JP2004034543A - Inkjet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet printer which can perform high-quality image formation by enabling stable ejection and stable hardening of a UV ink. <P>SOLUTION: The inkjet printer has a recording head and a transfer means for conveying a recording medium. Image formation is performed by ejecting the UV ink of a cation hardening type hardened by being irradiated with an ultra-violet light from the recording head to an image forming face of the recording medium conveyed by the transfer means. The inkjet printer is equipped with a head temperature control mechanism 6 for controlling the temperature of the UV ink in the recording head to a first target setting temperature, and a media temperature adjusting mechanism 5 for controlling the temperature of the recording medium where the UV ink ejected from the recording head impacts to perform image formation to a second target setting temperature. The temperature of the UV ink of the cation hardening type is controlled before the ink is ejected until the ink is hardened. The UV ink can be stably ejected and stably hardened also under a high humidity. <P>COPYRIGHT: (C)2004,JPO

Description

【００８１】
式（１）において、Ｒ１は、水素原子、メチル基、エチル基、プロピル基或いはブチル基等の炭素数１〜６個のアルキル基、炭素数１〜６個のフルオロアルキル基、アリル基、アリール基、フリル基又はチエニル基である。Ｒ２は、メチル基、エチル基、プロピル基或いは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−ブテニル基或いは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或いは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或いは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或いは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、又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或いは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。
【００８２】
次ぎに、２個のオキセタン環を有する化合物としては、下記一般式（２）で示される化合物等が挙げられる。
【化２】

式（２）において、Ｒ１は、前記一般式（１）におけるものと同様の基である。Ｒ３は、例えば、エチレン基、プロピレン基或いはブチレン基等の線状或いは分枝状アルキレン基、ポリ（エチレンオキシ）基或いはポリ（プロピレンオキシ）基等の線状或いは分枝状ポリ（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或いはブテニレン基等の線状或いは分枝状不飽和炭化水素基、カルボニル基、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、又はカルバモイル基を含むアルキレン基等である。
【００８３】
又、Ｒ３は、下記式（３）、（４）及び（５）で示される基から選択される多価基でもある。
【化３】

式（３）において、Ｒ４は、水素原子、メチル基、エチル基、プロピル基或いは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、プロポキシ基或いはブトキシ基等の炭素数１〜４個のアルコキシ基、塩素原子或いは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、低級アルキルカルボキシル基、カルボキシル基、又はカルバモイル基である。
【００８４】
【化４】

式（４）において、Ｒ５は、酸素原子、硫黄原子、メチレン基、ＮＨ、ＳＯ、ＳＯ２、Ｃ（ＣＦ３）２又はＣ（ＣＨ３）２である。
【００８５】
【化５】

式（５）において、Ｒ６は、メチル基、エチル基、プロピル基或いはブチル基等の炭素数１〜４個のアルキル基、又はアリール基である。ｎは、０〜２０００の整数である。Ｒ７はメチル基、エチル基、プロピル基或いはブチル基等の炭素数１〜４個のアルキル基、又はアリール基である。
【００８６】
Ｒ７は、下記式（６）で示される基から選択される基でもある。
【化６】

式（６）において、Ｒ８は、メチル基、エチル基、プロピル基及びブチル基等の炭素数１〜４個のアルキル基、又はアリール基である。ｍは、０〜１００の整数である。
【００８７】
２個のオキセタン環を有する化合物の具体例としては、下記式（７）及び（８）で示される化合物等が挙げられる。
【化７】

式（７）で示される化合物は、式（２）において、Ｒ１がエチル基、Ｒ３がカルボキシル基である化合物である。
【００８８】
【化８】

式（８）で示される化合物は、一般式（２）において、Ｒ１がエチル基、Ｒ３が式（５）でＲ６及びＲ７がメチル基、ｎが１である化合物である。
【００８９】
２個のオキセタン環を有する化合物において、上記した化合物以外の好ましい例としては、下記一般式（９）で示される化合物がある。式（９）において、Ｒ１は、前記一般式（１）におけるものと同様の基である。
【化９】

【００９０】
３〜４個のオキセタン環を有する化合物としては、下記一般式（１０）で示される化合物等が挙げられる。
【化１０】

式（１０）において、Ｒ１は、前記一般式（１）におけるものと同様の基である。Ｒ９は、例えば下記式（１１）〜（１３）で示される基等の炭素数１〜１２の分枝状アルキレン基、下記式（１４）で示される基等の分枝状ポリ（アルキレンオキシ）基又は下記式（１５）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。
【化１１】

式（１１）において、Ｒ１０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。
【００９１】
【化１２】

【化１３】

【化１４】

式（１４）において、ｌは１〜１０の整数である。
【００９２】
【化１５】

３〜４個のオキセタン環を有する化合物の具体例としては、下記式（１６）で示される化合物等が挙げられる。
【化１６】

【００９３】
さらに、上記した以外の１〜４個のオキセタン環を有する化合物の例としては、下記式（１７）で示される化合物がある。
【化１７】

式（１７）において、Ｒ８は式（６）におけるものと同様の基である。Ｒ１１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。
【００９４】
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。
【化１８】

【化１９】

【化２０】

【００９５】
上記オキセタン環を有する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。又、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。
【００９６】
これらの例として、例えば以下の化合物が挙げられる。
【化２１】

ここで、ｐは２０〜２００である。
【００９７】
【化２２】

ここで、ｑは１５〜１００である。
【００９８】
【化２３】

ここで、ｓは２０〜２００である。
【００９９】
本発明においては、インク硬化の際の記録媒体Ｒの収縮を抑える目的で、光重合性化合物として少なくとも１種のオキセタン化合物と、エポキシ化合物及びビニルエーテル化合物から選ばれる少なくとも１種の化合物とを含有することが好ましい。
【０１００】
上述のカチオン性光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−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。第１に、ジアゾニウム、アンモニウム、ヨ−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（Ｃ６Ｆ５）４−，ＰＦ６−，ＡｓＦ６−，ＳｂＦ６−，ＣＦ３ＳＯ３−塩を挙げることができる。対アニオンとしてボレート化合物をもつものが酸発生能力が高く好ましい。オニウム化合物の具体的な例を以下に示す。
【化２４】

【０１０１】
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る。具体的な化合物を以下に例示する。
【化２５】

【０１０２】
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る。以下に具体的な化合物を例示する。
【化２６】

【０１０３】
第４に、鉄アレン錯体を挙げることができる。
【化２７】

【０１０４】
本発明のインクは、特開平８−２４８５６１、特開平９−０３４１０６をはじめてとし、既に公知となっている活性エネルギ線の照射で発生した酸により新たに酸を発生する酸増殖剤を含有することが好ましい。酸増殖剤を用いることで、さらなる吐出安定性向上を可能とする。
本発明に係るインクでは、対イオンとしてアリールボレート化合物を有するジアゾニウム、ヨードニウム又はスルホニウムの芳香族オニウム化合物、鉄アレン錯体から選ばれる少なくとも１種の光酸発生剤が含有されることが好ましい。
【０１０５】
上述の色材としては、重合性化合物の主成分に溶解または分散できる色材が使用できるが、耐候性の点でから顔料が好ましい。
本発明で好ましく用いることのできる顔料を、以下に列挙する。
Ｃ．Ｉ　Ｐｉｇｍｅｎｔ　Ｙｅｌｌｏｗ−１、３、１２、１３、１４、１７、８１、８３、８７、９５、１０９、４２、
Ｃ．Ｉ　Ｐｉｇｍｅｎｔ　Ｏｒａｎｇｅ−１６、３６、３８、
Ｃ．Ｉ　Ｐｉｇｍｅｎｔ　Ｒｅｄ−５、２２、３８、４８：１、４８：２、４８：４、４９：１、５３：１、５７：１、６３：１、１４４、１４６、１８５、１０１、
Ｃ．Ｉ　Ｐｉｇｍｅｎｔ　Ｖｉｏｌｅｔ−１９、２３、
Ｃ．Ｉ　Ｐｉｇｍｅｎｔ　Ｂｌｕｅ−１５：１、１５：３、１５：４、１８、６０、２７、２９、
Ｃ．Ｉ　Ｐｉｇｍｅｎｔ　Ｇｒｅｅｎ−７、３６、
Ｃ．Ｉ　Ｐｉｇｍｅｎｔ　Ｗｈｉｔｅ−６、１８、２１、
Ｃ．Ｉ　Ｐｉｇｍｅｎｔ　Ｂｌａｃｋ−７、
【０１０６】
また、本発明において、プラスチックフィルムのような透明基材での色の隠蔽性を上げる為に、白インクを用いることが好ましい。特に、軟包装画像形成、ラベル画像形成においては、白インクを用いることが好ましいが、吐出量が多くなるため、前述した吐出安定性、記録媒体Ｒのカール・しわの発生の観点から、自ずと使用量に関しては制限がある。
【０１０７】
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Ａｖｅｃｉａ社のＳｏｌｓｐｅｒｓｅシリーズが挙げられる。
【０１０８】
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、本発明に用いる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。
【０１０９】
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。
本発明に係るインクにおいては、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。
【０１１０】
この例のＵＶ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、インク組成物の保存性を高めるため、重合禁止剤を２００〜２００００ｐｐｍ添加することができる。紫外線硬化型のインクは、加熱、低粘度化して射出することが好ましいので、熱重合によるヘッド詰まりを防ぐためにも重合禁止剤を入れることが好ましい。この他にも、必要に応じて、界面活性剤、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。
【０１１１】
記録媒体Ｒとの密着性を改善するため、極微量の有機溶剤を添加することも有効である。この場合、耐溶剤性やＶＯＣ（揮発性有機化合物）の問題が起こらない範囲での添加が有効であり、その使用量は０．１〜５％の範囲であり、好ましくは０．１〜３％である。また、加熱によりＵＶインクの硬化を促進させるために熱酸発生剤が含まれるものとしても良い。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。
【０１１２】
上述のようなＵＶインクは、インクジェット記録方式により記録媒体Ｒ上に吐出、描画し、次いで紫外線（活性エネルギ線）を照射してインクを硬化させることになる。
ここで、インクが着弾し、紫外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。スクリーン画像形成分野では、総インク膜厚が２０μｍを越えているのが現状であるが、記録媒体Ｒが薄いプラスチック材料であることが多い軟包装画像形成分野では、前述した記録媒体Ｒのカール・しわの問題でだけでなく、画像形成物全体のこし・質感が変わってしまうという問題が有るため使えない。
【０１１３】
インクの吐出条件としては、記録ヘッド及びインクを３０〜１００℃に加熱し、吐出することが吐出安定性の点で好ましい。活性エネルギ線硬化型インクは、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。
【０１１４】
また、本発明では、各ノズルより吐出する液滴量が２〜１５ｐｌであることが好ましい。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り、酸増殖剤が必須となる。
本発明の画像記録方法においては、発生光線の照射条件として、インク着弾後０．００１〜２．０秒の間に紫外線が照射されることが好ましく、より好ましくは０．００１〜１．０秒である。高精細な画像を形成するためには、照射タイミングができるだけ早いことが特に重要となる。
【０１１５】
光（紫外線）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、記録部へ紫外線を照射する方法が開示されている。本発明の画像形成方法においては、これらのいずれの照射方法も用いることができる。
【０１１６】
また、紫外線を照射を２段階に分け、まずインク着弾後０．００１〜２．０秒の間に前述の方法で紫外線を照射し、かつ、全印字終了後、更に活性エネルギ線を照射する方法も好ましい態様の１つである。紫外線の照射を２段階に分けることで、よりインク硬化の際に起こる記録媒体Ｒの収縮を抑えることが可能となる。
【０１１７】
この例では、硬化に有効な波長域における最高照度が０．１〜５０ｍＷ／ｃｍ２の低照度の紫外線を用いることが好ましい。従来、ＵＶインクジェット方式では、インク着弾後のドット広がり、滲みを抑制のために、硬化に有効な波長域における最高照度が５０ｍＷ／ｃｍ２を超える高照度の光源が用いられるのが通常であった。しかしながら、これらの光源を用いると、特にシュリンクラベルなどでは、記録媒体Ｒの収縮があまりにも大きく、実質上使用できないのが現状であった。この例では、酸増殖剤を用いることで、硬化に有効な波長域における最高照度が０．１〜５０ｍＷ／ｃｍ２の低照度の紫外線を用いても、高精細な画像を形成でき、かつ、記録媒体Ｒの収縮もない。
【０１１８】
紫外線照射で用いる光源の例としては、低圧水銀ランプ、ＵＶレーザー、キセノンフラッシュランプ、捕虫灯、ブラックライト、殺菌灯、冷陰極管、ＬＥＤをなどがあるが、これらに限定されない。
また、本発明では、硬化に有効な波長域における最高照度が５０〜３０００ｍＷ／ｃｍ２の紫外線を用いることも有効である。従来のＵＶインクジェット記録に用いられる高照度の光源であるが、上述のように記録媒体Ｒの収縮課題が有り、軟包装画像形成・ラベル画像形成分野では実質ＵＶインクジェット記録は使用されていなかった。本発明の構成では、この問題は解消され、従来使われている高照度の光源を用いても、各種プラスチックフィルムへの高精細画像の形成が可能となる。光源の例としては、例えば、高圧水銀ランプ、メタルハライドランプ、無電極ＵＶランプなどが有るが、これらに限定されない。
【０１１９】
この例で用いることのできる記録媒体Ｒ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、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、ＰＥフィルム、ＴＡＣフィルム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、ＰＶＡ、ゴム類などが使用できる。
【０１２０】
また、金属類や、ガラス類にも適用可能である。これらの記録媒体Ｒ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。
【０１２１】
これら、各種プラスチックフィルムの表面エネルギは大きく異なり、記録媒体Ｒ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、表面エネルギの低いＯＰＰフィルム、ＯＰＳフィルムや表面エネルギの比較的大きいＰＥＴまでを含む、表面エネルギが３５〜６０ｄｙｎ／ｃｍの広範囲の記録媒体Ｒに良好な高精細な画像を形成できる。
本発明において、包装の費用や生産コスト等の記録媒体Ｒのコスト、プリントの作製効率、各種のサイズのプリントに対応できる等の点で、長尺（ウェブ）な記録媒体Ｒを使用する方が有利である。
【０１２２】
次ぎに、本発明のインクジェットプリンタＡの動作について説明する。
インクジェットプリンタにおいては、インクカートリッジ、記録媒体Ｒ等をセットし、電源を投入することにより、画像形成可能な状態となる。
インクカートリッジからインクの供給が行われると、制御部３０は、ヘッド温度センサ１９の検知結果に基づいて、インク収納部１８内のインク温度を検知する。そして、制御部３０は、この検知された温度に対応した加熱温度データを選択し、その選択された加熱温度データに基づいて面ヒーター１６およびヘッドヒーター１３の出力状態を制御して、ヘッド内供給路１１のインクが所定温度範囲内（例えば、第一の目標設定温度の上下１℃の範囲内）となるように加熱を行う。
【０１２３】
次に、記録媒体Ｒが給紙されてから排紙されるまでの動作を説明する。
まず、ここでは、オペレータの手動操作により、操作盤、キーボード等の入力手段５３に設定情報が打ち込まれる。この場合、設定情報は、形態：ロール状のフィルム、材質：ＰＥＴ，厚み：０．０５ｍｍ等の記録媒体Ｒが有する性質に関する情報となっている。これにより、入力手段５３はインターフェース３１を介して設定情報を制御部３０に入力する。この設定情報は制御部３０のメモリ３３に記憶される。
インクジェットプリンタＡ内では、スピンドル（図示しない）にセットされた記録媒体Ｒの先端が給紙ガイド（図示しない）に沿って搬送ローラ１ａまで誘導され、記録媒体Ｒ先端の位置合わせが行われる。
【０１２４】
位置合わせされた記録媒体Ｒは、搬送ローラ１ａにより画像形成部２へ搬送される。この間、メディア温度検出手段５２としての温度センサ５２ａは、記録ヘッド２１により画像形成が行われるべき記録媒体Ｒの温度を検出する。温度センサ５２ａは、検出温度情報を、インターフェース３１を介して制御部３０に入力する。この検出温度情報は制御部３０のメモリ３３に記憶される。
そして、制御部３０のＣＰＵ３２は、メモリ３３に記憶された検出温度情報と、設定情報に対応する目標設定温度情報とを読み出し、比較演算する。そして、ＣＰＵ３２は、その演算結果に伴い記録媒体Ｒの温度の上昇又は下降が必要であると判断した場合には、作動信号をメディア温度調節手段５１にインターフェース３１を介して入力する。すると、メディア温度調節手段５１は作動する。この場合、ヒータ５１ａが作動してヒータ５１ａから輻射熱が発生し、記録媒体Ｒを画像形成面側から加熱する。
また、当該演算結果に伴い記録媒体Ｒの温度の上昇又は下降が不必要であると判断した場合には、ＣＰＵ３２は、作動信号をメディア温度調節手段５１に入力しない。従って、メディア温度調節手段５１としてのヒータ５１ａは作動せず、記録媒体Ｒの加熱は行われない。
このようにして、メディア温度調節機構５は、メディア温度検出手段５２による検出温度情報に基づいて、記録ヘッド２１により画像形成が行われる記録媒体Ｒの温度を第二の目標設定温度に制御している。
【０１２５】
引き続き、メディア温度調節機構５により温度が制御された状態で、記録媒体Ｒは、ガイド部材４により非画像形成面側が支持されるとともに搬送方向Ｆにガイドされる。なお、この記録媒体Ｒは、ガイド部材４により非画像形成面側が支持されるが、上述したようにプラテン４ａによって吸引保持された状態となっている。
【０１２６】
そして、非画像形成面が支持されている記録媒体Ｒの画像形成面に、記録ヘッド２１により画像形成が行われる。詳しくは、記録媒体Ｒの非画像形成面がプラテン４ａにより吸引保持された状態で、キャリッジ２２の動作に付随して記録ヘッド２１が走査方向に移動しながら記録媒体の画像形成面にＵＶインクを吐出し、画像形成が行われるのである。画像形成が行われた後の記録媒体Ｒは、記録ヘッド２１より搬送方向Ｆの下流側、すなわちＵＶランプ３の直下へと搬送される。
【０１２７】
引き続き、ＵＶランプ３の直下に搬送された記録媒体Ｒ、言い換えればＵＶインクが付着した記録媒体Ｒに、ＵＶランプ３からＵＶが照射され、記録媒体Ｒに付着したＵＶインクが硬化することになる。そして、以上の工程を経た記録媒体Ｒは、排紙ガイド（図示しない）を通過して排紙されるのである。
【０１２８】
なお、この実施の形態においては、ヘッド温度調節機構のヘッド温度制御手段とメディア温度調節機構のメディア温度制御手段が共通の制御装置で構成されている。これにより、インクジェットプリンタの構成要素が少なくて済むと共に、双方の制御を連動させて効率的にヘッド内のＵＶインクの温度制御と、ＵＶ照射前の記録媒体の温度制御を行うことができる。
また、本実施の形態では、目標設定温度を変更可能となっているが、ここでは、前記ヘッド温度調節機構と前記メディア温度調節機構が、一方の目標設定温度の変更に連動して他方の目標設定温度を変更するようになっている。このため、外部環境やＵＶインクの種類、記録媒体の種類等を総合的に判断した上で、各目標設定温度を適切な温度に設定することができ、より確実かつ効率的に高品質な画像形成を行うことができる。例えば、入力手段５３によって記録媒体Ｒの変更が入力されたときには、適切な第二の目標設定温度を導出すると共に、それに応じた第一の目標設定温度も導出できるようになっている。
【０１２９】
以上、本実施の形態に係るインクジェットプリンタＡによれば、ヘッド温度調節機構６によって、記録ヘッド２１内のＵＶインクの温度を第一の目標設定温度に制御できるため、一定の粘度に低粘度化したＵＶインクを吐出することができる。また、予めＵＶインクの温度を、高湿度状態でも硬化可能な温度に上げるとともに、ほぼ一定の温度に制御することができる。
【０１３０】
また、メディア温度調節機構５によって、記録媒体Ｒの温度を第二の目標設定温度に制御できるため、記録ヘッド内においてほぼ一定の温度に制御されてほぼ一定の粘度されるとともに記録媒体Ｒに着弾したＵＶインクを、今度は一定の温度に制御された記録媒体Ｒの温度に基づいて一定の粘度とすることができ、これにより、画像形成品質の向上を図ることができる。この場合、記録媒体Ｒの温度は常に一定した温度にされているので、この記録媒体Ｒに付着したＵＶインクは低粘性の状態から高粘性の状態になるまでの時間は、記録媒体Ｒの温度に起因して変化することはなくなる。
【０１３１】
従って、記録媒体Ｒ上でのＵＶインクの液滴径は常に安定したものとなる。さらに、ヘッド温度調節機構６によって、高湿度下でも充分にＵＶインクが硬化する温度である第一の目標設定温度に制御されたＵＶインクが、メディア温度調節機構５によって、同じく高湿度下でも充分にＵＶインクが硬化する温度に制御された記録媒体上に着弾することにより、高湿度下でも記録媒体Ｒ上に着弾した各インク滴（ドット）が、紫外線の照射によりほぼ同様の条件で確実に硬化することになる。
【０１３２】
以上のことから、記録媒体ＲへのＵＶインクの付着性、滲み性が常に安定するとともに、ＵＶインクのドット径が安定し、かつ、色混じりの無いものとなる。これにより、環境の影響を受け、記録ヘッド２１に供給される前のＵＶインクの温度と、画像形成前の記録媒体Ｒの温度が変化したとしても、ＵＶインク及び記録媒体Ｒの温度変化と、吐出されたＵＶインクの周囲の湿度とに起因して画像形成品質が劣化することのない、高品質な画像を形することができる。
【０１３３】
なお、記録ヘッド２１内でヘッド温度調節機構６により制御されるインクの温度と、メディア温度調節機構５により制御される記録媒体Ｒの温度とは、同じ温度となる可能性もあるが、基本的にそれぞれ別に決められ、異なる温度となる。すなわち、記録ヘッド２１内のインクの温度は、高湿度下でもＵＶインクが充分に硬化する温度で、かつ、ＵＶインクの粘度が記録ヘッドから安定して吐出できる粘度に低下する温度とされ、記録媒体Ｒの温度は、着弾して付着したＵＶインクが好ましいドット径となる粘度となり、かつ、高湿度下でも固まる温度とされる。そして、記録ヘッド２１から吐出されるインクの温度と、インクが着弾する記録媒体Ｒの温度とがほぼ一定となっているので、記録ヘッド２１から吐出されて記録媒体Ｒに着弾するＵＶインクは、いつでも、ほぼ同様に温度変化することになり、安定したドット径で、高品質の画像形成が可能となる。
【０１３４】
また、本実施の形態に係るインクジェットプリンタＡでは、ヘッド温度制御手段３０が、ヘッド温度検出手段１９の検出結果に基づいて、ヘッド温度調節手段１３，１６を制御するので、記録ヘッド２１内にあるＵＶインクの温度に対応させて、ヘッド温度調節手段１３，１６の出力を変更することができる。これにより、記録ヘッド内のＵＶインクの温度を第一の目標設定温度により確実に制御することができ、高品質の画像形成をより確実に保持することができる。
さらに、メディア温度制御手段３０が、メディア温度検出手段５２の検出結果に基づいて、メディア温度調節手段５１を制御するので、温度調節前の記録媒体Ｒの温度に対応させて、メディア温度調節手段５１の出力を変更することができる。これにより、記録媒体Ｒの温度を第二の目標設定温度により確実に制御することができ、高品質の画像形成をより確実に保持することができる。
【０１３５】
次に、上述したメディア温度調節機構５の変形例を図５〜図６を参照して説明する。なお、詳細には、図５〜図７に示す変形例において、図２に示すメディア温度調節手段５１又はメディア温度検出手段５２の少なくとも一方が異なり、それ以外の構成要素は上記例と同様である。従って、これら構成要素には上記例と同様の符号を付し、詳細な説明は割愛する。
【０１３６】
図５に示すように、メディア温度調節手段５１としてペルチェ素子を用いた加熱・冷却システムを適用する。この加熱・冷却システムは、ペルチェ素子を内蔵したペルチェ素子内蔵ローラ５１ｆ、５１ｇを備えている。これらペルチェ素子内蔵ローラ５１ｆ、５１ｇは、記録媒体Ｒを間に介在させるように互いに隣接して配置され、互いに逆回転駆動し記録媒体Ｒを挟持した状態で搬送方向Ｆへ搬送する。これらペルチェ素子内蔵ローラ５１ｆ、５１ｇにおいて、内蔵されたペルチェ素子が作動すると、挟持した記録媒体Ｒを画像形成面及び非画像形成面の両面側から加熱もしくは冷却できるようになっている。なお、ペルチェ素子は吸熱と放熱を同時に行うので、例えば、冷却を行う場合には、ペルチェ素子内蔵ローラ５１ｆ、５１ｇを空洞にし、この空洞となった部分にファン等によって送風し、放熱する必要がある。
【０１３７】
また、メディア温度検出手段５２として熱電対センサ５２ｂを適用する。熱電対センサ５２ｂは、二つの異なる種類の金属を環状に連結し二接点の温度差により発生する熱電量から記録媒体Ｒの温度を検出する。
従って、この場合、メディア温度検出手段５２としての熱電対センサ５２ｂによる検出温度情報に基づいて、このペルチェ素子を用いた冷却システムを作動させ、記録ヘッド２１により画像形成が行われる記録媒体Ｒを冷却し、この記録媒体Ｒの温度を目標設定温度に制御している。
【０１３８】
さらに、図６に示すように、メディア温度調節手段５１としてヒータ５１ｈ及び輻射ランプ５１ｉを用いた加熱システムを適用する。ヒータ５１ｈは、ガイド部材４の背面側に配置されている。ヒータ５１ｈが作動すると、ガイド部材４（又はプラテン４ａ）を媒介して、ガイド部材４（又はプラテン４ａ）により非画像形成面側が支持された記録媒体Ｒを、非画像形成面側から加熱できるようになっている。なお、ガイド部材４（又はプラテン４ａ）は、熱伝導率の大きい材料で形成されていることが好ましく、記録媒体Ｒを加熱することを迅速かつ効率的に媒介することのできる材料で形成されていることが好ましい。輻射ランプ５１ｉは、画像形成部２のキャリッジレール２３に固定されているとともに、赤外線を輻射するものである。輻射ランプ５１ｉが作動すると、赤外線を記録媒体Ｒの画像形成面側に輻射し、画像形成面側から記録媒体Ｒを加熱できるようになっている。また、メディア温度検出手段５２として図４に示すものと同様の熱電対センサ５２ｂを適用する。
従って、この場合、メディア温度検出手段５２としての熱電対センサ５２ｂによる検出温度情報に基づいて、これらヒータ５１ｈ及び輻射ランプ５１ｉを用いた加熱システムを作動させ、記録ヘッド２１により画像形成が行われる記録媒体Ｒを加熱し、この記録媒体Ｒの温度を目標設定温度に制御している。なお、この場合、ヒータ５１ｈ及び輻射ランプ５１ｉの一方だけの加熱システムを設けるようにして、記録媒体Ｒの温度を制御してもよい。
【０１３９】
以上、図５及び図６に示す変形例においても、図１に示す上記例と同様の効果を奏する。また、図１、図５及び図６に示した例では、メディア温度調節機構５により記録媒体Ｒの温度を第二の目標設定温度に制御しているが、記録媒体Ｒの冷却も可能とすれば、ＵＶ照射による記録媒体Ｒの温度が高温化するのを抑えることができ、記録媒体Ｒが変質するのを防止することができる。
なお、図１、図５及び図６に示した例では、記録ヘッド２１より搬送方向Ｆの上流側の位置又は記録ヘッド２１に対向する位置にメディア温度調節手段５１を設けて、画像形成が行われる前又は画像形成中（画像形成の前後を僅かに含む）の記録媒体Ｒの加熱もしくは加熱及び冷却を行っているが、それに加えて、メディア温度調節手段５１を記録ヘッド２１より搬送方向Ｆの下流側の位置（但しＵＶ照射手段よりは上流側）に設けて画像形成が行われた後の記録媒体Ｒの加熱又は冷却を行ってもよい。記録媒体Ｒは、基本的にＵＶインクが着弾する直前までに目標設定温度となるようにされ、着弾後もＵＶ照射が終わるまで、ほぼ目標設定温度を維持していることが好ましい。
【０１４０】
また、ここで、図６に示すヒータ５１ｈのように、メディア温度調節手段５１を記録媒体Ｒの非画像形成面側に備え、かつ、記録媒体Ｒの非画像形成面側から記録媒体Ｒの加熱もしくは加熱と冷却とを行うことが好ましい。何故なら、記録媒体Ｒの画像形成面側が温度調節手段５１による加熱もしくは加熱と冷却との影響を直接受けることはないので、画像形成面の表面が変質し画像形成品質に影響するということはなく、これにより、画像形成品質の劣化を防止でき、高品質の画像形成を保持することができるからである。また、図６に示すヒータ５１ｈのように、ガイド部材４（又はプラテン４ａ）の背面側にメディア温度調節手段５１を設ける場合には、ガイド部材４（又はプラテン４ａ）が熱伝導率の大きい材料で形成されていることが好ましく、記録媒体Ｒを加熱又は冷却することを迅速かつ効率的に媒介することのできる材料で形成されていることが好ましい。
【０１４１】
また、本実施の形態のインクジェットプリンタＡによれば、面ヒーター１６およびヘッドヒーター１３によって、記録ヘッド２１のインクが加熱されるので、記録ヘッド２１内に供給されたインクが、記録ヘッド２１の温度の影響で冷やされることを防止でき、記録ヘッド２１内においてもインクを安定吐出に必要なだけ低粘度化することができる。したがって、安定吐出が保たれ、明瞭な画像形成を行うことが可能となる。
また、万が一、記録ヘッド２１内のインクが冷やされ高粘度化してしまったとしても、面ヒーター１６およびヘッドヒーター１３により再びインクを加熱し低粘度化することができる。
【０１４２】
さらに、ヘッド温度制御手段（制御部３０）が、ヘッド温度センサ１９の検出結果に基づいて、面ヒーター１６およびヘッドヒーター１３を制御するので、記録ヘッド２１内にあるインクの温度に対応させて、面ヒーター１６およびヘッドヒーター１３の出力を変更することができる。つまり、記録ヘッド２１のインクの温度が、第一の目標設定温度以上（例えば、安定吐出に必要なだけ低粘度化している温度）であれば、面ヒーター１６およびヘッドヒーター１３の出力を弱め、第一の目標設定温度以下であれば、出力を強めることが可能となる。したがって、記録ヘッド２１内で効率的にインクを加熱できる。
【０１４３】
なお、今回開示された実施の形態は、すべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は上記した説明ではなくて特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。
【０１４４】
【実施例】
以下に、本発明の具体的な実施例を説明するが本発明はこれにより限定されるものではない。
この実施例で用いたカチオン硬化型インクの組成を表１に示す。また、比較例として用いたラジカル硬化型インクの組成を表２に示す。
【表１】

【表２】

【０１４５】
表１及び表２において、Ｋ、Ｃ、Ｍ、Ｙは、それぞれ、濃ブラック、濃シアン、濃マゼンダ、濃イエローのインクを示し、Ｌｋ、Ｌｃ、Ｌｍ、Ｌｙは、それぞれ、淡ブラック、淡シアン、淡マゼンダ、淡イエローのインクである。なお、各インクの成分は、各成分の質量％で表わした。
【０１４６】
また、表１における酸増殖剤は、下記のものである。
【化２８】

また、表１における開始剤（光酸発生剤）は、下記のものである。
【化２９】

また、表１及び表２に示される酸化チタンの粒径は、平均粒径である。
【０１４７】
また、この実施例で用いられたインクジェットプリンタは、基本的に図１に示す構成を有するものであるが、記録ヘッド２２をピエゾ素子を用いたピエゾ型インクジェットノズルを有するものとした。また、インク供給系は、インクタンク、供給パイプ（チューブ）、ヘッド直前の前室インクタンク、フィルター付配管、ピエゾ型インクジェットノズルを有する記録ヘッド２２からなり、前室タンクからヘッド部分まで断熱し、上述のように記録ヘッド２２を加熱できるようになったものである。
記録ヘッド２２は、２〜１５ｐｌのマルチサイズドットを７２０×７２０ｄｐｉ（ｄｐｉとは、１インチ、即ち２．５４ｃｍ当たりのドット数を表わす）の解像度で吐出できるよう駆動し、上述のインクを吐出するものとした。
着弾後の照射条件は、表３に示す通りとした。なお、記録媒体上の照度の調整は、図１に示すＵＶランプ３と記録媒体との距離の調整により行った。また、ＵＶランプ３は、記録ヘッド２２の両横に設置した。
【０１４８】
表３に実験条件を示す。
【表３】

そして、インクジェットプリンタによる画像形成は、表３に記載の記録材料からなるシート状の記録媒体Ｒに行われたもので、記録媒体Ｒは、表３に示す表面エネルギを有する幅６００ｍｍ、長さ１０００ｍの長尺なロール状の記録媒体Ｒに５００ｍ以上の画像形成を行った。画像には、文字とカラーの絵が含まれる。なお、文字としては、Ｙ、Ｍ、Ｃ、Ｋの各色の目標濃度で６ポイントＭＳ明朝体文字を印字した。
また、記録媒体Ｒとしては、ＯＰＰ（Ｏｒｉｅｎｔｅｄ　ｐｏｌｙｐｒｏｐｙｌｅｎｅ）、ＰＥＴ（ｐｏｌｙｅｓｔｅｒ）、ＯＮｙ（Ｏｒｉｅｎｔｅｄ　ｎｙｌｏｎ）、シュリンクＰＶＣ（Ｐｏｌｙｖｉｎｙｌ　ｃｈｌｏｒｉｄｅ）、シュリンクＯＰＳ（Ｏｒｉｅｎｔｅｄ　ｐｏｌｙｓｔｙｒｅｎｅ）、ユポ粘着紙（合成紙ユポ　ユポ・コーポレーション）を用いた。
【０１４９】
そして、比較例及び実施例における記録ヘッド２２内のＵＶインク温度（第一の目標設定温度）と、インク着弾時前後の記録媒体Ｒの温度は、以下のような設定とした。
試験Ｎｏ．１〜６（比較例）は、ＵＶインクとしてラジカル硬化型インクを用い、ＵＶインク及び上述の６種類の記録媒体Ｒは、加熱せず、温度制御を行わないものとした。　試験Ｎｏ．７〜１２（比較例）は、ＵＶインクとしてラジカル硬化型インクを用い、ＵＶインクが５０℃となるようにインクの加熱を制御し、上述の６種類の記録媒体Ｒが４０℃となるように記録媒体Ｒの加熱を制御した。
試験Ｎｏ．１３〜１８（比較例）は、ＵＶインクとしてカチオン硬化型インクを用い、ＵＶインクが５０℃となるように、インクの加熱を制御し、上述の６種類の記録媒体Ｒは加熱せず、温度制御を行わないものとした。
【０１５０】
試験Ｎｏ．１９〜２４（実施例）は、ＵＶインクとしてカチオン硬化型インクを用い、ＵＶインクが５０℃となるようにインクの加熱を制御し、上述の６種類の記録媒体Ｒが４０℃となるように記録媒体Ｒの加熱を制御した。
試験Ｎｏ．２５〜３０（実施例）は、ＵＶインクとしてカチオン硬化型インクを用い、ＵＶインクが５０℃となるようにインクの加熱を制御し、上述の６種類の記録媒体Ｒが５０℃となるように記録媒体Ｒの加熱を制御した。
【０１５１】
表４に実験結果を示す。
【表４】

表４における文字品質の◎、○、△、×は、上述の６ポイントの文字について、文字のガサツキをルーペで拡大して以下のような定義に基づいて評価したものである。
◎…ガサツキ無し。
○…僅かにガサツキが見える。
△…ガサツキが見えるが、文字として判別でき、ギリギリ使えるレベル。
×…ガサツキがひどく、文字がかすれて使えないレベル。
【０１５２】
色混じり（滲み）の◎、○、△、×は、形成された画像の隣合う各色ドットをルーペで拡大し、滲み具合を以下のような定義に基づいて目視評価したものである。
◎…隣り合うドット形状が真円を保ち、滲みがない。
○…隣り合うドット形状がほぼ真円を保ち、ほとんど滲みがない。
△…隣り合うドットが少し滲んでいてドット形状が少しくずれているが、ギリギリ使えるレベル。
×…隣り合うドットが滲んで混じり合っており、使えないレベル。
【０１５３】
印刷物のしわ、カールの◎、○、△、×は、印刷直後に印刷物を手に取り、照射・硬化によりしわやカールが発生していないかを目視評価した。
◎…しわ、カールが見られず良好。
○…ほとんどシワ、カールが見られずほぼ良好。
△…シワ、カールが僅かに見られるがなんとか実用に耐えられるレベル。
×…印刷物にしわがより、カールも見られ、使えないレベル。
なお、以上の評価は、１０００ｍの記録媒体Ｒに対して５００ｍ以上に渡って画像形成を行った際の、１０ｍ目と、１００ｍ目と、５００ｍ目とでそれぞれ評価を行った。
【０１５４】
表４に示すように、試験Ｎｏ．１〜６（比較例）のラジカル硬化型インクを用い、ＵＶインク及び記録媒体Ｒの温度制御をしなかったものは、文字品質と、色混じりと、印刷物のしわ及びカールとの全てが×という評価となった。
また、試験Ｎｏ．７〜１２（比較例）のラジカル硬化型インクを用い、ＵＶインク及び記録媒体Ｒをそれぞれ５０℃と４０℃とに制御したものについては、試験Ｎｏ．１〜６に対して大幅な改善が見られるが、記録媒体Ｒの材料によっては、文字品質と、色混じりと、印刷物のしわ及びカールとで、評価が△となるものがあり、実施例と比較して品質が劣っている。
【０１５５】
また、試験Ｎｏ．１３〜１８（比較例）のカチオン硬化型インクを用い、ＵＶインクを５０℃で制御し、記録媒体Ｒの温度を制御しなかったものについては、１０ｍでは、×の評価となるものは無かったが、１００ｍを超えると、色混じりとしわ及びカールとで評価が×となるものが増え、×でなくとも△となり、○となるものはなかった。
【０１５６】
また、試験Ｎｏ．１９〜３０（実施例）のカチオン硬化型インクを用い、ＵＶインク及び記録媒体Ｒをそれぞれ５０℃と、４０℃もしくは５０℃に制御したものについては、評価が△となるものがなく、一部に◎も見られた。また、インク温度が４０℃のＮｏ．１９〜２４に対して、インク温度５０℃のＮｏ．２５〜Ｎｏ．３０では、シュリンクＰＶＣ及びシュリンクＯＰＳを除く記録媒体で、印刷物のしわ及びカールに対して改善が見られ、温度が高い方が、良好な結果が得られる可能性があるが、記録媒体の種類によっては（例えば、熱で収縮しやすいシュリンクのフィルムなど）、加熱による影響がでる可能性がある。
【０１５７】
すなわち、熱に強い記録媒体Ｒ（例えば、耐熱温度が６０℃以上）ならば、４０℃以上、もしくは５０℃以上の加熱が好ましく、記録媒体Ｒの熱による影響がでるまでの温度、例えば、１００℃以下（耐熱温度が６０℃ならば６０℃以下）までの加熱で、良好な結果が得られると思われる。
一方、熱で収縮させるように形成されたシュリンクフィルムなどにおいては、例えば、室温より高く（例えば、２０℃以上）、５０℃以下や、４０℃以下が好ましい。
以上のように、本発明によれば、各種の記録媒体Ｒに対して、文字品質が良好で、色混じりや滲みがなく、かつ、記録媒体にしわやカールの生じることがない、高品質な画像形成が可能となった。
【０１５８】
【発明の効果】
本発明によれば、カチオン硬化型インクを用いてインクジェット記録方式で画像を形成するとともに、記録ヘッド内でカチオン硬化型インクを加熱し、かつ、記録媒体を加熱することにより、薄膜プラスチックフィルム等の柔らかい記録媒体にも、記録媒体を収縮させてシワが生じたりカールしたりすることなく、かつ、安定したドット径で画像を形成することができる。従って、様々な材質の記録媒体に対して高品質の画像形成が可能となる。
【図面の簡単な説明】
【図１】本実施の形態に係るインクジェットプリンタの画像形成部分を示す要部断面図である。
【図２】図１のインクジェットプリンタに備わる制御部の主要制御ブロック図である。
【図３】図１のインクジェットプリンタに備わる記録ヘッドを表す斜視図である。
【図４】図３の記録ヘッドの断面図であり、（ａ）は図３のＤ面に沿った断面図、（ｂ）は図３のＥ面に沿った断面図である。
【図５】前記画像形成部分の変形例を示す要部断面図である。
【図６】前記画像形成部分の変形例を示す要部断面図である。
【符号の説明】
Ａ　　インクジェットプリンタ
Ｆ　　搬送方向
Ｒ　　記録媒体
１ａ、１ｂ　搬送ローラ（搬送手段）
３　　ＵＶランプ（ＵＶ照射手段）
４　　ガイド部材
５　　メディア温度調節機構
６　　ヘッド温度調節機構
１１　　ヘッド内供給路（供給路）
１３　　ヘッドヒーター（ヘッド温度調節手段）
１５　　吐出口
１６　　面ヒーター（ヘッド温度調節手段）
１７　　インク入口部
１８　　インク収納部
１９　　ヘッド温度センサ（ヘッド温度検出手段）
３０　　制御部（ヘッド温度制御手段、メディア温度制御手段）
２１　　記録ヘッド
５１　　メディア温度調節手段
５１ａ　ヒータ（メディア温度調節手段の一部）
５１ｂ　リフレクタ（メディア温度調節手段の一部）
５１ｃ　コンプレッサー（メディア温度調節手段の一部）
５１ｄ　冷却部（メディア温度調節手段の一部）
５１ｅ　ホース（メディア温度調節手段の一部）
５１ｆ、５１ｇ　ペルチェ素子内蔵ローラ（メディア温度調節手段の一部）
５１ｈ　ヒータ（メディア温度調節手段の一部）
５１ｉ　輻射ランプ（メディア温度調節手段の一部）
５２　　メディア温度検出手段
５２ａ　温度センサ（メディア温度検出手段）
５２ｂ　熱電対センサ（メディア温度検出手段）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an inkjet printer capable of stably reproducing a high-definition image on many types of recording media.
[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, an ink jet recording system (ink jet printer) that emits and controls fine dots, ink with improved color reproduction range, durability, ejection suitability, etc., ink absorbency, color material coloring, and surface gloss It is possible to obtain image quality comparable to silver halide photography by using a combination of special paper with dramatically improved features.
[0003]
The image quality of today's ink jet recording system has been improved only when an ink jet printer and all of the ink and special paper used in the ink jet printer are available.
However, in an ink jet printer that requires special paper, since the recording medium is limited, the cost of the recording medium is increased, and the application range of the ink jet printer is narrowed.
Therefore, many attempts have been made to perform recording on a recording medium different from dedicated paper by an inkjet 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 system has been attracting attention in recent years because it has a relatively low odor compared to the solvent-based inkjet system, and is capable of recording on a recording medium that is quick-drying and does not absorb ink. JP-A-54667, JP-A-6-200204, and JP-T-2000-504778 disclose an ultraviolet-curable inkjet ink.
[0005]
However, even if these inks are used, the dot diameter after landing greatly changes depending on the type of recording medium and the working environment, and high-quality and high-definition images are formed on all recording media. It is impossible.
Further, the ink used in the conventional UV inkjet method has a problem that the recording medium is easily shrunk. In particular, thin-film plastic films used in flexible packaging such as food packaging and adhesive labels are particularly susceptible to shrinkage. As a result, the UV inkjet method has not yet been put to practical use in flexible packaging printing and label printing. is the current situation.
[0006]
[Problems to be solved by the invention]
By the way, as the UV ink (photo-curable ink), for example, a radical-curable ink and a cation-curable ink are known. It has been found that by using a cation-curable ink, it is possible to prevent shrinkage during image formation even in the above-mentioned thin-film plastic films and pressure-sensitive adhesive labels.
However, the cationic curable ink is easily affected by water (humidity). For example, when an image is formed by landing a UV ink on a recording medium, the ink is sufficiently exposed to ultraviolet light due to the influence of ambient humidity. There is a problem that the UV ink does not cure.
[0007]
In a UV inkjet printer, when the UV ink discharged from a recording head lands on a recording medium, it spreads along the surface of the recording medium from droplets to form dots. Here, in order to form a high-definition image on a recording medium, it is preferable that the diameter of each of a large number of dots formed on the recording medium does not greatly differ between the dots or between the formed images. As described above, if the UV ink is not cured in a short time after being irradiated with ultraviolet rays due to the influence of humidity or the like, the dot diameter changes and the dot diameter becomes unstable.
When an image is formed by a UV inkjet printer, inks of different colors are landed on a recording medium in a state of being overlapped or adjacent to each other. If the UV ink is not cured in a short time, inks of different colors are mixed with each other, and the image quality is adversely affected.
[0008]
Japanese Patent Application Laid-Open No. 2002-137375 discloses a proposal for solving the problem caused by the influence of water of the cation-curable ink, by heating an ultraviolet-curable ink (UV ink) that has landed on a print medium (recording medium). An ink-jet printer provided with a heating means for heating is described.
According to the above publication, it is described that the UV ink that has landed on the storage medium is heated, and the UV ink is cured even in a humid state by irradiating the UV ink with ultraviolet rays.
[0009]
However, heating the UV ink after it lands on the recording medium has a time lag until the temperature of the UV ink rises, and the time for the time lag depends on the ink temperature when ejected from the recording head. Become. Therefore, even if the UV ink can be sufficiently cured, the time from when the UV ink is heated to when the UV ink is cured is not always constant. Therefore, it was difficult to form a high-quality and high-definition image. Further, when the above-mentioned time lag becomes long, there is a possibility that UV inks of different colors are mixed.
[0010]
SUMMARY OF THE INVENTION An object of the present invention is to provide an ink-jet printer capable of recording a high-definition image with excellent character quality, no occurrence of color mixture, and various types of recording media.
[0011]
[Means for Solving the Problems]
The invention according to claim 1 includes a recording head that ejects ink, and a conveying unit that conveys a recording medium, wherein the active energy ray-curable ink that is cured by being irradiated with an active energy ray is used as the recording head. An ink jet printer for discharging an image onto the recording medium conveyed to the conveying means to form an image, the ink heating means for heating the active energy ray-curable ink in the recording head, and the recording head Medium heating means for heating the recording medium on which the active energy ray-curable ink ejected from the head lands to form an image by image formation before the active energy ray-curable ink lands, wherein the active energy ray-curable ink is cationic. An ink jet printer characterized by being a curing type.
[0012]
According to the first aspect of the present invention, active energy ray-curable ink (hereinafter, photocurable ink (when the active energy ray is light), UV ink (when the active energy ray is ultraviolet light), or cation-curable ink Is a cation-curing type, it is possible to prevent shrinkage during image formation even in a thin plastic film or an adhesive label.
In addition, the cation-curable ink may not be sufficiently cured due to the influence of the surrounding humidity at the time of curing. By doing so, when the cationically curable ink is cured by irradiation with active energy rays, the polymerization reaction of the cationically polymerizable substance contained in the cationically curable ink is promoted, and the cationically curable ink can be sufficiently cured.
[0013]
Furthermore, by heating the cation-curable ink in the recording head and heating the recording medium, the cation-curable ink is already heated at the stage when it is landed on the recording medium and has a high temperature. As a result, the polymerization reaction of the cationic polymerizable substance is accelerated, and the curing time of a large number of cationically curable ink droplets discharged from the recording head is stabilized, so that the dot diameter of the ink on the recording medium can be stabilized.
If only the recording medium is heated without heating the cation-curable ink in the recording head, the temperature of the cation-curable ink before landing on the recording medium may be low. The time from when the mold ink lands to when it is heated and reaches the temperature at which the polymerization of the cationic polymerizable substance is promoted may vary depending on the image formation, and it is not always sufficient to stabilize the dot diameter on the recording medium. Can not.
[0014]
The cation-curable ink (active energy ray-curable ink) has a high viscosity as an ink, but can be reduced in viscosity by heating. By heating in the recording head, the cation-curable ink is heated. Can be reduced in viscosity to stabilize the ejection amount from the recording head, so that the dot diameter of the ink on the recording medium can also be stabilized.
[0015]
From the above, while forming an image by an ink jet recording method using a cation-curable ink, heating the cation-curable ink in the recording head, and, by heating the recording medium, a soft thin film plastic film etc. An image can be formed on a recording medium with a stable dot diameter without wrinkling or curling due to contraction of the recording medium. Therefore, high-quality images can be formed on recording media of various materials.
[0016]
The invention according to claim 2 is the ink jet printer according to claim 1, wherein the medium heating unit heats the recording medium even after the activation energy ray-curable ink lands.
[0017]
According to the second aspect of the present invention, the cationically curable ink lands on the recording medium, and is irradiated with an active energy ray, so that the polymerizable compound starts polymerization and cures. By heating the recording medium not only before the ink lands but also after the ink lands, the polymerization reaction of the cationically polymerizable compound can be more stably promoted. Therefore, the effect of the invention described in claim 1 can be obtained more reliably.
[0018]
According to a third aspect of the present invention, there is provided the recording head, comprising: a recording head that discharges ink; and a transport unit that transports a recording medium. From, an inkjet printer that performs image formation by discharging to the recording medium conveyed to the conveyance unit,
A head temperature adjustment mechanism for controlling the temperature of the active energy ray-curable ink in the recording head within a first target set temperature range, and image formation by landing the active energy ray-curable ink ejected from the recording head And a medium temperature control mechanism for controlling the temperature of the recording medium in which the recording is performed within a second target set temperature range, wherein the active energy ray-curable ink is a cation-curable ink.
[0019]
According to the third aspect of the present invention, the temperature of the cation-curable ink is controlled within the first target set temperature range and the recording medium is controlled within the second target set temperature range. The target set temperature range is a temperature at which the polymerization reaction of the cationically polymerizable compound of the cationically curable ink is sufficiently promoted, and a temperature at which the cationically curable ink has a viscosity that can be stably ejected from the recording head, and The second target set temperature range is a temperature at which the polymerization reaction of the cationically polymerizable compound of the cationically curable ink landed on the recording medium is sufficiently accelerated, and the recording medium is irradiated with active energy rays and heated. The temperature can be set so as not to be adversely affected.
Further, when the type of the cation-curable ink and the type of the recording medium are not changed, the polymerization speed of the cation-curable ink is constant by making the first and second target set temperatures substantially constant, and In addition, the viscosity can be made constant, and the dot diameter of the ink on the recording medium can be more reliably stabilized.
That is, according to the third aspect of the invention, the operation and effect of the first aspect of the invention can be more reliably obtained.
[0020]
The medium temperature adjustment mechanism may control the temperature of the recording medium to be within the second target set temperature range before the active energy ray-curable ink lands, and the active energy ray The inkjet printer according to claim 3, wherein the control is performed within the second target set temperature range even after the cured ink lands.
[0021]
According to the invention as set forth in claim 4, the cationically curable ink lands on the recording medium, and after being irradiated with the active energy ray, the polymerizable compound starts to polymerize and cures. By controlling the recording medium at the second target set temperature not only before the ink lands but also after the ink lands, the polymerization reaction of the cationically polymerizable compound can be more stably promoted. Therefore, the effect of the invention described in claim 3 can be more reliably obtained.
[0022]
According to a fifth aspect of the present invention, the head temperature adjusting mechanism includes a head temperature detecting unit that detects a temperature of the active energy ray curable ink in the recording head, and a head temperature detecting unit that detects a temperature of the active energy ray curable ink in the recording head. 5. The apparatus according to claim 3, further comprising: an in-head ink heating unit that performs heating; and a head temperature control unit that controls the in-head ink heating unit based on a detection result of the head temperature detection unit. 6. Is an inkjet printer.
[0023]
According to the fifth aspect of the present invention, since the head temperature control means controls the head temperature adjustment means based on the detection result of the head temperature detection means, the head temperature control means corresponds to the temperature of the active energy ray ink in the recording head. Thus, the output of the head temperature adjusting means can be changed. That is, if the temperature of the active energy ray-curable ink in the recording head is equal to or higher than the first target set temperature, the output of the head temperature adjusting means is reduced, and if the temperature is equal to or lower than the first target set temperature, the output is increased. Becomes possible. Therefore, the active energy ray-curable ink can be efficiently heated in the recording head.
[0024]
7. The medium temperature adjusting mechanism according to claim 6, wherein the medium temperature adjusting mechanism detects a temperature of the recording medium, a medium heating section that heats the recording medium, and a detection result of the medium temperature detecting section. The inkjet printer according to any one of claims 3 to 5, further comprising: a media temperature control unit that controls the media heating unit based on the following.
[0025]
According to the invention described in claim 6, the medium temperature control means controls the medium temperature adjustment means based on the detection result of the medium temperature detection means, so that the medium temperature control means corresponds to the temperature of the recording medium before the temperature adjustment. The output of the media temperature adjusting means can be changed. That is, if the temperature of the recording medium is near the second target set temperature, the output of the medium temperature adjusting means can be reduced, and if it is not near the second target set temperature, the output can be increased. Therefore, it is possible to efficiently control the temperature of the recording medium.
[0026]
The invention according to claim 7, wherein the head temperature adjusting mechanism includes a head temperature detecting means for detecting a temperature of the active energy ray curable ink in the recording head, and a head temperature detecting mechanism for detecting the temperature of the active energy ray curable ink in the recording head. An in-head ink heating unit that performs heating; and a head temperature control unit that controls the in-head ink heating unit based on a detection result of the head temperature detection unit. A medium temperature detecting unit for detecting a temperature, a medium heating unit for heating the recording medium, and a medium temperature control unit for controlling the medium heating unit based on a detection result of the medium temperature detecting unit; The temperature control means and the medium temperature control means are constituted by a common control device. An ink jet printer according.
[0027]
According to the seventh aspect of the present invention, the effects of the fifth and sixth aspects are achieved, and the head temperature control means and the medium temperature control means are constituted by a common control device. The number of elements can be reduced, and the temperature control of the active energy ray-curable ink in the head and the temperature control of the recording medium can be efficiently performed by linking both controls.
[0028]
The invention according to claim 8, wherein the head temperature adjusting mechanism is capable of changing the first target set temperature range. It is a printer.
[0029]
According to the invention as set forth in claim 8, the head temperature adjusting mechanism can change the first target set temperature. Accordingly, an optimal first target set temperature can be set. The first target set temperature can be changed manually or automatically. In the case of the manual change, the first target set temperature is changed by the head temperature adjusting mechanism based on the change value input from input means such as a keyboard. The set temperature is set, and in the case of automatic setting, the head temperature adjusting mechanism automatically sets an appropriate first target set temperature from various conditions obtained from sensors and the like.
[0030]
According to a ninth aspect of the present invention, in the inkjet apparatus according to any one of the third to eighth aspects, the medium temperature adjustment mechanism is capable of changing the second target set temperature range. It is a printer.
[0031]
According to the ninth aspect of the present invention, the medium temperature adjusting mechanism can change the second target set temperature, such as a difference in an external environment such as an outside air temperature, a type of a recording medium such as a difference in paper, and the like. , An optimal second target set temperature can be set. Note that the change of the second target set temperature may be manual or automatic. In the case of manual, the media temperature adjustment mechanism sets the second target temperature based on the change value input from input means such as a keyboard. The set temperature is set, and in the case of automatic, the media temperature adjusting mechanism automatically sets an appropriate second target set temperature from various conditions obtained from sensors and the like.
[0032]
According to a tenth aspect of the present invention, the head temperature adjustment mechanism can change the first target set temperature range, and the medium temperature adjustment mechanism can change the second target set temperature range. The head temperature adjustment mechanism and the medium temperature adjustment mechanism are interlocked with a change in one of the first target set temperature range and the second target set temperature range. The inkjet printer according to any one of claims 3 to 7, wherein the other target set temperature is changed.
[0033]
According to the tenth aspect, the effects of the eighth and ninth aspects are achieved, and the head temperature adjustment mechanism and the medium temperature adjustment mechanism are configured to set the other target setting in conjunction with the change of one target setting temperature. Since the temperature is changed, each target set temperature can be set to an appropriate temperature after comprehensively determining the external environment, the type of active energy ray-curable ink, the type of recording medium, and the like. Thus, high-quality image formation can be performed more reliably and efficiently.
[0034]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the inkjet printer of the present invention will be described with reference to the drawings.
[0035]
FIG. 1 is a cross-sectional view of a main part of an ink jet printer for explaining an image forming process on a sheet-shaped recording medium in an easily understandable manner.
As shown in the figure, the inkjet printer A is schematically transported by transport rollers 1a and 1b that have a role of transporting a recording medium R such as a sheet of paper or a resin film, and the transport rollers 1a and 1b. An image forming unit 2 for forming an image on the recording medium R, a UV lamp (UV irradiating unit) 3 for irradiating the recording medium R on which ink has adhered with the image forming unit 2 with UV, and the recording medium R in the transport direction F And a guide member 4 for guiding. A transport path along which the recording medium R transported by the transport roller 1a is further transported by the transport roller 1b via the image forming unit 2 is established along the transport direction F.
[0036]
In this embodiment, an example in which a resin film (thin plastic film) wound in a roll is used as a paper supply source is shown, and this roll-shaped resin film is referred to as a “recording medium R”. Further, the recording medium R is not limited to the above-mentioned roll-shaped resin film but may be, for example, a cut sheet shape. Further, the storage medium may be various kinds of paper, various cloths or nonwoven fabrics. May be. Further, the recording medium R may be made of another material, for example, a metal. Further, the recording medium R is not limited to a sheet shape, but may be a plate shape.
[0037]
As shown in FIG. 1, the transport rollers 1 a and 1 b are spaced apart from each other at positions before and after an image is formed on the recording medium R in the image forming unit 2. The transport rollers 1a and 1b are driven to rotate in the same direction as each other, and have a function as a transport unit that sends out the recording medium R in the transport direction F.
[0038]
The image forming section 2 includes an ink-jet type recording head 21, a carriage 22 having the recording head 21, and a carriage rail 23 for guiding the movement of the carriage 22.
[0039]
In the recording head 21, there are inks (Y, M, C, K) of cyan (C), magenta (M), yellow (Y), black (B) and the like, each having a different density. In addition to the process color, a special color ink such as white or RGB may be used) is supplied by a tube or an ink cartridge (ink tank) (not shown). This ink has a high viscosity at room temperature, has a low viscosity when heated, and has a property of being cured when irradiated with UV. Hereinafter, this ink is referred to as “UV ink”. In this embodiment, a cationic curing type UV ink is used, and details of the UV ink will be described later.
[0040]
The carriage 22 has a recording head 21 and is connected to a carriage rail 23 via a connecting portion 22a. The carriage rail 23 is a rail that extends substantially perpendicular to the transport direction F of the recording medium R, and extends in a direction substantially perpendicular to the transport direction F (a direction from the front side to the back side or a direction from the back side to the front side in the plane of FIG. 1). The carriage 22 is guided. The direction in which the carriage rail 23 extends is referred to as a “scanning direction” and will be described below.
When an image is formed on the recording medium R, UV ink is ejected from the recording head 21 onto the recording medium R while the carriage 22 is guided by the carriage rail 23 and moves in the scanning direction. .
[0041]
The UV lamp (active energy ray irradiating means) 3 irradiates UV to the image forming surface of the recording medium R to which the UV ink has adhered after the process in the image forming unit 2. By irradiating UV, the UV ink attached to the recording medium R is cured. The UV lamp 3 is fixed to the above-mentioned carriage rail 23 via a connecting portion 3a.
[0042]
The guide member 4 is a plate-shaped member having a width equal to or larger than the width of the recording medium R. The guide member 4 is arranged to face the recording head 21, supports a recording medium R on which an image is formed by the recording head 21 from the non-image forming surface side, and guides the recording medium R in the transport direction F. Is what you do. The “non-image forming surface” is a surface on the opposite side of the image forming surface of the recording medium R, that is, a surface on which no image is formed.
Note that, in detail, a portion of the guide member 4 that is disposed to face the recording head 21 is a platen 4a. A suction chamber (not shown) is provided on the back side of the platen 4a, and a suction port (not shown) including a plurality of small holes communicating with the suction chamber is provided. The platen 4a suction-holds the non-image forming surface of the recording medium R.
[0043]
By combining the above-described components, the carriage 22 moves in the scanning direction while the recording medium R conveyed by the conveying rollers 1a and 1b is supported by the guide member 4 from the non-image forming surface side. Then, the UV ink is ejected from the recording head 21 onto the image forming surface of the recording medium R, and the image is formed.
[0044]
Here, the configuration of the characteristic portion of the present invention will be described.
The ink jet printer A is provided with a medium temperature adjusting mechanism 5 and a head temperature adjusting mechanism 6 shown in FIG.
The medium temperature adjusting mechanism 5 controls the temperature of the recording medium R on which an image is formed by the recording head 21 to a second target set temperature (for example, a range of the set temperature plus / minus 1 ° C.) so that the recording medium R is controlled. This controls the UV ink that has landed on R at a predetermined temperature. Further, by controlling the UV ink that has landed on the recording medium R to a predetermined temperature, the cationic ink is cured without being affected by humidity.
[0045]
As shown in FIG. 2, the medium temperature adjustment mechanism 5 schematically includes a medium temperature adjustment unit 51, a medium temperature detection unit 52, an input unit 53, and a medium temperature control unit (here, the control unit 30 corresponds to the control unit 30. ). The media temperature adjusting means 51, the media temperature detecting means 52, the input means 53, and the media temperature controlling means (control unit 30) are connected to each other via the interface 31.
[0046]
The medium temperature adjusting unit 51 is provided near at least a part of a conveying path of the recording medium R conveyed by the conveying rollers 1a and 1b as a conveying unit, and heats the recording medium R. During the temperature control, if the temperature of the recording medium R is too high due to heating or if the temperature around the recording medium R is too high, the medium temperature adjusting means is provided with not only a heating function but also a cooling function. It may be provided to control the temperature of the recording medium. Specifically, as shown in FIG. 1, the medium temperature adjusting means 51 is disposed on the image forming surface side of the recording medium R before the image is formed by the recording head 21, and includes a heater 51a and a reflector 51b. And
[0047]
The heater 51a has a function as a heat source extending in the width direction of the recording medium R (a direction from the front side to the back side or a direction from the back side to the front side in the plane of FIG. 1).
The reflector 51b is disposed so as to cover the heater 51a in a state where the image forming surface side of the recording medium R is open, and reflects the radiant heat from the heater 51a generated by operating the heater 51a.
Therefore, the heater 51a and the reflector 51b have a function as a medium temperature adjusting unit 51 for heating the recording medium R from the image forming surface side.
When the medium temperature adjusting means 51 has a cooling function, for example, a cooling means such as a heat pump or the like that performs cooling by vaporization heat, a Peltier element or the like can be used, and the cooling means can be cooled to about room temperature. If so, a cooling fin or a cooling fan can be used.
[0048]
The medium temperature detecting means 52 is arranged near at least a part of the conveying path of the recording medium R conveyed by the conveying rollers 1a and 1b in FIG. 1, and detects the temperature of the recording medium R. Specifically, the medium temperature detecting means 52 is arranged on the image forming surface side of the recording medium R before the image formation is performed by the recording head 21, and corresponds to the temperature sensor 52a shown in FIG. . As shown in FIG. 1, the temperature sensor 52a is a non-contact type sensor that is fixed to the above-described reflector 51b and does not directly contact the surface of the recording medium R. The temperature of the recording medium R is detected by the temperature sensor 52a. Then, the temperature sensor 52a as the temperature detecting means 52 inputs the temperature information of the recording medium R (hereinafter, referred to as "detected temperature information") as a detection result to the control unit 30, as shown in FIG.
[0049]
The input unit 53 is an operation panel, a keyboard, or the like, and inputs information (hereinafter, referred to as “setting information”) relating to the type (form, material, thickness, etc.) of the recording medium R to the control unit 30. The input unit 53 inputs the input setting information to the control unit 30 when the setting information is input to an operation panel, a keyboard, or the like by a manual operation of an operator. Specifically, the setting information is information on the properties of the recording medium R, such as the form: film, material: resin, and thickness: 0.05 mm.
[0050]
The control unit 30 includes a memory 33 and a CPU 32.
The memory 33 stores the detected temperature information output from the medium temperature detecting means 52, the setting information output from the input means, and the like. Further, the memory 33 stores information on target set temperatures corresponding to the set information (hereinafter, referred to as “target set temperature information”) as a data table. Therefore, in the memory 33, the target set temperature information can be switched according to the set information by the input means 53. Specifically, when setting information such as form: roll film, material: resin, and thickness: 0.05 mm is changed to setting information such as form: roll paper, material: paper, thickness: 0.01 mm, The target set temperature information is switched so that the target set temperature also switches from 40 ° C. to 50 ° C.
In addition, the target set temperature is changed based on a manual change of the set information by the input unit, and the target set temperature may be automatically changed by acquiring the set information and other conditions by a sensor or the like. is there.
[0051]
The CPU 32 reads out the detected temperature information and the target set temperature information stored in the memory 33, and performs various calculations such as comparing these information. When the CPU 32 determines that the temperature of the recording medium R needs to be increased or decreased according to the calculation result, the CPU 32 sends an operation signal for causing the medium temperature adjusting unit 51 to perform at least one of heating and cooling. If the CPU 32 determines that it is unnecessary to raise or lower the temperature of the recording medium R according to the calculation result, it does not send an operation signal to the medium temperature adjusting unit 51.
[0052]
The interface 31 mediates the transfer of various types of information and signals performed between the control unit 30 and the medium temperature adjusting unit 51, the medium temperature detecting unit 52, or the input unit 53 described above.
[0053]
Next, the head temperature adjusting mechanism 6 will be described.
The head temperature adjusting mechanism 6 controls the ink in the recording head 21 to a first target set temperature (for example, a range of the set temperature plus or minus 1 ° C.) to discharge the UV ink in a stable and low-viscosity state. In addition to controlling the temperature as high as possible, the temperature of the cationically curable UV ink is maintained at a constant temperature, and the ink is heated so as to be cured even under high humidity.
In other words, the head temperature adjustment mechanism controls the temperature of the ink that lands on the recording medium R, the temperature of which is controlled by the medium temperature adjustment mechanism 5, in the storage head 21 at a temperature at which the ink is hardened by ultraviolet irradiation even under high humidity. The temperature is controlled so as to lower the viscosity of the UV ink to a viscosity at which the ink can be ejected, and to maintain a substantially constant temperature without a temperature change due to environmental conditions and the like.
[0054]
As shown in FIG. 2, the head temperature adjustment mechanism 6 includes a head temperature adjustment unit (a surface heater 16 and a head heater 13), a head temperature detection unit (a head temperature sensor) 19, and a head temperature control unit ( Here, the control unit 30 corresponds). The head temperature adjusting unit, the head temperature detecting unit, and the head temperature controlling unit (control unit 30) are connected to each other via an interface 31.
[0055]
As shown in FIG. 3 or FIG. 4, the recording head 21 has an ink inlet 17 into which ink is injected, a plurality of ejection ports 15 for ejecting ink, and guides ink from the ink inlet 17 to the ejection port 15. Heating the ink from at least a part of the supply path (supply path) 11 in the head, a head temperature sensor (head temperature detecting means) 19 for detecting the ink temperature in the supply path 11 in the head, and the outside of the supply path 11 in the head. Surface heater (head temperature adjusting means (ink-in-head heating means)) 16 and head heater (head temperature adjusting means (ink-in-head heating means)) for heating ink in at least a part of supply path 11 in the head Are provided.
[0056]
As shown in FIGS. 4A and 4B, the ink inlet portion 17 is formed in a funnel shape that tapers from the side of the recording head 21 toward the inside. The ink inlet 17 is connected to an ink supply path (not shown), and ink is supplied from an ink tank (not shown) via the ink supply path.
[0057]
The ejection ports 15 are provided on the lower surface (nozzle surface 15a) of the recording head 21, and are arranged at regular intervals along a center line on the lower surface.
[0058]
In the process of guiding ink from the ink inlet 17 to the discharge port 15, the supply path 11 in the head includes an ink storage section 18 for temporarily storing ink and an ink nozzle 12 for guiding ink from the ink storage section 18 to the discharge port 15. Have.
[0059]
The ink storage section 18 is formed in a trapezoidal shape in a side view that becomes thinner toward the front (left side in FIG. 4A). The front end of the ink inlet 17 is connected to the rear surface of the ink container 18, and both the ink container 18 and the ink inlet communicate with each other.
In the ink storage section 18, a plurality of ink nozzles 12 for guiding ink to the discharge ports 15 are provided on the lower surface facing the nozzle surface 15a so as to correspond to each discharge port. That is, the ink nozzles 12 are arranged at equal intervals along the flow direction of the ink flowing from the ink inlet 17.
As described above, when the ink nozzles 12 are arranged along the ink flow direction, the pressure of the ink flowing into the ink nozzles 12 located at a position distant from the ink inlet 17 is weakened, and stable ejection may not be performed. There is. For this reason, in the present embodiment, the pressure of the ink flowing into each ink nozzle is prevented from fluctuating by forming the shape of the ink storage portion 18 into a trapezoidal shape in a side view that becomes thinner toward the front.
[0060]
A head temperature sensor (head temperature detecting means) 19 extends inward from the vicinity of the ink inlet 17, that is, from the rear surface of the ink storage 18, in order to detect the temperature of the ink flowing from the ink inlet 17. The state is provided.
[0061]
The surface heater 16 is formed in a U-shape so as to cover the in-head supply path 11 inside the recording head 21, and the surface heater 16 heats the ink in the in-head supply path 11 to reduce the viscosity.
[0062]
The head heater 13 is formed in a cylindrical shape, and is stretched from the front end to the rear end of the ink storage unit 18 so as to be in a state along the ink nozzles 12 below the ink storage unit 18. Then, the ink is heated by the head heater 13 so that each temperature of the ink ejected from each ejection port falls within a predetermined temperature range.
As described above, since the head heater 13 is in a state in which the ink nozzles 12 are arranged below the ink storage unit 18, it is possible to heat the ink before flowing into each of the ink nozzles 12 without variation.
[0063]
As shown in FIG. 2, the head temperature control means (corresponding to the control unit 30) is composed of an interface 31, a CPU 32, a memory 33, and the like, and interfaces with a control program and control data written in the memory 33. Various devices connected to the control unit 31 are controlled. In this embodiment, the head temperature control unit and the medium temperature control unit are configured by a common control device (that is, the control unit 30).
[0064]
The interface 31 is electrically connected to a surface heater (head temperature adjusting means) 16, a head heater (head temperature adjusting means) 13, a head temperature sensor (head temperature detecting means) 19 and the like.
[0065]
In the memory 32, various data in ink supply, various control programs and control data relating to the operation of each unit of the inkjet printer, and the like are written.
The various data in the ink supply include the remaining amount of ink in the ink tank, which is a reference for the replacement timing of the ink tank, the ink temperature, which is a reference for whether or not to heat the surface heater 16 and the head heater 13, and the surface heater 16, And heating temperature data of the head heater 13.
[0066]
The ink temperature, which is a criterion for determining whether or not to heat the surface heater 16 and the head heater 13, is set such that the ink is heated from the supply path 11 in the head to the discharge port 15 in a state where the surface heater 16 and the head heater 13 are not heated. Even when the ink is supplied, that is, even when the ink reaches the ejection port 15 while cooling, the temperature of the ink reaching the ejection port 15 is set to be equal to or higher than the temperature at which stable ejection is possible.
The heating temperature data of the surface heater 16 and the head heater 13 is determined in a predetermined temperature range in which the ink in the supply passage 11 in the head can be stably ejected (a temperature range in which the viscosity of the ink is 10 mPa · s or more and 50 mPa · s or less; The heating temperature of the surface heater 16 and the head heater 13 that can be heated to within a temperature range where the viscosity is 20 mPa · s or more and 40 mPa · s or less. The heating temperature depends on the ink temperature detected by the head temperature sensor 19. Is set. In other words, if the detected ink temperature is low, it is necessary to apply as much heat as possible to the ink.Therefore, it is necessary to set the heating temperature to a high temperature, and if the ink temperature is high, it is necessary to apply that much heat to the ink. Since there is no heating temperature is set to low.
[0067]
Note that the cationically curable UV ink used in this embodiment has a temperature at which the UV ink is cured by ultraviolet irradiation even in a high humidity state such as a humidity of 70% or more in the temperature range where the above viscosity is obtained. ing.
[0068]
The memory 33 includes a storage area for storing various data such as image data for forming an image, a work area for the CPU 32, and the like.
[0069]
The CPU 32 develops a program designated from among various programs stored in the memory 33 in a work area in the memory 33, and executes various processes according to the program in accordance with an input signal from each sensor. .
[0070]
Here, the ink used in the inkjet printer will be described.
The UV ink is of a cationically curable type as described above, and at least a cationically polymerizable compound which is polymerized and cured by UV irradiation and a cationically polymerizable compound for initiating the polymerization reaction of the cationically polymerizable compound by UV irradiation. It contains a photopolymerization initiator (photoacid generator) and a coloring material for producing a color as an ink. Further, at least a part of well-known various additives used for the cationically curable photocurable resin may be added to the UV ink. In this example, the UV ink is used. However, the UV ink is not limited to the one which is hardened by ultraviolet rays, and may use a cationic polymerization initiator which starts polymerization with active energy rays such as radiation and electromagnetic waves. . That is, the active energy ray is basically an electromagnetic wave including light such as ultraviolet light, infrared light, and visible light (the initiator which absorbs visible light has a color, which is not preferable). A type of ink is also being developed, and may be an electron beam. As described above, in this example, a case where ultraviolet rays are used as energy rays is described as an example.
[0071]
As the photocationically polymerizable compound, various known cationically polymerizable monomers can be used. For example, epoxy compounds exemplified 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. , Vinyl ether compounds, oxetane compounds and the like.
[0072]
Preferred as aromatic epoxides are di- or polyglycidyl ethers produced by the reaction of 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 thereof 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.
[0073]
As the alicyclic epoxide, cyclohexene oxide 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 is used. Or a compound containing cyclopentene oxide is preferred.
[0074]
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.
[0075]
Among these epoxides, in consideration of the rapid curing property, an aromatic epoxide and an alicyclic epoxide are preferable, and an alicyclic epoxide is particularly preferable. In the present invention, one of the above epoxides may be used alone, or two or more may be used in appropriate combination.
[0076]
Examples of the vinyl ether compound include, for example, 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 trimethylol. Di or trivinyl ether compounds such as propane 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-pro Vinyl ether, isopropyl vinyl ether, isopropenyl ether -O- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.
[0077]
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.
[0078]
The oxetane compound used in 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.
[0079]
When a compound having five or more oxetane rings is used, the viscosity of the composition becomes high, which makes it difficult to handle, and the glass transition temperature of the composition becomes high, so that the obtained cured product has sufficient tackiness. Will be gone. The compound having an oxetane ring used in the present invention is preferably a compound having 1 to 4 oxetane rings.
Examples of the compound having one oxetane ring include a compound represented by the following general formula (1).
[0080]
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[0081]
In the formula (1), R1 represents 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; Group, furyl group or thienyl group. R2 represents 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 1-propenyl group, a 2-propenyl group, a 2-methyl-1-propenyl group, a 2-methyl-2. -Aromatics such as alkenyl having 2 to 6 carbon atoms such as propenyl, 1-butenyl, 2-butenyl or 3-butenyl, phenyl, benzyl, fluorobenzyl, methoxybenzyl or phenoxyethyl; A group having a ring, an alkylcarbonyl group having 2 to 6 carbon atoms such as an ethylcarbonyl group, a propylcarbonyl group or a butylcarbonyl group, an alkoxy group having 2 to 6 carbon atoms such as an ethoxycarbonyl group, a propoxycarbonyl group or a butoxycarbonyl group; Carbonyl group, ethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group or Etc. pentylcarbamoyl group having a carbon number of 2-6 of a 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.
[0082]
Next, examples of the compound having two oxetane rings include a compound represented by the following general formula (2).
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In the formula (2), R1 is the same group as in the general formula (1). R3 is, 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. Group, linear or branched unsaturated hydrocarbon group such as propenylene group, methylpropenylene group or butenylene group, carbonyl group, alkylene group containing carbonyl group, alkylene group containing carboxyl group, or alkylene group containing carbamoyl group And so on.
[0083]
R3 is also a polyvalent group selected from the groups represented by the following formulas (3), (4) and (5).
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In the formula (3), R4 is a carbon atom such as 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, a methoxy group, an ethoxy group, a propoxy group or a butoxy group. A alkoxy group, a halogen atom such as a chlorine atom or a bromine atom, a nitro group, a cyano group, a mercapto group, a lower alkylcarboxyl group, a carboxyl group, or a carbamoyl group.
[0084]
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In the formula (4), R5 is an oxygen atom, a sulfur atom, a methylene group, NH, SO, SO2, C (CF3) 2 or C (CH3) 2.
[0085]
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In the formula (5), R6 is 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 an aryl group. n is an integer of 0 to 2000. R7 is 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 an aryl group.
[0086]
R7 is also a group selected from the group represented by the following formula (6).
Embedded image

In the formula (6), R8 is 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.
[0087]
Specific examples of the compound having two oxetane rings include compounds represented by the following formulas (7) and (8).
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The compound represented by the formula (7) is a compound in which R1 is an ethyl group and R3 is a carboxyl group in the formula (2).
[0088]
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The compound represented by the formula (8) is a compound in which, in the general formula (2), R1 is an ethyl group, R3 is the formula (5), R6 and R7 are methyl groups, and n is 1.
[0089]
Among the compounds having two oxetane rings, preferred examples other than the above-mentioned compounds include compounds represented by the following general formula (9). In the formula (9), R1 is the same group as in the general formula (1).
Embedded image

[0090]
Examples of the compound having 3 to 4 oxetane rings include a compound represented by the following general formula (10).
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In the formula (10), R1 is the same group as in the general formula (1). R9 is, for example, a branched alkylene group having 1 to 12 carbon atoms such as groups represented by the following formulas (11) to (13), or a branched poly (alkyleneoxy) such as a group represented by the following formula (14). And a branched polysiloxy group such as a group or a group represented by the following formula (15). j is 3 or 4.
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In the formula (11), R10 is a lower alkyl group such as a methyl group, an ethyl group or a propyl group.
[0091]
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In the formula (14), 1 is an integer of 1 to 10.
[0092]
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Specific examples of the compound having 3 to 4 oxetane rings include a compound represented by the following formula (16).
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[0093]
Further, examples of the compound having 1 to 4 oxetane rings other than those described above include a compound represented by the following formula (17).
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In the formula (17), R8 is the same group as in the formula (6). R11 is 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.
[0094]
Preferred specific examples of the oxetane compound used in the present invention include the following compounds.
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[0095]
The method for producing the compound having an oxetane ring 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. Other than these, compounds having a high molecular weight of about 1,000 to 5,000 and having 1 to 4 oxetane rings are also exemplified.
[0096]
Examples of these include the following compounds.
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Here, p is 20 to 200.
[0097]
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Here, q is 15 to 100.
[0098]
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Here, s is 20 to 200.
[0099]
In the present invention, at least one oxetane compound as a photopolymerizable compound and at least one compound selected from an epoxy compound and a vinyl ether compound are contained for the purpose of suppressing shrinkage of the recording medium R upon curing of the ink. Is preferred.
[0100]
As the above-mentioned cationic photopolymerization initiator, for example, a chemical amplification type photoresist or a compound used for photocationic polymerization is used (Organic Materials Research Society, "Organic Materials for Imaging", Bunshin Publishing Co., Ltd.). (1993), pp. 187-192). Examples of compounds suitable for the present invention are given below. First, B (C6F5) 4-, PF6-, AsF6-, SbF6-, CF3SO3- salts of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, and phosphonium can be given. Those having a borate compound as a counter anion are preferable because of high acid generating ability. Specific examples of the onium compound are shown below.
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[0101]
Second, a sulfonated compound that generates sulfonic acid can be given. Specific compounds are exemplified below.
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[0102]
Third, halides that photogenerate hydrogen halides can also be used. Specific compounds are shown below.
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[0103]
Fourth, an iron allene complex can be mentioned.
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[0104]
The ink of the present invention contains, for the first time, an acid proliferating agent that newly generates an acid by an acid generated by irradiation with active energy rays, which is disclosed in JP-A-8-248561 and JP-A-9-034106. Is preferred. The use of the acid multiplying agent enables further improvement in ejection stability.
The ink according to the present invention preferably contains at least one photoacid generator selected from aromatic onium compounds of diazonium, iodonium or sulfonium having an aryl borate compound as a counter ion, and iron arene complexes.
[0105]
As the above-mentioned coloring material, a coloring material that can be dissolved or dispersed in the main component of the polymerizable compound can be used, but a pigment is preferable in terms of weather resistance.
Pigments that can be preferably used in the present invention are listed below.
C. I Pigment Yellow-1, 3, 12, 13, 14, 17, 81, 83, 87, 95, 109, 42,
C. I Pigment Orange-16, 36, 38,
C. I Pigment Red-5, 22, 38, 48: 1, 48: 2, 48: 4, 49: 1, 53: 1, 57: 1, 63: 1, 144, 146, 185, 101,
C. I Pigment Violet-19, 23,
C. I Pigment Blue-15: 1, 15: 3, 15: 4, 18, 60, 27, 29,
C. I Pigment Green-7, 36,
C. I Pigment White-6, 18, 21,
C. I Pigment Black-7,
[0106]
Further, in the present invention, it is preferable to use a white ink in order to improve the color concealing property on a transparent substrate such as a plastic film. In particular, it is preferable to use white ink in the formation of a soft package image or a label image. However, since the ejection amount is large, the white ink is naturally used from the viewpoint of the ejection stability and the occurrence of curling and wrinkling of the recording medium R described above. There are restrictions on the amount.
[0107]
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. As the dispersant, a polymer dispersant is preferably used, and as the polymer dispersant, Solsperse series of Avecia is mentioned.
[0108]
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 dispersing medium is performed using a solvent or a polymerizable compound. However, in the case of the radiation-curable ink used in 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.
[0109]
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. 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 according to the present invention, the colorant concentration is preferably 1% by mass to 10% by mass of the whole ink.
[0110]
Various additives other than those described above can be used in the UV ink of this example. For example, in order to improve the storage stability of the ink composition, a polymerization inhibitor can be added in an amount of 200 to 20,000 ppm. Since it is preferable that the ultraviolet curable ink is heated and reduced in viscosity before ejection, it is preferable to add a polymerization inhibitor in order to prevent head clogging due to thermal polymerization. In addition, if necessary, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, waxes, etc. Can be added.
[0111]
In order to improve the adhesion to the recording medium R, it is also effective to add a trace amount of an organic solvent. In this case, the addition is effective within a range that does not cause a problem of solvent resistance and VOC (volatile organic compound), and the amount of use is 0.1 to 5%, preferably 0.1 to 3%. %. Further, a thermal acid generator may be included to accelerate the curing of the UV ink by heating. It is also possible to combine a radical polymerizable monomer and an initiator to obtain a radical-cation hybrid cured ink.
[0112]
The above-described UV ink is ejected and drawn on the recording medium R by an ink jet recording method, and then the ink is cured by irradiating ultraviolet rays (active energy rays).
Here, the total ink film thickness after the ink lands and is cured by irradiating ultraviolet rays is preferably 2 to 20 μm. In the field of screen image formation, the total ink film thickness is over 20 μm at present, but in the field of flexible packaging image formation where the recording medium R is often a thin plastic material, the curl It cannot be used not only because of the problem of wrinkles but also because of the problem that the stiffness and texture of the entire image-formed product change.
[0113]
As for the ink ejection conditions, it is preferable that the recording head and the ink are heated to 30 to 100 ° C. and ejected from the viewpoint of ejection stability. Active energy ray-curable inks have large fluctuations in viscosity due to temperature fluctuations, and fluctuations in viscosity directly affect the droplet size and droplet ejection speed, causing image quality degradation. 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.
[0114]
In the present invention, it is preferable that the amount of liquid droplets ejected from each nozzle is 2 to 15 pl. In order to form a high-definition image, it is necessary that the droplet amount is within this range. However, in the case of discharging with this droplet amount, the above-described discharge stability becomes particularly severe, and an acid multiplying agent is essential. Become.
In the image recording method of the present invention, as the irradiation condition of the generated light beam, it is preferable that ultraviolet light is irradiated during 0.001 to 2.0 seconds after the ink has landed, more preferably 0.001 to 1.0 seconds. It is. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.
[0115]
A basic method of irradiating light (ultraviolet light) 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. Pat. 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 ultraviolet rays. . In the image forming method of the present invention, any of these irradiation methods can be used.
[0116]
Further, a method of irradiating ultraviolet rays into two stages, first irradiating ultraviolet rays by 0.001 to 2.0 seconds after landing of the ink by the above-described method, and further irradiating active energy rays after completion of all printing. Is also one of the preferred embodiments. By dividing the irradiation of the ultraviolet light into two stages, it is possible to further suppress the contraction of the recording medium R that occurs when the ink is cured.
[0117]
In this example, it is preferable to use ultraviolet light of low illuminance having a maximum illuminance of 0.1 to 50 mW / cm2 in a wavelength range effective for curing. Conventionally, in the UV inkjet system, a light source having a high illuminance having a maximum illuminance exceeding 50 mW / cm2 in a wavelength region effective for curing has been generally used in order to suppress dot spread and bleeding after ink landing. However, when these light sources are used, particularly in the case of a shrink label or the like, the contraction of the recording medium R is so large that it cannot be practically used. In this example, by using an acid multiplying agent, a high-definition image can be formed and recorded even when ultraviolet light having a low illuminance of 0.1 to 50 mW / cm2 in a wavelength range effective for curing is used. There is no contraction of the medium R.
[0118]
Examples of the light source used for ultraviolet irradiation include, but are not limited to, a low-pressure mercury lamp, a UV laser, a xenon flash lamp, an insect lamp, a black light, a germicidal lamp, a cold cathode tube, and an LED.
In the present invention, it is also effective to use ultraviolet rays having a maximum illuminance of 50 to 3000 mW / cm2 in a wavelength range effective for curing. Although it is a high illuminance light source used for conventional UV inkjet recording, there is a problem of shrinkage of the recording medium R as described above, and practically UV inkjet recording has not been used in the field of soft packaging image formation / label image formation. According to the configuration of the present invention, this problem is solved, and a high-definition image can be formed on various plastic films using a conventionally used high-illuminance light source. Examples of the light source include, but are not limited to, a high-pressure mercury lamp, a metal halide lamp, and an electrodeless UV lamp.
[0119]
As the recording medium R that can be used in this example, in addition to ordinary uncoated paper, coated paper, etc., various non-absorbable plastics and films thereof used for so-called soft packaging can be used. Examples include PET film, OPS film, OPP film, ONy film, PVC film, PE film, and TAC film. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, PVA, rubbers and the like can be used.
[0120]
Further, the present invention can be applied to metals and glasses. Among these recording media R, the configuration 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 that 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.
[0121]
The surface energies of these various plastic films are greatly different, and it has been a problem that the dot diameter after ink landing varies depending on the recording medium R. According to the configuration of the present invention, a good high-definition image is formed on a wide range of recording media R having a surface energy of 35 to 60 dyn / cm, including an OPP film having a low surface energy, an OPS film, and a PET having a relatively large surface energy. it can.
In the present invention, it is better to use a long (web) recording medium R in terms of the cost of the recording medium R such as packaging cost and production cost, the production efficiency of prints, and the ability to cope with prints of various sizes. It is advantageous.
[0122]
Next, the operation of the inkjet printer A of the present invention will be described.
In an ink jet printer, an image can be formed by setting an ink cartridge, a recording medium R, and the like, and turning on the power.
When the ink is supplied from the ink cartridge, the control unit 30 detects the temperature of the ink in the ink storage unit 18 based on the detection result of the head temperature sensor 19. Then, the control unit 30 selects heating temperature data corresponding to the detected temperature, controls the output states of the surface heater 16 and the head heater 13 based on the selected heating temperature data, and controls the in-head supply. The heating is performed so that the ink in the passage 11 is within a predetermined temperature range (for example, within a range of 1 ° C. above and below the first target set temperature).
[0123]
Next, the operation from when the recording medium R is fed to when it is discharged will be described.
First, here, setting information is entered into input means 53 such as an operation panel and a keyboard by a manual operation of the operator. In this case, the setting information is information on the properties of the recording medium R such as a form: a roll-shaped film, a material: PET, and a thickness: 0.05 mm. Thus, the input unit 53 inputs the setting information to the control unit 30 via the interface 31. This setting information is stored in the memory 33 of the control unit 30.
In the inkjet printer A, the leading end of the recording medium R set on a spindle (not shown) is guided to the transport roller 1a along a paper feed guide (not shown), and the leading end of the recording medium R is aligned.
[0124]
The aligned recording medium R is transported to the image forming unit 2 by the transport roller 1a. During this time, the temperature sensor 52a as the medium temperature detecting means 52 detects the temperature of the recording medium R on which an image is to be formed by the recording head 21. The temperature sensor 52a inputs the detected temperature information to the control unit 30 via the interface 31. This detected temperature information is stored in the memory 33 of the control unit 30.
Then, the CPU 32 of the control unit 30 reads the detected temperature information stored in the memory 33 and the target set temperature information corresponding to the set information, and performs a comparison operation. If the CPU 32 determines that the temperature of the recording medium R needs to be increased or decreased according to the calculation result, the CPU 32 inputs an operation signal to the medium temperature adjusting unit 51 via the interface 31. Then, the medium temperature adjusting means 51 operates. In this case, the heater 51a operates to generate radiant heat from the heater 51a, thereby heating the recording medium R from the image forming surface side.
When it is determined that the temperature of the recording medium R does not need to be increased or decreased according to the calculation result, the CPU 32 does not input the operation signal to the medium temperature adjusting unit 51. Therefore, the heater 51a as the medium temperature adjusting means 51 does not operate, and the recording medium R is not heated.
In this way, the medium temperature adjusting mechanism 5 controls the temperature of the recording medium R on which an image is formed by the recording head 21 to the second target set temperature based on the temperature information detected by the medium temperature detecting means 52. I have.
[0125]
Subsequently, the recording medium R is guided in the transport direction F while the non-image forming surface side is supported by the guide member 4 in a state where the temperature is controlled by the medium temperature adjusting mechanism 5. Although the non-image forming surface side of the recording medium R is supported by the guide member 4, the recording medium R is in a state of being sucked and held by the platen 4a as described above.
[0126]
Then, an image is formed by the recording head 21 on the image forming surface of the recording medium R on which the non-image forming surface is supported. More specifically, in a state where the non-image forming surface of the recording medium R is suction-held by the platen 4a, the recording head 21 moves in the scanning direction along with the operation of the carriage 22 to apply UV ink to the image forming surface of the recording medium. Discharge and image formation are performed. The recording medium R on which the image formation has been performed is conveyed downstream of the recording head 21 in the conveying direction F, that is, immediately below the UV lamp 3.
[0127]
Subsequently, the recording medium R conveyed immediately below the UV lamp 3, that is, the recording medium R to which the UV ink has adhered is irradiated with UV from the UV lamp 3, and the UV ink adhered to the recording medium R is cured. . Then, the recording medium R that has gone through the above steps is discharged through a discharge guide (not shown).
[0128]
In this embodiment, the head temperature control means of the head temperature adjustment mechanism and the medium temperature control means of the medium temperature adjustment mechanism are constituted by a common control device. Accordingly, the number of components of the ink jet printer can be reduced, and the temperature control of the UV ink in the head and the temperature control of the recording medium before UV irradiation can be efficiently performed by interlocking both controls.
In the present embodiment, the target set temperature can be changed. However, in this embodiment, the head temperature adjustment mechanism and the medium temperature adjustment mechanism operate in conjunction with the change of one target set temperature. The set temperature is changed. For this reason, after comprehensively determining the external environment, the type of UV ink, the type of recording medium, and the like, each target set temperature can be set to an appropriate temperature, and more reliable and efficient high-quality images can be obtained. The formation can take place. For example, when a change of the recording medium R is input by the input unit 53, an appropriate second target set temperature can be derived, and a first target set temperature corresponding thereto can also be derived.
[0129]
As described above, according to the ink jet printer A according to the present embodiment, the temperature of the UV ink in the recording head 21 can be controlled to the first target set temperature by the head temperature adjusting mechanism 6, so that the viscosity is reduced to a certain level. UV ink can be ejected. In addition, the temperature of the UV ink can be raised in advance to a temperature at which it can be cured even in a high humidity state, and can be controlled to a substantially constant temperature.
[0130]
Further, since the temperature of the recording medium R can be controlled to the second target set temperature by the medium temperature adjusting mechanism 5, the temperature is controlled to be substantially constant in the recording head to have substantially constant viscosity, and the recording medium R lands on the recording medium R. The UV ink thus obtained can be made to have a constant viscosity based on the temperature of the recording medium R which is now controlled to a constant temperature, thereby improving the image forming quality. In this case, since the temperature of the recording medium R is always kept constant, the time required for the UV ink adhered to the recording medium R to change from a low-viscosity state to a high-viscosity state depends on the temperature of the recording medium R. Does not change.
[0131]
Accordingly, the diameter of the droplet of the UV ink on the recording medium R is always stable. Further, the UV ink controlled to the first target set temperature, which is a temperature at which the UV ink sufficiently cures even under high humidity, by the head temperature control mechanism 6, is sufficiently controlled by the medium temperature control mechanism 5 even under high humidity. The ink droplets (dots) landed on the recording medium R even under high humidity can be reliably illuminated on the recording medium R under substantially the same conditions by irradiating the ultraviolet light even when the ink lands on the recording medium controlled to a temperature at which the UV ink cures Will cure.
[0132]
From the above, the adhesion and bleeding of the UV ink to the recording medium R are always stable, the dot diameter of the UV ink is stable, and there is no color mixture. Accordingly, even if the temperature of the UV ink before being supplied to the recording head 21 and the temperature of the recording medium R before image formation change due to the influence of the environment, the temperature change of the UV ink and the recording medium R It is possible to form a high quality image without deteriorating the image forming quality due to the humidity around the ejected UV ink.
[0133]
Although the temperature of the ink controlled by the head temperature adjusting mechanism 6 and the temperature of the recording medium R controlled by the medium temperature adjusting mechanism 5 in the recording head 21 may be the same, there is a basic possibility. The temperature is determined differently for each. That is, the temperature of the ink in the recording head 21 is a temperature at which the UV ink sufficiently cures even under high humidity, and a temperature at which the viscosity of the UV ink drops to a viscosity that can be stably ejected from the recording head. The temperature of the medium R is a temperature at which the UV ink that has landed and adhered has a viscosity that provides a preferable dot diameter, and hardens even under high humidity. Since the temperature of the ink ejected from the recording head 21 and the temperature of the recording medium R on which the ink lands are substantially constant, the UV ink ejected from the recording head 21 and arriving on the recording medium R is: At any time, the temperature changes almost in the same manner, and a high quality image can be formed with a stable dot diameter.
[0134]
Further, in the ink jet printer A according to the present embodiment, the head temperature control means 30 controls the head temperature adjustment means 13 and 16 based on the detection result of the head temperature detection means 19, so that the head temperature control means 30 is in the recording head 21. The outputs of the head temperature adjusting means 13 and 16 can be changed according to the temperature of the UV ink. Thus, the temperature of the UV ink in the recording head can be reliably controlled by the first target set temperature, and high-quality image formation can be maintained more reliably.
Further, the medium temperature control means 30 controls the medium temperature adjustment means 51 based on the detection result of the medium temperature detection means 52, so that the medium temperature adjustment means 51 corresponds to the temperature of the recording medium R before the temperature adjustment. Output can be changed. Thus, the temperature of the recording medium R can be controlled more reliably by the second target set temperature, and high-quality image formation can be maintained more reliably.
[0135]
Next, a modified example of the above-described media temperature adjusting mechanism 5 will be described with reference to FIGS. In detail, in the modified examples shown in FIGS. 5 to 7, at least one of the medium temperature adjusting means 51 and the medium temperature detecting means 52 shown in FIG. 2 is different, and the other components are the same as those in the above example. . Therefore, these components are denoted by the same reference numerals as in the above example, and detailed description is omitted.
[0136]
As shown in FIG. 5, a heating / cooling system using a Peltier element as the medium temperature adjusting means 51 is applied. This heating / cooling system includes Peltier device built-in rollers 51f and 51g each having a built-in Peltier device. These Peltier element built-in rollers 51f and 51g are arranged adjacent to each other with the recording medium R interposed therebetween, and are driven to rotate in opposite directions to convey the recording medium R in the conveying direction F while sandwiching the recording medium R. When the built-in Peltier device operates in these Peltier device built-in rollers 51f and 51g, the sandwiched recording medium R can be heated or cooled from both sides of the image forming surface and the non-image forming surface. Since the Peltier element simultaneously absorbs and dissipates heat, for example, in the case of cooling, it is necessary to make the Peltier element built-in rollers 51f and 51g hollow, and to blow heat to the hollowed portion with a fan or the like to release the heat. is there.
[0137]
Further, a thermocouple sensor 52b is applied as the medium temperature detecting means 52. The thermocouple sensor 52b connects two different types of metals in a ring shape and detects the temperature of the recording medium R from the thermoelectric quantity generated by the temperature difference between the two contacts.
Therefore, in this case, the cooling system using the Peltier element is operated based on the temperature information detected by the thermocouple sensor 52b as the medium temperature detecting means 52, and the recording medium R on which the image is formed by the recording head 21 is cooled. Then, the temperature of the recording medium R is controlled to the target set temperature.
[0138]
Further, as shown in FIG. 6, a heating system using a heater 51h and a radiation lamp 51i as the medium temperature adjusting means 51 is applied. The heater 51h is arranged on the back side of the guide member 4. When the heater 51h is activated, the recording medium R whose non-image forming surface is supported by the guide member 4 (or platen 4a) can be heated from the non-image forming surface through the guide member 4 (or platen 4a). It has become. Note that the guide member 4 (or the platen 4a) is preferably formed of a material having high thermal conductivity, and is formed of a material that can mediate heating of the recording medium R quickly and efficiently. Is preferred. The radiation lamp 51i is fixed to the carriage rail 23 of the image forming unit 2 and radiates infrared rays. When the radiation lamp 51i operates, infrared rays are radiated to the image forming surface side of the recording medium R, and the recording medium R can be heated from the image forming surface side. Further, a thermocouple sensor 52b similar to the one shown in FIG.
Therefore, in this case, based on the temperature information detected by the thermocouple sensor 52b as the medium temperature detecting means 52, the heating system using the heater 51h and the radiation lamp 51i is operated, and the recording is performed by the recording head 21. The medium R is heated, and the temperature of the recording medium R is controlled to a target set temperature. In this case, the temperature of the recording medium R may be controlled by providing a heating system for only one of the heater 51h and the radiation lamp 51i.
[0139]
As described above, also in the modified examples shown in FIGS. 5 and 6, the same effects as in the above example shown in FIG. Further, in the examples shown in FIGS. 1, 5 and 6, the temperature of the recording medium R is controlled to the second target set temperature by the medium temperature adjusting mechanism 5, but it is possible to cool the recording medium R. For example, it is possible to prevent the temperature of the recording medium R from increasing due to UV irradiation, and to prevent the recording medium R from being deteriorated.
In the examples shown in FIGS. 1, 5 and 6, the medium temperature adjusting means 51 is provided at a position on the upstream side of the recording head 21 in the transport direction F or at a position facing the recording head 21 to perform image formation. Heating or heating and cooling of the recording medium R is performed before or during image formation (including slightly before and after image formation). In addition, the medium temperature adjusting means 51 is moved from the recording head 21 in the transport direction F by the recording head 21. Heating or cooling of the recording medium R after image formation may be provided at a downstream position (however, upstream of the UV irradiation means). It is preferable that the recording medium R is basically set to the target set temperature just before the UV ink lands, and that the print medium R keeps the target set temperature substantially until the UV irradiation ends even after the landing.
[0140]
Also, here, as in a heater 51h shown in FIG. 6, the medium temperature adjusting means 51 is provided on the non-image forming surface side of the recording medium R, and heats the recording medium R from the non-image forming surface side of the recording medium R. Alternatively, it is preferable to perform heating and cooling. Because the image forming surface side of the recording medium R is not directly affected by the heating or the heating and cooling by the temperature adjusting means 51, the surface of the image forming surface is not deteriorated and does not affect the image forming quality. Thereby, deterioration of image formation quality can be prevented, and high quality image formation can be maintained. When the media temperature adjusting means 51 is provided on the back side of the guide member 4 (or the platen 4a) as in the heater 51h shown in FIG. 6, the guide member 4 (or the platen 4a) is made of a material having a large thermal conductivity. It is preferable that the recording medium R be formed of a material that can mediate heating or cooling of the recording medium R quickly and efficiently.
[0141]
Further, according to the ink jet printer A of the present embodiment, since the ink of the recording head 21 is heated by the surface heater 16 and the head heater 13, the ink supplied to the recording head 21 Can be prevented from being cooled due to the influence of the ink, and the viscosity of the ink can be reduced in the recording head 21 as much as necessary for stable ejection. Therefore, stable ejection can be maintained, and clear image formation can be performed.
Further, even if the ink in the recording head 21 is cooled to increase the viscosity, the ink can be heated again by the surface heater 16 and the head heater 13 to reduce the viscosity.
[0142]
Further, since the head temperature control means (control section 30) controls the surface heater 16 and the head heater 13 based on the detection result of the head temperature sensor 19, the head temperature control means (control section 30) corresponds to the temperature of the ink in the recording head 21. The outputs of the surface heater 16 and the head heater 13 can be changed. That is, if the temperature of the ink of the recording head 21 is equal to or higher than the first target set temperature (for example, a temperature at which the viscosity is reduced as required for stable ejection), the outputs of the surface heater 16 and the head heater 13 are weakened, If the temperature is equal to or lower than the first target set temperature, the output can be increased. Therefore, the ink can be efficiently heated in the recording head 21.
[0143]
It should be noted that the embodiments disclosed this time are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0144]
【Example】
Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.
Table 1 shows the composition of the cation-curable ink used in this example. Table 2 shows the composition of the radical-curable ink used as a comparative example.
[Table 1]

[Table 2]

[0145]
In Tables 1 and 2, K, C, M, and Y indicate dark black, dark cyan, dark magenta, and dark yellow inks, respectively, and Lk, Lc, Lm, and Ly indicate light black and light cyan, respectively. , Light magenta and light yellow inks. The components of each ink are represented by mass% of each component.
[0146]
The acid proliferating agents in Table 1 are as follows.
Embedded image

The initiators (photoacid generators) in Table 1 are as follows.
Embedded image

The particle diameters of titanium oxide shown in Tables 1 and 2 are average particle diameters.
[0147]
The ink jet printer used in this embodiment basically has the configuration shown in FIG. 1, but has a recording head 22 having a piezo type ink jet nozzle using a piezo element. The ink supply system includes an ink tank, a supply pipe (tube), a front chamber ink tank immediately before the head, a pipe with a filter, and a recording head 22 having a piezo-type inkjet nozzle. As described above, the recording head 22 can be heated.
The recording head 22 drives the multi-size dots of 2 to 15 pl so that they can be discharged at a resolution of 720 × 720 dpi (dpi represents the number of dots per inch, that is, 2.54 cm), and discharges the above-described ink. It was taken.
The irradiation conditions after landing were as shown in Table 3. The illuminance on the recording medium was adjusted by adjusting the distance between the UV lamp 3 and the recording medium shown in FIG. The UV lamps 3 were installed on both sides of the recording head 22.
[0148]
Table 3 shows the experimental conditions.
[Table 3]

The image formation by the ink-jet printer was performed on a sheet-shaped recording medium R made of the recording materials shown in Table 3. The recording medium R had a surface energy shown in Table 3, a width of 600 mm, and a length of 1000 m. An image of 500 m or more was formed on a long roll-shaped recording medium R. The images include text and color pictures. As characters, 6-point MS Mincho characters were printed at target densities of Y, M, C, and K colors.
As the recording medium R, OPP (Oriented polypropylene), PET (Polyester), ONy (Oriented nylon), Shrink PVC (Polyvinyl chloride), Shrink OPS (Oriented polystyrene), Yupo adhesion paper (synthetic paper). Was used.
[0149]
The UV ink temperature in the print head 22 (first target set temperature) in the print head 22 and the temperature of the print medium R before and after the ink landed in the comparative example and the example were set as follows.
Test No. In Examples 1 to 6 (Comparative Examples), radical curable ink was used as the UV ink, and the UV ink and the above-described six types of recording media R were not heated and temperature control was not performed. Test No. 7 to 12 (Comparative Examples) use radical curable ink as the UV ink, and control the heating of the ink so that the UV ink is at 50 ° C. so that the above-described six types of recording media R are at 40 ° C. The heating of the recording medium R was controlled.
Test No. 13 to 18 (comparative examples) use a cationic curable ink as the UV ink, and control the heating of the ink so that the UV ink is at 50 ° C. Control was not performed.
[0150]
Test No. 19 to 24 (Examples) use a cationic curable ink as the UV ink and control the heating of the ink so that the UV ink is at 50 ° C. so that the above-described six types of recording media R are at 40 ° C. The heating of the recording medium R was controlled.
Test No. 25 to 30 (Examples) use a cationic curable ink as the UV ink and control the heating of the ink so that the UV ink is at 50 ° C. so that the above-described six types of recording media R are at 50 ° C. The heating of the recording medium R was controlled.
[0151]
Table 4 shows the experimental results.
[Table 4]

In Table 4, △, △, Δ, and × of the character qualities are obtained by enlarging the roughness of the characters with a loupe for the above-described six-point characters and evaluating them based on the following definition.
◎… No roughness.
○: Slight roughness is visible.
△: A rough level that can be seen as a character but can be distinguished as a character and can be used to the last minute.
×: The level is so rough that the letters are faint and cannot be used.
[0152]
◎, △, Δ, and × of color mixing (bleeding) are obtained by enlarging each adjacent color dot of the formed image with a loupe and visually evaluating the degree of bleeding based on the following definition.
A: Neighboring dot shapes keep a perfect circle, and there is no bleeding.
…: The adjacent dot shapes keep a substantially perfect circle, and there is almost no bleeding.
Δ: Adjacent dots are slightly blurred, and the dot shape is slightly distorted, but at a level that can be used barely.
×: A level that cannot be used because adjacent dots are blurred and mixed.
[0153]
Regarding wrinkles and curls of the printed matter, ◎, ○, Δ, and ×, the printed matter was picked up immediately after printing, and visually evaluated whether wrinkles and curls were generated by irradiation and curing.
…: Good without wrinkles and curls.
…: Almost good, almost no wrinkles or curls.
Δ: Wrinkles and curls were slightly observed, but somehow practically acceptable.
×: Unusable level where wrinkles and curls are seen in printed matter.
The above evaluations were performed at 10 m, 100 m, and 500 m when image formation was performed on a 1000 m recording medium R over 500 m or more.
[0154]
As shown in Table 4, Test No. When the temperature of the UV ink and the recording medium R was not controlled using the radical curable inks of Nos. 1 to 6 (Comparative Example), all of the character quality, color mixture, and wrinkles and curls of the printed matter were x. It was evaluated.
Test No. Test Nos. 7 to 12 (comparative examples) using UV curable inks and recording medium R controlled at 50 ° C. and 40 ° C., respectively, using radical curable inks of Test No. Although a significant improvement is seen with respect to Nos. 1 to 6, depending on the material of the recording medium R, the evaluation of the character quality, color mixture, and wrinkles and curls of the printed matter is evaluated as △. Inferior quality compared.
[0155]
Test No. Using the cationically curable inks of 13 to 18 (Comparative Examples), the UV ink was controlled at 50 ° C., and the temperature of the recording medium R was not controlled, there was no evaluation of × at 10 m. However, when it exceeded 100 m, the number of evaluations of x with color mixture, wrinkles and curls increased, and even if it was not x, it was evaluated as △ and none was evaluated as ○.
[0156]
Test No. With respect to those using a cationically curable ink of 19 to 30 (Example) and controlling the UV ink and the recording medium R at 50 ° C. and 40 ° C. or 50 ° C., respectively, there was no evaluation of Δ, and some ◎ was also seen. When the ink temperature was 40 ° C. For Nos. 19 to 24, Nos. Of ink temperature 50 ° C. 25-No. In No. 30, the wrinkles and curls of the printed matter were improved with respect to the recording medium except for the shrink PVC and the shrink OPS, and a higher temperature may provide better results, but depending on the type of the recording medium, (For example, a shrink film that is easily shrunk by heat) may be affected by heating.
[0157]
That is, if the recording medium R is resistant to heat (for example, the heat-resistant temperature is 60 ° C. or higher), heating at 40 ° C. or higher or 50 ° C. or higher is preferable. It is believed that good results can be obtained by heating to below 60 ° C (60 ° C or below if the heat resistant temperature is 60 ° C).
On the other hand, in a shrink film or the like formed to be contracted by heat, for example, the temperature is preferably higher than room temperature (for example, 20 ° C. or higher), 50 ° C. or lower, or 40 ° C. or lower.
As described above, according to the present invention, with respect to various recording media R, high quality, good character quality, no color mixing or bleeding, and no wrinkling or curling of the recording medium. Image formation is now possible.
[0158]
【The invention's effect】
According to the present invention, an image is formed by an ink jet recording method using a cation-curable ink, and the cation-curable ink is heated in a recording head, and by heating a recording medium, a thin-film plastic film or the like is formed. Even on a soft recording medium, an image can be formed with a stable dot diameter without wrinkling or curling due to contraction of the recording medium. Therefore, high-quality images can be formed on recording media of various materials.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part showing an image forming portion of an ink jet printer according to an embodiment.
FIG. 2 is a main control block diagram of a control unit provided in the ink jet printer of FIG. 1;
FIG. 3 is a perspective view illustrating a recording head provided in the inkjet printer of FIG.
4A and 4B are cross-sectional views of the recording head of FIG. 3, in which FIG. 4A is a cross-sectional view taken along a plane D in FIG. 3, and FIG. 4B is a cross-sectional view taken along a plane E in FIG.
FIG. 5 is a sectional view of a main part showing a modification of the image forming portion.
FIG. 6 is a sectional view of a main part showing a modification of the image forming portion.
[Explanation of symbols]
A Inkjet printer
F Transport direction
R recording medium
1a, 1b Conveying rollers (conveying means)
3 UV lamp (UV irradiation means)
4 Guide member
5 Media temperature control mechanism
6 Head temperature control mechanism
11 Supply path in head (supply path)
13 Head heater (head temperature control means)
15 Discharge port
16 surface heaters (head temperature control means)
17 Ink inlet
18 Ink storage section
19 Head temperature sensor (head temperature detecting means)
30 control part (head temperature control means, medium temperature control means)
21 Recording head
51 Media temperature control means
51a heater (part of media temperature control means)
51b Reflector (part of media temperature control means)
51c Compressor (part of media temperature control means)
51d Cooling unit (part of media temperature control means)
51e hose (part of media temperature control means)
51f, 51g Peltier element built-in roller (part of media temperature control means)
51h heater (part of media temperature control means)
51i radiation lamp (part of media temperature control means)
52 Media temperature detecting means
52a temperature sensor (medium temperature detecting means)
52b Thermocouple sensor (medium temperature detecting means)

Claims (10)

An active energy ray-curable ink that has a recording head that ejects ink and a transport unit that transports a recording medium and is cured by being irradiated with an active energy beam is transported from the print head to the transport unit. An inkjet printer that performs image formation by discharging onto the recording medium,
In-head ink heating means for heating the active energy ray-curable ink in the recording head,
A medium heating unit that heats the recording medium on which the active energy ray-curable ink ejected from the recording head lands and an image is formed before the active energy ray-curable ink lands,
An ink jet printer, wherein the active energy ray-curable ink is a cation-curable ink. 2. The ink jet printer according to claim 1, wherein the medium heating unit heats the recording medium even after the activation energy ray-curable ink lands. An active energy ray-curable ink that has a recording head that ejects ink and a transport unit that transports a recording medium and is cured by being irradiated with an active energy beam is transported from the print head to the transport unit. An inkjet printer that performs image formation by discharging onto the recording medium,
A head temperature adjustment mechanism for controlling the temperature of the active energy ray-curable ink in the recording head within a first target set temperature range,
A medium temperature adjustment mechanism for controlling the temperature of the recording medium on which the active energy ray-curable ink ejected from the recording head lands and an image is formed within a second target set temperature range,
An ink jet printer, wherein the active energy ray-curable ink is a cation-curable ink. The medium temperature adjusting mechanism controls the temperature of the recording medium within the second target set temperature range before the active energy ray-curable ink lands, and controls the temperature of the recording medium even after the active energy ray-curable ink lands. The inkjet printer according to claim 3, wherein the control is performed within a second target set temperature range. The head temperature adjusting mechanism includes a head temperature detecting unit that detects a temperature of the active energy ray curable ink in the recording head, and an in-head ink heating unit that heats the active energy ray curable ink in the recording head. 5. The ink jet printer according to claim 3, further comprising: a head temperature control unit for controlling the in-head ink heating unit based on a detection result of the head temperature detection unit. The medium temperature adjusting mechanism includes a medium temperature detecting unit that detects a temperature of the recording medium, a medium heating unit that heats the recording medium, and the medium heating unit based on a detection result of the medium temperature detecting unit. The inkjet printer according to any one of claims 3 to 5, further comprising a media temperature control unit for controlling. The head temperature adjusting mechanism includes a head temperature detecting unit that detects a temperature of the active energy ray curable ink in the recording head, and an in-head ink heating unit that heats the active energy ray curable ink in the recording head. A head temperature control unit that controls the in-head ink heating unit based on a detection result of the head temperature detection unit,
The medium temperature adjusting mechanism includes a medium temperature detecting unit that detects a temperature of the recording medium, a medium heating unit that heats the recording medium, and the medium heating unit based on a detection result of the medium temperature detecting unit. Media temperature control means for controlling,
The ink jet printer according to claim 3, wherein the head temperature control unit and the medium temperature control unit are configured by a common control device. The inkjet printer according to any one of claims 3 to 7, wherein the head temperature adjustment mechanism is capable of changing the first target set temperature range. The ink jet printer according to any one of claims 3 to 8, wherein the medium temperature adjustment mechanism is capable of changing the second target set temperature range. The head temperature adjustment mechanism is capable of changing the first target set temperature range,
The media temperature adjustment mechanism is capable of changing the second target set temperature range,
The head temperature adjustment mechanism and the medium temperature adjustment mechanism are configured to control the other target in conjunction with a change in one of the first target set temperature range and the second target set temperature range. The inkjet printer according to any one of claims 3 to 7, wherein a set temperature range is changed.

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