JP2004291272A - Thermo-sensitive recording material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermo-sensitive recording material minimized in ground fogging even when using a coloring agent having a salicylic acid residue and in a high temperature and a high humidity environment of over 50°C and 80%, having high sensitivity and exhibiting chemical resistance especially excellent in an image survival rate in resistance to a plasticizer and excellent in a heat resistant preservation property. <P>SOLUTION: The thermo-sensitive recording material has on a support a thermo-sensitive color developing layer made principally of a color developer to make the leuco dye develop color when being heated. A compound employed as a color developer contains an oligomer composition and a hindered amine derivative obtained by reaction of a poly-functional isocyanate compound of trivalence or higher expressed by formula (I): X(NCO)a with an aromatic amine expressed by formula (II). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

（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。）」、（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１０】

【００２０】
【化１１】

（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１２】

」、（４）「前記感熱発色層中に含有する該ヒンダートアミン誘導体として、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（１，２，２，６，６−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下記化合物（１）又は化合物（２）の少なくとも１種類を含有させ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；
【００２２】
【化１３】

【００２３】
【化１４】

」、（５）「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（４）項のいずれかに記載の感熱記録材料」、（６）「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（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（６）項のいずれかに記載の感熱記録材料」、（８）「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（７）項のいずれかに記載の感熱記録材料」、（９）「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記録層を有す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感熱記録材料」、（１０）「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（９）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（１，２，２，６，６−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（１，２，２，６，６−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（１，２，２，６，６−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（１，２，２，６，６−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。

【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】
（３）アンダーコート層形成液の調整

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]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heat-sensitive recording material, which reduces background fog even in a high-temperature and high-humidity environment of 50 ° C./80% or more, has high sensitivity, has excellent chemical resistance, particularly excellent image retention rate in plasticizer resistance, and has heat-resistant storage stability. The present invention relates to a thermosensitive recording material having excellent heat resistance.
[0002]
[Prior art]
In recent years, with the diversification of information and the expanding needs, various types of recording materials have been researched, developed, and put into practical use in the information recording field. Among them, thermosensitive recording materials include (1) simple images formed only by a heating process. And (2) the required device mechanism is simple and compact, and the recording material is easy to handle and inexpensive. And the like, the fields of recorders for medical measurement, the fields of low-speed and high-speed facsimile machines, the fields of automatic ticket vending machines (passenger tickets, admission tickets, etc.), the field of thermal copying machines, the label field of POS systems, and the like.
[0003]
Among the fields of use of these heat-sensitive recording materials, they are rapidly being used in the label field of POS systems, especially in fields where importance is placed on the reliability of images such as lunch boxes and prepared dishes, and organic materials used in packaging and the like are used. Used for applications that require high storage stability for plasticizers and fats and oils contained in polymer materials, and for applications that require storage stability for several years such as receipts and receipts, At present, the required quality for heat-sensitive recording materials is increasing year by year. For this purpose, auxiliaries such as a dye, a color developer, and a storage stabilizer have been developed, but there has not yet been found any one which can sufficiently satisfy the color sensitivity and the storage stability of an image.
[0004]
In general, heat-sensitive recording materials use an electron-donating dye precursor (leuco dye) and an electron-accepting color developer, and have excellent properties such as good appearance, good feel, and high color density. On the other hand, the recorded image area comes in contact with plastics such as polyvinyl chloride, etc., and is decolorized by plasticizers and additives contained in plastics, or comes in contact with chemicals contained in foods and cosmetics, etc. Therefore, there is a disadvantage that the reliability (preservability) of the recording material is poor, such that the recorded image portion is easily erased or the background portion is colored.
[0005]
Therefore, in order to improve the storage stability of the image area of the heat-sensitive recording material, developers for developing a leuco dye have been actively developed, and various types of compounds have been proposed. As one of such proposals, a method utilizing a compound having a urea group has been recently proposed. For example, Patent Literatures 1 and 2 disclose diphenylurea compounds. These compounds are known to have excellent image storability compared to phenolic developers, but the plasticizers tend to lower the density of the color image area due to contact with oil, and have sufficient properties. It is hard to say that it has image reliability. Further, these systems also have a drawback of low color image density, and have not reached a practical level.
[0006]
Patent Documents 3 and 4 disclose urea urethane compounds as compounds having a urea group and a urethane group. This compound also has, like the above-mentioned compounds, a performance excellent in image preservability as compared with the phenol-based developer, but the preservability of the image area against contact with a plasticizer and oil is insufficient, and The coloring density is also remarkably low, and it cannot be said that it is practical.
[0007]
On the other hand, a compound containing a urea group and another color developing group in the molecule has also been proposed, and a compound having a urea group and two salicylic acid residues in the molecule in Patent Document 5 is disclosed in Patent Document 6, A compound having a urea group and two benzoic acid residues in a molecule, and Patent Document 7 discloses a compound having a urea group and two hydroxyphenyl residues in a molecule. These compounds tend to improve the color density by the introduction of a color developing group other than the urea group into the molecule, but the reliability of the color image area is insufficient, and the plasticizer and the oil The contact reduces the image density and is not practical. Further, the salicylic acid residue has a strong acidity, and the compound contained in the molecule dissolves in water in an environment of 50 ° C./80% or more, reacts with the dye, and has a drawback that background fog occurs.
[0008]
Patent Literature 8 discloses a polyurea compound derived from a diisocyanate compound and a diamine compound. These compounds are not practical because of their low color-forming properties due to their high molecular weight polymers.
[0009]
Further, as a similar compound to a compound having a urea group, Patent Document 9 discloses -SO ₂ A compound having an -NHCONH- group is disclosed in Patent Document 10 as -SO ₂ Compounds having an -NHCONHCO-NH- group are mentioned. These compounds are also improved in color density, but all of them are not practical because the preservability of the image portion is insufficient and the fogging of the background portion is large.
[0010]
On the other hand, various types of polymer (oligomer) type color 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-based developers are not sufficient in storage characteristics of the image portion and the background portion, and have low color-forming characteristics (color-forming density / color-forming sensitivity) and are not practical.
[0011]
Among them, those having a high molecular weight have been developed as a color developer exhibiting high storage stability particularly to plasticizers and fats and oils. For example, Patent Document 13 describes a high-molecular color developer of a diphenylsulfonic acid derivative. Patent Document 11 described above discloses a (poly) 4-hydroxybenzoic acid derivative. For example, a high-molecular-weight developer of a diphenylsulfonic acid derivative using a low-melting-point developer or a sensitizer has been disclosed in order to supplement color development sensitivity (see Patent Documents 14 and 15). However, they use a low-melting point developer or sensitizer to increase the apparent color sensitivity in the low-energy region, thereby improving the apparent color sensitivity. On the other hand, a decrease in image density, that is, a decrease in image remaining rate is remarkably observed. This is because the apparent image color density portion is the image color density portion due to the low melting point developer or sensitizer, and is considered to be easily decolored with respect to plasticizers and oils. To put it simply, it means that the chemical resistance inherent in the high-molecular-weight developer loses the chemical resistance, which is the greatest feature, by means for increasing the color sensitivity. That is, in a high-molecular-weight developer, it is an issue to improve the color-forming sensitivity and at the same time maintain the image remaining rate in chemical resistance.
[0012]
In addition, as described above, by using a low-melting point developer and a sensitizer, a material that is eutectic with the leuco dye and the developer and causes a decrease in melting point is added. Although the sensitivity is improved, the coloring temperature is lowered, so that the background fog occurs at a low temperature together with the sensitivity improvement.
As a method that does not use these low-melting-point color developers and sensitizers, there have conventionally been various proposals for increasing the sensitivity of a heat-sensitive recording material by forming fine particles of a leuco dye. For example, a leuco dye having a volume average particle size of 2 μm or less is used (for example, refer to Patent Document 16). Two or more types of leuco dyes that are pulverized so that the average particle size becomes 2 μm or less are used. (For example, see Patent Document 17), and a thermal recording medium containing a leuco dye having an average particle diameter of 0.1 μm to 0.8 μm, a color former, and colloidal silica (for example, see Patent Document 18). ing.
[0013]
These leuco dyes are made into fine particles by using a water-soluble polymer such as cellulose or polyvinyl alcohol as a dispersant, and dispersing in water by a dispersing machine such as a ball mill, a sand mill, a high-speed jet mill, or an attritor until a predetermined particle size is reached. In this method, as the average particle diameter decreases, the proportion of the fine particle component increases. In particular, when the average particle diameter is 0.3 μm or less, the heat-resistant storage stability of the thermosensitive recording medium decreases. Further, when fine particles are formed by using polyvinyl alcohol as a dispersant, coloring (liquid fogging) of the dispersion liquid occurs, and thus there is a disadvantage that the background density of the heat-sensitive recording material increases. Further, a method has been proposed in which a leuco dye is finely divided by an emulsification method.
[0014]
For example, Patent Document 19 describes a method in which a solution of a leuco dye dissolved in an organic solvent is emulsified in water. However, a step of removing the organic solvent after emulsification is required, and background fog is generated by the residual organic solvent. There are drawbacks such as doing. Patent Document 20 proposes a method in which a leuco dye is emulsified together with a heat-fusible substance. However, the melting point of the leuco dye is lowered by the heat-fusible substance, and the heat-resistant storage stability is lowered. Patent Document 21 proposes a thermosensitive recording material in which the volume average particle size of the leuco dye is 0.3 μm or less and contains an ultraviolet absorber. Here, a method is disclosed in which the leuco dye is made into fine particles by hot-melting the dye and emulsifying it with a high-pressure homogenizer using a silicon-based emulsifier. Patent Document 22 proposes a leuco dye having an average particle size of 1.0 μm or less and emulsified and dispersed. As a method of emulsifying and dispersing in this proposal, a method of emulsifying and dispersing a leuco dye heated and melted by using a high-speed stirrer or a high-pressure spray from a nozzle using an emulsifier is described. The melting point of the leuco dye is usually 150 ° C. or higher, and a special device such as a high-pressure vessel is required to heat-melt the leuco dye and emulsify it in water as in the methods described in Patent Documents 21 and 22. However, mass production is difficult.
[0015]
[Patent Document 1]
JP-A-8-2110
[Patent Document 2]
JP-A-8-2111
[Patent Document 3]
JP-A-2000-143611
[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]
JP-A-5-169836
[Patent Document 10]
JP-A-11-26369
[Patent Document 11]
WO99 / 51444
[Patent Document 12]
JP 2001-30626 A
[Patent Document 13]
JP-A-8-333329
[Patent Document 14]
JP-A-10-297089
[Patent Document 15]
JP-A-10-297090
[Patent Document 16]
JP-A-57-47693
[Patent Document 17]
JP-A-7-223375
[Patent Document 18]
JP-A-7-186527
[Patent Document 19]
JP-A-61-217283
[Patent Document 20]
JP-A-56-164890
[Patent Document 21]
JP-A-7-186531
[Patent Document 22]
JP-A-7-223379
[0016]
[Problems to be solved by the invention]
An object of the present invention is to reduce background fog, to provide high sensitivity, and to have high chemical resistance, especially plastic resistance, even when a developer having a salicylic acid residue is used or in a high-temperature and high-humidity environment of 50 ° C./80% or more. It is an object of the present invention to provide a heat-sensitive recording material which is excellent in image retention ratio and excellent in heat-resistant storage stability.
[0017]
[Means for Solving the Problems]
The object of the present invention is to provide (1) a heat-sensitive recording material having a heat-sensitive coloring layer comprising, as a main component, a leuco dye and a color developing agent which forms the color of the leuco dye on heating. The compound used includes an oligomer composition 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), and a hindered amine derivative. A heat-sensitive recording material characterized by the following:
Embedded image
X (NCO) a (I)
[0018]
Embedded image

(Wherein X is a trivalent or higher valent group, a is an integer of 3 or higher, b and c are integers of 0 to 5, provided that b + c = 1 to 5. Z is a hydrogen atom or an alkyl group. , An allyl group or an aryl group, and in the case of an aryl group, it may form a condensed ring structure. D is an integer of 0 to 4 satisfying the relationship of b + c + d = 5.) " (2) the thermosensitive recording material according to the above (1), wherein X in the general formula (I) has a trivalent structure represented by the following formula (III) or (IV);
[0019]
Embedded image

[0020]
Embedded image

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

And (4) "as the hindered amine derivative contained in the thermosensitive coloring layer, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetra Carboxylate or tetrakis (1,2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or at least one of the following compounds (1) and (2) The thermosensitive recording material according to any one of the above items (1) to (3);
[0022]
Embedded image

[0023]
Embedded image

(5) "(1) wherein the thermosensitive coloring layer contains at least one kind of 2,4'-bishydroxydiphenylsulfone or 4-hydroxy-4'-allyloxydiphenylsulfone. Item 6) The weight of the oligomer composition and 2,4'-bishydroxydiphenylsulfone or 4-allyloxy-4'-hydroxydiphenylsulfone. The heat-sensitive recording material according to any one of the above items (1) to (5), wherein the ratio is between 2: 8 and 5: 5, (7) "as the leuco dye" 3-dibutylamino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-Np-toluidino) -6 (8) “Average of the leuco dye”, wherein any one of methyl-7-anilinofluoran is used, wherein the heat-sensitive recording material according to any one of the above (1) to (6) is used. (9) The thermosensitive recording material according to any one of (1) to (7), wherein a leuco dye dispersion having a particle size of 0.10 μm to 0.30 μm is used. Item (1) wherein an undercoat layer containing at least hollow particles is provided on a support, and the heat-sensitive recording layer according to any one of Items (1) to (7) is provided. And (10) “The hollow particles contained in the undercoat layer are made of a thermoplastic resin as a shell, have a hollow ratio of 30% or more, and have a weight average particle diameter of 0. The size of the (1) to (4) to 10 μm. It is solved by the thermal recording material "according to any one of claim to the (9) section.
[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 aromatic compound represented by the general formula (II) or (V) The oligomer composition obtained by the reaction with the aromatic amine has a large number of salicylic acid residues in the molecule, and thus generates background fog in a high-temperature and high-humidity environment of 50 ° C./80% or more. By containing a basic hindered amine derivative, by making the pH neutral, the solubility of the oligomer composition was reduced, and it became possible to suppress the occurrence of background fog. The oligomer of the present invention means one having a molecular weight of 2,000 to 10,000.
[0025]
Usually, the addition of a basic compound causes inhibition of color development, resulting in a decrease in sensitivity and a decrease in chemical resistance. However, the hindered amine derivative has a small decrease in sensitivity and a decrease in chemical resistance. This is probably because the hindered amine derivative has an appropriate basicity. Therefore, the combination of the hindered amine derivative and the oligomer composition can provide a heat-sensitive recording material having high sensitivity, excellent heat resistance storage stability, and excellent chemical resistance.
[0026]
By using a high molecular compound (1) (molecular weight: 2,000) or a compound (2) (molecular weight: 1900) as a hindered amine derivative, the activity at the time of thermal melting of a color-forming complex formed of a dye and a color developer It is considered that the coloring property and the chemical resistance are improved by lowering the chemical energy and further increasing the amorphous property after the heat melting.
In addition, polymer tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis (1,2,2,6,6-tetra Methyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate is a polymer having a molecular weight of 850 and a melting point of 140 ° C. and a high melting point, so that it is possible to achieve both chemical resistance and heat resistance. became.
[0027]
Further, the trivalent or higher polyvalent isocyanate compound represented by the general formula (I) or (III) or (IV) used in the present invention and the aromatic amine represented by the general formula (II) or (V) The amount of the oligomer composition obtained by the reaction is preferably 2 to 6 parts by weight based on 1 part by weight of the leuco dye. If the amount is less than 2 parts by weight, the color developability becomes insufficient. If the amount is more than 6 parts by weight, components that do not contribute to the color development increase, which hinders the color development and lowers the sensitivity. It is industrially undesirable to add an excessive amount of a component that does not contribute to color development.
[0028]
Hindered amine derivatives tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis (1,2,2,6,6- The addition amount of (tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or compound (1) or compound (2) is based on 1 part by weight of the leuco dye because it is a basic substance. On the other hand, when the content is 1 part by weight or more, a decoloring effect is generated and the color density is reduced. Therefore, it is preferable to add 0.1 to 0.5 part by weight.
[0029]
In addition, as the color developer that can be added in the present invention, the following can be mentioned. As such a developer, 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, 2,4′-bis 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-tert-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'-hydroxydiphenylsulfone, 4-benzyloxy-4'-hydroxydiphenylsulfone, 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, zinc 1-acetyloxy-2-naphthoate, 2-a Zinc tyloxy-1-naphthoate, zinc 2-acetyloxy-3-naphthoate, α, α-bis (4-hydroxyphenyl) -α-methyltoluene, antipyrine complex of zinc thiocyanate, 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 in a range that does not reduce the chemical resistance, and the oligomer composition in the thermosensitive coloring layer and 2,4′-bishydroxydiphenyl sulfone or 4-allyloxy-4′-hydroxy are preferably added. A heat-sensitive recording material characterized in that the weight ratio with diphenyl sulfone is between 2: 8 and 5: 5.
[0032]
The leuco dyes used in the thermosensitive coloring layer of the present invention are applied alone or in combination of two or more, and as such leuco dyes, those applied to this kind of thermosensitive material can be arbitrarily applied. However, in order to achieve both chemical resistance, high sensitivity and heat resistance, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl- 7-anilinofluoran, 3- (N-ethyl-Np-toluidino) -6-methyl-7-anilinofluoran, is most useful.
[0033]
Other specific examples include the following, for example.
Leuco compounds of dyes such as triphenylmethane, fluoran, phenothiazine, auramine, spiropyran, and indolinophthalide are preferably used. Specific examples of such a leuco dye include, for example, 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-chlorofluoran,
3-dimethylamino-5,7-dimethylfluoran,
3-N-methyl-N-isobutyl-6-methyl-7-anilinofluoran,
3-N-ethyl-N-isoamyl-6-methyl-7-anilinofluoran,
3-diethylamino-7-chlorofluoran,
3-diethylamino-7-methylfluoran,
3-diethylamino-7,8-benzfluoran,
3-diethylamino-6-methyl-7-chlorofluoran,
3- (Np-tolyl-N-ethylamino) -6-methyl-7-anilinofluoran,
3-pyrrolidino-6-methyl-7-anilinofluoran,
2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluoran,
2- {3,6-bis (diethylamino) -9- (o-chloroanilino) xanthylbenzoate lactam},
3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran,
3-diethylamino-7- (o-chloroanilino) fluoran,
3-dibutylamino-7- (o-chloroanilino) fluoran,
3-N-methyl-N-amylamino-6-methyl-7-anilinofluoran,
3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran,
3-diethylamino-6-methyl-7-anilinofluoran,
3-diethylamino-6-methyl-7- (2 ′, 4′-dimethylanilino) fluoran,
3- (N, N-diethylamino) -5-methyl-7- (N, N-dibenzylamino) fluoran,
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) fluoran,
3-pyrrolidino-7-trifluoromethylanilinofluoran,
3-diethylamino-5-chloro-7- (N-benzyl-trifluoromethylanilino) fluoran,
3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluoran,
3-diethylamino-5-chloro-7- (α-phenylethylamino) fluoran,
3-diethylamino-7- (o-methoxycarbonylphenylamino) fluoran,
3-diethylamino-5-methyl-7- (α-phenylethylamino) fluoran,
3-diethylamino-7-piperidinofluoran,
2-chloro-3- (N-methyltoluidino) -7- (pn-butylanilino) fluoran,
3- (N-methyl-N-isopropylamino) -6-methyl-7-anilinofluoran,
3-diethylamino-6-methyl-7- (3-methylanilino) fluoran,
3,6-bis (dimethylamino) fluorenespiro (9,3 ′)-6′-dimethylaminophthalide,
3- (N-benzyl-N-cyclohexylamino) -5,6-benzo-7-α-naphthylamino-4′-bromofluoran,
3-diethylamino-6-chloro-7-anilinofluoran,
3-N-ethyl-N- (2-ethoxypropyl) amino-6-methyl-7-anilinofluoran,
3-N-ethyl-N-tetrahydrofurfurylamino-6-methyl-7-anilinofluoran,
3-diethylamino-6-methyl-7-mesitidino-4 ′, 5′-benzofluoran,
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 "- Il) 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, the use of a high-molecular weight developer and the average particle diameter of the leuco dye is further adjusted to 0.10 to 0.30 μm to achieve a high level of sensitivity at a practical level, and reduce the particle diameter of the leuco dye. By doing so, the background fog tends to increase, but tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis (1 , 2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or the compound (1) or (2) is a basic substance It is effective in preventing background fogging, and 3-dibutylamino-6-methyl-7-anilinofluoran and 3-di (n-pentyl) amino-6-methyl-7-anilinofur as leuco dyes By selecting orchid, 3- (N-ethyl-N-p-toluidino) -6-methyl-7-anilinofluoran, heat sensitivity with less background fog, excellent heat storage stability and excellent chemical resistance The recording material was invented.
[0036]
The 0.10 to 0.30 μm leuco dye used in the present invention can be obtained by containing a surfactant in an amount of 5 to 20% by weight based on the leuco dye. If the amount of the surfactant is less than 5%, it is considered that the dispersion of the leuco dye becomes insufficient, the aggregation of the fine dispersion occurs, the dispersion does not proceed, and the particle size of the dye is not sufficiently small. On the other hand, if it exceeds 20%, it is considered that the surplus surfactant which does not participate in the dispersion hinders the color developing property and the storage stability of the thermosensitive recording material.
[0037]
Examples of the leuco dye surfactant having an average particle diameter of 0.10 to 0.30 μm used in the present invention include the following.
Polyoxyethylene octyl phenyl ether, polyoxyethylene-2-ethylhexyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene tridecyl ether, polyoxyethylene castor oil ether, polyoxyethylene cetyl ether, polyoxyethylene Stearyl luether, 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, polyethylene glycol, polyoxyethylene polyoxypropylene ether, polyvinyl alcohol, starch and derivatives thereof, hydroxymethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, cellulose derivatives such as ethyl cellulose, polyacrylic acid Soda, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, Water-soluble polymers such as polyacrylamide, sodium alginate, gelatin, and casein, as well as polyvinyl acetate and polyurethane Emulsions such as polyacrylic acid, polyacrylate, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / vinyl acetate copolymer, styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, etc. And anionic surfactants such as dodecylbenzenesulfonate, monoalkylsuccinatesulfonate, dialkylsuccinatesulfonate, octylphenoxyethoxysulfonate, and sodium naphthalenesulfonate 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]
Normally, when the leuco dye is finely dispersed by using polyvinyl alcohol or the like as a dispersant, the smaller the particle size, the higher the coloring density of the dispersion. Further, when mixed with a color developer, coloring becomes more intense, and in the case of heat-sensitive recording paper, the background density increases. As such a cause, the unsaponified portion of the polyvinyl alcohol is changed due to a high share due to the formation of fine particles, the pH of the dispersion is lowered due to the formation of acetic acid, and a partial color is formed, or a part of the dye particles is amorphous. It is presumed that the color will be easily developed. Tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis (1,2,2,6,6-tetramethyl-4- Addition of (piperidyl) -1,2,3,4-butanetetracarboxylate or the compound (1) or the compound (2) is also a basic substance, so is also effective in adjusting PH and is effective in preventing background fog. There is an estimate. Further, it is presumed that when the dispersion is carried out by using a nonionic surfactant as a main component as a dispersant, the decrease in pH is small and the non-crystallization of the dye can be prevented.
[0039]
As a dispersion method for adjusting the average particle size of the leuco dye of the present invention to 0.10 to 0.30 μm, a ball mill, an attritor, a sand mill, a high-pressure jet mill, or the like can be used, and a dispersion method using a medium is preferable. By using a zirconia media having a diameter of 0.5 mm or less, fine particles of the leuco dye can be achieved. It is also achieved by coarsely pulverizing 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 method for measuring the average particle diameter component of the present invention is, for example, a method using a laser analysis / scattering method (Microtrack HRA9320-X100 type, LA920 type manufactured by Horiba, Rasentec FBRM apparatus), a centrifugal sedimentation method, a Coulter counter, an electron microscope, etc. Can be measured by a commonly used measuring instrument. In addition, it is possible to increase the sensitivity by using a sensitivity enhancer 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, fatty acid metal salts such as zinc stearate, aluminum stearate, calcium stearate, zinc palmitate and zinc behenate, 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, gliacol carbonate, dibensil 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-aryloxyphenyl, p-propargyloxybiphenyl, dibenzoyloxymethane, dibenzoyloxypropane, dibenzyldisulfide, 1,1-diphenylethanol, 1,1-diphenylpropanol, p- Benzyloxybenzyl alcohol, 1,3-phenoxy-2-propanol, N- Cutadecylcarbamoyl-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 reduce heat resistance and chemical resistance.
[0042]
In the present invention, as described above, it is also possible to provide an undercoat layer containing hollow particles as a main component in order to increase the sensitivity of the coloring layer. As the hollow particles, for example, those having a hollow ratio of 30% or more and a weight average particle size 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 (inner diameter of hollow particles / outer diameter of hollow particles) × 100%. The undercoat layer weighs 2 to 10 g / m when dried ² , Preferably 2.5 to 7 g / m ² Can be provided.
[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 appropriately used, and specific examples thereof include the following. Can be
Polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate / methacryl Acid terpolymer, styrene / maleic anhydride copolymer alkaline salt, isobutylene / maleic anhydride copolymer alkaline salt, polyacrylamide, sodium alginate, gelatin, casein and other water-soluble polymers, as well as polyvinyl acetate Emers such as polyurethane, polyacrylic acid, polyacrylate, 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 cross-linked material can also be used.
[0044]
As the support in the present invention, any of recycled paper such as paper, synthetic paper, laminated paper and the like can be used. Further, an overcoat layer may be further provided after the support and the heat-sensitive recording layer are sequentially coated. As a material for forming the overcoat layer, the binder, filler, cross-linking agent, and the like used in the above-described heat-sensitive recording layer can be used.
[0045]
The recording method of the heat-sensitive recording material of the present invention is, for example, a hot pen, a thermal head, or laser heating depending on the purpose of use, and is not particularly limited.
[0046]
【Example】
Next, the present invention will be described in more detail with reference to examples. The following parts and percentages are all based on weight.
(1) Preparation of dispersion for forming thermosensitive coloring layer
[Solution A] having the following composition was dispersed with a sand grinder to obtain a dye dispersion having the physical properties shown in Table 1. The average particle size was measured using LA-700 manufactured by Horiba, Ltd.

[0047]
(2) Adjustment of heat-sensitive coloring liquid
10 parts of [Solution A] described in Table 1, 30 parts of [Solution B], 3 parts of [Solution C] described in Table 1, 10 parts of [Solution D] described in Table 1 and colloidal silica (solid content: 20%), A composition comprising 20 parts of styrene butadiene latex (solid content; 50%), 15 parts of stearic acid amide dispersion (solid content; 20%), and 1 part of dioctyl sulfosuccinic acid aqueous solution (solid content; 5%) is mixed and heat-sensitive. A color forming layer coating solution was prepared.
[0048]
(3) Preparation of undercoat layer forming liquid

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 liquid shown in Table 1 on a high quality paper having a dry coating amount of 3.0 g / m ² And dried. Then, using the thermosensitive coloring solution prepared in Table 1, the amount of dye adhered was 0.5 g / m2. ² , And then processed by 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)
The calendered product was subjected to a thermal printing test apparatus having a thin film head manufactured by Matsushita Electric Parts Co., Ltd. under the conditions of a head power of 0.45 W / dot, one line recording time of 20 msec / L, and a scanning density of 8 × 385 dots / mm. Printing was performed with a pulse width of 0.0 to 0.7 mmsec every 1 msec, the print density was measured with a Macbeth densitometer RD-914, and the pulse width at which the density was 1.0 was calculated. With reference to Comparative Example 1, the calculation is made as (pulse width of Comparative Example 1) / (pulse width of measured sample) = (sensitivity magnification). The higher the value, the better the sensitivity (thermal response). Table 2 shows the evaluation results.
(Image density)
The calendered product was printed with a pulse width of 0.5 msec using the thermal printing test apparatus described above, and the print density and the background density were measured with a Macbeth densitometer RD-914.
(Temperature and humidity resistance)
After the samples printed under the above conditions were left at 55 ° C./90% for 15 minutes, the density of the image portion and the background portion were measured.
(Heat-resistant)
After leaving each of the samples printed under the above conditions at 90 ° C. for 15 hours, the densities of the image portion and the background portion were measured.
(Plasticizer resistance)
On the sample printed under the above conditions, three sheets of Shin-Etsu Polymer PVC (Polymer Wrap 300) were placed on top of each other, and 10 × 10 cm ² The density of the image portion and the background portion after storage for 24 hours in an environment of 40 ° C. was measured by applying a load of 5 kg per unit using a Macbeth densitometer RD-914, and the image residual ratio was calculated as (density after test) / (test (Concentration before) × 100 (%).
[0053]
[Table 2]

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

Claims (10)

In a heat-sensitive recording material having a heat-sensitive coloring layer containing, as a main component, a leuco dye and a color developing agent for coloring the leuco dye on heating on a support, the compound used as the color developing agent is represented by the following general formula (I). A heat-sensitive recording material comprising a hindered amine derivative and an oligomer composition obtained by reacting a trivalent or higher polyvalent isocyanate compound with an aromatic amine represented by the following general formula (II).

(Wherein X is a trivalent or more valent 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. Z is a hydrogen atom or an alkyl group. , An allyl group or an aryl group, and in the case of an aryl group, it may form a condensed ring structure. D is an integer of 0 to 4 that satisfies 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.) 3. The heat-sensitive recording material according to claim 1, wherein the compound represented by the general formula (II) is an aminosalicylic acid derivative represented by the following formula (V).

As the hindered amine derivative contained in the thermosensitive coloring layer, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or tetrakis (1) , 2,2,6,6-tetramethyl-4-piperidyl) -1,2,3,4-butanetetracarboxylate or at least one of the following compounds (1) and (2). The heat-sensitive recording material according to any one of claims 1 to 3, wherein

5. The thermosensitive coloring layer according to claim 1, wherein the thermosensitive coloring layer contains at least one of 2,4'-bishydroxydiphenylsulfone and 4-hydroxy-4'-allyloxydiphenylsulfone. 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. 6. The heat-sensitive recording material according to any one of items 1 to 5, As the leuco dye, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-di (n-pentyl) amino-6-methyl-7-anilinofluoran, 3- (N-ethyl-N- The heat-sensitive recording material according to any one of claims 1 to 6, wherein any one of (p-toluidino) -6-methyl-7-anilinofluoran is used. The heat-sensitive recording material according to any one of claims 1 to 7, wherein a leuco dye dispersion having an average particle diameter of the leuco dye of 0.10 µm to 0.30 µm is used. The thermal recording according to any one of claims 1 to 8, wherein an undercoat layer containing at least hollow particles is provided on the support, and the thermal recording layer according to any one of claims 1 to 7 is provided. material. The hollow particles contained in the undercoat layer are formed of a thermoplastic resin as a shell, have a hollow ratio of 30% or more, and have a weight average particle diameter of 0.4 to 10 μm. The thermal recording material described in Crab.