JP4006665B2 - Positive photosensitive composition, positive photosensitive lithographic printing plate, and positive image forming method - Google Patents

Description

【００１０】
〔式(I) 中、環Ａ及び環Ｂは各々独立して、窒素原子を含む複素環を示し、環Ｃは、窒素原子を含む複素環、又は炭化水素環を示す。〕
【００１１】
【発明の実施の形態】
本発明のポジ型感光性組成物は、画像露光光源の光を吸収して熱に変換する光熱変換物質として、少なくとも、前記一般式(I) で表される近赤外線吸収色素を含有していることが必須である。
【００１２】
ここで、画像露光光源の光を吸収して熱に変換する光熱変換物質とは、吸収した光を熱に変換し得る化合物であって、本発明においては、波長域７００〜１３００ｎｍの近赤外線領域の一部又は全部に吸収帯を有する近赤外線吸収色素が特に有効である。これらの近赤外線吸収色素は、前記波長域の光を効率よく吸収する一方、紫外線領域の光は殆ど吸収しないか、吸収しても実質的に感応せず、白色灯に含まれるような弱い紫外線によっては感光性組成物を変成させる作用のない化合物である。
【００１３】
本発明における光熱変換物質の必須成分としての近赤外線吸収色素は、前記一般式(I) で表されるように、ジオキシシクロブタンの双性イオン化合物基とヒドロキシシクロブテノン基とを有するものであって、これらの基のそれぞれを有する色素は一般にスクアリリウム系色素として慣用されているものであるが、本発明においては、これらの基の両方を有しているビススクアリリウム系化合物であることが必須である。ジオキシシクロブタンの双性イオン化合物基、或いはヒドロキシシクロブテノン基のいずれか一方のみを有するスクアリリウム系化合物では、本発明の目的を達成できない。
【００１４】
ここで、環Ａ及び環Ｂの窒素原子を含む複素環としては、下記一般式(IIa) 、(IIb) 、又は(IIc) で表される、窒素原子を含む縮合環が、又、環Ｃの窒素原子を含む複素環としては、下記一般式(IIIa)、 (IIIb) 、又は(IIIc)で表される、四級化された窒素原子を含む縮合環が、それぞれ好ましく、特に、環Ａ及び環Ｂが一般式(IIa) で表される縮合環であり、且つ、環Ｃが一般式(IIIa)で表される縮合環である化合物が好ましい。
【００１５】
【化４】

【００１６】
〔式(II)及び式(III) 中、Ｒ¹ 、Ｒ⁴ 、及びＲ⁵ は各々独立して、置換基を有していてもよいアルキル基を示し、式(IIa) 、(IIb) 、(IIIa)、及び (IIIb) における縮合ベンゼン環、並びに、式(IIc) 及び(IIIc)における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く、Ｒ² 及びＲ³ は各々独立して、アルキル基を示し、これらは互いに連結して環を形成していてもよい。尚、式(IIIa)、 (IIIb) 、及び(IIIc)におけるＸ^- は対アニオンを示す。〕
【００１７】
ここで、Ｒ¹ 、Ｒ⁴ 、及びＲ⁵ のアルキル基は、炭素数１〜８程度のもので、具体的には、例えば、メチル、エチル、ｎ−プロピル、ｎ−ブチル、ｎ−ヘキシル、ｎ−ヘプチル、ｎ−オクチル等が挙げられ、それらの置換基としては、具体的には、例えば、メトキシ、エトキシ、プロポキシ、ブトキシ等のアルコキシ基、クロロ、ブロモ、フルオロ等のハロゲン原子、シクロペンチル、シクロヘキシル等のシクロアルキル基、フェニル、ナフチル等のアリール基、フェノキシ等のアリールオキシ基、クロロフェニル、ブロモフェニル、フルオロフェニル等のハロゲン原子置換フェニル基、水酸基、カルボン酸基又はそのエステル基、フリル、テトラヒドロフリル、チエニル、ピリジル等の複素環基等が挙げられる。
【００１８】
又、Ｒ² 及びＲ³ のアルキル基は、炭素数１〜４程度のもので、具体的には、例えば、メチル基、エチル基、ｎ−プロピル基、ｎ−ブチル基等が挙げられ、形成される環としては、具体的には、例えば、シクロペンタン、シクロヘキサン、シクロヘプタン等のシクロアルカン環、ノルボルナン、アダマンタン、ビシクロ［３．３．１］ノナン等の架橋環等が挙げられる。
【００１９】
又、式(IIa) 、(IIb) 、(IIIa)、及び (IIIb) における縮合ベンゼン環、並びに、式(IIc) 及び(IIIc)におけるキノリン環における置換基としては、アルキル基（この場合、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。）、アルコキシ基、ハロゲン原子、又はハロゲン原子置換アルキル基等が挙げられる。
【００２０】
尚、環Ｃの炭化水素環としては、置換基を有していてもよいベンゼン環等の芳香族環、又は置換基を有していてもよいシクロペンタジエニル、シクロヘキサジエニル等のシクロアルカジエニル環等が挙げられ、それらの置換基としては、アルキル基、アルコキシ基、アミノ基、又はハロゲン原子等が挙げられる。
【００２１】
尚、前記一般式(IIIa)、 (IIIb) 、及び(IIIc)における対アニオンＸ^- としては、具体的には、例えば、Ｃｌ^- 、Ｂｒ^- 、Ｉ^- 、ＣｌＯ₄ ^- 、ＰＦ₆ ^- 、及び、ＢＦ₄ ^- 、ＢＣｌ₄ ^- 等の無機硼酸等の無機酸アニオン、メチルスルホン酸、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、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。
【００２２】
本発明における前記一般式(I) で表されるビススクアリリウム系化合物は、例えば、特開平６−２６３７５８号公報等に記載の方法によって、具体的には、例えば、Ｎ−アルキル−２−メチルベンゾチアゾリウム塩等の、式(I) 中の環Ａ、環Ｂ、及び環Ｃに相当する複素環の窒素原子が４級アミン塩となっている複素環化合物と、スクエア酸とを、アルコール−ベンゼン混合溶媒中、１１０℃で７〜１５時間反応させることにより合成することができ、その際、複素環化合物を複数種使用すれば、環Ａ、環Ｂ、環Ｃが異なる化合物が得られる。
【００２３】
本発明における前記一般式(I) で表される近赤外線吸収色素の具体例を、前記一般式(I) における環Ａ及び環Ｂとしての前記一般式(IIa) 、(IIb) 、又は(IIc) の具体例、及び、環Ｃとしての前記一般式(IIIa)、 (IIIb) 、又は(IIIc)の具体例をそれぞれ表１として挙げることにより、以下に示す。
【００２４】
【表１】

【００２５】
【表２】

【００２６】
【表３】

【００２７】
本発明のポジ型感光性組成物における前記一般式(I) で表される近赤外線吸収色素の含有割合は、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。
【００２８】
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、前記一般式(I) で表される近赤外線吸収色素の外の近赤外線吸収色素が含有されていてもよく、その近赤外線吸収色素としては、窒素原子、酸素原子、又は硫黄原子等を含む複素環等がポリメチン（−ＣＨ＝）_n で結合された、広義の所謂シアニン系色素が代表的なものとして挙げられ、具体的には、例えば、キノリン系（所謂、狭義のシアニン系）、インドール系（所謂、インドシアニン系）、ベンゾチアゾール系（所謂、チオシアニン系）、アミノベンゼン系（所謂、ポリメチン系）、ピリリウム系、チアピリリウム系、スクアリリウム系、クロコニウム系、アズレニウム系等が挙げられ、中で、キノリン系、インドール系、ベンゾチアゾール系、アミノベンゼン系、ピリリウム系、又はチアピリリウム系が好ましい。
【００２９】
本発明のポジ型感光性組成物において、前記一般式(I) で表される近赤外線吸収色素以外の近赤外線吸収色素の含有割合は、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。
【００３０】
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。
【００３１】
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、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。
【００３２】
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。
【００３３】
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。
【００３４】
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。
【００３５】
前記ポリビニルフェノール樹脂は、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。
【００３６】
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。
【００３７】
本発明のポジ型感光性組成物における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。
【００３８】
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。
【００３９】
その溶解抑止剤としては、例えば、本願出願人による特願平９−２０５７８９号明細書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する酸発色性色素、同じく特願平９−３０１９１５号明細書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。中で、ラクトン骨格を有する酸発色性色素が好ましい。
【００４０】
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。
【００４１】
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。
【００４２】
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。
【００４３】
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。
【００４４】
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。
【００４５】
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。
【００４６】
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。
【００４７】
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。
【００４８】
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。
【００４９】
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。
【００５０】
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。
【００５１】
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。
【００５２】
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。
【００５３】
又、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。
【００５４】
【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。
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。
【００５５】
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 ７０００）１００重量部、光熱変換物質として、前記具体例( １ )で示した近赤外線吸収色素４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、シクロヘキサノン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。
【００５６】
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８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％の網点が再現する露光量として求めたところ、１４０ｍＪ／ｃｍ² であった。
【００５７】
更に、可視画性を評価するため、２８０ｍＪ／ｃｍ² の露光量での露光部と、非露光部を目視で確認したところ、露光部は非露光部に比べて明らかに色が薄くなっており露光画像がはっきりと確認できた。又、その露光部の反射濃度（ＯＤ₂₈₀ ）と非露光部の反射濃度（ＯＤ₀ ）を反射濃度計（Ｘ−Ｒｉｔｅ社製「Ｘ−Ｒｉｔｅ９３８」）を用いて測定し、非露光部の反射濃度（ＯＤ₀ ）に対する露光部の反射濃度（ＯＤ₂₈₀ ）の低下量（ＯＤ₀ −ＯＤ₂₈₀ ）の割合を求めたところ、１７％であった。
【００５８】
比較例１
感光性組成物層における光熱変換物質として、下記式で表されるスクアリリウム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近赤外線吸収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く、８００ｍＪ／ｃｍ² の露光量でも十分な画像が形成できなかった。又、可視画性も、２８０ｍＪ／ｃｍ² の露光量での露光部に変化は全く認められず、前記と同様にして求めた露光部の反射濃度の低下量の割合も０％であった。
【００５９】
【化５】

【００６０】
比較例２
感光性組成物層における光熱変換物質として、フタロシアニン系色素（日本触媒社製「イーエクスカラーＩＲ−３」）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、そのときの感度を、３％の網点が再現する露光量として求めたところ、２８０ｍＪ／ｃｍ² であった。更に、可視画性を評価するため、２８０ｍＪ／ｃｍ² の露光量での露光部と、非露光部を目視で確認したところ、露光部は非露光部に比べて若干色が薄くなっている程度であり、その露光部の反射濃度の低下量の割合も５％でしかなかった。
【００６１】
【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、露光部の可視画性が高く、非露光部と露光部とのコントラストに優れ、よって、製版作業性に優れると共に、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、並びにポジ画像形成方法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並びに画像形成方法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. 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 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, Japanese Patent Laid-Open No. 6-43333 discloses a negative photosensitive material in which a photoacid generator and a binder are combined with a specific squarylium-based dye. Japanese Patent No. -20629 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 novolac resin in an image form with a semiconductor laser or the like. JP-A-7-27029 discloses a method using an s-triazine compound instead of the latent Bronsted acid, and JP-A-9-43847 discloses a phthalocyanine-based, indolizine-based, croconate-based, cyanine-based compound. Contains near-infrared absorbing dyes such as squarylium and pyrylium, and changes the crystallinity of the photosensitive material by heating with near-infrared radiation. Resist material and a patterning process using the same to have been disclosed, respectively.
[0006]
However, according to the study by the present inventors, these conventional techniques are low in sensitivity to light in the near infrared region, and the difference in solubility between the exposed portion and the non-exposed portion in the developer is small. The non-image area is not sufficiently removed, the remaining film ratio of the image area is not sufficiently maintained, and therefore, there are practical disadvantages such as a narrow range of development conditions.
[0007]
[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, has high visibility in the exposed area, and is not exposed to light. The present invention aims to provide a positive photosensitive composition and a positive photosensitive lithographic printing plate that have excellent contrast between the exposed portion and the exposed portion, and thus have excellent platemaking workability and a wide range of development conditions, and a positive image forming method. And
[0008]
[Means for Solving the Problems]
The present inventors are a simple system that cannot expect a photochemical change between a photothermal conversion substance and an alkali-soluble resin comprising a near-infrared absorbing dye, and this type of photosensitive composition in which it is difficult to predict sensitivity due to the dye structure. As a result of intensive studies to obtain a photosensitive composition and a photosensitive lithographic printing plate capable of forming a positive image in which the above-mentioned drawbacks are eliminated, and a positive image forming method, a near-infrared absorbing dye having a specific structure is used as a photothermal conversion substance. The present invention has been completed by finding that a composition used together with an alkali-soluble resin can achieve the above-mentioned object. That is, the present invention provides a photothermal conversion substance and an alkali that absorb light from an image exposure light source and convert it into heat. A positive photosensitive composition containing a soluble resin, and containing at least a near-infrared absorbing dye represented by the following general formula (I) as the photothermal conversion substance: Positive photosensitive lithographic printing plate in which the layer of the photosensitive composition is formed on the surface of the support, and the lithographic printing plate with a laser beam having a wavelength range of 700 to 1300 nm. A gist is a positive image forming method in which development is performed after exposure.
[0009]
[Chemical 3]

[0010]
[In Formula (I), Ring A and Ring B each independently represent a heterocyclic ring containing a nitrogen atom, and Ring C represents a heterocyclic ring containing a nitrogen atom or a hydrocarbon ring. ]
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The positive photosensitive composition of the present invention contains at least a near-infrared absorbing dye represented by the general formula (I) as a photothermal conversion substance that absorbs light from an image exposure light source and converts it into heat. It is essential.
[0012]
Here, the photothermal conversion substance that absorbs the light of the image exposure light source and converts it into heat is a compound that can convert the absorbed light into heat, and in the present invention, the near infrared region in the wavelength range of 700 to 1300 nm. A near-infrared absorbing dye having an absorption band in part or all of is particularly effective. 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.
[0013]
The near-infrared absorbing dye as an essential component of the photothermal conversion material in the present invention has a zwitterionic compound group of dioxycyclobutane and a hydroxycyclobutenone group as represented by the general formula (I). The dye having each of these groups is generally used as a squarylium dye, but in the present invention, it is essential that the dye is a bis-squarylium compound having both of these groups. It is. A squarylium compound having only one of the zwitterionic compound group of dioxycyclobutane or the hydroxycyclobutenone group cannot achieve the object of the present invention.
[0014]
Here, as the heterocyclic ring containing the nitrogen atom of ring A and ring B, a condensed ring containing a nitrogen atom represented by the following general formula (IIa), (IIb), or (IIc) is also represented by ring C As the heterocyclic ring containing a nitrogen atom, a condensed ring containing a quaternized nitrogen atom represented by the following general formula (IIIa), (IIIb), or (IIIc) is preferable, respectively. And a compound in which ring B is a condensed ring represented by the general formula (IIa) and ring C is a condensed ring represented by the general formula (IIIa).
[0015]
[Formula 4]

[0016]
[In the formulas (II) and (III), R ¹ , R ⁴ , and R ⁵ each independently represents an alkyl group which may have a substituent, and the formulas (IIa), (IIb), The condensed benzene ring in (IIIa) and (IIIb) and the quinoline ring in formulas (IIc) and (IIIc) may have a substituent, in which case two adjacent substituents are linked to each other. May form a condensed benzene ring, and R ² and R ³ each independently represent an alkyl group, which may be linked to each other to form a ring. In the formulas (IIIa), (IIIb) and (IIIc), X ⁻ represents a counter anion. ]
[0017]
Here, the alkyl groups of R ¹ , R ⁴ , and R ⁵ have about 1 to 8 carbon atoms, and specifically include, for example, methyl, ethyl, n-propyl, n-butyl, n-hexyl, Specific examples thereof include n-heptyl, n-octyl, and the like. Specific examples of the substituent include alkoxy groups such as methoxy, ethoxy, propoxy, and butoxy, halogen atoms such as chloro, bromo, and fluoro, cyclopentyl, Cycloalkyl groups such as cyclohexyl, aryl groups such as phenyl and naphthyl, aryloxy groups such as phenoxy, halogen atom-substituted phenyl groups such as chlorophenyl, bromophenyl and fluorophenyl, hydroxyl groups, carboxylic acid groups or ester groups thereof, furyl, tetrahydro Examples include heterocyclic groups such as furyl, thienyl, pyridyl and the like.
[0018]
The alkyl groups of R ² and R ³ are those having about 1 to 4 carbon atoms, and specific examples include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, and the like. Specific examples of the ring include cycloalkane rings such as cyclopentane, cyclohexane and cycloheptane, and bridged rings such as norbornane, adamantane and bicyclo [3.3.1] nonane.
[0019]
In addition, the substituent in the condensed benzene ring in the formulas (IIa), (IIb), (IIIa), and (IIIb) and the quinoline ring in the formulas (IIc) and (IIIc) may be an alkyl group (in this case, adjacent Two substituents may be linked to each other to form a condensed benzene ring.), An alkoxy group, a halogen atom, or a halogen atom-substituted alkyl group.
[0020]
The hydrocarbon ring of ring C includes an aromatic ring such as a benzene ring which may have a substituent, or a cycloalkenyl such as cyclopentadienyl and cyclohexadienyl which may have a substituent. Examples thereof include an alkyl group, an alkoxy group, an amino group, and a halogen atom.
[0021]
Specific examples of the counter anion X ⁻ in the general formulas (IIIa), (IIIb), and (IIIc) include Cl ⁻ , Br ⁻ , I ⁻ , ClO ₄ ⁻ , PF ₆ ⁻ , and Inorganic acid anions such as inorganic boric acid such as BF ₄ ⁻ , BCl ₄ ⁻ , methyl sulfonic acid, benzene sulfonic acid, p-toluene sulfonic acid, naphthalene sulfonic acid, and methyl, ethyl, propyl, butyl, phenyl, methoxyphenyl And organic acid anions such as organic boric acid having an organic group such as naphthyl, difluorophenyl, pentafluorophenyl, thienyl and pyrrolyl.
[0022]
The bis-squarylium-based compound represented by the general formula (I) in the present invention is specifically prepared by, for example, a method described in JP-A-6-263758, for example, N-alkyl-2-methylbenzo A heterocyclic compound in which the nitrogen atom of the heterocyclic ring corresponding to ring A, ring B, and ring C in formula (I) is a quaternary amine salt, such as thiazolium salt, and squaric acid -It can be synthesized by reacting in a benzene mixed solvent at 110 ° C for 7 to 15 hours. In this case, if a plurality of heterocyclic compounds are used, compounds having different ring A, ring B and ring C can be obtained. .
[0023]
Specific examples of the near-infrared absorbing dye represented by the general formula (I) in the present invention include the general formula (IIa), (IIb) or (IIc) as the ring A and ring B in the general formula (I). ) And specific examples of the general formula (IIIa), (IIIb) or (IIIc) as ring C are shown in Table 1 below.
[0024]
[Table 1]

[0025]
[Table 2]

[0026]
[Table 3]

[0027]
The content ratio of the near-infrared absorbing dye represented by the general formula (I) in the positive photosensitive composition of the present invention is preferably 0.5 to 50% by weight, and 1 to 40% by weight. Is more preferable, and 2 to 30% by weight is particularly preferable.
[0028]
The positive photosensitive composition of the present invention may contain a near-infrared absorbing dye other than the near-infrared absorbing dye represented by the general formula (I) as the photothermal conversion substance. A typical example of the absorbing dye is a so-called cyanine dye in a broad sense in which a heterocyclic ring containing a nitrogen atom, an oxygen atom, a sulfur atom, or the like is bonded with polymethine (-CH =) _n. For example, quinoline type (so-called cyanine type), indole type (so-called indocyanine type), benzothiazole type (so-called thiocyanin type), aminobenzene type (so-called polymethine type), pyrylium type, thiapyrylium Examples include quinoline, indole, benzothiazole, aminobenzene, pyridinium, squarylium, croconium, and azulenium. Um system or thiapyrylium are preferred.
[0029]
In the positive photosensitive composition of the present invention, the content of the near-infrared absorbing dye other than the near-infrared absorbing dye represented by the general formula (I) is preferably 0 to 20% by weight, It is more preferably ˜15% by weight, particularly preferably 1 to 10% by weight.
[0030]
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.
[0031]
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 acidic 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 ketone such as acetone, methyl ethyl ketone, methyl isobutyl ketone, etc. In the invention, phenol as phenols, o-cresol, m-cresol, p-cresol, 2,5-xylenol, 3,5-xylenol, resorcinol, pyrogallol and formaldehyde, acetaldehyde as aldehydes or ketones, A polycondensate with propionaldehyde is preferred, 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.
[0032]
The novolak resin has a weight average molecular weight in terms of polystyrene by gel permeation chromatography measurement (M _W) is preferably 1,000 to 15,000, more preferably those of 1,500 to 10,000 is used.
[0033]
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 preferable, and those having the same weight average molecular weight (M _W ) are preferable.
[0034]
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.
[0035]
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.
[0036]
When 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 when the molecular weight is larger than the above range, the solubility in an alkaline developer is reduced. The omission of the image portion is insufficient, and the resist pattern tends to be difficult to obtain.
[0037]
The content of the alkali-soluble resin in the positive photosensitive composition of the present invention is preferably 1 to 98% by weight, more preferably 5 to 95% by weight, and 20 to 90% by weight. Is particularly preferred.
[0038]
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 in an alkaline developer between an exposed area and an unexposed area. Contains a dissolution inhibitor that has a function of reducing the solubility of the resin by forming hydrogen bonds with the soluble resin, and hardly absorbs light in the near infrared region and is not decomposed by light in the near infrared region. May be.
[0039]
Examples of the dissolution inhibitor include sulfonic acid esters, phosphoric acid esters, aromatic carboxylic acid esters, aromatic disulfones, and carboxylic acid anhydrides described in detail in Japanese Patent Application No. 9-205789 by the applicant of the present application. , Aromatic ketones, aromatic aldehydes, aromatic amines, aromatic ethers, and the like, which are also described in detail in Japanese Patent Application No. 9-291880, lactone skeleton, N, N-diarylamide skeleton, diarylmethylimino An acid color-forming dye having a skeleton, which is also described in detail in Japanese Patent Application No. 9-301915, and a base color-forming dye having a lactone skeleton, a thiolactone skeleton, and a sulfolactone skeleton, and Japanese Patent Application No. 9-331512 Nonionic surfactants described in detail in the specification can be mentioned. Of these, acid-coloring dyes having a lactone skeleton are preferred.
[0040]
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.
[0041]
In addition, the positive photosensitive composition of the present invention may contain, 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).
[0042]
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.
[0043]
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.
[0044]
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.
[0045]
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.
[0046]
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.
[0047]
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.
[0048]
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.
[0049]
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 as the area of the portion exceeding the 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. .
[0050]
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.
[0051]
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.
[0052]
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.
[0053]
The development is usually carried out at a temperature of preferably about 10 to 50 ° C., particularly preferably about 15 to 45 ° C. by immersion development, spray development, brush development, ultrasonic development and the like.
[0054]
【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.
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. The electrolytic etching treatment was performed under the conditions of a current density of 60 A / dm ² and 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, the temperature was 20 ° C, the current density was 3.5 A / dm ² , and the treatment time was 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. The average roughness Ra of the plate measured by a surface roughness meter (“SE-3DH” manufactured by Kosaka Laboratory Ltd.) was 0.60 μm.
[0055]
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. 100 parts by weight of novolak resin (M _W 7000), 4 parts by weight of the near-infrared absorbing dye shown in the specific example (1) and 10 parts by weight of crystal violet lactone as a photothermal conversion substance, and 900 parts by weight of cyclohexanone at room temperature A coating solution prepared by stirring for 5 minutes was applied using a wire bar, dried at 100 ° C. for 2 minutes, and then heat-treated at 55 ° C. for 16 hours to obtain a coating amount of 2.5 g / m ² . A positive photosensitive lithographic printing plate having a positive photosensitive composition layer was prepared.
[0056]
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 with an alkaline developer (8-fold diluted solution of “DP-4” manufactured by Fuji Photo Film Co., Ltd.) at 28 ° C. to reproduce a dot image of 1 to 99%. A printing plate was prepared. The sensitivity at that time was determined as the exposure amount reproduced by 3% halftone dots, and was 140 mJ / cm ² .
[0057]
Furthermore, in order to evaluate the visibility, when the exposed part and the non-exposed part at an exposure amount of 280 mJ / cm ² were visually confirmed, the exposed part was clearly lighter than the non-exposed part. The exposed image was clearly confirmed. Further, the reflection density (OD ₂₈₀ ) of the exposed part and the reflection density (OD ₀ ) of the non-exposed part are measured using a reflection densitometer (“X-Rite 938” manufactured by X-Rite), and the reflection of the non-exposed part is measured. The ratio of the decrease amount (OD ₀ -OD ₂₈₀ ) of the reflection density (OD ₂₈₀ ) of the exposed area to the density (OD ₀ ) was found to be 17%.
[0058]
Comparative Example 1
A positive photosensitive lithographic printing plate was produced in the same manner as in Example 1 except that only the squarylium dye represented by the following formula was used as the photothermal conversion substance in the photosensitive composition layer. A coating defect due to near infrared absorbing dye crystal particles was observed in the physical layer, and it was not a lithographic printing plate that could withstand practical use, and a sufficient image could not be formed even at an exposure amount of 800 mJ / cm ² . Further, in the visible image quality, no change was observed in the exposed portion at an exposure amount of 280 mJ / cm ² , and the ratio of the decrease in reflection density of the exposed portion obtained in the same manner as described above was 0%.
[0059]
[Chemical formula 5]

[0060]
Comparative Example 2
Positive photosensitive lithographic printing plate in the same manner as in Example 1 except that only a phthalocyanine-based dye (“EEX Color IR-3” manufactured by Nippon Shokubai Co., Ltd.) was used as the photothermal conversion material in the photosensitive composition layer. When the sensitivity at that time was determined as the exposure amount at which 3% of the halftone dots were reproduced, it was 280 mJ / cm ² . Furthermore, in order to evaluate visible image quality, when the exposed part and the non-exposed part at an exposure amount of 280 mJ / cm ² were visually confirmed, the exposed part was slightly thinner than the non-exposed part. The ratio of the decrease in the reflection density of the exposed area was only 5%.
[0061]
【The invention's effect】
According to the present invention, high sensitivity to light in the near-infrared region, high visibility of the exposed portion, excellent contrast between the non-exposed portion and the exposed portion, and thus excellent plate making workability, A positive photosensitive composition and a positive photosensitive lithographic printing plate having a wide range of development conditions, and a positive image forming method can be provided.
Furthermore, since the positive photosensitive composition of the present invention is excellent in solubility in a solvent, the photosensitive composition layer can be efficiently formed by coating on the surface of the support as a solution. An excellent lithographic printing plate and an image forming method can be provided.

Claims (5)

A positive photosensitive composition comprising a photothermal conversion material that absorbs light from an image exposure light source and converts it into heat, and an alkali-soluble resin, and the photothermal conversion material is represented by at least the following general formula (I): A positive photosensitive composition comprising a near-infrared absorbing dye.

[In Formula (I), Ring A and Ring B each independently represent a heterocyclic ring containing a nitrogen atom, and Ring C represents a heterocyclic ring containing a nitrogen atom or a hydrocarbon ring. ] Ring A and Ring B in the general formula (I) are condensed rings containing a nitrogen atom represented by the following general formula (IIa), (IIb), or (IIc), and ring C is The positive photosensitive composition according to claim 1, which is a condensed ring containing a quaternized nitrogen atom represented by the general formula (IIIa), (IIIb) or (IIIc).

[In the formulas (II) and (III), R ¹ , R ⁴ , and R ⁵ each independently represents an alkyl group which may have a substituent, and the formulas (IIa), (IIb), The condensed benzene ring in (IIIa) and (IIIb) and the quinoline ring in formulas (IIc) and (IIIc) may have a substituent, in which case two adjacent substituents are linked to each other. May form a condensed benzene ring, and R ² and R ³ each independently represent an alkyl group, which may be linked to each other to form a ring. In the formulas (IIIa), (IIIb) and (IIIc), X ⁻ represents a counter anion. ]   Quaternized nitrogen in which ring A and ring B are condensed rings containing a nitrogen atom represented by the general formula (IIa) and ring C is represented by the general formula (IIIa) The positive photosensitive composition according to claim 2, which is a condensed ring containing an atom. A positive photosensitive lithographic printing plate, comprising a layer of the positive photosensitive composition according to any one of claims 1 to 3 formed on a support surface. A positive image lithographic printing plate according to claim 4, wherein the positive photosensitive lithographic printing plate is image-exposed with a laser beam having a wavelength range of 700 to 1300 nm and then developed.