JP2004284139A - Imaging method and image exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging method which enables an image to be formed without passing through a liquid development process after image exposure and gives a lithographic printing plate with outstanding resistance to plate wear, and an image exposure device best-suited for this method. <P>SOLUTION: In this image exposure device 10, an image is formed by scanning and exposing to light an image recording layer of an original lithographic printing plate 12 mounted on an outer drum 20 with the help of an infrared laser beam emitted from an exposure head 26. The image recording layer of the original plate 12 contains a microcapsule encapsulating a polymerizable compound, a polymerization initiator and a photothermal converting agent. In addition, the image exposure device 10 is equipped with a hot blast nozzle 44 mounted on the downstream side, in the subscan direction, of the exposure head 26 together with the exposure head 26 on a carrier 68. A preheater 38 blows a hot blast to the original plate 12 through the hot blast nozzle 44. Thus the image recording layer of the original plate 12 is locally preheated by the hot blast just before the exposure of the image recording layer to light by means of the infrared laser. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００７１】
【化２】

【００７２】
【化３】

【００７３】
【化４】

【００７４】
光熱変換剤の添加量は、マイクロカプセル中に添加する場合には、全マイクロカプセル内包物の１〜５０質量％が好ましく、３〜２５質量％がより好ましい。
一方、光熱変換剤を画像記録層マトリックス中に添加する場合には、記録層固形分の１〜５０質量％が好ましく、３〜２５質量％がより好ましい。この範囲において、記録層の膜強度を損なうことなく、良好な感度が得られる。
【００７５】
（重合開始剤）
本発明に係る記録層には、画像記録層マトリックス中に、熱により反応開始物質を発生し、前記重合性化合物の反応を開始、促進する重合開始剤を添加する必要がある。この場合、重合開始剤を前記マイクロカプセル内および画像記録層マトリックス中の少なくとも一方に添加すればよいが、安定性の観点から、重合性化合物とマイクロカプセル壁を隔てて存在するよう、記録層マトリックス中に添加することが好ましい。
【００７６】
本発明に用いられる重合開始剤の種類としては、公知の酸発生剤またはラジカル発生剤が挙げられ、前者は、前記マイクロカプセル中の重合性化合物としてカチオン重合性化合物を用いた場合に使用され、後者は、同じく重合性化合物としてラジカル重合性化合物を用いた場合に使用される。
また、発生した酸またはラジカルにより変色する染料と組み合わせて焼きだし系を形成することもできる。
【００７７】
以下、これら重合開始剤について説明する。
＜酸発生剤＞
本発明において、前記カチオン重合性化合物と組合せて用いられる酸発生剤としては、熱を吸収して酸を発生するものであれば、特に制限はない。このような酸発生剤としては、公知の酸前駆体、酸発生剤が好適に用いられ、例えば、焼き出し画像形成用の酸発生剤、マイクロレジスト等に使用されている酸発生剤等が挙げられる。
【００７８】
より具体的には、特開２００２−２９１６２号、特開２００２−４６３６１号、特開２００２−１３７５６２号などに記載のトリハロメチル置換へテロ環化合物に代表される有機ハロゲン化合物、イミノスルフォネート等に代表される光分解してスルホン酸を発生する化合物、ジスルホン化合物、オニウム塩（例えばヨードニウム塩、ジアゾニウム塩、スルホニウム塩など）を挙げることができる。またこれらの酸を発生する基又は化合物をポリマーの主鎖又は側鎖に導入した化合物を用いることもできる。
【００７９】
以下、本発明に好適に使用し得る酸発生剤の具体例を挙げるが、本発明はこれらに限定されるものではない。
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【化５】

【００８１】
【化６】

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上記酸発生剤は２種以上を組み合わせて用いることもできる。
酸発生剤の添加量は、記録層全固形分の０．０１〜２０質量％が好ましく、０．１〜１０質量％がより好ましい。この範囲内で、機上現像性を損なわず、良好な反応開始又は促進効果が得られる。
【００８６】
＜ラジカル発生剤＞
本発明において、ラジカル重合性化合物と組合せて用いられるラジカル発生剤としては、熱を吸収してラジカルを発生するものであれば、特に制限はない。このようなラジカル発生剤としては、公知の熱ラジカル発生剤が好適に使用され、例えば、光ラジカル重合の光開始剤などが挙げられる。
具体的には、前記酸発生剤として挙げた、スルホン酸を発生する化合物、ジスルホン化合物、オニウム塩（例えば、ヨードニウム塩、ジアゾニウム塩、スルホニウム塩など）等を、ラジカル発生剤としても使用することができる。
【００８７】
具体例としては、前記に挙げた、化合物（ＡＩ−１）〜（ＡＩ−１７）、（ＡＮ−１）〜（ＡＮ−８）および（ＡＳ−１）〜（ＡＳ−１２）を挙げることができるが、本発明はこれらに限定されるものではない。
上記ラジカル発生剤は２種以上を組み合わせて用いることもできる。
ラジカル発生剤の添加量は、記録層全固形分の０．０１〜２０質量％が好ましく、０．１〜１０質量％がより好ましい。この範囲内で、機上現像性を損なわず、良好な反応開始又は促進効果が得られる。
【００８８】
本発明の方法においては、前記予備加熱工程における予備加熱により、重合開始剤（酸発生剤またはラジカル発生剤）の分解を開始・促進することにより、カプセル壁材が透過性となり系中に放出された重合性化合物と重合開始剤との硬化反応の効率が向上する効果が得られる。このため、予備加熱温度は重合開始剤の分解を開始、促進する温度以上とすることが好ましく、分解温度を少なくとも１０℃上回る温度とすることがさらに好ましい。重合開始剤の分解温度は、化合物の種類により異なるが、例えば、ジフェニルヨードニウムトリフルオロメタンスルホン酸（ＡＩ−７；本明細書に例示の酸発生剤）の場合は１６０℃程度であり、トリフェニルスルホニウムベンゾイル蟻酸（ＡＳ−１１；本明細書に例示のラジカル発生剤）の場合は２００℃程度である。
【００８９】
また、本発明は、前記予備加熱工程によって局所的に露光領域周辺が加熱することで、重合開始剤や重合性化合物の運動性を向上させ、重合反応の開始及び進行の効率を向上させるといった目的も有する。そのため、予備加熱後、該重合開始剤や重合性化合物の運動性が失活しないうちに、赤外線ビームの照射を行うことが好ましい。その場合、予備加熱を赤外線ビーム照射開始前１分から照射開始時までの期間内に完了させることが好ましい。
【００９０】
また、本発明に係る記録層には、焼き出し画像生成のため、酸またはラジカルによって変色する化合物を添加することができる。このような化合物としては、例えばジフェニルメタン系、トリフェニルメタン系、チアジン系、オキサジン系、キサンテン系、アンスラキノン系、イミノキノン系、アゾ系、アゾメチン系等の各種色素が有効に用いられる。
【００９１】
具体例としては、ブリリアントグリーン、エチルバイオレット、メチルグリーン、クリスタルバイオレット、ベイシックフクシン、メチルバイオレット２Ｂ、キナルジンレッド、ローズベンガル、メタニルイエロー、チモールスルホフタレイン、キシレノールブルー、メチルオレンジ、パラメチルレッド、コンゴーフレッド、ベンゾプルプリン４Ｂ、α−ナフチルレッド、ナイルブルー２Ｂ、ナイルブルーＡ、メチルバイオレット、マラカイドグリーン、パラフクシン、ビクトリアピュアブルーＢＯＨ［保土ケ谷化学（株）製］、オイルブルー＃６０３［オリエント化学工業（株）製］、オイルピンク＃３１２［オリエント化学工業（株）製］、オイルレッド５Ｂ［オリエント化学工業（株）製］、オイルスカーレット＃３０８［オリエント化学工業（株）製］、オイルレッドＯＧ［オリエント化学工業（株）製］、オイルレッドＲＲ［オリエント化学工業（株）製］、オイルグリーン＃５０２［オリエント化学工業（株）製］、スピロンレッドＢＥＨスペシャル［保土ケ谷化学工業（株）製］、ｍ−クレゾールパープル、クレゾールレッド、ローダミンＢ、ローダミン６Ｇ、スルホローダミンＢ、オーラミン、４−ｐ−ジエチルアミノフェニルイミノナフトキノン、２−カルボキシアニリノ−４−ｐ−ジエチルアミノフェニルイミノナフトキノン、２−カルボキシステアリルアミノ−４−ｐ−Ｎ，Ｎ−ビス（ヒドロキシエチル）アミノ−フェニルイミノナフトキノン、１−フェニル−３−メチル−４−ｐ−ジエチルアミノフェニルイミノ−５−ピラゾロン、１−β−ナフチル−４−ｐ−ジエチルアミノフェニルイミノ−５−ピラゾロン等の染料やｐ，ｐ’，ｐ”−ヘキサメチルトリアミノトリフェニルメタン（ロイコクリスタルバイオレット）、Ｐｅｒｇａｓｃｒｉｐｔ Ｂｌｕｅ ＳＲＢ（チバガイギー社製）等のロイコ染料が挙げられる。
【００９２】
上記の他に、感熱紙や感圧紙用の素材として知られているロイコ染料も好適なものとして挙げられる。具体例としては、クリスタルバイオレットラクトン、マラカイトグリーンラクトン、ベンゾイルロイコメチレンブルー、２−（Ｎ−フェニル−Ｎ−メチルアミノ）−６−（Ｎ−ｐ−トリル−Ｎ−エチル）アミノ−フルオラン、２−アニリノ−３−メチル−６−（Ｎ−エチル−ｐ−トルイジノ）フルオラン、３，６−ジメトキシフルオラン、３−（Ｎ，Ｎ−ジエチルアミノ）−５−メチル−７−（Ｎ，Ｎ−ジベンジルアミノ）−フルオラン、３−（Ｎ−シクロヘキシル−Ｎ−メチルアミノ）−６−メチル−７−アニリノフルオラン、３−（Ｎ，Ｎ−ジエチルアミノ）−６−メチル−７−アニリノフルオラン、３−（Ｎ，Ｎ−ジエチルアミノ）−６−メチル−７−キシリジノフルオラン、３−（Ｎ，Ｎ−ジエチルアミノ）−６−メチルー７−クロロフルオラン、３−（Ｎ，Ｎ−ジエチルアミノ）−６−メトキシ−７−アミノフルオラン、３−（Ｎ，Ｎ−ジエチルアミノ）−７−（４−クロロアニリノ）フルオラン、３−（Ｎ，Ｎ−ジエチルアミノ）−７−クロロフルオラン、３−（Ｎ，Ｎ−ジエチルアミノ）−７−ベンジルアミノフルオラン、３−（Ｎ，Ｎ−ジエチルアミノ）−７，８−ベンゾフロオラン、３−（Ｎ，Ｎ−ジブチルアミノ）−６−メチル−７−アニリノフルオラン、３−（Ｎ，Ｎ−ジブチルアミノ）−６−メチル−７−キシリジノフルオラン、３−ピペリジノ−６−メチル−７−アニリノフルオラン、３−ピロリジノ−６−メチル−７−アニリノフルオラン、３，３−ビス（１−エチル−２−メチルインドール−３−イル）フタリド、３，３−ビス（１−ｎ−ブチル−２−メチルインドール−３−イル）フタリド、３，３−ビス（ｐ−ジメチルアミノフェニル）−６−ジメチルアミノフタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−４−ザフタリド、３−（４−ジエチルアミノフェニル）−３−（１−エチル−２−メチルインドール−３−イル）フタリド、などが挙げられる。
酸またはラジカルによって変色する染料の好適な添加量は、それぞれ、記録層固形分に対して０．０１〜１０質量％の割合である。
【００９３】
（親水性樹脂）
本発明に係る記録層マトリックス中には、機上現像性や記録層自体の皮膜強度向上、さらに、電磁波加熱を実施する場合の加熱効率向上のため親水性樹脂を含有させてもよい。
親水性樹脂としては、例えばヒドロキシ基、アミノ基、カルボキシ基、リン酸基、スルホン酸基、アミド基などの親水性基を有するものが好ましい。
【００９４】
また、マイクロカプセルに内包される重合性化合物が有するエチレン性不飽和基、カチオン重合性基、または、熱重合性化合物が有する熱反応性基などの官能基と、親水性樹脂とが反応して架橋することによって、画像強度の向上やさらなる高耐刷化がなされるため、親水性樹脂として、これらの官能基と反応する基を有する樹脂を選択することが好ましい。例えば、カチオン重合性化合物がビニルオキシ基又はエポキシ基を有する場合は、親水性樹脂としては、ヒドロキシ基、カルボキシ基、リン酸基、スルホン酸基などを有するものが好ましい。中でも、ヒドロキシ基又はカルボキシ基を有する親水性樹脂が好ましい。
【００９５】
親水性樹脂の具体例として、アラビアゴム、カゼイン、ゼラチン、澱粉誘導体、ソヤガム、ヒドロキシプロピルセルロース、メチルセルロース、カルボキシメチルセルロース及びそのナトリウム塩、セルロースアセテート、アルギン酸ナトリウム、酢酸ビニル−マレイン酸コポリマー類、スチレン−マレイン酸コポリマー類、ポリアクリル酸類及びそれらの塩、ポリメタクリル酸類及びそれらの塩、ヒドロキシエチルメタクリレートのホモポリマー及びコポリマー、ヒドロキシエチルアクリレートのホモポリマー及びコポリマー、ヒドロキシプロピルメタクリレートのホモポリマー及びコポリマー、ヒドロキシプロピルアクリレートのホモポリマー及びコポリマー、ヒドロキシブチルメタクリレートのホモポリマー及びコポリマー、ヒドロキシブチルアクリレートのホモポリマー及びコポリマー、ポリエチレングリコール類、ヒドロキシプロピレンポリマー類、ポリビニルアルコール類、加水分解度が少なくとも６０質量％、好ましくは少なくとも８０質量％の加水分解ポリビニルアセテート、ポリビニルホルマール、ポリビニルピロリドン、アクリルアミドのホモポリマー及びコポリマー、メタクリルアミドのホモポリマー及びコポリマー、Ｎ−メチロールアクリルアミドのホモポリマー及びコポリマー、２−アクリルアミド−２−メチル−１−プロパンスルホン酸のホモポリマー及びコポリマー、２−メタクロイルオキシエチルホスホン酸のホモポリマー及びコポリマー等を挙げることができる。
上記親水性樹脂の添加量は、記録層全固形分中、２０質量％以下が好ましく、１０質量％以下がより好ましい。
【００９６】
また、上記親水性樹脂は印刷機上で未露光部が機上現像できる程度に架橋して用いてもよい。親水性樹脂を架橋するために使用される架橋剤としては、グリオキザール、メラミンホルムアルデヒド樹脂、尿素ホルムアルデヒド樹脂などのアルデヒド類、Ｎ−メチロール尿素やＮ−メチロールメラミン、メチロール化ポリアミド樹脂などのメチロール化合物、ジビニルスルホンやビス（β−ヒドロキシエチルスルホン酸）などの活性ビニル化合物、エピクロルヒドリンやポリエチレングリコ−ルジグリシジルエーテル、ポリアミド、ポリアミン、エピクロロヒドリン付加物、ポリアミドエピクロロヒドリン樹脂などのエポキシ化合物、モノクロル酢酸エステルやチオグリコール酸エステルなどのエステル化合物、ポリアクリル酸やメチルビニルエーテル／マレイン酸共重合物などのポリカルボン酸類、ホウ酸、チタニルスルフェート、Ｃｕ、Ａｌ、Ｓｎ、Ｖ、Ｃｒ塩などの無機系架橋剤、変性ポリアミドポリイミド樹脂などが挙げられる。その他、塩化アンモニウム、シランカップリング剤、チタネートカップリング剤等の架橋触媒を併用できる。
【００９７】
（その他の添加剤）
本発明に係る記録層マトリックス中には、さらに必要に応じて上記以外に種々の化合物を添加してもよい。
【００９８】
＜多官能モノマー＞
耐刷力を一層向上させるために多官能モノマーを添加することができる。この多官能モノマーとしては、マイクロカプセル中に入れられるモノマーとして例示したものを用いることができる。なかでも好ましいモノマーとしては、トリメチロールプロパントリアクリレート、ペンタエリスリトールトリアクリレートなどを挙げることができる。多官能モノマーの添加量は、記録層全固形分中、０．１〜１０質量％が好ましく、０．５〜５．０質量％がより好ましい。
【００９９】
＜熱重合防止剤＞
本発明においては、記録層塗布液の調製中又は保存中においてエチレン性不飽和化合物の不要な熱重合を阻止するために、少量の熱重合防止剤を添加することが望ましい。適当な熱重合防止剤としてはハイドロキノン、ｐ−メトキシフェノール、ジ−ｔ−ブチル−ｐ−クレゾール、ピロガロール、ｔ−ブチルカテコール、ベンゾキノン、４，４′−チオビス（３−メチル−６−ｔ−ブチルフェノール）、２，２′−メチレンビス（４−メチル−６−ｔ−ブチルフェノール）、Ｎ−ニトロソ−Ｎ−フェニルヒドロキシルアミンアルミニウム塩等が挙げられる。熱重合防止剤の添加量は、記録層全固形分中、０．０１〜５質量％が好ましい。
【０１００】
＜高級脂肪酸またはその誘導体＞
本発明に係る記録層マトリックス中には、必要に応じで、酸素による重合阻害を防止するために、ベヘン酸やベヘン酸アミドのような高級脂肪酸やその誘導体等を添加して、塗布後の乾燥の過程で記録層の表面に偏在させてもよい。高級脂肪酸やその誘導体の添加量は、記録層全固形分中、０．１〜１０質量％が好ましい。
【０１０１】
＜無機微粒子＞
本発明に係る記録層マトリックス中には無機微粒子を添加してもよく、無機微粒子としては、シリカ、アルミナ、酸化マグネシウム、酸化チタン、炭酸マグネシウム、アルギン酸カルシウム又はこれらの混合物などが好適な例として挙げられ、これらは光熱変換性でなくても皮膜の強化や表面粗面化による界面接着性の強化などに用いることができる。
【０１０２】
また、無機微粒子の平均粒径は５ｎｍ〜１０μｍのものが好ましく、より好ましくは１０ｎｍ〜１μｍである。粒径がこの範囲内で、マイクロカプセルや光熱変換剤の金属微粒子とも親水性樹脂内に安定に分散し、記録層の膜強度を充分に保持し、印刷汚れを生じにくい親水性に優れた非画像部を形成できる。
【０１０３】
このような無機微粒子は、コロイダルシリカ分散物などの市販品として容易に入手できる。無機微粒子の記録層への含有量は、記録層の全固形分の２０質量％以下が好ましく、より好ましくは１０質量％以下である。
【０１０４】
＜界面活性剤＞
本発明に係る記録層マトリックス中には、記録層の分散安定性、製版及び印刷性能向上や塗布性の向上のため、特開平２−１９５３５６号、特開昭５９−１２１０４４号、特開平４−１３１４９号及び特願２００１−１６９７３１号に記載されているノニオン系、アニオン系、カチオン系、両性又はフッ素系の界面活性剤を添加することができる。これらの界面活性剤の好適な添加量は、記録層全固形分の０．００５〜１質量％である。
【０１０５】
＜可塑剤＞
本発明に係る記録層マトリックス中には、必要に応じ、塗膜の柔軟性等を付与するために可塑剤を加えることができる。例えば、ポリエチレングリコール、クエン酸トリブチル、フタル酸ジエチル、フタル酸ジブチル、フタル酸ジヘキシル、フタル酸ジオクチル、リン酸トリクレジル、リン酸トリブチル、リン酸トリオクチル、オレイン酸テトラヒドロフルフリル等が用いられる。
【０１０６】
〔画像記録層の形成〕
本発明に係る記録層は、必要な上記各成分を溶剤に溶かして塗布液を調製し、塗布される。ここで使用する溶剤としては、エチレンジクロライド、シクロヘキサノン、メチルエチルケトン、メタノール、エタノール、プロパノール、エチレングリコールモノメチルエーテル、１−メトキシ−２−プロパノール、２−メトキシエチルアセテート、１−メトキシ−２−プロピルアセテート、ジメトキシエタン、乳酸メチル、乳酸エチル、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ，Ｎ−ジメチルホルムアミド、テトラメチルウレア、Ｎ−メチルピロリドン、ジメチルスルホキシド、スルホラン、γ−ブチロラクトン、トルエン、水等を挙げることができるが、これに限定されるものではない。これらの溶剤は、単独又は混合して使用される。塗布液の固形分濃度は、好ましくは１〜５０質量％である。
【０１０７】
また塗布、乾燥後に得られる支持体上の記録層塗布量（固形分）は、用途によって異なるが、一般的に０．５〜５．０ｇ／ｍ^２が好ましい。この範囲より塗布量が少なくなると、見かけの感度は大になるが、画像記録の機能を果たす記録層の皮膜特性は低下する。塗布する方法としては、種々の方法を用いることができる。例えば、バーコーター塗布、回転塗布、スプレー塗布、カーテン塗布、ディップ塗布、エアーナイフ塗布、ブレード塗布、ロール塗布等を挙げられる。
【０１０８】
〔オーバーコート層〕
本発明に係る平版印刷版原版は、保存時の親油性物質による汚染や取り扱い時の手指の接触による指紋跡汚染等から親水性の記録層表面を保護するため、記録層上に、特開２００１−１６２９６１号、特開２００２−１９３１８号に記載の水溶性樹脂を含有するオーバーコート層を設けることができる。
【０１０９】
オーバーコート層に用いられる水溶性樹脂の具体例としては、天然高分子では、アラビアガム、水溶性大豆多糖類、繊維素誘導体（例えば、カルボキシメチルセルロース、カルボキシエチルセルローズ、メチルセルロース等）、その変性体、ホワイトデキストリン、プルラン、酵素分解エーテル化デキストリン等、合成高分子では、ポリビニルアルコール（ポリ酢酸ビニルの加水分解率６５％以上のもの）、ポリアクリル酸、そのアルカリ金属塩又はアミン塩、ポリアクリル酸共重合体、そのアルカリ金属塩又はアミン塩、ポリメタクリル酸、そのアルカリ金属塩又はアミン塩、ビニルアルコール／アクリル酸共重合体及びそのアルカリ金属塩又はアミン塩、ポリアクリルアミド、その共重合体、ポリヒドロキシエチルアクリレート、ポリビニルピロリドン、その共重合体、ポリビニルメチルエーテル、ビニルメチルエーテル／無水マレイン酸共重合体、ポリ−２−アクリルアミド−２−メチル−１−プロパンスルホン酸、そのアルカリ金属塩又はアミン塩、ポリ−２−アクリルアミド−２−メチル−１−プロパンスルホン酸共重合体、そのアルカリ金属塩又はアミン塩、等を挙げることができる。目的に応じて、これらの樹脂を二種以上混合して用いることもできる。しかし、本発明はこれらの例に限定されるものではない。
【０１１０】
上記のオーバーコート層には、感度を向上させるため光熱変換剤を含有させることができる。好ましい光熱変換剤としては、水溶性の赤外線吸収色素が挙げられる。例えば、前記の記録層の説明中に示した（ＩＲ−１）〜（ＩＲ−１１）が好適に用いられる。
【０１１１】
その他、オーバーコート層には塗布の均一性を確保する目的で、水溶液塗布の場合には主に非イオン系界面活性剤を添加することができる。この様な非イオン界面活性剤の具体例としては、ソルビタントリステアレート、ソルビタンモノパルミテート、ソルビタントリオレート、ステアリン酸モノグリセリド、ポリオキシエチレンノニルフェニルエーテル、ポリオキシエチレンドデシルエーテル等を挙げることが出来る。上記非イオン界面活性剤のオーバーコート層の全固形物中に占める割合は、０．０５〜５質量％が好ましく、より好ましくは１〜３質量％である。
【０１１２】
さらに、上記オーバーコート層には、積み重ね保存時のプレート間のくっつきを防止するため、特開２００１−３４１４４８号記載のフッ素原子及びケイ素原子のうちいずれかを有する化合物を含有することができる。
本発明に係るオーバーコート層の厚みは、０．１〜４．０μｍが好ましく、０．１〜１．０μｍがより好ましい。この範囲内で、印刷機上でのオーバーコート層の除去性を損なうことなく、親油性物質による記録層の汚染を防止できる。
【０１１３】
〔支持体〕
本発明に係る平版印刷版原版に使用可能な支持体としては、寸度的に安定な板状物であり、例えば、紙、プラスチック（例えば、ポリエチレン、ポリプロピレン、ポリスチレン等）がラミネートされた紙、金属板（例えば、アルミニウム、亜鉛、銅等）、プラスチックフィルム（例えば、二酢酸セルロース、三酢酸セルロース、プロピオン酸セルロース、酪酸セルロース、酢酸酪酸セルロース、硝酸セルロース、ポリエチレンテレフタレート、ポリエチレン、ポリスチレン、ポリプロピレン、ポリカーボネート、ポリビニルアセタール等）、上記の如き金属がラミネート若しくは蒸着された紙又はプラスチックフィルム等が挙げられる。好ましい支持体としては、アルミニウム板が挙げられる。
【０１１４】
該アルミニウム板は、純アルミニウム板及びアルミニウムを主成分とし、微量の異元素を含む合金板であり、さらにはアルミニウム又はアルミニウム合金の薄膜にプラスチックがラミネートされているものである。アルミニウム合金に含まれる異元素には、ケイ素、鉄、マンガン、銅、マグネシウム、クロム、亜鉛、ビスマス、ニッケル、チタンなどがある。合金中の異元素の含有量は高々１０質量％以下である。また、ＤＣ鋳造法を用いたアルミニウム鋳塊からのアルミニウム板でも、連続鋳造法による鋳塊からのアルミニウム板であっても良い。しかし、本発明に適用されるアルミニウム板は、従来から公知公用の素材のアルミニウム板をも適宜に利用することができる。
本発明で用いられる上記の基板の厚みは０．０５ｍｍ〜０．６ｍｍ、好ましくは０．１ｍｍ〜０．４ｍｍ、特に好ましくは０．１５ｍｍ〜０．３ｍｍである。
【０１１５】
アルミニウム板を使用するに先立ち、表面の粗面化、陽極酸化などの表面処理をすることが好ましい。表面処理により、親水性の向上及び記録層との接着性の確保が容易になる。
アルミニウム板表面の粗面化処理は、種々の方法により行われるが、例えば、機械的に粗面化する方法、電気化学的に表面を溶解粗面化する方法及び化学的に表面を選択溶解させる方法により行われる。機械的方法としては、ボール研磨法、ブラシ研磨法、ブラスト研磨法、バフ研磨法などの公知の方法を用いることができる。化学的方法としては、特開昭５４−３１１８７号公報に記載されているような鉱酸のアルミニウム塩の飽和水溶液に浸漬する方法が適している。また、電気化学的な粗面化法としては塩酸又は硝酸などの酸を含む電解液中で交流又は直流により行う方法がある。また、特開昭５４−６３９０２号に開示されているように混合酸を用いた電解粗面化方法も利用することができる。上記の如き方法による粗面化は、アルミニウム板の表面の中心線平均粗さ（Ｒａ）が０．２〜１．０μｍとなるような範囲で施されることが好ましい。
【０１１６】
粗面化されたアルミニウム板は必要に応じて水酸化カリウムや水酸化ナトリウムなどの水溶液を用いてアルカリエッチング処理がされ、さらに中和処理された後、所望により耐摩耗性を高めるために陽極酸化処理が施される。
アルミニウム板の陽極酸化処理に用いられる電解質としては、多孔質酸化皮膜を形成する種々の電解質の使用が可能で、一般的には硫酸、塩酸、蓚酸、クロム酸又はそれらの混酸が用いられる。それらの電解質の濃度は電解質の種類によって適宜決められる。陽極酸化の処理条件は、用いる電解質により種々変わるので一概に特定し得ないが、一般的には電解質の濃度が１〜８０質量％溶液、液温は５〜７０℃、電流密度５〜６０Ａ／ｄｍ^２、電圧１〜１００Ｖ、電解時間１０秒〜５分の範囲であれば適当である。形成される酸化皮膜量は、１．０〜５．０ｇ／ｍ^２、特に１．５〜４．０ｇ／ｍ^２であることが好ましい。
【０１１７】
本発明で用いられる支持体としては、上記のような表面処理をされ陽極酸化皮膜を有する基板そのままでも良いが、上層との接着性、親水性、汚れ難さ、断熱性などの一層改良のため、必要に応じて、特開２００１−２５３１８１号や特開２００１−３２２３６５号に記載されている陽極酸化皮膜のマイクロポアの拡大処理、マイクロポアの封孔処理、及び親水性化合物を含有する水溶液に浸漬する表面親水化処理などを適宜選択して行うことができる。
上記親水化処理のための好適な親水性化合物として、ポリビニルホスホン酸、スルホン酸基をもつ化合物、糖類化合物、クエン酸、アルカリ金属珪酸塩、フッ化ジルコニウムカリウム、リン酸塩／無機フッ素化合物などが挙げられる。
【０１１８】
本発明に用いる支持体としてポリエステルフィルムなど表面の親水性が不十分な支持体を用いる場合は、親水層を塗布して表面を親水性にすることが望ましい。親水層としては、特開２００１−１９９１７５号に記載の、ベリリウム、マグネシウム、アルミニウム、珪素、チタン、硼素、ゲルマニウム、スズ、ジルコニウム、鉄、バナジウム、アンチモン及び遷移金属から選択される少なくとも一つの元素の酸化物又は水酸化物のコロイドを含有する塗布液を塗布してなる親水層が好ましい。中でも、珪素の酸化物又は水酸化物のコロイドを含有する塗布液を塗布してなる親水層が好ましい。
【０１１９】
本発明においては、記録層を塗布する前に、必要に応じて、特開２００１−２００１−３２２３６５号に記載の、例えばホウ酸亜鉛等の水溶性金属塩のような無機下塗層、又は例えばカルボキシメチルセルロース、デキストリン、ポリアクリル酸などの含有する有機下塗層が設けることができる。また、この下塗層には、前記光熱変換剤を含有させることができる。
【０１２０】
上記のようにして、本発明の方法を適用し得る平版印刷版原版を得ることができる。この平版印刷版原版は赤外線照射により画像形成され、現像処理を経ることなく印刷工程に付する機上現像型の平版印刷版原版である。
このような構成を有する平版印刷版原版を本発明の画像形成方法に適用することで、赤外線を用いた画像露光により、充分な強度を有する画像部が形成されるため、機上現像可能な平版印刷版原版の耐刷性が向上し、高画質の印刷物を多数枚得ることが可能となった。
【０１２１】
【実施例】
以下、実施例により、本発明を詳細に説明するが、本発明はこれらに限定されるものではない。
［支持体の作製］
【０１２２】
９９．５質量％以上のアルミニウムと、Ｆｅ ０．３０質量％、Ｓｉ ０．１０質量％、Ｔｉ ０．０２質量％、Ｃｕ ０．０１３質量％を含むＪＩＳ Ａ１０５０合金の溶湯に清浄化処理を施し、鋳造した。清浄化処理には、溶湯中の水素などの不要なガスを除去するために脱ガス処理し、セラミックチューブフィルタ処理をおこなった。鋳造法はＤＣ鋳造法で行った。凝固した板厚５００ｍｍの鋳塊を表面から１０ｍｍ面削し、金属間化合物が粗大化してしまわないように５５０℃で１０時間均質化処理を行った。
【０１２３】
次いで、４００℃で熱間圧延し、連続焼鈍炉中で５００℃６０秒中間焼鈍した後、冷間圧延を行って、板圧０．３０ｍｍのアルミニウム圧延板とした。圧延ロールの粗さを制御することにより、冷間圧延後の中心線平均表面粗さＲａを０．２μｍに制御した。その後、平面性を向上させるためにテンションレベラーにかけた。
【０１２４】
次に平版印刷版支持体とするための表面処理を行った。まず、アルミニウム板表面の圧延油を除去するため１０質量％アルミン酸ソーダ水溶液で５０℃３０秒間脱脂処理を行い、３０質量％硫酸水溶液で５０℃３０秒間中和、スマット除去処理を行った。次いで支持体と記録層の密着性を良好にし、かつ非画像部に保水性を与えるため、支持体の表面を粗面化する、いわゆる、砂目立て処理を行った。１質量％の硝酸と０．５質量％の硝酸アルミを含有する水溶液を４５℃に保ち、アルミウェブを水溶液中に流しながら、間接給電セルにより電流密度２０Ａ／ｄｍ^２、デューティー比１：１の交番波形でアノード側電気量２４０Ｃ／ｄｍ^２を与えることで電解砂目立てを行った。その後１０質量％アルミン酸ソーダ水溶液で５０℃３０秒間エッチング処理を行い、３０質量％硫酸水溶液で５０℃３０秒間中和、スマット除去処理を行った。さらに耐摩耗性、耐薬品性、保水性を向上させるために、陽極酸化によって支持体に酸化皮膜を形成させた。電解質として硫酸２０質量％水溶液を３５℃で用い、アルミウェブを電解質中に通搬しながら、間接給電セルにより１４Ａ／ｄｍ^２の直流で電解処理を行うことで２．５ｇ／ｍ^２の陽極酸化皮膜を作成した。
【０１２５】
この後印刷版非画像部としての親水性を確保するため、シリケート処理を行った。処理は３号珪酸ソーダ１．５質量％水溶液を７０℃に保ちアルミウェブの接触時間が１５秒となるよう通搬し、さらに水洗した。Ｓｉの付着量は１０ｍｇ／ｍ^２であった。以上のように作製した支持体の中心線表面粗さＲａは０．２５μｍであった。
［カチオン重合性化合物を内包するマイクロカプセルＡの合成］
【０１２６】
油相成分として、ビスフェノールＡのビス（ビニルオキシエチル）エーテル４．５ｇ、トリメチロールプロパンとキシリレンジイソシアナートとの付加体（三井武田ケミカル（株）製タケネートＤ−１１０Ｎ、マイクロカプセル壁材）５ｇ、ミリオネートＭＲ−２００（日本ポリウレタン（株）製芳香族イソシアネートオリゴマー、マイクロカプセル壁材）３．７５ｇ、赤外線吸収色素（本明細書記載のＩＲ−２７）１．５ｇ、パイオニンＡ４１Ｃ（竹本油脂（株）界面活性剤）０．１ｇを酢酸エチル１８．４ｇに溶解した。水相成分としてＰＶＡ２０５（クラレ製ポリビニルアルコール）の４質量％水溶液３７．５ｇを調製した。油相成分及び水相成分を、ホモジナイザーを用い１２０００ｒｐｍで１０分間乳化した。その後テトラエチレンペンタミン（５官能アミン、マイクロカプセル壁架橋剤）０．３８ｇを水２６ｇに溶解したものを添加し、水冷しながら３０分さらに６５℃で３時間攪拌した。このようにして得られたマイクロカプセルＡ液の固形分濃度は２４質量％であり、平均粒径は０．３μｍであった。
【０１２７】
［ラジカル重合性化合物を内包するマイクロカプセルＢの合成例］
油相成分として、ジペンタエリスリトールテトラアクリレート（日本化薬製 ＫＡＹＡＲＡＤ ＤＰＨＡ）４．５ｇ、トリメチロールプロパンとキシリレンジイソシアナートとの付加体（三井武田ケミカル（株）製タケネートＤ−１１０Ｎ、マイクロカプセル壁材）５ｇ、ミリオネートＭＲ−２００（日本ポリウレタン（株）製芳香族イソシアネートオリゴマー、マイクロカプセル壁材）３．７５ｇ、赤外線吸収色素（本明細書記載のＩＲ−２７）１．５ｇ、パイオニンＡ４１Ｃ（竹本油脂（株）界面活性剤）０．１ｇを酢酸エチル１８．４ｇに溶解した。水相成分としてＰＶＡ２０５（クラレ製ポリビニルアルコール）の４質量％水溶液３７．５ｇを調製した。油相成分及び水相成分を、ホモジナイザーを用い１２０００ｒｐｍで１０分間乳化した。その後テトラエチレンペンタミン（５官能アミン、マイクロカプセル壁架橋剤）０．３８ｇを水２６ｇに溶解したものを添加し、水冷しながら３０分さらに６５℃で３時間攪拌した。このようにして得られたマイクロカプセル液の固形分濃度は２４質量％であり、平均粒径は０．３μｍであった。
【０１２８】
〔実施例１〕
（平版印刷版原版Ａの作製）
上記製造例で得たアルミニウム基板上に、合成例のマイクロカプセルＡを含む下記の記録層塗布液をバー塗布した後、オーブンで１００℃６０秒の条件で乾燥し、記録層の乾燥塗布量１．０ｇ／ｍ^２の平版印刷版原版Ａを作製した。
＜記録層塗布液＞
・水 ３５．４ｇ
・前記合成例のマイクロカプセルＡ液 ９．０ｇ
・酸発生剤（本明細書に記載のＡＩ−７） ０．２４ｇ
【０１２９】
〔実施例２〕
（平版印刷版原版Ｂの作製）
上記製造例で得たアルミニウム基板上に、合成例のマイクロカプセルＢを含む下記の記録層塗布液をバー塗布した後、オーブンで１００℃６０秒の条件で乾燥し、記録層の乾燥塗布量１．０ｇ／ｍ^２の平版印刷版原版Ｂを作製した。
＜記録層塗布液＞
・水 ３５．４ｇ
・前記合成例のマイクロカプセルＢ液 ９．０ｇ
・酸発生剤（本明細書に例示のＡＳ−１１） ０．２４ｇ
【０１３０】
（露光・印刷および評価）
上記で得られた平版印刷版原版ＡおよびＢを、図１及び図２に基づいて説明した本発明の実施形態に係る画像露光装置１０へ装着し、平版印刷版原版における予備加熱領域の記録層を１６０℃〜１８０℃まで予備加熱した後、２５秒後に、水冷式４０Ｗ赤外線半導体レーザー搭載のＣｒｅｏ社製Ｔｒｅｎｄｓｅｔｔｅｒ３２４４ＶＸにて、出力１７Ｗ、外面ドラム回転数１００ｒｐｍ、解像度２４００ｄｐｉの条件で画像露光を行った。この露光中に、平版印刷版原版における予備加熱領域の記録層の温度は１００℃以上に保たれていた。これにより、記録層と支持体との界面付近でも、カプセルの浸透性化反応が効果的に進行すると共に、重合開始剤からの酸或いはラジカル中の発生反応も効果的に進行し、重合性化合物や活性種の高い運動性とあいまって、強固で耐刷性に優れた画像を形成できた。
【０１３１】
実施例の各平版印刷版原版を画像露光完了後、現像処理することなく、ハイデルベルグ社製印刷機ＳＯＲ−Ｍのシリンダーに取り付けた。４容量％ＩＦ１０２（富士写真フイルム（株）製）水溶液からなる湿し水とバリウス墨インキ（大日本インキ化学工業（株）製を用い、湿し水を供給した後、インキを供給し、さらに紙を供給して印刷を行った。
【０１３２】
この際、印刷工程の初期段階で非画像部における記録層が除去され、非画像部に汚れのない高画質の印刷物が得られた。その後も印刷を継続し、どれだけの枚数が、非画像部に汚れがなく、画像部が充分なインキ濃度を保って印刷できるかを目視にて測定し、耐刷性の指標とした。枚数が多いほど耐刷性に優れるものと評価する。
【０１３３】
結果は、実施例１の平版印刷版原版Ａが３．５万枚であり、実施例２の平版印刷版原版Ｂが２．５万枚であった。これにより、実施例１、２のどちらの平版印刷版原版も実用性に耐えうる優れた耐刷性を有していることが確認された。
【０１３４】
【発明の効果】
本発明によれば、デジタル信号に基づいた画像の走査露光、および、機上現像が可能であり、且つ、耐刷性に優れた平版印刷版原版の画像形成方法、および、それに用いる画像露光装置を得ることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態に係る画像露光装置の構成を示す側面図である。
【図２】図１に示される画像露光装置における露光ヘッド及びその送り機構の構成を示す斜視図である。
【符号の説明】
１０ 画像露光装置
１２ 平版印刷版原版
２０ アウタードラム（保持部材）
２６ 露光ヘッド（露光手段）
２８ 送り機構（送り機構）
３２ 光源装置（露光手段）
３８ 予備加熱装置（予備加熱手段）
４０ 加熱ファンユニット（予備加熱手段）
４２ フレキシブルダクト（予備加熱手段）
４４ 熱風ノズル（予備加熱手段）
５８ レンズユニット（露光ヘッド）
６０ ファイバホルダ（露光ヘッド）
６８ キャリア（キャリア部材）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming method and an image exposure apparatus, and more specifically, an image forming method of a lithographic printing plate capable of making a plate without performing scanning exposure of an image with an infrared beam and special liquid development processing, In addition, the present invention relates to an image exposure apparatus used therefor.
[0002]
[Prior art]
The development of laser technology in recent years has been remarkable, and in particular, solid-state lasers and semiconductor lasers (hereinafter referred to as “infrared lasers” where appropriate) that emit infrared rays with a wavelength of 760 nm to 1200 nm can be easily obtained with high output and small size. Became. In particular, in the field of lithographic printing, these infrared lasers are very useful as a recording light source for a CTP (Computer to Plate) system that directly makes a printing plate from digital data such as a computer.
[0003]
Accordingly, many studies have been made on the lithographic printing plate for the CPT system. Among them, as an aim to further streamline the process and solve the waste liquid treatment problem, development-free lithographic printing plate precursors that can be printed on a printing press without being developed after exposure have been studied, and various methods have been studied. Has been proposed.
[0004]
One method of eliminating the development process is to mount the exposed lithographic printing plate precursor on the cylinder of the printing press, and supply dampening water and ink while rotating the cylinder, so that the non-image area of the lithographic printing plate precursor There is a method called on-press development that removes the toner. That is, the lithographic printing plate precursor is exposed and mounted on a printing machine as it is, and the processing is completed in a normal printing process. This eliminates the need for a conventional liquid developing process using developing chemicals, thereby making it possible to rationalize the printing preparation process, eliminate the need for developing waste liquid processing, and the like.
[0005]
As such a lithographic printing plate precursor, there has been proposed a lithographic printing plate precursor containing a cross-linked hydrophilic layer on a substrate and containing a hot-melt material microencapsulated therein (see, for example, Patent Document 1). .) In this printing plate, the microcapsule collapses due to the action of heat generated in the laser exposure area, the lipophilic substance in the microcapsule dissolves, and the hydrophilic layer surface becomes hydrophobic.
[0006]
Other examples using microcapsules that also disintegrate by heat include microcapsules encapsulating a photopolymerizable monomer and a photosensitive resin, and lipophilic components that form an interaction with a three-dimensionally crosslinked hydrophilic layer. A lithographic printing plate precursor using a microcapsule enclosing a liquid crystal has also been proposed (see, for example, Patent Documents 2 and 3).
[0007]
These lithographic printing plate precursors do not require development processing. However, when a metal plate such as aluminum having high thermal conductivity is used as a support, heat to be used for image formation diffuses to the support, and image recording is performed. There is a problem in that the recording layer does not sufficiently cure at the interface with the layer support, and the strength of the image area is insufficient and the printing durability is poor.
[0008]
[Patent Document 1]
International Publication No. 94/23954 Pamphlet
[Patent Document 2]
Japanese Patent Laid-Open No. 62-250454
[Patent Document 3]
Japanese Patent No. 3206297
[0009]
[Problems to be solved by the invention]
An object of the present invention, which has been made to solve the above-mentioned conventional problems, is to enable image formation without passing through a special liquid development processing step by scanning exposure using an infrared beam, and has excellent printing durability. Another object is to provide an image forming method capable of obtaining a lithographic printing plate and an image exposure apparatus suitable for the image forming method.
[0010]
[Means for Solving the Problems]
As a result of intensive studies, the inventors of the present invention, before performing image exposure on a lithographic printing plate precursor provided with a recording layer containing specific microcapsules, include a predetermined region including an exposure area in the image recording layer of the lithographic printing plate precursor. The inventors have found that the above-described object can be achieved by locally heating the region in advance, and have solved the present invention.
[0011]
That is, the image forming method of the present invention is applied to a lithographic printing plate precursor provided with an image recording layer containing a microcapsule encapsulating a polymerizable compound, a polymerization initiator, and a photothermal conversion agent on a support. An image forming method for forming an image by irradiating and exposing a lithographic printing plate precursor with an infrared beam to form an image on an image recording layer of the lithographic printing plate precursor, and image recording of the lithographic printing plate precursor A preheating step of locally heating a preheating region including an exposure region irradiated with the infrared beam on a layer to a predetermined heating temperature before irradiation of the infrared beam to the exposure region included in the preheating region; And heating the preheating region to the preheating temperature is completed by the start of irradiation of the infrared beam to the exposure region included in the preheating region.
[0012]
Here, the heating up to the preheating temperature of the preheating region in the preheating step is preferably completed within a period from one minute before the start of irradiation of the infrared beam used for image exposure to the start of irradiation, It is more preferable to complete within the period from 30 seconds before the start of irradiation to the start of irradiation.
[0013]
In addition, the preheating temperature at this time is an effective temperature for accelerating the decomposition temperature of the initiator or the decomposition thereof, and does not reach the collapse (decomposition) temperature of the microcapsules. From the viewpoint of preventing stains in non-images, and more specifically, the preheating temperature is preferably in the range of 50 ° C to 230 ° C, and more preferably in the range of 50 to 200 ° C.
[0014]
The image exposure apparatus of the present invention is an image exposure apparatus used in the above-described image forming method, wherein a lithographic printing plate precursor can be mounted, a holding member that holds the mounted lithographic printing plate precursor, and the holding In the lithographic printing plate precursor, the lithographic printing plate precursor that is held by the member is exposed by an infrared beam to form an image on the image recording layer of the lithographic printing plate precursor, and the exposure device irradiates the infrared beam. And a preheating unit that locally heats the preheating region including the exposure region to the preheating temperature before irradiation of the infrared beam to the exposure region included in the preheating region.
[0015]
The lithographic printing plate precursor according to the invention is characterized in that the recording layer contains microcapsules encapsulating a polymerizable compound, a polymerization initiator, and a photothermal conversion agent. The image forming mechanism of such a lithographic printing plate precursor is as follows. The energy of infrared light in image exposure is converted into thermal energy by the photothermal conversion agent, and the heat causes the microcapsule wall to collapse or become permeable, and the encapsulated polymerizable compound is removed from the microcapsule. Released (exuded). Similarly, the reaction initiator generated from the polymerization initiator by the energy of image exposure serves as a polymerization initiator for the polymerizable compound released (exuded) out of the microcapsule, and the polymerization reaction starts and proceeds, The surface hydrophobic region, that is, the image portion is formed. However, with only the energy used for image exposure, an acid or radical in an amount (concentration) sufficient to make the microcapsule wall permeable and further activate the polymerization initiator to advance the curing reaction of the polymerizable compound. Is difficult to generate in the image recording layer, and as described above, thermal diffusion (heat absorption) from the recording layer to the support occurs near the interface between the recording layer and the support, and polymerization occurs. Since a sufficient amount of starting species necessary for the start and progress of the reaction is not supplied, the recording layer is not sufficiently cured, and a strong and excellent printing durability image cannot be formed.
[0016]
Here, in the image forming method of the present invention, before the lithographic printing plate precursor is subjected to image exposure, a predetermined region including the exposed region is preliminarily formed with energy that does not cause the microcapsules to collapse (usually up to about 270 ° C). The region including the exposed portion is partially heated (hereinafter referred to as “preheating” as appropriate). The preheating temperature is preferably about 50 ° C. to 230 ° C., and by this heating, the periphery of the exposure region is locally heated, and the region of the image recording layer has a higher temperature atmosphere than the peripheral portion. The mobility of the polymerizable compound is improved, and the efficiency of initiation and progression of the polymerization reaction is improved. Furthermore, by setting the heating temperature to a temperature at which the polymerization initiator in this region can be activated, for example, about 140 to 200 ° C., a sufficient amount of a reaction initiator is generated in advance from the polymerization initiator, and then the polymerization is performed. The image exposure can be performed before the initiator is almost deactivated. In this case, most of the energy from the image exposure is used to make the microcapsule wall permeable, and the microcapsules are efficiently disintegrated. Then, the polymerizable compound released (exuded) from the exposed region immediately and efficiently initiates a polymerization reaction with a sufficient amount of the reaction initiator generated by the preheating under the preferable conditions. Accordingly, it is considered that both effects can be combined to form a strong and excellent printing durability image.
In addition, since this preheating is performed only on a local region useful for improving the reactivity of image formation, including the image exposure region that is continuously performed, there is little energy loss, and preheating to image exposure are performed. In a preferred embodiment, the image exposure is carried out while the active species generated in advance is hardly inactivated while maintaining a high mobility of the active ingredient in the recording layer. It can contribute to the improvement of the polymerization reaction effectively.
[0017]
In the image exposure apparatus of the present invention, the preheating means includes a preheating area including an exposure area in the lithographic printing plate precursor to which an infrared beam is irradiated by the exposure means, and an infrared beam is applied to the exposure area included in the preheating area. Before the irradiation, it is heated locally to the preheating temperature. Thereby, after at least the image recording layer in the lithographic printing plate precursor is heated to a predetermined preheating temperature, the lithographic printing plate precursor can be scanned and exposed by an infrared beam. The polymerizable compound used for the purpose of breaking the capsule and released (exuded) from the microcapsule and a sufficient amount of the starting species can efficiently initiate or advance the polymerization reaction. In addition, this preheating means is controlled together with the exposure means, and the preheating is performed only in the local region useful for improving the reactivity of image formation, so that the supplied heat energy effectively contributes to the improvement of the reactivity. It also has the advantage of.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
[Configuration of image exposure apparatus]
First, an image exposure apparatus in which an image forming method according to the present invention is preferably implemented will be described with reference to the drawings.
[0019]
(First embodiment)
1 and 2 show an image exposure apparatus according to a first embodiment of the present invention. The image exposure apparatus 10 scans and exposes a lithographic printing plate precursor 12 with an infrared laser (hereinafter referred to as “IR laser L”) modulated based on digital image information, and the lithographic printing plate precursor 12 has digital image information. An image (latent image) corresponding to is formed. Here, the lithographic printing plate precursor 12 is a so-called non-processed printing plate that does not require special development processing, and is formed on a support made of aluminum or an aluminum alloy and on this support. An image recording layer is provided, and this image recording layer (hereinafter simply referred to as “recording layer”) contains at least microcapsules containing a polymerizable compound, a polymerization initiator, and a photothermal conversion agent.
[0020]
The polymerization initiator and the photothermal conversion agent such as the acid generator or radical initiator may be added to at least one of the inside of the microcapsule and the outside of the microcapsule, that is, the recording layer matrix. From the viewpoint of storage stability, the polymerization initiator is preferably added to the recording layer matrix. Moreover, it is preferable from a viewpoint of a sensitivity that a photothermal conversion agent is added in a microcapsule.
[0021]
As shown in FIG. 1, the image exposure apparatus 10 is provided with a casing 14 as an outer shell portion of the apparatus. The casing 14 has a side plate portion on one side along the width direction of the apparatus (direction of arrow W). A plate feeding table 16 for mounting a bundle of lithographic printing plate precursors 12 is attached to a platen, and a discharge tray 18 for discharging the exposed lithographic printing plate precursor 12 is provided on the upper side of the plate feeding table 16. It has been. In the casing 14, a cylindrical outer drum 20 on which one lithographic printing plate precursor 12 can be attached and detached is rotatably arranged. On the outer peripheral side of the outer drum 20, a chuck mechanism 22 for chucking the front end portion and the rear end portion of the planographic printing plate precursor 12 on the outer drum 20 is provided, and the planographic printing plate precursor 12 is attached to the outer drum 20. A guide roller 24 for winding on the outer peripheral surface is installed.
[0022]
An exposure head 26 facing the outer drum 20 and a feed mechanism 28 that supports the exposure head 26 so as to be movable along the sub-scanning direction are disposed in the casing 14. The exposure head 26 and the feed mechanism 28 scan and expose the lithographic printing plate precursor 12 mounted on the outer drum 20 by the IR laser L modulated based on the digital image information, and digitally record the lithographic printing plate precursor 12 on the recording layer. This is for forming an image corresponding to the image information. In the casing 14, a light source box 30 is disposed on the lower side of the outer drum 20, and an LD light source device 32 (see FIG. 2) for supplying the IR laser L to the exposure head 26 is disposed in the light source box 30. ) Is stored.
[0023]
As shown in FIG. 1, the image exposure apparatus 10 is provided with a feeding mechanism 34 for transporting the lithographic printing plate precursor 12 loaded on the plate feeding table 16 in the casing 14 to the outer drum 20. Yes. The feeding mechanism 34 includes a plurality of conveying rollers 35 and a plate-shaped guide member 36 arranged along the feeding path of the planographic printing plate precursor 12. Further, the feeding mechanism 34 separates one lithographic printing plate precursor 12 from a bundle of lithographic printing plate precursors 12 stacked on the plate feeding table 16 at the end on the plate feeding table 16 side. A separation mechanism (not shown) for supplying the planographic printing plate precursor 12 to the feeding path is provided.
[0024]
In the image exposure apparatus 10, when the planographic printing plate precursor 12 is conveyed to the vicinity of the upper end of the outer drum 20 by the feeding mechanism 34, the tip of the planographic printing plate precursor 12 is chucked on the outer drum 20 by the chuck mechanism 22. At the same time, the outer drum 20 starts to rotate in a predetermined forward rotation direction (the direction of arrow R1 in FIG. 1). As a result, the lithographic printing plate precursor 12 whose tip is restrained on the outer drum 20 by the tip clamp is wound while being pressed onto the outer peripheral surface of the outer drum 20 by the guide roller 24.
[0025]
In the image exposure apparatus 10, when the planographic printing plate precursor 12 is wound around the outer drum 20 to the rear end portion, the rear end portion of the planographic printing plate precursor 12 is chucked onto the outer drum 20 by the chuck mechanism 22. Thereby, the entire planographic printing plate precursor 12 is brought into close contact with the outer peripheral surface of the outer drum 20, and the mounting of the planographic printing plate precursor 12 to the outer drum 20 is completed. In the image exposure apparatus 10, the IR laser L emitted from the exposure head 26 while moving the exposure head 26 in the sub-scanning direction by the feed mechanism 28 with the lithographic printing plate precursor 12 mounted on the outer drum 20. Is irradiated onto the lithographic printing plate precursor 12 to perform sub-scanning exposure on the lithographic printing plate precursor 12. Further, the image exposure apparatus 10 can perform main scanning on the lithographic printing plate precursor 12 by rotating the outer drum 20 by a rotation amount corresponding to the main scanning pitch in the forward rotation direction in synchronization with the completion of one sub-scan. Become.
[0026]
As shown in FIG. 2, the exposure head 26 includes a lens unit 58 that includes a plurality of lenses and forms an imaging optical system, a pair of support plates that sandwich the tips of a plurality of optical fibers 70, and light. A fiber holder 60 made of a transparent protective plate or the like for protecting the tip surface of the fiber 70 is provided. The exposure head 26 is mounted on a plate-like carrier 68, and moves along the sub-scanning direction (the direction of arrow S in FIG. 2) together with the carrier 68. Here, the IR lasers L respectively emitted from the plurality of optical fibers 70 enter the lens unit 58 and are combined by the lens unit 58 and imaged on the lithographic printing plate precursor 12 mounted on the outer drum 20. Then, a beam spot having a predetermined shape and size is formed.
[0027]
The feed mechanism 28 includes a pair of guide rails 62 that support the carrier 68 so as to be slidable along the sub-scanning direction, and a screw shaft 66 that is coupled to the motor unit 64. A block-shaped female screw member 69 is fixed to the lower surface of the carrier 68, and a screw shaft 66 is screwed into a female screw hole formed in the female screw member 69. As a result, when the screw shaft 66 is rotated by the motor unit 64, the exposure head 26 is integrated with the carrier 68 along the sub-scanning direction in a direction corresponding to the rotation direction of the screw shaft 66 (forward direction or reverse direction). It moves by a distance corresponding to the amount of rotation of the screw shaft 66. In the image exposure apparatus 10 of this embodiment, the sub-scanning with respect to the planographic printing plate precursor 12 is performed only when the exposure head 26 moves forward.
[0028]
As shown in FIG. 2, the other ends of the plurality of optical fibers 70 are respectively connected to the plurality of semiconductor lasers 72 in the LD light source device 32. The semiconductor laser 72 in the LD light source device 32 is fixed on a plate-shaped heat sink 74. A connector array 76 is provided in the middle of the optical fiber 70, and the optical fiber 70 can be brought into contact with and separated from the fiber holder 60 side and the semiconductor laser 72 side through the connector array 76. . Thereby, for example, when one of the semiconductor lasers LD fails, the failed semiconductor laser 72 can be easily replaced without disassembling the fiber holder 60 or the like.
[0029]
In the feed mechanism 28, a tube-shaped cable bear 78 and a hook-shaped bear guide 80 are arranged below the guide rail 62 so as to extend in the sub-scanning direction. The cable bear 78 has a structure in which a large number of link pieces 82 divided in the longitudinal direction are linked in series, and has a structure flexible in the vertical direction. A portion (front end side) of the optical fiber 70 on the exposure head 26 side is inserted into the cable bear 78. Further, the bear guide 80 restricts the movement of the cable bear 78 in the front-rear direction while supporting the cable bear 78 from below. Thereby, when the exposure head 26 moves in the sub-scanning direction, the distal end side of the optical fiber 70 that moves together with the exposure head 26 is protected by the cable bear 78, and damage to the optical fiber 70 is prevented.
[0030]
In the image exposure apparatus 10, a preheating device 38 is disposed in the casing 14. The preheating device 38 heats the lithographic printing plate precursor 12 by hot air heating. As shown in FIG. 2, a heating fan unit 40 and a tubular hot air nozzle connected to the heating fan unit 40 through a flexible duct 42 are used. 44. The heating fan unit 40 is fixed to the casing 14, and the hot air nozzle 44 is mounted on the carrier 68 together with the exposure head 26. The flexible duct 42 is inserted through the cable bear 78 with a bundle of optical fibers 70 at the tip side.
[0031]
Here, the hot air nozzle 44 on the carrier 68 is disposed adjacent to the downstream side of the exposure head 26 along the sub-scanning direction. The hot air nozzle 44 is provided with an air outlet 46 having a predetermined opening shape at the tip thereof, and the air outlet 46 opens facing the outer peripheral surface of the outer drum 20.
[0032]
The heating fan unit 40 includes a heating unit 48 composed of a halogen heater, a ceramic heater, or the like that heats the air sucked from the outside of the casing 14, and an air supply unit that sends the heated air into the flexible duct 42 in a pressurized state. 50 is provided. The high-temperature air sent into the flexible duct 42 is supplied to the hot air nozzle 44 and blown as hot air from the outlet 46 of the hot air nozzle 44 to the planographic printing plate precursor 12 mounted on the outer drum 20. At this time, since the hot air nozzle 44 is adjacent to the downstream side in the sub-scanning direction of the exposure head 26, the hot air blown from the outlet 46 of the hot air nozzle 44 is the beam spot of the IR laser L on the planographic printing plate precursor 12. Is sprayed onto an area adjacent to the downstream side in the sub-scanning direction of an area to be projected and exposed (this is appropriately referred to as “exposure area”) (this is appropriately referred to as “pre-heating area”), and recording in this pre-heating area The layer is heated to a predetermined preheating temperature.
[0033]
Here, the preheating area has a size sufficiently larger than the beam spot (exposure area) along the sub-scanning direction and the main scanning direction. Thereby, the beam spot formed by the exposure head 26 exposes the exposure area included in the preheating area immediately after the preheating area in the planographic printing plate precursor 12 is heated to the preheating temperature. Further, the image exposure apparatus 10 is provided with a heating control unit (not shown) for controlling the preheating device 38, and this heating control unit controls the hot air supplied from the heating fan unit 40 to the hot air nozzle 44. The temperature and the air volume are controlled to adjust the temperature of the preheating area in the lithographic printing plate precursor 12 to the preheating temperature.
[0034]
A temperature sensor such as an infrared radiation thermometer is mounted on the carrier 68, the temperature (surface temperature) of the preheating region is measured by this temperature sensor, and a measurement signal corresponding to the surface temperature of the preheating region is sent to the heating control unit. You may make it output to. As a result, the heating control unit can feedback control the temperature of the preheating region based on the measurement signal, so that the temperature of the preheating region can be accurately adjusted to the preheating temperature.
[0035]
As shown in FIG. 1, the image exposure apparatus 10 is provided with a carry-out mechanism 84 for carrying the lithographic printing plate precursor 12 detached from the outer drum 20 to the discharge tray 18 in the casing 14. The unloading mechanism 84 includes a plurality of conveying rollers 86 and a plate-shaped guide member 88 arranged along the unloading path of the planographic printing plate precursor 12.
[0036]
In the image exposure apparatus 10, after the exposure (image formation) to the lithographic printing plate precursor 12 mounted on the outer drum 20 is completed, the outer drum 20 is rotated in the reverse direction (in the direction of arrow R <b> 2 in FIG. 1) and the chuck mechanism 22. The rear end and the front end of the planographic printing plate precursor 12 are sequentially released from the outer drum 20. In conjunction with this, the carry-out mechanism 84 rotates the transport roller 86 to start transporting the planographic printing plate precursor 12 sent from the outer drum 20 to the entrance of the discharge path to the discharge tray 18. The printing plate precursor 12 is discharged onto the discharge tray 18.
[0037]
Regarding the timing of the preheating, as described above, the heating to the preheating temperature is performed within a period from one minute before the start of irradiation of the infrared beam used for image exposure to the start of irradiation, and further, 30 seconds from the start of irradiation. It is preferable to complete within the period from before to the start of irradiation, but this can be appropriately selected depending on the exposure apparatus used, the heating apparatus, the active ingredient of the lithographic printing plate precursor, the desired sensitivity, and the like. The preheating timing can be controlled by adjusting the drum circumference of the exposure apparatus, the main scanning speed, the interval between the exposure head and the preheating head, and the like.
[0038]
The preheating device 38 of the image exposure apparatus 10 according to the present invention preheats the preheating area of the lithographic printing plate precursor 12 by blowing hot air directly onto the surface of the lithographic printing plate precursor 12. The apparatus is not limited to one using hot air. For example, a heating element such as a halogen heater or a ceramic heater is mounted on the carrier 68, and the lithographic printing plate precursor 12 is irradiated with infrared rays from the heating element to be a preheating region. In addition, a magnetron is mounted on the carrier 68, and an electromagnetic wave having a predetermined wavelength generated by the magnetron is irradiated to the image recording layer of the lithographic printing plate precursor 12, and a substance such as water in the image recording layer is irradiated. The electromagnetic wave is resonated and heated (electromagnetic wave heating), or an electromagnetic coil is mounted on the carrier 68, and the high frequency magnetic field from this electromagnetic coil is applied to the lithographic printing plate precursor. Is applied to the metallic support body in 12, it may be inductively heat the support.
[0039]
When performing the electromagnetic wave heating, for the purpose of effectively absorbing the electromagnetic wave and converting it to heat energy, it is preferable to include a component that can resonate with the electromagnetic wave and generate heat in the recording layer component. For example, when using a generally used 240 Hz electromagnetic wave, water corresponds to that component, and therefore, by containing a compound that retains water such as a hydrophilic resin or a water-soluble compound in the recording layer component, Water retention in the recording layer can be improved and efficient heat generation can be generated. Examples of the hydrophilic resin used herein include those described in the section of the hydrophilic resin described later in this specification. Among them, polysaccharides such as arabic rubber, soya rubber, hydroxypropyl cellulose, hydroxymethyl cellulose, polyacrylic acid, High molecular compounds having a hydroxyl group in the molecule such as sodium polyacrylate, hydroxypropyl acrylate and polyvinyl alcohol, and low molecular weight compounds such as sorbitol and glycerin are preferred from the viewpoint of improving the water retention of the recording layer.
[0040]
The lithographic printing plate precursor thus image-exposed and discharged from the image-exposure apparatus is then mounted on a printing machine without performing special development with a liquid developer, and using ink and fountain solution. Printing can be performed by a normal procedure. That is, the unexposed portion of the lithographic printing plate precursor after exposure is easily removed by an aqueous component contained in the fountain solution or an oily component such as ink in the initial stage of the printing process. Is exposed, and dampening water adheres to it to form a non-image area, and the hydrophobic area cured by exposure forms an ink-receptive image area.
These lithographic printing plate precursors can also be used for printing after being subjected to a development treatment using water or an appropriate aqueous solution as a developer.
[0041]
The lithographic printing plate precursor imaged by the method of the present invention has a so-called on-press development because the image area is sufficiently cured by the function of the preheating step performed locally efficiently and the strength of the image area is excellent. The high printing durability, which has been a problem in lithographic printing plates of the mold, has been realized, and it has become possible to obtain a large number of good printed matter.
Needless to say, the method of the present invention can be applied not only to scanning exposure based on digital data using an infrared laser but also to image exposure based on analog data as long as an infrared beam is used.
[0042]
(Configuration of lithographic printing plate precursor)
Next, the configuration of a lithographic printing plate precursor that can be suitably applied to the method of the present invention and that can form an image without requiring a liquid development processing step will be described in detail.
The lithographic printing plate precursor according to the invention comprises an image recording layer containing a microcapsule encapsulating a polymerizable compound on a support, a polymerization initiator, and a photothermal conversion agent.
[0043]
(Image recording layer)
(Microcapsules encapsulating polymerizable compounds)
Examples of the polymerizable compound used in the present invention include a cationic polymerizable compound and a radical polymerizable compound.
[0044]
<Cationically polymerizable compound>
The cationically polymerizable compound used in the present invention is not particularly limited as long as it is a compound having a cationically polymerizable group in the molecule. Among them, a compound having a vinyloxy group or an epoxy group is preferably used.
[0045]
Examples of the cationically polymerizable compound having a vinyloxy group suitable for the present invention include compounds described in JP-A-2002-29162.
Specifically, tetramethylene glycol divinyl ether, trimethylolpropane trivinyl ether, tetraethylene glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol trivinyl ether, pentaerythritol tetravinyl ether, 1,4-bis {2- (vinyloxy) ethyloxy } Benzene, 1,2-bis {2- (vinyloxy) ethyloxy} benzene, 1,3-bis {2- (vinyloxy) ethyloxy} benzene, 1,3,5-tris {2- (vinyloxy) ethyloxy} benzene, 4,4′-bis {2- (vinyloxy) ethyloxy} biphenyl, 4,4′-bis {2- (vinyloxy) ethyloxy} diphenyl ether, 4,4′-bis {2- (vinyloxy) ethyl Xyl} diphenylmethane, 1,4-bis {2- (vinyloxy) ethyloxy} naphthalene, 2,5-bis {2- (vinyloxy) ethyloxy} furan, 2,5-bis {2- (vinyloxy) ethyloxy} thiophene, , 5-bis {2- (vinyloxy) ethyloxy} imidazole, 2,2-bis [4- {2- (vinyloxy) ethyloxy} phenyl] propane {bis (vinyloxyethyl) ether of bisphenol A}, 2,2- And bis {4- (vinyloxymethyloxy) phenyl} propane, 2,2-bis {4- (vinyloxy) phenyl} propane, and the like. Among them, 2,2-bis [4- {2- (vinyloxy) ethyloxy } Phenyl] propane, bis (vinyloxyethyl) ether of bisphenol A, 2 2- bis {4- (vinyloxymethyl) phenyl} propane, 2,2-bis {4- (vinyloxy) phenyl} propane are especially preferred. The present invention is not limited to these.
[0046]
As the cationically polymerizable compound having an epoxy group suitable for the present invention, a compound having two or more epoxy groups is preferable, and a glycidyl ether compound obtained by a reaction of a polyhydric alcohol or a polyhydric phenol with epichlorohydrin or the like. Examples thereof include a prepolymer, and a polymer or copolymer of glycidyl acrylate or glycidyl methacrylate.
[0047]
Specific examples include propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl ether of hydrogenated bisphenol A, hydroquinone di- Glycidyl ether, resorcinol diglycidyl ether, diglycidyl ether or epichlorohydrin polyadduct of bisphenol A, diglycidyl ether or epichlorohydrin polyadduct of bisphenol F, diglycidyl ether of halogenated bisphenol A or epichloro Hydrine polyadduct, diglycidyl ether of biphenyl type bisphenol or epichlorohydrin polyadduct, novolac resin Examples include glycidyl etherified products, methyl methacrylate / glycidyl methacrylate copolymer, ethyl methacrylate / glycidyl methacrylate methacrylate, and the like. Among them, diglycidyl ether or epichlorohydrin polyadduct of bisphenol A, Diglycidyl ether or epichlorohydrin polyadduct of halogenated bisphenol A, diglycidyl ether or epichlorohydrin polyadduct of biphenyl type bisphenol are particularly preferred. The present invention is not limited to these.
[0048]
Commercially available products of the above compounds include, for example, Epicoat 1001 (molecular weight: about 900, epoxy equivalent: 450 to 500), Epicoat 1002 (molecular weight: about 1600, epoxy equivalent: 600 to 700), Epicoat 1004 (about) manufactured by Japan Epoxy Resin Co., Ltd. 1060, epoxy equivalent 875-975), Epicoat 1007 (molecular weight about 2900, epoxy equivalent 2000), Epicoat 1009 (molecular weight about 3750, epoxy equivalent 3000), Epicoat 1010 (molecular weight about 5500, epoxy equivalent 4000), Epicoat 1100L (epoxy equivalent) 4000), Epikote YX31575 (epoxy equivalent 1200), Sumitomo Chemical Co., Ltd. Sumiepoxy ESCN-195XHN, ESCN-195XL, ESCN-195XF, and the like.
[0049]
<Radically polymerizable compound>
The radically polymerizable compound used in the present invention is not particularly limited as long as it has an ethylenically unsaturated bond in the molecule.
Examples of the functional group containing an ethylenically unsaturated bond include an acryloyl group, a methacryloyl group, a vinyl group, and an allyl group. A compound having at least one, preferably two or more of these is preferably used. Such a group of compounds is widely known as a monomer or a crosslinking agent for a radically polymerizable compound in the industrial field, and in the present invention, these can be used without any particular limitation. The chemical form is a monomer, a prepolymer, that is, a dimer, a trimer, an oligomer, a polymer or a copolymer, or a mixture thereof.
[0050]
Examples of the radical polymerizable compound suitable for the present invention include compounds having an ethylenically unsaturated group described in JP-A No. 2001-277740.
Typical examples are trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol. Examples include di (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, adducts of trimethylolpropane diacrylate and xylylene diisocyanate.
Examples of the polymer or copolymer in the form of a compound having an ethylenically unsaturated group include allyl methacrylate copolymer, allyl methacrylate / methacrylic acid copolymer, allyl methacrylate / ethyl methacrylate copolymer, and allyl methacrylate. / Butyl methacrylate copolymer.
Of these, dipentaerythritol tetraacrylate and allyl methacrylate / methacrylic acid copolymer are particularly preferable. The present invention is not limited to these.
[0051]
<Other polymerizable compounds>
Furthermore, the inclusion of the microcapsule according to the present invention may contain a thermopolymerizable compound having the following heat-reactive group, in addition to the polymerizable compound.
Examples of the thermally polymerizable group include an isocyanate group that performs an addition reaction, a block thereof, and a functional group having an active hydrogen atom that is a reaction partner with the cationic polymerizable group or the ethylenically unsaturated group (for example, Amino group, hydroxy group, carboxy group, etc.),
A carboxy group that performs a condensation reaction, and a hydroxy group and an amino group that are reaction partners thereof,
Examples thereof include an acid anhydride that undergoes a ring-opening addition reaction, and an amino group and a hydroxy group that are reaction partners thereof.
[0052]
Suitable compounds having an isocyanate group for the present invention include tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, xylylene diisocyanate, naphthalene diisocyanate, cyclohexanephenylene diisocyanate, isophorone diester. Examples thereof include isocyanate, hexamethylene diisocyanate, cyclohexyl diisocyanate, and compounds obtained by blocking these with alcohol or amine.
[0053]
Examples of the compound having an amino group suitable for the present invention include ethylenediamine, diethylenetriamine, triethylenetetramine, hexamethylenediamine, propylenediamine, and polyethyleneimine.
Examples of the compound having a hydroxy group suitable for the present invention include compounds having a terminal methylol group, polyhydric alcohols such as pentaerythritol, and bisphenol / polyphenols.
[0054]
Examples of the compound having a carboxy group suitable for the present invention include aromatic polyvalent carboxylic acids such as pyromellitic acid, trimellitic acid, and phthalic acid, and aliphatic polyvalent carboxylic acids such as adipic acid.
Suitable acid anhydrides for the present invention include pyromellitic acid anhydride and benzophenone tetracarboxylic acid anhydride.
[0055]
Further, in the image recording layer according to the present invention, it is necessary to add a photothermal conversion agent and a polymerization initiator to at least one of the microcapsule and the recording layer matrix. These components are added to the microcapsule. At this time, the resultant is dissolved or dispersed in the same solvent as that of the inclusion, and is included. Further, usable photothermal conversion agents and polymerization initiators will be described later.
[0056]
As a method for microencapsulating each of the above components, known methods can be applied. For example, as a method for producing microcapsules, a method using coacervation found in U.S. Pat. Nos. 2,800,547 and 2,800,498, British Patent 990443, U.S. Pat. No. 3,287,154, Japanese Patent Publication Nos. 38-19574, 42-446 No. 42-711, interfacial polymerization method, US Pat. No. 3,418,250, US Pat. No. 3,660,304, method of polymer precipitation, US Pat. No. 3,796,669, method using isocyanate polyol wall material, US Pat. US Pat. No. 3,914,511 shows a method using an isocyanate wall material, US Pat. Nos. 4001140, 4087376, and 4089802 use a urea-formaldehyde system or a urea formaldehyde-resorcinol wall forming material, A method using a wall material such as melamine-formaldehyde resin and hydroxycellulose, as shown in U.S. Pat. No. 4,025,445, an in situ method by monomer polymerization as shown in JP-B-36-9163 and 51-9079, British Patent 930422, US Pat. No. 3,111,407 And the like, but are not limited thereto, such as the spray drying method found in British Patent Nos. 952807 and 967074.
[0057]
A preferable microcapsule wall material used in the present invention has properties that it can swell in a coating solvent and can form a three-dimensional crosslink. From such a viewpoint, the wall material of the microcapsule is preferably polyurea, polyurethane, polyester, polycarbonate, polyamide, and a mixture thereof, and particularly preferably polyurea and polyurethane. Further, a compound having a thermally reactive group may be introduced into the microcapsule wall.
The average particle diameter of the obtained microcapsules is preferably 0.01 to 3.0 μm, more preferably 0.05 to 2.0 μm, and particularly preferably 0.10 to 1.0 μm. Within this range, good resolution and stability over time can be obtained.
[0058]
In such a microcapsule, when the capsule wall material is disintegrated by heat or becomes permeable, the encapsulated polymerizable compound is released into the system, and a curing reaction occurs and proceeds. If the preheating temperature in the process reaches a temperature at which the capsule wall material becomes permeable, a curing reaction occurs in an undesired non-image area, and the non-image area is likely to be stained. It is preferable that the upper limit is a temperature lower than the temperature at which the heat treatment is performed, preferably 30 ° C. below the temperature at which the capsule wall material is permeable. The temperature at which the capsule wall material becomes permeable varies depending on the material forming the capsule wall material and the thickness of the wall material.For example, when an adduct of trimethylolpropane and xylylene diisocyanate is used as the capsule wall material, 286 ° C when the reaction product of trimethylolpropane and xylylene diisocyanate adduct, Millionate MR-200 (Nippon Polyurethane aromatic isocyanate) and tetraethylenepentamine is used as the wall material. Degree.
[0059]
In addition, such microcapsules may be combined with each other by heat, or may not be combined. In short, the inclusion in the microcapsule oozes out of the capsule surface or outside the microcapsule by image exposure using an infrared beam and causes a chemical reaction with the reaction initiator generated from the polymerization initiator described later, or the reaction starts. Any material can be used as long as it has a structure capable of entering a microcapsule wall and causing a chemical reaction to be cured. Further, such a polymerizable compound may react with a later-described hydrophilic resin or low molecular compound added to the recording layer as an optional component. In addition, the microcapsules may be reacted with each other by providing the microcapsules with different functional groups that are thermally reacted with each other. Therefore, it is preferable for image formation that the microcapsules are melted and united by heat, but it is not essential.
[0060]
The amount of such microcapsules added to the recording layer is preferably 50% by mass or more, and more preferably 70 to 98% by mass in terms of solid content in terms of solid content. Within this range, a good image can be formed and good printing durability can be obtained.
[0061]
In the recording layer containing microcapsules, a solvent capable of dissolving the inclusions of the microcapsules and swelling the wall material can be added to the microcapsule dispersion medium. By adding such a solvent, the diffusion of the microcapsule inclusions outside the capsule is promoted during image exposure.
Such a solvent depends on the microcapsule dispersion medium, the material of the microcapsule wall, the wall thickness, and the inclusion, but can be easily selected from many commercially available solvents. For example, in the case of a water-dispersible microcapsule comprising a crosslinked polyurea or polyurethane wall, alcohols, ethers, acetals, esters, ketones, polyhydric alcohols, amides, amines, fatty acids and the like are preferable.
[0062]
Specific compounds include methanol, ethanol, tertiary butanol, n-propanol, tetrahydrofuran, methyl lactate, ethyl lactate, methyl ethyl ketone, propylene glycol monomethyl ether, ethylene glycol diethyl ether, ethylene glycol monomethyl ether, γ-butyl lactone, N, Examples include N-dimethylformamide and N, N-dimethylacetamide, but the present invention is not limited thereto. Two or more of these solvents may be used in combination. A solvent that does not dissolve alone in the microcapsule dispersion medium but dissolves by mixing the above-mentioned solvents can also be used.
[0063]
The amount of such a solvent added depends on the combination of materials, but usually 5 to 95% by mass of the recording layer coating solution is effective, and a preferable range is 10 to 90% by mass, and a more preferable range is 15 It is -85 mass%.
[0064]
(Photothermal conversion agent)
In the recording layer according to the present invention, it is necessary to add a photothermal conversion agent having a function of absorbing light energy and converting it into heat. In this case, a photothermal conversion agent may be added to at least one of the microcapsule and the recording layer matrix. In the present invention, from the viewpoint that infrared energy can contribute to image forming efficiency, It is preferable to add.
[0065]
The photothermal conversion agent may be any substance that absorbs infrared rays, particularly near infrared rays (wavelength 700 to 1200 nm), and various known pigments, dyes or pigments, and metal fine particles can be used.
[0066]
For example, the pigments, dyes or dyes described in JP-A-2001-301350, JP-A-2002-137562, Journal of the Japan Printing Association, Vol. 38, pages 35-40 (2001) “New imaging materials, 2. Near infrared absorbing dyes” Dyes and fine metal particles are preferably used. As these pigments and metal fine particles, those subjected to a known surface treatment can be used as necessary.
[0067]
More specifically, as dyes or pigments, U.S. Pat. Nos. 4,756,993 and 4,973,572, JP-A-10-268512, JP-A-11-235883, JP-B-5-13514, JP-A-5-19702, and JP-A-2001-2001. Examples thereof include cyanine dyes, polymethine dyes, azomethine dyes, squarylium dyes, pyrylium and thiopyrylium salt dyes, dithiol metal complexes, and phthalocyanine dyes described in No. 347765. Particularly preferred are cyanine dyes, squarylium dyes, pyrylium salts, and phthalocyanine dyes.
[0068]
Examples of the pigment include insoluble azo pigments, azo lake pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene and perinone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments, Kinophthalone pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, inorganic pigments, carbon black, and the like can be used. Of these, carbon black is preferred.
As the metal fine particles, fine particles of Ag, Au, Cu, Sb, Ge and Pb are preferable, and fine particles of Ag, Au and Cu are more preferable.
[0069]
Specific examples of particularly suitable photothermal conversion agents are shown below, but the present invention is not limited thereto. Note that (IR-1) to (IR-11) are hydrophilic photothermal conversion agents suitable for addition to the image recording layer matrix, and (IR-21) to (IR-29) are A lipophilic photothermal conversion agent suitable for inclusion in capsules.
[0070]
[Chemical 1]

[0071]
[Chemical 2]

[0072]
[Chemical 3]

[0073]
[Formula 4]

[0074]
When added to the microcapsule, the addition amount of the photothermal conversion agent is preferably 1 to 50% by mass, more preferably 3 to 25% by mass based on the total content of the microcapsules.
On the other hand, when the photothermal conversion agent is added to the image recording layer matrix, 1 to 50% by mass of the solid content of the recording layer is preferable, and 3 to 25% by mass is more preferable. In this range, good sensitivity can be obtained without impairing the film strength of the recording layer.
[0075]
(Polymerization initiator)
In the recording layer according to the present invention, it is necessary to add a polymerization initiator that generates a reaction initiating substance by heat and starts and accelerates the reaction of the polymerizable compound in the image recording layer matrix. In this case, a polymerization initiator may be added to at least one of the inside of the microcapsule and the image recording layer matrix. From the viewpoint of stability, the recording layer matrix is present so as to be separated from the polymerizable compound and the microcapsule wall. It is preferable to add in.
[0076]
Examples of the polymerization initiator used in the present invention include known acid generators or radical generators. The former is used when a cationic polymerizable compound is used as the polymerizable compound in the microcapsule. The latter is also used when a radical polymerizable compound is used as the polymerizable compound.
It is also possible to form a printing system in combination with a dye that changes color due to the generated acid or radical.
[0077]
Hereinafter, these polymerization initiators will be described.
<Acid generator>
In the present invention, the acid generator used in combination with the cationic polymerizable compound is not particularly limited as long as it generates heat by absorbing heat. As such an acid generator, known acid precursors and acid generators are preferably used, and examples thereof include acid generators for print-out image formation, acid generators used in microresists, and the like. It is done.
[0078]
More specifically, organic halogen compounds typified by trihalomethyl-substituted heterocyclic compounds described in JP-A-2002-29162, JP-A-2002-46361, JP-A-2002-137562, etc., iminosulfonates, etc. And compounds capable of generating a sulfonic acid by photolysis represented by (2), disulfone compounds, onium salts (for example, iodonium salts, diazonium salts, sulfonium salts, etc.). Moreover, the compound which introduce | transduced the group or compound which generate | occur | produces these acids into the polymer principal chain or side chain can also be used.
[0079]
Hereinafter, although the specific example of the acid generator which can be used conveniently for this invention is given, this invention is not limited to these.
[0080]
[Chemical formula 5]

[0081]
[Chemical 6]

[0082]
[Chemical 7]

[0083]
[Chemical 8]

[0084]
[Chemical 9]

[0085]
Two or more of the above acid generators can be used in combination.
The addition amount of the acid generator is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass based on the total solid content of the recording layer. Within this range, good reaction initiation or acceleration effect can be obtained without impairing on-press developability.
[0086]
<Radical generator>
In the present invention, the radical generator used in combination with the radical polymerizable compound is not particularly limited as long as it absorbs heat and generates radicals. As such a radical generator, a known thermal radical generator is preferably used, and examples thereof include a photoinitiator for photoradical polymerization.
Specifically, compounds that generate sulfonic acid, disulfone compounds, onium salts (for example, iodonium salts, diazonium salts, sulfonium salts, etc.) mentioned as the acid generator may be used as radical generators. it can.
[0087]
Specific examples include the compounds (AI-1) to (AI-17), (AN-1) to (AN-8) and (AS-1) to (AS-12) mentioned above. However, the present invention is not limited to these.
Two or more of the above radical generators can be used in combination.
The addition amount of the radical generator is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, based on the total solid content of the recording layer. Within this range, good reaction initiation or acceleration effect can be obtained without impairing on-press developability.
[0088]
In the method of the present invention, the capsule wall material becomes permeable and released into the system by initiating and promoting the decomposition of the polymerization initiator (acid generator or radical generator) by preheating in the preheating step. The effect of improving the efficiency of the curing reaction between the polymerizable compound and the polymerization initiator can be obtained. For this reason, the preheating temperature is preferably equal to or higher than the temperature at which decomposition of the polymerization initiator starts and accelerates, and more preferably at least 10 ° C. above the decomposition temperature. The decomposition temperature of the polymerization initiator varies depending on the type of the compound. For example, in the case of diphenyliodonium trifluoromethanesulfonic acid (AI-7; an acid generator exemplified in the present specification), it is about 160 ° C., and triphenylsulfonium. In the case of benzoyl formic acid (AS-11; a radical generator exemplified in the present specification), the temperature is about 200 ° C.
[0089]
In addition, the present invention aims to improve the mobility of the polymerization initiator and the polymerizable compound and improve the efficiency of the initiation and progression of the polymerization reaction by locally heating the periphery of the exposed region by the preheating step. Also have. Therefore, it is preferable to irradiate with an infrared beam after preheating before the mobility of the polymerization initiator or polymerizable compound is not deactivated. In that case, it is preferable to complete preheating within a period from 1 minute before the start of infrared beam irradiation to the start of irradiation.
[0090]
The recording layer according to the present invention can be added with a compound that changes color by an acid or a radical in order to generate a printout image. As such a compound, for example, various dyes such as diphenylmethane, triphenylmethane, thiazine, oxazine, xanthene, anthraquinone, iminoquinone, azo, and azomethine are effectively used.
[0091]
Specific examples include brilliant green, ethyl violet, methyl green, crystal violet, basic fuchsin, methyl violet 2B, quinaldine red, rose bengal, methanyl yellow, thymol sulfophthalein, xylenol blue, methyl orange, paramethyl red, Congo Fred, Benzopurpurin 4B, α-Naphthyl Red, Nile Blue 2B, Nile Blue A, Methyl Violet, Malachide Green, Parafuchsin, Victoria Pure Blue BOH [manufactured by Hodogaya Chemical Co., Ltd.], Oil Blue # 603 [Orient Chemical Kogyo Co., Ltd.], Oil Pink # 312 [Orient Chemical Co., Ltd.], Oil Red 5B [Orient Chemical Co., Ltd.], Oil Scarlet # 308 [Orient Gaku Kogyo Co., Ltd.], Oil Red OG [Orient Chemical Co., Ltd.], Oil Red RR [Orient Chemical Co., Ltd.], Oil Green # 502 [Orient Chemical Co., Ltd.], Spiron Red BEH Special [made by Hodogaya Chemical Co., Ltd.], m-cresol purple, cresol red, rhodamine B, rhodamine 6G, sulforhodamine B, auramine, 4-p-diethylaminophenyliminonaphthoquinone, 2-carboxyanilino-4-p- Diethylaminophenyliminonaphthoquinone, 2-carboxystearylamino-4-pN, N-bis (hydroxyethyl) amino-phenyliminonaphthoquinone, 1-phenyl-3-methyl-4-p-diethylaminophenylimino-5-pyrazolone, 1-β-naphthyl-4- - dyes and p of diethylamino phenyl imino-5-pyrazolone, p ', p "- hexamethyl triamnotriphenylmethane (leuco crystal violet), and a leuco dye such as Pergascript Blue SRB (manufactured by Ciba-Geigy).
[0092]
In addition to the above, a leuco dye known as a material for thermal paper or pressure-sensitive paper is also suitable. Specific examples include crystal violet lactone, malachite green lactone, benzoylleucomethylene blue, 2- (N-phenyl-N-methylamino) -6- (Np-tolyl-N-ethyl) amino-fluorane, 2-anilino. -3-methyl-6- (N-ethyl-p-toluidino) fluorane, 3,6-dimethoxyfluorane, 3- (N, N-diethylamino) -5-methyl-7- (N, N-dibenzylamino) ) -Fluorane, 3- (N-cyclohexyl-N-methylamino) -6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) -6-methyl-7-anilinofluorane, 3 -(N, N-diethylamino) -6-methyl-7-xylidinofluorane, 3- (N, N-diethylamino) -6-methyl-7-chloro Fluorane, 3- (N, N-diethylamino) -6-methoxy-7-aminofluorane, 3- (N, N-diethylamino) -7- (4-chloroanilino) fluorane, 3- (N, N-diethylamino) -7-chlorofluorane, 3- (N, N-diethylamino) -7-benzylaminofluorane, 3- (N, N-diethylamino) -7,8-benzofluorane, 3- (N, N-dibutyl) Amino) -6-methyl-7-anilinofluorane, 3- (N, N-dibutylamino) -6-methyl-7-xylidinofluorane, 3-piperidino-6-methyl-7-anilinofluorane 3-pyrrolidino-6-methyl-7-anilinofluorane, 3,3-bis (1-ethyl-2-methylindol-3-yl) phthalide, 3,3-bis (1-n-butyl- -Methylindol-3-yl) phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl- 2-methylindol-3-yl) -4-zaphthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, and the like.
A suitable addition amount of the dye that changes color by acid or radical is a ratio of 0.01 to 10% by mass with respect to the solid content of the recording layer.
[0093]
(Hydrophilic resin)
The recording layer matrix according to the present invention may contain a hydrophilic resin in order to improve the on-press developability, the film strength of the recording layer itself, and the heating efficiency when performing electromagnetic wave heating.
As hydrophilic resin, what has hydrophilic groups, such as a hydroxyl group, an amino group, a carboxy group, a phosphoric acid group, a sulfonic acid group, an amide group, is preferable, for example.
[0094]
In addition, the hydrophilic resin reacts with a functional group such as an ethylenically unsaturated group, a cationic polymerizable group, or a thermally reactive group that the thermally polymerizable compound has in the polymerizable compound encapsulated in the microcapsule. Since crosslinking improves the image strength and further increases printing durability, it is preferable to select a resin having a group that reacts with these functional groups as the hydrophilic resin. For example, when the cationically polymerizable compound has a vinyloxy group or an epoxy group, the hydrophilic resin preferably has a hydroxy group, a carboxy group, a phosphoric acid group, a sulfonic acid group, or the like. Among these, a hydrophilic resin having a hydroxy group or a carboxy group is preferable.
[0095]
Specific examples of hydrophilic resins include gum arabic, casein, gelatin, starch derivatives, soya gum, hydroxypropylcellulose, methylcellulose, carboxymethylcellulose and its sodium salt, cellulose acetate, sodium alginate, vinyl acetate-maleic acid copolymers, styrene-malein Acid copolymers, polyacrylic acids and their salts, polymethacrylic acids and their salts, homopolymers and copolymers of hydroxyethyl methacrylate, homopolymers and copolymers of hydroxyethyl acrylate, homopolymers and copolymers of hydroxypropyl methacrylate, hydroxypropyl acrylate Homopolymers and copolymers, hydroxybutyl methacrylate homopolymers and copolymers, Homopolymers and copolymers of butyl acrylate, polyethylene glycols, hydroxypropylene polymers, polyvinyl alcohols, hydrolyzed polyvinyl acetate having a degree of hydrolysis of at least 60% by weight, preferably at least 80% by weight, polyvinyl formal, polyvinyl pyrrolidone, acrylamide Homopolymers and copolymers, methacrylamide homopolymers and copolymers, N-methylolacrylamide homopolymers and copolymers, 2-acrylamido-2-methyl-1-propanesulfonic acid homopolymers and copolymers, 2-methacryloyloxyethylphosphonic acid And homopolymers and copolymers thereof.
The amount of the hydrophilic resin added is preferably 20% by mass or less, more preferably 10% by mass or less, based on the total solid content of the recording layer.
[0096]
Further, the hydrophilic resin may be used after being cross-linked to such an extent that an unexposed portion can be developed on-press on a printing press. Examples of crosslinking agents used to crosslink hydrophilic resins include glyoxal, melamine formaldehyde resins, aldehydes such as urea formaldehyde resins, N-methylol urea, N-methylol melamine, methylol compounds such as methylolated polyamide resins, and divinyl. Active vinyl compounds such as sulfone and bis (β-hydroxyethylsulfonic acid), epoxy compounds such as epichlorohydrin, polyethylene glycol diglycidyl ether, polyamide, polyamine, epichlorohydrin adduct, polyamide epichlorohydrin resin, monochloroacetic acid Ester compounds such as esters and thioglycolic acid esters, polycarboxylic acids such as polyacrylic acid and methyl vinyl ether / maleic acid copolymer, boric acid, titanyl sulfate, C , Al, Sn, V, inorganic crosslinking agents such as Cr salts, and modified polyamide polyimide resin. In addition, a crosslinking catalyst such as ammonium chloride, a silane coupling agent, a titanate coupling agent can be used in combination.
[0097]
(Other additives)
In addition to the above, various compounds may be added to the recording layer matrix according to the present invention as necessary.
[0098]
<Multifunctional monomer>
In order to further improve the printing durability, a polyfunctional monomer can be added. As this polyfunctional monomer, those exemplified as the monomer put in the microcapsule can be used. Among them, preferable monomers include trimethylolpropane triacrylate, pentaerythritol triacrylate, and the like. The addition amount of the polyfunctional monomer is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5.0% by mass in the total solid content of the recording layer.
[0099]
<Thermal polymerization inhibitor>
In the present invention, it is desirable to add a small amount of a thermal polymerization inhibitor in order to prevent unnecessary thermal polymerization of the ethylenically unsaturated compound during preparation or storage of the recording layer coating solution. Suitable thermal polymerization inhibitors include hydroquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, t-butylcatechol, benzoquinone, 4,4'-thiobis (3-methyl-6-t-butylphenol ), 2,2'-methylenebis (4-methyl-6-t-butylphenol), N-nitroso-N-phenylhydroxylamine aluminum salt and the like. The addition amount of the thermal polymerization inhibitor is preferably 0.01 to 5% by mass in the total solid content of the recording layer.
[0100]
<Higher fatty acids or their derivatives>
In the recording layer matrix according to the present invention, if necessary, a higher fatty acid such as behenic acid or behenic acid amide or a derivative thereof is added to prevent polymerization inhibition by oxygen, and drying after coating is performed. In this process, it may be unevenly distributed on the surface of the recording layer. The addition amount of the higher fatty acid or its derivative is preferably 0.1 to 10% by mass in the total solid content of the recording layer.
[0101]
<Inorganic fine particles>
Inorganic fine particles may be added to the recording layer matrix according to the present invention, and suitable examples of inorganic fine particles include silica, alumina, magnesium oxide, titanium oxide, magnesium carbonate, calcium alginate, or a mixture thereof. Even if they are not photothermally convertible, they can be used for strengthening the film and enhancing interfacial adhesion by surface roughening.
[0102]
The average particle size of the inorganic fine particles is preferably 5 nm to 10 μm, more preferably 10 nm to 1 μm. Within this range, the microcapsules and the metal fine particles of the photothermal conversion agent are both stably dispersed in the hydrophilic resin, the film strength of the recording layer is sufficiently maintained, and the non-hydrophilic material having excellent hydrophilicity that hardly causes printing stains. An image portion can be formed.
[0103]
Such inorganic fine particles can be easily obtained as a commercial product such as a colloidal silica dispersion. The content of the inorganic fine particles in the recording layer is preferably 20% by mass or less, more preferably 10% by mass or less, based on the total solid content of the recording layer.
[0104]
<Surfactant>
In the recording layer matrix according to the present invention, JP-A-2-195356, JP-A-59-121044, JP-A-4-12044 are used for improving the dispersion stability of the recording layer, plate making and printing performance, and coating properties. Nonionic, anionic, cationic, amphoteric or fluorine-based surfactants described in No. 13149 and Japanese Patent Application No. 2001-169731 can be added. A suitable addition amount of these surfactants is 0.005 to 1% by mass of the total solid content of the recording layer.
[0105]
<Plasticizer>
In the recording layer matrix according to the present invention, a plasticizer can be added as needed to impart flexibility of the coating film. For example, polyethylene glycol, tributyl citrate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, tricresyl phosphate, tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryl oleate and the like are used.
[0106]
(Formation of image recording layer)
The recording layer according to the present invention is applied by preparing a coating solution by dissolving the necessary components described above in a solvent. Solvents used here include ethylene dichloride, cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxy Examples include ethane, methyl lactate, ethyl lactate, N, N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, γ-butyrolactone, toluene, water and the like. However, the present invention is not limited to this. These solvents are used alone or in combination. The solid content concentration of the coating solution is preferably 1 to 50% by mass.
[0107]
The recording layer coating amount (solid content) on the support obtained after coating and drying varies depending on the application, but is generally 0.5 to 5.0 g / m. ² Is preferred. When the coating amount is less than this range, the apparent sensitivity increases, but the film characteristics of the recording layer that performs the function of image recording deteriorate. Various methods can be used as a coating method. Examples thereof include bar coater coating, spin coating, spray coating, curtain coating, dip coating, air knife coating, blade coating, and roll coating.
[0108]
[Overcoat layer]
The lithographic printing plate precursor according to the present invention is provided on the recording layer in order to protect the hydrophilic recording layer surface from contamination with lipophilic substances during storage and fingerprint trace contamination due to finger contact during handling. An overcoat layer containing a water-soluble resin described in JP-A-162961 and JP-A-2002-19318 can be provided.
[0109]
Specific examples of water-soluble resins used in the overcoat layer include natural gums such as gum arabic, water-soluble soybean polysaccharide, fiber derivatives (eg, carboxymethyl cellulose, carboxyethyl cellulose, methyl cellulose, etc.), modified products thereof, For synthetic polymers such as white dextrin, pullulan, and enzymatically degraded etherified dextrin, polyvinyl alcohol (polyvinyl acetate having a hydrolysis rate of 65% or more), polyacrylic acid, its alkali metal salt or amine salt, and polyacrylic acid Polymer, alkali metal salt or amine salt thereof, polymethacrylic acid, alkali metal salt or amine salt thereof, vinyl alcohol / acrylic acid copolymer and alkali metal salt or amine salt thereof, polyacrylamide, copolymer thereof, polyhydroxy Ethyl acrylate, Polyvinyl Lupyrrolidone, its copolymer, polyvinyl methyl ether, vinyl methyl ether / maleic anhydride copolymer, poly-2-acrylamido-2-methyl-1-propanesulfonic acid, its alkali metal salt or amine salt, poly-2 -Acrylamido-2-methyl-1-propanesulfonic acid copolymer, its alkali metal salt or amine salt. Depending on the purpose, two or more of these resins may be mixed and used. However, the present invention is not limited to these examples.
[0110]
The overcoat layer may contain a photothermal conversion agent in order to improve sensitivity. A preferable photothermal conversion agent includes a water-soluble infrared absorbing dye. For example, (IR-1) to (IR-11) shown in the description of the recording layer are preferably used.
[0111]
In addition, a nonionic surfactant can be mainly added to the overcoat layer in the case of aqueous solution coating for the purpose of ensuring the uniformity of coating. Specific examples of such nonionic surfactants include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride, polyoxyethylene nonylphenyl ether, polyoxyethylene dodecyl ether and the like. . The proportion of the nonionic surfactant in the overcoat layer in the total solid is preferably 0.05 to 5 mass%, more preferably 1 to 3 mass%.
[0112]
Furthermore, the overcoat layer can contain a compound having any one of fluorine atoms and silicon atoms described in JP-A No. 2001-341448 in order to prevent sticking between plates during stacking and storage.
The thickness of the overcoat layer according to the present invention is preferably 0.1 to 4.0 μm, and more preferably 0.1 to 1.0 μm. Within this range, it is possible to prevent the recording layer from being contaminated by an oleophilic substance without impairing the removability of the overcoat layer on the printing press.
[0113]
[Support]
The support that can be used for the lithographic printing plate precursor according to the present invention is a dimensionally stable plate-like material, for example, paper, paper laminated with plastic (for example, polyethylene, polypropylene, polystyrene, etc.), Metal plate (eg, aluminum, zinc, copper, etc.), plastic film (eg, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate , Polyvinyl acetal, etc.), paper or plastic film on which the above metal is laminated or vapor-deposited. A preferable support is an aluminum plate.
[0114]
The aluminum plate is a pure aluminum plate and an alloy plate containing aluminum as a main component and containing a trace amount of different elements. Further, a plastic is laminated on a thin film of aluminum or an aluminum alloy. Examples of foreign elements contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. The content of foreign elements in the alloy is at most 10% by mass. Further, it may be an aluminum plate from an aluminum ingot using a DC casting method or an aluminum plate from an ingot by a continuous casting method. However, as the aluminum plate applied to the present invention, conventionally known and publicly available aluminum plates can be used as appropriate.
The thickness of the substrate used in the present invention is 0.05 mm to 0.6 mm, preferably 0.1 mm to 0.4 mm, and particularly preferably 0.15 mm to 0.3 mm.
[0115]
Prior to using the aluminum plate, it is preferable to perform a surface treatment such as roughening the surface or anodizing. By the surface treatment, it becomes easy to improve hydrophilicity and secure adhesion to the recording layer.
The surface of the aluminum plate is roughened by various methods. For example, a method of mechanically roughening, a method of electrochemically dissolving and roughening the surface, and a method of selectively dissolving the surface chemically. By the method. As the mechanical method, a known method such as a ball polishing method, a brush polishing method, a blast polishing method, or a buff polishing method can be used. As a chemical method, a method of immersing in a saturated aqueous solution of an aluminum salt of a mineral acid as described in JP-A No. 54-31187 is suitable. In addition, as an electrochemical surface roughening method, there is a method of performing alternating current or direct current in an electrolytic solution containing an acid such as hydrochloric acid or nitric acid. Further, as disclosed in JP-A-54-63902, an electrolytic surface roughening method using a mixed acid can also be used. The roughening by the method as described above is preferably performed in such a range that the center line average roughness (Ra) of the surface of the aluminum plate is 0.2 to 1.0 μm.
[0116]
The roughened aluminum plate is subjected to alkali etching treatment using an aqueous solution of potassium hydroxide or sodium hydroxide as necessary, and further neutralized, and then anodized to increase wear resistance as desired. Processing is performed.
As the electrolyte used for the anodizing treatment of the aluminum plate, various electrolytes that form a porous oxide film can be used. In general, sulfuric acid, hydrochloric acid, oxalic acid, chromic acid, or a mixed acid thereof is used. The concentration of these electrolytes is appropriately determined depending on the type of electrolyte. The treatment conditions for anodization vary depending on the electrolyte used, and thus cannot be specified in general. However, in general, the electrolyte concentration is 1 to 80% by mass solution, the liquid temperature is 5 to 70 ° C., and the current density is 5 to 60 A / day. dm ² A voltage of 1 to 100 V and an electrolysis time of 10 seconds to 5 minutes are suitable. The amount of oxide film formed is 1.0 to 5.0 g / m. ² , Especially 1.5-4.0 g / m ² It is preferable that
[0117]
As the support used in the present invention, the substrate having the above-mentioned surface treatment and having an anodized film may be used as it is, but for further improvement in adhesion to the upper layer, hydrophilicity, resistance to contamination, heat insulation and the like. If necessary, an aqueous solution containing an anodized film micropore enlargement treatment, micropore sealing treatment, and a hydrophilic compound described in JP-A Nos. 2001-253181 and 2001-322365 The surface hydrophilization treatment to be immersed can be appropriately selected and performed.
Suitable hydrophilic compounds for the hydrophilization treatment include polyvinylphosphonic acid, compounds having sulfonic acid groups, saccharide compounds, citric acid, alkali metal silicates, potassium potassium fluoride, phosphate / inorganic fluorine compounds, and the like. Can be mentioned.
[0118]
When using a support having insufficient surface hydrophilicity, such as a polyester film, as the support used in the present invention, it is desirable to apply a hydrophilic layer to make the surface hydrophilic. The hydrophilic layer includes at least one element selected from beryllium, magnesium, aluminum, silicon, titanium, boron, germanium, tin, zirconium, iron, vanadium, antimony, and a transition metal described in JP-A No. 2001-199175. A hydrophilic layer formed by applying a coating solution containing an oxide or hydroxide colloid is preferred. Among these, a hydrophilic layer formed by applying a coating solution containing a silicon oxide or hydroxide colloid is preferable.
[0119]
In the present invention, before applying the recording layer, an inorganic subbing layer such as a water-soluble metal salt such as zinc borate described in JP-A-2001-322365, or An organic subbing layer containing carboxymethyl cellulose, dextrin, polyacrylic acid or the like can be provided. The undercoat layer can contain the photothermal conversion agent.
[0120]
As described above, a lithographic printing plate precursor to which the method of the present invention can be applied can be obtained. This lithographic printing plate precursor is an on-press development type lithographic printing plate precursor that is image-formed by infrared irradiation and is subjected to a printing process without undergoing development processing.
By applying the lithographic printing plate precursor having such a configuration to the image forming method of the present invention, an image portion having sufficient strength is formed by image exposure using infrared rays, so that the lithographic plate that can be developed on-machine The printing durability of the printing plate precursor has been improved, and it has become possible to obtain a large number of high-quality printed materials.
[0121]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these.
[Production of support]
[0122]
Cleaning treatment was applied to molten metal of JIS A1050 alloy containing 99.5 mass% or more of aluminum and Fe 0.30 mass%, Si 0.10 mass%, Ti 0.02 mass%, and Cu 0.013 mass%. And cast. In the cleaning process, a degassing process was performed to remove unnecessary gases such as hydrogen in the molten metal, and a ceramic tube filter process was performed. The casting method was a DC casting method. The solidified 500 mm thick ingot was chamfered 10 mm from the surface and homogenized at 550 ° C. for 10 hours so as not to coarsen the intermetallic compound.
[0123]
Next, after hot rolling at 400 ° C. and intermediate annealing at 500 ° C. for 60 seconds in a continuous annealing furnace, cold rolling was performed to obtain an aluminum rolled plate having a plate pressure of 0.30 mm. By controlling the roughness of the rolling roll, the centerline average surface roughness Ra after cold rolling was controlled to 0.2 μm. Then, it applied to the tension leveler in order to improve planarity.
[0124]
Next, the surface treatment for making a lithographic printing plate support was performed. First, in order to remove the rolling oil on the surface of the aluminum plate, degreasing treatment was carried out with a 10% by mass sodium aluminate aqueous solution at 50 ° C. for 30 seconds, and neutralization and smut removal treatment were carried out with a 30% by mass sulfuric acid aqueous solution at 50 ° C. for 30 seconds. Next, in order to improve the adhesion between the support and the recording layer and to provide water retention to the non-image area, a so-called graining treatment was performed to roughen the surface of the support. An aqueous solution containing 1% by mass of nitric acid and 0.5% by mass of aluminum nitrate is maintained at 45 ° C., and the current density is 20 A / dm by an indirect power feeding cell while flowing the aluminum web into the aqueous solution. ² , Anode side electricity quantity 240C / dm with alternating waveform with duty ratio 1: 1 ² Electrolytic graining was performed by giving Thereafter, an etching treatment was performed with a 10% by mass aqueous sodium aluminate solution at 50 ° C. for 30 seconds, and a 30% by mass sulfuric acid aqueous solution was subjected to neutralization and smut removal treatment at 50 ° C. for 30 seconds. Furthermore, in order to improve wear resistance, chemical resistance and water retention, an oxide film was formed on the support by anodic oxidation. A 20% by weight aqueous solution of sulfuric acid was used as the electrolyte at 35 ° C., and the aluminum web was carried into the electrolyte while the indirect power supply cell was used to provide 14 A / dm. ² 2.5 g / m by electrolytic treatment with direct current ² An anodic oxide film was prepared.
[0125]
Thereafter, a silicate treatment was performed in order to ensure hydrophilicity as a non-image portion of the printing plate. The treatment was carried in such a way that a No. 3 sodium silicate 1.5 mass% aqueous solution was kept at 70 ° C. so that the contact time of the aluminum web was 15 seconds and further washed with water. The amount of Si deposited is 10 mg / m ² Met. The center line surface roughness Ra of the support produced as described above was 0.25 μm.
[Synthesis of Microcapsule A Encapsulating Cationic Polymerizable Compound]
[0126]
As an oil phase component, 4.5 g of bis (vinyloxyethyl) ether of bisphenol A, an adduct of trimethylolpropane and xylylene diisocyanate (Takenate D-110N, manufactured by Mitsui Takeda Chemical Co., Ltd., microcapsule wall material) 5 g Millionate MR-200 (Nippon Polyurethane Co., Ltd. aromatic isocyanate oligomer, microcapsule wall material) 3.75 g, Infrared absorbing dye (IR-27 described herein) 1.5 g, Pionine A41C (Takemoto Yushi Co., Ltd.) ) Surfactant) 0.1 g was dissolved in 18.4 g of ethyl acetate. As an aqueous phase component, 37.5 g of a 4 mass% aqueous solution of PVA205 (Kuraray polyvinyl alcohol) was prepared. The oil phase component and the aqueous phase component were emulsified at 12000 rpm for 10 minutes using a homogenizer. Thereafter, a solution obtained by dissolving 0.38 g of tetraethylenepentamine (pentafunctional amine, microcapsule wall cross-linking agent) in 26 g of water was added, followed by stirring at 65 ° C. for 3 minutes while cooling with water. The microcapsule A liquid thus obtained had a solid content concentration of 24% by mass and an average particle size of 0.3 μm.
[0127]
[Synthesis Example of Microcapsule B Encapsulating Radical Polymerizable Compound]
As oil phase components, 4.5 g of dipentaerythritol tetraacrylate (KAYARAD DPHA manufactured by Nippon Kayaku), adduct of trimethylolpropane and xylylene diisocyanate (Takenate D-110N manufactured by Mitsui Takeda Chemical Co., Ltd.), microcapsule wall Material) 5 g, Millionate MR-200 (Nippon Polyurethane Co., Ltd. aromatic isocyanate oligomer, microcapsule wall material) 3.75 g, Infrared absorbing dye (IR-27 described in this specification) 1.5 g, Pionine A41C (Takemoto (Oil (surfactant) surfactant) 0.1 g was dissolved in ethyl acetate 18.4 g. As an aqueous phase component, 37.5 g of a 4 mass% aqueous solution of PVA205 (Kuraray polyvinyl alcohol) was prepared. The oil phase component and the aqueous phase component were emulsified at 12000 rpm for 10 minutes using a homogenizer. Thereafter, a solution obtained by dissolving 0.38 g of tetraethylenepentamine (pentafunctional amine, microcapsule wall cross-linking agent) in 26 g of water was added, followed by stirring at 65 ° C. for 3 minutes while cooling with water. The microcapsule solution thus obtained had a solid content concentration of 24% by mass and an average particle size of 0.3 μm.
[0128]
[Example 1]
(Preparation of lithographic printing plate precursor A)
The following recording layer coating solution containing the microcapsules A of the synthesis example was bar-coated on the aluminum substrate obtained in the above production example, and then dried in an oven at 100 ° C. for 60 seconds. 0.0 g / m ² A lithographic printing plate precursor A was prepared.
<Recording layer coating solution>
・ 35.4g of water
-Microcapsule A liquid 9.0 g in the above synthesis example
Acid generator (AI-7 as described herein) 0.24 g
[0129]
[Example 2]
(Preparation of lithographic printing plate precursor B)
The following recording layer coating solution containing the microcapsule B of the synthesis example was bar coated on the aluminum substrate obtained in the above production example, and then dried in an oven at 100 ° C. for 60 seconds. 0.0 g / m ² A lithographic printing plate precursor B was prepared.
<Recording layer coating solution>
・ 35.4g of water
-Microcapsule B liquid 9.0 g in the above synthesis example
Acid generator (AS-11 exemplified in this specification) 0.24 g
[0130]
(Exposure / printing and evaluation)
The lithographic printing plate precursors A and B obtained above are mounted on the image exposure apparatus 10 according to the embodiment of the present invention described with reference to FIGS. 1 and 2, and the recording layer in the preheating area in the lithographic printing plate precursor Was preheated to 160 ° C. to 180 ° C., and after 25 seconds, image exposure was performed with a Trendsetter 3244VX manufactured by Creo equipped with a water-cooled 40 W infrared semiconductor laser under the conditions of an output of 17 W, an outer drum rotation speed of 100 rpm, and a resolution of 2400 dpi. . During this exposure, the temperature of the recording layer in the preheating region of the lithographic printing plate precursor was kept at 100 ° C. or higher. As a result, even in the vicinity of the interface between the recording layer and the support, the capsule permeabilization reaction proceeds effectively, and the generation reaction in the acid or radical from the polymerization initiator also proceeds effectively. Combined with the high mobility of the active species, it was possible to form a strong and excellent printing durability image.
[0131]
Each lithographic printing plate precursor of the example was attached to a cylinder of a printing machine SOR-M manufactured by Heidelberg without developing after image exposure. 4% by volume IF102 (manufactured by Fuji Photo Film Co., Ltd.) using dampening water and Barius ink ink (manufactured by Dainippon Ink & Chemicals, Inc.), supplying dampening water, supplying ink, and Paper was supplied for printing.
[0132]
At this time, the recording layer in the non-image area was removed at the initial stage of the printing process, and a high-quality printed matter without the stain on the non-image area was obtained. After that, printing was continued, and the number of sheets was visually measured to determine whether the non-image area was free of stains and the image area could be printed with a sufficient ink density, and used as an index of printing durability. The larger the number, the better the printing durability.
[0133]
As a result, the lithographic printing plate precursor A of Example 1 was 35,000 sheets, and the lithographic printing plate precursor B of Example 2 was 25,000 sheets. Thereby, it was confirmed that both lithographic printing plate precursors of Examples 1 and 2 have excellent printing durability that can withstand practicality.
[0134]
【The invention's effect】
According to the present invention, an image forming method of a lithographic printing plate precursor capable of scanning exposure of an image based on a digital signal and on-press development and having excellent printing durability, and an image exposure apparatus used therefor Can be obtained.
[Brief description of the drawings]
FIG. 1 is a side view showing a configuration of an image exposure apparatus according to a first embodiment of the present invention.
2 is a perspective view showing a configuration of an exposure head and its feed mechanism in the image exposure apparatus shown in FIG. 1. FIG.
[Explanation of symbols]
10 Image exposure equipment
12 Planographic printing plate precursor
20 Outer drum (holding member)
26 Exposure head (exposure means)
28 Feeding mechanism (feeding mechanism)
32 Light source device (exposure means)
38 Preheating device (preheating means)
40 Heating fan unit (preheating means)
42 Flexible duct (preheating means)
44 Hot air nozzle (preheating means)
58 Lens unit (exposure head)
60 Fiber holder (exposure head)
68 Carrier (carrier member)

Claims (5)

An image forming method for forming an image on a lithographic printing plate precursor comprising an image recording layer comprising a microcapsule encapsulating a polymerizable compound, a polymerization initiator, and a photothermal conversion agent on a support. ,
An image exposure step of irradiating and exposing the lithographic printing plate precursor with an infrared beam to form an image on the image recording layer of the lithographic printing plate precursor;
The preheating area including the exposure area irradiated with the infrared beam on the image recording layer of the lithographic printing plate precursor is locally heated to a predetermined heating temperature before irradiation of the infrared beam with respect to the exposure area included in the preheating area. A preheating step of heating,
An image forming method, wherein heating of the preheating area to the preheating temperature is completed by the start of irradiation of an infrared beam to an exposure area included in the preheating area. The heating up to the preheating temperature of the preheating region in the preheating step is completed within a period from one minute before the start of irradiation of the infrared beam to the exposure region included in the preheating region until the start of irradiation. The image forming method according to claim 1. The image forming method according to claim 1, wherein a preheating temperature in the preheating step is in a range of 50 ° C. to 230 ° C. 3. An image exposure apparatus used in the image forming method according to claim 1, 2 or 3,
A holding member for holding the lithographic printing plate precursor, the lithographic printing plate precursor being mountable;
Exposure means for exposing the lithographic printing plate precursor held by the holding member with an infrared beam to form an image on the image recording layer of the lithographic printing plate precursor;
The preheating area including the exposure area in the lithographic printing plate precursor irradiated with the infrared beam by the exposure means is locally heated to the preheating temperature before irradiation of the infrared beam to the exposure area included in the preheating area. Preheating means;
An image exposure apparatus comprising: An exposure head that forms a beam spot of an infrared beam on the lithographic printing plate precursor mounted on the holding member in the exposure means, a carrier member on which the exposure head is mounted, and the carrier member during exposure of the lithographic printing plate precursor And a feed mechanism for moving the exposure head in the sub-scanning direction,
In addition, the preheating means is mounted on the carrier member so as to be positioned downstream of the exposure head along the sub-scanning direction, and moves in the sub-scanning direction together with the exposure head during exposure of the planographic printing plate precursor 5. The image exposure apparatus according to claim 4, further comprising a heat supply unit configured to supply heat energy or electromagnetic energy to the preheating region to heat the preheating region to the preheating temperature.

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