JP3832711B2 - Reversible thermosensitive coloring composition and reversible thermosensitive recording medium using the same - Google Patents

Description

」によって達成される。
【００１０】
また、更に（２）「前記（１）項に記載の可逆性感熱発色組成物を主成分として含有する記録層を支持体上に設けることを特徴とする可逆性感熱記録媒体」によって達成される。
【００１１】
本発明の可逆性感熱発色組成物は、基本的に前記の顕色剤と発色剤を組み合わせることによって構成されるものである。本発明で用いる発色剤は電子供与性を示すものであり、それ自体無色或いは淡色の染料前駆体（ロイコ染料）であり、特に限定されず、従来公知のもの、例えばフタリド系化合物、アザフタリド系化合物、フルオラン系化合物、フェノチアジン系化合物、ロイコオーラミン系化合物などから選択できる。
【００１２】
発色剤の具体例としては、例えば次の化合物が挙げられるが、これらに限定されるものではない。
２−アニリノ−３−メチル−６−ジエチルアミノフルオラン、２−（ｏ−クロロアニリノ）−６−ジブチルアミノフルオラン、２−（Ｎ−メチル−ｏ−クロロアニリノ）−６−ジブチルアミノフルオラン、２−アニリノ−３−メチル−６−（Ｎ−ｎ−プロピル−Ｎ−メチルアミノ）フルオラン、２−アニリノ−６−（Ｎ−ｎ−ヘキシル−Ｎ−エチルアミノ）フルオラン、２，３−ジメチル−６−ジメチルアミノフルオラン、２−（ｏ−クロロアニリノ）−３−クロロ−６−ジメチルアミノフルオラン、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−３−イル）−４−アザフタリド等。
【００１３】
次に本発明の可逆性感熱記録媒体において発色剤と組み合わせて用いられる顕色剤について説明する。顕色剤には、すでに特開平５−１２４３６０号公報に長鎖炭化水素基をもつリン酸化合物、脂肪酸化合物、フェノール化合物の代表例とともに開示されているように、顕色剤と発色剤が凝集構造を形成することにより発色が安定化し、また両者のうち少なくとも一方の化合物の分子が凝集あるいは結晶化することにより、発色剤と顕色剤が相分離して消色するため、分子内に発色剤を発色させることができる顕色能をもつ構造と、分子間の凝集力をコントロールする構造を併せ持つ化合物が使用される。顕色能をもつ構造としては、一般の感熱記録媒体と同様に、たとえば、フェノール性水酸基、カルボキシル基、リン酸基などの酸性の基を有するものが用いられるが、これらに限らず発色剤を発色できる基を持つものであればよい。これらには、たとえばチオ尿素基、カルボン酸金属塩などがある。分子間の凝集力をコントロールする代表的な構造としては、長鎖アルキル基などの炭化水素基がある。この炭化水素基の炭素数は、一般的には８以上であることが良好な発色・消色特性を得る上で好ましい。また、この炭化水素基には不飽和結合が含まれていてもよく、また分枝状の炭化水素基も包含される。この場合も、主鎖部分は炭素数８以上であることが好ましい。また、この炭化水素基は、たとえば、ハロゲン原子、水酸基、アルコキシ基などの基で置換されていてもよい。
【００１４】
上記のように顕色剤は、顕色能を持つ構造と炭化水素基で代表される凝集力を制御する構造が連結した構造をもつ。この連結部分には下記に示すようなヘテロ原子を含む２価の基、または、これらの基が複数個組み合わせた基をはさんで結合していてもよい。
また、フェニレン、ナフチレンなどの芳香環または複素環などをはさんで結合していてもよいし、これら両方をはさんでいてもよい。
炭化水素基は、その鎖状構造中に上記と同様な２価の基、すなわち芳香環やヘテロ原子を含む２価の基を有するものであってもよい。
【００１５】
以下、本発明に用いられる顕色剤について具体的に例示する。
・有機リン酸系の顕色剤
有機リン酸系の顕色剤としては以下のような化合物が例示できる。
ドデシルホスホン酸、テトラデシルホスホン酸、ヘキサデシルホスホン酸、オクタデシルホスホン酸、エイコシルホスホン酸、ドコシルホスホン酸、テトラコシルホスホン酸、リン酸ジテトラデシルエステル、リン酸ジヘキサデシルエステル、リン酸ジオクタデシルエステル、リン酸ジエイコシルエステル、リン酸ジベヘニルエステルなど。
【００１６】
・脂肪族カルボン化合物
脂肪族カルボン化合物としては以下のような化合物が例示できる。
２−ヒドロキシテトラデカン酸、２−ヒドロキシヘキサデカン酸、２−ヒドロキシオクタデカン酸、２−ヒドロキシエイコサン酸、２−ヒドロキシドコサン酸、２−ブロモヘキサデカン酸、２−ブロモオクタデカン酸、２−ブロモエイコサン酸、２−ブロモドコサン酸、３−ブロモオクタデカン酸、３−ブロモドコサン酸、２，３−ジブロモオクタデカン酸、２−フルオロドデカン酸、２−フルオロテトラデカン酸、２−フルオロヘキサデカン酸、２−フルオロオクタデカン酸、２−フルオロエイコサン酸、２−フルオロドコサン酸、２−ヨードヘキサデカン酸、２−ヨードオクタデカン酸、３−ヨードヘキサデカン酸、３−ヨードオクタデカン酸、パーフルオクタデカン酸など。
【００１７】
・脂肪族ジカルボン酸およびトリカルボン酸化合物
脂肪族ジカルボン酸およびトリカルボン酸化合物としては以下のような化合物が例示できる。
２−ドデシルオキシこはく酸、２−テトラデシルオキシこはく酸、２−ヘキサデシルオキシこはく酸、２−オクタデシルオキシこはく酸、２−エイコシルオキシこはく酸、２−ドデシルオキシこはく酸、２−ドデシルチオこはく酸、２−テトラデシルチオこはく酸、２−ヘキサデシルチオこはく酸、２−オクタデシルチオこはく酸、２−エイコシルチオこはく酸、２−ドコシルチオこはく酸、２−テトラコシルチオこはく酸、２−ヘキサデシルジチオこはく酸、２−オクタデシルジチオこはく酸、２−エイコシルジチオこはく酸、ドデシルこはく酸、テトラデシルこはく酸、ペンタデシルこはく酸、ヘキサデシルこはく酸、オクタデシルこはく酸、エイコシルこはく酸、ドコシルこはく酸、２，３−ジヘキサデシルこはく酸、２，３−ジオクタデシルこはく酸、２−メチル−３−ヘキサデシルこはく酸、２−メチル−３−オクタデシルこはく酸、２−オクタデシル−３−ヘキサデシルこはく酸、ヘキサデシルマロン酸、オクタデシルマロン酸、エイコシルマロン酸、ドコシルマロン酸、ジヘキサデシルマロン酸、ジオクタデシルマロン酸、ジドコシルマロン酸、メチルオクタデシルマロン酸、２−ヘキサデシルグルタル酸、２−オクタデシルグルタル酸、２−エイコシルグルタル酸、ドコシルグルタル酸、２−ペンタデシルアジピン酸、２−オクタデシルアジピン酸、２−エイコシルアジピン酸、２−ドコシルアジピン酸、２−ヘキサデカノイルオキシプロパン−１，２，３−トリカルボン酸、２−オクタデカノイルオキシプロパン−１，２，３−トリカルボン酸など。
【００１８】
顕色剤には、分子間凝集力を制御する構造をもつフェノール化合物も好ましく用いられる。これには、たとえば下記の一般式（２）で表わされるフェノール化合物が例示できる。
【００１９】
【化３】

【００２０】
一般式（２）で表わされるフェノール化合物の具体例を下記表１にｐ，ｑ，ｒ，ｓ，Ｘ，Ａ，Ｙ，Ｚの数または構造で示す。ただし、これらのそれぞれの具体例においてフェノール部のｎは１〜３であり、たとえば４−ヒドロキシフェニル、３−ヒドロキシフェニル、２−ヒドロキシフェニル、２，４−ジヒドロキシフェニル、３，４−ジヒドロキシフェニルまたは３，４，５−トリヒドロキシフェニルなどの水酸基を少なくとも一つ以上有するフェニル基である。このフェニル基には、水酸基以外の置換基を有していてもよい。また、フェノール性水酸基を有するものであれば、他の芳香環であってもよい。
【００２１】
【表１−１】

【００２２】
【表１−２】

本発明においては顕色剤として上記に記載した化合物に限られるものではなく、その他の電子受容性の種々の化合物を使用することができる。
【００２３】
次に、本発明の具体例としては、下記一般式（１）におけるＲとして、表２に示した化合物等が挙げられる。
【００２４】
【化４】

【００２５】
【表２】

【００２６】
本発明の可逆性感熱発色組成物は、加熱温度およびまたは加熱後の冷却速度により相対的に発色した状態と消色した状態を形成しうるものである。この基本的な発色・消色現像を説明する。図１はこの組成物の発色濃度と温度との関係を示したものである。はじめ消色状態（Ａ）にある組成物を昇温していくと、溶融し始める温度Ｔ₁で発色が起こり溶融発色状態（Ｂ）となる。溶融発色状態（Ｂ）から急冷すると発色状態のまま室温に下げることができ、固まった発色状態（Ｃ）となる。この発色状態が得られるかどうかは、溶融状態からの降温の速度に依存しており、徐冷では降温の過程で消色が起き、はじめと同じ消色状態（Ａ）あるいは急冷発色状態（Ｃ）より相対的に濃度の低い状態が形成される。一方、急冷発色状態（Ｃ）をふたたび昇温していくと発色温度より低い温度Ｔ₂で消色が起き（ＤからＥ）、ここから降温するとはじめと同じ消色状態（Ａ）に戻る。実際の発色温度、消色温度は、用いる顕色剤と発色剤の組み合わせにより変化するので目的に合わせて選択できる。また溶融発色状態の濃度と急冷したときの発色濃度は、必ずしも一致するものではなく、異なる場合もある。
【００２７】
本発明の組成物では、溶融状態から急冷して得た発色状態（Ｃ）は顕色剤と発色剤が分子どうしで接触反応しうる状態で混合された状態であり、これは固体状態を形成していることが多い。この状態は顕色剤と発色剤が凝集して発色を保持した状態であり、この凝集構造の形成により発色が安定化していると考えられる。一方、消色状態は両者が相分離した状態である。この状態は少なくとも一方の化合物の分子が集合してドメインを形成したり結晶化した状態であり、凝集あるいは結晶化することにより発色剤と顕色剤が分離して安定化した状態であると考えられる。本発明では多くの場合、両者が相分離し顕色剤が結晶化することによってより完全な消色が起きる。図１に示した溶融状態から徐冷による消色及び発色状態からの昇温による消色は、いずれもこの温度で凝集構造が変化し、相分離や顕色剤の結晶化が起きている。
【００２８】
本発明の組成物を可逆性感熱記録媒体として用いる場合、発色記録の形成はサーマルヘッドなどによりいったん溶融混合する温度に加熱し、急冷すればよい。また、消色は加熱状態から徐冷する方法と発色温度よりやや低い温度に加熱する方法の二つである。しかし、これらは両者が相分離したり、少なくとも一方が結晶化する温度に一時的に保持するという意味で同じである。発色状態の形成で急冷するのは、この相分離温度または結晶化温度に保持しないようにするためである。ここにおける急冷と徐冷はひとつの組成物に対して相対的なものであり、その境界は発色剤と顕色剤の組み合わせにより変化する。
【００２９】
組成物中の発色剤と顕色剤の割合は、使用する化合物の組み合わせにより適切な範囲が変化するが、おおむねモル比で発色剤１に対し顕色剤が０．１〜２０の範囲であり、好ましくは０．２〜１０の範囲である、この範囲より顕色剤が少なくても多くても発色状態の濃度が低下し問題となる。
【００３０】
本発明の可逆性感熱記録媒体は、支持体上に前記の組成物を主成分として含む記録層を設けたものである。支持体としては紙、樹脂フィルム、合成紙、金属箔、ガラスまたはこれらの複合体などであり、記録層を保持できるものであればよい。
【００３１】
記録層は本発明の組成物が存在していればどのようなものでもよいが、一般的にはバインダー樹脂中に発色剤と顕色剤が細かく均一に分散した状態のものが用いられる。発色剤と顕色剤は個々に粒子を形成していてもよいが、より好ましくは複合された粒子として分散された状態のものである。これは発色剤と顕色剤をいったん溶融したり溶解することによって達成できる。このような記録層の形成は、各材料をそれぞれ溶剤中で分散溶解したのち混合した液、あるいは各材料を混合して溶剤中で分散又は溶解した液を支持体上に塗布し、乾燥することによって行われる。発色剤と顕色剤はマイクロカプセル中に内包して用いることもできる。
【００３２】
本発明の可逆性感熱記録媒体には、必要に応じて記録層の塗布特性や発色消色特性を改善したり制御するための添加剤を用いることができる。これらの添加剤には、例えば分散剤、界面活性剤、導電剤、充填剤、滑剤、酸化防止剤、光安定化剤、紫外線吸収剤、発色安定化剤、消色促進剤などがある。
【００３３】
記録層の形成に用いられるバインダー樹脂としては、例えばポリ塩化ビニル、ポリ酢酸ビニル、塩化ビニル酢酸ビニル共重合体、エチルセルロース、ポリスチレン、スチレン系共重合体、フェノキシ樹脂、ポリエステル、芳香族ポリエステル、ポリウレタン、ポリカーボネート、ポリアクリル酸エステル、ポリメタクリル酸エステル、アクリル酸系共重合体、マレイン酸系共重合体、ポリビニルアルコール、変性ポリビニルアルコール、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、デンプン類などがある。これらのバインダー樹脂の役割は、組成物の各材料が記録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。例えば熱、紫外線、電子線などでバインダー樹脂を架橋させてもよい。
【００３４】
本発明の可逆性感熱記録媒体は、基本的に支持体上に上記の記録層が設けられたものであるが、記録媒体としての特性を向上するため、保護層、接着層、中間層、アンダーコート層、バックコート層などを設けることができる。
【００３５】
サーマルヘッドを用いた印字では熱と圧力のため記録層の表面が変形し、いわゆる打痕ができる場合がある。これを防止するため表面に保護層を設けることが好ましい。保護層には、ポリビニルアルコール、スチレン無水マレイン酸共重合体、カルボキシ変性ポリエチレン、メラミン−ホルムアルデヒド樹脂、尿素−ホルムアルデヒド樹脂のほか、紫外線硬化樹脂、および電子線硬化樹脂などが使用できる。また、保護層中には紫外線吸収剤などの添加剤を含有させることができる。
【００３６】
記録層と保護層の接着性向上、保護層の塗布による記録層の変質防止、保護層中の添加剤の記録層への移行を防止する目的で、両者の間に中間層を設けることも好ましい。また、記録層の上に設置される保護層、中間層には酸素透過性の低い樹脂を用いることが好ましい。記録層中の発色剤及び顕色剤の酸化を防止または低減することが可能になる。
【００３７】
また、印加した熱を有効に利用するため支持体と記録層の間に断熱性のアンダーコート層を設けることができる。断熱層は有機又は無機の微小中空体粒子をバインダー樹脂を用いて塗布することにより形成できる。支持体と記録層の接着性の改善や支持体への記録層材料の浸透防止を目的としたアンダーコート層を設けることもできる。
【００３８】
中間層、アンダーコート層には、前記の記録層用の樹脂と同様の樹脂を用いることができる。また、保護層、中間層、記録層及びアンダーコート層には炭酸カルシウム、炭酸マグネシウム、酸化チタン、酸化ケイ素、水酸化アルミニウム、カオリン、タルクなどのフィラーを含有させることができる。その他、滑剤、界面活性剤分散剤などを含有させることもできる。支持体の滑性、搬送性を向上させ、或いはカールを防止するために支持体の反対側にバックコート層を設けることもできる。
【００３９】
本発明の可逆性感熱記録媒体を用いて発色画像を形成させるためには、いったん発色温度以上に加熱したのち急冷されるようにすればよい。具体的には、たとえばサーマルヘッドやレーザー光で短時間加熱すると記録層が局部的に加熱されるため、直ちに熱が拡散し急激な冷却が起こり、発色状態が固定できる。一方、消色させるためには適当な熱源を用いて比較的長時間加熱し冷却するか、発色温度よりやや低い消色温度に一時的に加熱すればよい。長時間加熱すると記録媒体の広い範囲が昇温し、その後の冷却は遅くなり、徐冷となるため、その過程で消色が起きる。この場合の加熱方法には、熱ローラ、熱スタンプ、熱風などを用いてもよいし、サーマルヘッドを用いて長時間加熱してもよい。記録層を消色温度域に加熱するためには、例えばサーマルヘッドへの印加電圧やパルス幅を調節することによって、印加エネルギーを記録時よりやや低下させればよい。この方法を用いれば、サーマルヘッドだけで記録・消去ができ、いわゆるオーバーライトが可能になる。もちろん、熱ローラ、熱スタンプ、加熱バー等によって消色温度域に加熱して消去することもできる。
【００４０】
【実施例】
以下、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」および「％」はいずれも重量を基準とするものである。
実施例１
下記組成物を乳鉢で粉砕混合した。
［発色剤］
２−アニリノ−３−メチル−６−ジブチルアミノフルオラン １部
［顕色剤］
【００４１】
【化５】

［発色消色制御剤］
表２中のＮｏ．５の化合物 １部
この混合物の適当量を厚さ１．２ｍｍのガラス板上にのせて、ホットプレート上で２００℃に加熱、混融した。続いて、この混融混合物の上からカバーグラスをかぶせて融液を一様な厚さに広げ、すぐにガラス板ごと全体を用意しておいた氷水中に沈めて急冷した。降温後、すぐに取り出し付着した水を除き、薄膜状の黒色に発色した本発明の組成物を得た。
次に、上記の発色状態の組成物試料を１１０℃に加熱したホットプレート上に置くと瞬時に消色した。再び、この消色した組成物試料を２００℃に加熱すると黒色を呈した。このことから、本発明の組成物は発色、消色の繰り返し特性を有することが確認された。
【００４２】
実施例２
下記組成物をボールミルを用いて粒径１〜４μｍまで粉砕分散した。
［発色剤］
２−アニリノ−３−メチル−６−ジブチルアミノフルオラン ２部
［顕色剤］
【００４３】
【化６】

［発色消色制御剤］
表２中のＮｏ．５の化合物 ４部
フェノキシ樹脂（ユニオンカーバイド社製、ＰＫＨＨ）の
１５％テトラヒドロフラン（ＴＨＦ）溶液 １５０部
【００４４】
得られた分散液に日本ポリウレタン社製コロネートＨＬ（アダクト型ヘキサメチレンジイソシアネート ７５％酢酸エチル溶液）２０部を加え、よく撹拌し記録層塗布液を調製した。
上記組成の記録層塗布液を、厚さ１００μｍのポリエステルフィルム上にワイヤーバーを用い塗布し、８０℃で乾燥した後、１００℃で１０分、６０℃で２４時間加熱して、膜厚６．０μｍの記録層を設けた。
この記録層上に下記組成よりなる保護層液をワイヤーバーを用いて塗工した後、照射エネルギー８０Ｗ／ｃｍの紫外線ランプ下を９ｍ／分の搬送速度で通して硬化して膜厚３μｍの保護層を設け、本発明の可逆性感熱記録媒体を作製した。［保護層液］
ウレタンアクリレート系紫外線硬化性樹脂
（大日本インキ社製、Ｃ７−１５７） １０部
酢酸エチル ９０部
【００４５】
作製した記録媒体を大倉電機社製感熱印字装置にて、電圧１３．３Ｖ、パルス幅１．２ｍｓｅｃで印字した。印字部の濃度をマクベス濃度計ＲＤ９１４にて測定したところ、画像濃度は１．００であった。次に、この印字サンプルを熱傾斜試験機で１１０℃で０．５秒間加熱して消去した。消去部及び地肌部の濃度を同様に測定した。消し残り濃度は０．０１であった。
課題に対応して、発色性は画像濃度で、消色性は消し残り濃度で保存性は濃度保持率で評価した。
また、印字サンプルを５０℃乾燥条件下で２４時間保存したところ、画像部の濃度保持率は７８％であった。ここで濃度保持率は下記式で表わされる。
【００４６】
【数１】

また、消し残り濃度は、消去後の濃度と地肌濃度の差であり下記式で表わされる。
【００４７】
【数２】
消し残り濃度＝（消去後の画像濃度）−（地肌濃度）
【００４８】
実施例３
実施例２中の顕色剤を下記のものに変えた以外は、実施例２と同様にして可逆性感熱記録媒体を作製した。
［顕色剤］
【００４９】
【化７】

作製した可逆性感熱記録媒体を実施例２と同様に評価したところ、画像濃度が１．０４、１１０℃、０．５秒での消し残り濃度が０．０１であり、５０℃乾燥条件での濃度保持率が８２％であった。
【００５０】
実施例４
実施例２中の発色剤２−アニリノ−３−メチル−６−ジブチルアミノフルオランの代わりに、３，３−ビス（２−エトキシ−４−ジエチルアミノフェニル）−４−アザフタリドを用いた以外は、実施例２と同様にして可逆性感熱記録媒体を作製した。
作製した可逆性感熱記録媒体を実施例２と同様に評価したところ、画像濃度が０．８９、１１０℃、０．５秒での消し残り濃度が０．０２であり、５０℃乾燥条件での濃度保持率が７８％であった。
【００５１】
実施例５
実施例２中の発色消色制御剤を表２のＮｏ．５からＮｏ．６に代えた以外は実施例２と同様にして可逆性感熱記録媒体を作製した。
作製した可逆性感熱記録媒体を実施例２と同様に評価したところ、画像濃度が１．０２、１１０℃、０．５秒での消し残り濃度が０．０２であり、５０℃乾燥条件での濃度保持率が７９％であった。
【００５２】
実施例６
実施例２中の発色消色制御剤を表２のＮｏ．５からＮｏ．４に代えた以外は実施例２と同様にして可逆性感熱記録媒体を作製した。
作製した可逆性感熱記録媒体を実施例２と同様に評価したところ、画像濃度が１．０４、１１０℃、０．５秒での消し残り濃度が０．０２であり、５０℃乾燥条件での濃度保持率が７８％であった。
【００５３】
比較例１
実施例２中で発色消色制御剤を使用しなかった以外は、実施例２と同様にして可逆性感熱記録媒体を作製した。
作製した可逆性感熱記録媒体を実施例２と同様に評価したところ、画像濃度が１．０２、１１０℃、０．５秒での消し残り濃度が０．０５であり、５０℃乾燥条件での濃度保持率が５４％であった。
【００５４】
【発明の効果】
以上、詳細且つ具体的な説明より明らかなように、本発明の可逆性感熱発色組成物及び可逆性感熱記録媒体は、発色消色制御剤として前記一般式（１）で表わされる化合物を用いたことから、保存特性及び消去特性が良好な実用性の高いものである。
【図面の簡単な説明】
【図１】本発明の化合物感熱発色組成物の発色・消色特性を示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention uses a reversible thermosensitive coloring composition utilizing a coloring reaction between an electron-donating color-forming compound and an electron-accepting compound, and can control the formation of a color image and erase it by controlling thermal energy. The present invention relates to a reversible thermosensitive recording medium.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, thermal recording media using a color development reaction between an electron donating color developing compound (hereinafter also referred to as a color former or a leuco dye) and an electron accepting compound (hereinafter also referred to as a developer) are widely known. It is used in printers such as facsimile machines, word processors, and scientific measuring machines. However, any of these conventional recording media in practical use has irreversible color development, and once recorded images cannot be erased and used repeatedly.
[0003]
On the other hand, according to the patent gazette, a recording medium capable of reversibly developing and decoloring has been proposed. For example, a recording medium using a combination of gallic acid and phloroglucinol as a developer (JP-A-60- No. 193691), a compound using a compound such as phenolphthalein or thymolphthalein as a developer (Japanese Patent Laid-Open No. 61-237684), a homogeneous solution of a color former, a developer and a carboxylic acid ester. (As disclosed in JP-A-62-138556, JP-A-62-138568, and JP-A-62-140881), and those using an ascorbic acid derivative as a developer (JP-A-63) -173684), and a developer using a salt of bis (hydroxyphenyl) acetic acid or gallic acid and a higher aliphatic amine as a developer (Japanese Patent Laid-Open No. 2-188293) Distribution and JP 2-188294 Patent Publication) have been disclosed.
However, the conventional reversible thermosensitive recording media described above still have problems in terms of both the stability of color development and the decoloring property, or the stability in color density and repetition. It is not satisfactory as a medium.
[0004]
Furthermore, the present inventors previously used an organic phosphoric acid compound, aliphatic carboxylic acid compound or phenol compound having a long-chain aliphatic hydrocarbon group as a developer in Japanese Patent Application Laid-Open No. 5-124360. By combining with the leuco dye, which is an agent, color development and color erasure can be easily performed under heating and cooling conditions, and the color development state and color erasure state can be stably maintained at room temperature. And a reversible thermosensitive color-developing composition capable of stably repeating decoloring and a reversible thermosensitive recording medium using the same for the recording layer. This has a practical level of performance in terms of the balance between color stability and color erasability and color density, but it can be further improved in terms of compatibility with a wide range of usage environments and color erasing conditions. There was room for it. Thereafter, the use of a specific structure for a phenol compound having a long-chain aliphatic hydrocarbon group has been proposed (Japanese Patent Laid-Open No. 6-210954), but this also has a similar problem.
[0005]
As described above, a reversible thermosensitive recording medium that can repeat color development and decoloring has been proposed. This type of recording medium has storage characteristics (against temperature, humidity, and light) and high-speed erasure characteristics. However, a reversible thermosensitive recording medium satisfying this has not been obtained.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a reversible thermosensitive coloring composition and a reversible thermosensitive recording medium that have high storage stability in a colored state and at the same time have excellent decoloring properties.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have achieved the storage stability of the colored state against heat by using a coloring / decoloring control agent (specific carbamic acid ester compound) having a specific structure. It has been found that the high-speed erasing characteristics can be obtained while at the same time being excellent in erasing properties.
The reason for improving the storage stability against heat is that, in the color development state, the color development / decoloration control agent mainly enters into the color aggregation structure composed of the dye and the developer having long-chain alkyl, thereby creating a more stable structure. This is thought to be because the color development structure at a high temperature is stably maintained. Further, in the decoloring process, it is considered that the unerased residue at the time of decoloring is reduced in order to promote crystallization to the decolored state because it takes a cohesive structure stronger than the cohesive force of only the developers.
[0008]
That is, the above-described problem is that (1) “using an electron-donating color-forming compound and an electron-accepting compound of the present invention, and a relatively colored state and decoloring depending on the heating temperature and / or the cooling rate after heating A reversible thermosensitive color-forming composition capable of forming a formed state, wherein the reversible thermosensitive color-forming composition contains a compound represented by the following general formula (1) as a color development / decoloration control agent: Coloring composition,
[0009]
[Chemical 2]

Is achieved.
[0010]
Further, it is achieved by (2) “a reversible thermosensitive recording medium, characterized in that a recording layer containing the reversible thermosensitive coloring composition described in (1) above as a main component is provided on a support”. .
[0011]
The reversible thermosensitive coloring composition of the present invention is basically constituted by combining the developer and the coloring agent. The color former used in the present invention exhibits an electron donating property, and is itself a colorless or light-colored dye precursor (leuco dye), and is not particularly limited, and conventionally known ones such as phthalide compounds and azaphthalide compounds. , A fluoran compound, a phenothiazine compound, a leucooramine compound, and the like.
[0012]
Specific examples of the color former include, but are not limited to, the following compounds.
2-anilino-3-methyl-6-diethylaminofluorane, 2- (o-chloroanilino) -6-dibutylaminofluorane, 2- (N-methyl-o-chloroanilino) -6-dibutylaminofluorane, 2- Anilino-3-methyl-6- (Nn-propyl-N-methylamino) fluorane, 2-anilino-6- (Nn-hexyl-N-ethylamino) fluorane, 2,3-dimethyl-6 Dimethylaminofluorane, 2- (o-chloroanilino) -3-chloro-6-dimethylaminofluorane, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindo-3) -Yl) -4-azaphthalide and the like.
[0013]
Next, the color developer used in combination with the color former in the reversible thermosensitive recording medium of the present invention will be described. As disclosed in Japanese Patent Laid-Open No. 5-124360 with representative examples of phosphoric acid compounds, fatty acid compounds, and phenolic compounds having a long-chain hydrocarbon group, the developer and the color former are aggregated. By forming the structure, color development is stabilized, and at least one of the molecules of the two molecules aggregates or crystallizes, so the color former and the developer are phase-separated and decolored. A compound having both a structure capable of developing a color capable of developing an agent and a structure controlling the cohesive force between molecules is used. As the structure having a color developing ability, for example, those having an acidic group such as a phenolic hydroxyl group, a carboxyl group, and a phosphoric acid group are used, as in general heat-sensitive recording media. Any material having a group capable of coloring can be used. These include, for example, thiourea groups, carboxylic acid metal salts, and the like. A typical structure for controlling the cohesive force between molecules is a hydrocarbon group such as a long-chain alkyl group. In general, the number of carbon atoms of the hydrocarbon group is preferably 8 or more in order to obtain good color forming / decoloring characteristics. Further, the hydrocarbon group may contain an unsaturated bond, and a branched hydrocarbon group is also included. Also in this case, the main chain portion preferably has 8 or more carbon atoms. The hydrocarbon group may be substituted with a group such as a halogen atom, a hydroxyl group, or an alkoxy group.
[0014]
As described above, the developer has a structure in which a structure having a developing ability and a structure for controlling cohesive force represented by a hydrocarbon group are connected. The linking moiety may be bonded via a divalent group containing a heteroatom as shown below, or a group in which a plurality of these groups are combined.
Further, an aromatic ring or a heterocyclic ring such as phenylene or naphthylene may be bonded, or both of them may be interposed.
The hydrocarbon group may have a divalent group similar to the above in the chain structure, that is, a divalent group containing an aromatic ring or a hetero atom.
[0015]
Hereinafter, the developer used in the present invention is specifically exemplified.
Organic phosphoric acid developer Examples of the organic phosphoric acid developer include the following compounds.
Dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid, docosylphosphonic acid, tetracosylphosphonic acid, ditetradecyl phosphate, dihexadecyl phosphate, phosphoric acid Dioctadecyl ester, dieicosyl phosphate, dibehenyl phosphate, etc.
[0016]
-Aliphatic carboxylic compound Examples of the aliphatic carboxylic compound include the following compounds.
2-hydroxytetradecanoic acid, 2-hydroxyhexadecanoic acid, 2-hydroxyoctadecanoic acid, 2-hydroxyeicosanoic acid, 2-hydroxydocosanoic acid, 2-bromohexadecanoic acid, 2-bromooctadecanoic acid, 2-bromoeicosanoic acid 2-bromodocosanoic acid, 3-bromooctadecanoic acid, 3-bromodocosanoic acid, 2,3-dibromooctadecanoic acid, 2-fluorododecanoic acid, 2-fluorotetradecanoic acid, 2-fluorohexadecanoic acid, 2-fluorooctadecanoic acid, 2 -Fluoroeicosanoic acid, 2-fluorodocosanoic acid, 2-iodohexadecanoic acid, 2-iodooctadecanoic acid, 3-iodohexadecanoic acid, 3-iodooctadecanoic acid, perfluorooctadecanoic acid and the like.
[0017]
Aliphatic dicarboxylic acid and tricarboxylic acid compound Examples of the aliphatic dicarboxylic acid and tricarboxylic acid compound include the following compounds.
2-dodecyloxy succinic acid, 2-tetradecyloxy succinic acid, 2-hexadecyloxy succinic acid, 2-octadecyloxy succinic acid, 2-eicosyloxy succinic acid, 2-dodecyloxy succinic acid, 2-dodecylthiosuccinic acid 2-tetradecylthiosuccinic acid, 2-hexadecylthiosuccinic acid, 2-octadecylthiosuccinic acid, 2-eicosylthiosuccinic acid, 2-docosylthiosuccinic acid, 2-tetracosylthiosuccinic acid, 2-hexadecyldithiosuccinic acid, 2-octadecyl dithiosuccinic acid, 2-eicosyl dithiosuccinic acid, dodecyl succinic acid, tetradecyl succinic acid, pentadecyl succinic acid, hexadecyl succinic acid, octadecyl succinic acid, eicosyl succinic acid, docosyl succinic acid, 2,3-dihexadecyl succinic acid, 2 , 3-Dioc Decyl succinic acid, 2-methyl-3-hexadecyl succinic acid, 2-methyl-3-octadecyl succinic acid, 2-octadecyl-3-hexadecyl succinic acid, hexadecylmalonic acid, octadecylmalonic acid, eicosylmalonic acid, docosylmalonic acid , Dihexadecylmalonic acid, dioctadecylmalonic acid, didocosylmalonic acid, methyloctadecylmalonic acid, 2-hexadecylglutaric acid, 2-octadecylglutaric acid, 2-eicosylglutaric acid, docosylglutaric acid, 2-pentadecyladipine Acid, 2-octadecyl adipic acid, 2-eicosyl adipic acid, 2-docosyl adipic acid, 2-hexadecanoyloxypropane-1,2,3-tricarboxylic acid, 2-octadecanoyloxypropane-1,2 , 3-tricarboxylic acid and the like.
[0018]
As the developer, a phenol compound having a structure for controlling intermolecular cohesive force is also preferably used. For example, a phenol compound represented by the following general formula (2) can be exemplified.
[0019]
[Chemical 3]

[0020]
Specific examples of the phenol compound represented by the general formula (2) are shown in the following Table 1 by the number or structure of p, q, r, s, X, A, Y, and Z. However, in each of these specific examples, n of the phenol part is 1 to 3, for example, 4-hydroxyphenyl, 3-hydroxyphenyl, 2-hydroxyphenyl, 2,4-dihydroxyphenyl, 3,4-dihydroxyphenyl or A phenyl group having at least one hydroxyl group such as 3,4,5-trihydroxyphenyl. This phenyl group may have a substituent other than a hydroxyl group. Moreover, as long as it has a phenolic hydroxyl group, another aromatic ring may be sufficient.
[0021]
[Table 1-1]

[0022]
[Table 1-2]

In the present invention, the developer is not limited to the compounds described above, and other various electron-accepting compounds can be used.
[0023]
Next, specific examples of the present invention include compounds shown in Table 2 as R in the following general formula (1).
[0024]
[Formula 4]

[0025]
[Table 2]

[0026]
The reversible thermosensitive coloring composition of the present invention can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. This basic color development / decolorization development will be described. FIG. 1 shows the relationship between the color density of this composition and the temperature. When the temperature of the composition initially in the decolored state (A) is raised, color development occurs at a temperature T ₁ at which melting starts, and a molten color state (B) is obtained. When rapidly cooled from the melt color state (B), the color state can be lowered to room temperature and a solid color state (C) is obtained. Whether or not this color development state is obtained depends on the rate of temperature decrease from the molten state, and in slow cooling, the color disappears during the temperature decrease, and the same color disappearance state (A) or rapid color development state (C ) A relatively low concentration state is formed. On the other hand, when the rapid cooling coloring state (C) is raised again, decoloring occurs at a temperature T ₂ lower than the coloring temperature (D to E), and when the temperature is lowered from here, the same decoloring state (A) is restored. The actual color developing temperature and color erasing temperature vary depending on the combination of the developer and color former used, and can be selected according to the purpose. Further, the density of the melt coloring state and the coloring density when rapidly cooled are not necessarily the same and may be different.
[0027]
In the composition of the present invention, the colored state (C) obtained by quenching from the molten state is a state in which the developer and the color former are mixed in a state where they can contact each other and form a solid state. Often doing. This state is a state where the developer and the color former are aggregated to maintain the color development, and it is considered that the color development is stabilized by the formation of this aggregated structure. On the other hand, the decolored state is a state in which both phases are separated. This state is a state in which molecules of at least one compound aggregate to form a domain or crystallize, and the color former and developer are separated and stabilized by aggregation or crystallization. It is done. In many cases, in the present invention, more complete color erasure occurs due to phase separation of the two and crystallization of the developer. In both the decolorization by slow cooling from the melted state shown in FIG. 1 and the decoloration by heating from the colored state, the aggregation structure changes at this temperature, and phase separation and crystallization of the developer occur.
[0028]
When the composition of the present invention is used as a reversible thermosensitive recording medium, color recording may be formed by heating to a temperature at which it is once melt mixed with a thermal head or the like and then rapidly cooling. Further, decolorization is two methods, a method of slowly cooling from a heated state and a method of heating to a temperature slightly lower than the coloring temperature. However, they are the same in the sense that they are phase-separated or at least temporarily held at a temperature at which one crystallizes. The reason for rapid cooling in the formation of the colored state is to prevent the temperature from being maintained at this phase separation temperature or crystallization temperature. The rapid cooling and slow cooling here are relative to one composition, and the boundary thereof changes depending on the combination of the color former and the developer.
[0029]
The appropriate range of the ratio between the color former and the developer in the composition varies depending on the combination of the compounds used, but the developer is generally in the range of 0.1 to 20 relative to the color former 1 in molar ratio. However, it is preferably in the range of 0.2 to 10, and if the amount of the developer is less than this range, the density of the colored state is lowered, which causes a problem.
[0030]
The reversible thermosensitive recording medium of the present invention has a recording layer comprising the above composition as a main component on a support. The support is paper, resin film, synthetic paper, metal foil, glass, or a composite of these, as long as it can hold the recording layer.
[0031]
The recording layer may be any layer as long as the composition of the present invention is present. Generally, a recording layer in which a color former and a developer are finely and uniformly dispersed in a binder resin is used. The color former and the developer may individually form particles, but are more preferably in a state of being dispersed as composite particles. This can be achieved by once melting and dissolving the color former and developer. For forming such a recording layer, each material is dispersed and dissolved in a solvent and then mixed, or a liquid in which each material is mixed and dispersed or dissolved in a solvent is applied onto a support and dried. Is done by. The color former and the developer can be used in a microcapsule.
[0032]
In the reversible thermosensitive recording medium of the present invention, an additive for improving or controlling the recording layer coating characteristics and color developing / decoloring characteristics can be used as necessary. These additives include, for example, a dispersant, a surfactant, a conductive agent, a filler, a lubricant, an antioxidant, a light stabilizer, an ultraviolet absorber, a color stabilizer, and a decoloring accelerator.
[0033]
Examples of the binder resin used for forming the recording layer include polyvinyl chloride, polyvinyl acetate, vinyl chloride vinyl acetate copolymer, ethyl cellulose, polystyrene, styrene copolymer, phenoxy resin, polyester, aromatic polyester, polyurethane, Examples include polycarbonate, polyacrylic acid ester, polymethacrylic acid ester, acrylic acid copolymer, maleic acid copolymer, polyvinyl alcohol, modified polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, and starches. The role of these binder resins is to keep the materials of the composition uniformly dispersed without being displaced by the application of heat for recording and erasing. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. For example, the binder resin may be cross-linked by heat, ultraviolet light, electron beam or the like.
[0034]
The reversible thermosensitive recording medium of the present invention basically has the above-mentioned recording layer provided on a support. However, in order to improve the properties as a recording medium, a protective layer, an adhesive layer, an intermediate layer, an underlayer A coat layer, a back coat layer, and the like can be provided.
[0035]
In printing using a thermal head, the surface of the recording layer may be deformed due to heat and pressure, and so-called dents may be formed. In order to prevent this, it is preferable to provide a protective layer on the surface. For the protective layer, polyvinyl alcohol, styrene maleic anhydride copolymer, carboxy-modified polyethylene, melamine-formaldehyde resin, urea-formaldehyde resin, ultraviolet curable resin, electron beam curable resin, and the like can be used. Moreover, additives, such as a ultraviolet absorber, can be contained in a protective layer.
[0036]
In order to improve the adhesion between the recording layer and the protective layer, to prevent the recording layer from being altered by the application of the protective layer, and to prevent the additives in the protective layer from being transferred to the recording layer, it is also preferable to provide an intermediate layer therebetween. . Further, it is preferable to use a resin having low oxygen permeability for the protective layer and the intermediate layer provided on the recording layer. It becomes possible to prevent or reduce the oxidation of the color former and developer in the recording layer.
[0037]
In order to effectively use the applied heat, a heat insulating undercoat layer can be provided between the support and the recording layer. The heat insulating layer can be formed by applying organic or inorganic fine hollow particles using a binder resin. An undercoat layer may be provided for the purpose of improving the adhesion between the support and the recording layer and preventing the recording layer material from penetrating into the support.
[0038]
For the intermediate layer and the undercoat layer, the same resin as that for the recording layer can be used. The protective layer, intermediate layer, recording layer and undercoat layer can contain fillers such as calcium carbonate, magnesium carbonate, titanium oxide, silicon oxide, aluminum hydroxide, kaolin and talc. In addition, a lubricant, a surfactant dispersant and the like can be contained. A back coat layer can be provided on the opposite side of the support in order to improve the lubricity and transportability of the support or to prevent curling.
[0039]
In order to form a color image using the reversible thermosensitive recording medium of the present invention, the color image may be rapidly cooled after being heated above the color development temperature. Specifically, for example, when the recording layer is heated for a short time with a thermal head or laser light, the recording layer is locally heated, so that the heat is immediately diffused and abrupt cooling occurs and the color development state can be fixed. On the other hand, in order to erase the color, it may be heated and cooled for a relatively long time using an appropriate heat source, or may be temporarily heated to a color erasing temperature slightly lower than the coloring temperature. When heated for a long time, the temperature of a wide range of the recording medium rises, and the subsequent cooling becomes slow and slow cooling. As a heating method in this case, a heat roller, a heat stamp, hot air, or the like may be used, or heating may be performed for a long time using a thermal head. In order to heat the recording layer to the color erasing temperature range, for example, the applied energy may be lowered slightly from the time of recording by adjusting the voltage applied to the thermal head and the pulse width. If this method is used, recording / erasing can be performed only by the thermal head, and so-called overwriting becomes possible. Of course, the image can be erased by heating to a decoloring temperature range with a heat roller, a heat stamp, a heating bar or the like.
[0040]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples. In the examples, “parts” and “%” are based on weight.
Example 1
The following composition was pulverized and mixed in a mortar.
[Coloring agent]
2-anilino-3-methyl-6-dibutylaminofluorane 1 part [developer]
[0041]
[Chemical formula 5]

[Coloring / decoloring control agent]
No. in Table 2 Compound No. 5 1 part An appropriate amount of this mixture was placed on a glass plate having a thickness of 1.2 mm and heated and mixed at 200 ° C. on a hot plate. Subsequently, a cover glass was placed on the melt mixture to spread the melt to a uniform thickness, and the whole glass plate was immediately submerged in ice water prepared to be rapidly cooled. Immediately after the temperature was lowered, the adhering water was removed, and a thin film-like black color composition was obtained.
Next, when the composition sample in the colored state was placed on a hot plate heated to 110 ° C., the color was instantaneously erased. Again, when this decolored composition sample was heated to 200 ° C., it appeared black. From this, it was confirmed that the composition of the present invention has repetitive characteristics of coloring and decoloring.
[0042]
Example 2
The following composition was pulverized and dispersed to a particle size of 1 to 4 μm using a ball mill.
[Coloring agent]
2-anilino-3-methyl-6-dibutylaminofluorane 2 parts [developer]
[0043]
[Chemical 6]

[Coloring / decoloring control agent]
No. in Table 2 Compound of 5 4 parts 150 parts of 15% tetrahydrofuran (THF) solution of phenoxy resin (manufactured by Union Carbide, PKHH)
20 parts of Coronate HL (adduct type hexamethylene diisocyanate 75% ethyl acetate solution) manufactured by Nippon Polyurethane Co., Ltd. was added to the obtained dispersion and stirred well to prepare a recording layer coating solution.
The recording layer coating solution having the above composition was applied on a polyester film having a thickness of 100 μm using a wire bar, dried at 80 ° C., and then heated at 100 ° C. for 10 minutes and at 60 ° C. for 24 hours. A recording layer of 0 μm was provided.
A protective layer solution having the following composition was coated on the recording layer using a wire bar, and then cured by passing through a UV lamp with an irradiation energy of 80 W / cm at a conveyance speed of 9 m / min to protect the film with a thickness of 3 μm. A layer was provided to produce a reversible thermosensitive recording medium of the present invention. [Protective layer solution]
Urethane acrylate UV curable resin (C7-157, manufactured by Dainippon Ink Co., Ltd.) 10 parts Ethyl acetate 90 parts
The produced recording medium was printed with a thermal printing apparatus manufactured by Okura Electric Co., Ltd. at a voltage of 13.3 V and a pulse width of 1.2 msec. When the density of the printed portion was measured with a Macbeth densitometer RD914, the image density was 1.00. Next, this print sample was erased by heating at 110 ° C. for 0.5 seconds with a thermal inclination tester. The density | concentration of the erased part and the background part was measured similarly. The unerased concentration was 0.01.
Corresponding to the problem, the color developing property was evaluated by the image density, the decoloring property was evaluated by the unerased density, and the storage property was evaluated by the density retention rate.
Further, when the print sample was stored for 24 hours under dry conditions at 50 ° C., the density retention of the image area was 78%. Here, the density retention is expressed by the following equation.
[0046]
[Expression 1]

The unerased density is the difference between the density after erasure and the background density, and is expressed by the following equation.
[0047]
[Expression 2]
Unerased density = (image density after erasure)-(background density)
[0048]
Example 3
A reversible thermosensitive recording medium was produced in the same manner as in Example 2 except that the developer in Example 2 was changed to the following.
[Developer]
[0049]
[Chemical 7]

The produced reversible thermosensitive recording medium was evaluated in the same manner as in Example 2. As a result, the image density was 1.04, 110 ° C., the unerased density at 0.5 seconds was 0.01, and the drying condition was 50 ° C. The concentration retention was 82%.
[0050]
Example 4
Except for using 3,3-bis (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide instead of the color former 2-anilino-3-methyl-6-dibutylaminofluorane in Example 2, A reversible thermosensitive recording medium was produced in the same manner as in Example 2.
The produced reversible thermosensitive recording medium was evaluated in the same manner as in Example 2. As a result, the image density was 0.89, 110 ° C., the unerased density at 0.5 seconds was 0.02, and the drying condition was 50 ° C. The concentration retention was 78%.
[0051]
Example 5
The color development / decoloration controlling agent in Example 2 was changed to No. 1 in Table 2. 5 to No. A reversible thermosensitive recording medium was produced in the same manner as in Example 2 except that it was changed to 6.
The produced reversible thermosensitive recording medium was evaluated in the same manner as in Example 2. As a result, the image density was 1.02, 110 ° C., the unerased density at 0.5 seconds was 0.02, and the drying condition was 50 ° C. The density retention was 79%.
[0052]
Example 6
The color development / decoloration controlling agent in Example 2 was changed to No. 1 in Table 2. 5 to No. A reversible thermosensitive recording medium was produced in the same manner as in Example 2 except that it was changed to 4.
The produced reversible thermosensitive recording medium was evaluated in the same manner as in Example 2. As a result, the image density was 1.04, 110 ° C., the unerased density at 0.5 seconds was 0.02, and the drying condition was 50 ° C. The concentration retention was 78%.
[0053]
Comparative Example 1
A reversible thermosensitive recording medium was produced in the same manner as in Example 2 except that no color development / decoloration controlling agent was used in Example 2.
The produced reversible thermosensitive recording medium was evaluated in the same manner as in Example 2. As a result, the image density was 1.02, 110 ° C., the unerased density at 0.5 seconds was 0.05, and the drying condition was 50 ° C. The concentration retention was 54%.
[0054]
【The invention's effect】
As described above, as is clear from the detailed and specific description, the reversible thermosensitive coloring composition and the reversible thermosensitive recording medium of the present invention use the compound represented by the general formula (1) as a color development / decoloration controlling agent. Therefore, the storage property and the erasing property are excellent and the practicality is high.
[Brief description of the drawings]
FIG. 1 is a graph showing color development / decolorization characteristics of a compound thermosensitive coloring composition of the present invention.

Claims (2)

In a reversible thermosensitive coloring composition that uses an electron-donating color-forming compound and an electron-accepting compound and can form a relatively colored state and a decolored state depending on the heating temperature and / or the cooling rate after heating. A reversible thermosensitive coloring composition comprising a compound represented by the following general formula (1) as a coloring and decoloring control agent in the reversible thermosensitive coloring composition.

A reversible thermosensitive recording medium comprising a recording layer containing the reversible thermosensitive coloring composition according to claim 1 as a main component on a support.

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