JP4299550B2 - Planographic printing plate precursor - Google Patents

Description

【００３９】
【化２】

【００４０】
【化３】

【００４１】
また、上記一般式（１）及び（２）で表される官能基を有するモノマーの具体例を以下に示す。
【００４２】
【化４】

【００４３】
【化５】

【００４４】
【化６】

【００４５】
かかる熱により脱炭酸を起こす極性変換ポリマーは、上記一般式（１）及び（２）で表される官能基を有するモノマー１種の単独重合体であっても、２種以上の共重合体であってもよい。また、本発明の効果を損なわない限り、他のモノマーとの共重合体であってもよい。
また、極性変換ポリマーも、１種類を用いてもよいし、２種以上を併用してもよい。
【００４６】
〔光熱変換物質〕
本発明の第二のネガ型感光層は、必要に応じて、露光により発熱する光熱変換物質を含有させてもよいし、また、第一のネガ型感光層が露光により発熱する余熱を利用することもできるため光熱変換物質を含有させなくてもよく、用いられる化合物や使用用途により、感度及び耐刷性が発現し易い態様を選択することができる。含有される光熱変換物質としては、７００〜１２００ｎｍの少なくとも一部に吸収帯を有する光吸収物質であればよく、種々の顔料、染料及び金属微粒子を用いることができる。
【００４７】
顔料としては、市販の顔料及びカラーインデックス（Ｃ．Ｉ．）便覧、「最新顔料便覧」（日本顔料技術協会編、１９７７年刊）、「最新顔料応用技術」（ＣＭＣ出版、１９８６年刊）、「印刷インキ技術」（ＣＭＣ出版、１９８４年刊）に記載されている赤外吸収性の顔料が利用できる。
【００４８】
これら顔料は、添加される層に対する分散性を向上させるため、必要に応じて公知の表面処理を施して用いることができる。表面処理の方法には、親水性樹脂や親油性樹脂を表面コートする方法、界面活性剤を付着させる方法、反応性物質（例えば、シリカゾル、アルミナゾル、シランカップリング剤やエポキシ化合物、イソシアナート化合物等）を顔料表面に結合させる方法等が考えられる。
【００４９】
第二のネガ型感光層に添加する顔料は、水溶性の樹脂と分散しやすく、かつ親水性を損わないように、親水性樹脂やシリカゾルで表面がコートされたものが望ましい。顔料の粒径は０．０１μｍ〜１μｍの範囲にあることが好ましく、０．０１μｍ〜０．５μｍの範囲にあることが更に好ましい。顔料を分散する方法としては、インク製造やトナー製造等に用いられる公知の分散技術が使用できる。特に好ましい顔料としては、カーボンブラックを挙げることができる。
【００５０】
染料としては、市販の染料及び文献（例えば「染料便覧」有機合成化学協会編集、昭和４５年刊、「化学工業」１９８６年５月号Ｐ．４５〜５１の「近赤外吸収色素」、「９０年代機能性色素の開発と市場動向」第２章２．３項（１９９０）シーエムシー）若しくは特許に記載されている公知の染料が利用できる。具体的には、アゾ染料、金属錯塩アゾ染料、ピラゾロンアゾ染料、アントラキノン染料、フタロシアニン染料、カルボニウム染料、キノンイミン染料、ポリメチン染料、シアニン染料等の赤外線吸収染料が好ましい。
【００５１】
更に、例えば、特開昭５８−１２５２４６号、特開昭５９−８４３５６号、特開昭６０−７８７８７号等に記載されているシアニン染料、特開昭５８−１７３６９６号、特開昭５８−１８１６９０号、特開昭５８−１９４５９５号等に記載されているメチン染料、特開昭５８−１１２７９３号、特開昭５８−２２４７９３号、特開昭５９−４８１８７号、特開昭５９−７３９９６号、特開昭６０−５２９４０号、特開昭６０−６３７４４号等に記載されているナフトキノン染料、特開昭５８−１１２７９２号等に記載されているスクワリリウム染料、英国特許４３４，８７５号記載のシアニン染料や米国特許第４，７５６，９９３号記載の染料、米国特許第４，９７３，５７２号記載のシアニン染料、特開平１０−２６８５１２号記載の染料、特開平１１−２３５８８３号記載のフタロシアニン化合物を挙げることができる。
【００５２】
また、染料として米国特許第５，１５６，９３８号記載の近赤外吸収増感剤も好適に用いられ、また、米国特許第３，８８１，９２４号記載の置換されたアリールベンゾ（チオ）ピリリウム塩、特開昭５７−１４２６４５号記載のトリメチンチアピリリウム塩、特開昭５８−１８１０５１号、同５８−２２０１４３号、同５９−４１３６３号、同５９−８４２４８号、同５９−８４２４９号、同５９−１４６０６３号、同５９−１４６０６１号に記載されているピリリウム系化合物、特開昭５９−２１６１４６号記載のシアニン染料、米国特許第４，２８３，４７５号に記載のペンタメチンチオピリリウム塩等や特公平５−１３５１４号、同５−１９７０２号公報に開示されているピリリウム化合物、エポリン社製エポライトＩＩＩ−１７８、エポライトＩＩＩ−１３０、エポライトＩＩＩ−１２５等も好ましく用いられる。
【００５３】
これらの中で、第二のネガ型感光層に添加するのに好ましい染料は水溶性染料で、以下に具体例を示す。但し、本発明はこれらに限定されるものではない。
【００５４】
【化７】

【００５５】
【化８】

【００５６】
〔親水性樹脂〕
本発明の第二のネガ型感光層は、現像性や第二のネガ型感光層自体の皮膜強度の向上のため親水性樹脂を含有させることができる。親水性樹脂としては、例えばヒドロキシル基、カルボキシル基、リン酸基、スルホン酸基、アミド基などの親水基を有するものが好ましい。又、親水性樹脂は、ビニルオキシ基と反応し架橋することによって画像強度が高まり、高耐刷化されるので、ビニルオキシ基と反応する官能基、例えば、ヒドロキシル基、カルボキシル基、リン酸基、スルホン酸基を有するものが好ましい。中でも、ヒドロキシル基又はカルボキシル基を有する親水性樹脂が好ましい。
【００５７】
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、水溶性大豆多糖類、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、ならびに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。
【００５８】
第二のネガ型感光層の膜質量は、０．０１〜４ｇ／ｍ²が好ましく、０．０５〜２．５ｇ／ｍ²がより好ましく、０．１〜１．５ｇ／ｍ²が現像性、画像形成性の観点から更に好ましい。
【００５９】
＜（Ａ）重合性化合物、及び、（Ｂ）重合開始系を含む第一のネガ型感光層＞
本発明における第一のネガ型感光層は、（Ａ）重合性化合物、及び、（Ｂ）重合開始系を含むことを必須とし、その他、必要に応じて、他の成分を添加することができる。
このような第一のネガ型感光層は、まず、赤外線レーザーを照射することにより、露光部分において、そのレーザ光及び／又は熱により（Ｂ）重合開始系から重合開始種（ラジカル、カチオン、アニオン種等）を発生する。その後、この発生した重合開始種により、共存する該重合開始種により重合可能な化合物（（Ａ）重合性化合物）が重合反応を起こし、露光部のみが現像液に不溶性となって像を形成する一方、非露光部は現像除去されて、所望の画像が形成される。このような画像形成プロセスによって、第一のネガ型感光層は、画像を形成することができる。
以下に、（Ａ）重合性化合物と、（Ｂ）重合開始系について説明する。
【００６０】
〔（Ａ）重合性化合物〕
本発明において用いられる（Ａ）重合性化合物は、重合開始種のラジカルにより重合反応が開始される重合性化合物である。
本発明に使用される、ラジカルにより重合反応が開始される重合性化合物は、少なくとも一個のエチレン性不飽和二重結合を有する重合性化合物であり、末端エチレン性不飽和結合を少なくとも１個、好ましくは２個以上有する化合物から選ばれる。このような化合物群は当該産業分野において広く知られるものであり、本発明においてはこれらを特に限定無く用いることができる。これらは、例えばモノマー、プレポリマー、すなわち２量体、３量体及びオリゴマー、又はそれらの混合物ならびにそれらの共重合体などの化学的形態をもつ。モノマー及びその共重合体の例としては、不飽和カルボン酸（例えば、アクリル酸、メタクリル酸、イタコン酸、クロトン酸、イソクロトン酸、マレイン酸など）や、そのエステル類、アミド類が挙げられ、好ましくは、不飽和カルボン酸と脂肪族多価アルコール化合物とのエステル、不飽和カルボン酸と脂肪族多価アミン化合物とのアミド類が用いられる。また、ヒドロキシル基や、アミノ基、メルカプト基等の求核性置換基を有する不飽和カルボン酸エステル、アミド類と単官能若しくは多官能イソシアネート類、エポキシ類との付加反応物、単官能若しくは、多官能のカルボン酸との脱水縮合反応物等も好適に使用される。また、イソシアナート基やエポキシ基等の親電子性置換基を有する不飽和カルボン酸エステル又はアミド類と、単官能若しくは多官能のアルコール類、アミン類及びチオール類との付加反応物、更に、ハロゲン基やトシルオキシ基等の脱離性置換基を有する不飽和カルボン酸エステル又はアミド類と、単官能若しくは多官能のアルコール類、アミン類及びチオール類との置換反応物も好適である。また、別の例として、上記の不飽和カルボン酸の代わりに、不飽和ホスホン酸、スチレン等に置き換えた化合物群を使用することも可能である。
【００６１】
脂肪族多価アルコール化合物と不飽和カルボン酸とのエステルである重合性化合物であるアクリル酸エステル、メタクリル酸エステル、イタコン酸エステル、クロトン酸エステル、イソクロトン酸エステル、マレイン酸エステルの具体例は、特開２００１−１３３９６９号公報の段落番号［００３７］〜［００４２］に記載されており、これらを本発明にも適用することができる。
【００６２】
その他のエステルの例として、例えば、特公昭４６−２７９２６、特公昭５１−４７３３４、特開昭５７−１９６２３１記載の脂肪族アルコール系エステル類や、特開昭５９−５２４０、特開昭５９−５２４１、特開平２−２２６１４９記載の芳香族系骨格を有するもの、特開平１−１６５６１３記載のアミノ基を含有するもの等も好適に用いられる。
【００６３】
また、脂肪族多価アミン化合物と不飽和カルボン酸とのアミドのモノマーの具体例としては、メチレンビス−アクリルアミド、メチレンビス−メタクリルアミド、１，６−ヘキサメチレンビス−アクリルアミド、１，６−ヘキサメチレンビス−メタクリルアミド、ジエチレントリアミントリスアクリルアミド、キシリレンビスアクリルアミド、キシリレンビスメタクリルアミド等がある。
その他の好ましいアミド系モノマーの例としては、特公昭５４−２１７２６記載のシクロへキシレン構造を有すものを挙げることができる。
【００６４】
また、イソシアネートと水酸基の付加反応を用いて製造されるウレタン系付加重合性化合物も好適であり、そのような具体例としては、例えば、特公昭４８−４１７０８号公報中に記載されている１分子に２個以上のイソシアネート基を有するポリイソシアネート化合物に、下記式（Ｖ）で示される水酸基を含有するビニルモノマーを付加させた１分子中に２個以上の重合性ビニル基を含有するビニルウレタン化合物等が挙げられる。
【００６５】
一般式（Ｖ）
ＣＨ₂＝Ｃ（Ｒ⁴¹）ＣＯＯＣＨ₂ＣＨ（Ｒ⁴²）ＯＨ
（ただし、Ｒ⁴¹及びＲ⁴²は、Ｈ又はＣＨ₃を示す。）
【００６６】
また、特開昭５１−３７１９３号、特公平２−３２２９３号、特公平２−１６７６５号に記載されているようなウレタンアクリレート類や、特公昭５８−４９８６０号、特公昭５６−１７６５４号、特公昭６２−３９４１７、特公昭６２−３９４１８号記載のエチレンオキサイド系骨格を有するウレタン化合物類も好適である。
【００６７】
更に、特開昭６３−２７７６５３、特開昭６３−２６０９０９号、特開平１−１０５２３８号に記載される、分子内にアミノ構造やスルフィド構造を有する重合性化合物類を用いてもよい。
【００６８】
その他の例としては、特開昭４８−６４１８３号、特公昭４９−４３１９１号、特公昭５２−３０４９０号、各公報に記載されているようなポリエステルアクリレート類、エポキシ樹脂と（メタ）アクリル酸を反応させたエポキシアクリレート類等の多官能のアクリレートやメタクリレートを挙げることができる。また、特公昭４６−４３９４６号、特公平１−４０３３７号、特公平１−４０３３６号記載の特定の不飽和化合物や、特開平２−２５４９３号記載のビニルホスホン酸系化合物等も挙げることができる。また、ある場合には、特開昭６１−２２０４８号記載のペルフルオロアルキル基を含有する構造が好適に使用される。更に日本接着協会誌ｖｏｌ．２０、Ｎｏ．７、３００〜３０８ページ（１９８４年）に光硬化性モノマー及びオリゴマーとして紹介されているものも使用することができる。
【００６９】
これらの重合性化合物について、どの様な構造を用いるか、単独で使用するか併用するか、添加量はどうかといった、使用方法の詳細は、最終的な記録材料の性能設計、即ち、本発明においては現像液を想定したモデル液を用いた場合の静電容量値上昇速度比を０．７以下とするという目的にあわせて、適宜設定される。例えば、次のような観点から選択される。感度の点では１分子あたりの不飽和基含量が多い構造が好ましく、多くの場合、２官能以上がこのましい。また、画像部すなわち硬化膜の強度を高くするためには、３官能以上のものがよく、更に、異なる官能数・異なる重合性基を有する化合物（例えば、アクリル酸エステル系化合物、メタクリル酸エステル系化合物、スチレン系化合物等）を組み合わせて用いることで、感光性と強度の両方を調節する方法も有効である。本発明の感光性組成物の物性である静電容量値上昇速度比は、硬化速度と膜強度の双方が重要なファクターであり、このような手段が有効であるといえる。
大きな分子量の化合物や、疎水性の高い化合物は感度や膜強度に優れる反面、現像スピードや現像液中での析出といった点で好ましく無い場合がある。また、感光層中の他の成分（例えばバインダーポリマー、開始剤、着色剤等）との相溶性、分散性に対しても、ラジカル重合化合物の選択・使用法は重要な要因であり、例えば、低純度化合物の使用や、２種以上化合物の併用によって、相溶性を向上させうることがある。また、支持体、オーバーコート層等の密着性を向上せしめる目的で特定の構造を選択することもあり得る。感光層中の重合性化合物の配合比に関しては、多い方が感度的に有利であるが、多すぎる場合には、好ましく無い相分離が生じたり、感光層の粘着性による製造工程上の問題（例えば、感光層成分の転写、粘着に由来する製造不良）や、現像液からの析出が生じる等の問題を生じうる。これらの観点から、重合性化合物の好ましい配合比は、多くの場合、組成物全成分に対して５〜８０質量％、好ましくは２０〜７５質量％である。また、これらは単独で用いても２種以上併用してもよい。そのほか、重合性化合物の使用法は、酸素に対する重合阻害の大小、解像度、かぶり性、屈折率変化、表面粘着性等の観点から適切な構造、配合、添加量を任意に選択できる。
【００７０】
〔（Ｂ）重合開始系〕
本発明における（Ｂ）重合開始系は、赤外線レーザによる露光により重合開始種を発生させる機能を有する。このような重合開始種の発生機構には、通常、（Ｂ−１）重合開始種の発生剤と（Ｂ−２）赤外線吸収剤とが用いられる。つまり、（Ｂ）重合開始系は、露光部において（Ｂ−２）赤外線吸収剤が赤外線レーザ光を効率よく吸収し、その光及び／又は熱により（Ｂ−１）重合開始種の発生剤が分解し、重合開始種を発生させるという系である。
以下、このような開始系に用いられる、（Ｂ−１）重合開始種の発生剤と（Ｂ−２）赤外線吸収剤とについてそれぞれ説明する。
【００７１】
（（Ｂ−１）重合開始種の発生剤）
本発明において用いられる（Ｂ−１）重合開始種の発生剤は、後述する赤外線吸収剤と組み合わせて用い、赤外線レーザーを照射した際に重合開始種を発生する化合物を指す。本発明における（Ｂ−１）重合開始種の発生剤は、ラジカル重合開始剤である。
以下、本発明において好適な重合開始種としてラジカルを発生するラジカル重合開始剤（以下、ラジカル発生剤と称する。）について詳細に説明するが、本発明がこれに限定されるものではない。
本発明において用いられるラジカル発生剤は、ラジカル発生剤としては、オニウム塩、トリハロメチル基を有するトリアジン化合物、過酸化物、アゾ系重合開始剤、アジド化合物、キノンジアジド、ボレート化合物、ケトオキシムエステル化合物、ヘキサアリールビイミダゾール化合物、芳香族ケトン化合物、メタロセン化合物、ジスルホン酸化合物などが挙げられるが、オニウム塩が高感度であり、好ましい。本発明においてラジカル重合開始剤として好適に用い得るオニウム塩について説明する。好ましいオニウム塩としては、ヨードニウム塩、ジアゾニウム塩、スルホニウム塩が挙げられる。本発明において、これらのオニウム塩は酸発生剤ではなく、ラジカル重合の開始剤として機能する。本発明において好適に用いられるオニウム塩は、下記一般式（II）〜（IV）で表されるオニウム塩である。
【００７２】
【化９】

【００７３】
式（II）中、Ａｒ¹¹とＡｒ¹²は、それぞれ独立に、置換基を有していてもよい炭素原子数２０個以下のアリール基を示す。このアリール基が置換基を有する場合の好ましい置換基としては、ハロゲン原子、ニトロ基、炭素原子数１２個以下のアルキル基、炭素原子数１２個以下のアルコキシ基、又は炭素原子数１２個以下のアリールオキシ基が挙げられる。Ｚ^11-はハロゲンイオン、過塩素酸イオン、テトラフルオロボレートイオン、ヘキサフルオロホスフェートイオン、カルボキシレートイオン、及びスルホン酸イオンからなる群より選択される対イオンを表し、好ましくは、過塩素酸イオン、ヘキサフルオロフォスフェートイオン、カルボキシレートイオン、及びアリールスルホン酸イオンである。
【００７４】
式（III）中、Ａｒ²¹は、置換基を有していてもよい炭素原子数２０個以下のアリール基を示す。好ましい置換基としては、ハロゲン原子、ニトロ基、炭素原子数１２個以下のアルキル基、炭素原子数１２個以下のアルコキシ基、炭素原子数１２個以下のアリールオキシ基、炭素原子数１２個以下のアルキルアミノ基、炭素原子数１２個以下のジアルキルアミノ基、炭素原子数１２個以下のアリールアミノ基又は、炭素原子数１２個以下のジアリールアミノ基が挙げられる。Ｚ^21-はＺ^11-と同義の対イオンを表す。
【００７５】
式（IV）中、Ｒ³¹、Ｒ³²及びＲ³³は、それぞれ同じでも異なっていてもよく、置換基を有していてもよい炭素原子数２０個以下の炭化水素基を示す。好ましい置換基としては、ハロゲン原子、ニトロ基、炭素原子数１２個以下のアルキル基、炭素原子数１２個以下のアルコキシ基、又は炭素原子数１２個以下のアリールオキシ基が挙げられる。Ｚ^31-はＺ^11-と同義の対イオンを表す。
【００７６】
本発明において、ラジカル発生剤として好適に用いることのできるオニウム塩の具体例としては、特開２００１−１３３９６９号公報の段落番号［００３０］〜［００３３］に記載されたものを挙げることができる。
【００７７】
本発明において用いられるラジカル発生剤は、極大吸収波長が４００ｎｍ以下であることが好ましく、更に３６０ｎｍ以下であることが好ましい。このように吸収波長を紫外線領域にすることにより、平版印刷版原版の取り扱いを白灯下で実施することができる。
【００７８】
これらのラジカル発生剤は、感光層塗布液の全固形分に対し０．１〜５０質量％、好ましくは０．５〜３０質量％、特に好ましくは１〜２０質量％の割合で感光層塗布液中に添加することができる。添加量が０．１質量％未満であると感度が低くなり、また５０質量％を越えると印刷時非画像部に汚れが発生する。これらのラジカル発生剤は、１種のみを用いてもよいし、２種以上を併用してもよい。また、これらのラジカル発生剤は他の成分と同一の層に添加してもよいし、別の層を設けそこへ添加してもよい。
【００７９】
（（Ｂ−２）赤外線吸収剤）
本発明において使用される（Ｂ−２）赤外線吸収剤は、赤外線レーザ光を効率よく吸収することができるものであり、具体的には、波長７６０ｎｍから１２００ｎｍに吸収極大を有する染料又は顔料が挙げられる。
染料としては、市販の染料及び例えば「染料便覧」（有機合成化学協会編集、昭和４５年刊）等の文献に記載されている公知のものが利用できる。具体的には、アゾ染料、金属錯塩アゾ染料、ピラゾロンアゾ染料、ナフトキノン染料、アントラキノン染料、フタロシアニン染料、カルボニウム染料、キノンイミン染料、メチン染料、シアニン染料、スクワリリウム色素、ピリリウム塩、金属チオレート錯体等の染料が挙げられる。
【００８０】
好ましい染料としては、例えば、特開昭５８−１２５２４６号、特開昭５９−８４３５６号、特開昭５９−２０２８２９号、特開昭６０−７８７８７号等に記載されているシアニン染料、特開昭５８−１７３６９６号、特開昭５８−１８１６９０号、特開昭５８−１９４５９５号等に記載されているメチン染料、特開昭５８−１１２７９３号、特開昭５８−２２４７９３号、特開昭５９−４８１８７号、特開昭５９−７３９９６号、特開昭６０−５２９４０号、特開昭６０−６３７４４号等に記載されているナフトキノン染料、特開昭５８−１１２７９２号等に記載されているスクワリリウム色素、英国特許４３４，８７５号記載のシアニン染料等を挙げることができる。
【００８１】
また、米国特許第５，１５６，９３８号記載の近赤外吸収増感剤も好適に用いられ、また、米国特許第３，８８１，９２４号記載の置換されたアリールベンゾ（チオ）ピリリウム塩、特開昭５７−１４２６４５号（米国特許第４，３２７，１６９号）記載のトリメチンチアピリリウム塩、特開昭５８−１８１０５１号、同５８−２２０１４３号、同５９−４１３６３号、同５９−８４２４８号、同５９−８４２４９号、同５９−１４６０６３号、同５９−１４６０６１号に記載されているピリリウム系化合物、特開昭５９−２１６１４６号記載のシアニン色素、米国特許第４，２８３，４７５号に記載のペンタメチンチオピリリウム塩等や特公平５−１３５１４号、同５−１９７０２号に開示されているピリリウム化合物も好ましく用いられる。
また、染料として好ましい別の例として米国特許第４，７５６，９９３号明細書中に式（Ｉ）、（ＩＩ）として記載されている近赤外吸収染料を挙げることができる。
【００８２】
これらの染料のうち特に好ましいものとしては、シアニン色素、スクワリリウム色素、ピリリウム塩、ニッケルチオレート錯体が挙げられる。更に、シアニン色素が好ましく、特に下記一般式（Ｉ）で示されるシアニン色素が最も好ましい。
【００８３】
【化１０】

【００８４】
前記一般式（Ｉ）中、Ｘ¹は、ハロゲン原子、Ｘ²−Ｌ¹、又はＮ（Ｌ²）（Ｌ³）を示す。ここで、Ｘ²は酸素原子又は、硫黄原子を示し、Ｌ¹、Ｌ²及びＬ³は、それぞれ独立に、炭素原子数１〜１２の炭化水素基を示す。Ｒ¹及びＲ²は、それぞれ独立に、炭素原子数１〜１２の炭化水素基を示す。感光層塗布液の保存安定性から、Ｒ¹及びＲ²は、炭素原子数２個以上の炭化水素基であることが好ましく、更に、Ｒ¹とＲ²とは互いに結合し、５員環又は６員環を形成していることが特に好ましい。
【００８５】
Ａｒ¹、Ａｒ²は、それぞれ同じでも異なっていてもよく、置換基を有していてもよい芳香族炭化水素基を示す。好ましい芳香族炭化水素基としては、ベンゼン環及びナフタレン環が挙げられる。また、好ましい置換基としては、炭素原子数１２個以下の炭化水素基、ハロゲン原子、炭素原子数１２個以下のアルコキシ基が挙げられる。Ｙ¹、Ｙ²は、それぞれ同じでも異なっていてもよく、硫黄原子又は炭素原子数１２個以下のジアルキルメチレン基を示す。Ｒ³、Ｒ⁴は、それぞれ同じでも異なっていてもよく、置換基を有していてもよい炭素原子数２０個以下の炭化水素基を示す。好ましい置換基としては、炭素原子数１２個以下のアルコキシ基、カルボキシル基、スルホ基が挙げられる。Ｒ⁵、Ｒ⁶、Ｒ⁷及びＲ⁸は、それぞれ同じでも異なっていてもよく、水素原子又は炭素原子数１２個以下の炭化水素基を示す。原料の入手性から、好ましくは水素原子である。また、Ｚ^1-は、電荷の中和が必要な場合の対アニオンを示す。例えば、Ｒ¹〜Ｒ⁸のいずれかがアニオン性置換基により置換され、電荷が中和されている場合は、Ｚ^1-は必要ない。好ましいＺ^1-は、感光層塗布液の保存安定性から、ハロゲンイオン、過塩素酸イオン、テトラフルオロボレートイオン、ヘキサフルオロホスフェートイオン、及びスルホン酸イオンであり、特に好ましくは、過塩素酸イオン、ヘキサフルオロフォスフェートイオン、及びアリールスルホン酸イオンである。
【００８６】
本発明において、好適に用いることのできる一般式（Ｉ）で示されるシアニン色素の具体例としては、特開２００１−１３３９６９号公報の段落番号［００１７］〜［００１９］に記載されたものを挙げることができる。
【００８７】
本発明において使用される顔料としては、市販の顔料及びカラーインデックス（Ｃ．Ｉ．）便覧、「最新顔料便覧」（日本顔料技術協会編、１９７７年刊）、「最新顔料応用技術」（ＣＭＣ出版、１９８６年刊）、「印刷インキ技術」ＣＭＣ出版、１９８４年刊）に記載されている顔料が利用できる。
顔料の種類としては、黒色顔料、黄色顔料、オレンジ色顔料、褐色顔料、赤色顔料、紫色顔料、青色顔料、緑色顔料、蛍光顔料、金属粉顔料、その他、ポリマー結合色素が挙げられる。具体的には、不溶性アゾ顔料、アゾレーキ顔料、縮合アゾ顔料、キレートアゾ顔料、フタロシアニン系顔料、アントラキノン系顔料、ペリレン及びペリノン系顔料、チオインジゴ系顔料、キナクリドン系顔料、ジオキサジン系顔料、イソインドリノン系顔料、キノフタロン系顔料、染付けレーキ顔料、アジン顔料、ニトロソ顔料、ニトロ顔料、天然顔料、蛍光顔料、無機顔料、カーボンブラック等が使用できる。これらの顔料のうち好ましいものはカーボンブラックである。
【００８８】
これら顔料は表面処理をせずに用いてもよく、表面処理を施して用いてもよい。表面処理の方法には、樹脂やワックスを表面コートする方法、界面活性剤を付着させる方法、反応性物質（例えば、シランカップリング剤、エポキシ化合物、ポリイソシアネート等）を顔料表面に結合させる方法等が考えられる。上記の表面処理方法は、「金属石鹸の性質と応用」（幸書房）、「印刷インキ技術」（ＣＭＣ出版、１９８４年刊）及び「最新顔料応用技術」（ＣＭＣ出版、１９８６年刊）に記載されている。
【００８９】
顔料の粒径は０．０１μｍ〜１０μｍの範囲にあることが好ましく、０．０５μｍ〜１μｍの範囲にあることが更に好ましく、特に０．１μｍ〜１μｍの範囲にあることが好ましい。顔料の粒径が０．０１μｍ未満のときは分散物の感光層塗布液中での安定性の点で好ましくなく、また、１０μｍを越えると感光層の均一性の点で好ましくない。
【００９０】
顔料を分散する方法としては、インク製造やトナー製造等に用いられる公知の分散技術が使用できる。分散機としては、超音波分散器、サンドミル、アトライター、パールミル、スーパーミル、ボールミル、インペラー、デスパーザー、ＫＤミル、コロイドミル、ダイナトロン、３本ロールミル、加圧ニーダー等が挙げられる。詳細は、「最新顔料応用技術」（ＣＭＣ出版、１９８６年刊）に記載されている。
【００９１】
これらの（Ｂ−２）赤外線吸収剤の添加量は、本発明の平版印刷版原版の感光層として用いる際に、感光層の波長７６０ｎｍ〜１２００ｎｍの範囲における吸収極大での光学濃度が、０．１〜３．０の範囲となるようにすることが好ましい。この範囲をはずれた場合、感度が低くなる傾向がある。光学濃度は前記赤外線吸収剤の添加量と感光層の厚みとにより決定されるため、所定の光学濃度は両者の条件を制御することにより得られる。感光層の光学濃度は常法により測定することができる。測定方法としては、例えば、透明、或いは白色の支持体上に、乾燥後の塗布量が平版印刷版として必要な範囲において適宜決定された厚みの感光層を形成し、透過型の光学濃度計で測定する方法、アルミニウム等の反射性の支持体上に感光層を形成し、反射濃度を測定する方法等が挙げられる。
【００９２】
〔バインダーポリマー〕
本発明の平版印刷版原版の第一のネガ型感光層においては、形成する感光層の皮膜特性向上などの目的で、バインダーポリマーを併用することが好ましい。このバインダーポリマーとしては、線状有機ポリマーを用いることが好ましい。このような「線状有機ポリマー」としては、公知のものを任意に使用できる。好ましくは水現像或いは弱アルカリ水現像を可能とするために、水或いは弱アルカリ水可溶性又は膨潤性である線状有機ポリマーが選択される。線状有機ポリマーは、感光層を形成するための皮膜形成剤としてだけでなく、水、弱アルカリ水或いは有機溶剤現像剤としての用途に応じて選択使用される。例えば、水可溶性有機ポリマーを用いると水現像が可能になる。このような線状有機ポリマーとしては、側鎖にカルボン酸基を有するラジカル重合体、例えば特開昭５９−４４６１５号、特公昭５４−３４３２７号、特公昭５８−１２５７７号、特公昭５４−２５９５７号、特開昭５４−９２７２３号、特開昭５９−５３８３６号、特開昭５９−７１０４８号に記載されているもの、すなわち、メタクリル酸共重合体、アクリル酸共重合体、イタコン酸共重合体、クロトン酸共重合体、マレイン酸共重合体、部分エステル化マレイン酸共重合体等がある。また同様に側鎖にカルボン酸基を有する酸性セルロース誘導体がある。この他に水酸基を有する重合体に環状酸無水物を付加させたものなどが有用である。
【００９３】
特にこれらの中で、アリル基、（メタ）アクリロイル基、（メタ）アクリルアミド基、ビニルフェニル基等のエチレン性不飽和二重結合と、カルボキシル基と、を側鎖に有する（メタ）アクリル樹脂或いはウレタン樹脂が、膜強度、感度、現像性のバランスに優れており、好適である。
【００９４】
また、特公平７−１２００４号、特公平７−１２００４１号、特公平７−１２００４２号、特公平８−１２４２４号、特開昭６３−２８７９４４号、特開昭６３−２８７９４７号、特開平１−２７１７４１号、特開平１１−３５２６９１号等に記載される酸基を含有するウレタン系バインダーポリマーは、非常に、強度に優れるので、耐刷性・低露光適性の点で有利である。
【００９５】
更にこの他に水溶性線状有機ポリマーとして、ポリビニルピロリドンやポリエチレンオキサイド等が有用である。また硬化皮膜の強度を上げるためにアルコール可溶性ナイロンや２，２−ビス−（４−ヒドロキシフェニル）−プロパンとエピクロロヒドリンのポリエーテル等も有用である。
【００９６】
本発明で使用されるポリマーの質量平均分子量については好ましくは５０００以上であり、更に好ましくは１万〜３０万の範囲であり、数平均分子量については好ましくは１０００以上であり、更に好ましくは２０００〜２５万の範囲である。多分散度（質量平均分子量／数平均分子量）は１以上が好ましく、更に好ましくは１．１〜１０の範囲である。
【００９７】
これらのポリマーは、ランダムポリマー、ブロックポリマー、グラフトポリマー等いずれでもよいが、ランダムポリマーであることが好ましい。
【００９８】
本発明で使用されるポリマーは従来公知の方法により合成できる。合成する際に用いられる溶媒としては、例えば、テトラヒドロフラン、エチレンジクロリド、シクロヘキサノン、メチルエチルケトン、アセトン、メタノール、エタノール、エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル、２−メトキシエチルアセテート、ジエチレングリコールジメチルエーテル、１−メトキシ−２−プロパノール、１−メトキシ−２−プロピルアセテート、Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジメチルアセトアミド、トルエン、酢酸エチル、乳酸メチル、乳酸エチル、ジメチルスルホキシド、水等が挙げられる。これらの溶媒は単独で又は２種以上混合して用いられる。
【００９９】
本発明で使用されるポリマーを合成する際に用いられるラジカル重合開始剤としては、アゾ系開始剤、過酸化物開始剤等公知の化合物が使用できる。
【０１００】
本発明で使用されるバインダーポリマーは単独で用いても混合して用いてもよい。これらポリマーは、感光層塗布液の全固形分に対し２０〜９５質量％、好ましくは３０〜９０質量％の割合で感光層中に添加される。添加量が２０質量％未満の場合は、画像形成した際、画像部の強度が不足する。また添加量が９５質量％を越える場合は、画像形成されない。またラジカル重合可能なエチレン性不飽和二重結合を有する化合物と線状有機ポリマーは、質量比で１／９〜７／３の範囲とするのが好ましい。
【０１０１】
〔その他の成分〕
本発明の平版印刷版原版の第一のネガ型感光層には、前記の成分のみならず、平版印刷版原版としての特性やハンドリング性などを改良するため、更に必要に応じて種々の化合物を添加してもよい。
例えば、可視光域に大きな吸収を持つ染料を画像の着色剤として使用することができる。具体的には、オイルイエロー＃１０１、オイルイエロー＃１０３、オイルピンク＃３１２、オイルグリーンＢＧ、オイルブルーＢＯＳ、オイルブルー＃６０３、オイルブラックＢＹ、オイルブラックＢＳ、オイルブラックＴ−５０５（以上オリエント化学工業（株）製）、ビクトリアピュアブルー、クリスタルバイオレット（ＣＩ４２５５５）、メチルバイオレット（ＣＩ４２５３５）、エチルバイオレット、ローダミンＢ（ＣＩ１４５１７０Ｂ）、マラカイトグリーン（ＣＩ４２０００）、メチレンブルー（ＣＩ５２０１５）等、及び特開昭６２−２９３２４７号に記載されている染料を挙げることができる。また、フタロシアニン系顔料、アゾ系顔料、カーボンブラック、酸化チタンなどの顔料も好適に用いることができる。
【０１０２】
これらの着色剤は、画像形成後、画像部と非画像部の区別がつきやすいので、添加する方が好ましい。なお、添加量は、感光層塗布液全固形分に対し、０．０１〜１０質量％の割合である。
【０１０３】
また、本発明においては、感光層塗布液の調製中或いは保存中においてラジカル重合可能なエチレン性不飽和二重結合を有する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、全組成物の質量に対して約０．０１質量％〜約５質量％が好ましい。また必要に応じて、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誘導体等を添加して、塗布後の乾燥の過程で感光層の表面に偏在させてもよい。高級脂肪酸誘導体の添加量は、全組成物の約０．１質量％〜約１０質量％が好ましい。
【０１０４】
また、感光層塗布液中には、現像条件に対する処理の安定性を広げるため、特開昭６２−２５１７４０号や特開平３−２０８５１４号に記載されているような非イオン界面活性剤、特開昭５９−１２１０４４号、特開平４−１３１４９号に記載されているような両性界面活性剤を添加することができる。
【０１０５】
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等が挙げられる。
【０１０６】
両性界面活性剤の具体例としては、アルキルジ（アミノエチル）グリシン、アルキルポリアミノエチルグリシン塩酸塩、２−アルキル−Ｎ−カルボキシエチル−Ｎ−ヒドロキシエチルイミダゾリニウムベタイン、Ｎ−テトラデシル−Ｎ，Ｎ−ベタイン型（例えば、商品名アモーゲンＫ、第一工業（株）製）等が挙げられる。
【０１０７】
上記非イオン界面活性剤及び両性界面活性剤の感光層塗布液中に占める割合は、０．０５〜１５質量％が好ましく、より好ましくは０．１〜５質量％である。その他、目的に応じて密着向上剤、現像改良剤、紫外線吸収剤、スベリ剤等の添加剤を好適に配合することができる。
【０１０８】
更に、本発明に係る感光層塗布液中には、必要に応じ、塗膜の柔軟性等を付与するために可塑剤が加えられる。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。
【０１０９】
本発明の平版印刷版原版を製造するには、通常、感光層塗布液に必要な上記各成分を溶媒に溶かして、適当な支持体上に塗布すればよい。ここで使用する溶媒としては、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。これらの溶媒は単独又は混合して使用される。溶媒中の上記成分（添加剤を含む全固形分）の濃度は、好ましくは１〜５０質量％である。
【０１１０】
また塗布、乾燥後に得られる支持体上の感光層塗布量（固形分）は、用途によって異なるが、平版印刷版原版についていえば一般的に０．５〜５．０ｇ／ｍ²が好ましい。塗布量が少なくなるにつれて、見かけの感度は大になるが、画像記録の機能を果たす感光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が、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ることができる。
【０１１１】
本発明に係る感光層塗布液には、塗布性を良化するための界面活性剤、例えば、特開昭６２−１７０９５０号に記載されているようなフッ素系界面活性剤を添加することができる。好ましい添加量は、全感光層の材料固形分中０．０１〜１質量％、更に好ましくは０．０５〜０．５質量％である。
【０１１２】
＜支持体＞
本発明の平版印刷版原版において用いられる支持体としては、寸度的に安定な板状物であれば特に制限はなく、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例示される。好ましい支持体としては、ポリエステルフィルム又はアルミニウム板が挙げられる。
【０１１３】
中でも、本発明の平版印刷版原版に用いる支持体としては、軽量で表面処理性、加工性、耐食性に優れたアルミニウム板を使用することが好ましい。この目的に供されるアルミニウム材質としては、ＪＩＳ １０５０材、ＪＩＳ １１００材、ＪＩＳ １０７０材、Ａｌ−Ｍｇ系合金、Ａｌ−Ｍｎ系合金、Ａｌ−Ｍｎ−Ｍｇ系合金、Ａｌ−Ｚｒ系合金。Ａｌ−Ｍｇ−Ｓｉ系合金などが挙げられる。
【０１１４】
好適なアルミニウム板は、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前記の如き合金板であり、更にアルミニウムがラミネート若しくは蒸着されたプラスチックフィルムでもよい。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１０質量％以下である。アルミニウム板としては、純アルミニウムが好ましいが、完全に純粋なアルミニウムは精錬技術上製造が困難であるので、僅かに異元素を含有するものでもよい。このように、アルミニウム板は、その組成が特定されるものではなく、従来より公知公用の素材のアルミニウム板を適宜に利用することができる。前記アルミニウム板の厚みとしては、およそ０．１〜０．６ｍｍ程度が好ましく、０．１５〜０．４ｍｍがより好ましく、０．２〜０．３ｍｍが特に好ましい。
【０１１５】
前記アルミニウム板を粗面化するに先立ち、所望により、表面の圧延油を除去するための例えば界面活性剤、有機溶剤又はアルカリ性水溶液などによる脱脂処理が行われる。アルミニウム板の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。また、電気化学的な粗面化法としては塩酸又は硝酸電解液中で交流又は直流により行う方法がある。
【０１１６】
このように粗面化されたアルミニウム板は、必要に応じてアルカリエッチング処理及び中和処理された後、所望により表面の保水性や耐摩耗性を高めるために陽極酸化処理が施される。陽極酸化による、陽極酸化皮膜の量は、１．０ｇ／ｍ²以上が好ましい。陽極酸化皮膜の量が、１．０ｇ／ｍ²未満の場合には、耐刷性が不十分であったり、平版印刷版として用いた場合には、非画像部に傷が付き易くなって、印刷時に傷の部分にインキが付着するいわゆる「傷汚れ」が生じ易くなることがある。前記陽極酸化処理を施された後、前記アルミニウムの表面は、必要に応じて親水化処理が施される。
【０１１７】
また、このようなアルミニウム支持体は陽極酸化処理後に有機酸又はその塩による処理又は、感光層塗布の下塗り層を適用して用いることができる。
【０１１８】
なお、支持体と感光層との密着性を高めるための中間層を設けてもよい。密着性の向上のためには、一般に中間層は、ジアゾ樹脂や、例えばアルミニウムに吸着するリン酸化合物等からなっている。中間層の厚さは任意であり、露光した時に、上層の感光層と均一な結合形成反応を行い得る厚みでなければならない。通常、乾燥固体で約１〜１００ｍｇ／ｍ²の塗布割合がよく、５〜４０ｍｇ／ｍ²が特に良好である。中間層中におけるジアゾ樹脂の使用割合は、３０〜１００％、好ましくは６０〜１００％である。
【０１１９】
支持体表面に以上のような処理或いは、下塗りなどが施された後、支持体の裏面には、必要に応じてバックコートが設けられる。かかるバックコートとしては特開平５−４５８８５号公報記載の有機高分子化合物及び特開平６−３５１７４号記載の有機又は無機金属化合物を加水分解及び重縮合させて得られる金属酸化物からなる被覆層が好ましく用いられる。
【０１２０】
支持体として好ましい特性としては、中心線平均粗さで０．１０〜１．２μｍである。０．１０μｍより低いと感光層と密着性が低下し、著しい耐刷の低下を生じてしまう。１．２μｍより大きい場合、印刷時の汚れ性が悪化してしまう。更に支持体の色濃度としては、反射濃度値として０．１５〜０．６５であり、０．１５より白い場合、画像露光時のハレーションが強すぎ画像形成に支障をきたしてしまい、０．６５より黒い場合、現像後の検版作業において画像が見難くく、著しく検版性が悪いものとなってしまう。
【０１２１】
以上のようにして、所定の処理を行って得られた支持体上に、先に述べた第一及び第二のネガ型感光層、更には、表面保護層、バックコート層等の他の任意の層を形成することで、本発明のネガ型の平版印刷版原版を得ることができる。
【０１２２】
＜赤外線レーザ露光＞
本発明の平版印刷版原版は、赤外線レーザ露光により画像記録が行われる。本発明においては、波長７６０ｎｍから１２００ｎｍの赤外線を放射する固体レーザ及び半導体レーザにより画像露光されることが好ましい。レーザの出力は１００ｍＷ以上が好ましく、露光時間を短縮するため、マルチビームレーザデバイスを用いることが好ましい。また、１画素あたりの露光時間は２０μ秒以内であることが好ましい。記録材料に照射されるエネルギーは１０〜３００ｍＪ／ｃｍ²であることが好ましい。露光のエネルギーが低すぎると感光層の硬化が十分に進行しないことがある。また、露光のエネルギーが高すぎると感光層がレーザーアブレーションされ、画像が損傷することがある。
【０１２３】
本発明における露光は光源の光ビームをオーバーラップさせて露光する。オーバーラップとは副走査ピッチ幅がビーム径より小さいことをいう。オーバーラップは、例えばビーム径をビーム強度の半値幅（ＦＷＨＭ）で表わしたとき、ＦＷＨＭ／副走査ピッチ幅（オーバーラップ係数）で定量的に表現することができる。本発明ではこのオーバーラップ係数が０．１以上であることが好ましい。
【０１２４】
本発明に使用する露光装置の光源の走査方式は特に限定はなく、円筒外面走査方式、円筒内面走査方式、平面走査方式などを用いることができる。また、光源のチャンネルは単チャンネルでもマルチチャンネルでもよいが、円筒外面方式の場合にはマルチチャンネルが好ましく用いられる。
【０１２５】
＜現像＞
本発明の平版印刷版原版の現像、製版に用いられる現像液及び補充液としては従来より知られているアルカリ水溶液が使用できる。この現像液として用いられるアルカリ水溶液をモデル液として用いて静電容量値上昇速度比を測定することで、この感光層の現像液にたいするディスクリミネーションを予測することができ、静電容量値上昇速度比が０．７であれば良好なディスクリミネーションが得られ、網点制限性も著しく改良される。
例えば、ケイ酸ナトリウム、同カリウム、第３リン酸ナトリウム、同カリウム、同アンモニウム、第２リン酸ナトリウム、同カリウム、同アンモニウム、炭酸ナトリウム、同カリウム、同アンモニウム、炭酸水素ナトリウム、同カリウム、同アンモニウム、ほう酸ナトリウム、同カリウム、同アンモニウム、水酸化ナトリウム、同アンモニウム、同カリウム及び同リチウムなどの無機アルカリ塩が挙げられる。また、モノメチルアミン、ジメチルアミン、トリメチルアミン、モノエチルアミン、ジエチルアミン、トリエチルアミン、モノイソプロピルアミン、ジイソプロピルアミン、トリイソプロピルアミン、ｎ−ブチルアミン、モノエタノールアミン、ジエタノールアミン、トリエタノールアミン、モノイソプロパノールアミン、ジイソプロパノールアミン、エチレンイミン、エチレンジアミン、ピリジンなどの有機アルカリ剤も用いられる。これらのアルカリ剤は単独若しくは２種以上を組み合わせて用いられる。
【０１２６】
これらのアルカリ剤の中で特に好ましい現像液は、ケイ酸ナトリウム、ケイ酸カリウム等のケイ酸塩水溶液である。その理由はケイ酸塩の成分である酸化珪素ＳｉＯ₂とアルカリ金属酸化物Ｍ₂Ｏの比率と濃度によって現像性の調節が可能となるためであり、例えば、特開昭５４−６２００４号公報、特公昭５７−７４２７号公報に記載されているようなアルカリ金属ケイ酸塩が有効に用いられる。
【０１２７】
自動現像機を用いて現像する場合には、現像液よりもアルカリ強度の高い水溶液（補充液）を現像液に加えることによって、長時間現像タンク中の現像液を交換することなく、多量のＰＳ版を処理できることが知られている。本発明においてもこの補充方式が好ましく適用される。現像液及び補充液には現像性の促進や抑制、現像カスの分散及び印刷版画像部の親インキ性を高める目的で必要に応じて種々の界面活性剤や有機溶剤を添加できる。
【０１２８】
好ましい界面活性剤としては、アニオン系、カチオン系、ノニオン系及び両性界面活性剤が挙げられる。更に現像液及び補充液には必要に応じて、ハイドロキノン、レゾルシン、亜硫酸、亜硫酸水素酸などの無機酸のナトリウム塩、カリウム塩等の還元剤、更に有機カルボン酸、消泡剤、硬水軟化剤を加えることもできる。
【０１２９】
上記現像液及び補充液を用いて現像処理された印刷版は水洗水、界面活性剤等を含有するリンス液、アラビアガムや澱粉誘導体を含む不感脂化液で後処理される。本発明の画像記録材料を印刷版として使用する場合の後処理としては、これらの処理を種々組み合わせて用いることができる。
【０１３０】
自動現像機は、一般に現像部と後処理部からなり、印刷用版材を搬送する装置と各処理液槽とスプレー装置とからなり、露光済みの印刷版を水平に搬送しながら、ポンプで汲み上げた各処理液をスプレーノズルから吹き付けて現像処理するものである。また、最近は処理液が満たされた処理液槽中に液中ガイドロール等によって印刷用版材を浸漬搬送させて処理する方法も知られている。このような自動処理においては、各処理液に処理量や稼働時間等に応じて補充液を補充しながら処理することができる。また、電気伝導度をセンサーにて感知し、自動的に補充することもできる。また、実質的に未使用の処理液で処理するいわゆる使い捨て処理方式も適用できる。本発明の方法によれば、経時的な炭酸ガスによる現像性の低下や現像液に起因する耐刷性の低下の懸念がないため、これらの自動現像機のいずれにも本発明の方法を好適に適用することができる。
【０１３１】
以上のようにして得られた平版印刷版は所望により不感脂化ガムを塗布したのち、印刷工程に供することができるが、より一層の高耐刷力の平版印刷版としたい場合にはバーニング処理が施される。
平版印刷版をバーニングする場合には、バーニング前に特公昭６１−２５１８号、同５５−２８０６２号、特開昭６２−３１８５９号、同６１−１５９６５５号の各公報に記載されているような整面液で処理することが好ましい。
【０１３２】
その方法としては、該整面液を浸み込ませたスポンジや脱脂綿にて、平版印刷版上に塗布するか、整面液を満たしたバット中に印刷版を浸漬して塗布する方法や、自動コーターによる塗布等が適用される。また、塗布した後でスキージ又はスキージローラーで、その塗布量を均一にすることは、より好ましい結果を与える。整面液の塗布量は一般に０．０３〜０．８ｇ／ｍ²（乾燥質量）が適当である。
【０１３３】
整面液が塗布された平版印刷版は、必要であれば乾燥された後、バーニングプロセッサー（例えば、富士写真フイルム（株）より販売されているバーニングプロセッサー：ＢＰ−１３００）等で高温に加熱される。この場合の加熱温度及び時間は、画像を形成している成分の種類にもよるが、１８０〜３００℃の範囲で１〜２０分の範囲が好ましい。
【０１３４】
バーニング処理された平版印刷版は、必要に応じて適宜、水洗、ガム引き等の従来行なわれている処理を施こすことができるが、水溶性高分子化合物等を含有する整面液が使用された場合にはガム引きなどのいわゆる不感脂化処理を省略することができる。
【０１３５】
本発明の平版印刷版は、耐刷性に優れるため、オフセット印刷機等にかけられ印刷を行った場合、高画質の印刷物が多数枚得られる。
【０１３６】
【実施例】
以下、実施例により、本発明を詳細に説明するが、本発明はこれらに制限されるものではない。
【０１３７】
［比較例Ａ］
（支持体の作成）
９９．５％以上のアルミニウムと、Ｆｅ０．３０％、Ｓｉ０．１０％、Ｔｉ０．０２％、Ｃｕ０．０１３％を含むＪＩＳ Ａ １０５０合金の溶湯を清浄化処理を施し、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。
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、板厚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。
【０１３８】
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％アルミン酸ソーダ水溶液で５０℃３０秒間脱脂処理を行い、３０％硫酸水溶液で５０℃３０秒間中和、スマット除去処理を行った。
【０１３９】
次いで支持体と感光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％の硝酸と０．５％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／ｄｍ²、デューティー比１：１の交番波形でアノード側電気量２４０Ｃ／ｄｍ²を与えることで電解砂目立てを行った。その後１０％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％硫酸水溶液で５０℃３０秒間中和、スマット除去処理を行った。
【０１４０】
更に耐摩耗性、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％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／ｄｍ²の直流で電解処理を行うことで２．５ｇ／ｍ²の陽極酸化皮膜を作成した。以上により作成した支持体のＲａ（中心線表面粗さ）は０．５μｍであった。
【０１４１】
（第一のネガ型感光層の形成）
次に、下記第一のネガ型感光層塗布液１を調整し、上記の表面処理を施したアルミニウム板にワイヤーバーを用いて塗布し、温風式乾燥装置にて１１５℃で４５秒間乾燥して、第一のネガ型感光層を形成した。乾燥後の被覆量は１．３ｇ／ｍ²の範囲内であった。
【０１４２】
＜第一のネガ型感光層塗布液１＞
・赤外線吸収剤［ＩＲ−▲１▼］（下記構造） ０．１ｇ
・ラジカル発生剤［ＯＳ−１］（下記構造） ０．１５ｇ
・重合性化合物 １ｇ
（ジペンタエリスリトールヘキサアクリレート及びジペンタエリスリトールペンタアクリレートの混合物、商品名：ＤＰＨＡ、日本化薬製）
・バインダーポリマー（Ｐ−１） １ｇ
・エチルバイオレットＣｌ塩 ０．０６ｇ
・フッ素系界面活性剤 ０．０１ｇ
（メガファックＫＦ３０９、大日本インキ化学工業（株）製）
・メチルエチルケトン １４．０ｇ
・メタノール ６．５ｇ
・１−メトキシ−２−プロパノール １０．０ｇ
【０１４３】
感光層塗布液１に用いた赤外線吸収剤［ＩＲ−▲１▼］及びオニウム塩［ＯＳ−１］の構造を以下に示す。
【０１４４】
【化１１】

【０１４５】
また、感光層塗布液１に用いたバインダーポリマー（Ｐ−１）の合成法を以下に示す。
１０００ｍｌ三口フラスコにＮ，Ｎ−ジメチルアセトアミド：７０ｇを入れ、窒素気流下、７０℃まで加熱した。下記構造の化合物（Ａ−１）：３３．５ｇ、メタクリルアミド：６．８ｇ、メタクリル酸メチル：１２．０ｇ、メタクリル酸：６．９ｇ、Ｖ−５９（和光純薬製）：０．５３８ｇのＮ，Ｎ−ジメチルアセトアミド：７０ｇ溶液を、２．５時間かけて滴下した。滴下終了後、９０まで加熱し、更に２時間撹拌した。室温まで、反応溶液を冷却した後、水：３．５Ｌに投入し、高分子化合物を析出させた。析出した高分子化合物を濾取、水で洗浄、乾燥し高分子化合物を４８．５ｇ得た。得られた高分子化合物をポリスチレンを標準物質としたゲルパーミエーションクロマトグラフィー法（ＧＰＣ）により、質量平均分子量を測定した結果、１２４，０００であった。また滴定により酸価を求めたところ、１．３０ｍｅｑ／ｇ（計算値１．３５ｍｅｑ／ｇ）であり、正常に重合が行われたことが確認された。
２００ｍｌ三口フラスコに、得られた高分子化合物：２６．０ｇ、ｐ−メトキシフェノール：０．１ｇを入れ、Ｎ，Ｎ−ジメチルアセトアミド：６０ｇに溶解した。溶解した後に、氷水を入れた氷浴にて冷却した。混合液温度が：５℃以下になった後に、１、８−ジアザビシクロ〔５．４．０〕−７−ウンデセン（ＤＢＵ）：３０．４ｇを滴下ロート用いて、１時間かけて滴下した。滴下終了後、氷浴を外して更に８時間撹拌した。反応液を、濃塩酸：１７ｍｌを溶解させた水：２Ｌに投入しバインダーポリマー（Ｐ−１）を析出させた。析出したバインダーポリマー（Ｐ−１）を濾取、水で洗浄、乾燥し高分子化合物を１８．２ｇ得た。得られたバインダーポリマー（Ｐ−１）のＨ−ＮＭＲを測定したところ、化合物（Ａ−１）由来の側鎖基の１００％がエチレンメタクリレート基に変換されたことが確認された。また、ポリスチレンを標準物質としたゲルパーミエーションクロマトグラフィー法（ＧＰＣ）により、質量平均分子量を測定した結果、１１４，０００であった。更に、滴定により酸価を求めたところ、０．９ｍｅｑ／ｇ（計算値０．８ｍｅｑ／ｇ）であった。
【０１４６】
【化１２】

【０１４７】
（第二のネガ型感光層の形成）
次に、下記第二のネガ型感光層塗布液１を調整し、上記の第一のネガ型感光層上にワイヤーバーを用いて塗布し、温風式乾燥装置にて６０℃で１２０秒間乾燥して、第二のネガ型感光層を形成した。乾燥後の被覆量は０．５ｇ／ｍ²であった。
【０１４８】
＜第二のネガ型感光層塗布液１＞
・イオン交換水 ９０．６ｇ
・熱融着微粒子分散液（１） ９．０９ｇ
【０１４９】
（熱融着微粒子分散液（１）の調製）
スチレン：１００ｇ、水：２００ｇ、界面活性剤ＸＬ−１０２Ｆ（ライオン（株）製）（４．７％水溶液）：１０ｇを三ツ口フラスコに入れ、窒素を注入しながら、８０℃に昇温した。その後、約３０分攪拌後、Ｋ₂Ｓ₂Ｏ₈を１ｇ添加し、８０℃で６時間乳化重合を行い、粒径約１μｍの樹脂粒子（ポリスチレン）を得た。そして、固形分濃度３３％のポリスチレン粒子分散液を調製した。
【０１５０】
［露光］
得られたネガ型平版印刷版原版を、水冷式４０Ｗ赤外線半導体レーザを搭載したＣｒｅｏ社製Ｔｒｅｎｄｓｅｔｔｅｒ３２４４ＶＦＳにて、出力９Ｗ、外面ドラム回転数２１０ｒｐｍ、版面エネルギー１００ｍＪ／ｃｍ²、解像度１７５ｌｐｉの条件で露光した。
【０１５１】
［現像処理］
露光した平版印刷版原版を富士写真フイルム（株）製自動現像機ＬＰ−９４０Ｈを用い現像処理した。
現像液は下記モデル現像液を用い、現像浴の温度は３０℃とした。また、フィニッシャーは、富士写真フイルム（株）製ＦＮ−６の１：１水希釈液を用いた。
【０１５２】
〔モデル現像液〕
・水酸化カリウム ０．７ｇ
・炭酸カリウム １．７ｇ
・ポリエチレングリコールモノナフチルエーテル ５３ｇ
・エチレンジアミン４酢酸４ナトリウム塩 １．５ｇ
・水 ９５５ｇ
【０１５３】
［印刷］
このようにして得られた平版印刷版をハイデルベルグ社製印刷機ＳＯＲ−Ｍを用いて印刷した。
【０１５４】
［評価］
１．現像液浸透評価
上記モデル現像液を調整し、現像液浸透性比を算出した。
露光したベタ画像を１ｃｍ×１ｃｍの窓を開けたテープ（スコッチテープ３Ｍ製）で覆い、対電極（先に記した支持体を使用）と上記モデル液（２５℃）の入った容器に浸漬し、電極間の１Ｖ、１ｋＨｚ正弦波交流をかけた時の静電容量値をＬＣＲメーター（３５２２−５０、ＨＩＯＫＩ社製）１秒間毎に測定した。同様にして未露光部も測定した、その比を算出した。
【０１５５】
２．耐刷性評価
上記印刷工程において、どれだけの枚数が十分なインキの濃度を保って印刷できるかを目視にて評価した。結果を表１に示す。
【０１５６】
［比較例Ｂ及び比較例Ｃ］
比較例Ａにおいて、第二のネガ型感光層の乾燥後の被覆量を、それぞれ、１ｇ／ｍ^２、３ｇ／ｍ^２に代えた他は、比較例Ａと同様にして、平版印刷版原版を作製した。その後、得られた平版印刷版原版を、比較例Ａと同様にして、露光、現像に供し、同様の評価を行った。結果を表１に示す。
【０１５７】
［実施例１］
比較例Ａにおいて、第二のネガ型感光層を以下のように形成した他は、比較例Ａと同様にして、平版印刷版原版を作製した。
【０１５８】
（第二のネガ型感光層の形成）
次に、下記第二のネガ型感光層塗布液２を調整し、比較例Ａと同様の第一のネガ型感光層上にワイヤーバーを用いて塗布し、温風式乾燥装置にて６０℃で１２０秒間乾燥して、第二のネガ型感光層を形成した。乾燥後の被覆量は０．５ｇ／ｍ^２であった。
【０１５９】
＜第二のネガ型感光層塗布液２＞
・イオン交換水 ８４．２ｇ
・疎水性化合物含有マイクロカプセル分散液（１） １５．８ｇ
・ポリビニルアルコール ２ｇ
【０１６０】
（疎水性化合物含有マイクロカプセル分散液（１）の調製）
油層成分として、エポキシ樹脂エピコート１００４（油化シェルエポキシ製）：３０ｇ、トリメチロールプロパンとキシレンジイソシアネート付加体の５０％酢酸エチル溶液Ｄ１１０Ｎ（武田薬品工業製）：３０ｇ、光熱変換剤（［ＩＲ−▲２▼］、下記構造）：０．３ｇ、アニオン系界面活性剤パイオニンＡ４１Ｃ（竹本油脂製）：０．５ｇを、酢酸エチル：９０ｇに溶解した。水層成分としては、ＰＶＡ２１７ＥＥ（クラレ製）２％水溶液：２００ｇを調製した。油層成分及び水層成分をホモジナイザーを用いて１００００ｒｐｍで乳化した。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１９％であり、平均粒径は０．３μｍであった。
【０１６１】
【化１３】

【０１６２】
［露光、現像、及び評価］
得られた平版印刷版原版を、比較例Ａと同様にして、露光、現像に供し、同様の評価を行った。評価結果を表１に示す。
【０１６３】
［実施例２及び実施例３］
実施例１において、第二のネガ型感光層の乾燥後の被覆量を、それぞれ、１ｇ／ｍ^２、３ｇ／ｍ^２に代えた他は、実施例１と同様にして、平版印刷版原版を作製した。その後、得られた平版印刷版原版を、比較例Ａと同様にして、露光、現像に供し、同様の評価を行った。評価結果を表１に示す。
【０１６４】
［実施例４］
比較例Ａにおいて、第二のネガ型感光層を以下のように形成した他は、比較例Ａと同様にして、平版印刷版原版を作製した。
【０１６５】
（第二のネガ型感光層の形成）
次に、下記第二のネガ型感光層塗布液３を調整し、比較例Ａと同様の第一のネガ型感光層上にワイヤーバーを用いて塗布し、温風式乾燥装置にて６０℃で１２０秒間乾燥して、第二のネガ型感光層を形成した。乾燥後の被覆量は０．５ｇ／ｍ^２であった。
【０１６６】
＜第二のネガ型感光層塗布液３＞
・イオン交換水 ８２ｇ
・極性変換ポリマー（Ｐ−２） ２．０ｇ
・光熱変換物質［ＩＲ−▲３▼］（下記構造） ０．６ｇ
【０１６７】
【化１４】

【０１６８】
（極性変換ポリマー（Ｐ−２）の合成）
３リットルの三口フラスコに水：１０００ｍｌ、ｐ−スチレンスルホニルクロリド：１００ｇ、亜硫酸ナトリウム：１２６ｇ、炭酸ナトリウム：１０６ｇ、触媒量のハイドロキノンを入れて内温４５℃を保ちながら加熱撹拌した。１時間後、クロロ酢酸ナトリウム：１７４ｇ、ヨウ化カリウム：１２ｇを投入し、内温７０℃まで上げて、更に５時間攪拌した。反応後、室温まで自然冷却させ、氷浴下で濃塩酸をｐＨ１になるまで滴下したところ、固体の析出が見られた。析出物をろ過し、十分水で洗浄して乾燥させて９５ｇの白色粉体を得た。尚、この生成物の純度はＨＰＬＣ測定により９９％であった。
続いて、２００ｍｌ三口フラスコに、得られた白色粉末：２０ｇ、及びジメチルアセトアミド：４０ｇを入れ、６５℃窒素気流下、２，２’−アゾビス（２，４−ジメチルバレロニトリル）：０．２ｇを加えた。そして、同温度に保ち、６時間撹拌した。その後、室温に戻し、水：１リットル中で再沈を行い、ポリマー固体を得た。ＧＰＣにより質量平均分子量１．２万のポリマーであることが分かった。
得られたポリマー：１０ｇ、メタノール：４４ｍｌ中に、氷浴下、ナトリウムメトキシド（２８％メタノール溶液）：８．５ｇをゆっくり滴下した。５分間撹拌させた後、析出した固体をろ過、乾燥させることにより極性変換ポリマー（Ｐ−２）９．１ｇを得た。
【０１６９】
［露光、現像、及び評価］
得られた平版印刷版原版を、比較例Ａと同様にして、露光、現像に供し、同様の評価を行った。評価結果を表１に示す。
【０１７０】
［実施例５及び実施例６］
実施例４において、第二のネガ型感光層の乾燥後の被覆量を、それぞれ、１ｇ／ｍ^２、３ｇ／ｍ^２に代えた他は、実施例４と同様にして、平版印刷版原版を作製した。その後、得られた平版印刷版原版を、比較例Ａと同様にして、比較例Ａと同様にして、露光、現像に供し、同様の評価を行った。評価結果を表１に示す。
【０１７１】
［比較例１］
比較例Ａにおいて、第二のネガ型感光層を形成せず、第一のネガ型感光層のみを形成した他は、比較例Ａと同様にして、平版印刷版原版を作製した。その後、得られた平版印刷版原版を、比較例Ａと同様にして、露光、現像に供し、同様の評価を行った。評価結果を表１に示す。
【０１７２】
［比較例２］
比較例Ａにおいて、第二のネガ型感光層を以下のように形成した他は、比較例Ａと同様にして、平版印刷版原版を作製した。
【０１７３】
（第二のネガ型感光層の形成）
次に、下記第二のネガ型感光層塗布液４を調整し、比較例Ａと同様の第一のネガ型感光層上にワイヤーバーを用いて塗布し、温風式乾燥装置にて６０℃で１２０秒間乾燥して、第二のネガ型感光層を形成した。乾燥後の被覆量は１ｇ／ｍ^２であった。
【０１７４】
＜第二のネガ型感光層塗布液４＞
・イオン交換水 ９０．６ｇ
・ポリアクリル酸（分子量、２万） ９．０９ｇ
・光熱変換物質［ＩＲ−▲３▼］（上記構造） ０．３ｇ
【０１７５】
［露光、現像、及び評価］
得られた平版印刷版原版を、比較例Ａと同様にして、露光、現像に供し、同様の評価を行った。評価結果を表１に示す。
【０１７６】
【表１】

【０１７７】
表１によれば、実施例１〜６の平版印刷版原版は、第二のネガ型感光層の被覆量に関らず、比較例１及び２の平版印刷版原版に比べ、現像液浸透性比が低く、耐刷性に優れていることが明らかとなった。
【０１７８】
【発明の効果】
本発明によれば、赤外線を放射する固体レーザ及び半導体レーザを用いて、コンピューター等のデジタルデータから記録することにより直接製版が可能であり、かつ、耐刷性の優れるネガ型の平版印刷版原版を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lithographic printing plate precursor having sensitivity in the infrared wavelength region, and more particularly to a so-called negative lithographic printing plate precursor capable of direct plate making using an infrared laser from a digital signal of a computer or the like.
[0002]
[Prior art]
The development of lasers in recent years has been remarkable, and in particular, solid-state lasers and semiconductor lasers (hereinafter sometimes referred to as “infrared lasers”) that emit infrared rays with a wavelength of 760 nm to 1200 nm are easily available with high output and small size. It became so. These infrared lasers are very useful as a recording light source when a printing plate is directly made by digital data of a computer or the like. Therefore, in recent years, there is an increasing demand for an image recording material having high sensitivity to such an infrared recording light source, that is, an image recording material whose solubility in a developing solution is greatly changed by infrared irradiation.
[0003]
  As an image recording material that can be recorded by such an infrared laser, an image recording material comprising an onium salt, a phenol resin, and a spectral sensitizer has been proposed (for example, see Patent Document 1). This image recording material is a positive-type image recording material that utilizes a dissolution inhibiting effect on a developing solution expressed by an onium salt and a phenol resin, and is not an image recording material that forms a negative image as in the present invention. On the other hand, as a negative image recording material, a recording material composed of an infrared absorber, an acid generator, a resole resin, and a novolac resin has been proposed (for example, see Patent Document 2). However, such a negative type image recording material requires a heat treatment after laser exposure in order to form an image. Therefore, a negative type image recording material that does not require a heat treatment after exposure is desired. It had been.
  On the other hand, for example, an image recording material comprising a cyanine dye having a specific structure, an iodonium salt, and an addition-polymerizable compound having an ethylenically unsaturated double bond that does not require heat treatment after imagewise exposure (for example, However, this image recording material has a polymerization reaction that does not proceed sufficiently, and the resistance of the exposed portion to the developer is insufficient, and the strength of the formed image portion is low. Insufficient printing durabilitysoThere was a problem that there was.
  An image recording material having a hot-melt resin layer on an alkali-soluble layer (for example, see Patent Document 4) has also been proposed, but has a problem of low sensitivity.
[0004]
[Patent Document 1]
US Pat. No. 4,708,925
[Patent Document 2]
US Pat. No. 5,340,699
[Patent Document 3]
Japanese Examined Patent Publication No. 7-103171
[Patent Document 4]
JP-A-9-286172
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a negative lithographic printing plate precursor that can be directly made by recording from digital data such as a computer using a solid-state laser and a semiconductor laser that emit infrared rays, and has excellent printing durability. Is to provide.
[0006]
[Means for Solving the Problems]
The inventors of the present invention provide an infrared laser by forming a lithographic printing plate precursor having a configuration in which a second photosensitive layer whose developer permeability is lowered by exposure irradiation is provided on a first photosensitive layer that causes a curing reaction. Has been found to be excellent in printing durability of the image area, and the present invention has been completed.
Means for solving the above-mentioned problems are as follows. That is,
[0007]
  The present inventionThe support comprises at least (A) a polymerizable compound having an ethylenically unsaturated double bond, and (B) an infrared absorber and a radical polymerization initiator, and has a function of generating radicals by exposure with an infrared laser. A first negative photosensitive layer comprising a polymerization initiation system having,Hydrophobic compound-containing microcapsules and hydrophilic resin that is hydrophobized by heatAt least one ofA lithographic printing plate precursor comprising: a second negative photosensitive layer containing, in this order, having a developer permeability low by infrared laser exposure.
[0008]
  In the second negative photosensitive layer, means for reducing developer permeability by infrared laser exposure include (1) a method of thermally fusing fine particles of heat-fused by the heat of infrared laser light, and (2) hydrophobicity. (3) Method to convert hydrophilic compound to hydrophobic compound (Method using polar conversion polymer)TheUseIn the present invention, it is necessary to use (2) and (3). Therefore, the second negative photosensitive layer has,Hydrophobic compound-containing microcapsules and polarity-converting polymerAt least one ofIt is necessary to contain.
  The second negative photosensitive layer may be an ink receiving layer.
  Here, in the present invention, the second negative photosensitive layer preferably contains a hydrophobic compound-containing microcapsule. Among them, the hydrophobic compound in the hydrophobic compound-containing microcapsule is a compound that undergoes a crosslinking reaction by heat. It is preferable that
  In the present invention, it is also a preferred embodiment that the second negative photosensitive layer contains a hydrophilic resin that is hydrophobized by heat.
  Furthermore, in the present invention, the film mass of the second negative photosensitive layer is 0.1 to 1.5 g / m.²It is preferable that
[0009]
In the present invention, “developer permeability” is calculated from a capacitance value. Such a capacitance value is obtained from the impedance between the electrodes using a 1 kHz sine wave alternating current by immersing the photosensitive composition and the counter electrode coated on the conductor substrate (aluminum) in a developing solution. Actual measurement requires that the conductor substrate not be in direct contact with the developer. For this reason, it covers and immerses with the shielding material which a developing solution does not osmose | permit except the window of the fixed area on the photosensitive composition coating surface side. The capacitance value increases with the penetration of the developer into the photosensitive composition through the window. The larger the rising speed, the faster the developer penetration.
In the present invention, the developer permeability was judged from the ratio of the capacitance value in the exposed area to the unexposed area after 10 seconds.
(Developer permeability ratio) = (Capacitance value in exposed area) / (Capacitance value in unexposed area) The lower the developer permeability ratio, the more the developer penetration inhibition in the exposed area was expressed. Represents. That is, the smaller the developer permeability ratio, the greater the discrimination of the unexposed and exposed areas with respect to the developer, resulting in better image formability. The developer permeability ratio is preferably 0.7 or less, more preferably 0.5 or less, and still more preferably 0.3 or less.
[0010]
  In the first negative photosensitive layerIsThe (B) polymerization initiation system is an infrared absorber.With radical polymerization initiatorKaraAnd alsoRadical polymerizable compoundIt is necessary to contain.
  The second negative photosensitive layer may not contain a photothermal conversion substance.
[0011]
Although the operation of the present invention is not clear, it is presumed as follows.
According to the lithographic printing plate precursor of the present invention, the exposed portion by the infrared laser further has a developer penetration inhibiting action on the first negative photosensitive layer in which the penetration of the developer is inhibited due to the curing reaction. It has a second negative photosensitive layer that develops, and due to its action, the dissolution resistance to the developer is greatly improved. In addition, due to the developer penetration inhibiting action of the second negative photosensitive layer, in the step of immersing the lithographic printing plate precursor in the developer, the film property is deteriorated due to undesired penetration of the developer into the first negative photosensitive layer. It is suppressed. As a result, the lithographic printing plate precursor according to the present invention has a very high resistance to the developer in the exposed area (image area), and it is considered that excellent printing durability can be obtained.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the lithographic printing plate precursor according to the invention will be described in detail.
  The lithographic printing plate precursor according to the invention comprises, on a support, at least (A) a polymerizable compound having an ethylenically unsaturated double bond, and (B) an infrared absorber and a radical polymerization initiator, and an infrared laser. A first negative photosensitive layer comprising a polymerization initiation system having a function of generating radicals upon exposure with,Hydrophobic compound-containing microcapsules and hydrophilic resin that is hydrophobized by heatAt least one ofAnd a second negative photosensitive layer that has low developer permeability due to infrared laser exposure in this order. In the present invention, the first negative photosensitive layer and the second negative photosensitive layer may be collectively referred to simply as a photosensitive layer.
  First, the second negative photosensitive layer whose developer permeability is lowered by infrared laser exposure, which is a characteristic part of the present invention, will be described.
[0013]
<Second negative photosensitive layer whose developer permeability is lowered by infrared laser exposure>
In the present invention, the second negative photosensitive layer may be a layer whose developer permeability is lowered by infrared laser exposure. In the second negative photosensitive layer, the developer penetrates and is removed more easily in the unexposed part than in the first negative photosensitive layer, but the exposed part is in the first negative type during development. For example, in the subsequent printing process, depending on the degree of interfacial adhesion between the first negative photosensitive layer and the second negative photosensitive layer, the first negative may be suppressed. It may be removed from the mold type photosensitive layer, or on the contrary, it may remain firmly adhered on the first negative type photosensitive layer. When the exposed portion of the second negative photosensitive layer is removed, the first negative photosensitive layer, which will be described later, becomes the surface layer of the image portion and becomes the ink receiving layer, but when it remains on the plate, Since the second negative photosensitive layer serves as the surface layer of the image portion, it requires ink acceptability.
[0014]
The “developer permeability” in the present invention is determined from the ratio of the capacitance value in the exposed area to the unexposed area after 10 seconds (developer permeability ratio) as described above. The developer permeability ratio is preferably 0.7 or less, more preferably 0.5 or less, and still more preferably 0.3 or less. When the developer permeability ratio is within this range, the discrimination between the unexposed area and the exposed area with respect to the developer is large, indicating that the developer penetration suppression in the exposed area is excellent.
[0015]
  In the second negative photosensitive layer of the present invention, the means for lowering the developer permeability by infrared laser exposure is preferably a mechanism that is not inhibited by oxygen or water. Specifically, the following method is used. Is used. That is,In the second negative photosensitive layer,(1) a method of thermally fusing fine particles of heat fusion by heat of infrared laser light, (2) a method of utilizing melting of a hydrophobic compound-containing microcapsule, and (3) converting a hydrophilic compound into a hydrophobic compound. Method (method using polar conversion polymer)TheUseIn the present invention, it is necessary to use (2) and (3). Hereinafter, each method will be described.
[0016]
[(1) Method of thermally fusing fine particles of heat fusion by heat of infrared laser light]
In the method (1), the heat-fused fine particles in the second negative photosensitive layer are at least partially fused and bonded to each other by heat generated by infrared laser exposure, so that the developer can penetrate. A region to be suppressed is formed.
As the heat-sealing fine particles used here, both low molecules and polymers can be used. From the viewpoint of production suitability and storage stability, particles based on a hydrophobic polymer are preferred. Hydrophobic polymer particles are obtained by phase inversion emulsification, emulsion polymerization, soap-free emulsion polymerization, seed polymerization, dispersion polymerization, solvent evaporation, suspension polymerization, coacervation, interfacial polymerization, spray drying. The polymer particle which can be adjusted with well-known synthesis methods, such as these, is applicable. In particular, particles prepared by a phase inversion emulsification method, a solvent evaporation method, and the like and dispersed in water are preferable from the viewpoint of ease of preparation of a light-sensitive material.
[0017]
  As the hydrophobic polymer, known thermoplastic polymers and thermosetting polymers that can be made into particles can be used. The molecular weight of such a polymer is preferably 3000 to 1 million.. GoodSuitable thermoplastic fine particle polymers include Research Disclosure No. 1 of January 1992. 33303, JP-A-9-123387, JP-A-9-131850, JP-A-9-171249, JP-A-9-171250, and EP931647, and the like. Specific examples include homopolymers or copolymers of ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinyl carbazole, or mixtures thereof. Can do.
[0018]
Furthermore, these polymers may have a reactive functional group. Functional groups include radically polymerizable groups such as acrylate groups, methacrylate groups, vinyl groups and allyl groups, cationic polymerizable groups such as epoxy groups and vinyl ether groups, addition groups such as amino groups, hydroxyl groups, carboxyl groups, isocyanates and acid anhydrides. Examples thereof include reactive groups and groups protecting them.
[0019]
Thermosetting polymer particles suitable as a hydrophobic polymer include resins having a phenol skeleton, urea resins (for example, urea derivatives such as urea or methoxymethylated urea converted to resins with aldehydes such as formaldehyde), and melamine polymers. Examples thereof include resins (for example, those obtained by converting melamine or derivatives thereof with aldehydes such as formaldehyde), alkyd resins, unsaturated polyester resins, polyurethane resins, epoxy resins, and the like.
[0020]
Examples of the resin having a phenol skeleton include phenol skeletons such as novolak resins, resole resins, hydroxystyrene resins, and N- (p-hydroxyphenyl) methacrylamide obtained by converting phenol, cresol and the like with aldehydes such as formaldehyde. Examples thereof include methacrylamide or acrylamide resin, and methacrylate or acrylate resin having a phenol skeleton such as p-hydroxyphenyl methacrylate.
[0021]
The average particle diameter of the heat fusion fine particles is preferably 0.01 to 3 μm, more preferably 0.05 to 1.0 μm, and particularly preferably 0.02 to 0.4 μm. In this range, good resolution and stability over time can be obtained.
[0022]
The amount of the heat-sealing fine particles added is preferably 40% by mass or more, more preferably 60% by mass or more, based on the solid content of the second negative photosensitive layer. In this range, it is possible to suppress developer penetration.
[0023]
[(2) Method of Utilizing Melting of Hydrophobic Compound-Containing Microcapsules by Heat of Infrared Laser Light]
In the method (2), the hydrophobic compound-containing microcapsules in the second negative photosensitive layer are released from the hydrophobic compound by the heat generated by the infrared laser exposure, and the region where the penetration of the developing solution is suppressed. It is to form.
As the hydrophobic compound contained in the microcapsule used here, a hydrophobic low molecular weight compound, an oligomer, or a thermoplastic or thermosetting polymer as described in the description of the hydrophobic polymer particles used in the method (1) above. Any of the classes can be used.
[0024]
Further, these hydrophobic compounds are preferably compounds that undergo a crosslinking reaction by heat, and more preferably compounds that have a functional group that undergoes a thermal crosslinking reaction (hereinafter referred to as a thermally reactive group). Examples of the thermally reactive group include an ethylenically unsaturated group (for example, acryloyl group, methacryloyl group, vinyl group, and allyl group) that undergoes a polymerization reaction, an isocyanate group that undergoes an addition reaction, or a block thereof, and a reaction partner thereof. A functional group having an active hydrogen atom (for example, an amino group, a hydroxyl group, a carboxyl group, etc.), an epoxy group that similarly performs an addition reaction, and an amino group, a carboxyl group or a hydroxyl group that is a reaction partner thereof, and a carboxyl group that performs a condensation reaction Examples thereof include a hydroxyl group or an amino group, an acid anhydride that performs a ring-opening addition reaction, and an amino group or a hydroxyl group. However, as long as a chemical bond is formed, any functional group capable of performing any reaction may be used, and the functional group is not limited to the above functional group.
A hydrophobic compound having such a heat-reactive group can increase the image strength by heat reaction and realize high printing durability.
[0025]
Microcapsules containing such a compound having a thermally reactive group include, for example, acrylate groups, methacrylate groups, vinyl groups, allyl groups, epoxy groups, amino groups, hydroxyl groups, carboxyl groups, isocyanates, acid anhydrides and the like. It can be obtained by encapsulating a compound having a heat-reactive group such as a group protected in the microcapsule, or introducing these compounds into the outer wall of the microcapsule. In addition, the compound having a thermoreactive group may be encapsulated in the microcapsule and simultaneously introduced into the outer wall of the microcapsule.
[0026]
As the compound having a heat-reactive group contained in the microcapsule, a compound group described in JP-A Nos. 2001-277740 and 2001-277742 can be used.
[0027]
In order to make the compound having a thermally reactive group diffused from the microcapsule on the surface of the microcapsule in the second negative photosensitive layer and in the vicinity of the surface, for example, the outer wall of the microcapsule is There are means for dispersing in a solvent for swelling.
[0028]
The material of the outer wall of the preferable microcapsule used in the present invention is one having three-dimensional crosslinking. 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. A compound having a thermoreactive group as described above may be introduced into the outer wall of the microcapsule.
[0029]
As a method for microencapsulating a compound having a heat-reactive group as an inclusion, a known microencapsulation method can be applied. For example, as a method for producing microcapsules, a method using coacervation found in US Pat. Nos. 2,800,547 and 2,800,498, British Patent 990443, US Pat. No. 3,287,154, Japanese Patent Publication No. 38-19574, and 42-446 No. 42-711, a method using an interfacial polymerization method, US Pat. No. 3,418,250, US Pat. No. 3,660,304, a method using polymer precipitation, US Pat. No. 3,796,669, a method using an isocyanate polyol wall material, US Pat. A method using an isocyanate wall material found in U.S. Pat. No. 3,914,511, a method using a urea-formaldehyde-based or urea-formaldehyde-resorcinol-based wall forming material found in U.S. Pat. Nos. 4001140, 4087376, and 4089802, A method using a wall material such as melamine-formaldehyde resin and hydroxycellulose, as shown in Japanese Patent No. 4025445, an in situ method by monomer polymerization as shown in Japanese Patent Publication Nos. 36-9163 and 51-9079, British Patent No. 930422, US The spray drying method found in Japanese Patent No. 3,111,407 and the electrolytic dispersion cooling method shown in British Patent Nos. 952,807 and 967,074 are not limited thereto.
[0030]
The solvent that swells the outer wall of the microcapsule depends on the microcapsule dispersion solvent (also referred to as a solvent or a coating solution), the material and wall thickness of the microcapsule wall, and the compound contained in the microcapsule. It can be easily selected from the solvents that have been used. 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.
More 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, N-dimethylformamide, N, N-dimethylacetamide and the like are not limited thereto. Two or more of these solvents may be used.
[0031]
A solvent that does not dissolve in the microcapsule dispersion solvent but dissolves when the solvent is mixed can also be used. The amount of the solvent that swells the outer wall of the microcapsule is determined depending on the combination of materials. When the amount is less than the appropriate value, image formation is insufficient, and when the amount is large, the stability of the dispersion deteriorates. Usually, 5 to 95% by mass of the coating solution is effective, and a preferable range is 10 to 90% by mass, and a more preferable range is 15 to 85% by mass.
[0032]
The average particle size of the microcapsules is preferably 0.01 to 20 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 are obtained, which is preferable.
[0033]
The amount of the microcapsule added to the second negative photosensitive layer is preferably 50% by mass or more, and more preferably 60% by mass or more, based on the solid content of the second negative photosensitive layer. Within this range, suppression of developer penetration by exposure can be obtained.
[0034]
[(3) Method of Converting Hydrophilic Compound to Hydrophobic Compound by Heat of Infrared Laser Light (Method Using Polarity Conversion Polymer)]
  In the method (3), the hydrophilic compound constituting the second negative photosensitive layer is converted into a hydrophobic compound by heat generated by infrared laser exposure, thereby forming a region that suppresses the penetration of the developer. That's it.
  As a hydrophilic compound to be converted into a hydrophobic compound used in this method, a conventionally known hydrophilic resin that is hydrophobized by heat (hereinafter, referred to as a polar conversion polymer as appropriate).Used.Specific examples of this hydrophilic resin include sulfones disclosed in JP-A-5-77574, JP-A-4-125189, US Pat. No. 5,187,047 and JP-A-62-195646. Resins that are hydrophobized by desulfonating acid groups, resins that are hydrophobized by dehydrating and cyclizing polymers having carboxylic acid groups disclosed in US Pat. No. 4,081,572, and decarboxylation by heat Examples thereof include a hydrophilic resin having a carboxylic acid group and a carboxylic acid group to be raised.
[0035]
The polarity conversion polymer having any one of a carboxylic acid group and a carboxylic acid group causing decarboxylation by heat, which can be used in the present invention, is not particularly limited, but the polarity conversion polymer is represented by the following general formulas (1) and (2). It is preferable to have a functional group having any of the structures represented.
-X-C (-R¹, -R²-CO₂H (1)
-X-C (-R^Three, -R^Four-CO₂ ^-M⁺(2)
(In the general formulas (1) and (2), X represents -O-, -S-, -Se-, -NR.^Five-, -CO-, -SO-, -SO₂-, -PO-, -SiR^FiveR⁶-, -CS-, R¹, R², R^Three, R^Four, R^FiveAnd R⁶Each independently represents a monovalent group, and M represents an ion having a positive charge. )
[0036]
R in the general formulas (1) and (2)¹, R², R^Three, R^Four, R^FiveAnd R⁶Specific examples of are: hydrogen, alkyl group, aryl group, alkynyl group, alkenyl group, -F, -Cl, -Br, -I, -CN, -R.^Ten, -OR^Ten, -OCOR^Ten, -OCOOR^Ten, -OCONR^TenR¹¹, -OSO₂R^Ten, -COR^Ten, -COOR^Ten, -CONR^TenR¹¹, -NR^TenR¹¹, -NR^Ten-COR¹¹, -NR^Ten-COOR¹¹, -NR^Ten-CONR¹¹R¹², -SR^Ten, -SOR^Ten, -SO₂R^Ten, -SO_ThreeR^TenEtc. Where R^Ten, R¹¹, R¹²And are hydrogen, an alkyl group, an aryl group, an alkenyl group, and an alkynyl group.
Of these, R¹, R², R^Three, R^Four, R^FiveAnd R⁶Preferred are hydrogen, an alkyl group, an aryl group, an alkynyl group, and an alkenyl group.
[0037]
Specific examples of the functional groups represented by the general formulas (1) and (2) are shown below.
[0038]
[Chemical 1]

[0039]
[Chemical formula 2]

[0040]
[Chemical 3]

[0041]
Specific examples of the monomer having a functional group represented by the general formulas (1) and (2) are shown below.
[0042]
[Formula 4]

[0043]
[Chemical formula 5]

[0044]
[Chemical 6]

[0045]
Such a polarity conversion polymer that causes decarboxylation by heat may be a homopolymer of one kind of monomer having the functional groups represented by the above general formulas (1) and (2), or two or more kinds of copolymers. There may be. Moreover, as long as the effect of this invention is not impaired, the copolymer with another monomer may be sufficient.
In addition, one type of polar conversion polymer may be used, or two or more types may be used in combination.
[0046]
[Photothermal conversion material]
The second negative photosensitive layer of the present invention may contain a photothermal conversion substance that generates heat upon exposure, if necessary, and utilizes the residual heat generated by the first negative photosensitive layer upon exposure. Therefore, it is not necessary to contain a photothermal conversion substance, and it is possible to select an aspect in which sensitivity and printing durability are easily developed depending on the compound used and the intended use. The light-to-heat conversion substance contained may be a light-absorbing substance having an absorption band in at least part of 700 to 1200 nm, and various pigments, dyes and metal fine particles can be used.
[0047]
Examples of pigments include commercially available pigment and color index (CI) manuals, “Latest Pigment Handbook” (edited by the Japan Pigment Technology Association, published in 1977), “Latest Pigment Applied Technology” (published by CMC, published in 1986), “Printing” Infrared absorbing pigments described in "Ink Technology" (CMC Publishing, 1984) can be used.
[0048]
These pigments can be used after being subjected to a known surface treatment, if necessary, in order to improve the dispersibility in the layer to which they are added. Surface treatment includes surface coating with hydrophilic resin or lipophilic resin, method of attaching a surfactant, reactive substance (for example, silica sol, alumina sol, silane coupling agent, epoxy compound, isocyanate compound, etc. Or the like may be bonded to the pigment surface.
[0049]
The pigment added to the second negative photosensitive layer is preferably a pigment whose surface is coated with a hydrophilic resin or silica sol so that it is easily dispersed with a water-soluble resin and does not impair the hydrophilic property. The particle diameter of the pigment is preferably in the range of 0.01 μm to 1 μm, and more preferably in the range of 0.01 μm to 0.5 μm. As a method for dispersing the pigment, a known dispersion technique used in ink production, toner production, or the like can be used. A particularly preferred pigment is carbon black.
[0050]
Examples of the dye include commercially available dyes and literature (for example, “Dye Handbook” edited by the Society of Synthetic Organic Chemistry, published in 1970, “Chemical Industry”, May 1986, P. 45-51, “Near Infrared Absorbing Dye”, “90 Development and market trends of age functional pigments ", Chapter 2, 2.3 (1990) CMC) or known dyes described in patents can be used. Specifically, infrared absorbing dyes such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, polymethine dyes, and cyanine dyes are preferable.
[0051]
Further, for example, cyanine dyes described in JP-A-58-125246, JP-A-59-84356, JP-A-60-78787, JP-A-58-173696, JP-A-58-181690 Methine dyes described in JP-A-58-194595, JP-A-58-112793, JP-A-58-224793, JP-A-59-48187, JP-A-59-73996, Naphthoquinone dyes described in JP-A-60-52940, JP-A-60-63744, etc., squarylium dyes described in JP-A-58-112792, etc., cyanine dyes described in British Patent 434,875 And dyes described in US Pat. No. 4,756,993, cyanine dyes described in US Pat. No. 4,973,572, dyes described in JP-A-10-268512 It may be mentioned phthalocyanine compounds of JP-A 11-235883 Patent forth.
[0052]
Further, near infrared absorption sensitizers described in US Pat. No. 5,156,938 are also preferably used as dyes, and substituted arylbenzo (thio) pyrylium described in US Pat. No. 3,881,924. Salt, trimethine thiapyrylium salt described in JP-A-57-142645, JP-A-58-181051, JP-A-58-220143, JP-A-59-41363, JP-A-59-84248, JP-A-59-84249, Pyryllium compounds described in 59-146063 and 59-146061, cyanine dyes described in JP-A-59-216146, pentamethine thiopyrylium salts described in US Pat. No. 4,283,475, etc. And pyrilium compounds disclosed in JP-B-5-13514 and JP-5-19702, Epolite III-178 manufactured by Eporin. Epolight III-130, Epolight III-125 and the like is also preferably used.
[0053]
Among these, a preferred dye to be added to the second negative photosensitive layer is a water-soluble dye, and specific examples are shown below. However, the present invention is not limited to these.
[0054]
[Chemical 7]

[0055]
[Chemical 8]

[0056]
[Hydrophilic resin]
The second negative photosensitive layer of the present invention can contain a hydrophilic resin in order to improve developability and film strength of the second negative photosensitive layer itself. As hydrophilic resin, what has hydrophilic groups, such as a hydroxyl group, a carboxyl group, a phosphoric acid group, a sulfonic acid group, an amide group, is preferable, for example. In addition, the hydrophilic resin reacts with the vinyloxy group and crosslinks to increase the image strength and increase the printing durability. Therefore, a functional group that reacts with the vinyloxy group, such as a hydroxyl group, a carboxyl group, a phosphate group, a sulfone group. Those having an acid group are preferred. Among these, a hydrophilic resin having a hydroxyl group or a carboxyl group is preferable.
[0057]
Specific examples of hydrophilic resins include gum arabic, casein, gelatin, starch derivatives, water-soluble soybean polysaccharide, hydroxypropylcellulose, methylcellulose, carboxymethylcellulose and its sodium salt, cellulose acetate, sodium alginate, vinyl acetate-maleic acid copolymers Styrene-maleic 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 Homopolymers and copolymers of hydroxypropyl acrylate, homopolymers and copolymers of hydroxybutyl methacrylate, Homopolymers and copolymers of droxybutyl acrylate, polyethylene glycols, hydroxypropylene polymers, polyvinyl alcohols, and hydrolyzed polyvinyl acetate, polyvinyl formal, polyvinyl pyrrolidone having a degree of hydrolysis of at least 60% by weight, preferably at least 80% by weight Homopolymers and copolymers of acrylamide, homopolymers and copolymers of methacrylamide, homopolymers and copolymers of N-methylolacrylamide, homopolymers and copolymers of 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-methacryloyloxy Mention may be made of homopolymers and copolymers of ethylphosphonic acid.
[0058]
The film mass of the second negative photosensitive layer is 0.01 to 4 g / m.²Is preferred, 0.05 to 2.5 g / m²Is more preferable, 0.1 to 1.5 g / m²Is more preferable from the viewpoints of developability and image formability.
[0059]
<(A) Polymerizable compound and (B) First negative photosensitive layer containing a polymerization initiation system>
The first negative photosensitive layer in the present invention must contain (A) a polymerizable compound and (B) a polymerization initiation system, and other components can be added as necessary. .
Such a first negative photosensitive layer is first irradiated with an infrared laser, and at the exposed portion, the laser beam and / or heat causes (B) a polymerization initiating species (radical, cation, anion). Seeds). Thereafter, the generated polymerization initiating species causes the compound ((A) polymerizable compound) polymerizable by the coexisting polymerization initiating species to undergo a polymerization reaction, and only the exposed portion becomes insoluble in the developer to form an image. On the other hand, the non-exposed portion is developed and removed to form a desired image. By such an image forming process, the first negative photosensitive layer can form an image.
Hereinafter, (A) the polymerizable compound and (B) the polymerization initiation system will be described.
[0060]
[(A) polymerizable compound]
  The polymerizable compound (A) used in the present invention is,Polymerization starting speciesofPolymerizable compound whose polymerization reaction is initiated by radicalsIt is.
  The polymerizable compound used in the present invention, in which the polymerization reaction is initiated by a radical, is a polymerizable compound having at least one ethylenically unsaturated double bond, and preferably has at least one terminal ethylenically unsaturated bond. Is selected from compounds having two or more. Such a compound group is widely known in the industrial field, and can be used without any particular limitation in the present invention. These have chemical forms such as monomers, prepolymers, i.e. dimers, trimers and oligomers, or mixtures thereof and copolymers thereof. Examples of monomers and copolymers thereof include unsaturated carboxylic acids (for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.), and esters and amides thereof. In this case, an ester of an unsaturated carboxylic acid and an aliphatic polyhydric alcohol compound, or an amide of an unsaturated carboxylic acid and an aliphatic polyvalent amine compound is used. In addition, unsaturated carboxylic acid esters having nucleophilic substituents such as hydroxyl groups, amino groups, mercapto groups, amides and monofunctional or polyfunctional isocyanates, addition reaction products of epoxies, monofunctional or polyfunctional A dehydration condensation reaction product with a functional carboxylic acid is also preferably used. In addition, an addition reaction product of an unsaturated carboxylic acid ester or amide having an electrophilic substituent such as an isocyanate group or an epoxy group with a monofunctional or polyfunctional alcohol, amine or thiol, halogen A substitution reaction product of an unsaturated carboxylic acid ester or amide having a leaving substituent such as a group or a tosyloxy group with a monofunctional or polyfunctional alcohol, amine or thiol is also suitable. As another example, it is also possible to use a group of compounds substituted with unsaturated phosphonic acid, styrene or the like instead of the unsaturated carboxylic acid.
[0061]
Specific examples of acrylic acid ester, methacrylic acid ester, itaconic acid ester, crotonic acid ester, isocrotonic acid ester and maleic acid ester which are polymerizable compounds which are esters of aliphatic polyhydric alcohol compounds and unsaturated carboxylic acids are These are described in paragraph numbers [0037] to [0042] of Japanese Utility Model Publication No. 2001-133969, and these can be applied to the present invention.
[0062]
Examples of other esters include aliphatic alcohol esters described in JP-B-46-27926, JP-B-51-47334, JP-A-57-196231, JP-A-59-5240, JP-A-59-5241. Those having an aromatic skeleton described in JP-A-2-226149 and those containing an amino group described in JP-A-1-165613 are also preferably used.
[0063]
Specific examples of amide monomers of aliphatic polyvalent amine compounds and unsaturated carboxylic acids include methylene bis-acrylamide, methylene bis-methacrylamide, 1,6-hexamethylene bis-acrylamide, 1,6-hexamethylene bis. -Methacrylamide, diethylenetriamine trisacrylamide, xylylene bisacrylamide, xylylene bismethacrylamide and the like.
Examples of other preferable amide monomers include those having a cyclohexylene structure described in JP-B-54-21726.
[0064]
In addition, urethane-based addition polymerizable compounds produced by using an addition reaction of isocyanate and hydroxyl group are also suitable, and specific examples thereof include, for example, one molecule described in JP-B-48-41708. A vinyl urethane compound containing two or more polymerizable vinyl groups in one molecule obtained by adding a vinyl monomer containing a hydroxyl group represented by the following formula (V) to a polyisocyanate compound having two or more isocyanate groups. Etc.
[0065]
General formula (V)
CH₂= C (R⁴¹) COOCH₂CH (R⁴²) OH
(However, R⁴¹And R⁴²Is H or CH_ThreeIndicates. )
[0066]
Also, urethane acrylates such as those described in JP-A-51-37193, JP-B-2-32293, and JP-B-2-16765, JP-B-58-49860, JP-B-56-17654, Urethane compounds having an ethylene oxide skeleton described in JP-B-62-39417 and JP-B-62-39418 are also suitable.
[0067]
Furthermore, polymerizable compounds having an amino structure or a sulfide structure in the molecule described in JP-A-63-277653, JP-A-63-260909, and JP-A-1-105238 may be used.
[0068]
Other examples include polyester acrylates, epoxy resins and (meth) acrylic acid as described in JP-A-48-64183, JP-B-49-43191, JP-B-52-30490, and JP-A-52-30490. Mention may be made of polyfunctional acrylates and methacrylates such as reacted epoxy acrylates. Further, specific unsaturated compounds described in JP-B-46-43946, JP-B-1-40337 and JP-B-1-40336, vinylphosphonic acid compounds described in JP-A-2-25493, and the like can also be mentioned. . In some cases, a structure containing a perfluoroalkyl group described in JP-A-61-22048 is preferably used. Furthermore, Journal of Japan Adhesion Association vol. 20, no. 7, pages 300 to 308 (1984), which are introduced as photocurable monomers and oligomers, can also be used.
[0069]
For these polymerizable compounds, the details of the method of use, such as what structure is used, whether it is used alone or in combination, and how much is added, is the final performance design of the recording material, that is, in the present invention. Is appropriately set in accordance with the purpose of setting the capacitance value increase rate ratio to 0.7 or less when a model solution assuming a developer is used. For example, it is selected from the following viewpoints. From the viewpoint of sensitivity, a structure having a high unsaturated group content per molecule is preferable, and in many cases, a bifunctional or higher functionality is preferable. Further, in order to increase the strength of the image area, that is, the cured film, those having three or more functionalities are preferable, and compounds having different functional numbers and different polymerizable groups (for example, acrylate ester compounds, methacrylate esters). It is also effective to adjust both photosensitivity and strength by using a combination of a compound, a styrene compound, and the like. The rate of increase in the capacitance value, which is a physical property of the photosensitive composition of the present invention, is an important factor in both the curing speed and the film strength, and it can be said that such means is effective.
A compound having a large molecular weight or a compound having high hydrophobicity is excellent in sensitivity and film strength, but may not be preferable in terms of development speed and precipitation in a developer. In addition, the compatibility and dispersibility with other components in the photosensitive layer (for example, binder polymer, initiator, colorant, etc.) are also important factors in selecting and using the radically polymerized compound. Compatibility may be improved by the use of a low-purity compound or a combination of two or more compounds. In addition, a specific structure may be selected for the purpose of improving the adhesion of the support, overcoat layer and the like. Regarding the compounding ratio of the polymerizable compound in the photosensitive layer, a larger amount is more advantageous in terms of sensitivity. However, when the amount is too large, an undesirable phase separation occurs or a problem in the production process due to the adhesiveness of the photosensitive layer ( For example, problems such as transfer of photosensitive layer components and manufacturing defects due to adhesion) and precipitation from a developer may occur. From these viewpoints, the preferable blending ratio of the polymerizable compound is often 5 to 80% by mass, preferably 20 to 75% by mass with respect to the total components of the composition. These may be used alone or in combination of two or more. In addition, as for the method of using the polymerizable compound, an appropriate structure, blending, and addition amount can be arbitrarily selected from the viewpoints of polymerization inhibition with respect to oxygen, resolution, fogging property, refractive index change, surface tackiness, and the like.
[0070]
[(B) polymerization initiation system]
The polymerization initiation system (B) in the present invention has a function of generating polymerization initiation species by exposure with an infrared laser. For the mechanism for generating such polymerization initiating species, (B-1) a polymerization initiating species generator and (B-2) an infrared absorber are usually used. In other words, (B) the polymerization initiation system is such that (B-2) the infrared absorber efficiently absorbs the infrared laser beam in the exposed portion, and (B-1) the initiator of the polymerization initiation species is generated by the light and / or heat. It is a system that decomposes and generates polymerization initiation species.
Hereinafter, (B-1) a polymerization initiating species generator and (B-2) an infrared absorber used in such an initiation system will be described.
[0071]
((B-1) Generator of polymerization initiation species)
  The (B-1) polymerization initiation species generator used in the present invention refers to a compound that generates a polymerization initiation species when irradiated with an infrared laser, in combination with an infrared absorber described later.(B-1) Polymerization Initiating Species Generator in the Present InventionIs a radical polymerization initiatorIt is.
  Hereinafter, a radical polymerization initiator (hereinafter referred to as a radical generator) that generates radicals as a suitable polymerization initiation species in the present invention will be described in detail, but the present invention is not limited thereto.
  The radical generator used in the present invention includes, as a radical generator, an onium salt, a triazine compound having a trihalomethyl group, a peroxide, an azo polymerization initiator, an azide compound, a quinonediazide, a borate compound, a ketoxime ester compound, A hexaarylbiimidazole compound, an aromatic ketone compound, a metallocene compound, a disulfonic acid compound and the like can be mentioned, and an onium salt is preferred because of its high sensitivity. An onium salt that can be suitably used as a radical polymerization initiator in the present invention will be described. Preferred onium salts include iodonium salts, diazonium salts, and sulfonium salts. In the present invention, these onium salts function not as acid generators but as radical polymerization initiators. The onium salt suitably used in the present invention is an onium salt represented by the following general formulas (II) to (IV).
[0072]
[Chemical 9]

[0073]
In formula (II), Ar¹¹And Ar¹²Each independently represents an aryl group having 20 or less carbon atoms, which may have a substituent. Preferred substituents when this aryl group has a substituent include a halogen atom, a nitro group, an alkyl group having 12 or less carbon atoms, an alkoxy group having 12 or less carbon atoms, or a carbon atom having 12 or less carbon atoms. An aryloxy group is mentioned. Z^11-Represents a counter ion selected from the group consisting of halogen ion, perchlorate ion, tetrafluoroborate ion, hexafluorophosphate ion, carboxylate ion, and sulfonate ion, preferably perchlorate ion, hexafluorophosphine Fate ions, carboxylate ions, and aryl sulfonate ions.
[0074]
In formula (III), Ar^{twenty one}Represents an aryl group having 20 or less carbon atoms which may have a substituent. Preferred examples of the substituent include a halogen atom, a nitro group, an alkyl group having 12 or less carbon atoms, an alkoxy group having 12 or less carbon atoms, an aryloxy group having 12 or less carbon atoms, and 12 or less carbon atoms. Examples thereof include an alkylamino group, a dialkylamino group having 12 or less carbon atoms, an arylamino group having 12 or less carbon atoms, or a diarylamino group having 12 or less carbon atoms. Z^{twenty one-}Is Z^11-Represents a counter ion having the same meaning as.
[0075]
In formula (IV), R³¹, R³²And R³³These may be the same or different and each represents a hydrocarbon group having 20 or less carbon atoms which may have a substituent. Preferable substituents include a halogen atom, a nitro group, an alkyl group having 12 or less carbon atoms, an alkoxy group having 12 or less carbon atoms, or an aryloxy group having 12 or less carbon atoms. Z^31-Is Z^11-Represents a counter ion having the same meaning as.
[0076]
In the present invention, specific examples of onium salts that can be suitably used as a radical generator include those described in paragraphs [0030] to [0033] of JP-A No. 2001-133969.
[0077]
The radical generator used in the present invention preferably has a maximum absorption wavelength of 400 nm or less, and more preferably 360 nm or less. By making the absorption wavelength in the ultraviolet region in this way, the lithographic printing plate precursor can be handled under white light.
[0078]
These radical generators are 0.1 to 50% by mass, preferably 0.5 to 30% by mass, and particularly preferably 1 to 20% by mass with respect to the total solid content of the photosensitive layer coating solution. Can be added inside. When the addition amount is less than 0.1% by mass, the sensitivity is lowered, and when it exceeds 50% by mass, the non-image area is stained during printing. These radical generators may be used alone or in combination of two or more. Moreover, these radical generators may be added to the same layer as other components, or another layer may be provided and added thereto.
[0079]
((B-2) Infrared absorber)
The (B-2) infrared absorbent used in the present invention is capable of efficiently absorbing infrared laser light, and specifically includes dyes or pigments having an absorption maximum from a wavelength of 760 nm to 1200 nm. It is done.
As the dye, commercially available dyes and known dyes described in documents such as “Dye Handbook” (edited by the Society for Synthetic Organic Chemistry, published in 1970) can be used. Specifically, dyes such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, metal thiolate complexes, etc. Is mentioned.
[0080]
Preferred dyes include, for example, cyanine dyes described in JP-A-58-125246, JP-A-59-84356, JP-A-59-202829, JP-A-60-78787, and the like. Methine dyes described in JP-A-58-173696, JP-A-58-181690, JP-A-58-194595, JP-A-58-112793, JP-A-58-224793, JP-A-59- 48187, JP-A-59-73996, JP-A-60-52940, JP-A-60-63744, etc., naphthoquinone dyes, JP-A-58-112792, etc. And cyanine dyes described in British Patent 434,875.
[0081]
Also, a near infrared absorption sensitizer described in US Pat. No. 5,156,938 is preferably used, and a substituted arylbenzo (thio) pyrylium salt described in US Pat. No. 3,881,924, Trimethine thiapyrylium salts described in JP-A-57-142645 (US Pat. No. 4,327,169), JP-A-58-181051, 58-220143, 59-41363, 59-84248 Nos. 59-84249, 59-146063, 59-146061, pyranlium compounds, cyanine dyes described in JP-A-59-216146, US Pat. No. 4,283,475 The pentamethine thiopyrylium salts described above and the pyrylium compounds disclosed in Japanese Patent Publication Nos. 5-13514 and 5-19702 are also preferably used. .
Another example of a preferable dye is a near-infrared absorbing dye described as formulas (I) and (II) in US Pat. No. 4,756,993.
[0082]
Among these dyes, particularly preferred are cyanine dyes, squarylium dyes, pyrylium salts, and nickel thiolate complexes. Further, a cyanine dye is preferable, and a cyanine dye represented by the following general formula (I) is most preferable.
[0083]
[Chemical Formula 10]

[0084]
In the general formula (I), X¹Is a halogen atom, X²-L¹Or N (L²) (L^Three). Where X²Represents an oxygen atom or a sulfur atom, and L¹, L²And L^ThreeEach independently represents a hydrocarbon group having 1 to 12 carbon atoms. R¹And R²Each independently represents a hydrocarbon group having 1 to 12 carbon atoms. From the storage stability of the photosensitive layer coating solution, R¹And R²Is preferably a hydrocarbon group having 2 or more carbon atoms, and further R¹And R²Are particularly preferably bonded to each other to form a 5-membered ring or a 6-membered ring.
[0085]
Ar¹, Ar²These may be the same or different and each represents an aromatic hydrocarbon group which may have a substituent. Preferred aromatic hydrocarbon groups include a benzene ring and a naphthalene ring. Moreover, as a preferable substituent, a C12 or less hydrocarbon group, a halogen atom, and a C12 or less alkoxy group are mentioned. Y¹, Y²May be the same or different and each represents a sulfur atom or a dialkylmethylene group having 12 or less carbon atoms. R^Three, R^FourThese may be the same or different and each represents a hydrocarbon group having 20 or less carbon atoms which may have a substituent. Preferred substituents include alkoxy groups having 12 or less carbon atoms, carboxyl groups, and sulfo groups. R^Five, R⁶, R⁷And R⁸Each may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 12 or less carbon atoms. From the availability of raw materials, a hydrogen atom is preferred. Z^1-Indicates the counter anion when charge neutralization is required. For example, R¹~ R⁸Is substituted with an anionic substituent and the charge is neutralized, Z^1-Is not necessary. Preferred Z^1-Are halogen ions, perchlorate ions, tetrafluoroborate ions, hexafluorophosphate ions, and sulfonate ions, particularly preferably perchlorate ions, hexafluorophosphates, from the viewpoint of storage stability of the photosensitive layer coating solution. Ions and aryl sulfonate ions.
[0086]
Specific examples of the cyanine dye represented by formula (I) that can be suitably used in the present invention include those described in paragraph numbers [0017] to [0019] of JP-A No. 2001-133969. be able to.
[0087]
Examples of the pigment used in the present invention include commercially available pigments and color index (CI) manual, “Latest Pigment Handbook” (edited by Japan Pigment Technology Association, published in 1977), “Latest Pigment Application Technology” (CMC Publishing, 1986), “Printing Ink Technology”, CMC Publishing, 1984) can be used.
Examples of the pigment include black pigments, yellow pigments, orange pigments, brown pigments, red pigments, purple pigments, blue pigments, green pigments, fluorescent pigments, metal powder pigments, and other polymer-bonded dyes. Specifically, 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 In addition, quinophthalone pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, inorganic pigments, carbon black, and the like can be used. Among these pigments, carbon black is preferable.
[0088]
These pigments may be used without surface treatment, or may be used after surface treatment. The surface treatment method includes a method of surface coating with a resin or wax, a method of attaching a surfactant, a method of bonding a reactive substance (eg, silane coupling agent, epoxy compound, polyisocyanate, etc.) to the pigment surface, etc. Can be considered. The above-mentioned surface treatment methods are described in “Characteristics and Applications of Metal Soap” (Shobobo), “Printing Ink Technology” (CMC Publishing, 1984) and “Latest Pigment Application Technology” (CMC Publishing, 1986). Yes.
[0089]
The particle size of the pigment is preferably in the range of 0.01 μm to 10 μm, more preferably in the range of 0.05 μm to 1 μm, and particularly preferably in the range of 0.1 μm to 1 μm. When the particle diameter of the pigment is less than 0.01 μm, it is not preferable from the viewpoint of stability of the dispersion in the photosensitive layer coating solution, and when it exceeds 10 μm, it is not preferable from the viewpoint of uniformity of the photosensitive layer.
[0090]
As a method for dispersing the pigment, a known dispersion technique used in ink production, toner production, or the like can be used. Examples of the disperser include an ultrasonic disperser, a sand mill, an attritor, a pearl mill, a super mill, a ball mill, an impeller, a disperser, a KD mill, a colloid mill, a dynatron, a three-roll mill, and a pressure kneader. Details are described in "Latest Pigment Applied Technology" (CMC Publishing, 1986).
[0091]
The amount of these (B-2) infrared absorbers added is such that when used as the photosensitive layer of the lithographic printing plate precursor according to the invention, the optical density at the absorption maximum in the wavelength range of 760 nm to 1200 nm of the photosensitive layer is 0.00. It is preferable to be in the range of 1 to 3.0. When this range is deviated, the sensitivity tends to be low. Since the optical density is determined by the amount of the infrared absorber added and the thickness of the photosensitive layer, the predetermined optical density can be obtained by controlling both conditions. The optical density of the photosensitive layer can be measured by a conventional method. As a measuring method, for example, on a transparent or white support, a photosensitive layer having a thickness appropriately determined in a range where the coating amount after drying is necessary as a lithographic printing plate is formed, and a transmission type optical densitometer is used. Examples thereof include a method of measuring, a method of forming a photosensitive layer on a reflective support such as aluminum, and measuring a reflection density.
[0092]
[Binder polymer]
In the first negative photosensitive layer of the lithographic printing plate precursor according to the invention, a binder polymer is preferably used in combination for the purpose of improving the film properties of the photosensitive layer to be formed. As this binder polymer, a linear organic polymer is preferably used. As such a “linear organic polymer”, a known one can be arbitrarily used. Preferably, a linear organic polymer that is soluble or swellable in water or weak alkaline water is selected to enable water development or weak alkaline water development. The linear organic polymer is selected and used not only as a film-forming agent for forming a photosensitive layer but also according to its use as water, weak alkaline water or an organic solvent developer. For example, when a water-soluble organic polymer is used, water development becomes possible. Examples of such linear organic polymers include radical polymers having a carboxylic acid group in the side chain, such as JP-A-59-44615, JP-B-54-34327, JP-B-58-12777, and JP-B-54-25957. , JP 54-92723, JP 59-53836, JP 59-71048, ie, methacrylic acid copolymer, acrylic acid copolymer, itaconic acid copolymer. Examples thereof include a polymer, a crotonic acid copolymer, a maleic acid copolymer, and a partially esterified maleic acid copolymer. Similarly, there is an acidic cellulose derivative having a carboxylic acid group in the side chain. In addition, those obtained by adding a cyclic acid anhydride to a polymer having a hydroxyl group are useful.
[0093]
Among these, in particular, a (meth) acrylic resin having an ethylenically unsaturated double bond such as an allyl group, a (meth) acryloyl group, a (meth) acrylamide group, or a vinylphenyl group, and a carboxyl group in the side chain or A urethane resin is preferable because it is excellent in the balance of film strength, sensitivity, and developability.
[0094]
In addition, Japanese Patent Publication No. 7-2004, Japanese Patent Publication No. 7-120041, Japanese Patent Publication No. 7-120042, Japanese Patent Publication No. 8-12424, Japanese Patent Laid-Open No. 63-287944, Japanese Patent Laid-Open No. 63-287947, Japanese Patent Laid-Open No. Urethane-based binder polymers containing acid groups described in No. 271741, JP-A-11-352691 and the like are very excellent in strength, and are advantageous in terms of printing durability and suitability for low exposure.
[0095]
In addition, polyvinyl pyrrolidone, polyethylene oxide, and the like are useful as the water-soluble linear organic polymer. In order to increase the strength of the cured film, alcohol-soluble nylon, polyether of 2,2-bis- (4-hydroxyphenyl) -propane and epichlorohydrin, and the like are also useful.
[0096]
The mass average molecular weight of the polymer used in the present invention is preferably 5000 or more, more preferably 10,000 to 300,000, and the number average molecular weight is preferably 1000 or more, and more preferably 2000 to 2000 The range is 250,000. The polydispersity (mass average molecular weight / number average molecular weight) is preferably 1 or more, more preferably in the range of 1.1-10.
[0097]
These polymers may be random polymers, block polymers, graft polymers or the like, but are preferably random polymers.
[0098]
The polymer used in the present invention can be synthesized by a conventionally known method. Solvents used in the synthesis include, for example, tetrahydrofuran, ethylene dichloride, cyclohexanone, methyl ethyl ketone, acetone, methanol, ethanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, 2-methoxyethyl acetate, diethylene glycol dimethyl ether, 1-methoxy. Examples include 2-propanol, 1-methoxy-2-propyl acetate, N, N-dimethylformamide, N, N-dimethylacetamide, toluene, ethyl acetate, methyl lactate, ethyl lactate, dimethyl sulfoxide, and water. These solvents are used alone or in combination of two or more.
[0099]
As the radical polymerization initiator used for synthesizing the polymer used in the present invention, known compounds such as azo initiators and peroxide initiators can be used.
[0100]
The binder polymer used in the present invention may be used alone or in combination. These polymers are added to the photosensitive layer in a proportion of 20 to 95% by mass, preferably 30 to 90% by mass, based on the total solid content of the photosensitive layer coating solution. When the addition amount is less than 20% by mass, the strength of the image portion is insufficient when an image is formed. If the amount added exceeds 95% by mass, no image is formed. Moreover, it is preferable that the compound which has an ethylenically unsaturated double bond which can be radically polymerized, and a linear organic polymer shall be 1 / 9-7 / 3 by mass ratio.
[0101]
[Other ingredients]
In the first negative photosensitive layer of the lithographic printing plate precursor according to the invention, not only the above-mentioned components, but also various compounds as necessary are added to improve characteristics and handling properties as a lithographic printing plate precursor. It may be added.
For example, a dye having a large absorption in the visible light region can be used as an image colorant. Specifically, Oil Yellow # 101, Oil Yellow # 103, Oil Pink # 312, Oil Green BG, Oil Blue BOS, Oil Blue # 603, Oil Black BY, Oil Black BS, Oil Black T-505 (orientated chemistry) Kogyo Co., Ltd.), Victoria Pure Blue, Crystal Violet (CI42555), Methyl Violet (CI42535), Ethyl Violet, Rhodamine B (CI145170B), Malachite Green (CI42000), Methylene Blue (CI522015), etc. And dyes described in No. 293247. In addition, pigments such as phthalocyanine pigments, azo pigments, carbon black, and titanium oxide can also be suitably used.
[0102]
These colorants are preferably added since it is easy to distinguish an image area from a non-image area after image formation. The added amount is 0.01 to 10% by mass with respect to the total solid content of the photosensitive layer coating solution.
[0103]
In the present invention, a small amount of a thermal polymerization inhibitor is added in order to prevent unnecessary thermal polymerization of a compound having an ethylenically unsaturated double bond capable of radical polymerization during preparation or storage of the photosensitive layer coating solution. It is desirable to do. 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-tert-butylphenol), N-nitroso-N-phenylhydroxylamine aluminum salt and the like. The addition amount of the thermal polymerization inhibitor is preferably about 0.01% by mass to about 5% by mass with respect to the mass of the entire composition. If necessary, a higher fatty acid derivative such as behenic acid or behenic acid amide may be added to prevent polymerization inhibition due to oxygen, and it may be unevenly distributed on the surface of the photosensitive layer in the course of drying after coating. . The amount of the higher fatty acid derivative added is preferably about 0.1% by mass to about 10% by mass of the total composition.
[0104]
Further, in the photosensitive layer coating solution, nonionic surfactants as described in JP-A-62-251740 and JP-A-3-208514 are disclosed in order to broaden the processing stability against development conditions. Amphoteric surfactants such as those described in JP-A-59-121044 and JP-A-4-13149 can be added.
[0105]
Specific examples of the nonionic surfactant include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride, polyoxyethylene nonylphenyl ether and the like.
[0106]
Specific examples of amphoteric surfactants include alkyldi (aminoethyl) glycine, alkylpolyaminoethylglycine hydrochloride, 2-alkyl-N-carboxyethyl-N-hydroxyethylimidazolinium betaine, N-tetradecyl-N, N- Examples include betaine type (for example, trade name Amorgen K, manufactured by Dai-ichi Kogyo Co., Ltd.).
[0107]
The proportion of the nonionic surfactant and amphoteric surfactant in the photosensitive layer coating solution is preferably 0.05 to 15% by mass, more preferably 0.1 to 5% by mass. In addition, additives such as an adhesion improver, a development improver, an ultraviolet absorber, and a slipping agent can be suitably blended depending on the purpose.
[0108]
Furthermore, in the photosensitive layer coating solution according to the present invention, a plasticizer is 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.
[0109]
In order to produce the lithographic printing plate precursor according to the invention, the above-mentioned components necessary for the photosensitive layer coating solution are usually dissolved in a solvent and coated on a suitable support. 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 concentration of the above components (total solid content including additives) in the solvent is preferably 1 to 50% by mass.
[0110]
The coating amount (solid content) of the photosensitive layer on the support obtained after coating and drying varies depending on the application, but generally speaking, it is 0.5 to 5.0 g / m for lithographic printing plate precursors.²Is preferred. As the coating amount decreases, the apparent sensitivity increases, but the film properties of the photosensitive layer that performs the image recording function decrease.
Various methods can be used as the coating method, and examples thereof include bar coater coating, spin coating, spray coating, curtain coating, dip coating, air knife coating, blade coating, and roll coating.
[0111]
In the photosensitive layer coating solution according to the present invention, a surfactant for improving coating properties, for example, a fluorine-based surfactant described in JP-A-62-170950 can be added. . A preferable addition amount is 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass, based on the solid content of the material of the entire photosensitive layer.
[0112]
<Support>
The support used in the lithographic printing plate precursor according to the invention is not particularly limited as long as it is a dimensionally stable plate-like material. For example, paper, plastic (for example, polyethylene, polypropylene, polystyrene, etc.) is laminated. Paper, metal plates (eg, aluminum, zinc, copper, etc.), plastic films (eg, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, Examples thereof include polypropylene, polycarbonate, polyvinyl acetal, and the like, and paper or plastic film on which the above metal is laminated or vapor-deposited. A preferable support includes a polyester film or an aluminum plate.
[0113]
Among these, as the support used for the lithographic printing plate precursor according to the invention, it is preferable to use an aluminum plate that is lightweight and excellent in surface treatment, workability, and corrosion resistance. As the aluminum material used for this purpose, JIS 1050 material, JIS 1100 material, JIS 1070 material, Al-Mg alloy, Al-Mn alloy, Al-Mn-Mg alloy, Al-Zr alloy. Examples include Al—Mg—Si based alloys.
[0114]
A suitable aluminum plate is a pure aluminum plate or an alloy plate as described above containing aluminum as a main component and containing a trace amount of foreign elements, and may also be a plastic film on which aluminum is laminated or vapor-deposited. Examples of foreign elements contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel, and titanium. Content of the different element in an alloy is 10 mass% or less. As the aluminum plate, pure aluminum is preferable. However, since pure aluminum is difficult to manufacture in terms of refining technology, it may contain a slightly different element. Thus, the composition of the aluminum plate is not specified, and conventionally known and used aluminum plates can be appropriately used. The thickness of the aluminum plate is preferably about 0.1 to 0.6 mm, more preferably 0.15 to 0.4 mm, and particularly preferably 0.2 to 0.3 mm.
[0115]
Prior to roughening the aluminum plate, a degreasing treatment with, for example, a surfactant, an organic solvent, or an alkaline aqueous solution for removing rolling oil on the surface is performed as desired. The surface roughening treatment of the aluminum plate is performed by various methods. For example, a method of mechanically roughening, a method of electrochemically dissolving and roughening a surface, and a method of selectively dissolving a surface chemically. This is done by the method of 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. Further, as an electrochemical surface roughening method, there is a method of performing alternating current or direct current in hydrochloric acid or nitric acid electrolyte.
[0116]
The roughened aluminum plate is subjected to an alkali etching treatment and neutralization treatment as necessary, and then subjected to an anodization treatment to enhance the water retention and wear resistance of the surface as desired. The amount of anodized film by anodization is 1.0 g / m.²The above is preferable. The amount of anodized film is 1.0 g / m²If it is less than 1, the printing durability is insufficient, or when used as a lithographic printing plate, the non-image area is likely to be scratched, and so-called “scratches that cause ink to adhere to the scratched area during printing. “Stain” may easily occur. After the anodizing treatment, the surface of the aluminum is subjected to a hydrophilic treatment as necessary.
[0117]
In addition, such an aluminum support can be used after anodizing treatment, treatment with an organic acid or a salt thereof, or application of an undercoat layer coated with a photosensitive layer.
[0118]
An intermediate layer for improving the adhesion between the support and the photosensitive layer may be provided. In order to improve the adhesion, the intermediate layer is generally composed of a diazo resin, a phosphoric acid compound adsorbed on aluminum, for example. The thickness of the intermediate layer is arbitrary, and it must be a thickness capable of performing a uniform bond forming reaction with the upper photosensitive layer when exposed. Usually about 1 to 100 mg / m dry solid²The application rate of 5-40 mg / m is good²Is particularly good. The ratio of the diazo resin used in the intermediate layer is 30 to 100%, preferably 60 to 100%.
[0119]
After the above-described treatment or undercoating is applied to the support surface, a back coat is provided on the back surface of the support as necessary. As such a back coat, a coating layer made of a metal oxide obtained by hydrolysis and polycondensation of an organic polymer compound described in JP-A-5-45885 and an organic or inorganic metal compound described in JP-A-6-35174 is used. Preferably used.
[0120]
As a characteristic preferable as a support, the center line average roughness is 0.10 to 1.2 μm. If it is lower than 0.10 μm, the adhesion with the photosensitive layer is lowered, resulting in a significant reduction in printing durability. When it is larger than 1.2 μm, the stain property at the time of printing deteriorates. Further, the color density of the support is 0.15 to 0.65 as the reflection density value. If the density is whiter than 0.15, the halation at the time of image exposure is too strong, which hinders image formation. In the case of a blacker color, it is difficult to see the image in the plate inspection work after development, and the plate inspection property is extremely poor.
[0121]
As described above, on the support obtained by carrying out the predetermined treatment, the first and second negative photosensitive layers described above, and further any other optional such as a surface protective layer, a back coat layer, etc. By forming this layer, the negative lithographic printing plate precursor of the present invention can be obtained.
[0122]
<Infrared laser exposure>
The lithographic printing plate precursor according to the invention is image-recorded by infrared laser exposure. In the present invention, image exposure is preferably performed by a solid-state laser and a semiconductor laser that emit infrared rays having a wavelength of 760 nm to 1200 nm. The laser output is preferably 100 mW or more, and a multi-beam laser device is preferably used in order to shorten the exposure time. The exposure time per pixel is preferably within 20 μsec. The energy applied to the recording material is 10 to 300 mJ / cm.²It is preferable that If the exposure energy is too low, curing of the photosensitive layer may not proceed sufficiently. If the exposure energy is too high, the photosensitive layer may be laser ablated and the image may be damaged.
[0123]
The exposure in the present invention is performed by overlapping the light beams of the light sources. Overlap means that the sub-scanning pitch width is smaller than the beam diameter. The overlap can be expressed quantitatively by FWHM / sub-scanning pitch width (overlap coefficient), for example, when the beam diameter is expressed by the half width (FWHM) of the beam intensity. In the present invention, the overlap coefficient is preferably 0.1 or more.
[0124]
The scanning method of the light source of the exposure apparatus used in the present invention is not particularly limited, and a cylindrical outer surface scanning method, a cylindrical inner surface scanning method, a planar scanning method, or the like can be used. The channel of the light source may be a single channel or a multi-channel, but in the case of a cylindrical outer surface system, a multi-channel is preferably used.
[0125]
<Development>
As the developer and replenisher used for the development and plate making of the lithographic printing plate precursor according to the invention, conventionally known alkaline aqueous solutions can be used. By measuring the capacitance value increase rate ratio using the alkaline aqueous solution used as the developer as a model solution, it is possible to predict the discrimination of the developer in the photosensitive layer, and the capacitance value increase rate. If the ratio is 0.7, good discrimination is obtained and the halftone dot limitability is remarkably improved.
For example, sodium silicate, potassium, tribasic sodium phosphate, potassium, ammonium, dibasic sodium phosphate, potassium, ammonium, sodium carbonate, potassium, ammonium, sodium bicarbonate, potassium, Examples include inorganic alkali salts such as ammonium, sodium borate, potassium, ammonium, sodium hydroxide, ammonium, potassium, and lithium. Moreover, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, Organic alkali agents such as ethyleneimine, ethylenediamine, and pyridine are also used. These alkali agents are used alone or in combination of two or more.
[0126]
Among these alkali agents, particularly preferred developers are aqueous silicate solutions such as sodium silicate and potassium silicate. The reason is silicon oxide SiO which is a component of silicate.₂And alkali metal oxide M₂This is because the developability can be adjusted by the ratio and concentration of O. For example, alkali metal silicates described in JP-A No. 54-62004 and JP-B No. 57-7427 are effective. Used for.
[0127]
When developing using an automatic developing machine, an aqueous solution (replenisher) having a higher alkali strength than the developer is added to the developer so that a large amount of PS can be obtained without replacing the developer in the developer tank for a long time. It is known that plates can be processed. This replenishment method is also preferably applied in the present invention. Various surfactants and organic solvents can be added to the developer and replenisher as necessary for the purpose of promoting and suppressing developability, dispersing development residue, and improving ink affinity of the printing plate image area.
[0128]
Preferred surfactants include anionic, cationic, nonionic and amphoteric surfactants. If necessary, the developer and replenisher may contain reducing agents such as hydroquinone, resorcin, sulfurous acid, bisulfite, and other inorganic acids such as sodium salts and potassium salts, organic carboxylic acids, antifoaming agents, and hard water softeners. It can also be added.
[0129]
The printing plate developed using the developer and the replenisher is post-treated with water-washing water, a rinsing solution containing a surfactant and the like, a desensitizing solution containing gum arabic and starch derivatives. As the post-treatment when the image recording material of the present invention is used as a printing plate, these treatments can be used in various combinations.
[0130]
An automatic developing machine generally consists of a developing section and a post-processing section. It consists of an apparatus that transports the printing plate material, each processing liquid tank, and a spray device. The exposed printing plate is pumped up while being transported horizontally. Each processing solution is sprayed from a spray nozzle for development processing. In addition, recently, a method is also known in which a printing plate material is immersed and conveyed in a processing liquid tank filled with a processing liquid by a submerged guide roll or the like. In such automatic processing, each processing solution can be processed while being supplemented with a replenisher according to the processing amount, operating time, and the like. In addition, the electrical conductivity can be detected by a sensor and replenished automatically. In addition, a so-called disposable processing method in which processing is performed with a substantially unused processing solution can also be applied. According to the method of the present invention, there is no fear of deterioration in developability due to carbon dioxide gas over time and printing durability due to the developer, so the method of the present invention is suitable for any of these automatic processors. Can be applied to.
[0131]
The lithographic printing plate obtained as described above can be subjected to a printing process after applying a desensitized gum if desired. However, if it is desired to obtain a lithographic printing plate with a higher printing durability, a burning treatment is performed. Is given.
In the case of burning a lithographic printing plate, before burning, an adjustment as described in JP-B-61-2518, JP-A-55-28062, JP-A-62-31859, JP-A-61-159655 is used. It is preferable to treat with a surface liquid.
[0132]
As its method, with a sponge or absorbent cotton soaked with the surface-adjusting liquid, it is applied onto a lithographic printing plate, or a method in which the printing plate is immersed and applied in a vat filled with the surface-adjusting liquid, Application by an automatic coater is applied. Further, it is more preferable to make the coating amount uniform with a squeegee or a squeegee roller after coating. The coating amount of the surface conditioning liquid is generally 0.03 to 0.8 g / m²(Dry mass) is appropriate.
[0133]
The lithographic printing plate coated with the surface conditioning liquid is dried if necessary and then heated to a high temperature with a burning processor (for example, burning processor BP-1300 sold by Fuji Photo Film Co., Ltd.). The In this case, the heating temperature and time are in the range of 180 to 300 ° C. and preferably in the range of 1 to 20 minutes, although depending on the type of components forming the image.
[0134]
The burned lithographic printing plate can be subjected to conventional treatments such as washing and gumming as needed, but a surface-conditioning solution containing a water-soluble polymer compound or the like is used. In such a case, a so-called desensitizing treatment such as gumming can be omitted.
[0135]
Since the lithographic printing plate of the present invention is excellent in printing durability, a large number of high-quality prints can be obtained when printing is performed on an offset printing machine or the like.
[0136]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not restrict | limited to these.
[0137]
[Comparative Example A]
(Create support)
  A molten metal of JIS A 1050 alloy containing 99.5% or more of aluminum and Fe 0.30%, Si 0.10%, Ti 0.02% and Cu 0.013% was subjected to cleaning treatment 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.
  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 thickness 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.
[0138]
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% sodium aluminate aqueous solution at 50 ° C. for 30 seconds, and neutralization and smut removal treatment were carried out with a 30% sulfuric acid aqueous solution at 50 ° C. for 30 seconds.
[0139]
Next, in order to improve the adhesion between the support and the photosensitive 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% nitric acid and 0.5% aluminum nitrate is kept 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: 1²Electrolytic graining was performed by giving Thereafter, etching treatment was performed with a 10% sodium aluminate aqueous solution at 50 ° C. for 30 seconds, and neutralization and smut removal treatment were performed with a 30% sulfuric acid aqueous solution at 50 ° C. for 30 seconds.
[0140]
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% sulfuric acid aqueous solution was used as the electrolyte at 35 ° C., and the aluminum web was carried through the electrolyte while the indirect power supply cell was used.²2.5 g / m by electrolytic treatment with direct current²An anodic oxide film was prepared. Ra (centerline surface roughness) of the support prepared as described above was 0.5 μm.
[0141]
(Formation of the first negative photosensitive layer)
Next, the following first negative photosensitive layer coating solution 1 is prepared, applied to the aluminum plate subjected to the above surface treatment using a wire bar, and dried at 115 ° C. for 45 seconds with a hot air dryer. Thus, a first negative photosensitive layer was formed. The coating amount after drying is 1.3 g / m²It was in the range.
[0142]
<First negative photosensitive layer coating solution 1>
・ Infrared absorber [IR-1] (structure shown below) 0.1 g
-Radical generator [OS-1] (the following structure) 0.15 g
・ Polymerizable compound 1g
(A mixture of dipentaerythritol hexaacrylate and dipentaerythritol pentaacrylate, trade name: DPHA, manufactured by Nippon Kayaku)
・ Binder polymer (P-1) 1g
・ Ethyl violet Cl salt 0.06g
・ Fluorine-based surfactant 0.01g
(Megafuck KF309, manufactured by Dainippon Ink & Chemicals, Inc.)
・ Methyl ethyl ketone 14.0g
・ Methanol 6.5g
・ 1-methoxy-2-propanol 10.0g
[0143]
The structures of the infrared absorber [IR- [1]] and the onium salt [OS-1] used in the photosensitive layer coating solution 1 are shown below.
[0144]
Embedded image

[0145]
Moreover, the synthesis | combining method of the binder polymer (P-1) used for the photosensitive layer coating liquid 1 is shown below.
70 g of N, N-dimethylacetamide was placed in a 1000 ml three-necked flask and heated to 70 ° C. under a nitrogen stream. Compound (A-1) having the following structure: 33.5 g, methacrylamide: 6.8 g, methyl methacrylate: 12.0 g, methacrylic acid: 6.9 g, V-59 (manufactured by Wako Pure Chemical Industries): 0.538 g A 70 g solution of N, N-dimethylacetamide was added dropwise over 2.5 hours. After completion of dropping, the mixture was heated to 90 and further stirred for 2 hours. After the reaction solution was cooled to room temperature, it was poured into 3.5 L of water to precipitate a polymer compound. The precipitated polymer compound was collected by filtration, washed with water and dried to obtain 48.5 g of a polymer compound. As a result of measuring the mass average molecular weight of the obtained polymer compound by gel permeation chromatography (GPC) using polystyrene as a standard substance, it was 124,000. Further, when the acid value was determined by titration, it was 1.30 meq / g (calculated value: 1.35 meq / g), and it was confirmed that the polymerization was normally performed.
The obtained polymer compound: 26.0 g and p-methoxyphenol: 0.1 g were placed in a 200 ml three-necked flask and dissolved in N, N-dimethylacetamide: 60 g. After dissolution, the mixture was cooled in an ice bath containing ice water. After the temperature of the liquid mixture reached 5 ° C. or lower, 1,8-diazabicyclo [5.4.0] -7-undecene (DBU): 30.4 g was added dropwise using a dropping funnel over 1 hour. After completion of the dropwise addition, the ice bath was removed and the mixture was further stirred for 8 hours. The reaction solution was poured into 2 L of water in which 17 ml of concentrated hydrochloric acid was dissolved to precipitate a binder polymer (P-1). The precipitated binder polymer (P-1) was collected by filtration, washed with water and dried to obtain 18.2 g of a polymer compound. When H-NMR of the obtained binder polymer (P-1) was measured, it was confirmed that 100% of the side chain groups derived from the compound (A-1) were converted to ethylene methacrylate groups. The mass average molecular weight measured by gel permeation chromatography (GPC) using polystyrene as a standard substance was 114,000. Furthermore, when the acid value was determined by titration, it was 0.9 meq / g (calculated value 0.8 meq / g).
[0146]
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[0147]
(Formation of second negative photosensitive layer)
Next, the following second negative photosensitive layer coating solution 1 is prepared, applied onto the first negative photosensitive layer using a wire bar, and dried at 60 ° C. for 120 seconds using a hot air dryer. Then, a second negative photosensitive layer was formed. The coating amount after drying is 0.5 g / m²Met.
[0148]
<Second negative photosensitive layer coating solution 1>
・ Ion exchange water 90.6g
-Thermal fusion fine particle dispersion (1) 9.09 g
[0149]
(Preparation of thermal fusion fine particle dispersion (1))
Styrene: 100 g, water: 200 g, surfactant XL-102F (manufactured by Lion Corporation) (4.7% aqueous solution): 10 g was placed in a three-necked flask and heated to 80 ° C. while injecting nitrogen. Then, after stirring for about 30 minutes, K₂S₂O₈1 g was added, and emulsion polymerization was carried out at 80 ° C. for 6 hours to obtain resin particles (polystyrene) having a particle size of about 1 μm. Then, a polystyrene particle dispersion having a solid content concentration of 33% was prepared.
[0150]
[exposure]
The obtained negative lithographic printing plate precursor was output by a Creo Trendsetter 3244VFS equipped with a water-cooled 40 W infrared semiconductor laser, output 9 W, outer drum rotation speed 210 rpm, plate energy 100 mJ / cm.², Exposure was performed under conditions of a resolution of 175 lpi.
[0151]
[Development processing]
The exposed lithographic printing plate precursor was developed using an automatic processor LP-940H manufactured by Fuji Photo Film Co., Ltd.
The following model developer was used as the developer, and the temperature of the developer bath was 30 ° C. As the finisher, a 1: 1 water dilution of FN-6 manufactured by Fuji Photo Film Co., Ltd. was used.
[0152]
[Model developer]
・ 0.7g potassium hydroxide
-Potassium carbonate 1.7g
・ Polyethylene glycol mononaphthyl ether 53g
・ Ethylenediaminetetraacetic acid tetrasodium salt 1.5g
・ 955g water
[0153]
[printing]
The lithographic printing plate thus obtained was printed using a printing machine SOR-M manufactured by Heidelberg.
[0154]
[Evaluation]
1. Evaluation of developer penetration
The model developer was adjusted, and the developer permeability ratio was calculated.
Cover the exposed solid image with tape with a 1cm x 1cm window (made of Scotch tape 3M) and immerse it in a container containing the counter electrode (using the support described above) and the above model solution (25 ° C). The electrostatic capacitance value when 1 V between the electrodes and a 1 kHz sine wave alternating current were applied was measured every second for LCR meter (3522-50, manufactured by HIoki Corporation). Similarly, the unexposed area was also measured and the ratio was calculated.
[0155]
2. Evaluation of printing durability
In the printing process, how many sheets can be printed while maintaining a sufficient ink density was visually evaluated. The results are shown in Table 1.
[0156]
[Comparative Example Bas well asComparative Example C]
  Comparative Example AThe coating amount after drying of the second negative photosensitive layer was 1 g / m, respectively.²3g / m²Other than that,Comparative Example AA lithographic printing plate precursor was prepared in the same manner as described above. Then, the obtained lithographic printing plate precursorComparative Example AIn the same manner, the same evaluation was performed for exposure and development. The results are shown in Table 1.
[0157]
[Example1]
  Comparative Example AExcept that the second negative photosensitive layer was formed as follows:Comparative Example AA lithographic printing plate precursor was prepared in the same manner as described above.
[0158]
(Formation of second negative photosensitive layer)
  Next, the following second negative photosensitive layer coating solution 2 is prepared,Comparative Example AA second negative photosensitive layer was formed by applying a wire bar on the same first negative photosensitive layer as in Example 1 and drying at 60 ° C. for 120 seconds with a hot air dryer. The coating amount after drying is 0.5 g / m²Met.
[0159]
<Second negative photosensitive layer coating solution 2>
・ Ion-exchanged water 84.2g
Hydrophobic compound-containing microcapsule dispersion (1) 15.8 g
・ Polyvinyl alcohol 2g
[0160]
(Preparation of hydrophobic compound-containing microcapsule dispersion (1))
As an oil layer component, epoxy resin Epicoat 1004 (manufactured by oiled shell epoxy): 30 g, 50% ethyl acetate solution D110N of trimethylolpropane and xylene diisocyanate adduct (manufactured by Takeda Pharmaceutical): 30 g, photothermal conversion agent ([IR- ▲ 2 ▼], the following structure): 0.3 g, anionic surfactant Piionin A41C (manufactured by Takemoto Yushi): 0.5 g was dissolved in ethyl acetate: 90 g. As an aqueous layer component, PVA217EE (made by Kuraray) 2% aqueous solution: 200 g was prepared. The oil layer component and the water layer component were emulsified at 10,000 rpm using a homogenizer. The thus obtained microcapsule liquid had a solid content concentration of 19% and an average particle size of 0.3 μm.
[0161]
Embedded image

[0162]
[Exposure, development, and evaluation]
  The resulting lithographic printing plate precursorComparative Example AIn the same manner, the same evaluation was performed for exposure and development. The evaluation results are shown in Table 1.
[0163]
[Example2as well asExample 3]
  Example1The coating amount after drying of the second negative photosensitive layer was 1 g / m, respectively.²3g / m²Other than replacing with, Example1A lithographic printing plate precursor was prepared in the same manner as described above. Then, the obtained lithographic printing plate precursorComparative Example AIn the same manner, the same evaluation was performed for exposure and development. The evaluation results are shown in Table 1.
[0164]
[Example4]
  Comparative Example AExcept that the second negative photosensitive layer was formed as follows:Comparative Example AA lithographic printing plate precursor was prepared in the same manner as described above.
[0165]
(Formation of second negative photosensitive layer)
  Next, the following second negative photosensitive layer coating solution 3 is prepared,Comparative Example AA second negative photosensitive layer was formed by applying a wire bar on the same first negative photosensitive layer as in Example 1 and drying at 60 ° C. for 120 seconds with a hot air dryer. The coating amount after drying is 0.5 g / m²Met.
[0166]
<Second negative photosensitive layer coating solution 3>
・ Ion exchange water 82g
・ Polar conversion polymer (P-2) 2.0g
・ Photothermal conversion material [IR-3] (structure below) 0.6g
[0167]
Embedded image

[0168]
(Synthesis of polar conversion polymer (P-2))
Water: 1000 ml, p-styrenesulfonyl chloride: 100 g, sodium sulfite: 126 g, sodium carbonate: 106 g, a catalytic amount of hydroquinone were placed in a 3 liter three-necked flask, and the mixture was heated and stirred while maintaining an internal temperature of 45 ° C. After 1 hour, sodium chloroacetate (174 g) and potassium iodide (12 g) were added, the internal temperature was raised to 70 ° C., and the mixture was further stirred for 5 hours. After the reaction, the mixture was naturally cooled to room temperature, and concentrated hydrochloric acid was added dropwise to pH 1 in an ice bath, and solid precipitation was observed. The precipitate was filtered, sufficiently washed with water and dried to obtain 95 g of white powder. The purity of this product was 99% by HPLC measurement.
Subsequently, the obtained white powder: 20 g and dimethylacetamide: 40 g were put into a 200 ml three-necked flask, and 2,2′-azobis (2,4-dimethylvaleronitrile): 0.2 g was added under a nitrogen stream at 65 ° C. added. The mixture was kept at the same temperature and stirred for 6 hours. Thereafter, the temperature was returned to room temperature, and reprecipitation was performed in 1 liter of water to obtain a polymer solid. It was found by GPC that the polymer had a mass average molecular weight of 12,000.
8.5 g of sodium methoxide (28% methanol solution): was slowly added dropwise to the obtained polymer (10 g) and methanol (44 ml) in an ice bath. After stirring for 5 minutes, the precipitated solid was filtered and dried to obtain 9.1 g of a polar conversion polymer (P-2).
[0169]
[Exposure, development, and evaluation]
  The resulting lithographic printing plate precursorComparative Example AIn the same manner, the same evaluation was performed for exposure and development. The evaluation results are shown in Table 1.
[0170]
[Example5as well asExample 6]
  Example4The coating amount after drying of the second negative photosensitive layer was 1 g / m, respectively.²3g / m²Other than replacing with, Example4A lithographic printing plate precursor was prepared in the same manner as described above. Then, the obtained lithographic printing plate precursorComparative Example ALikeComparative Example AIn the same manner, the same evaluation was performed for exposure and development. The evaluation results are shown in Table 1.
[0171]
[Comparative Example 1]
  Comparative Example AIn, except that the second negative photosensitive layer was not formed, only the first negative photosensitive layer was formed,Comparative Example AA lithographic printing plate precursor was prepared in the same manner as described above. Then, the obtained lithographic printing plate precursorComparative Example AIn the same manner, the same evaluation was performed for exposure and development. The evaluation results are shown in Table 1.
[0172]
[Comparative Example 2]
  Comparative Example AExcept that the second negative photosensitive layer was formed as follows:Comparative Example AA lithographic printing plate precursor was prepared in the same manner as described above.
[0173]
(Formation of second negative photosensitive layer)
  Next, the following second negative photosensitive layer coating solution 4 is prepared,Comparative Example AA second negative photosensitive layer was formed by applying a wire bar on the same first negative photosensitive layer as in Example 1 and drying at 60 ° C. for 120 seconds with a hot air dryer. The coating amount after drying is 1 g / m²Met.
[0174]
<Second negative photosensitive layer coating solution 4>
・ Ion exchange water 90.6g
・ Polyacrylic acid (molecular weight, 20,000) 9.09 g
・ Photothermal conversion material [IR-3] (above structure) 0.3g
[0175]
[Exposure, development, and evaluation]
  The resulting lithographic printing plate precursorComparative Example AIn the same manner, the same evaluation was performed for exposure and development. The evaluation results are shown in Table 1.
[0176]
[Table 1]

[0177]
  According to Table 1, Examples 1 to6The lithographic printing plate precursor of FIG. 1 has a lower developer permeability ratio and excellent printing durability than the lithographic printing plate precursors of Comparative Examples 1 and 2, regardless of the coating amount of the second negative photosensitive layer. It became clear.
[0178]
【The invention's effect】
According to the present invention, a negative lithographic printing plate precursor that is capable of direct plate making by recording from digital data such as a computer using a solid-state laser and a semiconductor laser that emits infrared rays and that has excellent printing durability. Can be provided.

Claims (5)

The support comprises at least (A) a polymerizable compound having an ethylenically unsaturated double bond, and (B) an infrared absorber and a radical polymerization initiator, and has a function of generating radicals by exposure with an infrared laser. A first negative photosensitive layer containing a polymerization initiation system , a hydrophobic compound-containing microcapsule, and at least one of a hydrophilic resin that is hydrophobized by heat. A lithographic printing plate precursor comprising a second negative photosensitive layer in this order.   2. The lithographic printing plate precursor as claimed in claim 1, wherein the second negative photosensitive layer contains a hydrophobic compound-containing microcapsule.   The lithographic printing plate precursor as claimed in claim 2, wherein the hydrophobic compound in the hydrophobic compound-containing microcapsule is a compound that undergoes a crosslinking reaction by heat.   The lithographic printing plate precursor as claimed in claim 1, wherein the second negative photosensitive layer contains a hydrophilic resin that is hydrophobized by heat. Said second film by weight of the negative photosensitive layer, the lithographic printing plate precursor as claimed in any one of claims 1 to 4, characterized in that a 0.1 to 1.5 g / m ^2.