle are prevented, and the discharge stability is further improved. , High-speed printing can be easily performed. Further, the ink composition can be imparted with appropriate permeability to a recording medium.
[0132]
According to the present invention, by adding a specific nonionic surfactant to the ink composition, foaming and drying in the discharge nozzle are more unlikely to occur, and stable inkjet recording can be performed. The resulting ink composition is obtained.
[0133]
According to the present invention, a cyan ink composition containing a specific cyan pigment, a magenta ink composition containing a specific magenta pigment, a yellow ink composition containing a specific yellow pigment, and a black ink containing a specific black pigment An ink composition and an ink set composed of two or more types selected from the above four types of color ink compositions are obtained. When an image is formed on a recording medium in which silicon-containing polyvinylpyrrolidone is held on the surface and / or inside using each of the four types of color ink compositions, a clear, high-density cyan, magenta, yellow, or black color is obtained. A recorded image is obtained. When the ink set is used, a recorded image in which each color image is clear, has a high image density, and has a very good color balance can be obtained.
[0134]
According to the present invention, an image is formed on a recording medium having silicon-containing polyvinylpyrrolidone on its surface and / or inside by using an ink jet method by using any one of the ink compositions described above. Thus, a high-quality recorded image can be obtained.
[0135]
According to the present invention, there is provided a piezo-type or bubble-type ink-jet ink head that can continuously and stably discharge the ink composition of the present invention and can easily perform high-speed printing. You.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a simplified configuration of an ink head of the present invention.
FIG. 2 is an enlarged view showing a part of a configuration of a head plate constituting the ink head shown in FIG. 1;
FIG. 3 is a sectional view of the ink head shown in FIG. 1 as viewed from an extending direction of an ink chamber.
FIG. 4 is an exploded perspective view showing a simplified configuration of the ink head of the present invention.
FIG. 5 is a plan view showing a part of the configuration of the ink head shown in FIG. 4;
6 is a diagram showing a state in which droplets of an ink composition are ejected from an ink chamber, and shows a cross-sectional configuration taken along a cutting plane line II of the ink head shown in FIG. 5;
[Explanation of symbols]
1, 2 ink head
10,100 head plate
11 Bottom wall
11a One end
11b The other end
12, 12a, 12b Partition wall
13, 13a, 13b, 13c, 104, 105 Driving electrode
20 Top plate
21 Ink supply path
30 Nozzle plate
31 Discharge port
40, 40a, 40b, 40c Ink chamber
50 ink tank
51 Opening
60 Ink composition
61 droplet
62 bubbles
70, 71, 72 Arrow
101 substrate
102 partition wall
103 heater

Claims (16)

A water-based ink for forming a recorded image on a recording medium holding polyvinylpyrrolidone containing silicon on its surface and / or inside, wherein the ink contains a pigment as a coloring material and the balance is water. Composition. The ink composition according to claim 1, wherein the pigment is a self-dispersed pigment having a hydrophilic group introduced into the surface of the pigment. 3. The ink composition according to claim 1, further comprising one or more selected from water-soluble organic solvents. The ink composition according to claim 3, wherein the water-soluble organic solvent is a glycol ether and / or a polyhydric alcohol. The ink composition according to claim 3, wherein the water-soluble organic solvent is a water-soluble organic solvent having a saturated vapor pressure at 20 ° C. of 6.6665 Pa or less. The ink composition according to any one of claims 1 to 5, further comprising one or more selected from nonionic surfactants. The ink composition according to claim 6, wherein the nonionic surfactant is a compound having an acetylene group. The pigment includes one or more cyan pigments selected from Pigment Blue 15: 3, Pigment Blue 15: 4, and Pigment Blue 15: 6. Ink composition. The ink composition according to any one of claims 1 to 7, wherein the pigment includes one or more magenta pigments selected from Pigment Red 122, Pigment Red 209, and Pigment Violet 19. The pigment according to any one of claims 1 to 7, wherein the pigment contains one or more yellow pigments selected from Pigment Yellow 74, Pigment Yellow 128, Pigment Yellow 138, Pigment Yellow 150, and Pigment Yellow 180. 3. The ink composition according to claim 1. The ink composition according to any one of claims 1 to 7, wherein the pigment contains carbon black. An ink set comprising two or more selected from the ink composition according to claim 8, the ink composition according to claim 9, the ink composition according to claim 10, and the ink composition according to claim 11. A method of forming an image on a recording medium by discharging droplets of the ink composition by an ink jet method onto a recording medium having polyvinylpyrrolidone containing silicon on its surface and / or inside, the method comprising forming an image on the recording medium. An image forming method, comprising: the ink composition according to any one of claims 1 to 11 or the ink set according to claim 12. A recorded image formed on a recording medium by the image forming method according to claim 13. An ink tank for storing the ink composition according to any one of claims 1 to 11 or the ink set according to claim 12,
An ink chamber having an ejection port for ejecting droplets of the ink composition or the ink set, and an ink chamber to which the ink composition or the ink set is supplied from the ink tank;
A piezoelectric element that generates strain in response to an applied voltage,
A piezoelectric element provided in at least a part of the ink chamber and applying pressure to the ink composition or the ink set contained in the ink chamber,
An electrode provided for applying a voltage to the piezoelectric element. An ink tank for storing the ink composition according to any one of claims 1 to 11 or the ink set according to claim 12,
An ink chamber to which the ink composition or the ink set is supplied from the ink tank, the ink chamber having an ejection port for ejecting droplets of the ink composition or the ink set, and the ink chamber is provided in at least a part of the ink chamber; A heating element for applying pressure to the ink composition or the ink set by heating the ink composition or the ink set contained in the ink chamber to generate air bubbles;
An electrode provided for applying a voltage to the heating element.

Images