JP3712347B2 - Reversible thermosensitive recording material - Google Patents

Description

式（１）中、Ｘａ及びＸｂは、一方が硫黄原子を表し、他方が両末端に炭化水素基を含まない−ＣＯＮＨ−結合を最小構成単位とする二価の水素結合基を表す。Ｒ¹は炭素数１から２４の１価の炭化水素基を表す。Ｒ²及びＡは炭素数１から１８の二価の炭化水素基を表す。
【００１３】
【化６】

式（２）中、Ｘｃは両末端に炭化水素基を含まない−ＣＯＮＨ−結合を最小構成単位とする二価の基を表す。Ｒ³は炭素数１から２４の一価の炭化水素基を表す。Ｒ⁴は炭素数１から１８の二価の炭化水素基を表す。
【００１４】
【化７】

式（３）中、Ｘｄは両末端に炭化水素基を含まない−ＣＯＮＨ−結合を最小構成単位とする二価の基を表す。Ｒ⁵は窒素原子を含まない炭素数１から２４の一価の炭化水素基を表す。Ｒ⁷は炭素数１から２４の一価の炭化水素基を表す。Ｒ⁶は炭素数１から１８の二価の炭化水素基を表す。
【００１５】
一般式（１）で表される化合物中、Ｒ¹は炭素数１から２４の一価の炭化水素基を表すが、好ましくは炭素数６から２０の一価の炭化水素基である。Ａ及びＲ²は炭素数１から１８の二価の炭化水素基を表すが、好ましくは炭素数１から１２の炭化水素基である。Ａ、Ｒ¹及びＲ²は具体的には主として、各々アルキレン基及びアルキル基を表すが、それぞれその基中に芳香環を含んでいてもよい。一方、Ｘａ及びＸｂは、一方が硫黄原子を表し、他方が両末端に炭化水素基を含まない−ＣＯＮＨ−結合を最小構成単位とする二価の基（以下、ＨＢＧと呼称）を表す。例えば、Ｘａが硫黄原子の場合は、ＸｂがＨＢＧを表し、また逆に、ＸａがＨＢＧの場合は、Ｘｂは硫黄原子を表す。ＨＢＧの具体例としては、アミド（−ＣＯＮＨ−、−ＮＨＣＯ−）、尿素（−ＮＨＣＯＮＨ−）、ウレタン（−ＮＨＣＯＯ−、−ＯＣＯＮＨ−）、ジアシルアミン（−ＣＯＮＨＣＯ−）、ジアシルヒドラジド（−ＣＯＮＨＮＨＣＯ−）、シュウ酸ジアミド（−ＮＨＣＯＣＯＮＨ−）、アシル尿素（−ＣＯＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＯ−）、３−アシルカルバジン酸エステル（−ＣＯＮＨＮＨＣＯＯ−）、セミカルバジド（−ＮＨＣＯＮＨＮＨ−、−ＮＨＮＨＣＯＮＨ−）、アシルセミカルバジド（−ＣＯＮＨＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＮＨＣＯ−）、ジアシルアミノメタン（−ＣＯＮＨＣＨ₂ＮＨＣＯ−）、１−アシルアミノ−１−ウレイドメタン（−ＣＯＮＨＣＨ₂ＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＨ₂ＮＨＣＯ−）、マロンアミド（−ＮＨＣＯＣＨ₂ＣＯＮＨ−）等の基が挙げられる。
【００１６】
以下に、一般式（１）で示される消去促進剤の具体例を化８〜化９に挙げるが、本発明はこれに限定されるものではない。
【００１７】
【化８】

【００１８】
【化９】

【００１９】
一般式（２）で表される化合物中、Ｒ³は一般式（１）のＲ¹と同義である。同様にＲ⁴はＲ²と同義である。ＸｃはＨＢＧを表し、その具体例は一般式（１）に列挙した結合基と同義である。
【００２０】
以下に、一般式（２）で示される可逆性顕色剤の具体例を化１０に挙げるが、本発明はこれに限定されるものではない。
【００２１】
【化１０】

【００２２】
一般式（３）で表される化合物中、Ｒ⁵は窒素原子を含まない炭素数１から２４の一価の炭化水素基を表すが、好ましくは炭素数６から２０の窒素原子を含まない一価の炭化水素基である。Ｒ⁷は一般式（１）のＲ¹と同義である。同様にＲ⁶はＲ²と同義である。ＸｄはＨＢＧを表し、その具体例は一般式（１）に列挙した結合基と同義である。
【００２３】
一般式（３）で表される化合物の具体例としては以下の化１１に示す化合物が挙げられるが本発明はこれに限定されない。
【００２４】
【化１１】

【００２５】
また、本発明には一般式（４）で表されるフェノール性化合物を可逆性顕色剤として用いられる。
【００２６】
【化１２】

式（４）中、Ｘｆ及びＸｇは酸素原子、硫黄原子または両末端に炭化水素基を含まない−ＣＯＮＨ−結合を最小構成単位とする二価の基を表す。Ｒ⁸は単結合または炭素数１〜１２の２価の炭化水素基を表す。Ｒ⁹は炭素数１から１８の二価の炭化水素基を表す。Ｒ¹⁰は炭素数１から２４の一価の炭化水素基を表す。ｎは０〜４の整数を表し、ｎが２以上のとき繰り返されるＲ⁹及びＸｇは同一であっても異なっていてもよい。また、ｎ＝０のとき、Ｘｆは両末端に炭化水素基を含まない−ＣＯＮＨ−結合を最小構成単位とする二価の基である。ｎが１以上のとき、Ｘｆ及びＸｇから選ばれる少なくともひとつは、両末端に炭化水素基を含まない−ＣＯＮＨ−結合を最小構成単位とする二価の基である。
【００２７】
一般式（４）で表される化合物中、Ｒ¹⁰は炭素数１から２４の一価の炭化水素基を表すが、好ましくは炭素数６から２０の一価の炭化水素基である。Ｒ⁸は単結合または炭素数１から１２の二価の炭化水素基を表す。Ｒ⁹は炭素数１から１８の二価の炭化水素基を表すが、好ましくは炭素数１から１２の炭化水素基である。Ｒ⁸、Ｒ⁹及びＲ¹⁰は具体的には主として、各々アルキレン基及びアルキル基を表すが、それぞれその基中に芳香環を含んでいてもよい。一方、Ｘｆ及びＸｇは酸素原子、硫黄原子またはＨＢＧを表すが、ＨＢＧの具体例は一般式（１）に列挙した結合基と同義である。ｎは０〜４の整数を表し、ｎが２〜４のとき繰り返されるＲ⁹及びＸ^gは、同一であっても異なっていてもよい。また、ｎが０のとき、ＸｆはＨＢＧである。ｎが１以上のとき、Ｘｆ及びＸｇから選ばれる少なくともひとつは、ＨＢＧである。
【００２８】
一般式（４）で表される化合物の具体例としては以下の化１３及び化１４に示す化合物が挙げられるが本発明はこれに限定されない。
【００２９】
【化１３】

【００３０】
【化１４】

【００３１】
一般式（１）、（２）あるいは（３）で表される化合物の好ましい使用量は、一般式（４）で表される可逆性顕色剤に対し０．１重量％以上１０００重量％以下であり、より好ましくは０．５重量％以上２００重量％以下である。更に、印字画像の耐熱保存性を考慮すれば、１重量％以上１００重量％以下が最も好ましい。また、一般式（１）、（２）あるいは（３）で表される化合物は、単独でも２種以上を併用し混合しても用いることができる。
【００３２】
本発明による可逆性顕色剤はそれぞれ１種または２種以上を混合して使用してもよく、無色ないし淡色の染料前駆体に対する本発明による可逆性顕色剤の使用量は、５〜５０００重量％、好ましくは１０〜３０００重量％である。
【００３３】
本発明に用いられる無色ないし淡色の染料前駆体としては一般に感圧記録紙や感熱記録紙等に用いられる公知な化合物に代表されるが、特に制限されるものではない。具体的な例としては、例えば下記に挙げるものなどがあるが、本発明はこれに限定されるものではない。
【００３４】
（１）トリアリールメタン系化合物
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（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）フタリド、３−（ｐ−ジメチルアミノフェニル）−３−（１，２−ジメチルインドール−３−イル）フタリド、３−（ｐ−ジメチルアミノフェニル）−３−（２−メチルインドール−３−イル）フタリド、３−（ｐ−ジメチルアミノフェニル）−３−（２−フェニルインドール−３−イル）フタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）フタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−４−アザフタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−４，７−ジアザフタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−７−アザフタリド、３−（ｐ−ジメチルアミノフェニル）−３−（２−フェニルインドール−３−イル）フタリド、３，３−ビス（１，２−ジメチルインドール−３−イル）−５−ジメチルアミノフタリド、３，３−ビス（１，２−ジメチルインドール−３−イル）−６−ジメチルアミノフタリド、３，３−ビス（９−エチルカルバゾール−３−イル）−５−ジメチルアミノフタリド、３，３−ビス（２−フェニルインドール−３−イル）−５−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−メチルピロール−２−イル）−６−ジメ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）−４−アザフタリド等。
【００３５】
（２）ジフェニルメタン系化合物
４，４′−ビス（ジメチルアミノフェニル）ベンズヒドリルベンジルエーテル、Ｎ−クロロフェニルロイコオーラミン、Ｎ−２，４，５−トリクロロフェニルロイコオーラミン等。
【００３６】
（３）キサンテン系化合物
ローダミンＢアニリノラクタム、ローダミンＢ−ｐ−クロロアニリノラクタム、３−ジエチルアミノ−７−ジベンジルアミノフルオラン、３−ジエチルアミノ−７−オクチルアミノフルオラン、３−ジエチルアミノ−７−フェニルフルオラン、３−ジエチルアミノ−７−フェノキシフルオラン、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−６−クロロ−７−メチルフルオラン、３−ジエチルアミノ−７−（３，４−ジクロロアニリノ）フルオラン、３−ジエチルアミノ−７−（２−クロロアニリノ）フルオラン、
【００３７】
３−ジエチルアミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−トリル）アミノ−６−メチル−７−アニリノフルオラン、３−ピペリジノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−トリル）アミノ−６−メチル−７−フェネチルフルオラン、３−ジエチルアミノ−７−（４−ニトロアニリノ）フルオラン、３−ジブチルアミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−メチル−Ｎ−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−イソアミル）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−（Ｎ−エチル−Ｎ−テトラヒドロフリル）アミノ−６−メチル−７−アニリノフルオラン等。
【００３８】
（４）チアジン系化合物
ベンゾイルロイコメチレンブルー、ｐ−ニトロベンゾイルロイコメチレンブルー等。
【００３９】
（５）スピロ系化合物
３−メチルスピロジナフトピラン、３−エチルスピロジナフトピラン、３，３′−ジクロロスピロジナフトピラン、３−ベンジルスピロジナフトピラン、３−メチルナフト−（３−メトキシベンゾ）スピロピラン、３−プロピルスピロベンゾピラン等。
【００４０】
前記無色ないし淡色の染料前駆体は単独でも、または２種以上を混合して使用してもよい。
【００４１】
本発明の可逆性感熱記録材料の製造方法の具体例としては、染料前駆体と可逆性顕色剤を主成分とし、これに本発明による化合物を添加し、支持体上に塗布して可逆性感熱記録層を形成する方法が挙げられる。
【００４２】
染料前駆体と可逆性顕色剤及び本発明による化合物を可逆性感熱記録層に含有させるための塗液作製方法としては、各々の化合物を単独で溶媒に溶解もしくは分散媒に分散してから混合する方法、各々の化合物を混ぜ合わせてから溶媒に溶解もしくは分散媒に分散する方法、各々の化合物を加熱溶解し均一化した後冷却し、溶媒に溶解もしくは分散媒に分散する方法等が挙げられるが、特に限定されるものではない。分散時には必要なら分散剤を用いてもよい。水を分散媒として使う場合の分散剤としてはポリビニルアルコール等の水溶性高分子や各種の界面活性剤が利用できる。水系の分散の際は、エタノール等の水溶性有機溶媒を混合してもよい。この他に炭化水素類に代表される有機溶媒が分散媒の場合は、レシチンや燐酸エステル類等を分散剤に用いてもよい。
【００４３】
また、可逆性感熱記録層の強度を向上する等の目的でバインダーを可逆性感熱記録層中に添加する事も可能である。バインダーの具体例としては、デンプン類、ヒドロキシエチルセルロース、メチルセルロース、カルボキシメチルセルロース、ゼラチン、カゼイン、ポリビニルアルコール、変性ポリビニルアルコール、ポリアクリル酸ソーダ、アクリル酸アミド／アクリル酸エステル共重合体、アクリル酸アミド／アクリル酸エステル／メタクリル酸３元共重合体、スチレン／無水マレイン酸共重合体のアルカリ塩、エチレン／無水マレイン酸共重合体のアルカリ塩等の水溶性高分子、ポリ酢酸ビニル、ポリウレタン、ポリアクリル酸エステル、スチレン／ブタジエン共重合体、アクリロニトリル／ブタジエン共重合体、アクリル酸メチル／ブタジエン共重合体、エチレン／酢酸ビニル共重合体、エチレン／塩化ビニル共重合体、ポリ塩化ビニル、エチレン／塩化ビニリデン共重合体、ポリ塩化ビニリデン等のラテックス類が挙げられる。これらのバインダーの役割は、組成物の各素材が印字、消去の熱印加によって片寄ることなく均一に分散した状態を保つことにある。したがって、バインダー樹脂には耐熱性の高い樹脂を用いることが好ましい。最近になって、プリペイドカード、ストアドカードといった付加価値の高い可逆性感熱記録材料が用いられることが多くなり、それに伴い、耐熱性、耐水性、更には接着性といった高耐久品が要求されるようになってきている。このような要求に対しては、硬化性樹脂は特に好ましい。
【００４４】
硬化性樹脂としては、例えば熱硬化性樹脂、電子線硬化樹脂、紫外線硬化樹脂等が挙げられる。熱硬化性樹脂としては、例えばフェノキシ樹脂、ポリビニルブチラール樹脂、セルロースアセテートプロピオネート樹脂等の水酸基、カルボキシル基が架橋剤と反応し、硬化するものが挙げられる。この際の架橋剤としては、例えば、イソシアネート類、アミン類、フェノール類、エポキシ類等が挙げられる。
【００４５】
電子線及び硬化線樹脂に用いられるモノマーとしては、アクリル系に代表される単官能性モノマー、二官能モノマー、多官能モノマー等が挙げられるが、特に紫外線架橋の際には光重合開始剤、光重合促進剤を用いる。
【００４６】
また、可逆性感熱記録層の発色感度を調節するための添加剤として、熱可融性物質を可逆性感熱記録層中に含有させることもできる。６０℃〜２００℃の融点を有するものが好ましく、特に８０℃〜１８０℃の融点を有するものが好ましい。一般の感熱記録紙に用いられている増感剤を使用することもできる。これらの化合物としては、Ｎ−ヒドロキシメチルステアリン酸アミド、ベヘン酸アミド、ステアリン酸アミド、パルミチン酸アミドなどのワックス類、２−ベンジルオキシナフタレン等のナフトール誘導体、ｐ−ベンジルビフェニル、４−アリルオキシビフェニル等のビフェニル誘導体、１，２−ビス（３−メチルフェノキシ）エタン、２，２′−ビス（４−メトキシフェノキシ）ジエチルエーテル、ビス（４−メトキシフェニル）エーテル等のポリエーテル化合物、炭酸ジフェニル、シュウ酸ジベンジル、シュウ酸ビス（ｐ−メチルベンジル）エステル等の炭酸またはシュウ酸ジエステル誘導体等があげられ、２種以上併用して添加することもできる。
【００４７】
本発明の可逆性感熱記録材料に用いられる支持体としては、紙、各種不織布、織布、ポリエチレンテレフタレートやポリプロピレン等の合成樹脂フィルム、ポリエチレン、ポリプロピレン等の合成樹脂をラミネートした紙、合成紙、金属箔、ガラス等、あるいはこれらを組み合わせた複合シートを目的に応じて任意に用いることができるが、これらに限定されるものではなく、これらは不透明、半透明或いは透明のいずれであってもよい。地肌を白色その他の特定の色に見せるために、白色顔料や有色染顔料や気泡を支持体中又は表面に含有させても良い。特にフィルム類等水性塗布を行なう場合で支持体の親水性が小さく可逆性感熱記録層の塗布困難な場合は、コロナ放電等による表面の親水化処理やバインダーに用いるのと同様の水溶性高分子類を、支持体表面に塗布するなどの易接着処理してもよい。
【００４８】
本発明の可逆性感熱記録材料の層構成は、可逆性感熱記録層のみであっても良い。必要に応じて、可逆性感熱記録層上に保護層を設けることも又、可逆性感熱記録層と支持体の間に水溶性高分子や白色ないし有色染顔料や中空粒子のいずれか一つ以上を含む中間層を設けることもできる。この場合、保護層及び／または中間層は２層ないしは３層以上の複数の層から構成されていてもよい。可逆性感熱記録層も各成分を一層ずつに含有させたり層別に配合比率を変化させたりして２層以上の多層にしてもよい。更に、可逆性感熱記録層中及び／または他の層及び／または可逆性感熱記録層が設けられている面と反対側の面に、電気的、光学的、磁気的に情報が記録可能な材料を含んでも良い。また、可逆性感熱記録層が設けられている面と反対側の面にブロッキング防止、カール防止、帯電防止を目的としてバックコート層を設けることもできる。
【００４９】
なお、本発明における各層を支持体上に積層し、本発明の可逆性感熱記録材料を形成する方法は特に制限されるものではなく、従来の方法により形成することができる。例えば、エアーナイフコーター、ブレードコーター、バーコーター、カーテンコーター等の塗抹装置、平版、凸版、凹版、フレキソ、グラビア、スクリーン、ホットメルト等の方式による各種印刷機等を用いる事が出来る。更に通常の乾燥工程の他、ＵＶ照射・ＥＢ照射により各層を保持させる事が出来る。
【００５０】
可逆性感熱記録層は、各成分を微粉砕して得られる各々の分散液を混合し、支持体上に塗布乾燥する方法、各成分を溶媒に溶解して得られる各々の溶液を混合し、支持体上に塗布乾燥する方法などにより得ることができる。乾燥条件は水等の分散媒ないし溶媒によっても異なる。この他に各成分を混合し加熱して可融分を溶融し熱時塗布する方法もある。
【００５１】
また、可逆性感熱記録層及び／または保護層及び／または中間層には、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、酸化ケイ素、水酸化アルミニウム、尿素−ホルマリン樹脂等の顔料、その他に、ヘッド摩耗防止、スティッキング防止等の目的でステアリン酸亜鉛、ステアリン酸カルシウム等の高級脂肪酸金属塩、パラフィン、酸化パラフィン、ポリエチレン、酸化ポリエチレン、ステアリン酸アミド、カスターワックス等のワックス類を、また、ジオクチルスルホコハク酸ナトリウム等の分散剤、更に界面活性剤、蛍光染料、紫外線吸収剤などを含有させることもできる。
【００５２】
次に、本発明の可逆性感熱記録材料の発色及び消色方法について述べる。発色を行うには、加熱に引き続き急速な冷却が起これば良く、例えばサーマルヘッド、レーザー光等による加熱により可能である。又、加熱後ゆっくり冷却すれば消色し、例えばサーマルヘッド、熱ロール、熱スタンプ、高周波加熱、熱風、電熱ヒーター及びタングステンランプ、ハロゲンランプ等の光源などからの輻射熱等を用いることにより行うことができる。
【００５３】
【作用】
本発明の感熱記録材料の画像形成及び消去原理は未だ明確ではないが、以下の様に考えられる。無色ないし淡色の染料前駆体は、フェノール性化合物のような可逆性顕色剤と共に加熱すると染料前駆体から可逆性顕色剤への電子移動が起こり発色する。この時、可逆性顕色剤分子は発色した染料分子の極めて近傍に存在していると考えられる。また、発色した染料分子から可逆性顕色剤分子を引き離すと、発色した染料分子は再び電子を受け取り、発色前の染料前駆体の状態となる。本発明は加熱により、可逆性顕色剤分子と染料分子との距離を変化させ発色及び消色を行うものと考えられる。
【００５４】
更に詳しく述べるならば、これまでに可逆性顕色剤の多くは、その構造の中に脂肪鎖を持つため、染料前駆体分子及び発色した染料分子との相溶性が低く、凝固した状態では互いに殆ど溶け合わないと考えられる。また、加熱溶融状態の様に染料前駆体分子と可逆性顕色剤分子が自由に運動できる状態では、染料前駆体分子と可逆性顕色剤分子は互いにある割合で溶け合い、発色状態となる。それ故、発色している溶融状態の混合物をゆっくり冷却すると、降温するに従い可逆性顕色剤分子と染料分子は互いに溶け合わなくなり相分離し、消色する。特に、本発明に好ましく使用される一般式（４）で表される可逆性顕色剤は分子内に、アミド結合等の水素結合能力を持つ結合を含有しているため、分子間水素結合により速やかに結晶化してしまうと考えられる。一方、急速に冷却を行うと、相分離する前、即ち発色状態のままで固化するため、発色状態が固定され固化後も発色状態が安定に保持される。
【００５５】
本発明に於いて用いられる一般式（１）、（２）あるいは（３）で表される消色促進剤は、上記可逆性顕色剤と同様に分子内に脂肪鎖及びアミド結合等の水素結合能力を持つ結合を併せ持つため、加熱により発色状態が崩れ可逆性顕色剤が染料と分離する際の結晶化の核として作用すると考えられる。さらに、本発明で用いられる消色促進剤は分子内に硫黄原子を有する化合物であり、この硫黄原子はメチレンよりも原子サイズが大きく、脂肪鎖の凝集をある程度低下させると考えられる。この様な化合物は融点以上に加熱した後、室温まで放冷した場合、再固化するのにある程度の時間を必要とするものが多い。即ちこの特性は、降温後の染料前駆体と可逆性顕色剤の相分離時に、消色時間をより助長しているものと考えられ、その結果、より低温度で消色可能となった。
【００５６】
【実施例】
以下の実施例によって本発明を更に詳しく説明する。実施例中の部数や百分率は重量基準である。
【００５７】
実施例に使用した染料前駆体を化１５に示す。
【００５８】
【化１５】

【００５９】
実施例１
（Ａ）可逆性感熱塗液の作製
例示化合物（ＢＫ−１）４０部と例示化合物（４−１）１００部を８％ポリビニルアセタール（積水化学工業製、ＢＬ−１、アセタール化度６３モル％）のテトラヒドロフラン（ＴＨＦ）溶液９１００部と共にペイントコンディショナーで粉砕し可逆性顕色剤分散液（Ａ液）を得た。更に、例示化合物（１−１）２０部をＴＨＦ２０部と共にペイントコンディショナーで粉砕し消色促進剤分散液（Ｂ液）を得た。これらＡ液及びＢ液の２種の分散液を混合し、可逆性感熱塗液を作製した。
【００６０】
（Ｂ）可逆性感熱記録層の塗工
（Ａ）で作製した可逆性感熱塗液にコロネートＬ（日本ポリウレタン株式会社製）２９部を加えた後、ポリエチレンテレフタレート（ＰＥＴ）シートに、固形分塗抹量４.０ｇ／ｍ²となる様に塗抹した。６０℃で２４時間乾燥し、スーパーカレンダーで処理して可逆性感熱記録材料を得た。
【００６１】
（Ｃ）保護層の塗工
（Ｂ）で作製した塗工シート上に、アロニックスＭ８０３０（東亞合成化学工業製）９０部、Ｎ−ビニル−２−ピロリドン５部、イルガキュア５００（日本チバガイギー製）５部、及びニップシールＥ２２０Ａ（日本シリカ製）１０部を加え攪拌後、保護層の塗液とし、１.０ｇ／ｍ²となるように塗工した後、紫外線照射装置にて硬化を行い、保護層を有する可逆性感熱記録材料を得た。
【００６２】
実施例１と同様に、本発明に好ましく用いられる一般式（４）で表される可逆性顕色剤、染料前駆体及び一般式（１）〜（３）で表される消色促進剤の組み合わせを表１に示す。
【００６３】
【表１】

【００６４】
比較例に使用した消色促進剤を化１６に示す。
【００６５】
【化１６】

【００６６】
比較例１
実施例６で用いた例示化合物（２−１）を使用しなかった他は、実施例６と同様にして可逆性感熱記録材料を得た。
【００６７】
比較例２
実施例３で用いた例示化合物（１−７）の代わりに例示化合物（５−１）を使用した他は、実施例３と同様にして可逆性感熱記録材料を得た。
【００６８】
比較例３
実施例８で用いた例示化合物（３−８）の代わりに例示化合物（５−２）を使用した他は、実施例８と同様にして可逆性感熱記録材料を得た。
【００６９】
比較例４
実施例１０で用いた例示化合物（１−６）を使用しなかった他は、実施例１０と同様にして可逆性感熱記録材料を得た。
【００７０】
比較例５
実施例１２で用いた例示化合物（２−２）の代わりに例示化合物（５−１）を使用した他は、実施例１２と同様にして可逆性感熱記録材料を得た。
【００７１】
比較例６
実施例１４で用いた例示化合物（３−１）の代わりに例示化合物（５−３）を使用した他は、実施例１４と同様にして可逆性感熱記録材料を得た。
【００７２】
試験１（発色濃度＝熱応答性）
実施例１〜１６及び比較例１〜６で得た可逆性感熱記録材料を、京セラ製印字ヘッドＫＪＴ−２５６−８ＭＧＦ１付き大倉電気製感熱ファクシミリ印字試験機ＴＨ−ＰＭＤを用いて印加パルス１.１ミリ秒で印加電圧２６ボルトの条件で 印字し、得られた発色画像の濃度を濃度計マクベスＲＤ９１８を用いて測定した。
【００７３】
試験２（画像の消去性）
実施例１〜１６及び比較例１〜６で得た可逆性感熱記録材料を、京セラ製印字ヘッドＫＪＴ−２５６−８ＭＧＦ１付き大倉電気製感熱ファクシミリ印字試験機ＴＨ−ＰＭＤを用いて印加パルス１.１ミリ秒で印加電圧２６ボルトの条件で 印字し、これを熱スタンプを用いて１２０℃で１秒間加熱した後、試験１と同様にして濃度を測定した。
【００７４】
試験３（消色開始温度）
実施例１〜１６及び比較例１〜６で得た可逆性感熱記録材料を、京セラ製印字ヘッドＫＪＴ−２５６−８ＭＧＦ１付き大倉電気製感熱ファクシミリ印字試験機ＴＨ−ＰＭＤを用いて印加パルス１.１ミリ秒で印加電圧２６ボルトの条件で 印字し、これを熱スタンプを用いて８０℃から１７０℃まで１０℃間隔で計１０箇所、各々１秒間加熱した後、試験１と同様にしてそれぞれの濃度を測定した。印字画像の光学濃度が０.１５を下回った加熱温度を消色開始温度とした。
【００７５】
試験４（発色濃度の経時変化＝画像安定性）
実施例１〜１６及び比較例１〜６で得た可逆性感熱記録材料を、京セラ製印字ヘッドＫＪＴ−２５６−８ＭＧＦ１付き大倉電気製感熱ファクシミリ印字試験機ＴＨ−ＰＭＤを用いて、印加パルス１.１ミリ秒で印加電圧２６ボルトの条件 で印字し、温度５０℃、相対湿度２０％の雰囲気下に２４時間保存した後、試験１と同様にして、発色部の濃度を測定し、下記数１により画像残存率を計算した。
【００７６】
【数１】

【００７７】
実施例１〜１６及び比較例１〜６の試験１〜４の結果を表２に示した。
【００７８】
【表２】

【００７９】
【発明の効果】
表２に示したように、無色ないし淡色の染料前駆体と、加熱後の冷却速度の違いにより該染料前駆体に可逆的な色調変化を生じせしめる可逆性顕色剤とを含有する可逆性感熱記録材料において、一般式（１）〜（３）で表される消色促進剤を含有させることにより、明瞭なコントラストで画像の形成・消去が可能で、日常生活の環境下で経時的に安定な画像が保持可能であり、更に画像の消去温度領域を下げる事も可能となり、より実用性の高い可逆性感熱記録材料を得ることができた。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reversible thermosensitive recording material capable of forming and erasing images by controlling thermal energy.
[0002]
[Prior art]
In general, a heat-sensitive recording material is obtained by providing a heat-sensitive recording layer mainly comprising an electron-donating colorless or light-colored dye precursor and an electron-accepting developer on a support. By heating with a laser beam or the like, the dye precursor and the developer react instantaneously to obtain a recorded image, which is disclosed in Japanese Patent Publication Nos. 43-4160 and 45-14039. .
[0003]
In general, since such a heat-sensitive recording material cannot form an image once erased and return to the state before the image formation again, when information is further recorded, the image is not formed. There was no choice but to add to. For this reason, the area of the thermal recording portion is limited, so that all necessary information cannot be recorded.
[0004]
In recent years, a reversible thermosensitive recording material capable of repeatedly forming and erasing images has been devised in order to cope with such problems. For example, Japanese Patent Application Laid-Open Nos. 54-119377, 63-39377, and 63-41186 are composed of a resin base material and organic small molecules dispersed in the resin base material. Thermal recording materials are described. However, since this method reversibly changes the transparency of the heat-sensitive recording material by heat energy, it cannot be said that the contrast between the image forming portion and the image non-forming portion is sufficient.
[0005]
In the methods described in JP-A-50-81157 and JP-A-50-105555, the formed image changes depending on the environmental temperature. However, these two states cannot be stably maintained for an arbitrary period at room temperature.
[0006]
Furthermore, Japanese Patent Application Laid-Open No. 59-120492 describes a method of maintaining the image forming state / erased state by utilizing the hysteresis characteristic of the color component and maintaining the recording material in the hysteresis temperature range. In this method, a heating source and a cooling source are required for image formation and erasure, and the temperature range in which the image formation state and the erasure state can be maintained is limited to the hysteresis temperature range. It is still insufficient for use in
[0007]
On the other hand, in JP-A-2-188293, JP-A-2-188294, and International Publication No. WO90 / 11898, a reversible feeling composed of a leuco dye and a color-reducing agent that develops and decolors the leuco dye by heating. A thermal recording medium is described. The developer / subtractor is an amphoteric compound having an acidic group that develops color of the leuco dye and a basic group that erases the developed leuco dye. One is preferentially generated, and coloring and decoloring are performed. However, with this method, it is impossible to completely switch between the color developing reaction and the color erasing reaction only by controlling the heat energy, and since both reactions occur at a certain ratio simultaneously, a sufficient color density cannot be obtained, and the color erasing reaction cannot be obtained. Cannot be performed completely, and sufficient contrast cannot be obtained. Further, since the decoloring action of the basic group also acts on the color development part at room temperature, the phenomenon that the density of the color development part decreases with time is unavoidable. Further, JP-A-5-124360 describes a reversible thermosensitive recording medium that develops and decolors a leuco dye by heating. As a reversible developer, an organic phosphonic acid compound, an α-hydroxy aliphatic carboxylic acid. Specific phenol compounds such as fatty acid dicarboxylic acid and alkylthiophenol having 12 or more aliphatic groups, alkyloxyphenol, alkylcarbamoylphenol, gallic acid alkyl ester are exemplified. However, this recording medium cannot solve the two problems of low color density or incomplete erasing at the same time. Furthermore, the stability over time of the image is not satisfactory in practice. Further, in JP-A-5-294063, various kinds of fatty acid, wax, higher alcohol, phosphoric acid / benzoic acid / phthalic acid or oxyacid are used as a decoloring accelerator for improving the erasability of the reversible thermosensitive recording medium. Esters, silicone oils, liquid crystal compounds, surfactants, fatty acid saturated hydrocarbons having 10 or more carbon atoms, and the like have been disclosed, but their effects are small and the image density at the time of erasure is high, so it cannot be said that they are practical.
[0008]
As described above, the conventional technology has a clear image contrast, enables the formation and complete erasure of high-density images, and is a practical reversible thermosensitive recording capable of maintaining a stable image over time in the environment of daily life. The production of the material has been difficult. On the other hand, the applicants already disclosed in Japanese Patent Application Laid-Open Nos. 7-179043 and 7-214907 cause reversible color change, that is, color development and decoloration, by heating a colorless or light dye precursor. We have found that reversible developers exist, but in order to obtain better image quality and easy-to-use recording media, the image density during erasing, the erasing start temperature, and the erasing temperature range are improved. There was room to do.
[0009]
Thereafter, a reversible thermosensitive recording medium using a specific compound serving as a color-decoloration controlling agent for a long-chain aliphatic hydrocarbon compound containing a heteroatom has been proposed in JP-A No. 11-70731. Thus, a satisfactory reversible thermosensitive recording material has not been obtained.
[0010]
[Problems to be solved by the invention]
An object of the present invention is to provide a heat-sensitive recording material capable of forming and erasing an image with a good contrast and capable of retaining a stable image over time in an environment of daily life. More specifically, the image density at the time of erasing is lower, there is less unerased, and the erasing temperature can be uniformly erased at a lower temperature and in a wide temperature range, and the erasing characteristics at a higher speed. It is an object of the present invention to provide a reversible heat-sensitive recording material having a good quality.
[0011]
[Means for Solving the Problems]
The present inventors include a reversible developer containing a colorless or pale dye precursor on a support and a reversible developer that causes a reversible color change in the dye precursor due to a difference in cooling rate after heating. In the heat-sensitive recording material, by containing at least one compound having a sulfur atom, a hydrogen bond group and a hydrocarbon group in the molecule as a decoloring accelerator, the image can be completely erased in a wide temperature range. The present invention was completed by finding that a reversible thermosensitive recording material that can be carried out uniformly, has image stability that is practically acceptable in daily life, and that can be printed and erased at a higher speed is obtained. It came to do.
[0012]
That is, according to the present invention, a novel hydrocarbon compound having a sulfur atom and a hydrogen bonding group represented by the following general formulas (1) to (3) is provided.
[Chemical formula 5]

In the formula (1), Xa and Xb each represents a sulfur atom, and the other represents a divalent hydrogen bond group having a —CONH— bond that does not contain a hydrocarbon group at both ends as a minimum structural unit. R ¹ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms. R ² and A represent a divalent hydrocarbon group having 1 to 18 carbon atoms.
[0013]
[Chemical 6]

In the formula (2), Xc represents a divalent group having a —CONH— bond that does not contain a hydrocarbon group at both ends as a minimum structural unit. R ³ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms. R ⁴ represents a divalent hydrocarbon group having 1 to 18 carbon atoms.
[0014]
[Chemical 7]

In formula (3), Xd represents a divalent group having —CONH— bonds that do not contain a hydrocarbon group at both ends as the minimum structural unit. R ⁵ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms that does not contain a nitrogen atom. R ⁷ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms. R ⁶ represents a divalent hydrocarbon group having 1 to 18 carbon atoms.
[0015]
In the compound represented by the general formula (1), R ¹ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms, preferably a monovalent hydrocarbon group having 6 to 20 carbon atoms. A and R ² each represent a divalent hydrocarbon group having 1 to 18 carbon atoms, preferably a hydrocarbon group having 1 to 12 carbon atoms. Specifically, A, R ¹ and R ² mainly represent an alkylene group and an alkyl group, respectively, but each group may contain an aromatic ring. On the other hand, Xa and Xb represent a divalent group (hereinafter referred to as HBG) in which one represents a sulfur atom and the other has a —CONH— bond that does not contain a hydrocarbon group at both ends and has a minimum structural unit. For example, when Xa is a sulfur atom, Xb represents HBG, and conversely, when Xa is HBG, Xb represents a sulfur atom. Specific examples of HBG include amide (—CONH—, —NHCO—), urea (—NHCONH—), urethane (—NHCOO—, —OCONH—), diacylamine (—CONHCO—), diacyl hydrazide (—CONHNHCO—). ), Oxalic acid diamide (-NHCONCONH-), acyl urea (-CONHCONH-, -NHCONHCO-), 3-acylcarbazic acid ester (-CONHNHCOO-), semicarbazide (-NHCONNHNH-, -NHNHCONH-), acyl semicarbazide ( -CONHNHCONH -, - NHCONHNHCO-), diacyl aminomethane (-CONHCH ₂ NHCO -), 1- acylamino-1- Ureidometan _{(-CONHCH 2 NHCONH -, - NHCONHCH} 2 NHCO-), Ma N'amido (-NHCOCH ₂ CONH-) group and the like.
[0016]
Specific examples of the erasing accelerator represented by the general formula (1) are shown in Chemical Formulas 8 to 9, below, but the present invention is not limited thereto.
[0017]
[Chemical 8]

[0018]
[Chemical 9]

[0019]
In the compound represented by the general formula (2), R ³ has the same meaning as R ^{1 in the} general formula (1). Similarly, R ⁴ has the same meaning as R ² . Xc represents HBG, and specific examples thereof are synonymous with the bonding groups listed in the general formula (1).
[0020]
Specific examples of the reversible developer represented by the general formula (2) are shown in Chemical Formula 10 below, but the present invention is not limited thereto.
[0021]
[Chemical Formula 10]

[0022]
In the compound represented by the general formula (3), R ⁵ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms that does not contain a nitrogen atom, preferably one that does not contain a nitrogen atom having 6 to 20 carbon atoms. Valent hydrocarbon group. R ⁷ has the same meaning as R ^{1 in the} general formula (1). Similarly, R ⁶ has the same meaning as R ² . Xd represents HBG, and specific examples thereof are synonymous with the bonding groups listed in the general formula (1).
[0023]
Specific examples of the compound represented by the general formula (3) include a compound represented by the following chemical formula 11, but the present invention is not limited thereto.
[0024]
Embedded image

[0025]
In the present invention, the phenolic compound represented by the general formula (4) is used as a reversible developer.
[0026]
Embedded image

In formula (4), Xf and Xg represent an oxygen atom, a sulfur atom, or a divalent group having a —CONH— bond that does not contain a hydrocarbon group at both ends as a minimum structural unit. R ⁸ represents a single bond or a divalent hydrocarbon group having 1 to 12 carbon atoms. R ⁹ represents a divalent hydrocarbon group having 1 to 18 carbon atoms. R ¹⁰ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms. n represents an integer of 0 to 4, and when n is 2 or more, R ⁹ and Xg that are repeated may be the same or different. In addition, when n = 0, Xf is a divalent group having a minimum constituent unit of a —CONH— bond that does not contain a hydrocarbon group at both ends. When n is 1 or more, at least one selected from Xf and Xg is a divalent group having —CONH— bonds that do not contain a hydrocarbon group at both ends as a minimum structural unit.
[0027]
In the compound represented by the general formula (4), R ¹⁰ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms, preferably a monovalent hydrocarbon group having 6 to 20 carbon atoms. R ⁸ represents a single bond or a divalent hydrocarbon group having 1 to 12 carbon atoms. R ⁹ represents a divalent hydrocarbon group having 1 to 18 carbon atoms, preferably a hydrocarbon group having 1 to 12 carbon atoms. Specifically, R ⁸ , R ⁹ and R ¹⁰ mainly represent an alkylene group and an alkyl group, respectively, but each group may contain an aromatic ring. On the other hand, Xf and Xg represent an oxygen atom, a sulfur atom or HBG, and specific examples of HBG are synonymous with the bonding groups listed in the general formula (1). n represents an integer of 0 to 4, and when n is 2 to 4, R ⁹ and X ^{g that} are repeated may be the same or different. When n is 0, Xf is HBG. When n is 1 or more, at least one selected from Xf and Xg is HBG.
[0028]
Specific examples of the compound represented by the general formula (4) include compounds shown in the following chemical formulas 13 and 14, but the present invention is not limited thereto.
[0029]
Embedded image

[0030]
Embedded image

[0031]
The preferred amount of the compound represented by the general formula (1), (2) or (3) is 0.1% by weight or more and 1000% by weight or less with respect to the reversible developer represented by the general formula (4). More preferably, it is 0.5 wt% or more and 200 wt% or less. Further, considering the heat-resistant storage stability of the printed image, the content is most preferably 1% by weight or more and 100% by weight or less. The compounds represented by the general formula (1), (2) or (3) can be used alone or in combination of two or more.
[0032]
The reversible color developer according to the present invention may be used alone or in combination of two or more. The amount of the reversible color developer according to the present invention for a colorless or light dye precursor is 5 to 5000. % By weight, preferably 10 to 3000% by weight.
[0033]
The colorless or light-colored dye precursor used in the present invention is generally represented by known compounds used for pressure-sensitive recording paper, heat-sensitive recording paper, etc., but is not particularly limited. Specific examples include the following, but the present invention is not limited thereto.
[0034]
(1) Triarylmethane compounds 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- ( p-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- ( p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) Phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4- Azaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4,7-diazaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -7-azaphthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3- Bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3- Bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, -p- dimethylaminophenyl-3- (1-methylpyrrole-2-yl) -6-dimethylaminophthalide, 3,3-bis (p- dimethylaminophenyl) -4-azaphthalide, and the like.
[0035]
(2) Diphenylmethane compounds 4,4'-bis (dimethylaminophenyl) benzhydrylbenzyl ether, N-chlorophenyl leucooramine, N-2,4,5-trichlorophenyl leucooramine and the like.
[0036]
(3) Xanthene compounds Rhodamine B anilinolactam, rhodamine Bp-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7 -Phenylfluorane, 3-diethylamino-7-phenoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7- (3,4 Dichloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane,
[0037]
3-diethylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-ani Linofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-phenethylfluorane, 3-diethylamino-7- (4-nitroanilino) fluorane, 3-dibutylamino-6-methyl-7 -Anilinofluorane, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-ani Linofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tetrahydrofuryl) amino-6-methyl 7-anilinofluoran like.
[0038]
(4) Thiazine compounds benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, and the like.
[0039]
(5) Spiro compounds 3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyrans, 3,3'-dichlorospirodinaphthopyrans, 3-benzylspirodinaphthopyrans, 3-methylnaphthyl (3-methoxybenzo) ) Spiropyran, 3-propyl spirobenzopyran and the like.
[0040]
The colorless or light dye precursors may be used alone or in admixture of two or more.
[0041]
Specific examples of the method for producing the reversible thermosensitive recording material of the present invention include a dye precursor and a reversible developer as main components, and the compound according to the present invention is added thereto and coated on a support to reversible feel. The method of forming a thermal recording layer is mentioned.
[0042]
The coating liquid preparation method for incorporating the dye precursor, the reversible developer, and the compound according to the present invention into the reversible thermosensitive recording layer includes dissolving each compound alone in a solvent or dispersing in a dispersion medium and mixing. A method in which each compound is mixed and then dissolved in a solvent or dispersed in a dispersion medium, a method in which each compound is dissolved by heating, homogenized, cooled, and dissolved in a solvent or dispersed in a dispersion medium. However, it is not particularly limited. If necessary, a dispersing agent may be used during dispersion. When water is used as a dispersion medium, water-soluble polymers such as polyvinyl alcohol and various surfactants can be used as the dispersant. In aqueous dispersion, a water-soluble organic solvent such as ethanol may be mixed. In addition, when an organic solvent typified by hydrocarbons is a dispersion medium, lecithin, phosphate esters, or the like may be used as a dispersant.
[0043]
It is also possible to add a binder to the reversible thermosensitive recording layer for the purpose of improving the strength of the reversible thermosensitive recording layer. Specific examples of the binder include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic. Water-soluble polymers such as acid ester / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylic acid Esters, styrene / butadiene copolymers, acrylonitrile / butadiene copolymers, methyl acrylate / butadiene copolymers, ethylene / vinyl acetate copolymers, ethylene / vinyl chloride copolymers, polyvinyl chloride, ethylene Vinylidene chloride copolymers, latexes such as polyvinylidene chloride. The role of these binders is to keep the materials of the composition uniformly dispersed without being displaced by the application of heat for printing and erasing. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. Recently, reversible thermosensitive recording materials with high added value such as prepaid cards and stored cards are often used, and accordingly, highly durable products such as heat resistance, water resistance, and adhesiveness are required. It is becoming. For such a requirement, a curable resin is particularly preferable.
[0044]
Examples of the curable resin include a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. Examples of the thermosetting resin include those that are cured by reacting a hydroxyl group or a carboxyl group with a crosslinking agent, such as phenoxy resin, polyvinyl butyral resin, and cellulose acetate propionate resin. Examples of the crosslinking agent at this time include isocyanates, amines, phenols, epoxies, and the like.
[0045]
Monomers used for electron beams and cured wire resins include monofunctional monomers typified by acrylics, bifunctional monomers, polyfunctional monomers, and the like. A polymerization accelerator is used.
[0046]
Further, as an additive for adjusting the color development sensitivity of the reversible thermosensitive recording layer, a thermofusible substance can be contained in the reversible thermosensitive recording layer. Those having a melting point of 60 ° C. to 200 ° C. are preferred, and those having a melting point of 80 ° C. to 180 ° C. are particularly preferred. Sensitizers used for general heat-sensitive recording paper can also be used. These compounds include N-hydroxymethyl stearamide, behenamide, stearamide, and palmitic acid amides, naphthol derivatives such as 2-benzyloxynaphthalene, p-benzylbiphenyl, 4-allyloxybiphenyl. Biphenyl derivatives such as 1,2-bis (3-methylphenoxy) ethane, 2,2′-bis (4-methoxyphenoxy) diethyl ether, polyether compounds such as bis (4-methoxyphenyl) ether, diphenyl carbonate, Examples include carbonic acid or oxalic acid diester derivatives such as dibenzyl oxalate and bis (p-methylbenzyl) oxalate, and two or more of them can be used in combination.
[0047]
Supports used in the reversible thermosensitive recording material of the present invention include paper, various nonwoven fabrics, woven fabrics, synthetic resin films such as polyethylene terephthalate and polypropylene, paper laminated with synthetic resins such as polyethylene and polypropylene, synthetic paper, metal Foil, glass, etc., or a composite sheet combining these can be arbitrarily used depending on the purpose, but is not limited to these, and these may be opaque, translucent or transparent. In order to make the background appear white or other specific colors, a white pigment, a colored dye pigment, or air bubbles may be included in the support or on the surface. In particular, when water-based coatings such as films are used and the hydrophilicity of the support is small and it is difficult to coat the reversible thermosensitive recording layer, the same water-soluble polymer as used for the surface hydrophilization treatment by corona discharge or the like or the binder is used. An adhesive may be applied to the surface of the support to facilitate adhesion.
[0048]
The layer structure of the reversible thermosensitive recording material of the present invention may be only the reversible thermosensitive recording layer. If necessary, a protective layer may be provided on the reversible thermosensitive recording layer, and any one or more of a water-soluble polymer, white or colored dye pigment, and hollow particles may be provided between the reversible thermosensitive recording layer and the support. An intermediate layer containing can also be provided. In this case, the protective layer and / or the intermediate layer may be composed of a plurality of layers of two layers or three or more layers. The reversible thermosensitive recording layer may also be composed of two or more layers by adding each component one by one or changing the blending ratio for each layer. Further, a material capable of recording information electrically, optically, and magnetically in the reversible thermosensitive recording layer and / or on the surface opposite to the other layer and / or the surface on which the reversible thermosensitive recording layer is provided. May be included. In addition, a backcoat layer can be provided on the surface opposite to the surface on which the reversible thermosensitive recording layer is provided for the purpose of preventing blocking, curling and antistatic.
[0049]
The method for laminating each layer in the present invention on a support and forming the reversible thermosensitive recording material of the present invention is not particularly limited, and can be formed by a conventional method. For example, smearing devices such as an air knife coater, blade coater, bar coater, curtain coater, etc., and various printing machines such as lithographic plates, relief plates, intaglio plates, flexo, gravure, screen, hot melt, etc. can be used. Furthermore, each layer can be held by UV irradiation and EB irradiation in addition to a normal drying process.
[0050]
The reversible thermosensitive recording layer is a method of mixing each dispersion obtained by finely pulverizing each component, coating and drying on a support, mixing each solution obtained by dissolving each component in a solvent, It can be obtained by a method of coating and drying on a support. Drying conditions vary depending on the dispersion medium or solvent such as water. In addition, there is a method in which each component is mixed and heated to melt the fusible component and applied while hot.
[0051]
The reversible thermosensitive recording layer and / or protective layer and / or intermediate layer includes diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea. -Pigments such as formalin resin, in addition to higher fatty acid metal salts such as zinc stearate and calcium stearate for the purpose of preventing head wear and sticking, paraffin, oxidized paraffin, polyethylene, polyethylene oxide, stearamide, caster wax, etc. In addition, a dispersant such as sodium dioctyl sulfosuccinate, a surfactant, a fluorescent dye, an ultraviolet absorber, and the like can also be contained.
[0052]
Next, the coloring and decoloring methods of the reversible thermosensitive recording material of the present invention will be described. In order to perform color development, it is sufficient that rapid cooling occurs following heating, and for example, heating by a thermal head, laser light or the like is possible. Moreover, if it cools slowly after heating, it will decolorize, for example, using a thermal head, a heat roll, a heat stamp, high-frequency heating, hot air, an electric heater, and radiant heat from a light source such as a tungsten lamp and a halogen lamp. it can.
[0053]
[Action]
The image forming and erasing principles of the heat-sensitive recording material of the present invention are not yet clear, but are considered as follows. When a colorless or light-colored dye precursor is heated together with a reversible developer such as a phenolic compound, electron transfer from the dye precursor to the reversible developer occurs and color develops. At this time, it is considered that the reversible developer molecule exists in the very vicinity of the colored dye molecule. Further, when the reversible developer molecule is pulled away from the colored dye molecule, the colored dye molecule receives electrons again and becomes a dye precursor state before coloring. In the present invention, it is considered that coloring and decoloring are performed by changing the distance between the reversible developer molecule and the dye molecule by heating.
[0054]
In more detail, since many of the reversible developers so far have a fatty chain in their structure, they have low compatibility with the dye precursor molecule and the colored dye molecule, and in the solidified state, It is thought that it hardly melts. In addition, in a state where the dye precursor molecule and the reversible developer molecule can freely move as in the heat-melted state, the dye precursor molecule and the reversible developer molecule are melted at a certain ratio to form a color state. Therefore, when the colored mixture that has been colored is cooled slowly, the reversible developer molecule and the dye molecule become insoluble and phase-separate and decolorize as the temperature decreases. In particular, since the reversible developer represented by the general formula (4) preferably used in the present invention contains a bond having a hydrogen bonding ability such as an amide bond in the molecule, the intermolecular hydrogen bond causes It is thought that it crystallizes quickly. On the other hand, when rapidly cooled, it solidifies before phase separation, that is, in a colored state, so that the colored state is fixed and the colored state is stably maintained even after solidification.
[0055]
The decolorization accelerator represented by the general formula (1), (2) or (3) used in the present invention is a hydrogen atom such as an aliphatic chain and an amide bond in the molecule, like the reversible developer. Since it has a bond having a binding ability, it is considered that the color development state is lost by heating and it acts as a crystallization nucleus when the reversible developer is separated from the dye. Further, the decoloring accelerator used in the present invention is a compound having a sulfur atom in the molecule, and this sulfur atom has an atomic size larger than that of methylene, and is considered to reduce the aggregation of fatty chains to some extent. Many of these compounds require a certain amount of time to re-solidify when heated to room temperature or higher and then allowed to cool to room temperature. That is, this characteristic is considered to further promote the decoloring time during the phase separation of the dye precursor and the reversible developer after the temperature decrease, and as a result, the color can be decolored at a lower temperature.
[0056]
【Example】
The following examples further illustrate the present invention. The parts and percentages in the examples are based on weight.
[0057]
The dye precursor used in the examples is shown in Chemical formula 15.
[0058]
Embedded image

[0059]
Example 1
(A) Preparation of reversible thermosensitive coating liquid 40 parts of the exemplified compound (BK-1) and 100 parts of the exemplified compound (4-1) were 8% polyvinyl acetal (Sekisui Chemical Co., Ltd., BL-1, acetalization degree 63 mol%) ) Was pulverized with a paint conditioner together with 9100 parts of a tetrahydrofuran (THF) solution to obtain a reversible developer dispersion (liquid A). Furthermore, 20 parts of Exemplified Compound (1-1) was pulverized with 20 parts of THF with a paint conditioner to obtain a decolorization accelerator dispersion (liquid B). These two types of dispersion liquids A and B were mixed to prepare a reversible thermosensitive coating liquid.
[0060]
(B) Coating of reversible thermosensitive recording layer After adding 29 parts of Coronate L (manufactured by Nippon Polyurethane Co., Ltd.) to the reversible thermosensitive coating liquid prepared in (A), a solid content smear is applied to a polyethylene terephthalate (PET) sheet. was spread as the amount 4.0g / m ^2. The material was dried at 60 ° C. for 24 hours and treated with a super calendar to obtain a reversible thermosensitive recording material.
[0061]
(C) Coating of protective layer 90 parts of Aronix M8030 (manufactured by Toagosei Co., Ltd.), 5 parts of N-vinyl-2-pyrrolidone, Irgacure 500 (manufactured by Ciba Geigy Japan) 5 on the coated sheet prepared in (B) And 10 parts of nip seal E220A (manufactured by Nippon Silica), and after stirring, a coating solution for the protective layer was applied to 1.0 g / m ² , followed by curing with an ultraviolet irradiation device and a protective layer. A reversible thermosensitive recording material having
[0062]
As in Example 1, the reversible developer represented by the general formula (4), the dye precursor, and the decolorization accelerator represented by the general formulas (1) to (3) preferably used in the present invention. The combinations are shown in Table 1.
[0063]
[Table 1]

[0064]
The decoloring accelerator used in the comparative example is shown in Chemical formula 16.
[0065]
Embedded image

[0066]
Comparative Example 1
A reversible thermosensitive recording material was obtained in the same manner as in Example 6 except that the exemplified compound (2-1) used in Example 6 was not used.
[0067]
Comparative Example 2
A reversible thermosensitive recording material was obtained in the same manner as in Example 3, except that the exemplified compound (5-1) was used instead of the exemplified compound (1-7) used in Example 3.
[0068]
Comparative Example 3
A reversible thermosensitive recording material was obtained in the same manner as in Example 8, except that the exemplified compound (5-2) was used instead of the exemplified compound (3-8) used in Example 8.
[0069]
Comparative Example 4
A reversible thermosensitive recording material was obtained in the same manner as in Example 10 except that the exemplified compound (1-6) used in Example 10 was not used.
[0070]
Comparative Example 5
A reversible thermosensitive recording material was obtained in the same manner as in Example 12 except that the exemplified compound (5-1) was used instead of the exemplified compound (2-2) used in Example 12.
[0071]
Comparative Example 6
A reversible thermosensitive recording material was obtained in the same manner as in Example 14 except that the exemplified compound (5-3) was used instead of the exemplified compound (3-1) used in Example 14.
[0072]
Test 1 (color density = thermal response)
The reversible thermosensitive recording materials obtained in Examples 1 to 16 and Comparative Examples 1 to 6 were subjected to application pulse 1.1 using an Okura Electric thermosensitive facsimile printing tester TH-PMD with a Kyocera print head KJT-256-8MGF1. Printing was performed in milliseconds at an applied voltage of 26 volts, and the density of the resulting color image was measured using a densitometer Macbeth RD918.
[0073]
Test 2 (image erasability)
The reversible thermosensitive recording materials obtained in Examples 1 to 16 and Comparative Examples 1 to 6 were subjected to application pulse 1.1 using an Okura Electric thermosensitive facsimile printing tester TH-PMD with a Kyocera print head KJT-256-8MGF1. Printing was performed in milliseconds at an applied voltage of 26 volts, and this was heated at 120 ° C. for 1 second using a heat stamp, and then the density was measured in the same manner as in Test 1.
[0074]
Test 3 (decoloration start temperature)
The reversible thermosensitive recording materials obtained in Examples 1 to 16 and Comparative Examples 1 to 6 were subjected to application pulse 1.1 using an Okura Electric thermosensitive facsimile printing tester TH-PMD with a Kyocera print head KJT-256-8MGF1. Printing was performed in milliseconds under the condition of an applied voltage of 26 volts, and this was heated for 1 second each at 10 ° C. intervals from 80 ° C. to 170 ° C. using a heat stamp. Was measured. The heating temperature at which the optical density of the printed image fell below 0.15 was defined as the decolorization start temperature.
[0075]
Test 4 (Change in color density over time = image stability)
The reversible thermosensitive recording materials obtained in Examples 1 to 16 and Comparative Examples 1 to 6 were subjected to an applied pulse of 1. using Okura Electric thermosensitive facsimile printing tester TH-PMD with Kyocera print head KJT-256-8MGF1. After printing for 1 millisecond under an applied voltage of 26 volts and storing for 24 hours in an atmosphere at a temperature of 50 ° C. and a relative humidity of 20%, the density of the colored portion was measured in the same manner as in Test 1, and the following formula 1 The image residual ratio was calculated by
[0076]
[Expression 1]

[0077]
The results of Tests 1 to 4 of Examples 1 to 16 and Comparative Examples 1 to 6 are shown in Table 2.
[0078]
[Table 2]

[0079]
【The invention's effect】
As shown in Table 2, a reversible thermosensitive material containing a colorless or light-colored dye precursor and a reversible developer that causes a reversible color change in the dye precursor due to a difference in cooling rate after heating. By including a decoloring accelerator represented by the general formulas (1) to (3) in the recording material, it is possible to form and erase an image with clear contrast and is stable over time in the environment of daily life. A reversible thermosensitive recording material with higher practicality could be obtained.

Claims (2)

In a reversible thermosensitive recording material comprising a colorless or pale dye precursor on a support and a reversible developer that causes a reversible color change in the dye precursor due to a difference in cooling rate after heating, As a decoloring accelerator, at least one compound represented by the following general formulas (1), (2) and (3) is used, and as a reversible developer, a compound represented by the following general formula (4) A reversible thermosensitive recording material using at least one kind .

(In the formula 1, Xa and Xb, one represents a sulfur atom, .R ¹ and the other represents a divalent hydrogen bonding group of -CONH- bond that does not contain hydrocarbon groups at both ends to minimize structural units Represents a monovalent hydrocarbon group having 1 to 24 carbon atoms, and R ² and A represent a divalent hydrocarbon group having 1 to 18 carbon atoms.)

(In Formula 2, Xc represents a divalent group having a —CONH— bond that does not contain a hydrocarbon group at both ends as a minimum structural unit. R ³ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms. R ⁴ represents a divalent hydrocarbon group having 1 to 18 carbon atoms.)

(In Formula 3, Xd represents a divalent group having a —CONH— bond that does not contain a hydrocarbon group at both ends as a minimum constituent unit. R ⁵ is a monovalent group having 1 to 24 carbon atoms that does not contain a nitrogen atom. Represents a hydrocarbon group, R ⁷ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms, and R ⁶ represents a divalent hydrocarbon group having 1 to 18 carbon atoms.)

(In Formula 4, Xf and Xg represent an oxygen atom, a sulfur atom, or a divalent group having a —CONH— bond that does not include a hydrocarbon group at both ends as a minimum structural unit. R ⁸ is a single bond or a carbon number of 1 Represents a divalent hydrocarbon group having ˜12, R ⁹ represents a divalent hydrocarbon group having 1 to 18 carbon atoms, R ¹⁰ represents a monovalent hydrocarbon group having 1 to 24 carbon atoms, and n represents Represents an integer of 0 to 4, and R ⁹ and Xg repeated when n is 2 or more may be the same or different, and when n = 0, Xf includes a hydrocarbon group at both ends. A divalent group having a —CONH— bond as the minimum constituent unit, and when n is 1 or more, at least one selected from Xf and Xg is a minimum of a —CONH— bond that does not contain a hydrocarbon group at both ends. (It is a divalent group as a structural unit.)   2. The reversible thermosensitive recording material according to claim 1, wherein the hydrocarbon group of the decoloring accelerator is an aliphatic hydrocarbon group.