JP4076149B2 - Thermal recording material - Google Patents

Description

【００１８】
【化９】

（式中Ｘは３価以上の基、ａは３以上の整数を示す。ｂ、ｃは０〜５の整数であり、但し、ｂ＋ｃ＝１〜５を満足する。Ｚは水素原子、アルキル基、アリル基、アリール基を示し、アリール基の場合は縮合環の構造を形成しているものであってもよい。ｄはｂ＋ｃ＋ｄ＝５の関係を満足する０〜４の整数である。）
【化１０】

【化１１】

（２）「前記一般式（Ｉ）におけるＸが下記式（III）又は（IV）で表わされる３価の構造であることを特徴とする前記第（１）項に記載の感熱記録材料；
【００１９】
【化１２】

【００２０】
【化１３】

（式中Ｙは、２価の基を示す。）」、（３）「前記一般式（II）で表わされる化合物が下記式（Ｖ）で表わされるアミノサリチル酸誘導体であることを特徴とする前記第（１）項又は第（２）項に記載の感熱記録材料；
【００２１】
【化１４】

【００２３】
（４）「前記感熱発色層中に２，４’−ビスヒドロキシジフェニルスルホン又は４−ヒドロキシ−４’−アリルオキシジフェニルスルホンの少なくとも１種類を含有することを特徴とする前記第（１）項乃至第（３）項のいずれかに記載の感熱記録材料」、（５）「前記オリゴマー組成物と２，４’−ビスヒドロキシジフェニルスルホン又は４−アリルオキシ−４’−ヒドロキシジフェニルスルホンとの重量比が、２：８〜５：５の間であることを特徴とする前記第（１）項乃至第（４）項のいずれかに記載の感熱記録材料」、（６）「前記ロイコ染料として３−ジブチルアミノ−６−メチル−７−アニリノフルオラン、３−ジ（ｎ−ペンチル）アミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−ｐ−トルイジノ）−６−メチル−７−アニリノフルオランのいずれかを用いることを特徴とする前記第（１）項乃至第（５）項のいずれかに記載の感熱記録材料」、（７）「前記ロイコ染料の平均粒子径が０．１０μｍ〜０．３０μｍであるロイコ染料分散液を用いることを特徴とする前記第（１）項乃至第（６）項のいずれかに記載の感熱記録材料」、（８）「支持体上に、少なくとも中空粒子を含むアンダーコート層を設け、前記第（１）項乃至第（７）項のいずれかに記載の感熱発色層を有することを特徴とする前記第（１）項乃至第（７）項のいずれかに記載の感熱記録材料」、（９）「前記アンダーコート層に含まれる中空粒子は、熱可塑性樹脂を殻とし、中空率３０％以上で重量平均粒子径０．４〜１０μｍの大きさであることを特徴とする前記第（１）項乃至第（８）項のいずれかに記載の熱記録材料」によって解決される。
【００２４】
本発明において、高分子量の顕色剤である一般式（Ｉ）又は(III)又は（IV）で表わされる３価以上の多価イソシアネート化合物と一般式（II）又は（Ｖ）で表わされる芳香族アミンとの反応によって得られるオリゴマー組成物はサリチル酸残基を分子内に多く有することより、５０℃／８０％以上の高温高湿環境において、地肌カブリを発生する。塩基性であるヒンダートアミン誘導体を含有することで、ｐＨを中性にすることにより、該オリゴマー組成物の溶解度が低下し、地肌カブリの発生を抑えることが可能となった。本発明のオリゴマーは、分子量２０００〜１００００のものを意味している。
【００２５】
通常、塩基性化合物を添加すると発色阻害を生じ、感度の低下、耐薬品性の低下を招くが、ヒンダートアミン誘導体は感度の低下、耐薬品性の低下が少ない。これは、ヒンダートアミン誘導体の塩基性度が適度であることによるものと考えられる。よって、ヒンダートアミン誘導体とオリゴマー組成物の組み合わせは、高感度で、耐熱保存性、耐薬品性に優れる感熱記録材料を提供できる。
【００２６】
ヒンダートアミン誘導体として、高分子の化合物（１）（分子量２０００）、又は化合物（２）（分子量１９００）を用いることで、染料と顕色剤で形成される発色複合体の熱溶融時の活性化エネルギーを低下させ、更に熱溶融後のアモルファス性を高めることで、発色性及び耐薬品性を向上させているものと考えられる。
また、高分子のテトラキス（１，２，２，６，６−ペンタメチル−４−ピペリジル）−１，２，３，４−ブタンテトラカルボキシレート又はテトラキス（２，２，６，６−テトラメチル−４−ピペリジル）−１，２，３，４−ブタンテトラカルボキシレートは、分子量８５０、融点１４０℃と高分子で、高い融点であることから、耐薬品性と耐熱性の両立が可能となった。
【００２７】
また、本発明において使用される一般式（Ｉ）又は(III)又は（IV）で表わされる３価以上の多価イソシアネート化合物と一般式（II）又は（Ｖ）で表わされる芳香族アミンとの反応によって得られるオリゴマー組成物は、ロイコ染料１重量部に対して、２〜６重量部であることが好ましい。２重量部未満では発色性が不充分になり、６重量部を超えると発色に関与しない成分が多くなり、発色を妨げ、感度が低下すると考えられる。また発色に関与しない成分を過剰に添加することは工業的に望ましくない。
【００２８】
ヒンダートアミン誘導体であるテトラキス（１，２，２，６，６−ペンタメチル−４−ピペリジル）−１，２，３，４−ブタンテトラカルボキシレート又はテトラキス（２，２，６，６−テトラメチル−４−ピペリジル）−１，２，３，４−ブタンテトラカルボキシレート又は化合物（１）、又は化合物（２）の添加量は、塩基性物質であることから、ロイコ染料１重量部に対して、1重量部以上になると消色効果が発生し、発色濃度が低下することから、０．１〜０．５重量部の添加が好ましい。
【００２９】
また、本発明において添加できる顕色剤としては次のようなものが挙げられる。このような顕色剤としては、この種の感熱材料に適用されているものが任意に適用されるが、耐薬品性・高感度及び耐熱性を両立させるためには、２，４’−ビスヒドロキシジフェニルスルホン、４−アリルオキシ−４’−ヒドロキシジフェニルスルホンが最も有用である。
【００３０】
それ以外の具体例としては、例えば、以下に示すようなものが挙げられる。
４，４’−イソプロピリデンビスフェノール、４，４’−イソプロピリデンビス（ｏ−メチルフェノール）、４，４’−ｓｅｃ−ブチリデンビスフェノール、４，４’−イソプロピリデンビス（２−ｔｅｒ−ブチルフェノール）、４，４’−メチレンビス（オキシエチレンチオ）ジフェノール、ｐ−ニトロ安息香酸亜鉛、１，３，５−トリス（４−ｔｅｒ−ブチル−３−ヒドロキシ−２，６−ジメチルベンジル）イソシアヌル酸、２，２−（３，４−ジヒドロキシフェニルプロパン）、ビス（４−ヒドロキシ−３−メチルフェニルスルフィド）、４−（β−（ｐ−メトキシフェノキシ）エトキシ）サリチル酸、１，７−ビス（４−ヒドロキシフェニルチオ）−３，５−ジオキサヘプタン、１，５−ビス（ヒドロキシフェニルチオ）−５−オキサヘプタン、フタル酸モノベンジルエステルモノカルシウム塩、４，４’−シクロヘキシリデンビスフェノール、４，４’−イソプロピリデンビス（２−クロロフェノール）、２，２’−メチレンビス（４−メチル−６−ｔｅｒ−ブチルフェノール）、４，４’−ブチリデンビス（６−ｔｅｒ−ブチル−２−メチル）フェノール、１，１，３−トリス（２−メチル−４−ヒドロキシ−５−ターシャリ−ブチルフェニル）ブタン、１，１，３−トリス（２−メチル−４−ヒドロキシ−５−シクロヘキシルフェニル）ブタン、４，４’−チオビス（６−ｔｅｒ−ブチル２−メチル）フェノール、４，４’−フェノールスルホン、４−イソプロピルオキシ−４’−ヒドロキシジフェニルスルホン、４−ベンジロキシ−４’−ヒドロキシジフェニルスルホン、４，４’−ジフェノールスルホキシド、ｐ−ヒドロキシ安息香酸イソプロピル、ｐ−ヒドロキシ安息香酸ベンジル、プロトカテキュ酸ベンジル、没食子酸ステアリル、没食子酸ラウリル、没食子酸オクチル、１，３−ビス（４−ヒドロキシフェニルチオ）−プロパン、Ｎ，Ｎ−ジフェニルチオ尿素、Ｎ，Ｎ−ジ（ｍ−クロロフェニル）チオ尿素、サリチルアニリド、ビス（４−ヒドロキシフェニル）酢酸メチルエステル、ビス（４−ヒドロキシフェニル）酢酸ベンジルエステル、１，３−ビス（４−ヒドロキシクミル）ベンゼン、１，４−ビス（４−ヒドロキシクミル）ベンゼン、２，２’−ジアリル−４，４’−ジフェノールスルホン、３，４−ジヒドロキシフェニル−４’−メチルジフェニルスルホン、１−アセチルオキシ−２−ナフトエ酸亜鉛、２−アセチルオキシ−１−ナフトエ酸亜鉛、２−アセチルオキシ−３−ナフトエ酸亜鉛、α，α−ビス（４−ヒドロキシフェニル）−α−メチルトルエン、チオシアン酸亜鉛のアンチピリン錯体、テトラブロモビスフェノールＡ、テトラブロモビスフェノールＳ、４，４’−チオビス（２−メチルフェノール）、４，４’−チオビス（２−クロロフェノール）、スルホニルアミノカルボニルアミド基を有する化合物等。
【００３１】
これらの顕色剤は、耐薬品性を低下させない範囲での添加が好ましいく、該感熱発色層中の前記オリゴマー組成物と２，４’−ビスヒドロキシジフェニルスルホン又は４−アリルオキシ−４’−ヒドロキシジフェニルスルホンとの重量比が、２：８〜５：５の間であることを特徴とする感熱記録材料である。
【００３２】
本発明の感熱発色層において使用されるロイコ染料は、単独又は２種以上混合して適用されるが、このようなロイコ染料としては、この種の感熱材料に適用されているものが任意に適用されるが、耐薬品性・高感度及び耐熱性を両立させるためには、３−ジブチルアミノ−６−メチル−７−アニリノフルオラン、３−ジ（ｎ−ペンチル）アミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−ｐ−トルイジノ）−６−メチル−７−アニリノフルオランが最も有用である。
【００３３】
それ以外の具体例としては、例えば、以下に示すようなものが挙げられる。
トリフェニルメタン系、フルオラン系、フエノチアジン系、オーラミン系、スピロピラン系、インドリノフタリド系等の染料のロイコ化合物が好ましく用いられる。このようなロイコ染料の具体例としては、例えば、以下に示すようなものが挙げられる。
【００３４】
３，３−ビス（ｐ−ジメチルアミノフェニル）−フタリド、
３，３−ビス（ｐ−ジメチルアミノフェニル）−６−ジメチルアミノフタリド（別名クリスタルバイオレットラクトン）、
３，３−ビス（ｐ−ジメチルアミノフェニル）−６−ジエチルアミノフタリド、
３，３−ビス（ｐ−ジメチルアミノフェニル）−６−クロルフタリド、
３，３−ビス（ｐ−ジブチルアミノフェニル）フタリド、
３−シクロヘキシルアミノ−６−クロルフルオラン、
３−ジメチルアミノ−５，７−ジメチルフルオラン、
３−Ｎ−メチル−Ｎ−イソブチル−６−メチル−７−アニリノフルオラン、
３−Ｎ−エチル−Ｎ−イソアミル−６−メチル−７−アニリノフルオラン、
３−ジエチルアミノ−７−クロロフルオラン、
３−ジエチルアミノ−７−メチルフルオラン、
３−ジエチルアミノ−７，８−ベンズフルオラン、
３−ジエチルアミノ−６−メチル−７−クロルフルオラン、
３−（Ｎ−ｐ−トリル−Ｎ−エチルアミノ）−６−メチル−７−アニリノフルオラン、
３−ピロリジノ−６−メチル−７−アニリノフルオラン、
２−｛Ｎ−（３’−トリフルオルメチルフェニル）アミノ｝−６−ジエチルアミノフルオラン、
２−｛３，６−ビス（ジエチルアミノ）−９−（ｏ−クロルアニリノ）キサンチル安息香酸ラクタム｝、
３−ジエチルアミノ−６−メチル−７−（ｍ−トリクロロメチルアニリノ）フルオラン、
３−ジエチルアミノ−７−（ｏ−クロルアニリノ）フルオラン、
３−ジブチルアミノ−７−（ｏ−クロルアニリノ）フルオラン、
３−Ｎ−メチル−Ｎ−アミルアミノ−６−メチル−７−アニリノフルオラン、
３−Ｎ−メチル−Ｎ−シクロヘキシルアミノ−６−メチル−７−アニリノフルオラン、
３−ジエチルアミノ−６−メチル−７−アニリノフルオラン、
３−ジエチルアミノ−６−メチル−７−（２’，４’−ジメチルアニリノ）フルオラン、
３−（Ｎ，Ｎ−ジエチルアミノ）−５−メチル−７−（Ｎ，Ｎ−ジベンジルアミノ）フルオラン、
ベンゾイルロイコメチレンブルー、
６’−クロロ−８’−メトキシ−ベンゾインドリノ−スピロピラン、
６’−ブロモ−３’−メトキシ−ベンゾインドリノ−スピロピラン、
３−（２’−ヒドロキシ−４’−ジメチルアミノフェニル）−３−（２’−メトキシ−５’−クロルフェニル）フタリド、
３−（２’−ヒドロキシ−４’−ジメチルアミノフェニル）−３−（２’−メトキシ−５’−ニトロフェニル）フタリド、
３−（２’−ヒドロキシ−４’−ジエチルアミノフェニル）−３−（２’−メトキシ−５’−メチルフェニル）フタリド、
３−（２’−メトキシ−４’−ジメチルアミノフェニル）−３−（２’−ヒドロキシ−４’−クロル−５’−メチルフェニル）フタリド、
３−モルホリノ−７−（Ｎ−プロピル−トリフルオロメチルアニリノ）フルオラン、
３−ピロリジノ−７−トリフルオロメチルアニリノフルオラン、
３−ジエチルアミノ−５−クロロ−７−（Ｎ−ベンジル−トリフルオロメチルアニリノ）フルオラン、
３−ピロリジノ−７−（ジ−ｐ−クロルフェニル）メチルアミノフルオラン、
３−ジエチルアミノ−５−クロル−７−（α−フェニルエチルアミノ）フルオラン、
３−ジエチルアミノ−７−（ｏ−メトキシカルボニルフェニルアミノ）フルオラン、
３−ジエチルアミノ−５−メチル−７−（α−フェニルエチルアミノ）フルオラン、
３−ジエチルアミノ−７−ピペリジノフルオラン、
２−クロロ−３−（Ｎ−メチルトルイジノ）−７−（ｐ−ｎ−ブチルアニリノ）フルオラン、
３−（Ｎ−メチル−Ｎ−イソプロピルアミノ）−６−メチル−７−アニリノフルオラン、
３−ジエチルアミノ−６−メチル−７−（３−メチルアニリノ）フルオラン、
３，６−ビス（ジメチルアミノ）フルオレンスピロ（９，３’）−６’−ジメチルアミノフタリド、
３−（Ｎ−ベンジル−Ｎ−シクロヘキシルアミノ）−５，６−ベンゾ−７−α−ナフチルアミノ−４’−ブロモフルオラン、
３−ジエチルアミノ−６−クロル−７−アニリノフルオラン、
３−Ｎ−エチル−Ｎ−（２−エトキシプロピル）アミノ−６−メチル−７−アニリノフルオラン、
３−Ｎ−エチル−Ｎ−テトラヒドロフルフリルアミノ−６−メチル−７−アニリノフルオラン、
３−ジエチルアミノ−６−メチル−７−メシチジノ−４’，５’−ベンゾフルオラン、
３−（ｐ−ジメチルアミノフェニル）−３−｛１，１−ビス（ｐ−ジメチルアミノフェニル）エチレン−２−イル｝フタリド、
３−（ｐ−ジメチルアミノフェニル）−３−｛１，１−ビス（ｐ−ジメチルアミノフェニル）エチレン−２−イル｝−６−ジメチルアミノフタリド、
３−（ｐ−ジメチルアミノフェニル）−３−（１−ｐ−ジメチルアミノフェニル−１−フェニルエチレン−２−イル）フタリド、
３−（ｐ−ジメチルアミノフェニル）−３−（１−ｐ−ジメチルアミノフェニル−１−ｐ−クロロフェニルエチレン−２−イル）−６−ジメチルアミノフタリド、
３−（４’−ジメチルアミノ−２’−メトキシ）−３−（１''−ｐ−ジメチルアミノフェニル−１''−ｐ−クロロフェニル−１''，３''−ブタジエン−４''−イル）ベンゾフタリド、
３−（４’−ジメチルアミノ−２’−ベンジルオキシ）−３−（１''−ｐ−ジメチルアミノフェニル−１''−フェニル−１''，３''−ブタジエン−４''−イル）ベンゾフタリド、
３−ジメチルアミノ−６−ジメチルアミノ−フルオレン−９−スピロ−３’（６’−ジメチルアミノ）フタリド、
３，３−ビス｛２−（ｐ−ジメチルアミノフェニル）−２−（ｐ−メトキシフェニル）エテニル｝−４，５，６，７−テトラクロロフタリド、
３−ビス｛１，１−ビス（４−ピロリジノフェニル）エチレン−２−イル｝−５，６−ジクロロ−４，７−ジブロモフタリド、
ビス（ｐ−ジメチルアミノスチリル）−１−ナフタレンスルホニルメタン、
ビス（ｐ−ジメチルアミノスチリル）−１−ｐ−トリルスルホニルメタン等。
【００３５】
また、本発明では高分子量の顕色剤の併用と更にロイコ染料の平均粒子径が０．１０〜０．３０μｍにすることで実用レベルの高感度化を達成し、ロイコ染料の粒子径を小さくすることにより、地肌カブリが大きくなる傾向があるが、テトラキス（１，２，２，６，６−ペンタメチル−４−ピペリジル）−１，２，３，４−ブタンテトラカルボキシレート、又はテトラキス（２，２，６，６−テトラメチル−４−ピペリジル）−１，２，３，４−ブタンテトラカルボキシレート、又は前記化合物（１）、又は化合物（２）が塩基性物質であることから地肌カブリ防止に効果があること、また、ロイコ染料として３−ジブチルアミノ−６−メチル−７−アニリノフルオラン、３−ジ（ｎ−ペンチル）アミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−ｐ−トルイジノ）−６−メチル−７−アニリノフルオランを選択することにより、地肌カブリが少なく、耐熱保存性に優れ且つ耐薬品性の優れた感熱記録材料を発明するに至った。
【００３６】
本発明において使用される０．１０〜０．３０μｍのロイコ染料は、ロイコ染料に対して、界面活性剤を重量部で５〜２０％含有して得ることが可能である。界面活性剤が５％未満ではロイコ染料の分散が不充分になり、微分散物の凝集が起り、分散が進まなくなり、染料の粒径が充分に小さくならいと考えられる。また２０％を超えると分散に関与しない余剰の界面活性剤が感熱記録材料の発色性及び保存性を妨げると考えられる。
【００３７】
本発明に使用される平均粒子径が０．１０〜０．３０μｍのロイコ染料の界面活性剤は、例えば以下のものが挙げられる。
ポリオキシエチレンオクチルフェニルエーテル、ポリオキシエチレン−２−エチルヘキシルエーテル、ポリオキシエチレンラウリルエーテル、ポリオキシエチレンオレイルエーテル、ポリオキシエチレントリデシルエーテル、ポリオキシエチレンひまし油エーテル、ポリオキシエチレンセチルエーテル、ポリオキシエチレンステアリルルエーテル、ポリオキシアルキレンアルキルエーテル、ポリオキシエチレンオレエート、ポリオキシエチレンノニルフェニルエーテル、ソルビタンラウリレート、ソルビタンステアレート、ソルビタンオレエート、ソルビタントリオレエート、ポリオキシエチレンソルビタンラウレート、ポリオキシエチレンソルビタンステアレート、ポリオキシエチレンソルビタンオレエート、ポリオキシエチレンソルビタントリオレエート、ポリオキシエチレンポリスチレンフェニルエーテル、ポリエレングリコール、ポリオキシエチレンポリオキシプロピレンエーテル、ポリビニルアルコール、殿粉及びその誘導体、ヒドロキシメチルセルロース、ヒドロキシエチルセルロース、カルボキシメチルセルロース、メチルセルロース、エチルセルロース等のセルロース誘導体、ポリアクリル酸ソーダ、ポリビニルピロリドン、アクリルアミド／アクリル酸エステル共重合体、アクリルアミド／アクリル酸エステル／メタクリル酸三元共重合体、スチレン／無水マレイン酸共重合体アルカリ塩、イソブチレン／無水マレイン酸共重合体アルカリ塩、ポリアクリルアミド、アルギン酸ソーダ、ゼラチン、カゼイン等の水溶性高分子の他、ポリ酢酸ビニル、ポリウレタン、ポリアクリル酸、ポリアクリル酸エステル、塩化ビニル／酢酸ビニル共重合体、ポリブチルメタクリレート、エチレン／酢酸ビニル共重合体等のエマルジョンやスチレン／ブタジエン共重合体、スチレン／ブタジエン／アクリル系共重合体等のラテックス等であり、アニオン系界面活性剤としてはドデシルベンゼンスルホン酸塩、モノアルキルサキシネートスルホン酸塩、ジアルキルサクシネートスルホン酸塩、オクチルフェノキシエトキシスルホン酸塩、ナフタレンスルホン酸ホルマリン縮合物のナトリュウム塩、ポリオキシエチレンアリルエーテル硫酸エステルナトリウム塩、ラウリン酸カリウム塩、オレイン酸ナトリウム塩、ひまし油ナトリウム石鹸、オクチルサルフェート金属塩、ラウリルサルフェート金属塩、α−オレフィンスルホンサン塩、ラウリン酸アミドスルホネート金属塩、オレイン酸アミドスルホネート金属塩。
【００３８】
通常ポリビニルアルコール等を分散剤として用いてロイコ染料の微粒子化分散した場合、粒径を小さくするほど分散液の着色濃度は高くなる。さらに顕色剤と混合した場合さらに着色が激しくなり、感熱記録紙とした場合には地肌濃度が高くなる。このような原因としては微粒子化するために高いシェアーによりポリビニルアルコールの未鹸化部分が変化し、酢酸ができることで分散液のＰＨが低下し一部発色することや、染料粒子の一部が非結晶化し、発色し易くなるものと推定している。テトラキス（１，２，２，６，６−ペンタメチル−４−ピペリジル）−１，２，３，４−ブタンテトラカルボキシレート、又はテトラキス（２，２，６，６−テトラメチル−４−ピペリジル）−１，２，３，４−ブタンテトラカルボキシレート又は前記化合物（１）又は化合物（２）の添加は塩基性物質であることからＰＨの調整にも効果があり、地肌カブリ防止に効果がある推定している。また、分散剤としてノニオン系界面活性剤を主成分として用いて分散した場合にはＰＨの低下が少なく、染料の非結晶化を防止することができるものと推定している。
【００３９】
本発明のロイコ染料の平均粒径を０．１０〜０．３０μｍにする分散方法としてはボールミル、アトライター、サンドミル、高圧ジェットミル等を用いることができるが、メディアを用いた分散方式が好ましく、用いるメディアは直径が０．５ｍｍ以下のジルコニアメディアを用いることにより、ロイコ染料の微粒子化は達成される。また、ジルコニアメディア径が０．５ｍｍ〜１．０ｍｍのものを用いて粗粉砕し、ついで０．５ｍｍ以下の径のメディアを用いて分散することなどで達成される。
【００４０】
本発明の平均粒子径成分の測定方法は、例えばレーザー解析・散乱法によるもの（マイクロトラックＨＲＡ９３２０−Ｘ１００型、堀場製作所製ＬＡ９２０型、レーゼンテックＦＢＲＭ装置）や遠心沈降方式、コールターカウンター、電子顕微鏡等、通常用いられている測定機により測定することができる。また、染料や顕色剤と共に感度向上剤を併用させることで高感度化することが可能である。
【００４１】
感度向上剤の具体例としては、以下に示すものが挙げられる。
ステアリン酸、ベヘン酸等の脂肪酸類、ステアリン酸アミド、パルチミン酸アミド等の脂肪酸アミド類、ステアリン酸亜鉛、ステアリン酸アルミニウム、ステアリン酸カルシウム、パルチミン酸亜鉛、ベヘン酸亜鉛等の脂肪酸金属塩類、ｐ−ベンジルビフェニル、ターフェニル、トリフェニルメタン、ｐ−ベンジルオキシ安息香酸ベンジル、β−ベンジルオキシナフタレン、β−ナフトエ酸フェニル、１−ヒドロキシ−２−ナフト酸フェニル、１−ヒドロキシ−２−ナフトエ酸メチル、ジフェニルカーボネート、グレヤコールカーボネート、テレフタル酸ジベンシル、テレフタル酸ジメチル、１，４−ジメトキシナフタレン、１，４−ジエトキシナフタレン、１，４−ジベンジロキシナフタレン、１，２−ジフェノキシエタン、１，２−ビス（３−メチルフェノキシ）エタン、１，２−ビス（４−メチルフェノキシ）エタン、１，４−ジフェノキシ−２−ブテン、１，２−ビス（４−メトキシフェニルチオ）エタン、ジベンゾイルメタン、１，４−ジフェニルチオブタン、１，４−ジフェニルチオ−２−ブテン、１，３−ビス（２−ビニルオキシエトキシ）ベンゼン、１，４−ビス（２−ビニルオキシエトキシ）ベンゼン、ｐ−（２−ビニルオキシエトキシ）ビフェル、ｐ−アリールオキシプフェニル、ｐ−プロパギルオキシビフェニル、ジベンゾイルオキシメタン、ジベンゾイルオキシプロパン、ジベンジルジスルフィド、１，１−ジフェニルエタノール、１，１−ジフェニルプロパノール、ｐ−ベンジルオキシベンジルアルコール、１，３−フェノキシ−２−プロパノール、Ｎ−オクタデシルカルバモイル−ｐ−メトキシカルボニルベンゼン、Ｎ−オクタデシルカルバモイルベンゼン、１，２−ビス（４−メトキシフェノキシ）プロパン、１，５−ビス（４−メトキシフェノキシ）−３−オキサペンタン、シュウ酸ジベンジル、シュウ酸ビス（４−メチルベンジル）、シュウ酸ビス（４−クロロベンジル）、４−アセチルビフェニル等。これらの増感剤は耐熱性・耐薬品性を低下させない範囲での添加が好ましい。
【００４２】
また本発明においては、先述したように発色層の感度を上げるために、中空粒子を主成分とするアンダーコート層を設けることも可能である。中空粒子としては、例えば熱可塑性樹脂を殻として中空率３０％以上で重量平均粒子径０．５〜１０μｍのものが利用可能である。ここでいう中空率とは中空粒子の外径と内径の比であり、（中空粒子の内径／中空粒子の外径）×１００％で表わされる。アンダーコート層は乾燥時の重量が２〜１０ｇ／ｍ^２、好ましくは２．５〜７ｇ／ｍ^２の範囲で設けることができる。
【００４３】
本発明の感熱記録材料を製造するために、上記材料を支持体上に結合支持させる場合、慣用の種々の結合剤を適宜用いることができ、その具体例としては、例えば、以下のものが挙げられる。
ポリビニルアルコール、殿粉及びその誘導体、ヒドロキシメチルセルロース、ヒドロキシエチルセルロース、カルボキシメチルセルロース、メチルセルロース、エチルセルロース等のセルロース誘導体、ポリアクリル酸ソーダ、ポリビニルピロリドン、アクリルアミド／アクリル酸エステル共重合体、アクリルアミド／アクリル酸エステル／メタクリル酸三元共重合体、スチレン／無水マレイン酸共重合体アルカリ塩、イソブチレン／無水マレイン酸共重合体アルカリ塩、ポリアクリルアミド、アルギン酸ソーダ、ゼラチン、カゼイン等の水溶性高分子の他、ポリ酢酸ビニル、ポリウレタン、ポリアクリル酸、ポリアクリル酸エステル、塩化ビニル／酢酸ビニル共重合体、ポリブチルメタクリレート、エチレン／酢酸ビニル共重合体等のエマルジョンやスチレン／ブタジエン共重合体、スチレン／ブタジエン／アクリル系共重合体等のラテックス等。またフィラー材料としてケイソウ土、タルク、カオリン、焼成カオリン、炭酸カルシウム、炭酸マグネシウム、酸化チタン、酸化亜鉛、酸化けい素、水酸化アルミニウム等を用いることができ、また架橋材料も使用することができる。
【００４４】
本発明における支持体として紙、合成紙、ラミネート紙等、再生紙のいずれも用いることができる。また支持体と感熱記録層を順次塗工した上に更にオーバーコート層設けてもよい。オーバーコート層を形成する材料は、前記した感熱記録層に使用した結合剤、フィラー、架橋剤等が使用できる。
【００４５】
本発明の感熱記録材料の記録方法は、使用目的によって熱ペン、サーマルヘッド、レーザー加熱等であり、特に限定されない。
【００４６】
【実施例】
次に、本発明を実施例により更に詳細に説明する。なお、以下の部及び％はいずれも重量基準である。
（１）感熱発色層形成分散液の調整
下記組成の〔Ａ液〕をサンドグラインダーで分散し、表１に示す物性の染料分散液を得た。平均粒径は（株）堀場製作所製ＬＡ−７００を用いて測定した。
〔Ａ液〕
表１記載の染料 ２０部
ポリビニルアルコールの１０％水溶液 ２０部
水 ６０部
下記組成の〔Ｂ液〕〜〔Ｄ液〕の各液をサンドグラインダーを用いて、平均粒径が１．０μｍ程度となるように調製した。
〔Ｂ液〕
一般式（Ｉ）又は（III）又は（IV）で表わされる３価以上の多価イソシアネート化合物と一般式（II）又は（Ｖ）で表わされる芳香族アミンとの反応によって得られるオリゴマー組成物（分子量：４７００） ２０部
ポリビニルアルコールの１０％水溶液 ２０部
非晶質シリカ １０部
水 ５０部
〔Ｃ液〕
表１記載の化合物 ２０部
ポリビニルアルコールの１０％水溶液 ２０部
水 ６０部
〔Ｄ液〕
表１記載の化合物 ２０部
ポリビニルアルコールの１０％水溶液 ２０部
水 ６０部
【００４７】
（２）感熱発色塗工液の調整
表１記載の〔Ａ液〕１０部、〔Ｂ液〕３０部、表１記載の〔Ｃ液〕３部、表１記載の〔Ｄ液〕とコロイダルシリカ（固形分；２０％）１０部、スチレンブタジエンラテックス（固形分；５０％）２０部、ステアリン酸アミド分散液（固形分；２０％）１５部、ジオクチルスルホコハク酸水溶液（固形分；５％）１部からなる組成物を混合して感熱発色層塗工液を調整した。
【００４８】

上記混合物を撹拌分散して、アンダーコート層形成液を調整した。
【００４９】
実施例及び比較例
坪量６０ｇ／ｍ^２の上質紙上に表１記載のアンダーコート液を用い、乾燥塗布量が３．０ｇ／ｍ^２になるように塗工し、乾燥した後、表１記載で調整した感熱発色塗工液を用い、染料付着量が０．５ｇ／ｍ^２になるように塗布乾燥（付着量は乾燥付着量）し、その後スーパーキャレンダーにて処理し本発明の感熱記録材料を得た。
【００５０】
【表１−１】

【００５１】
【表１−２】

【００５２】
＜評価法＞
（感度倍率）
キャレンダー済品を松下電器部品（株）製薄膜ヘッドを有する感熱印字実験装置にて、ヘッド電力０．４５Ｗ／ドット１ライン記録時間２０ｍｓｅｃ／Ｌ、走査密度８×３８５ドット／ｍｍ条件下で、１ｍｓｅｃ毎にパルス巾０．０〜０．７ｍｍｓｅｃに印字し、印字濃度をマクベス濃度計ＲＤ−９１４にて測定し、濃度が１．０となるパルス巾を計算した。比較例１を基準として、（比較例１のパルス巾）／（測定したサンプルのパルス巾）＝（感度倍率）として計算する。値が大きいほど感度（熱応答性）が良好である。評価結果を表２に示す。
（画像濃度）
キャレンダー済品を上記感熱印字実験装置を用いパルス巾０．５ｍｓｅｃに印字し、印字濃度及び地肌濃度をマクベス濃度計ＲＤ−９１４にて測定した。
（耐温湿度性）
上記の条件で印字したサンプルをそれぞれ５５℃／９０％で１５分間放置した後、画像部、地肌部の濃度を測定した。
（耐熱性）
上記の条件で印字したサンプルをそれぞれ９０℃、で１５時間放置した後、画像部、地肌部の濃度を測定した。
（耐可塑剤性）
上記の条件で印字したサンプルに、信越ポリマー製塩ビラップ（ポリマラップ３００）を３枚重ねて乗せ、１０×１０ｃｍ^２あたり荷重５ｋｇをかけ、４０℃の環境下で２４時間保存後の画像部および地肌部の濃度をマクベス濃度計ＲＤ−９１４にて測定し、画像残存率として、（テスト後の濃度）／（試験前の濃度）×１００（％）で表わす。
【００５３】
【表２】

【００５４】
表２の結果より、実施例及び比較例について説明する。
実施例１〜５おいては、５種のヒンダートアミン誘導体を添加した場合の耐温湿度性試験及びの耐熱性試験後の地肌カブリが改善し、さらに感度向上と耐可塑剤性試験後の残存率を示している。
実施例６〜９においては、顕色剤との組み合わせによる感度向上と耐温湿度性試験及び耐熱性試験後の地肌カブリ及び耐可塑剤性試験後の残存率を示している。
実施例１０〜１２においては、他の染料との組み合わせにおいて、耐温湿度性試験後の地肌かぶりの改善について示している。
実施例１３〜１４おいては、実施例１２に対して染料の平均粒子径を０．１０μｍ〜０．３０μｍにすることでの感度の向上を示す。
実施例１５においては、実施例１４に対してプラスチック中空粒子を含むアンダーコート層にすることでの感度の向上を示す。
比較例１においては公知の技術として、顕色剤として高分子量の顕色剤を単独で用いた場合の比較例を示しており、耐可塑剤性試験後の画像残存率は高い水準を維持しているが、実施例１〜５に対して耐温湿度性試験及び耐熱性試験後の地肌カブリが大きく、感度が低い。
比較例２〜３においては、公知の技術として、感度向上剤、顕色剤との組み合わせを示しており、感度向上効果はあるが、耐温湿度性試験及び耐熱性試験後の地肌カブリが大きく、また、耐可塑剤性試験後の画像残存率が低くなっている。
比較例５〜６においては、公知の技術として染料の平均粒子径０．１０μｍ〜０．３０μｍとの組み合わせを示しており、感度向上効果はあるが、試験前の地肌カブリ、耐温湿度性試験及び耐熱性試験後の地肌カブリが大きく、また、耐可塑剤性試験後の画像残存率が低くなっている。
これらの比較例と本発明を比較すると感度向上と試験前の地肌カブリ、耐温湿度性試験及び耐熱性試験後の地肌カブリ及び耐可塑剤性の画像残存率を両立しており、その効果は明白である。
【００５５】
【発明の効果】
以上、詳細かつ具体的な説明より明らかなように、本発明の感熱記録材料は、５０℃／８０％以上の高温高湿環境においても地肌カブリを少なくし、高感度で、耐薬品性、特に耐可塑剤性において画像残存率に優れ、耐熱保存性に優れた感熱記録材料を提供するものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat-sensitive recording material, which reduces background fogging even in a high-temperature and high-humidity environment of 50 ° C./80% or more, has high sensitivity, excellent chemical resistance, particularly plasticizer resistance, and excellent image remaining rate, and heat-resistant storage stability. The present invention relates to a heat-sensitive recording material having excellent resistance.
[0002]
[Prior art]
In recent years, with the diversification of information and the expansion of needs, various recording materials have been researched and developed and put into practical use in the information recording field. Among these, thermosensitive recording materials are (1) simple images only by heating processes. (2) The necessary mechanism of the device is simple and compact, and the recording material is easy to handle and inexpensive. Therefore, the information processing field (desktop computer, computer) Output), medical measurement recorder field, low / high-speed facsimile field, automatic ticket machine field (passage ticket, admission ticket, etc.), thermal copying machine field, POS system label field, and so on.
[0003]
Among the fields of use of these heat-sensitive recording materials, they are rapidly being used in the POS system label field, especially in fields where importance is placed on image reliability such as lunch boxes and prepared dishes. Used for applications requiring high storage stability for plasticizers and oils and fats contained in polymer materials, and used for applications requiring storage stability for several years such as receipts and receipts, Currently, the required quality of thermal recording materials is increasing year by year. For this reason, auxiliary agents such as dyes, developers, and storage stabilizers have been developed, but no one has yet been found that can satisfactorily satisfy the color development sensitivity and storage stability of images.
[0004]
In general, a heat-sensitive recording material uses an electron-donating dye precursor (leuco dye) and an electron-accepting developer, and has excellent characteristics such as good appearance, good touch, and high color density. On the other hand, the recorded image part comes into contact with plastics such as polyvinyl chloride, is erased by plasticizers and additives contained in the plastics, or comes into contact with chemicals contained in foods and cosmetics. In addition, the recording image portion has a disadvantage that the recording material is inferior in color or the background portion is colored, and the reliability (storability) as a recording material is poor.
[0005]
Therefore, in order to improve the storage stability of the image area of the heat-sensitive recording material, development of a color developer for developing a leuco dye has been actively carried out, and various types of compounds have been proposed. As one of such proposals, a method using a compound having a urea group has recently been proposed. For example, Patent Documents 1 and 2 list diphenylurea compounds. These compounds are known to have excellent image storability compared to phenolic developers, but there is a tendency for the density of the color image area to decrease due to contact with plasticizers and oils. It is hard to say that it has image reliability. Furthermore, these systems have the disadvantage that the color image density is low and have not reached a practical level.
[0006]
Patent Documents 3 and 4 list urea urethane compounds as compounds having a urea group and a urethane group. Similar to the above compounds, this compound also has performance superior in image storability compared to phenol-based developers, but is insufficient in image storability against contact with plasticizers and oils. It is difficult to say that the color density is extremely low and practical.
[0007]
On the other hand, a compound containing a urea group and another color developing group in the molecule has also been proposed. Patent Document 5 discloses a compound having two urea groups and salicylic acid residues in the molecule. A compound having two urea groups and benzoic acid residues in the molecule is disclosed in Patent Document 7, and a compound having two urea groups and hydroxyphenyl residues in the molecule is mentioned. These compounds tend to improve the color density when a color developing group other than a urea group is introduced into the molecule, but the reliability of the color image portion is insufficient, and the plasticizer and oil It is difficult to say that it is practical because the image density decreases due to contact. Further, the salicylic acid residue has a strong acidity, and the compound contained in the molecule has a disadvantage that it is dissolved in water and reacts with the dye in an environment of 50 ° C./80% or more to cause background fogging.
[0008]
Patent Document 8 discloses a polyurea compound derived from a diisocyanate compound and a diamine compound. Since these compounds are polymers having a large molecular weight, they have low color development characteristics and are not practical.
[0009]
Furthermore, as a similar compound of a compound having a urea group, Patent Document 9 discloses -SO. ₂ A compound having a —NHCONH— group is disclosed in Patent Document 10 as —SO ₂ Examples include compounds having a —NHCONHCO—NH— group. These compounds have also been improved in color density, but all of them are not practical because the storage stability of the image area is insufficient or the fogging of the background area is large.
[0010]
On the other hand, various types of polymer (oligomer) type developers have been proposed based on the idea of increasing the molecular weight. Typical examples thereof include the condensation reaction products of 4-hydroxybenzoic acid and polyhydric alcohols described in Patent Documents 11 and 12. However, these oligomer developers are not practical because the storage characteristics of the image area and the storage characteristics of the background area are not sufficient, and the color development characteristics (color density and color sensitivity) are low.
[0011]
Among these, a developer having a high molecular weight has been developed as a color developer exhibiting high storage stability particularly for plasticizers and oils and fats. For example, Patent Document 13 describes a polymeric developer of a diphenylsulfonic acid derivative. In addition, Patent Document 11 described above describes (poly) 4-hydroxybenzoic acid derivatives. For example, a high-molecular-weight developer of a diphenylsulfonic acid derivative has been disclosed that uses a low-melting-point developer or sensitizer in order to supplement color development sensitivity (see Patent Documents 14 and 15, etc.). However, these improve the apparent color sensitivity by using a low-melting color developer or sensitizer to look up the image color density in the low energy region. On the other hand, a decrease in image density, that is, a decrease in image remaining rate is noticeable. This is because the apparent color density of the image is due to the low color melting point developer and sensitizer, and the color is easily erased from plasticizers and oils. In short, the chemical resistance inherently possessed by the high molecular weight developer means that the chemical resistance, which is the greatest feature, is lost by the means for increasing the color development sensitivity. That is, in a high molecular weight developer, there is a problem of improving both the color development sensitivity and the image remaining rate in chemical resistance.
[0012]
In addition, as described above, by using a low melting point developer or sensitizer, a material that is eutectic with the leuco dye or developer and causing a melting point drop is added, but when the melting point is lowered Although the sensitivity is improved, the coloring temperature is lowered, so that the background fog is generated at a low temperature as the sensitivity is improved.
As a method not using such a low melting point developer or sensitizer, there have been various proposals for increasing the sensitivity of a heat-sensitive recording material by finely forming a leuco dye. For example, a leuco dye having a volume average particle size of 2 μm or less is used (see, for example, Patent Document 16), and two or more kinds of leuco dyes are simultaneously pulverized to have an average particle size of 2 μm or less. (For example, see Patent Document 17), a thermal recording material (for example, see Patent Document 18) containing a leuco dye having an average particle size of 0.1 μm to 0.8 μm, a colorant and colloidal silica, and the like have been proposed. ing.
[0013]
These fine particles of leuco dye use a water-soluble polymer such as cellulose or polyvinyl alcohol as a dispersing agent, and disperse in water to a predetermined particle size by a dispersing machine such as a ball mill, a sand mill, a high-speed jet mill, or an attritor. In this method, the proportion of the fine particle component increases as the average particle diameter is reduced, and the heat-resistant storage stability of the heat-sensitive recording material decreases particularly when the average particle diameter is 0.3 μm or less. Further, when microparticulation is performed using polyvinyl alcohol as a dispersant, the dispersion liquid is colored (liquid fogging), so that the background density of the heat-sensitive recording material is increased. In addition, a method of making leuco dye into fine particles by an emulsification method has been proposed.
[0014]
For example, Patent Document 19 describes a method of emulsifying a solution in which a leuco dye is dissolved in an organic solvent in water. However, a step for removing the organic solvent after emulsification is necessary, and background fogging occurs due to the residual organic solvent. There are disadvantages such as. Patent Document 20 proposes a method of emulsifying a leuco dye together with a heat-fusible substance. However, the melting point is lowered by the heat-fusible substance, and the heat-resistant storage stability is lowered. Patent Document 21 proposes a heat-sensitive recording material having a volume average particle size of leuco dye of 0.3 μm or less and containing an ultraviolet absorber. Here, the leuco dye fine particle formation is described as a system in which the dye is heated and melted and emulsified with a high-pressure homogenizer using a silicon-based emulsifier. Patent Document 22 proposes a leuco dye that is emulsified and dispersed with an average particle size of 1.0 μm or less. The method of emulsifying and dispersing in this proposal describes a method in which a leuco dye heated and melted is emulsified and dispersed by high-pressure spraying from a high-speed stirrer or nozzle using an emulsifier. The melting point of the leuco dye is usually 150 ° C. or higher, and a special apparatus such as a high-pressure vessel is required to heat-melt and emulsify the leuco dye in water as in the methods described in Patent Documents 21 and 22. Mass production is difficult.
[0015]
[Patent Document 1]
JP-A-8-2110
[Patent Document 2]
JP-A-8-2111
[Patent Document 3]
JP 2000-143611 A
[Patent Document 4]
WO00 / 14058
[Patent Document 5]
JP-A-8-244355
[Patent Document 6]
JP-A-8-197851
[Patent Document 7]
JP-A-8-2109
[Patent Document 8]
JP-A-11-115314
[Patent Document 9]
Japanese Patent Laid-Open No. 5-169836
[Patent Document 10]
JP 11-263769 A
[Patent Document 11]
WO99 / 51444
[Patent Document 12]
JP 2001-30626 A
[Patent Document 13]
JP-A-8-333329
[Patent Document 14]
Japanese Patent Laid-Open No. 10-297089
[Patent Document 15]
Japanese Patent Laid-Open No. 10-297090
[Patent Document 16]
JP 57-47693 A
[Patent Document 17]
Japanese Patent Laid-Open No. 7-223375
[Patent Document 18]
JP-A-7-186527
[Patent Document 19]
Japanese Patent Application Laid-Open No. 61-217283
[Patent Document 20]
JP-A-56-164890
[Patent Document 21]
Japanese Patent Laid-Open No. 7-186531
[Patent Document 22]
JP-A-7-223379
[0016]
[Problems to be solved by the invention]
The object of the present invention is to reduce background fogging, high sensitivity, chemical resistance, particularly plastic resistance, even when using a developer having a salicylic acid residue or in a high temperature and high humidity environment of 50 ° C./80% or higher. It is an object to provide a heat-sensitive recording material having excellent image residual ratio and excellent heat-resistant storage stability.
[0017]
[Means for Solving the Problems]
The above-mentioned problem is as follows: (1) In the heat-sensitive recording material having a heat-sensitive color-developing layer mainly composed of a leuco dye and a color-developer that develops the leuco dye on heating on the support. The compound used is obtained by reacting a trivalent or higher polyvalent isocyanate compound represented by the following general formula (I) with an aromatic amine represented by the following general formula (II). With a molecular weight of 2000-10000 Oligomer composition and Bis (2,2,6,6-tetramethyl-4-piperidyl sebacate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate Rate or tetrakis (2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or at least one of the following compound (1) or compound (2) A heat-sensitive recording material comprising a hindered amine derivative;
[Chemical 8]

[0018]
[Chemical 9]

(Wherein X is a trivalent or higher group, a is an integer of 3 or more, b and c are integers of 0 to 5, provided that b + c = 1 to 5 is satisfied, and Z is a hydrogen atom or an alkyl group. An aryl group or an aryl group, and in the case of an aryl group, a condensed ring structure may be formed, and d is an integer of 0 to 4 satisfying the relationship of b + c + d = 5.)
[Chemical Formula 10]

Embedded image

(2) “The thermal recording material according to item (1), wherein X in the general formula (I) is a trivalent structure represented by the following formula (III) or (IV):
[0019]
Embedded image

[0020]
Embedded image

(Wherein Y represents a divalent group) ”, (3)“ The compound represented by the general formula (II) is an aminosalicylic acid derivative represented by the following formula (V) ”: The heat-sensitive recording material according to item (1) or (2);
[0021]
Embedded image

[0023]
(4) “The thermosensitive coloring layer contains at least one of 2,4′-bishydroxydiphenylsulfone or 4-hydroxy-4′-allyloxydiphenylsulfone,” (1) to (1), (3) The heat-sensitive recording material according to any one of the items ", (5) The weight ratio of the oligomer composition to 2,4′-bishydroxydiphenylsulfone or 4-allyloxy-4′-hydroxydiphenylsulfone is between 2: 8 and 5: 5. Item (1) to No. (4) The heat-sensitive recording material according to any one of the items ", (6) “3-Dibutylamino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N Any one of (p-toluidino) -6-methyl-7-anilinofluorane is used. (5) The heat-sensitive recording material according to any one of the items ", (7) “The leuco dye dispersion liquid having an average particle diameter of the leuco dye of 0.10 μm to 0.30 μm is used. (6) The heat-sensitive recording material according to any one of the items ", (8) “An undercoat layer containing at least hollow particles is provided on a support, and the heat-sensitive material according to any one of (1) to (7)”. Coloring Item (1) to Item 2, characterized by comprising layers (7) The heat-sensitive recording material according to any one of the items ", (9) “The hollow particles contained in the undercoat layer have a thermoplastic resin as a shell, and have a hollow ratio of 30% or more and a weight average particle diameter of 0.4 to 10 μm. Thru (8) The thermal recording material according to any one of the items is solved.
[0024]
In the present invention, a trivalent or higher polyvalent isocyanate compound represented by the general formula (I) or (III) or (IV), which is a high molecular weight developer, and an aroma represented by the general formula (II) or (V) Since the oligomer composition obtained by the reaction with a group amine has many salicylic acid residues in the molecule, it causes background fogging in a high temperature and high humidity environment of 50 ° C./80% or more. By including a basic hindered amine derivative, the solubility of the oligomer composition is lowered by making the pH neutral, and the generation of background fogging can be suppressed. The oligomer of the present invention means one having a molecular weight of 2000 to 10,000.
[0025]
Usually, when a basic compound is added, color development is inhibited, resulting in a decrease in sensitivity and chemical resistance. However, hindered amine derivatives have little decrease in sensitivity and chemical resistance. This is considered due to the fact that the basicity of the hindered amine derivative is moderate. Therefore, the combination of the hindered amine derivative and the oligomer composition can provide a heat sensitive recording material with high sensitivity and excellent heat resistance storage stability and chemical resistance.
[0026]
The activity at the time of heat melting of a color forming complex formed of a dye and a developer by using a high molecular compound (1) (molecular weight 2000) or a compound (2) (molecular weight 1900) as a hindered amine derivative It is considered that the coloring property and chemical resistance are improved by lowering the chemical energy and further increasing the amorphous property after heat melting.
Further, polymeric tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis (2 , 2,6,6-Tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate is a high polymer with a molecular weight of 850 and a melting point of 140 ° C. And heat resistance can be achieved.
[0027]
Further, a trivalent or higher polyvalent isocyanate compound represented by the general formula (I) or (III) or (IV) used in the present invention and an aromatic amine represented by the general formula (II) or (V) The oligomer composition obtained by the reaction is preferably 2 to 6 parts by weight with respect to 1 part by weight of the leuco dye. When the amount is less than 2 parts by weight, the color developability is insufficient, and when the amount exceeds 6 parts by weight, there are many components that do not participate in the color development, thereby preventing the color development and reducing the sensitivity. In addition, it is industrially undesirable to add excessive components that do not participate in color development.
[0028]
Tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis which are hindered amine derivatives (2 , 2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or compound (1) or compound (2) is added in a basic substance. The addition of 0.1 to 0.5 parts by weight is preferred since the decoloring effect occurs when the amount is 1 part by weight or more relative to 1 part by weight of the leuco dye, and the color density decreases.
[0029]
Examples of the developer that can be added in the present invention include the following. As such a developer, those applied to this kind of heat-sensitive material are arbitrarily applied. In order to achieve both chemical resistance, high sensitivity and heat resistance, 2,4′-bis is used. Hydroxydiphenyl sulfone, 4-allyloxy-4′-hydroxydiphenyl sulfone is most useful.
[0030]
Other specific examples include the following, for example.
4,4′-isopropylidenebisphenol, 4,4′-isopropylidenebis (o-methylphenol), 4,4′-sec-butylidenebisphenol, 4,4′-isopropylidenebis (2-ter-butylphenol) 4,4′-methylenebis (oxyethylenethio) diphenol, zinc p-nitrobenzoate, 1,3,5-tris (4-ter-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanuric acid, 2,2- (3,4-dihydroxyphenylpropane), bis (4-hydroxy-3-methylphenylsulfide), 4- (β- (p-methoxyphenoxy) ethoxy) salicylic acid, 1,7-bis (4- Hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (hydroxyphenylthio) -5-oxahepta Phthalic acid monobenzyl ester monocalcium salt, 4,4′-cyclohexylidenebisphenol, 4,4′-isopropylidenebis (2-chlorophenol), 2,2′-methylenebis (4-methyl-6-ter -Butylphenol), 4,4'-butylidenebis (6-ter-butyl-2-methyl) phenol, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, 4,4′-thiobis (6-ter-butyl-2-methyl) phenol, 4,4′-phenolsulfone, 4-isopropyl Oxy-4′-hydroxydiphenyl sulfone, 4-benzyloxy-4′-hydroxydiphenyl sulfone, 4,4′-di Enol sulfoxide, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, benzyl protocatechuate, stearyl gallate, lauryl gallate, octyl gallate, 1,3-bis (4-hydroxyphenylthio) -propane, N, N-diphenylthiourea, N, N-di (m-chlorophenyl) thiourea, salicylanilide, bis (4-hydroxyphenyl) acetic acid methyl ester, bis (4-hydroxyphenyl) acetic acid benzyl ester, 1,3-bis ( 4-hydroxycumyl) benzene, 1,4-bis (4-hydroxycumyl) benzene, 2,2′-diallyl-4,4′-diphenolsulfone, 3,4-dihydroxyphenyl-4′-methyldiphenyl Sulfone, 1-acetyloxy-2-naphthoic acid zinc, 2-a Zyloxy-1-naphthoate zinc, 2-acetyloxy-3-naphthoate zinc, α, α-bis (4-hydroxyphenyl) -α-methyltoluene, zinc thiocyanate antipyrine complex, tetrabromobisphenol A, tetrabromo Bisphenol S, 4,4′-thiobis (2-methylphenol), 4,4′-thiobis (2-chlorophenol), compounds having a sulfonylaminocarbonylamide group, and the like.
[0031]
These developers are preferably added within a range that does not lower the chemical resistance. The oligomer composition in the thermosensitive coloring layer and 2,4′-bishydroxydiphenylsulfone or 4-allyloxy-4′-hydroxy The thermosensitive recording material is characterized in that the weight ratio to diphenylsulfone is between 2: 8 and 5: 5.
[0032]
The leuco dyes used in the heat-sensitive color forming layer of the present invention are applied singly or in combination of two or more. As such leuco dyes, those applied to this kind of heat-sensitive material are arbitrarily applied. However, in order to achieve both chemical resistance, high sensitivity and heat resistance, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl- 7-anilinofluorane, 3- (N-ethyl-Np-toluidino) -6-methyl-7-anilinofluorane is most useful.
[0033]
Other specific examples include the following, for example.
A leuco compound of a dye such as triphenylmethane, fluoran, phenothiazine, auramine, spiropyran, or indinophthalide is preferably used. Specific examples of such leuco dyes include those shown below.
[0034]
3,3-bis (p-dimethylaminophenyl) -phthalide,
3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone),
3,3-bis (p-dimethylaminophenyl) -6-diethylaminophthalide,
3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide,
3,3-bis (p-dibutylaminophenyl) phthalide,
3-cyclohexylamino-6-chlorofluorane,
3-dimethylamino-5,7-dimethylfluorane,
3-N-methyl-N-isobutyl-6-methyl-7-anilinofluorane,
3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluorane,
3-diethylamino-7-chlorofluorane,
3-diethylamino-7-methylfluorane,
3-diethylamino-7,8-benzfluorane,
3-diethylamino-6-methyl-7-chlorofluorane,
3- (Np-tolyl-N-ethylamino) -6-methyl-7-anilinofluorane,
3-pyrrolidino-6-methyl-7-anilinofluorane,
2- {N- (3′-trifluoromethylphenyl) amino} -6-diethylaminofluorane,
2- {3,6-bis (diethylamino) -9- (o-chloroanilino) xanthyl benzoate lactam},
3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane,
3-diethylamino-7- (o-chloroanilino) fluorane,
3-dibutylamino-7- (o-chloroanilino) fluorane,
3-N-methyl-N-amylamino-6-methyl-7-anilinofluorane,
3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane,
3-diethylamino-6-methyl-7-anilinofluorane,
3-diethylamino-6-methyl-7- (2 ′, 4′-dimethylanilino) fluorane,
3- (N, N-diethylamino) -5-methyl-7- (N, N-dibenzylamino) fluorane,
Benzoyl leucomethylene blue,
6'-chloro-8'-methoxy-benzoindolino-spiropyran,
6′-bromo-3′-methoxy-benzoindolino-spiropyran,
3- (2′-hydroxy-4′-dimethylaminophenyl) -3- (2′-methoxy-5′-chlorophenyl) phthalide,
3- (2′-hydroxy-4′-dimethylaminophenyl) -3- (2′-methoxy-5′-nitrophenyl) phthalide,
3- (2′-hydroxy-4′-diethylaminophenyl) -3- (2′-methoxy-5′-methylphenyl) phthalide,
3- (2′-methoxy-4′-dimethylaminophenyl) -3- (2′-hydroxy-4′-chloro-5′-methylphenyl) phthalide,
3-morpholino-7- (N-propyl-trifluoromethylanilino) fluorane,
3-pyrrolidino-7-trifluoromethylanilinofluorane,
3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluorane,
3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane,
3-diethylamino-5-chloro-7- (α-phenylethylamino) fluorane,
3-diethylamino-7- (o-methoxycarbonylphenylamino) fluorane,
3-diethylamino-5-methyl-7- (α-phenylethylamino) fluorane,
3-diethylamino-7-piperidinofluorane,
2-chloro-3- (N-methyltoluidino) -7- (pn-butylanilino) fluorane,
3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluorane,
3-diethylamino-6-methyl-7- (3-methylanilino) fluorane,
3,6-bis (dimethylamino) fluorene spiro (9,3 ′)-6′-dimethylaminophthalide,
3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4′-bromofluorane,
3-diethylamino-6-chloro-7-anilinofluorane,
3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl-7-anilinofluorane,
3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluorane,
3-diethylamino-6-methyl-7-mesitidino-4 ′, 5′-benzofluorane,
3- (p-dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) ethylene-2-yl} phthalide,
3- (p-dimethylaminophenyl) -3- {1,1-bis (p-dimethylaminophenyl) ethylene-2-yl} -6-dimethylaminophthalide,
3- (p-dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-1-phenylethylene-2-yl) phthalide,
3- (p-dimethylaminophenyl) -3- (1-p-dimethylaminophenyl-1-p-chlorophenylethylene-2-yl) -6-dimethylaminophthalide,
3- (4′-dimethylamino-2′-methoxy) -3- (1 ″ -p-dimethylaminophenyl-1 ″ -p-chlorophenyl-1 ″, 3 ″ -butadiene-4 ″- Yl) benzophthalide,
3- (4′-Dimethylamino-2′-benzyloxy) -3- (1 ″ -p-dimethylaminophenyl-1 ″ -phenyl-1 ″, 3 ″ -butadiene-4 ″ -yl ) Benzophthalide,
3-dimethylamino-6-dimethylamino-fluorene-9-spiro-3 ′ (6′-dimethylamino) phthalide,
3,3-bis {2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl} -4,5,6,7-tetrachlorophthalide,
3-bis {1,1-bis (4-pyrrolidinophenyl) ethylene-2-yl} -5,6-dichloro-4,7-dibromophthalide,
Bis (p-dimethylaminostyryl) -1-naphthalenesulfonylmethane,
Bis (p-dimethylaminostyryl) -1-p-tolylsulfonylmethane and the like.
[0035]
Further, in the present invention, a combination of a high molecular weight developer and an average particle diameter of the leuco dye of 0.10 to 0.30 μm achieves a practical level of sensitivity, and the particle diameter of the leuco dye is reduced. The background fog tends to increase, but tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis (2 , 2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, or the compound (1) or compound (2) is a basic substance, so It is effective for prevention, and as leuco dyes, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3 By selecting-(N-ethyl-Np-toluidino) -6-methyl-7-anilinofluorane, a thermosensitive recording material with less background fogging, excellent heat resistance storage stability and chemical resistance is obtained. It came to invent.
[0036]
The 0.10 to 0.30 μm leuco dye used in the present invention can be obtained by containing 5 to 20% by weight of a surfactant relative to the leuco dye. If the surfactant is less than 5%, the dispersion of the leuco dye becomes insufficient, aggregation of the fine dispersion occurs, the dispersion does not progress, and the particle size of the dye is considered to be sufficiently small. On the other hand, if it exceeds 20%, it is considered that an excessive surfactant that does not participate in dispersion hinders the color development and storage stability of the heat-sensitive recording material.
[0037]
Examples of the leuco dye surfactant having an average particle size of 0.10 to 0.30 μm used in the present invention include the following.
Polyoxyethylene octylphenyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene tridecyl ether, polyoxyethylene castor oil ether, polyoxyethylene cetyl ether, polyoxyethylene Stearyll ether, polyoxyalkylene alkyl ether, polyoxyethylene oleate, polyoxyethylene nonylphenyl ether, sorbitan laurate, sorbitan stearate, sorbitan oleate, sorbitan trioleate, polyoxyethylene sorbitan laurate, polyoxyethylene sorbitan stearate Rate, polyoxyethylene sorbitan oleate, polyoxyethylene sorbita Trioleate, polyoxyethylene polystyrene phenyl ether, polyylene glycol, polyoxyethylene polyoxypropylene ether, polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, polyacrylic acid Soda, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, In addition to water-soluble polymers such as polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane Polyacrylic acid, polyacrylic ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer emulsion, styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, etc. As anionic surfactants, sodium dodecyl benzene sulfonate, monoalkyl succinate sulfonate, dialkyl succinate sulfonate, octyl phenoxy ethoxy sulfonate, naphthalene sulfonate formalin condensate Salt, polyoxyethylene allyl ether sulfate sodium salt, potassium laurate, sodium oleate, castor oil sodium soap, octyl sulfate metal salt, lauryl sulfate metal salt, α-olefin sulfate Nsan salts, lauric acid amide sulfonate metal salts, amides sulfonate metal salt of oleic acid.
[0038]
In general, when polyvinyl alcohol or the like is used as a dispersant and the leuco dye is finely dispersed, the color density of the dispersion increases as the particle diameter decreases. Further, when mixed with a developer, coloring becomes more intense, and when a thermal recording paper is used, the background density increases. This is because the unsaponified portion of polyvinyl alcohol changes due to high shear due to fine particles, and acetic acid is generated, resulting in a decrease in pH of the dispersion and partial color development, and some of the dye particles are amorphous. It is presumed that it will be easily colored. Tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate, or tetrakis (2 , 2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or the addition of compound (1) or compound (2) is a basic substance, Adjustment is also effective, and it is estimated that it is effective in preventing background fogging. Further, it is presumed that when a nonionic surfactant is used as a main component as a dispersant and dispersed, the pH is hardly lowered and the non-crystallization of the dye can be prevented.
[0039]
A ball mill, an attritor, a sand mill, a high-pressure jet mill or the like can be used as a dispersion method for setting the average particle size of the leuco dye of the present invention to 0.10 to 0.30 μm, but a dispersion method using media is preferable. By using a zirconia medium having a diameter of 0.5 mm or less as a medium to be used, fine formation of the leuco dye can be achieved. Further, it can be achieved by coarsely pulverizing using a zirconia medium having a diameter of 0.5 mm to 1.0 mm and then dispersing using a medium having a diameter of 0.5 mm or less.
[0040]
The measurement method of the average particle size component of the present invention is, for example, by a laser analysis / scattering method (Microtrac HRA9320-X100 type, Horiba LA920 type, Lazentec FBRM apparatus), centrifugal sedimentation method, Coulter counter, electron microscope, etc. It can be measured by a commonly used measuring machine. Moreover, it is possible to increase the sensitivity by using a sensitivity improver together with a dye or a developer.
[0041]
Specific examples of the sensitivity improver include the following.
Fatty acids such as stearic acid and behenic acid, fatty acid amides such as stearic acid amide and palmitic acid amide, zinc stearate, aluminum stearate, calcium stearate, zinc palmitate, zinc behenate and fatty acid metal salts such as p-benzyl Biphenyl, terphenyl, triphenylmethane, benzyl p-benzyloxybenzoate, β-benzyloxynaphthalene, phenyl β-naphthoate, phenyl 1-hydroxy-2-naphthoate, methyl 1-hydroxy-2-naphthoate, diphenyl Carbonate, gray alcohol carbonate, dibencil terephthalate, dimethyl terephthalate, 1,4-dimethoxynaphthalene, 1,4-diethoxynaphthalene, 1,4-dibenzyloxynaphthalene, 1,2-diphenoxyethane, 1,2 -Screw ( 3-methylphenoxy) ethane, 1,2-bis (4-methylphenoxy) ethane, 1,4-diphenoxy-2-butene, 1,2-bis (4-methoxyphenylthio) ethane, dibenzoylmethane, 1, 4-diphenylthiobutane, 1,4-diphenylthio-2-butene, 1,3-bis (2-vinyloxyethoxy) benzene, 1,4-bis (2-vinyloxyethoxy) benzene, p- (2- Vinyloxyethoxy) bifer, p-aryloxypphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane, dibenzyldisulfide, 1,1-diphenylethanol, 1,1-diphenylpropanol, p- Benzyloxybenzyl alcohol, 1,3-phenoxy-2-propanol, N- Kutadecylcarbamoyl-p-methoxycarbonylbenzene, N-octadecylcarbamoylbenzene, 1,2-bis (4-methoxyphenoxy) propane, 1,5-bis (4-methoxyphenoxy) -3-oxapentane, dibenzyl oxalate, Bis (4-methylbenzyl) oxalate, bis (4-chlorobenzyl) oxalate, 4-acetylbiphenyl and the like. These sensitizers are preferably added within a range that does not lower the heat resistance and chemical resistance.
[0042]
In the present invention, as described above, an undercoat layer mainly composed of hollow particles can be provided in order to increase the sensitivity of the color developing layer. As the hollow particles, for example, those having a hollow ratio of 30% or more and a weight average particle diameter of 0.5 to 10 μm using a thermoplastic resin as a shell can be used. The hollow ratio here is the ratio of the outer diameter to the inner diameter of the hollow particles, and is represented by (the inner diameter of the hollow particles / the outer diameter of the hollow particles) × 100%. The undercoat layer has a dry weight of 2 to 10 g / m. ² , Preferably 2.5-7 g / m ² It can be provided in the range.
[0043]
In order to produce the heat-sensitive recording material of the present invention, when the above material is bonded and supported on a support, various conventional binders can be used as appropriate. Specific examples thereof include the following. It is done.
Polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, polyacrylic acid soda, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid Acid terpolymers, styrene / maleic anhydride copolymer alkali salts, isobutylene / maleic anhydride copolymer alkali salts, polyacrylamide, sodium alginate, gelatin, casein and other water-soluble polymers, as well as polyvinyl acetate Such as polyurethane, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer John and styrene / butadiene copolymer, styrene / butadiene / latex such as acrylic copolymer. As the filler material, diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide and the like can be used, and a crosslinking material can also be used.
[0044]
Any of recycled paper such as paper, synthetic paper, and laminated paper can be used as the support in the present invention. Further, an overcoat layer may be further provided on the support and the heat-sensitive recording layer sequentially applied. As the material for forming the overcoat layer, the binder, filler, cross-linking agent and the like used in the above-mentioned heat-sensitive recording layer can be used.
[0045]
The recording method of the heat-sensitive recording material of the present invention is not particularly limited, and is a thermal pen, a thermal head, laser heating or the like depending on the purpose of use.
[0046]
【Example】
Next, the present invention will be described in more detail with reference to examples. The following parts and percentages are based on weight.
(1) Preparation of thermosensitive coloring layer forming dispersion
[Liquid A] having the following composition was dispersed with a sand grinder to obtain a dye dispersion having physical properties shown in Table 1. The average particle diameter was measured using LA-700 manufactured by Horiba, Ltd.
[Liquid A]
Dye listed in Table 1 20 parts
20 parts of a 10% aqueous solution of polyvinyl alcohol
60 parts of water
Each liquid of [B liquid]-[D liquid] of the following composition was prepared using a sand grinder so that an average particle diameter might be set to about 1.0 micrometer.
[Liquid B]
Oligomer composition obtained by reaction of trivalent or higher polyvalent isocyanate compound represented by general formula (I) or (III) or (IV) with aromatic amine represented by general formula (II) or (V) ( (Molecular weight: 4700) 20 parts
20 parts of a 10% aqueous solution of polyvinyl alcohol
10 parts of amorphous silica
50 parts of water
[C liquid]
20 parts of the compounds listed in Table 1
20 parts of a 10% aqueous solution of polyvinyl alcohol
60 parts of water
[Liquid D]
20 parts of the compounds listed in Table 1
20 parts of a 10% aqueous solution of polyvinyl alcohol
60 parts of water
[0047]
(2) Adjustment of thermosensitive coloring coating solution
[Part A] 10 parts, [Part B] 30 parts, Table 1 [C liquid] 3 parts, Table 1 [D liquid] and colloidal silica (solid content: 20%) 10 parts, A composition comprising 20 parts of styrene butadiene latex (solid content: 50%), 15 parts of stearamide dispersion (solid content: 20%), and 1 part of dioctylsulfosuccinic acid aqueous solution (solid content: 5%) was mixed to produce heat. A coloring layer coating solution was prepared.
[0048]

The mixture was stirred and dispersed to prepare an undercoat layer forming liquid.
[0049]
Examples and Comparative Examples
Basis weight 60g / m ² Using the undercoat solution shown in Table 1 on high-quality paper, the dry coating amount is 3.0 g / m. ² After coating and drying, using the thermosensitive coloring coating solution prepared in Table 1, the dye adhesion amount is 0.5 g / m. ² Then, it was coated and dried (the amount of adhesion was the amount of adhesion), and then processed with a super calender to obtain the heat-sensitive recording material of the present invention.
[0050]
[Table 1-1]

[0051]
[Table 1-2]

[0052]
<Evaluation method>
(Sensitivity magnification)
In the thermal printing experimental apparatus having a thin film head manufactured by Matsushita Electric Parts Co., Ltd., the calendered product was subjected to a head power of 0.45 W / dot 1 line recording time of 20 msec / L and a scanning density of 8 × 385 dots / mm. Printing was performed at a pulse width of 0.0 to 0.7 mmsec every 1 msec, the printing density was measured with a Macbeth densitometer RD-914, and the pulse width at which the density was 1.0 was calculated. Using Comparative Example 1 as a reference, calculation is made as (pulse width of Comparative Example 1) / (pulse width of measured sample) = (sensitivity magnification). The larger the value, the better the sensitivity (thermal response). The evaluation results are shown in Table 2.
(Image density)
The calendered product was printed with a pulse width of 0.5 msec using the above thermal printing experimental apparatus, and the print density and background density were measured with a Macbeth densitometer RD-914.
(Temperature and humidity resistance)
Samples printed under the above conditions were allowed to stand at 55 ° C./90% for 15 minutes, and then the density of the image area and background area was measured.
(Heat-resistant)
The samples printed under the above conditions were each left at 90 ° C. for 15 hours, and then the density of the image area and the background area was measured.
(Plasticizer resistance)
Place 3 sheets of vinyl chloride wrap (Polymer Wrap 300) made of Shin-Etsu Polymer on the sample printed under the above conditions. ² The density of the image area and the background area after being stored for 24 hours in a 40 ° C. environment was measured with a Macbeth densitometer RD-914, and the residual ratio of the image was ((density after test) / (test (Previous concentration) × 100 (%).
[0053]
[Table 2]

[0054]
From the results in Table 2, examples and comparative examples will be described.
In Examples 1 to 5, the background fogging after the temperature and humidity resistance test and the heat resistance test when 5 types of hindered amine derivatives were added was improved, and further after the sensitivity improvement and the plasticizer resistance test The remaining rate is shown.
In Examples 6 to 9, the sensitivity improvement by combination with the developer, the background fog after the temperature and humidity resistance test and the heat resistance test, and the residual ratio after the plasticizer resistance test are shown.
In Examples 10-12, it shows about improvement of the background fog after a temperature-and-humidity resistance test in combination with other dyes.
In Examples 13 to 14, the sensitivity is improved by setting the average particle size of the dye to 0.10 μm to 0.30 μm compared to Example 12.
In Example 15, an improvement in sensitivity is shown by using an undercoat layer containing hollow plastic particles as compared with Example 14.
In Comparative Example 1, as a known technique, a comparative example in which a high molecular weight developer is used alone as a developer is shown, and the image remaining rate after the plasticizer resistance test is maintained at a high level. However, the background fogging after the temperature and humidity resistance test and the heat resistance test is large with respect to Examples 1 to 5, and the sensitivity is low.
In Comparative Examples 2-3, as a known technique, a combination with a sensitivity improver and a developer is shown, and although there is a sensitivity improvement effect, the background fogging after the temperature and humidity resistance test and the heat resistance test is large. In addition, the image remaining rate after the plasticizer resistance test is low.
In Comparative Examples 5-6, the combination of the average particle diameter of the dye with 0.10 μm to 0.30 μm is shown as a known technique, and although there is an effect of improving the sensitivity, the background fogging before the test, the temperature and humidity resistance test In addition, the background fogging after the heat resistance test is large, and the image remaining rate after the plasticizer resistance test is low.
When these comparative examples and the present invention are compared, the sensitivity improvement and the background fogging before the test, the background fogging after the temperature and humidity resistance test and the heat resistance test, and the image residual ratio of the plasticizer resistance are compatible, and the effect is It is obvious.
[0055]
【The invention's effect】
As described above, as is clear from the detailed and specific description, the heat-sensitive recording material of the present invention reduces background fogging even in a high-temperature and high-humidity environment of 50 ° C./80% or more, and has high sensitivity and chemical resistance. The present invention provides a heat-sensitive recording material that is excellent in plasticizer resistance and excellent in image residual ratio and excellent in heat-resistant storage stability.

Claims (9)

In a thermosensitive recording material having a thermosensitive color-developing layer mainly composed of a leuco dye and a color developer that develops the leuco dye when heated, a compound used as the color developer is represented by the following general formula (I). An oligomer composition having a molecular weight of 2000 to 10000 obtained by reaction of a trivalent or higher polyvalent isocyanate compound with an aromatic amine represented by the following general formula (II), and bis (2,2,6,6-tetramethyl) -4-piperidyl sebacate, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis (2,2,6,6-tetra hindered consisting of at least one-4-piperidyl) -1,2,3,4-butane tetracarboxylate or the following compound (1) or compound (2) Heat-sensitive recording material characterized by containing Toamin derivatives.

(Wherein X is a trivalent or higher group, a is an integer of 3 or more, b and c are integers of 0 to 5, provided that b + c = 1 to 5 is satisfied, and Z is a hydrogen atom or an alkyl group. An aryl group or an aryl group, and in the case of an aryl group, a condensed ring structure may be formed, and d is an integer of 0 to 4 satisfying the relationship of b + c + d = 5.)

2. The heat-sensitive recording material according to claim 1, wherein X in the general formula (I) has a trivalent structure represented by the following formula (III) or (IV).

(In the formula, Y represents a divalent group.) The heat-sensitive recording material according to claim 1 or 2, wherein the compound represented by the general formula (II) is an aminosalicylic acid derivative represented by the following formula (V).

According to any one of claims 1 to 3, characterized in that it contains at least one of the heat-sensitive coloring layer 2,4'-bis-hydroxydiphenyl sulfone or 4-hydroxy-4'-allyloxy diphenyl sulfone Thermal recording material. The weight ratio of the oligomer composition to 2,4'-bishydroxydiphenylsulfone or 4-allyloxy-4'-hydroxydiphenylsulfone is between 2: 8 and 5: 5. 5. The heat-sensitive recording material according to any one of 4 to 4 . As the leuco dye, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-di (n-pentyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N--) p- toluidino) -6-methyl-7-anilino heat-sensitive recording material according to any one of claims 1 to 5, characterized by using any of the fluoran. The heat-sensitive recording material according to any one of claims 1 to 6 , wherein a leuco dye dispersion liquid having an average particle diameter of the leuco dye of 0.10 to 0.30 µm is used. The thermosensitive recording according to any one of claims 1 to 7, wherein an undercoat layer containing at least hollow particles is provided on the support, and the thermosensitive coloring layer according to any one of claims 1 to 7 is provided. material. The hollow particles contained in the undercoat layer, a thermoplastic resin as a shell, one of the claims 1 to 8, characterized in that a hollow ratio of 30% or more the size of the weight-average particle diameter 0.4~10μm The thermal recording material according to any one of the above.