JP3693472B2 - Reversible thermosensitive recording material - Google Patents

Description

【００１８】
【化２】

【００１９】
【化３】

【００２０】
【化４】

【００２１】
【化５】

【００２２】
【化６】

【００２３】
【化７】

【００２４】
【化８】

【００２５】
【化９】

【００２６】
本発明において用いられる光開始剤は、一般的な光開始剤、例えばベンゾフェノン、１−ヒドロキシ−シクロヘキシル−フェニルケトンなどであってよい。さらに、増感剤を添加してもよい。ＵＶ照射条件は、６０〜２００ｗ／ｃｍ、１〜２０ｍ／ｍｉｎであってよく、窒素雰囲気中で処理することが望ましい。
【００２７】
また、本発明における有機低分子物質ａ、ｂ、ｃのうち、有機低分子物質ａは好ましくはｍｐ６０〜９０℃のものである。ｍｐ６０℃以下のものは、コントラスト不足であり、可逆性が悪い。ｍｐ９０℃以上のものは樹脂中に分散しない。さらに具体的には、有機低分子物質ａとしては、ラウリン酸、ミリスチン酸、ペンタデカン酸、パルミチン酸、ステアリン酸、ベヘン酸、ノナデカン酸、アラギン酸、ヘンイコサン酸、トリコサン酸、リグノセリン酸、ペンタコサン酸、セロチン酸、ヘプタコサン酸、モンタン酸、メリシン酸、オレイン酸等の脂肪族モノカルボン酸、例えば高級脂肪酸を挙げることができる。
【００２８】
本発明で用いる有機低分子物質ｂの多価アルコールジ脂肪酸エステルとしては、下記の一般式で表わされるものが挙げられる。
ＣＨ₃(ＣＨ₂)ｍ−ＣＯＯ(ＣＨ₂)ｎＯＯＣ(ＣＨ₂)ｍ−ＣＨ₃
（式中、ｎは２〜４０、好ましくは３〜３０、更に好ましくは４〜２２の整数である。ｍは０〜３８、好ましくは１〜２８、更に好ましくは２〜２０の整数である。）
【００２９】
具体的には以下のものが挙げられる。
１，２−エタンジオールジアルカン酸エステル
１，３−プロパンジオールジアルカン酸エステル
１，４−ブタンジオールジアルカン酸エステル
１，５−ペンタンジオールジアルカン酸エステル
１，６−ヘキサンジオールジアルカン酸エステル
１，７−ヘプタンジオールジアルカン酸エステル
１，８−オクタンジオールジアルカン酸エステル
１，９−ノナンジオールジアルカン酸エステル
１，１０−デカンジオールジアルカン酸エステル
１，１１−ウンデカンジオールジアルカン酸エステル
【００３０】
１，１２−ドデカンジオールジアルカン酸エステル
１，１３−トリデカンジオールジアルカン酸エステル
１，１４−テトラデカンジオールジアルカン酸エステル
１，１５−ペンタデカンジオールジアルカン酸エステル
１，１６−ヘキサデカンジオールジアルカン酸エステル
１，１７−ヘプタデカンジオールジアルカン酸エステル
１，１８−オクタデカンジオールジアルカン酸エステル
１，１９−ノナデカンジオールジアルカン酸エステル
１，２０−イコサンジオールジアルカン酸エステル
１，２１−ヘンイコサンジオールジアルカン酸エステル
１，２２−ドコサンジオールジアルカン酸エステル
【００３１】
１，２３−トリコサンジオールジアルカン酸エステル
１，２４−テトラコサンジオールジアルカン酸エステル
１，２５−ペンタコサンジオールジアルカン酸エステル
１，２６−ヘキサコサンジオールジアルカン酸エステル
１，２７−ヘプタコサンジオールジアルカン酸エステル
１，２８−オクタコサンジオールジアルカン酸エステル
１，２９−ノナコサンジオールジアルカン酸エステル
１，３０−トリアコンタンジオールジアルカン酸エステル
１，３１−ヘントリアコンタンジオールジアルカン酸エステル
１，３２−ドトリアコンタンジオールジアルカン酸エステル
１，３３−トリトリアコンタンジオールジアルカン酸エステル
１，３４−テトラトリアコンタンジオールジアルカン酸エステル
【００３２】
また、本発明で用いられる成分ｂの脂肪酸エステルは、例えば下記一般式（Ｉ）で表わされるものである。
Ｒ₁−ＣＯＯ−Ｒ₂ 一般式（Ｉ）
（式中、Ｒ₁、Ｒ₂は炭素数１０以上のアルキル基を表わす。）
脂肪酸エステルの炭素数は２０以上が好ましく２５以上が更に好ましく、３０以上が特に好ましい。炭素数が多くなると白濁度が高く、繰り返し使用の際の耐久性が向上するという特徴を有する。脂肪酸エステルの融点は５０℃以上が好ましい。
これらは一種又は二種以上を選択して用いられる。
【００３３】
本発明で用いられる脂肪酸エステルの具体例を以下に示す。
ラウリン酸オクタデシル
ラウリン酸ドコシル
ミリスチン酸ドコシル
パルミチン酸ドデシル
パルミチン酸テトラデシル
パルミチン酸ペンタデシル
パルミチン酸ヘキサデシル
パルミチン酸オクタデシル
パルミチン酸トリアコンチル
パルミチン酸オクタデシル
パルミチン酸ドコシル
【００３４】
ステアリン酸ビニル
ステアリン酸プロピル
ステアリン酸イソプロピル
ステアリン酸ブチル
ステアリン酸アミル
ステアリン酸ヘプチル
ステアリン酸オクチル
ステアリン酸テトラデシル
ステアリン酸ヘキサデシル
【００３５】
ステアリン酸ヘプタデシル
ステアリン酸オクタデシル
ステアリン酸ドコシル
ステアリン酸ヘキサコシル
ステアリン酸トリアコンチル
ベヘン酸ドデシル
ベヘン酸オクタデシル
ベヘン酸ドコシル
リグノセリン酸トラコシル
メリシン酸ミリシル
【００３６】
さらに、本発明で用いる成分ｂの二塩基酸エステルとしては、モノエステル、ジエステルのいずれかでもよく、下記一般式（II）で表わされるものが挙げられる。
Ｒ−ＯＯＣ−(ＣＨ₂)ｎ−ＣＯＯＲ’ 一般式（II）
（式中、Ｒ、Ｒ’は水素原子、又は炭素数１〜３０のアルキル基を表わし、Ｒ、Ｒ’は同一であっても異なっていてもよいが、同時に水素原子である場合を除く。ｎは０〜４０の整数を表わす。）
【００３７】
上記一般式（Ｉ）で表わされる二塩基酸エステルにおいて、Ｒ、Ｒ’のアルキル基の炭素数は１〜２２が好ましく、ｎは１〜３０が好ましく、２〜２０がさらに好ましい。また融点は５０℃以上が好ましい。
【００３８】
具体的には、
シュウ酸エステル
マロン酸エステル
コハク酸エステル
グルタル酸エステル
アジピン酸エステル
ピメリン酸エステル
スベリン酸エステル
アゼライン酸エステル
セバシン酸エステル
【００３９】
１−，９−ノナメチレンジカルボン酸エステル
１−，１０−デカメチレンジカルボン酸エステル
１−，１１−ウンデカメチレンジカルボン酸エステル
１−，１２−ドデカメチレンジカルボン酸エステル
１−，１３−トリデカメチレンジカルボン酸エステル
１−，１４−テトラデカメチレンジカルボン酸エステル
１−，１５−ペンタデカメチレンジカルボン酸エステル
１−，１６−ヘキサデカメチレンジカルボン酸エステル
１−，１７−ヘプタデカメチレンジカルボン酸エステル
【００４０】
１−，１８−オクタデカメチレンジカルボン酸エステル
１−，１９−ノナデカメチレンジカルボン酸エステル
１−，２０−エイコサメチレンジカルボン酸エステル
１−，２１−ヘンエイコサメチレンジカルボン酸エステル
１−，２２−ドコサメチレンジカルボン酸エステル
１−，２４−テトラコサメチレンジカルボン酸エステル
１−，２８−オクタコサメチレンジカルボン酸エステル
１−，３２−ドトリアコンタンメチレンジカルボン酸エステル等が挙げられる。
【００４１】
とくに、本発明で用いられる融点１００℃以上の有機低分子物質ｃとしては脂肪族飽和ジカルボン酸が挙げられるが、これらに限定されるものではない。
これらは、一種又は二種以上選択して用いられる。
【００４２】
これら融点１００℃以上の有機低分子物質ｃの具体例を以下に示す。
脂肪族飽和ジカルボン酸の、例えば融点１００〜１３０℃程度の有機低分子物質ｃの具体例としては、例えば、コハク酸、グルタル酸、アジピン酸、ピメリン酸、スベリン酸、アゼライン酸、セバシン酸、ウンデカン二酸、ドデカン二酸、テトラデカン二酸、ペンタデカン二酸、ヘキサデカン二酸、ヘプタデカン二酸、オクタデカン二酸、ノナデカン二酸、エイコサン二酸、ヘンエイコサン二酸、ドコサン二酸等が挙げられる。
【００４３】
本発明の可逆性感熱記録材料の感熱層の厚みは１〜３０μｍが好ましく、２〜２０μｍが更に好ましい。感熱層が厚すぎると層内での熱の分布が発生し均一に透明化することが困難となる。また、感熱層が薄すぎると白濁度が低下しコントラストが低くなる。さらに、感熱層中の有機低分子物質の量を増加させると白濁度を増すことができる。
【００４４】
樹脂母材に用いる樹脂には、プラスチックフィルム、ガラス、金属などの支持体上に塗布乾燥して積層の感熱層を形成すると、支持体との接着性が弱いものもあり、支持体と感熱層との間に接着層を設け、感熱層が剥れないようにすることも可能である。接着層の樹脂としては、支持体との接着性がよく、且つ感熱記録層の成分に悪影響を与えないものならば特に限定されず、例えば、塩化ビニル系樹脂、ポリエステル系樹脂、アクリル系樹脂、ポリアミド系樹脂等が挙げられる。特に金属、金属薄膜上には接着性が悪く、塩化ビニルとリン酸エステルを主成分とした共重合体等が接着層材料として好適に用いられる。接着層の厚みとしては、０．１〜５μｍぐらいが好ましく、更に０．３〜２μｍぐらいが好ましい。
【００４５】
また、この記録材料の画像を反射画像として用いる場合には、記録層の背面に光を反射する層を設けると記録層の厚みを薄くしてもコントラストを上げることができる。具体的にはＡｌ、Ｎｉ、Ｓｎ等を蒸着して設けた反射層が挙げることができる（特開昭６４−１４０７９号公報を参照）。
【００４６】
そして、磁気記録層と可逆性感熱層を組み合わせたカードを作成することも可能である。特に磁気記録層上に可逆性感熱層を設ける場合には、表面を滑性にするために樹脂を主成分とした平滑層を設け、その上に光を反射する層を設け、更にその上に場合により接着層を介して感熱層を設ければよい（実開平２−３８７６号公報）。他にも、光記録層顕色剤とロイコ染料で発色する感熱記録層、ＩＣ記録層を、この感熱層と一緒に具備してもよい。
【００４７】
さらに、本発明の感熱層上に、サーマルヘッド等の書き込み法による加熱手段の熱と圧力で表面が変形して透明部の透明度が低下するのを防ぐため、保護層を設けてもよい。感熱層上に積層する保護層（厚さ０．１〜５μｍ）の材料としてはシリコーン系ゴム、シリコーン樹脂（特開昭６３−２２１０８７号公報に記載）、ポリシロキサングラフトポリマー（特開昭６３−３１７３８５号公報に記載）や紫外線硬化樹脂又は電子線硬化樹脂（特開平２−５６６号公報に記載）等が挙げられる。さらに、搬送性の点より、フィラーを添加したり、滑剤を添加したりする。
【００４８】
いずれの場合も、塗布時に溶剤を用いるが、その溶剤は、感熱層の樹脂ならびに有機低分子物質を溶解しにくいほうが望ましい。
感熱層の樹脂及び有機低分子物質を溶解しにくい溶剤としてはｎ−ヘキサン、メチルアルコール、エチルアルコール、イソプロピルアルコール等が挙げられ、特にアルコール系の溶剤がコスト面から望ましい。
【００４９】
さらに、保護層形成液の溶剤やモノマー成分等から可逆性記録材料を保護するために、保護層と可逆性記録材料との間に中間層を設けることができる（特開平１−１３３７８１号公報）。
【００５０】
中間層の材料としては感熱層中の樹脂母材として挙げたものの他に下記のような熱硬化性樹脂、熱可逆性樹脂が使用可能である。
すなわち、具体的には、ポリエチレン、ポリプロピレン、ポリスチレン、ポリビニルアルコール、ポリビニルブチラール、ポリウレタン、飽和ポリエステル、不飽和ポリエステル、エポキシ樹脂、フェノール樹脂、ポリカーボネート、ポリアミド等が挙げられる。
【００５１】
中間層の厚さは用途により異なるが０．１〜２μｍくらいが好ましい。これ以下になると、保護効果が下がり、これ以上となると熱感度が低下する。
また、感熱層と支持体、又は感熱層と着色層、光反射層との間に、空気等の低屈折率層を設け、コントラストを向上させることも可能である。
【００５２】
なお、有機低分子物質ａ、ｂ、ｃの中に、有機低分子物質ａ、ｂ、ｃの各ｍｐ以下の不純物が１５％以上含まれると、印字消去において、低温環境による白濁、急冷による白濁がみられるので、これら有機低分子物質の純度は全て８６％以上であることが必要である。これらを印字する装置の条件は、サーマルヘッドが０．２〜０．３ｍＪ／ｄｏｔ（パルス幅２〜５ｍｓｅｃ）必要である。消去する装置は、サーマルヘッドとセラミックバーがあるが、これらは、小型軽量タイプとなる。サーマルヘッドでの条件は０．５〜１．０ｍＪ／ｄｏｔ（パルス幅１０〜２０ｍｓｅｃ）。セラミックバー（幅１〜５ｃｍ）での条件は表面温度１００〜１１０℃、ラインスピード１０〜５０ｍｍ／ｓｅｃである。圧力はカード形態に合せて最適化を考慮する必要である。
【００５３】
【実施例】
以下、実施例により本発明をさらに具体的に説明するが、本発明はこれら実施例に限定されるものではない。実施例中の部及び％はともに重量基準である。
実施例１
大日本インキ化学工業製ＤＳ−１７１１のＰＥＴ（ポリエチレンテレフタレート）磁気フィルム上に、アルミ蒸着加工し、できた基材のＰＥＴ面上に
塩化ビニル酢酸ビニルリン酸エステル共重合体 ５部
（デンカ製 １０００Ｐ）
ＭＥＫ（メチルエチルケトン） ２０部
トルエン ２０部
よりなる液をマイクログラビア法により塗布し、１３０℃で加熱乾燥して、厚み１〜２μｍの接着層を設けた。
【００５４】
一方、

よりなる液を、前記接着層上に、押出ダイで塗布し、１２０℃加熱乾燥して、さらに、記録層が完全に白濁する前（６０〜９０℃の温度）に、ＵＶ１２０ｗ／ｃｍ、１０ｍ／ｍｉｎ処理して、硬化させて厚み１０〜１１μｍの感熱層（図９参照）を設けた。
【００５５】
さらに、この感熱層上に
アクリル系樹脂（大日本インキ製 Ｃ７−１５７） １０部
イソプロピルアルコール １０部
炭酸カルシウム ３部
をボールミル分散して、ワイヤーバー塗布し９０℃加熱乾燥して、ＵＶ８０ｗ／ｃｍ、１０ｍ／ｍｉｎ処理して、硬化させることにより、２〜３μ厚の保護層を設けて、可逆性感熱記録材料をつくった。なお、記録層のみをＴＨＦで溶かして、にごったものを、スポイトで採集すると、大きさ２５０〜２０００Åのマイクロゲル状のものを得た（図３）。図６にこのゲル状体の顕微鏡写真（×７８０００倍）が示される。また図８には、ＴＨＦによる処理前の該ゲル状体を含有している感熱層断面の状態の顕微鏡写真（×４００００倍）が示される。
【００５６】
実施例２
実施例１の接着層上に

【００５７】
よりなる液を押出ダイで塗布し、１２０℃加熱乾燥し、記録層が完全白濁する前に、ＵＶ１２０ｗ／ｃｍで処理して、厚み１０〜１１μの感熱層（図９）を設けた。
さらに、この上に、実施例１の保護層を設けて可逆性感熱記録材料をつくった。なお、記録層のみをＴＨＦで溶かすと、図５に模式的に示されるような片状のものを得た。
【００５８】
実施例３
実施例２の記録層のかわりに、

【００５９】
よりなる液を押出ダイで塗布し、１２０℃加熱乾燥し、記録層が完全白濁する前に、ＵＶ１２０ｗ／ｃｍで処理して、厚み１０〜１１μの感熱層（図９）を設けた。
なお、記録層のみをＴＨＦで溶かすと、図５に模式的に示されるような板片状のアクリルポリマーを含んだもの２０部を得た。図７には、このアクリルポリマーを含んだこの板片状のゲル状体のＳＥＭ顕微鏡写真（７５０倍）が示される。
【００６０】
実施例４
実施例３の記録層のＡのかわりに
塩化ビニル酢酸ビニル共重合体 ４０部（Ａ）
［（デンカ製１０００ＭＴ）Ｔｇ７０℃］
塩化ビニルプロピオン酸ビニル共重合体 ２０部（Ｂ）
［（東ソ製 ＱＳ５３０）Ｔｇ６０℃］
とした可逆性感熱記録材料をつくった。記録層のみをＴＨＦで溶かすと、図５に模式的に示されるような板片状のアクリルポリマーを含んだものが得られた。
【００６１】
実施例５
実施例３の記録層のＡのかわりに
塩化ビニル酢酸ビニル共重合体 ２０部（Ａ）
［（デンカ製１０００ＭＴ）Ｔｇ９０℃］
塩化ビニル酢酸ビニル共重合体 ４０部（Ｂ）
［（デンカ製１０００ＭＴ３）Ｔｇ６５℃］
とした可逆性感熱記録材料をつくった。
【００６２】
比較例１
１−ヒドロキシ−シクロヘキシル−フェニルケトンを添加せず、ＵＶ処理のかわりに、加速電圧１００ＫＶ、照射線量１０Ｍｒａｄ、照射スピード１０ｍ／ｍｉｎのＥＢ処理にて全面架橋した以外は実施例２と同様にして可逆性感熱記録材料を得た。
【００６３】
比較例２
アクリルモノマー、１−ヒドロキシ−シクロヘキシル−フェニルケトンを添加せず、その分１０００ＭＴ２を７０部にして乾燥のみした以外は実施例２と同様にして可逆性感熱記録材料を得た。
これら各可逆性感熱記録材料について、情報の消去性、繰り返し使用時の耐久性、副作用としての動的粘弾を試験した。その結果は表１に示される。
【００６４】
【表１】

【００６５】
消去性は、サーマルヘッド１４００Ωの端面型、パルス幅２０ｍｓｅｃで、消去したとき、像濃度を、最高濃度（通常は１．１０〜１．１５）から少なくとも０．２低下させるのに要するエネルギー量（ｍＪ／ｄｏｔ）。
可逆性感熱記録材料は、ＪＩＳサイズ（５．５ｃｍ×８．６ｃｍ）のカードに加工して、プリンタＲ３０００（九州松下製）で印字消去テストした。
耐久性は１回目及び５００回繰り返し時（５００回目）の白さの濃度。
その他は、副作用を明記。
濃度はマクベス濃度計、ＲＤ９１４を使用。
動的粘弾性は、セイコー電子のＴＭＡを使用。
【００６６】
【発明の効果】
以上、詳細かつ具体的に説明したように、本発明の可逆性感熱記録材料は、１．消去性がよく、耐久性がよい。電子線硬化による記録層の変色もなく、下地にアルミ蒸着のときの腐食もなく、２．耐久性がよく、３．安定して、耐久性がよく、かつコントラストもよく、４．消去性、耐久性、コントラストがよく、５．経時消去性がよく、６．クラックの発生がなく、７．消去幅の拡大ができ、コントラストも高く、８．消去と印字の感度がよく、耐熱性がよいという優れた効果を発揮する。
【図面の簡単な説明】
【図１】本発明の可逆性感熱記録材料における像形成−像消去の機構を説明する図である。
【図２】本発明の可逆性感熱記録材料における感熱層を模式的に説明する図である。
【図３】本発明の可逆性感熱記録材料における樹脂成分Ｃと樹脂成分Ａの会合体を模式的に説明する図である。
【図４】本発明の可逆性感熱記録材料における別の感熱層を模式的に説明する図である。
【図５】本発明の可逆性感熱記録材料における樹脂成分Ｃと樹脂成分Ａの別の会合体を模式的に説明する図である。
【図６】本発明の可逆性感熱記録材料を溶剤処理した後に得られる樹脂成分Ａと樹脂成分Ｃの会合体の１例を示す電子顕微鏡写真（４００００倍）である。
【図７】本発明の可逆性感熱記録材料を溶剤処理した後に得られる樹脂成分Ａと樹脂成分Ｃの会合体の別の１例を示す位相差電子顕微鏡写真（７５０倍）である。
【図８】本発明の可逆性感熱記録材料の感熱層断面に見られる樹脂成分Ａと樹脂成分Ｃの会合体の１例を示す電子顕微鏡写真（７８０００倍）である。
【図９】本発明に係る可逆性感熱記録材料の層構成の１具体例を示す図である。
【符号の説明】
Ａ 樹脂成分
Ｂ 樹脂成分
Ｃ 樹脂成分
ａ 有機低分子物質
ｂ 有機低分子物質
ｃ 有機低分子物質[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reversible thermosensitive recording material, and in particular, an improved reversible thermosensitive sensor that can repeatedly display (write) and erase information using reversible transparency or color tone change depending on the temperature of a thermosensitive layer. The present invention relates to a recording medium, a card made therefrom, and a reversible thermosensitive recording apparatus that records information on the recording medium, erases the recorded information, and records other information.
[0002]
[Prior art]
In recent years, a reversible thermosensitive recording material that can perform temporary image formation (information writing) and can erase the image (erasing information) when it is no longer needed has been attracting attention. A reversible thermosensitive recording material in which an organic low molecular weight substance such as a higher fatty acid is dispersed in a resin matrix such as a vinyl chloride-vinyl acetate copolymer having a low glass transition temperature is known (Japanese Patent Application Laid-Open No. Sho-sho). 54-119377, JP-A-55-154198). As shown in FIG. 1 (a), such a reversible thermosensitive recording material is mainly composed of a resin base material and an organic low molecular weight substance dispersed in the resin base material on a support, and depends on temperature. And a heat-sensitive layer whose transparency changes reversibly. The recording / reproducing method of this reversible thermosensitive recording material is shown in FIG._FourRecording by applying heat at the above temperature, T₂To T_ThreeRegeneration is performed by applying heat in a specific temperature range up to. When this reversible thermosensitive recording material is heated, the temperature T₁Gradually becomes transparent, and at the beginning the temperature T₂~ T_ThreeWhen it is heated to transparent, it becomes transparent.₀It remains transparent even when returned to the normal temperature below. This is the temperature T₁The resin begins to soften from the vicinity, and as the softening progresses, the resin shrinks and reduces the interface between the resin and the organic substance particles or the voids in the particles.₂~ T_ThreeThen, the organic low molecular weight material becomes semi-molten and becomes transparent by filling the remaining void with molten organic low molecular weight material, and when it is cooled with the seed crystal remaining, it will crystallize at a relatively high temperature, while the resin is still This is considered to be because the resin follows the volume change of the particles accompanying crystallization due to the softened state and voids are not formed and the transparent state is maintained.
[0003]
T_FourWhen heated to the above temperature, a translucent state intermediate between maximum transparency and maximum opacity is achieved. Next, when this temperature is lowered, the first cloudy opaque state is restored without taking the transparent state again. This is the temperature T_FourAfter the organic low molecular weight material is completely melted as described above, it becomes supercooled and T₀It is considered that crystallization occurs at a slightly higher temperature, and at that time, the resin cannot follow the volume change accompanying crystallization and voids are generated.
However, the temperature-transparency change curve shown in FIG. 1 is only a representative example, and changing the material may change the transparency of each state depending on the material.
[0004]
On the other hand, a heat-sensitive layer whose main component is a resin base material and an electron-donating color-forming compound and an electron-accepting compound dispersed in the resin base material, and the color tone reversibly changes depending on temperature. A recording / reproducing method of a reversible thermosensitive recording material having an overcoat layer is shown in FIG. T in FIG. 1 (b)₂Recorded by applying heat at a temperature above ', and T₀’To T₁Regeneration is performed by applying heat in a specific temperature range up to '. A thermal head is mainly used for recording, and a hot stamp, a heat block, a ceramic heater, or a thermal head is used for reproduction.
In FIG. 1A (representing a change in transparency due to heat), a heat-sensitive layer mainly composed of a resin base material and an organic low molecular weight substance dispersed in the resin base material is, for example, T₀It is in an opaque state at the following normal temperature.
[0005]
Conventional reversible thermosensitive recording materials have the disadvantage that the thermosensitive layer and the like are destroyed by receiving heat and pressure from a thermal head or the like by repeated use. Therefore, in order to remedy this drawback, a thermosetting resin is used (Japanese Patent Laid-Open No. 7-132681), or the heat-sensitive layer is cured using an electron beam or an ultraviolet resin (Japanese Patent Laid-Open No. 7-172072). However, when a thermosetting resin is used, curing of the heat sensitive layer proceeds with time, and the reversible characteristics of the heat sensitive layer change. In addition, resin curing with an electron beam causes discoloration due to deoxidation due to a reaction, and when the support is a metal, it reacts to cause corrosion. Resin curing with ultraviolet rays tends to lack contrast when used repeatedly. The lack of contrast is caused by the fact that the organic low molecular weight particles are large and light refraction occurs at the interface with the resin binder, resulting in turbidity.
In JP-A-5-193258, in the heat sensitive layer or in the anchor layer provided between the support and the heat sensitive layer, a spherical shape for reducing the decrease in white turbidity and improving the durability, It describes that spacer particles such as branches and needles are dispersed. While this technique certainly provides a substantial improvement, it tends to lack contrast.
[0006]
[Problems to be solved by the invention]
The problem in the present invention is to solve the above-mentioned problems in the prior art, prevent deterioration of erasability over time, in which information recorded by heat is hard to disappear with time, improve durability, and durability including heat resistance. It is to provide a reversible thermosensitive recording material that exhibits improved whiteness and transparency by improving the durability, contrast and durability, and erasing when the reversible thermosensitive recording material is used repeatedly. Provides a reversible thermosensitive recording material with an expanded width, optimal durability, erase width and erasability over time, and provides a reversible thermosensitive recording material with optimal durability, erase width and erasability over time, and reversible It is to improve the sensitivity of erasure and printing in the heat-sensitive recording material. At the same time, another side effect is to be reduced in the reversible thermosensitive recording material. It is another object of the present invention to provide a card having the optimum function and to provide the optimum erasing / printing apparatus with a reduced size and weight.
[0007]
[Means for Solving the Problems]
We use curable resins (thermosetting resins, ultraviolet curable resins, electron beam curable resins, etc.) as resin base materials and non-curable resins that have been used in the past (vinyl chloride resins, vinyl chloride-vinyl acetate). As a result of intensive studies on the correlation between the curable resin and the non-curable resin in a mixed system of a copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, etc., the curable resin is reversible thermosensitive. The recording material is almost completely matrix-like and is firmly fixed so that the non-curable resin is not released from the matrix even when treated with a suitable solvent of non-curable resin such as THF (tetrahydrofuran). Although the desired reusability of the reversible thermosensitive recording material is not achieved under certain conditions, at least a substantial amount when treated with a solvent for a non-curable resin such as THF It has been found that when the curable resin is gently crosslinked to such an extent that the non-curable resin is released into the solvent, a more preferable reusability of the reversible thermosensitive recording material is achieved. In such a preferable reversible thermosensitive recording material, it was found that the cross-linked product of the curable resin was dispersed in a lump. Further, as a result of examining the crosslinked product itself of the curable resin dispersed in a lump, the crosslinked product of the curable resin dispersed in a lump is also at least partially wound with the non-curable resin. I found out that it existed in an intricate form, and came to actually know the shape in that case. Furthermore, the crosslinked product of curable resin dispersed in a lump is used to cure the curable resin before the occurrence of white turbidity due to the other organic low molecular weight substance when preparing the reversible thermosensitive recording material. It has been found that it is advantageously produced by
[0008]
Due to the above-described cloudy image formation-image erasure mechanism in the reversible thermosensitive recording material, such a preferable massive dispersion is not limited to the case of a mixed system of a curable resin and a non-curable resin. Naturally, it can also be produced in the case of a mixed system of a resin having a high glass transition temperature (Tg) and a low resin. Furthermore, we have studied in detail the effects of the glass transition temperature (Tg) of the resin used, the influence of the dynamic elastic modulus, and the influence of the melting point of the organic low molecular weight substance used, and such aggregates exist. Among the reversible thermosensitive recording materials, more preferable ones were confirmed.
[0009]
  Therefore, the above-mentioned problem is (1) “in a reversible thermosensitive recording material containing a resin and a low molecular weight organic substance on at least one surface of a support, the resin has two or more glass transition temperatures (Tg). ) Include different resins, the resin T having a high Tg is an ultraviolet curable resin, the resin A having a low Tg is a vinyl chloride, a vinyl chloride copolymer, a vinylidene chloride copolymer, and the resin AAnd a monomer for forming the resin C,And a thermosensitive layer coating solution containing the above-mentioned organic low molecular weight substance.Before heat-dried and the heat-sensitive layer becomes completely cloudy (60-90 ° C)A reversible thermosensitive recording material characterized in that the resin C is dispersed in a microgel form in the thermosensitive layer by irradiation with ultraviolet rays, (2) “Tg of the resin C is 180 ° C. or higher. The reversible thermosensitive recording material according to the above item (1) ”, (3)“ The resin is composed of two types of resin A having a low Tg and resin C having a high Tg, and C / A is expressed by weight ratio. 1/99 to 40/60, wherein the reversible thermosensitive recording material according to the above item (1) or (2) ”, (4)“ Furthermore, a vinyl chloride copolymer is used as the resin B. The reversible thermosensitive recording material according to item (1) or (2) above, wherein Tg is A> B ”, (5)“ the organic low-molecular substance is: It is composed of at least three components b and c, and the melting point (mp) is low such that b <a <c. The reversible thermosensitive recording material according to any one of the paragraph (1) to (4) of this section, characterized in that it comprises a child agent. However,
  a component is monocarboxylic acid (mp60-90 degreeC),
  The b component is a fatty acid ester, a polyhydric alcohol difatty acid ester, a dibasic acid ester (mp 50 to 80 ° C.),
  c component means fatty acid saturated dicarboxylic acid (mp100-130 degreeC), respectively. Is achieved.
[0010]
Hereinafter, the present invention will be described in detail. In the reversible thermosensitive recording material of the present invention, in the reversible thermosensitive layer, the resin A contains the resin C which is agglomerated in addition to the organic low molecule. The size of the lump is preferably a microgel of 100 mm or more from the viewpoint of the durability of the heat-sensitive layer. On the other hand, when it is 10,000 m or more, the contrast tends to decrease.
This resin C eliminates changes over time (deterioration) due to repeated use of the resin A, prevents an increase in the degree of cure over time due to the use of conventional thermosetting resins, decomposes the resin by electron beam curing, and breaks the support It is possible to prevent deterioration of erasability due to ultraviolet curing. The resin A in the present invention can be a resin of a general reversible thermosensitive layer such as a vinyl chloride polymer, a vinyl chloride copolymer, and a vinylidene chloride copolymer.
[0011]
In the present invention, the resin C in the form of a microgel is associated with and integrated with the resin A as schematically shown in FIGS. 1 and 2, and the heat sensitive layer (recording layer) can be dissolved with an organic solvent. Only the aggregates settle without being dissolved. The reversible thermosensitive recording layer is generally deformed by heat and pressure of a thermal head or the like. However, in the recording layer of the present invention, the microgel resin C is in an associated state such as entangled with the resin A. Hard to do. Therefore, the reversible thermosensitive recording material of the present invention does not change with time and has good durability.
Further, in the present invention, when the resin C is configured in a plate shape as schematically shown in FIGS. 3 and 4 (for example, a thickness of 1 to 10 μm and a length of 1 to 30 mm), durability is further improved. The harder the resin C as the core of the aggregate, the higher the Tg, the smaller the deformation of the heat-sensitive layer, the better the durability of the reversible thermosensitive recording material, and the glass used for erasing and printing generally at a temperature of 180 ° C or higher. A transition point (Tg) is more preferable. The blending ratio of the resin A and the resin C is preferably a weight ratio of C / A = 1/99 to 40/60. If the resin C is too much, reversibility, printing and erasure are not exhibited. When the amount of the resin C is too small, the change with time is large and the durability is not good.
The resin C in the present invention generally refers to one obtained by UV-curing one or two or more acrylic monomers such as acrylic ester, acrylic urethane, and acrylic epoxy that are cured by ultraviolet rays using a photoinitiator. Of these, preferred are those UV-cured using monomers such as acrylic ester and acrylic urethane. The curing method is preferably blended with the resin A and then cured.
[0012]
Further, when the heat is selectively transmitted to the resin A by a thermal head or the like, the resin B which has a Tg lower than the Tg of the resin A and has a Tg lower than that of the resin A, which is easily deformed by pressure and does not impair the function of the resin A. Is advantageously used in combination with resin A. By including the resin B, the erasing ability of the heat-sensitive layer can be afforded, and repeated erasability is further improved. The resin B may be a resin of the same series as the resin A, for example, a copolymer of vinyl chloride and a vinyl ester of a fatty acid having 3 or more carbon atoms, a monomer having vinyl chloride, ethylene, an aliphatic group part and an acid group part. Ternary copolymers with (or dimers, trimers, oligomers, etc.), such as vinyl chloride and other suitable groups containing vinyl chloride as a nucleus and further containing an aliphatic group part and an acid group part (and / or acid residue part) It may be a copolymer with various monomers (or dimers, trimers, oligomers).
[0013]
On the other hand, the present invention includes the combined use of three types of organic low-molecular substances a, b and c as organic low-molecular substances. (However, a component means monocarboxylic acid (mp60-90 degreeC), b component means a fatty acid ester, a polyhydric-alcohol difatty acid ester, dibasic acid ester (mp50-80 degreeC), respectively. , Fatty acid dicarboxylic acid (mp 100-130 ° C.), and melting point (mp) is in a relationship of b <a <c.)
[0014]
In the combination of the resin A and the low molecular weight organic substance in the conventional reversible thermosensitive recording material, there is a limit to the expansion of the contrast of the thermosensitive recording layer and the erasing width of the information. Not suitable for ℃. In addition, although the printing density is reduced due to storage, in the present invention, these problems are solved by using the organic low-molecular substances a, b, and c together. The organic low molecular weight materials a and c alone cannot solve the above problem, and the organic low molecular weight materials b and c alone cannot solve the above problem. In the case of only the organic low-molecular substances a and c, it is impossible to expect an increase in the erase width.
On the other hand, for the convenience of forming a reversible thermosensitive layer by solution coating, it is desirable that these organic low molecular substances have an mp of 90 ° C. or lower for organic low molecular substances a and 80 ° C. or lower for b. Moreover, the organic low molecular weight substances a and b must be compatible. Furthermore, unless mp is 60 ° C. or higher for organic low molecular weight substance a and 50 ° C. or higher for b, it is impossible to use the obtained reversible thermosensitive recording material in an environment of 40 ° C. or lower. The difference in mp between the organic low molecular weight substances a and b brings about a difference in crystallization speed in the heat sensitive layer.
[0015]
When the reversible thermosensitive recording material of the present invention is composed of the resin components A, B and C, the dynamic viscoelasticity of the rubber region is 10^Five-10⁷dyn / cm²Is desirable. 10^Fivedyn / cm²If it is below, it will be hard and brittle.⁷dyn / cm²If it is above, the particles are deformed and the durability of the reversible thermosensitive recording material is lost.
[0016]
Examples of acrylic monomers for these resin components include the following monomers.
[0017]
[Chemical 1]

[0018]
[Chemical 2]

[0019]
[Chemical 3]

[0020]
[Formula 4]

[0021]
[Chemical formula 5]

[0022]
[Chemical 6]

[0023]
[Chemical 7]

[0024]
[Chemical 8]

[0025]
[Chemical 9]

[0026]
The photoinitiator used in the present invention may be a common photoinitiator, such as benzophenone, 1-hydroxy-cyclohexyl-phenylketone and the like. Further, a sensitizer may be added. The UV irradiation conditions may be 60 to 200 w / cm and 1 to 20 m / min, and it is desirable to perform the treatment in a nitrogen atmosphere.
[0027]
Of the organic low-molecular substances a, b and c in the present invention, the organic low-molecular substance a is preferably mp 60 to 90 ° C. Those with mp of 60 ° C. or lower have insufficient contrast and poor reversibility. Those with mp of 90 ° C. or higher are not dispersed in the resin. More specifically, the organic low molecular weight substance a includes lauric acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, behenic acid, nonadecanoic acid, alginate, henicosanoic acid, tricosanoic acid, lignoceric acid, pentacosanoic acid, Mention may be made of aliphatic monocarboxylic acids such as serotic acid, heptacosanoic acid, montanic acid, melicic acid, oleic acid, for example higher fatty acids.
[0028]
Examples of the polyhydric alcohol difatty acid ester of the organic low molecular weight substance b used in the present invention include those represented by the following general formula.
CH_Three(CH₂) m-COO (CH₂) nOOC (CH₂m-CH_Three
(In the formula, n is an integer of 2-40, preferably 3-30, more preferably 4-22. M is an integer of 0-38, preferably 1-28, more preferably 2-20. )
[0029]
Specific examples include the following.
1,2-ethanediol dialkanoic acid ester
1,3-propanediol dialkanoic acid ester
1,4-butanediol dialkanoic acid ester
1,5-pentanediol dialkanoic acid ester
1,6-hexanediol dialkanoic acid ester
1,7-heptanediol dialkanoic acid ester
1,8-octanediol dialkanoic acid ester
1,9-nonanediol dialkanoic acid ester
1,10-decanediol dialkanoic acid ester
1,11-undecanediol dialkanoic acid ester
[0030]
1,12-dodecanediol dialkanoic acid ester
1,13-tridecanediol dialkanoic acid ester
1,14-tetradecanediol dialkanoic acid ester
1,15-pentadecanediol dialkanoic acid ester
1,16-hexadecanediol dialkanoic acid ester
1,17-heptadecanediol dialkanoic acid ester
1,18-octadecanediol dialkanoic acid ester
1,19-nonadecanediol dialkanoic acid ester
1,20-icosanediol dialkanoic acid ester
1,2-henicosanediol dialkanoic acid ester
1,2-docosanediol dialkanoic acid ester
[0031]
1,3-tricosanediol dialkanoic acid ester
1,24-tetracosanediol dialkanoic acid ester
1,25-pentacosanediol dialkanoic acid ester
1,26 hexacosanediol dialkanoic acid ester
1,27-heptacosanediol dialkanoic acid ester
1,28-octacosanediol dialkanoic acid ester
1,29-Nonacosanediol dialkanoic acid ester
1,30-triacontanediol dialkanoic acid ester
1,31-Hentriacontanediol dialkanoic acid ester
1,32-Dotriacontanediol dialkanoic acid ester
1,33-tritriacontanediol dialkanoic acid ester
1,34-tetratriacontanediol dialkanoic acid ester
[0032]
Moreover, the fatty acid ester of the component b used by this invention is represented by the following general formula (I), for example.
R₁-COO-R₂ Formula (I)
(Wherein R₁, R₂Represents an alkyl group having 10 or more carbon atoms. )
The number of carbon atoms of the fatty acid ester is preferably 20 or more, more preferably 25 or more, and particularly preferably 30 or more. When the number of carbon atoms increases, the white turbidity is high and the durability during repeated use is improved. The melting point of the fatty acid ester is preferably 50 ° C. or higher.
These are used alone or in combination of two or more.
[0033]
Specific examples of the fatty acid ester used in the present invention are shown below.
Octadecyl laurate
Docosyl laurate
Docosyl myristate
Dodecyl palmitate
Tetradecyl palmitate
Pentadecyl palmitate
Hexadecyl palmitate
Octadecyl palmitate
Triacontyl palmitate
Octadecyl palmitate
Docosyl palmitate
[0034]
Vinyl stearate
Propyl stearate
Isopropyl stearate
Butyl stearate
Amyl stearate
Heptyl stearate
Octyl stearate
Tetradecyl stearate
Hexadecyl stearate
[0035]
Heptadecyl stearate
Octadecyl stearate
Docosyl stearate
Hexacosyl stearate
Triacontyl stearate
Dodecyl behenate
Octadecyl behenate
Docosyl behenate
Tracosyl lignocerate
Myricyl melicate
[0036]
Furthermore, the dibasic acid ester of component b used in the present invention may be either a monoester or a diester, and examples thereof include those represented by the following general formula (II).
R-OOC- (CH₂) n-COOR 'General formula (II)
(In the formula, R and R ′ represent a hydrogen atom or an alkyl group having 1 to 30 carbon atoms, and R and R ′ may be the same or different, except for the case where they are simultaneously a hydrogen atom. n represents an integer of 0 to 40.)
[0037]
In the dibasic acid ester represented by the above general formula (I), the alkyl group of R and R ′ preferably has 1 to 22 carbon atoms, n is preferably 1 to 30, and more preferably 2 to 20. The melting point is preferably 50 ° C. or higher.
[0038]
In particular,
Oxalic acid ester
Malonic acid ester
Succinic acid ester
Glutaric acid ester
Adipic acid ester
Pimelic acid ester
Suberic acid ester
Azelaic acid ester
Sebacic acid ester
[0039]
1-, 9-nonamethylene dicarboxylic acid ester
1-, 10-Decamethylene dicarboxylic acid ester
1-, 11-Undecamethylene dicarboxylic acid ester
1-, 12-dodecamethylene dicarboxylic acid ester
1-, 13-tridecamethylene dicarboxylic acid ester
1-, 14-tetradecamethylene dicarboxylic acid ester
1-, 15-pentadecamethylene dicarboxylic acid ester
1-, 16-hexadecamethylene dicarboxylic acid ester
1-, 17-heptadecamethylene dicarboxylic acid ester
[0040]
1-, 18-octadecamethylene dicarboxylic acid ester
1-, 19-Nonadecamethylene dicarboxylic acid ester
1-, 20-eicosamethylene dicarboxylic acid ester
1-, 21-heneicosamethylene dicarboxylic acid ester
1-, 22-docosamethylene dicarboxylic acid ester
1-, 24-tetracosamethylene dicarboxylic acid ester
1-, 28-octacosamethylene dicarboxylic acid ester
Examples thereof include 1-, 32-dotriacontane methylene dicarboxylic acid ester.
[0041]
In particular, the organic low molecular weight substance c having a melting point of 100 ° C. or higher used in the present invention includes aliphatic saturated dicarboxylic acids, but is not limited thereto.
These are used alone or in combination of two or more.
[0042]
Specific examples of these organic low-molecular substances c having a melting point of 100 ° C. or higher are shown below.
Specific examples of the aliphatic low molecular weight substance c having a melting point of about 100 to 130 ° C. include, for example, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecane. Examples include diacid, dodecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, eicosane diacid, heneicosane diacid, docosane diacid and the like.
[0043]
The thickness of the thermosensitive layer of the reversible thermosensitive recording material of the present invention is preferably 1 to 30 μm, more preferably 2 to 20 μm. If the heat-sensitive layer is too thick, heat distribution occurs in the layer, and it becomes difficult to make it transparent uniformly. On the other hand, if the heat sensitive layer is too thin, the turbidity is lowered and the contrast is lowered. Furthermore, the turbidity can be increased by increasing the amount of the low molecular weight organic substance in the heat sensitive layer.
[0044]
Some resins used as resin base materials have poor adhesion to the support when coated and dried on a support such as plastic film, glass, or metal to form a laminated heat-sensitive layer. It is also possible to provide an adhesive layer between and to prevent the heat-sensitive layer from peeling off. The resin of the adhesive layer is not particularly limited as long as it has good adhesion to the support and does not adversely affect the components of the heat-sensitive recording layer. For example, vinyl chloride resin, polyester resin, acrylic resin, Examples thereof include polyamide-based resins. In particular, adhesiveness is poor on a metal or metal thin film, and a copolymer or the like mainly composed of vinyl chloride and phosphate is preferably used as the adhesive layer material. The thickness of the adhesive layer is preferably about 0.1 to 5 μm, more preferably about 0.3 to 2 μm.
[0045]
Further, when an image of this recording material is used as a reflection image, if a layer that reflects light is provided on the back surface of the recording layer, the contrast can be increased even if the thickness of the recording layer is reduced. Specifically, a reflective layer provided by vapor deposition of Al, Ni, Sn or the like can be given (see Japanese Patent Application Laid-Open No. 64-14079).
[0046]
It is also possible to create a card that combines a magnetic recording layer and a reversible thermosensitive layer. In particular, when a reversible thermosensitive layer is provided on a magnetic recording layer, a smooth layer mainly composed of a resin is provided to make the surface slippery, and a layer that reflects light is provided thereon, and further thereon. In some cases, a heat-sensitive layer may be provided through an adhesive layer (Japanese Utility Model Laid-Open No. 2-3876). In addition, a thermal recording layer that develops color with an optical recording layer developer and a leuco dye, and an IC recording layer may be provided together with the thermal layer.
[0047]
Furthermore, a protective layer may be provided on the heat-sensitive layer of the present invention in order to prevent the surface from being deformed by the heat and pressure of a heating means such as a thermal head and the like, thereby reducing the transparency of the transparent portion. Examples of the material for the protective layer (thickness 0.1 to 5 μm) laminated on the heat sensitive layer include silicone rubber, silicone resin (described in JP-A-62-221087), and polysiloxane graft polymer (JP-A-63-1). 317385), an ultraviolet curable resin or an electron beam curable resin (described in JP-A-2-566), and the like. Further, from the viewpoint of transportability, a filler is added or a lubricant is added.
[0048]
In either case, a solvent is used at the time of coating, but it is desirable that the solvent is less likely to dissolve the resin of the heat sensitive layer and the organic low molecular weight substance.
Examples of the solvent that hardly dissolves the resin and the organic low molecular weight substance in the heat sensitive layer include n-hexane, methyl alcohol, ethyl alcohol, isopropyl alcohol, and the like, and alcohol-based solvents are particularly desirable from the viewpoint of cost.
[0049]
Furthermore, an intermediate layer can be provided between the protective layer and the reversible recording material in order to protect the reversible recording material from the solvent, monomer component, etc. of the protective layer forming liquid (Japanese Patent Laid-Open No. 1-133781). .
[0050]
As the material for the intermediate layer, the following thermosetting resins and thermoreversible resins can be used in addition to those listed as the resin base material in the thermosensitive layer.
Specifically, polyethylene, polypropylene, polystyrene, polyvinyl alcohol, polyvinyl butyral, polyurethane, saturated polyester, unsaturated polyester, epoxy resin, phenol resin, polycarbonate, polyamide and the like can be mentioned.
[0051]
The thickness of the intermediate layer varies depending on the use, but is preferably about 0.1 to 2 μm. If it becomes less than this, a protective effect will fall, and if it becomes more than this, thermal sensitivity will fall.
It is also possible to improve contrast by providing a low refractive index layer such as air between the heat sensitive layer and the support or between the heat sensitive layer and the colored layer and the light reflecting layer.
[0052]
If the organic low molecular weight substances a, b, and c contain impurities of 15% or less of each of the organic low molecular weight substances a, b, and c, white turbidity due to low-temperature environment or white turbidity due to rapid cooling during printing erasure Therefore, the purity of these organic low molecular substances must be 86% or more. The condition of the apparatus for printing these is that the thermal head needs 0.2 to 0.3 mJ / dot (pulse width 2 to 5 msec). The erasing device includes a thermal head and a ceramic bar, which are small and light. Conditions for the thermal head are 0.5 to 1.0 mJ / dot (pulse width 10 to 20 msec). The conditions for the ceramic bar (width 1 to 5 cm) are a surface temperature of 100 to 110 ° C. and a line speed of 10 to 50 mm / sec. The pressure needs to be optimized in accordance with the card form.
[0053]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples. Both parts and% in the examples are based on weight.
Example 1
On the PET surface of the base material produced by aluminum deposition on a PET (polyethylene terephthalate) PET-1711 magnetic film made by Dainippon Ink & Chemicals, Inc.
5 parts vinyl chloride vinyl acetate phosphate copolymer
(Denka 1000P)
MEK (methyl ethyl ketone) 20 parts
20 parts of toluene
The resulting liquid was applied by a microgravure method and dried by heating at 130 ° C. to provide an adhesive layer having a thickness of 1 to 2 μm.
[0054]
on the other hand,

The liquid consisting of the above was applied onto the adhesive layer with an extrusion die, heated and dried at 120 ° C., and before the recording layer became completely cloudy (temperature of 60 to 90 ° C.), UV 120 w / cm, 10 m / A heat-sensitive layer (see FIG. 9) having a thickness of 10 to 11 μm was provided by performing a min treatment and curing.
[0055]
Furthermore, on this heat sensitive layer
Acrylic resin (C7-157, manufactured by Dainippon Ink) 10 parts
10 parts isopropyl alcohol
Calcium carbonate 3 parts
Is dispersed by ball milling, coated with a wire bar, heated and dried at 90 ° C., treated with UV 80 w / cm, 10 m / min, and cured to provide a protective layer having a thickness of 2 to 3 μm. I made it. In addition, when only the recording layer was dissolved in THF and the dusted material was collected with a dropper, a microgel-like material having a size of 250 to 2000 mm was obtained (FIG. 3). FIG. 6 shows a micrograph (× 78000 times) of this gel-like body. FIG. 8 shows a photomicrograph (× 40000 times) of the state of the cross section of the heat-sensitive layer containing the gel-like material before the treatment with THF.
[0056]
Example 2
On the adhesive layer of Example 1

[0057]
The resulting solution was applied with an extrusion die, heated and dried at 120 ° C., and treated with UV 120 w / cm before the recording layer became completely cloudy to provide a heat-sensitive layer having a thickness of 10 to 11 μm (FIG. 9).
Further, a protective layer of Example 1 was provided thereon to produce a reversible thermosensitive recording material. When only the recording layer was dissolved in THF, a piece-like material as schematically shown in FIG. 5 was obtained.
[0058]
Example 3
Instead of the recording layer of Example 2,

[0059]
The resulting solution was applied with an extrusion die, heated and dried at 120 ° C., and treated with UV 120 w / cm before the recording layer became completely cloudy to provide a heat-sensitive layer having a thickness of 10 to 11 μm (FIG. 9).
When only the recording layer was dissolved in THF, 20 parts containing a plate-like acrylic polymer as schematically shown in FIG. 5 were obtained. FIG. 7 shows an SEM micrograph (magnification 750) of the plate-like gel-like body containing the acrylic polymer.
[0060]
Example 4
Instead of A in the recording layer of Example 3
40 parts of vinyl chloride vinyl acetate copolymer (A)
[(Denka 1000MT) Tg 70 ° C]
20 parts of vinyl chloride propionate copolymer (B)
[(Tosoh QS530) Tg60 ° C]
A reversible thermosensitive recording material was produced. When only the recording layer was dissolved in THF, a plate-like acrylic polymer as schematically shown in FIG. 5 was obtained.
[0061]
Example 5
Instead of A in the recording layer of Example 3
20 parts of vinyl chloride vinyl acetate copolymer (A)
[(DENKA 1000MT) Tg 90 ° C]
40 parts of vinyl chloride vinyl acetate copolymer (B)
[(Denka 1000MT3) Tg65 ° C]
A reversible thermosensitive recording material was produced.
[0062]
Comparative Example 1
Reversible in the same manner as in Example 2 except that 1-hydroxy-cyclohexyl-phenyl ketone was not added, and instead of UV treatment, the entire surface was crosslinked by EB treatment with an acceleration voltage of 100 KV, an irradiation dose of 10 Mrad, and an irradiation speed of 10 m / min. A heat-sensitive recording material was obtained.
[0063]
Comparative Example 2
A reversible thermosensitive recording material was obtained in the same manner as in Example 2 except that the acrylic monomer and 1-hydroxy-cyclohexyl-phenyl ketone were not added, and the amount of 1000MT2 was changed to 70 parts.
Each of these reversible thermosensitive recording materials was tested for information erasability, durability during repeated use, and dynamic viscoelasticity as a side effect. The results are shown in Table 1.
[0064]
[Table 1]

[0065]
The erasability is the end face type of a thermal head of 1400Ω, the pulse width of 20 msec, and the amount of energy required to reduce the image density by at least 0.2 from the maximum density (usually 1.10 to 1.15) when erasing ( mJ / dot).
The reversible thermosensitive recording material was processed into a JIS size (5.5 cm × 8.6 cm) card and subjected to a print erasure test with a printer R3000 (manufactured by Kyushu Matsushita).
Durability is the density of whiteness at the first and 500th repetition (500th).
Other side effects are specified.
Concentration uses Macbeth densitometer, RD914.
Dynamic viscoelasticity uses Seiko TMA.
[0066]
【The invention's effect】
As described above in detail and specifically, the reversible thermosensitive recording material of the present invention has the following features. Good erasability and good durability. 1. There is no discoloration of the recording layer due to electron beam curing, and there is no corrosion when depositing aluminum on the substrate. 2. Good durability. 3. Stable, durable and has good contrast. 4. Good erasability, durability and contrast. 5. Good erasability with time, 6. No cracks are generated. 7. The erasure width can be expanded and the contrast is high. It has excellent erasing and printing sensitivity and excellent heat resistance.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a mechanism of image formation and image erasure in a reversible thermosensitive recording material of the present invention.
FIG. 2 is a diagram schematically illustrating a heat-sensitive layer in the reversible heat-sensitive recording material of the present invention.
FIG. 3 is a diagram schematically illustrating an association of resin component C and resin component A in the reversible thermosensitive recording material of the present invention.
FIG. 4 is a diagram schematically illustrating another thermosensitive layer in the reversible thermosensitive recording material of the present invention.
FIG. 5 is a diagram schematically illustrating another aggregate of resin component C and resin component A in the reversible thermosensitive recording material of the present invention.
FIG. 6 is an electron micrograph (40000 times) showing an example of an aggregate of resin component A and resin component C obtained after solvent treatment of the reversible thermosensitive recording material of the present invention.
FIG. 7 is a phase contrast electron micrograph (magnification 750) showing another example of the association of resin component A and resin component C obtained after solvent treatment of the reversible thermosensitive recording material of the present invention.
FIG. 8 is an electron micrograph (magnified 78,000 times) showing an example of an aggregate of resin component A and resin component C found in the heat-sensitive layer cross section of the reversible thermosensitive recording material of the present invention.
FIG. 9 is a view showing one specific example of a layer structure of a reversible thermosensitive recording material according to the present invention.
[Explanation of symbols]
A resin component
B resin component
C Resin component
a Organic low molecular weight substance
b Organic low molecular weight substances
c Organic low molecular weight substances

Claims (5)

In a reversible thermosensitive recording material containing a resin and a low molecular weight organic substance on at least one surface of the support, the resin contains two or more kinds of resins having different glass transition temperatures (Tg), and a resin C having a high Tg is provided. Resin A, which is an ultraviolet curable resin and has a low Tg, is vinyl chloride, vinyl chloride copolymer, vinylidene chloride copolymer, and includes resin A , a monomer that forms resin C, and the above-mentioned organic low-molecular substance The heat-sensitive layer coating liquid is heated and dried , and the resin C is dispersed in a microgel form in the heat-sensitive layer by irradiating with ultraviolet rays before the heat-sensitive layer becomes completely cloudy (60 to 90 ° C.). A reversible thermosensitive recording material.   The reversible thermosensitive recording material according to claim 1, wherein the resin C has a Tg of 180 ° C. or more.   3. The resin according to claim 1 or 2, wherein the resin comprises two types of resin A having a low Tg and resin C having a high Tg, and C / A is 1/99 to 40/60 by weight. The reversible thermosensitive recording material described.   The reversible thermosensitive recording material according to claim 1, further comprising a vinyl chloride copolymer as the resin B, wherein Tg is A> B. The organic low-molecular substance includes at least three components of the following a, b, and c, and includes a low-molecular substance having a melting point (mp) of b <a <c. The reversible thermosensitive recording material according to any one of claims 1 to 4. However,
a component is monocarboxylic acid (mp60-90 degreeC),
b component is fatty acid ester, polyhydric alcohol difatty acid ester, dibasic acid ester (mp 50-80 degreeC),
c component means fatty acid saturated dicarboxylic acid (mp100-130 degreeC), respectively.

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