JP2004351643A - Inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording method using an active ray curing ink excellent in bleeding resistance, curing property, adhesion with a base material and crease resistance even in a variety of temperature and humidity environments. <P>SOLUTION: The inkjet recording method heats and jets an ink containing a photopolymerization compound onto a base material by an inkjet system, cures the ink within 1.0 second of impact on the base material by irradiating the ink with active light, and setting time of 0.05 seconds or longer and 5.0 seconds or shorter is required for curing of the impact ink. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００５１】
一般式（１）において、Ｒ^１は水素原子やメチル基、エチル基、プロピル基、ブチル基等の炭素数１〜６のアルキル基、炭素数１〜６のフルオロアルキル基、アリル基、アリール基、フリル基またはチエニル基である。Ｒ^２は、メチル基、エチル基、プロピル基、ブチル基等の炭素数１〜６個のアルキル基、１−プロペニル基、２−プロペニル基、２−メチル−１−プロペニル基、２−メチル−２−プロペニル基、１−ブテニル基、２−ブテニル基、３−ブテニル基等の炭素数２〜６個のアルケニル基、フェニル基、ベンジル基、フルオロベンジル基、メトキシベンジル基、フェノキシエチル基等の芳香環を有する基、エチルカルボニル基、プロピルカルボニル基、ブチルカルボニル基等の炭素数２〜６個のアルキルカルボニル基、エトキシカルボニル基、プロポキシカルボニル基、ブトキシカルボニル基等の炭素数２〜６個のアルコキシカルボニル基、またはエチルカルバモイル基、プロピルカルバモイル基、ブチルカルバモイル基、ペンチルカルバモイル基等の炭素数２〜６個のＮ−アルキルカルバモイル基等である。本発明で使用するオキセタン化合物としては、１個のオキセタン環を有する化合物を使用することが、得られる組成物が粘着性に優れ、低粘度で作業性に優れるため、特に好ましい。
【００５２】
２個のオキセタン環を有する化合物の一例としては、下記一般式（２）で示される化合物等が挙げられる。
【００５３】
【化２】

【００５４】
一般式（２）において、Ｒ^１は、上記一般式（１）におけるそれと同様の基である。Ｒ^３は、例えば、エチレン基、プロピレン基、ブチレン基等の線状または分枝状アルキレン基、ポリ（エチレンオキシ）基、ポリ（プロピレンオキシ）基等の線状または分枝状ポリ（アルキレンオキシ）基、プロペニレン基、メチルプロペニレン基、ブテニレン基等の線状または分枝状不飽和炭化水素基、またはカルボニル基またはカルボニル基を含むアルキレン基、カルボキシル基を含むアルキレン基、カルバモイル基を含むアルキレン基等である。
【００５５】
また、Ｒ^３としては、下記一般式（３）、（４）及び（５）で示される基から選択される多価基も挙げることができる。
【００５６】
【化３】

【００５７】
一般式（３）において、Ｒ^４は、水素原子やメチル基、エチル基、プロピル基、ブチル基等の炭素数１〜４個のアルキル基、メトキシ基、エトキシ基、プロポキシ基、ブトキシ基等の炭素数１〜４個のアルコキシ基、塩素原子、臭素原子等のハロゲン原子、ニトロ基、シアノ基、メルカプト基、低級アルコキシカルボニル基、カルボキシル基、またはカルバモイル基である。
【００５８】
【化４】

【００５９】
一般式（４）において、Ｒ^５は、酸素原子、硫黄原子、メチレン基、ＮＨ、ＳＯ、ＳＯ_２、Ｃ（ＣＦ_３）_２、又はＣ（ＣＨ_３）_２を表す。
【００６０】
【化５】

【００６１】
一般式（５）において、Ｒ^６は、メチル基、エチル基、プロピル基、ブチル基等の炭素数１〜４個のアルキル基、またはアリール基である。ｎは０〜２０００の整数である。Ｒ^７はメチル基、エチル基、プロピル基、ブチル基の炭素数１〜４個のアルキル基、またはアリール基である。Ｒ^７としては、更に、下記一般式（６）で示される基から選択される基も挙げることができる。
【００６２】
【化６】

【００６３】
一般式（６）において、Ｒ^８は、メチル基、エチル基、プロピル基、ブチル基等の炭素数１〜４個のアルキル基、またはアリール基である。ｍは０〜１００の整数である。
【００６４】
２個のオキセタン環を有する化合物の具体例としては、下記化合物が挙げられる。
【００６５】
【化７】

【００６６】
例示化合物１は、前記一般式（２）において、Ｒ^１がエチル基、Ｒ^３がカルボキシル基である化合物である。また、例示化合物２は、前記一般式（２）において、Ｒ^１がエチル基、Ｒ^３が前記一般式（５）でＲ^６及びＲ^７がメチル基、ｎが１である化合物である。
【００６７】
２個のオキセタン環を有する化合物において、上記の化合物以外の好ましい例としては、下記一般式（７）で示される化合物がある。一般式（７）において、Ｒ^１は、前記一般式（１）のＲ^１と同義である。
【００６８】
【化８】

【００６９】
また、３〜４個のオキセタン環を有する化合物の一例としては、下記一般式（８）で示される化合物が挙げられる。
【００７０】
【化９】

【００７１】
一般式（８）において、Ｒ^１は、前記一般式（１）におけるＲ^１と同義である。Ｒ^９としては、例えば、下記Ａ〜Ｃで示される基等の炭素数１〜１２の分枝状アルキレン基、下記Ｄで示される基等の分枝状ポリ（アルキレンオキシ）基又は下記Ｅで示される基等の分枝状ポリシロキシ基等が挙げられる。ｊは、３又は４である。
【００７２】
【化１０】

【００７３】
上記Ａにおいて、Ｒ^１０はメチル基、エチル基又はプロピル基等の低級アルキル基である。また、上記Ｄにおいて、ｐは１〜１０の整数である。
【００７４】
３〜４個のオキセタン環を有する化合物の一例としては、例示化合物３が挙げられる。
【００７５】
【化１１】

【００７６】
さらに、上記説明した以外の１〜４個のオキセタン環を有する化合物の例としては、下記一般式（９）で示される化合物が挙げられる。
【００７７】
【化１２】

【００７８】
一般式（９）において、Ｒ^８は前記一般式（６）のＲ^８と同義である。Ｒ^１１はメチル基、エチル基、プロピル基又はブチル基等の炭素数１〜４のアルキル基又はトリアルキルシリル基であり、ｒは１〜４である。
【００７９】
本発明で使用するオキセタン化合物の好ましい具体例としては、以下に示す化合物がある。
【００８０】
【化１３】

【００８１】
上述したオキセタン環を有する各化合物の製造方法は、特に限定されず、従来知られた方法に従えばよく、例えば、パティソン（Ｄ．Ｂ．Ｐａｔｔｉｓｏｎ，Ｊ．Ａｍ．Ｃｈｅｍ．Ｓｏｃ．，３４５５，７９（１９５７））が開示している、ジオールからのオキセタン環合成法等がある。また、これら以外にも、分子量１０００〜５０００程度の高分子量を有する１〜４個のオキセタン環を有する化合物も挙げられる。これらの具体的化合物例としては、以下の化合物が挙げられる。
【００８２】
【化１４】

【００８３】
本発明に係る光重合性化合物として、上記説明したラジカル重合性化合物あるいはカチオ重合性化合物のいずれも用いることができるが、紫外線の照射強度（ｍＷ）を変更しても、硬化感度が変動しにくい、すなわち照度不軌の小さい化合物好ましく、この観点では、酸素により重合阻害を受けるラジカル重合性化合物よりも、カチオン重合性化合物の方がより好ましい。特に、インク液滴サイズの小さなインクジェット記録システムでは、小点の硬化性がラジカル重合性化合物よりも、カチオン重合性化合物の方が良好であり、好ましい。
【００８４】
本発明においては、インク中に、光重合開始剤及び光酸発生剤の少なくとも１つを含有することが好ましい。
【００８５】
本発明においては、硬化反応をより効率的に行なうために、公知の光重合開始剤を添加して硬化させることが好ましい。光重合開始剤としては、分子内結合開裂型と分子内水素引き抜き型の２種に大別できる。
【００８６】
分子内結合開裂型の光重合開始剤としては、例えば、ジエトキシアセトフェノン、２−ヒドロキシ−２−メチル−１−フェニルプロパン−１−オン、ベンジルジメチルケタール、１−（４−イソプロピルフェニル）−２−ヒドロキシ−２−メチルプロパン−１−オン、４−（２−ヒドロキシエトキシ）フェニル−（２−ヒドロキシ−２−プロピル）ケトン、１−ヒドロキシシクロヘキシル−フェニルケトン、２−メチル−２−モルホリノ（４−チオメチルフェニル）プロパン−１−オン、２−ベンジル−２−ジメチルアミノ−１−（４−モルホリノフェニル）−ブタノンの如きアセトフェノン系；ベンゾイン、ベンゾインメチルエーテル、ベンゾインイソプロピルエーテルの如きベンゾイン類；２，４，６−トリメチルベンゾインジフェニルホスフィンオキシドの如きアシルホスフィンオキシド系；ベンジル、メチルフェニルグリオキシエステル、などが挙げられる。
【００８７】
一方、分子内水素引き抜き型の光重合開始剤としては、例えば、ベンゾフェノン、ｏ−ベンゾイル安息香酸メチル−４−フェニルベンゾフェノン、４，４′−ジクロロベンゾフェノン、ヒドロキシベンゾフェノン、４−ベンゾイル−４′−メチル−ジフェニルサルファイド、アクリル化ベンゾフェノン、３，３′，４，４′−テトラ（ｔ−ブチルペルオキシカルボニル）ベンゾフェノン、３，３′−ジメチル−４−メトキシベンゾフェノンの如きベンゾフェノン系；２−イソプロピルチオキサントン、２，４−ジメチルチオキサントン、２，４−ジエチルチオキサントン、２，４−ジクロロチオキサントンの如きチオキサントン系；ミヒラ−ケトン、４，４′−ジエチルアミノベンゾフェノンの如きアミノベンゾフェノン系；１０−ブチル−２−クロロアクリドン、２−エチルアンスラキノン、９，１０−フェナンスレンキノン、カンファーキノン、などが挙げられる。光重合開始剤を使用する場合の配合量は、活性光線硬化性組成物の０．０１〜１０．００質量％の範囲が好ましい。
【００８８】
カチオン重合開始剤としては、例えば、化学増幅型フォトレジストや光カチオン重合に利用される化合物が用いられる（有機エレクトロニクス材料研究会編、「イメージング用有機材料」、ぶんしん出版（１９９３年）、１８７〜１９２ページ参照）。本発明に好適な化合物の例を以下に挙げる。
【００８９】
第１に、ジアゾニウム、アンモニウム、ヨードニウム、スルホニウム、ホスホニウムなどの芳香族オニウム化合物のＢ（Ｃ_６Ｆ_５）_４ ⁻、ＰＦ_６ ⁻、ＡｓＦ_６ ⁻、ＳｂＦ_６ ⁻、ＣＦ_３ＳＯ_３ ⁻塩を挙げることができる。
【００９０】
本発明で用いることのできるオニウム化合物の具体的な例を、以下に示す。
【００９１】
【化１５】

【００９２】
第２に、スルホン酸を発生するスルホン化物を挙げることができ、その具体的な化合物を、以下に例示する。
【００９３】
【化１６】

【００９４】
第３に、ハロゲン化水素を光発生するハロゲン化物も用いることができ、以下にその具体的な化合物を例示する。
【００９５】
【化１７】

【００９６】
第４に、鉄アレン錯体を挙げることができる。
【００９７】
【化１８】

【００９８】
また、本発明に係るインク組成物は、紫外線の照射により硬化するが、硬化反応をより効率的に行なうために、光増感剤を併用することもできる。そのような光増感剤としては、例えば、トリエタノールアミン、メチルジエタノールアミン、トリイソプロパノールアミン、４−ジメチルアミノ安息香酸メチル、４−ジメチルアミノ安息香酸エチル、４−ジメチルアミノ安息香酸イソアミル、安息香酸（２−ジメチルアミノ）エチル、４−ジメチルアミノ安息香酸（ｎ−ブトキシ）エチル、４−ジメチルアミノ安息香酸２−エチルヘキシルの如きアミン類、シアニン、フタロシアニン、メロシアニン、ポルフィリン、スピロ化合物、フェロセン、フルオレン、フルギド、イミダゾール、ペリレン、フェナジン、フェノチアジン、ポリエン、アゾ化合物、ジフェニルメタン、トリフェニルメタン、ポリメチンアクリジン、クマリン、ケトクマリン、キナクリドン、インジゴ、スチリル、ピリリウム化合物、ピロメテン化合物、ピラゾロトリアゾール化合物、ベンゾチアゾール化合物、バルビツール酸誘導体、チオバルビツール酸誘導体等が挙げられ、更に、欧州特許第５６８，９９３号、米国特許第４，５０８，８１１号、同第５，２２７，２２７号、特開２００１−１２５２５５号、特開平１１−２７１９６９号等に記載の化合物も用いられる。光増感剤の使用量は、活性光線硬化性組成物中０．０１〜１０．００質量％の範囲が好ましい。
【００９９】
本発明に係るインクでは、着色剤としては、重合性化合物の主成分に溶解または分散できる各種色材を使用することができるが、耐候性の観点から顔料が好ましい。
【０１００】
本発明のインクジェットインクに用いることのできる顔料としては、カーボンブラック、酸化チタン、炭酸カルシウム等の無彩色無機顔料または有彩色の有機顔料を使用することができる。有機顔料としては、例えば、トルイジンレッド、トルイジンマルーン、ハンザイエロー、ベンジジンイエロー、ピラゾロンレッドなどの不溶性アゾ顔料、リトールレッド、ヘリオボルドー、ピグメントスカーレット、パーマネントレッド２Ｂなどの溶性アゾ顔料、アリザリン、インダントロン、チオインジゴマルーンなどの建染染料からの誘導体、フタロシアニンブルー、フタロシアニングリーンなどのフタロシアニン系有機顔料、キナクリドンレッド、キナクリドンマゼンタなどのキナクリドン系有機顔料、ペリレンレッド、ペリレンスカーレットなどのペリレン系有機顔料、イソインドリノンイエロー、イソインドリノンオレンジなどのイソインドリノン系有機顔料、ピランスロンレッド、ピランスロンオレンジなどのピランスロン系有機顔料、チオインジゴ系有機顔料、縮合アゾ系有機顔料、ベンズイミダゾロン系有機顔料、キノフタロンイエローなどのキノフタロン系有機顔料、イソインドリンイエローなどのイソインドリン系有機顔料、その他の顔料として、フラバンスロンイエロー、アシルアミドイエロー、ニッケルアゾイエロー、銅アゾメチンイエロー、ペリノンオレンジ、アンスロンオレンジ、ジアンスラキノニルレッド、ジオキサジンバイオレット等が挙げられる。
【０１０１】
有機顔料をカラーインデックス（Ｃ．Ｉ．）ナンバーで例示すると、Ｃ．Ｉ．ピグメントイエロー１２、１３、１４、１７、２０、２４、７４、８３、８６、９３、１０９、１１０、１１７、１２５、１２８、１２９、１３７、１３８、１３９、１４７、１４８、１５０、１５１、１５３、１５４、１５５、１６６、１６８、１８０、１８５、Ｃ．Ｉ．ピグメントオレンジ１６、３６、４３、５１、５５、５９、６１、Ｃ．Ｉ．ピグメントレッド９、４８、４９、５２、５３、５７、９７、１２２、１２３、１４６、１４９、１６８、１７７、１８０、１９２、２０２、２０６、２１５、２１６、２１７、２２０、２２３、２２４、２２６、２２７、２２８、２３８、２４０、Ｃ．Ｉ．ピグメントバイオレット１９、２３、２９、３０、３７、４０、５０、Ｃ．Ｉ．ピグメントブルー１５、１５：１、１５：３、１５：４、１５：６、２２、６０、６４、Ｃ．Ｉ．ピグメントグリーン７、３６、Ｃ．Ｉ．ピグメントブラウン２３、２５、２６等が挙げられる。
【０１０２】
上記顔料の中で、キナクリドン系有機顔料、フタロシアニン系有機顔料、ベンズイミダゾロン系有機顔料、イソインドリノン系有機顔料、縮合アゾ系有機顔料、キノフタロン系有機顔料、イソインドリン系有機顔料等は耐光性が優れているため好ましい。
【０１０３】
上記顔料の分散には、例えば、ボールミル、サンドミル、アトライター、ロールミル、アジテータ、ヘンシェルミキサ、コロイドミル、超音波ホモジナイザー、パールミル、湿式ジェットミル、ペイントシェーカー等を用いることができる。また、顔料の分散を行う際に、分散剤を添加することも可能である。分散剤としては、高分子分散剤を用いることが好ましく、高分子分散剤としては、例えば、Ａｖｅｃｉａ社のＳｏｌｓｐｅｒｓｅシリーズや、味の素ファインテクノ社のＰＢシリーズが挙げられる。また、分散助剤として、各種顔料に応じたシナージストを用いることも可能である。これらの分散剤および分散助剤は、顔料１００質量部に対し、１〜５０質量部添加することが好ましい。分散媒体は、溶剤または重合性化合物を用いて行うが、本発明の照射線硬化型インクでは、インク着弾直後に反応・硬化させるため、無溶剤であることが好ましい。溶剤が硬化画像に残ってしまうと、耐溶剤性の劣化、残留する溶剤のＶＯＣの問題が生じる。よって、分散媒体は溶剤では無く重合性化合物、その中でも最も粘度の低いモノマーを選択することが分散適性上好ましい。
【０１０４】
顔料の分散は、顔料粒子の平均粒径を０．０８〜０．５μｍとすることが好ましく、最大粒径は０．３〜１０μｍ、好ましくは０．３〜３μｍとなるよう、顔料、分散剤、分散媒体の選定、分散条件、ろ過条件を適宜設定することが好ましい。この粒径管理によって、ヘッドノズルの詰まりを抑制し、インクの保存安定性、インク透明性および硬化感度を維持することができる。本発明のインクにおいては、色材濃度としては、インク全体の１質量％乃至１０質量％であることが好ましい。
【０１０５】
本発明に係るインクには、上記説明した以外に様々な添加剤を用いることができる。例えば、レベリング添加剤、マット剤、膜物性を調整するためのポリエステル系樹脂、ポリウレタン系樹脂、ビニル系樹脂、アクリル系樹脂、ゴム系樹脂、ワックス類を添加することができる。また、保存安定性を改良する目的で、公知のあらゆる塩基性化合物を用いることができるが、代表的なものとして、塩基性アルカリ金属化合物、塩基性アルカリ土類金属化合物、アミンなどの塩基性有機化合物などがあげられる。また、ラジカル重合性モノマーと開始剤を組み合わせ、ラジカル・カチオンのハイブリッド型硬化インクとすることも可能である。
【０１０６】
本発明のインクジェット記録方法で用いることのできる基材としては、通常の非コート紙、コート紙などの他、いわゆる軟包装に用いられる各種非吸収性のプラスチックおよびそのフィルムを用いることができ、各種プラスチックフィルムとしては、例えば、ポリエチレンテレフタレート（ＰＥＴ）フィルム、延伸ポリスチレン（ＯＰＳ）フィルム、延伸ポリプロピレン（ＯＰＰ）フィルム、延伸ナイロン（ＯＮｙ）フィルム、ポリ塩化ビニル（ＰＶＣ）フィルム、ポリエチレン（ＰＥ）フィルム、トリアセチルセルロース（ＴＡＣ）フィルム等を挙げることができる。その他のプラスチックとしては、ポリカーボネート、アクリル樹脂、ＡＢＳ、ポリアセタール、ポリビニルアルコール（ＰＶＡ）、ゴム類などが使用できる。また、金属類や、ガラス類にも適用可能である。これらの基材の中でも、特に熱でシュリンク可能な、ＰＥＴフィルム、ＯＰＳフィルム、ＯＰＰフィルム、ＯＮｙフィルム、ＰＶＣフィルムへ画像を形成する場合に本発明の構成は、有効となる。これらの基材は、インクの硬化収縮、硬化反応時の発熱などにより、フィルムのカール、変形が生じやすいばかりでなく、インク膜が基材の収縮に追従し難い。
【０１０７】
これら、各種プラスチックフィルムの表面エネルギーは大きく異なり、基材によってインク着弾後のドット径が変わってしまうことが、従来から問題となっていた。本発明の構成では、表面エネルギーの低いＯＰＰフィルム、ＯＰＳフィルムや表面エネルギーの比較的大きいＰＥＴまでを含む、表面エネルギーが３５〜６０ｍＮ／ｍの広範囲の記録材料で、良好な高精細な画像を形成できる。
【０１０８】
次に、本発明で用いることのできる画像形成方法について説明する。
本発明に係る画像形成方法においては、前述の様に、上記のインクをインクジェット記録方式により基材上に吐出、描画し、次いで、１．０秒以内に、０．０５秒以上、５．０秒以下の時間を要して、紫外線などの活性光線を照射してインクを硬化させる方法である。
【０１０９】
本発明では、基材上にインクが着弾し、活性光線を照射して硬化した後の総インク膜厚が２〜２０μｍであることが好ましい。スクリーン印刷分野の活性光線硬化型インクジェット記録では、総インク膜厚が２０μｍを越えているのが現状であるが、基材が薄いプラスチック材料であることが多い軟包装印刷分野では、前述した基材のカール・皺の問題でだけでなく、印刷物全体のこし・質感が変わってしまうという問題が有るため、過剰な膜厚のインク吐出は好ましくない。
【０１１０】
尚、ここで「総インク膜厚」とは基材に描画されたインクの膜厚の最大値を意味し、単色でも、それ以外の２色重ね（２次色）、３色重ね、４色重ね（白インクベース）のインクジェット記録方式で記録を行った場合でも総インク膜厚の意味するところは同様である。
【０１１１】
インクの吐出条件としては、インクジェット記録ヘッド及びインクを３５〜１００℃に加熱し、吐出することが吐出安定性の点で好ましい。活性光線硬化型のインクは、温度変動による粘度変動幅が大きく、粘度変動はそのまま液滴サイズ、液滴射出速度に大きく影響を与え、画質劣化を起こすため、インク温度を上げながらその温度を一定に保つことが必要である。インク温度の制御幅としては、設定温度±５℃、好ましくは設定温度±２℃、更に好ましくは設定温度±１℃である。
【０１１２】
また、本発明では、各ノズルより吐出する最小の液滴量が２〜１５ｐｌであることが好ましい。本来、高精細画像を形成するためには、液滴量がこの範囲であることが必要であるが、この液滴量で吐出する場合、前述した吐出安定性が特に厳しくなる。
【０１１３】
活性光線の照射方法として、その基本的な方法が、特開昭６０−１３２７６７号に開示されている。これによると、ヘッドユニットの両側に光源を設け、シャトル方式でヘッドと光源を走査する。照射は、インク着弾後、一定時間を置いて行われることになる。更に、駆動を伴わない別光源によって硬化を完了させる。米国特許第６，１４５，９７９号では、照射方法として、光ファイバーを用いた方法や、コリメートされた光源をヘッドユニット側面に設けた鏡面に当て、記録部へＵＶ光を照射する方法が開示されている。本発明に係る画像形成方法においては、これらの何れの照射方法も用いることが出来る。
【０１１４】
次いで、本発明で用いることのできるインクジェット記録装置（以下、単に記録装置という）について説明する。
【０１１５】
以下、本発明に係る記録装置について、図面を適宜参照しながら説明する。尚、図面の記録装置はあくまでも本発明で好ましく用いることができる記録装置の一態様であり、本発明では、ここで例示する記録装置の図面に限定されない。
【０１１６】
図１は、本発明で用いることのできるインクジェット記録装置で、シリアルプリント方式で用いる要部の構成の一例を示す正面図である。記録装置１は、ヘッドキャリッジ２、記録ヘッド３、照射手段４、プラテン部５等を備えて構成される。この記録装置１は、基材Ｐの下にプラテン部５が設置されている。プラテン部５は、紫外線を吸収する機能を有しており、基材Ｐを通過してきた余分な紫外線を吸収する。その結果、高精細な画像を非常に安定に再現できる。
【０１１７】
基材Ｐは、ガイド部材６に案内され、搬送手段（図示せず）の作動により、図１における手前から奥の方向に移動する。ヘッド走査手段（図示せず）は、ヘッドキャリッジ２を図１におけるＹ方向に往復移動させることにより、ヘッドキャリッジ２に保持された記録ヘッド３の走査を行なう。
【０１１８】
ヘッドキャリッジ２は基材Ｐの上側に設置され、基材Ｐ上の画像印刷に用いる色の数に応じて後述する記録ヘッド３を複数個、吐出口を下側に配置して収納する。ヘッドキャリッジ２は、図１におけるＹ方向に往復自在な形態で記録装置１本体に対して設置されており、ヘッド走査手段の駆動により、図１におけるＹ方向に往復移動する。
【０１１９】
尚、図１ではヘッドキャリッジ２がイエロー（Ｙ）、マゼンタ（Ｍ）、シアン（Ｃ）、ブラック（Ｋ）の記録ヘッド３を収納するものとして描図を行なっているが、実施の際にはヘッドキャリッジ２に収納される記録ヘッド３の色数は適宜決められるものである。
【０１２０】
記録ヘッド３は、インク供給手段（図示せず）により供給された活性光線硬化型のインク（例えば、ＵＶ硬化インク）を、内部に複数個備えられた吐出手段（図示せず）の作動により、吐出口から基材Ｐに向けて吐出する。記録ヘッド３により吐出されるＵＶインクは色材、重合性モノマー、開始剤等を含んで組成されており、紫外線の照射を受けることで開始剤が触媒として作用することに伴なうモノマーの架橋、重合反応によって硬化する性質を有する。
【０１２１】
記録ヘッド３は、基材Ｐの一端からヘッド走査手段の駆動により、図１におけるＹ方向に基材Ｐの他端まで移動するという走査の間に、基材Ｐにおける一定の領域（着弾可能領域）に対して、ＵＶインクをインク滴として吐出し、該着弾可能領域にインク滴を着弾させる。
【０１２２】
上記走査を適宜回数行ない、１領域の着弾可能領域に向けてＵＶインクの吐出を行なった後、搬送手段で基材Ｐを図１における手前から奥方向に適宜移動させ、再びヘッド走査手段による走査を行ないながら、記録ヘッド３により上記着弾可能領域に対し、図１における奥方向に隣接した次の着弾可能領域に対してＵＶインクの吐出を行なう。
【０１２３】
上述の操作を繰り返し、ヘッド走査手段及び搬送手段と連動して記録ヘッド３からＵＶインクを吐出することにより、基材Ｐ上にＵＶインク滴の集合体からなる画像が形成される。
【０１２４】
照射手段４は、特定の波長領域の紫外線を安定した露光エネルギーで発光する紫外線ランプ及び特定の波長の紫外線を透過するフィルターを備えて構成される。ここで、紫外線ランプとしては、水銀ランプ、メタルハライドランプ、エキシマーレーザー、紫外線レーザー、熱陰極管、冷陰極管、ブラックライト、ＬＥＤ（ｌｉｇｈｔ ｅｍｉｔｔｉｎｇ ｄｉｏｄｅ）等が適用可能であり、帯状のメタルハライドランプ、冷陰極管、水銀ランプもしくはブラックライトが好ましい。
【０１２５】
照射手段４は、記録ヘッド３がヘッド走査手段の駆動による１回の走査によってＵＶインクを吐出する着弾可能領域のうち、記録装置（ＵＶインクジェットプリンタ）１で設定できる最大のものとほぼ同じ形状か、着弾可能領域よりも大きな形状を有する。
【０１２６】
照射手段４はヘッドキャリッジ２の両脇に、基材Ｐに対してほぼ平行に、固定して設置される。
【０１２７】
前述したようにインク吐出部の照度を調整する手段としては、記録ヘッド３全体を遮光することはもちろんであるが、加えて照射手段４と基材Ｐの距離ｈ１より、記録ヘッド３のインク吐出部３１と基材Ｐとの距離ｈ２を大きくしたり（ｈ１＜ｈ２）、記録ヘッド３と照射手段４との距離ｄを離したり（ｄを大きく）することが有効である。又、記録ヘッド３と照射手段４の間を蛇腹構造７にすると更に好ましい。
【０１２８】
ここで、照射手段４で照射される紫外線の波長は、照射手段４に備えられた紫外線ランプ又はフィルターを交換することで適宜変更することができる。
【０１２９】
以上の様に、図１においては、シリアルプリント方式を例として、説明したが、そのほかにも、図２に示すような各インクジェット印字方式のインクジェット記録装置を用いることができる。
【０１３０】
図２において、図２のａ）は、記録ヘッド１９を基材２０の幅手方向に配置し、記録媒体を搬送しながら印字及び照射手段２４より活性光線を照射する方法（ラインヘッド方式）であり、図２のｂ）は、記録ヘッド１９が副走査方向に移動しながら印字し、更に照射手段２４より活性光線を照射する方法（フラットヘッド方式）であり、図２のｃ）は、上記説明した記録ヘッド２４が基材上の幅手方向を走査しながら印字し、更に両端に設けた照射手段２４より活性光線を照射する方法（シリアルプリント方式）であり、いずれの方式も用いることができる。
【０１３１】
【実施例】
以下、本発明の実施例を挙げて具体的に説明するが、本発明の実施態様はこれらの例に限定されるものではない。
【０１３２】
実施例１
《インクの調製》
下記の構成からなるカチオン重合性インクを調製した。
【０１３３】

《インクジェット画像の形成》
〔インクジェット記録装置〕
図１に記載の構成からなるシリアル方式のインクジェット記録装置を用い、それに上記調製したカチオン重合性インクを装填した。
【０１３４】
紫外線の照射手段としては、Ｉｎｔｅｇｒａｔｉｏｎ社製のＶｚｅｒｏを用い、表１に記載の照度となる様に出力電圧を適宜調整し、また、基材へのインク着弾から紫外線照射までのタイミングは、最も遅い条件でも０．８秒以内に開始する様に照射間隔を制御した。
【０１３５】
また、記録ヘッドには、ノズルピッチを３６０ｄｐｉとし、４〜２４ｐｌの範囲で異なるインク液滴サイズを出射できるピエゾタイプのインクジェットノズルを装着した。また、インク供給部、インク流路及びインクジェットノズルは、ヒーターにより５５℃まで加温が可能とした。なお、本発明でいうｄｐｉとは、２．５４ｃｍあたりのドット数を表す。
【０１３６】
〔画像印字〕
下記の１〜３の印字環境下で、上記インクジェット記録装置を用いて、７２０ｄｐｉ×７２０ｄｐｉ、１画素あたりの最大インク液適量１２ｐｌ、ベタ画像の最大インク付着量８．９ｇ／ｍ^２とし、４パスで、ドット画像及びベタ画像を出力して画像１〜６を形成した。なお、基材としては、ポリエチレンテレフタレートフィルムを使用した。また、上記基材面上の外気の風速は、１ｍ／ｓ未満となる様に制御した。
【０１３７】
印字環境１：絶対湿度０．００３％（▲１▼１５℃、２８％ＲＨ、▲２▼２１℃、２１％ＲＨ、▲３▼２５℃、１５％ＲＨの３条件）
印字環境２：絶対湿度０．００９％（▲１▼１５℃、８５％ＲＨ、▲２▼２１℃、６２％ＲＨ、▲３▼２５℃、３４％ＲＨの３条件）
印字環境３：絶対湿度０．０１５％（▲１▼２０℃、９０％ＲＨ、▲２▼２５℃、７５％ＲＨ、▲３▼３０℃、５７％ＲＨの３条件）
〔印字画像の評価〕
以上の様にして印字した各画像について、下記の評価を行った。なお、各印字環境における結果は、▲１▼〜▲３▼の条件の平均値として表示した。
【０１３８】
（硬化所要時間の測定）
上記方法に従って画像形成する際に、硬化に要したパス数（紫外線照射装置の通過回数）から、硬化所要時間を求めた。なお、この硬化所要時間には、紫外線が照射されない時間も含むものとする。
【０１３９】
（シワの評価）
上記条件で、ベタ画像を印字し、シワの発生の有無を目視観察し、下記の基準に則りシワの評価を行った。
【０１４０】
○：ベタ画像が均一でグロスがあり、シワの発生がない
△：ややシワの発生が認められるが、許容される品質レベルである
×：シワの発生が認められ、グロス及び反射濃度の低下が認められ、許容限界外の品質である
（インク滲みの評価）
上記条件で、グラデーションパターン画像を印字し、下記の基準に則りインク滲みの評価を行った。
【０１４１】
○：ハイライト部からシャドー部まで、インク滲みによるノイズが認められない
△：中間濃度部で、インク滲みに起因するノイズが僅かに認められるが、許容される品質レベルである
×：中濃度部からシャドー部にかけて、インク滲みが発生し、ノイズが大きい
（硬化性の評価）
上記形成した各ベタ画像表面を指触してタックの有無について評価し、下記の基準に則り硬化性の評価を行った。
【０１４２】
○：紫外線照射後のベタ画像で、タッキネスが全く認められない
△：紫外線照射後のベタ画像で、ややタッキネスが認められる
×：紫外線照射後のベタ画像で、明らかなタッキネスが認められる
（密着性の評価）
上記形成した各ベタ画像に、碁盤目状にカッターで切れ目を入れ、その表面に粘着テープを貼り付け、次いで、粘着テープを剥離した際の基材上のベタ画像の残存状態を目視観察し、下記の基準に則り密着性の評価を行った。
【０１４３】
○：テープ剥離による画像の変化が全くない
△：テープ剥離により、画像の一部が欠落している
×：テープ剥離により、ほとんどの画像が欠落している
以上により得られた各結果を、表１に示す。
【０１４４】
【表１】

【０１４５】
表１より明らかなように、基材上にインクを着弾した後、１．０秒以内に着弾したインクに紫外線を照射し、かつ紫外線照射からインク硬化までの所要時間を０．０５〜５．０秒とした本発明のインクジェット記録方法により作成した本発明の画像は、比較例に対し、シワの発生を抑えると共に、インク滲み耐性、硬化性及び密着性のいずれの性能も良好であることが分かる。
【０１４６】
実施例２
実施例１に記載の画像２の記録方法において、紫外線照度を７５ｍＷ／ｃｍ^２の一定条件とし、照射光源とインクジェットノズルとの距離を適宜調整して、インク着弾後紫外線照射までの時間（Ｔ）を表２に記載の条件に変更した以外は同様にして、画像７〜１１を作成し、実施例１に記載の方法と同様にして、各評価を行い、得られた結果を表２に示す。
【０１４７】
【表２】

【０１４８】
表２より明らかなように、基材にインクを着弾させた後、紫外線照射までの間隔を１．０秒以内とした本発明の画像は、比較例に対し、インク滲み耐性、硬化性及び密着性を損なうことなく、シワ耐性が改良されていることが分かる。
【０１４９】
実施例３
《インクの調製》
下記の構成からなるラジカル重合性インクを調製した。
【０１５０】

《インクジェット画像の形成》
実施例１に記載のインクジェット画像の形成において、カチオン重合性インクに代えて、上記調製したラジカル重合性インクを用い、基材へのインク着弾から紫外線照射までの時間を０．７秒とし、更に、印字環境の酸素濃度、紫外線光源の照度を、表３に記載の様に変更した以外は同様にして、画像１２〜１６を作成し、実施例１に記載の方法と同様にして、各評価を行い、得られた結果を表３に示す。
【０１５１】
【表３】

【０１５２】
表３より明らかなように、ラジカル重合性化合物を含有するインクを用いても、実施例１と同様に、基材にインクを着弾させた後、紫外線照射までの間隔を１．０秒以内とし、かつ紫外線照射からインク硬化までの所要時間を０．０５〜５．０秒とした本発明のインクジェット記録方法により作成した本発明の画像は、比較例に対し、シワの発生を抑えると共に、インク滲み耐性、硬化性及び密着性のいずれの性能も良好であることが分かる。
【０１５３】
【発明の効果】
本発明により、様々な温湿度環境下であっても、インク滲み耐性、硬化性、基材との密着性に優れ、かつシワ耐性が良好な活性光線硬化型インクを用いたインクジェット記録方法を提供することができた。
【図面の簡単な説明】
【図１】本発明で用いることのできるインクジェット記録装置で、シリアルプリント方式で用いる要部の構成の一例を示す正面図である。
【図２】本発明で用いることのできるインクジェット印字方式の一例を示す概略図である。
【符号の説明】
１ 記録装置
２ ヘッドキャリッジ
３、１９ 記録ヘッド
４、２４ 照射手段
５ プラテン部
６ ガイド部材
７ 蛇腹構造
Ｐ、２０ 基材[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a novel ink-jet recording method, and more particularly, to an ink-jet recording using an actinic ray-curable ink capable of reacting and curing by irradiating actinic rays such as visible light, ultraviolet rays, infrared rays, γ rays, and electron beams. About the method.
[0002]
[Prior art]
In recent years, the ink jet recording method has been applied to various printing fields such as photographs, various printings, special printings such as markings and color filters, since images can be easily and inexpensively formed. In particular, a recording device that emits and controls fine dots, and ink with improved color gamut, durability, ejection suitability, etc., ink absorptivity, coloring of coloring materials, surface gloss, etc. have been dramatically improved. Using special paper, it is also possible to obtain image quality comparable to silver halide photography. Improvement in image quality of today's ink jet recording system has been achieved only when all of the recording device, ink, and special paper are provided.
[0003]
However, an ink jet system that requires special paper has a problem that the recording medium is limited and the cost of the recording medium is increased. Therefore, many attempts have been made to perform recording on a transfer receiving medium different from special paper by an ink jet method. Specifically, a phase-change inkjet method using a wax ink that is solid at room temperature, a solvent-based inkjet method using a fast-drying organic solvent-based ink, and a UV inkjet method that performs crosslinking by ultraviolet (UV) light after recording. It is.
[0004]
Above all, the UV inkjet method has attracted attention in recent years because it has a relatively low odor compared to the solvent-based inkjet method, and is capable of recording on a recording medium that is quick-drying and does not absorb ink. An ink is disclosed (for example, refer to Patent Documents 1 to 3).
[0005]
However, even if these inks are used, the dot diameter after landing greatly changes depending on the type of recording material and the working environment, and it is not possible to form high-definition images on various recording materials. It is possible.
[0006]
Generally, there are radical polymerization type and cationic polymerization type as UV ink, and the cationic polymerization type is not affected by polymerization inhibition of oxygen, and among the cationic polymerization monomers used, ionic polymerizable monomers such as oxetane and epoxy are used. Attention has been paid to its advantages such as low odor and little curing shrinkage.
[0007]
The cationic polymerization type UV ink is susceptible to humidity because of ionic polymerization using an acid as a catalyst. In addition, since the activation energy of the reaction is larger than that of the radical polymerization, there is a problem that the temperature dependence is large.
[0008]
Normally, a cationic polymerizable ink or coating material employs a means for increasing reactivity by heating the substrate or the ink. However, when the ink is heated and the viscosity is reduced and then ejected, the temperature of the ink jet nozzle becomes high and the sensitivity of ink mist and the like attached to the ink jet nozzle surface becomes high. Due to the influence of ultraviolet light leakage, clogging of the nozzle is likely to occur.
[0009]
To solve the above problem, Japanese Patent Application No. 2002-258714 specifies a preferable temperature difference in order to balance the sensitivity of the ink on the substrate surface and the sensitivity of the ink on the inkjet nozzle surface. However, in the ink jet recording method, when the base material or the ink is heated, there is another problem that wrinkles occur due to thermal convection inside the ink, a difference in reactivity between the ink surface layer and the inside, and the like.
[0010]
Further, for the purpose of improving the generation of wrinkles, a method has been proposed in which ink is applied onto a film and an image is formed using a belt conveyor type ultraviolet irradiation device (for example, see Patent Document 4). In such a method, there is a problem that the time until the irradiation of the ultraviolet rays is long and the ink bleeds.
[0011]
[Patent Document 1]
Japanese Patent Publication No. 5-54667
[0012]
[Patent Document 2]
JP 2000-504778 A
[0013]
[Patent Document 3]
International Publication No. 99/29787 pamphlet
[0014]
[Patent Document 4]
JP 2002-258714 A
[0015]
[Problems to be solved by the invention]
Accordingly, the present invention has been made in view of the above problems, and has as its object to improve ink bleeding resistance, curability, adhesion to a substrate, and wrinkle resistance even under various temperature and humidity environments. The present invention provides an ink jet recording method using an actinic ray-curable ink, which is excellent in the above.
[0016]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following configurations.
[0017]
1. Ink jet recording in which an ink containing a photopolymerizable compound is heated by an ink jet method and emitted onto a substrate, and the ink is irradiated with actinic rays within 1.0 second after the ink lands on the substrate to be cured. The method according to claim 1, wherein a time required for curing the landing ink by the actinic ray is 0.05 seconds or more and 5.0 seconds or less.
[0018]
2. Means for setting the time required for curing the landing ink to be 0.05 seconds or more and 5.0 seconds or less are means for controlling the illuminance of the active light beam, means for controlling the wavelength of the generated light beam, 2. The ink jet recording method according to the item 1, wherein the method is at least one selected from a control unit, a unit for controlling the absolute humidity of the printing environment, and a unit for controlling the oxygen concentration of the printing environment.
[0019]
3. 3. The inkjet recording method according to the above item 1 or 2, wherein the photopolymerizable compound is a cationic polymerizable compound.
[0020]
Hereinafter, details of the present invention will be described.
In the ink jet recording method of the present invention, the ink containing the photopolymerizable compound is heated by the ink jet method and emitted onto the base material, and the ink is activated to landed ink within 1.0 second after landing on the base material. In the ink jet recording method of curing by irradiating a light beam, a time required for curing the landing ink by the active light beam is 0.05 seconds or more and 5.0 seconds or less.
[0021]
The present inventor has conducted intensive studies on conditions for improving ink curability and wrinkles under the condition of irradiating ultraviolet rays immediately after the ink droplets have landed on the base material in order to improve the image quality of the inkjet image. It has been found that the objective and effect of the present invention can be obtained by satisfying the requirements specified in the present invention. That is, in order to suppress the occurrence of wrinkles, it is an important requirement to suppress thermal convection in the ink film, and various printing conditions, specifically, so that the time until the ink is cured is optimal. By means of optimally controlling the illuminance of actinic rays, the wavelength of the generated rays, the temperature of the ink droplets landed, the absolute humidity of the printing environment, or the oxygen concentration of the printing environment, high-quality and wrinkle-free It has been found that no inkjet image can be obtained, and the present invention has been reached.
[0022]
The present invention is characterized in that the time required for curing the ink droplets landed by actinic rays is 0.05 seconds or more and 5.0 seconds or less, but preferably 0.1 seconds or more and 5.0 seconds or less. Or less, more preferably 0.1 seconds or more and 2.0 seconds or less.
[0023]
The time required for curing the ink droplets in the present invention is defined as the time during which the fluidity of the ink droplets disappears.
[0024]
If the time required for curing the ink droplets is 0.05 seconds or more, it is possible to prevent wrinkles from occurring due to a rapid reaction. It is considered that the rapid reaction in the ink causes wrinkles because the relaxation time of the locally generated stress is short, and the amount of heat generated by the reaction increases at one time, and thermal convection and the like are likely to occur. If the time required for curing the ink droplets is 5.0 seconds or less, the occurrence of ink bleeding due to the flow of the printed ink droplets can be prevented. It is possible to prevent the curability of the ink from decreasing due to the penetration.
[0025]
Further, in the ink jet recording method of the present invention, the time for starting the irradiation of the actinic ray is performed within 1.0 second after the ink lands on the base material, and is preferably 0.01 time. To 1.0 second, more preferably 0.01 to 0.3 second. By setting the irradiation start time of the actinic ray within 1.0 second, it is possible to prevent excessive bleeding of the landed ink droplets and obtain stable ink curability regardless of the type of the base material.
[0026]
Means for setting the time required for curing the ink droplets landed by actinic rays defined by the present invention to be 0.05 seconds or more and 5.0 seconds or less is not particularly limited, but in the present invention, the method described below is used. It is preferable to use at least one of the following.
[0027]
Method 1: Method of optimally controlling the illuminance of ultraviolet light by using ultraviolet light as an active light source
Illuminance is 10 to 500 mW / cm²Is preferably controlled in the range, more preferably 10 to 100 mW / cm.²Range. The irradiation energy is 0.1 to 150 mJ / cm.²Is preferred. The method for setting the illuminance range described above is not particularly limited, but for example, the type of the ultraviolet irradiation light source, the output voltage, a slit provided between the light source and the base material, or the distance between the light source and the base material is appropriately adjusted. do it.
[0028]
Method 2: A method of using ultraviolet light as an active light source and optimally controlling the wavelength of the ultraviolet light
The wavelength is preferably from 280 to 380 nm, more preferably from 280 to 340 nm. The method for setting the wavelength of the ultraviolet light is not particularly limited, and for example, the type of the ultraviolet light source may be appropriately selected.
[0029]
Method 3: A method of controlling the temperature of the landed ink
The control temperature range of the landed ink is preferably 35 to 100 ° C, more preferably 35 to 80 ° C. The method of controlling the temperature of the landed ink droplets within the temperature range described above is not particularly limited. For example, by appropriately setting the temperature of the ejected ink, the temperature of the inkjet head, and the temperature of the printing environment, Can be achieved. Further, a method of providing a heater for heating the base material on the back surface of the base material and heating the base material to a desired temperature, or a method of heating by radiation from the base material surface is also preferable.
[0030]
Method 4: Method for controlling the absolute humidity of the printing environment
The absolute humidity of the printing environment is preferably from 0.003 to 0.015%, and more preferably from 0.005 to 0.010%.
[0031]
Method 5: Method for controlling oxygen concentration in printing environment
The oxygen concentration in the printing environment is preferably 5 to 30% by volume, more preferably 8 to 20% by volume.
[0032]
For the ink containing the radical polymerizable compound as the photopolymerizable compound, it is preferable to use Method 1, Method 2, Method 3, or Method 5 alone or in combination among the methods listed above. For an ink containing a cationically polymerizable compound as a polymerizable compound, it is preferable to use Method 1 to Method 4 alone or in combination among the above-listed methods.
[0033]
Next, the details of the ink according to the present invention will be described.
First, the photopolymerizable compound used in the present invention will be described.
[0034]
One of the polymerizable compounds that can be used in the present invention is a radical polymerizable compound, and examples thereof include JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, and JP-A-10-863. And Japanese Patent Application No. 7-231444.
[0035]
The radically polymerizable compound is a compound having a radically polymerizable ethylenically unsaturated bond, and may be any compound as long as it has at least one radically polymerizable ethylenically unsaturated bond in the molecule. , Oligomers, polymers and the like having a chemical form. Only one radically polymerizable compound may be used, or two or more radically polymerizable compounds may be used in an optional ratio in order to improve desired properties.
[0036]
Examples of the compound having a radically polymerizable ethylenically unsaturated bond include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid and maleic acid, and salts, esters, urethanes and amides thereof. And anhydrides, acrylonitrile, styrene, and various other radically polymerizable compounds such as unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes. Specifically, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, bis (4-acryloxypolyethoxyphenyl) propane, neopentyl glycol Diacrylate, 1,6-hexanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol Tetraacrylate, dipentaery Litol tetraacrylate, trimethylolpropane triacrylate, tetramethylol methane tetraacrylate, oligoester acrylate, N-methylol acrylamide, diacetone acrylamide, acrylic acid derivatives such as epoxy acrylate, methyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate , Lauryl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, 1,6-hexanediol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylol Methacryl derivatives such as tantrimethacrylate, trimethylolpropanetrimethacrylate, and 2,2-bis (4-methacryloxypolyethoxyphenyl) propane; and derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate and triallyl trimellitate More specifically, Shinzo Yamashita eds., "Handbook of Crosslinking Agents" (Taisei Co., Ltd., 1981); Kiyomi Kato eds., "Handbook of UV / EB Curing (Raw Materials)" (1985, Polymer Publishing) Association); Radtec Research Association, “Applications and Markets of UV / EB Curing Technology”, 79 pages, (1989, CMC); Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun) Commercially available products described in or the like or radically polymerizable or crosslinkable monomers known in the industry, Oligomers and polymers can be used.
[0037]
The amount of the radical polymerizable compound to be added is preferably from 1 to 97% by mass, more preferably from 30 to 95% by mass, based on the ink composition.
[0038]
In the present invention, a cationically polymerizable compound can be used as one of the polymerizable compounds, and various known cationically polymerizable monomers can be used as the cationically polymerizable monomer. For example, epoxy disclosed in JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, and JP-A-2001-220526 are exemplified. Compounds, vinyl ether compounds, oxetane compounds and the like.
[0039]
Preferred as aromatic epoxides are di- or polyglycidyl ethers prepared by reacting a polyhydric phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof with epichlorohydrin, such as bisphenol A or its alkylene oxide. Examples include di- or polyglycidyl ether of an adduct, di- or polyglycidyl ether of a hydrogenated bisphenol A or an alkylene oxide adduct thereof, and a novolak-type epoxy resin. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.
[0040]
The alicyclic epoxide is obtained by epoxidizing a compound having a cycloalkane ring such as at least one cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Compounds containing cyclohexene oxide or cyclopentene oxide are preferred.
[0041]
Preferred examples of the aliphatic epoxide include di- or polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof, and typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol and Diglycidyl ethers of alkylene glycols such as diglycidyl ether of 1,6-hexanediol, polyglycidyl ethers of polyhydric alcohols such as di- or triglycidyl ether of glycerin or alkylene oxide adduct thereof, polyethylene glycol or alkylene oxide adduct thereof Of polyalkylene glycols such as diglycidyl ethers of polypropylene glycol or diglycidyl ether of an alkylene oxide adduct thereof Glycidyl ether, and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.
[0042]
Among these epoxides, an aromatic epoxide and an alicyclic epoxide are preferable, and an alicyclic epoxide is particularly preferable, in consideration of the rapid curing property. In the present invention, one of the above epoxides may be used alone, or two or more may be used in appropriate combination.
[0043]
Examples of the vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexane dimethanol divinyl ether, and Di- or trivinyl ether compounds such as methylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl ether, n-propyl Pills vinyl ether, isopropyl vinyl ether, isopropenyl ether -O- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.
[0044]
Among these vinyl ether compounds, di- or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable in consideration of curability, adhesion, and surface hardness. In the present invention, one of the above vinyl ether compounds may be used alone, or two or more thereof may be used in an appropriate combination.
[0045]
In the present invention, it is preferable to contain at least one oxetane compound as a photopolymerizable compound for the purpose of suppressing shrinkage of the recording material upon curing of the ink.
[0046]
The oxetane compound according to the present invention is a compound having an oxetane ring, and any known oxetane compound as disclosed in JP-A-2001-220526 and JP-A-2001-310937 can be used.
[0047]
In the oxetane compound according to the present invention, when a compound having five or more oxetane rings is used, the viscosity of the ink composition becomes high, so that handling becomes difficult, or the glass transition temperature of the ink composition becomes high, The resulting cured product has insufficient tackiness. The compound having an oxetane ring used in the present invention is preferably a compound having 1 to 4 oxetane rings.
[0048]
Hereinafter, specific examples of the compound having an oxetane ring according to the present invention will be described, but the present invention is not limited thereto.
[0049]
As an example of the compound having one oxetane ring, a compound represented by the following general formula (1) can be given.
[0050]
Embedded image

[0051]
In the general formula (1), R¹Is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group, a furyl group or a thienyl group. R²Is an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group, a butyl group, a 1-propenyl group, a 2-propenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2- Aromatic rings such as alkenyl groups having 2 to 6 carbon atoms such as propenyl group, 1-butenyl group, 2-butenyl group and 3-butenyl group, phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group, phenoxyethyl group and the like. A group having 2 to 6 carbon atoms, such as an alkylcarbonyl group having 2 to 6 carbon atoms, such as an ethylcarbonyl group, a propylcarbonyl group, or a butylcarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group, or a butoxycarbonyl group. Group, ethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group, pentylcarbamoyl group, etc. Of 2-6 carbon atoms which is N- alkylcarbamoyl group. As the oxetane compound used in the present invention, it is particularly preferable to use a compound having one oxetane ring, since the resulting composition has excellent tackiness, low viscosity and excellent workability.
[0052]
Examples of the compound having two oxetane rings include a compound represented by the following general formula (2).
[0053]
Embedded image

[0054]
In the general formula (2), R¹Is a group similar to that in the general formula (1). R³Is, for example, a linear or branched alkylene group such as an ethylene group, a propylene group or a butylene group, or a linear or branched poly (alkyleneoxy) group such as a poly (ethyleneoxy) group or a poly (propyleneoxy) group. Linear or branched unsaturated hydrocarbon groups such as propenylene group, methylpropenylene group, butenylene group, or carbonyl group or alkylene group containing carbonyl group, alkylene group containing carboxyl group, alkylene group containing carbamoyl group, etc. It is.
[0055]
Also, R³Examples thereof include polyvalent groups selected from the groups represented by the following general formulas (3), (4) and (5).
[0056]
Embedded image

[0057]
In the general formula (3), R⁴Is an alkyl group having 1 to 4 carbon atoms such as a hydrogen atom, a methyl group, an ethyl group, a propyl group, or a butyl group; an alkoxy group having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group, a propoxy group, or a butoxy group. , A nitro group, a cyano group, a mercapto group, a lower alkoxycarbonyl group, a carboxyl group, or a carbamoyl group.
[0058]
Embedded image

[0059]
In the general formula (4), R⁵Represents an oxygen atom, a sulfur atom, a methylene group, NH, SO, SO₂, C (CF₃)₂Or C (CH₃)₂Represents
[0060]
Embedded image

[0061]
In the general formula (5), R⁶Is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, and a butyl group, or an aryl group. n is an integer of 0 to 2000. R⁷Is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, and a butyl group, or an aryl group. R⁷Examples further include groups selected from groups represented by the following general formula (6).
[0062]
Embedded image

[0063]
In the general formula (6), R⁸Is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, and a butyl group, or an aryl group. m is an integer of 0 to 100.
[0064]
Specific examples of the compound having two oxetane rings include the following compounds.
[0065]
Embedded image

[0066]
Exemplified compound 1 is a compound represented by the general formula (2)¹Is an ethyl group, R³Is a carboxyl group. In addition, Exemplified Compound 2 is a compound represented by the general formula (2)¹Is an ethyl group, R³Is R in the general formula (5).⁶And R⁷Is a methyl group and n is 1.
[0067]
Among the compounds having two oxetane rings, preferred examples other than the above compounds include compounds represented by the following general formula (7). In the general formula (7), R¹Is the R of the above general formula (1)¹Is synonymous with
[0068]
Embedded image

[0069]
In addition, as an example of the compound having 3 to 4 oxetane rings, a compound represented by the following general formula (8) can be given.
[0070]
Embedded image

[0071]
In the general formula (8), R¹Is R in the general formula (1).¹Is synonymous with R⁹Examples thereof include a branched alkylene group having 1 to 12 carbon atoms such as a group represented by the following A to C, a branched poly (alkyleneoxy) group such as a group represented by the following D, or the following E: And a branched polysiloxy group such as a group. j is 3 or 4.
[0072]
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[0073]
In the above A, R¹⁰Is a lower alkyl group such as a methyl group, an ethyl group or a propyl group. In the above D, p is an integer of 1 to 10.
[0074]
As an example of the compound having 3 to 4 oxetane rings, Exemplified Compound 3 is given.
[0075]
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[0076]
Further, examples of the compound having 1 to 4 oxetane rings other than those described above include a compound represented by the following general formula (9).
[0077]
Embedded image

[0078]
In the general formula (9), R⁸Is R in the above general formula (6)⁸Is synonymous with R¹¹Is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, or a trialkylsilyl group, and r is 1 to 4.
[0079]
Preferred specific examples of the oxetane compound used in the present invention include the following compounds.
[0080]
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[0081]
The method for producing each compound having an oxetane ring described above is not particularly limited, and may be in accordance with a conventionally known method. For example, Pattisson (DB Pattison, J. Am. Chem. Soc., 3455, 79) (1957)) discloses an oxetane ring synthesis method from a diol. In addition to these, compounds having 1 to 4 oxetane rings having a high molecular weight of about 1,000 to 5,000 are also exemplified. Specific examples of these compounds include the following compounds.
[0082]
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[0083]
As the photopolymerizable compound according to the present invention, any of the above-described radical polymerizable compounds or cation polymerizable compounds can be used, but the curing sensitivity does not easily change even when the irradiation intensity (mW) of ultraviolet rays is changed. That is, a compound having a small illuminance failure is preferable. From this viewpoint, a cationically polymerizable compound is more preferable than a radically polymerizable compound which is inhibited from undergoing polymerization by oxygen. In particular, in an ink jet recording system having a small ink droplet size, a cationic polymerizable compound is more preferable than a radical polymerizable compound in curability at a small point, and is preferable.
[0084]
In the present invention, the ink preferably contains at least one of a photopolymerization initiator and a photoacid generator.
[0085]
In the present invention, in order to carry out the curing reaction more efficiently, it is preferable to add a known photopolymerization initiator for curing. Photopolymerization initiators can be broadly classified into two types: intramolecular bond cleavage type and intramolecular hydrogen abstraction type.
[0086]
Examples of the intramolecular bond cleavage type photopolymerization initiator include diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, and 1- (4-isopropylphenyl) -2. -Hydroxy-2-methylpropan-1-one, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4 Acetophenones such as -thiomethylphenyl) propan-1-one and 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone; benzoins such as benzoin, benzoin methyl ether and benzoin isopropyl ether; , 4,6-trimethylbenzoindiphenyl Scan fins oxides such acylphosphine oxide of benzil, methyl phenylglyoxylate esters.
[0087]
On the other hand, examples of the intramolecular hydrogen abstraction type photopolymerization initiator include, for example, benzophenone, methyl-4-phenylbenzophenone o-benzoylbenzoate, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl Benzophenones such as diphenyl sulfide, acrylated benzophenone, 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone, 3,3'-dimethyl-4-methoxybenzophenone; 2-isopropylthioxanthone, Thioxanthones such as 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone and 2,4-dichlorothioxanthone; aminobenzophenones such as Michler's ketone and 4,4'-diethylaminobenzophenone; 10-butyl- - chloro acridone, 2-ethyl anthraquinone, 9,10-phenanthrenequinone, camphorquinone, and the like. When the photopolymerization initiator is used, the compounding amount is preferably in the range of 0.01 to 10.00% by mass of the actinic ray-curable composition.
[0088]
As the cationic polymerization initiator, for example, a chemical amplification type photoresist or a compound used for photocationic polymerization is used (Organic Materials Research Society, edited by "Organic Materials for Imaging", Bunshin Publishing (1993), 187). 192 pages). Examples of compounds suitable for the present invention are given below.
[0089]
First, B (C) of an aromatic onium compound such as diazonium, ammonium, iodonium, sulfonium, and phosphonium is used.₆F₅)₄ ⁻, PF₆ ⁻, AsF₆ ⁻, SbF₆ ⁻, CF₃SO₃ ⁻Salts may be mentioned.
[0090]
Specific examples of the onium compound that can be used in the present invention are shown below.
[0091]
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[0092]
Secondly, sulfonated compounds that generate sulfonic acid can be given, and specific compounds thereof are exemplified below.
[0093]
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[0094]
Thirdly, halides that generate hydrogen halide light can also be used, and specific compounds thereof are shown below.
[0095]
Embedded image

[0096]
Fourth, an iron allene complex can be mentioned.
[0097]
Embedded image

[0098]
Further, the ink composition according to the present invention is cured by irradiation with ultraviolet rays, but may be used in combination with a photosensitizer in order to perform the curing reaction more efficiently. Examples of such a photosensitizer include triethanolamine, methyldiethanolamine, triisopropanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, benzoic acid ( Amines such as 2-dimethylamino) ethyl, 4-dimethylamino (n-butoxy) ethyl, 2-ethylhexyl 4-dimethylaminobenzoate, cyanine, phthalocyanine, merocyanine, porphyrin, spiro compound, ferrocene, fluorene, fulgide , Imidazole, perylene, phenazine, phenothiazine, polyene, azo compound, diphenylmethane, triphenylmethane, polymethine acridine, coumarin, ketocoumarin, quinacridone, indigo, styryl, pyrili Compounds, pyromethene compounds, pyrazolotriazole compounds, benzothiazole compounds, barbituric acid derivatives, thiobarbituric acid derivatives, and the like. Further, European Patent No. 568,993, US Patent No. 4,508,811, Compounds described in JP-A-5,227,227, JP-A-2001-125255, JP-A-11-271969 and the like can also be used. The use amount of the photosensitizer is preferably in the range of 0.01 to 10.00% by mass in the actinic ray-curable composition.
[0099]
In the ink according to the present invention, various colorants that can be dissolved or dispersed in the main component of the polymerizable compound can be used as the colorant, but pigments are preferable from the viewpoint of weather resistance.
[0100]
As pigments that can be used in the inkjet ink of the present invention, achromatic inorganic pigments such as carbon black, titanium oxide, and calcium carbonate or chromatic organic pigments can be used. As organic pigments, for example, insoluble azo pigments such as toluidine red, toluidine maroon, Hanza yellow, benzidine yellow, pyrazolone red, etc., soluble azo pigments such as litol red, helio bordeaux, pigment scarlet, permanent red 2B, alizarin, indanthrone Derivatives from vat dyes such as thioindigo maroon, phthalocyanine blue, phthalocyanine-based organic pigments such as phthalocyanine green, quinacridone red, quinacridone-based organic pigments such as quinacridone magenta, perylene red, perylene-based organic pigments such as perylene scarlet, and the like. Isoindolinone-based organic pigments such as indolinone yellow and isoindolinone orange, and pyranthrone-based pigments such as pyranthrone red and pyranthrone orange Pigments, thioindigo-based organic pigments, condensed azo-based organic pigments, benzimidazolone-based organic pigments, quinophthalone-based organic pigments such as quinophthalone yellow, isoindoline-based organic pigments such as isoindoline yellow, and other pigments such as flavanthrone yellow and acyl Examples include amide yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, and dioxazine violet.
[0101]
When an organic pigment is exemplified by a color index (CI) number, C.I. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185, C.I. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, C.I. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 146, 149, 168, 177, 180, 192, 202, 206, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, C.I. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, C.I. I. Pigment Green 7, 36, C.I. I. Pigment Brown 23, 25, 26 and the like.
[0102]
Among the above pigments, quinacridone-based organic pigments, phthalocyanine-based organic pigments, benzimidazolone-based organic pigments, isoindolinone-based organic pigments, condensed azo-based organic pigments, quinophthalone-based organic pigments, and isoindoline-based organic pigments are light-fast. Is preferred because it is excellent.
[0103]
For dispersion of the pigment, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, and the like can be used. In dispersing the pigment, a dispersant may be added. It is preferable to use a polymer dispersant as the dispersant. Examples of the polymer dispersant include Solsperse series of Avecia and PB series of Ajinomoto Fine Techno. In addition, as a dispersing aid, a synergist corresponding to various pigments can be used. These dispersants and dispersing aids are preferably added in an amount of 1 to 50 parts by mass based on 100 parts by mass of the pigment. The dispersion medium is performed using a solvent or a polymerizable compound. However, in the irradiation-curable ink of the present invention, it is preferable to use no solvent in order to react and cure immediately after the ink lands. If the solvent remains in the cured image, problems such as deterioration of the solvent resistance and VOC of the remaining solvent occur. Therefore, it is preferable from the viewpoint of dispersibility that the dispersion medium is not a solvent but a polymerizable compound, and among them, a monomer having the lowest viscosity is selected.
[0104]
The pigment is dispersed preferably such that the average particle size of the pigment particles is 0.08 to 0.5 μm, and the maximum particle size is 0.3 to 10 μm, preferably 0.3 to 3 μm. It is preferable that the selection of the dispersion medium, the dispersion conditions, and the filtration conditions are appropriately set. By controlling the particle size, clogging of the head nozzle can be suppressed, and the storage stability of the ink, the transparency of the ink, and the curing sensitivity can be maintained. In the ink of the present invention, the colorant concentration is preferably 1% by mass to 10% by mass of the whole ink.
[0105]
Various additives other than those described above can be used in the ink according to the present invention. For example, a leveling additive, a matting agent, a polyester-based resin, a polyurethane-based resin, a vinyl-based resin, an acrylic-based resin, a rubber-based resin, and waxes for adjusting film properties can be added. In addition, for the purpose of improving storage stability, any known basic compound can be used. Typical examples thereof include basic alkali metal compounds, basic alkaline earth metal compounds, and basic organic compounds such as amines. And the like. It is also possible to combine a radical polymerizable monomer and an initiator to obtain a radical-cation hybrid cured ink.
[0106]
As the base material that can be used in the ink jet recording method of the present invention, in addition to ordinary uncoated paper and coated paper, various non-absorbable plastics and films thereof used for so-called soft packaging can be used. Examples of the plastic film include a polyethylene terephthalate (PET) film, an expanded polystyrene (OPS) film, an expanded polypropylene (OPP) film, an expanded nylon (ONy) film, a polyvinyl chloride (PVC) film, a polyethylene (PE) film, An acetyl cellulose (TAC) film and the like can be mentioned. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, polyvinyl alcohol (PVA), rubbers and the like can be used. Further, the present invention can be applied to metals and glasses. Among these base materials, the structure of the present invention is particularly effective when an image is formed on a PET film, an OPS film, an OPP film, an ONy film, or a PVC film which can be shrunk by heat. These base materials not only tend to curl and deform the film due to the curing shrinkage of the ink and the heat generated during the curing reaction, but also make it difficult for the ink film to follow the shrinkage of the base material.
[0107]
These various plastic films have greatly different surface energies, and there has conventionally been a problem that the dot diameter after ink landing varies depending on the base material. In the configuration of the present invention, a good high-definition image is formed with a wide range of recording materials having a surface energy of 35 to 60 mN / m, including an OPP film having a low surface energy, an OPS film, and a PET having a relatively large surface energy. it can.
[0108]
Next, an image forming method that can be used in the present invention will be described.
In the image forming method according to the present invention, as described above, the above-described ink is discharged and drawn on the base material by the inkjet recording method, and then, within 1.0 second, 0.05 seconds or more and 5.0 seconds or less. In this method, the ink is cured by irradiating an actinic ray such as an ultraviolet ray with a time of less than a second.
[0109]
In the present invention, the total ink film thickness after the ink lands on the base material and is cured by irradiation with actinic rays is preferably 2 to 20 μm. In the actinic ray-curable inkjet recording in the screen printing field, the total ink film thickness currently exceeds 20 μm, but in the flexible packaging printing field where the base material is often a thin plastic material, the aforementioned base material is used. In addition to the problem of curl and wrinkles, there is a problem that the stiffness and texture of the entire printed matter is changed.
[0110]
Here, the “total ink film thickness” means the maximum value of the film thickness of the ink drawn on the base material, and a single color, other two-color superposition (secondary color), three-color superposition, and four colors The same applies to the meaning of the total ink film thickness even when recording is performed by the superposition (white ink base) ink jet recording method.
[0111]
As the ink ejection conditions, it is preferable that the ink jet recording head and the ink are heated to 35 to 100 ° C. and ejected from the viewpoint of ejection stability. Actinic ray-curable inks have large fluctuations in viscosity due to temperature fluctuations.Viscosity fluctuations directly affect the droplet size and droplet ejection speed and degrade image quality. It is necessary to keep it. The control range of the ink temperature is set temperature ± 5 ° C., preferably set temperature ± 2 ° C., and more preferably set temperature ± 1 ° C.
[0112]
Further, in the present invention, it is preferable that the minimum droplet amount ejected from each nozzle is 2 to 15 pl. Originally, in order to form a high-definition image, the droplet amount needs to be within this range. However, when the droplet amount is discharged, the above-described discharge stability becomes particularly severe.
[0113]
A basic method of irradiating actinic rays is disclosed in JP-A-60-132767. According to this, light sources are provided on both sides of the head unit, and the head and the light source are scanned in a shuttle system. Irradiation is performed at a fixed time after the ink has landed. Further, the curing is completed by another light source without driving. U.S. Patent No. 6,145,979 discloses a method using an optical fiber or a method in which a collimated light source is applied to a mirror provided on a side surface of a head unit to irradiate a recording unit with UV light. I have. In the image forming method according to the present invention, any of these irradiation methods can be used.
[0114]
Next, an ink jet recording apparatus (hereinafter, simply referred to as a recording apparatus) that can be used in the present invention will be described.
[0115]
Hereinafter, a recording apparatus according to the present invention will be described with reference to the drawings as appropriate. It should be noted that the recording device shown in the drawings is merely an example of a recording device that can be preferably used in the present invention, and the present invention is not limited to the drawings of the recording devices exemplified here.
[0116]
FIG. 1 is a front view showing an example of a configuration of a main part used in a serial printing method in an ink jet recording apparatus that can be used in the present invention. The recording apparatus 1 includes a head carriage 2, a recording head 3, an irradiation unit 4, a platen unit 5, and the like. In the recording apparatus 1, a platen unit 5 is provided below a base material P. The platen portion 5 has a function of absorbing ultraviolet light, and absorbs extra ultraviolet light that has passed through the base material P. As a result, a high-definition image can be reproduced very stably.
[0117]
The base material P is guided by the guide member 6, and moves from the near side to the far side in FIG. 1 by the operation of the conveying means (not shown). The head scanning means (not shown) scans the recording head 3 held by the head carriage 2 by reciprocating the head carriage 2 in the Y direction in FIG.
[0118]
The head carriage 2 is installed on the upper side of the base material P, and accommodates a plurality of recording heads 3 described below according to the number of colors used for image printing on the base material P, with discharge ports arranged on the lower side. The head carriage 2 is mounted on the main body of the recording apparatus 1 so as to be reciprocable in the Y direction in FIG. 1, and reciprocates in the Y direction in FIG. 1 by driving the head scanning unit.
[0119]
In FIG. 1, the head carriage 2 is illustrated as storing the recording heads 3 for yellow (Y), magenta (M), cyan (C), and black (K). The number of colors of the recording head 3 housed in the head carriage 2 is determined as appropriate.
[0120]
The recording head 3 receives the actinic ray-curable ink (for example, UV curable ink) supplied by the ink supply means (not shown) by the operation of a plurality of ejection means (not shown) provided therein. Discharge is performed toward the substrate P from the discharge port. The UV ink ejected by the recording head 3 is composed of a coloring material, a polymerizable monomer, an initiator, and the like, and the monomer is cross-linked due to the initiator acting as a catalyst when irradiated with ultraviolet rays. It has the property of being cured by a polymerization reaction.
[0121]
The recording head 3 is moved from one end of the base material P to the other end of the base material P in the Y direction in FIG. 1 by driving the head scanning unit. ), The UV ink is ejected as ink droplets, and the ink droplets land on the landable area.
[0122]
The above scanning is performed an appropriate number of times, and after the UV ink is ejected toward one landable area, the base material P is appropriately moved from the near side to the back side in FIG. The recording head 3 discharges UV ink to the next landable area adjacent in the depth direction in FIG. 1 to the landable area.
[0123]
By repeating the above operation and ejecting the UV ink from the recording head 3 in conjunction with the head scanning means and the transport means, an image composed of an aggregate of UV ink droplets is formed on the base material P.
[0124]
The irradiating unit 4 includes an ultraviolet lamp that emits ultraviolet light of a specific wavelength region with stable exposure energy and a filter that transmits ultraviolet light of a specific wavelength. Here, as the ultraviolet lamp, a mercury lamp, a metal halide lamp, an excimer laser, an ultraviolet laser, a hot cathode tube, a cold cathode tube, a black light, an LED (light emitting diode) and the like are applicable. Cathode tubes, mercury lamps or black lights are preferred.
[0125]
The irradiating means 4 has the same shape as the largest one that can be set by the recording apparatus (UV inkjet printer) 1 in the landable area where the recording head 3 ejects UV ink by one scan by driving the head scanning means. , And has a shape larger than the landable area.
[0126]
The irradiating means 4 is fixedly installed on both sides of the head carriage 2 substantially parallel to the base material P.
[0127]
As described above, the means for adjusting the illuminance of the ink ejection unit not only shields the entire recording head 3 from light, but also adjusts the ink ejection of the recording head 3 based on the distance h1 between the irradiation unit 4 and the base material P. It is effective to increase the distance h2 between the portion 31 and the base material P (h1 <h2) or increase the distance d between the recording head 3 and the irradiation unit 4 (increase d). Further, it is more preferable that a bellows structure 7 is provided between the recording head 3 and the irradiation means 4.
[0128]
Here, the wavelength of the ultraviolet light irradiated by the irradiation means 4 can be appropriately changed by exchanging an ultraviolet lamp or a filter provided in the irradiation means 4.
[0129]
As described above, in FIG. 1, the serial printing method has been described as an example, but in addition, an ink jet recording apparatus of each ink jet printing method as shown in FIG. 2 can be used.
[0130]
In FIG. 2, a) in FIG. 2 is a method (line head method) in which the recording head 19 is arranged in the width direction of the base material 20 and the printing and irradiating means 24 irradiates the recording medium with actinic rays while conveying the recording medium. FIG. 2B shows a method in which the recording head 19 performs printing while moving in the sub-scanning direction, and further irradiates an actinic ray from the irradiation means 24 (flat head method). FIG. The printing method described above is a method (serial printing method) in which printing is performed while the recording head 24 scans in the width direction on the base material, and an actinic ray is irradiated from the irradiation means 24 provided at both ends. it can.
[0131]
【Example】
Hereinafter, the present invention will be described specifically with reference to examples, but embodiments of the present invention are not limited to these examples.
[0132]
Example 1
《Preparation of ink》
A cationic polymerizable ink having the following composition was prepared.
[0133]

<< Formation of inkjet image >>
[Inkjet recording device]
A serial ink jet recording apparatus having the configuration shown in FIG. 1 was used, and the above prepared cationically polymerizable ink was loaded therein.
[0134]
As the means for irradiating the ultraviolet rays, Vzero manufactured by Integration was used, and the output voltage was appropriately adjusted so that the illuminance shown in Table 1 was obtained. The timing from the ink landing on the base material to the irradiation with the ultraviolet rays was the latest. The irradiation interval was controlled to start within 0.8 seconds even under the conditions.
[0135]
The recording head was equipped with a piezo type inkjet nozzle capable of emitting different ink droplet sizes in a range of 4 to 24 pl with a nozzle pitch of 360 dpi. Further, the ink supply section, the ink flow path, and the inkjet nozzle can be heated to 55 ° C. by a heater. In the present invention, "dpi" refers to the number of dots per 2.54 cm.
[0136]
(Image printing)
Under the following printing conditions (1) to (3), using the above-mentioned ink jet recording apparatus, 720 dpi × 720 dpi, a proper amount of ink liquid per pixel of 12 pl, and a maximum ink adhesion amount of a solid image of 8.9 g / m.²In four passes, a dot image and a solid image were output to form images 1 to 6. In addition, a polyethylene terephthalate film was used as a substrate. The wind speed of the outside air on the substrate surface was controlled to be less than 1 m / s.
[0137]
Printing environment 1: 0.003% absolute humidity (1 condition: 15 ° C, 28% RH, 2 condition: 21 ° C, 21% RH, 3 condition: 25 ° C, 15% RH)
Printing environment 2: 0.009% absolute humidity (1 condition: 15 ° C, 85% RH, 2 condition: 21 ° C, 62% RH, 3 condition: 25 ° C, 34% RH)
Printing environment 3: 0.015% absolute humidity (1 condition: 20 ° C, 90% RH, 2 condition: 25 ° C, 75% RH, 3 condition: 30 ° C, 57% RH)
[Evaluation of printed image]
The following evaluation was performed for each image printed as described above. In addition, the result in each printing environment was displayed as an average value of the conditions of (1) to (3).
[0138]
(Measurement of curing time)
When forming an image according to the above method, the required curing time was determined from the number of passes required for curing (the number of passes through an ultraviolet irradiation device). The time required for curing includes the time during which no ultraviolet light is irradiated.
[0139]
(Evaluation of wrinkles)
Under the above conditions, a solid image was printed, the occurrence of wrinkles was visually observed, and wrinkles were evaluated according to the following criteria.
[0140]
：: Uniform solid image with gloss and no wrinkles
Δ: Slight wrinkles are observed, but at an acceptable quality level
×: Wrinkling was observed, gloss and reflection density were reduced, and the quality was out of the allowable limit.
(Evaluation of ink bleeding)
Under the above conditions, a gradation pattern image was printed, and ink bleeding was evaluated according to the following criteria.
[0141]
：: No noise due to ink bleeding was observed from highlight to shadow
Δ: In the intermediate density portion, noise caused by ink bleeding is slightly recognized, but the quality level is acceptable.
×: Ink bleeds from the middle density part to the shadow part, and noise is large.
(Evaluation of curability)
The surface of each of the formed solid images was touched with a finger to evaluate the presence or absence of tack, and the curability was evaluated according to the following criteria.
[0142]
：: no tackiness was observed at all in a solid image after ultraviolet irradiation
Δ: Some tackiness is observed in a solid image after ultraviolet irradiation.
×: Clear tackiness is recognized in a solid image after ultraviolet irradiation.
(Evaluation of adhesion)
In each of the solid images formed above, a cut is made with a cutter in a grid pattern, an adhesive tape is attached to the surface thereof, and then the residual state of the solid image on the substrate when the adhesive tape is peeled is visually observed. The adhesion was evaluated according to the following criteria.
[0143]
：: no change in image due to tape peeling
Δ: Part of the image is missing due to tape peeling
×: Most images are missing due to tape peeling
Table 1 shows the results obtained as described above.
[0144]
[Table 1]

[0145]
As is clear from Table 1, after the ink has landed on the base material, the landed ink is irradiated with ultraviolet rays within 1.0 second, and the time required from ultraviolet irradiation to ink curing is 0.05 to 5. The image of the present invention created by the inkjet recording method of the present invention with 0 seconds, with respect to the comparative example, suppresses the occurrence of wrinkles and has good ink bleeding resistance, curability, and adhesion. I understand.
[0146]
Example 2
In the recording method of image 2 described in Example 1, the ultraviolet illuminance was set to 75 mW / cm.²In the same manner as above, except that the time (T) from the time of ink landing to the time of ultraviolet irradiation was changed to the condition shown in Table 2, the images 7 to 11 were similarly adjusted. Was prepared, and each evaluation was performed in the same manner as in the method described in Example 1. Table 2 shows the obtained results.
[0147]
[Table 2]

[0148]
As is apparent from Table 2, the image of the present invention in which the interval between the time when the ink was landed on the base material and the time when ultraviolet irradiation was performed was 1.0 second or less was compared with the comparative example. It can be seen that the wrinkle resistance is improved without impairing the properties.
[0149]
Example 3
《Preparation of ink》
A radical polymerizable ink having the following composition was prepared.
[0150]

<< Formation of inkjet image >>
In the formation of the ink-jet image described in Example 1, the radical polymerizable ink prepared above was used in place of the cationic polymerizable ink, and the time from landing of the ink on the base material to irradiation with ultraviolet light was 0.7 seconds, and The images 12 to 16 were prepared in the same manner except that the oxygen concentration of the printing environment and the illuminance of the ultraviolet light source were changed as described in Table 3, and the evaluation was performed in the same manner as in the method described in Example 1. The results are shown in Table 3.
[0151]
[Table 3]

[0152]
As is clear from Table 3, even when an ink containing a radical polymerizable compound was used, the time interval between the irradiation of the ink on the base material and the irradiation with ultraviolet rays was set to within 1.0 second, as in Example 1. The image of the present invention created by the inkjet recording method of the present invention in which the time required from the irradiation of ultraviolet rays to the curing of the ink was 0.05 to 5.0 seconds, the generation of wrinkles and the ink It can be seen that all of the performances of bleeding resistance, curability and adhesion are good.
[0153]
【The invention's effect】
According to the present invention, there is provided an ink jet recording method using an actinic ray curable ink having excellent ink bleeding resistance, curability, adhesion to a substrate, and excellent wrinkle resistance even under various temperature and humidity environments. We were able to.
[Brief description of the drawings]
FIG. 1 is a front view showing an example of a configuration of a main part used in a serial print system in an ink jet recording apparatus that can be used in the present invention.
FIG. 2 is a schematic view showing an example of an ink jet printing system that can be used in the present invention.
[Explanation of symbols]
1 Recording device
2 Head carriage
3, 19 Recording head
4, 24 irradiation means
5 Platen section
6 Guide member
7 Bellows structure
P, 20 base material

Claims (3)

Ink jet recording in which an ink containing a photopolymerizable compound is heated by an ink jet method and emitted onto a substrate, and the ink is irradiated with actinic rays within 1.0 second after the ink lands on the substrate to be cured. The method according to claim 1, wherein a time required for curing the landing ink by the actinic ray is 0.05 seconds or more and 5.0 seconds or less. The means for setting the time required for curing the landing ink to be 0.05 seconds or more and 5.0 seconds or less is a means for controlling the illuminance of the active light beam, a means for controlling the wavelength of the generated light beam, and a method for controlling the temperature of the landed ink droplet. 2. The ink jet recording method according to claim 1, wherein the method is at least one selected from control means, means for controlling the absolute humidity of the printing environment, and means for controlling the oxygen concentration of the printing environment. The ink jet recording method according to claim 1, wherein the photopolymerizable compound is a cationic polymerizable compound.

Images