JP3946940B2 - Positive photosensitive composition and positive photosensitive lithographic printing plate - Google Patents

Description

【００１４】
〔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 は置換基として、色素分子中で共鳴してイミニウムカチオンを生じるアミノビニル結合を含む置換基を少なくとも有するトリ、ペンタ、ヘプタ、ノナ、又はウンデカメチン基を示し、該ペンタ、ヘプタ、ノナ、又はウンデカメチン基上の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、シクロアルケノン環、シクロアルケンジオン環、又はシクロアルケンチオ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_a ^- は対アニオンを示す。〕
【００１５】
ここで、式(Ia)、(Ib)、及び(Ic)中のＲ¹ 及びＲ² がアルキル基であるときの炭素数は、通常１〜１５、好ましくは１〜１０、アルケニル基、アルキニル基であるときの炭素数は、通常２〜１５、好ましくは２〜１０であり、フェニル基も含めたそれらの置換基としては、炭素数が通常１〜１５、好ましくは１〜１０のアルコキシ基、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 における前記アミノビニル結合を含む置換基以外の置換基としては、同上炭素数のアルキル基、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、同上炭素数のアルキル基、同上炭素数のアルコキシ基、ニトロ基、又はハロゲン原子等が挙げられる。
【００１６】
又、本発明における色素の基本構造として、前記シアニン系色素の中で、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。
【００１７】
【化６】

【００１８】
〔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 は置換基として、色素分子中で共鳴してイミニウムカチオンを生じるアミノビニル結合を含む置換基を少なくとも有するトリ、ペンタ、ヘプタ、ノナ、又はウンデカメチン基を示し、該ペンタ、ヘプタ、ノナ、又はウンデカメチン基上の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、シクロアルケノン環、シクロアルケンジオン環、又はシクロアルケンチオ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_a ^- は対アニオンを示す。〕
【００１９】
ここで、式(II)中のＲ³ 及びＲ⁴ がアルキル基であるときの炭素数は、通常１〜１５、好ましくは１〜１０、アルケニル基、アルキニル基であるときの炭素数は、通常２〜１５、好ましくは２〜１０であり、フェニル基も含めたそれらの置換基としては、炭素数が通常１〜１５、好ましくは１〜１０のアルコキシ基、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 における前記アミノビニル結合を含む置換基以外の置換基としては、同上炭素数のアルキル基、アミノ基、又はハロゲン原子等が挙げられ、縮合ベンゼン環における置換基としては、同上炭素数のアルキル基、同上炭素数のアルコキシ基、ニトロ基、又はハロゲン原子等が挙げられる。
【００２０】
又、本発明における色素の基本構造として、前記シアニン系色素の中で、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(IIIa)、(IIIb)、又は(IIIc)で表されるものが好ましい。
【００２１】
【化７】

【００２２】
〔式(IIIa)、(IIIb)、及び(IIIc)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、Ｒ⁵ 、Ｒ⁶ 、Ｒ⁷ 、及びＲ⁸ は各々独立して、水素原子又はアルキル基、又は、Ｒ⁵ とＲ⁷ 、及びＲ⁶ とＲ⁸ 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、Ｌ³ は置換基として、色素分子中で共鳴してイミニウムカチオンを生じるアミノビニル結合を含む置換基を少なくとも有するモノ、トリ、ペンタ、又はヘプタメチン基を示し、該トリ、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、シクロアルケノン環、シクロアルケンジオン環、又はシクロアルケンチオ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_a ^- は対アニオンを示す。〕
【００２３】
ここで、式(IIIa)、(IIIb)、及び(IIIc)中のＲ⁵ 、Ｒ⁶ 、Ｒ⁷ 、及びＲ⁸ がアルキル基であるときの炭素数は、通常１〜１５、好ましくは１〜１０であり、Ｌ³ における前記アミノビニル結合を含む置換基以外の置換基としては、同上炭素数のアルキル基、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、フェニル基等のアリール基等が挙げられる。
【００２４】
又、本発明における色素の基本構造として、ポリメチン系色素としては、特に、下記一般式(IV)で表されるものが好ましい。
【００２５】
【化８】

【００２６】
〔式(IV)中、Ｒ⁹ 、Ｒ¹⁰、Ｒ¹¹、及びＲ¹²は各々独立して、アルキル基を示し、Ｒ¹³及びＲ¹⁴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、Ｌ⁴ は置換基として、色素分子中で共鳴してイミニウムカチオンを生じるアミノビニル結合を含む置換基を少なくとも有するモノ、トリ、ペンタ、又はヘプタメチン基を示し、該トリ、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、シクロアルケノン環、シクロアルケンジオン環、又はシクロアルケンチオ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_a ^- は対アニオンを示す。〕
【００２７】
ここで、式(IV)中のＲ⁹ 、Ｒ¹⁰、Ｒ¹¹、及びＲ¹²のアルキル基の炭素数は、通常１〜１５、好ましくは１〜１０、Ｒ¹³及びＲ¹⁴がアリール基であるときの炭素数は、通常６〜２０、好ましくは６〜１５であり、Ｒ¹³及びＲ¹⁴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、同上炭素数のアルキル基、同上炭素数のアルコキシ基、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、Ｌ⁴ における前記アミノビニル結合を含む置換基以外の置換基としては、同上炭素数のアルキル基、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、同上炭素数のアルキル基、同上炭素数のアルコキシ基、ニトロ基、又はハロゲン原子等が挙げられる。
【００２８】
尚、前記一般式(Ia 〜c)、(II)、(IIIa 〜c)、及び(IV)における対アニオンＸ_a ^- としては、具体的には、例えば、Ｃｌ^- 、Ｂｒ^- 、Ｉ^- 、ＣｌＯ₄ ^- 、ＰＦ₆ ^- 、ＳｂＦ₆ ^- 、ＡｓＦ₆ ^- 、及び、ＢＦ₄ ^- 、ＢＣｌ₄ ^- 等の無機硼素酸等の無機酸アニオン、並びに、ベンゼンスルホン酸、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、フルオロフェニル、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素酸等の有機酸アニオンを挙げることができる。
【００２９】
本発明における色素の基本構造として、以上の前記一般式(Ia 〜c)で表されるキノリン系、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、前記一般式(IIIa 〜c)で表されるピリリウム系又はチアピリリウム系等のシアニン系色素、及び前記一般式(IV)で表されるポリメチン系色素の中で、本発明においては、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が特に好ましい。
【００３０】
又、前記各式におけるＬ¹ 、Ｌ² 、Ｌ³ 、及びＬ⁴ を含めたポリメチン鎖として、波長域７００〜８５０ｎｍに対してはヘプタメチン鎖であるものが、波長域８５０〜９５０ｎｍに対してはノナメチン鎖であるものが、波長域９５０〜１３００ｎｍに対してはウンデカメチン鎖であるものが、それぞれ好ましい。
【００３１】
本発明における色素は、前記基本構造のポリメチン鎖上に、色素分子中で共鳴してイミニウムカチオンを生じるアミノビニル結合を含む置換基を有する構造のものであることが必須であり、その色素の共鳴機構は、例えば、ノナメチン鎖を介して窒素原子が結合している構造の色素を例にとると、下式の如くなる。
【００３２】
【化９】

【００３３】
本発明において、ポリメチン鎖上のアミノビニル結合を含む置換基としては、具体的には、下記一般式(Va)で表されるものが挙げられ、これらは、別のポリメチン鎖を介して色素のポリメチン鎖に結合していてもよい。
【００３４】
【化１０】

【００３５】
〔式(Va)中、Ｒ^a は、置換基を有していてもよいアミノ基を示し、ビニル基は置換基を有していてもよく、アミノ基における置換基とビニル基における置換基が互いに連結し複素環を形成していてもよい。〕
【００３６】
ここで、式(Va)中のアミノ基及びビニル基における置換基としては、炭素数が１〜５のアルキル基、フェニル基、ナフチル基、炭素数が２〜５の複素環基、又は水酸基等が挙げられる。
【００３７】
前記一般式(Va)で表されるものの中で、下記一般式(Vb)で表されるものが好ましい。
【００３８】
【化１１】

【００３９】
〔式(Vb)中、Ｗ¹ は、酸素原子、硫黄原子、窒素原子、又はジアルキルメチレン基を示し、Ｒ^b は、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リール基、又は水素原子を示し、複素環は４〜６員環であり、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環を形成していてもよい。〕
【００４０】
更に、前記一般式(Vb)で表されるものの中で、下記一般式(Vc)で表されるものが特に好ましい。
【００４１】
【化１２】

【００４２】
〔式(Vc)中、Ｗ¹ は、酸素原子、硫黄原子、窒素原子、又はジアルキルメチレン基を示し、Ｒ^c は、置換基を有していてもよいアルキル基、又は置換基を有していてもよいアリール基を示し、縮合環は芳香族炭化水素環を示す。〕
【００４３】
ここで、式(Vb)中のＲ^b 、及び式(Vc)中のＲ^c がアルキル基であるときの炭素数は、通常１〜５、アリール基であるときの炭素数は、通常６〜１０であり、それらにおける置換基、及び、複素環における置換基としては、炭素数が１〜５のアルコキシ基、炭素数が２〜５のアシル基、炭素数が２〜５のアシルオキシ基、炭素数が２〜５のアルコキシカルボニル基、フェニル基、ナフチル基等が挙げられ、式(Vb)及び(Vc)中のＷ¹ がジアルキルメチレン基であるときの炭素数は通常３〜１５である。
【００４４】
以上の、ポリメチン鎖上のアミノビニル結合を含む置換基としての好適な例を以下に示す。
【００４５】
【化１３】

【００４６】
本発明における光熱変換物質として、以上の、ポリメチン鎖上に、色素分子中で共鳴してイミニウムカチオンを生じるアミノビニル結合を含む置換基を有する構造のシアニン系色素、及びポリメチン系色素の具体例を以下に示す。尚、以下の具体例中、Ａは、アミノビニル結合を含む置換基であり、Ｘ_a ^- は、Ｃｌ^- 、Ｂｒ^- 、Ｉ^- 、ＣｌＯ₄ ^- 、ＰＦ₆ ^- 、ＢＦ₄ ^- 、ｐ−トルエンスルホン酸、又は１−ナフタレンスルホン酸等の対アニオンである。
【００４７】
【化１４】

【００４８】
【化１５】

【００４９】
【化１６】

【００５０】
【化１７】

【００５１】
【化１８】

【００５２】
【化１９】

【００５３】
【化２０】

【００５４】
【化２１】

【００５５】
【化２２】

【００５６】
尚、ポリメチン鎖を介して複素原子が結合された構造を基本構造とし、該ポリメチン鎖上に、色素分子中で共鳴してイミニウムカチオンを生じるアミノビニル結合を含む置換基を有するこれらの色素は、例えば、Slominskii,Yu.L. et al.,Inst.Org.Khim.,Kiev,USSR.J.Inf.Rec.Mater,16,23(1988)に記載されている方法、具体的には、例えば、塩素原子を置換基として有するポリメチン鎖を介して複素環が結合された構造の色素と、相当する活性水素を有する２−メチルチアゾネート塩等の化合物との反応等により、合成することができる。
【００５７】
本発明のポジ型感光性組成物において、光熱変換物質としての前記色素の含有割合は、０．５〜５０重量％であるのが好ましく、１〜４０重量％であるのが更に好ましく、２〜３０重量％であるのが特に好ましい。
【００５８】
尚、本発明のポジ型感光性組成物において、光熱変換物質として、ポリメチン鎖上に、色素分子中で共鳴してイミニウムカチオンを生じるアミノビニル結合を含む置換基を有する構造の前記色素の外に、ポリメチン鎖上にそれらのアミノビニル結合を含む置換基を有さない構造の色素を含有してもよく、それらの色素としては、前記一般式(Ia 〜c)、(II)、(IIIa 〜c)、及び(IV)におけるＬ¹ 、Ｌ²、Ｌ³ 、及びＬ⁴ がそれらのアミノビニル結合を含む置換基を有さないポリメチン鎖であって、且つ、対アニオンとして、前記一般式(Ia 〜c)、(II)、(IIIa 〜c)、及び(IV)において挙げたと同様の無機酸アニオンや有機酸アニオンを有するものを挙げることができる。
【００５９】
本発明のポジ型感光性組成物において、光熱変換物質として、ポリメチン鎖上にそれらのアミノビニル結合を含む置換基を有さない構造の色素の含有割合は、０〜２０重量％であるのが好ましく、０．１〜１５重量％であるのが更に好ましく、１〜１０重量％であるのが特に好ましい。
【００６０】
本発明のポジ型感光性組成物において、アルカリ可溶性樹脂としては、フェノール性水酸基を有する樹脂、具体的には、例えば、ノボラック樹脂、レゾール樹脂、ポリビニルフェノール樹脂、フェノール性水酸基を有するアクリル酸誘導体の共重合体等が挙げられ、中で、ノボラック樹脂、レゾール樹脂、又はポリビニルフェノール樹脂が好ましく、特に、ノボラック樹脂が好ましい。
【００６１】
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、４，４’−ビフェニルジオール、ビスフェノール−Ａ、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、フロログリシノール等のフェノール類の少なくとも１種を、酸触媒下、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、ピロガロールと、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していてもよく、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。
【００６２】
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（Ｍ_W ）が、好ましくは１，０００〜１５，０００、更に好ましくは１，５００〜１０，０００のものが用いられる。
【００６３】
又、レゾール樹脂は、ノボラック樹脂の重縮合における酸触媒に代えてアルカリ触媒を用いる以外は同様にして重縮合させた樹脂であって、本発明においては、前記ノボラック樹脂におけると同様の、フェノール類及びその混合組成、及び、アルデヒド類又はケトン類が好ましく、又、同様の重量平均分子量（Ｍ_W ）のものが好ましい。
【００６４】
又、ポリビニルフェノール樹脂は、例えば、ｏ−ヒドロキシスチレン、ｍ−ヒドロキシスチレン、ｐ−ヒドロキシスチレン、ジヒドロキシスチレン、トリヒドロキシスチレン、テトラヒドロキシスチレン、ペンタヒドロキシスチレン、２−（ｏ−ヒドロキシフェニル）プロピレン、２−（ｍ−ヒドロキシフェニル）プロピレン、２−（ｐ−ヒドロキシフェニル）プロピレン等のヒドロキシスチレン類（尚、これらは、ベンゼン環に塩素、臭素、沃素、弗素等のハロゲン原子、あるいは炭素数１〜４のアルキル基を置換基として有していてもよい。）の単独または２種以上を、ラジカル重合開始剤又はカチオン重合開始剤の存在下で重合させた樹脂であって、中で、本発明においては、ベンゼン環に炭素数１〜４のアルキル基を置換基として有していてもよいヒドロキシスチレン類の重合体が好ましく、特に、無置換のベンゼン環のヒドロキシスチレン類の重合体が好ましい。
【００６５】
前記ポリビニルフェノール樹脂は、又、一部水素添加を行ったものでもよく、ｔｅｒｔ−ブトキシカルボニル基、ピラニル基、フリル基等で一部の水酸基を保護したものでもよい。又、重量平均分子量（Ｍ_W ）が、好ましくは１，０００〜１００，０００、特に好ましくは１，５００〜５０，０００のものが用いられる。
【００６６】
ノボラック樹脂、レゾール樹脂、及びポリビニルフェノール樹脂の分子量が、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。
【００６７】
本発明のポジ型感光性組成物において、前記アルカリ可溶性樹脂の含有割合は、１〜９８重量％であるのが好ましく、５〜９５重量％であるのが更に好ましく、２０〜９０重量％であるのが特に好ましい。
【００６８】
尚、本発明のポジ型感光性組成物には、前記光熱変換物質と前記アルカリ可溶性樹脂の他に、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、前記アルカリ可溶性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。
【００６９】
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号公報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する酸発色性色素、同じく特開平１１−１４３０７６号公報に詳細に記載されている、ラクトン骨格、チオラクトン骨格、スルホラクトン骨格を有する塩基発色性色素、同じく特開平１０−３４１４００号公報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。中で、ラクトン骨格を有する酸発色性色素が好ましい。
【００７０】
本発明のポジ型感光性組成物に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。
【００７１】
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。
【００７２】
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、１〜３０重量％であるのが更に好ましく、２〜２０重量％であるのが特に好ましい。
【００７３】
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１０重量％以下、好ましくは０．１〜５重量％の範囲で含有されていてもよい。
【００７４】
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。
【００７５】
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。
【００７６】
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、６０〜１７０℃程度、好ましくは７０〜１５０℃程度、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分間程度が採られる。
【００７７】
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。
【００７８】
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、７００〜１３００ｎｍ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。
【００７９】
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。
【００８０】
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 以上とすることが更に好ましい。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て、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。
【００８１】
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。
【００８２】
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。
【００８３】
【実施例】
以下、本発明を実施例により更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。
【００８４】
実施例１
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２８℃、電流密度６０Ａ／ｄｍ² 、処理時間４０秒の条件で電解エッチング処理を行った。次いで４重量％水酸化ナトリウム水溶液中で６０℃、１２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３．５Ａ／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。表面粗度計（小坂研究所社製、「ＳＥ−３ＤＨ」）によるこの板の平均粗さＲａの値は０．６０μｍであった。
【００８５】
得られたアルミニウム板支持体表面に、アルカリ可溶性樹脂として、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２０：５０：３０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るノボラック樹脂（Ｍ_W ７，０００）１００重量部、光熱変換物質として、アミノビニル結合を含む置換基を有する下記式のシアニン系色素３重量部、及びクリスタルバイオレットラクトン１０重量部を、メチルセロソルブ９００重量部に室温で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１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。用いた色素等は、１０分間の攪拌で完全に溶解し、均一な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が得られた。
【００８６】
【化２３】

【００８７】
得られたポジ型感光性平版印刷版につき、８３０ｎｍの半導体レーザーを光源とする露光装置（クレオ社製、「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１０倍希釈液）を用いて２８℃で現像処理を行い、１〜９９％の網点画像を再現させた印刷版を作製した。そのときの感度を、３％の網点画像が再現する露光量として求めたところ、１５０ｍＪ／ｃｍ² であった。
【００８８】
比較例１
感光性組成物層における光熱変換物質として、実施例１で用いたシアニン系色素におけるアミノビニル結合を含む置換基を有さないシアニン系色素のみを用いた外は、実施例１と同様にして、ポジ型感光性平版印刷版を作製したが、感光性組成物層中に色素の結晶粒子による塗布欠陥が見られ、実用に耐える平版印刷版ではなかった。
【００８９】
比較例２
感光性組成物層における光熱変換物質として、実施例１で用いたシアニン系色素に代えて、ポリメチン鎖上にジフェニルアミノ基を置換基として有する下記式のシアニン系色素を用いた外は、実施例１と同様にして、ポジ型感光性平版印刷版を作製したが、３００ｍＪ／ｃｍ² の露光量で画像露光しても画像が形成されなかった。
【００９０】
【化２４】

【００９１】
【発明の効果】
本発明によれば、近赤外線領域の光に対して高感度であって、画像部と非画像部とのコントラストに優れ、よって、現像条件の幅の広い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。更に、本発明のポジ型感光性組成物は、溶媒に対する溶解性に優れるので、溶液としての支持体表面への塗布による感光性組成物層の形成を効率的に行うことができ、生産性の優れた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 used for lithographic printing plates, color proofs for printing proofing, color filter resists for liquid crystal displays and plasma displays, photoresists for integrated circuits of semiconductor elements, copper etching resists for wiring boards and gravure plates, 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 of a compound that generates an acid by photoacid generator (photoacid generator) 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 come to be seen. For example, JP-A-6-43633 discloses a photosensitive material in which a specific squarylium dye is combined with a photoacid generator and a binder, and as a similar technique, JP-A-7-20629 is disclosed. Japanese Laid-Open Patent Publication No. 7-271029 discloses a method for producing a lithographic printing plate by exposing a photosensitive composition layer containing an infrared absorbing dye, a latent Bronsted acid, a resole resin and a novolak resin to an image with a semiconductor laser or the like. JP-A-9-43847 discloses a method in which an s-triazine compound is used instead of the latent Bronsted acid, and JP-A-9-43847 changes the crystallinity of a photosensitive material by heating with infrared irradiation. A resist material and a pattern forming method using the resist material are disclosed.
[0006]
However, according to the study of the present inventors, these conventional techniques have low sensitivity to light in the near infrared region, and the difference in solubility between the exposed portion and the non-exposed portion with respect to the developer is small. The image portion is not sufficiently removed, the remaining film ratio of the image portion is not sufficiently maintained, and therefore, there are practical disadvantages such as a narrow range of development conditions.
[0007]
In contrast, 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 composed of a near-infrared absorbing dye having a structure in which a hetero atom is bonded via a polymethine chain cannot be expected, It was found that a photosensitive composition capable of forming a positive image with the above-mentioned drawbacks eliminated was obtained, and a patent application was first filed (see JP-A-10-268512), and further improvements were under consideration. .
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described prior art. Therefore, the present invention is highly sensitive to light in the near infrared region, and has excellent contrast between the image portion and the non-image portion. Accordingly, an object is to provide a positive photosensitive composition and a positive photosensitive lithographic printing plate having a wide range of development conditions.
[0009]
[Means for Solving the Problems]
  As a result of intensive studies to solve the above problems, the present inventor is a dye having a basic structure having a structure in which a hetero atom is bonded via a polymethine chain, and having a specific substituent on the polymethine chain The present invention has been completed by finding that a composition using an alkali-soluble resin as a light-to-heat conversion substance can achieve the above object, that is, the present invention is a light-to-heat conversion that absorbs light from an image exposure light source and converts it into heat. A positive photosensitive composition comprising a substance and an alkali-soluble resin, wherein the photothermal conversion substance is a dye having a basic structure of a structure in which heteroatoms are bonded via a polymethine chain, the polymethine chain On the resonance in the dye moleculeIminiumA positive photosensitive composition comprising a dye having a substituent containing an aminovinyl bond that generates a cation, and a positive photosensitive lithographic printing plate comprising a layer of the photosensitive composition formed on the support surface Is the gist.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
  In the positive photosensitive composition of the present invention, the photothermal conversion substance that absorbs the light from the image exposure light source and converts it into heat is a compound that can convert the absorbed light into heat. As a photothermal conversion substance, a dye having a basic structure in which a hetero atom is bonded via a polymethine chain, which resonates in the dye molecule on the polymethine chain.IminiumIt contains a dye having a substituent containing an aminovinyl bond that generates a cation. Here, “resonate in the dye molecule” means, in other words, “resonate with the chromophore of the dye”, and the π electron of the chromophore in the dye molecule when the dye has the substituent. The system spreads, and the absorption peak is usually shifted to the longer wavelength side by 20 nm or more. In particular, the absorption efficiency in the near-infrared region of the wavelength region of 700 to 1300 nm can be improved. While these near-infrared absorbing dyes efficiently absorb light in the above-mentioned wavelength region, they absorb little light in the ultraviolet region or are substantially insensitive even when absorbed, and are weak ultraviolet rays contained in white lamps. Some compounds do not have the action of modifying the photosensitive composition.
[0011]
In the present invention, these dyes are polymethine (—CH═)._nA structure in which a hetero atom such as a nitrogen atom, an oxygen atom, or a sulfur atom is bonded through a chain is a basic structure, and as the basic structure, typically, these hetero atoms form a heterocycle, So-called cyanine dyes having a structure in which a heterocycle is bonded via a polymethine chain, specifically, for example, quinoline (so-called cyanine-based), indole (so-called indocyanine), benzothiazole And so-called polymethine dyes having a structure in which acyclic heteroatoms are bonded via a polymethine chain, and the like (e.g., so-called thiocyanine series), pyrylium series, thiapyrylium series, squarylium series, croconium series, azurenium series, etc. Cyanine dyes such as quinoline, indole, benzothiazole, pyrylium, thiapyrylium, and polymethine dyes Preferred.
[0012]
As the basic structure of the dye 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.
[0013]
[Chemical formula 5]

[0014]
  [In formulas (Ia), (Ib), and (Ic), R¹ And R² Each 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, L¹ Resonates as a substituent in the dye moleculeIminiumA tri, penta, hepta, nona, or undecametine group having at least a substituent containing an aminovinyl bond that generates a cation, and the two substituents on the penta, hepta, nona, or undecametin group are linked to each other to form a carbon number 5 to 7 cycloalkene ring, cycloalkeneone ring, cycloalkenedione ring, or cycloalkenethione ring may be formed, and the quinoline ring may have a substituent, in which case two adjacent two The substituents may be connected to each other to form a condensed benzene ring. X_a ^- Represents a counter anion. ]
[0015]
Where R in the formulas (Ia), (Ib), and (Ic)¹And R²When C is an alkyl group, the carbon number is usually 1 to 15, preferably 1 to 10, and when it is an alkenyl group or an alkynyl group, the carbon number is usually 2 to 15, preferably 2 to 10, and a phenyl group As those substituents including those, an alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, a phenoxy group, a hydroxy group, a phenyl group, or the like can be given.¹Examples of the substituent other than the substituent containing the aminovinyl bond in the above include an alkyl group having the same carbon number, an amino group, or a halogen atom, and the substituent in the quinoline ring includes the same alkyl group having the same carbon number as above. Examples thereof include an alkoxy group having a carbon number, a nitro group, and a halogen atom.
[0016]
As the basic structure of the dye in the present invention, among the cyanine dyes, the indole and benzothiazole dyes are particularly preferably those represented by the following general formula (II).
[0017]
[Chemical 6]

[0018]
  [In formula (II), Y¹ And Y² Each independently represents a dialkylmethylene group or a sulfur atom;^Three And R^Four Each 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, L² Resonates as a substituent in the dye moleculeIminiumA tri, penta, hepta, nona, or undecametine group having at least a substituent containing an aminovinyl bond that generates a cation, and the two substituents on the penta, hepta, nona, or undecametin group are linked to each other to form a carbon number 5 to 7 cycloalkene ring, cycloalkenone ring, cycloalkenedione ring, or cycloalkenethione ring may be formed, and the fused benzene ring may have a substituent, and in that case, adjacent 2 Two substituents may be connected to each other to form a condensed benzene ring. X_a ^- Represents a counter anion. ]
[0019]
Here, R in the formula (II)^ThreeAnd R^FourWhen C is an alkyl group, the carbon number is usually 1 to 15, preferably 1 to 10, and when it is an alkenyl group or an alkynyl group, the carbon number is usually 2 to 15, preferably 2 to 10, and a phenyl group As those substituents including those, an alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, a phenoxy group, a hydroxy group, a phenyl group, or the like can be given.²Examples of the substituent other than the substituent containing the aminovinyl bond in the above include an alkyl group having the same carbon number, an amino group, or a halogen atom, and the substituent in the condensed benzene ring includes an alkyl group having the same carbon number, Examples thereof include an alkoxy group having a carbon number, a nitro group, and a halogen atom.
[0020]
As the basic structure of the dye in the present invention, among the cyanine dyes, the pyrylium and thiapyrylium dyes are particularly represented by the following general formula (IIIa), (IIIb), or (IIIc): Those are preferred.
[0021]
[Chemical 7]

[0022]
  [In the formulas (IIIa), (IIIb), and (IIIc), Z¹ And Z² Each independently represents an oxygen atom or a sulfur atom, and R^Five , R⁶ , R⁷ And R⁸ Each independently represents a hydrogen atom or an alkyl group, or R^Five And R⁷ And R⁶ And R⁸ May be linked to each other to form a cycloalkene ring having 5 or 6 carbon atoms.^Three Resonates as a substituent in the dye moleculeIminium1 represents a mono, tri, penta, or heptamethine group having at least a substituent containing an aminovinyl bond that generates a cation, and the two substituents on the tri, penta, or heptamethine group are linked to each other to have 5 to 7 carbon atoms It may form a cycloalkene ring, a cycloalkeneone ring, a cycloalkenedione ring, or a cycloalkenethione ring, and the pyrylium ring and the thiapyrylium ring may have a substituent, in which case two adjacent substitutions The groups may be connected to each other to form a condensed benzene ring. X_a ^- Represents a counter anion. ]
[0023]
Where R in formulas (IIIa), (IIIb), and (IIIc)^Five, R⁶, R⁷And R⁸Carbon number when is an alkyl group is usually 1-15, preferably 1-10, and L^ThreeExamples of the substituent other than the substituent containing the aminovinyl bond in the above include an alkyl group having the same carbon number, an amino group, or a halogen atom, and the substituent in the pyrylium ring and the thiapyrylium ring is an aryl such as a phenyl group. Groups and the like.
[0024]
In addition, as the basic structure of the dye in the present invention, a polymethine dye is particularly preferably represented by the following general formula (IV).
[0025]
[Chemical 8]

[0026]
  [In formula (IV), R⁹ , R^Ten, R¹¹And R¹²Each independently represents an alkyl group, R¹³And R¹⁴Each independently represents an aryl group, a furyl group or a thienyl group which may have a substituent, and L^Four Resonates as a substituent in the dye moleculeIminium1 represents a mono, tri, penta, or heptamethine group having at least a substituent containing an aminovinyl bond that generates a cation, and the two substituents on the tri, penta, or heptamethine group are linked to each other to have 5 to 7 carbon atoms A cycloalkene ring, a cycloalkenone ring, a cycloalkenedione ring, or a cycloalkenethione ring may be formed, and the quinone ring and the benzene ring may have a substituent. X_a ^- Represents a counter anion. ]
[0027]
Here, R in the formula (IV)⁹, R^Ten, R¹¹And R¹²The carbon number of the alkyl group is usually 1-15, preferably 1-10, R¹³And R¹⁴The number of carbons when is an aryl group is usually 6-20, preferably 6-15, and R¹³And R¹⁴Specifically, 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 having the same carbon number, an alkoxy group having the same carbon number, a dialkylamino group, a hydroxy group, or a halogen atom;^FourExamples of the substituent other than the substituent containing the aminovinyl bond in the above include an alkyl group having the same carbon number, an amino group, or a halogen atom, and the substituents in the quinone ring and the benzene ring are alkyl having the same carbon number. Group, an alkoxy group having the same carbon number, a nitro group, or a halogen atom.
[0028]
The counter anions X in the general formulas (Ia to c), (II), (IIIa to c), and (IV)_a ^-Specifically, for example, Cl^-, Br^-, I^-, ClO_Four ^-, PF₆ ^-, SbF₆ ^-, AsF₆ ^-And BF_Four ^-, BCl_Four ^-Inorganic acid anions such as inorganic boric acid, and the like, as well as benzenesulfonic acid, toluenesulfonic acid, naphthalenesulfonic acid, acetic acid, and methyl, ethyl, propyl, butyl, phenyl, methoxyphenyl, naphthyl, fluorophenyl, difluorophenyl, Mention may be made of organic acid anions such as organoboric acids having an organic group such as pentafluorophenyl, thienyl, pyrrolyl and the like.
[0029]
As the basic structure of the dye in the present invention, the quinoline type represented by the above general formula (Ia to c), the indole type or benzothiazole type represented by the general formula (II), the general formula (IIIa to c) In the present invention, the indole represented by the general formula (II) is a cyanine dye such as a pyrylium-based or thiapyrylium-based dye represented by the formula (IV) and the polymethine-based dye represented by the general formula (IV). And benzothiazole dyes are particularly preferred.
[0030]
In addition, L in each of the above formulas¹, L², L^Three, And L^FourAs a polymethine chain including those having a heptamethine chain for a wavelength range of 700 to 850 nm, a nonamethine chain for a wavelength range of 850 to 950 nm, and an undecametin chain for a wavelength range of 950 to 1300 nm Are preferred respectively.
[0031]
  The dye in the present invention resonates in the dye molecule on the polymethine chain having the basic structure.IminiumIt is essential to have a structure having a substituent containing an aminovinyl bond that generates a cation, and the resonance mechanism of the dye is, for example, a dye having a structure in which a nitrogen atom is bonded via a nonamethine chain. Then, it becomes like the following formula.
[0032]
[Chemical 9]

[0033]
In the present invention, specific examples of the substituent containing an aminovinyl bond on the polymethine chain include those represented by the following general formula (Va), and these are those of the dye via another polymethine chain. It may be bound to a polymethine chain.
[0034]
[Chemical Formula 10]

[0035]
[In formula (Va), R^aRepresents an amino group which may have a substituent, the vinyl group may have a substituent, and the substituent in the amino group and the substituent in the vinyl group are connected to each other to form a heterocyclic ring. May be. ]
[0036]
Here, as a substituent in the amino group and vinyl group in the formula (Va), an alkyl group having 1 to 5 carbon atoms, a phenyl group, a naphthyl group, a heterocyclic group having 2 to 5 carbon atoms, a hydroxyl group, or the like Is mentioned.
[0037]
Among those represented by the general formula (Va), those represented by the following general formula (Vb) are preferable.
[0038]
Embedded image

[0039]
[W in formula (Vb)¹Represents an oxygen atom, a sulfur atom, a nitrogen atom, or a dialkylmethylene group, and R^bRepresents an alkyl group which may have a substituent, an aryl group which may have a substituent, or a hydrogen atom, the heterocyclic ring is a 4- to 6-membered ring, and has a substituent. In this case, two adjacent substituents may be connected to each other to form a condensed ring. ]
[0040]
Furthermore, among those represented by the general formula (Vb), those represented by the following general formula (Vc) are particularly preferable.
[0041]
Embedded image

[0042]
[W in formula (Vc)¹Represents an oxygen atom, a sulfur atom, a nitrogen atom, or a dialkylmethylene group, and R^cRepresents an alkyl group which may have a substituent, or an aryl group which may have a substituent, and the condensed ring represents an aromatic hydrocarbon ring. ]
[0043]
Here, R in the formula (Vb)^bAnd R in formula (Vc)^cThe number of carbons when is an alkyl group is usually 1 to 5, and the number of carbons when an aryl group is usually 6 to 10, and the substituents in them and the substituents in the heterocyclic ring are carbon numbers. Is an alkoxy group having 1 to 5 carbon atoms, an acyl group having 2 to 5 carbon atoms, an acyloxy group having 2 to 5 carbon atoms, an alkoxycarbonyl group having 2 to 5 carbon atoms, a phenyl group, a naphthyl group, and the like. W in (Vb) and (Vc)¹The number of carbons when is a dialkylmethylene group is usually 3-15.
[0044]
Suitable examples of the above substituents containing aminovinyl bonds on the polymethine chain are shown below.
[0045]
Embedded image

[0046]
  As the photothermal conversion material in the present invention, the above-described polymethine chain resonates in the dye molecule.IminiumSpecific examples of cyanine dyes and polymethine dyes having a structure having a substituent containing an aminovinyl bond that generates a cation are shown below. In the following specific examples, A is a substituent containing an aminovinyl bond, and X_a ^- Is Cl^- , Br^- , I^- , ClO_Four ^- , PF₆ ^- , BF_Four ^- , P-toluenesulfonic acid, or 1-naphthalenesulfonic acid.
[0047]
Embedded image

[0048]
Embedded image

[0049]
Embedded image

[0050]
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[0051]
Embedded image

[0052]
Embedded image

[0053]
Embedded image

[0054]
Embedded image

[0055]
Embedded image

[0056]
  The basic structure is a structure in which a heteroatom is bonded via a polymethine chain, and resonates in the dye molecule on the polymethine chain.IminiumThese dyes with substituents containing aminovinyl bonds that give rise to cations are described, for example, in Slominskii, Yu.L. et al., Inst.Org.Khim., Kiev, USSR.J.Inf.Rec. Mater, 16, 23 (1988), specifically, for example, a dye having a structure in which a heterocyclic ring is bonded via a polymethine chain having a chlorine atom as a substituent, and 2-methyl having a corresponding active hydrogen. It can be synthesized by reaction with a compound such as a thiazonate salt.
[0057]
In the positive photosensitive composition of the present invention, the content of the dye as a photothermal conversion substance is preferably 0.5 to 50% by weight, more preferably 1 to 40% by weight, 30% by weight is particularly preferred.
[0058]
  In the positive photosensitive composition of the present invention, the photothermal conversion substance resonates in the dye molecule on the polymethine chain.IminiumIn addition to the above-mentioned dye having a substituent containing an aminovinyl bond that generates a cation, the dye may have a structure having no substituent containing the aminovinyl bond on the polymethine chain. As L in the general formulas (Ia to c), (II), (IIIa to c), and (IV).¹ , L², L^Three , And L^Four Is a polymethine chain having no substituent containing an aminovinyl bond, and as a counter anion, in the general formulas (Ia to c), (II), (IIIa to c), and (IV) The thing which has the same inorganic acid anion and organic acid anion as mentioned can be mentioned.
[0059]
In the positive photosensitive composition of the present invention, the content ratio of the dye having a structure not having a substituent containing an aminovinyl bond on the polymethine chain as a photothermal conversion substance is 0 to 20% by weight. Preferably, it is 0.1 to 15% by weight, more preferably 1 to 10% by weight.
[0060]
In the positive photosensitive composition of the present invention, the alkali-soluble resin may be a resin having a phenolic hydroxyl group, specifically, for example, a novolac resin, a resole resin, a polyvinylphenol resin, or an acrylic acid derivative having a phenolic hydroxyl group. Among them, a novolak resin, a resole resin, or a polyvinylphenol resin is preferable, and a novolak resin is particularly preferable.
[0061]
The novolak resin 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, 4,4′-biphenyldiol, bisphenol-A, pyrocatechol, resorcinol, hydroquinone, pyrogallol, 1,2,4-benzenetriol, phloroglicinol, etc. At least one of the phenols of the aldehyde under an acid catalyst, for example, aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, furfural (in addition to paraformaldehyde instead of formaldehyde) , Or paraaldehyde instead of acetaldehyde), or a resin polycondensed with at least one of ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc. In phenol, phenol, o-cresol, m-cresol, p-cresol, 2,5-xylenol, 3,5-xylenol, resorcinol, pyrogallol and formaldehyde, acetaldehyde, propion as aldehydes or ketones A polycondensate with an aldehyde is preferable, and the mixing ratio of m-cresol: p-cresol: 2,5-xylenol: 3,5-xylenol: resorcinol in a molar ratio of 40 to 100: 0 to 50: 0 to 20 : 0-20: 0-20 mixed phenols, or Phenol: m-cresol: a mixing ratio molar ratio of p- cresol 1-100: 0-70: 0-60 and mixed phenol, preferably polycondensate of formaldehyde. In addition, the positive photosensitive composition of this invention may contain the solvent inhibitor mentioned later, and in that case, m-cresol: p-cresol: 2,5-xylenol: 3,5-xylenol: resorcinol The mixing ratio of 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 in molar ratio. A polycondensate of mixed phenols of -100: 0 to 60: 0 to 40 and formaldehyde is preferable.
[0062]
The novolak resin is a polystyrene-reduced weight average molecular weight (M) measured by gel permeation chromatography._W) Is preferably 1,000 to 15,000, more preferably 1,500 to 10,000.
[0063]
The resol resin is a resin polycondensed in the same manner except that an alkali catalyst is used in place of the acid catalyst in the polycondensation of the novolak resin. In the present invention, the phenols are the same as those in the novolak resin. And mixed compositions thereof, and aldehydes or ketones are preferred, and the same weight average molecular weight (M_W) Is preferred.
[0064]
Polyvinylphenol resins include, for example, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, dihydroxystyrene, trihydroxystyrene, tetrahydroxystyrene, pentahydroxystyrene, 2- (o-hydroxyphenyl) propylene, 2 Hydroxystyrenes such as-(m-hydroxyphenyl) propylene and 2- (p-hydroxyphenyl) propylene (note that these are halogen atoms such as chlorine, bromine, iodine and fluorine on the benzene ring, or carbon atoms of 1 to 4 In the presence of a radical polymerization initiator or a cationic polymerization initiator, and in the present invention, Has a C1-C4 alkyl group as a substituent on the benzene ring. Preferably the polymer of which may hydroxystyrenes have, in particular, polymers of hydroxystyrene unsubstituted benzene ring.
[0065]
The polyvinyl phenol resin may be partially hydrogenated, or may be partially protected with a tert-butoxycarbonyl group, pyranyl group, furyl group, or the like. The weight average molecular weight (M_W) Is preferably 1,000 to 100,000, particularly preferably 1,500 to 50,000.
[0066]
If the molecular weight of the novolak resin, resol resin, and polyvinylphenol resin is smaller than the above range, a sufficient coating film as a resist cannot be obtained, and if it is larger than the above range, the solubility in an alkali developer is reduced. The omission of the image portion is insufficient, and the resist pattern tends to be difficult to obtain.
[0067]
In the positive photosensitive composition of the present invention, the content of the alkali-soluble resin is preferably 1 to 98% by weight, more preferably 5 to 95% by weight, and 20 to 90% by weight. Is particularly preferred.
[0068]
The positive photosensitive composition of the present invention contains, in addition to the photothermal conversion substance and the alkali-soluble resin, for the purpose of increasing the difference in solubility between the exposed area and the unexposed area in an alkaline developer. It has a function of reducing the solubility of the resin by forming a hydrogen bond with the soluble resin, and contains a dissolution inhibitor that absorbs almost no light in the near infrared region and is not decomposed by light in the near infrared region. May be.
[0069]
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. Acids having a lactone skeleton, an N, N-diarylamide skeleton, a diarylmethylimino skeleton, which are also described in detail in JP-A-11-190903, such as aromatic ketones, aromatic aldehydes, aromatic amines, aromatic ethers, etc. Color-forming dyes, also described in detail in JP-A-11-143076, and base-coloring dyes having a lactone skeleton, thiolactone skeleton, and sulfolactone skeleton, also described in detail in JP-A-10-341400 And nonionic surfactants. Of these, acid-coloring dyes having a lactone skeleton are preferred.
[0070]
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.
[0071]
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).
[0072]
The content of the colorant in the positive photosensitive composition of the present invention is preferably 0 to 50% by weight, more preferably 1 to 30% by weight, and 2 to 20% by weight. Particularly preferred.
[0073]
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 an amount of 10% by weight or less, preferably 0.1 to 5% by weight.
[0074]
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.
[0075]
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 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.
[0076]
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. The drying temperature at that time is, for example, about 60 to 170 ° C., preferably about 70 to 150 ° C., and the drying time is, for example, about 5 seconds to 10 minutes, preferably about 10 seconds to 5 minutes. It is done.
[0077]
In addition, the support includes a metal plate such as aluminum, zinc, copper, steel, 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. 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.
[0078]
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 by heat generated by absorbing light, a light source that generates a near infrared laser beam of 700 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.
[0079]
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 of the laser beam on the surface of the photosensitive composition layer (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 be measured by exposing a photosensitive composition exhibiting a reciprocity law.
[0080]
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 · cm²More preferably, the above is used. When the light intensity is in the above range, the sensitivity characteristics of the positive photosensitive composition layer in the present invention can be improved, and the scanning exposure time can be shortened, which is a great advantage in practice.
[0081]
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.
[0082]
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.
[0083]
【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.
[0084]
Example 1
An aluminum plate (thickness 0.24 mm) was degreased at 60 ° C. for 1 minute in a 5 wt% sodium hydroxide aqueous solution, and then at a temperature of 28 ° C. in a hydrochloric acid aqueous solution having a concentration of 0.5 mol / liter. , Current density 60A / dm²The electrolytic etching treatment was performed under the condition of a treatment time of 40 seconds. Next, desmutting treatment was performed in a 4 wt% aqueous sodium hydroxide solution at 60 ° C. for 12 seconds, and then in a 20 wt% sulfuric acid solution at a temperature of 20 ° C. and a current density of 3.5 A / dm.²The anodizing treatment was performed under the condition of a treatment time of 1 minute. 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. The average roughness Ra of the plate measured by a surface roughness meter (“SE-3DH” manufactured by Kosaka Laboratory Ltd.) was 0.60 μm.
[0085]
On the surface of the obtained aluminum plate support, it consists of a polycondensate of formaldehyde and a mixed phenol having a mixing ratio of phenol: m-cresol: p-cresol of 20:50:30 in molar ratio as an alkali-soluble resin. Novolac resin (M_W7,000) 100 parts by weight, 3 parts by weight of a cyanine dye having a substituent containing an aminovinyl bond as a photothermal conversion substance, and 10 parts by weight of crystal violet lactone are added to 900 parts by weight of methyl cellosolve at room temperature. The coating solution prepared by stirring for 5 minutes was applied using a wire bar, dried at 100 ° C. for 1 minute, and then heat-treated at 55 ° C. for 16 hours to obtain a coating amount of 2.5 g / m.²A positive photosensitive lithographic printing plate having a positive photosensitive composition layer was prepared. The dye used was completely dissolved by stirring for 10 minutes, and a positive photosensitive lithographic printing plate having a uniform positive photosensitive composition layer was obtained.
[0086]
Embedded image

[0087]
About the obtained positive photosensitive lithographic printing plate, a 200-line, 1-99% network with various exposure energies using an exposure apparatus (“Trend Setter 3244T” manufactured by Creo Co., Ltd.) using a semiconductor laser of 830 nm as a light source. The dot image is exposed and then developed at 28 ° C. using an alkaline developer (10-fold diluted solution of “DP-4” manufactured by Fuji Photo Film Co., Ltd.) to reproduce a 1-99% dot image. A printing plate was prepared. The sensitivity at that time was determined as the exposure amount at which a 3% halftone image was reproduced, and was found to be 150 mJ / cm.²Met.
[0088]
Comparative Example 1
Except for using only the cyanine dye having no substituent containing an aminovinyl bond in the cyanine dye used in Example 1 as the light-to-heat conversion substance in the photosensitive composition layer, the same as in Example 1, Although a positive photosensitive lithographic printing plate was produced, coating defects due to dye crystal particles were observed in the photosensitive composition layer, and the lithographic printing plate was not practical.
[0089]
Comparative Example 2
Except for using the cyanine dye of the following formula having a diphenylamino group as a substituent on the polymethine chain instead of the cyanine dye used in Example 1 as the photothermal conversion substance in the photosensitive composition layer, 1, a positive photosensitive lithographic printing plate was prepared. 300 mJ / cm²An image was not formed even when the image was exposed with the exposure amount.
[0090]
Embedded image

[0091]
【The invention's effect】
According to the present invention, a positive photosensitive composition and a positive photosensitive composition that are highly sensitive to light in the near-infrared region, have excellent contrast between an image area and a non-image area, and thus have a wide range of development conditions. Sexual lithographic printing plates can be provided. Furthermore, since the positive photosensitive composition of the present invention is excellent in solubility in a solvent, it is possible to efficiently form a photosensitive composition layer by coating on the surface of a support as a solution, and to improve productivity. An excellent lithographic printing plate can be provided.

Claims (7)

A positive photosensitive composition comprising a photothermal conversion substance that absorbs light from an image exposure light source and converts it into heat, and an alkali-soluble resin, wherein the photothermal conversion substance is a heteroatom of a heterocyclic ring via a polymethine chain. Substitution represented by the following general formula (Va), which includes an aminovinyl bond that resonates in the dye molecule and generates an iminium cation on the polymethine chain A positive photosensitive composition comprising a dye having a group.

[In the formula (Va), R ^a represents an amino group which may have a substituent, the vinyl group may have a substituent, and the substituent in the amino group and the substituent in the vinyl group are They may be connected to each other to form a heterocyclic ring. ]   The positive photosensitive composition according to claim 1, wherein the dye as the photothermal conversion substance is a cyanine dye having a basic structure in which a heterocyclic ring is bonded via a polymethine chain. The positive photosensitive composition according to claim 2, wherein the cyanine dye as the photothermal conversion substance is a near-infrared absorbing dye represented by the following general formula (II).

[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 as a substituent in the dye molecule A tri, penta, hepta, nona, or undecametin group having at least a substituent containing an aminovinyl bond that resonates to produce an iminium cation, wherein the two substituents on the penta, hepta, nona, or undecametin group are It may be linked to form a C5-C7 cycloalkene ring, cycloalkeneone ring, cycloalkenedione ring, or cycloalkenethione ring, and the condensed benzene ring may have a substituent. Ku, in which case, may form a fused benzene ring by combining two adjacent substituents together. X _a ⁻ represents a counter anion. ] The positive photosensitive composition according to any one of claims 1 to 3, wherein the substituent containing an aminovinyl bond on the polymethine chain is represented by the following general formula (Vb).

[In Formula (Vb), W ¹ represents an oxygen atom, a sulfur atom, a nitrogen atom, or a dialkylmethylene group, and R ^b has an alkyl group that may have a substituent, or a substituent. May be an aryl group or a hydrogen atom, and the heterocycle is a 4- to 6-membered ring and may have a substituent. In this case, two adjacent substituents are connected to each other to form a condensed ring. You may do it. ] The positive photosensitive composition according to any one of claims 1 to 3, wherein the substituent containing an aminovinyl bond on the polymethine chain is represented by the following general formula (Vc).

[In Formula (Vc), W ¹ represents an oxygen atom, a sulfur atom, a nitrogen atom, or a dialkylmethylene group, and R ^c has an alkyl group which may have a substituent, or a substituent. An aryl group which may be substituted, and the condensed ring represents an aromatic hydrocarbon ring. ]   The positive photosensitive composition according to claim 1, wherein the alkali-soluble resin is a novolac resin.   A positive photosensitive lithographic printing plate comprising a layer of the positive photosensitive composition according to any one of claims 1 to 6 formed on a support surface.