JP3860361B2 - Positive photosensitive composition, positive photosensitive lithographic printing plate, and positive image forming method - Google Patents

Description

【００２０】
〔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。〕
【００２１】
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。
【００２２】
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。
【００２３】
【化２】

【００２４】
〔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。〕
【００２５】
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。
【００２６】
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。
【００２７】
【化３】

【００２８】
〔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。〕
【００２９】
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。
【００３０】
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。
【００３１】
【化４】

【００３２】
〔式(IVa) 、(IVa) 、及び(IVc) 中、Ｚ¹ 及びＺ² 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。〕
【００３３】
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。
【００３４】
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。
【００３５】
【化５】

【００３６】
〔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。〕
【００３７】
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。
【００３８】
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。
【００３９】
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。
【００４０】
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。
【００４１】
【化６】

【００４２】
【化７】

【００４３】
【化８】

【００４４】
【化９】

【００４５】
【化１０】

【００４６】
【化１１】

【００４７】
【化１２】

【００４８】
【化１３】

【００４９】
【化１４】

【００５０】
【化１５】

【００５１】
【化１６】

【００５２】
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、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って、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、中で、本発明においては、フェノール類としてのフェノール、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、レゾルシノールと、アルデヒド類又はケトン類としてのホルムアルデヒド、アセトアルデヒド、プロピオンアルデヒドとの重縮合体が好ましく、特に、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：レゾルシノールの混合割合がモル比で４０〜１００：０〜５０：０〜２０：０〜２０：０〜２０の混合フェノール類、又は、フェノール：ｍ−クレゾール：ｐ−クレゾールの混合割合がモル比で１〜１００：０〜７０：０〜６０の混合フェノール類と、ホルムアルデヒドとの重縮合体が好ましい。尚、本発明のポジ型感光性組成物は後述する溶剤抑止剤を含有することが好ましく、その場合は、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：レゾルシノールの混合割合がモル比で７０〜１００：０〜３０：０〜２０：０〜２０：０〜２０の混合フェノール類、又は、フェノール：ｍ−クレゾール：ｐ−クレゾールの混合割合がモル比で１０〜１００：０〜６０：０〜４０の混合フェノール類と、ホルムアルデヒドとの重縮合体が好ましい。
【００５３】
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、好ましくは１，５００〜２０，０００、更に好ましくは２，０００〜１５，０００、特に好ましくは３，０００〜１２，０００のものが用いられる。重量平均分子量が前記範囲よりよりも小さいとレジストとしての十分な塗膜が得られず、前記範囲よりも大きいとアルカリ現像液に対する溶解性が小さくなり、非画像部の抜けが不十分となってレジストのパターンが得られにくくなる傾向となる。
【００５４】
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するが、両者の合計量に対するそれぞれの含有割合は、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％であるのが好ましく、前者が１〜４０重量％、後者が９９〜６０重量％であるのが更に好ましく、前者が２〜３０重量％、後者が９８〜７０重量％であるのが特に好ましい。
【００５５】
そして、前記光熱変換物質と前記ノボラック樹脂を含有してなる本発明のポジ型感光性組成物は、該組成物全体におけるノボラック樹脂も含む全フェノール性水酸基含有化合物に対する、分子量１，５００以下のフェノール性水酸基含有化合物の割合が３５〜７０重量％であるもの、分子量１，０００以下のフェノール性水酸基含有化合物の割合が２５〜６０重量％であるもの、又は、分子量８００以下のフェノール性水酸基含有化合物の割合が２０〜５５重量％であるもの、のいずれかのものであり、分子量１，５００以下のフェノール性水酸基含有化合物の割合が３５〜７０重量％で、分子量１，０００以下のフェノール性水酸基含有化合物の割合が２５〜６０重量％であり、且つ、分子量８００以下のフェノール性水酸基含有化合物の割合が２０〜５５重量％であるものが最も好ましい。
【００５６】
又、前記分子量１，５００以下のフェノール性水酸基含有化合物の割合としては３５〜６０重量％であるのが好ましく、分子量１，０００以下のフェノール性水酸基含有化合物の割合としては２５〜５５重量％であるのが好ましく、分子量８００以下のフェノール性水酸基含有化合物の割合としては２０〜５０重量％であるのが好ましい。
【００５７】
組成成全体におけるノボラック樹脂も含む全フェノール性水酸基含有化合物に対する、分子量１，５００以下のフェノール性水酸基含有化合物の割合、分子量１，０００以下のフェノール性水酸基含有化合物の割合、及び、分子量８００以下のフェノール性水酸基含有化合物の割合が、共に、前記範囲未満では、ポジ型感光性組成物としての感度が不足し、一方、前記範囲超過では、現像液に対する膜強度の劣るものとなる。
【００５８】
ここで、フェノール性水酸基含有化合物としては、フェノール性水酸基を有する化合物である限り特に限定されるものではなく、従って、前記ノボラック樹脂の原料フェノール類単量体、その２量体以上のオリゴマー、及び重合体等、並びに、前記ノボラック樹脂の原料フェノール類以外のフェノール類単量体、その２量体以上のオリゴマー、及び重合体等、のいずれをも対象とし得る。
【００５９】
そして、後者のノボラック樹脂の原料フェノール類以外のフェノール類等は、前記光熱変換物質と前記ノボラック樹脂に更に加えられて本発明の組成物を構成し、又、前者のノボラック樹脂の原料フェノール類等は、ノボラック樹脂中に通常含有される未反応物或いは副生オリゴマー等のフェノール類等の残存量を精製操作等により調整して、それら原料フェノール類に由来するものとして残存するか、或いは、後者のノボラック樹脂の原料フェノール類以外のフェノール類等と同様に更に加えられて本発明の組成物を構成する。
【００６０】
本発明のポジ型感光性組成物におけるこれらのフェノール性水酸基含有化合物としては、具体的には、１個以上のベンゼン環を有する単環式、環集合式、縮合多環式等の一価、二価、三価等のフェノール類であって、前記ノボラック樹脂の原料フェノール類として挙げたと同様のフェノール類の外、例えば、２，４，６−トリメチルフェノール、ｐ−メトキシフェノール、ｐ−カルボキシフェノール、ｐ−アセチルフェノール等の単環式、４−ヒドロキシフェニルフェニルメタン、ビス（４−ヒドロキシフェニル）メタン、ビス（４−ヒドロキシフェニル）フェニルメタン、１，１−ビス（４’−ヒドロキシフェニル）エタン、１，１，１−トリス（４’−ヒドロキシフェニル）エタン、１，１−ビス（４’−ヒドロキシフェニル）シクロヘキサン、４，４’−ジヒドロキシジフェニルエーテル、４，４’−ジヒドロキシジフェニルケトン、４，４’−ジヒドロキシジフェニルスルフィド、４，４’−ジヒドロキシジフェニルスルホキシド、４，４’−ジヒドロキシジフェニルスルホン類等の環集合式、９−アントロール、及び下記の構造で表される化合物(1) 、(2) 、(3) 等の縮合多環式等の化合物が挙げられ、ベンゼン環の置換基としてアルキル基、アルコキシ基、アシル基、カルボキシ基を有するものが好ましく、炭素数１０以下のアルキル基、アルコキシ基を有するものが特に好ましい。
【００６１】
【化１７】

【００６２】
以上のフェノール性水酸基含有化合物の中で、本発明においては、酸素原子の数に対する炭素原子の数の比が２〜２０である化合物が好ましく、３〜１５である化合物が更に好ましく、３〜１０である化合物が特に好ましい。
【００６３】
本発明のポジ型感光性組成物が、前述の如き、特定分子量のフェノール性水酸基含有化合物を特定量含有することにより、感度、及び画像部と非画像部とのコントラスト等に優れることとなる理由は定かではないが、ノボラック樹脂のコンフォメーション変化等の化学変化以外の変化に起因する潜像形成能が改善されるためと考えられる。
【００６４】
尚、本発明のポジ型感光性組成物には、前記光熱変換物質、前記ノボラック樹脂、及び所望により加えられる前記フェノール性水酸基含有化合物の他に、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、且つ、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。
【００６５】
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、同じく特願平９−２９１８８０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９−３３１５１２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。
【００６６】
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。
【００６７】
又、本発明のポジ型感光性組成物には、必要に応じて、例えば、ビクトリアピュアブルー（４２５９５）、クリスタルバイオレット（４２５５５）、クリスタルバイオレットラクトン、オーラミンＯ（４１０００）、カチロンブリリアントフラビン（ベーシック１３）、ローダミン６ＧＣＰ（４５１６０）、ローダミンＢ（４５１７０）、サフラニンＯＫ７０：１００（５０２４０）、エリオグラウシンＸ（４２０８０）、ファーストブラックＨＢ（２６１５０）、Ｎｏ．１２０／リオノールイエロー（２１０９０）、リオノールイエローＧＲＯ（２１０９０）、シムラーファーストイエロー８ＧＦ（２１１０５）、ベンジジンイエロー４Ｔ−５６４Ｄ（２１０９５）、シムラーファーストレッド４０１５（１２３５５）、リオノールレッドＢ４４０１（１５８５０）、ファーストゲンブルーＴＧＲ−Ｌ（７４１６０）、リオノールブルーＳＭ（２６１５０）等の顔料又は染料等の着色剤が含有されていてもよい。尚、ここで、前記の括弧内の数字はカラーインデックス（Ｃ．Ｉ．）を意味する。
【００６８】
本発明のポジ型感光性組成物における前記着色剤の含有割合は、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。
【００６９】
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。
【００７０】
尚、一般に、ポジ型感光性組成物が紫外線領域の光に感受性を有する化合物を含まないものであると、感度、及び画像部と非画像部とのコントラスト等が劣る傾向にあり、従って、本発明の前記ポジ型感光性組成物としては、オニウム塩、ジアゾニウム塩、キノンジアジド基含有化合物等の、紫外線領域の光に感受性を有する化合物を含まず、紫外線領域の光に対して実質的に感受性を有さないものであるとき、その感度、及び画像部と非画像部とのコントラスト等の面での本発明の効果をより顕著に発現することができることから、好ましい。
【００７１】
ここで、紫外線領域の光に対して実質的に感受性を有さないとは、３６０〜４５０ｎｍの波長の光による照射の前後で、アルカリ現像液に対する溶解性に実質的有意差を生じず、実用的な意味での画像形成能を有さないことを意味し、例えば、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時間放置した後の組成物のアルカリ現像液に対する溶解性が、放置前に比して実質的変化を生じない結果を示す。
【００７２】
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。
【００７３】
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。
【００７４】
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、０．３〜７μｍ、好ましくは０．５〜５μｍ、特に好ましくは１〜３μｍの範囲とする。尚、その際の乾燥温度としては、例えば、３０〜１７０℃程度、好ましくは４０〜１５０℃程度が採られる。
【００７５】
尚、本発明の効果を一層確実ならしめるために、例えば、４０〜１００℃程度、好ましくは４０〜７０℃程度の温度で、１分〜５０時間程度、好ましくは３０分〜２０時間程度の加熱処理を施すことが好ましい。
【００７６】
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板であり、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。
【００７７】
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。
【００７８】
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。
【００７９】
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。
【００８０】
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。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。
【００８１】
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。
【００８２】
【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。
【００８３】
実施例１〜４、比較例１〜２
アルミニウム板（厚さ０．２４ｍｍ）を、５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、０．５モル／リットルの濃度の塩酸水溶液中で、温度２５℃、電流密度６０Ａ／ｄｍ² 、処理時間３０秒の条件で電解エッチング処理を行った。次いで５重量％の水酸化ナトリウム水溶液中で６０℃、１０秒間のデスマット処理を施した後、２０重量％硫酸溶液中で、温度２０℃、電流密度３Ａ／ｄｍ² 、処理時間１分の条件で陽極酸化処理を行った。更に、８０℃の熱水で２０秒間熱水封孔処理を行い、平版印刷版支持体用のアルミニウム板を作製した。
【００８４】
得られたアルミニウム板支持体表面に、光熱変換物質として前記具体例(II-9)で示したインドール系色素４重量部、ノボラック樹脂として下記の▲１▼〜▲３▼の樹脂１００重量部、フェノール性水酸基含有化合物として下記の▲４▼〜▲６▼の化合物を表１に示す量用い又は用いずに、及び、クリスタルバイオレットラクトン１０重量部を、シクロヘキサノン１２０６重量部に加え、室温で１０分間攪拌して調液した塗布液をワイヤーバーを用いて塗布し、１００℃で２分間乾燥させた後、５５℃で１６時間加熱処理することにより、塗膜量２．５ｇ／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。
【００８５】
ノボラック樹脂
▲１▼フェノール：ｍ−クレゾール：ｐ−クレゾールの混合割合がモル比で５０：３０：２０の混合フェノール類と、ホルムアルデヒドとの重縮合体からなり、重量平均分子量１０，０００であって、ノボラック樹脂も含む全フェノール性水酸基含有化合物に対する、分子量１，５００以下のフェノール性水酸基含有化合物の割合が３８重量％、分子量１，０００以下のフェノール性水酸基含有化合物の割合が３０重量％、分子量８００以下のフェノール性水酸基含有化合物の割合が２５重量％のノボラック樹脂。
【００８６】
▲２▼ｍ−クレゾール：ｐ−クレゾールの混合割合がモル比で７０：３０の混合フェノール類と、ホルムアルデヒドとの重縮合体からなり、重量平均分子量１０，８００であって、ノボラック樹脂も含む全フェノール性水酸基含有化合物に対する、分子量１，５００以下のフェノール性水酸基含有化合物の割合が３１重量％、分子量１，０００以下のフェノール性水酸基含有化合物の割合が２３重量％、分子量８００以下のフェノール性水酸基含有化合物の割合が１９重量％のノボラック樹脂。
【００８７】
▲３▼ｍ−クレゾール：ｐ−クレゾールの混合割合がモル比で９０：１０の混合フェノール類と、ホルムアルデヒドとの重縮合体からなり、重量平均分子量１０，０００であって、ノボラック樹脂も含む全フェノール性水酸基含有化合物に対する、分子量１，５００以下のフェノール性水酸基含有化合物の割合が３０重量％、分子量１，０００以下のフェノール性水酸基含有化合物の割合が２２重量％、分子量８００以下のフェノール性水酸基含有化合物の割合が１８重量％のノボラック樹脂。
【００８８】
尚、前記ノボラック樹脂における全フェノール性水酸基含有化合物に対する、各分子量化合物の割合は、東ソー社製ゲルパーミエーションクロマトグラフィー「ＨＬＣ−８０２０」を用い、カラムとして東ソー社製「ＴＳＫｇｅｌＧＭＨ_X Ｌ−Ｎ」の３０ｃｍを２本、検出器としてＲＩを用いて、移動層にテトラハイドロフラン（特級）、インジェクション量１００μｌ、流速１．０ｍｌ／分の条件で測定した。
【００８９】
フェノール性水酸基含有化合物
▲４▼前記具体例〔化１７〕の化合物(1)
▲５▼前記具体例〔化１７〕の化合物(2)
▲６▼前記具体例〔化１７〕の化合物(3)
【００９０】
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」）を用いて各種の露光エネルギーで２００線、１〜９９％の網点画像を画像露光し、次いで、アルカリ現像液（富士写真フィルム社製「ＤＰ−４」の８倍希釈液）に２８℃で現像処理を行うことにより、１〜９９％の網点画像を再現させた印刷版を作製し、そのときの感度を３％の網点が再現する露光エネルギー量として求め、結果を表１に示した。
【００９１】
更に、得られた印刷版の膜強度を以下に示す基準で評価し、結果を表１に示した。
Ａ；強固な膜強度で網点を再現。
Ｂ；やや劣るが、実用上問題ない膜強度で網点を再現。
Ｃ；露光部が現像液に溶解せず。（画像形成できず。）
【００９２】
実施例５〜８、比較例３〜４
前記実施例で得られたアルミニウム板支持体表面に、光熱変換物質として前記具体例(II-9)で示したインドール系色素４重量部、ノボラック樹脂として前記の▲１▼〜▲３▼の樹脂１００重量部、フェノール性水酸基含有化合物として前記の▲１▼〜▲３▼の化合物を表１に示す量用い又は用いずに、及び、クリスタルバイオレットラクトン１０重量部、１，２−シクロヘキサンジカルボン酸５重量部、ポリエチレングリコール（数平均分子量２，０００）３重量部を、メトキシエタノール９６６重量部とエトキシエタノール２４０重量部に加え、室温で１０分間攪拌して調液した塗布液をワイヤーバーを用いて塗布し、８５℃で２分間乾燥させた後、５５℃で１６時間加熱処理することにより、塗膜量２．５ｇ／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、前記実施例と同様にして、画像露光し、現像して、感度、及び膜強度を評価し、結果を表１に示した。
【００９３】
【表１】

【００９４】
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。
【００９５】
【発明の効果】
本発明によれば、感度、及び画像部と非画像部とのコントラストに優れると共に、現像液に対する膜強度にも優れ、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. TECHNICAL FIELD The present invention relates to a positive photosensitive composition and a positive photosensitive lithographic printing plate having high sensitivity to light in a region, and a positive image forming method, and in particular, a positive photosensitive composition suitable for direct plate making using a semiconductor laser, a YAG laser, or the like. And a positive photosensitive lithographic printing plate and a positive image forming method.
[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 further disclosed in JP-A-7-285275 as a binder, a substance that absorbs light and generates heat, and a heat An image forming material is disclosed that includes a substance that is degradable and substantially reduces the solubility of the binder in a state where it does not decompose.
[0006]
In addition, these conventional techniques are sensitive to light in the ultraviolet region, and the reaction proceeds during handling under a white fluorescent lamp, so that it is difficult to obtain a stable quality product. JP-A-9-43847 contains a resin that is hardly soluble in an alkali developer and an infrared absorber, and is heated by infrared irradiation or the like to change its 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.
[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, in the negative photosensitive composition that requires heat treatment after exposure, the image obtained by the processing conditions is not always stable in the above-described conventional technique, In a positive photosensitive composition that does not require heat treatment after exposure, the sensitivity and the contrast between the image part (non-exposed part) and the non-image part (exposed part) are insufficient. It has problems such as not being sufficiently removed, and the remaining film ratio of the image area is not sufficiently maintained. In particular, changes other than chemical changes may cause a difference in solubility between the exposed and unexposed areas. In the positive compositions disclosed in JP-A-9-43847 and WO97 / 39894, 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 is obtained. It was found that a photosensitive composition that can be formed was obtained, and a patent application (Japanese Patent Laid-Open No. 10-268512) was previously filed, but it was 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 sensitivity and contrast between an image area and a non-image area, excellent in film strength against a developer, and more preferably in the ultraviolet region. It is an object of the present invention to provide a positive photosensitive composition, a positive photosensitive lithographic printing plate, and a positive image forming method that are insensitive to light and excellent in handleability under a white fluorescent lamp.
[0011]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention mainly used a composition that uses a photothermal conversion substance and a novolac resin for light in the near infrared region in the presence of a specific phenolic hydroxyl group-containing compound. 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 novolak resin. A positive photosensitive composition in which the ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,500 or less to the total phenolic hydroxyl group-containing compound including the novolak resin in the whole composition is 35 to 70% by weight, The gist.
[0012]
The present invention also relates to 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, including the novolac resin in the entire composition. The gist is a positive photosensitive composition in which the ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,000 or less to the phenolic hydroxyl group-containing compound is 25 to 60% by weight.
[0013]
The present invention also relates to 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, including the novolac resin in the entire composition. The gist is a positive photosensitive composition in which the ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 800 or less to the phenolic hydroxyl group-containing compound is 20 to 55% by weight.
[0014]
The present invention also relates to 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, including the novolac resin in the entire composition. The ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,500 or less to the phenolic hydroxyl group-containing compound is 35 to 70% by weight, and the ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,000 or less is 25 to 60% by weight, The gist of the present invention is a positive photosensitive composition in which the proportion of the phenolic hydroxyl group-containing compound having a molecular weight of 800 or less is 20 to 55% by weight.
[0015]
Furthermore, the present invention relates to a positive photosensitive lithographic printing plate in which a layer of any of the above-mentioned positive photosensitive compositions is formed on the surface of a support, and the lithographic printing plate to a semiconductor laser or a YAG laser. The gist of the present invention is a positive image forming method in which an image is exposed to light and then developed with an alkali developer.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
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 pigments, 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 1,300 nm, Absorptive dyes are 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.
[0017]
Typical examples of these light-absorbing dyes include so-called cyanine dyes in a broad sense in which a heterocyclic ring containing a nitrogen atom, an oxygen atom, or a sulfur atom is bonded with polymethine (-CH =) _n. Specifically, for example, quinoline (so-called cyanine), indole (so-called indocyanine), benzothiazole (so-called thiocyanine), aminobenzene (so-called polymethine), pyrylium Type, thiapyrylium type, squarylium type, croconium type, azurenium type, etc., among which quinoline type, indole type, benzothiazole type, aminobenzene type, pyrylium type, or thiapyrylium type are preferable, and in addition, aminium Typical dyes such as those based on dye, imonium, phthalocyanine and anthraquinone And the like.
[0018]
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.
[0019]
[Chemical 1]

[0020]
[In the formulas (Ia), (Ib), and (Ic), R ¹ and R ² are each independently an optionally substituted alkyl group or an optionally substituted alkenyl group. , An alkynyl group that may have a substituent, or a phenyl group that may have a substituent, L ¹ represents a tri, penta, or heptamethine group that may have a substituent, Two substituents on the penta or heptamethine group may be linked to each other to form a cycloalkene ring having 5 to 7 carbon atoms, and the quinoline ring may have a substituent, in which case These two substituents may be linked to each other to form a condensed benzene ring. X ⁻ represents a counter anion. ]
[0021]
Preferable examples of the substituent in formula (Ia), R ¹ and R ² in (Ib), and (Ic), an alkoxy group, a phenoxy group, hydroxy group, or a phenyl group and the like, substitution of L ¹ Examples of the group include an alkyl group, an amino group, and a halogen atom. Examples of the substituent in the quinoline ring include an alkyl group, an alkoxy group, a nitro group, and a halogen atom.
[0022]
Further, as the indole and benzothiazole dyes, those represented by the following general formula (II) are particularly preferable.
[0023]
[Chemical 2]

[0024]
[In Formula (II), Y ¹ and Y ² each independently represent a dialkylmethylene group or a sulfur atom, and R ³ and R ⁴ each independently represent 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 phenyl group which may have a substituent, L ² may have a substituent A good tri, penta, or heptamethine group, and two substituents on the penta or heptamethine group may be linked to each other to form a C5-C7 cycloalkene ring, and the condensed benzene ring is a substituent In this case, two adjacent substituents may be connected to each other to form a condensed benzene ring. X ⁻ represents a counter anion. ]
[0025]
Here, examples of the substituent in R ³ and R ⁴ in the formula (II) include an alkoxy group, a phenoxy group, a hydroxy group, and a phenyl group, and the substituent in L ² includes an alkyl group and an amino group. Or a halogen atom, and the substituent on the benzene ring includes an alkyl group, an alkoxy group, a nitro group, or a halogen atom.
[0026]
As the aminobenzene dye, those represented by the following general formula (III) are particularly preferable.
[0027]
[Chemical 3]

[0028]
[In the formula (III), R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represents an alkyl group, and R ⁹ and R ¹⁰ may each independently have a substituent. An aryl group, a furyl group, or a thienyl group, L ³ represents an optionally substituted mono, tri, or pentamethine group, and two substituents on the tri or pentamethine group are linked to each other. A C5-C7 cycloalkene ring may be formed, and the quinone ring and the benzene ring may have a substituent. X ⁻ represents a counter anion. ]
[0029]
Here, specific examples of R ⁹ and R ¹⁰ in formula (III) include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a 2-furyl group, a 3-furyl group, a 2-thienyl group, 3- Thienyl group and the like, and examples of the substituent include an alkyl group, an alkoxy group, a dialkylamino group, a hydroxy group, and a halogen atom, and the substituent in L ³ includes an alkyl group, an amino group, or A halogen atom etc. are mentioned, As a substituent in a quinone ring and a benzene ring, an alkyl group, an alkoxy group, a nitro group, or a halogen atom etc. are mentioned.
[0030]
As the pyrylium-based and thiapyrylium-based dyes, those represented by the following general formula (IVa), (IVb), or (IVc) are particularly preferable.
[0031]
[Formula 4]

[0032]
[In formulas (IVa), (IVa), and (IVc), Z ¹ and Z ² each independently represent an oxygen atom or a sulfur atom, and R ¹¹ , R ¹² , R ¹³ , and R ¹⁴ are each independently A hydrogen atom or an alkyl group, or R ¹¹ and R ¹³ , and R ¹² and R ¹⁴ may be connected to each other to form a cycloalkene ring having 5 or 6 carbon atoms, and L ⁴ is a substituent. A mono-, tri-, or pentamethine group that may have a substituent, and two substituents on the tri- or pentamethine group may be linked to each other to form a C5-C7 cycloalkene ring, The pyrylium ring and the thiapyrylium ring may have a substituent, and in that case, two adjacent substituents may be connected to each other to form a condensed benzene ring. X ⁻ represents a counter anion. ]
[0033]
Here, examples of the substituent in L ⁴ in the formulas (IVa), (IVa), and (IVc) include an alkyl group, an amino group, or a halogen atom, and examples of the substituent in the pyrylium ring and the thiapyrylium ring include And aryl groups such as a phenyl group and a naphthyl group.
[0034]
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.
[0035]
[Chemical formula 5]

[0036]
[In the formulas (Va) and (Vb), R ¹⁵ , R ¹⁶ , R ¹⁷ , and R ¹⁸ are each independently a hydrogen atom, a halogen atom, an optionally substituted alkyl group, or a substituent. An alkenyl group which may have a substituent, an alkynyl group which may have a substituent, or an alkoxy group which may have a substituent, wherein R ¹⁹ and R ²⁰ are each independently a substituted An alkyl group which may have a group, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, an alkoxy group which may have a substituent, a substituent An acyloxy group which may have or a phenyl group which may have a substituent, and the benzene ring and 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. ]
[0037]
Here, the substituents in R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , R ¹⁹ , and R ²⁰ in formulas (Va) and (Vb) are alkyl groups, alkoxy groups, carboxy groups, acyloxy groups, Examples thereof include an alkoxycarbonyl group, a hydroxy group, an amino group, an alkylamino group, a halogenated alkyl group, or a halogen atom. Examples of the substituent in the benzene ring and iminoquinone ring include an alkyl group, an alkoxy group, an acyl group, a nitro group, Or a halogen atom etc. are mentioned.
[0038]
Among these aminium dyes and imonium dyes, R ¹⁵ , R ¹⁶ , R ¹⁷ and R ^{18 in the} general formulas (Va) and (Vb) are alkyl groups, and R ¹⁹ and R ²⁰ are also Particularly preferred is an alkyl group, or a group in which R ¹⁹ and R ²⁰ are a phenyl group having a dialkylamino group as a substituent.
[0039]
The counter anions X ⁻ in the general formulas (Ia to c), (II), (III), (IVa to c), and (Va to b) are, for example, Cl ⁻ , Br ⁻ , I ⁻ , Inorganic acid anions such as inorganic boric acid such as ClO ₄ ⁻ , PF ₆ ⁻ , SbF ₆ ⁻ , and BF ₄ ⁻ , benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, acetic acid, and methyl, ethyl, propyl And organic acid anions such as organic boric acid having an organic group such as butyl, phenyl, methoxyphenyl, naphthyl, difluorophenyl, pentafluorophenyl, thienyl, and pyrrolyl.
[0040]
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.
[0041]
[Chemical 6]

[0042]
[Chemical 7]

[0043]
[Chemical 8]

[0044]
[Chemical 9]

[0045]
[Chemical Formula 10]

[0046]
Embedded image

[0047]
Embedded image

[0048]
Embedded image

[0049]
Embedded image

[0050]
Embedded image

[0051]
Embedded image

[0052]
The novolak resin in the positive photosensitive composition of the present invention is commonly used as a phenolic hydroxyl group-containing alkali-soluble resin in the binder resin of this type of photosensitive composition. 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, 4,4'-biphenyldiol, 2,2-bis (4'-hydroxyphenyl) propane, etc. At least of phenols The seed is used under an acidic catalyst, for example, aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, furfural (in addition, paraformaldehyde may be used instead of formaldehyde, and paraaldehyde may be used instead of acetaldehyde), or , Acetone, methyl ethyl ketone, ketones such as methyl isobutyl ketone, and the like, and in the present invention, phenol, o-cresol, m-cresol, p -Preferred are polycondensates of cresol, 2,5-xylenol, 3,5-xylenol, resorcinol and formaldehyde, acetaldehyde, propionaldehyde as aldehydes or ketones, in particular m-cresol: Mixed phenols having a mixing ratio of resole: 2,5-xylenol: 3,5-xylenol: resorcinol in a molar ratio of 40 to 100: 0 to 50: 0 to 20: 0 to 20: 0 to 20, or phenol: Preferred is a polycondensate of formaldehyde and a mixed phenol having a mixing ratio of m-cresol: p-cresol of 1 to 100: 0 to 70: 0 to 60 in terms of molar ratio. In addition, it is preferable that the positive photosensitive composition of this invention contains the solvent inhibitor mentioned later, and in that case, m-cresol: p-cresol: 2,5-xylenol: 3,5-xylenol: resorcinol The mixing ratio is 70 to 100: 0 to 30: 0 to 20: 0 to 20: 0 to 20 in molar ratio, or the mixing ratio of phenol: m-cresol: p-cresol is 10 to 10 in molar ratio. A polycondensate of 100: 0 to 60: 0 to 40 mixed phenols with formaldehyde is preferred.
[0053]
The novolak resin has a polystyrene-reduced weight average molecular weight of preferably 1,500 to 20,000, more preferably 2,000 to 15,000, and particularly preferably 3,000 to 12,000, as measured by gel permeation chromatography. 000 is used. If the weight average molecular weight is smaller than the above range, a sufficient coating film as a resist cannot be obtained. If the weight average molecular weight is larger than the above range, the solubility in an alkali developer is reduced, and the non-image area is insufficiently omitted. It tends to be difficult to obtain a resist pattern.
[0054]
The positive photosensitive composition of the present invention has the photothermal conversion substance and the novolak resin as a basic composition, and the respective content ratios relative to the total amount of both are 0.5 to 50% by weight of the former photothermal conversion substance, The latter novolak resin is preferably 99.5 to 50% by weight, the former 1 to 40% by weight, the latter 99 to 60% by weight more preferably, the former 2 to 30% by weight and the latter 98%. Particularly preferred is ˜70% by weight.
[0055]
The positive photosensitive composition of the present invention comprising the photothermal conversion substance and the novolak resin is a phenol having a molecular weight of 1,500 or less relative to the total phenolic hydroxyl group-containing compound including the novolac resin in the entire composition. A compound having a molecular weight of 35 to 70% by weight, a compound having a molecular weight of 1,000 or less, a compound having a molecular weight of 25 to 60% by weight, or a compound having a molecular weight of 800 or less The proportion of the phenolic hydroxyl group-containing compound having a molecular weight of 1,500 or less is 35 to 70% by weight and the molecular weight of 1,000 or less. Of the phenolic hydroxyl group-containing compound having a proportion of the containing compound of 25 to 60% by weight and a molecular weight of 800 or less. What if it is 20 to 55% by weight is most preferred.
[0056]
The proportion of the phenolic hydroxyl group-containing compound having a molecular weight of 1,500 or less is preferably 35 to 60% by weight, and the proportion of the phenolic hydroxyl group-containing compound having a molecular weight of 1,000 or less is 25 to 55% by weight. The proportion of the phenolic hydroxyl group-containing compound having a molecular weight of 800 or less is preferably 20 to 50% by weight.
[0057]
The ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,500 or less, the ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,000 or less, and the molecular weight of 800 or less to the total phenolic hydroxyl group-containing compound including the novolak resin in the entire composition. When the proportion of the phenolic hydroxyl group-containing compound is less than the above range, the sensitivity as a positive photosensitive composition is insufficient. On the other hand, when the proportion exceeds the above range, the film strength against the developer is inferior.
[0058]
Here, the phenolic hydroxyl group-containing compound is not particularly limited as long as it is a compound having a phenolic hydroxyl group, and therefore, the phenolic monomer of the novolak resin, an oligomer of its dimer or more, and Any of polymers, etc., and phenolic monomers other than the starting phenols of the novolak resin, oligomers of dimers or more thereof, polymers and the like can be targeted.
[0059]
And the phenols other than the raw material phenols of the latter novolak resin are further added to the photothermal conversion substance and the novolak resin to constitute the composition of the present invention, and the raw material phenols of the former novolak resin, etc. Is prepared by adjusting the residual amount of phenols such as unreacted substances or by-product oligomers normally contained in the novolak resin by a purification operation or the like, or the latter is derived from those raw material phenols, or the latter The composition of the present invention is further added in the same manner as phenols other than the raw material phenols of the novolak resin.
[0060]
As these phenolic hydroxyl group-containing compounds in the positive photosensitive composition of the present invention, specifically, monovalents such as monocyclic, ring aggregates, condensed polycyclics having one or more benzene rings, Divalent and trivalent phenols other than the same phenols as mentioned as the starting phenol for the novolak resin, such as 2,4,6-trimethylphenol, p-methoxyphenol, p-carboxyphenol Monocyclic such as p-acetylphenol, 4-hydroxyphenylphenylmethane, bis (4-hydroxyphenyl) methane, bis (4-hydroxyphenyl) phenylmethane, 1,1-bis (4′-hydroxyphenyl) ethane 1,1,1-tris (4′-hydroxyphenyl) ethane, 1,1-bis (4′-hydroxyphenyl) cyclohexa , 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl ketone, 4,4′-dihydroxydiphenyl sulfide, 4,4′-dihydroxydiphenyl sulfoxide, 4,4′-dihydroxydiphenyl sulfones, etc. , 9-anthrol, and condensed polycyclic compounds such as compounds (1), (2), and (3) represented by the following structures, and alkyl groups and alkoxy groups as substituents on the benzene ring: And those having an acyl group or a carboxy group are preferred, and those having an alkyl group or alkoxy group having 10 or less carbon atoms are particularly preferred.
[0061]
Embedded image

[0062]
Among the phenolic hydroxyl group-containing compounds described above, in the present invention, a compound having a ratio of the number of carbon atoms to the number of oxygen atoms of 2 to 20 is preferred, a compound of 3 to 15 is more preferred, and 3 to 10 is preferred. Is particularly preferred.
[0063]
The reason why the positive photosensitive composition of the present invention contains a specific amount of a phenolic hydroxyl group-containing compound having a specific molecular weight, as described above, is excellent in sensitivity, contrast between an image area and a non-image area, and the like. Although it is not certain, it is considered that the latent image forming ability due to a change other than a chemical change such as a conformational change of a novolak resin is improved.
[0064]
In the positive photosensitive composition of the present invention, in addition to the photothermal conversion substance, the novolak resin, and the phenolic hydroxyl group-containing compound that is optionally added, the exposed portion and the unexposed portion are dissolved in an alkaline developer. For the purpose of increasing the difference in properties, it has the function of reducing the solubility of the resin by forming hydrogen bonds with the novolak resin, and absorbs almost no light in the near infrared region. It may contain a dissolution inhibitor that is not decomposed by.
[0065]
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. A lactone skeleton, an N, N-diarylamide skeleton, a diarylmethylimino skeleton, which are described in detail in Japanese Patent Application No. 9-291880, such as aromatic ketones, aromatic aldehydes, aromatic amines, aromatic ethers, etc. Examples thereof include acid color-forming dyes that also serve as colorants, and nonionic surfactants described in detail in Japanese Patent Application No. 9-331512.
[0066]
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.
[0067]
In addition, the positive photosensitive composition of the present invention may include, for example, Victoria Pure Blue (42595), Crystal Violet (42555), Crystal Violet Lactone, Auramin O (41000), Catillon Brilliant Flavin (Basic). 13), Rhodamine 6GCP (45160), Rhodamine B (45170), Safranin OK70: 100 (50240), Erioglaucine X (42080), Fast Black HB (26150), No. 13 120 / Lionol Yellow (21090), Lionol Yellow GRO (21090), Shimla First Yellow 8GF (21105), Benzidine Yellow 4T-564D (21095), Shimler First Red 4015 (12355), Lionol Red B4401 (15850), Coloring agents such as pigments or dyes such as Fast Gen Blue TGR-L (74160) and Lionol Blue SM (26150) may be contained. Here, the number in the parenthesis means a color index (CI).
[0068]
The content of the colorant 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. Is particularly preferred.
[0069]
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.
[0070]
In general, if the positive photosensitive composition does not contain a compound sensitive to light in the ultraviolet region, the sensitivity and the contrast between the image area and the non-image area tend to be inferior. The positive photosensitive composition of the present invention does not include compounds having sensitivity to light in the ultraviolet region, such as onium salts, diazonium salts, and quinonediazide group-containing compounds, and is substantially sensitive to light in the ultraviolet region. When it is not present, the effects of the present invention in terms of the sensitivity and the contrast between the image portion and the non-image portion can be more remarkably exhibited, which is preferable.
[0071]
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). The results show that the solubility of the composition in an alkali developer after being left for 10 hours under irradiation does not substantially change as compared with that before being left.
[0072]
The positive photosensitive composition of the present invention is usually coated on the surface of the support as a solution in which each of the components is dissolved in an appropriate solvent, and then heated and dried to form a photosensitive composition layer on the surface of the support. A positive photosensitive lithographic printing plate on which is formed.
[0073]
Here, the solvent is not particularly limited as long as it has sufficient solubility with respect to 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 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, etc. 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.
[0074]
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 in the range of 0.3 to 7 μm, preferably 0.5 to 5 μm, particularly preferably 1 to 3 μm. In addition, as drying temperature in that case, about 30-170 degreeC, for example, Preferably about 40-150 degreeC is taken.
[0075]
In order to make the effect of the present invention more reliable, for example, heating at a temperature of about 40 to 100 ° C., preferably about 40 to 70 ° C., for about 1 minute to 50 hours, preferably about 30 minutes to 20 hours. It is preferable to perform the treatment.
[0076]
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, an aluminum plate is preferable, and surface treatment such as graining treatment by electrolytic etching or brush polishing in hydrochloric acid or nitric acid solution, anodizing treatment in sulfuric acid solution, and sealing treatment as necessary is performed. An applied aluminum plate is more preferable. As the roughness of the support surface, average roughness R _a as defined in JIS B0601, usually, 0.3 to 1.0 [mu] m, preferably about 0.4～0.8Myuemu.
[0077]
Examples of the light source for image exposure of the positive photosensitive composition layer in the present invention mainly include laser light sources such as HeNe laser, argon ion laser, YAG laser, HeCd laser, semiconductor laser, and ruby laser. In the case of forming an image with 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.
[0078]
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. / cm ²⁾ may be dependent on the light intensity of the laser beam for receiving ^{(mJ / s · cm 2)} . Here, the light intensity of the laser beam is obtained by dividing the amount of energy (mJ / s) per unit time of the laser beam measured by an optical power meter by the irradiation area (cm ² ) of the laser beam on the surface of the photosensitive composition layer. Can be obtained. The irradiation area of the laser beam is usually defined by the area of the portion exceeding 1 / e ² intensity of the laser peak intensity, but can be measured by exposing a photosensitive composition exhibiting a reciprocity law in a simple manner. .
[0079]
In the present invention, the light intensity of the light source is preferably 2.0 × 10 ⁶ mJ / s · cm ² or more, and more preferably 1.0 × 10 ⁷ mJ / s · cm ² or more. 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.
[0080]
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, monoisopropanolamine, 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. 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.
[0081]
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.
[0082]
【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.
[0083]
Examples 1-4, Comparative Examples 1-2
An aluminum plate (thickness 0.24 mm) was degreased in a 5% by weight sodium hydroxide aqueous solution at 60 ° C. for 1 minute, and then in a hydrochloric acid aqueous solution having a concentration of 0.5 mol / liter, a temperature of 25 ° C. The electrolytic etching treatment was performed under the conditions of a current density of 60 A / dm ² and a treatment time of 30 seconds. Next, desmutting treatment was carried out in a 5 wt% aqueous sodium hydroxide solution at 60 ° C for 10 seconds, and then in a 20 wt% sulfuric acid solution at a temperature of 20 ° C, a current density of 3 A / dm ² , and a treatment time of 1 minute. Anodizing treatment was performed. Further, hot water sealing treatment was performed with hot water at 80 ° C. for 20 seconds to produce an aluminum plate for a lithographic printing plate support.
[0084]
On the surface of the obtained aluminum plate support, 4 parts by weight of the indole dye shown in the specific example (II-9) as a photothermal conversion substance, and 100 parts by weight of the following resins (1) to (3) as novolak resins, With or without using the following compounds (4) to (6) as the phenolic hydroxyl group-containing compound, 10 parts by weight of crystal violet lactone is added to 1206 parts by weight of cyclohexanone, and 10 minutes at room temperature. A coating solution prepared by stirring is applied using a wire bar, dried at 100 ° C. for 2 minutes, and then heat-treated at 55 ° C. for 16 hours to form a positive coating with a coating amount of 2.5 g / m ² . A positive photosensitive lithographic printing plate having a photosensitive composition layer was prepared.
[0085]
Novolak resin ( 1) Phenol: m-cresol: p-cresol is a polycondensate of mixed phenols of 50:30:20 in molar ratio and formaldehyde, and has a weight average molecular weight of 10,000. The ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,500 or less to the total phenolic hydroxyl group-containing compound including novolak resin is 38% by weight, the ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,000 or less is 30% by weight, the molecular weight A novolac resin in which the proportion of a phenolic hydroxyl group-containing compound of 800 or less is 25% by weight.
[0086]
(2) A mixture of m-cresol: p-cresol in a molar ratio of 70:30 and a polycondensate of formaldehyde and a polycondensate having a weight average molecular weight of 10,800 and including novolak resin The ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,500 or less to the phenolic hydroxyl group-containing compound is 31% by weight, the ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,000 or less is 23% by weight, and the phenolic hydroxyl group having a molecular weight of 800 or less. A novolak resin containing 19% by weight of the compound.
[0087]
(3) A mixture of m-cresol: p-cresol in a molar ratio of 90:10 and a polycondensate of formaldehyde and a polycondensate having a weight average molecular weight of 10,000, including novolak resin. The ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,500 or less to the phenolic hydroxyl group-containing compound is 30% by weight, the ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,000 or less is 22% by weight, and the phenolic hydroxyl group having a molecular weight of 800 or less. A novolac resin containing 18% by weight of the compound.
[0088]
In addition, the ratio of each molecular weight compound with respect to the total phenolic hydroxyl group-containing compound in the novolak resin was determined by using a gel permeation chromatography “HLC-8020” manufactured by Tosoh Corporation and “TSKgelGMH _X L-N” manufactured by Tosoh Corporation as a column. Two 30 cm pieces were measured using RI as a detector. Tetrahydrofuran (special grade) was used for the moving bed, the injection amount was 100 μl, and the flow rate was 1.0 ml / min.
[0089]
Phenolic hydroxyl group-containing compound ( 4) Compound (1) of the above specific example [Chemical Formula 17]
(5) Compound (2) of the above specific example [Chemical Formula 17]
(6) Compound (3) of the above specific example [Chemical Formula 17]
[0090]
For each of the obtained positive-type photosensitive lithographic printing plates, 200 lines, 1 to 99% at various exposure energies using an exposure apparatus (Creo, “Trend Setter 3244T”) using a semiconductor laser with a wavelength of 830 nm as a light source. 1 to 99% of the halftone dot image was obtained by subjecting the halftone dot image to image exposure, and then developing it at 28 ° C. in an alkaline developer (8-fold diluted solution of “DP-4” manufactured by Fuji Photo Film Co., Ltd.). A printing plate was produced, and the sensitivity at that time was determined as the amount of exposure energy reproduced by a 3% halftone dot. The results are shown in Table 1.
[0091]
Further, the film strength of the obtained printing plate was evaluated according to the following criteria, and the results are shown in Table 1.
A: Reproduction of halftone dots with strong film strength.
B: Reproduces halftone dots with a film strength that is slightly inferior but practically acceptable.
C: The exposed part was not dissolved in the developer. (Image cannot be formed.)
[0092]
Examples 5-8, Comparative Examples 3-4
On the surface of the aluminum plate support obtained in the above examples, 4 parts by weight of the indole dyes shown in the specific example (II-9) as a photothermal conversion substance, and the above resins (1) to (3) as novolak resins 100 parts by weight, 10 parts by weight of crystal violet lactone, 10 parts by weight of 1,2-cyclohexanedicarboxylic acid 5 with or without the use of the compounds (1) to (3) shown above as phenolic hydroxyl group-containing compounds Part by weight, 3 parts by weight of polyethylene glycol (number average molecular weight 2,000) were added to 966 parts by weight of methoxyethanol and 240 parts by weight of ethoxyethanol, and the coating solution prepared by stirring at room temperature for 10 minutes was prepared using a wire bar. coated, dried for 2 minutes at 85 ° C., by 16 hours of heat treatment at 55 ° C., the positive photosensitive composition layer of Nurimakuryou 2.5 g / m ² To prepare a positive photosensitive lithographic printing plate having, in the same manner as in the above embodiment, image exposed and developed, sensitivity, and to evaluate the film strength, and the results are shown in Table 1.
[0093]
[Table 1]

[0094]
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.
[0095]
【The invention's effect】
According to the present invention, the sensitivity and the contrast between the image area and the non-image area are excellent, the film strength against the developer is excellent, and more preferably, it is insensitive to the light in the ultraviolet region and is under a white fluorescent lamp. It is possible to provide a positive photosensitive composition and a positive photosensitive lithographic printing plate which are excellent in handleability.

Claims (6)

  A positive-type 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, the total phenolic hydroxyl group-containing compound including the novolac resin in the entire composition The ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,500 or less is 35 to 70% by weight, the ratio of the phenolic hydroxyl group-containing compound having a molecular weight of 1,000 or less is 25 to 60% by weight, and the molecular weight is 800 or less. A positive photosensitive composition, wherein the proportion of the phenolic hydroxyl group-containing compound is 20 to 55% by weight.   The positive photosensitive composition according to claim 1, 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 1,300 μm. The positive photosensitive composition according to claim 1 , which does not contain a compound sensitive to light in the ultraviolet region. Alkali solubility of the composition after standing for 10 hours to white fluorescent lamp of 400 lux of light intensity, according to any one of claims 1 to 3 does not cause change in comparison with the prior standing Positive photosensitive composition.   A positive photosensitive lithographic printing plate comprising a layer of the positive photosensitive composition according to any one of claims 1 to 4 formed on a support surface.   A positive image lithographic printing plate according to claim 5, wherein the positive photosensitive lithographic printing plate is image-exposed with a semiconductor laser or a YAG laser and then developed with an alkali developer.