JP4417528B2 - Positive photosensitive composition and positive photosensitive lithographic printing plate - Google Patents

Description

【００１７】
〔式(Ia)、(Ib)、及び(Ic)中、Ｒ¹ 及びＲ² は各々独立して、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、置換基を有していてもよいアルキニル基、又は置換基を有していてもよいフェニル基を示し、Ｌ¹ は置換基を有していてもよいトリ、ペンタ、又はヘプタメチン基を示し、該ペンタ又はヘプタメチン基上の２つの置換基が互いに連結して炭素数５〜７のシクロアルケン環を形成していてもよく、キノリン環は置換基を有していてもよく、その場合、隣接する２つの置換基が互いに連結して縮合ベンゼン環を形成していてもよい。Ｘ^- は対アニオンを示す。〕
【００１８】
ここで、式(Ia)、(Ib)、及び(Ic)中のＲ¹ 及びＲ² における置換基としては、アルコキシ基、フェノキシ基、ヒドロキシ基、又はフェニル基等が挙げられ、Ｌ¹ における置換基としては、アルキル基、アミノ基、又はハロゲン原子等が挙げられ、キノリン環における置換基としては、アルキル基、アルコキシ基、ニトロ基、又はハロゲン原子等が挙げられる。
【００１９】
又、インドール系、及びベンゾチアゾール系色素としては、特に、下記一般式(II)で表されるものが好ましい。
【００２０】
【化２】

【００２１】
〔式(II)中、Ｙ¹ 及びＹ² は各々独立して、ジアルキルメチレン基又は硫黄原子を示し、Ｒ³ 及びＲ⁴ は各々独立して、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、置換基を有していてもよいアルキニル基、又は置換基を有していてもよいフェニル基を示し、Ｌ² は置換基を有していてもよいトリ、ペンタ、又はヘプタメチン基を示し、該ペンタ又はヘプタメチン基上の２つの置換基が互いに連結して炭素数５〜７のシクロアルケン環を形成していてもよく、縮合ベンゼン環は置換基を有していてもよく、その場合、隣接する２つの置換基が互いに連結して縮合ベンゼン環を形成していてもよい。Ｘ^- は対アニオンを示す。〕
【００２２】
ここで、式(II)中のＲ³ 及びＲ⁴ における置換基としては、アルコキシ基、フェノキシ基、ヒドロキシ基、又はフェニル基等が挙げられ、Ｌ² における置換基としては、アルキル基、アミノ基、又はハロゲン原子等が挙げられ、ベンゼン環における置換基としては、アルキル基、アルコキシ基、ニトロ基、又はハロゲン原子等が挙げられる。
【００２３】
又、アミノベンゼン系色素としては、特に、下記一般式(III) で表されるものが好ましい。
【００２４】
【化３】

【００２５】
〔式(III) 中、Ｒ⁵ 、Ｒ⁶ 、Ｒ⁷ 、及びＲ⁸ は各々独立して、アルキル基を示し、Ｒ⁹ 及びＲ¹⁰は各々独立して、置換基を有していてもよいアリール基、フリル基、又はチエニル基を示し、Ｌ³ は置換基を有していてもよいモノ、トリ、又はペンタメチン基を示し、該トリ又はペンタメチン基上の２つの置換基が互いに連結して炭素数５〜７のシクロアルケン環を形成していてもよく、キノン環及びベンゼン環は置換基を有していてもよい。Ｘ^- は対アニオンを示す。〕
【００２６】
ここで、式(III) 中のＲ⁹ 及びＲ¹⁰として具体的には、フェニル基、１−ナフチル基、２−ナフチル基、２−フリル基、３−フリル基、２−チエニル基、３−チエニル基等が挙げられ、それらの置換基としては、アルキル基、アルコキシ基、ジアルキルアミノ基、ヒドロキシ基、又はハロゲン原子等が挙げられ、Ｌ³ における置換基としては、アルキル基、アミノ基、又はハロゲン原子等が挙げられ、キノン環及びベンゼン環における置換基としては、アルキル基、アルコキシ基、ニトロ基、又はハロゲン原子等が挙げられる。
【００２７】
又、ピリリウム系、及びチアピリリウム系色素としては、特に、下記一般式(IVa) 、(IVb) 、又は(IVc) で表されるものが好ましい。
【００２８】
【化４】

【００２９】
〔式(IVa) 、(IVb) 、及び(IVc) 中、Ｙ³ 及びＹ⁴ は各々独立して、酸素原子又は硫黄原子を示し、Ｒ¹¹、Ｒ¹²、Ｒ¹³、及びＲ¹⁴は各々独立して、水素原子又はアルキル基、又は、Ｒ¹¹とＲ¹³、及びＲ¹²とＲ¹⁴が互いに連結して炭素数５又は６のシクロアルケン環を形成していてもよく、Ｌ⁴ は置換基を有していてもよいモノ、トリ、又はペンタメチン基を示し、該トリ又はペンタメチン基上の２つの置換基が互いに連結して炭素数５〜７のシクロアルケン環を形成していてもよく、ピリリウム環及びチアピリリウム環は置換基を有していてもよく、その場合、隣接する２つの置換基が互いに連結して縮合ベンゼン環を形成していてもよい。Ｘ^- は対アニオンを示す。〕
【００３０】
ここで、式(IVa) 、(IVa) 、及び(IVc) 中のＬ⁴ における置換基としては、アルキル基、アミノ基、又はハロゲン原子等が挙げられ、ピリリウム環及びチアピリリウム環における置換基としては、フェニル基、ナフチル基等のアリール基等が挙げられる。
【００３１】
更に、アミニウム系、及びイモニウム系色素としては、Ｎ，Ｎ−ジアリールイミニウム塩骨格を少なくとも１個有する下記一般式(Va)、又は(Vb)で表されるものが好ましい。
【００３２】
【化５】

【００３３】
〔式(Va)、及び(Vb)中、Ｒ¹⁵、Ｒ¹⁶、Ｒ¹⁷、及びＲ¹⁸は各々独立して、水素原子、ハロゲン原子、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、置換基を有していてもよいアルキニル基、又は置換基を有していてもよいアルコキシ基を示し、Ｒ¹⁹、及びＲ²⁰は各々独立して、置換基を有していてもよいアルキル基、置換基を有していてもよいアルケニル基、置換基を有していてもよいアルキニル基、置換基を有していてもよいアルコキシ基、置換基を有していてもよいアシルオキシ基、又は置換基を有していてもよいフェニル基を示し、ベンゼン環及びイミノキノン環は置換基を有していてもよい。Ｘ^- は対アニオンを示す。尚、式(Vb)中の電子結合（─）は他の電子結合との共鳴状態を示す。〕
【００３４】
ここで、式(Va)、及び(Vb)中のＲ¹⁵、Ｒ¹⁶、Ｒ¹⁷、Ｒ¹⁸、Ｒ¹⁹、及びＲ²⁰における置換基としては、アルキル基、アルコキシ基、カルボキシ基、アシルオキシ基、アルコキシカルボニル基、ヒドロキシ基、アミノ基、アルキルアミノ基、ハロゲン化アルキル基、又はハロゲン原子等が挙げられ、ベンゼン環及びイミノキノン環における置換基としては、アルキル基、アルコキシ基、アシル基、ニトロ基、又はハロゲン原子等が挙げられる。
【００３５】
これらのアミニウム系、及びイモニウム系色素の中では、前記一般式(Va)、及び(Vb)中のＲ¹⁵、Ｒ¹⁶、Ｒ¹⁷、及びＲ¹⁸がアルキル基で、Ｒ¹⁹、及びＲ²⁰もアルキル基であるか、Ｒ¹⁹、及びＲ²⁰がジアルキルアミノ基を置換基として有するフェニル基であるものが、特に好ましい。
【００３６】
尚、前記一般式(Ia 〜c)、(II)、(III) 、(IVa〜c)、及び(Va 〜b)における対アニオンＸ^- としては、例えば、Ｃｌ^- 、Ｂｒ^- 、Ｉ^- 、ＣｌＯ₄ ^- 、ＰＦ₆ ^- 、ＳｂＦ₆ ^- 、及び、ＢＦ₄ ^- 等の無機硼酸等の無機酸アニオン、ベンゼンスルホン酸、ｐ−トルエンスルホン酸、ナフタレンスルホン酸、酢酸、及び、メチル、エチル、プロピル、ブチル、フェニル、メトキシフェニル、ナフチル、ジフルオロフェニル、ペンタフルオロフェニル、チエニル、ピロリル等の有機基を有する有機硼酸等の有機酸アニオンを挙げることができる。
【００３７】
以上、前記一般式(Ia 〜c)で表されるキノリン系色素、前記一般式(II)で表されるインドール系又はベンゾチアゾール系色素、前記一般式(III) で表されるアミノベンゼン系色素、前記一般式(IVa〜c)で表されるピリリウム系又はチアピリリウム系色素、及び前記一般式(Va 〜b)で表されるアミニウム系又はイモニウム系色素の各具体例を以下に示す。
【００３８】
【化６】

【００３９】
【化７】

【００４０】
【化８】

【００４１】
【化９】

【００４２】
【化１０】

【００４３】
【化１１】

【００４４】
【化１２】

【００４５】
【化１３】

【００４６】
【化１４】

【００４７】
【化１５】

【００４８】
【化１６】

【００４９】
又、本発明のポジ型感光性組成物におけるノボラック樹脂は、例えば、フェノール、ｏ−クレゾール、ｍ−クレゾール、ｐ−クレゾール、２，５−キシレノール、３，５−キシレノール、ｏ−エチルフェノール、ｍ−エチルフェノール、ｐ−エチルフェノール、プロピルフェノール、ｎ−ブチルフェノール、ｔｅｒｔ−ブチルフェノール、１−ナフトール、２−ナフトール、ピロカテコール、レゾルシノール、ハイドロキノン、ピロガロール、１，２，４−ベンゼントリオール、フロログルシノール、４，４’−ビフェニルジオール、２，２−ビス（４’−ヒドロキシフェニル）プロパン等のフェノール類の少なくとも１種を、酸性触媒下、例えば、ホルムアルデヒド、アセトアルデヒド、プロピオンアルデヒド、ベンズアルデヒド、フルフラール等のアルデヒド類（尚、ホルムアルデヒドに代えてパラホルムアルデヒドを、アセトアルデヒドに代えてパラアルデヒドを、用いてもよい。）、又は、アセトン、メチルエチルケトン、メチルイソブチルケトン等のケトン類、の少なくとも１種と重縮合させた樹脂であって、フェノール性水酸基含有アルカリ可溶性樹脂としてこの種感光性組成物のバインダー樹脂に慣用されているものである。
【００５０】
中で、本発明におけるノボラック樹脂は、ｏ−クレゾールが６０モル％以上を占めるフェノール類から構成されたものであることが必須であり、ｏ−クレゾールが７０モル％以上であるのが好ましい。又、ｏ−クレゾールは９５モル％以下であるのが好ましく、９０モル％以下であるのが更に好ましい。ｏ−クレゾールの占める割合が前記範囲未満では、感光性組成物としての現像ラチチュードを広いものとはし得ず、一方、前記範囲超過では、アルカリ現像液に対する溶解性が低下する傾向となる。一方、残余のフェノール類としては、フェノール、ｍ−クレゾール、ｐ−クレゾール等が挙げられるが、フェノールが５モル％以上、更には１０モル％以上を占めるのが好ましく、フェノールは３０モル％以下であると現像ラチュードがより広いものとなり好ましい。
【００５１】
尚、従来のｏ−キノンジアジド基含有化合物等を含む紫外線露光用のポジ型感光性組成物におけるバインダー樹脂としてのノボラック樹脂を構成するフェノール類として、ｏ−クレゾールを用いた場合、その占める割合が高くなるに従ってアルカリ現像液に対する溶解性が低下する傾向となるためアルカリ現像タイプのポジ型感光性組成物には不向きとされていたのに対して、光熱変換物質とノボラック樹脂を含む本発明のポジ型感光性組成物において、フェノール類としてのｏ−クレゾールを、しかもかなり高い割合で用いたノボラック樹脂が、本発明の目的を達成し得ることは、全く予期できないことであった。
【００５２】
尚、本発明における前記ノボラック樹脂は、ゲルパーミエーションクロマトグラフィー測定によるポリスチレン換算の重量平均分子量が、５０００〜１５０００のものであるのが好ましく、６０００〜１２０００のものであるのが特に好ましい。
【００５３】
本発明のポジ型感光性組成物は、前記光熱変換物質と前記ノボラック樹脂を基本組成とし、両者の合計量に対するそれぞれの含有割合は、通常、前者光熱変換物質が０．５〜５０重量％、後者ノボラック樹脂が９９．５〜５０重量％であり好ましくは前者が１〜４０重量％、後者が９９〜６０重量％であり更に好ましくは、前者が２〜３０重量％、後者が９８〜７０重量％であり、特に、前者が２〜１０重量％、後者が９８〜９０重量％であるのが特に好ましい。
【００５４】
尚、本発明のポジ型感光性組成物は、前記光熱変換物質及びノボラック樹脂の他に、本発明の性能を損わない範囲で、ノボラック樹脂以外のアルカリ可溶性樹脂、例えば、アクリル酸及び／又はメタクリル酸を共重合成分とする、いわゆるアクリル系樹脂等を含有することも可能である。
又、本発明のポジ型感光性組成物には、前記光熱変換物質、及び前記ノボラック樹脂の他に、露光部と非露光部のアルカリ現像液に対する溶解性の差を増大させる目的で、前記ノボラック樹脂と水素結合を形成して該樹脂の溶解性を低下させる機能を有し、かつ、近赤外線領域の光を殆ど吸収せず、近赤外線領域の光で分解されない溶解抑止剤が含有されていてもよい。
【００５５】
その溶解抑止剤としては、例えば、本願出願人による特開平１０−２６８５１２号公報に詳細に記載されているスルホン酸エステル、燐酸エステル、芳香族カルボン酸エステル、芳香族ジスルホン、カルボン酸無水物、芳香族ケトン、芳香族アルデヒド、芳香族アミン、芳香族エーテル等、同じく特開平１１−１９０９０３号明細書に詳細に記載されている、ラクトン骨格、Ｎ，Ｎ−ジアリールアミド骨格、ジアリールメチルイミノ骨格を有し着色剤を兼ねた酸発色性色素、同じく特願平１０−３４１４００号明細書に詳細に記載されている非イオン性界面活性剤等を挙げることができる。
【００５６】
本発明のポジ型感光性組成物における前記溶解抑止剤の含有割合は、０〜５０重量％であるのが好ましく、０〜３０重量％であるのが更に好ましく、０〜２０重量％であるのが特に好ましい。
【００５７】
又、本発明のポジ型感光性組成物には、必要に応じて、吸収極大（λ_max ）が７００ｎｍ以下であって前記光熱変換物質とは区別され、発色の原因がカチオン又はアニオンの非極在化によるイオン性色素、例えば、シアニン系色素、ピリリウム系色素、チアピリリウム系色素、スクアリリウム系色素、クロコニウム系色素、アズレニウム系色素、ジフェニルメタン系色素、トリフェニルメタン系色素、オキサジン系色素、アジン系色素、ピオローゲン色素、キサンテン系色素、ローダシアニン系色素、スチリル系色素等が含有されていてもよい。これらの中で好ましいものは、トリフェニルメチル基を部分構造として有するトリフェニルメタン系色素であり、具体的にＣ．Ｉ．Ｎｏ．で表すと、例えば、Ｃ．Ｉ．Ｂａｓｉｃ Ｖｉｏｌｅｔ ３（例えば、東京化成社製「Ｃｒｙｓｔａｌ Ｖｉｏｌｅｔ」等。）、Ｃ．Ｉ．Ｂａｓｉｃ Ｂｌｕｅ ５（例えば、住友化学工業社製「Ｐｒｉｍｏｃｙａｎｉｎｅ ＢＸ ｃｏｎｃ．」等。）、Ｃ．Ｉ．Ｂａｓｉｃ Ｂｌｕｅ ７（例えば、保土ヶ谷化学社製「Ａｉｚｅｎ Ｖｉｃｔｏｒｉａ Ｐｕｒｅ Ｂｌｕｅ ＢＯＨ」等。）、Ｃ．Ｉ．Ｂａｓｉｃ Ｂｌｕｅ ２６（例えば、保土ヶ谷化学社製「Ａｉｚｅｎ Ｖｉｃｔｏｒｉａ Ｂｌｕｅ ＢＨ」等。）、Ｃ．Ｉ．Ｂａｓｉｃ Ｇｒｅｅｎ １（例えば、保土ヶ谷化学社製「Ａｉｚｅｎ Ｄｉａｍｏｎｄ Ｇｒｅｅｎ ＧＨ」等。）、Ｃ．Ｉ．Ａｃｉｄ Ｂｌｕｅ １（例えば、保土ヶ谷化学社製「Ａｉｚｅｎ Ｂｒｉｌｌｉａｎｔ Ａｃｉｄ Ｐｕｒｅ Ｂｌｕｅ ＶＨ」等。）、Ｃ．Ｉ．Ｓｏｌｖｅｎｔ Ｂｌｕｅ２（例えば、ＢＡＳＦ社製「Ｖｉｃｔｏｒｉａ Ｂｌｕｅ Ｆ４Ｒ」等。）等が挙げられる。
【００５８】
本発明のポジ型感光性組成物における前記イオン性色素の含有割合は、０〜５０重量％であるのが好ましく、０．５〜３０重量％であるのが更に好ましく、１〜２０重量％であるのが特に好ましい。
【００５９】
本発明のポジ型感光性組成物には、前記成分以外に、例えば、塗布性改良剤、現像性改良剤、密着性改良剤、感度改良剤、感脂化剤等の通常用いられる各種の添加剤が更に、好ましくは１０重量％以下、更に好ましくは５重量％以下の範囲で含有されていてもよい。
現像性改良剤としては、好ましくはｐＫａが２以上の有機酸及びその有機酸の無水物が挙げられる。
【００６０】
その有機酸及びその無水物としては、例えば、特開昭６０−８８９４２号、特開昭６３−２７６０４８号、特開平２−９６７５４号各公報等に記載されたものが用いられ、具体的には、グリセリン酸、メチルマロン酸、ジメチルマロン酸、プロピルマロン酸、コハク酸、リンゴ酸、メソ酒石酸、グルタル酸、β−メチルグルタル酸、β，β−ジメチルグルタル酸、β−エチルグルタル酸、β，β−ジエチルグルタル酸、β−プロピルグルタル酸、β，β−メチルプロピルグルタル酸、ピメリン酸、スベリン酸、セバシン酸等の脂肪族飽和カルボン酸、マレイン酸、フマル酸、グルタコン酸等の脂肪族不飽和カルボン酸、１，１−シクロブタンジカルボン酸、１，３−シクロブタンジカルボン酸、１，１−シクロペンタンジカルボン酸、１，２−シクロペンタンジカルボン酸、１，１−シクロヘキサンジカルボン酸、１，２−シクロヘキサンジカルボン酸、１，３−シクロヘキサンジカルボン酸、１，４−シクロヘキサンジカルボン酸等の炭素環式飽和カルボン酸、１，２−シクロヘキセンジカルボン酸、２，３−ジヒドロキシ安息香酸、３，４−ジメチル安息香酸、３，４−ジメトキシ安息香酸、３，５−ジメトキシ安息香酸、ｐ−トルイル酸、２−ヒドロキシ−ｐ−トルイル酸、２−ヒドロキシ−ｍ−トルイル酸、２−ヒドロキシ−ｏ−トルイル酸、マンデル酸、没食子酸、フタル酸、イソフタル酸、テレフタル酸等の炭素環式不飽和カルボン酸、及び、メルドラム酸、アスコルビン酸、無水コハク酸、無水グルタル酸、無水マレイン酸、シクロヘキセンジカルボン酸無水物、シクロヘキサンジカルボン酸無水物、無水フタル酸等の無水物を挙げることができる。
これらの内、脂肪族ジカルボン酸が好ましく、脂環式ジカルボン酸が更に好ましい。
【００６１】
本発明の前記ポジ型感光性組成物は、通常、前記各成分を適当な溶媒に溶解した溶液として支持体表面に塗布した後、加熱、乾燥し、必要により後加熱することにより、支持体表面に感光性組成物層が形成されたポジ型感光性平版印刷版とされる。
【００６２】
ここで、その溶媒としては、使用成分に対して十分な溶解度を持ち、良好な塗膜性を与えるものであれば特に制限はないが、例えば、メチルセロソルブ、エチルセロソルブ、メチルセロソルブアセテート、エチルセロソルブアセテート等のセロソルブ系溶媒、プロピレングリコールモノメチルエーテル、プロピレングリコールモノエチルエーテル、プロピレングリコールモノブチルエーテル、プロピレングリコールモノメチルエーテルアセテート、プロピレングリコールモノエチルエーテルアセテート、プロピレングリコールモノブチルエーテルアセテート、ジプロピレングリコールジメチルエーテル等のプロピレングリコール系溶媒、酢酸ブチル、酢酸アミル、酪酸エチル、酪酸ブチル、ジエチルオキサレート、ピルビン酸エチル、エチル−２−ヒドロキシブチレート、エチルアセトアセテート、乳酸メチル、乳酸エチル、３−メトキシプロピオン酸メチル等のエステル系溶媒、ヘプタノール、ヘキサノール、ジアセトンアルコール、フルフリルアルコール等のアルコール系溶媒、シクロヘキサノン、メチルアミルケトン等のケトン系溶媒、ジメチルホルムアミド、ジメチルアセトアミド、Ｎ−メチルピロリドン等の高極性溶媒、酢酸、あるいはこれらの混合溶媒、更にはこれらに芳香族炭化水素を添加したもの等が挙げられる。溶媒の使用割合は、感光性組成物の総量に対して、通常、重量比で１〜２０倍程度の範囲である。
【００６３】
又、その塗布方法としては、従来公知の方法、例えば、回転塗布、ワイヤーバー塗布、ディップ塗布、エアーナイフ塗布、ロール塗布、ブレード塗布、及びカーテン塗布等を用いることができる。塗布量は用途により異なるが、乾燥膜厚として、通常、３〜７０ｍｇ／ｄｍ²、好ましくは５〜５０ｍｇ／ｄｍ²、特に好ましくは１０〜３０ｍｇ／ｄｍ²の範囲とする。尚、その際の乾燥温度としては、例えば、２０〜１７０℃程度、好ましくは３０〜１５０℃程度が採られる。乾燥時間としては、例えば５秒〜１０分間程度、好ましくは１０秒〜５分程度がとられる。尚、画像形成時のコントラストの向上及び画像形成性の経時安定性の向上等を目的として、例えば４０〜１２０℃程度、好ましくは４０〜７０℃程度の温度で５分〜１００時間程度、好ましくは３０分〜７５分程度の後加熱処理を施こすことが好ましい。
【００６４】
又、その支持体としては、アルミニウム、亜鉛、銅、鋼等の金属板、アルミニウム、亜鉛、銅、鉄、クロム、ニッケル等をメッキ又は蒸着した金属板、紙、樹脂を塗布した紙、アルミニウム等の金属箔を貼着した紙、プラスチックフィルム、親水化処理したプラスチックフィルム、及びガラス板等が挙げられる。中で、好ましいのはアルミニウム又はアルミニウム合金支持体であり、塩酸又は硝酸溶液中での電解エッチング又はブラシ研磨による砂目立て処理、硫酸溶液中での陽極酸化処理、及び必要に応じて封孔処理等の表面処理が施されたアルミニウム板がより好ましい。又、支持体表面の粗さとしては、ＪＩＳ Ｂ０６０１に規定される平均粗さＲ_a で、通常、０．３〜１．０μｍ、好ましくは０．４〜０．８μｍ程度とする。
【００６５】
本発明でのポジ型感光性組成物層を画像露光する光源としては、主として、ＨｅＮｅレーザー、アルゴンイオンレーザー、ＹＡＧレーザー、ＨｅＣｄレーザー、半導体レーザー、ルビーレーザー等のレーザー光源が挙げられるが、特に、光を吸収して発生した熱により画像形成させる場合には、６５０〜１３００ｎｍの近赤外レーザー光線を発生する光源が好ましく、例えば、ルビーレーザー、ＹＡＧレーザー、半導体レーザー、ＬＥＤ等の固体レーザーを挙げることができ、特に、小型で長寿命な半導体レーザーやＹＡＧレーザーが好ましい。これらの光源により、通常、走査露光した後、現像液にて現像し画像が形成される。
【００６６】
尚、レーザー光源は、通常、レンズにより集光された高強度の光線（ビーム）として感光性組成物層表面を走査するが、それに感応する本発明での感光性組成物層の感度特性（ｍＪ／ｃｍ² ）は受光するレーザービームの光強度（ｍＪ／ｓ・ｃｍ² ）に依存することがある。ここで、レーザービームの光強度は、光パワーメーターにより測定したレーザービームの単位時間当たりのエネルギー量（ｍＪ／ｓ）を感光性組成物層表面におけるレーザービームの照射面積（ｃｍ² ）で除することにより求めることができる。レーザービームの照射面積は、通常、レーザーピーク強度の１／ｅ² 強度を越える部分の面積で定義されるが、簡易的には相反則を示す感光性組成物を感光させて測定することもできる。
【００６７】
本発明において、光源の光強度としては、２．０×１０⁶ ｍＪ／ｓ・ｃｍ² 以上とすることが好ましく、１．０×１０⁷ ｍＪ／ｓ・ｃｍ² 以上とすることが特に好ましい。光強度が前記範囲であれば、本発明でのポジ型感光性組成物層の感度特性を向上させ得る、走査露光時間を短くすることができ実用的に大きな利点となる。
本発明のポジ型感光性平版印刷版は、上記画像露光後、アルカリ現像液で現像することにより印刷版を得ることができる。
【００６８】
本発明の前記ポジ型感光性平版印刷版を画像露光したポジ型感光体の現像に用いる現像液としては、例えば、珪酸ナトリウム、珪酸カリウム、珪酸リチウム、珪酸アンモニウム、メタ珪酸ナトリウム、メタ珪酸カリウム、水酸化ナトリウム、水酸化カリウム、水酸化リチウム、炭酸ナトリウム、重炭酸ナトリウム、炭酸カリウム、第二燐酸ナトリウム、第三燐酸ナトリウム、第二燐酸アンモニウム、第三燐酸アンモニウム、硼酸ナトリウム、硼酸カリウム、硼酸アンモニウム等の無機アルカリ塩、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、モノブチルアミン、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等の有機アミン化合物の０．１〜５重量％程度の水溶液からなるアルカリ現像液を用いる。中で、無機アルカリ塩である珪酸ナトリウム、珪酸カリウム等のアルカリ金属の珪酸塩が好ましい。ここで、アルカリ金属の珪酸塩の二酸化珪素としての含有量は０．５〜１０重量％が好ましく、更に１〜８重量％が好ましく、又、アルカリ金属のモル濃度に対する二酸化珪素のモル濃度比が０．１〜１．５、更には０．３〜１であるのが好ましい。又、ｐＨは１２以上が好ましく、上限は１４以下が好ましい。尚、現像液には、必要に応じて、アニオン性界面活性剤、ノニオン性界面活性剤、両性界面活性剤等の界面活性剤や、アルコール等の有機溶媒を加えることができる。
【００６９】
尚、現像は、浸漬現像、スプレー現像、ブラシ現像、超音波現像等により、通常、好ましくは１０〜５０℃程度、特に好ましくは１５〜４５℃程度の温度でなされる。
【００７０】
本発明は本出願人による特開平１０−２６８５１２の改良に係り、光熱変換物質とノボラック樹脂とを基本組成とし、熱分解性物質を含有せず、化学変化を期待し得ない極めて単純な系でポジ型画像を形成することができるものである点は、該先の出願と同一の画像形成原理に基づくと考えている。即ち、この画像形成が、化学変化以外の変化によって行われることは、例えば、一旦光照射を行った本発明における感光性組成物を５０℃付近で２４時間加熱した場合、露光直後には増加した露光部のアルカリ可溶性が、しばしば露光前に近い状態に戻るという可逆現象が認められることからも推察できる。更に、本発明における感光性組成物自体のガラス転移温度又は軟化点とその可逆現象の起こり易さとは、ガラス転移温度又は軟化温度が低い程その可逆現象が起こり易いという関係が認められることもその証左である。
【００７１】
本発明における感光性組成物がこのような機構でポジ型画像を形成する理由は必ずしも明らかではないが、光熱変換物質によって吸収された光エネルギーが、熱に変換され、その熱を受けた部分のアルカリ可溶性高分子物質がコンフォメーション変化等の何らかの化学変化以外の変化を起こし、その部分のアルカリ可溶性が高まることによって、アルカリ現像液により画像が形成されるものと考えられ、このとこの詳細は、本願出願人による特開平１０−２６８５１２号明細書に記載されている。
【００７２】
【実施例】
以下、本発明を実施例によりさらに具体的に説明するが、本発明はその要旨を越えない限り、以下の実施例に限定されるものではない。
【００７３】
実施例１〜４、比較例１〜２
アルミニウム板（厚さ０．２４ｍｍ）を、３重量％の水酸化ナトリウム水溶液中で６０℃で１分間脱脂処理を行った後、１．２重量％の塩酸水溶液中で、温度２５℃、電流密度８０Ａ／ｄｍ² 、処理時間１０秒の条件で電解エッチング処理を行った。次いで水洗後、１重量％の水酸化ナトリウム水溶液中で５０℃、３秒間のデスマット処理を施し、水洗後、３０重量％硫酸溶液中で、温度３０℃、電流密度１０Ａ／ｄｍ² 、処理時間１５秒の条件で陽極酸化処理を行った。更に、９０℃、ｐＨ９の熱水で熱水封孔処理を行い、水洗、乾燥して平版印刷版支持体用のアルミニウム板を作製した。
【００７４】
得られたアルミニウム板支持体表面に、表１に示す組成に調製した各塗布溶液をワイヤーバーを用いて塗布し、８５℃で３分間乾燥させた後、５５℃で２４時間加熱して安定化させることにより、塗膜量２．３ｇ／ｍ² のポジ型感光性組成物層を有するポジ型感光性平版印刷版を作製した。
【００７５】
尚、表１中のノボラック樹脂は、それぞれ以下のものを表す。
▲１▼ｏ−クレゾール８０モル％、フェノール２０モル％の混合フェノール類とホルムアルデヒドとの重縮合体（重量平均分子量９８００）。
▲２▼ｏ−クレゾール８０モル％、フェノール２０モル％の混合フェノール類とホルムアルデヒドとの重縮合体（重量平均分子量７８００）。
▲３▼ｏ−クレゾール８０モル％、フェノール２０モル％の混合フェノール類とホルムアルデヒドとの重縮合体（重量平均分子量７２００）。
▲４▼ｏ−クレゾール７０モル％、フェノール３０モル％の混合フェノール類とホルムアルデヒドとの重縮合体（重量平均分子量１０４００）。
▲５▼ｍ−クレゾール３０モル％、ｐ−クレゾール２０モル％、フェノール５０モル％の混合フェノール類とホルムアルデヒドとの重縮合体（重量平均分子量９８００、住友デュレス社製「ＳＫ−１８８」）。
▲６▼ｏ−クレゾール５０％、フェノール５０％の混合フェノール類とホルムアルデヒドとの重縮合体（重量平均分子量６２００）
【００７６】
得られた各ポジ型感光性平版印刷版につき、波長８３０ｎｍの半導体レーザーを光源とする露光装置（Ｃｒｅｏ社製、「Ｔｒｅｎｄ Ｓｅｔｔｅｒ ３２４４Ｔ」）を用いて１６０ｍＪ／ｃｍ² で画像露光し、次いで、アルカリ現像液（富士写真フィルム社製「ＤＰ−４」の７倍希釈液）に２８℃で浸漬して現像するにおいて、露光部の膜が充分に除去され、非露光部の残膜率が９０％以上を保持している最短時間及び最長時間（但し、実用的な面から６０秒までとした。）を測定し、現像ラチチュードを評価し、結果を表１に併記した。
【００７７】
ここで、残膜率は、反射濃度を反射濃度計（マクベス社製「ＲＤ−５１４」）を用いて測定することにより、以下の式に基づいて算出した。
残膜率（％）＝［（現像後の非露光部の反射濃度−支持体表面の反射濃度）／（現像前の版面の反射濃度−支持体表面の反射濃度）］×１００
【００７８】
【表１】

【００７９】
尚、前記の各ポジ型感光性平版印刷版は、白色蛍光灯（三菱電機社製３６Ｗ白色蛍光灯「ネオルミスーパーＦＬＲ４０Ｓ−Ｗ／Ｍ／３６」）の４００ルクスの光強度照射下に１０時間放置した後、前記と同様の現像処理を行った場合、いずれの実施例及び比較例においても実質的な膜減りはなく、白色蛍光灯下における取扱性は良好であった。
【００８０】
【発明の効果】
本発明によれば、画像部と非画像部とのコントラストに優れ、現像ラチチュードが広く、画像部の残膜率も十分に保持され、更に望ましくは、紫外線領域の光に対して感応せず、白色蛍光灯下における取扱性にも優れるポジ型感光性組成物及びポジ型感光性平版印刷版を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention is mainly used in photosensitive lithographic printing plates, proofs for simple proof printing, copper etching resists for wiring boards and gravure, color filter resists used in flat display production, photoresists for LSI production, etc. The present invention relates to a positive photosensitive composition and a positive photosensitive lithographic printing plate that are highly sensitive to light in a region, and in particular, a positive photosensitive composition and a positive photosensitive composition that are suitable for direct plate making using a semiconductor laser, a YAG laser, or the like. Related to lithographic printing plates.
[0002]
[Prior art]
Conventionally, as the positive photosensitive composition, for example, an o-quinonediazide group-containing compound that becomes insoluble in alkali by generating indene carboxylic acid upon irradiation with light, an organic polymer substance having an o-nitrocarbinol ester group, or light There are known compositions and the like of a compound (photoacid generator) that generates an acid by an acid and a compound that is hydrolyzed by an acid and becomes alkali-soluble.
[0003]
On the other hand, with the advancement of computer image processing technology, a photosensitive or thermal direct plate making system that directly forms a resist image by laser light or a thermal head, etc., without outputting digital image information to a silver salt mask film is attracting attention. Has been. In particular, a high-resolution laser-sensitive direct plate-making system using a high-power semiconductor laser, a YAG laser, or the like is strongly desired to be realized from the viewpoints of downsizing, ambient light during plate-making work, and plate material cost. Yes.
[0004]
On the other hand, conventionally, as an image forming method using laser sensitivity or heat sensitivity, a method of forming a color material image using a sublimation transfer dye and a method of preparing a lithographic printing plate are known. Specifically, for example, a method of producing a lithographic printing plate using a crosslinking reaction of a diazo compound, a method of producing a lithographic printing plate using a decomposition reaction of nitrocellulose, and the like are known.
[0005]
In recent years, a technique in which a long-wavelength light-absorbing dye is combined with a chemically amplified photoresist has been scattered. For example, JP-A-6-43633 discloses an image containing a specific squarylium dye, a photoacid generator, and a binder. JP-A-7-20629 discloses an image-forming material containing an infrared-absorbing dye, a latent Bronsted acid, a resole resin, and a novolac resin, and JP-A-7-271029 discloses a forming material. An image forming material using an s-triazine compound instead of the latent Bronsted acid is disclosed.
These conventional techniques relating to image forming materials containing long-wavelength light-absorbing dyes are also sensitive to light in the ultraviolet region, and the reaction proceeds during handling under a white fluorescent lamp, so that they have stable quality. There is a problem that it is difficult to obtain.
Further, JP-A-7-285275 discloses a binder, a substance that absorbs light and generates heat, and a substance that is thermally decomposable and substantially reduces the solubility of the binder when it is not decomposed. An image forming material is disclosed.
[0006]
JP-A-7-285275 describes that a water-insoluble and alkaline water-soluble resin is preferable as a binder, and various resins including an o-cresol formaldehyde resin are exemplified. By the way, the thermally decomposable dissolution inhibitor in the technology of the publication is a substance that is decomposed by the heat generated when the “substance that absorbs light and generates heat” absorbs laser light, and includes an onium salt, a diazonium salt, and Although it has been described that quinonediazide compounds are applicable, since these compounds are sensitive to light in the ultraviolet region, there is a problem in handleability under white light as in the above-described technique.
On the other hand, Japanese Patent Application Laid-Open No. 9-43847 contains a resin that is sparingly soluble in an alkali developer and an infrared absorber, and is heated by infrared irradiation or the like to change crystallinity and become alkali-soluble. The positive type composition that does not change is contained in WO97 / 39894, and contains an aqueous developable polymer and a compound that inhibits the aqueous developability of the polymer. Heat sensitive positive compositions that do not change upon irradiation are each disclosed.
In addition, the positive photosensitive compositions disclosed in JP-A-9-43847 and WO97 / 39894 disclose that the composition contains a novolak resin.
[0007]
These positive compositions disclosed in JP-A-9-43847 and WO97 / 39894 contain a compound that undergoes a chemical change upon exposure, and the chemical change causes a difference in solubility between the exposed and unexposed areas. Unlike the composition in the prior art described above, which causes a difference in solubility due to a change other than a chemical change and does not contain a compound sensitive to light in the ultraviolet region, It has advantages such as excellent handleability.
[0008]
However, according to the study by the present inventors, the above-described conventional technology has a drawback that an image obtained depending on the processing conditions is not always stable in a negative photosensitive composition that requires heat treatment after exposure. Further, in a positive photosensitive composition that does not require a heat treatment after exposure, sensitivity and contrast between an image part (non-exposed part) and a non-image part (exposed part) are insufficient, and as a result, non-image The development latitude is narrow, such that the image is not sufficiently removed or the remaining film ratio of the image area is not sufficiently maintained, and particularly the dissolution of the exposed and unexposed areas due to changes other than chemical changes. In the positive compositions disclosed in Japanese Patent Application Laid-Open Nos. 9-43847 and WO97 / 39894 that cause a difference in sex, it has been found that the tendency is remarkable.
[0009]
On the other hand, the applicant of the present application is a simple system in which a photochemical change between a photothermal conversion substance and an alkali-soluble resin such as a novolac resin for light in the near infrared region cannot be expected, and a positive image that solves the above-described problems It was found that a photosensitive composition that can be formed was obtained, and a patent application was previously filed (Japanese Patent Laid-Open No. 10-268512). The photosensitive composition also discloses that it contains a novolak resin, and various compounds are listed as the phenol component and aldehyde component constituting the novolak. However, the photosensitive composition is still not practically sufficient.
[0010]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described prior art, and is excellent in contrast between an image portion (unexposed portion) and a non-image portion (exposed portion) before and after exposure, that is, an image portion and a non-image portion. The difference in solubility in alkaline developer is large, the development latitude is wide, the remaining film ratio of the image area is sufficiently maintained, and more preferably, it is insensitive to light in the ultraviolet region and is easy to handle under a white fluorescent lamp. Another object of the present invention is to provide a positive photosensitive composition and a positive photosensitive lithographic printing plate.
[0011]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventor has mainly used a photothermal conversion substance for light in the near-infrared region and a specific novolac resin, that is, a composition using a novolak resin containing a relatively large amount of o-cresol. The present invention has been completed and the present invention has been completed. That is, the present invention is a positive type comprising a photothermal conversion substance that absorbs light from an image exposure light source and converts it into heat and a novolac resin. A photosensitive composition, the composition does not contain a thermally decomposable substance that decomposes by the action of heat generated by the light-heat converting substance absorbing light from an image exposure light source, and the novolac resin comprises: It exists in the positive photosensitive composition which is comprised from the phenols which o-cresol accounts for 60 mol% or more. Another gist includes a photothermal conversion substance that absorbs light from an image exposure light source and converts it into heat and a novolac resin, and is a positive photosensitive composition that is substantially insensitive to light in the ultraviolet region. In the product, the novolak resin exists in a positive photosensitive composition in which o-cresol is composed of phenols in which 60 mol% or more is contained. Another gist is a positive photosensitive lithographic printing plate in which a layer made of the above photosensitive composition is formed on the surface of a support.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The positive photosensitive composition of the present invention is a thermally decomposable substance (hereinafter referred to as “thermally decomposable substance”) that is decomposed by the action of heat generated by the light-to-heat conversion substance described below by absorbing light from the image exposure light source. It is premised on not containing. Such thermally decomposable substances are onium salts, diazonium salts and quinonediazide compounds as described in JP-A-7-28527, and the photosensitive composition of the present invention does not contain such thermally decomposable compounds. Thus, it is not substantially sensitive to light in the ultraviolet region, and can be handled under a white light. Further, since the photosensitive composition of the present invention does not contain such a thermally decomposable compound, the thermally decomposable substance is decomposed by image exposure, and the premise is different from the technology involved in the formation of the decomposed image. .
[0013]
Here, “substantially insensitive to light in the ultraviolet region” means that there is no substantial difference in solubility in an alkali developer before and after irradiation with light having a wavelength of 360 to 450 nm. The light intensity of 400 lux of a white fluorescent lamp (36W white fluorescent lamp “Neolmi Super FLR40S-W / M / 36” manufactured by Mitsubishi Electric Corporation). It means that the solubility of the composition in an alkali developer after being left for 10 hours under irradiation does not cause a substantial change compared with that before being left.
In the positive photosensitive composition of the present invention, the light-to-heat conversion substance that absorbs light from an image exposure light source and converts it into heat is not particularly limited as long as it is a compound that can convert absorbed light into heat. Among organic and inorganic pigments and dyes, organic dyes, metals, metal oxides, metal carbides, metal borides and the like having an absorption band in part or all of the near infrared region of 650 to 1300 nm, light absorbing dyes Is particularly effective. These light-absorbing dyes efficiently absorb light in the above-mentioned wavelength range, but hardly absorb light in the ultraviolet region, or are not substantially sensitive to absorption, and are weak by ultraviolet rays contained in white light. Is a compound having no action of modifying the photosensitive composition.
[0014]
As these light-absorbing dyes, a heterocyclic ring containing a nitrogen atom, an oxygen atom, a sulfur atom or the like is polymethine (—CH═)._nTypical examples include so-called cyanine dyes in a broad sense, which are bonded to each other. Specific examples include quinoline (so-called cyanine-based), indole (so-called indocyanine), and benzothiazole. System (so-called thiocyanine system), aminobenzene system (so-called polymethine system), pyrylium system, thiapyrylium system, squarylium system, croconium system, azurenium system, etc., among which quinoline system, indole system, benzothiazole system, Aminobenzene-based, pyrylium-based, or thiapyrylium-based are preferable. In addition, other dyes such as aminium-based, imonium-based, phthalocyanine-based, anthraquinone-based are also exemplified, and among them, aminium-based, imonium-based A dye is preferred.
[0015]
In the present invention, among the cyanine dyes, those represented by the following general formula (Ia), (Ib), or (Ic) are particularly preferable as the quinoline dyes.
[0016]
[Chemical 1]

[0017]
[In formulas (Ia), (Ib), and (Ic), R¹And R²Each independently has an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, or a substituent. Represents a good phenyl group, L¹Represents a tri, penta, or heptamethine group which may have a substituent, and two substituents on the penta or heptamethine group are connected to each other to form a C5-C7 cycloalkene ring. In addition, the quinoline ring may have a substituent, and in this case, two adjacent substituents may be connected to each other to form a condensed benzene ring. X^-Represents a counter anion. ]
[0018]
Where R in the formulas (Ia), (Ib), and (Ic)¹And R²Examples of the substituent in the group include an alkoxy group, a phenoxy group, a hydroxy group, and a phenyl group.¹Examples of the substituent in the group include an alkyl group, an amino group, and a halogen atom, and examples of the substituent in the quinoline ring include an alkyl group, an alkoxy group, a nitro group, and a halogen atom.
[0019]
Further, as the indole and benzothiazole dyes, those represented by the following general formula (II) are particularly preferable.
[0020]
[Chemical 2]

[0021]
[In formula (II), Y¹And Y²Each independently represents a dialkylmethylene group or a sulfur atom;^ThreeAnd R^FourEach independently has an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, or a substituent. Represents a good phenyl group, L²Represents a tri, penta, or heptamethine group which may have a substituent, and two substituents on the penta or heptamethine group are connected to each other to form a C5-C7 cycloalkene ring. Alternatively, the condensed benzene ring may have a substituent, and in this case, two adjacent substituents may be connected to each other to form a condensed benzene ring. X^-Represents a counter anion. ]
[0022]
Here, R in the formula (II)^ThreeAnd R^FourExamples of the substituent in the group include an alkoxy group, a phenoxy group, a hydroxy group, and a phenyl group.²Examples of the substituent in the group include an alkyl group, an amino group, and a halogen atom, and examples of the substituent in the benzene ring include an alkyl group, an alkoxy group, a nitro group, and a halogen atom.
[0023]
As the aminobenzene dye, those represented by the following general formula (III) are particularly preferable.
[0024]
[Chemical Formula 3]

[0025]
[In formula (III), R^Five, R⁶, R⁷And R⁸Each independently represents an alkyl group, R⁹And R^TenEach independently represents an aryl group, a furyl group or a thienyl group which may have a substituent, and L^ThreeRepresents a mono-, tri-, or pentamethine group which may have a substituent, and two substituents on the tri- or pentamethine group are connected to each other to form a C5-C7 cycloalkene ring. In addition, the quinone ring and the benzene ring may have a substituent. X^-Represents a counter anion. ]
[0026]
Here, R in the formula (III)⁹And R^TenSpecifically, a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-furyl group, a 3-furyl group, a 2-thienyl group, a 3-thienyl group, and the like can be mentioned. An alkyl group, an alkoxy group, a dialkylamino group, a hydroxy group, or a halogen atom;^ThreeExamples of the substituent in the group include an alkyl group, an amino group, and a halogen atom, and examples of the substituent in the quinone ring and the benzene ring include an alkyl group, an alkoxy group, a nitro group, and a halogen atom.
[0027]
As the pyrylium-based and thiapyrylium-based dyes, those represented by the following general formula (IVa), (IVb), or (IVc) are particularly preferable.
[0028]
[Formula 4]

[0029]
[In formula (IVa), (IVb) and (IVc), Y^ThreeAnd Y^FourEach independently represents an oxygen atom or a sulfur atom, and R¹¹, R¹², R¹³And R¹⁴Each independently represents a hydrogen atom or an alkyl group, or R¹¹And R¹³And R¹²And R¹⁴May be linked to each other to form a cycloalkene ring having 5 or 6 carbon atoms.^FourRepresents a mono-, tri-, or pentamethine group which may have a substituent, and two substituents on the tri- or pentamethine group are connected to each other to form a C5-C7 cycloalkene ring. Alternatively, the pyrylium ring and the thiapyrylium ring may have a substituent, and in this case, two adjacent substituents may be connected to each other to form a condensed benzene ring. X^-Represents a counter anion. ]
[0030]
Where L in formulas (IVa), (IVa) and (IVc)^FourExamples of the substituent in the group include an alkyl group, an amino group, and a halogen atom, and examples of the substituent in the pyrylium ring and the thiapyrylium ring include an aryl group such as a phenyl group and a naphthyl group.
[0031]
Further, as the aminium-based and imonium-based dyes, those represented by the following general formula (Va) or (Vb) having at least one N, N-diaryliminium salt skeleton are preferable.
[0032]
[Chemical formula 5]

[0033]
[In the formulas (Va) and (Vb), R¹⁵, R¹⁶, R¹⁷And R¹⁸Each independently represents a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, or a substituted group. An alkoxy group which may have a group, R¹⁹And R²⁰Each independently represents an alkyl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, or a substituent. A good alkoxy group, an acyloxy group which may have a substituent, or a phenyl group which may have a substituent are shown, and the benzene ring and the iminoquinone ring may have a substituent. X^-Represents a counter anion. In addition, the electronic bond (-) in Formula (Vb) shows the resonance state with another electronic bond. ]
[0034]
Here, R in the formulas (Va) and (Vb)¹⁵, R¹⁶, R¹⁷, R¹⁸, R¹⁹And R²⁰Examples of the substituent in the alkyl group, alkoxy group, carboxy group, acyloxy group, alkoxycarbonyl group, hydroxy group, amino group, alkylamino group, halogenated alkyl group, or halogen atom include a benzene ring and an iminoquinone ring. Examples of the substituent include an alkyl group, an alkoxy group, an acyl group, a nitro group, or a halogen atom.
[0035]
Among these aminium dyes and imonium dyes, R in the general formulas (Va) and (Vb) is used.¹⁵, R¹⁶, R¹⁷And R¹⁸Is an alkyl group and R¹⁹And R²⁰Is an alkyl group or R¹⁹And R²⁰Is particularly preferably a phenyl group having a dialkylamino group as a substituent.
[0036]
Incidentally, the counter anion X in the general formulas (Ia to c), (II), (III), (IVa to c), and (Va to b)^-For example, Cl^-, Br^-, I^-, ClO_Four ^-, PF₆ ^-, SbF₆ ^-And BF_Four ^-Inorganic acid anions such as inorganic boric acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, acetic acid, and methyl, ethyl, propyl, butyl, phenyl, methoxyphenyl, naphthyl, difluorophenyl, pentafluorophenyl, Examples thereof include organic acid anions such as organic boric acid having an organic group such as thienyl and pyrrolyl.
[0037]
The quinoline dyes represented by the general formulas (Ia to c), the indole or benzothiazole dyes represented by the general formula (II), and the aminobenzene dyes represented by the general formula (III) Specific examples of the pyrylium or thiapyrylium dyes represented by the general formulas (IVa to c) and the aminium or imonium dyes represented by the general formulas (Va to b) are shown below.
[0038]
[Chemical 6]

[0039]
[Chemical 7]

[0040]
[Chemical 8]

[0041]
[Chemical 9]

[0042]
[Chemical Formula 10]

[0043]
Embedded image

[0044]
Embedded image

[0045]
Embedded image

[0046]
Embedded image

[0047]
Embedded image

[0048]
Embedded image

[0049]
The novolak resin in the positive photosensitive composition of the present invention includes, for example, phenol, o-cresol, m-cresol, p-cresol, 2,5-xylenol, 3,5-xylenol, o-ethylphenol, m -Ethylphenol, p-ethylphenol, propylphenol, n-butylphenol, tert-butylphenol, 1-naphthol, 2-naphthol, pyrocatechol, resorcinol, hydroquinone, pyrogallol, 1,2,4-benzenetriol, phloroglucinol, At least one kind of phenols such as 4,4′-biphenyldiol and 2,2-bis (4′-hydroxyphenyl) propane is treated with an acidic catalyst, for example, formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, furfur. At least one of aldehydes (eg, paraformaldehyde instead of formaldehyde, paraaldehyde instead of acetaldehyde) or ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone And a phenolic hydroxyl group-containing alkali-soluble resin commonly used as a binder resin for this type of photosensitive composition.
[0050]
Among them, the novolak resin in the present invention is essential to be composed of phenols in which o-cresol accounts for 60 mol% or more, and o-cresol is preferably 70 mol% or more. In addition, o-cresol is preferably 95 mol% or less, and more preferably 90 mol% or less. When the proportion of o-cresol is less than the above range, the development latitude as the photosensitive composition cannot be widened. On the other hand, when it exceeds the above range, the solubility in an alkaline developer tends to decrease. On the other hand, examples of the remaining phenols include phenol, m-cresol, p-cresol, etc., and phenol preferably occupies 5 mol% or more, more preferably 10 mol% or more, and phenol is 30 mol% or less. If it exists, a development latitude will become wider and it is preferable.
[0051]
In addition, when o-cresol is used as the phenols constituting the novolak resin as the binder resin in the positive photosensitive composition for ultraviolet exposure containing a conventional o-quinonediazide group-containing compound, the proportion of the proportion is high. As the solubility in alkali developer tends to decrease, the positive development composition of the present invention containing a photothermal conversion substance and a novolak resin is not suitable for an alkaline development type positive photosensitive composition. It was completely unexpected that the novolak resin using o-cresol as a phenol and a considerably high ratio in the photosensitive composition could achieve the object of the present invention.
[0052]
The novolak resin in the present invention preferably has a polystyrene-reduced weight average molecular weight of 5,000 to 15,000, particularly preferably 6,000 to 12,000, as measured by gel permeation chromatography.
[0053]
The positive photosensitive composition of the present invention has the photothermal conversion substance and the novolak resin as a basic composition, and the content of each of the total amount of both is usually 0.5 to 50% by weight of the former photothermal conversion substance, The latter novolak resin is 99.5 to 50% by weight, preferably 1 to 40% by weight of the former, 99 to 60% by weight, and more preferably 2 to 30% by weight of the former and 98 to 70% by weight of the latter. It is particularly preferable that the former is 2 to 10% by weight and the latter is 98 to 90% by weight.
[0054]
In addition to the photothermal conversion substance and the novolac resin, the positive photosensitive composition of the present invention is an alkali-soluble resin other than the novolac resin, such as acrylic acid and / or the like, as long as the performance of the present invention is not impaired. It is also possible to contain a so-called acrylic resin or the like containing methacrylic acid as a copolymerization component.
In addition to the photothermal conversion substance and the novolak resin, the positive photosensitive composition of the present invention includes the novolak for the purpose of increasing the difference in solubility in an alkaline developer between an exposed area and an unexposed area. It has a function of reducing the solubility of the resin by forming hydrogen bonds with the resin, and it contains a dissolution inhibitor that hardly absorbs light in the near infrared region and is not decomposed by light in the near infrared region. Also good.
[0055]
Examples of the dissolution inhibitor include sulfonic acid esters, phosphoric acid esters, aromatic carboxylic acid esters, aromatic disulfones, carboxylic acid anhydrides, aromatics described in detail in JP-A-10-268512 by the applicant of the present application. Aromatic ketones, aromatic aldehydes, aromatic amines, aromatic ethers, etc., which also have a lactone skeleton, an N, N-diarylamide skeleton, and a diarylmethylimino skeleton, which are also described in detail in JP-A-11-190903. Examples thereof include acid color-forming dyes that also serve as colorants, and nonionic surfactants described in detail in Japanese Patent Application No. 10-341400.
[0056]
The content of the dissolution inhibitor in the positive photosensitive composition of the present invention is preferably 0 to 50% by weight, more preferably 0 to 30% by weight, and 0 to 20% by weight. Is particularly preferred.
[0057]
In addition, the positive photosensitive composition of the present invention may have an absorption maximum (λ_max) Is 700 nm or less and is distinguished from the photothermal conversion substance, and the cause of color development is an ionic dye due to non-polarization of a cation or anion, for example, a cyanine dye, a pyrylium dye, a thiapyrylium dye, a squarylium dye , A croconium dye, an azurenium dye, a diphenylmethane dye, a triphenylmethane dye, an oxazine dye, an azine dye, a viologen dye, a xanthene dye, a rhodocyanine dye, a styryl dye, etc. . Among these, a triphenylmethane dye having a triphenylmethyl group as a partial structure is preferable. I. No. For example, C.I. I. Basic Violet 3 (for example, “Crystal Violet” manufactured by Tokyo Chemical Industry Co., Ltd.), C.I. I. Basic Blue 5 (for example, “Primocyanine BX conc.” Manufactured by Sumitomo Chemical Co., Ltd.), C.I. I. Basic Blue 7 (for example, “Aizen Victoria Pure Blue BOH” manufactured by Hodogaya Chemical Co., Ltd.), C.I. I. Basic Blue 26 (for example, “Aizen Victoria Blue BH” manufactured by Hodogaya Chemical Co., Ltd.), C.I. I. Basic Green 1 (for example, “Aizen Diamond Green GH” manufactured by Hodogaya Chemical Co., Ltd.), C.I. I. Acid Blue 1 (for example, “Aizen Brilliant Acid Pure Blue VH” manufactured by Hodogaya Chemical Co., Ltd.), C.I. I. Solvent Blue2 (for example, “Victoria Blue F4R” manufactured by BASF) and the like.
[0058]
The content of the ionic dye in the positive photosensitive composition of the present invention is preferably 0 to 50% by weight, more preferably 0.5 to 30% by weight, and 1 to 20% by weight. It is particularly preferred.
[0059]
In addition to the above-mentioned components, the positive photosensitive composition of the present invention includes various commonly used additives such as a coatability improver, a developability improver, an adhesion improver, a sensitivity improver, and a sensitizer. The agent may further be contained in the range of preferably 10% by weight or less, more preferably 5% by weight or less.
As the developability improver, an organic acid having a pKa of 2 or more and an anhydride of the organic acid are preferably used.
[0060]
Examples of the organic acid and its anhydride include those described in JP-A-60-88942, JP-A-63-276048, JP-A-2-96754, and the like. Glyceric acid, methylmalonic acid, dimethylmalonic acid, propylmalonic acid, succinic acid, malic acid, mesotartaric acid, glutaric acid, β-methylglutaric acid, β, β-dimethylglutaric acid, β-ethylglutaric acid, β, Aliphatic saturated carboxylic acids such as β-diethylglutaric acid, β-propylglutaric acid, β, β-methylpropylglutaric acid, pimelic acid, suberic acid, and sebacic acid, and aliphatic non-aliphatic acids such as maleic acid, fumaric acid, and glutaconic acid. Saturated carboxylic acid, 1,1-cyclobutanedicarboxylic acid, 1,3-cyclobutanedicarboxylic acid, 1,1-cyclopentanedicarboxylic acid, 1,2-cycl Carboxylic saturated carboxylic acids such as pentanedicarboxylic acid, 1,1-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexenedicarboxylic acid Acid, 2,3-dihydroxybenzoic acid, 3,4-dimethylbenzoic acid, 3,4-dimethoxybenzoic acid, 3,5-dimethoxybenzoic acid, p-toluic acid, 2-hydroxy-p-toluic acid, 2- Hydroxy-m-toluic acid, 2-hydroxy-o-toluic acid, mandelic acid, gallic acid, carbocyclic unsaturated carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, meldrum acid, ascorbic acid, succinic anhydride Acid, glutaric anhydride, maleic anhydride, cyclohexenedicarboxylic anhydride, cyclohexane Sanji carboxylic acid anhydride, may be mentioned anhydrides such as phthalic anhydride.
Of these, aliphatic dicarboxylic acids are preferred, and alicyclic dicarboxylic acids are more preferred.
[0061]
The positive photosensitive composition of the present invention is usually applied to the surface of the support as a solution obtained by dissolving the above components in an appropriate solvent, and then heated, dried, and post-heated as necessary. A positive photosensitive lithographic printing plate having a photosensitive composition layer formed thereon.
[0062]
Here, the solvent is not particularly limited as long as it has sufficient solubility for the components used and gives good coating properties. For example, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve Cellosolve solvents such as acetate, propylene glycol such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol dimethyl ether Solvents, butyl acetate, amyl acetate, ethyl butyrate, butyl butyrate, diethyl oxalate, ethyl pyruvate, ethyl Ester solvents such as 2-hydroxybutyrate, ethyl acetoacetate, methyl lactate, ethyl lactate, methyl 3-methoxypropionate, alcohol solvents such as heptanol, hexanol, diacetone alcohol, furfuryl alcohol, cyclohexanone, methyl amyl ketone Ketone solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone and the like, acetic acid, or a mixed solvent thereof, and those obtained by adding an aromatic hydrocarbon thereto. The use ratio of the solvent is usually in the range of about 1 to 20 times by weight with respect to the total amount of the photosensitive composition.
[0063]
As the coating method, conventionally known methods such as spin coating, wire bar coating, dip coating, air knife coating, roll coating, blade coating, and curtain coating can be used. The coating amount varies depending on the application, but the dry film thickness is usually 3 to 70 mg / dm.², Preferably 5 to 50 mg / dm², Particularly preferably 10-30 mg / dm²The range. In addition, as drying temperature in that case, about 20-170 degreeC, for example, Preferably about 30-150 degreeC is taken. The drying time is, for example, about 5 seconds to 10 minutes, preferably about 10 seconds to 5 minutes. For the purpose of improving the contrast at the time of image formation and improving the temporal stability of image formability, for example, about 40 to 120 ° C., preferably about 40 to 70 ° C., about 5 minutes to 100 hours, preferably It is preferable to perform post-heating treatment for about 30 minutes to 75 minutes.
[0064]
In addition, as the support, a metal plate such as aluminum, zinc, copper, steel, etc., a metal plate plated or vapor-deposited with aluminum, zinc, copper, iron, chromium, nickel, paper, paper coated with resin, aluminum, etc. Paper, plastic film, hydrophilized plastic film, glass plate, and the like with a metal foil attached thereto. Among them, preferred is an aluminum or aluminum alloy support, graining treatment by electrolytic etching or brush polishing in hydrochloric acid or nitric acid solution, anodizing treatment in sulfuric acid solution, and sealing treatment if necessary. An aluminum plate subjected to the surface treatment is more preferable. Further, as the roughness of the support surface, the average roughness R defined in JIS B0601_aIn general, the thickness is about 0.3 to 1.0 μm, preferably about 0.4 to 0.8 μm.
[0065]
The light source for image exposure of the positive photosensitive composition layer in the present invention mainly includes laser light sources such as HeNe laser, argon ion laser, YAG laser, HeCd laser, semiconductor laser, ruby laser, etc. In the case of forming an image by heat generated by absorbing light, a light source that generates a near infrared laser beam of 650 to 1300 nm is preferable, and examples thereof include solid lasers such as ruby laser, YAG laser, semiconductor laser, and LED. In particular, a small and long-life semiconductor laser or YAG laser is preferable. With these light sources, scanning exposure is usually performed, and then development is performed with a developer to form an image.
[0066]
The laser light source usually scans the surface of the photosensitive composition layer as a high-intensity light beam (beam) collected by a lens. The sensitivity characteristic (mJ) of the photosensitive composition layer according to the present invention is sensitive to the scanning. / Cm²) Is the light intensity (mJ / s · cm) of the received laser beam.²). Here, the light intensity of the laser beam is the amount of energy (mJ / s) per unit time of the laser beam measured by an optical power meter, and the irradiation area (cm²) Can be obtained by dividing by. The irradiation area of the laser beam is usually 1 / e of the laser peak intensity.²Although it is defined by the area of the portion exceeding the strength, it can also be measured by exposing a photosensitive composition showing a reciprocity law.
[0067]
In the present invention, the light intensity of the light source is 2.0 × 10⁶mJ / s · cm²It is preferable to make it more than 1.0 × 10⁷mJ / s · cm²The above is particularly preferable. When the light intensity is in the above range, the scanning exposure time that can improve the sensitivity characteristics of the positive photosensitive composition layer in the present invention can be shortened, which is a great practical advantage.
The positive photosensitive lithographic printing plate of the present invention can be obtained by developing with an alkali developer after the image exposure.
[0068]
Examples of the developer used for developing the positive photosensitive material obtained by image exposure of the positive photosensitive lithographic printing plate of the present invention include sodium silicate, potassium silicate, lithium silicate, ammonium silicate, sodium metasilicate, potassium metasilicate, Sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, dibasic sodium phosphate, tribasic sodium phosphate, dibasic ammonium phosphate, tribasic ammonium phosphate, sodium borate, potassium borate, ammonium borate Inorganic alkali salts such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, monobutylamine, monoethanolamine, diethanolamine, triethanol Triethanolamine, mono-isopropanolamine, an alkali developer comprising an aqueous solution of about 0.1 to 5% by weight of an organic amine compound diisopropanolamine used. Among them, alkali metal silicates such as sodium silicate and potassium silicate which are inorganic alkali salts are preferable. Here, the content of alkali metal silicate as silicon dioxide is preferably 0.5 to 10% by weight, more preferably 1 to 8% by weight, and the molar concentration ratio of silicon dioxide to the molar concentration of alkali metal is It is preferably 0.1 to 1.5, more preferably 0.3 to 1. The pH is preferably 12 or more, and the upper limit is preferably 14 or less. In addition, surfactants, such as anionic surfactant, nonionic surfactant, and amphoteric surfactant, and organic solvents, such as alcohol, can be added to a developing solution as needed.
[0069]
The development is usually carried out by immersion development, spray development, brush development, ultrasonic development or the like, preferably at a temperature of about 10 to 50 ° C., particularly preferably about 15 to 45 ° C.
[0070]
The present invention relates to the improvement of Japanese Patent Application Laid-Open No. 10-268512 by the present applicant, and is a very simple system having a photothermal conversion substance and a novolak resin as a basic composition, does not contain a pyrolyzable substance, and cannot expect a chemical change. The point that a positive image can be formed is considered to be based on the same image forming principle as that of the previous application. That is, the fact that this image formation is performed by a change other than a chemical change, for example, increased immediately after exposure when the photosensitive composition of the present invention once irradiated with light was heated at around 50 ° C. for 24 hours. It can be inferred from the fact that the alkali solubility in the exposed area often reverts to a state close to that before exposure. Furthermore, the relationship between the glass transition temperature or softening point of the photosensitive composition in the present invention and the ease of the reversible phenomenon is that the reversible phenomenon is more likely to occur as the glass transition temperature or the softening temperature is lower. This is evidence.
[0071]
The reason why the photosensitive composition of the present invention forms a positive image by such a mechanism is not necessarily clear, but the light energy absorbed by the light-to-heat conversion substance is converted into heat, and the portion of the portion that has received the heat is subjected to the heat. It is considered that an alkali-developing polymer material causes a change other than some chemical change such as a conformational change, and the alkali-solubility of the portion increases, whereby an image is formed by an alkali developer. This is described in Japanese Patent Application Laid-Open No. 10-268512 by the present applicant.
[0072]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
[0073]
Examples 1-4, Comparative Examples 1-2
An aluminum plate (thickness 0.24 mm) was degreased in a 3% by weight sodium hydroxide aqueous solution at 60 ° C. for 1 minute, and then in a 1.2% by weight hydrochloric acid aqueous solution at a temperature of 25 ° C. and a current density. 80A / dm²The electrolytic etching treatment was performed under the condition of a treatment time of 10 seconds. Next, after washing with water, desmutting treatment was performed at 50 ° C. for 3 seconds in a 1% by weight aqueous sodium hydroxide solution.²Anodizing was performed under the condition of a processing time of 15 seconds. Further, hot water sealing treatment was performed with hot water of 90 ° C. and pH 9, washed with water and dried to prepare an aluminum plate for a lithographic printing plate support.
[0074]
Each coating solution prepared to the composition shown in Table 1 is applied to the surface of the obtained aluminum plate support using a wire bar, dried at 85 ° C for 3 minutes, and then heated at 55 ° C for 24 hours for stabilization. The coating amount is 2.3 g / m²A positive photosensitive lithographic printing plate having a positive photosensitive composition layer was prepared.
[0075]
In addition, the novolak resin in Table 1 represents the following, respectively.
(1) A polycondensate of a mixed phenol of 80 mol% o-cresol and 20 mol% of phenol and formaldehyde (weight average molecular weight 9800).
(2) Polycondensate of mixed phenols of 80 mol% o-cresol and 20 mol% phenol and formaldehyde (weight average molecular weight 7800).
(3) Polycondensate of mixed phenols of 80 mol% o-cresol and 20 mol% phenol and formaldehyde (weight average molecular weight 7200).
(4) Polycondensate of mixed phenols of 70 mol% o-cresol and 30 mol% phenol and formaldehyde (weight average molecular weight 10400).
(5) A polycondensate of mixed phenols of 30 mol% m-cresol, 20 mol% p-cresol and 50 mol% phenol with formaldehyde (weight average molecular weight 9800, “SK-188” manufactured by Sumitomo Durres).
(6) Polycondensate of mixed phenols of 50% o-cresol and 50% phenol and formaldehyde (weight average molecular weight 6200)
[0076]
Each of the obtained positive photosensitive lithographic printing plates was 160 mJ / cm using an exposure apparatus (“Trend Setter 3244T” manufactured by Creo) using a semiconductor laser having a wavelength of 830 nm as a light source.²Then, the film was exposed to an alkali developer (7-fold diluted solution of “DP-4” manufactured by Fuji Photo Film Co., Ltd.) at 28 ° C. The shortest time and the longest time during which the remaining film ratio of the part was maintained at 90% or more (however, from the practical aspect, up to 60 seconds) were measured, the development latitude was evaluated, and the results are also shown in Table 1. did.
[0077]
Here, the residual film ratio was calculated based on the following equation by measuring the reflection density using a reflection densitometer (“RD-514” manufactured by Macbeth).
Residual film ratio (%) = [(reflection density of unexposed portion after development−reflection density of support surface) / (reflection density of plate surface before development−reflection density of support surface)] × 100
[0078]
[Table 1]

[0079]
Each of the positive photosensitive lithographic printing plates described above was subjected to a light intensity irradiation of 400 lux of a white fluorescent lamp (36W white fluorescent lamp “Neolmi Super FLR40S-W / M / 36” manufactured by Mitsubishi Electric Corporation) for 10 hours. When the development process similar to that described above was performed after leaving it to stand, there was no substantial film reduction in any of the Examples and Comparative Examples, and the handleability under a white fluorescent lamp was good.
[0080]
【The invention's effect】
According to the present invention, the contrast between the image area and the non-image area is excellent, the development latitude is wide, the remaining film ratio of the image area is sufficiently maintained, and more desirably, it is not sensitive to light in the ultraviolet region, A positive photosensitive composition and a positive photosensitive lithographic printing plate excellent in handleability under a white fluorescent lamp can be provided.

Claims (12)

A positive photosensitive composition comprising a photothermal conversion material that absorbs light from an image exposure light source and converts it into heat, and a novolac resin, wherein the photothermal conversion material converts the light from the image exposure light source. The novolak resin does not contain a pyrolyzable substance that is decomposed by the action of heat generated by absorption, and the novolak resin is composed of phenols in which o-cresol accounts for 60 mol% or more. Positive photosensitive composition. A positive photosensitive composition comprising a photothermal conversion substance that absorbs light from an image exposure light source and converts it into heat and a novolac resin, and is substantially insensitive to light in the ultraviolet region, the novolac A positive photosensitive composition, wherein the resin is composed of phenols in which o-cresol accounts for 60 mol% or more. The positive photosensitive composition according to claim 1, wherein the novolak resin is composed of phenols in which o-cresol accounts for 70 mol% or more. The positive photosensitive composition according to any one of claims 1 to 3, wherein the novolak resin is composed of a phenol having 95 mol% or less of o-cresol. The positive photosensitive composition according to any one of claims 1 to 4, wherein 5 to 40 mol% of the phenols constituting the novolak resin is phenol. The positive photosensitive composition according to claim 5, wherein the phenol in the phenols constituting the novolak resin is 10 mol% or more. The positive photosensitive composition according to claim 5 or 6, wherein the phenol in the phenol constituting the novolak resin is 30 mol% or less. The positive photosensitive composition according to any one of claims 1 to 7, wherein the novolak resin has a weight average molecular weight of 5,000 to 15,000. The positive photosensitive composition according to any one of claims 1 to 8, wherein the photothermal conversion substance is a light-absorbing dye having an absorption band in a part or all of a wavelength range of 650 to 1300 nm. The positive photosensitive composition according to claim 1, which is substantially insensitive to light in the ultraviolet region. 2. The positive photosensitive property according to claim 1, wherein the solubility of the composition in an alkaline developer after being left for 10 hours under a white fluorescent lamp having a light intensity of 400 lux does not substantially change as compared with that before being left as it is. Composition. A positive photosensitive lithographic printing plate comprising a layer of the positive photosensitive composition according to any one of claims 1 to 11 formed on a support surface.